* [PATCH v3] blockdev-backup: Add error handling option for copy-before-write jobs
@ 2025-04-14 1:18 Raman Dzehtsiar
2025-04-14 5:06 ` Markus Armbruster
0 siblings, 1 reply; 3+ messages in thread
From: Raman Dzehtsiar @ 2025-04-14 1:18 UTC (permalink / raw)
To: qemu-devel
Cc: Wen Congyang, Hanna Reitz, Kevin Wolf,
Vladimir Sementsov-Ogievskiy, John Snow, Xie Changlong,
Markus Armbruster, Eric Blake, qemu-block, Raman Dzehtsiar
This patch extends the blockdev-backup QMP command to allow users to specify
how to behave when IO errors occur during copy-before-write operations.
Previously, the behavior was fixed and could not be controlled by the user.
The new 'on-cbw-error' option can be set to one of two values:
- 'break-guest-write': Forwards the IO error to the guest and triggers
the on-source-error policy. This preserves snapshot integrity at the
expense of guest IO operations.
- 'break-snapshot': Allows the guest OS to continue running normally,
but invalidates the snapshot and aborts related jobs. This prioritizes
guest operation over backup consistency.
This enhancement provides more flexibility for backup operations in different
environments where requirements for guest availability versus backup
consistency may vary.
The default behavior remains unchanged to maintain backward compatibility.
Signed-off-by: Raman Dzehtsiar <Raman.Dzehtsiar@gmail.com>
---
block/backup.c | 3 +-
block/copy-before-write.c | 2 +
block/copy-before-write.h | 1 +
block/replication.c | 4 +-
blockdev.c | 6 ++
include/block/block_int-global-state.h | 2 +
qapi/block-core.json | 4 +
tests/qemu-iotests/tests/copy-before-write | 90 +++++++++++++++++++
.../qemu-iotests/tests/copy-before-write.out | 4 +-
9 files changed, 112 insertions(+), 4 deletions(-)
diff --git a/block/backup.c b/block/backup.c
index 79652bf57b..0151e84395 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/copy-before-write.c b/block/copy-before-write.c
index fd470f5f92..00af0b18ac 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 2a5d4ba693..eb93364e85 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 0020f33843..748cf648ec 100644
--- a/block/replication.c
+++ b/block/replication.c
@@ -584,7 +584,9 @@ 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 1d1f27cfff..818ec42511 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/include/block/block_int-global-state.h b/include/block/block_int-global-state.h
index eb2d92a226..0d93783763 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 b1937780e1..d35326167d 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1622,6 +1622,9 @@
# @discard-source: Discard blocks on source which have already been
# copied to the target. (Since 9.1)
#
+# @on-cbw-error: optional policy defining behavior on I/O errors in
+# copy-before-write jobs; defaults to break-guest-write. (Since 10.0)
+#
# @x-perf: Performance options. (Since 6.0)
#
# Features:
@@ -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',
diff --git a/tests/qemu-iotests/tests/copy-before-write b/tests/qemu-iotests/tests/copy-before-write
index 498c558008..23d70c7fe7 100755
--- a/tests/qemu-iotests/tests/copy-before-write
+++ b/tests/qemu-iotests/tests/copy-before-write
@@ -99,6 +99,66 @@ 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
@@ -123,6 +183,36 @@ read failed: Permission denied
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_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):
diff --git a/tests/qemu-iotests/tests/copy-before-write.out b/tests/qemu-iotests/tests/copy-before-write.out
index 89968f35d7..2f7d3902f2 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
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v3] blockdev-backup: Add error handling option for copy-before-write jobs
2025-04-14 1:18 [PATCH v3] blockdev-backup: Add error handling option for copy-before-write jobs Raman Dzehtsiar
@ 2025-04-14 5:06 ` Markus Armbruster
2025-04-14 9:15 ` Raman Dzehtsiar
0 siblings, 1 reply; 3+ messages in thread
From: Markus Armbruster @ 2025-04-14 5:06 UTC (permalink / raw)
To: Raman Dzehtsiar
Cc: qemu-devel, Wen Congyang, Hanna Reitz, Kevin Wolf,
Vladimir Sementsov-Ogievskiy, John Snow, Xie Changlong,
Eric Blake, qemu-block
Raman Dzehtsiar <raman.dzehtsiar@gmail.com> writes:
> This patch extends the blockdev-backup QMP command to allow users to specify
> how to behave when IO errors occur during copy-before-write operations.
> Previously, the behavior was fixed and could not be controlled by the user.
>
> The new 'on-cbw-error' option can be set to one of two values:
> - 'break-guest-write': Forwards the IO error to the guest and triggers
> the on-source-error policy. This preserves snapshot integrity at the
> expense of guest IO operations.
> - 'break-snapshot': Allows the guest OS to continue running normally,
> but invalidates the snapshot and aborts related jobs. This prioritizes
> guest operation over backup consistency.
>
> This enhancement provides more flexibility for backup operations in different
> environments where requirements for guest availability versus backup
> consistency may vary.
>
> The default behavior remains unchanged to maintain backward compatibility.
>
> Signed-off-by: Raman Dzehtsiar <Raman.Dzehtsiar@gmail.com>
[...]
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index b1937780e1..d35326167d 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -1622,6 +1622,9 @@
> # @discard-source: Discard blocks on source which have already been
> # copied to the target. (Since 9.1)
> #
> +# @on-cbw-error: optional policy defining behavior on I/O errors in
> +# copy-before-write jobs; defaults to break-guest-write. (Since 10.0)
> +#
This will come out like
• on-cbw-error (OnCbwError, optional) – optional policy defining
behavior on I/O errors in copy-before-write jobs; defaults to
break-guest-write. (Since 10.0)
Scratch "optional", please.
Also, make it 10.1, and keep the member documentation ordered like ...
> # @x-perf: Performance options. (Since 6.0)
> #
> # Features:
> @@ -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',
... the actual members.
[...]
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v3] blockdev-backup: Add error handling option for copy-before-write jobs
2025-04-14 5:06 ` Markus Armbruster
@ 2025-04-14 9:15 ` Raman Dzehtsiar
0 siblings, 0 replies; 3+ messages in thread
From: Raman Dzehtsiar @ 2025-04-14 9:15 UTC (permalink / raw)
To: Markus Armbruster
Cc: qemu-devel, Wen Congyang, Hanna Reitz, Kevin Wolf,
Vladimir Sementsov-Ogievskiy, John Snow, Xie Changlong,
Eric Blake, qemu-block
Hi Markus,
Thanks for taking the time to review this patch.
[...]
> > +# @on-cbw-error: optional policy defining behavior on I/O errors in
> > +# copy-before-write jobs; defaults to break-guest-write. (Since 10.0)
[...]
> Scratch "optional", please.
Good point. I've removed "optional" from the description.
[...]
> Also, make it 10.1, and keep the member documentation ordered like ...
>
> > # @x-perf: Performance options. (Since 6.0)
> > #
> > # Features:
> > @@ -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',
>
> ... the actual members.
[...]
The documentation entries have been reordered to match the member
list, and the version tag has been updated to 10.1.
Both issues have been addressed in v4 of the patch.
Thanks again, and kind regards,
Raman Dzehtsiar
^ permalink raw reply [flat|nested] 3+ messages in thread
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2025-04-14 1:18 [PATCH v3] blockdev-backup: Add error handling option for copy-before-write jobs Raman Dzehtsiar
2025-04-14 5:06 ` Markus Armbruster
2025-04-14 9:15 ` Raman Dzehtsiar
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