[PATCH 3.13 144/163] ocfs2/dlm: do not get resource spinlock if lockres is new

Kamal Mostafa kamal at canonical.com
Thu Oct 9 21:02:49 UTC 2014 -stable review patch.  If anyone has any objections, please let me know.


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

commit 5760a97c7143c208fa3a8f8cad0ed7dd672ebd28 upstream.

There is a deadlock case which reported by Guozhonghua:

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);
 	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,
+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

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