From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933355AbbJHWYz (ORCPT ); Thu, 8 Oct 2015 18:24:55 -0400 Received: from ipmail06.adl6.internode.on.net ([150.101.137.145]:33469 "EHLO ipmail06.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753650AbbJHWYx (ORCPT ); Thu, 8 Oct 2015 18:24:53 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: A2DzCwDK7BZWPCSkLHlegyeBQoZbohYGixmFGoYKgxOCCnkCAgEBAoFWTQEBAQEBAQcBAQEBQT+EJgEBAQMBJxMcIwULCAMYCSUPBSUDBxoTiCYHw1ABAQEHAgEfGYYThUWEKGUHhC4BBJYKjRCBYIdekkSEeSozAYYggUkBAQE Date: Fri, 9 Oct 2015 09:24:50 +1100 From: Dave Chinner To: Ross Zwisler Cc: linux-kernel@vger.kernel.org, xfs@oss.sgi.com Subject: Re: [PATCH] xfs: clarify lock ordering comment Message-ID: <20151008222450.GH32150@dastard> References: <1444341481-14139-1-git-send-email-ross.zwisler@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1444341481-14139-1-git-send-email-ross.zwisler@linux.intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 08, 2015 at 03:58:01PM -0600, Ross Zwisler wrote: > Replace "i_mmap_lock" with "mmap_lock" in the lock ordering comment above > xfs_filemap_page_mkwrite(). The lock in question is actually the > XFS_MMAPLOCK_SHARED rw_semaphore (no leading "i"), and this comment is struct xfs_inode { .... mrlock_t i_mmaplock; /* inode mmap IO lock */ .... > easily confused with the "i_mmap_lock_[read|write]" functions that operate > on struct address_space->i_mmap_rwsem. This clarification is especially > important because address_space->i_mmap_rwsem is taken down in the DAX > code as part of this fault path. > > Signed-off-by: Ross Zwisler > --- > fs/xfs/xfs_file.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index f429662..b190033 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -1477,7 +1477,7 @@ xfs_file_llseek( > * > * mmap_sem (MM) > * sb_start_pagefault(vfs, freeze) > - * i_mmap_lock (XFS - truncate serialisation) > + * mmap_lock (XFS - truncate serialisation) As per above, the XFS lock is "i_mmaplock"... The lock names are annotated with the subsystem the lock belongs to to avoid this confusion. Along with the lock ordering (inside sb_start_pagefault) this should indicate that it's not the "i_mmap_lock (MM - vma serialisation)" lock... ;) Cheers, Dave. -- Dave Chinner david@fromorbit.com