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: Wed, 17 Dec 2014 00:24:37 -0800 Message-ID: <20141217082437.GA9301@infradead.org> References: <20141215162705.GA23887@quack.suse.cz> <20141215165615.GA19041@infradead.org> <20141215221100.GA4637@mew> <20141216083543.GA32425@infradead.org> <20141216085624.GA25256@mew> <20141217080610.GA20335@infradead.org> <20141217082020.GH22149@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Omar Sandoval , Jan Kara , 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 To: Al Viro Return-path: Content-Disposition: inline In-Reply-To: <20141217082020.GH22149@ZenIV.linux.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Wed, Dec 17, 2014 at 08:20:21AM +0000, Al Viro wrote: > Where the hell would those other references come from? We open the damn > thing in sys_swapon(), never put it into descriptor tables, etc. and > the only reason why we use filp_close() instead of fput() is that we > would miss ->flush() otherwise. > > Said that, why not simply *open* it with O_DIRECT to start with and be done > with that? It's not as if those guys came preopened by caller - swapon(2) > gets a pathname and does opening itself. Oops, should have dug deeper into the code. For some reason I assumed the fd is passed in from userspace. The suggestion from Al is much better, given that we never do normal I/O on the swapfile, just the bmap + direct bio submission which I hope could go away in favor of the direct I/O variant in the long run.