From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54246) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XgUxv-0007j9-AO for qemu-devel@nongnu.org; Tue, 21 Oct 2014 04:38:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XgUxq-00023Y-PC for qemu-devel@nongnu.org; Tue, 21 Oct 2014 04:38:51 -0400 Received: from [58.251.49.30] (port=53315 helo=mail.sangfor.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XgUxo-0001zZ-Rm for qemu-devel@nongnu.org; Tue, 21 Oct 2014 04:38:46 -0400 Date: Tue, 21 Oct 2014 16:38:01 +0800 From: "Zhang Haoyu" Message-ID: <201410211637596311287@sangfor.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] [PATCH bugfix] snapshot: add bdrv_drain_all() to bdrv_snapshot_delete() to avoid concurrency problem List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel Cc: Kevin Wolf , qemu-stable , Stefan Hajnoczi , Max Reitz If there are still pending i/o while deleting snapshot, because deleting snapshot is done in non-coroutine context, and the pending i/o read/write (bdrv_co_do_rw) is done in coroutine context, so it's possible to cause concurrency problem between above two operations. Add bdrv_drain_all() to bdrv_snapshot_delete() to avoid this problem. Signed-off-by: Zhang Haoyu --- block/snapshot.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/block/snapshot.c b/block/snapshot.c index 85c52ff..ebc386a 100644 --- a/block/snapshot.c +++ b/block/snapshot.c @@ -236,6 +236,10 @@ int bdrv_snapshot_delete(BlockDriverState *bs, error_setg(errp, "snapshot_id and name are both NULL"); return -EINVAL; } + + /* drain all pending i/o before deleting snapshot */ + bdrv_drain_all(); + if (drv->bdrv_snapshot_delete) { return drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp); } -- 1.7.12.4