From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: Re: [PATCH] ext4: introduce per-inode DAX flag Date: Fri, 25 Aug 2017 12:28:37 -0400 Message-ID: <20170825162837.urica6l4eamu356w@thunk.org> References: <20170807121212.nuiho4afmdjf5vsd@rh_laptop> <20170808090016.lxfbcrhoybmyfvlc@rh_laptop> <20170811100147.GB7064@infradead.org> <20170811121132.bj5y77scrvkgy7uo@rh_laptop> <20170811125849.GA15300@infradead.org> <20170811134130.o46y5jpekrpj5qvw@rh_laptop> <20170824182057.amdirlrbugezrahy@thunk.org> <20170825075415.GA748@infradead.org> <20170825151445.ycf5xomoxvebgaez@thunk.org> <20170825154032.GA1827@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org, Lukas Czerner , linux-xfs@vger.kernel.org To: Christoph Hellwig Return-path: Received: from imap.thunk.org ([74.207.234.97]:54864 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934326AbdHYQ2l (ORCPT ); Fri, 25 Aug 2017 12:28:41 -0400 Content-Disposition: inline In-Reply-To: <20170825154032.GA1827@infradead.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Aug 25, 2017 at 08:40:32AM -0700, Christoph Hellwig wrote: > On Fri, Aug 25, 2017 at 11:14:45AM -0400, Theodore Ts'o wrote: > > > I don't know of anyone that actually uses the flag. If someone did > > > that would probably run into problems like changing that changing it > > > on a file that's currently mmaped would crash an burn badly. > > > > Crash and burn meaning the *kernel* will crash and burn? Or will data > > be damaged? > > > > Given that, maybe XFS should withdraw support for the DAX and hope no > > one is actually using it? > > Nah, -o dax works very well. It's just the flag instead of the -o dax > option or rather switching it on a mapped file will probably be very dangerous. Sorry, I was suggested XFS withdrawing support for the pre-file dax flag. I thought part of the argument for why ext4 should accept this patch is that XFS already has the per-file DAX flag? - Ted