From: Jan Kara Subject: Re: [RFC PATCH 0/7] dax, ext4: Synchronous page faults Date: Tue, 1 Aug 2017 13:26:03 +0200 Message-ID: <20170801112603.GG4215@quack2.suse.cz> References: <20170727131245.28279-1-jack@suse.cz> <20170727215713.GA22000@linux.intel.com> <20170728093821.GB29433@quack2.suse.cz> <20170801110241.GE6742@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Jan Kara , linux-nvdimm , Dave Chinner , linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andy Lutomirski , Linux FS Devel , "linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" To: Christoph Hellwig Return-path: Content-Disposition: inline In-Reply-To: <20170801110241.GE6742-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" List-Id: linux-ext4.vger.kernel.org On Tue 01-08-17 04:02:41, Christoph Hellwig wrote: > On Fri, Jul 28, 2017 at 11:38:21AM +0200, Jan Kara wrote: > > Well, you are right I can make the implementation work with struct file > > flag as well - let's call it O_DAXDSYNC. However there are filesystem > > operations where you may need to answer question: Is there any fd with > > O_DAXDSYNC open against this inode (for operations that change file offset > > -> block mapping)? And in that case inode flag is straightforward while > > file flag is a bit awkward (you need to implement counter of fd's with that > > flag in the inode). > > We can still keep and inode flag as the internal implementation > detail. As mentioned earlier the right flag to control behavior > of a mapping is an mmap flag. And the initial naive implementation > would simply mark the inode as sync once the first MAP_SYNC open happens > on it. We could then move to more precise tracking if/when needed. OK, makes sense and I like the MAP_SYNC proposal. I'll change it in my implementation. Honza -- Jan Kara SUSE Labs, CR