From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 2/5] dm: implement REQ_FLUSH/FUA support for bio-based dm Date: Wed, 01 Sep 2010 15:56:09 +0200 Message-ID: <4C7E5B79.3080709@kernel.org> References: <1283162296-13650-1-git-send-email-tj@kernel.org> <1283162296-13650-3-git-send-email-tj@kernel.org> <20100901134343.GA25260@redhat.com> <4C7E5A38.9050001@kernel.org> <20100901135433.GB25251@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: jaxboe@fusionio.com, k-ueda@ct.jp.nec.com, j-nomura@ce.jp.nec.com, jamie@shareable.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-raid@vger.kernel.org, hch@lst.de, dm-devel@redhat.com To: Mike Snitzer Return-path: In-Reply-To: <20100901135433.GB25251@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 09/01/2010 03:54 PM, Mike Snitzer wrote: >> It just doesn't happen anymore. If the underlying device doesn't >> support FLUSH/FUA, the block layer simply make those parts noop. IOW, >> it no longer distinguishes between writeback cache which doesn't >> support cache flush at all and writethrough cache. Devices which have >> WB cache w/o flush very difficult to come by these days and there's >> nothing much we can do anyway, so it doesn't make sense to require >> everyone to implement -EOPNOTSUPP. >> >> One scheduled feature is to implement falling back to REQ_FLUSH when >> the device advertises REQ_FUA but fails to process it, but one way or >> the other, the goal is encapsulating REQ_FLUSH/FUA support in block >> layer proper. If FLUSH/FUA can be retried using a different strategy, >> it should be done inside request_queue proper instead of pushing retry >> logic to all its users. > > OK, so maybe add this info to the patch header one of the primary > FLUSH+FUA conversion patches? Sure. Thanks. -- tejun