In the context of backup fleecing, discarding the source will not work
when the fleecing image has a larger granularity than the one used for
block-copy operations (can happen if the backup target has smaller
cluster size), because cbw_co_pdiscard_snapshot() will align down the
discard requests and thus effectively ignore then.
To make @discard-source work in such a scenario, allow specifying the
minimum cluster size used for block-copy operations and thus in
particular also the granularity for discard requests to the source.
Suggested-by: Vladimir Sementsov-Ogievskiy <vsement...@yandex-team.ru>
Acked-by: Markus Armbruster <arm...@redhat.com> (QAPI schema)
Signed-off-by: Fiona Ebner <f.eb...@proxmox.com>
---
Changes in v3:
* Use PRI{i,u}64 macros
* Do not leak qdict in error case
block/backup.c | 2 +-
block/copy-before-write.c | 9 +++++++++
block/copy-before-write.h | 1 +
blockdev.c | 3 +++
qapi/block-core.json | 9 +++++++--
5 files changed, 21 insertions(+), 3 deletions(-)
diff --git a/block/backup.c b/block/backup.c
index 3dd2e229d2..a1292c01ec 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -458,7 +458,7 @@ BlockJob *backup_job_create(const char *job_id,
BlockDriverState *bs,
}
cbw = bdrv_cbw_append(bs, target, filter_node_name, discard_source,
- &bcs, errp);
+ perf->min_cluster_size, &bcs, errp);
if (!cbw) {
goto error;
}
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index a919b1f41b..e835987e52 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -548,6 +548,7 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
BlockDriverState *target,
const char *filter_node_name,
bool discard_source,
+ uint64_t min_cluster_size,
BlockCopyState **bcs,
Error **errp)
{
@@ -567,6 +568,14 @@ 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));
+ if (min_cluster_size > INT64_MAX) {
+ error_setg(errp, "min-cluster-size too large: %" PRIu64 " > %" PRIi64,
+ min_cluster_size, INT64_MAX);
+ qobject_unref(opts);
+ return NULL;
+ }
+ qdict_put_int(opts, "min-cluster-size", (int64_t)min_cluster_size);
+
top = bdrv_insert_node(source, opts, flags, errp);
if (!top) {
return NULL;
diff --git a/block/copy-before-write.h b/block/copy-before-write.h
index 01af0cd3c4..2a5d4ba693 100644
--- a/block/copy-before-write.h
+++ b/block/copy-before-write.h
@@ -40,6 +40,7 @@ BlockDriverState *bdrv_cbw_append(BlockDriverState *source,
BlockDriverState *target,
const char *filter_node_name,
bool discard_source,
+ uint64_t min_cluster_size,
BlockCopyState **bcs,
Error **errp);
void bdrv_cbw_drop(BlockDriverState *bs);
diff --git a/blockdev.c b/blockdev.c
index 835064ed03..6740663fda 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2655,6 +2655,9 @@ static BlockJob *do_backup_common(BackupCommon *backup,
if (backup->x_perf->has_max_chunk) {
perf.max_chunk = backup->x_perf->max_chunk;
}
+ if (backup->x_perf->has_min_cluster_size) {
+ perf.min_cluster_size = backup->x_perf->min_cluster_size;
+ }
}
if ((backup->sync == MIRROR_SYNC_MODE_BITMAP) ||
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 80e32db8aa..9a54bfb15f 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1551,11 +1551,16 @@
# it should not be less than job cluster size which is calculated
# as maximum of target image cluster size and 64k. Default 0.
#
+# @min-cluster-size: Minimum size of blocks used by copy-before-write
+# and background copy operations. Has to be a power of 2. No
+# effect if smaller than the maximum of the target's cluster size
+# and 64 KiB. Default 0. (Since 9.1)
+#
# Since: 6.0
##
{ 'struct': 'BackupPerf',
- 'data': { '*use-copy-range': 'bool',
- '*max-workers': 'int', '*max-chunk': 'int64' } }
+ 'data': { '*use-copy-range': 'bool', '*max-workers': 'int',
+ '*max-chunk': 'int64', '*min-cluster-size': 'size' } }
##
# @BackupCommon:
--
2.39.2
