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qcow2: Fix write_zeroes with partially allocated backing file cluster

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In order to correctly check whether a given cluster is read as zero, we
don't only need to check whether bdrv_get_block_status_above() sets
BDRV_BLOCK_ZERO, but also if all sectors for the whole cluster have the
same status.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Denis V. Lunev <den@openvz.org>
This commit is contained in:
Kevin Wolf 2016-05-17 18:42:23 +02:00
parent f575f145f4
commit 5efdf53227
1 changed files with 2 additions and 1 deletions
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3
block/qcow2.c
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@ -2412,7 +2412,7 @@ static bool is_zero_cluster(BlockDriverState *bs, int64_t start)
BlockDriverState *file;
int64_t res = bdrv_get_block_status_above(bs, NULL, start,
s->cluster_sectors, &nr, &file);
return res >= 0 && (res & BDRV_BLOCK_ZERO);
return res >= 0 && (res & BDRV_BLOCK_ZERO) && nr == s->cluster_sectors;
}
static bool is_zero_cluster_top_locked(BlockDriverState *bs, int64_t start)
@ -2423,6 +2423,7 @@ static bool is_zero_cluster_top_locked(BlockDriverState *bs, int64_t start)
int ret;
ret = qcow2_get_cluster_offset(bs, start << BDRV_SECTOR_BITS, &nr, &off);
assert(nr == s->cluster_sectors);
return ret == QCOW2_CLUSTER_UNALLOCATED || ret == QCOW2_CLUSTER_ZERO;
}