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David Alan Gilbert" , "Matthew Wilcox (Oracle)" , Vlastimil Babka , Baolin Wang , Miaohe Lin , Yang Shi , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, James Houghton X-Spam-Status: No, score=-9.6 required=5.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1754177644883175310?= X-GMAIL-MSGID: =?utf-8?q?1754177644883175310?= This enables high-granularity mapping support in GUP. In case it is confusing, pfn_offset is the offset (in PAGE_SIZE units) that vaddr points to within the subpage that hpte points to. Signed-off-by: James Houghton --- mm/hugetlb.c | 59 ++++++++++++++++++++++++++++++++-------------------- 1 file changed, 37 insertions(+), 22 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 73672d806172..30fea414d9ee 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -6532,11 +6532,9 @@ static void record_subpages_vmas(struct page *page, struct vm_area_struct *vma, } static inline bool __follow_hugetlb_must_fault(struct vm_area_struct *vma, - unsigned int flags, pte_t *pte, + unsigned int flags, pte_t pteval, bool *unshare) { - pte_t pteval = huge_ptep_get(pte); - *unshare = false; if (is_swap_pte(pteval)) return true; @@ -6611,11 +6609,13 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, int err = -EFAULT, refs; while (vaddr < vma->vm_end && remainder) { - pte_t *pte; + pte_t *ptep, pte; spinlock_t *ptl = NULL; bool unshare = false; int absent; - struct page *page; + unsigned long pages_per_hpte; + struct page *page, *subpage; + struct hugetlb_pte hpte; /* * If we have a pending SIGKILL, don't keep faulting pages and @@ -6632,13 +6632,19 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, * each hugepage. We have to make sure we get the * first, for the page indexing below to work. * - * Note that page table lock is not held when pte is null. + * hugetlb_full_walk will mask the address appropriately. + * + * Note that page table lock is not held when ptep is null. */ - pte = hugetlb_walk(vma, vaddr & huge_page_mask(h), - huge_page_size(h)); - if (pte) - ptl = huge_pte_lock(h, mm, pte); - absent = !pte || huge_pte_none(huge_ptep_get(pte)); + if (hugetlb_full_walk(&hpte, vma, vaddr)) { + ptep = NULL; + absent = true; + } else { + ptl = hugetlb_pte_lock(&hpte); + ptep = hpte.ptep; + pte = huge_ptep_get(ptep); + absent = huge_pte_none(pte); + } /* * When coredumping, it suits get_dump_page if we just return @@ -6649,13 +6655,20 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, */ if (absent && (flags & FOLL_DUMP) && !hugetlbfs_pagecache_present(h, vma, vaddr)) { - if (pte) + if (ptep) spin_unlock(ptl); hugetlb_vma_unlock_read(vma); remainder = 0; break; } + if (!absent && pte_present(pte) && + !hugetlb_pte_present_leaf(&hpte, pte)) { + /* We raced with someone splitting the PTE, so retry. */ + spin_unlock(ptl); + continue; + } + /* * We need call hugetlb_fault for both hugepages under migration * (in which case hugetlb_fault waits for the migration,) and @@ -6671,7 +6684,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, vm_fault_t ret; unsigned int fault_flags = 0; - if (pte) + if (ptep) spin_unlock(ptl); hugetlb_vma_unlock_read(vma); @@ -6720,8 +6733,10 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, continue; } - pfn_offset = (vaddr & ~huge_page_mask(h)) >> PAGE_SHIFT; - page = pte_page(huge_ptep_get(pte)); + pfn_offset = (vaddr & ~hugetlb_pte_mask(&hpte)) >> PAGE_SHIFT; + subpage = pte_page(pte); + pages_per_hpte = hugetlb_pte_size(&hpte) / PAGE_SIZE; + page = compound_head(subpage); VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) && !PageAnonExclusive(page), page); @@ -6731,22 +6746,22 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, * and skip the same_page loop below. */ if (!pages && !vmas && !pfn_offset && - (vaddr + huge_page_size(h) < vma->vm_end) && - (remainder >= pages_per_huge_page(h))) { - vaddr += huge_page_size(h); - remainder -= pages_per_huge_page(h); - i += pages_per_huge_page(h); + (vaddr + pages_per_hpte < vma->vm_end) && + (remainder >= pages_per_hpte)) { + vaddr += pages_per_hpte; + remainder -= pages_per_hpte; + i += pages_per_hpte; spin_unlock(ptl); hugetlb_vma_unlock_read(vma); continue; } /* vaddr may not be aligned to PAGE_SIZE */ - refs = min3(pages_per_huge_page(h) - pfn_offset, remainder, + refs = min3(pages_per_hpte - pfn_offset, remainder, (vma->vm_end - ALIGN_DOWN(vaddr, PAGE_SIZE)) >> PAGE_SHIFT); if (pages || vmas) - record_subpages_vmas(nth_page(page, pfn_offset), + record_subpages_vmas(nth_page(subpage, pfn_offset), vma, refs, likely(pages) ? pages + i : NULL, vmas ? vmas + i : NULL);