bcachefs: More btree iterator fixes

 - check for getting to the end of the btree in bch2_path_verify_locks
   and __btree_path_traverse_all(), this fixes an infinite loop in
   __btree_path_traverse_all().
 - relax requirement in bch2_btree_node_upgrade() that we must want an
   intent lock, this fixes bugs with paths that point to interior nodes
   (nonzero level).
 - bch2_btree_node_update_key(): fix it to upgrade the path to an intent
   lock, if necessary
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/btree_iter.c

@@ -170,11 +170,20 @@ static bool bch2_btree_node_upgrade(struct btree_trans *trans,
 {
 	struct btree *b = path->l[level].b;
 
-	EBUG_ON(btree_lock_want(path, level) != BTREE_NODE_INTENT_LOCKED);
-
 	if (!is_btree_node(path, level))
 		return false;
 
+	switch (btree_lock_want(path, level)) {
+	case BTREE_NODE_UNLOCKED:
+		BUG_ON(btree_node_locked(path, level));
+		return true;
+	case BTREE_NODE_READ_LOCKED:
+		BUG_ON(btree_node_intent_locked(path, level));
+		return bch2_btree_node_relock(trans, path, level);
+	case BTREE_NODE_INTENT_LOCKED:
+		break;
+	}
+
 	if (btree_node_intent_locked(path, level))
 		return true;
 
@@ -368,7 +377,8 @@ static void bch2_btree_path_verify_locks(struct btree_path *path)
 	unsigned l;
 
 	if (!path->nodes_locked) {
-		BUG_ON(path->uptodate == BTREE_ITER_UPTODATE);
+		BUG_ON(path->uptodate == BTREE_ITER_UPTODATE &&
+		       btree_path_node(path, path->level));
 		return;
 	}
 
@@ -1356,7 +1366,8 @@ static int __btree_path_traverse_all(struct btree_trans *trans, int ret,
 
 		EBUG_ON(!(trans->paths_allocated & (1ULL << path->idx)));
 
-		if (path->nodes_locked)
+		if (path->nodes_locked ||
+		    !btree_path_node(path, path->level))
 			i++;
 	}
 

fs/bcachefs/btree_update_interior.c

@@ -1945,9 +1945,16 @@ int bch2_btree_node_update_key(struct btree_trans *trans, struct btree_iter *ite
 {
 	struct bch_fs *c = trans->c;
 	struct btree *new_hash = NULL;
+	struct btree_path *path = iter->path;
 	struct closure cl;
 	int ret = 0;
 
+	if (!btree_node_intent_locked(path, b->c.level) &&
+	    !bch2_btree_path_upgrade(trans, path, b->c.level + 1)) {
+		btree_trans_restart(trans);
+		return -EINTR;
+	}
+
 	closure_init_stack(&cl);
 
 	/*
@@ -1966,8 +1973,10 @@ int bch2_btree_node_update_key(struct btree_trans *trans, struct btree_iter *ite
 		new_hash = bch2_btree_node_mem_alloc(c);
 	}
 
+	path->intent_ref++;
 	ret = __bch2_btree_node_update_key(trans, iter, b, new_hash,
 					   new_key, skip_triggers);
+	--path->intent_ref;
 
 	if (new_hash) {
 		mutex_lock(&c->btree_cache.lock);