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 pud_t *pud; 108 109 /* The only possible pmd mapping has been handled on last iteration */ 110 if (pvmw->pmd && !pvmw->pte) 111 return not_found(pvmw); 112 113 /* Only for THP, seek to next pte entry makes sense */ 114 if (pvmw->pte) { 115 if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page)) 116 return not_found(pvmw); 117 goto next_pte; 118 } 119 120 if (unlikely(PageHuge(pvmw->page))) { 121 /* when pud is not present, pte will be NULL */ 122 pvmw->pte = huge_pte_offset(mm, pvmw->address); 123 if (!pvmw->pte) 124 return false; 125 126 pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte); 127 spin_lock(pvmw->ptl); 128 if (!check_pte(pvmw)) 129 return not_found(pvmw); 130 return true; 131 } 132 restart: 133 pgd = pgd_offset(mm, pvmw->address); 134 if (!pgd_present(*pgd)) 135 return false; 136 pud = pud_offset(pgd, pvmw->address); 137 if (!pud_present(*pud)) 138 return false; 139 pvmw->pmd = pmd_offset(pud, pvmw->address); 140 if (pmd_trans_huge(*pvmw->pmd)) { 141 pvmw->ptl = pmd_lock(mm, pvmw->pmd); 142 if (!pmd_present(*pvmw->pmd)) 143 return not_found(pvmw); 144 if (likely(pmd_trans_huge(*pvmw->pmd))) { 145 if (pvmw->flags & PVMW_MIGRATION) 146 return not_found(pvmw); 147 if (pmd_page(*pvmw->pmd) != page) 148 return not_found(pvmw); 149 return true; 150 } else { 151 /* THP pmd was split under us: handle on pte level */ 152 spin_unlock(pvmw->ptl); 153 pvmw->ptl = NULL; 154 } 155 } else { 156 if (!check_pmd(pvmw)) 157 return false; 158 } 159 if (!map_pte(pvmw)) 160 goto next_pte; 161 while (1) { 162 if (check_pte(pvmw)) 163 return true; 164 next_pte: do { 165 pvmw->address += PAGE_SIZE; 166 if (pvmw->address >= 167 __vma_address(pvmw->page, pvmw->vma) + 168 hpage_nr_pages(pvmw->page) * PAGE_SIZE) 169 return not_found(pvmw); 170 /* Did we cross page table boundary? */ 171 if (pvmw->address % PMD_SIZE == 0) { 172 pte_unmap(pvmw->pte); 173 if (pvmw->ptl) { 174 spin_unlock(pvmw->ptl); 175 pvmw->ptl = NULL; 176 } 177 goto restart; 178 } else { 179 pvmw->pte++; 180 } 181 } while (pte_none(*pvmw->pte)); 182 183 if (!pvmw->ptl) { 184 pvmw->ptl = pte_lockptr(mm, pvmw->pmd); 185 spin_lock(pvmw->ptl); 186 } 187 } 188 } 189 190 /** 191 * page_mapped_in_vma - check whether a page is really mapped in a VMA 192 * @page: the page to test 193 * @vma: the VMA to test 194 * 195 * Returns 1 if the page is mapped into the page tables of the VMA, 0 196 * if the page is not mapped into the page tables of this VMA. Only 197 * valid for normal file or anonymous VMAs. 198 */ 199 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) 200 { 201 struct page_vma_mapped_walk pvmw = { 202 .page = page, 203 .vma = vma, 204 .flags = PVMW_SYNC, 205 }; 206 unsigned long start, end; 207 208 start = __vma_address(page, vma); 209 end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1); 210 211 if (unlikely(end < vma->vm_start || start >= vma->vm_end)) 212 return 0; 213 pvmw.address = max(start, vma->vm_start); 214 if (!page_vma_mapped_walk(&pvmw)) 215 return 0; 216 page_vma_mapped_walk_done(&pvmw); 217 return 1; 218 } 219