Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2021-01-26' into staging

Block patches:
- Make backup block jobs use asynchronous requests with the block-copy
  module
- Use COR filter node for stream block jobs
- Make coroutine-sigaltstack’s qemu_coroutine_new() function thread-safe
- Report error string when file locking fails with an unexpected errno
- iotest fixes, additions, and some refactoring

# gpg: Signature made Tue 26 Jan 2021 14:16:59 GMT
# gpg:                using RSA key 91BEB60A30DB3E8857D11829F407DB0061D5CF40
# gpg:                issuer "mreitz@redhat.com"
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>" [full]
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2021-01-26: (53 commits)
  iotests/178: Pass value to invalid option
  iotests/118: Drop 'change' test
  iotests: Add test for the regression fixed in c8bf9a9169
  block: report errno when flock fcntl fails
  simplebench: add bench-backup.py
  simplebench: bench_block_job: add cmd_options argument
  simplebench/bench_block_job: use correct shebang line with python3
  block/block-copy: drop unused argument of block_copy()
  block/block-copy: drop unused block_copy_set_progress_callback()
  qapi: backup: disable copy_range by default
  backup: move to block-copy
  block/backup: drop extra gotos from backup_run()
  block/block-copy: make progress_bytes_callback optional
  iotests: 257: prepare for backup over block-copy
  iotests: 219: prepare for backup over block-copy
  iotests: 185: prepare for backup over block-copy
  iotests/129: Limit backup's max-chunk/max-workers
  iotests: 56: prepare for backup over block-copy
  qapi: backup: add max-chunk and max-workers to x-perf struct
  job: call job_enter from job_pause
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

51 files changed, 1797 insertions, 547 deletions

diff --git a/block.c b/block.c
index 8b9d457..91a66d4 100644
--- a/block.c
+++ b/block.c
@@ -4660,6 +4660,31 @@ static void bdrv_delete(BlockDriverState *bs)
     g_free(bs);
 }
 
+BlockDriverState *bdrv_insert_node(BlockDriverState *bs, QDict *node_options,
+                                   int flags, Error **errp)
+{
+    BlockDriverState *new_node_bs;
+    Error *local_err = NULL;
+
+    new_node_bs = bdrv_open(NULL, NULL, node_options, flags, errp);
+    if (new_node_bs == NULL) {
+        error_prepend(errp, "Could not create node: ");
+        return NULL;
+    }
+
+    bdrv_drained_begin(bs);
+    bdrv_replace_node(bs, new_node_bs, &local_err);
+    bdrv_drained_end(bs);
+
+    if (local_err) {
+        bdrv_unref(new_node_bs);
+        error_propagate(errp, local_err);
+        return NULL;
+    }
+
+    return new_node_bs;
+}
+
 /*
  * Run consistency checks on an image
  *
diff --git a/block/backup-top.c b/block/backup-top.c
index fe6883c..6e7e7bf 100644
--- a/block/backup-top.c
+++ b/block/backup-top.c
@@ -61,7 +61,7 @@ static coroutine_fn int backup_top_cbw(BlockDriverState *bs, uint64_t offset,
     off = QEMU_ALIGN_DOWN(offset, s->cluster_size);
     end = QEMU_ALIGN_UP(offset + bytes, s->cluster_size);
 
-    return block_copy(s->bcs, off, end - off, NULL);
+    return block_copy(s->bcs, off, end - off, true);
 }
 
 static int coroutine_fn backup_top_co_pdiscard(BlockDriverState *bs,
@@ -186,6 +186,7 @@ BlockDriverState *bdrv_backup_top_append(BlockDriverState *source,
                                          BlockDriverState *target,
                                          const char *filter_node_name,
                                          uint64_t cluster_size,
+                                         BackupPerf *perf,
                                          BdrvRequestFlags write_flags,
                                          BlockCopyState **bcs,
                                          Error **errp)
@@ -244,7 +245,8 @@ BlockDriverState *bdrv_backup_top_append(BlockDriverState *source,
 
     state->cluster_size = cluster_size;
     state->bcs = block_copy_state_new(top->backing, state->target,
-                                      cluster_size, write_flags, &local_err);
+                                      cluster_size, perf->use_copy_range,
+                                      write_flags, &local_err);
     if (local_err) {
         error_prepend(&local_err, "Cannot create block-copy-state: ");
         goto fail;
diff --git a/block/backup-top.h b/block/backup-top.h
index e5cabfa..b28b003 100644
--- a/block/backup-top.h
+++ b/block/backup-top.h
@@ -33,6 +33,7 @@ BlockDriverState *bdrv_backup_top_append(BlockDriverState *source,
                                          BlockDriverState *target,
                                          const char *filter_node_name,
                                          uint64_t cluster_size,
+                                         BackupPerf *perf,
                                          BdrvRequestFlags write_flags,
                                          BlockCopyState **bcs,
                                          Error **errp);
diff --git a/block/backup.c b/block/backup.c
index 9afa0bf..cc525d5 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -22,7 +22,6 @@
 #include "block/block-copy.h"
 #include "qapi/error.h"
 #include "qapi/qmp/qerror.h"
-#include "qemu/ratelimit.h"
 #include "qemu/cutils.h"
 #include "sysemu/block-backend.h"
 #include "qemu/bitmap.h"
@@ -44,40 +43,17 @@ typedef struct BackupBlockJob {
     BlockdevOnError on_source_error;
     BlockdevOnError on_target_error;
     uint64_t len;
-    uint64_t bytes_read;
     int64_t cluster_size;
+    BackupPerf perf;
 
     BlockCopyState *bcs;
+
+    bool wait;
+    BlockCopyCallState *bg_bcs_call;
 } BackupBlockJob;
 
 static const BlockJobDriver backup_job_driver;
 
-static void backup_progress_bytes_callback(int64_t bytes, void *opaque)
-{
-    BackupBlockJob *s = opaque;
-
-    s->bytes_read += bytes;
-}
-
-static int coroutine_fn backup_do_cow(BackupBlockJob *job,
-                                      int64_t offset, uint64_t bytes,
-                                      bool *error_is_read)
-{
-    int ret = 0;
-    int64_t start, end; /* bytes */
-
-    start = QEMU_ALIGN_DOWN(offset, job->cluster_size);
-    end = QEMU_ALIGN_UP(bytes + offset, job->cluster_size);
-
-    trace_backup_do_cow_enter(job, start, offset, bytes);
-
-    ret = block_copy(job->bcs, start, end - start, error_is_read);
-
-    trace_backup_do_cow_return(job, offset, bytes, ret);
-
-    return ret;
-}
-
 static void backup_cleanup_sync_bitmap(BackupBlockJob *job, int ret)
 {
     BdrvDirtyBitmap *bm;
@@ -157,53 +133,96 @@ static BlockErrorAction backup_error_action(BackupBlockJob *job,
     }
 }
 
-static bool coroutine_fn yield_and_check(BackupBlockJob *job)
+static void coroutine_fn backup_block_copy_callback(void *opaque)
 {
-    uint64_t delay_ns;
-
-    if (job_is_cancelled(&job->common.job)) {
-        return true;
-    }
-
-    /*
-     * We need to yield even for delay_ns = 0 so that bdrv_drain_all() can
-     * return. Without a yield, the VM would not reboot.
-     */
-    delay_ns = block_job_ratelimit_get_delay(&job->common, job->bytes_read);
-    job->bytes_read = 0;
-    job_sleep_ns(&job->common.job, delay_ns);
+    BackupBlockJob *s = opaque;
 
-    if (job_is_cancelled(&job->common.job)) {
-        return true;
+    if (s->wait) {
+        s->wait = false;
+        aio_co_wake(s->common.job.co);
+    } else {
+        job_enter(&s->common.job);
     }
-
-    return false;
 }
 
 static int coroutine_fn backup_loop(BackupBlockJob *job)
 {
-    bool error_is_read;
-    int64_t offset;
-    BdrvDirtyBitmapIter *bdbi;
+    BlockCopyCallState *s = NULL;
     int ret = 0;
+    bool error_is_read;
+    BlockErrorAction act;
+
+    while (true) { /* retry loop */
+        job->bg_bcs_call = s = block_copy_async(job->bcs, 0,
+                QEMU_ALIGN_UP(job->len, job->cluster_size),
+                job->perf.max_workers, job->perf.max_chunk,
+                backup_block_copy_callback, job);
+
+        while (!block_copy_call_finished(s) &&
+               !job_is_cancelled(&job->common.job))
+        {
+            job_yield(&job->common.job);
+        }
 
-    bdbi = bdrv_dirty_iter_new(block_copy_dirty_bitmap(job->bcs));
-    while ((offset = bdrv_dirty_iter_next(bdbi)) != -1) {
-        do {
-            if (yield_and_check(job)) {
-                goto out;
-            }
-            ret = backup_do_cow(job, offset, job->cluster_size, &error_is_read);
-            if (ret < 0 && backup_error_action(job, error_is_read, -ret) ==
-                           BLOCK_ERROR_ACTION_REPORT)
-            {
-                goto out;
-            }
-        } while (ret < 0);
+        if (!block_copy_call_finished(s)) {
+            assert(job_is_cancelled(&job->common.job));
+            /*
+             * Note that we can't use job_yield() here, as it doesn't work for
+             * cancelled job.
+             */
+            block_copy_call_cancel(s);
+            job->wait = true;
+            qemu_coroutine_yield();
+            assert(block_copy_call_finished(s));
+            ret = 0;
+            goto out;
+        }
+
+        if (job_is_cancelled(&job->common.job) ||
+            block_copy_call_succeeded(s))
+        {
+            ret = 0;
+            goto out;
+        }
+
+        if (block_copy_call_cancelled(s)) {
+            /*
+             * Job is not cancelled but only block-copy call. This is possible
+             * after job pause. Now the pause is finished, start new block-copy
+             * iteration.
+             */
+            block_copy_call_free(s);
+            continue;
+        }
+
+        /* The only remaining case is failed block-copy call. */
+        assert(block_copy_call_failed(s));
+
+        ret = block_copy_call_status(s, &error_is_read);
+        act = backup_error_action(job, error_is_read, -ret);
+        switch (act) {
+        case BLOCK_ERROR_ACTION_REPORT:
+            goto out;
+        case BLOCK_ERROR_ACTION_STOP:
+            /*
+             * Go to pause prior to starting new block-copy call on the next
+             * iteration.
+             */
+            job_pause_point(&job->common.job);
+            break;
+        case BLOCK_ERROR_ACTION_IGNORE:
+            /* Proceed to new block-copy call to retry. */
+            break;
+        default:
+            abort();
+        }
+
+        block_copy_call_free(s);
     }
 
- out:
-    bdrv_dirty_iter_free(bdbi);
+out:
+    block_copy_call_free(s);
+    job->bg_bcs_call = NULL;
     return ret;
 }
 
@@ -235,7 +254,7 @@ static void backup_init_bcs_bitmap(BackupBlockJob *job)
 static int coroutine_fn backup_run(Job *job, Error **errp)
 {
     BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
-    int ret = 0;
+    int ret;
 
     backup_init_bcs_bitmap(s);
 
@@ -244,14 +263,19 @@ static int coroutine_fn backup_run(Job *job, Error **errp)
         int64_t count;
 
         for (offset = 0; offset < s->len; ) {
-            if (yield_and_check(s)) {
-                ret = -ECANCELED;
-                goto out;
+            if (job_is_cancelled(job)) {
+                return -ECANCELED;
+            }
+
+            job_pause_point(job);
+
+            if (job_is_cancelled(job)) {
+                return -ECANCELED;
             }
 
             ret = block_copy_reset_unallocated(s->bcs, offset, &count);
             if (ret < 0) {
-                goto out;
+                return ret;
             }
 
             offset += count;
@@ -272,11 +296,37 @@ static int coroutine_fn backup_run(Job *job, Error **errp)
             job_yield(job);
         }
     } else {
-        ret = backup_loop(s);
+        return backup_loop(s);
     }
 
- out:
-    return ret;
+    return 0;
+}
+
+static void coroutine_fn backup_pause(Job *job)
+{
+    BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
+
+    if (s->bg_bcs_call && !block_copy_call_finished(s->bg_bcs_call)) {
+        block_copy_call_cancel(s->bg_bcs_call);
+        s->wait = true;
+        qemu_coroutine_yield();
+    }
+}
+
+static void coroutine_fn backup_set_speed(BlockJob *job, int64_t speed)
+{
+    BackupBlockJob *s = container_of(job, BackupBlockJob, common);
+
+    /*
+     * block_job_set_speed() is called first from block_job_create(), when we
+     * don't yet have s->bcs.
+     */
+    if (s->bcs) {
+        block_copy_set_speed(s->bcs, speed);
+        if (s->bg_bcs_call) {
+            block_copy_kick(s->bg_bcs_call);
+        }
+    }
 }
 
 static const BlockJobDriver backup_job_driver = {
@@ -289,7 +339,9 @@ static const BlockJobDriver backup_job_driver = {
         .commit                 = backup_commit,
         .abort                  = backup_abort,
         .clean                  = backup_clean,
-    }
+        .pause                  = backup_pause,
+    },
+    .set_speed = backup_set_speed,
 };
 
 static int64_t backup_calculate_cluster_size(BlockDriverState *target,
@@ -335,6 +387,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
                   BitmapSyncMode bitmap_mode,
                   bool compress,
                   const char *filter_node_name,
+                  BackupPerf *perf,
                   BlockdevOnError on_source_error,
                   BlockdevOnError on_target_error,
                   int creation_flags,
@@ -386,6 +439,29 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
         return NULL;
     }
 
+    cluster_size = backup_calculate_cluster_size(target, errp);
+    if (cluster_size < 0) {
+        goto error;
+    }
+
+    if (perf->max_workers < 1) {
+        error_setg(errp, "max-workers must be greater than zero");
+        return NULL;
+    }
+
+    if (perf->max_chunk < 0) {
+        error_setg(errp, "max-chunk must be zero (which means no limit) or "
+                   "positive");
+        return NULL;
+    }
+
+    if (perf->max_chunk && perf->max_chunk < cluster_size) {
+        error_setg(errp, "Required max-chunk (%" PRIi64 ") is less than backup "
+                   "cluster size (%" PRIi64 ")", perf->max_chunk, cluster_size);
+        return NULL;
+    }
+
+
     if (sync_bitmap) {
         /* If we need to write to this bitmap, check that we can: */
         if (bitmap_mode != BITMAP_SYNC_MODE_NEVER &&
@@ -418,11 +494,6 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
         goto error;
     }
 
-    cluster_size = backup_calculate_cluster_size(target, errp);
-    if (cluster_size < 0) {
-        goto error;
-    }
-
     /*
      * If source is in backing chain of target assume that target is going to be
      * used for "image fleecing", i.e. it should represent a kind of snapshot of
@@ -441,7 +512,8 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
                   (compress ? BDRV_REQ_WRITE_COMPRESSED : 0),
 
     backup_top = bdrv_backup_top_append(bs, target, filter_node_name,
-                                        cluster_size, write_flags, &bcs, errp);
+                                        cluster_size, perf,
+                                        write_flags, &bcs, errp);
     if (!backup_top) {
         goto error;
     }
@@ -464,9 +536,10 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
     job->bcs = bcs;
     job->cluster_size = cluster_size;
     job->len = len;
+    job->perf = *perf;
 
-    block_copy_set_progress_callback(bcs, backup_progress_bytes_callback, job);
     block_copy_set_progress_meter(bcs, &job->common.job.progress);
+    block_copy_set_speed(bcs, speed);
 
     /* Required permissions are already taken by backup-top target */
     block_job_add_bdrv(&job->common, "target", target, 0, BLK_PERM_ALL,
diff --git a/block/block-copy.c b/block/block-copy.c
index cd9bc47..39ae481 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -26,11 +26,34 @@
 #define BLOCK_COPY_MAX_BUFFER (1 * MiB)
 #define BLOCK_COPY_MAX_MEM (128 * MiB)
 #define BLOCK_COPY_MAX_WORKERS 64
+#define BLOCK_COPY_SLICE_TIME 100000000ULL /* ns */
 
 static coroutine_fn int block_copy_task_entry(AioTask *task);
 
 typedef struct BlockCopyCallState {
-    bool failed;
+    /* IN parameters. Initialized in block_copy_async() and never changed. */
+    BlockCopyState *s;
+    int64_t offset;
+    int64_t bytes;
+    int max_workers;
+    int64_t max_chunk;
+    bool ignore_ratelimit;
+    BlockCopyAsyncCallbackFunc cb;
+    void *cb_opaque;
+
+    /* Coroutine where async block-copy is running */
+    Coroutine *co;
+
+    /* To reference all call states from BlockCopyState */
+    QLIST_ENTRY(BlockCopyCallState) list;
+
+    /* State */
+    int ret;
+    bool finished;
+    QemuCoSleepState *sleep_state;
+    bool cancelled;
+
+    /* OUT parameters */
     bool error_is_read;
 } BlockCopyCallState;
 
@@ -65,7 +88,8 @@ typedef struct BlockCopyState {
     bool use_copy_range;
     int64_t copy_size;
     uint64_t len;
-    QLIST_HEAD(, BlockCopyTask) tasks;
+    QLIST_HEAD(, BlockCopyTask) tasks; /* All tasks from all block-copy calls */
+    QLIST_HEAD(, BlockCopyCallState) calls;
 
     BdrvRequestFlags write_flags;
 
@@ -86,11 +110,11 @@ typedef struct BlockCopyState {
     bool skip_unallocated;
 
     ProgressMeter *progress;
-    /* progress_bytes_callback: called when some copying progress is done. */
-    ProgressBytesCallbackFunc progress_bytes_callback;
-    void *progress_opaque;
 
     SharedResource *mem;
+
+    uint64_t speed;
+    RateLimit rate_limit;
 } BlockCopyState;
 
 static BlockCopyTask *find_conflicting_task(BlockCopyState *s,
@@ -134,10 +158,11 @@ static BlockCopyTask *block_copy_task_create(BlockCopyState *s,
                                              int64_t offset, int64_t bytes)
 {
     BlockCopyTask *task;
+    int64_t max_chunk = MIN_NON_ZERO(s->copy_size, call_state->max_chunk);
 
     if (!bdrv_dirty_bitmap_next_dirty_area(s->copy_bitmap,
                                            offset, offset + bytes,
-                                           s->copy_size, &offset, &bytes))
+                                           max_chunk, &offset, &bytes))
     {
         return NULL;
     }
@@ -218,7 +243,7 @@ static uint32_t block_copy_max_transfer(BdrvChild *source, BdrvChild *target)
 }
 
 BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
-                                     int64_t cluster_size,
+                                     int64_t cluster_size, bool use_copy_range,
                                      BdrvRequestFlags write_flags, Error **errp)
 {
     BlockCopyState *s;
@@ -260,24 +285,16 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
          * We enable copy-range, but keep small copy_size, until first
          * successful copy_range (look at block_copy_do_copy).
          */
-        s->use_copy_range = true;
+        s->use_copy_range = use_copy_range;
         s->copy_size = MAX(s->cluster_size, BLOCK_COPY_MAX_BUFFER);
     }
 
     QLIST_INIT(&s->tasks);
+    QLIST_INIT(&s->calls);
 
     return s;
 }
 
-void block_copy_set_progress_callback(
-        BlockCopyState *s,
-        ProgressBytesCallbackFunc progress_bytes_callback,
-        void *progress_opaque)
-{
-    s->progress_bytes_callback = progress_bytes_callback;
-    s->progress_opaque = progress_opaque;
-}
-
 void block_copy_set_progress_meter(BlockCopyState *s, ProgressMeter *pm)
 {
     s->progress = pm;
@@ -420,12 +437,11 @@ static coroutine_fn int block_copy_task_entry(AioTask *task)
 
     ret = block_copy_do_copy(t->s, t->offset, t->bytes, t->zeroes,
                              &error_is_read);
-    if (ret < 0 && !t->call_state->failed) {
-        t->call_state->failed = true;
+    if (ret < 0 && !t->call_state->ret) {
+        t->call_state->ret = ret;
         t->call_state->error_is_read = error_is_read;
     } else {
         progress_work_done(t->s->progress, t->bytes);
-        t->s->progress_bytes_callback(t->bytes, t->s->progress_opaque);
     }
     co_put_to_shres(t->s->mem, t->bytes);
     block_copy_task_end(t, ret);
@@ -544,15 +560,17 @@ int64_t block_copy_reset_unallocated(BlockCopyState *s,
  * Returns 1 if dirty clusters found and successfully copied, 0 if no dirty
  * clusters found and -errno on failure.
  */
-static int coroutine_fn block_copy_dirty_clusters(BlockCopyState *s,
-                                                  int64_t offset, int64_t bytes,
-                                                  bool *error_is_read)
+static int coroutine_fn
+block_copy_dirty_clusters(BlockCopyCallState *call_state)
 {
+    BlockCopyState *s = call_state->s;
+    int64_t offset = call_state->offset;
+    int64_t bytes = call_state->bytes;
+
     int ret = 0;
     bool found_dirty = false;
     int64_t end = offset + bytes;
     AioTaskPool *aio = NULL;
-    BlockCopyCallState call_state = {false, false};
 
     /*
      * block_copy() user is responsible for keeping source and target in same
@@ -564,11 +582,11 @@ static int coroutine_fn block_copy_dirty_clusters(BlockCopyState *s,
     assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
     assert(QEMU_IS_ALIGNED(bytes, s->cluster_size));
 
-    while (bytes && aio_task_pool_status(aio) == 0) {
+    while (bytes && aio_task_pool_status(aio) == 0 && !call_state->cancelled) {
         BlockCopyTask *task;
         int64_t status_bytes;
 
-        task = block_copy_task_create(s, &call_state, offset, bytes);
+        task = block_copy_task_create(s, call_state, offset, bytes);
         if (!task) {
             /* No more dirty bits in the bitmap */
             trace_block_copy_skip_range(s, offset, bytes);
@@ -599,6 +617,21 @@ static int coroutine_fn block_copy_dirty_clusters(BlockCopyState *s,
         }
         task->zeroes = ret & BDRV_BLOCK_ZERO;
 
+        if (s->speed) {
+            if (!call_state->ignore_ratelimit) {
+                uint64_t ns = ratelimit_calculate_delay(&s->rate_limit, 0);
+                if (ns > 0) {
+                    block_copy_task_end(task, -EAGAIN);
+                    g_free(task);
+                    qemu_co_sleep_ns_wakeable(QEMU_CLOCK_REALTIME, ns,
+                                              &call_state->sleep_state);
+                    continue;
+                }
+            }
+
+            ratelimit_calculate_delay(&s->rate_limit, task->bytes);
+        }
+
         trace_block_copy_process(s, task->offset);
 
         co_get_from_shres(s->mem, task->bytes);
@@ -607,7 +640,7 @@ static int coroutine_fn block_copy_dirty_clusters(BlockCopyState *s,
         bytes = end - offset;
 
         if (!aio && bytes) {
-            aio = aio_task_pool_new(BLOCK_COPY_MAX_WORKERS);
+            aio = aio_task_pool_new(call_state->max_workers);
         }
 
         ret = block_copy_task_run(aio, task);
@@ -633,15 +666,19 @@ out:
 
         aio_task_pool_free(aio);
     }
-    if (error_is_read && ret < 0) {
-        *error_is_read = call_state.error_is_read;
-    }
 
     return ret < 0 ? ret : found_dirty;
 }
 
+void block_copy_kick(BlockCopyCallState *call_state)
+{
+    if (call_state->sleep_state) {
+        qemu_co_sleep_wake(call_state->sleep_state);
+    }
+}
+
 /*
- * block_copy
+ * block_copy_common
  *
  * Copy requested region, accordingly to dirty bitmap.
  * Collaborate with parallel block_copy requests: if they succeed it will help
@@ -649,16 +686,18 @@ out:
  * it means that some I/O operation failed in context of _this_ block_copy call,
  * not some parallel operation.
  */
-int coroutine_fn block_copy(BlockCopyState *s, int64_t offset, int64_t bytes,
-                            bool *error_is_read)
+static int coroutine_fn block_copy_common(BlockCopyCallState *call_state)
 {
     int ret;
 
+    QLIST_INSERT_HEAD(&call_state->s->calls, call_state, list);
+
     do {
-        ret = block_copy_dirty_clusters(s, offset, bytes, error_is_read);
+        ret = block_copy_dirty_clusters(call_state);
 
-        if (ret == 0) {
-            ret = block_copy_wait_one(s, offset, bytes);
+        if (ret == 0 && !call_state->cancelled) {
+            ret = block_copy_wait_one(call_state->s, call_state->offset,
+                                      call_state->bytes);
         }
 
         /*
@@ -670,11 +709,110 @@ int coroutine_fn block_copy(BlockCopyState *s, int64_t offset, int64_t bytes,
          * 2. We have waited for some intersecting block-copy request
          *    It may have failed and produced new dirty bits.
          */
-    } while (ret > 0);
+    } while (ret > 0 && !call_state->cancelled);
+
+    call_state->finished = true;
+
+    if (call_state->cb) {
+        call_state->cb(call_state->cb_opaque);
+    }
+
+    QLIST_REMOVE(call_state, list);
 
     return ret;
 }
 
+int coroutine_fn block_copy(BlockCopyState *s, int64_t start, int64_t bytes,
+                            bool ignore_ratelimit)
+{
+    BlockCopyCallState call_state = {
+        .s = s,
+        .offset = start,
+        .bytes = bytes,
+        .ignore_ratelimit = ignore_ratelimit,
+        .max_workers = BLOCK_COPY_MAX_WORKERS,
+    };
+
+    return block_copy_common(&call_state);
+}
+
+static void coroutine_fn block_copy_async_co_entry(void *opaque)
+{
+    block_copy_common(opaque);
+}
+
+BlockCopyCallState *block_copy_async(BlockCopyState *s,
+                                     int64_t offset, int64_t bytes,
+                                     int max_workers, int64_t max_chunk,
+                                     BlockCopyAsyncCallbackFunc cb,
+                                     void *cb_opaque)
+{
+    BlockCopyCallState *call_state = g_new(BlockCopyCallState, 1);
+
+    *call_state = (BlockCopyCallState) {
+        .s = s,
+        .offset = offset,
+        .bytes = bytes,
+        .max_workers = max_workers,
+        .max_chunk = max_chunk,
+        .cb = cb,
+        .cb_opaque = cb_opaque,
+
+        .co = qemu_coroutine_create(block_copy_async_co_entry, call_state),
+    };
+
+    qemu_coroutine_enter(call_state->co);
+
+    return call_state;
+}
+
+void block_copy_call_free(BlockCopyCallState *call_state)
+{
+    if (!call_state) {
+        return;
+    }
+
+    assert(call_state->finished);
+    g_free(call_state);
+}
+
+bool block_copy_call_finished(BlockCopyCallState *call_state)
+{
+    return call_state->finished;
+}
+
+bool block_copy_call_succeeded(BlockCopyCallState *call_state)
+{
+    return call_state->finished && !call_state->cancelled &&
+        call_state->ret == 0;
+}
+
+bool block_copy_call_failed(BlockCopyCallState *call_state)
+{
+    return call_state->finished && !call_state->cancelled &&
+        call_state->ret < 0;
+}
+
+bool block_copy_call_cancelled(BlockCopyCallState *call_state)
+{
+    return call_state->cancelled;
+}
+
+int block_copy_call_status(BlockCopyCallState *call_state, bool *error_is_read)
+{
+    assert(call_state->finished);
+    if (error_is_read) {
+        *error_is_read = call_state->error_is_read;
+    }
+    return call_state->ret;
+}
+
+void block_copy_call_cancel(BlockCopyCallState *call_state)
+{
+    call_state->cancelled = true;
+    block_copy_kick(call_state);
+}
+
 BdrvDirtyBitmap *block_copy_dirty_bitmap(BlockCopyState *s)
 {
     return s->copy_bitmap;
@@ -684,3 +822,18 @@ void block_copy_set_skip_unallocated(BlockCopyState *s, bool skip)
 {
     s->skip_unallocated = skip;
 }
+
+void block_copy_set_speed(BlockCopyState *s, uint64_t speed)
+{
+    s->speed = speed;
+    if (speed > 0) {
+        ratelimit_set_speed(&s->rate_limit, speed, BLOCK_COPY_SLICE_TIME);
+    }
+
+    /*
+     * Note: it's good to kick all call states from here, but it should be done
+     * only from a coroutine, to not crash if s->calls list changed while
+     * entering one call. So for now, the only user of this function kicks its
+     * only one call_state by hand.
+     */
+}
diff --git a/block/copy-on-read.c b/block/copy-on-read.c
index 2816e61..9cad9e1 100644
--- a/block/copy-on-read.c
+++ b/block/copy-on-read.c
@@ -23,11 +23,26 @@
 #include "qemu/osdep.h"
 #include "block/block_int.h"
 #include "qemu/module.h"
+#include "qapi/error.h"
+#include "qapi/qmp/qdict.h"
+#include "block/copy-on-read.h"
+
+
+typedef struct BDRVStateCOR {
+    bool active;
+    BlockDriverState *bottom_bs;
+    bool chain_frozen;
+} BDRVStateCOR;
 
 
 static int cor_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
+    BlockDriverState *bottom_bs = NULL;
+    BDRVStateCOR *state = bs->opaque;
+    /* Find a bottom node name, if any */
+    const char *bottom_node = qdict_get_try_str(options, "bottom");
+
     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
                                BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
                                false, errp);
@@ -35,6 +50,8 @@ static int cor_open(BlockDriverState *bs, QDict *options, int flags,
         return -EINVAL;
     }
 
+    bs->supported_read_flags = BDRV_REQ_PREFETCH;
+
     bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
         (BDRV_REQ_FUA & bs->file->bs->supported_write_flags);
 
@@ -42,6 +59,44 @@ static int cor_open(BlockDriverState *bs, QDict *options, int flags,
         ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
             bs->file->bs->supported_zero_flags);
 
+    if (bottom_node) {
+        bottom_bs = bdrv_find_node(bottom_node);
+        if (!bottom_bs) {
+            error_setg(errp, "Bottom node '%s' not found", bottom_node);
+            qdict_del(options, "bottom");
+            return -EINVAL;
+        }
+        qdict_del(options, "bottom");
+
+        if (!bottom_bs->drv) {
+            error_setg(errp, "Bottom node '%s' not opened", bottom_node);
+            return -EINVAL;
+        }
+
+        if (bottom_bs->drv->is_filter) {
+            error_setg(errp, "Bottom node '%s' is a filter", bottom_node);
+            return -EINVAL;
+        }
+
+        if (bdrv_freeze_backing_chain(bs, bottom_bs, errp) < 0) {
+            return -EINVAL;
+        }
+        state->chain_frozen = true;
+
+        /*
+         * We do freeze the chain, so it shouldn't be removed. Still, storing a
+         * pointer worth bdrv_ref().
+         */
+        bdrv_ref(bottom_bs);
+    }
+    state->active = true;
+    state->bottom_bs = bottom_bs;
+
+    /*
+     * We don't need to call bdrv_child_refresh_perms() now as the permissions
+     * will be updated later when the filter node gets its parent.
+     */
+
     return 0;
 }
 
@@ -57,6 +112,17 @@ static void cor_child_perm(BlockDriverState *bs, BdrvChild *c,
                            uint64_t perm, uint64_t shared,
                            uint64_t *nperm, uint64_t *nshared)
 {
+    BDRVStateCOR *s = bs->opaque;
+
+    if (!s->active) {
+        /*
+         * While the filter is being removed
+         */
+        *nperm = 0;
+        *nshared = BLK_PERM_ALL;
+        return;
+    }
+
     *nperm = perm & PERM_PASSTHROUGH;
     *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED;
 
@@ -74,21 +140,67 @@ static int64_t cor_getlength(BlockDriverState *bs)
 }
 
 
-static int coroutine_fn cor_co_preadv(BlockDriverState *bs,
-                                      uint64_t offset, uint64_t bytes,
-                                      QEMUIOVector *qiov, int flags)
+static int coroutine_fn cor_co_preadv_part(BlockDriverState *bs,
+                                           uint64_t offset, uint64_t bytes,
+                                           QEMUIOVector *qiov,
+                                           size_t qiov_offset,
+                                           int flags)
 {
-    return bdrv_co_preadv(bs->file, offset, bytes, qiov,
-                          flags | BDRV_REQ_COPY_ON_READ);
+    int64_t n;
+    int local_flags;
+    int ret;
+    BDRVStateCOR *state = bs->opaque;
+
+    if (!state->bottom_bs) {
+        return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset,
+                                   flags | BDRV_REQ_COPY_ON_READ);
+    }
+
+    while (bytes) {
+        local_flags = flags;
+
+        /* In case of failure, try to copy-on-read anyway */
+        ret = bdrv_is_allocated(bs->file->bs, offset, bytes, &n);
+        if (ret <= 0) {
+            ret = bdrv_is_allocated_above(bdrv_backing_chain_next(bs->file->bs),
+                                          state->bottom_bs, true, offset,
+                                          n, &n);
+            if (ret > 0 || ret < 0) {
+                local_flags |= BDRV_REQ_COPY_ON_READ;
+            }
+            /* Finish earlier if the end of a backing file has been reached */
+            if (n == 0) {
+                break;
+            }
+        }
+
+        /* Skip if neither read nor write are needed */
+        if ((local_flags & (BDRV_REQ_PREFETCH | BDRV_REQ_COPY_ON_READ)) !=
+            BDRV_REQ_PREFETCH) {
+            ret = bdrv_co_preadv_part(bs->file, offset, n, qiov, qiov_offset,
+                                      local_flags);
+            if (ret < 0) {
+                return ret;
+            }
+        }
+
+        offset += n;
+        qiov_offset += n;
+        bytes -= n;
+    }
+
+    return 0;
 }
 
 
-static int coroutine_fn cor_co_pwritev(BlockDriverState *bs,
-                                       uint64_t offset, uint64_t bytes,
-                                       QEMUIOVector *qiov, int flags)
+static int coroutine_fn cor_co_pwritev_part(BlockDriverState *bs,
+                                            uint64_t offset,
+                                            uint64_t bytes,
+                                            QEMUIOVector *qiov,
+                                            size_t qiov_offset, int flags)
 {
-
-    return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);
+    return bdrv_co_pwritev_part(bs->file, offset, bytes, qiov, qiov_offset,
+                                flags);
 }
 
 
@@ -129,16 +241,31 @@ static void cor_lock_medium(BlockDriverState *bs, bool locked)
 }
 
 
+static void cor_close(BlockDriverState *bs)
+{
+    BDRVStateCOR *s = bs->opaque;
+
+    if (s->chain_frozen) {
+        s->chain_frozen = false;
+        bdrv_unfreeze_backing_chain(bs, s->bottom_bs);
+    }
+
+    bdrv_unref(s->bottom_bs);
+}
+
+
 static BlockDriver bdrv_copy_on_read = {
     .format_name                        = "copy-on-read",
+    .instance_size                      = sizeof(BDRVStateCOR),
 
     .bdrv_open                          = cor_open,
+    .bdrv_close                         = cor_close,
     .bdrv_child_perm                    = cor_child_perm,
 
     .bdrv_getlength                     = cor_getlength,
 
-    .bdrv_co_preadv                     = cor_co_preadv,
-    .bdrv_co_pwritev                    = cor_co_pwritev,
+    .bdrv_co_preadv_part                = cor_co_preadv_part,
+    .bdrv_co_pwritev_part               = cor_co_pwritev_part,
     .bdrv_co_pwrite_zeroes              = cor_co_pwrite_zeroes,
     .bdrv_co_pdiscard                   = cor_co_pdiscard,
     .bdrv_co_pwritev_compressed         = cor_co_pwritev_compressed,
@@ -150,6 +277,39 @@ static BlockDriver bdrv_copy_on_read = {
     .is_filter                          = true,
 };
 
+
+void bdrv_cor_filter_drop(BlockDriverState *cor_filter_bs)
+{
+    BdrvChild *child;
+    BlockDriverState *bs;
+    BDRVStateCOR *s = cor_filter_bs->opaque;
+
+    child = bdrv_filter_child(cor_filter_bs);
+    if (!child) {
+        return;
+    }
+    bs = child->bs;
+
+    /* Retain the BDS until we complete the graph change. */
+    bdrv_ref(bs);
+    /* Hold a guest back from writing while permissions are being reset. */
+    bdrv_drained_begin(bs);
+    /* Drop permissions before the graph change. */
+    s->active = false;
+    /* unfreeze, as otherwise bdrv_replace_node() will fail */
+    if (s->chain_frozen) {
+        s->chain_frozen = false;
+        bdrv_unfreeze_backing_chain(cor_filter_bs, s->bottom_bs);
+    }
+    bdrv_child_refresh_perms(cor_filter_bs, child, &error_abort);
+    bdrv_replace_node(cor_filter_bs, bs, &error_abort);
+
+    bdrv_drained_end(bs);
+    bdrv_unref(bs);
+    bdrv_unref(cor_filter_bs);
+}
+
+
 static void bdrv_copy_on_read_init(void)
 {
     bdrv_register(&bdrv_copy_on_read);
diff --git a/block/copy-on-read.h b/block/copy-on-read.h
new file mode 100644
index 0000000..7bf405d
--- /dev/null
+++ b/block/copy-on-read.h
@@ -0,0 +1,32 @@
+/*
+ * Copy-on-read filter block driver
+ *
+ * The filter driver performs Copy-On-Read (COR) operations
+ *
+ * Copyright (c) 2018-2020 Virtuozzo International GmbH.
+ *
+ * Author:
+ *   Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef BLOCK_COPY_ON_READ
+#define BLOCK_COPY_ON_READ
+
+#include "block/block_int.h"
+
+void bdrv_cor_filter_drop(BlockDriverState *cor_filter_bs);
+
+#endif /* BLOCK_COPY_ON_READ */
diff --git a/block/file-posix.c b/block/file-posix.c
index 00cdaaa..11aafa9 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -216,6 +216,20 @@ typedef struct RawPosixAIOData {
 static int cdrom_reopen(BlockDriverState *bs);
 #endif
 
+/*
+ * Elide EAGAIN and EACCES details when failing to lock, as this
+ * indicates that the specified file region is already locked by
+ * another process, which is considered a common scenario.
+ */
+#define raw_lock_error_setg_errno(errp, err, fmt, ...)                  \
+    do {                                                                \
+        if ((err) == EAGAIN || (err) == EACCES) {                       \
+            error_setg((errp), (fmt), ## __VA_ARGS__);                  \
+        } else {                                                        \
+            error_setg_errno((errp), (err), (fmt), ## __VA_ARGS__);     \
+        }                                                               \
+    } while (0)
+
 #if defined(__NetBSD__)
 static int raw_normalize_devicepath(const char **filename, Error **errp)
 {
@@ -836,7 +850,8 @@ static int raw_apply_lock_bytes(BDRVRawState *s, int fd,
         if ((perm_lock_bits & bit) && !(locked_perm & bit)) {
             ret = qemu_lock_fd(fd, off, 1, false);
             if (ret) {
-                error_setg(errp, "Failed to lock byte %d", off);
+                raw_lock_error_setg_errno(errp, -ret, "Failed to lock byte %d",
+                                          off);
                 return ret;
             } else if (s) {
                 s->locked_perm |= bit;
@@ -844,7 +859,7 @@ static int raw_apply_lock_bytes(BDRVRawState *s, int fd,
         } else if (unlock && (locked_perm & bit) && !(perm_lock_bits & bit)) {
             ret = qemu_unlock_fd(fd, off, 1);
             if (ret) {
-                error_setg(errp, "Failed to unlock byte %d", off);
+                error_setg_errno(errp, -ret, "Failed to unlock byte %d", off);
                 return ret;
             } else if (s) {
                 s->locked_perm &= ~bit;
@@ -857,7 +872,8 @@ static int raw_apply_lock_bytes(BDRVRawState *s, int fd,
         if ((shared_perm_lock_bits & bit) && !(locked_shared_perm & bit)) {
             ret = qemu_lock_fd(fd, off, 1, false);
             if (ret) {
-                error_setg(errp, "Failed to lock byte %d", off);
+                raw_lock_error_setg_errno(errp, -ret, "Failed to lock byte %d",
+                                          off);
                 return ret;
             } else if (s) {
                 s->locked_shared_perm |= bit;
@@ -866,7 +882,7 @@ static int raw_apply_lock_bytes(BDRVRawState *s, int fd,
                    !(shared_perm_lock_bits & bit)) {
             ret = qemu_unlock_fd(fd, off, 1);
             if (ret) {
-                error_setg(errp, "Failed to unlock byte %d", off);
+                error_setg_errno(errp, -ret, "Failed to unlock byte %d", off);
                 return ret;
             } else if (s) {
                 s->locked_shared_perm &= ~bit;
@@ -890,9 +906,10 @@ static int raw_check_lock_bytes(int fd, uint64_t perm, uint64_t shared_perm,
             ret = qemu_lock_fd_test(fd, off, 1, true);
             if (ret) {
                 char *perm_name = bdrv_perm_names(p);
-                error_setg(errp,
-                           "Failed to get \"%s\" lock",
-                           perm_name);
+
+                raw_lock_error_setg_errno(errp, -ret,
+                                          "Failed to get \"%s\" lock",
+                                          perm_name);
                 g_free(perm_name);
                 return ret;
             }
@@ -905,9 +922,10 @@ static int raw_check_lock_bytes(int fd, uint64_t perm, uint64_t shared_perm,
             ret = qemu_lock_fd_test(fd, off, 1, true);
             if (ret) {
                 char *perm_name = bdrv_perm_names(p);
-                error_setg(errp,
-                           "Failed to get shared \"%s\" lock",
-                           perm_name);
+
+                raw_lock_error_setg_errno(errp, -ret,
+                                          "Failed to get shared \"%s\" lock",
+                                          perm_name);
                 g_free(perm_name);
                 return ret;
             }
diff --git a/block/io.c b/block/io.c
index 95b1c56..d203435 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1453,6 +1453,9 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
     if (flags & BDRV_REQ_COPY_ON_READ) {
         int64_t pnum;
 
+        /* The flag BDRV_REQ_COPY_ON_READ has reached its addressee */
+        flags &= ~BDRV_REQ_COPY_ON_READ;
+
         ret = bdrv_is_allocated(bs, offset, bytes, &pnum);
         if (ret < 0) {
             goto out;
@@ -1474,9 +1477,11 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
         goto out;
     }
 
+    assert(!(flags & ~bs->supported_read_flags));
+
     max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
     if (bytes <= max_bytes && bytes <= max_transfer) {
-        ret = bdrv_driver_preadv(bs, offset, bytes, qiov, qiov_offset, 0);
+        ret = bdrv_driver_preadv(bs, offset, bytes, qiov, qiov_offset, flags);
         goto out;
     }
 
@@ -1489,7 +1494,8 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
 
             ret = bdrv_driver_preadv(bs, offset + bytes - bytes_remaining,
                                      num, qiov,
-                                     qiov_offset + bytes - bytes_remaining, 0);
+                                     qiov_offset + bytes - bytes_remaining,
+                                     flags);
             max_bytes -= num;
         } else {
             num = bytes_remaining;
diff --git a/block/monitor/block-hmp-cmds.c b/block/monitor/block-hmp-cmds.c
index d15a2be..afd75ab 100644
--- a/block/monitor/block-hmp-cmds.c
+++ b/block/monitor/block-hmp-cmds.c
@@ -507,9 +507,10 @@ void hmp_block_stream(Monitor *mon, const QDict *qdict)
     int64_t speed = qdict_get_try_int(qdict, "speed", 0);
 
     qmp_block_stream(true, device, device, base != NULL, base, false, NULL,
-                     false, NULL, qdict_haskey(qdict, "speed"), speed, true,
-                     BLOCKDEV_ON_ERROR_REPORT, false, false, false, false,
-                     &error);
+                     false, NULL, false, NULL,
+                     qdict_haskey(qdict, "speed"), speed, true,
+                     BLOCKDEV_ON_ERROR_REPORT, false, NULL, false, false, false,
+                     false, &error);
 
     hmp_handle_error(mon, error);
 }
diff --git a/block/replication.c b/block/replication.c
index 0c70215..97be7ef 100644
--- a/block/replication.c
+++ b/block/replication.c
@@ -454,6 +454,7 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
     int64_t active_length, hidden_length, disk_length;
     AioContext *aio_context;
     Error *local_err = NULL;
+    BackupPerf perf = { .use_copy_range = true, .max_workers = 1 };
 
     aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(aio_context);
@@ -558,6 +559,7 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
         s->backup_job = backup_job_create(
                                 NULL, s->secondary_disk->bs, s->hidden_disk->bs,
                                 0, MIRROR_SYNC_MODE_NONE, NULL, 0, false, NULL,
+                                &perf,
                                 BLOCKDEV_ON_ERROR_REPORT,
                                 BLOCKDEV_ON_ERROR_REPORT, JOB_INTERNAL,
                                 backup_job_completed, bs, NULL, &local_err);
diff --git a/block/stream.c b/block/stream.c
index 236384f..1fa742b 100644
--- a/block/stream.c
+++ b/block/stream.c
@@ -17,8 +17,10 @@
 #include "block/blockjob_int.h"
 #include "qapi/error.h"
 #include "qapi/qmp/qerror.h"
+#include "qapi/qmp/qdict.h"
 #include "qemu/ratelimit.h"
 #include "sysemu/block-backend.h"
+#include "block/copy-on-read.h"
 
 enum {
     /*
@@ -33,10 +35,11 @@ typedef struct StreamBlockJob {
     BlockJob common;
     BlockDriverState *base_overlay; /* COW overlay (stream from this) */
     BlockDriverState *above_base;   /* Node directly above the base */
+    BlockDriverState *cor_filter_bs;
+    BlockDriverState *target_bs;
     BlockdevOnError on_error;
     char *backing_file_str;
     bool bs_read_only;
-    bool chain_frozen;
 } StreamBlockJob;
 
 static int coroutine_fn stream_populate(BlockBackend *blk,
@@ -44,39 +47,28 @@ static int coroutine_fn stream_populate(BlockBackend *blk,
 {
     assert(bytes < SIZE_MAX);
 
-    return blk_co_preadv(blk, offset, bytes, NULL,
-                         BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH);
-}
-
-static void stream_abort(Job *job)
-{
-    StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
-
-    if (s->chain_frozen) {
-        BlockJob *bjob = &s->common;
-        bdrv_unfreeze_backing_chain(blk_bs(bjob->blk), s->above_base);
-    }
+    return blk_co_preadv(blk, offset, bytes, NULL, BDRV_REQ_PREFETCH);
 }
 
 static int stream_prepare(Job *job)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
-    BlockJob *bjob = &s->common;
-    BlockDriverState *bs = blk_bs(bjob->blk);
-    BlockDriverState *unfiltered_bs = bdrv_skip_filters(bs);
+    BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
     BlockDriverState *base = bdrv_filter_or_cow_bs(s->above_base);
+    BlockDriverState *unfiltered_base = bdrv_skip_filters(base);
     Error *local_err = NULL;
     int ret = 0;
 
-    bdrv_unfreeze_backing_chain(bs, s->above_base);
-    s->chain_frozen = false;
+    /* We should drop filter at this point, as filter hold the backing chain */
+    bdrv_cor_filter_drop(s->cor_filter_bs);
+    s->cor_filter_bs = NULL;
 
     if (bdrv_cow_child(unfiltered_bs)) {
         const char *base_id = NULL, *base_fmt = NULL;
-        if (base) {
-            base_id = s->backing_file_str;
-            if (base->drv) {
-                base_fmt = base->drv->format_name;
+        if (unfiltered_base) {
+            base_id = s->backing_file_str ?: unfiltered_base->filename;
+            if (unfiltered_base->drv) {
+                base_fmt = unfiltered_base->drv->format_name;
             }
         }
         bdrv_set_backing_hd(unfiltered_bs, base, &local_err);
@@ -94,13 +86,17 @@ static void stream_clean(Job *job)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
     BlockJob *bjob = &s->common;
-    BlockDriverState *bs = blk_bs(bjob->blk);
+
+    if (s->cor_filter_bs) {
+        bdrv_cor_filter_drop(s->cor_filter_bs);
+        s->cor_filter_bs = NULL;
+    }
 
     /* Reopen the image back in read-only mode if necessary */
     if (s->bs_read_only) {
         /* Give up write permissions before making it read-only */
         blk_set_perm(bjob->blk, 0, BLK_PERM_ALL, &error_abort);
-        bdrv_reopen_set_read_only(bs, true, NULL);
+        bdrv_reopen_set_read_only(s->target_bs, true, NULL);
     }
 
     g_free(s->backing_file_str);
@@ -110,9 +106,7 @@ static int coroutine_fn stream_run(Job *job, Error **errp)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
     BlockBackend *blk = s->common.blk;
-    BlockDriverState *bs = blk_bs(blk);
-    BlockDriverState *unfiltered_bs = bdrv_skip_filters(bs);
-    bool enable_cor = !bdrv_cow_child(s->base_overlay);
+    BlockDriverState *unfiltered_bs = bdrv_skip_filters(s->target_bs);
     int64_t len;
     int64_t offset = 0;
     uint64_t delay_ns = 0;
@@ -124,21 +118,12 @@ static int coroutine_fn stream_run(Job *job, Error **errp)
         return 0;
     }
 
-    len = bdrv_getlength(bs);
+    len = bdrv_getlength(s->target_bs);
     if (len < 0) {
         return len;
     }
     job_progress_set_remaining(&s->common.job, len);
 
-    /* Turn on copy-on-read for the whole block device so that guest read
-     * requests help us make progress.  Only do this when copying the entire
-     * backing chain since the copy-on-read operation does not take base into
-     * account.
-     */
-    if (enable_cor) {
-        bdrv_enable_copy_on_read(bs);
-    }
-
     for ( ; offset < len; offset += n) {
         bool copy;
         int ret;
@@ -197,10 +182,6 @@ static int coroutine_fn stream_run(Job *job, Error **errp)
         }
     }
 
-    if (enable_cor) {
-        bdrv_disable_copy_on_read(bs);
-    }
-
     /* Do not remove the backing file if an error was there but ignored. */
     return error;
 }
@@ -212,7 +193,6 @@ static const BlockJobDriver stream_job_driver = {
         .free          = block_job_free,
         .run           = stream_run,
         .prepare       = stream_prepare,
-        .abort         = stream_abort,
         .clean         = stream_clean,
         .user_resume   = block_job_user_resume,
     },
@@ -220,59 +200,113 @@ static const BlockJobDriver stream_job_driver = {
 
 void stream_start(const char *job_id, BlockDriverState *bs,
                   BlockDriverState *base, const char *backing_file_str,
+                  BlockDriverState *bottom,
                   int creation_flags, int64_t speed,
-                  BlockdevOnError on_error, Error **errp)
+                  BlockdevOnError on_error,
+                  const char *filter_node_name,
+                  Error **errp)
 {
     StreamBlockJob *s;
     BlockDriverState *iter;
     bool bs_read_only;
     int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
-    BlockDriverState *base_overlay = bdrv_find_overlay(bs, base);
+    BlockDriverState *base_overlay;
+    BlockDriverState *cor_filter_bs = NULL;
     BlockDriverState *above_base;
-
-    if (!base_overlay) {
-        error_setg(errp, "'%s' is not in the backing chain of '%s'",
-                   base->node_name, bs->node_name);
-        return;
-    }
-
-    /*
-     * Find the node directly above @base.  @base_overlay is a COW overlay, so
-     * it must have a bdrv_cow_child(), but it is the immediate overlay of
-     * @base, so between the two there can only be filters.
-     */
-    above_base = base_overlay;
-    if (bdrv_cow_bs(above_base) != base) {
-        above_base = bdrv_cow_bs(above_base);
-        while (bdrv_filter_bs(above_base) != base) {
-            above_base = bdrv_filter_bs(above_base);
+    QDict *opts;
+
+    assert(!(base && bottom));
+    assert(!(backing_file_str && bottom));
+
+    if (bottom) {
+        /*
+         * New simple interface. The code is written in terms of old interface
+         * with @base parameter (still, it doesn't freeze link to base, so in
+         * this mean old code is correct for new interface). So, for now, just
+         * emulate base_overlay and above_base. Still, when old interface
+         * finally removed, we should refactor code to use only "bottom", but
+         * not "*base*" things.
+         */
+        assert(!bottom->drv->is_filter);
+        base_overlay = above_base = bottom;
+    } else {
+        base_overlay = bdrv_find_overlay(bs, base);
+        if (!base_overlay) {
+            error_setg(errp, "'%s' is not in the backing chain of '%s'",
+                       base->node_name, bs->node_name);
+            return;
         }
-    }
 
-    if (bdrv_freeze_backing_chain(bs, above_base, errp) < 0) {
-        return;
+        /*
+         * Find the node directly above @base.  @base_overlay is a COW overlay,
+         * so it must have a bdrv_cow_child(), but it is the immediate overlay
+         * of @base, so between the two there can only be filters.
+         */
+        above_base = base_overlay;
+        if (bdrv_cow_bs(above_base) != base) {
+            above_base = bdrv_cow_bs(above_base);
+            while (bdrv_filter_bs(above_base) != base) {
+                above_base = bdrv_filter_bs(above_base);
+            }
+        }
     }
 
     /* Make sure that the image is opened in read-write mode */
     bs_read_only = bdrv_is_read_only(bs);
     if (bs_read_only) {
-        if (bdrv_reopen_set_read_only(bs, false, errp) != 0) {
-            bs_read_only = false;
-            goto fail;
+        int ret;
+        /* Hold the chain during reopen */
+        if (bdrv_freeze_backing_chain(bs, above_base, errp) < 0) {
+            return;
+        }
+
+        ret = bdrv_reopen_set_read_only(bs, false, errp);
+
+        /* failure, or cor-filter will hold the chain */
+        bdrv_unfreeze_backing_chain(bs, above_base);
+
+        if (ret < 0) {
+            return;
         }
     }
 
-    /* Prevent concurrent jobs trying to modify the graph structure here, we
-     * already have our own plans. Also don't allow resize as the image size is
-     * queried only at the job start and then cached. */
-    s = block_job_create(job_id, &stream_job_driver, NULL, bs,
-                         basic_flags | BLK_PERM_GRAPH_MOD,
+    opts = qdict_new();
+
+    qdict_put_str(opts, "driver", "copy-on-read");
+    qdict_put_str(opts, "file", bdrv_get_node_name(bs));
+    /* Pass the base_overlay node name as 'bottom' to COR driver */
+    qdict_put_str(opts, "bottom", base_overlay->node_name);
+    if (filter_node_name) {
+        qdict_put_str(opts, "node-name", filter_node_name);
+    }
+
+    cor_filter_bs = bdrv_insert_node(bs, opts, BDRV_O_RDWR, errp);
+    if (!cor_filter_bs) {
+        goto fail;
+    }
+
+    if (!filter_node_name) {
+        cor_filter_bs->implicit = true;
+    }
+
+    s = block_job_create(job_id, &stream_job_driver, NULL, cor_filter_bs,
+                         BLK_PERM_CONSISTENT_READ,
                          basic_flags | BLK_PERM_WRITE,
                          speed, creation_flags, NULL, NULL, errp);
     if (!s) {
         goto fail;
     }
 
+    /*
+     * Prevent concurrent jobs trying to modify the graph structure here, we
+     * already have our own plans. Also don't allow resize as the image size is
+     * queried only at the job start and then cached.
+     */
+    if (block_job_add_bdrv(&s->common, "active node", bs, 0,
+                           basic_flags | BLK_PERM_WRITE, &error_abort)) {
+        goto fail;
+    }
+
     /* Block all intermediate nodes between bs and base, because they will
      * disappear from the chain after this operation. The streaming job reads
      * every block only once, assuming that it doesn't change, so forbid writes
@@ -293,8 +327,9 @@ void stream_start(const char *job_id, BlockDriverState *bs,
     s->base_overlay = base_overlay;
     s->above_base = above_base;
     s->backing_file_str = g_strdup(backing_file_str);
+    s->cor_filter_bs = cor_filter_bs;
+    s->target_bs = bs;
     s->bs_read_only = bs_read_only;
-    s->chain_frozen = true;
 
     s->on_error = on_error;
     trace_stream_start(bs, base, s);
@@ -302,8 +337,10 @@ void stream_start(const char *job_id, BlockDriverState *bs,
     return;
 
 fail:
+    if (cor_filter_bs) {
+        bdrv_cor_filter_drop(cor_filter_bs);
+    }
     if (bs_read_only) {
         bdrv_reopen_set_read_only(bs, true, NULL);
     }
-    bdrv_unfreeze_backing_chain(bs, above_base);
 }
diff --git a/blockdev.c b/blockdev.c
index 2431448..93417f6 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2500,19 +2500,39 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
                       bool has_base, const char *base,
                       bool has_base_node, const char *base_node,
                       bool has_backing_file, const char *backing_file,
+                      bool has_bottom, const char *bottom,
                       bool has_speed, int64_t speed,
                       bool has_on_error, BlockdevOnError on_error,
+                      bool has_filter_node_name, const char *filter_node_name,
                       bool has_auto_finalize, bool auto_finalize,
                       bool has_auto_dismiss, bool auto_dismiss,
                       Error **errp)
 {
-    BlockDriverState *bs, *iter;
+    BlockDriverState *bs, *iter, *iter_end;
     BlockDriverState *base_bs = NULL;
+    BlockDriverState *bottom_bs = NULL;
     AioContext *aio_context;
     Error *local_err = NULL;
-    const char *base_name = NULL;
     int job_flags = JOB_DEFAULT;
 
+    if (has_base && has_base_node) {
+        error_setg(errp, "'base' and 'base-node' cannot be specified "
+                   "at the same time");
+        return;
+    }
+
+    if (has_base && has_bottom) {
+        error_setg(errp, "'base' and 'bottom' cannot be specified "
+                   "at the same time");
+        return;
+    }
+
+    if (has_bottom && has_base_node) {
+        error_setg(errp, "'bottom' and 'base-node' cannot be specified "
+                   "at the same time");
+        return;
+    }
+
     if (!has_on_error) {
         on_error = BLOCKDEV_ON_ERROR_REPORT;
     }
@@ -2525,12 +2545,6 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
     aio_context = bdrv_get_aio_context(bs);
     aio_context_acquire(aio_context);
 
-    if (has_base && has_base_node) {
-        error_setg(errp, "'base' and 'base-node' cannot be specified "
-                   "at the same time");
-        goto out;
-    }
-
     if (has_base) {
         base_bs = bdrv_find_backing_image(bs, base);
         if (base_bs == NULL) {
@@ -2538,7 +2552,6 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
             goto out;
         }
         assert(bdrv_get_aio_context(base_bs) == aio_context);
-        base_name = base;
     }
 
     if (has_base_node) {
@@ -2553,11 +2566,35 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
         }
         assert(bdrv_get_aio_context(base_bs) == aio_context);
         bdrv_refresh_filename(base_bs);
-        base_name = base_bs->filename;
     }
 
-    /* Check for op blockers in the whole chain between bs and base */
-    for (iter = bs; iter && iter != base_bs;
+    if (has_bottom) {
+        bottom_bs = bdrv_lookup_bs(NULL, bottom, errp);
+        if (!bottom_bs) {
+            goto out;
+        }
+        if (!bottom_bs->drv) {
+            error_setg(errp, "Node '%s' is not open", bottom);
+            goto out;
+        }
+        if (bottom_bs->drv->is_filter) {
+            error_setg(errp, "Node '%s' is a filter, use a non-filter node "
+                       "as 'bottom'", bottom);
+            goto out;
+        }
+        if (!bdrv_chain_contains(bs, bottom_bs)) {
+            error_setg(errp, "Node '%s' is not in a chain starting from '%s'",
+                       bottom, device);
+            goto out;
+        }
+        assert(bdrv_get_aio_context(bottom_bs) == aio_context);
+    }
+
+    /*
+     * Check for op blockers in the whole chain between bs and base (or bottom)
+     */
+    iter_end = has_bottom ? bdrv_filter_or_cow_bs(bottom_bs) : base_bs;
+    for (iter = bs; iter && iter != iter_end;
          iter = bdrv_filter_or_cow_bs(iter))
     {
         if (bdrv_op_is_blocked(iter, BLOCK_OP_TYPE_STREAM, errp)) {
@@ -2573,9 +2610,6 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
         goto out;
     }
 
-    /* backing_file string overrides base bs filename */
-    base_name = has_backing_file ? backing_file : base_name;
-
     if (has_auto_finalize && !auto_finalize) {
         job_flags |= JOB_MANUAL_FINALIZE;
     }
@@ -2583,8 +2617,9 @@ void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
         job_flags |= JOB_MANUAL_DISMISS;
     }
 
-    stream_start(has_job_id ? job_id : NULL, bs, base_bs, base_name,
-                 job_flags, has_speed ? speed : 0, on_error, &local_err);
+    stream_start(has_job_id ? job_id : NULL, bs, base_bs, backing_file,
+                 bottom_bs, job_flags, has_speed ? speed : 0, on_error,
+                 filter_node_name, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
         goto out;
@@ -2794,6 +2829,7 @@ static BlockJob *do_backup_common(BackupCommon *backup,
 {
     BlockJob *job = NULL;
     BdrvDirtyBitmap *bmap = NULL;
+    BackupPerf perf = { .max_workers = 64 };
     int job_flags = JOB_DEFAULT;
 
     if (!backup->has_speed) {
@@ -2818,6 +2854,18 @@ static BlockJob *do_backup_common(BackupCommon *backup,
         backup->compress = false;
     }
 
+    if (backup->x_perf) {
+        if (backup->x_perf->has_use_copy_range) {
+            perf.use_copy_range = backup->x_perf->use_copy_range;
+        }
+        if (backup->x_perf->has_max_workers) {
+            perf.max_workers = backup->x_perf->max_workers;
+        }
+        if (backup->x_perf->has_max_chunk) {
+            perf.max_chunk = backup->x_perf->max_chunk;
+        }
+    }
+
     if ((backup->sync == MIRROR_SYNC_MODE_BITMAP) ||
         (backup->sync == MIRROR_SYNC_MODE_INCREMENTAL)) {
         /* done before desugaring 'incremental' to print the right message */
@@ -2891,6 +2939,7 @@ static BlockJob *do_backup_common(BackupCommon *backup,
                             backup->sync, bmap, backup->bitmap_mode,
                             backup->compress,
                             backup->filter_node_name,
+                            &perf,
                             backup->on_source_error,
                             backup->on_target_error,
                             job_flags, NULL, NULL, txn, errp);
diff --git a/blockjob.c b/blockjob.c
index 98ac8af..db3a216 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -256,6 +256,7 @@ static bool job_timer_pending(Job *job)
 
 void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
 {
+    const BlockJobDriver *drv = block_job_driver(job);
     int64_t old_speed = job->speed;
 
     if (job_apply_verb(&job->job, JOB_VERB_SET_SPEED, errp)) {
@@ -270,6 +271,11 @@ void block_job_set_speed(BlockJob *job, int64_t speed, Error **errp)
     ratelimit_set_speed(&job->limit, speed, BLOCK_JOB_SLICE_TIME);
 
     job->speed = speed;
+
+    if (drv->set_speed) {
+        drv->set_speed(job, speed);
+    }
+
     if (speed && speed <= old_speed) {
         return;
     }
diff --git a/include/block/block-copy.h b/include/block/block-copy.h
index aac85e1..338f2ea 100644
--- a/include/block/block-copy.h
+++ b/include/block/block-copy.h
@@ -18,19 +18,15 @@
 #include "block/block.h"
 #include "qemu/co-shared-resource.h"
 
-typedef void (*ProgressBytesCallbackFunc)(int64_t bytes, void *opaque);
+typedef void (*BlockCopyAsyncCallbackFunc)(void *opaque);
 typedef struct BlockCopyState BlockCopyState;
+typedef struct BlockCopyCallState BlockCopyCallState;
 
 BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
-                                     int64_t cluster_size,
+                                     int64_t cluster_size, bool use_copy_range,
                                      BdrvRequestFlags write_flags,
                                      Error **errp);
 
-void block_copy_set_progress_callback(
-        BlockCopyState *s,
-        ProgressBytesCallbackFunc progress_bytes_callback,
-        void *progress_opaque);
-
 void block_copy_set_progress_meter(BlockCopyState *s, ProgressMeter *pm);
 
 void block_copy_state_free(BlockCopyState *s);
@@ -39,7 +35,56 @@ int64_t block_copy_reset_unallocated(BlockCopyState *s,
                                      int64_t offset, int64_t *count);
 
 int coroutine_fn block_copy(BlockCopyState *s, int64_t offset, int64_t bytes,
-                            bool *error_is_read);
+                            bool ignore_ratelimit);
+
+/*
+ * Run block-copy in a coroutine, create corresponding BlockCopyCallState
+ * object and return pointer to it. Never returns NULL.
+ *
+ * Caller is responsible to call block_copy_call_free() to free
+ * BlockCopyCallState object.
+ *
+ * @max_workers means maximum of parallel coroutines to execute sub-requests,
+ * must be > 0.
+ *
+ * @max_chunk means maximum length for one IO operation. Zero means unlimited.
+ */
+BlockCopyCallState *block_copy_async(BlockCopyState *s,
+                                     int64_t offset, int64_t bytes,
+                                     int max_workers, int64_t max_chunk,
+                                     BlockCopyAsyncCallbackFunc cb,
+                                     void *cb_opaque);
+
+/*
+ * Free finished BlockCopyCallState. Trying to free running
+ * block-copy will crash.
+ */
+void block_copy_call_free(BlockCopyCallState *call_state);
+
+/*
+ * Note, that block-copy call is marked finished prior to calling
+ * the callback.
+ */
+bool block_copy_call_finished(BlockCopyCallState *call_state);
+bool block_copy_call_succeeded(BlockCopyCallState *call_state);
+bool block_copy_call_failed(BlockCopyCallState *call_state);
+bool block_copy_call_cancelled(BlockCopyCallState *call_state);
+int block_copy_call_status(BlockCopyCallState *call_state, bool *error_is_read);
+
+void block_copy_set_speed(BlockCopyState *s, uint64_t speed);
+void block_copy_kick(BlockCopyCallState *call_state);
+
+/*
+ * Cancel running block-copy call.
+ *
+ * Cancel leaves block-copy state valid: dirty bits are correct and you may use
+ * cancel + <run block_copy with same parameters> to emulate pause/resume.
+ *
+ * Note also, that the cancel is async: it only marks block-copy call to be
+ * cancelled. So, the call may be cancelled (block_copy_call_cancelled() reports
+ * true) but not yet finished (block_copy_call_finished() reports false).
+ */
+void block_copy_call_cancel(BlockCopyCallState *call_state);
 
 BdrvDirtyBitmap *block_copy_dirty_bitmap(BlockCopyState *s);
 void block_copy_set_skip_unallocated(BlockCopyState *s, bool skip);
diff --git a/include/block/block.h b/include/block/block.h
index a193545..81fcaad 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -72,9 +72,11 @@ typedef enum {
     BDRV_REQ_NO_FALLBACK        = 0x100,
 
     /*
-     * BDRV_REQ_PREFETCH may be used only together with BDRV_REQ_COPY_ON_READ
-     * on read request and means that caller doesn't really need data to be
-     * written to qiov parameter which may be NULL.
+     * BDRV_REQ_PREFETCH makes sense only in the context of copy-on-read
+     * (i.e., together with the BDRV_REQ_COPY_ON_READ flag or when a COR
+     * filter is involved), in which case it signals that the COR operation
+     * need not read the data into memory (qiov) but only ensure they are
+     * copied to the top layer (i.e., that COR operation is done).
      */
     BDRV_REQ_PREFETCH  = 0x200,
 
@@ -358,6 +360,8 @@ void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
                  Error **errp);
 void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
                        Error **errp);
+BlockDriverState *bdrv_insert_node(BlockDriverState *bs, QDict *node_options,
+                                   int flags, Error **errp);
 
 int bdrv_parse_aio(const char *mode, int *flags);
 int bdrv_parse_cache_mode(const char *mode, int *flags, bool *writethrough);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index b9ef61f..d01fc23 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -881,6 +881,10 @@ struct BlockDriverState {
     /* I/O Limits */
     BlockLimits bl;
 
+    /*
+     * Flags honored during pread
+     */
+    unsigned int supported_read_flags;
     /* Flags honored during pwrite (so far: BDRV_REQ_FUA,
      * BDRV_REQ_WRITE_UNCHANGED).
      * If a driver does not support BDRV_REQ_WRITE_UNCHANGED, those
@@ -1143,6 +1147,9 @@ int is_windows_drive(const char *filename);
  *                  See @BlockJobCreateFlags
  * @speed: The maximum speed, in bytes per second, or 0 for unlimited.
  * @on_error: The action to take upon error.
+ * @filter_node_name: The node name that should be assigned to the filter
+ *                    driver that the stream job inserts into the graph above
+ *                    @bs. NULL means that a node name should be autogenerated.
  * @errp: Error object.
  *
  * Start a streaming operation on @bs.  Clusters that are unallocated
@@ -1154,8 +1161,11 @@ int is_windows_drive(const char *filename);
  */
 void stream_start(const char *job_id, BlockDriverState *bs,
                   BlockDriverState *base, const char *backing_file_str,
+                  BlockDriverState *bottom,
                   int creation_flags, int64_t speed,
-                  BlockdevOnError on_error, Error **errp);
+                  BlockdevOnError on_error,
+                  const char *filter_node_name,
+                  Error **errp);
 
 /**
  * commit_start:
@@ -1256,6 +1266,8 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
  * @sync_mode: What parts of the disk image should be copied to the destination.
  * @sync_bitmap: The dirty bitmap if sync_mode is 'bitmap' or 'incremental'
  * @bitmap_mode: The bitmap synchronization policy to use.
+ * @perf: Performance options. All actual fields assumed to be present,
+ *        all ".has_*" fields are ignored.
  * @on_source_error: The action to take upon error reading from the source.
  * @on_target_error: The action to take upon error writing to the target.
  * @creation_flags: Flags that control the behavior of the Job lifetime.
@@ -1274,6 +1286,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
                             BitmapSyncMode bitmap_mode,
                             bool compress,
                             const char *filter_node_name,
+                            BackupPerf *perf,
                             BlockdevOnError on_source_error,
                             BlockdevOnError on_target_error,
                             int creation_flags,
diff --git a/include/block/blockjob_int.h b/include/block/blockjob_int.h
index e2824a3..6633d83 100644
--- a/include/block/blockjob_int.h
+++ b/include/block/blockjob_int.h
@@ -52,6 +52,8 @@ struct BlockJobDriver {
      * besides job->blk to the new AioContext.
      */
     void (*attached_aio_context)(BlockJob *job, AioContext *new_context);
+
+    void (*set_speed)(BlockJob *job, int64_t speed);
 };
 
 /**
diff --git a/job.c b/job.c
index 8fecf38..3aaaeba 100644
--- a/job.c
+++ b/job.c
@@ -553,6 +553,9 @@ static bool job_timer_not_pending(Job *job)
 void job_pause(Job *job)
 {
     job->pause_count++;
+    if (!job->paused) {
+        job_enter(job);
+    }
 }
 
 void job_resume(Job *job)
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 3484986..9f555d5 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1372,6 +1372,30 @@
   'data': { 'node': 'str', 'overlay': 'str' } }
 
 ##
+# @BackupPerf:
+#
+# Optional parameters for backup. These parameters don't affect
+# functionality, but may significantly affect performance.
+#
+# @use-copy-range: Use copy offloading. Default false.
+#
+# @max-workers: Maximum number of parallel requests for the sustained background
+#               copying process. Doesn't influence copy-before-write operations.
+#               Default 64.
+#
+# @max-chunk: Maximum request length for the sustained background copying
+#             process. Doesn't influence copy-before-write operations.
+#             0 means unlimited. If max-chunk is non-zero then it should not be
+#             less than job cluster size which is calculated as maximum of
+#             target image cluster size and 64k. Default 0.
+#
+# Since: 6.0
+##
+{ 'struct': 'BackupPerf',
+  'data': { '*use-copy-range': 'bool',
+            '*max-workers': 'int', '*max-chunk': 'int64' } }
+
+##
 # @BackupCommon:
 #
 # @job-id: identifier for the newly-created block job. If
@@ -1426,6 +1450,8 @@
 #                    above node specified by @drive. If this option is not given,
 #                    a node name is autogenerated. (Since: 4.2)
 #
+# @x-perf: Performance options. (Since 6.0)
+#
 # Note: @on-source-error and @on-target-error only affect background
 #       I/O.  If an error occurs during a guest write request, the device's
 #       rerror/werror actions will be used.
@@ -1440,7 +1466,7 @@
             '*on-source-error': 'BlockdevOnError',
             '*on-target-error': 'BlockdevOnError',
             '*auto-finalize': 'bool', '*auto-dismiss': 'bool',
-            '*filter-node-name': 'str' } }
+            '*filter-node-name': 'str', '*x-perf': 'BackupPerf'  } }
 
 ##
 # @DriveBackup:
@@ -2517,10 +2543,14 @@
 # @device: the device or node name of the top image
 #
 # @base: the common backing file name.
-#        It cannot be set if @base-node is also set.
+#        It cannot be set if @base-node or @bottom is also set.
 #
 # @base-node: the node name of the backing file.
-#             It cannot be set if @base is also set. (Since 2.8)
+#             It cannot be set if @base or @bottom is also set. (Since 2.8)
+#
+# @bottom: the last node in the chain that should be streamed into
+#          top. It cannot be set if @base or @base-node is also set.
+#          It cannot be filter node. (Since 6.0)
 #
 # @backing-file: The backing file string to write into the top
 #                image. This filename is not validated.
@@ -2543,6 +2573,11 @@
 #            'stop' and 'enospc' can only be used if the block device
 #            supports io-status (see BlockInfo).  Since 1.3.
 #
+# @filter-node-name: the node name that should be assigned to the
+#                    filter driver that the stream job inserts into the graph
+#                    above @device. If this option is not given, a node name is
+#                    autogenerated. (Since: 6.0)
+#
 # @auto-finalize: When false, this job will wait in a PENDING state after it has
 #                 finished its work, waiting for @block-job-finalize before
 #                 making any block graph changes.
@@ -2571,8 +2606,9 @@
 ##
 { 'command': 'block-stream',
   'data': { '*job-id': 'str', 'device': 'str', '*base': 'str',
-            '*base-node': 'str', '*backing-file': 'str', '*speed': 'int',
-            '*on-error': 'BlockdevOnError',
+            '*base-node': 'str', '*backing-file': 'str', '*bottom': 'str',
+            '*speed': 'int', '*on-error': 'BlockdevOnError',
+            '*filter-node-name': 'str',
             '*auto-finalize': 'bool', '*auto-dismiss': 'bool' } }
 
 ##
@@ -3953,6 +3989,24 @@
   'data': { 'throttle-group': 'str',
             'file' : 'BlockdevRef'
              } }
+
+##
+# @BlockdevOptionsCor:
+#
+# Driver specific block device options for the copy-on-read driver.
+#
+# @bottom: The name of a non-filter node (allocation-bearing layer) that
+#          limits the COR operations in the backing chain (inclusive), so
+#          that no data below this node will be copied by this filter.
+#          If option is absent, the limit is not applied, so that data
+#          from all backing layers may be copied.
+#
+# Since: 6.0
+##
+{ 'struct': 'BlockdevOptionsCor',
+  'base': 'BlockdevOptionsGenericFormat',
+  'data': { '*bottom': 'str' } }
+
 ##
 # @BlockdevOptions:
 #
@@ -4005,7 +4059,7 @@
       'bochs':      'BlockdevOptionsGenericFormat',
       'cloop':      'BlockdevOptionsGenericFormat',
       'compress':   'BlockdevOptionsGenericFormat',
-      'copy-on-read':'BlockdevOptionsGenericFormat',
+      'copy-on-read':'BlockdevOptionsCor',
       'dmg':        'BlockdevOptionsGenericFormat',
       'file':       'BlockdevOptionsFile',
       'ftp':        'BlockdevOptionsCurlFtp',
diff --git a/scripts/simplebench/bench-backup.py b/scripts/simplebench/bench-backup.py
new file mode 100755
index 0000000..33a1ecf
--- /dev/null
+++ b/scripts/simplebench/bench-backup.py
@@ -0,0 +1,167 @@
+#!/usr/bin/env python3
+#
+# Bench backup block-job
+#
+# Copyright (c) 2020 Virtuozzo International GmbH.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+import argparse
+import json
+
+import simplebench
+from results_to_text import results_to_text
+from bench_block_job import bench_block_copy, drv_file, drv_nbd
+
+
+def bench_func(env, case):
+    """ Handle one "cell" of benchmarking table. """
+    cmd_options = env['cmd-options'] if 'cmd-options' in env else {}
+    return bench_block_copy(env['qemu-binary'], env['cmd'],
+                            cmd_options,
+                            case['source'], case['target'])
+
+
+def bench(args):
+    test_cases = []
+
+    sources = {}
+    targets = {}
+    for d in args.dir:
+        label, path = d.split(':')  # paths with colon not supported
+        sources[label] = drv_file(path + '/test-source')
+        targets[label] = drv_file(path + '/test-target')
+
+    if args.nbd:
+        nbd = args.nbd.split(':')
+        host = nbd[0]
+        port = '10809' if len(nbd) == 1 else nbd[1]
+        drv = drv_nbd(host, port)
+        sources['nbd'] = drv
+        targets['nbd'] = drv
+
+    for t in args.test:
+        src, dst = t.split(':')
+
+        test_cases.append({
+            'id': t,
+            'source': sources[src],
+            'target': targets[dst]
+        })
+
+    binaries = []  # list of (<label>, <path>, [<options>])
+    for i, q in enumerate(args.env):
+        name_path = q.split(':')
+        if len(name_path) == 1:
+            label = f'q{i}'
+            path_opts = name_path[0].split(',')
+        else:
+            assert len(name_path) == 2  # paths with colon not supported
+            label = name_path[0]
+            path_opts = name_path[1].split(',')
+
+        binaries.append((label, path_opts[0], path_opts[1:]))
+
+    test_envs = []
+
+    bin_paths = {}
+    for i, q in enumerate(args.env):
+        opts = q.split(',')
+        label_path = opts[0]
+        opts = opts[1:]
+
+        if ':' in label_path:
+            # path with colon inside is not supported
+            label, path = label_path.split(':')
+            bin_paths[label] = path
+        elif label_path in bin_paths:
+            label = label_path
+            path = bin_paths[label]
+        else:
+            path = label_path
+            label = f'q{i}'
+            bin_paths[label] = path
+
+        x_perf = {}
+        is_mirror = False
+        for opt in opts:
+            if opt == 'mirror':
+                is_mirror = True
+            elif opt == 'copy-range=on':
+                x_perf['use-copy-range'] = True
+            elif opt == 'copy-range=off':
+                x_perf['use-copy-range'] = False
+            elif opt.startswith('max-workers='):
+                x_perf['max-workers'] = int(opt.split('=')[1])
+
+        if is_mirror:
+            assert not x_perf
+            test_envs.append({
+                    'id': f'mirror({label})',
+                    'cmd': 'blockdev-mirror',
+                    'qemu-binary': path
+                })
+        else:
+            test_envs.append({
+                'id': f'backup({label})\n' + '\n'.join(opts),
+                'cmd': 'blockdev-backup',
+                'cmd-options': {'x-perf': x_perf} if x_perf else {},
+                'qemu-binary': path
+            })
+
+    result = simplebench.bench(bench_func, test_envs, test_cases, count=3)
+    with open('results.json', 'w') as f:
+        json.dump(result, f, indent=4)
+    print(results_to_text(result))
+
+
+class ExtendAction(argparse.Action):
+    def __call__(self, parser, namespace, values, option_string=None):
+        items = getattr(namespace, self.dest) or []
+        items.extend(values)
+        setattr(namespace, self.dest, items)
+
+
+if __name__ == '__main__':
+    p = argparse.ArgumentParser('Backup benchmark', epilog='''
+ENV format
+
+    (LABEL:PATH|LABEL|PATH)[,max-workers=N][,use-copy-range=(on|off)][,mirror]
+
+    LABEL                short name for the binary
+    PATH                 path to the binary
+    max-workers          set x-perf.max-workers of backup job
+    use-copy-range       set x-perf.use-copy-range of backup job
+    mirror               use mirror job instead of backup''',
+                                formatter_class=argparse.RawTextHelpFormatter)
+    p.add_argument('--env', nargs='+', help='''\
+Qemu binaries with labels and options, see below
+"ENV format" section''',
+                   action=ExtendAction)
+    p.add_argument('--dir', nargs='+', help='''\
+Directories, each containing "test-source" and/or
+"test-target" files, raw images to used in
+benchmarking. File path with label, like
+label:/path/to/directory''',
+                   action=ExtendAction)
+    p.add_argument('--nbd', help='''\
+host:port for remote NBD image, (or just host, for
+default port 10809). Use it in tests, label is "nbd"
+(but you cannot create test nbd:nbd).''')
+    p.add_argument('--test', nargs='+', help='''\
+Tests, in form source-dir-label:target-dir-label''',
+                   action=ExtendAction)
+
+    bench(p.parse_args())
diff --git a/scripts/simplebench/bench-example.py b/scripts/simplebench/bench-example.py
index d9c7f7b..4864435 100644
--- a/scripts/simplebench/bench-example.py
+++ b/scripts/simplebench/bench-example.py
@@ -25,7 +25,7 @@ from bench_block_job import bench_block_copy, drv_file, drv_nbd
 
 def bench_func(env, case):
     """ Handle one "cell" of benchmarking table. """
-    return bench_block_copy(env['qemu_binary'], env['cmd'],
+    return bench_block_copy(env['qemu_binary'], env['cmd'], {}
                             case['source'], case['target'])
 
 
diff --git a/scripts/simplebench/bench_block_job.py b/scripts/simplebench/bench_block_job.py
index 9808d69..7332845 100755
--- a/scripts/simplebench/bench_block_job.py
+++ b/scripts/simplebench/bench_block_job.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Benchmark block jobs
 #
@@ -78,16 +78,19 @@ def bench_block_job(cmd, cmd_args, qemu_args):
 
 
 # Bench backup or mirror
-def bench_block_copy(qemu_binary, cmd, source, target):
+def bench_block_copy(qemu_binary, cmd, cmd_options, source, target):
     """Helper to run bench_block_job() for mirror or backup"""
     assert cmd in ('blockdev-backup', 'blockdev-mirror')
 
     source['node-name'] = 'source'
     target['node-name'] = 'target'
 
-    return bench_block_job(cmd,
-                           {'job-id': 'job0', 'device': 'source',
-                            'target': 'target', 'sync': 'full'},
+    cmd_options['job-id'] = 'job0'
+    cmd_options['device'] = 'source'
+    cmd_options['target'] = 'target'
+    cmd_options['sync'] = 'full'
+
+    return bench_block_job(cmd, cmd_options,
                            [qemu_binary,
                             '-blockdev', json.dumps(source),
                             '-blockdev', json.dumps(target)])
diff --git a/tests/qemu-iotests/030 b/tests/qemu-iotests/030
index 890784b..832fe4a 100755
--- a/tests/qemu-iotests/030
+++ b/tests/qemu-iotests/030
@@ -246,7 +246,9 @@ class TestParallelOps(iotests.QMPTestCase):
             node_name = 'node%d' % i
             job_id = 'stream-%s' % node_name
             pending_jobs.append(job_id)
-            result = self.vm.qmp('block-stream', device=node_name, job_id=job_id, base=self.imgs[i-2], speed=1024)
+            result = self.vm.qmp('block-stream', device=node_name,
+                                 job_id=job_id, bottom=f'node{i-1}',
+                                 speed=1024)
             self.assert_qmp(result, 'return', {})
 
         for job in pending_jobs:
@@ -277,12 +279,14 @@ class TestParallelOps(iotests.QMPTestCase):
         self.assert_no_active_block_jobs()
 
         # Set a speed limit to make sure that this job blocks the rest
-        result = self.vm.qmp('block-stream', device='node4', job_id='stream-node4', base=self.imgs[1], speed=1024*1024)
+        result = self.vm.qmp('block-stream', device='node4',
+                             job_id='stream-node4', base=self.imgs[1],
+                             filter_node_name='stream-filter', speed=1024*1024)
         self.assert_qmp(result, 'return', {})
 
         result = self.vm.qmp('block-stream', device='node5', job_id='stream-node5', base=self.imgs[2])
         self.assert_qmp(result, 'error/desc',
-            "Node 'node4' is busy: block device is in use by block job: stream")
+            "Node 'stream-filter' is busy: block device is in use by block job: stream")
 
         result = self.vm.qmp('block-stream', device='node3', job_id='stream-node3', base=self.imgs[2])
         self.assert_qmp(result, 'error/desc',
@@ -295,7 +299,7 @@ class TestParallelOps(iotests.QMPTestCase):
         # block-commit should also fail if it touches nodes used by the stream job
         result = self.vm.qmp('block-commit', device='drive0', base=self.imgs[4], job_id='commit-node4')
         self.assert_qmp(result, 'error/desc',
-            "Node 'node4' is busy: block device is in use by block job: stream")
+            "Node 'stream-filter' is busy: block device is in use by block job: stream")
 
         result = self.vm.qmp('block-commit', device='drive0', base=self.imgs[1], top=self.imgs[3], job_id='commit-node1')
         self.assert_qmp(result, 'error/desc',
diff --git a/tests/qemu-iotests/056 b/tests/qemu-iotests/056
index 0e6b859..b459a3f 100755
--- a/tests/qemu-iotests/056
+++ b/tests/qemu-iotests/056
@@ -308,8 +308,13 @@ class BackupTest(iotests.QMPTestCase):
         event = self.vm.event_wait(name="BLOCK_JOB_ERROR",
                                    match={'data': {'device': 'drive0'}})
         self.assertNotEqual(event, None)
-        # OK, job should be wedged
-        res = self.vm.qmp('query-block-jobs')
+        # OK, job should pause, but it can't do it immediately, as it can't
+        # cancel other parallel requests (which didn't fail)
+        with iotests.Timeout(60, "Timeout waiting for backup actually paused"):
+            while True:
+                res = self.vm.qmp('query-block-jobs')
+                if res['return'][0]['status'] == 'paused':
+                    break
         self.assert_qmp(res, 'return[0]/status', 'paused')
         res = self.vm.qmp('block-job-dismiss', id='drive0')
         self.assert_qmp(res, 'error/desc',
diff --git a/tests/qemu-iotests/109.out b/tests/qemu-iotests/109.out
index 6e73406..8f839b4 100644
--- a/tests/qemu-iotests/109.out
+++ b/tests/qemu-iotests/109.out
@@ -42,6 +42,8 @@ read 512/512 bytes at offset 0
 {"execute":"quit"}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "standby", "id": "src"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 1024, "offset": 1024, "speed": 0, "type": "mirror"}}
@@ -91,6 +93,8 @@ read 512/512 bytes at offset 0
 {"execute":"quit"}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "standby", "id": "src"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 197120, "offset": 197120, "speed": 0, "type": "mirror"}}
@@ -140,6 +144,8 @@ read 512/512 bytes at offset 0
 {"execute":"quit"}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "standby", "id": "src"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 327680, "offset": 327680, "speed": 0, "type": "mirror"}}
@@ -189,6 +195,8 @@ read 512/512 bytes at offset 0
 {"execute":"quit"}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "standby", "id": "src"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 1024, "offset": 1024, "speed": 0, "type": "mirror"}}
@@ -238,6 +246,8 @@ read 512/512 bytes at offset 0
 {"execute":"quit"}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "standby", "id": "src"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 65536, "offset": 65536, "speed": 0, "type": "mirror"}}
@@ -287,6 +297,8 @@ read 512/512 bytes at offset 0
 {"execute":"quit"}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "standby", "id": "src"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 2560, "offset": 2560, "speed": 0, "type": "mirror"}}
@@ -335,6 +347,8 @@ read 512/512 bytes at offset 0
 {"execute":"quit"}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "standby", "id": "src"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 2560, "offset": 2560, "speed": 0, "type": "mirror"}}
@@ -383,6 +397,8 @@ read 512/512 bytes at offset 0
 {"execute":"quit"}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "standby", "id": "src"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 31457280, "offset": 31457280, "speed": 0, "type": "mirror"}}
@@ -431,6 +447,8 @@ read 512/512 bytes at offset 0
 {"execute":"quit"}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "standby", "id": "src"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 327680, "offset": 327680, "speed": 0, "type": "mirror"}}
@@ -479,6 +497,8 @@ read 512/512 bytes at offset 0
 {"execute":"quit"}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "standby", "id": "src"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 2048, "offset": 2048, "speed": 0, "type": "mirror"}}
@@ -507,6 +527,8 @@ WARNING: Image format was not specified for 'TEST_DIR/t.raw' and probing guessed
 {"execute":"quit"}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "standby", "id": "src"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 512, "offset": 512, "speed": 0, "type": "mirror"}}
@@ -528,6 +550,8 @@ Images are identical.
 {"execute":"quit"}
 {"return": {}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "SHUTDOWN", "data": {"guest": false, "reason": "host-qmp-quit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "standby", "id": "src"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "ready", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "src"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "src", "len": 512, "offset": 512, "speed": 0, "type": "mirror"}}
diff --git a/tests/qemu-iotests/118 b/tests/qemu-iotests/118
index 1a2e219..cae52ff 100755
--- a/tests/qemu-iotests/118
+++ b/tests/qemu-iotests/118
@@ -1,8 +1,7 @@
 #!/usr/bin/env python3
 # group: rw
 #
-# Test case for the QMP 'change' command and all other associated
-# commands
+# Test case for media change monitor commands
 #
 # Copyright (C) 2015 Red Hat, Inc.
 #
@@ -74,23 +73,6 @@ class ChangeBaseClass(iotests.QMPTestCase):
 
 class GeneralChangeTestsBaseClass(ChangeBaseClass):
 
-    def test_change(self):
-        # 'change' requires a drive name, so skip the test for blockdev
-        if not self.use_drive:
-            return
-
-        result = self.vm.qmp('change', device='drive0', target=new_img,
-                                       arg=iotests.imgfmt)
-        self.assert_qmp(result, 'return', {})
-
-        self.wait_for_open()
-        self.wait_for_close()
-
-        result = self.vm.qmp('query-block')
-        if self.has_real_tray:
-            self.assert_qmp(result, 'return[0]/tray_open', False)
-        self.assert_qmp(result, 'return[0]/inserted/image/filename', new_img)
-
     def test_blockdev_change_medium(self):
         result = self.vm.qmp('blockdev-change-medium',
                              id=self.device_name, filename=new_img,
diff --git a/tests/qemu-iotests/118.out b/tests/qemu-iotests/118.out
index bf5bfd5..0a70391 100644
--- a/tests/qemu-iotests/118.out
+++ b/tests/qemu-iotests/118.out
@@ -1,5 +1,5 @@
-.......................................................................................................................................................................
+...........................................................................................................................................................
 ----------------------------------------------------------------------
-Ran 167 tests
+Ran 155 tests
 
 OK
diff --git a/tests/qemu-iotests/124 b/tests/qemu-iotests/124
index 3b21bc4..90cdbd8 100755
--- a/tests/qemu-iotests/124
+++ b/tests/qemu-iotests/124
@@ -23,6 +23,7 @@
 
 import os
 import iotests
+from iotests import try_remove
 
 
 def io_write_patterns(img, patterns):
@@ -30,13 +31,6 @@ def io_write_patterns(img, patterns):
         iotests.qemu_io('-c', 'write -P%s %s %s' % pattern, img)
 
 
-def try_remove(img):
-    try:
-        os.remove(img)
-    except OSError:
-        pass
-
-
 def transaction_action(action, **kwargs):
     return {
         'type': action,
diff --git a/tests/qemu-iotests/129 b/tests/qemu-iotests/129
index f57a2e1..5251e26 100755
--- a/tests/qemu-iotests/129
+++ b/tests/qemu-iotests/129
@@ -21,68 +21,87 @@
 
 import os
 import iotests
-import time
 
 class TestStopWithBlockJob(iotests.QMPTestCase):
     test_img = os.path.join(iotests.test_dir, 'test.img')
     target_img = os.path.join(iotests.test_dir, 'target.img')
     base_img = os.path.join(iotests.test_dir, 'base.img')
+    overlay_img = os.path.join(iotests.test_dir, 'overlay.img')
 
     def setUp(self):
         iotests.qemu_img('create', '-f', iotests.imgfmt, self.base_img, "1G")
         iotests.qemu_img('create', '-f', iotests.imgfmt, self.test_img,
                          "-b", self.base_img, '-F', iotests.imgfmt)
-        iotests.qemu_io('-f', iotests.imgfmt, '-c', 'write -P0x5d 1M 128M', self.test_img)
-        self.vm = iotests.VM().add_drive(self.test_img)
+        iotests.qemu_io('-f', iotests.imgfmt, '-c', 'write -P0x5d 1M 128M',
+                        self.test_img)
+        self.vm = iotests.VM()
+        self.vm.add_object('throttle-group,id=tg0,x-bps-total=1024')
+
+        source_drive = 'driver=throttle,' \
+                       'node-name=source,' \
+                       'throttle-group=tg0,' \
+                       f'file.driver={iotests.imgfmt},' \
+                       f'file.file.filename={self.test_img}'
+
+        self.vm.add_drive(None, source_drive)
         self.vm.launch()
 
     def tearDown(self):
-        params = {"device": "drive0",
-                  "bps": 0,
-                  "bps_rd": 0,
-                  "bps_wr": 0,
-                  "iops": 0,
-                  "iops_rd": 0,
-                  "iops_wr": 0,
-                 }
-        result = self.vm.qmp("block_set_io_throttle", conv_keys=False,
-                             **params)
         self.vm.shutdown()
+        for img in (self.test_img, self.target_img, self.base_img,
+                    self.overlay_img):
+            iotests.try_remove(img)
 
     def do_test_stop(self, cmd, **args):
         """Test 'stop' while block job is running on a throttled drive.
         The 'stop' command shouldn't drain the job"""
-        params = {"device": "drive0",
-                  "bps": 1024,
-                  "bps_rd": 0,
-                  "bps_wr": 0,
-                  "iops": 0,
-                  "iops_rd": 0,
-                  "iops_wr": 0,
-                 }
-        result = self.vm.qmp("block_set_io_throttle", conv_keys=False,
-                             **params)
-        self.assert_qmp(result, 'return', {})
         result = self.vm.qmp(cmd, **args)
         self.assert_qmp(result, 'return', {})
+
         result = self.vm.qmp("stop")
         self.assert_qmp(result, 'return', {})
         result = self.vm.qmp("query-block-jobs")
-        self.assert_qmp(result, 'return[0]/busy', True)
+
+        self.assert_qmp(result, 'return[0]/status', 'running')
         self.assert_qmp(result, 'return[0]/ready', False)
 
     def test_drive_mirror(self):
         self.do_test_stop("drive-mirror", device="drive0",
-                          target=self.target_img,
-                          sync="full")
+                          target=self.target_img, format=iotests.imgfmt,
+                          sync="full", buf_size=65536)
 
     def test_drive_backup(self):
+        # Limit max-chunk and max-workers so that block-copy will not
+        # launch so many workers working on so much data each that
+        # stop's bdrv_drain_all() would finish the job
         self.do_test_stop("drive-backup", device="drive0",
-                          target=self.target_img,
-                          sync="full")
+                          target=self.target_img, format=iotests.imgfmt,
+                          sync="full",
+                          x_perf={ 'max-chunk': 65536,
+                                   'max-workers': 8 })
 
     def test_block_commit(self):
-        self.do_test_stop("block-commit", device="drive0")
+        # Add overlay above the source node so that we actually use a
+        # commit job instead of a mirror job
+
+        iotests.qemu_img('create', '-f', iotests.imgfmt, self.overlay_img,
+                         '1G')
+
+        result = self.vm.qmp('blockdev-add', **{
+                                 'node-name': 'overlay',
+                                 'driver': iotests.imgfmt,
+                                 'file': {
+                                     'driver': 'file',
+                                     'filename': self.overlay_img
+                                 }
+                             })
+        self.assert_qmp(result, 'return', {})
+
+        result = self.vm.qmp('blockdev-snapshot',
+                             node='source', overlay='overlay')
+        self.assert_qmp(result, 'return', {})
+
+        self.do_test_stop('block-commit', device='drive0', top_node='source')
 
 if __name__ == '__main__':
     iotests.main(supported_fmts=["qcow2"],
diff --git a/tests/qemu-iotests/141.out b/tests/qemu-iotests/141.out
index 6d8652e..c4c15fb 100644
--- a/tests/qemu-iotests/141.out
+++ b/tests/qemu-iotests/141.out
@@ -165,7 +165,7 @@ wrote 1048576/1048576 bytes at offset 0
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "job0"}}
 {'execute': 'blockdev-del',
           'arguments': {'node-name': 'drv0'}}
-{"error": {"class": "GenericError", "desc": "Node drv0 is in use"}}
+{"error": {"class": "GenericError", "desc": "Node 'drv0' is busy: block device is in use by block job: stream"}}
 {'execute': 'block-job-cancel',
           'arguments': {'device': 'job0'}}
 {"return": {}}
diff --git a/tests/qemu-iotests/178 b/tests/qemu-iotests/178
index 3b1a7ad..8df241e 100755
--- a/tests/qemu-iotests/178
+++ b/tests/qemu-iotests/178
@@ -57,7 +57,7 @@ $QEMU_IMG measure --image-opts # missing filename
 $QEMU_IMG measure -f qcow2 # missing filename
 $QEMU_IMG measure -l snap1 # missing filename
 $QEMU_IMG measure -o , # invalid option list
-$QEMU_IMG measure -l snapshot.foo # invalid snapshot option
+$QEMU_IMG measure -l snapshot.foo=bar # invalid snapshot option
 $QEMU_IMG measure --output foo # invalid output format
 $QEMU_IMG measure --size -1 # invalid image size
 $QEMU_IMG measure -O foo "$TEST_IMG" # unknown image file format
diff --git a/tests/qemu-iotests/178.out.qcow2 b/tests/qemu-iotests/178.out.qcow2
index c799776..fe193fd 100644
--- a/tests/qemu-iotests/178.out.qcow2
+++ b/tests/qemu-iotests/178.out.qcow2
@@ -11,7 +11,7 @@ qemu-img: --image-opts, -f, and -l require a filename argument.
 qemu-img: --image-opts, -f, and -l require a filename argument.
 qemu-img: Invalid option list: ,
 qemu-img: Invalid parameter 'snapshot.foo'
-qemu-img: Failed in parsing snapshot param 'snapshot.foo'
+qemu-img: Failed in parsing snapshot param 'snapshot.foo=bar'
 qemu-img: --output must be used with human or json as argument.
 qemu-img: Invalid image size specified. Must be between 0 and 9223372036854775807.
 qemu-img: Unknown file format 'foo'
diff --git a/tests/qemu-iotests/178.out.raw b/tests/qemu-iotests/178.out.raw
index 20e17da..445e460 100644
--- a/tests/qemu-iotests/178.out.raw
+++ b/tests/qemu-iotests/178.out.raw
@@ -11,7 +11,7 @@ qemu-img: --image-opts, -f, and -l require a filename argument.
 qemu-img: --image-opts, -f, and -l require a filename argument.
 qemu-img: Invalid option list: ,
 qemu-img: Invalid parameter 'snapshot.foo'
-qemu-img: Failed in parsing snapshot param 'snapshot.foo'
+qemu-img: Failed in parsing snapshot param 'snapshot.foo=bar'
 qemu-img: --output must be used with human or json as argument.
 qemu-img: Invalid image size specified. Must be between 0 and 9223372036854775807.
 qemu-img: Unknown file format 'foo'
diff --git a/tests/qemu-iotests/185 b/tests/qemu-iotests/185
index 7bc8fe5..f2ec5c5 100755
--- a/tests/qemu-iotests/185
+++ b/tests/qemu-iotests/185
@@ -183,7 +183,8 @@ _send_qemu_cmd $h \
                       'target': '$TEST_IMG.copy',
                       'format': '$IMGFMT',
                       'sync': 'full',
-                      'speed': 65536 } }" \
+                      'speed': 65536,
+                      'x-perf': {'max-chunk': 65536} } }" \
     "return"
 
 # If we don't sleep here 'quit' command races with disk I/O
diff --git a/tests/qemu-iotests/185.out b/tests/qemu-iotests/185.out
index eab55d2..9dedc8e 100644
--- a/tests/qemu-iotests/185.out
+++ b/tests/qemu-iotests/185.out
@@ -88,7 +88,8 @@ Formatting 'TEST_DIR/t.qcow2.copy', fmt=qcow2 cluster_size=65536 extended_l2=off
                       'target': 'TEST_DIR/t.IMGFMT.copy',
                       'format': 'IMGFMT',
                       'sync': 'full',
-                      'speed': 65536 } }
+                      'speed': 65536,
+                      'x-perf': { 'max-chunk': 65536 } } }
 Formatting 'TEST_DIR/t.qcow2.copy', fmt=qcow2 cluster_size=65536 extended_l2=off compression_type=zlib size=67108864 lazy_refcounts=off refcount_bits=16
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "disk"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "disk"}}
diff --git a/tests/qemu-iotests/219 b/tests/qemu-iotests/219
index 16c3ca7..d1757e9 100755
--- a/tests/qemu-iotests/219
+++ b/tests/qemu-iotests/219
@@ -204,13 +204,13 @@ with iotests.FilePath('disk.img') as disk_path, \
     # but related to this also automatic state transitions like job
     # completion), but still get pause points often enough to avoid making this
     # test very slow, it's important to have the right ratio between speed and
-    # buf_size.
+    # copy-chunk-size.
     #
-    # For backup, buf_size is hard-coded to the source image cluster size (64k),
-    # so we'll pick the same for mirror. The slice time, i.e. the granularity
-    # of the rate limiting is 100ms. With a speed of 256k per second, we can
-    # get four pause points per second. This gives us 250ms per iteration,
-    # which should be enough to stay deterministic.
+    # Chose 64k copy-chunk-size both for mirror (by buf_size) and backup (by
+    # x-max-chunk). The slice time, i.e. the granularity of the rate limiting
+    # is 100ms. With a speed of 256k per second, we can get four pause points
+    # per second. This gives us 250ms per iteration, which should be enough to
+    # stay deterministic.
 
     test_job_lifecycle(vm, 'drive-mirror', has_ready=True, job_args={
         'device': 'drive0-node',
@@ -227,6 +227,7 @@ with iotests.FilePath('disk.img') as disk_path, \
                 'target': copy_path,
                 'sync': 'full',
                 'speed': 262144,
+                'x-perf': {'max-chunk': 65536},
                 'auto-finalize': auto_finalize,
                 'auto-dismiss': auto_dismiss,
             })
diff --git a/tests/qemu-iotests/245 b/tests/qemu-iotests/245
index 86f00f2..cfdeb90 100755
--- a/tests/qemu-iotests/245
+++ b/tests/qemu-iotests/245
@@ -893,20 +893,24 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # hd1 <- hd0
         result = self.vm.qmp('block-stream', conv_keys = True, job_id = 'stream0',
-                             device = 'hd1', auto_finalize = False)
+                             device = 'hd1', filter_node_name='cor',
+                             auto_finalize = False)
         self.assert_qmp(result, 'return', {})
 
-        # We can't reopen with the original options because that would
-        # make hd1 read-only and block-stream requires it to be read-write
-        # (Which error message appears depends on whether the stream job is
-        # already done with copying at this point.)
+        # We can't reopen with the original options because there is a filter
+        # inserted by stream job above hd1.
         self.reopen(opts, {},
-            ["Can't set node 'hd1' to r/o with copy-on-read enabled",
-             "Cannot make block node read-only, there is a writer on it"])
+                    "Cannot change the option 'backing.backing.file.node-name'")
+
+        # We can't reopen hd1 to read-only, as block-stream requires it to be
+        # read-write
+        self.reopen(opts['backing'], {'read-only': True},
+                    "Cannot make block node read-only, there is a writer on it")
 
         # We can't remove hd2 while the stream job is ongoing
         opts['backing']['backing'] = None
-        self.reopen(opts, {'backing.read-only': False}, "Cannot change 'backing' link from 'hd1' to 'hd2'")
+        self.reopen(opts['backing'], {'read-only': False},
+                    "Cannot change 'backing' link from 'hd1' to 'hd2'")
 
         # We can detach hd1 from hd0 because it doesn't affect the stream job
         opts['backing'] = None
diff --git a/tests/qemu-iotests/257 b/tests/qemu-iotests/257
index a2f4b5a..7cd2520 100755
--- a/tests/qemu-iotests/257
+++ b/tests/qemu-iotests/257
@@ -192,6 +192,7 @@ def blockdev_backup(vm, device, target, sync, **kwargs):
                         target=target,
                         sync=sync,
                         filter_node_name='backup-top',
+                        x_perf={'max-workers': 1},
                         **kwargs)
     return result
 
diff --git a/tests/qemu-iotests/257.out b/tests/qemu-iotests/257.out
index 64dd460..a7ba512 100644
--- a/tests/qemu-iotests/257.out
+++ b/tests/qemu-iotests/257.out
@@ -30,7 +30,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -78,7 +78,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -92,7 +92,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -205,7 +205,7 @@ expecting 15 dirty sectors; have 15. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -219,7 +219,7 @@ expecting 15 dirty sectors; have 15. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -290,7 +290,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -338,7 +338,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -354,7 +354,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"action": "report", "device": "backup_1", "operation": "read"}, "event": "BLOCK_JOB_ERROR", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 {"data": {"device": "backup_1", "error": "Input/output error", "len": 393216, "offset": 65536, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
@@ -416,7 +416,7 @@ expecting 14 dirty sectors; have 14. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -430,7 +430,7 @@ expecting 14 dirty sectors; have 14. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -501,7 +501,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -549,7 +549,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -563,7 +563,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -676,7 +676,7 @@ expecting 15 dirty sectors; have 15. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -690,7 +690,7 @@ expecting 15 dirty sectors; have 15. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -761,7 +761,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -809,7 +809,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -823,7 +823,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -936,7 +936,7 @@ expecting 15 dirty sectors; have 15. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -950,7 +950,7 @@ expecting 15 dirty sectors; have 15. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -1021,7 +1021,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -1069,7 +1069,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -1085,7 +1085,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"action": "report", "device": "backup_1", "operation": "read"}, "event": "BLOCK_JOB_ERROR", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 {"data": {"device": "backup_1", "error": "Input/output error", "len": 393216, "offset": 65536, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
@@ -1147,7 +1147,7 @@ expecting 14 dirty sectors; have 14. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -1161,7 +1161,7 @@ expecting 14 dirty sectors; have 14. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -1232,7 +1232,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -1280,7 +1280,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -1294,7 +1294,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -1407,7 +1407,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -1421,7 +1421,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -1492,7 +1492,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -1540,7 +1540,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -1554,7 +1554,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -1667,7 +1667,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -1681,7 +1681,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -1752,7 +1752,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -1800,7 +1800,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -1816,7 +1816,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"action": "report", "device": "backup_1", "operation": "read"}, "event": "BLOCK_JOB_ERROR", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 {"data": {"device": "backup_1", "error": "Input/output error", "len": 393216, "offset": 65536, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
@@ -1878,7 +1878,7 @@ expecting 13 dirty sectors; have 13. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -1892,7 +1892,7 @@ expecting 13 dirty sectors; have 13. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -1963,7 +1963,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -2011,7 +2011,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -2025,7 +2025,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "bitmap", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -2138,7 +2138,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -2152,7 +2152,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -2223,7 +2223,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -2271,7 +2271,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -2285,7 +2285,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "full", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "full", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -2398,7 +2398,7 @@ expecting 15 dirty sectors; have 15. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -2412,7 +2412,7 @@ expecting 15 dirty sectors; have 15. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -2483,7 +2483,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -2531,7 +2531,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -2547,7 +2547,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "full", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "full", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"action": "report", "device": "backup_1", "operation": "read"}, "event": "BLOCK_JOB_ERROR", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 {"data": {"device": "backup_1", "error": "Input/output error", "len": 67108864, "offset": 983040, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
@@ -2609,7 +2609,7 @@ expecting 14 dirty sectors; have 14. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -2623,7 +2623,7 @@ expecting 14 dirty sectors; have 14. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -2694,7 +2694,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -2742,7 +2742,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -2756,7 +2756,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "full", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "full", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -2869,7 +2869,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -2883,7 +2883,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -2954,7 +2954,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3002,7 +3002,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3016,7 +3016,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "full", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "full", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -3129,7 +3129,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3143,7 +3143,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -3214,7 +3214,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3262,7 +3262,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3278,7 +3278,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "full", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "full", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"action": "report", "device": "backup_1", "operation": "read"}, "event": "BLOCK_JOB_ERROR", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 {"data": {"device": "backup_1", "error": "Input/output error", "len": 67108864, "offset": 983040, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
@@ -3340,7 +3340,7 @@ expecting 1014 dirty sectors; have 1014. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3354,7 +3354,7 @@ expecting 1014 dirty sectors; have 1014. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -3425,7 +3425,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3473,7 +3473,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3487,7 +3487,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "full", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "full", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -3600,7 +3600,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3614,7 +3614,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -3685,7 +3685,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3733,7 +3733,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3747,7 +3747,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "top", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "top", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -3860,7 +3860,7 @@ expecting 15 dirty sectors; have 15. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3874,7 +3874,7 @@ expecting 15 dirty sectors; have 15. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -3945,7 +3945,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -3993,7 +3993,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4009,7 +4009,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "top", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "top", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"action": "report", "device": "backup_1", "operation": "read"}, "event": "BLOCK_JOB_ERROR", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 {"data": {"device": "backup_1", "error": "Input/output error", "len": 458752, "offset": 65536, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
@@ -4071,7 +4071,7 @@ expecting 14 dirty sectors; have 14. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4085,7 +4085,7 @@ expecting 14 dirty sectors; have 14. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -4156,7 +4156,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4204,7 +4204,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4218,7 +4218,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "top", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "top", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -4331,7 +4331,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4345,7 +4345,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -4416,7 +4416,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4464,7 +4464,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4478,7 +4478,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "top", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "top", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -4591,7 +4591,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4605,7 +4605,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -4676,7 +4676,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4724,7 +4724,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4740,7 +4740,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "top", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "top", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"action": "report", "device": "backup_1", "operation": "read"}, "event": "BLOCK_JOB_ERROR", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 {"data": {"device": "backup_1", "error": "Input/output error", "len": 458752, "offset": 65536, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
@@ -4802,7 +4802,7 @@ expecting 14 dirty sectors; have 14. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4816,7 +4816,7 @@ expecting 14 dirty sectors; have 14. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -4887,7 +4887,7 @@ write -P0x76 0x3ff0000 0x10000
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_0", "sync": "full", "target": "ref_target_0", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4935,7 +4935,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_1", "sync": "full", "target": "ref_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_1", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -4949,7 +4949,7 @@ expecting 6 dirty sectors; have 6. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "top", "target": "backup_target_1"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_1", "sync": "top", "target": "backup_target_1", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 
 --- Write #2 ---
@@ -5062,7 +5062,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "ref_backup_2", "sync": "full", "target": "ref_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"data": {"device": "ref_backup_2", "len": 67108864, "offset": 67108864, "speed": 0, "type": "backup"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 
@@ -5076,7 +5076,7 @@ expecting 12 dirty sectors; have 12. OK!
 {"execute": "job-dismiss", "arguments": {"id": "bdc-fmt-job"}}
 {"return": {}}
 {}
-{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2"}}
+{"execute": "blockdev-backup", "arguments": {"auto-finalize": false, "bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "backup_2", "sync": "bitmap", "target": "backup_target_2", "x-perf": {"max-workers": 1}}}
 {"return": {}}
 {"execute": "job-finalize", "arguments": {"id": "backup_2"}}
 {"return": {}}
@@ -5139,155 +5139,155 @@ qemu_img compare "TEST_DIR/PID-img" "TEST_DIR/PID-fbackup2" ==> Identical, OK!
 
 -- Sync mode incremental tests --
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "must provide a valid bitmap name for 'incremental' sync mode"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "must provide a valid bitmap name for 'incremental' sync mode"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "must provide a valid bitmap name for 'incremental' sync mode"}}
 
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "must provide a valid bitmap name for 'incremental' sync mode"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap sync mode must be 'on-success' when using sync mode 'incremental'"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap sync mode must be 'on-success' when using sync mode 'incremental'"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap sync mode must be 'on-success' when using sync mode 'incremental'"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "incremental", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap sync mode must be 'on-success' when using sync mode 'incremental'"}}
 
 -- Sync mode bitmap tests --
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "must provide a valid bitmap name for 'bitmap' sync mode"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "must provide a valid bitmap name for 'bitmap' sync mode"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "must provide a valid bitmap name for 'bitmap' sync mode"}}
 
-{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "must provide a valid bitmap name for 'bitmap' sync mode"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "bitmap", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap sync mode must be given when providing a bitmap"}}
 
 -- Sync mode full tests --
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Cannot specify bitmap sync mode without a bitmap"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Cannot specify bitmap sync mode without a bitmap"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Cannot specify bitmap sync mode without a bitmap"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap sync mode 'never' has no meaningful effect when combined with sync mode 'full'"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "full", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap sync mode must be given when providing a bitmap"}}
 
 -- Sync mode top tests --
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Cannot specify bitmap sync mode without a bitmap"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Cannot specify bitmap sync mode without a bitmap"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Cannot specify bitmap sync mode without a bitmap"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap sync mode 'never' has no meaningful effect when combined with sync mode 'top'"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "top", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap sync mode must be given when providing a bitmap"}}
 
 -- Sync mode none tests --
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Cannot specify bitmap sync mode without a bitmap"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Cannot specify bitmap sync mode without a bitmap"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Cannot specify bitmap sync mode without a bitmap"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap404", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap 'bitmap404' could not be found"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "on-success", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "sync mode 'none' does not produce meaningful bitmap outputs"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "always", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "sync mode 'none' does not produce meaningful bitmap outputs"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "bitmap-mode": "never", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "sync mode 'none' does not produce meaningful bitmap outputs"}}
 
-{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target"}}
+{"execute": "blockdev-backup", "arguments": {"bitmap": "bitmap0", "device": "drive0", "filter-node-name": "backup-top", "job-id": "api_job", "sync": "none", "target": "backup_target", "x-perf": {"max-workers": 1}}}
 {"error": {"class": "GenericError", "desc": "Bitmap sync mode must be given when providing a bitmap"}}
 
diff --git a/tests/qemu-iotests/297 b/tests/qemu-iotests/297
index 85bc1c0..a37910b 100755
--- a/tests/qemu-iotests/297
+++ b/tests/qemu-iotests/297
@@ -1,4 +1,4 @@
-#!/usr/bin/env bash
+#!/usr/bin/env python3
 # group: meta
 #
 # Copyright (C) 2020 Red Hat, Inc.
@@ -16,30 +16,98 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-seq=$(basename $0)
-echo "QA output created by $seq"
+import os
+import re
+import shutil
+import subprocess
+import sys
 
-status=1	# failure is the default!
+import iotests
 
-# get standard environment
-. ./common.rc
 
-if ! type -p "pylint-3" > /dev/null; then
-    _notrun "pylint-3 not found"
-fi
-if ! type -p "mypy" > /dev/null; then
-    _notrun "mypy not found"
-fi
+# TODO: Empty this list!
+SKIP_FILES = (
+    '030', '040', '041', '044', '045', '055', '056', '057', '065', '093',
+    '096', '118', '124', '132', '136', '139', '147', '148', '149',
+    '151', '152', '155', '163', '165', '169', '194', '196', '199', '202',
+    '203', '205', '206', '207', '208', '210', '211', '212', '213', '216',
+    '218', '219', '222', '224', '228', '234', '235', '236', '237', '238',
+    '240', '242', '245', '246', '248', '255', '256', '257', '258', '260',
+    '262', '264', '266', '274', '277', '280', '281', '295', '296', '298',
+    '299', '302', '303', '304', '307',
+    'nbd-fault-injector.py', 'qcow2.py', 'qcow2_format.py', 'qed.py'
+)
 
-pylint-3 --score=n iotests.py
 
-MYPYPATH=../../python/ mypy --warn-unused-configs --disallow-subclassing-any \
-    --disallow-any-generics --disallow-incomplete-defs \
-    --disallow-untyped-decorators --no-implicit-optional \
-    --warn-redundant-casts --warn-unused-ignores \
-    --no-implicit-reexport iotests.py
+def is_python_file(filename):
+    if not os.path.isfile(filename):
+        return False
 
-# success, all done
-echo "*** done"
-rm -f $seq.full
-status=0
+    if filename.endswith('.py'):
+        return True
+
+    with open(filename) as f:
+        try:
+            first_line = f.readline()
+            return re.match('^#!.*python', first_line) is not None
+        except UnicodeDecodeError:  # Ignore binary files
+            return False
+
+
+def run_linters():
+    files = [filename for filename in (set(os.listdir('.')) - set(SKIP_FILES))
+             if is_python_file(filename)]
+
+    iotests.logger.debug('Files to be checked:')
+    iotests.logger.debug(', '.join(sorted(files)))
+
+    print('=== pylint ===')
+    sys.stdout.flush()
+
+    # Todo notes are fine, but fixme's or xxx's should probably just be
+    # fixed (in tests, at least)
+    env = os.environ.copy()
+    qemu_module_path = os.path.join(os.path.dirname(__file__),
+                                    '..', '..', 'python')
+    try:
+        env['PYTHONPATH'] += os.pathsep + qemu_module_path
+    except KeyError:
+        env['PYTHONPATH'] = qemu_module_path
+    subprocess.run(('pylint-3', '--score=n', '--notes=FIXME,XXX', *files),
+                   env=env, check=False)
+
+    print('=== mypy ===')
+    sys.stdout.flush()
+
+    # We have to call mypy separately for each file.  Otherwise, it
+    # will interpret all given files as belonging together (i.e., they
+    # may not both define the same classes, etc.; most notably, they
+    # must not both define the __main__ module).
+    env['MYPYPATH'] = env['PYTHONPATH']
+    for filename in files:
+        p = subprocess.run(('mypy',
+                            '--warn-unused-configs',
+                            '--disallow-subclassing-any',
+                            '--disallow-any-generics',
+                            '--disallow-incomplete-defs',
+                            '--disallow-untyped-decorators',
+                            '--no-implicit-optional',
+                            '--warn-redundant-casts',
+                            '--warn-unused-ignores',
+                            '--no-implicit-reexport',
+                            filename),
+                           env=env,
+                           check=False,
+                           stdout=subprocess.PIPE,
+                           stderr=subprocess.STDOUT,
+                           universal_newlines=True)
+
+        if p.returncode != 0:
+            print(p.stdout)
+
+
+for linter in ('pylint-3', 'mypy'):
+    if shutil.which(linter) is None:
+        iotests.notrun(f'{linter} not found')
+
+iotests.script_main(run_linters)
diff --git a/tests/qemu-iotests/297.out b/tests/qemu-iotests/297.out
index 6acc843..f2e1314 100644
--- a/tests/qemu-iotests/297.out
+++ b/tests/qemu-iotests/297.out
@@ -1,3 +1,2 @@
-QA output created by 297
-Success: no issues found in 1 source file
-*** done
+=== pylint ===
+=== mypy ===
diff --git a/tests/qemu-iotests/300 b/tests/qemu-iotests/300
index 23aca59..43264d8 100755
--- a/tests/qemu-iotests/300
+++ b/tests/qemu-iotests/300
@@ -23,12 +23,15 @@ import os
 import random
 import re
 from typing import Dict, List, Optional, Union
+
 import iotests
+
+# Import qemu after iotests.py has amended sys.path
+# pylint: disable=wrong-import-order
 import qemu
 
 BlockBitmapMapping = List[Dict[str, Union[str, List[Dict[str, str]]]]]
 
-assert iotests.sock_dir is not None
 mig_sock = os.path.join(iotests.sock_dir, 'mig_sock')
 
 
@@ -112,10 +115,14 @@ class TestDirtyBitmapMigration(iotests.QMPTestCase):
         If @msg is None, check that there has not been any error.
         """
         self.vm_b.shutdown()
+
+        log = self.vm_b.get_log()
+        assert log is not None  # Loaded after shutdown
+
         if msg is None:
-            self.assertNotIn('qemu-system-', self.vm_b.get_log())
+            self.assertNotIn('qemu-system-', log)
         else:
-            self.assertIn(msg, self.vm_b.get_log())
+            self.assertIn(msg, log)
 
     @staticmethod
     def mapping(node_name: str, node_alias: str,
@@ -447,9 +454,13 @@ class TestBlockBitmapMappingErrors(TestDirtyBitmapMigration):
 
         # Check for the error in the source's log
         self.vm_a.shutdown()
+
+        log = self.vm_a.get_log()
+        assert log is not None  # Loaded after shutdown
+
         self.assertIn(f"Cannot migrate bitmap '{name}' on node "
                       f"'{self.src_node_name}': Name is longer than 255 bytes",
-                      self.vm_a.get_log())
+                      log)
 
         # Expect abnormal shutdown of the destination VM because of
         # the failed migration
diff --git a/tests/qemu-iotests/310 b/tests/qemu-iotests/310
new file mode 100755
index 0000000..9d9c928
--- /dev/null
+++ b/tests/qemu-iotests/310
@@ -0,0 +1,117 @@
+#!/usr/bin/env python3
+# group: rw quick
+#
+# Copy-on-read tests using a COR filter with a bottom node
+#
+# Copyright (C) 2018 Red Hat, Inc.
+# Copyright (c) 2020 Virtuozzo International GmbH
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+import iotests
+from iotests import log, qemu_img, qemu_io_silent
+
+# Need backing file support
+iotests.script_initialize(supported_fmts=['qcow2'],
+                          supported_platforms=['linux'])
+
+log('')
+log('=== Copy-on-read across nodes ===')
+log('')
+
+# This test is similar to the 216 one by Max Reitz <mreitz@redhat.com>
+# The difference is that this test case involves a bottom node to the
+# COR filter driver.
+
+with iotests.FilePath('base.img') as base_img_path, \
+     iotests.FilePath('mid.img') as mid_img_path, \
+     iotests.FilePath('top.img') as top_img_path, \
+     iotests.VM() as vm:
+
+    log('--- Setting up images ---')
+    log('')
+
+    assert qemu_img('create', '-f', iotests.imgfmt, base_img_path, '64M') == 0
+    assert qemu_io_silent(base_img_path, '-c', 'write -P 1 0M 1M') == 0
+    assert qemu_io_silent(base_img_path, '-c', 'write -P 1 3M 1M') == 0
+    assert qemu_img('create', '-f', iotests.imgfmt, '-b', base_img_path,
+                    '-F', iotests.imgfmt, mid_img_path) == 0
+    assert qemu_io_silent(mid_img_path,  '-c', 'write -P 3 2M 1M') == 0
+    assert qemu_io_silent(mid_img_path,  '-c', 'write -P 3 4M 1M') == 0
+    assert qemu_img('create', '-f', iotests.imgfmt, '-b', mid_img_path,
+                    '-F', iotests.imgfmt, top_img_path) == 0
+    assert qemu_io_silent(top_img_path,  '-c', 'write -P 2 1M 1M') == 0
+
+#      0 1 2 3 4
+# top    2
+# mid      3   3
+# base 1     1
+
+    log('Done')
+
+    log('')
+    log('--- Doing COR ---')
+    log('')
+
+    vm.launch()
+
+    log(vm.qmp('blockdev-add',
+               node_name='node0',
+               driver='copy-on-read',
+               bottom='node2',
+               file={
+                   'driver': iotests.imgfmt,
+                   'file': {
+                       'driver': 'file',
+                       'filename': top_img_path
+                   },
+                   'backing': {
+                       'node-name': 'node2',
+                       'driver': iotests.imgfmt,
+                       'file': {
+                           'driver': 'file',
+                           'filename': mid_img_path
+                       },
+                       'backing': {
+                           'driver': iotests.imgfmt,
+                           'file': {
+                               'driver': 'file',
+                               'filename': base_img_path
+                           }
+                       },
+                   }
+               }))
+
+    # Trigger COR
+    log(vm.qmp('human-monitor-command',
+               command_line='qemu-io node0 "read 0 5M"'))
+
+    vm.shutdown()
+
+    log('')
+    log('--- Checking COR result ---')
+    log('')
+
+    # Detach backing to check that we can read the data from the top level now
+    assert qemu_img('rebase', '-u', '-b', '', '-f', iotests.imgfmt,
+                    top_img_path) == 0
+
+    assert qemu_io_silent(top_img_path,  '-c', 'read -P 0 0 1M') == 0
+    assert qemu_io_silent(top_img_path,  '-c', 'read -P 2 1M 1M') == 0
+    assert qemu_io_silent(top_img_path,  '-c', 'read -P 3 2M 1M') == 0
+    assert qemu_io_silent(top_img_path,  '-c', 'read -P 0 3M 1M') == 0
+    assert qemu_io_silent(top_img_path,  '-c', 'read -P 3 4M 1M') == 0
+
+    log('Done')
diff --git a/tests/qemu-iotests/310.out b/tests/qemu-iotests/310.out
new file mode 100644
index 0000000..a70aa5c
--- /dev/null
+++ b/tests/qemu-iotests/310.out
@@ -0,0 +1,15 @@
+
+=== Copy-on-read across nodes ===
+
+--- Setting up images ---
+
+Done
+
+--- Doing COR ---
+
+{"return": {}}
+{"return": ""}
+
+--- Checking COR result ---
+
+Done
diff --git a/tests/qemu-iotests/313 b/tests/qemu-iotests/313
new file mode 100755
index 0000000..a75655b
--- /dev/null
+++ b/tests/qemu-iotests/313
@@ -0,0 +1,104 @@
+#!/usr/bin/env bash
+# group: rw auto quick
+#
+# Test for the regression fixed in commit c8bf9a9169
+#
+# Copyright (C) 2020 Igalia, S.L.
+# Author: Alberto Garcia <berto@igalia.com>
+# Based on a test case by Maxim Levitsky <mlevitsk@redhat.com>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=berto@igalia.com
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+status=1    # failure is the default!
+
+_cleanup()
+{
+    _cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt qcow2
+_supported_proto file
+_supported_os Linux
+_unsupported_imgopts cluster_size refcount_bits extended_l2 compat=0.10 data_file
+
+# The cluster size must be at least the granularity of the mirror job (4KB)
+# Note that larger cluster sizes will produce very large images (several GBs)
+cluster_size=4096
+refcount_bits=64 # Make it equal to the L2 entry size for convenience
+options="cluster_size=${cluster_size},refcount_bits=${refcount_bits}"
+
+# Number of refcount entries per refcount blocks
+ref_entries=$(( ${cluster_size} * 8 / ${refcount_bits} ))
+
+# Number of data clusters needed to fill a refcount block
+# Equals ${ref_entries} minus two (one L2 table and one refcount block)
+data_clusters_per_refblock=$(( ${ref_entries} - 2 ))
+
+# Number of entries in the refcount cache
+ref_blocks=4
+
+# Write enough data clusters to fill the refcount cache and allocate
+# one more refcount block.
+# Subtract 3 clusters from the total: qcow2 header, refcount table, L1 table
+total_data_clusters=$(( ${data_clusters_per_refblock} * ${ref_blocks} + 1 - 3 ))
+
+# Total size to write in bytes
+total_size=$(( ${total_data_clusters} * ${cluster_size} ))
+
+echo
+echo '### Create the image'
+echo
+TEST_IMG_FILE=$TEST_IMG.base _make_test_img -o $options $total_size | _filter_img_create_size
+
+echo
+echo '### Write data to allocate more refcount blocks than the cache can hold'
+echo
+$QEMU_IO -c "write -P 1 0 $total_size" $TEST_IMG.base | _filter_qemu_io
+
+echo
+echo '### Create an overlay'
+echo
+_make_test_img -F $IMGFMT -b $TEST_IMG.base -o $options | _filter_img_create_size
+
+echo
+echo '### Fill the overlay with zeroes'
+echo
+$QEMU_IO -c "write -z 0 $total_size" $TEST_IMG | _filter_qemu_io
+
+echo
+echo '### Commit changes to the base image'
+echo
+$QEMU_IMG commit $TEST_IMG
+
+echo
+echo '### Check the base image'
+echo
+$QEMU_IMG check $TEST_IMG.base
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/313.out b/tests/qemu-iotests/313.out
new file mode 100644
index 0000000..adb9f7b
--- /dev/null
+++ b/tests/qemu-iotests/313.out
@@ -0,0 +1,29 @@
+QA output created by 313
+
+### Create the image
+
+Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=SIZE
+
+### Write data to allocate more refcount blocks than the cache can hold
+
+wrote 8347648/8347648 bytes at offset 0
+7.961 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+### Create an overlay
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=SIZE backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+
+### Fill the overlay with zeroes
+
+wrote 8347648/8347648 bytes at offset 0
+7.961 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+### Commit changes to the base image
+
+Image committed.
+
+### Check the base image
+
+No errors were found on the image.
+Image end offset: 8396800
+*** done
diff --git a/tests/qemu-iotests/common.rc b/tests/qemu-iotests/common.rc
index 2935465..297acf9 100644
--- a/tests/qemu-iotests/common.rc
+++ b/tests/qemu-iotests/common.rc
@@ -821,9 +821,10 @@ _supported_cache_modes()
 # Check whether the filesystem supports O_DIRECT
 _check_o_direct()
 {
-    $QEMU_IMG create -f raw "$TEST_IMG".test_o_direct 1M > /dev/null
-    out=$($QEMU_IO -f raw -t none -c quit "$TEST_IMG".test_o_direct 2>&1)
-    rm -f "$TEST_IMG".test_o_direct
+    testfile="$TEST_DIR"/_check_o_direct
+    $QEMU_IMG create -f raw "$testfile" 1M > /dev/null
+    out=$($QEMU_IO -f raw -t none -c quit "$testfile" 2>&1)
+    rm -f "$testfile"
 
     [[ "$out" != *"O_DIRECT"* ]]
 }
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index bc5bc32..a0d0bf1 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -318,4 +318,6 @@
 307 rw quick export
 308 rw
 309 rw auto quick
+310 rw quick
 312 rw quick
+313 rw auto quick
diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 2e89c0a..335e6fe 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -75,12 +75,20 @@ qemu_opts = os.environ.get('QEMU_OPTIONS', '').strip().split(' ')
 
 imgfmt = os.environ.get('IMGFMT', 'raw')
 imgproto = os.environ.get('IMGPROTO', 'file')
-test_dir = os.environ.get('TEST_DIR')
-sock_dir = os.environ.get('SOCK_DIR')
 output_dir = os.environ.get('OUTPUT_DIR', '.')
-cachemode = os.environ.get('CACHEMODE')
-aiomode = os.environ.get('AIOMODE')
-qemu_default_machine = os.environ.get('QEMU_DEFAULT_MACHINE')
+
+try:
+    test_dir = os.environ['TEST_DIR']
+    sock_dir = os.environ['SOCK_DIR']
+    cachemode = os.environ['CACHEMODE']
+    aiomode = os.environ['AIOMODE']
+    qemu_default_machine = os.environ['QEMU_DEFAULT_MACHINE']
+except KeyError:
+    # We are using these variables as proxies to indicate that we're
+    # not being run via "check". There may be other things set up by
+    # "check" that individual test cases rely on.
+    sys.stderr.write('Please run this test via the "check" script\n')
+    sys.exit(os.EX_USAGE)
 
 socket_scm_helper = os.environ.get('SOCKET_SCM_HELPER', 'socket_scm_helper')
 
@@ -507,12 +515,15 @@ class FilePath:
         return False
 
 
+def try_remove(img):
+    try:
+        os.remove(img)
+    except OSError:
+        pass
+
 def file_path_remover():
     for path in reversed(file_path_remover.paths):
-        try:
-            os.remove(path)
-        except OSError:
-            pass
+        try_remove(path)
 
 
 def file_path(*names, base_dir=test_dir):
@@ -1286,14 +1297,6 @@ def execute_setup_common(supported_fmts: Sequence[str] = (),
     """
     # Note: Python 3.6 and pylint do not like 'Collection' so use 'Sequence'.
 
-    # We are using TEST_DIR and QEMU_DEFAULT_MACHINE as proxies to
-    # indicate that we're not being run via "check". There may be
-    # other things set up by "check" that individual test cases rely
-    # on.
-    if test_dir is None or qemu_default_machine is None:
-        sys.stderr.write('Please run this test via the "check" script\n')
-        sys.exit(os.EX_USAGE)
-
     debug = '-d' in sys.argv
     if debug:
         sys.argv.remove('-d')
diff --git a/util/coroutine-sigaltstack.c b/util/coroutine-sigaltstack.c
index aade82a..e99b8a4 100644
--- a/util/coroutine-sigaltstack.c
+++ b/util/coroutine-sigaltstack.c
@@ -157,6 +157,7 @@ Coroutine *qemu_coroutine_new(void)
     sigset_t sigs;
     sigset_t osigs;
     sigjmp_buf old_env;
+    static pthread_mutex_t sigusr2_mutex = PTHREAD_MUTEX_INITIALIZER;
 
     /* The way to manipulate stack is with the sigaltstack function. We
      * prepare a stack, with it delivering a signal to ourselves and then
@@ -186,6 +187,12 @@ Coroutine *qemu_coroutine_new(void)
     sa.sa_handler = coroutine_trampoline;
     sigfillset(&sa.sa_mask);
     sa.sa_flags = SA_ONSTACK;
+
+    /*
+     * sigaction() is a process-global operation.  We must not run
+     * this code in multiple threads at once.
+     */
+    pthread_mutex_lock(&sigusr2_mutex);
     if (sigaction(SIGUSR2, &sa, &osa) != 0) {
         abort();
     }
@@ -234,6 +241,8 @@ Coroutine *qemu_coroutine_new(void)
      * Restore the old SIGUSR2 signal handler and mask
      */
     sigaction(SIGUSR2, &osa, NULL);
+    pthread_mutex_unlock(&sigusr2_mutex);
+
     pthread_sigmask(SIG_SETMASK, &osigs, NULL);
 
     /*