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

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@huawei.com>
Reviewed-by: joyce.xue <xuejiufei@huawei.com>
Reported-by: Guozhonghua <guozhonghua@h3c.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 8 deletions

diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c
index 3ec906ef5d9a..e3cfa0227026 100644
--- a/fs/ocfs2/dlm/dlmmaster.c
+++ b/fs/ocfs2/dlm/dlmmaster.c
@@ -655,12 +655,9 @@ 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,
@@ -668,6 +665,13 @@ 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)
 {
@@ -894,10 +898,8 @@ 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