ocfs2: cluster: fix potential deadlock on &o2net_debug_lock

&o2net_debug_lock is acquired by timer o2net_idle_timer() along the
following call chain. Thus the acquisition of the lock under process
context should disable bottom half, otherwise deadlock could happen if the
timer happens to preempt the execution while the lock is held in process
context on the same CPU.

<timer interrupt>
-> o2net_idle_timer()
-> queue_delayed_work()
-> sc_put()
-> sc_kref_release()
-> o2net_debug_del_sc()
-> spin_lock(&o2net_debug_lock);

Several lock acquisition of &o2net_debug_lock under process context do not
disable irq or bottom half. The patch fixes these potential deadlocks
scenerio by using spin_lock_bh() on &o2net_debug_lock.

This flaw was found by an experimental static analysis tool I am
developing for irq-related deadlock. x86_64 allmodconfig using gcc shows
no new warning.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Chengfeng Ye <[e-mail]>
Cc: Mark Fasheh <[e-mail]>
Cc: Joel Becker <[e-mail]>
Cc: Junxiao Bi <[e-mail]>
Cc: Joseph Qi <[e-mail]>
Cc: Gang He <[e-mail]>
Cc: Jun Piao <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

fs/ocfs2/cluster/netdebug.c

···
 
 void o2net_debug_add_nst(struct o2net_send_tracking *nst)
 {
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	list_add(&nst->st_net_debug_item, &send_tracking);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 }
 
 void o2net_debug_del_nst(struct o2net_send_tracking *nst)
 {
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	if (!list_empty(&nst->st_net_debug_item))
 		list_del_init(&nst->st_net_debug_item);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 }
 
 static struct o2net_send_tracking
···
 {
 	struct o2net_send_tracking *nst, *dummy_nst = seq->private;
 
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	nst = next_nst(dummy_nst);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 
 	return nst;
 }
···
 {
 	struct o2net_send_tracking *nst, *dummy_nst = seq->private;
 
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	nst = next_nst(dummy_nst);
 	list_del_init(&dummy_nst->st_net_debug_item);
 	if (nst)
 		list_add(&dummy_nst->st_net_debug_item,
 			 &nst->st_net_debug_item);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 
 	return nst; /* unused, just needs to be null when done */
 }
···
 	ktime_t now;
 	s64 sock, send, status;
 
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	nst = next_nst(dummy_nst);
 	if (!nst)
 		goto out;
···
 		   (long long)status);
 
 out:
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 
 	return 0;
 }
···
 
 void o2net_debug_add_sc(struct o2net_sock_container *sc)
 {
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	list_add(&sc->sc_net_debug_item, &sock_containers);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 }
 
 void o2net_debug_del_sc(struct o2net_sock_container *sc)
 {
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	list_del_init(&sc->sc_net_debug_item);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 }
 
 struct o2net_sock_debug {
···
 	struct o2net_sock_debug *sd = seq->private;
 	struct o2net_sock_container *sc, *dummy_sc = sd->dbg_sock;
 
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	sc = next_sc(dummy_sc);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 
 	return sc;
 }
···
 	struct o2net_sock_debug *sd = seq->private;
 	struct o2net_sock_container *sc, *dummy_sc = sd->dbg_sock;
 
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	sc = next_sc(dummy_sc);
 	list_del_init(&dummy_sc->sc_net_debug_item);
 	if (sc)
 		list_add(&dummy_sc->sc_net_debug_item, &sc->sc_net_debug_item);
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 
 	return sc; /* unused, just needs to be null when done */
 }
···
 	struct o2net_sock_debug *sd = seq->private;
 	struct o2net_sock_container *sc, *dummy_sc = sd->dbg_sock;
 
-	spin_lock(&o2net_debug_lock);
+	spin_lock_bh(&o2net_debug_lock);
 	sc = next_sc(dummy_sc);
 
 	if (sc) {
···
 			sc_show_sock_stats(seq, sc);
 	}
 
-	spin_unlock(&o2net_debug_lock);
+	spin_unlock_bh(&o2net_debug_lock);
 
 	return 0;
 }