From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([208.118.235.92]:52889)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <stefanha@gmail.com>) id 1US16K-0007NU-Mx
	for qemu-devel@nongnu.org; Tue, 16 Apr 2013 04:18:54 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <stefanha@gmail.com>) id 1US16F-0001Yo-VR
	for qemu-devel@nongnu.org; Tue, 16 Apr 2013 04:18:52 -0400
Received: from mail-wi0-x233.google.com ([2a00:1450:400c:c05::233]:60866)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <stefanha@gmail.com>) id 1US16F-0001Ya-Mg
	for qemu-devel@nongnu.org; Tue, 16 Apr 2013 04:18:47 -0400
Received: by mail-wi0-f179.google.com with SMTP id hn17so185127wib.12
	for <qemu-devel@nongnu.org>; Tue, 16 Apr 2013 01:18:46 -0700 (PDT)
Date: Tue, 16 Apr 2013 10:18:43 +0200
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130416081843.GD6308@stefanha-thinkpad.redhat.com>
References: <1365852442-28941-5-git-send-email-namei.unix@gmail.com>
	<1366042504-18354-1-git-send-email-namei.unix@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1366042504-18354-1-git-send-email-namei.unix@gmail.com>
Subject: Re: [Qemu-devel] [PATCH v5] sheepdog: add discard/trim support for
 sheepdog
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: Liu Yuan <namei.unix@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>, sheepdog@lists.wpkg.org, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>

On Tue, Apr 16, 2013 at 12:15:04AM +0800, Liu Yuan wrote:
> @@ -727,6 +730,20 @@ static void coroutine_fn aio_read_response(void *opaque)
>              rsp.result = SD_RES_SUCCESS;
>          }
>          break;
> +    case AIOCB_DISCARD_OBJ:
> +        switch (rsp.result) {
> +        case SD_RES_INVALID_PARMS:
> +            error_report("you are running the old sheep that doesn't support "
> +                         "discard command.\n");

error_report() does not need '\n'.

The recently added ssh block driver has a similar case when the server
does not support fsync.  It does the following:

1. Print the error message once only per volume, avoid filling up logs
   on the host.
2. Include details of the volume/server in case the users is connected
   to multiple volumes/servers.  This allows them to figure out which
   server is outdated.

This makes the error messages safe from denial-of-service and includes
more useful information.