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authorMax Reitz <mreitz@redhat.com>2015-02-10 15:02:31 -0500
committerMax Reitz <mreitz@redhat.com>2015-03-16 12:10:30 -0400
commit14a58a4e0c2e98a7d9232e1c229a531ca231133b (patch)
treeda3f084b64c003b0c87a915cdd94980cb5742a11 /block
parent2867ce4ab86c77579e94c6bb2b6e44ddfcf67f5d (diff)
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qcow2: Respect new_block in alloc_refcount_block()
When choosing a new place for the refcount table, alloc_refcount_block() tries to infer the number of clusters used so far from its argument cluster_index (which comes from the idea that if any cluster with an index greater than cluster_index was in use, the refcount table would have to be big enough already to describe cluster_index). However, there is a cluster that may be at or after cluster_index, and which is not covered by the refcount structures, and that is the new refcount block new_block. Therefore, it should be taken into account for the blocks_used calculation. Also, because new_block already describes (or is intended to describe) cluster_index, we may not put the new refcount structures there. Signed-off-by: Max Reitz <mreitz@redhat.com> Message-id: 1423598552-24301-2-git-send-email-mreitz@redhat.com Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
Diffstat (limited to 'block')
-rw-r--r--block/qcow2-refcount.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index dc8d186..6cbae1d 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -466,8 +466,20 @@ static int alloc_refcount_block(BlockDriverState *bs,
*/
BLKDBG_EVENT(bs->file, BLKDBG_REFTABLE_GROW);
- /* Calculate the number of refcount blocks needed so far */
- uint64_t blocks_used = DIV_ROUND_UP(cluster_index, s->refcount_block_size);
+ /* Calculate the number of refcount blocks needed so far; this will be the
+ * basis for calculating the index of the first cluster used for the
+ * self-describing refcount structures which we are about to create.
+ *
+ * Because we reached this point, there cannot be any refcount entries for
+ * cluster_index or higher indices yet. However, because new_block has been
+ * allocated to describe that cluster (and it will assume this role later
+ * on), we cannot use that index; also, new_block may actually have a higher
+ * cluster index than cluster_index, so it needs to be taken into account
+ * here (and 1 needs to be added to its value because that cluster is used).
+ */
+ uint64_t blocks_used = DIV_ROUND_UP(MAX(cluster_index + 1,
+ (new_block >> s->cluster_bits) + 1),
+ s->refcount_block_size);
if (blocks_used > QCOW_MAX_REFTABLE_SIZE / sizeof(uint64_t)) {
return -EFBIG;