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    SubjectRe: [PATCH v3 4/5] hugetlb: convert PageHugeTemporary() to HPageTemporary flag
    On Fri 22-01-21 11:52:30, Mike Kravetz wrote:
    > Use new hugetlb specific HPageTemporary flag to replace the
    > PageHugeTemporary() interfaces. PageHugeTemporary does contain
    > a PageHuge() check. However, this interface is only used within
    > hugetlb code where we know we are dealing with a hugetlb page.
    > Therefore, the check can be eliminated.

    A dedicated flag is definitely something I would go for if that was
    available back then when I introduced it.

    > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
    > Reviewed-by: Oscar Salvador <osalvador@suse.de>

    Acked-by: Michal Hocko <mhocko@suse.com>

    Thanks!
    > ---
    > 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 cd1960541f2a..3c86c3a0e144 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,
    > };
    >
    > @@ -530,6 +535,7 @@ 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 4da1a29ac5e2..70ffa1027988 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 */
    > @@ -1860,7 +1838,7 @@ 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;
    > @@ -1891,7 +1869,7 @@ 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;
    > }
    > @@ -5612,12 +5590,12 @@ 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

    --
    Michal Hocko
    SUSE Labs

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