From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH UPDATED 4/5] dm: implement REQ_FLUSH/FUA support for request-based dm Date: Wed, 01 Sep 2010 13:20:08 +0200 Message-ID: <4C7E36E8.2000705@kernel.org> References: <1283162296-13650-1-git-send-email-tj@kernel.org> <1283162296-13650-5-git-send-email-tj@kernel.org> <20100830132836.GB5283@redhat.com> <4C7BB932.1070405@kernel.org> <4C7BD202.4040700@kernel.org> <20100830194731.GA10702@redhat.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Mikulas Patocka Cc: dm-devel@redhat.com, Mike Snitzer List-Id: dm-devel.ids Hello, On 09/01/2010 12:31 PM, Mikulas Patocka wrote: > My recommended approach to this (on non-request-based dm) is to simply let > the current barrier infrastructure be as it is --- you don't need to > change it now, you can simply map FUA write to barrier write and FLUSH to > zero-data barrier --- and it won't cause any data corruption. It will just > force unneeded I/O queue draining. > > Once FLUSH+FUA interface is finalized and committed upstream, we can > remove that I/O queue draining from dm to improve performance. Unfortunately, it doesn't work that way. The current dm implementation depends on block layer holding the queue while a barrier sequence is in progress which the new implementation doesn't do anymore (the whole point of this conversion BTW). Thanks. -- tejun