* [PULL v3 8/8] blockdev-backup: Add error handling option for copy-before-write jobs
2025-05-12 15:29 [PULL v3 0/8] block-job patches 2025-04-29 Vladimir Sementsov-Ogievskiy
@ 2025-05-12 15:29 ` Vladimir Sementsov-Ogievskiy
2025-05-14 13:18 ` [PULL v3 0/8] block-job patches 2025-04-29 Stefan Hajnoczi
1 sibling, 0 replies; 3+ messages in thread
From: Vladimir Sementsov-Ogievskiy @ 2025-05-12 15:29 UTC (permalink / raw)
To: qemu-block
Cc: qemu-devel, vsementsov, stefanha, Raman Dzehtsiar,
Raman Dzehtsiar, Markus Armbruster
From: Raman Dzehtsiar <raman.dzehtsiar@gmail.com>
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>
Message-ID: <20250414090025.828660-1-Raman.Dzehtsiar@gmail.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
[vsementsov: fix long lines]
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Tested-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
---
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 | 95 +++++++++++++++++++
.../qemu-iotests/tests/copy-before-write.out | 4 +-
9 files changed, 117 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 d6625c51fe..07f274de9e 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 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 22061227ca..91c70e24a7 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',
diff --git a/tests/qemu-iotests/tests/copy-before-write b/tests/qemu-iotests/tests/copy-before-write
index 498c558008..236cb8ac37 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
@@ -123,6 +185,39 @@ 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
--
2.48.1
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