Re: [patch] do_no_pfn handler

[Carsten Otte]

Linus Torvalds wrote:
> Now, the kernel page table accessor macros are certainly generic enough 
> that you could have your own "COW bits" macro, and make this all an 
> architecture-specific feature (and simply not allow it on architectures 
> that don't have a sw-usable COW bit)
> 
> It so happens that S390 seems to be one of the very few architectures that 
> doesn't have room for that bit in its regular page table layout, and 
> that's arguably a design problem for S390. But you _could_ just allocate 
> extra memory for page tables, and put the COW bit there. The VM wouldn't 
> care - at that point it would fit in the "larger picture" of just having 
> the COW information directly in the page tables (even if the "page tables" 
> would be partly just sw-defined).
Interresting idea. Sounds more feasible then splitting vmas, I am going to think about it. Thanks!
-- 

Carsten Otte
IBM Linux technology center
ARCH=s390
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