Re: [PATCH] mm: memory: check userfaultfd_wp() in vmf_orig_pte_uffd_wp()

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 2024/4/17 16:23, Kefeng Wang wrote:
> Directly call vmf_orig_pte_uffd_wp() in do_anonymous_page() and
> set_pte_range() to save a uffd_wp and add userfaultfd_wp() check
> in vmf_orig_pte_uffd_wp() to avoid the unnecessary function calls
> in the most sense, lat_pagefault testcase does show improvement
> though very small(~1%).
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>   mm/memory.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 5ae2409d3cb9..a6afc96001e6 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -117,6 +117,9 @@ static bool vmf_orig_pte_uffd_wp(struct vm_fault *vmf)


	 if (!IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP))
         	return false;

Will add config check too,

>   	if (!(vmf->flags & FAULT_FLAG_ORIG_PTE_VALID))
>   		return false;
>   
> +	if (!userfaultfd_wp(vmf->vma))
> +		return false;
> +

but wait for review.

>   	return pte_marker_uffd_wp(vmf->orig_pte);
>   }
>   
> @@ -4388,7 +4391,6 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf)
>    */
>   static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
>   {
> -	bool uffd_wp = vmf_orig_pte_uffd_wp(vmf);
>   	struct vm_area_struct *vma = vmf->vma;
>   	unsigned long addr = vmf->address;
>   	struct folio *folio;
> @@ -4488,7 +4490,7 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
>   	folio_add_new_anon_rmap(folio, vma, addr);
>   	folio_add_lru_vma(folio, vma);
>   setpte:
> -	if (uffd_wp)
> +	if (vmf_orig_pte_uffd_wp(vmf))
>   		entry = pte_mkuffd_wp(entry);
>   	set_ptes(vma->vm_mm, addr, vmf->pte, entry, nr_pages);
>   
> @@ -4663,7 +4665,6 @@ void set_pte_range(struct vm_fault *vmf, struct folio *folio,
>   		struct page *page, unsigned int nr, unsigned long addr)
>   {
>   	struct vm_area_struct *vma = vmf->vma;
> -	bool uffd_wp = vmf_orig_pte_uffd_wp(vmf);
>   	bool write = vmf->flags & FAULT_FLAG_WRITE;
>   	bool prefault = in_range(vmf->address, addr, nr * PAGE_SIZE);
>   	pte_t entry;
> @@ -4678,7 +4679,7 @@ void set_pte_range(struct vm_fault *vmf, struct folio *folio,
>   
>   	if (write)
>   		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> -	if (unlikely(uffd_wp))
> +	if (unlikely(vmf_orig_pte_uffd_wp(vmf)))
>   		entry = pte_mkuffd_wp(entry);
>   	/* copy-on-write page */
>   	if (write && !(vma->vm_flags & VM_SHARED)) {