bcachefs: Don't downgrade in traverse()

Downgrading of btree iterators is something that should only happen
explicitly.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/btree_key_cache.c

@@ -341,12 +341,10 @@ int bch2_btree_iter_traverse_cached(struct btree_iter *iter)
 
 	iter->uptodate = BTREE_ITER_NEED_PEEK;
 
-	if (!(iter->flags & BTREE_ITER_INTENT))
-		bch2_btree_iter_downgrade(iter);
-	else if (!iter->locks_want) {
-		if (!__bch2_btree_iter_upgrade(iter, 1))
+	if ((iter->flags & BTREE_ITER_INTENT) &&
+	    !iter->locks_want &&
+	    __bch2_btree_iter_upgrade(iter, 1))
 		ret = -EINTR;
-	}
 
 	return ret;
 err: