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SubjectRe: [PATCH v9 14/24] mm: Introduce __maybe_mkwrite()
On Tue, 13 Mar 2018, Laurent Dufour wrote:

> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index dfa81a638b7c..a84ddc218bbd 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -684,13 +684,18 @@ void free_compound_page(struct page *page);
> * pte_mkwrite. But get_user_pages can cause write faults for mappings
> * that do not have writing enabled, when used by access_process_vm.
> */
> -static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
> +static inline pte_t __maybe_mkwrite(pte_t pte, unsigned long vma_flags)
> {
> - if (likely(vma->vm_flags & VM_WRITE))
> + if (likely(vma_flags & VM_WRITE))
> pte = pte_mkwrite(pte);
> return pte;
> }
>
> +static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
> +{
> + return __maybe_mkwrite(pte, vma->vm_flags);
> +}
> +
> int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
> struct page *page);
> int finish_fault(struct vm_fault *vmf);
> diff --git a/mm/memory.c b/mm/memory.c
> index 0a0a483d9a65..af0338fbc34d 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2472,7 +2472,7 @@ static inline void wp_page_reuse(struct vm_fault *vmf)
>
> flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
> entry = pte_mkyoung(vmf->orig_pte);
> - entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> + entry = __maybe_mkwrite(pte_mkdirty(entry), vmf->vma_flags);
> if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1))
> update_mmu_cache(vma, vmf->address, vmf->pte);
> pte_unmap_unlock(vmf->pte, vmf->ptl);
> @@ -2549,8 +2549,8 @@ static int wp_page_copy(struct vm_fault *vmf)
> inc_mm_counter_fast(mm, MM_ANONPAGES);
> }
> flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
> - entry = mk_pte(new_page, vma->vm_page_prot);
> - entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> + entry = mk_pte(new_page, vmf->vma_page_prot);
> + entry = __maybe_mkwrite(pte_mkdirty(entry), vmf->vma_flags);
> /*
> * Clear the pte entry and flush it first, before updating the
> * pte with the new entry. This will avoid a race condition

Don't you also need to do this in do_swap_page()?

diff --git a/mm/memory.c b/mm/memory.c
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3067,9 +3067,9 @@ int do_swap_page(struct vm_fault *vmf)

inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
dec_mm_counter_fast(vma->vm_mm, MM_SWAPENTS);
- pte = mk_pte(page, vma->vm_page_prot);
+ pte = mk_pte(page, vmf->vma_page_prot);
if ((vmf->flags & FAULT_FLAG_WRITE) && reuse_swap_page(page, NULL)) {
- pte = maybe_mkwrite(pte_mkdirty(pte), vma);
+ pte = __maybe_mkwrite(pte_mkdirty(pte), vmf->vma_flags);
vmf->flags &= ~FAULT_FLAG_WRITE;
ret |= VM_FAULT_WRITE;
exclusive = RMAP_EXCLUSIVE;
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