Re: [RFC 4/8] Enhance fallback functions in libs to support higher order pages

From: Matt Mackall
Date: Tue Apr 24 2007 - 19:14:34 EST


On Fri, Apr 20, 2007 at 12:10:43PM -0700, Christoph Lameter wrote:
> On Fri, 20 Apr 2007, Dave Kleikamp wrote:
>
> > On Fri, 2007-04-20 at 12:05 +0100, Mel Gorman wrote:
> >
> > > comments about missing page_cache_size() covered elsewhere. However, I
> > > note that Dave Kleikamp might be interested in this changing of
> > > page_cache_size() from the perspective of page cache tails. I've added
> > > him to the cc so he can take a quick look.
> >
> > Yeah. I'm working on patches for storing file tails in buffers
> > allocated from the slab cache, and the tail will be represented by a
> > fake struct page. (This is primarily for kernels with a larger page
> > size). So my version of page_cache_size(page) may return a different
> > size for different pages belonging to the same mapping. I'm in the
> > midst of cleaning up the patches and plan to post them to linux-mm by
> > Monday.
>
> I am not sure what the point of that patchset would be in this context
> given that this is about support for arbitrary page sizes. If the
> filesystem wants it then it can reduce the page size for small files.

Shaggy's suggestion is to emulate pages with _negative_ orders.

--
Mathematics is the supreme nostalgia of our time.
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