From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56456) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YpxWL-0004n2-Ny for qemu-devel@nongnu.org; Wed, 06 May 2015 07:29:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YpxWK-00056j-Rk for qemu-devel@nongnu.org; Wed, 06 May 2015 07:29:45 -0400 From: Kevin Wolf Date: Wed, 6 May 2015 13:29:34 +0200 Message-Id: <1430911774-19006-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PATCH] qcow2: Flush pending discards before allocating cluster List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com 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 --- 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