From 57a196a58421a4b0c45949ae7309f21829aaa77f Mon Sep 17 00:00:00 2001 From: Mike Kravetz Date: Sun, 18 Sep 2022 19:13:48 -0700 Subject: hugetlb: simplify hugetlb handling in follow_page_mask During discussions of this series [1], it was suggested that hugetlb handling code in follow_page_mask could be simplified. At the beginning of follow_page_mask, there currently is a call to follow_huge_addr which 'may' handle hugetlb pages. ia64 is the only architecture which provides a follow_huge_addr routine that does not return error. Instead, at each level of the page table a check is made for a hugetlb entry. If a hugetlb entry is found, a call to a routine associated with that entry is made. Currently, there are two checks for hugetlb entries at each page table level. The first check is of the form: if (p?d_huge()) page = follow_huge_p?d(); the second check is of the form: if (is_hugepd()) page = follow_huge_pd(). We can replace these checks, as well as the special handling routines such as follow_huge_p?d() and follow_huge_pd() with a single routine to handle hugetlb vmas. A new routine hugetlb_follow_page_mask is called for hugetlb vmas at the beginning of follow_page_mask. hugetlb_follow_page_mask will use the existing routine huge_pte_offset to walk page tables looking for hugetlb entries. huge_pte_offset can be overwritten by architectures, and already handles special cases such as hugepd entries. [1] https://lore.kernel.org/linux-mm/cover.1661240170.git.baolin.wang@linux.alibaba.com/ [mike.kravetz@oracle.com: remove vma (pmd sharing) per Peter] Link: https://lkml.kernel.org/r/20221028181108.119432-1-mike.kravetz@oracle.com [mike.kravetz@oracle.com: remove left over hugetlb_vma_unlock_read()] Link: https://lkml.kernel.org/r/20221030225825.40872-1-mike.kravetz@oracle.com Link: https://lkml.kernel.org/r/20220919021348.22151-1-mike.kravetz@oracle.com Signed-off-by: Mike Kravetz Suggested-by: David Hildenbrand Reviewed-by: David Hildenbrand Reviewed-by: Baolin Wang Tested-by: Baolin Wang Cc: Aneesh Kumar K.V Cc: Christophe Leroy Cc: Michael Ellerman Cc: Muchun Song Cc: Naoya Horiguchi Signed-off-by: Andrew Morton --- mm/hugetlb.c | 172 +++++++++++++++++++---------------------------------------- 1 file changed, 56 insertions(+), 116 deletions(-) (limited to 'mm/hugetlb.c') diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 546df97c31e4..0af18c1e4b31 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6209,6 +6209,62 @@ static inline bool __follow_hugetlb_must_fault(unsigned int flags, pte_t *pte, return false; } +struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, + unsigned long address, unsigned int flags) +{ + struct hstate *h = hstate_vma(vma); + struct mm_struct *mm = vma->vm_mm; + unsigned long haddr = address & huge_page_mask(h); + struct page *page = NULL; + spinlock_t *ptl; + pte_t *pte, entry; + + /* + * FOLL_PIN is not supported for follow_page(). Ordinary GUP goes via + * follow_hugetlb_page(). + */ + if (WARN_ON_ONCE(flags & FOLL_PIN)) + return NULL; + +retry: + pte = huge_pte_offset(mm, haddr, huge_page_size(h)); + if (!pte) + return NULL; + + ptl = huge_pte_lock(h, mm, pte); + entry = huge_ptep_get(pte); + if (pte_present(entry)) { + page = pte_page(entry) + + ((address & ~huge_page_mask(h)) >> PAGE_SHIFT); + /* + * Note that page may be a sub-page, and with vmemmap + * optimizations the page struct may be read only. + * try_grab_page() will increase the ref count on the + * head page, so this will be OK. + * + * try_grab_page() should always succeed here, because we hold + * the ptl lock and have verified pte_present(). + */ + if (WARN_ON_ONCE(!try_grab_page(page, flags))) { + page = NULL; + goto out; + } + } else { + if (is_hugetlb_entry_migration(entry)) { + spin_unlock(ptl); + __migration_entry_wait_huge(pte, ptl); + goto retry; + } + /* + * hwpoisoned entry is treated as no_page_table in + * follow_page_mask(). + */ + } +out: + spin_unlock(ptl); + return page; +} + long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, struct page **pages, struct vm_area_struct **vmas, unsigned long *position, unsigned long *nr_pages, @@ -7201,122 +7257,6 @@ __weak unsigned long hugetlb_mask_last_page(struct hstate *h) * These functions are overwritable if your architecture needs its own * behavior. */ -struct page * __weak -follow_huge_addr(struct mm_struct *mm, unsigned long address, - int write) -{ - return ERR_PTR(-EINVAL); -} - -struct page * __weak -follow_huge_pd(struct vm_area_struct *vma, - unsigned long address, hugepd_t hpd, int flags, int pdshift) -{ - WARN(1, "hugepd follow called with no support for hugepage directory format\n"); - return NULL; -} - -struct page * __weak -follow_huge_pmd_pte(struct vm_area_struct *vma, unsigned long address, int flags) -{ - struct hstate *h = hstate_vma(vma); - struct mm_struct *mm = vma->vm_mm; - struct page *page = NULL; - spinlock_t *ptl; - pte_t *ptep, pte; - - /* - * FOLL_PIN is not supported for follow_page(). Ordinary GUP goes via - * follow_hugetlb_page(). - */ - if (WARN_ON_ONCE(flags & FOLL_PIN)) - return NULL; - -retry: - ptep = huge_pte_offset(mm, address, huge_page_size(h)); - if (!ptep) - return NULL; - - ptl = huge_pte_lock(h, mm, ptep); - pte = huge_ptep_get(ptep); - if (pte_present(pte)) { - page = pte_page(pte) + - ((address & ~huge_page_mask(h)) >> PAGE_SHIFT); - /* - * try_grab_page() should always succeed here, because: a) we - * hold the pmd (ptl) lock, and b) we've just checked that the - * huge pmd (head) page is present in the page tables. The ptl - * prevents the head page and tail pages from being rearranged - * in any way. So this page must be available at this point, - * unless the page refcount overflowed: - */ - if (WARN_ON_ONCE(!try_grab_page(page, flags))) { - page = NULL; - goto out; - } - } else { - if (is_hugetlb_entry_migration(pte)) { - spin_unlock(ptl); - __migration_entry_wait_huge(ptep, ptl); - goto retry; - } - /* - * hwpoisoned entry is treated as no_page_table in - * follow_page_mask(). - */ - } -out: - spin_unlock(ptl); - return page; -} - -struct page * __weak -follow_huge_pud(struct mm_struct *mm, unsigned long address, - pud_t *pud, int flags) -{ - struct page *page = NULL; - spinlock_t *ptl; - pte_t pte; - - if (WARN_ON_ONCE(flags & FOLL_PIN)) - return NULL; - -retry: - ptl = huge_pte_lock(hstate_sizelog(PUD_SHIFT), mm, (pte_t *)pud); - if (!pud_huge(*pud)) - goto out; - pte = huge_ptep_get((pte_t *)pud); - if (pte_present(pte)) { - page = pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT); - if (WARN_ON_ONCE(!try_grab_page(page, flags))) { - page = NULL; - goto out; - } - } else { - if (is_hugetlb_entry_migration(pte)) { - spin_unlock(ptl); - __migration_entry_wait(mm, (pte_t *)pud, ptl); - goto retry; - } - /* - * hwpoisoned entry is treated as no_page_table in - * follow_page_mask(). - */ - } -out: - spin_unlock(ptl); - return page; -} - -struct page * __weak -follow_huge_pgd(struct mm_struct *mm, unsigned long address, pgd_t *pgd, int flags) -{ - if (flags & (FOLL_GET | FOLL_PIN)) - return NULL; - - return pte_page(*(pte_t *)pgd) + ((address & ~PGDIR_MASK) >> PAGE_SHIFT); -} - int isolate_hugetlb(struct page *page, struct list_head *list) { int ret = 0; -- cgit v1.2.3