ext4: refactor ext4_punch_hole()

The current implementation of ext4_punch_hole() contains complex
position calculations and stale error tags. To improve the code's
clarity and maintainability, it is essential to clean up the code and
improve its readability, this can be achieved by: a) simplifying and
renaming variables; b) eliminating unnecessary position calculations;
c) writing back all data in data=journal mode, and drop page cache from
the original offset to the end, rather than using aligned blocks,
d) renaming the stale error tags.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://patch.msgid.link/20241220011637.1157197-5-yi.zhang@huaweicloud.com


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