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Thu, 05 Jan 2023 02:19:23 -0800 (PST) Date: Thu, 5 Jan 2023 10:18:17 +0000 In-Reply-To: <20230105101844.1893104-1-jthoughton@google.com> Mime-Version: 1.0 References: <20230105101844.1893104-1-jthoughton@google.com> X-Mailer: git-send-email 2.39.0.314.g84b9a713c41-goog Message-ID: <20230105101844.1893104-20-jthoughton@google.com> Subject: [PATCH 19/46] hugetlb: add HGM support for follow_hugetlb_page From: James Houghton To: Mike Kravetz , Muchun Song , Peter Xu Cc: David Hildenbrand , David Rientjes , Axel Rasmussen , Mina Almasry , "Zach O'Keefe" , Manish Mishra , Naoya Horiguchi , "Dr . 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-Rspamd-Queue-Id: 0ACAA180003 X-Stat-Signature: 45zif1t6idktirttrxpwy168h6yrww5t X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1672913963-585750 X-HE-Meta: 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 4swN0qRR 6/FivZLvaPZRNx8hIa84j5u3XTJu1XCnF9AKcOsNOxkgRgGcSVnajtq5gps+3sbJUGrjcxXDAgDYm5A/qro0tDKcDc2as0Lsjj436+J9dijChxOdCR/uXu3gwjLzfeqi45UdZGtUas6+7J2B0XqZhzTNOATvaXm5A5slJcSgJH2IaZ5yudpNPOBBaacsNVeGHy+rkf9cSnhgtrYYl/Nn5scWkAaSBEHqcryNPQUIkur0A/Q7I+x4V8+y1+wI3ZMftDRKGruFqFJ2kN6jrytmk92VlZEH2t+ZCGPs0SPKs1flit/gR/D2hf8ERdNFwlr0UtT0Kgh5g2bilW2tTlwulbNJPAt273cmD69dPXGV2MM0OrGPw1xv4E085sYKLbP+aVUdACwcGcmEG5l2Oll1Ap8/HyjuEJMlokXefvIcogx1gP/I6PTQAHqifMx5muwex++5V X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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);