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block: add subcluster_size field to BlockDriverInfo

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This is going to be used in the subsequent commit as requests alignment
(in particular, during copy-on-read).  This value only makes sense for
the formats which support subclusters (currently QCOW2 only).  If this
field isn't set by driver's own bdrv_get_info() implementation, we
simply set it equal to the cluster size thus treating each cluster as
having a single subcluster.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20230711172553.234055-2-andrey.drobyshev@virtuozzo.com>
This commit is contained in:
Andrey Drobyshev 2023-07-11 20:25:51 +03:00 committed by Stefan Hajnoczi
parent f187609f27
commit c54483b6f4
3 changed files with 13 additions and 0 deletions
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7
block.c
View file

@ -6480,6 +6480,13 @@ int coroutine_fn bdrv_co_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
}
memset(bdi, 0, sizeof(*bdi));
ret = drv->bdrv_co_get_info(bs, bdi);
if (bdi->subcluster_size == 0) {
/*
* If the driver left this unset, subclusters are not supported.
* Then it is safe to treat each cluster as having only one subcluster.
*/
bdi->subcluster_size = bdi->cluster_size;
}
if (ret < 0) {
return ret;
}

1
block/qcow2.c
View file

@ -5197,6 +5197,7 @@ qcow2_co_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
{
BDRVQcow2State *s = bs->opaque;
bdi->cluster_size = s->cluster_size;
bdi->subcluster_size = s->subcluster_size;
bdi->vm_state_offset = qcow2_vm_state_offset(s);
bdi->is_dirty = s->incompatible_features & QCOW2_INCOMPAT_DIRTY;
return 0;

5
include/block/block-common.h
View file

@ -132,6 +132,11 @@ typedef struct BlockZoneWps {
typedef struct BlockDriverInfo {
/* in bytes, 0 if irrelevant */
int cluster_size;
/*
* A fraction of cluster_size, if supported (currently QCOW2 only); if
* disabled or unsupported, set equal to cluster_size.
*/
int subcluster_size;
/* offset at which the VM state can be saved (0 if not possible) */
int64_t vm_state_offset;
bool is_dirty;