From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:35669)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <stefanha@gmail.com>) id 1WnouE-0003OV-J2
	for qemu-devel@nongnu.org; Fri, 23 May 2014 08:49:11 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <stefanha@gmail.com>) id 1Wnou4-0005me-5n
	for qemu-devel@nongnu.org; Fri, 23 May 2014 08:49:01 -0400
Received: from mail-ee0-x22b.google.com ([2a00:1450:4013:c00::22b]:57348)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <stefanha@gmail.com>) id 1Wnou3-0005mW-Uu
	for qemu-devel@nongnu.org; Fri, 23 May 2014 08:48:52 -0400
Received: by mail-ee0-f43.google.com with SMTP id d17so3611710eek.16
	for <qemu-devel@nongnu.org>; Fri, 23 May 2014 05:48:51 -0700 (PDT)
Date: Fri, 23 May 2014 14:46:31 +0200
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20140523124631.GA5990@stefanha-thinkpad.hitronhub.home>
References: <1400815403-7719-1-git-send-email-famz@redhat.com>
	<1400815403-7719-8-git-send-email-famz@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1400815403-7719-8-git-send-email-famz@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 7/7] block: Add backing_blocker in
 BlockDriverState
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: Kevin Wolf <kwolf@redhat.com>, Benoit Canet <benoit@irqsave.net>, jcody@redhat.com, qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>

On Fri, May 23, 2014 at 11:23:23AM +0800, Fam Zheng wrote:
> This makes use of op_blocker and blocks all the operations except for
> commit target, on each BlockDriverState->backing_hd.
> 
> The asserts for op_blocker in bdrv_swap are removed because with this
> change, the target of block commit has at least the backing blocker of
> its child, so the assertion is not true. Callers should do their check.
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  block.c                   | 22 ++++++++++++++++++----
>  block/mirror.c            |  2 +-
>  include/block/block_int.h |  3 +++
>  3 files changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/block.c b/block.c
> index 91c866c..b5aeca2 100644
> --- a/block.c
> +++ b/block.c
> @@ -1097,14 +1097,29 @@ fail:
>  void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd)
>  {
>  
> +    if (bs->backing_hd) {
> +        assert(bs->backing_blocker);
> +        bdrv_op_unblock_all(bs->backing_hd, bs->backing_blocker);
> +    } else if (backing_hd) {
> +        error_setg(&bs->backing_blocker,
> +                   "device is used as backing hd of '%s'",
> +                   bs->device_name);
> +    }
> +
>      bs->backing_hd = backing_hd;
>      if (!backing_hd) {
> +        error_free(bs->backing_blocker);

bs->backing_block = NULL;

...to make the assert(bs->backing_blocker) above more useful.