dlm: convert res_lock to spinlock

Convert the rsb struct res_lock from a mutex to a spinlock
in preparation for processing messages in softirq context.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

Author: Alexander Aring

fs/dlm/dlm_internal.h

@@ -320,7 +320,7 @@ struct dlm_lkb {
 struct dlm_rsb {
 	struct dlm_ls		*res_ls;	/* the lockspace */
 	struct kref		res_ref;
-	struct mutex		res_mutex;
+	spinlock_t		res_lock;
 	unsigned long		res_flags;
 	int			res_length;	/* length of rsb name */
 	int			res_nodeid;

fs/dlm/lock.c

@@ -415,7 +415,7 @@ static int get_rsb_struct(struct dlm_ls *ls, const void *name, int len,
 	r->res_ls = ls;
 	r->res_length = len;
 	memcpy(r->res_name, name, len);
-	mutex_init(&r->res_mutex);
+	spin_lock_init(&r->res_lock);
 
 	INIT_LIST_HEAD(&r->res_lookup);
 	INIT_LIST_HEAD(&r->res_grantqueue);

fs/dlm/lock.h

@@ -69,12 +69,12 @@ static inline int is_master(struct dlm_rsb *r)
 
 static inline void lock_rsb(struct dlm_rsb *r)
 {
-	mutex_lock(&r->res_mutex);
+	spin_lock(&r->res_lock);
 }
 
 static inline void unlock_rsb(struct dlm_rsb *r)
 {
-	mutex_unlock(&r->res_mutex);
+	spin_unlock(&r->res_lock);
 }
 
 #endif