From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from [140.186.70.92] (port=36258 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1ODfLG-00016y-49
	for qemu-devel@nongnu.org; Sun, 16 May 2010 11:01:22 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69)
	(envelope-from <stefanha@gmail.com>) id 1ODfLE-0005kO-KH
	for qemu-devel@nongnu.org; Sun, 16 May 2010 11:01:21 -0400
Received: from mail-vw0-f45.google.com ([209.85.212.45]:37722)
	by eggs.gnu.org with esmtp (Exim 4.69)
	(envelope-from <stefanha@gmail.com>) id 1ODfLE-0005kD-HO
	for qemu-devel@nongnu.org; Sun, 16 May 2010 11:01:20 -0400
Received: by vws1 with SMTP id 1so307526vws.4
	for <qemu-devel@nongnu.org>; Sun, 16 May 2010 08:01:19 -0700 (PDT)
MIME-Version: 1.0
In-Reply-To: <20100516132557.GB26872@lst.de>
References: <1273873950-25756-1-git-send-email-stefanha@linux.vnet.ibm.com>
	<20100516132557.GB26872@lst.de>
Date: Sun, 16 May 2010 16:01:19 +0100
Message-ID: <AANLkTilnoYl8sDdbqPVt8J7y1emWgYxZaAyr0_s5TWsp@mail.gmail.com>
Subject: Re: [Qemu-devel] [PATCH] virtio-blk: Avoid zeroing every request
	structure
From: Stefan Hajnoczi <stefanha@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/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: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Christoph Hellwig <hch@lst.de>
Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, qemu-devel@nongnu.org

On Sun, May 16, 2010 at 2:25 PM, Christoph Hellwig <hch@lst.de> wrote:
> On Fri, May 14, 2010 at 10:52:30PM +0100, Stefan Hajnoczi wrote:
>> diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
>> index b05d15e..d270225 100644
>> --- a/hw/virtio-blk.c
>> +++ b/hw/virtio-blk.c
>> @@ -105,8 +105,10 @@ static void virtio_blk_flush_complete(void *opaque,=
 int ret)
>>
>> =A0static VirtIOBlockReq *virtio_blk_alloc_request(VirtIOBlock *s)
>> =A0{
>> - =A0 =A0VirtIOBlockReq *req =3D qemu_mallocz(sizeof(*req));
>> + =A0 =A0VirtIOBlockReq *req =3D qemu_malloc(sizeof(*req));
>> =A0 =A0 =A0req->dev =3D s;
>> + =A0 =A0req->qiov.size =3D 0;
>> + =A0 =A0req->next =3D NULL;
>> =A0 =A0 =A0return req;
>
> Looks good, but you shouldn't even need to initialize req->qiov.size, we
> do this later by calling qemu_iovec_init_external before using it.

virtio_blk_req_complete() uses req->qiov.size and may be called by
virtio_blk_handle_flush() or virtio_blk_handle_scsi() without being
initialized.  It's a little ugly that we use the qiov like that.

Stefan