[3.13.y.z extended stable] Patch "ocfs2/dlm: do not get resource spinlock if lockres is new" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ocfs2/dlm: do not get resource spinlock if lockres is new

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.9.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 7a72503a51ef010d9991315ac11ca4cdbfc0d409 Mon Sep 17 00:00:00 2001
From: Joseph Qi <joseph.qi at huawei.com>
Date: Thu, 25 Sep 2014 16:05:16 -0700
Subject: ocfs2/dlm: do not get resource spinlock if lockres is new

commit 5760a97c7143c208fa3a8f8cad0ed7dd672ebd28 upstream.

There is a deadlock case which reported by Guozhonghua:
  https://oss.oracle.com/pipermail/ocfs2-devel/2014-September/010079.html

This case is caused by &res->spinlock and &dlm->master_lock
misordering in different threads.

It was introduced by commit 8d400b81cc83 ("ocfs2/dlm: Clean up refmap
helpers").  Since lockres is new, it doesn't not require the
&res->spinlock.  So remove it.

Fixes: 8d400b81cc83 ("ocfs2/dlm: Clean up refmap helpers")
Signed-off-by: Joseph Qi <joseph.qi at huawei.com>
Reviewed-by: joyce.xue <xuejiufei at huawei.com>
Reported-by: Guozhonghua <guozhonghua at h3c.com>
Cc: Joel Becker <jlbec at evilplan.org>
Cc: Mark Fasheh <mfasheh at suse.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/ocfs2/dlm/dlmmaster.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index af3f7aa..1be3398 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -650,12 +650,9 @@ void dlm_lockres_clear_refmap_bit(struct dlm_ctxt *dlm,
 	clear_bit(bit, res->refmap);
 }

-
-void dlm_lockres_grab_inflight_ref(struct dlm_ctxt *dlm,
+static void __dlm_lockres_grab_inflight_ref(struct dlm_ctxt *dlm,
 				   struct dlm_lock_resource *res)
 {
-	assert_spin_locked(&res->spinlock);
-
 	res->inflight_locks++;

 	mlog(0, "%s: res %.*s, inflight++: now %u, %ps()\n", dlm->name,
@@ -663,6 +660,13 @@ void dlm_lockres_grab_inflight_ref(struct dlm_ctxt *dlm,
 	     __builtin_return_address(0));
 }

+void dlm_lockres_grab_inflight_ref(struct dlm_ctxt *dlm,
+				   struct dlm_lock_resource *res)
+{
+	assert_spin_locked(&res->spinlock);
+	__dlm_lockres_grab_inflight_ref(dlm, res);
+}
+
 void dlm_lockres_drop_inflight_ref(struct dlm_ctxt *dlm,
 				   struct dlm_lock_resource *res)
 {
@@ -852,10 +856,8 @@ lookup:
 	/* finally add the lockres to its hash bucket */
 	__dlm_insert_lockres(dlm, res);

-	/* Grab inflight ref to pin the resource */
-	spin_lock(&res->spinlock);
-	dlm_lockres_grab_inflight_ref(dlm, res);
-	spin_unlock(&res->spinlock);
+	/* since this lockres is new it doesn't not require the spinlock */
+	__dlm_lockres_grab_inflight_ref(dlm, res);

 	/* get an extra ref on the mle in case this is a BLOCK
 	 * if so, the creator of the BLOCK may try to put the last
--
1.9.1