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 <address@hidden>
---
block/qcow2.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/block/qcow2.c b/block/qcow2.c
index a6012dc..c197ff3 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -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;
}