Re: [patch 1/5] mm: remap_vmalloc_range

[Nick Piggin <npiggin@suse.de>]

On Fri, Apr 21, 2006 at 12:29:38AM -0700, Andrew Morton wrote:
> 
> When replacing calls to remap_pfn_rage() with calls to remap_valloc_range():
> 
> - remap_pfn_range() sets VM_IO|VM_RESERVED|VM_PFNMAP on the user's vma. 
>   remap_valloc_range() sets only VM_RESERVED.

Yep, it doesn't use PFNMAPs (we can always user the underlying struct
 page), nor is it IO space. The only change that should be seen, as
noted in patch 4/5, is that get_user_pages will work on all mappings
now. I don't think there is a downside to this?

> 
> - remap_pfn_range() has special handling for COWable user vma's, but
>   remap_valloc_range() does not.

That's only for PFNMAPs. COW should continue to work fine.

> 
> - are vma->vm_start and vma->vm_end always a multiple of PAGE_SIZE?  (I
>   always forget).  If not, remap_valloc_range() looks a tad buggy.

I hope so.

> 
> 
> pls explain.
> 
> 
> - remap_valloc_range() can use ~PAGE_MASK, not PAGE_SIZE-1

I initially did that when coding the function in mm/memory.c, but when
adding all the vmalloc range checking I tried to stick with vmalloc
convention.

> 
> - remap_valloc_range() would lose a whole buncha typecasts if you use the
>   gcc pointer-arith-with-void* extension.

Should I?

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