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 <kuniyu@amazon.com>
Acked-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20240129190435.57228-2-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/unix/garbage.c

@@ -145,7 +145,7 @@ static void scan_children(struct sock *x, void (*func)(struct unix_sock *),
 			/* 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);
@@ -213,8 +213,8 @@ static void __unix_gc(struct work_struct *work)
 
 		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);
@@ -294,7 +294,7 @@ static void __unix_gc(struct work_struct *work)
 		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

@@ -51,10 +51,10 @@ void unix_inflight(struct user_struct *user, struct file *fp)
 
 	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() */
@@ -71,8 +71,8 @@ void unix_notinflight(struct user_struct *user, struct file *fp)
 	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)