fsck parallel check

[Wojciech Puchar]

>> But it is very good idea to do this on SSD with multiple partitions.
>
> Why do you state that?
>
>> From my perspective it is more that one thread is "good enough":
> fsck should be I/O bound, more threads on a single ssd should just
> lead to I/O queue building and no net reduction in time to complete.
>
> Do you have some data that contridicts that?
>
i do checked it. You may check it too.

In practice.