From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60651) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y9H0A-0004Rv-5Z for qemu-devel@nongnu.org; Thu, 08 Jan 2015 12:36:30 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Y9Gzp-0006nT-PP for qemu-devel@nongnu.org; Thu, 08 Jan 2015 12:36:06 -0500 Received: from e39.co.us.ibm.com ([32.97.110.160]:44691) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Y9Gzp-0006n2-HN for qemu-devel@nongnu.org; Thu, 08 Jan 2015 12:35:45 -0500 Received: from /spool/local by e39.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 8 Jan 2015 10:35:45 -0700 From: Michael Roth Date: Thu, 8 Jan 2015 11:33:59 -0600 Message-Id: <1420738472-23267-56-git-send-email-mdroth@linux.vnet.ibm.com> In-Reply-To: <1420738472-23267-1-git-send-email-mdroth@linux.vnet.ibm.com> References: <1420738472-23267-1-git-send-email-mdroth@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH 55/88] 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@nongnu.org Cc: qemu-stable@nongnu.org From: Zhang Haoyu 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 Reviewed-by: Paolo Bonzini Message-id: 201410211637596311287@sangfor.com Signed-off-by: Stefan Hajnoczi (cherry picked from commit 3432a1929ee18e08787ce35476abd74f2c93a17c) Signed-off-by: Michael Roth --- block/snapshot.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/block/snapshot.c b/block/snapshot.c index 85c52ff..698e1a1 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); } -- 1.9.1