Message-Id: <200603090012.k290CDg13307@unix-os.sc.intel.com>
From: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
To: "'David Gibson'" <david@gibson.dropbear.id.au>
Cc: "'Zhang, Yanmin'" <yanmin_zhang@linux.intel.com>,
       <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] ftruncate on huge page couldn't extend hugetlb file
Date: Wed, 8 Mar 2006 16:12:13 -0800
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David Gibson wrote on Wednesday, March 08, 2006 3:58 PM
> > Hmm??  I don't think you need to extend the reservation when extending
> > hugetlb file via ftruncate.  You don't have any vma that pass beyond
> > current size.  So making a reservation is a wrong thing to do here.
> 
> Fwiw, I think truncate *should* extend the reservation.  We have a
> separate thread arguing about whether we should be reserving by inode
> length, as I've implemented, or by which ranges are actually mapped
> (as apw's old path implemented).  As long as it *is* by inode length -
> so it's conceptually all about the logical file in hugetlbfs, not
> about any of its mappings - I think it makes sense for an extending
> truncate() to extend the reservation.  It's not reserving them for any
> particular mapping, it's reserving them for page cache pages.

But you already make reservation at mmap time.  If you reserve it again
when extending the file, won't you double count?

- Ken

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