From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:58081)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <stefanha@gmail.com>) id 1VT6CG-0001BC-F7
	for qemu-devel@nongnu.org; Mon, 07 Oct 2013 04:29:52 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <stefanha@gmail.com>) id 1VT6C7-0006Ts-UB
	for qemu-devel@nongnu.org; Mon, 07 Oct 2013 04:29:44 -0400
Received: from mail-wi0-x22a.google.com ([2a00:1450:400c:c05::22a]:44427)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <stefanha@gmail.com>) id 1VT6C7-0006Tl-O7
	for qemu-devel@nongnu.org; Mon, 07 Oct 2013 04:29:35 -0400
Received: by mail-wi0-f170.google.com with SMTP id cb5so4940269wib.3
	for <qemu-devel@nongnu.org>; Mon, 07 Oct 2013 01:29:35 -0700 (PDT)
Date: Mon, 7 Oct 2013 10:29:32 +0200
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20131007082932.GC6254@stefanha-thinkpad.redhat.com>
References: <1380029714-5239-1-git-send-email-pl@kamp.de>
	<1380029714-5239-9-git-send-email-pl@kamp.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1380029714-5239-9-git-send-email-pl@kamp.de>
Subject: Re: [Qemu-devel] [PATCHv3 08/20] block: honour BlockLimits in
 bdrv_co_discard
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: Peter Lieven <pl@kamp.de>
Cc: kwolf@redhat.com, stefanha@redhat.com, qemu-devel@nongnu.org, anthony@codemonkey.ws, pbonzini@redhat.com, ronniesahlberg@gmail.com

On Tue, Sep 24, 2013 at 03:35:02PM +0200, Peter Lieven wrote:
> @@ -4245,7 +4250,37 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
>      }
>  
>      if (bs->drv->bdrv_co_discard) {
> -        return bs->drv->bdrv_co_discard(bs, sector_num, nb_sectors);
> +        int max_discard = bs->bl.max_discard ?
> +                          bs->bl.max_discard : MAX_DISCARD_DEFAULT;
> +
> +        while (nb_sectors > 0) {
> +            int ret;
> +            int num = nb_sectors;
> +
> +            /* align request */
> +            if (bs->bl.discard_alignment &&
> +                num >= bs->bl.discard_alignment &&
> +                sector_num % bs->bl.discard_alignment) {
> +                if (num > bs->bl.discard_alignment) {
> +                    num = bs->bl.discard_alignment;
> +                }
> +                num -= sector_num % bs->bl.discard_alignment;
> +            }

Is it always possible to discard at arbitrary sector offsets?