ext4: Provide function to handle transaction restarts

mainline inclusion
from mainline-5.5-rc1
commit a4130367
category: bugfix
bugzilla: 25031
CVE: NA
---------------------------

Provide ext4_journal_ensure_credits_fn() function to ensure transaction
has given amount of credits and call helper function to prepare for
restarting a transaction. This allows to remove some boilerplate code
from various places, add proper error handling for the case where
transaction extension or restart fails, and reduces following changes
needed for proper revoke record reservation tracking.

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191105164437.32602-10-jack@suse.cz


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

Conflict:
  fs/ext4/ext4.h

Signed-off-by: zhangyi (F) <yi.zhang@huawei.com>
Reviewed-by: Yang Erkun <yangerkun@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>