From patchwork Thu Jun 4 07:45:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dave Chinner X-Patchwork-Id: 11587237 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 40A06913 for ; Thu, 4 Jun 2020 07:46:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3290F206C3 for ; Thu, 4 Jun 2020 07:46:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726047AbgFDHqN (ORCPT ); Thu, 4 Jun 2020 03:46:13 -0400 Received: from mail106.syd.optusnet.com.au ([211.29.132.42]:49418 "EHLO mail106.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727043AbgFDHqN (ORCPT ); Thu, 4 Jun 2020 03:46:13 -0400 Received: from dread.disaster.area (pa49-180-124-177.pa.nsw.optusnet.com.au [49.180.124.177]) by mail106.syd.optusnet.com.au (Postfix) with ESMTPS id 4311A5AAA3A for ; Thu, 4 Jun 2020 17:46:09 +1000 (AEST) Received: from discord.disaster.area ([192.168.253.110]) by dread.disaster.area with esmtp (Exim 4.92.3) (envelope-from ) id 1jgkZj-00049V-DF for linux-xfs@vger.kernel.org; Thu, 04 Jun 2020 17:46:07 +1000 Received: from dave by discord.disaster.area with local (Exim 4.93) (envelope-from ) id 1jgkZj-0017GX-48 for linux-xfs@vger.kernel.org; Thu, 04 Jun 2020 17:46:07 +1000 From: Dave Chinner To: linux-xfs@vger.kernel.org Subject: [PATCH 01/30] xfs: Don't allow logging of XFS_ISTALE inodes Date: Thu, 4 Jun 2020 17:45:37 +1000 Message-Id: <20200604074606.266213-2-david@fromorbit.com> X-Mailer: git-send-email 2.26.2.761.g0e0b3e54be In-Reply-To: <20200604074606.266213-1-david@fromorbit.com> References: <20200604074606.266213-1-david@fromorbit.com> MIME-Version: 1.0 X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=QIgWuTDL c=1 sm=1 tr=0 a=k3aV/LVJup6ZGWgigO6cSA==:117 a=k3aV/LVJup6ZGWgigO6cSA==:17 a=nTHF0DUjJn0A:10 a=20KFwNOVAAAA:8 a=yPCof4ZbAAAA:8 a=E4R3UMY25Q1b2mD5dw0A:9 Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org From: Dave Chinner In tracking down a problem in this patchset, I discovered we are reclaiming dirty stale inodes. This wasn't discovered until inodes were always attached to the cluster buffer and then the rcu callback that freed inodes was assert failing because the inode still had an active pointer to the cluster buffer after it had been reclaimed. Debugging the issue indicated that this was a pre-existing issue resulting from the way the inodes are handled in xfs_inactive_ifree. When we free a cluster buffer from xfs_ifree_cluster, all the inodes in cache are marked XFS_ISTALE. Those that are clean have nothing else done to them and so eventually get cleaned up by background reclaim. i.e. it is assumed we'll never dirty/relog an inode marked XFS_ISTALE. On journal commit dirty stale inodes as are handled by both buffer and inode log items to run though xfs_istale_done() and removed from the AIL (buffer log item commit) or the log item will simply unpin it because the buffer log item will clean it. What happens to any specific inode is entirely dependent on which log item wins the commit race, but the result is the same - stale inodes are clean, not attached to the cluster buffer, and not in the AIL. Hence inode reclaim can just free these inodes without further care. However, if the stale inode is relogged, it gets dirtied again and relogged into the CIL. Most of the time this isn't an issue, because relogging simply changes the inode's location in the current checkpoint. Problems arise, however, when the CIL checkpoints between two transactions in the xfs_inactive_ifree() deferops processing. This results in the XFS_ISTALE inode being redirtied and inserted into the CIL without any of the other stale cluster buffer infrastructure being in place. Hence on journal commit, it simply gets unpinned, so it remains dirty in memory. Everything in inode writeback avoids XFS_ISTALE inodes so it can't be written back, and it is not tracked in the AIL so there's not even a trigger to attempt to clean the inode. Hence the inode just sits dirty in memory until inode reclaim comes along, sees that it is XFS_ISTALE, and goes to reclaim it. This reclaiming of a dirty inode caused use after free, list corruptions and other nasty issues later in this patchset. Hence this patch addresses a violation of the "never log XFS_ISTALE inodes" caused by the deferops processing rolling a transaction and relogging a stale inode in xfs_inactive_free. It also adds a bunch of asserts to catch this problem in debug kernels so that we don't reintroduce this problem in future. Reproducer for this issue was generic/558 on a v4 filesystem. Signed-off-by: Dave Chinner Reviewed-by: Brian Foster Reviewed-by: Darrick J. Wong --- fs/xfs/libxfs/xfs_trans_inode.c | 2 ++ fs/xfs/xfs_icache.c | 3 ++- fs/xfs/xfs_inode.c | 25 ++++++++++++++++++++++--- 3 files changed, 26 insertions(+), 4 deletions(-) diff --git a/fs/xfs/libxfs/xfs_trans_inode.c b/fs/xfs/libxfs/xfs_trans_inode.c index b5dfb66548422..4504d215cd590 100644 --- a/fs/xfs/libxfs/xfs_trans_inode.c +++ b/fs/xfs/libxfs/xfs_trans_inode.c @@ -36,6 +36,7 @@ xfs_trans_ijoin( ASSERT(iip->ili_lock_flags == 0); iip->ili_lock_flags = lock_flags; + ASSERT(!xfs_iflags_test(ip, XFS_ISTALE)); /* * Get a log_item_desc to point at the new item. @@ -89,6 +90,7 @@ xfs_trans_log_inode( ASSERT(ip->i_itemp != NULL); ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL)); + ASSERT(!xfs_iflags_test(ip, XFS_ISTALE)); /* * Don't bother with i_lock for the I_DIRTY_TIME check here, as races diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c index 0a5ac6f9a5834..dbba4c1946386 100644 --- a/fs/xfs/xfs_icache.c +++ b/fs/xfs/xfs_icache.c @@ -1141,7 +1141,7 @@ xfs_reclaim_inode( goto out_ifunlock; xfs_iunpin_wait(ip); } - if (xfs_iflags_test(ip, XFS_ISTALE) || xfs_inode_clean(ip)) { + if (xfs_inode_clean(ip)) { xfs_ifunlock(ip); goto reclaim; } @@ -1228,6 +1228,7 @@ xfs_reclaim_inode( xfs_ilock(ip, XFS_ILOCK_EXCL); xfs_qm_dqdetach(ip); xfs_iunlock(ip, XFS_ILOCK_EXCL); + ASSERT(xfs_inode_clean(ip)); __xfs_inode_free(ip); return error; diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index 64f5f9a440aed..53a1d64782c35 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -1740,10 +1740,31 @@ xfs_inactive_ifree( return error; } + /* + * We do not hold the inode locked across the entire rolling transaction + * here. We only need to hold it for the first transaction that + * xfs_ifree() builds, which may mark the inode XFS_ISTALE if the + * underlying cluster buffer is freed. Relogging an XFS_ISTALE inode + * here breaks the relationship between cluster buffer invalidation and + * stale inode invalidation on cluster buffer item journal commit + * completion, and can result in leaving dirty stale inodes hanging + * around in memory. + * + * We have no need for serialising this inode operation against other + * operations - we freed the inode and hence reallocation is required + * and that will serialise on reallocating the space the deferops need + * to free. Hence we can unlock the inode on the first commit of + * the transaction rather than roll it right through the deferops. This + * avoids relogging the XFS_ISTALE inode. + * + * We check that xfs_ifree() hasn't grown an internal transaction roll + * by asserting that the inode is still locked when it returns. + */ xfs_ilock(ip, XFS_ILOCK_EXCL); - xfs_trans_ijoin(tp, ip, 0); + xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL); error = xfs_ifree(tp, ip); + ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL)); if (error) { /* * If we fail to free the inode, shut down. The cancel @@ -1756,7 +1777,6 @@ xfs_inactive_ifree( xfs_force_shutdown(mp, SHUTDOWN_META_IO_ERROR); } xfs_trans_cancel(tp); - xfs_iunlock(ip, XFS_ILOCK_EXCL); return error; } @@ -1774,7 +1794,6 @@ xfs_inactive_ifree( xfs_notice(mp, "%s: xfs_trans_commit returned error %d", __func__, error); - xfs_iunlock(ip, XFS_ILOCK_EXCL); return 0; }