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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F123CC433EF for ; Thu, 12 May 2022 00:57:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245328AbiELA5T (ORCPT ); Wed, 11 May 2022 20:57:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38756 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245021AbiELA5S (ORCPT ); Wed, 11 May 2022 20:57:18 -0400 Received: from mail104.syd.optusnet.com.au (mail104.syd.optusnet.com.au [211.29.132.246]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 68D376928D for ; Wed, 11 May 2022 17:57:17 -0700 (PDT) Received: from dread.disaster.area (pa49-181-2-147.pa.nsw.optusnet.com.au [49.181.2.147]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id 3DE11534683; Thu, 12 May 2022 10:57:14 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1nox8i-00AteZ-Hu; Thu, 12 May 2022 10:57:12 +1000 Date: Thu, 12 May 2022 10:57:12 +1000 From: Dave Chinner To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org Subject: Re: [PATCH 05/18] xfs: separate out initial attr_set states Message-ID: <20220512005712.GL1098723@dread.disaster.area> References: <20220509004138.762556-1-david@fromorbit.com> <20220509004138.762556-6-david@fromorbit.com> <20220510231234.GI27195@magnolia> <20220511010651.GZ1098723@dread.disaster.area> <20220511010848.GB27195@magnolia> <20220511013851.GD1098723@dread.disaster.area> <20220511083513.GJ1098723@dread.disaster.area> <20220511153952.GF27195@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220511153952.GF27195@magnolia> X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.4 cv=e9dl9Yl/ c=1 sm=1 tr=0 ts=627c5b6b a=ivVLWpVy4j68lT4lJFbQgw==:117 a=ivVLWpVy4j68lT4lJFbQgw==:17 a=kj9zAlcOel0A:10 a=oZkIemNP1mAA:10 a=7-415B0cAAAA:8 a=PyqHtWom7uurtRGdfgcA:9 a=CjuIK1q_8ugA:10 a=biEYGPWJfzWAr4FL6Ov7:22 Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Wed, May 11, 2022 at 08:39:52AM -0700, Darrick J. Wong wrote: > On Wed, May 11, 2022 at 06:35:13PM +1000, Dave Chinner wrote: > > On Wed, May 11, 2022 at 11:38:51AM +1000, Dave Chinner wrote: > > > On Tue, May 10, 2022 at 06:08:48PM -0700, Darrick J. Wong wrote: > > > > On Wed, May 11, 2022 at 11:06:51AM +1000, Dave Chinner wrote: > > > > > I'm going to leave this for the moment (cleanup note made) because I > > > > > don't want to have to find out that I missed a corner case somewhere > > > > > they hard way right now. It's basically there to stop log recovery > > > > > crashing hard, which only occurs when the experimental larp code is > > > > > running, so I think this is safe to leave for a later cleanup. > > > > > > > > Hmm, in that case, can this become: > > > > > > > > if (!args->dp->i_afp) { > > > > ASSERT(0); > > > > return XFS_DAS_DONE; > > > > } > > > > > > OK. > > > > Ok, now generic/051 has reminded me exactly what this was for. > > > > Shortform attr remove will remove the attr and the attr fork from > > this code: > > > > case XFS_DAS_SF_REMOVE: > > error = xfs_attr_sf_removename(args); > > attr->xattri_dela_state = xfs_attr_complete_op(attr, > > xfs_attr_init_add_state(args)); > > break; > > > > But if we are doing this as part of a REPLACE operation and we > > still need to add the new attr, it calls xfs_attr_init_add_state() > > to get the add state we should start with. That then hits the > > null args->dp->i_afp case because the fork got removed. > > > > This can't happen if we are doing a replace op, so we'd then check > > if it's a shortform attr fork and return XFS_DAS_SF_ADD for the > > replace to then execute. But it's not a replace op, so we can > > have a null attr fork. > > > > I'm going to restore the old code with a comment so that I don't > > forget this again. > > > > /* > > * If called from the completion of a attr remove to determine > > * the next state, the attribute fork may be null. This can occur on > > * a pure remove, but we grab the next state before we check if a > > * replace operation is being performed. Hence if the attr fork is > > * null, it's a pure remove operation and we are done. > > */ > > Ahh, I see -- sf_removename will /never/ kill i_afp if we're doing a > DA_OP_REPLACE or ADDNAME, and leaf_removename also won't do that if > we're doing DA_OP_REPLACE. IOWs, only a removexattr operation can > result in i_afp being freed. > > And the XATTR_CREATE operation always guarantee that i_afp is non-null > before we start, so xfs_attr_defer_add should never be called with > args->dp->i_afp == NULL, hence it'll never hit that state. > > Would you mind adding a sentence to the comment? > > "A pure create ensures the existence of i_afp and never encounters this > state." Sure. -Dave. -- Dave Chinner david@fromorbit.com