* [PATCH v3 1/2] copy-before-write: allow specifying minimum cluster size
2024-07-11 12:09 [PATCH v3 0/2] backup: allow specifying minimum cluster size Fiona Ebner
@ 2024-07-11 12:09 ` Fiona Ebner
2024-07-12 12:53 ` Vladimir Sementsov-Ogievskiy
2024-07-11 12:09 ` [PATCH v3 2/2] backup: add minimum cluster size to performance options Fiona Ebner
2024-07-12 13:02 ` [PATCH v3 0/2] backup: allow specifying minimum cluster size Vladimir Sementsov-Ogievskiy
2 siblings, 1 reply; 6+ messages in thread
From: Fiona Ebner @ 2024-07-11 12:09 UTC (permalink / raw)
To: qemu-devel; +Cc: qemu-block, armbru, eblake, hreitz, kwolf, vsementsov, jsnow
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.
The type 'size' (corresponding to uint64_t in C) is used in QAPI to
rule out negative inputs and for consistency with already existing
@cluster-size parameters. Since block_copy_calculate_cluster_size()
uses int64_t for its result, a check that the input is not too large
is added in block_copy_state_new() before calling it. The calculation
in block_copy_calculate_cluster_size() is done in the target int64_t
type.
Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Acked-by: Markus Armbruster <armbru@redhat.com> (QAPI schema)
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
Changes in v3:
* Pass min_cluster_size option directly without checking
has_min_cluster_size, because the default is 0 anyways.
* Calculate maximum of passed-in argument and default once at the
beginning of block_copy_calculate_cluster_size()
* Update warning message to reflect actual value used
* Use PRI{i,u}64 macros
block/block-copy.c | 36 ++++++++++++++++++++++++++----------
block/copy-before-write.c | 5 ++++-
include/block/block-copy.h | 1 +
qapi/block-core.json | 8 +++++++-
4 files changed, 38 insertions(+), 12 deletions(-)
diff --git a/block/block-copy.c b/block/block-copy.c
index 7e3b378528..59bee538eb 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -310,6 +310,7 @@ void block_copy_set_copy_opts(BlockCopyState *s, bool use_copy_range,
}
static int64_t block_copy_calculate_cluster_size(BlockDriverState *target,
+ int64_t min_cluster_size,
Error **errp)
{
int ret;
@@ -319,6 +320,9 @@ static int64_t block_copy_calculate_cluster_size(BlockDriverState *target,
GLOBAL_STATE_CODE();
GRAPH_RDLOCK_GUARD_MAINLOOP();
+ min_cluster_size = MAX(min_cluster_size,
+ (int64_t)BLOCK_COPY_CLUSTER_SIZE_DEFAULT);
+
target_does_cow = bdrv_backing_chain_next(target);
/*
@@ -329,13 +333,13 @@ static int64_t block_copy_calculate_cluster_size(BlockDriverState *target,
ret = bdrv_get_info(target, &bdi);
if (ret == -ENOTSUP && !target_does_cow) {
/* Cluster size is not defined */
- warn_report("The target block device doesn't provide "
- "information about the block size and it doesn't have a "
- "backing file. The default block size of %u bytes is "
- "used. If the actual block size of the target exceeds "
- "this default, the backup may be unusable",
- BLOCK_COPY_CLUSTER_SIZE_DEFAULT);
- return BLOCK_COPY_CLUSTER_SIZE_DEFAULT;
+ warn_report("The target block device doesn't provide information about "
+ "the block size and it doesn't have a backing file. The "
+ "(default) block size of %" PRIi64 " bytes is used. If the "
+ "actual block size of the target exceeds this value, the "
+ "backup may be unusable",
+ min_cluster_size);
+ return min_cluster_size;
} else if (ret < 0 && !target_does_cow) {
error_setg_errno(errp, -ret,
"Couldn't determine the cluster size of the target image, "
@@ -345,16 +349,17 @@ static int64_t block_copy_calculate_cluster_size(BlockDriverState *target,
return ret;
} else if (ret < 0 && target_does_cow) {
/* Not fatal; just trudge on ahead. */
- return BLOCK_COPY_CLUSTER_SIZE_DEFAULT;
+ return min_cluster_size;
}
- return MAX(BLOCK_COPY_CLUSTER_SIZE_DEFAULT, bdi.cluster_size);
+ return MAX(min_cluster_size, bdi.cluster_size);
}
BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
BlockDriverState *copy_bitmap_bs,
const BdrvDirtyBitmap *bitmap,
bool discard_source,
+ uint64_t min_cluster_size,
Error **errp)
{
ERRP_GUARD();
@@ -365,7 +370,18 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
GLOBAL_STATE_CODE();
- cluster_size = block_copy_calculate_cluster_size(target->bs, errp);
+ if (min_cluster_size > INT64_MAX) {
+ error_setg(errp, "min-cluster-size too large: %" PRIu64 " > %" PRIi64,
+ min_cluster_size, INT64_MAX);
+ return NULL;
+ } else if (min_cluster_size && !is_power_of_2(min_cluster_size)) {
+ error_setg(errp, "min-cluster-size needs to be a power of 2");
+ return NULL;
+ }
+
+ cluster_size = block_copy_calculate_cluster_size(target->bs,
+ (int64_t)min_cluster_size,
+ errp);
if (cluster_size < 0) {
return NULL;
}
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index 853e01a1eb..a919b1f41b 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -417,6 +417,7 @@ static BlockdevOptions *cbw_parse_options(QDict *options, Error **errp)
qdict_extract_subqdict(options, NULL, "bitmap");
qdict_del(options, "on-cbw-error");
qdict_del(options, "cbw-timeout");
+ qdict_del(options, "min-cluster-size");
out:
visit_free(v);
@@ -476,8 +477,10 @@ static int cbw_open(BlockDriverState *bs, QDict *options, int flags,
bs->file->bs->supported_zero_flags);
s->discard_source = flags & BDRV_O_CBW_DISCARD_SOURCE;
+
s->bcs = block_copy_state_new(bs->file, s->target, bs, bitmap,
- flags & BDRV_O_CBW_DISCARD_SOURCE, errp);
+ flags & BDRV_O_CBW_DISCARD_SOURCE,
+ opts->min_cluster_size, errp);
if (!s->bcs) {
error_prepend(errp, "Cannot create block-copy-state: ");
return -EINVAL;
diff --git a/include/block/block-copy.h b/include/block/block-copy.h
index bdc703bacd..dd5cc82f3b 100644
--- a/include/block/block-copy.h
+++ b/include/block/block-copy.h
@@ -28,6 +28,7 @@ BlockCopyState *block_copy_state_new(BdrvChild *source, BdrvChild *target,
BlockDriverState *copy_bitmap_bs,
const BdrvDirtyBitmap *bitmap,
bool discard_source,
+ uint64_t min_cluster_size,
Error **errp);
/* Function should be called prior any actual copy request */
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 096bdbe0aa..80e32db8aa 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -4638,12 +4638,18 @@
# @on-cbw-error parameter will decide how this failure is handled.
# Default 0. (Since 7.1)
#
+# @min-cluster-size: Minimum size of blocks used by copy-before-write
+# 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: 6.2
##
{ 'struct': 'BlockdevOptionsCbw',
'base': 'BlockdevOptionsGenericFormat',
'data': { 'target': 'BlockdevRef', '*bitmap': 'BlockDirtyBitmap',
- '*on-cbw-error': 'OnCbwError', '*cbw-timeout': 'uint32' } }
+ '*on-cbw-error': 'OnCbwError', '*cbw-timeout': 'uint32',
+ '*min-cluster-size': 'size' } }
##
# @BlockdevOptions:
--
2.39.2
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH v3 2/2] backup: add minimum cluster size to performance options
2024-07-11 12:09 [PATCH v3 0/2] backup: allow specifying minimum cluster size Fiona Ebner
2024-07-11 12:09 ` [PATCH v3 1/2] copy-before-write: " Fiona Ebner
@ 2024-07-11 12:09 ` Fiona Ebner
2024-07-12 12:56 ` Vladimir Sementsov-Ogievskiy
2024-07-12 13:02 ` [PATCH v3 0/2] backup: allow specifying minimum cluster size Vladimir Sementsov-Ogievskiy
2 siblings, 1 reply; 6+ messages in thread
From: Fiona Ebner @ 2024-07-11 12:09 UTC (permalink / raw)
To: qemu-devel; +Cc: qemu-block, armbru, eblake, hreitz, kwolf, vsementsov, jsnow
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 <vsementsov@yandex-team.ru>
Acked-by: Markus Armbruster <armbru@redhat.com> (QAPI schema)
Signed-off-by: Fiona Ebner <f.ebner@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
^ permalink raw reply related [flat|nested] 6+ messages in thread