From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58859) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZaUCf-0004Mr-0L for qemu-devel@nongnu.org; Fri, 11 Sep 2015 15:41:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZaUCe-0005eO-62 for qemu-devel@nongnu.org; Fri, 11 Sep 2015 15:41:44 -0400 From: Kevin Wolf Date: Fri, 11 Sep 2015 21:41:03 +0200 Message-Id: <1442000463-22777-24-git-send-email-kwolf@redhat.com> In-Reply-To: <1442000463-22777-1-git-send-email-kwolf@redhat.com> References: <1442000463-22777-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PULL 23/23] qcow2: Make qcow2_alloc_bytes() more explicit 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 From: Max Reitz In case of -EAGAIN returned by update_refcount(), we should discard the cluster offset we were trying to allocate and request a new one, because in theory that old offset might now be taken by a refcount block. In practice, this was not the case due to update_refcount() generally returning strictly monotonic increasing cluster offsets. However, this behavior is not set in stone, and it is also not obvious when looking at qcow2_alloc_bytes() alone, so we should not rely on it. Reported-by: Kevin Wolf Signed-off-by: Max Reitz Signed-off-by: Kevin Wolf --- block/qcow2-refcount.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 5f67798..3579c4d 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -949,11 +949,17 @@ int64_t qcow2_alloc_bytes(BlockDriverState *bs, int size) if (!offset || ROUND_UP(offset, s->cluster_size) != new_cluster) { offset = new_cluster; + free_in_cluster = s->cluster_size; + } else { + free_in_cluster += s->cluster_size; } } assert(offset); ret = update_refcount(bs, offset, size, 1, false, QCOW2_DISCARD_NEVER); + if (ret < 0) { + offset = 0; + } } while (ret == -EAGAIN); if (ret < 0) { return ret; -- 1.8.3.1