Patch "dealing with the rest of shrink_dentry_list() livelock" has been added to the 3.14-stable tree

Patch "dealing with the rest of shrink_dentry_list() livelock" has been added to the 3.14-stable tree

[gregkh]

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

    dealing with the rest of shrink_dentry_list() livelock

to the 3.14-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:
     dealing-with-the-rest-of-shrink_dentry_list-livelock.patch
and it can be found in the queue-3.14 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 b2b80195d8829921506880f6dccd21cabd163d0d Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Thu, 29 May 2014 09:11:45 -0400
Subject: dealing with the rest of shrink_dentry_list() livelock

From: Al Viro <viro@zeniv.linux.org.uk>

commit b2b80195d8829921506880f6dccd21cabd163d0d upstream.

We have the same problem with ->d_lock order in the inner loop, where
we are dropping references to ancestors.  Same solution, basically -
instead of using dentry_kill() we use lock_parent() (introduced in the
previous commit) to get that lock in a safe way, recheck ->d_count
(in case if lock_parent() has ended up dropping and retaking ->d_lock
and somebody managed to grab a reference during that window), trylock
the inode->i_lock and use __dentry_kill() to do the rest.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/dcache.c |   22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -886,8 +886,26 @@ static void shrink_dentry_list(struct li
 		 * fragmentation.
 		 */
 		dentry = parent;
-		while (dentry && !lockref_put_or_lock(&dentry->d_lockref))
-			dentry = dentry_kill(dentry, 1);
+		while (dentry && !lockref_put_or_lock(&dentry->d_lockref)) {
+			parent = lock_parent(dentry);
+			if (dentry->d_lockref.count != 1) {
+				dentry->d_lockref.count--;
+				spin_unlock(&dentry->d_lock);
+				if (parent)
+					spin_unlock(&parent->d_lock);
+				break;
+			}
+			inode = dentry->d_inode;	/* can't be NULL */
+			if (unlikely(!spin_trylock(&inode->i_lock))) {
+				spin_unlock(&dentry->d_lock);
+				if (parent)
+					spin_unlock(&parent->d_lock);
+				cpu_relax();
+				continue;
+			}
+			__dentry_kill(dentry);
+			dentry = parent;
+		}
 	}
 }
 


Patches currently in stable-queue which might be from viro@zeniv.linux.org.uk are

queue-3.14/lock_parent-don-t-step-on-stale-d_parent-of-all-but-freed-one.patch
queue-3.14/lift-the-already-marked-killed-case-into-shrink_dentry_list.patch
queue-3.14/expand-dentry_kill-dentry-0-in-shrink_dentry_list.patch
queue-3.14/bcache-fix-a-leak-in-bch_cached_dev_run.patch
queue-3.14/dcache-add-missing-lockdep-annotation.patch
queue-3.14/dealing-with-the-rest-of-shrink_dentry_list-livelock.patch
queue-3.14/split-dentry_kill.patch
queue-3.14/shrink_dentry_list-take-parent-s-d_lock-earlier.patch
queue-3.14/dentry_kill-doesn-t-need-the-second-argument-now.patch