af_unix: Replace BUG_ON() with WARN_ON_ONCE().

This is a prep patch for the last patch in this series so that
checkpatch will not warn about BUG_ON().

Signed-off-by: Kuniyuki Iwashima <[e-mail]>
Acked-by: Jens Axboe <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

net/unix/garbage.c

···
 			/* An embryo cannot be in-flight, so it's safe
 			 * to use the list link.
 			 */
-			BUG_ON(!list_empty(&u->link));
+			WARN_ON_ONCE(!list_empty(&u->link));
 			list_add_tail(&u->link, &embryos);
 		}
 		spin_unlock(&x->sk_receive_queue.lock);
···
 
 		total_refs = file_count(u->sk.sk_socket->file);
 
-		BUG_ON(!u->inflight);
-		BUG_ON(total_refs < u->inflight);
+		WARN_ON_ONCE(!u->inflight);
+		WARN_ON_ONCE(total_refs < u->inflight);
 		if (total_refs == u->inflight) {
 			list_move_tail(&u->link, &gc_candidates);
 			__set_bit(UNIX_GC_CANDIDATE, &u->gc_flags);
···
 		list_move_tail(&u->link, &gc_inflight_list);
 
 	/* All candidates should have been detached by now. */
-	BUG_ON(!list_empty(&gc_candidates));
+	WARN_ON_ONCE(!list_empty(&gc_candidates));
 
 	/* Paired with READ_ONCE() in wait_for_unix_gc(). */
 	WRITE_ONCE(gc_in_progress, false);

net/unix/scm.c

···
 
 	if (u) {
 		if (!u->inflight) {
-			BUG_ON(!list_empty(&u->link));
+			WARN_ON_ONCE(!list_empty(&u->link));
 			list_add_tail(&u->link, &gc_inflight_list);
 		} else {
-			BUG_ON(list_empty(&u->link));
+			WARN_ON_ONCE(list_empty(&u->link));
 		}
 		u->inflight++;
 		/* Paired with READ_ONCE() in wait_for_unix_gc() */
···
 	spin_lock(&unix_gc_lock);
 
 	if (u) {
-		BUG_ON(!u->inflight);
-		BUG_ON(list_empty(&u->link));
+		WARN_ON_ONCE(!u->inflight);
+		WARN_ON_ONCE(list_empty(&u->link));
 
 		u->inflight--;
 		if (!u->inflight)