Re: [PATCH 02/16] mm/huge_memory: access vm_page_prot with READ_ONCE in remove_migration_pmd

[Kirill A. Shutemov]

On Thu, Jun 23, 2022 at 01:06:13AM +0800, Miaohe Lin wrote:
> vma->vm_page_prot is read lockless from the rmap_walk, it may be updated
> concurrently. Using READ_ONCE to prevent the risk of reading intermediate
> values.

Have you checked all other vm_page_prot reads that they hold mmap_lock?

I think the right fix would be to provide a helper to read vm_page_prot
which does READ_ONCE() and use it everywhere. This seems more sustainable.

-- 
 Kirill A. Shutemov