From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754338AbYL2MwA (ORCPT ); Mon, 29 Dec 2008 07:52:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752426AbYL2Mvw (ORCPT ); Mon, 29 Dec 2008 07:51:52 -0500 Received: from verein.lst.de ([213.95.11.210]:44632 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752051AbYL2Mvv (ORCPT ); Mon, 29 Dec 2008 07:51:51 -0500 Date: Mon, 29 Dec 2008 13:50:50 +0100 From: Christoph Hellwig To: Jonathan Corbet Cc: LKML , Oleg Nesterov , bfields@fieldses.org, xfs-masters@oss.sgi.com, Andi Kleen , Al Viro , Alan Cox Subject: Re: [xfs-masters] RFC: Fix f_flags races without the BKL Message-ID: <20081229125050.GA22909@lst.de> References: <20081229041352.6bbdf57c@tpl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081229041352.6bbdf57c@tpl> User-Agent: Mutt/1.3.28i X-Spam-Score: 0 () Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 29, 2008 at 04:13:52AM -0700, Jonathan Corbet wrote: > Accesses to the f_flags field have always involved a read-modify-write > operation, and have always been racy in the absence of the BKL. The recent > BKL-removal work made this problem worse, but it has been there for a very > long time. The race is quite small, and, arguably, has never affected > anybody, but it's still worth fixing. > > After pondering for a while, I couldn't come up with anything better than a > global file->f_flags mutex. There's no point in bloating struct file with > a mutex just for this purpose; it's hard to imagine that there will be any > real contention for this lock. What speaks against having on in fs_struct so that it's at least not globally serialized?