From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:33787)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <paolo.bonzini@gmail.com>) id 1Zvi1c-00074A-66
	for qemu-devel@nongnu.org; Mon, 09 Nov 2015 03:42:05 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <paolo.bonzini@gmail.com>) id 1Zvi1b-0002Z0-9T
	for qemu-devel@nongnu.org; Mon, 09 Nov 2015 03:42:04 -0500
Sender: Paolo Bonzini <paolo.bonzini@gmail.com>
References: <1447039178-17208-1-git-send-email-arei.gonglei@huawei.com>
From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <56405C50.1010600@redhat.com>
Date: Mon, 9 Nov 2015 09:41:52 +0100
MIME-Version: 1.0
In-Reply-To: <1447039178-17208-1-git-send-email-arei.gonglei@huawei.com>
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH v2] virtio-blk: trivial code optimization
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: arei.gonglei@huawei.com, qemu-devel@nongnu.org
Cc: stefanha@redhat.com, qemu-block@nongnu.org



On 09/11/2015 04:19, arei.gonglei@huawei.com wrote:
> +             * 1. requests are not sequential
> +             * 2. merge would exceed maximum number of IOVs
> +             * 3. merge would exceed maximum transfer length of backend device
> +             */
> +            if (sector_num + nb_sectors != req->sector_num ||
> +                niov > IOV_MAX - req->qiov.niov ||
> +                req->qiov.size / BDRV_SECTOR_SIZE + nb_sectors > max_xfer_len) {

Hi Gonglei,

the third condition should also be changed to "new > max - old".

Thanks,

Paolo