Patch "xfs: wait on new inodes during quotaoff dquot release" has been added to the 4.9-stable tree

Patch "xfs: wait on new inodes during quotaoff dquot release" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    xfs: wait on new inodes during quotaoff dquot release

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     xfs-wait-on-new-inodes-during-quotaoff-dquot-release.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From e20c8a517f259cb4d258e10b0cd5d4b30d4167a0 Mon Sep 17 00:00:00 2001
From: Brian Foster <bfoster@redhat.com>
Date: Wed, 26 Apr 2017 08:30:40 -0700
Subject: xfs: wait on new inodes during quotaoff dquot release

From: Brian Foster <bfoster@redhat.com>

commit e20c8a517f259cb4d258e10b0cd5d4b30d4167a0 upstream.

The quotaoff operation has a race with inode allocation that results
in a livelock. An inode allocation that occurs before the quota
status flags are updated acquires the appropriate dquots for the
inode via xfs_qm_vop_dqalloc(). It then inserts the XFS_INEW inode
into the perag radix tree, sometime later attaches the dquots to the
inode and finally clears the XFS_INEW flag. Quotaoff expects to
release the dquots from all inodes in the filesystem via
xfs_qm_dqrele_all_inodes(). This invokes the AG inode iterator,
which skips inodes in the XFS_INEW state because they are not fully
constructed. If the scan occurs after dquots have been attached to
an inode, but before XFS_INEW is cleared, the newly allocated inode
will continue to hold a reference to the applicable dquots. When
quotaoff invokes xfs_qm_dqpurge_all(), the reference count of those
dquot(s) remain elevated and the dqpurge scan spins indefinitely.

To address this problem, update the xfs_qm_dqrele_all_inodes() scan
to wait on inodes marked on the XFS_INEW state. We wait on the
inodes explicitly rather than skip and retry to avoid continuous
retry loops due to a parallel inode allocation workload. Since
quotaoff updates the quota state flags and uses a synchronous
transaction before the dqrele scan, and dquots are attached to
inodes after radix tree insertion iff quota is enabled, one INEW
waiting pass through the AG guarantees that the scan has processed
all inodes that could possibly hold dquot references.

Reported-by: Eryu Guan <eguan@redhat.com>
Signed-off-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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/xfs/xfs_qm_syscalls.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/xfs/xfs_qm_syscalls.c
+++ b/fs/xfs/xfs_qm_syscalls.c
@@ -759,5 +759,6 @@ xfs_qm_dqrele_all_inodes(
 	uint		 flags)
 {
 	ASSERT(mp->m_quotainfo);
-	xfs_inode_ag_iterator(mp, xfs_dqrele_inode, flags, NULL);
+	xfs_inode_ag_iterator_flags(mp, xfs_dqrele_inode, flags, NULL,
+				    XFS_AGITER_INEW_WAIT);
 }


Patches currently in stable-queue which might be from bfoster@redhat.com are

queue-4.9/xfs-fix-missed-holes-in-seek_hole-implementation.patch
queue-4.9/xfs-fix-indlen-accounting-error-on-partial-delalloc-conversion.patch
queue-4.9/xfs-bad-assertion-for-delalloc-an-extent-that-start-at-i_size.patch
queue-4.9/xfs-bmapx-shouldn-t-barf-on-inline-format-directories.patch
queue-4.9/xfs-drop-iolock-from-reclaim-context-to-appease-lockdep.patch
queue-4.9/xfs-update-ag-iterator-to-support-wait-on-new-inodes.patch
queue-4.9/xfs-use-dedicated-log-worker-wq-to-avoid-deadlock-with-cil-wq.patch
queue-4.9/xfs-fix-up-quotacheck-buffer-list-error-handling.patch
queue-4.9/xfs-wait-on-new-inodes-during-quotaoff-dquot-release.patch
queue-4.9/xfs-rework-the-inline-directory-verifiers.patch
queue-4.9/xfs-use-b_state-to-fix-buffer-i-o-accounting-release-race.patch
queue-4.9/xfs-avoid-mount-time-deadlock-in-cow-extent-recovery.patch
queue-4.9/xfs-actually-report-xattr-extents-via-iomap.patch
queue-4.9/xfs-support-ability-to-wait-on-new-inodes.patch
queue-4.9/xfs-verify-inline-directory-data-forks.patch
queue-4.9/xfs-prevent-multi-fsb-dir-readahead-from-reading-random-blocks.patch