Re: [patch 1/5] mm: remap_vmalloc_range

[Nick Piggin <npiggin@suse.de>]

On Fri, Apr 21, 2006 at 12:17:12AM -0700, Andrew Morton wrote:
> Nick Piggin <npiggin@suse.de> wrote:
> >
> > Add a remap_vmalloc_range and get rid of as many remap_pfn_range and
> > vm_insert_page loops as possible.
> > 
> > remap_vmalloc_range can do a whole lot of nice range checking even
> > if the caller gets it wrong (which it looks like one or two do).
> > 
> > 
> > -		if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED)) {
> > -		if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED)) {
> > -		if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED)) {
> > -		if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED))
> > -		if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED)) {
> > -		if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED)) {
> > -		if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED))
> > -		if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED))
> > -		if (remap_pfn_range(vma, start, page + vma->vm_pgoff,
> > -						PAGE_SIZE, vma->vm_page_prot))
> > -		if (remap_pfn_range(vma, addr, pfn, PAGE_SIZE, PAGE_READONLY))
> 
> You've removed the ability for the caller to set the pte protections - it
> now always uses vma->vm_page_prot.
> 
> please explain...

They should use vma->vm_page_prot?

The callers affected are the PAGE_SHARED ones (the others are unchanged).
Isn't it correct to provide readonly mappings if userspace asks for it?

I assumed this is why Linus went this way too with the new vm_insert_page
interface.