On Thu, Mar 03, 2016 at 07:51:50PM +0300, Kirill A. Shutemov wrote:
> Truncate and punch hole that only cover part of THP range is implemented
> by zero out this part of THP.
>
> This have visible effect on fallocate(FALLOC_FL_PUNCH_HOLE) behaviour.
> As we don't really create hole in this case, lseek(SEEK_HOLE) may have
> inconsistent results depending what pages happened to be allocated.
> Not sure if it should be considered ABI break or not.
Looks like this shouldn't be a problem. man 2 fallocate:
Within the specified range, partial filesystem blocks are zeroed,
and whole filesystem blocks are removed from the file. After a
successful call, subsequent reads from this range will return
zeroes.
It means we effectively have 2M filesystem block size.
And I don't see any guarantee about subsequent lseek(SEEK_HOLE) beheviour.
--
Kirill A. Shutemov
