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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 CF0ABC433E0 for ; Sun, 7 Mar 2021 23:04:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9DEFD65159 for ; Sun, 7 Mar 2021 23:04:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233236AbhCGXDn (ORCPT ); Sun, 7 Mar 2021 18:03:43 -0500 Received: from mail109.syd.optusnet.com.au ([211.29.132.80]:54509 "EHLO mail109.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232266AbhCGXDM (ORCPT ); Sun, 7 Mar 2021 18:03:12 -0500 Received: from dread.disaster.area (pa49-179-130-210.pa.nsw.optusnet.com.au [49.179.130.210]) by mail109.syd.optusnet.com.au (Postfix) with ESMTPS id A537C645AD; Mon, 8 Mar 2021 10:03:08 +1100 (AEDT) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1lJ2Op-0022Tx-Op; Mon, 08 Mar 2021 10:01:23 +1100 Date: Mon, 8 Mar 2021 10:01:23 +1100 From: Dave Chinner To: "Darrick J. Wong" Cc: linux-xfs@vger.kernel.org, hch@lst.de, dchinner@redhat.com, christian.brauner@ubuntu.com Subject: Re: [PATCH 3/4] xfs: force log and push AIL to clear pinned inodes when aborting mount Message-ID: <20210307230123.GY4662@dread.disaster.area> References: <161514874040.698643.2749449122589431232.stgit@magnolia> <161514875722.698643.971171271199400538.stgit@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <161514875722.698643.971171271199400538.stgit@magnolia> Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Sun, Mar 07, 2021 at 12:25:57PM -0800, Darrick J. Wong wrote: > From: Darrick J. Wong > > If we allocate quota inodes in the process of mounting a filesystem but > then decide to abort the mount, it's possible that the quota inodes are > sitting around pinned by the log. Now that inode reclaim relies on the > AIL to flush inodes, we have to force the log and push the AIL in > between releasing the quota inodes and kicking off reclaim to tear down > all the incore inodes. Do this by extracting the bits we need from the > unmount path and reusing them. > > This was originally found during a fuzz test of metadata directories > (xfs/1546), but the actual symptom was that reclaim hung up on the quota > inodes. > > Signed-off-by: Darrick J. Wong > --- > fs/xfs/xfs_mount.c | 100 ++++++++++++++++++++++++++++------------------------ > 1 file changed, 54 insertions(+), 46 deletions(-) Seems reasonable. > > > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c > index 52370d0a3f43..556ce373145f 100644 > --- a/fs/xfs/xfs_mount.c > +++ b/fs/xfs/xfs_mount.c > @@ -634,6 +634,57 @@ xfs_check_summary_counts( > return xfs_initialize_perag_data(mp, mp->m_sb.sb_agcount); > } > > +/* > + * Force the log contents and checkpoint them into the filesystem, the reclaim > + * inodes in preparation to unmount. "then reclaim" Ignoring the typo, the comment doesn't add anything useful - you're saying what the function does, not why. I'd prefer you lift all the comments in the code up into the header, explaining why each step is needed/taken. Something like: /* * Flush and reclaim dirty inodes in preparation for unmount. Inodes and * internal inode structures can be sitting in the CIL and AIL at this point, so * we need to unpin them, write them back and/or reclaim them before unmount can * proceed. * * An inode cluster that has been freed can have its buffer still pinned in * memory because the transaction is still sitting in a iclog. The stale inodes * on that buffer will be pinned to the buffer until the transaction hits the * disk and the callbacks run. Pushing the AIL will skip the stale inodes and * may never see the pinned buffer, so nothing will push out the iclog and unpin * the buffer. * * Hence we need to force the log to unpin everything first. However, log forces * don't wait for the discards they issue to complete, so we have to explicitly * wait for them to complete here as well. * * Then we can tell the world we are unmounting so that error handling knows * that the filesystem is going away and we should error out anything that we * have been retrying in the background. This will prevent never-ending retries * in AIL pushing from hanging the unmount. * * Finally, we can push the AIL to clean all the remaining dirty objects, then * reclaim the remaining inodes that are still in memory at this point in * time. */ static void xfs_unmount_flush_inodes( struct xfs_mount *mp) { xfs_log_force(mp, XFS_LOG_SYNC); xfs_extent_busy_wait_all(mp); flush_workqueue(xfs_discard_wq); mp->m_flags |= XFS_MOUNT_UNMOUNTING; xfs_ail_push_all_sync(mp->m_ail); cancel_delayed_work_sync(&mp->m_reclaim_work); xfs_reclaim_inodes(mp); xfs_health_unmount(mp); } Everything else looks fine. Cheers, Dave. -- Dave Chinner david@fromorbit.com