From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:53702)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <stefanha@redhat.com>) id 1V1ZF0-0003Q6-Gt
	for qemu-devel@nongnu.org; Tue, 23 Jul 2013 05:50:49 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <stefanha@redhat.com>) id 1V1ZEx-0007Iv-Cy
	for qemu-devel@nongnu.org; Tue, 23 Jul 2013 05:50:46 -0400
Received: from mx1.redhat.com ([209.132.183.28]:16289)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <stefanha@redhat.com>) id 1V1ZEw-0007Iq-TZ
	for qemu-devel@nongnu.org; Tue, 23 Jul 2013 05:50:43 -0400
Received: from int-mx12.intmail.prod.int.phx2.redhat.com
	(int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25])
	by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r6N9og71001408
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK)
	for <qemu-devel@nongnu.org>; Tue, 23 Jul 2013 05:50:42 -0400
Date: Tue, 23 Jul 2013 11:50:40 +0200
From: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20130723095040.GE20256@stefanha-thinkpad.redhat.com>
References: <1374054136-28741-1-git-send-email-famz@redhat.com>
	<1374054136-28741-7-git-send-email-famz@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1374054136-28741-7-git-send-email-famz@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v2 06/11] xen_disk: simplify blk_disconnect
	with refcnt
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Fam Zheng <famz@redhat.com>
Cc: kwolf@redhat.com, hbrock@redhat.com, qemu-devel@nongnu.org, rjones@redhat.com, imain@redhat.com, pbonzini@redhat.com

On Wed, Jul 17, 2013 at 05:42:11PM +0800, Fam Zheng wrote:
> We call bdrv_attach_dev when initializing whether or not bs is created
> locally, so call bdrv_detach_dev and let the refcnt handle the
> lifecycle.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  hw/block/xen_disk.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
> index 247f32f..ae17acc 100644
> --- a/hw/block/xen_disk.c
> +++ b/hw/block/xen_disk.c
> @@ -910,12 +910,7 @@ static void blk_disconnect(struct XenDevice *xendev)
>      struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev, xendev);
>  
>      if (blkdev->bs) {
> -        if (!blkdev->dinfo) {
> -            /* close/delete only if we created it ourself */
> -            bdrv_close(blkdev->bs);
> -            bdrv_detach_dev(blkdev->bs, blkdev);
> -            bdrv_delete(blkdev->bs);
> -        }
> +        bdrv_detach_dev(blkdev->bs, blkdev);
>          blkdev->bs = NULL;
>      }
>      xen_be_unbind_evtchn(&blkdev->xendev);

This reminds me that bdrv_detach_dev() needs a comment documenting that
it decrements the refcount; bs may be deleted when the function returns
and must not be accessed anymore.