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