Re: [PATCH v2 3/3] mm/hugetlb: Use a folio in hugetlb_fault()

[Sidhartha Kumar <sidhartha.kumar@oracle.com>]

On 6/5/23 11:20 PM, Peng Zhang wrote:
> From: ZhangPeng <zhangpeng362@huawei.com>
> 
> We can replace seven implicit calls to compound_head() with one by using
> folio.
> 
> Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
> ---
>   mm/hugetlb.c | 18 +++++++++---------
>   1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index e58f8001fd92..e34329e25abe 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -6062,7 +6062,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>   	vm_fault_t ret;
>   	u32 hash;
>   	pgoff_t idx;
> -	struct page *page = NULL;
> +	struct folio *folio = NULL;
>   	struct folio *pagecache_folio = NULL;
>   	struct hstate *h = hstate_vma(vma);
>   	struct address_space *mapping;
> @@ -6181,14 +6181,14 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>   	 * pagecache_folio, so here we need take the former one
>   	 * when page != pagecache_folio or !pagecache_folio.
>   	 */

This comment should also be updated as page is no longer a variable in 
this function.

> -	page = pte_page(entry);
> -	if (page_folio(page) != pagecache_folio)
> -		if (!trylock_page(page)) {
> +	folio = page_folio(pte_page(entry));
> +	if (folio != pagecache_folio)
> +		if (!folio_trylock(folio)) {
>   			need_wait_lock = 1;
>   			goto out_ptl;
>   		}
>   
> -	get_page(page);
> +	folio_get(folio);
>   
>   	if (flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) {
>   		if (!huge_pte_write(entry)) {
> @@ -6204,9 +6204,9 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>   						flags & FAULT_FLAG_WRITE))
>   		update_mmu_cache(vma, haddr, ptep);
>   out_put_page:
> -	if (page_folio(page) != pagecache_folio)
> -		unlock_page(page);
> -	put_page(page);
> +	if (folio != pagecache_folio)
> +		folio_unlock(folio);
> +	folio_put(folio);
>   out_ptl:
>   	spin_unlock(ptl);
>   
> @@ -6225,7 +6225,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>   	 * here without taking refcount.
>   	 */
>   	if (need_wait_lock)
> -		wait_on_page_locked(page);
> +		folio_wait_locked(folio);
>   	return ret;
>   }
>   

Besides updating the comment.
Reviewed-by Sidhartha Kumar <sidhartha.kumar@oracle.com>