From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH] autofs4 - remove hashed check in validate_wait() Date: Sun, 7 Jun 2009 22:08:14 -0700 Message-ID: <20090607220814.cc7519f6.akpm@linux-foundation.org> References: <20090608032537.7088.1870.stgit@zeus.themaw.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: autofs mailing list , linux-fsdevel , Kernel Mailing List To: Ian Kent Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:39995 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751146AbZFHFKf (ORCPT ); Mon, 8 Jun 2009 01:10:35 -0400 In-Reply-To: <20090608032537.7088.1870.stgit@zeus.themaw.net> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, 08 Jun 2009 11:25:37 +0800 Ian Kent wrote: > The recent ->lookup() deadlock correction required the directory > inode mutex to be dropped while waiting for expire completion. We > were concerned about side effects from this change and one has > been identified. > > When checking if a mount has already completed prior to adding a > new mount request to the wait queue we check if the dentry is hashed > and, if so, if it is a mount point. But, if a mount successfully > completed while we slept on the wait queue mutex the dentry must > exist for the mount to have completed so the test is not really > needed. > > Mounts can also be done on top of a global root dentry, so for the > above case, where a mount request completes and the wait queue entry > has already been removed, the hashed test returning false can cause > an incorrect callback to the daemon. Also, d_mountpoint() is not > sufficient to check if a mount has completed for the multi-mount > case when we don't have a real mount at the base of the tree. > I've been scratching my head trying to work out if this is a needed-in-2.6.30 fix, but all I got was a bald spot. Help?