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 /* Only for THP, seek to next pte entry makes sense */ 115 if (pvmw->pte) { 116 if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page)) 117 return not_found(pvmw); 118 goto next_pte; 119 } 120 121 if (unlikely(PageHuge(pvmw->page))) { 122 /* when pud is not present, pte will be NULL */ 123 pvmw->pte = huge_pte_offset(mm, pvmw->address); 124 if (!pvmw->pte) 125 return false; 126 127 pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte); 128 spin_lock(pvmw->ptl); 129 if (!check_pte(pvmw)) 130 return not_found(pvmw); 131 return true; 132 } 133 restart: 134 pgd = pgd_offset(mm, pvmw->address); 135 if (!pgd_present(*pgd)) 136 return false; 137 p4d = p4d_offset(pgd, pvmw->address); 138 if (!p4d_present(*p4d)) 139 return false; 140 pud = pud_offset(p4d, pvmw->address); 141 if (!pud_present(*pud)) 142 return false; 143 pvmw->pmd = pmd_offset(pud, pvmw->address); 144 if (pmd_trans_huge(*pvmw->pmd)) { 145 pvmw->ptl = pmd_lock(mm, pvmw->pmd); 146 if (!pmd_present(*pvmw->pmd)) 147 return not_found(pvmw); 148 if (likely(pmd_trans_huge(*pvmw->pmd))) { 149 if (pvmw->flags & PVMW_MIGRATION) 150 return not_found(pvmw); 151 if (pmd_page(*pvmw->pmd) != page) 152 return not_found(pvmw); 153 return true; 154 } else { 155 /* THP pmd was split under us: handle on pte level */ 156 spin_unlock(pvmw->ptl); 157 pvmw->ptl = NULL; 158 } 159 } else { 160 if (!check_pmd(pvmw)) 161 return false; 162 } 163 if (!map_pte(pvmw)) 164 goto next_pte; 165 while (1) { 166 if (check_pte(pvmw)) 167 return true; 168 next_pte: do { 169 pvmw->address += PAGE_SIZE; 170 if (pvmw->address >= 171 __vma_address(pvmw->page, pvmw->vma) + 172 hpage_nr_pages(pvmw->page) * PAGE_SIZE) 173 return not_found(pvmw); 174 /* Did we cross page table boundary? */ 175 if (pvmw->address % PMD_SIZE == 0) { 176 pte_unmap(pvmw->pte); 177 if (pvmw->ptl) { 178 spin_unlock(pvmw->ptl); 179 pvmw->ptl = NULL; 180 } 181 goto restart; 182 } else { 183 pvmw->pte++; 184 } 185 } while (pte_none(*pvmw->pte)); 186 187 if (!pvmw->ptl) { 188 pvmw->ptl = pte_lockptr(mm, pvmw->pmd); 189 spin_lock(pvmw->ptl); 190 } 191 } 192 } 193 194 /** 195 * page_mapped_in_vma - check whether a page is really mapped in a VMA 196 * @page: the page to test 197 * @vma: the VMA to test 198 * 199 * Returns 1 if the page is mapped into the page tables of the VMA, 0 200 * if the page is not mapped into the page tables of this VMA. Only 201 * valid for normal file or anonymous VMAs. 202 */ 203 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) 204 { 205 struct page_vma_mapped_walk pvmw = { 206 .page = page, 207 .vma = vma, 208 .flags = PVMW_SYNC, 209 }; 210 unsigned long start, end; 211 212 start = __vma_address(page, vma); 213 end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1); 214 215 if (unlikely(end < vma->vm_start || start >= vma->vm_end)) 216 return 0; 217 pvmw.address = max(start, vma->vm_start); 218 if (!page_vma_mapped_walk(&pvmw)) 219 return 0; 220 page_vma_mapped_walk_done(&pvmw); 221 return 1; 222 } 223