Re: [PATCH 3/9] mm/hugetlb_cgroup: convert set_hugetlb_cgroup*() to folios

[Mike Kravetz]

On 10/13/22 20:12, Sidhartha Kumar wrote:
> Allows __prep_new_huge_page() to operate on a folio by converting
> set_hugetlb_cgroup*() to take in a folio.
> 
> Signed-off-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1758,19 +1758,21 @@ static void __prep_account_new_huge_page(struct hstate *h, int nid)
>  	h->nr_huge_pages_node[nid]++;
>  }
>  
> -static void __prep_new_huge_page(struct hstate *h, struct page *page)
> +static void __prep_new_hugetlb_folio(struct hstate *h, struct folio *folio)
>  {
> -	hugetlb_vmemmap_optimize(h, page);
> -	INIT_LIST_HEAD(&page->lru);
> -	set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
> -	hugetlb_set_page_subpool(page, NULL);
> -	set_hugetlb_cgroup(page, NULL);
> -	set_hugetlb_cgroup_rsvd(page, NULL);
> +	hugetlb_vmemmap_optimize(h, &folio->page);
> +	INIT_LIST_HEAD(&folio->lru);
> +	folio->_folio_dtor = HUGETLB_PAGE_DTOR;

Seems like we should have a routine 'set_folio_dtor' that has the same
functionality as set_compound_page_dtor.  Here, we loose the check for a
valid DTOR value (although not terribly valuable).

Not required for this patch, but something to note.

> +	hugetlb_set_folio_subpool(folio, NULL);
> +	set_hugetlb_cgroup(folio, NULL);
> +	set_hugetlb_cgroup_rsvd(folio, NULL);
>  }
>  
>  static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
>  {
> -	__prep_new_huge_page(h, page);
> +	struct folio *folio = page_folio(page);
> +
> +	__prep_new_hugetlb_folio(h, folio);
>  	spin_lock_irq(&hugetlb_lock);
>  	__prep_account_new_huge_page(h, nid);
>  	spin_unlock_irq(&hugetlb_lock);
> @@ -2731,8 +2733,10 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
>  					struct list_head *list)
>  {
>  	gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
> -	int nid = page_to_nid(old_page);
> +	struct folio *old_folio = page_folio(old_page);
> +	int nid = folio_nid(old_folio);
>  	struct page *new_page;
> +	struct folio *new_folio;
>  	int ret = 0;
>  
>  	/*
> @@ -2745,16 +2749,17 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
>  	new_page = alloc_buddy_huge_page(h, gfp_mask, nid, NULL, NULL);
>  	if (!new_page)
>  		return -ENOMEM;
> -	__prep_new_huge_page(h, new_page);
> +	new_folio = page_folio(new_page);
> +	__prep_new_hugetlb_folio(h, new_folio);
>  
>  retry:
>  	spin_lock_irq(&hugetlb_lock);
> -	if (!PageHuge(old_page)) {
> +	if (!folio_test_hugetlb(old_folio)) {
>  		/*
>  		 * Freed from under us. Drop new_page too.
>  		 */
>  		goto free_new;
> -	} else if (page_count(old_page)) {
> +	} else if (folio_ref_count(old_folio)) {
>  		/*
>  		 * Someone has grabbed the page, try to isolate it here.
>  		 * Fail with -EBUSY if not possible.
> @@ -2763,7 +2768,7 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
>  		ret = isolate_hugetlb(old_page, list);
>  		spin_lock_irq(&hugetlb_lock);
>  		goto free_new;
> -	} else if (!HPageFreed(old_page)) {
> +	} else if (!folio_test_hugetlb(old_folio)) {

Should that be?
	} else if (!folio_test_hugetlb_freed(old_folio)) {

-- 
Mike Kravetz

>  		/*
>  		 * Page's refcount is 0 but it has not been enqueued in the
>  		 * freelist yet. Race window is small, so we can succeed here if
> @@ -2801,7 +2806,7 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
>  free_new:
>  	spin_unlock_irq(&hugetlb_lock);
>  	/* Page has a zero ref count, but needs a ref to be freed */
> -	set_page_refcounted(new_page);
> +	folio_ref_unfreeze(new_folio, 1);
>  	update_and_free_page(h, new_page, false);
>  
>  	return ret;