Re: [RFC/PATCH] prepare_unmapped_area

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

> Eeek, this is more than fugly.  Dave Hansen suggested to move these
> checks into a file operation in response to Adam Litke's hugetlb cleanups,
> and this patch shows he was right :)

No, you don't understand... There is a fops for get_unmapped_area for
the "special" file. It's currently not called for MAP_FIXED but that can
be fixed easily enough (in fact, I have a few ideas to clean up some of
that code, it's already horrible today).

The problem is to prevent something -else- from being mapped into one of
those 256MB area once it's been switched to a different page size.

Right now, this is done via this hugetlbfs specific hack. I want to
have instead some way to have the arch "validate" the address after
get_unmapped_area(), in addition, hugetlbfs wants to "prepare" but that
could indeed be done in hugetlbfs provided fops->get_unmapped_area() if
we call it for MAP_FIXED as well.

Ben.


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