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 52 if (!is_migration_entry(entry)) 53 return false; 54 if (migration_entry_to_page(entry) - pvmw->page >= 55 hpage_nr_pages(pvmw->page)) { 56 return false; 57 } 58 if (migration_entry_to_page(entry) < pvmw->page) 59 return false; 60 #else 61 WARN_ON_ONCE(1); 62 #endif 63 } else { 64 if (is_swap_pte(*pvmw->pte)) { 65 swp_entry_t entry; 66 67 entry = pte_to_swp_entry(*pvmw->pte); 68 if (is_device_private_entry(entry) && 69 device_private_entry_to_page(entry) == pvmw->page) 70 return true; 71 } 72 73 if (!pte_present(*pvmw->pte)) 74 return false; 75 76 /* THP can be referenced by any subpage */ 77 if (pte_page(*pvmw->pte) - pvmw->page >= 78 hpage_nr_pages(pvmw->page)) { 79 return false; 80 } 81 if (pte_page(*pvmw->pte) < pvmw->page) 82 return false; 83 } 84 85 return true; 86 } 87 88 /** 89 * page_vma_mapped_walk - check if @pvmw->page is mapped in @pvmw->vma at 90 * @pvmw->address 91 * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags 92 * must be set. pmd, pte and ptl must be NULL. 93 * 94 * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point 95 * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is 96 * adjusted if needed (for PTE-mapped THPs). 97 * 98 * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page 99 * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in 100 * a loop to find all PTEs that map the THP. 101 * 102 * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry 103 * regardless of which page table level the page is mapped at. @pvmw->pmd is 104 * NULL. 105 * 106 * Retruns false if there are no more page table entries for the page in 107 * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped. 108 * 109 * If you need to stop the walk before page_vma_mapped_walk() returned false, 110 * use page_vma_mapped_walk_done(). It will do the housekeeping. 111 */ 112 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) 113 { 114 struct mm_struct *mm = pvmw->vma->vm_mm; 115 struct page *page = pvmw->page; 116 pgd_t *pgd; 117 p4d_t *p4d; 118 pud_t *pud; 119 120 /* The only possible pmd mapping has been handled on last iteration */ 121 if (pvmw->pmd && !pvmw->pte) 122 return not_found(pvmw); 123 124 if (pvmw->pte) 125 goto next_pte; 126 127 if (unlikely(PageHuge(pvmw->page))) { 128 /* when pud is not present, pte will be NULL */ 129 pvmw->pte = huge_pte_offset(mm, pvmw->address, 130 PAGE_SIZE << compound_order(page)); 131 if (!pvmw->pte) 132 return false; 133 134 pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte); 135 spin_lock(pvmw->ptl); 136 if (!check_pte(pvmw)) 137 return not_found(pvmw); 138 return true; 139 } 140 restart: 141 pgd = pgd_offset(mm, pvmw->address); 142 if (!pgd_present(*pgd)) 143 return false; 144 p4d = p4d_offset(pgd, pvmw->address); 145 if (!p4d_present(*p4d)) 146 return false; 147 pud = pud_offset(p4d, pvmw->address); 148 if (!pud_present(*pud)) 149 return false; 150 pvmw->pmd = pmd_offset(pud, pvmw->address); 151 if (pmd_trans_huge(*pvmw->pmd) || is_pmd_migration_entry(*pvmw->pmd)) { 152 pvmw->ptl = pmd_lock(mm, pvmw->pmd); 153 if (likely(pmd_trans_huge(*pvmw->pmd))) { 154 if (pvmw->flags & PVMW_MIGRATION) 155 return not_found(pvmw); 156 if (pmd_page(*pvmw->pmd) != page) 157 return not_found(pvmw); 158 return true; 159 } else if (!pmd_present(*pvmw->pmd)) { 160 if (thp_migration_supported()) { 161 if (!(pvmw->flags & PVMW_MIGRATION)) 162 return not_found(pvmw); 163 if (is_migration_entry(pmd_to_swp_entry(*pvmw->pmd))) { 164 swp_entry_t entry = pmd_to_swp_entry(*pvmw->pmd); 165 166 if (migration_entry_to_page(entry) != page) 167 return not_found(pvmw); 168 return true; 169 } 170 } else 171 WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!"); 172 return not_found(pvmw); 173 } else { 174 /* THP pmd was split under us: handle on pte level */ 175 spin_unlock(pvmw->ptl); 176 pvmw->ptl = NULL; 177 } 178 } else { 179 if (!check_pmd(pvmw)) 180 return false; 181 } 182 if (!map_pte(pvmw)) 183 goto next_pte; 184 while (1) { 185 if (check_pte(pvmw)) 186 return true; 187 next_pte: 188 /* Seek to next pte only makes sense for THP */ 189 if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page)) 190 return not_found(pvmw); 191 do { 192 pvmw->address += PAGE_SIZE; 193 if (pvmw->address >= pvmw->vma->vm_end || 194 pvmw->address >= 195 __vma_address(pvmw->page, pvmw->vma) + 196 hpage_nr_pages(pvmw->page) * PAGE_SIZE) 197 return not_found(pvmw); 198 /* Did we cross page table boundary? */ 199 if (pvmw->address % PMD_SIZE == 0) { 200 pte_unmap(pvmw->pte); 201 if (pvmw->ptl) { 202 spin_unlock(pvmw->ptl); 203 pvmw->ptl = NULL; 204 } 205 goto restart; 206 } else { 207 pvmw->pte++; 208 } 209 } while (pte_none(*pvmw->pte)); 210 211 if (!pvmw->ptl) { 212 pvmw->ptl = pte_lockptr(mm, pvmw->pmd); 213 spin_lock(pvmw->ptl); 214 } 215 } 216 } 217 218 /** 219 * page_mapped_in_vma - check whether a page is really mapped in a VMA 220 * @page: the page to test 221 * @vma: the VMA to test 222 * 223 * Returns 1 if the page is mapped into the page tables of the VMA, 0 224 * if the page is not mapped into the page tables of this VMA. Only 225 * valid for normal file or anonymous VMAs. 226 */ 227 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) 228 { 229 struct page_vma_mapped_walk pvmw = { 230 .page = page, 231 .vma = vma, 232 .flags = PVMW_SYNC, 233 }; 234 unsigned long start, end; 235 236 start = __vma_address(page, vma); 237 end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1); 238 239 if (unlikely(end < vma->vm_start || start >= vma->vm_end)) 240 return 0; 241 pvmw.address = max(start, vma->vm_start); 242 if (!page_vma_mapped_walk(&pvmw)) 243 return 0; 244 page_vma_mapped_walk_done(&pvmw); 245 return 1; 246 } 247