Patch "xfs: drop iolock from reclaim context to appease lockdep" has been added to the 4.9-stable tree

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

xfs: drop iolock from reclaim context to appease lockdep

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-drop-iolock-from-reclaim-context-to-appease-lockdep.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 <[email protected]> know about it.

From: Brian Foster <[email protected]>
Date: Tue, 11 Apr 2017 10:50:05 -0700
Subject: xfs: drop iolock from reclaim context to appease lockdep

From: Brian Foster <[email protected]>

commit 3b4683c294095b5f777c03307ef8c60f47320e12 upstream.

Lockdep complains about use of the iolock in inode reclaim context because it doesn't understand that reclaim has the last reference to the inode, and thus an iolock->reclaim->iolock deadlock is not possible.

The iolock is technically not necessary in xfs_inactive() and was only added to appease an assert in xfs_free_eofblocks(), which can be called from other non-reclaim contexts. Therefore, just kill the assert and drop the use of the iolock from reclaim context to quiet lockdep.

---
 fs/xfs/xfs_bmap_util.c |    8 +++-----
 fs/xfs/xfs_inode.c     |    9 +++++----
 2 files changed, 8 insertions(+), 9 deletions(-)

@@ -911,9 +911,9 @@ xfs_can_free_eofblocks(struct xfs_inode
 }
 
 /*
- * This is called by xfs_inactive to free any blocks beyond eof
- * when the link count isn't zero and by xfs_dm_punch_hole() when
- * punching a hole to EOF.
+ * This is called to free any blocks beyond eof. The caller must hold
+ * IOLOCK_EXCL unless we are in the inode reclaim path and have the only
+ * reference to the inode.
  */
 int
 xfs_free_eofblocks(

@@ -928,8 +928,6 @@ xfs_free_eofblocks(
 	struct xfs_bmbt_irec	imap;
 	struct xfs_mount	*mp = ip->i_mount;
 
-	ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
-
 	/*
 	 * Figure out if there are any blocks beyond the end
 	 * of the file.  If not, then there is nothing to do.

@@ -1915,12 +1915,13 @@ xfs_inactive(
 		 * force is true because we are evicting an inode from the
 		 * cache. Post-eof blocks must be freed, lest we end up with
 		 * broken free space accounting.
+		 *
+		 * Note: don't bother with iolock here since lockdep complains
+		 * about acquiring it in reclaim context. We have the only
+		 * reference to the inode at this point anyways.
 		 */
-		if (xfs_can_free_eofblocks(ip, true)) {
-			xfs_ilock(ip, XFS_IOLOCK_EXCL);
+		if (xfs_can_free_eofblocks(ip, true))
 			xfs_free_eofblocks(ip);
-			xfs_iunlock(ip, XFS_IOLOCK_EXCL);
-		}
 
 		return;
 	}

Patches currently in stable-queue which might be from [email protected] 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