> On 26 Aug 2019, at 19.29, Al Viro <v...@zeniv.linux.org.uk> wrote:
>
> On Mon, Aug 26, 2019 at 03:48:38AM +0100, Al Viro wrote:
>
>> We might be able to paper over that mess by doing what /dev/st does -
>> checking that file_count(file) == 1 in ->flush() instance and doing commit
>> there in such case. It's not entirely reliable, though, and it's definitely
>> not something I'd like to see spreading.
>
> This "not entirely reliable" turns out to be an understatement.
> If you have /proc/*/fdinfo/* being read from at the time of final close(2),
> you'll get file_count(file) > 1 the last time ->flush() is called. In other
> words, we'd get the data not committed at all.
>
...
> PS: just dropping the check in st_flush() is probably a bad idea -
> as it is, it can't overlap with st_write() and after such change it
> will…
Yes, don’t just drop it. The tape semantics require that a file mark is written
when the last opener closes this sequential device. This is why the check is
there. Of course, it is good if someone finds a better solution for this.
Thanks,
Kai
