Re: [PATCH v2 4/5] hugetlb: convert PageHugeTemporary() to HPageTemporary flag

Oscar Salvador
2021-01-20T10:30:33Z

On Tue, Jan 19, 2021 at 05:30:48PM -0800, Mike Kravetz wrote:
> Use new hugetlb specific HPageTemporary flag to replace the
> PageHugeTemporary() interfaces.
>
> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>

I would have added a brief comment explaining why it is ok to drop
the PageHuge() check in PageHugeTemporary.
AFAICS, the paths checking it already know they are handling with a
hugetlb page, but still it is better to mention it in the changelog
in case someone wonders.

Other than that looks good to me:

Reviewed-by: Oscar Salvador <osalvador@suse.de>

> ---
> include/linux/hugetlb.h | 6 ++++++
> mm/hugetlb.c | 36 +++++++-----------------------------
> 2 files changed, 13 insertions(+), 29 deletions(-)
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 1e17529c8b81..ec329b9cc0fc 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -483,10 +483,15 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
> * HPG_migratable - Set after a newly allocated page is added to the page
> * cache and/or page tables. Indicates the page is a candidate for
> * migration.
> + * HPG_temporary - - Set on a page that is temporarily allocated from the buddy
> + * allocator. Typically used for migration target pages when no pages
> + * are available in the pool. The hugetlb free page path will
> + * immediately free pages with this flag set to the buddy allocator.
> */
> enum hugetlb_page_flags {
> HPG_restore_reserve = 0,
> HPG_migratable,
> + HPG_temporary,
> __NR_HPAGEFLAGS,
> };
>
> @@ -534,6 +539,7 @@ static inline void ClearHPage##uname(struct page *page) \
> */
> HPAGEFLAG(RestoreReserve, restore_reserve)
> HPAGEFLAG(Migratable, migratable)
> +HPAGEFLAG(Temporary, temporary)
>
> #ifdef CONFIG_HUGETLB_PAGE
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 6e32751489e8..0d2bfc2b6adc 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1353,28 +1353,6 @@ struct hstate *size_to_hstate(unsigned long size)
> return NULL;
> }
>
> -/*
> - * Internal hugetlb specific page flag. Do not use outside of the hugetlb
> - * code
> - */
> -static inline bool PageHugeTemporary(struct page *page)
> -{
> - if (!PageHuge(page))
> - return false;
> -
> - return (unsigned long)page[2].mapping == -1U;
> -}
> -
> -static inline void SetPageHugeTemporary(struct page *page)
> -{
> - page[2].mapping = (void *)-1U;
> -}
> -
> -static inline void ClearPageHugeTemporary(struct page *page)
> -{
> - page[2].mapping = NULL;
> -}
> -
> static void __free_huge_page(struct page *page)
> {
> /*
> @@ -1422,9 +1400,9 @@ static void __free_huge_page(struct page *page)
> if (restore_reserve)
> h->resv_huge_pages++;
>
> - if (PageHugeTemporary(page)) {
> + if (HPageTemporary(page)) {
> list_del(&page->lru);
> - ClearPageHugeTemporary(page);
> + ClearHPageTemporary(page);
> update_and_free_page(h, page);
> } else if (h->surplus_huge_pages_node[nid]) {
> /* remove the page from active list */
> @@ -1863,7 +1841,7 @@ static struct page *alloc_surplus_huge_page(struct hstate *h, gfp_t gfp_mask,
> * codeflow
> */
> if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages) {
> - SetPageHugeTemporary(page);
> + SetHPageTemporary(page);
> spin_unlock(&hugetlb_lock);
> put_page(page);
> return NULL;
> @@ -1894,7 +1872,7 @@ static struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask,
> * We do not account these pages as surplus because they are only
> * temporary and will be released properly on the last reference
> */
> - SetPageHugeTemporary(page);
> + SetHPageTemporary(page);
>
> return page;
> }
> @@ -5607,12 +5585,12 @@ void move_hugetlb_state(struct page *oldpage, struct page *newpage, int reason)
> * here as well otherwise the global surplus count will not match
> * the per-node's.
> */
> - if (PageHugeTemporary(newpage)) {
> + if (HPageTemporary(newpage)) {
> int old_nid = page_to_nid(oldpage);
> int new_nid = page_to_nid(newpage);
>
> - SetPageHugeTemporary(oldpage);
> - ClearPageHugeTemporary(newpage);
> + SetHPageTemporary(oldpage);
> + ClearHPageTemporary(newpage);
>
> spin_lock(&hugetlb_lock);
> if (h->surplus_huge_pages_node[old_nid]) {
> --
> 2.29.2
>

--
Oscar Salvador
SUSE L3