Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751557AbaLPIfu (ORCPT ); Tue, 16 Dec 2014 03:35:50 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:35885 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750899AbaLPIfs (ORCPT ); Tue, 16 Dec 2014 03:35:48 -0500 Date: Tue, 16 Dec 2014 00:35:43 -0800 From: Christoph Hellwig To: Omar Sandoval Cc: Jan Kara , Alexander Viro , 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: <20141216083543.GA32425@infradead.org> References: <20141215162705.GA23887@quack.suse.cz> <20141215165615.GA19041@infradead.org> <20141215221100.GA4637@mew> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141215221100.GA4637@mew> 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 Mon, Dec 15, 2014 at 02:11:00PM -0800, Omar Sandoval wrote: > Ok, I got the swap code working with ->read_iter/->write_iter without > too much trouble. I wanted to double check before I submit if there's > any gotchas involved with adding the O_DIRECT flag to a file pointer > after it has been opened -- swapon opens the swapfile before we know if > we're using the SWP_FILE infrastructure, and we need to add O_DIRECT so > ->{read,write}_iter use direct I/O, but we can't add O_DIRECT to the > original open without excluding filesystems that support the old bmap > path but not direct I/O. In general just adding O_DIRECT is a problem. However given that the swap file is locked against any other access while in use it seems ok in this particular case. Just make sure to clear it on swapoff, and write a detailed comment explaining the situation. -- 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/