bcachefs: Fix bch2_btree_node_fill() for !path

We shouldn't be doing the unlock/relock dance when we're not using a
path - this fixes an assertion pop when called from btree node scan.

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

fs/bcachefs/btree_cache.c

@@ -709,7 +709,6 @@ static noinline struct btree *bch2_btree_node_fill(struct btree_trans *trans,
  struct bch_fs *c = trans->c;
  struct btree_cache *bc = &c->btree_cache;
  struct btree *b;
- u32 seq;
 
  if (unlikely(level >= BTREE_MAX_DEPTH)) {
  int ret = bch2_fs_topology_error(c, "attempting to get btree node at level %u, >= max depth %u",
@@ -775,34 +774,26 @@ static noinline struct btree *bch2_btree_node_fill(struct btree_trans *trans,
  }
 
  set_btree_node_read_in_flight(b);
-
  six_unlock_write(&b->c.lock);
- seq = six_lock_seq(&b->c.lock);
- six_unlock_intent(&b->c.lock);
 
- /* Unlock before doing IO: */
- if (path && sync)
- bch2_trans_unlock_noassert(trans);
-
- bch2_btree_node_read(trans, b, sync);
+ if (path) {
+ u32 seq = six_lock_seq(&b->c.lock);
 
- if (!sync)
- return NULL;
+ /* Unlock before doing IO: */
+ six_unlock_intent(&b->c.lock);
+ bch2_trans_unlock_noassert(trans);
 
- if (path) {
- int ret = bch2_trans_relock(trans) ?:
- bch2_btree_path_relock_intent(trans, path);
- if (ret) {
- BUG_ON(!trans->restarted);
- return ERR_PTR(ret);
- }
- }
+ bch2_btree_node_read(trans, b, sync);
 
- if (!six_relock_type(&b->c.lock, lock_type, seq)) {
- BUG_ON(!path);
+  if (!sync)
+  return NULL;
 
- trace_and_count(c, trans_restart_relock_after_fill, trans, _THIS_IP_, path);
- return ERR_PTR(btree_trans_restart(trans, BCH_ERR_transaction_restart_relock_after_fill));
+ if (!six_relock_type(&b->c.lock, lock_type, seq))
+ b = NULL;
+ } else {
+ bch2_btree_node_read(trans, b, sync);
+ if (lock_type == SIX_LOCK_read)
+ six_lock_downgrade(&b->c.lock);
  }
 
  return b;
@@ -1135,18 +1126,19 @@ int bch2_btree_node_prefetch(struct btree_trans *trans,
 {
  struct bch_fs *c = trans->c;
  struct btree_cache *bc = &c->btree_cache;
- struct btree *b;
 
  BUG_ON(path && !btree_node_locked(path, level + 1));
  BUG_ON(level >= BTREE_MAX_DEPTH);
 
- b = btree_cache_find(bc, k);
+ struct btree *b = btree_cache_find(bc, k);
  if (b)
  return 0;
 
  b = bch2_btree_node_fill(trans, path, k, btree_id,
  level, SIX_LOCK_read, false);
- return PTR_ERR_OR_ZERO(b);
+ if (!IS_ERR_OR_NULL(b))
+ six_unlock_read(&b->c.lock);
+ return bch2_trans_relock(trans) ?: PTR_ERR_OR_ZERO(b);
 }
 
 void bch2_btree_node_evict(struct btree_trans *trans, const struct bkey_i *k)