From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34709) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d5auq-0002o2-Op for qemu-devel@nongnu.org; Tue, 02 May 2017 12:44:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d5auq-0000kh-0T for qemu-devel@nongnu.org; Tue, 02 May 2017 12:44:44 -0400 Date: Wed, 3 May 2017 00:44:35 +0800 From: Fam Zheng Message-ID: <20170502164435.GA8307@lemon.lan> References: <20170502163558.7611-1-famz@redhat.com> <20170502163558.7611-19-famz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170502163558.7611-19-famz@redhat.com> Subject: Re: [Qemu-devel] [PATCH v17 18/23] block: Reuse bs as backing hd for drive-backup sync=none List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , qemu-block@nongnu.org, Max Reitz , eblake@redhat.com, qemu-stable@nongnu.org On Wed, 05/03 00:35, Fam Zheng wrote: > Opening the backing image for the second time is bad, especially here > when it is also in use as the active image as the source. The > drive-backup job itself doesn't read from target->backing for COW, > instead it gets data from the write notifier, so it's not a big problem. > However, exporting the target to NBD etc. won't work, because of the > likely stale metadata cache. > > Use BDRV_O_NO_BACKING in this case and manually set up the backing > BdrvChild. > > Cc: qemu-stable@nongnu.org > Signed-off-by: Fam Zheng Actually Cc qemu-stable. (git-publish does unified Cc for each patch in a whole series, hence the noise. Sorry.) Fam