From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37548) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XlGAm-0004Qh-4M for qemu-devel@nongnu.org; Mon, 03 Nov 2014 06:51:53 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XlGAh-0000CN-Fp for qemu-devel@nongnu.org; Mon, 03 Nov 2014 06:51:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33594) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XlGAh-0000CA-8n for qemu-devel@nongnu.org; Mon, 03 Nov 2014 06:51:43 -0500 From: Stefan Hajnoczi Date: Mon, 3 Nov 2014 11:50:19 +0000 Message-Id: <1415015456-25086-17-git-send-email-stefanha@redhat.com> In-Reply-To: <1415015456-25086-1-git-send-email-stefanha@redhat.com> References: <1415015456-25086-1-git-send-email-stefanha@redhat.com> Subject: [Qemu-devel] [PULL 16/53] 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: Peter Maydell , Zhang Haoyu , Stefan Hajnoczi 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 --- 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); } -- 1.9.3