From: Dave Chinner dchinner@redhat.com
[ Upstream commit 96355d5a1f0ee6dcc182c37db4894ec0c29f1692 ]
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 dchinner@redhat.com Reviewed-by: Brian Foster bfoster@redhat.com Reviewed-by: Darrick J. Wong darrick.wong@oracle.com Signed-off-by: Darrick J. Wong darrick.wong@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 2b8ccb5b975df..e59507a24a839 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 8bf1d15be3f6a..67c232283a171 100644 --- a/fs/xfs/xfs_icache.c +++ b/fs/xfs/xfs_icache.c @@ -1136,7 +1136,7 @@ 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; } @@ -1223,6 +1223,7 @@ 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 8845faa8161a9..e38dd625e914b 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -1744,10 +1744,31 @@ 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 @@ -1760,7 +1781,6 @@ xfs_inactive_ifree( xfs_force_shutdown(mp, SHUTDOWN_META_IO_ERROR); } xfs_trans_cancel(tp); - xfs_iunlock(ip, XFS_ILOCK_EXCL); return error; }
@@ -1778,7 +1798,6 @@ xfs_inactive_ifree( xfs_notice(mp, "%s: xfs_trans_commit returned error %d", __func__, error);
- xfs_iunlock(ip, XFS_ILOCK_EXCL); return 0; }