ext4: hold s_fc_lock while during fast commit

ext4: hold s_fc_lock while during fast commit

Leaving s_fc_lock in between during commit in ext4_fc_perform_commit()
function leaves room for subtle concurrency bugs where ext4_fc_del() may
delete an inode from the fast commit list, leaving list in an inconsistent
state.

Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20250508175908.1004880-10-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>