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