1 #include <linux/mm.h> 2 #include <linux/rmap.h> 3 #include <linux/hugetlb.h> 4 #include <linux/swap.h> 5 #include <linux/swapops.h> 6 7 #include "internal.h" 8 9 static inline bool check_pmd(struct page_vma_mapped_walk *pvmw) 10 { 11 pmd_t pmde; 12 /* 13 * Make sure we don't re-load pmd between present and !trans_huge check. 14 * We need a consistent view. 15 */ 16 pmde = READ_ONCE(*pvmw->pmd); 17 return pmd_present(pmde) && !pmd_trans_huge(pmde); 18 } 19 20 static inline bool not_found(struct page_vma_mapped_walk *pvmw) 21 { 22 page_vma_mapped_walk_done(pvmw); 23 return false; 24 } 25 26 static bool map_pte(struct page_vma_mapped_walk *pvmw) 27 { 28 pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address); 29 if (!(pvmw->flags & PVMW_SYNC)) { 30 if (pvmw->flags & PVMW_MIGRATION) { 31 if (!is_swap_pte(*pvmw->pte)) 32 return false; 33 } else { 34 if (!pte_present(*pvmw->pte)) 35 return false; 36 } 37 } 38 pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd); 39 spin_lock(pvmw->ptl); 40 return true; 41 } 42 43 static bool check_pte(struct page_vma_mapped_walk *pvmw) 44 { 45 if (pvmw->flags & PVMW_MIGRATION) { 46 #ifdef CONFIG_MIGRATION 47 swp_entry_t entry; 48 if (!is_swap_pte(*pvmw->pte)) 49 return false; 50 entry = pte_to_swp_entry(*pvmw->pte); 51 if (!is_migration_entry(entry)) 52 return false; 53 if (migration_entry_to_page(entry) - pvmw->page >= 54 hpage_nr_pages(pvmw->page)) { 55 return false; 56 } 57 if (migration_entry_to_page(entry) < pvmw->page) 58 return false; 59 #else 60 WARN_ON_ONCE(1); 61 #endif 62 } else { 63 if (!pte_present(*pvmw->pte)) 64 return false; 65 66 /* THP can be referenced by any subpage */ 67 if (pte_page(*pvmw->pte) - pvmw->page >= 68 hpage_nr_pages(pvmw->page)) { 69 return false; 70 } 71 if (pte_page(*pvmw->pte) < pvmw->page) 72 return false; 73 } 74 75 return true; 76 } 77 78 /** 79 * page_vma_mapped_walk - check if @pvmw->page is mapped in @pvmw->vma at 80 * @pvmw->address 81 * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags 82 * must be set. pmd, pte and ptl must be NULL. 83 * 84 * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point 85 * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is 86 * adjusted if needed (for PTE-mapped THPs). 87 * 88 * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page 89 * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in 90 * a loop to find all PTEs that map the THP. 91 * 92 * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry 93 * regardless of which page table level the page is mapped at. @pvmw->pmd is 94 * NULL. 95 * 96 * Retruns false if there are no more page table entries for the page in 97 * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped. 98 * 99 * If you need to stop the walk before page_vma_mapped_walk() returned false, 100 * use page_vma_mapped_walk_done(). It will do the housekeeping. 101 */ 102 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) 103 { 104 struct mm_struct *mm = pvmw->vma->vm_mm; 105 struct page *page = pvmw->page; 106 pgd_t *pgd; 107 p4d_t *p4d; 108 pud_t *pud; 109 110 /* The only possible pmd mapping has been handled on last iteration */ 111 if (pvmw->pmd && !pvmw->pte) 112 return not_found(pvmw); 113 114 if (pvmw->pte) 115 goto next_pte; 116 117 if (unlikely(PageHuge(pvmw->page))) { 118 /* when pud is not present, pte will be NULL */ 119 pvmw->pte = huge_pte_offset(mm, pvmw->address, 120 PAGE_SIZE << compound_order(page)); 121 if (!pvmw->pte) 122 return false; 123 124 pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte); 125 spin_lock(pvmw->ptl); 126 if (!check_pte(pvmw)) 127 return not_found(pvmw); 128 return true; 129 } 130 restart: 131 pgd = pgd_offset(mm, pvmw->address); 132 if (!pgd_present(*pgd)) 133 return false; 134 p4d = p4d_offset(pgd, pvmw->address); 135 if (!p4d_present(*p4d)) 136 return false; 137 pud = pud_offset(p4d, pvmw->address); 138 if (!pud_present(*pud)) 139 return false; 140 pvmw->pmd = pmd_offset(pud, pvmw->address); 141 if (pmd_trans_huge(*pvmw->pmd)) { 142 pvmw->ptl = pmd_lock(mm, pvmw->pmd); 143 if (!pmd_present(*pvmw->pmd)) 144 return not_found(pvmw); 145 if (likely(pmd_trans_huge(*pvmw->pmd))) { 146 if (pvmw->flags & PVMW_MIGRATION) 147 return not_found(pvmw); 148 if (pmd_page(*pvmw->pmd) != page) 149 return not_found(pvmw); 150 return true; 151 } else { 152 /* THP pmd was split under us: handle on pte level */ 153 spin_unlock(pvmw->ptl); 154 pvmw->ptl = NULL; 155 } 156 } else { 157 if (!check_pmd(pvmw)) 158 return false; 159 } 160 if (!map_pte(pvmw)) 161 goto next_pte; 162 while (1) { 163 if (check_pte(pvmw)) 164 return true; 165 next_pte: 166 /* Seek to next pte only makes sense for THP */ 167 if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page)) 168 return not_found(pvmw); 169 do { 170 pvmw->address += PAGE_SIZE; 171 if (pvmw->address >= pvmw->vma->vm_end || 172 pvmw->address >= 173 __vma_address(pvmw->page, pvmw->vma) + 174 hpage_nr_pages(pvmw->page) * PAGE_SIZE) 175 return not_found(pvmw); 176 /* Did we cross page table boundary? */ 177 if (pvmw->address % PMD_SIZE == 0) { 178 pte_unmap(pvmw->pte); 179 if (pvmw->ptl) { 180 spin_unlock(pvmw->ptl); 181 pvmw->ptl = NULL; 182 } 183 goto restart; 184 } else { 185 pvmw->pte++; 186 } 187 } while (pte_none(*pvmw->pte)); 188 189 if (!pvmw->ptl) { 190 pvmw->ptl = pte_lockptr(mm, pvmw->pmd); 191 spin_lock(pvmw->ptl); 192 } 193 } 194 } 195 196 /** 197 * page_mapped_in_vma - check whether a page is really mapped in a VMA 198 * @page: the page to test 199 * @vma: the VMA to test 200 * 201 * Returns 1 if the page is mapped into the page tables of the VMA, 0 202 * if the page is not mapped into the page tables of this VMA. Only 203 * valid for normal file or anonymous VMAs. 204 */ 205 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) 206 { 207 struct page_vma_mapped_walk pvmw = { 208 .page = page, 209 .vma = vma, 210 .flags = PVMW_SYNC, 211 }; 212 unsigned long start, end; 213 214 start = __vma_address(page, vma); 215 end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1); 216 217 if (unlikely(end < vma->vm_start || start >= vma->vm_end)) 218 return 0; 219 pvmw.address = max(start, vma->vm_start); 220 if (!page_vma_mapped_walk(&pvmw)) 221 return 0; 222 page_vma_mapped_walk_done(&pvmw); 223 return 1; 224 } 225