ext4: add periodic superblock update check

This patch introduces a mechanism to periodically check and update
the superblock within the ext4 file system. The main purpose of this
patch is to keep the disk superblock up to date. The update will be
performed if more than one hour has passed since the last update, and
if more than 16MB of data have been written to disk.

This check and update is performed within the ext4_journal_commit_callback
function, ensuring that the superblock is written while the disk is
active, rather than based on a timer that may trigger during disk idle
periods.

Discussion https://www.spinics.net/lists/linux-ext4/msg85865.html



Signed-off-by: Vitaliy Kuznetsov <vk.en.mail@gmail.com>
Link: https://lore.kernel.org/r/20230810143852.40228-1-vk.en.mail@gmail.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>