1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/mm.h> 3 #include <linux/rmap.h> 4 #include <linux/hugetlb.h> 5 #include <linux/swap.h> 6 #include <linux/swapops.h> 7 8 #include "internal.h" 9 10 static inline bool not_found(struct page_vma_mapped_walk *pvmw) 11 { 12 page_vma_mapped_walk_done(pvmw); 13 return false; 14 } 15 16 static bool map_pte(struct page_vma_mapped_walk *pvmw) 17 { 18 pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address); 19 if (!(pvmw->flags & PVMW_SYNC)) { 20 if (pvmw->flags & PVMW_MIGRATION) { 21 if (!is_swap_pte(*pvmw->pte)) 22 return false; 23 } else { 24 if (!pte_present(*pvmw->pte)) 25 return false; 26 } 27 } 28 pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd); 29 spin_lock(pvmw->ptl); 30 return true; 31 } 32 33 static bool check_pte(struct page_vma_mapped_walk *pvmw) 34 { 35 if (pvmw->flags & PVMW_MIGRATION) { 36 #ifdef CONFIG_MIGRATION 37 swp_entry_t entry; 38 if (!is_swap_pte(*pvmw->pte)) 39 return false; 40 entry = pte_to_swp_entry(*pvmw->pte); 41 42 if (!is_migration_entry(entry)) 43 return false; 44 if (migration_entry_to_page(entry) - pvmw->page >= 45 hpage_nr_pages(pvmw->page)) { 46 return false; 47 } 48 if (migration_entry_to_page(entry) < pvmw->page) 49 return false; 50 #else 51 WARN_ON_ONCE(1); 52 #endif 53 } else { 54 if (is_swap_pte(*pvmw->pte)) { 55 swp_entry_t entry; 56 57 entry = pte_to_swp_entry(*pvmw->pte); 58 if (is_device_private_entry(entry) && 59 device_private_entry_to_page(entry) == pvmw->page) 60 return true; 61 } 62 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 pmd_t pmde; 110 111 /* The only possible pmd mapping has been handled on last iteration */ 112 if (pvmw->pmd && !pvmw->pte) 113 return not_found(pvmw); 114 115 if (pvmw->pte) 116 goto next_pte; 117 118 if (unlikely(PageHuge(pvmw->page))) { 119 /* when pud is not present, pte will be NULL */ 120 pvmw->pte = huge_pte_offset(mm, pvmw->address, 121 PAGE_SIZE << compound_order(page)); 122 if (!pvmw->pte) 123 return false; 124 125 pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte); 126 spin_lock(pvmw->ptl); 127 if (!check_pte(pvmw)) 128 return not_found(pvmw); 129 return true; 130 } 131 restart: 132 pgd = pgd_offset(mm, pvmw->address); 133 if (!pgd_present(*pgd)) 134 return false; 135 p4d = p4d_offset(pgd, pvmw->address); 136 if (!p4d_present(*p4d)) 137 return false; 138 pud = pud_offset(p4d, pvmw->address); 139 if (!pud_present(*pud)) 140 return false; 141 pvmw->pmd = pmd_offset(pud, pvmw->address); 142 /* 143 * Make sure the pmd value isn't cached in a register by the 144 * compiler and used as a stale value after we've observed a 145 * subsequent update. 146 */ 147 pmde = READ_ONCE(*pvmw->pmd); 148 if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) { 149 pvmw->ptl = pmd_lock(mm, pvmw->pmd); 150 if (likely(pmd_trans_huge(*pvmw->pmd))) { 151 if (pvmw->flags & PVMW_MIGRATION) 152 return not_found(pvmw); 153 if (pmd_page(*pvmw->pmd) != page) 154 return not_found(pvmw); 155 return true; 156 } else if (!pmd_present(*pvmw->pmd)) { 157 if (thp_migration_supported()) { 158 if (!(pvmw->flags & PVMW_MIGRATION)) 159 return not_found(pvmw); 160 if (is_migration_entry(pmd_to_swp_entry(*pvmw->pmd))) { 161 swp_entry_t entry = pmd_to_swp_entry(*pvmw->pmd); 162 163 if (migration_entry_to_page(entry) != page) 164 return not_found(pvmw); 165 return true; 166 } 167 } 168 return not_found(pvmw); 169 } else { 170 /* THP pmd was split under us: handle on pte level */ 171 spin_unlock(pvmw->ptl); 172 pvmw->ptl = NULL; 173 } 174 } else if (!pmd_present(pmde)) { 175 return false; 176 } 177 if (!map_pte(pvmw)) 178 goto next_pte; 179 while (1) { 180 if (check_pte(pvmw)) 181 return true; 182 next_pte: 183 /* Seek to next pte only makes sense for THP */ 184 if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page)) 185 return not_found(pvmw); 186 do { 187 pvmw->address += PAGE_SIZE; 188 if (pvmw->address >= pvmw->vma->vm_end || 189 pvmw->address >= 190 __vma_address(pvmw->page, pvmw->vma) + 191 hpage_nr_pages(pvmw->page) * PAGE_SIZE) 192 return not_found(pvmw); 193 /* Did we cross page table boundary? */ 194 if (pvmw->address % PMD_SIZE == 0) { 195 pte_unmap(pvmw->pte); 196 if (pvmw->ptl) { 197 spin_unlock(pvmw->ptl); 198 pvmw->ptl = NULL; 199 } 200 goto restart; 201 } else { 202 pvmw->pte++; 203 } 204 } while (pte_none(*pvmw->pte)); 205 206 if (!pvmw->ptl) { 207 pvmw->ptl = pte_lockptr(mm, pvmw->pmd); 208 spin_lock(pvmw->ptl); 209 } 210 } 211 } 212 213 /** 214 * page_mapped_in_vma - check whether a page is really mapped in a VMA 215 * @page: the page to test 216 * @vma: the VMA to test 217 * 218 * Returns 1 if the page is mapped into the page tables of the VMA, 0 219 * if the page is not mapped into the page tables of this VMA. Only 220 * valid for normal file or anonymous VMAs. 221 */ 222 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) 223 { 224 struct page_vma_mapped_walk pvmw = { 225 .page = page, 226 .vma = vma, 227 .flags = PVMW_SYNC, 228 }; 229 unsigned long start, end; 230 231 start = __vma_address(page, vma); 232 end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1); 233 234 if (unlikely(end < vma->vm_start || start >= vma->vm_end)) 235 return 0; 236 pvmw.address = max(start, vma->vm_start); 237 if (!page_vma_mapped_walk(&pvmw)) 238 return 0; 239 page_vma_mapped_walk_done(&pvmw); 240 return 1; 241 } 242