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 * All callers that get here will already hold the 173 * i_mmap_rwsem. Therefore, no additional locks need to be 174 * taken before calling hugetlb_walk(). 175 */ 176 pvmw->pte = hugetlb_walk(vma, pvmw->address, size); 177 if (!pvmw->pte) 178 return false; 179 180 pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte); 181 if (!check_pte(pvmw)) 182 return not_found(pvmw); 183 return true; 184 } 185 186 end = vma_address_end(pvmw); 187 if (pvmw->pte) 188 goto next_pte; 189 restart: 190 do { 191 pgd = pgd_offset(mm, pvmw->address); 192 if (!pgd_present(*pgd)) { 193 step_forward(pvmw, PGDIR_SIZE); 194 continue; 195 } 196 p4d = p4d_offset(pgd, pvmw->address); 197 if (!p4d_present(*p4d)) { 198 step_forward(pvmw, P4D_SIZE); 199 continue; 200 } 201 pud = pud_offset(p4d, pvmw->address); 202 if (!pud_present(*pud)) { 203 step_forward(pvmw, PUD_SIZE); 204 continue; 205 } 206 207 pvmw->pmd = pmd_offset(pud, pvmw->address); 208 /* 209 * Make sure the pmd value isn't cached in a register by the 210 * compiler and used as a stale value after we've observed a 211 * subsequent update. 212 */ 213 pmde = READ_ONCE(*pvmw->pmd); 214 215 if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) || 216 (pmd_present(pmde) && pmd_devmap(pmde))) { 217 pvmw->ptl = pmd_lock(mm, pvmw->pmd); 218 pmde = *pvmw->pmd; 219 if (!pmd_present(pmde)) { 220 swp_entry_t entry; 221 222 if (!thp_migration_supported() || 223 !(pvmw->flags & PVMW_MIGRATION)) 224 return not_found(pvmw); 225 entry = pmd_to_swp_entry(pmde); 226 if (!is_migration_entry(entry) || 227 !check_pmd(swp_offset_pfn(entry), pvmw)) 228 return not_found(pvmw); 229 return true; 230 } 231 if (likely(pmd_trans_huge(pmde) || pmd_devmap(pmde))) { 232 if (pvmw->flags & PVMW_MIGRATION) 233 return not_found(pvmw); 234 if (!check_pmd(pmd_pfn(pmde), pvmw)) 235 return not_found(pvmw); 236 return true; 237 } 238 /* THP pmd was split under us: handle on pte level */ 239 spin_unlock(pvmw->ptl); 240 pvmw->ptl = NULL; 241 } else if (!pmd_present(pmde)) { 242 /* 243 * If PVMW_SYNC, take and drop THP pmd lock so that we 244 * cannot return prematurely, while zap_huge_pmd() has 245 * cleared *pmd but not decremented compound_mapcount(). 246 */ 247 if ((pvmw->flags & PVMW_SYNC) && 248 transhuge_vma_suitable(vma, pvmw->address) && 249 (pvmw->nr_pages >= HPAGE_PMD_NR)) { 250 spinlock_t *ptl = pmd_lock(mm, pvmw->pmd); 251 252 spin_unlock(ptl); 253 } 254 step_forward(pvmw, PMD_SIZE); 255 continue; 256 } 257 if (!map_pte(pvmw)) 258 goto next_pte; 259 this_pte: 260 if (check_pte(pvmw)) 261 return true; 262 next_pte: 263 do { 264 pvmw->address += PAGE_SIZE; 265 if (pvmw->address >= end) 266 return not_found(pvmw); 267 /* Did we cross page table boundary? */ 268 if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) { 269 if (pvmw->ptl) { 270 spin_unlock(pvmw->ptl); 271 pvmw->ptl = NULL; 272 } 273 pte_unmap(pvmw->pte); 274 pvmw->pte = NULL; 275 goto restart; 276 } 277 pvmw->pte++; 278 if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) { 279 pvmw->ptl = pte_lockptr(mm, pvmw->pmd); 280 spin_lock(pvmw->ptl); 281 } 282 } while (pte_none(*pvmw->pte)); 283 284 if (!pvmw->ptl) { 285 pvmw->ptl = pte_lockptr(mm, pvmw->pmd); 286 spin_lock(pvmw->ptl); 287 } 288 goto this_pte; 289 } while (pvmw->address < end); 290 291 return false; 292 } 293 294 /** 295 * page_mapped_in_vma - check whether a page is really mapped in a VMA 296 * @page: the page to test 297 * @vma: the VMA to test 298 * 299 * Returns 1 if the page is mapped into the page tables of the VMA, 0 300 * if the page is not mapped into the page tables of this VMA. Only 301 * valid for normal file or anonymous VMAs. 302 */ 303 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) 304 { 305 struct page_vma_mapped_walk pvmw = { 306 .pfn = page_to_pfn(page), 307 .nr_pages = 1, 308 .vma = vma, 309 .flags = PVMW_SYNC, 310 }; 311 312 pvmw.address = vma_address(page, vma); 313 if (pvmw.address == -EFAULT) 314 return 0; 315 if (!page_vma_mapped_walk(&pvmw)) 316 return 0; 317 page_vma_mapped_walk_done(&pvmw); 318 return 1; 319 } 320