Merge tag 'pull-block-jobs-2025-04-29-v3' of https://gitlab.com/vsementsov/qemu into staging

block-job patches

- deprecate some old block-job- APIs
- on-cbw-error option for backup
- more efficient zero handling in block commit

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* tag 'pull-block-jobs-2025-04-29-v3' of https://gitlab.com/vsementsov/qemu:
  blockdev-backup: Add error handling option for copy-before-write jobs
  qapi/block-core: deprecate some block-job- APIs
  qapi: synchronize jobs and block-jobs documentation
  block: add test non-active commit with zeroed data
  block: allow commit to unmap zero blocks
  block: refactor error handling of commit_iteration
  block: move commit_run loop to separate function
  block: get type of block allocation in commit_run

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

14 files changed, 476 insertions, 65 deletions

diff --git a/block/backup.c b/block/backup.c
index 79652bf..0151e84 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -361,6 +361,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
                   BackupPerf *perf,
                   BlockdevOnError on_source_error,
                   BlockdevOnError on_target_error,
+                  OnCbwError on_cbw_error,
                   int creation_flags,
                   BlockCompletionFunc *cb, void *opaque,
                   JobTxn *txn, Error **errp)
@@ -458,7 +459,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
     }
 
     cbw = bdrv_cbw_append(bs, target, filter_node_name, discard_source,
-                          perf->min_cluster_size, &bcs, errp);
+                          perf->min_cluster_size, &bcs, on_cbw_error, errp);
     if (!cbw) {
         goto error;
     }
diff --git a/block/commit.c b/block/commit.c
index 5df3d05..7cc8c0f 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -15,6 +15,8 @@
 #include "qemu/osdep.h"
 #include "qemu/cutils.h"
 #include "trace.h"
+#include "block/block-common.h"
+#include "block/coroutines.h"
 #include "block/block_int.h"
 #include "block/blockjob_int.h"
 #include "qapi/error.h"
@@ -126,6 +128,84 @@ static void commit_clean(Job *job)
     blk_unref(s->top);
 }
 
+static int commit_iteration(CommitBlockJob *s, int64_t offset,
+                            int64_t *requested_bytes, void *buf)
+{
+    BlockErrorAction action;
+    int64_t bytes = *requested_bytes;
+    int ret = 0;
+    bool error_in_source = true;
+
+    /* Copy if allocated above the base */
+    WITH_GRAPH_RDLOCK_GUARD() {
+        ret = bdrv_co_common_block_status_above(blk_bs(s->top),
+            s->base_overlay, true, true, offset, COMMIT_BUFFER_SIZE,
+            &bytes, NULL, NULL, NULL);
+    }
+
+    trace_commit_one_iteration(s, offset, bytes, ret);
+
+    if (ret < 0) {
+        goto fail;
+    }
+
+    if (ret & BDRV_BLOCK_ALLOCATED) {
+        if (ret & BDRV_BLOCK_ZERO) {
+            /*
+             * If the top (sub)clusters are smaller than the base
+             * (sub)clusters, this will not unmap unless the underlying device
+             * does some tracking of these requests. Ideally, we would find
+             * the maximal extent of the zero clusters.
+             */
+            ret = blk_co_pwrite_zeroes(s->base, offset, bytes,
+                                       BDRV_REQ_MAY_UNMAP);
+            if (ret < 0) {
+                error_in_source = false;
+                goto fail;
+            }
+        } else {
+            assert(bytes < SIZE_MAX);
+
+            ret = blk_co_pread(s->top, offset, bytes, buf, 0);
+            if (ret < 0) {
+                goto fail;
+            }
+
+            ret = blk_co_pwrite(s->base, offset, bytes, buf, 0);
+            if (ret < 0) {
+                error_in_source = false;
+                goto fail;
+            }
+        }
+
+        /*
+         * Whether zeroes actually end up on disk depends on the details of
+         * the underlying driver. Therefore, this might rate limit more than
+         * is necessary.
+         */
+        block_job_ratelimit_processed_bytes(&s->common, bytes);
+    }
+
+    /* Publish progress */
+
+    job_progress_update(&s->common.job, bytes);
+
+    *requested_bytes = bytes;
+
+    return 0;
+
+fail:
+    action = block_job_error_action(&s->common, s->on_error,
+                                    error_in_source, -ret);
+    if (action == BLOCK_ERROR_ACTION_REPORT) {
+        return ret;
+    }
+
+    *requested_bytes = 0;
+
+    return 0;
+}
+
 static int coroutine_fn commit_run(Job *job, Error **errp)
 {
     CommitBlockJob *s = container_of(job, CommitBlockJob, common.job);
@@ -156,9 +236,6 @@ static int coroutine_fn commit_run(Job *job, Error **errp)
     buf = blk_blockalign(s->top, COMMIT_BUFFER_SIZE);
 
     for (offset = 0; offset < len; offset += n) {
-        bool copy;
-        bool error_in_source = true;
-
         /* Note that even when no rate limit is applied we need to yield
          * with no pending I/O here so that bdrv_drain_all() returns.
          */
@@ -166,38 +243,11 @@ static int coroutine_fn commit_run(Job *job, Error **errp)
         if (job_is_cancelled(&s->common.job)) {
             break;
         }
-        /* Copy if allocated above the base */
-        ret = blk_co_is_allocated_above(s->top, s->base_overlay, true,
-                                        offset, COMMIT_BUFFER_SIZE, &n);
-        copy = (ret > 0);
-        trace_commit_one_iteration(s, offset, n, ret);
-        if (copy) {
-            assert(n < SIZE_MAX);
-
-            ret = blk_co_pread(s->top, offset, n, buf, 0);
-            if (ret >= 0) {
-                ret = blk_co_pwrite(s->base, offset, n, buf, 0);
-                if (ret < 0) {
-                    error_in_source = false;
-                }
-            }
-        }
-        if (ret < 0) {
-            BlockErrorAction action =
-                block_job_error_action(&s->common, s->on_error,
-                                       error_in_source, -ret);
-            if (action == BLOCK_ERROR_ACTION_REPORT) {
-                return ret;
-            } else {
-                n = 0;
-                continue;
-            }
-        }
-        /* Publish progress */
-        job_progress_update(&s->common.job, n);
 
-        if (copy) {
-            block_job_ratelimit_processed_bytes(&s->common, n);
+        ret = commit_iteration(s, offset, &n, buf);
+
+        if (ret < 0) {
+            return ret;
         }
     }
 
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index fd470f5..00af0b1 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -551,6 +551,7 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
                                   bool discard_source,
                                   uint64_t min_cluster_size,
                                   BlockCopyState **bcs,
+                                  OnCbwError on_cbw_error,
                                   Error **errp)
 {
     BDRVCopyBeforeWriteState *state;
@@ -568,6 +569,7 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
     }
     qdict_put_str(opts, "file", bdrv_get_node_name(source));
     qdict_put_str(opts, "target", bdrv_get_node_name(target));
+    qdict_put_str(opts, "on-cbw-error", OnCbwError_str(on_cbw_error));
 
     if (min_cluster_size > INT64_MAX) {
         error_setg(errp, "min-cluster-size too large: %" PRIu64 " > %" PRIi64,
diff --git a/block/copy-before-write.h b/block/copy-before-write.h
index 2a5d4ba..eb93364 100644
--- a/block/copy-before-write.h
+++ b/block/copy-before-write.h
@@ -42,6 +42,7 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
                                   bool discard_source,
                                   uint64_t min_cluster_size,
                                   BlockCopyState **bcs,
+                                  OnCbwError on_cbw_error,
                                   Error **errp);
 void bdrv_cbw_drop(BlockDriverState *bs);
 
diff --git a/block/replication.c b/block/replication.c
index d6625c5..07f274d 100644
--- a/block/replication.c
+++ b/block/replication.c
@@ -583,7 +583,9 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
                                 0, MIRROR_SYNC_MODE_NONE, NULL, 0, false, false,
                                 NULL, &perf,
                                 BLOCKDEV_ON_ERROR_REPORT,
-                                BLOCKDEV_ON_ERROR_REPORT, JOB_INTERNAL,
+                                BLOCKDEV_ON_ERROR_REPORT,
+                                ON_CBW_ERROR_BREAK_GUEST_WRITE,
+                                JOB_INTERNAL,
                                 backup_job_completed, bs, NULL, &local_err);
         if (local_err) {
             error_propagate(errp, local_err);
diff --git a/blockdev.c b/blockdev.c
index 1d1f27c..818ec42 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2641,6 +2641,7 @@ static BlockJob *do_backup_common(BackupCommon *backup,
     BdrvDirtyBitmap *bmap = NULL;
     BackupPerf perf = { .max_workers = 64 };
     int job_flags = JOB_DEFAULT;
+    OnCbwError on_cbw_error = ON_CBW_ERROR_BREAK_GUEST_WRITE;
 
     if (!backup->has_speed) {
         backup->speed = 0;
@@ -2745,6 +2746,10 @@ static BlockJob *do_backup_common(BackupCommon *backup,
         job_flags |= JOB_MANUAL_DISMISS;
     }
 
+    if (backup->has_on_cbw_error) {
+        on_cbw_error = backup->on_cbw_error;
+    }
+
     job = backup_job_create(backup->job_id, bs, target_bs, backup->speed,
                             backup->sync, bmap, backup->bitmap_mode,
                             backup->compress, backup->discard_source,
@@ -2752,6 +2757,7 @@ static BlockJob *do_backup_common(BackupCommon *backup,
                             &perf,
                             backup->on_source_error,
                             backup->on_target_error,
+                            on_cbw_error,
                             job_flags, NULL, NULL, txn, errp);
     return job;
 }
diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
index 1a1b423..44d3427 100644
--- a/docs/about/deprecated.rst
+++ b/docs/about/deprecated.rst
@@ -148,6 +148,37 @@ options are removed in favor of using explicit ``blockdev-create`` and
 ``blockdev-add`` calls. See :doc:`/interop/live-block-operations` for
 details.
 
+``block-job-pause`` (since 10.1)
+''''''''''''''''''''''''''''''''
+
+Use ``job-pause`` instead. The only difference is that ``job-pause``
+always reports GenericError on failure when ``block-job-pause`` reports
+DeviceNotActive when block-job is not found.
+
+``block-job-resume`` (since 10.1)
+'''''''''''''''''''''''''''''''''
+
+Use ``job-resume`` instead. The only difference is that ``job-resume``
+always reports GenericError on failure when ``block-job-resume`` reports
+DeviceNotActive when block-job is not found.
+
+``block-job-complete`` (since 10.1)
+'''''''''''''''''''''''''''''''''''
+
+Use ``job-complete`` instead. The only difference is that ``job-complete``
+always reports GenericError on failure when ``block-job-complete`` reports
+DeviceNotActive when block-job is not found.
+
+``block-job-dismiss`` (since 10.1)
+''''''''''''''''''''''''''''''''''
+
+Use ``job-dismiss`` instead.
+
+``block-job-finalize`` (since 10.1)
+'''''''''''''''''''''''''''''''''''
+
+Use ``job-finalize`` instead.
+
 ``query-migrationthreads`` (since 9.2)
 ''''''''''''''''''''''''''''''''''''''
 
diff --git a/include/block/block_int-global-state.h b/include/block/block_int-global-state.h
index eb2d92a..0d93783 100644
--- a/include/block/block_int-global-state.h
+++ b/include/block/block_int-global-state.h
@@ -179,6 +179,7 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
  *        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.
+ * @on_cbw_error: The action to take upon error in copy-before-write operations.
  * @creation_flags: Flags that control the behavior of the Job lifetime.
  *                  See @BlockJobCreateFlags
  * @cb: Completion function for the job.
@@ -198,6 +199,7 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
                             BackupPerf *perf,
                             BlockdevOnError on_source_error,
                             BlockdevOnError on_target_error,
+                            OnCbwError on_cbw_error,
                             int creation_flags,
                             BlockCompletionFunc *cb, void *opaque,
                             JobTxn *txn, Error **errp);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index b193778..91c70e2 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1602,6 +1602,9 @@
 #     default 'report' (no limitations, since this applies to a
 #     different block device than @device).
 #
+# @on-cbw-error: policy defining behavior on I/O errors in
+#     copy-before-write jobs; defaults to break-guest-write.  (Since 10.1)
+#
 # @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.  When true, this job will
@@ -1641,6 +1644,7 @@
             '*compress': 'bool',
             '*on-source-error': 'BlockdevOnError',
             '*on-target-error': 'BlockdevOnError',
+            '*on-cbw-error': 'OnCbwError',
             '*auto-finalize': 'bool', '*auto-dismiss': 'bool',
             '*filter-node-name': 'str',
             '*discard-source': 'bool',
@@ -2956,18 +2960,24 @@
 #
 # Pause an active background block operation.
 #
-# This command returns immediately after marking the active background
-# block operation for pausing.  It is an error to call this command if
-# no operation is in progress or if the job is already paused.
+# This command returns immediately after marking the active job for
+# pausing.  Pausing an already paused job is an error.
 #
-# The operation will pause as soon as possible.  No event is emitted
-# when the operation is actually paused.  Cancelling a paused job
-# automatically resumes it.
+# The job will pause as soon as possible, which means transitioning
+# into the PAUSED state if it was RUNNING, or into STANDBY if it was
+# READY.  The corresponding JOB_STATUS_CHANGE event will be emitted.
+#
+# Cancelling a paused job automatically resumes it.
 #
 # @device: The job identifier.  This used to be a device name (hence
 #     the name of the parameter), but since QEMU 2.7 it can have other
 #     values.
 #
+# Features:
+#
+# @deprecated: This command is deprecated.  Use @job-pause
+#     instead.
+#
 # Errors:
 #     - If no background operation is active on this device,
 #       DeviceNotActive
@@ -2975,6 +2985,7 @@
 # Since: 1.3
 ##
 { 'command': 'block-job-pause', 'data': { 'device': 'str' },
+  'features': ['deprecated'],
   'allow-preconfig': true }
 
 ##
@@ -2982,9 +2993,8 @@
 #
 # Resume an active background block operation.
 #
-# This command returns immediately after resuming a paused background
-# block operation.  It is an error to call this command if no
-# operation is in progress or if the job is not paused.
+# This command returns immediately after resuming a paused job.
+# Resuming an already running job is an error.
 #
 # This command also clears the error status of the job.
 #
@@ -2992,6 +3002,11 @@
 #     the name of the parameter), but since QEMU 2.7 it can have other
 #     values.
 #
+# Features:
+#
+# @deprecated: This command is deprecated.  Use @job-resume
+#     instead.
+#
 # Errors:
 #     - If no background operation is active on this device,
 #       DeviceNotActive
@@ -2999,15 +3014,21 @@
 # Since: 1.3
 ##
 { 'command': 'block-job-resume', 'data': { 'device': 'str' },
+  'features': ['deprecated'],
   'allow-preconfig': true }
 
 ##
 # @block-job-complete:
 #
-# Manually trigger completion of an active background block operation.
-# This is supported for drive mirroring, where it also switches the
-# device to write to the target path only.  The ability to complete is
-# signaled with a BLOCK_JOB_READY event.
+# Manually trigger completion of an active job in the READY or STANDBY
+# state.  Completing the job in any other state is an error.
+#
+# This is supported only for drive mirroring, where it also switches
+# the device to write to the target path only. Note that drive
+# mirroring includes drive-mirror, blockdev-mirror and block-commit
+# job (only in case of "active commit", when the node being commited
+# is used by the guest). The ability to complete is signaled with a
+# BLOCK_JOB_READY event.
 #
 # This command completes an active background block operation
 # synchronously.  The ordering of this command's return with the
@@ -3017,12 +3038,15 @@
 # rerror/werror arguments that were specified when starting the
 # operation.
 #
-# A cancelled or paused job cannot be completed.
-#
 # @device: The job identifier.  This used to be a device name (hence
 #     the name of the parameter), but since QEMU 2.7 it can have other
 #     values.
 #
+# Features:
+#
+# @deprecated: This command is deprecated.  Use @job-complete
+#     instead.
+#
 # Errors:
 #     - If no background operation is active on this device,
 #       DeviceNotActive
@@ -3030,15 +3054,19 @@
 # Since: 1.3
 ##
 { 'command': 'block-job-complete', 'data': { 'device': 'str' },
+  'features': ['deprecated'],
   'allow-preconfig': true }
 
 ##
 # @block-job-dismiss:
 #
-# For jobs that have already concluded, remove them from the
-# block-job-query list.  This command only needs to be run for jobs
-# which were started with QEMU 2.12+ job lifetime management
-# semantics.
+# Deletes a job that is in the CONCLUDED state.  This command only
+# needs to be run explicitly for jobs that don't have automatic
+# dismiss enabled. In turn, automatic dismiss may be enabled only
+# for jobs that have @auto-dismiss option, which are drive-backup,
+# blockdev-backup, drive-mirror, blockdev-mirror, block-commit and
+# block-stream. @auto-dismiss is enabled by default for these
+# jobs.
 #
 # This command will refuse to operate on any job that has not yet
 # reached its terminal state, JOB_STATUS_CONCLUDED.  For jobs that
@@ -3047,26 +3075,43 @@
 #
 # @id: The job identifier.
 #
+# Features:
+#
+# @deprecated: This command is deprecated.  Use @job-dismiss
+#     instead.
+#
 # Since: 2.12
 ##
 { 'command': 'block-job-dismiss', 'data': { 'id': 'str' },
+  'features': ['deprecated'],
   'allow-preconfig': true }
 
 ##
 # @block-job-finalize:
 #
-# Once a job that has manual=true reaches the pending state, it can be
-# instructed to finalize any graph changes and do any necessary
-# cleanup via this command.  For jobs in a transaction, instructing
-# one job to finalize will force ALL jobs in the transaction to
-# finalize, so it is only necessary to instruct a single member job to
-# finalize.
+# Instructs all jobs in a transaction (or a single job if it is not
+# part of any transaction) to finalize any graph changes and do any
+# necessary cleanup.  This command requires that all involved jobs are
+# in the PENDING state.
+#
+# For jobs in a transaction, instructing one job to finalize will
+# force ALL jobs in the transaction to finalize, so it is only
+# necessary to instruct a single member job to finalize.
+#
+# The command is applicable only to jobs which have @auto-finalize option
+# and only when this option is set to false.
 #
 # @id: The job identifier.
 #
+# Features:
+#
+# @deprecated: This command is deprecated.  Use @job-finalize
+#     instead.
+#
 # Since: 2.12
 ##
 { 'command': 'block-job-finalize', 'data': { 'id': 'str' },
+  'features': ['deprecated'],
   'allow-preconfig': true }
 
 ##
diff --git a/qapi/job.json b/qapi/job.json
index cfc3bee..b03f80b 100644
--- a/qapi/job.json
+++ b/qapi/job.json
@@ -156,6 +156,9 @@
 # This command returns immediately after resuming a paused job.
 # Resuming an already running job is an error.
 #
+# This command also clears the error status for block-jobs (stream,
+# commit, mirror, backup).
+#
 # @id: The job identifier.
 #
 # Since: 3.0
@@ -184,7 +187,23 @@
 ##
 # @job-complete:
 #
-# Manually trigger completion of an active job in the READY state.
+# Manually trigger completion of an active job in the READY or STANDBY
+# state.  Completing the job in any other state is an error.
+#
+# This is supported only for drive mirroring, where it also switches
+# the device to write to the target path only. Note that drive
+# mirroring includes drive-mirror, blockdev-mirror and block-commit
+# job (only in case of "active commit", when the node being commited
+# is used by the guest). The ability to complete is signaled with a
+# BLOCK_JOB_READY event.
+#
+# This command completes an active background block operation
+# synchronously.  The ordering of this command's return with the
+# BLOCK_JOB_COMPLETED event is not defined.  Note that if an I/O error
+# occurs during the processing of this command: 1) the command itself
+# will fail; 2) the error will be processed according to the
+# rerror/werror arguments that were specified when starting the
+# operation.
 #
 # @id: The job identifier.
 #
@@ -197,7 +216,11 @@
 #
 # Deletes a job that is in the CONCLUDED state.  This command only
 # needs to be run explicitly for jobs that don't have automatic
-# dismiss enabled.
+# dismiss enabled. In turn, automatic dismiss may be enabled only
+# for jobs that have @auto-dismiss option, which are drive-backup,
+# blockdev-backup, drive-mirror, blockdev-mirror, block-commit and
+# block-stream. @auto-dismiss is enabled by default for these
+# jobs.
 #
 # This command will refuse to operate on any job that has not yet
 # reached its terminal state, JOB_STATUS_CONCLUDED.  For jobs that
@@ -222,6 +245,9 @@
 # force ALL jobs in the transaction to finalize, so it is only
 # necessary to instruct a single member job to finalize.
 #
+# The command is applicable only to jobs which have @auto-finalize option
+# and only when this option is set to false.
+#
 # @id: The identifier of any job in the transaction, or of a job that
 #     is not part of any transaction.
 #
diff --git a/tests/qemu-iotests/tests/commit-zero-blocks b/tests/qemu-iotests/tests/commit-zero-blocks
new file mode 100755
index 0000000..de00273
--- /dev/null
+++ b/tests/qemu-iotests/tests/commit-zero-blocks
@@ -0,0 +1,96 @@
+#!/usr/bin/env bash
+# group: rw quick
+#
+# Test for commit of discarded blocks
+#
+# This tests committing a live snapshot where some of the blocks that
+# are present in the base image are discarded in the intermediate image.
+# This intends to check that these blocks are also discarded in the base
+# image after the commit.
+#
+# Copyright (C) 2024 Vincent Vanlaer.
+#
+# 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=libvirt-e6954efa@volkihar.be
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+status=1	# failure is the default!
+
+_cleanup()
+{
+    _cleanup_qemu
+    _rm_test_img "${TEST_IMG}.base"
+    _rm_test_img "${TEST_IMG}.mid"
+    _cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+cd ..
+. ./common.rc
+. ./common.filter
+. ./common.qemu
+
+_supported_fmt qcow2
+_supported_proto file
+
+size="1M"
+
+TEST_IMG="$TEST_IMG.base" _make_test_img $size
+TEST_IMG="$TEST_IMG.mid" _make_test_img -b "$TEST_IMG.base" -F $IMGFMT $size
+_make_test_img -b "${TEST_IMG}.mid" -F $IMGFMT $size
+
+$QEMU_IO -c "write -P 0x01 64k 128k" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "discard 64k 64k" "$TEST_IMG.mid" | _filter_qemu_io
+
+echo
+echo "=== Base image info before commit ==="
+TEST_IMG="${TEST_IMG}.base" _img_info | _filter_img_info
+$QEMU_IMG map --output=json "$TEST_IMG.base" | _filter_qemu_img_map
+
+echo
+echo "=== Middle image info before commit ==="
+TEST_IMG="${TEST_IMG}.mid" _img_info | _filter_img_info
+$QEMU_IMG map --output=json "$TEST_IMG.mid" | _filter_qemu_img_map
+
+echo
+echo === Running QEMU Live Commit Test ===
+echo
+
+qemu_comm_method="qmp"
+_launch_qemu -drive file="${TEST_IMG}",if=virtio,id=test
+h=$QEMU_HANDLE
+
+_send_qemu_cmd $h "{ 'execute': 'qmp_capabilities' }" "return"
+
+_send_qemu_cmd $h "{ 'execute': 'block-commit',
+                                 'arguments': { 'device': 'test',
+                                 'top': '"${TEST_IMG}.mid"',
+                                 'base': '"${TEST_IMG}.base"'} }" '"status": "null"'
+
+_cleanup_qemu
+
+echo
+echo "=== Base image info after commit ==="
+TEST_IMG="${TEST_IMG}.base" _img_info | _filter_img_info
+$QEMU_IMG map --output=json "$TEST_IMG.base" | _filter_qemu_img_map
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/tests/commit-zero-blocks.out b/tests/qemu-iotests/tests/commit-zero-blocks.out
new file mode 100644
index 0000000..85bdc46
--- /dev/null
+++ b/tests/qemu-iotests/tests/commit-zero-blocks.out
@@ -0,0 +1,54 @@
+QA output created by commit-zero-blocks
+Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=1048576
+Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.mid backing_fmt=IMGFMT
+wrote 131072/131072 bytes at offset 65536
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+discard 65536/65536 bytes at offset 65536
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+=== Base image info before commit ===
+image: TEST_DIR/t.IMGFMT.base
+file format: IMGFMT
+virtual size: 1 MiB (1048576 bytes)
+[{ "start": 0, "length": 65536, "depth": 0, "present": false, "zero": true, "data": false, "compressed": false},
+{ "start": 65536, "length": 131072, "depth": 0, "present": true, "zero": false, "data": true, "compressed": false, "offset": OFFSET},
+{ "start": 196608, "length": 851968, "depth": 0, "present": false, "zero": true, "data": false, "compressed": false}]
+
+=== Middle image info before commit ===
+image: TEST_DIR/t.IMGFMT.mid
+file format: IMGFMT
+virtual size: 1 MiB (1048576 bytes)
+backing file: TEST_DIR/t.IMGFMT.base
+backing file format: IMGFMT
+[{ "start": 0, "length": 65536, "depth": 1, "present": false, "zero": true, "data": false, "compressed": false},
+{ "start": 65536, "length": 65536, "depth": 0, "present": true, "zero": true, "data": false, "compressed": false},
+{ "start": 131072, "length": 65536, "depth": 1, "present": true, "zero": false, "data": true, "compressed": false, "offset": OFFSET},
+{ "start": 196608, "length": 851968, "depth": 1, "present": false, "zero": true, "data": false, "compressed": false}]
+
+=== Running QEMU Live Commit Test ===
+
+{ 'execute': 'qmp_capabilities' }
+{"return": {}}
+{ 'execute': 'block-commit',
+                                 'arguments': { 'device': 'test',
+                                 'top': 'TEST_DIR/t.IMGFMT.mid',
+                                 'base': 'TEST_DIR/t.IMGFMT.base'} }
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "test"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "test"}}
+{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "waiting", "id": "test"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "pending", "id": "test"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "test", "len": 1048576, "offset": 1048576, "speed": 0, "type": "commit"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "concluded", "id": "test"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "null", "id": "test"}}
+
+=== Base image info after commit ===
+image: TEST_DIR/t.IMGFMT.base
+file format: IMGFMT
+virtual size: 1 MiB (1048576 bytes)
+[{ "start": 0, "length": 65536, "depth": 0, "present": false, "zero": true, "data": false, "compressed": false},
+{ "start": 65536, "length": 65536, "depth": 0, "present": true, "zero": true, "data": false, "compressed": false},
+{ "start": 131072, "length": 65536, "depth": 0, "present": true, "zero": false, "data": true, "compressed": false, "offset": OFFSET},
+{ "start": 196608, "length": 851968, "depth": 0, "present": false, "zero": true, "data": false, "compressed": false}]
+*** done
diff --git a/tests/qemu-iotests/tests/copy-before-write b/tests/qemu-iotests/tests/copy-before-write
index 498c558..236cb8a 100755
--- a/tests/qemu-iotests/tests/copy-before-write
+++ b/tests/qemu-iotests/tests/copy-before-write
@@ -99,6 +99,68 @@ class TestCbwError(iotests.QMPTestCase):
         log = iotests.filter_qemu_io(log)
         return log
 
+    def do_cbw_error_via_blockdev_backup(self, on_cbw_error=None):
+        self.vm.cmd('blockdev-add', {
+            'node-name': 'source',
+            'driver': iotests.imgfmt,
+            'file': {
+                'driver': 'file',
+                'filename': source_img
+            }
+        })
+
+        self.vm.cmd('blockdev-add', {
+            'node-name': 'target',
+            'driver': iotests.imgfmt,
+            'file': {
+                'driver': 'blkdebug',
+                'image': {
+                    'driver': 'file',
+                    'filename': temp_img
+                },
+                'inject-error': [
+                    {
+                        'event': 'write_aio',
+                        'errno': 5,
+                        'immediately': False,
+                        'once': True
+                    }
+                ]
+            }
+        })
+
+        blockdev_backup_options = {
+            'device': 'source',
+            'target': 'target',
+            'sync': 'none',
+            'job-id': 'job-id',
+            'filter-node-name': 'cbw'
+        }
+
+        if on_cbw_error:
+            blockdev_backup_options['on-cbw-error'] = on_cbw_error
+
+        self.vm.cmd('blockdev-backup', blockdev_backup_options)
+
+        self.vm.cmd('blockdev-add', {
+            'node-name': 'access',
+            'driver': 'snapshot-access',
+            'file': 'cbw'
+        })
+
+        result = self.vm.qmp('human-monitor-command',
+                             command_line='qemu-io cbw "write 0 1M"')
+        self.assert_qmp(result, 'return', '')
+
+        result = self.vm.qmp('human-monitor-command',
+                             command_line='qemu-io access "read 0 1M"')
+        self.assert_qmp(result, 'return', '')
+
+        self.vm.shutdown()
+        log = self.vm.get_log()
+        log = iotests.filter_qemu_io(log)
+        return log
+
     def test_break_snapshot_on_cbw_error(self):
         """break-snapshot behavior:
         Guest write succeed, but further snapshot-read fails, as snapshot is
@@ -125,6 +187,39 @@ read 1048576/1048576 bytes at offset 0
 1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 """)
 
+    def test_break_snapshot_policy_forwarding(self):
+        """Ensure CBW filter accepts break-snapshot policy
+        specified in blockdev-backup QMP command.
+        """
+        log = self.do_cbw_error_via_blockdev_backup('break-snapshot')
+        self.assertEqual(log, """\
+wrote 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read failed: Permission denied
+""")
+
+    def test_break_guest_write_policy_forwarding(self):
+        """Ensure CBW filter accepts break-guest-write policy
+        specified in blockdev-backup QMP command.
+        """
+        log = self.do_cbw_error_via_blockdev_backup('break-guest-write')
+        self.assertEqual(log, """\
+write failed: Input/output error
+read 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+""")
+
+    def test_default_on_cbw_error_policy_forwarding(self):
+        """Ensure break-guest-write policy is used by default when
+        on-cbw-error is not explicitly specified.
+        """
+        log = self.do_cbw_error_via_blockdev_backup()
+        self.assertEqual(log, """\
+write failed: Input/output error
+read 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+""")
+
     def do_cbw_timeout(self, on_cbw_error):
         self.vm.cmd('object-add', {
             'qom-type': 'throttle-group',
diff --git a/tests/qemu-iotests/tests/copy-before-write.out b/tests/qemu-iotests/tests/copy-before-write.out
index 89968f3..2f7d390 100644
--- a/tests/qemu-iotests/tests/copy-before-write.out
+++ b/tests/qemu-iotests/tests/copy-before-write.out
@@ -1,5 +1,5 @@
-....
+.......
 ----------------------------------------------------------------------
-Ran 4 tests
+Ran 7 tests
 
 OK