ext4: add EXT4_LBLK_TO_PG and EXT4_PG_TO_LBLK for block/page conversion

ext4: add EXT4_LBLK_TO_PG and EXT4_PG_TO_LBLK for block/page conversion

As BS > PS support is coming, all block number to page index (and
vice-versa) conversions must now go via bytes. Added EXT4_LBLK_TO_PG()
and EXT4_PG_TO_LBLK() macros to simplify these conversions and handle
both BS <= PS and BS > PS scenarios cleanly.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Message-ID: <20251121090654.631996-11-libaokun@huaweicloud.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>