From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 2/8] swap: lock i_mutex for swap_writepage direct_IO Date: Tue, 23 Dec 2014 01:37:10 -0800 Message-ID: <20141223093710.GA29096@infradead.org> References: <20141215162705.GA23887@quack.suse.cz> <20141215165615.GA19041@infradead.org> <20141220065133.GC22149@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , Omar Sandoval , Andrew Morton , Trond Myklebust , David Sterba , linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Al Viro Return-path: Content-Disposition: inline In-Reply-To: <20141220065133.GC22149-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org On Sat, Dec 20, 2014 at 06:51:33AM +0000, Al Viro wrote: > > The problem is that the use of ->direct_IO by the swap code is a gross > > layering violation. ->direct_IO is a callback for the filesystem, and > > the swap code need to call ->read_iter instead of ->readpage and > > ->write_tier instead of ->direct_IO, and leave the locking to the > > filesystem. > > The thing is, ->read_iter() and ->write_iter() might decide to fall back to > buffered IO path. XFS is unusual in that respect - there O_DIRECT ends up > with short write in such case. Other filesystems, OTOH... We'll just need a ->swap_activate method that makes sure we really do direct I/O. For all filesystems currently suporting swap just checking that all blocks are allocated (as the ->bmap path already does) should be enough. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html