range_tree_clear
ret = range_tree_clear(&arena->rt, vmf->pgoff, 1);
ret = range_tree_clear(&arena->rt, pgoff, page_cnt);
ret = range_tree_clear(&arena->rt, pgoff, page_cnt);
ret = range_tree_clear(&arena->rt, pgoff, page_cnt);
err = range_tree_clear(rt, start, len);
int range_tree_clear(struct range_tree *rt, u32 start, u32 len);