bcachefs: fix bch2_btree_key_cache_drop()

When evicting, we shouldn't leave a pointer to the key cache entry lying
around - that screws up btree path asserts we're adding.

Signed-off-by: Kent Overstreet <[email protected]>

Author: Kent Overstreet

fs/bcachefs/btree_key_cache.c

@@ -613,8 +613,18 @@ void bch2_btree_key_cache_drop(struct btree_trans *trans,
 	bkey_cached_free(bc, ck);
 
 	mark_btree_node_locked(trans, path, 0, BTREE_NODE_UNLOCKED);
-	btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
-	path->should_be_locked = false;
+
+	struct btree_path *path2;
+	unsigned i;
+	trans_for_each_path(trans, path2, i)
+		if (path2->l[0].b == (void *) ck) {
+			__bch2_btree_path_unlock(trans, path2);
+			path2->l[0].b = ERR_PTR(-BCH_ERR_no_btree_node_drop);
+			path2->should_be_locked = false;
+			btree_path_set_dirty(path2, BTREE_ITER_NEED_TRAVERSE);
+		}
+
+	bch2_trans_verify_locks(trans);
 }
 
 static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,