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 <vsement...@yandex-team.ru>
Signed-off-by: Fiona Ebner <f.eb...@proxmox.com>
---
Changes in v2:
* Use 'size' type in QAPI.
* Remove option in cbw_parse_options(), i.e. before parsing generic
blockdev options.
block/block-copy.c | 22 ++++++++++++++++++----
block/copy-before-write.c | 10 +++++++++-
include/block/block-copy.h | 1 +
qapi/block-core.json | 8 +++++++-
4 files changed, 35 insertions(+), 6 deletions(-)
diff --git a/block/block-copy.c b/block/block-copy.c
index 7e3b378528..36eaecaaf4 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;
@@ -335,7 +336,7 @@ static int64_t
block_copy_calculate_cluster_size(BlockDriverState *target,
"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;
+ return MAX(min_cluster_size, (int64_t)BLOCK_COPY_CLUSTER_SIZE_DEFAULT);
} else if (ret < 0 && !target_does_cow) {
error_setg_errno(errp, -ret,
"Couldn't determine the cluster size of the target image, "
@@ -345,16 +346,18 @@ 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 MAX(min_cluster_size, (int64_t)BLOCK_COPY_CLUSTER_SIZE_DEFAULT);
}
- return MAX(BLOCK_COPY_CLUSTER_SIZE_DEFAULT, bdi.cluster_size);
+ return MAX(min_cluster_size,
+ (int64_t)MAX(BLOCK_COPY_CLUSTER_SIZE_DEFAULT,
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 +368,18 @@ 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: %lu > %ld",
+ 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 cd65524e26..ef0bc4dcfe 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);
@@ -432,6 +433,7 @@ static int cbw_open(BlockDriverState *bs, QDict *options,
int flags,
BDRVCopyBeforeWriteState *s = bs->opaque;
BdrvDirtyBitmap *bitmap = NULL;
int64_t cluster_size;
+ uint64_t min_cluster_size = 0;
g_autoptr(BlockdevOptions) full_opts = NULL;
BlockdevOptionsCbw *opts;
int ret;
@@ -476,8 +478,14 @@ 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;
+
+ if (opts->has_min_cluster_size) {
+ min_cluster_size = opts->min_cluster_size;
+ }
+
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,
+ 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 df5e07debd..8fc0a4b234 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -4642,12 +4642,18 @@
# @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
