qcow2_alloc_bytes() may reuse a cluster multiple times, in which case
the refcount is increased accordingly. However, if this would lead to an
overflow the function should instead just not reuse this cluster and
allocate a new one.
Signed-off-by: Max Reitz <mre...@redhat.com>
Reviewed-by: Eric Blake <ebl...@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
---
block/qcow2-refcount.c | 31 ++++++++++++++++++++++++++++++-
1 file changed, 30 insertions(+), 1 deletion(-)
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index db81647..fd28a13 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -780,9 +780,11 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
BDRVQcowState *s = bs->opaque;
int64_t offset, cluster_offset, new_cluster;
int free_in_cluster, ret;
+ uint64_t refcount;
BLKDBG_EVENT(bs->file, BLKDBG_CLUSTER_ALLOC_BYTES);
assert(size > 0 && size <= s->cluster_size);
+ redo:
if (s->free_byte_offset == 0) {
offset = qcow2_alloc_clusters(bs, s->cluster_size);
if (offset < 0) {
@@ -790,12 +792,25 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
}
s->free_byte_offset = offset;
}
- redo:
+
free_in_cluster = s->cluster_size -
offset_into_cluster(s, s->free_byte_offset);
if (size <= free_in_cluster) {
/* enough space in current cluster */
offset = s->free_byte_offset;
+
+ if (offset_into_cluster(s, offset) != 0) {
+ /* We will have to increase the refcount of this cluster; if the
+ * maximum has been reached already, this cluster cannot be used */
+ ret = qcow2_get_refcount(bs, offset >> s->cluster_bits, &refcount);
+ if (ret < 0) {
+ return ret;
+ } else if (refcount == s->refcount_max) {
+ s->free_byte_offset = 0;
+ goto redo;
+ }
+ }
+
s->free_byte_offset += size;
free_in_cluster -= size;
if (free_in_cluster == 0)
@@ -816,6 +831,20 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size)
if ((cluster_offset + s->cluster_size) == new_cluster) {
/* we are lucky: contiguous data */
offset = s->free_byte_offset;
+
+ /* Same as above: In order to reuse the cluster, the refcount has
to
+ * be increased; if that will not work, we are not so lucky after
+ * all */
+ ret = qcow2_get_refcount(bs, offset >> s->cluster_bits, &refcount);
+ if (ret < 0) {
+ qcow2_free_clusters(bs, new_cluster, s->cluster_size,
+ QCOW2_DISCARD_NEVER);
+ return ret;
+ } else if (refcount == s->refcount_max) {
+ s->free_byte_offset = offset;
+ goto redo;
+ }
+
ret = qcow2_update_cluster_refcount(bs, offset >> s->cluster_bits,
1, false, QCOW2_DISCARD_NEVER);
if (ret < 0) {
--
1.9.3
