From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756172AbZBIRtR (ORCPT ); Mon, 9 Feb 2009 12:49:17 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752747AbZBIRtF (ORCPT ); Mon, 9 Feb 2009 12:49:05 -0500 Received: from e6.ny.us.ibm.com ([32.97.182.146]:41379 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751724AbZBIRtD (ORCPT ); Mon, 9 Feb 2009 12:49:03 -0500 Subject: Re: [cgroup or VFS ?] WARNING: at fs/namespace.c:636 mntput_no_expire+0xac/0xf2() From: Dave Hansen To: Al Viro Cc: Andrew Morton , containers@lists.osdl.org, Paul Menage , LKML , Arjan van de Ven In-Reply-To: <20090209093414.GU28946@ZenIV.linux.org.uk> References: <49617D35.4040805@cn.fujitsu.com> <20090209004046.3ce1dde0.akpm@linux-foundation.org> <20090209093414.GU28946@ZenIV.linux.org.uk> Content-Type: text/plain Date: Mon, 09 Feb 2009 09:48:59 -0800 Message-Id: <1234201739.20090.194.camel@nimitz> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2009-02-09 at 09:34 +0000, Al Viro wrote: > On Mon, Feb 09, 2009 at 12:40:46AM -0800, Andrew Morton wrote: > > > Thread 1: > > > for ((; ;)) > > > { > > > mount -t cgroup -o cpuset xxx /mnt > /dev/null 2>&1 > > > mkdir /mnt/0 > /dev/null 2>&1 > > > rmdir /mnt/0 > /dev/null 2>&1 > > > umount /mnt > /dev/null 2>&1 > > > } > > > > > > Thread 2: > > > { > > > mount -t cpuset xxx /mnt > /dev/null 2>&1 > > > umount /mnt > /dev/null 2>&1 > > > } > > How cute... Same mountpoint in both, so these mount(2) will sometimes > fail (cgroup picks the same sb on the same options, AFAICS) and fail > silently due to these redirects... > > That's a lovely way to stress-test a large part of ro-bind stuff *and* > umount()-related code. Could you do C equivalent of the above (just > the same syscalls in loop, nothing fancier) and do time-stamped > strace? Could you also add a printk of what ->__mnt_writers was at the time of the WARN_ON()? That will hopefully at least tell us whether we're looking at a real leak or just a single missed mnt_want/drop_write(). Also hopefully in which direction the thing is biased. With the mount not being around long I'm not horribly hopeful, but it can't hurt. -- Dave