From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50189) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UzXxf-0005uH-Ff for qemu-devel@nongnu.org; Wed, 17 Jul 2013 16:04:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UzXxc-0003n6-F1 for qemu-devel@nongnu.org; Wed, 17 Jul 2013 16:04:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:28831) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UzXxc-0003m9-3e for qemu-devel@nongnu.org; Wed, 17 Jul 2013 16:04:28 -0400 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r6HK4RvF012824 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 17 Jul 2013 16:04:27 -0400 From: Ian Main Date: Wed, 17 Jul 2013 13:04:21 -0700 Message-Id: <1374091462-18391-4-git-send-email-imain@redhat.com> In-Reply-To: <1374091462-18391-1-git-send-email-imain@redhat.com> References: <1374091462-18391-1-git-send-email-imain@redhat.com> Subject: [Qemu-devel] [PATCH V4 3/4] Add backing drive while performing backup. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Ian Main This patch adds the original source drive as a backing drive to our target image so that the target image will appear complete during backup. This is especially useful for SYNC_MODE_NONE as it allows export via NBD to have a complete point-in-time snapshot available for export. Signed-off-by: Ian Main --- block/backup.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/block/backup.c b/block/backup.c index 68abd23..e086e76 100644 --- a/block/backup.c +++ b/block/backup.c @@ -323,6 +323,10 @@ static void coroutine_fn backup_run(void *opaque) hbitmap_free(job->bitmap); + /* Set the target backing drive back to NULL before calling delete or + * it will also delete the underlying drive. */ + target->backing_hd = NULL; + bdrv_iostatus_disable(target); bdrv_delete(target); @@ -362,6 +366,15 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target, return; } + /* Manually set the backing hd to be the backup source drive so + * that all reads done while we are backing up will be passed + * on to the original source drive. This allows reading from the + * image while the backup is in progress, or in the case of + * SYNC_MODE_NONE allows a complete image to be present for export. + * Note that we do this for all modes including SYNC_MODE_TOP as + * even then it allows on-the-fly reading. */ + target->backing_hd = bs; + job->on_source_error = on_source_error; job->on_target_error = on_target_error; job->target = target; -- 1.8.1.4