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
10static inline bool not_found(struct page_vma_mapped_walk *pvmw)
11{
12 page_vma_mapped_walk_done(pvmw);
13 return false;
14}
15
16static bool map_pte(struct page_vma_mapped_walk *pvmw, pmd_t *pmdvalp,
17 spinlock_t **ptlp)
18{
19 pte_t ptent;
20
21 if (pvmw->flags & PVMW_SYNC) {
22 /* Use the stricter lookup */
23 pvmw->pte = pte_offset_map_lock(mm: pvmw->vma->vm_mm, pmd: pvmw->pmd,
24 addr: pvmw->address, ptlp: &pvmw->ptl);
25 *ptlp = pvmw->ptl;
26 return !!pvmw->pte;
27 }
28
29again:
30 /*
31 * It is important to return the ptl corresponding to pte,
32 * in case *pvmw->pmd changes underneath us; so we need to
33 * return it even when choosing not to lock, in case caller
34 * proceeds to loop over next ptes, and finds a match later.
35 * Though, in most cases, page lock already protects this.
36 */
37 pvmw->pte = pte_offset_map_rw_nolock(mm: pvmw->vma->vm_mm, pmd: pvmw->pmd,
38 addr: pvmw->address, pmdvalp, ptlp);
39 if (!pvmw->pte)
40 return false;
41
42 ptent = ptep_get(ptep: pvmw->pte);
43
44 if (pvmw->flags & PVMW_MIGRATION) {
45 if (!is_swap_pte(pte: ptent))
46 return false;
47 } else if (is_swap_pte(pte: ptent)) {
48 swp_entry_t entry;
49 /*
50 * Handle un-addressable ZONE_DEVICE memory.
51 *
52 * We get here when we are trying to unmap a private
53 * device page from the process address space. Such
54 * page is not CPU accessible and thus is mapped as
55 * a special swap entry, nonetheless it still does
56 * count as a valid regular mapping for the page
57 * (and is accounted as such in page maps count).
58 *
59 * So handle this special case as if it was a normal
60 * page mapping ie lock CPU page table and return true.
61 *
62 * For more details on device private memory see HMM
63 * (include/linux/hmm.h or mm/hmm.c).
64 */
65 entry = pte_to_swp_entry(pte: ptent);
66 if (!is_device_private_entry(entry) &&
67 !is_device_exclusive_entry(entry))
68 return false;
69 } else if (!pte_present(a: ptent)) {
70 return false;
71 }
72 spin_lock(lock: *ptlp);
73 if (unlikely(!pmd_same(*pmdvalp, pmdp_get_lockless(pvmw->pmd)))) {
74 pte_unmap_unlock(pvmw->pte, *ptlp);
75 goto again;
76 }
77 pvmw->ptl = *ptlp;
78
79 return true;
80}
81
82/**
83 * check_pte - check if [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages) is
84 * mapped at the @pvmw->pte
85 * @pvmw: page_vma_mapped_walk struct, includes a pair pte and pfn range
86 * for checking
87 * @pte_nr: the number of small pages described by @pvmw->pte.
88 *
89 * page_vma_mapped_walk() found a place where pfn range is *potentially*
90 * mapped. check_pte() has to validate this.
91 *
92 * pvmw->pte may point to empty PTE, swap PTE or PTE pointing to
93 * arbitrary page.
94 *
95 * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration
96 * entry that points to [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages)
97 *
98 * If PVMW_MIGRATION flag is not set, returns true if pvmw->pte points to
99 * [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages)
100 *
101 * Otherwise, return false.
102 *
103 */
104static bool check_pte(struct page_vma_mapped_walk *pvmw, unsigned long pte_nr)
105{
106 unsigned long pfn;
107 pte_t ptent = ptep_get(ptep: pvmw->pte);
108
109 if (pvmw->flags & PVMW_MIGRATION) {
110 swp_entry_t entry;
111 if (!is_swap_pte(pte: ptent))
112 return false;
113 entry = pte_to_swp_entry(pte: ptent);
114
115 if (!is_migration_entry(entry))
116 return false;
117
118 pfn = swp_offset_pfn(entry);
119 } else if (is_swap_pte(pte: ptent)) {
120 swp_entry_t entry;
121
122 /* Handle un-addressable ZONE_DEVICE memory */
123 entry = pte_to_swp_entry(pte: ptent);
124 if (!is_device_private_entry(entry) &&
125 !is_device_exclusive_entry(entry))
126 return false;
127
128 pfn = swp_offset_pfn(entry);
129 } else {
130 if (!pte_present(a: ptent))
131 return false;
132
133 pfn = pte_pfn(pte: ptent);
134 }
135
136 if ((pfn + pte_nr - 1) < pvmw->pfn)
137 return false;
138 if (pfn > (pvmw->pfn + pvmw->nr_pages - 1))
139 return false;
140 return true;
141}
142
143/* Returns true if the two ranges overlap. Careful to not overflow. */
144static bool check_pmd(unsigned long pfn, struct page_vma_mapped_walk *pvmw)
145{
146 if ((pfn + HPAGE_PMD_NR - 1) < pvmw->pfn)
147 return false;
148 if (pfn > pvmw->pfn + pvmw->nr_pages - 1)
149 return false;
150 return true;
151}
152
153static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size)
154{
155 pvmw->address = (pvmw->address + size) & ~(size - 1);
156 if (!pvmw->address)
157 pvmw->address = ULONG_MAX;
158}
159
160/**
161 * page_vma_mapped_walk - check if @pvmw->pfn is mapped in @pvmw->vma at
162 * @pvmw->address
163 * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
164 * must be set. pmd, pte and ptl must be NULL.
165 *
166 * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
167 * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
168 * adjusted if needed (for PTE-mapped THPs).
169 *
170 * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
171 * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
172 * a loop to find all PTEs that map the THP.
173 *
174 * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
175 * regardless of which page table level the page is mapped at. @pvmw->pmd is
176 * NULL.
177 *
178 * Returns false if there are no more page table entries for the page in
179 * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
180 *
181 * If you need to stop the walk before page_vma_mapped_walk() returned false,
182 * use page_vma_mapped_walk_done(). It will do the housekeeping.
183 */
184bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
185{
186 struct vm_area_struct *vma = pvmw->vma;
187 struct mm_struct *mm = vma->vm_mm;
188 unsigned long end;
189 spinlock_t *ptl;
190 pgd_t *pgd;
191 p4d_t *p4d;
192 pud_t *pud;
193 pmd_t pmde;
194
195 /* The only possible pmd mapping has been handled on last iteration */
196 if (pvmw->pmd && !pvmw->pte)
197 return not_found(pvmw);
198
199 if (unlikely(is_vm_hugetlb_page(vma))) {
200 struct hstate *hstate = hstate_vma(vma);
201 unsigned long size = huge_page_size(h: hstate);
202 /* The only possible mapping was handled on last iteration */
203 if (pvmw->pte)
204 return not_found(pvmw);
205 /*
206 * All callers that get here will already hold the
207 * i_mmap_rwsem. Therefore, no additional locks need to be
208 * taken before calling hugetlb_walk().
209 */
210 pvmw->pte = hugetlb_walk(vma, addr: pvmw->address, sz: size);
211 if (!pvmw->pte)
212 return false;
213
214 pvmw->ptl = huge_pte_lock(h: hstate, mm, pte: pvmw->pte);
215 if (!check_pte(pvmw, pte_nr: pages_per_huge_page(h: hstate)))
216 return not_found(pvmw);
217 return true;
218 }
219
220 end = vma_address_end(pvmw);
221 if (pvmw->pte)
222 goto next_pte;
223restart:
224 do {
225 pgd = pgd_offset(mm, pvmw->address);
226 if (!pgd_present(pgd: *pgd)) {
227 step_forward(pvmw, PGDIR_SIZE);
228 continue;
229 }
230 p4d = p4d_offset(pgd, address: pvmw->address);
231 if (!p4d_present(p4d: *p4d)) {
232 step_forward(pvmw, P4D_SIZE);
233 continue;
234 }
235 pud = pud_offset(p4d, address: pvmw->address);
236 if (!pud_present(pud: *pud)) {
237 step_forward(pvmw, PUD_SIZE);
238 continue;
239 }
240
241 pvmw->pmd = pmd_offset(pud, address: pvmw->address);
242 /*
243 * Make sure the pmd value isn't cached in a register by the
244 * compiler and used as a stale value after we've observed a
245 * subsequent update.
246 */
247 pmde = pmdp_get_lockless(pmdp: pvmw->pmd);
248
249 if (pmd_trans_huge(pmd: pmde) || is_pmd_migration_entry(pmd: pmde)) {
250 pvmw->ptl = pmd_lock(mm, pmd: pvmw->pmd);
251 pmde = *pvmw->pmd;
252 if (!pmd_present(pmd: pmde)) {
253 swp_entry_t entry;
254
255 if (!thp_migration_supported() ||
256 !(pvmw->flags & PVMW_MIGRATION))
257 return not_found(pvmw);
258 entry = pmd_to_swp_entry(pmd: pmde);
259 if (!is_migration_entry(entry) ||
260 !check_pmd(pfn: swp_offset_pfn(entry), pvmw))
261 return not_found(pvmw);
262 return true;
263 }
264 if (likely(pmd_trans_huge(pmde))) {
265 if (pvmw->flags & PVMW_MIGRATION)
266 return not_found(pvmw);
267 if (!check_pmd(pfn: pmd_pfn(pmd: pmde), pvmw))
268 return not_found(pvmw);
269 return true;
270 }
271 /* THP pmd was split under us: handle on pte level */
272 spin_unlock(lock: pvmw->ptl);
273 pvmw->ptl = NULL;
274 } else if (!pmd_present(pmd: pmde)) {
275 /*
276 * If PVMW_SYNC, take and drop THP pmd lock so that we
277 * cannot return prematurely, while zap_huge_pmd() has
278 * cleared *pmd but not decremented compound_mapcount().
279 */
280 if ((pvmw->flags & PVMW_SYNC) &&
281 thp_vma_suitable_order(vma, addr: pvmw->address,
282 PMD_ORDER) &&
283 (pvmw->nr_pages >= HPAGE_PMD_NR)) {
284 spinlock_t *ptl = pmd_lock(mm, pmd: pvmw->pmd);
285
286 spin_unlock(lock: ptl);
287 }
288 step_forward(pvmw, PMD_SIZE);
289 continue;
290 }
291 if (!map_pte(pvmw, pmdvalp: &pmde, ptlp: &ptl)) {
292 if (!pvmw->pte)
293 goto restart;
294 goto next_pte;
295 }
296this_pte:
297 if (check_pte(pvmw, pte_nr: 1))
298 return true;
299next_pte:
300 do {
301 pvmw->address += PAGE_SIZE;
302 if (pvmw->address >= end)
303 return not_found(pvmw);
304 /* Did we cross page table boundary? */
305 if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
306 if (pvmw->ptl) {
307 spin_unlock(lock: pvmw->ptl);
308 pvmw->ptl = NULL;
309 }
310 pte_unmap(pte: pvmw->pte);
311 pvmw->pte = NULL;
312 pvmw->flags |= PVMW_PGTABLE_CROSSED;
313 goto restart;
314 }
315 pvmw->pte++;
316 } while (pte_none(pte: ptep_get(ptep: pvmw->pte)));
317
318 if (!pvmw->ptl) {
319 spin_lock(lock: ptl);
320 if (unlikely(!pmd_same(pmde, pmdp_get_lockless(pvmw->pmd)))) {
321 pte_unmap_unlock(pvmw->pte, ptl);
322 pvmw->pte = NULL;
323 goto restart;
324 }
325 pvmw->ptl = ptl;
326 }
327 goto this_pte;
328 } while (pvmw->address < end);
329
330 return false;
331}
332
333#ifdef CONFIG_MEMORY_FAILURE
334/**
335 * page_mapped_in_vma - check whether a page is really mapped in a VMA
336 * @page: the page to test
337 * @vma: the VMA to test
338 *
339 * Return: The address the page is mapped at if the page is in the range
340 * covered by the VMA and present in the page table. If the page is
341 * outside the VMA or not present, returns -EFAULT.
342 * Only valid for normal file or anonymous VMAs.
343 */
344unsigned long page_mapped_in_vma(const struct page *page,
345 struct vm_area_struct *vma)
346{
347 const struct folio *folio = page_folio(page);
348 struct page_vma_mapped_walk pvmw = {
349 .pfn = page_to_pfn(page),
350 .nr_pages = 1,
351 .vma = vma,
352 .flags = PVMW_SYNC,
353 };
354
355 pvmw.address = vma_address(vma, page_pgoff(folio, page), 1);
356 if (pvmw.address == -EFAULT)
357 goto out;
358 if (!page_vma_mapped_walk(&pvmw))
359 return -EFAULT;
360 page_vma_mapped_walk_done(&pvmw);
361out:
362 return pvmw.address;
363}
364#endif
365