From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 16AAAC35641 for ; Fri, 21 Feb 2020 23:00:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ED48D24653 for ; Fri, 21 Feb 2020 23:00:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729179AbgBUXAq (ORCPT ); Fri, 21 Feb 2020 18:00:46 -0500 Received: from mga17.intel.com ([192.55.52.151]:31741 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726802AbgBUXAp (ORCPT ); Fri, 21 Feb 2020 18:00:45 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Feb 2020 15:00:45 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,470,1574150400"; d="scan'208";a="240468956" Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by orsmga006.jf.intel.com with ESMTP; 21 Feb 2020 15:00:44 -0800 Date: Fri, 21 Feb 2020 15:00:44 -0800 From: Ira Weiny To: Dave Chinner Cc: linux-kernel@vger.kernel.org, Alexander Viro , "Darrick J. Wong" , Dan Williams , Christoph Hellwig , "Theodore Y. Ts'o" , Jan Kara , linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH V4 02/13] fs/xfs: Clarify lockdep dependency for xfs_isilocked() Message-ID: <20200221230043.GA6762@iweiny-DESK2.sc.intel.com> References: <20200221004134.30599-1-ira.weiny@intel.com> <20200221004134.30599-3-ira.weiny@intel.com> <20200221013451.GU10776@dread.disaster.area> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200221013451.GU10776@dread.disaster.area> User-Agent: Mutt/1.11.1 (2018-12-01) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Feb 21, 2020 at 12:34:51PM +1100, Dave Chinner wrote: > On Thu, Feb 20, 2020 at 04:41:23PM -0800, ira.weiny@intel.com wrote: > > From: Ira Weiny > > > > xfs_isilocked() can't work fully without CONFIG_LOCKDEP. However, > > making xfs_isilocked() dependant on CONFIG_LOCKDEP is not feasible > > because it is used for more than the i_rwsem. Therefore a short-circuit > > was provided via debug_locks. However, this caused confusion while > > working through the xfs locking. > > > > Rather than use debug_locks as a flag specify this clearly using > > IS_ENABLED(CONFIG_LOCKDEP). > > > > Signed-off-by: Ira Weiny > > > > --- > > Changes from V3: > > Reordered to be a "pre-cleanup" patch > > > > Changes from V2: > > This patch is new for V3 > > --- > > fs/xfs/xfs_inode.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c > > index c5077e6326c7..35df324875db 100644 > > --- a/fs/xfs/xfs_inode.c > > +++ b/fs/xfs/xfs_inode.c > > @@ -364,7 +364,7 @@ xfs_isilocked( > > > > if (lock_flags & (XFS_IOLOCK_EXCL|XFS_IOLOCK_SHARED)) { > > if (!(lock_flags & XFS_IOLOCK_SHARED)) > > - return !debug_locks || > > + return !IS_ENABLED(CONFIG_LOCKDEP) || > > lockdep_is_held_type(&VFS_I(ip)->i_rwsem, 0); > > This breaks expected lockdep behaviour. > > We need to use debug_locks here because lockdep turns off lock > checking via debug_locks when lockdep encounters a locking > inconsistency. We only want to know about the first locking > problem, not spew cascading lock problems over and over once we > already know there is a locking problem. Ah... ok... Seems like that should be part of the lockdep interface... I'll drop the patch for now, Ira > > IOWs, checking debug_locks is required here for the same reason it > is used in lockdep_assert_held_{read/write}(). essentially we are > open coding lockdep_assert_held_write() here because this function > is only called from within ASSERT() statements and we don't want > multiple WARN/BUGs being issued when this triggers.... > > Cheers, > > Dave. > -- > Dave Chinner > david@fromorbit.com