From ecbda7a22576591a84f44de1be0150faf6001f1c Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 6 May 2015 13:21:51 +0200 Subject: [PATCH] qcow2: Flush pending discards before allocating cluster 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. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf Reviewed-by: Max Reitz --- block/qcow2-refcount.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index f47260b808..83467c31c3 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++) {