Patch "ocfs2: fix BUG in ocfs2_downconvert_thread_do_work()" has been added to the 4.1-stable tree

Patch "ocfs2: fix BUG in ocfs2_downconvert_thread_do_work()" has been added to the 4.1-stable tree

[gregkh]

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

    ocfs2: fix BUG in ocfs2_downconvert_thread_do_work()

to the 4.1-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:
     ocfs2-fix-bug-in-ocfs2_downconvert_thread_do_work.patch
and it can be found in the queue-4.1 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 209f7512d007980fd111a74a064d70a3656079cf Mon Sep 17 00:00:00 2001
From: Joseph Qi <joseph.qi@huawei.com>
Date: Thu, 6 Aug 2015 15:46:23 -0700
Subject: ocfs2: fix BUG in ocfs2_downconvert_thread_do_work()

From: Joseph Qi <joseph.qi@huawei.com>

commit 209f7512d007980fd111a74a064d70a3656079cf upstream.

The "BUG_ON(list_empty(&osb->blocked_lock_list))" in
ocfs2_downconvert_thread_do_work can be triggered in the following case:

ocfs2dc has firstly saved osb->blocked_lock_count to local varibale
processed, and then processes the dentry lockres.  During the dentry
put, it calls iput and then deletes rw, inode and open lockres from
blocked list in ocfs2_mark_lockres_freeing.  And this causes the
variable `processed' to not reflect the number of blocked lockres to be
processed, which triggers the BUG.

Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ocfs2/dlmglue.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -4025,9 +4025,13 @@ static void ocfs2_downconvert_thread_do_
 	osb->dc_work_sequence = osb->dc_wake_sequence;
 
 	processed = osb->blocked_lock_count;
-	while (processed) {
-		BUG_ON(list_empty(&osb->blocked_lock_list));
-
+	/*
+	 * blocked lock processing in this loop might call iput which can
+	 * remove items off osb->blocked_lock_list. Downconvert up to
+	 * 'processed' number of locks, but stop short if we had some
+	 * removed in ocfs2_mark_lockres_freeing when downconverting.
+	 */
+	while (processed && !list_empty(&osb->blocked_lock_list)) {
 		lockres = list_entry(osb->blocked_lock_list.next,
 				     struct ocfs2_lock_res, l_blocked_list);
 		list_del_init(&lockres->l_blocked_list);


Patches currently in stable-queue which might be from joseph.qi@huawei.com are

queue-4.1/ocfs2-fix-bug-in-ocfs2_downconvert_thread_do_work.patch
queue-4.1/ocfs2-fix-shift-left-overflow.patch