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/leafops.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, pmd_t *pmdvalp, 17 spinlock_t **ptlp) 18 { 19 bool is_migration; 20 pte_t ptent; 21 22 if (pvmw->flags & PVMW_SYNC) { 23 /* Use the stricter lookup */ 24 pvmw->pte = pte_offset_map_lock(pvmw->vma->vm_mm, pvmw->pmd, 25 pvmw->address, &pvmw->ptl); 26 *ptlp = pvmw->ptl; 27 return !!pvmw->pte; 28 } 29 30 is_migration = pvmw->flags & PVMW_MIGRATION; 31 again: 32 /* 33 * It is important to return the ptl corresponding to pte, 34 * in case *pvmw->pmd changes underneath us; so we need to 35 * return it even when choosing not to lock, in case caller 36 * proceeds to loop over next ptes, and finds a match later. 37 * Though, in most cases, page lock already protects this. 38 */ 39 pvmw->pte = pte_offset_map_rw_nolock(pvmw->vma->vm_mm, pvmw->pmd, 40 pvmw->address, pmdvalp, ptlp); 41 if (!pvmw->pte) 42 return false; 43 44 ptent = ptep_get(pvmw->pte); 45 46 if (pte_none(ptent)) { 47 return false; 48 } else if (pte_present(ptent)) { 49 if (is_migration) 50 return false; 51 } else if (!is_migration) { 52 softleaf_t entry; 53 54 /* 55 * Handle un-addressable ZONE_DEVICE memory. 56 * 57 * We get here when we are trying to unmap a private 58 * device page from the process address space. Such 59 * page is not CPU accessible and thus is mapped as 60 * a special swap entry, nonetheless it still does 61 * count as a valid regular mapping for the page 62 * (and is accounted as such in page maps count). 63 * 64 * So handle this special case as if it was a normal 65 * page mapping ie lock CPU page table and return true. 66 * 67 * For more details on device private memory see HMM 68 * (include/linux/hmm.h or mm/hmm.c). 69 */ 70 entry = softleaf_from_pte(ptent); 71 if (!softleaf_is_device_private(entry) && 72 !softleaf_is_device_exclusive(entry)) 73 return false; 74 } 75 spin_lock(*ptlp); 76 if (unlikely(!pmd_same(*pmdvalp, pmdp_get_lockless(pvmw->pmd)))) { 77 pte_unmap_unlock(pvmw->pte, *ptlp); 78 goto again; 79 } 80 pvmw->ptl = *ptlp; 81 82 return true; 83 } 84 85 /** 86 * check_pte - check if [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages) is 87 * mapped at the @pvmw->pte 88 * @pvmw: page_vma_mapped_walk struct, includes a pair pte and pfn range 89 * for checking 90 * @pte_nr: the number of small pages described by @pvmw->pte. 91 * 92 * page_vma_mapped_walk() found a place where pfn range is *potentially* 93 * mapped. check_pte() has to validate this. 94 * 95 * pvmw->pte may point to empty PTE, swap PTE or PTE pointing to 96 * arbitrary page. 97 * 98 * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration 99 * entry that points to [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages) 100 * 101 * If PVMW_MIGRATION flag is not set, returns true if pvmw->pte points to 102 * [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages) 103 * 104 * Otherwise, return false. 105 * 106 */ 107 static bool check_pte(struct page_vma_mapped_walk *pvmw, unsigned long pte_nr) 108 { 109 unsigned long pfn; 110 pte_t ptent = ptep_get(pvmw->pte); 111 112 if (pvmw->flags & PVMW_MIGRATION) { 113 const softleaf_t entry = softleaf_from_pte(ptent); 114 115 if (!softleaf_is_migration(entry)) 116 return false; 117 118 pfn = softleaf_to_pfn(entry); 119 } else if (pte_present(ptent)) { 120 pfn = pte_pfn(ptent); 121 } else { 122 const softleaf_t entry = softleaf_from_pte(ptent); 123 124 /* Handle un-addressable ZONE_DEVICE memory */ 125 if (!softleaf_is_device_private(entry) && 126 !softleaf_is_device_exclusive(entry)) 127 return false; 128 129 pfn = softleaf_to_pfn(entry); 130 } 131 132 if ((pfn + pte_nr - 1) < pvmw->pfn) 133 return false; 134 if (pfn > (pvmw->pfn + pvmw->nr_pages - 1)) 135 return false; 136 return true; 137 } 138 139 /* Returns true if the two ranges overlap. Careful to not overflow. */ 140 static bool check_pmd(unsigned long pfn, struct page_vma_mapped_walk *pvmw) 141 { 142 if ((pfn + HPAGE_PMD_NR - 1) < pvmw->pfn) 143 return false; 144 if (pfn > pvmw->pfn + pvmw->nr_pages - 1) 145 return false; 146 return true; 147 } 148 149 static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size) 150 { 151 pvmw->address = (pvmw->address + size) & ~(size - 1); 152 if (!pvmw->address) 153 pvmw->address = ULONG_MAX; 154 } 155 156 /** 157 * page_vma_mapped_walk - check if @pvmw->pfn is mapped in @pvmw->vma at 158 * @pvmw->address 159 * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags 160 * must be set. pmd, pte and ptl must be NULL. 161 * 162 * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point 163 * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is 164 * adjusted if needed (for PTE-mapped THPs). 165 * 166 * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page 167 * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in 168 * a loop to find all PTEs that map the THP. 169 * 170 * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry 171 * regardless of which page table level the page is mapped at. @pvmw->pmd is 172 * NULL. 173 * 174 * Returns false if there are no more page table entries for the page in 175 * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped. 176 * 177 * If you need to stop the walk before page_vma_mapped_walk() returned false, 178 * use page_vma_mapped_walk_done(). It will do the housekeeping. 179 */ 180 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) 181 { 182 struct vm_area_struct *vma = pvmw->vma; 183 struct mm_struct *mm = vma->vm_mm; 184 unsigned long end; 185 spinlock_t *ptl; 186 pgd_t *pgd; 187 p4d_t *p4d; 188 pud_t *pud; 189 pmd_t pmde; 190 191 /* The only possible pmd mapping has been handled on last iteration */ 192 if (pvmw->pmd && !pvmw->pte) 193 return not_found(pvmw); 194 195 if (unlikely(is_vm_hugetlb_page(vma))) { 196 struct hstate *hstate = hstate_vma(vma); 197 unsigned long size = huge_page_size(hstate); 198 /* The only possible mapping was handled on last iteration */ 199 if (pvmw->pte) 200 return not_found(pvmw); 201 /* 202 * All callers that get here will already hold the 203 * i_mmap_rwsem. Therefore, no additional locks need to be 204 * taken before calling hugetlb_walk(). 205 */ 206 pvmw->pte = hugetlb_walk(vma, pvmw->address, size); 207 if (!pvmw->pte) 208 return false; 209 210 pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte); 211 if (!check_pte(pvmw, pages_per_huge_page(hstate))) 212 return not_found(pvmw); 213 return true; 214 } 215 216 end = vma_address_end(pvmw); 217 if (pvmw->pte) 218 goto next_pte; 219 restart: 220 do { 221 pgd = pgd_offset(mm, pvmw->address); 222 if (!pgd_present(*pgd)) { 223 step_forward(pvmw, PGDIR_SIZE); 224 continue; 225 } 226 p4d = p4d_offset(pgd, pvmw->address); 227 if (!p4d_present(*p4d)) { 228 step_forward(pvmw, P4D_SIZE); 229 continue; 230 } 231 pud = pud_offset(p4d, pvmw->address); 232 if (!pud_present(*pud)) { 233 step_forward(pvmw, PUD_SIZE); 234 continue; 235 } 236 237 pvmw->pmd = pmd_offset(pud, pvmw->address); 238 /* 239 * Make sure the pmd value isn't cached in a register by the 240 * compiler and used as a stale value after we've observed a 241 * subsequent update. 242 */ 243 pmde = pmdp_get_lockless(pvmw->pmd); 244 245 if (pmd_trans_huge(pmde) || pmd_is_migration_entry(pmde)) { 246 pvmw->ptl = pmd_lock(mm, pvmw->pmd); 247 pmde = *pvmw->pmd; 248 if (!pmd_present(pmde)) { 249 softleaf_t entry; 250 251 if (!thp_migration_supported() || 252 !(pvmw->flags & PVMW_MIGRATION)) 253 return not_found(pvmw); 254 entry = softleaf_from_pmd(pmde); 255 256 if (!softleaf_is_migration(entry) || 257 !check_pmd(softleaf_to_pfn(entry), pvmw)) 258 return not_found(pvmw); 259 return true; 260 } 261 if (likely(pmd_trans_huge(pmde))) { 262 if (pvmw->flags & PVMW_MIGRATION) 263 return not_found(pvmw); 264 if (!check_pmd(pmd_pfn(pmde), pvmw)) 265 return not_found(pvmw); 266 return true; 267 } 268 /* THP pmd was split under us: handle on pte level */ 269 spin_unlock(pvmw->ptl); 270 pvmw->ptl = NULL; 271 } else if (!pmd_present(pmde)) { 272 const softleaf_t entry = softleaf_from_pmd(pmde); 273 274 if (softleaf_is_device_private(entry)) { 275 pvmw->ptl = pmd_lock(mm, pvmw->pmd); 276 return true; 277 } 278 279 if ((pvmw->flags & PVMW_SYNC) && 280 thp_vma_suitable_order(vma, pvmw->address, 281 PMD_ORDER) && 282 (pvmw->nr_pages >= HPAGE_PMD_NR)) 283 sync_with_folio_pmd_zap(mm, pvmw->pmd); 284 285 step_forward(pvmw, PMD_SIZE); 286 continue; 287 } 288 if (!map_pte(pvmw, &pmde, &ptl)) { 289 if (!pvmw->pte) 290 goto restart; 291 goto next_pte; 292 } 293 this_pte: 294 if (check_pte(pvmw, 1)) 295 return true; 296 next_pte: 297 do { 298 pvmw->address += PAGE_SIZE; 299 if (pvmw->address >= end) 300 return not_found(pvmw); 301 /* Did we cross page table boundary? */ 302 if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) { 303 if (pvmw->ptl) { 304 spin_unlock(pvmw->ptl); 305 pvmw->ptl = NULL; 306 } 307 pte_unmap(pvmw->pte); 308 pvmw->pte = NULL; 309 pvmw->flags |= PVMW_PGTABLE_CROSSED; 310 goto restart; 311 } 312 pvmw->pte++; 313 } while (pte_none(ptep_get(pvmw->pte))); 314 315 if (!pvmw->ptl) { 316 spin_lock(ptl); 317 if (unlikely(!pmd_same(pmde, pmdp_get_lockless(pvmw->pmd)))) { 318 pte_unmap_unlock(pvmw->pte, ptl); 319 pvmw->pte = NULL; 320 goto restart; 321 } 322 pvmw->ptl = ptl; 323 } 324 goto this_pte; 325 } while (pvmw->address < end); 326 327 return false; 328 } 329 330 #ifdef CONFIG_MEMORY_FAILURE 331 /** 332 * page_mapped_in_vma - check whether a page is really mapped in a VMA 333 * @page: the page to test 334 * @vma: the VMA to test 335 * 336 * Return: The address the page is mapped at if the page is in the range 337 * covered by the VMA and present in the page table. If the page is 338 * outside the VMA or not present, returns -EFAULT. 339 * Only valid for normal file or anonymous VMAs. 340 */ 341 unsigned long page_mapped_in_vma(const struct page *page, 342 struct vm_area_struct *vma) 343 { 344 const struct folio *folio = page_folio(page); 345 struct page_vma_mapped_walk pvmw = { 346 .pfn = page_to_pfn(page), 347 .nr_pages = 1, 348 .vma = vma, 349 .flags = PVMW_SYNC, 350 }; 351 352 pvmw.address = vma_address(vma, page_pgoff(folio, page), 1); 353 if (pvmw.address == -EFAULT) 354 goto out; 355 if (!page_vma_mapped_walk(&pvmw)) 356 return -EFAULT; 357 page_vma_mapped_walk_done(&pvmw); 358 out: 359 return pvmw.address; 360 } 361 #endif 362