On Thu, Apr 04, 2019 at 01:52:55PM +0300, Amir Goldstein wrote: > If new file is on the same fs as old file, acct_pin_kill(old) fail to > file_start_write_trylock() and skip writing the old file, because > sb_writers (of new) is already taken by acct_on(). The above is BS, BTW. sb_start_write() does *not* make file_start_write_trylock() to fail. It's basically percpu_down_read() vs. percpu_down_read_trylock(). sb_wait_write() would have file_start_write_trylock() fail (as it should - its caller is freeze_super(); we want an exclusion with attempts to start extra writes there). sb_start_write() sure as hell doesn't - if it would have, we would get its failures from things like e.g. truncate(2) somewhere on the same fs. We don't want to mess with anything freeze-related in acct_on(), but the bug you are refering to in this part really doesn't exist.
