From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755529AbYINWMn (ORCPT ); Sun, 14 Sep 2008 18:12:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753793AbYINWMe (ORCPT ); Sun, 14 Sep 2008 18:12:34 -0400 Received: from ns2.suse.de ([195.135.220.15]:34222 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752429AbYINWMd (ORCPT ); Sun, 14 Sep 2008 18:12:33 -0400 Date: Mon, 15 Sep 2008 00:12:31 +0200 From: Nick Piggin To: Ingo Molnar Cc: Andrew Morton , Peter Zijlstra , Linux Kernel Mailing List , mpm@selenic.com Subject: [patch] mm: tiny-shmem fix lor, mmap_sem vs i_mutex Message-ID: <20080914221231.GG27080@wotan.suse.de> References: <1221046892.30429.85.camel@twins.programming.kicks-ass.net> <20080910114755.GA9696@elte.hu> <20080910121217.GA16013@elte.hu> <20080910144812.GB18644@wotan.suse.de> <1221058864.30429.291.camel@twins.programming.kicks-ass.net> <20080910152651.GE18644@wotan.suse.de> <20080911082709.GA14378@elte.hu> <20080914073906.GA6184@elte.hu> <20080914004442.4f8e851f.akpm@linux-foundation.org> <20080914080631.GA10720@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080914080631.GA10720@elte.hu> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Sep 14, 2008 at 10:06:31AM +0200, Ingo Molnar wrote: > > * Andrew Morton wrote: > > > > [ 6460.634452] > > > [ 6460.634465] ======================================================= > > > [ 6460.634494] [ INFO: possible circular locking dependency detected ] > > > [ 6460.634517] 2.6.27-rc6-tip-00290-g8e229c3-dirty #1 > > > [ 6460.634535] ------------------------------------------------------- > > > [ 6460.634555] gdm-simple-gree/4778 is trying to acquire lock: > > > [ 6460.634574] (&mm->mmap_sem){----}, at: [] might_fault+0x36/0x73 > > > [ 6460.634639] > > > [ 6460.634645] but task is already holding lock: > > > [ 6460.634662] (&dev->ev_mutex){--..}, at: [] inotify_read+0xd8/0x16e > > > [ 6460.634715] > > > [ 6460.634721] which lock already depends on the new lock. > > > > Yes, there's a thread in my intray called "inotify_read's ev_mutex vs > > do_page_fault's mmap_sem...". It's a bit flakey-looking, but there's > > a patch in there. > > ah, thx. I picked up the patch into tip/out-of-tree. (see below for a > tided up changelog) Please queue it up as v2.6.27 material. (i'll report > it if anything breaks due to the patch) > > Ingo > > ---------------> > >From 1eb0a42e4eb3283521ee1de99adbf567874b622f Mon Sep 17 00:00:00 2001 > From: Nick Piggin > Date: Thu, 11 Sep 2008 06:12:51 +1000 > Subject: [PATCH] mm: fix locking, inotify_read's ev_mutex vs do_page_fault's mmap_sem... I would call this "fs: fix inotify locking....", it's not really an mm bug if another subsystem misuses mm's APIs. But that's a nitpick. Here is the other patch I did too. tiny-shmem calls do_truncate in shmem_file_setup. do_truncate takes i_mutex, and shmem_file_setup is called with mmap_sem held. However i_mutex nests outside mmap_sem. Copy the code in shmem.c to avoid this problem. Signed-off-by: Nick Piggin --- Index: linux-2.6/mm/tiny-shmem.c =================================================================== --- linux-2.6.orig/mm/tiny-shmem.c +++ linux-2.6/mm/tiny-shmem.c @@ -65,31 +65,25 @@ struct file *shmem_file_setup(char *name if (!dentry) goto put_memory; + error = -ENFILE; + file = get_empty_filp(); + if (!file) + goto put_dentry; + error = -ENOSPC; inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0); if (!inode) - goto put_dentry; - - d_instantiate(dentry, inode); - error = -ENFILE; - file = alloc_file(shm_mnt, dentry, FMODE_WRITE | FMODE_READ, - &ramfs_file_operations); - if (!file) - goto put_dentry; - - inode->i_nlink = 0; /* It is unlinked */ - - /* notify everyone as to the change of file size */ - error = do_truncate(dentry, size, 0, file); - if (error < 0) goto close_file; + d_instantiate(dentry, inode); + inode->i_size = size; + inode->i_nlink = 0; /* It is unlinked */ + init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ, + &ramfs_file_operations); return file; close_file: put_filp(file); - return ERR_PTR(error); - put_dentry: dput(dentry); put_memory: