Use the existed helper instead of open coding it, avoid dereferencing
bitmap directly to prepare inventing a new bitmap.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240826074452.1490072-10-yukuai1@huaweicloud.comSigned-off-by: Song Liu <song@kernel.org>