bcachefs: Fix a rare path in bch2_btree_path_peek_slot()

In the drop_alloc tests, we may end up calling
bch2_btree_iter_peek_slot() on an interior level that doesn't exist.
Previously, this would hit the path->uptodate assertion in
bch2_btree_path_peek_slot(); this path first checks a NULL btree node,
which is how we know we're at the end of the btree.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index 283764225d133337d629589985a36904fbb0b319..0bb156e6152a06bfa97bc24ad8c2b9985b36dfde 100644 (file)
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -1544,14 +1544,17 @@ struct btree_path *bch2_path_get(struct btree_trans *trans,
 inline struct bkey_s_c bch2_btree_path_peek_slot(struct btree_path *path, struct bkey *u)
 {
 
+       struct btree_path_level *l = path_l(path);
+       struct bkey_packed *_k;
        struct bkey_s_c k;
 
-       if (!path->cached) {
-               struct btree_path_level *l = path_l(path);
-               struct bkey_packed *_k;
+       if (unlikely(!l->b))
+               return bkey_s_c_null;
 
-               EBUG_ON(path->uptodate != BTREE_ITER_UPTODATE);
+       EBUG_ON(path->uptodate != BTREE_ITER_UPTODATE);
+       EBUG_ON(!btree_node_locked(path, path->level));
 
+       if (!path->cached) {
                _k = bch2_btree_node_iter_peek_all(&l->iter, l->b);
                k = _k ? bkey_disassemble(l->b, _k, u) : bkey_s_c_null;
 
@@ -1566,7 +1569,6 @@ inline struct bkey_s_c bch2_btree_path_peek_slot(struct btree_path *path, struct
                        (path->btree_id != ck->key.btree_id ||
                         bkey_cmp(path->pos, ck->key.pos)));
                EBUG_ON(!ck || !ck->valid);
-               EBUG_ON(path->uptodate != BTREE_ITER_UPTODATE);
 
                *u = ck->k->k;
                k = bkey_i_to_s_c(ck->k);
@@ -2381,6 +2383,8 @@ struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_iter *iter)
                }
 
                k = bch2_btree_path_peek_slot(iter->path, &iter->k);
+               if (unlikely(!k.k))
+                       goto out_no_locked;
        } else {
                struct bpos next;
 
@@ -2412,7 +2416,7 @@ struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_iter *iter)
                }
 
                if (unlikely(bkey_err(k)))
-                       return k;
+                       goto out_no_locked;
 
                next = k.k ? bkey_start_pos(k.k) : POS_MAX;