From 3565fce3a6597e91b8dee3e8e36ebf70f8b7ef9b Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Fri, 15 Jan 2016 16:56:55 -0800 Subject: mm, x86: get_user_pages() for dax mappings A dax mapping establishes a pte with _PAGE_DEVMAP set when the driver has established a devm_memremap_pages() mapping, i.e. when the pfn_t return from ->direct_access() has PFN_DEV and PFN_MAP set. Later, when encountering _PAGE_DEVMAP during a page table walk we lookup and pin a struct dev_pagemap instance to keep the result of pfn_to_page() valid until put_page(). Signed-off-by: Dan Williams Tested-by: Logan Gunthorpe Cc: Dave Hansen Cc: Mel Gorman Cc: Peter Zijlstra Cc: Andrea Arcangeli Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/huge_memory.c | 75 ++++++++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 60 insertions(+), 15 deletions(-) (limited to 'mm/huge_memory.c') diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 82bed2bec3ed..b2db98136af9 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -23,6 +23,7 @@ #include #include #include +#include #include #include #include @@ -974,6 +975,63 @@ int vmf_insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr, return VM_FAULT_NOPAGE; } +static void touch_pmd(struct vm_area_struct *vma, unsigned long addr, + pmd_t *pmd) +{ + pmd_t _pmd; + + /* + * We should set the dirty bit only for FOLL_WRITE but for now + * the dirty bit in the pmd is meaningless. And if the dirty + * bit will become meaningful and we'll only set it with + * FOLL_WRITE, an atomic set_bit will be required on the pmd to + * set the young bit, instead of the current set_pmd_at. + */ + _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); + if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, + pmd, _pmd, 1)) + update_mmu_cache_pmd(vma, addr, pmd); +} + +struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr, + pmd_t *pmd, int flags) +{ + unsigned long pfn = pmd_pfn(*pmd); + struct mm_struct *mm = vma->vm_mm; + struct dev_pagemap *pgmap; + struct page *page; + + assert_spin_locked(pmd_lockptr(mm, pmd)); + + if (flags & FOLL_WRITE && !pmd_write(*pmd)) + return NULL; + + if (pmd_present(*pmd) && pmd_devmap(*pmd)) + /* pass */; + else + return NULL; + + if (flags & FOLL_TOUCH) + touch_pmd(vma, addr, pmd); + + /* + * device mapped pages can only be returned if the + * caller will manage the page reference count. + */ + if (!(flags & FOLL_GET)) + return ERR_PTR(-EEXIST); + + pfn += (addr & ~PMD_MASK) >> PAGE_SHIFT; + pgmap = get_dev_pagemap(pfn, NULL); + if (!pgmap) + return ERR_PTR(-EFAULT); + page = pfn_to_page(pfn); + get_page(page); + put_dev_pagemap(pgmap); + + return page; +} + int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr, struct vm_area_struct *vma) @@ -1331,21 +1389,8 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, page = pmd_page(*pmd); VM_BUG_ON_PAGE(!PageHead(page), page); - if (flags & FOLL_TOUCH) { - pmd_t _pmd; - /* - * We should set the dirty bit only for FOLL_WRITE but - * for now the dirty bit in the pmd is meaningless. - * And if the dirty bit will become meaningful and - * we'll only set it with FOLL_WRITE, an atomic - * set_bit will be required on the pmd to set the - * young bit, instead of the current set_pmd_at. - */ - _pmd = pmd_mkyoung(pmd_mkdirty(*pmd)); - if (pmdp_set_access_flags(vma, addr & HPAGE_PMD_MASK, - pmd, _pmd, 1)) - update_mmu_cache_pmd(vma, addr, pmd); - } + if (flags & FOLL_TOUCH) + touch_pmd(vma, addr, pmd); if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { /* * We don't mlock() pte-mapped THPs. This way we can avoid -- cgit v1.2.3