returning non-ram via ->nopage, was Re: [patch] mspec driver for 2.6.12-rc2-mm3

From: Christoph Hellwig
Date: Mon Apr 25 2005 - 09:49:08 EST

Jes has this shiny new IA64 uncached foo bar whizbang driver (see the patch
which has a nopage routine that calls remap_pfn_range from ->nopage for
uncached memory that's not part of the mem map. Because ->nopage wants
to return a struct page * he's allocating a normal kernel page and actually
returns that one - to get the page he wants into the pagetables his does
all the pagetable manipulation himself before (See the glory details of
pagetable walks and modification inside a driver in the patch above).

I don't think these hacks are acceptable for a driver, especially as the
problem can easily be solved by calling remap_pfn_range in ->mmap - except
SGI also wants node locality..
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