Before a freed cluster can be reused, pending discards for this cluster
must be processed.
The original assumption was that this was not a problem because discards
are only cached during discard/write zeroes operations, which are
synchronous so that no concurrent write requests can cause cluster
allocations.
However, the discard/write zeroes operation itself can allocate a new L2
table (and it has to in order to put zero flags there), so make sure we
can cope with the situation.
This fixes https://bugs.launchpad.net/bugs/1349972.
Signed-off-by: Kevin Wolf kw...@redhat.com
---
block/qcow2-refcount.c | 5 +
1 file changed, 5 insertions(+)
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index f47260b..83467c3 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -833,6 +833,11 @@ static int64_t alloc_clusters_noref(BlockDriverState *bs,
uint64_t size)
uint64_t i, nb_clusters, refcount;
int ret;
+/* We can't allocate clusters if they may still be queued for discard. */
+if (s-cache_discards) {
+qcow2_process_discards(bs, 0);
+}
+
nb_clusters = size_to_clusters(s, size);
retry:
for(i = 0; i nb_clusters; i++) {
--
1.8.3.1
