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SubjectRe: [RFC] On paging of kernel VM.
Hi,

On Mon, Sep 09, 2002 at 10:20:53AM +0100, David Woodhouse wrote:
> I think I'd like to introduce 'real' VMAs into kernel space, so that areas
> in the vmalloc range can have 'real' vm_ops and more to the point a real
> nopage function.

The alternative is a kmap-style mechanism for temporarily mapping
pages beyond physical memory on demand. That would avoid the space
limits we have on vmalloc etc; there's only a few tens of MB of
address space we can use for mmap tricks in kernel space, so
persistent maps are seriously constrained if you've got a lot of flash
you want to map.

And with a kmap interface, your locking problems are much simpler ---
you can trap accesses at source and you don't have to go hunting ptes
to invalidate.

Cheers,
Stephen
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