From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([208.118.235.92]:43960)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <paolo.bonzini@gmail.com>) id 1SWlF6-0008Is-Op
	for qemu-devel@nongnu.org; Tue, 22 May 2012 05:19:05 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <paolo.bonzini@gmail.com>) id 1SWlEz-0006Pv-1x
	for qemu-devel@nongnu.org; Tue, 22 May 2012 05:19:00 -0400
Received: from mail-pz0-f45.google.com ([209.85.210.45]:33114)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <paolo.bonzini@gmail.com>) id 1SWlEy-0006PN-Pb
	for qemu-devel@nongnu.org; Tue, 22 May 2012 05:18:52 -0400
Received: by dadv2 with SMTP id v2so9684103dad.4
	for <qemu-devel@nongnu.org>; Tue, 22 May 2012 02:18:50 -0700 (PDT)
Sender: Paolo Bonzini <paolo.bonzini@gmail.com>
Message-ID: <4FBB59F4.90600@redhat.com>
Date: Tue, 22 May 2012 11:18:44 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
MIME-Version: 1.0
References: <1337287349-7664-1-git-send-email-josh.durgin@inktank.com>
In-Reply-To: <1337287349-7664-1-git-send-email-josh.durgin@inktank.com>
Content-Type: text/plain; charset=ISO-8859-15
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH] rbd: hook up cache options
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: Josh Durgin <josh.durgin@inktank.com>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org

Il 17/05/2012 22:42, Josh Durgin ha scritto:
> +     * Fallback to more conservative semantics if setting cache
> +     * options fails. Ignore errors from setting rbd_cache because the
> +     * only possible error is that the option does not exist, and
> +     * librbd defaults to no caching. If write through caching cannot
> +     * be set up, fall back to no caching.
> +     */
> +    if (flags & BDRV_O_NOCACHE) {
> +        rados_conf_set(s->cluster, "rbd_cache", "false");
> +    } else {
> +        rados_conf_set(s->cluster, "rbd_cache", "true");
> +        if (!(flags & BDRV_O_CACHE_WB)) {
> +            r = rados_conf_set(s->cluster, "rbd_cache_max_dirty", "0");
> +            if (r < 0) {
> +                rados_conf_set(s->cluster, "rbd_cache", "false");
> +            }
> +        }
> +    }

Last time I looked at ceph, rbd_flush was not a full flush of the cache;
it only ensured that the pending requests were sent.  So my questions are:

1) has this changed?  does rbd_flush now flush dirty items when
rbd_cache_max_dirty > 0?

2) should the usage of a cache be conditional on LIBRBD_VERSION_CODE >=
LIBRBD_VERSION(0, 1, 1)?

Thanks,

Paolo