Re: [PATCH V3 2/2] mm/mmap: Drop generic protection_map[] array

[Anshuman Khandual]

On 6/17/22 13:30, hch@xxxxxxxxxxxxx wrote:
> On Fri, Jun 17, 2022 at 05:48:11AM +0000, Christophe Leroy wrote:
>> Is it a good idea to duplicate vm_get_page_prot() in each architecture ? 
> 
> It is a completely trivial array index.  And I really like the idea
> of not having the protection_map in common code - it really is an
> implementation detail.  But what we could do is something like
> 
> #define DECLARE_VM_GET_PAGE_PROT				\
> pgprot_t vm_get_page_prot(unsigned long vm_flags)		\
> {								\
>         return protection_map[vm_flags &			\
> 		(VM_READ | VM_WRITE | VM_EXEC | VM_SHARED)];	\
> }								\
> EXPORT_SYMBOL(vm_get_page_prot);
> 
> as a helper for the architectures.

Agreed, this will ensure the exact same implementation for all platforms
(except those custom vm_get_page_prot), without deviations and mistakes.