bcachefs: Fix an assertion

We can end up in a strange situation where a btree_path points to a node
being freed even after pointers to it should have been replaced by
pointers to the new node - if the btree node has been reused since the
pointer to it was created.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/btree_update_interior.c

@@ -165,7 +165,8 @@ static void bch2_btree_node_free_inmem(struct btree_trans *trans,
 	struct btree_path *path;
 
 	trans_for_each_path(trans, path)
-		BUG_ON(path->l[b->c.level].b == b);
+		BUG_ON(path->l[b->c.level].b == b &&
+		       path->l[b->c.level].lock_seq == b->c.lock.state.seq);
 
 	six_lock_write(&b->c.lock, NULL, NULL);