From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753998Ab2DYPUq (ORCPT ); Wed, 25 Apr 2012 11:20:46 -0400 Received: from fieldses.org ([174.143.236.118]:51410 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752620Ab2DYPUp (ORCPT ); Wed, 25 Apr 2012 11:20:45 -0400 Date: Wed, 25 Apr 2012 11:20:41 -0400 From: "J. Bruce Fields" To: Al Viro Cc: Linus Torvalds , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [git pull] vfs and fs fixes Message-ID: <20120425152041.GA751@fieldses.org> References: <20120417052511.GU6589@ZenIV.linux.org.uk> <20120417180129.GW6589@ZenIV.linux.org.uk> <20120417182825.GX6589@ZenIV.linux.org.uk> <20120417211419.GC27426@fieldses.org> <20120417234423.GY6589@ZenIV.linux.org.uk> <20120418215238.GA11959@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120418215238.GA11959@fieldses.org> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 18, 2012 at 05:52:38PM -0400, J. Bruce Fields wrote: > On Wed, Apr 18, 2012 at 12:44:24AM +0100, Al Viro wrote: > > On Tue, Apr 17, 2012 at 03:08:26PM -0700, Linus Torvalds wrote: > > > > Or I could increment that counter for all the conflicting operations and > > > > rely on it instead of the i_mutex. ?I was trying to avoid adding > > > > something like that (an inc, a dec, another error path) to every > > > > operation. ?And hoping to avoid adding another field to struct inode. > > > > Oh well. > > > > > > We could just say that we can do a double inode lock, but then > > > standardize on the order. And the only sane order is comparing inode > > > pointers, not inode numbers like ext4 apparently does. > > > > > > With a standard order, I don't think it would be at all wrong to just > > > take the inode lock on rename. > > > > In principle, yes, but have you tried to grep for i_mutex? Note that > > we have *another* place where multiple ->i_mutex might be held on > > non-directories (and unless I'm missing something, ext4 move_extent.c > > stuff doesn't play well with it): quota writes. Which can, AFAICS, > > happen while write(2) is holding ->i_mutex on a regular file. So > > it's not _that_ easy - we want something like "and quota file is goes > > last" > > So the idea would be to always take the i_mutex on non-quota files > before taking it on quota files? > > I tried pulling the ext4 thing into fs/inode.c, modifying the order to > do that, and then doing the rename change on top of that. Patches follow, with the ordering change at the end. And a documentation fix that I suppose could go in whenever. --b.