From mboxrd@z Thu Jan 1 00:00:00 1970 From: Amir Goldstein Subject: Re: [Lsf] Preliminary Agenda and Activities for LSF Date: Fri, 1 Apr 2011 20:26:13 -0700 Message-ID: References: <1301373398.2590.20.camel@mulgrave.site> <4D91BF90.8070909@redhat.com> <1301445210.2731.14.camel@mingming-laptop> <20110330021742.GL3008@dastard> <4D9313E2.6080006@gmail.com> <20110401151907.GG21075@thunk.org> <20110401214652.GC25355@noexit> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Theodore Tso , Ric Wheeler , Dave Chinner , lsf@lists.linux-foundation.org, "linux-scsi@vger.kernel.org" , James Bottomley , device-mapper development , linux-fsdevel , Ric Wheeler , Yongqiang Yang To: Joel Becker Return-path: In-Reply-To: <20110401214652.GC25355@noexit> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Fri, Apr 1, 2011 at 2:46 PM, Joel Becker wrote: > On Fri, Apr 01, 2011 at 09:30:04AM -0700, Amir Goldstein wrote: >> when writing DIO to indirect mapped file holes, we fall back to buff= ered write >> (so we won't expose stale data in the case of a crash) concurrent DI= O reads >> to that file (before data writeback) can expose stale data. right? >> do you consider this case mixing buffered and DIO access? >> do you consider that as a problem? > > =A0 =A0 =A0 =A0I do not consider this 'mixing', nor do I consider it = a problem. > ocfs2 does exactly this for holes, unwritten extents, and CoW. =A0It = does > not violate the user's expectation that the data will be on disk when > the write(2) returns. > =A0 =A0 =A0 =A0Falling back to buffered on read(2) is a different sto= ry; the > caller wants the current state of the disk block, not five minutes ag= o. > So we can't do that. =A0But we also don't need to. the issue is with DIO read exposing uninitialized data on disk is a security issue. it's not about giving the read what is expects to see. > =A0 =A0 =A0 =A0O_DIRECT users that are worried about any possible spa= ce usage in > the page cache have already pre-allocated their disk blocks and don't > get here. > > Joel > > -- > > "Under capitalism, man exploits man. =A0Under Communism, it's just > =A0 the opposite." > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 - Joh= n Kenneth Galbraith > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0http://www.jlbec.org/ > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0jlbec@evilplan.org > -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html