Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755003Ab0HQNNw (ORCPT ); Tue, 17 Aug 2010 09:13:52 -0400 Received: from verein.lst.de ([213.95.11.210]:38332 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752380Ab0HQNNu (ORCPT ); Tue, 17 Aug 2010 09:13:50 -0400 Date: Tue, 17 Aug 2010 15:13:09 +0200 From: Christoph Hellwig To: Tejun Heo Cc: Mike Snitzer , jaxboe@fusionio.com, linux-fsdevel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, hch@lst.de, James.Bottomley@suse.de, tytso@mit.edu, chris.mason@oracle.com, swhiteho@redhat.com, konishi.ryusuke@lab.ntt.co.jp, dm-devel@redhat.com, vst@vlnb.net, jack@suse.cz, rwheeler@redhat.com, hare@suse.de, neilb@suse.de, rusty@rustcorp.com.au, mst@redhat.com, Tejun Heo Subject: Re: [PATCH 5/5] dm: implement REQ_FLUSH/FUA support Message-ID: <20100817131309.GA2963@lst.de> References: <1281977523-19335-1-git-send-email-tj@kernel.org> <1281977523-19335-6-git-send-email-tj@kernel.org> <20100816190203.GA22299@redhat.com> <4C6A5780.2090100@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C6A5780.2090100@kernel.org> User-Agent: Mutt/1.3.28i X-Spam-Score: 0 () Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 942 Lines: 20 On Tue, Aug 17, 2010 at 11:33:52AM +0200, Tejun Heo wrote: > > That logic wasn't just about retries (at least not in the latest > > kernel). With commit 708e929513502fb0 the -EOPNOTSUPP checking also > > serves to optimize the barrier+discard case (when discards aren't > > supported). > > With the patch applied, there's no second flush. Those requests would > now be REQ_FLUSH + REQ_DISCARD. The first can't be avoided anyway and > there won't be the second flush to begin with, so I don't think this > worsens anything. In fact the pre-flush is completely superflous for discards, but that's a separate discussion and should not be changed as part of this patchset but rather explicitly. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/