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qcow2: Add subcluster-related fields to BDRVQcow2State

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This patch adds the following new fields to BDRVQcow2State:

- subclusters_per_cluster: Number of subclusters in a cluster
- subcluster_size: The size of each subcluster, in bytes
- subcluster_bits: No. of bits so 1 << subcluster_bits = subcluster_size

Images without subclusters are treated as if they had exactly one
subcluster per cluster (i.e. subcluster_size = cluster_size).

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <55bfeac86b092fa2c9d182a95cbeb479ff7eca4f.1594396418.git.berto@igalia.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Alberto Garcia 2020-07-10 18:12:51 +02:00 committed by Max Reitz
parent a3c7d91625
commit d0346b5591
2 changed files with 10 additions and 0 deletions
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5
block/qcow2.c
View File

@ -1444,6 +1444,11 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
}
}
s->subclusters_per_cluster =
has_subclusters(s) ? QCOW_EXTL2_SUBCLUSTERS_PER_CLUSTER : 1;
s->subcluster_size = s->cluster_size / s->subclusters_per_cluster;
s->subcluster_bits = ctz32(s->subcluster_size);
/* Check support for various header values */
if (header.refcount_order > 6) {
error_setg(errp, "Reference count entry width too large; may not "

5
block/qcow2.h
View File

@ -78,6 +78,8 @@
/* The cluster reads as all zeros */
#define QCOW_OFLAG_ZERO (1ULL << 0)
#define QCOW_EXTL2_SUBCLUSTERS_PER_CLUSTER 32
#define MIN_CLUSTER_BITS 9
#define MAX_CLUSTER_BITS 21
@ -295,6 +297,9 @@ typedef struct BDRVQcow2State {
int cluster_bits;
int cluster_size;
int l2_slice_size;
int subcluster_bits;
int subcluster_size;
int subclusters_per_cluster;
int l2_bits;
int l2_size;
int l1_size;