bcachefs: Improve bch2_btree_node_relock()

This moves the IS_ERR_OR_NULL() check to the inline part, since that's a
fast path event.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_locking.c

@@ -208,9 +208,6 @@ bool __bch2_btree_node_relock(struct btree_trans *trans,
 	struct btree *b = btree_path_node(path, level);
 	int want = __btree_lock_want(path, level);
 
-	if (!is_btree_node(path, level))
-		goto fail;
-
 	if (race_fault())
 		goto fail;
 
@@ -221,9 +218,6 @@ bool __bch2_btree_node_relock(struct btree_trans *trans,
 		return true;
 	}
 fail:
-	if (b != ERR_PTR(-BCH_ERR_no_btree_node_cached) &&
-	    b != ERR_PTR(-BCH_ERR_no_btree_node_init) &&
-	    b != ERR_PTR(-BCH_ERR_no_btree_node_up))
 	trace_btree_node_relock_fail(trans, _RET_IP_, path, level);
 	return false;
 }

fs/bcachefs/btree_locking.h

@@ -325,7 +325,8 @@ static inline bool bch2_btree_node_relock(struct btree_trans *trans,
 		btree_node_locked_type(path, level) != __btree_lock_want(path, level));
 
 	return likely(btree_node_locked(path, level)) ||
-		__bch2_btree_node_relock(trans, path, level);
+		(!IS_ERR_OR_NULL(path->l[level].b) &&
+		 __bch2_btree_node_relock(trans, path, level));
 }
 
 /* upgrade */