From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264502AbTLCMET (ORCPT ); Wed, 3 Dec 2003 07:04:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264504AbTLCMET (ORCPT ); Wed, 3 Dec 2003 07:04:19 -0500 Received: from e4.ny.us.ibm.com ([32.97.182.104]:59548 "EHLO e4.ny.us.ibm.com") by vger.kernel.org with ESMTP id S264502AbTLCMD4 (ORCPT ); Wed, 3 Dec 2003 07:03:56 -0500 Date: Wed, 3 Dec 2003 17:32:44 +0530 From: Maneesh Soni To: James W McMechan Cc: hugh@veritas.com, linux-kernel@vger.kernel.org, wli@holomorphy.com, viro@parcelfarce.linux.theplanet.co.uk, akpm@osdl.org Subject: Re: Oops with tmpfs on both 2.4.22 & 2.6.0-test11 Message-ID: <20031203120244.GA1311@in.ibm.com> Reply-To: maneesh@in.ibm.com References: <20031203.030618.-346209.0.mcmechanjw@juno.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20031203.030618.-346209.0.mcmechanjw@juno.com> User-Agent: Mutt/1.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 03, 2003 at 03:06:14AM -0800, James W McMechan wrote: [..] > > > > The cursor adjustment in dcache_dir_lseek() (fs/libfs.c: line 90) > > always puts the cursor just before the last looked dentry in the > > while loop. > > > > But it is problematic when we have an empty directory and > > (file->f_pos == 2) > > In this case we have the loop counter p pointing to the cursor and > > doing list_del and list_add_tail of the same list node results in oops. > > > This is where I get mildly lost, from what you are saying here I > would have expected a test on list_empty rather than on > fpos==2 also this occurs in every file, will starting in a different > pos in the list cause problems? The cursor dentry is added in d_subdirs list in the ->open call for the directory. So even if directory is empty from a user point of view, the d_subdirs list will ateast have the cursor dentry. In other words when we come to ->lseek or ->readdir call, we will not have empty d_subdirs list. > > With further testing it also Oops even when the dir is not empty > I did a "touch /dev/shm/1 /dev/shm/2 /dev/shm/3" to put some > entries in the dir first and the original still oops at offset 2 > > I should do more testing, to see if I can find out what happens > on non empty dirs, because I was thinking it was due to the > dir being empty, which now appears not to be true. humm.. yeah.. the original case will always oops for offset 2 irrespective of whether directory is empty or not. Because in case of non-empty dir also we will have p pointing to cursor dentry for offset 2. Thanks for letting me know one more fact. > > > The following patch takes (file->f_post == 2) as a special case and > > adjusts the cursor dentry by putting it right at the beginning of the > > d_subdirs list. > > > Also is the new variable dentry needed or just a optimization? > It looks functionally equivalent, but perhaps it is needed for > something I am not seeing at the moment. That's just to make code readable, without this it will have line beyond 80 columns and also it has to de-reference multiple levels of pointers. Thanks Maneesh -- Maneesh Soni Linux Technology Center, IBM Software Lab, Bangalore, India email: maneesh@in.ibm.com Phone: 91-80-5044999 Fax: 91-80-5268553 T/L : 9243696