Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755642AbZGNU45 (ORCPT ); Tue, 14 Jul 2009 16:56:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754698AbZGNU44 (ORCPT ); Tue, 14 Jul 2009 16:56:56 -0400 Received: from qmta08.emeryville.ca.mail.comcast.net ([76.96.30.80]:42679 "EHLO QMTA08.emeryville.ca.mail.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752322AbZGNU4z (ORCPT ); Tue, 14 Jul 2009 16:56:55 -0400 To: Andrew Morton , Al Viro Cc: Tyler Hicks , Dustin Kirkland , linux-kernel@vger.kernel.org Subject: [PATCH/RESEND] fs/super.c: lockdep annotate s_vfs_rename_mutex X-Message-Flag: Warning: May contain useful information X-Priority: 1 X-MSMail-Priority: High References: <87prcdmqnl.fsf@shaolin.home.digitalvampire.org> From: Roland Dreier Date: Tue, 14 Jul 2009 13:56:33 -0700 In-Reply-To: <87prcdmqnl.fsf@shaolin.home.digitalvampire.org> (Roland Dreier's message of "Mon, 06 Jul 2009 14:45:50 -0700") Message-ID: <87k52bdlvi.fsf@shaolin.home.digitalvampire.org> User-Agent: Gnus/5.1008 (Gnus v5.10.8) XEmacs/21.4.21 (linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3573 Lines: 87 Doing a cross-directory rename on a stacked filesystem (such as eg ecryptfs) triggers a lockdep false positive, since the vfs first does lock_rename() and then calls into the top filesystem, which then does lock_rename() again and calls into the lower filesystem. This can't actually deadlock, since the two filesystems have separate s_vfs_rename_mutexes and the upper filesystem's mutex is always taken before the lower filesystem's. So teach lockdep this by putting each filesystem's rename mutex into its own class. This fixes lockdep warnings such as the following seen with ecryptfs on top of ext4: ============================================= [ INFO: possible recursive locking detected ] 2.6.31-2-generic #14~rbd3 --------------------------------------------- firefox-3.5/4162 is trying to acquire lock: (&s->s_vfs_rename_mutex){+.+.+.}, at: [] lock_rename+0x41/0xf0 but task is already holding lock: (&s->s_vfs_rename_mutex){+.+.+.}, at: [] lock_rename+0x41/0xf0 other info that might help us debug this: 3 locks held by firefox-3.5/4162: #0: (&s->s_vfs_rename_mutex){+.+.+.}, at: [] lock_rename+0x41/0xf0 #1: (&sb->s_type->i_mutex_key#11/1){+.+.+.}, at: [] lock_rename+0x6a/0xf0 #2: (&sb->s_type->i_mutex_key#11/2){+.+.+.}, at: [] lock_rename+0x7f/0xf0 stack backtrace: Pid: 4162, comm: firefox-3.5 Tainted: G C 2.6.31-2-generic #14~rbd3 Call Trace: [] print_deadlock_bug+0xf4/0x100 [] validate_chain+0x4c6/0x750 [] __lock_acquire+0x237/0x430 [] lock_acquire+0xa5/0x150 [] __mutex_lock_common+0x4d/0x3d0 [] mutex_lock_nested+0x46/0x60 [] lock_rename+0x41/0xf0 [] ecryptfs_rename+0xca/0x170 [] vfs_rename_dir+0x13e/0x160 [] vfs_rename+0xee/0x290 [] sys_renameat+0x252/0x280 [] sys_rename+0x1b/0x20 [] system_call_fastpath+0x16/0x1b Cc: Tyler Hicks Cc: Dustin Kirkland Signed-off-by: Roland Dreier --- Didn't see any response the first time I sent this out -- does this make sense as the right way to fix this issue? fs/super.c | 1 + include/linux/fs.h | 1 + 2 files changed, 2 insertions(+), 0 deletions(-) diff --git a/fs/super.c b/fs/super.c index 2761d3e..0a45b5a 100644 --- a/fs/super.c +++ b/fs/super.c @@ -98,6 +98,7 @@ static struct super_block *alloc_super(struct file_system_type *type) s->s_count = S_BIAS; atomic_set(&s->s_active, 1); mutex_init(&s->s_vfs_rename_mutex); + lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key); mutex_init(&s->s_dquot.dqio_mutex); mutex_init(&s->s_dquot.dqonoff_mutex); init_rwsem(&s->s_dquot.dqptr_sem); diff --git a/include/linux/fs.h b/include/linux/fs.h index 0872372..feaf9e0 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1750,6 +1750,7 @@ struct file_system_type { struct lock_class_key s_lock_key; struct lock_class_key s_umount_key; + struct lock_class_key s_vfs_rename_key; struct lock_class_key i_lock_key; struct lock_class_key i_mutex_key; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/