[PATCH v3 08/22] mm: Allow page table accessors to be non-idempotent

[David Hildenbrand (Red Hat)]

On 11/27/25 17:57, Ryan Roberts wrote:
> On 13/11/2025 01:45, Samuel Holland wrote:
>> Currently, some functions such as pte_offset_map() are passed both
>> pointers to hardware page tables, and pointers to previously-read PMD
>> entries on the stack. To ensure correctness in the first case, these
>> functions must use the page table accessor function (pmdp_get()) to
>> dereference the supplied pointer. However, this means pmdp_get() is
>> called twice in the second case. This double call must be avoided if
>> pmdp_get() applies some non-idempotent transformation to the value.
>>
>> Avoid the double transformation by calling set_pmd() on the stack
>> variables where necessary to keep set_pmd()/pmdp_get() calls balanced.
> 
> I don't think this is a good solution.

Agreed,

	set_pmd(&pmd, pmd);

is rather horrible.

-- 
Cheers

David