Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755378AbaLWJhU (ORCPT ); Tue, 23 Dec 2014 04:37:20 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:60201 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755190AbaLWJhQ (ORCPT ); Tue, 23 Dec 2014 04:37:16 -0500 Date: Tue, 23 Dec 2014 01:37:10 -0800 From: Christoph Hellwig To: Al Viro Cc: Jan Kara , Omar Sandoval , Andrew Morton , Trond Myklebust , David Sterba , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/8] swap: lock i_mutex for swap_writepage direct_IO 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 Content-Disposition: inline In-Reply-To: <20141220065133.GC22149@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.23 (2014-03-12) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@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-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/