block/backup: move in-flight requests handling from backup to block-copy

Move synchronization mechanism to block-copy, to be able to use one
block-copy instance from backup job and backup-top filter in parallel.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20191001131409.14202-2-vsementsov@virtuozzo.com
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

2 files changed, 43 insertions, 52 deletions

diff --git a/block/backup.c b/block/backup.c
index 4613b8c..d918836 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -29,13 +29,6 @@
 
 #define BACKUP_CLUSTER_SIZE_DEFAULT (1 << 16)
 
-typedef struct CowRequest {
-    int64_t start_byte;
-    int64_t end_byte;
-    QLIST_ENTRY(CowRequest) list;
-    CoQueue wait_queue; /* coroutines blocked on this request */
-} CowRequest;
-
 typedef struct BackupBlockJob {
     BlockJob common;
     BlockDriverState *source_bs;
@@ -51,50 +44,12 @@ typedef struct BackupBlockJob {
     uint64_t bytes_read;
     int64_t cluster_size;
     NotifierWithReturn before_write;
-    QLIST_HEAD(, CowRequest) inflight_reqs;
 
     BlockCopyState *bcs;
 } BackupBlockJob;
 
 static const BlockJobDriver backup_job_driver;
 
-/* See if in-flight requests overlap and wait for them to complete */
-static void coroutine_fn wait_for_overlapping_requests(BackupBlockJob *job,
-                                                       int64_t start,
-                                                       int64_t end)
-{
-    CowRequest *req;
-    bool retry;
-
-    do {
-        retry = false;
-        QLIST_FOREACH(req, &job->inflight_reqs, list) {
-            if (end > req->start_byte && start < req->end_byte) {
-                qemu_co_queue_wait(&req->wait_queue, NULL);
-                retry = true;
-                break;
-            }
-        }
-    } while (retry);
-}
-
-/* Keep track of an in-flight request */
-static void cow_request_begin(CowRequest *req, BackupBlockJob *job,
-                              int64_t start, int64_t end)
-{
-    req->start_byte = start;
-    req->end_byte = end;
-    qemu_co_queue_init(&req->wait_queue);
-    QLIST_INSERT_HEAD(&job->inflight_reqs, req, list);
-}
-
-/* Forget about a completed request */
-static void cow_request_end(CowRequest *req)
-{
-    QLIST_REMOVE(req, list);
-    qemu_co_queue_restart_all(&req->wait_queue);
-}
-
 static void backup_progress_bytes_callback(int64_t bytes, void *opaque)
 {
     BackupBlockJob *s = opaque;
@@ -116,7 +71,6 @@ static int coroutine_fn backup_do_cow(BackupBlockJob *job,
                                       bool *error_is_read,
                                       bool is_write_notifier)
 {
-    CowRequest cow_request;
     int ret = 0;
     int64_t start, end; /* bytes */
 
@@ -127,14 +81,9 @@ static int coroutine_fn backup_do_cow(BackupBlockJob *job,
 
     trace_backup_do_cow_enter(job, start, offset, bytes);
 
-    wait_for_overlapping_requests(job, start, end);
-    cow_request_begin(&cow_request, job, start, end);
-
     ret = block_copy(job->bcs, start, end - start, error_is_read,
                      is_write_notifier);
 
-    cow_request_end(&cow_request);
-
     trace_backup_do_cow_return(job, offset, bytes, ret);
 
     qemu_co_rwlock_unlock(&job->flush_rwlock);
@@ -316,7 +265,6 @@ static int coroutine_fn backup_run(Job *job, Error **errp)
     BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
     int ret = 0;
 
-    QLIST_INIT(&s->inflight_reqs);
     qemu_co_rwlock_init(&s->flush_rwlock);
 
     backup_init_copy_bitmap(s);
diff --git a/block/block-copy.c b/block/block-copy.c
index 3fc9152..61e5ea5 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -19,6 +19,41 @@
 #include "block/block-copy.h"
 #include "sysemu/block-backend.h"
 
+static void coroutine_fn block_copy_wait_inflight_reqs(BlockCopyState *s,
+                                                       int64_t start,
+                                                       int64_t end)
+{
+    BlockCopyInFlightReq *req;
+    bool waited;
+
+    do {
+        waited = false;
+        QLIST_FOREACH(req, &s->inflight_reqs, list) {
+            if (end > req->start_byte && start < req->end_byte) {
+                qemu_co_queue_wait(&req->wait_queue, NULL);
+                waited = true;
+                break;
+            }
+        }
+    } while (waited);
+}
+
+static void block_copy_inflight_req_begin(BlockCopyState *s,
+                                          BlockCopyInFlightReq *req,
+                                          int64_t start, int64_t end)
+{
+    req->start_byte = start;
+    req->end_byte = end;
+    qemu_co_queue_init(&req->wait_queue);
+    QLIST_INSERT_HEAD(&s->inflight_reqs, req, list);
+}
+
+static void coroutine_fn block_copy_inflight_req_end(BlockCopyInFlightReq *req)
+{
+    QLIST_REMOVE(req, list);
+    qemu_co_queue_restart_all(&req->wait_queue);
+}
+
 void block_copy_state_free(BlockCopyState *s)
 {
     if (!s) {
@@ -79,6 +114,8 @@ BlockCopyState *block_copy_state_new(
     s->use_copy_range =
         !(write_flags & BDRV_REQ_WRITE_COMPRESSED) && s->copy_range_size > 0;
 
+    QLIST_INIT(&s->inflight_reqs);
+
     /*
      * We just allow aio context change on our block backends. block_copy() user
      * (now it's only backup) is responsible for source and target being in same
@@ -266,6 +303,7 @@ int coroutine_fn block_copy(BlockCopyState *s,
     int64_t end = bytes + start; /* bytes */
     void *bounce_buffer = NULL;
     int64_t status_bytes;
+    BlockCopyInFlightReq req;
 
     /*
      * block_copy() user is responsible for keeping source and target in same
@@ -276,6 +314,9 @@ int coroutine_fn block_copy(BlockCopyState *s,
     assert(QEMU_IS_ALIGNED(start, s->cluster_size));
     assert(QEMU_IS_ALIGNED(end, s->cluster_size));
 
+    block_copy_wait_inflight_reqs(s, start, bytes);
+    block_copy_inflight_req_begin(s, &req, start, end);
+
     while (start < end) {
         int64_t dirty_end;
 
@@ -329,5 +370,7 @@ int coroutine_fn block_copy(BlockCopyState *s,
         qemu_vfree(bounce_buffer);
     }
 
+    block_copy_inflight_req_end(&req);
+
     return ret;
 }