| Message ID | 1353935123-24199-23-git-send-email-benoit@irqsave.net |
|---|---|
| State | New |
| Headers | show |
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c index 8db1b2a..0042742 100644 --- a/block/qcow2-cluster.c +++ b/block/qcow2-cluster.c @@ -699,6 +699,10 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m) qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table); for (i = 0; i < m->nb_clusters; i++) { + if (be64_to_cpu(l2_table[l2_index + i]) == + (cluster_offset + (i << s->cluster_bits))) { + continue; + } /* if two concurrent writes happen to the same unallocated cluster * each write allocates separate cluster and writes data concurrently. * The first one to complete updates l2 table with pointer to its
In the case of a race condition between two writes a l2 entry can be written without QCOW_OFLAG_COPIED before the first write fill it. This patch simply check if the l2 entry has the correct offset without QCOW_OFLAG_COPIED and do nothing. Signed-off-by: Benoit Canet <benoit@irqsave.net> --- block/qcow2-cluster.c | 4 ++++ 1 file changed, 4 insertions(+)