There are no functional changes, and the new helper will be used in
multiple places in following patches to avoid dereferencing bitmap
directly.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20240826074452.1490072-3-yukuai1@huaweicloud.comSigned-off-by: Song Liu <song@kernel.org>