RE: [PATCH] ftruncate on huge page couldn't extend hugetlb file

["Chen, Kenneth W" <kenneth.w.chen@intel.com>]

David Gibson wrote on Wednesday, March 08, 2006 4:23 PM
> > But you already make reservation at mmap time.  If you reserve it again
> > when extending the file, won't you double count?
> 
> Well, I'd generally expect extending truncate() to come before mmap(),
> but in any case hugetlb_extend_reservation() is safe against double
> counting (it's idempotent if called twice with the same number of
> pages).  The semantics are "ensure the this many pages total are
> guaranteed available, that is, either reserved or already
> instantiated".

It's kind of peculiar that kernel reserve hugetlb page at the time of
extending truncate.  Maybe there is a close correlation between mmap
size to the file size.  But these two aren't the same and and shouldn't
be mixed.

- Ken