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 /* 25 * We get here when we are trying to unmap a private 26 * device page from the process address space. Such 27 * page is not CPU accessible and thus is mapped as 28 * a special swap entry, nonetheless it still does 29 * count as a valid regular mapping for the page (and 30 * is accounted as such in page maps count). 31 * 32 * So handle this special case as if it was a normal 33 * page mapping ie lock CPU page table and returns 34 * true. 35 * 36 * For more details on device private memory see HMM 37 * (include/linux/hmm.h or mm/hmm.c). 38 */ 39 if (is_swap_pte(*pvmw->pte)) { 40 swp_entry_t entry; 41 42 /* Handle un-addressable ZONE_DEVICE memory */ 43 entry = pte_to_swp_entry(*pvmw->pte); 44 if (!is_device_private_entry(entry) && 45 !is_device_exclusive_entry(entry)) 46 return false; 47 } else if (!pte_present(*pvmw->pte)) 48 return false; 49 } 50 } 51 pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd); 52 spin_lock(pvmw->ptl); 53 return true; 54 } 55 56 /** 57 * check_pte - check if @pvmw->page is mapped at the @pvmw->pte 58 * @pvmw: page_vma_mapped_walk struct, includes a pair pte and page for checking 59 * 60 * page_vma_mapped_walk() found a place where @pvmw->page is *potentially* 61 * mapped. check_pte() has to validate this. 62 * 63 * pvmw->pte may point to empty PTE, swap PTE or PTE pointing to 64 * arbitrary page. 65 * 66 * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration 67 * entry that points to @pvmw->page or any subpage in case of THP. 68 * 69 * If PVMW_MIGRATION flag is not set, returns true if pvmw->pte points to 70 * pvmw->page or any subpage in case of THP. 71 * 72 * Otherwise, return false. 73 * 74 */ 75 static bool check_pte(struct page_vma_mapped_walk *pvmw) 76 { 77 unsigned long pfn; 78 79 if (pvmw->flags & PVMW_MIGRATION) { 80 swp_entry_t entry; 81 if (!is_swap_pte(*pvmw->pte)) 82 return false; 83 entry = pte_to_swp_entry(*pvmw->pte); 84 85 if (!is_migration_entry(entry) && 86 !is_device_exclusive_entry(entry)) 87 return false; 88 89 pfn = swp_offset_pfn(entry); 90 } else if (is_swap_pte(*pvmw->pte)) { 91 swp_entry_t entry; 92 93 /* Handle un-addressable ZONE_DEVICE memory */ 94 entry = pte_to_swp_entry(*pvmw->pte); 95 if (!is_device_private_entry(entry) && 96 !is_device_exclusive_entry(entry)) 97 return false; 98 99 pfn = swp_offset_pfn(entry); 100 } else { 101 if (!pte_present(*pvmw->pte)) 102 return false; 103 104 pfn = pte_pfn(*pvmw->pte); 105 } 106 107 return (pfn - pvmw->pfn) < pvmw->nr_pages; 108 } 109 110 /* Returns true if the two ranges overlap. Careful to not overflow. */ 111 static bool check_pmd(unsigned long pfn, struct page_vma_mapped_walk *pvmw) 112 { 113 if ((pfn + HPAGE_PMD_NR - 1) < pvmw->pfn) 114 return false; 115 if (pfn > pvmw->pfn + pvmw->nr_pages - 1) 116 return false; 117 return true; 118 } 119 120 static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size) 121 { 122 pvmw->address = (pvmw->address + size) & ~(size - 1); 123 if (!pvmw->address) 124 pvmw->address = ULONG_MAX; 125 } 126 127 /** 128 * page_vma_mapped_walk - check if @pvmw->pfn is mapped in @pvmw->vma at 129 * @pvmw->address 130 * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags 131 * must be set. pmd, pte and ptl must be NULL. 132 * 133 * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point 134 * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is 135 * adjusted if needed (for PTE-mapped THPs). 136 * 137 * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page 138 * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in 139 * a loop to find all PTEs that map the THP. 140 * 141 * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry 142 * regardless of which page table level the page is mapped at. @pvmw->pmd is 143 * NULL. 144 * 145 * Returns false if there are no more page table entries for the page in 146 * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped. 147 * 148 * If you need to stop the walk before page_vma_mapped_walk() returned false, 149 * use page_vma_mapped_walk_done(). It will do the housekeeping. 150 */ 151 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) 152 { 153 struct vm_area_struct *vma = pvmw->vma; 154 struct mm_struct *mm = vma->vm_mm; 155 unsigned long end; 156 pgd_t *pgd; 157 p4d_t *p4d; 158 pud_t *pud; 159 pmd_t pmde; 160 161 /* The only possible pmd mapping has been handled on last iteration */ 162 if (pvmw->pmd && !pvmw->pte) 163 return not_found(pvmw); 164 165 if (unlikely(is_vm_hugetlb_page(vma))) { 166 struct hstate *hstate = hstate_vma(vma); 167 unsigned long size = huge_page_size(hstate); 168 /* The only possible mapping was handled on last iteration */ 169 if (pvmw->pte) 170 return not_found(pvmw); 171 172 /* when pud is not present, pte will be NULL */ 173 pvmw->pte = huge_pte_offset(mm, pvmw->address, size); 174 if (!pvmw->pte) 175 return false; 176 177 pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte); 178 if (!check_pte(pvmw)) 179 return not_found(pvmw); 180 return true; 181 } 182 183 end = vma_address_end(pvmw); 184 if (pvmw->pte) 185 goto next_pte; 186 restart: 187 do { 188 pgd = pgd_offset(mm, pvmw->address); 189 if (!pgd_present(*pgd)) { 190 step_forward(pvmw, PGDIR_SIZE); 191 continue; 192 } 193 p4d = p4d_offset(pgd, pvmw->address); 194 if (!p4d_present(*p4d)) { 195 step_forward(pvmw, P4D_SIZE); 196 continue; 197 } 198 pud = pud_offset(p4d, pvmw->address); 199 if (!pud_present(*pud)) { 200 step_forward(pvmw, PUD_SIZE); 201 continue; 202 } 203 204 pvmw->pmd = pmd_offset(pud, pvmw->address); 205 /* 206 * Make sure the pmd value isn't cached in a register by the 207 * compiler and used as a stale value after we've observed a 208 * subsequent update. 209 */ 210 pmde = READ_ONCE(*pvmw->pmd); 211 212 if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) || 213 (pmd_present(pmde) && pmd_devmap(pmde))) { 214 pvmw->ptl = pmd_lock(mm, pvmw->pmd); 215 pmde = *pvmw->pmd; 216 if (!pmd_present(pmde)) { 217 swp_entry_t entry; 218 219 if (!thp_migration_supported() || 220 !(pvmw->flags & PVMW_MIGRATION)) 221 return not_found(pvmw); 222 entry = pmd_to_swp_entry(pmde); 223 if (!is_migration_entry(entry) || 224 !check_pmd(swp_offset_pfn(entry), pvmw)) 225 return not_found(pvmw); 226 return true; 227 } 228 if (likely(pmd_trans_huge(pmde) || pmd_devmap(pmde))) { 229 if (pvmw->flags & PVMW_MIGRATION) 230 return not_found(pvmw); 231 if (!check_pmd(pmd_pfn(pmde), pvmw)) 232 return not_found(pvmw); 233 return true; 234 } 235 /* THP pmd was split under us: handle on pte level */ 236 spin_unlock(pvmw->ptl); 237 pvmw->ptl = NULL; 238 } else if (!pmd_present(pmde)) { 239 /* 240 * If PVMW_SYNC, take and drop THP pmd lock so that we 241 * cannot return prematurely, while zap_huge_pmd() has 242 * cleared *pmd but not decremented compound_mapcount(). 243 */ 244 if ((pvmw->flags & PVMW_SYNC) && 245 transhuge_vma_suitable(vma, pvmw->address) && 246 (pvmw->nr_pages >= HPAGE_PMD_NR)) { 247 spinlock_t *ptl = pmd_lock(mm, pvmw->pmd); 248 249 spin_unlock(ptl); 250 } 251 step_forward(pvmw, PMD_SIZE); 252 continue; 253 } 254 if (!map_pte(pvmw)) 255 goto next_pte; 256 this_pte: 257 if (check_pte(pvmw)) 258 return true; 259 next_pte: 260 do { 261 pvmw->address += PAGE_SIZE; 262 if (pvmw->address >= end) 263 return not_found(pvmw); 264 /* Did we cross page table boundary? */ 265 if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) { 266 if (pvmw->ptl) { 267 spin_unlock(pvmw->ptl); 268 pvmw->ptl = NULL; 269 } 270 pte_unmap(pvmw->pte); 271 pvmw->pte = NULL; 272 goto restart; 273 } 274 pvmw->pte++; 275 if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) { 276 pvmw->ptl = pte_lockptr(mm, pvmw->pmd); 277 spin_lock(pvmw->ptl); 278 } 279 } while (pte_none(*pvmw->pte)); 280 281 if (!pvmw->ptl) { 282 pvmw->ptl = pte_lockptr(mm, pvmw->pmd); 283 spin_lock(pvmw->ptl); 284 } 285 goto this_pte; 286 } while (pvmw->address < end); 287 288 return false; 289 } 290 291 /** 292 * page_mapped_in_vma - check whether a page is really mapped in a VMA 293 * @page: the page to test 294 * @vma: the VMA to test 295 * 296 * Returns 1 if the page is mapped into the page tables of the VMA, 0 297 * if the page is not mapped into the page tables of this VMA. Only 298 * valid for normal file or anonymous VMAs. 299 */ 300 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) 301 { 302 struct page_vma_mapped_walk pvmw = { 303 .pfn = page_to_pfn(page), 304 .nr_pages = 1, 305 .vma = vma, 306 .flags = PVMW_SYNC, 307 }; 308 309 pvmw.address = vma_address(page, vma); 310 if (pvmw.address == -EFAULT) 311 return 0; 312 if (!page_vma_mapped_walk(&pvmw)) 313 return 0; 314 page_vma_mapped_walk_done(&pvmw); 315 return 1; 316 } 317