From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay1.corp.sgi.com [137.38.102.111]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with ESMTP id mBO2M1Hj032046 for ; Tue, 23 Dec 2008 20:22:01 -0600 Message-ID: <49519D18.3080307@sgi.com> Date: Wed, 24 Dec 2008 13:23:20 +1100 From: Lachlan McIlroy MIME-Version: 1.0 Subject: Re: [Fwd: [PATCH] Fix race in xfs_write() between direct and buffered I/O with DMAPI] References: <493779B1.3010703@sgi.com> <20081208225125.GA15647@infradead.org> <493DFDBD.7060909@sgi.com> <20081209092240.GA23915@infradead.org> <20081222085311.GB24795@infradead.org> <49503378.2080508@sgi.com> <20081223084013.GA7604@infradead.org> <49518BF2.2020709@sgi.com> <87wsdq727n.fsf@cxhome.ath.cx> In-Reply-To: <87wsdq727n.fsf@cxhome.ath.cx> Reply-To: lachlan@sgi.com List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Niv Sardi Cc: Christoph Hellwig , xfs-oss Niv Sardi wrote: > Lachlan McIlroy writes: > >> Christoph Hellwig wrote: >> >>> On Tue, Dec 23, 2008 at 11:40:24AM +1100, Lachlan McIlroy wrote: >>>> Christoph Hellwig wrote: >>>>> Do you need more input on this one? >>>> Actually I just might. Based on your last reponse I wasn't sure if >>>> you wanted me to make further changes. >>> Well, my reponse was that I think we could do it more effecient, but the >>> patch still looks correct to me. >> Okay great. I'll check it in and we can improve it later when I understand >> what you meant! >> >>>> Then I got side-tracked wondering >>>> why we even have the 'goto retry' in the dmapi post event - why retry the >>>> write if we get ENOSPC when we don't if dmapi is not enabled? Could the >>>> write get stuck in an infinite loop? >>> We only retry on ENOSPC if the dmapi nospace even is enabled, or am I >>> missing something? >> I don't think you're missing anything here. I don't understand how the >> DMAPI stuff works but I imagined the event was there to indicate that the >> write failed but what I don't understand is why that justifies a retry. >> Is there something about DMAPI that needs the write to succeed? > > yes > > http://www.opengroup.org/onlinepubs/9657099/chap3.htm#tagcjh_04_02_04 Oh no, not the DMAPI spec - I don't want to go there! Sounds like the XFS_SEND_NAMESP() event can choose to fail and that will prevent an infinite loop. Thanks Niv. _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs