Re: [PATCH 1/2] mm: move mm counter updating out of set_pte_range()

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

On 2024/4/12 10:57, Kefeng Wang wrote:
> In order to support batch mm counter updating in filemap_map_pages(),
> move mm counter updating out of set_pte_range(), the folios are file
> from filemap, and distinguish folios type by vmf->flags and vma->vm_flags
> from another caller finish_fault().
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
>   mm/filemap.c | 4 ++++
>   mm/memory.c  | 8 +++++---
>   2 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 92e2d43e4c9d..04b813f0146c 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3540,6 +3540,8 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
>   skip:
>   		if (count) {
>   			set_pte_range(vmf, folio, page, count, addr);
> +			add_mm_counter(vmf->vma->vm_mm, mm_counter_file(folio),
> +				       count);
>   			folio_ref_add(folio, count);
>   			if (in_range(vmf->address, addr, count * PAGE_SIZE))
>   				ret = VM_FAULT_NOPAGE;
> @@ -3554,6 +3556,7 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
>   
>   	if (count) {
>   		set_pte_range(vmf, folio, page, count, addr);
> +		add_mm_counter(vmf->vma->vm_mm, mm_counter_file(folio), count);
>   		folio_ref_add(folio, count);
>   		if (in_range(vmf->address, addr, count * PAGE_SIZE))
>   			ret = VM_FAULT_NOPAGE;
> @@ -3590,6 +3593,7 @@ static vm_fault_t filemap_map_order0_folio(struct vm_fault *vmf,
>   		ret = VM_FAULT_NOPAGE;
>   
>   	set_pte_range(vmf, folio, page, 1, addr);
> +	add_mm_counter(vmf->vma->vm_mm, mm_counter_file(folio), 1);
>   	folio_ref_inc(folio);
>   
>   	return ret;
> diff --git a/mm/memory.c b/mm/memory.c
> index 78422d1c7381..69bc63a5d6c8 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4685,12 +4685,10 @@ void set_pte_range(struct vm_fault *vmf, struct folio *folio,
>   		entry = pte_mkuffd_wp(entry);
>   	/* copy-on-write page */
>   	if (write && !(vma->vm_flags & VM_SHARED)) {
> -		add_mm_counter(vma->vm_mm, MM_ANONPAGES, nr);
>   		VM_BUG_ON_FOLIO(nr != 1, folio);
>   		folio_add_new_anon_rmap(folio, vma, addr);
>   		folio_add_lru_vma(folio, vma);
>   	} else {
> -		add_mm_counter(vma->vm_mm, mm_counter_file(folio), nr);
>   		folio_add_file_rmap_ptes(folio, page, nr, vma);
>   	}
>   	set_ptes(vma->vm_mm, addr, vmf->pte, entry, nr);
> @@ -4727,9 +4725,11 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
>   	struct vm_area_struct *vma = vmf->vma;
>   	struct page *page;
>   	vm_fault_t ret;
> +	int is_cow = (vmf->flags & FAULT_FLAG_WRITE) &&
> +		     !(vma->vm_flags & VM_SHARED);

oops, bool is enough.

>   
>   	/* Did we COW the page? */
> -	if ((vmf->flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED))
> +	if (is_cow)
>   		page = vmf->cow_page;
>   	else
>   		page = vmf->page;
> @@ -4765,8 +4765,10 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
>   	/* Re-check under ptl */
>   	if (likely(!vmf_pte_changed(vmf))) {
>   		struct folio *folio = page_folio(page);
> +		int type = is_cow ? MM_ANONPAGES : mm_counter_file(folio);
>   
>   		set_pte_range(vmf, folio, page, 1, vmf->address);
> +		add_mm_counter(vma->vm_mm, type, 1);
>   		ret = 0;
>   	} else {
>   		update_mmu_tlb(vma, vmf->address, vmf->pte);