From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266360AbUGJTiV (ORCPT ); Sat, 10 Jul 2004 15:38:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266358AbUGJTiV (ORCPT ); Sat, 10 Jul 2004 15:38:21 -0400 Received: from wombat.indigo.net.au ([202.0.185.19]:54540 "EHLO wombat.indigo.net.au") by vger.kernel.org with ESMTP id S266360AbUGJTiM (ORCPT ); Sat, 10 Jul 2004 15:38:12 -0400 Date: Sun, 11 Jul 2004 03:25:34 +0800 (WST) From: raven@themaw.net To: Thomas Moestl cc: autofs mailing list , nfs@lists.sourceforge.net, Kernel Mailing List Subject: Re: umount() and NFS races in 2.4.26 In-Reply-To: <20040710181912.GA800@timesink.dyndns.org> Message-ID: References: <20040708180709.GA7704@timesink.dyndns.org> <20040710181912.GA800@timesink.dyndns.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-MailScanner: Found to be clean X-MailScanner-SpamCheck: not spam, SpamAssassin (score=-1.2, required 8, EMAIL_ATTRIBUTION, IN_REP_TO, NO_REAL_NAME, QUOTED_EMAIL_TEXT, RCVD_IN_ORBS, REFERENCES, REPLY_WITH_QUOTES, USER_AGENT_PINE) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 10 Jul 2004, Thomas Moestl wrote: > Hello, > > On Sat, 2004/07/10 at 14:57:46 +0800, raven@themaw.net wrote: > > > Hi, > > > > > > after deploying an SMP machine at work, we started to experience Oopses > > > in file-system related code relatively frequently. Investigation > > > revealed that they were caused by references using junk pointers from > > > freed super blocks via dangling inodes from unmounted file systems; > > > Oopses would always be preceded by the warning > > > VFS: Busy inodes after unmount. Self-destruct in 5 seconds. Have a nice day... > > > on an unmount (unmount activity is high on this machine due to heavy use > > > of the automounter). The predecessor to this machine, a UP system with > > > otherwise almost identical configuration, did never encounter such > > > problems, so I went looking for possible SMP races. > > > > This has been reported many times by users of autofs, especially people > > with a ot of mount/umount activity. > > > > As James pointed out my latest autofs4 patch resolved the issue for him. > > However, on the NFS list Greg Banks pointed out that this may be hiding a > > problem that exists in NFS. So it would be good if the NFS folk could > > investigate this further. > > > > Never the less I'm sure there is a race in waitq.c of autofs4 in > > 2.4 that seems to cause this problem. This is one of the things > > addressed by my patch. > > The system in question still uses autofs3. While I believe that the > waitq race is also present there (it could probably cause directory > lookups to hang, if I understand it correctly), I do not think that > any autofs3 code could cause exactly those symptoms that I have > observed. For that, it would have to obtain dentries of the file > systems that it has mounted, but the old code never does that. All autofs has to do is not delete a directory before exiting for this error to occur. Ian