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
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 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(mm: pvmw->vma->vm_mm, pmd: pvmw->pmd,
25 addr: pvmw->address, ptlp: &pvmw->ptl);
26 *ptlp = pvmw->ptl;
27 return !!pvmw->pte;
28 }
29
30 is_migration = pvmw->flags & PVMW_MIGRATION;
31again:
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(mm: pvmw->vma->vm_mm, pmd: pvmw->pmd,
40 addr: pvmw->address, pmdvalp, ptlp);
41 if (!pvmw->pte)
42 return false;
43
44 ptent = ptep_get(ptep: pvmw->pte);
45
46 if (pte_none(pte: ptent)) {
47 return false;
48 } else if (pte_present(a: 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(pte: ptent);
71 if (!softleaf_is_device_private(entry) &&
72 !softleaf_is_device_exclusive(entry))
73 return false;
74 }
75 spin_lock(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 */
107static bool check_pte(struct page_vma_mapped_walk *pvmw, unsigned long pte_nr)
108{
109 unsigned long pfn;
110 pte_t ptent = ptep_get(ptep: pvmw->pte);
111
112 if (pvmw->flags & PVMW_MIGRATION) {
113 const softleaf_t entry = softleaf_from_pte(pte: ptent);
114
115 if (!softleaf_is_migration(entry))
116 return false;
117
118 pfn = softleaf_to_pfn(entry);
119 } else if (pte_present(a: ptent)) {
120 pfn = pte_pfn(pte: ptent);
121 } else {
122 const softleaf_t entry = softleaf_from_pte(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. */
140static 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
149static 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 */
180bool 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(h: 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, addr: pvmw->address, sz: size);
207 if (!pvmw->pte)
208 return false;
209
210 pvmw->ptl = huge_pte_lock(h: hstate, mm, pte: pvmw->pte);
211 if (!check_pte(pvmw, pte_nr: pages_per_huge_page(h: 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;
219restart:
220 do {
221 pgd = pgd_offset(mm, pvmw->address);
222 if (!pgd_present(pgd: *pgd)) {
223 step_forward(pvmw, PGDIR_SIZE);
224 continue;
225 }
226 p4d = p4d_offset(pgd, address: pvmw->address);
227 if (!p4d_present(p4d: *p4d)) {
228 step_forward(pvmw, P4D_SIZE);
229 continue;
230 }
231 pud = pud_offset(p4d, address: pvmw->address);
232 if (!pud_present(pud: *pud)) {
233 step_forward(pvmw, PUD_SIZE);
234 continue;
235 }
236
237 pvmw->pmd = pmd_offset(pud, address: 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(pmdp: pvmw->pmd);
244
245 if (pmd_trans_huge(pmd: pmde) || pmd_is_migration_entry(pmd: pmde)) {
246 pvmw->ptl = pmd_lock(mm, pmd: pvmw->pmd);
247 pmde = *pvmw->pmd;
248 if (!pmd_present(pmd: 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(pmd: pmde);
255
256 if (!softleaf_is_migration(entry) ||
257 !check_pmd(pfn: 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(pfn: pmd_pfn(pmd: 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(lock: pvmw->ptl);
270 pvmw->ptl = NULL;
271 } else if (!pmd_present(pmd: pmde)) {
272 /*
273 * If PVMW_SYNC, take and drop THP pmd lock so that we
274 * cannot return prematurely, while zap_huge_pmd() has
275 * cleared *pmd but not decremented compound_mapcount().
276 */
277 const softleaf_t entry = softleaf_from_pmd(pmd: pmde);
278
279 if (softleaf_is_device_private(entry)) {
280 pvmw->ptl = pmd_lock(mm, pmd: pvmw->pmd);
281 return true;
282 }
283
284 if ((pvmw->flags & PVMW_SYNC) &&
285 thp_vma_suitable_order(vma, addr: pvmw->address,
286 PMD_ORDER) &&
287 (pvmw->nr_pages >= HPAGE_PMD_NR)) {
288 spinlock_t *ptl = pmd_lock(mm, pmd: pvmw->pmd);
289
290 spin_unlock(lock: ptl);
291 }
292 step_forward(pvmw, PMD_SIZE);
293 continue;
294 }
295 if (!map_pte(pvmw, pmdvalp: &pmde, ptlp: &ptl)) {
296 if (!pvmw->pte)
297 goto restart;
298 goto next_pte;
299 }
300this_pte:
301 if (check_pte(pvmw, pte_nr: 1))
302 return true;
303next_pte:
304 do {
305 pvmw->address += PAGE_SIZE;
306 if (pvmw->address >= end)
307 return not_found(pvmw);
308 /* Did we cross page table boundary? */
309 if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
310 if (pvmw->ptl) {
311 spin_unlock(lock: pvmw->ptl);
312 pvmw->ptl = NULL;
313 }
314 pte_unmap(pte: pvmw->pte);
315 pvmw->pte = NULL;
316 pvmw->flags |= PVMW_PGTABLE_CROSSED;
317 goto restart;
318 }
319 pvmw->pte++;
320 } while (pte_none(pte: ptep_get(ptep: pvmw->pte)));
321
322 if (!pvmw->ptl) {
323 spin_lock(lock: ptl);
324 if (unlikely(!pmd_same(pmde, pmdp_get_lockless(pvmw->pmd)))) {
325 pte_unmap_unlock(pvmw->pte, ptl);
326 pvmw->pte = NULL;
327 goto restart;
328 }
329 pvmw->ptl = ptl;
330 }
331 goto this_pte;
332 } while (pvmw->address < end);
333
334 return false;
335}
336
337#ifdef CONFIG_MEMORY_FAILURE
338/**
339 * page_mapped_in_vma - check whether a page is really mapped in a VMA
340 * @page: the page to test
341 * @vma: the VMA to test
342 *
343 * Return: The address the page is mapped at if the page is in the range
344 * covered by the VMA and present in the page table. If the page is
345 * outside the VMA or not present, returns -EFAULT.
346 * Only valid for normal file or anonymous VMAs.
347 */
348unsigned long page_mapped_in_vma(const struct page *page,
349 struct vm_area_struct *vma)
350{
351 const struct folio *folio = page_folio(page);
352 struct page_vma_mapped_walk pvmw = {
353 .pfn = page_to_pfn(page),
354 .nr_pages = 1,
355 .vma = vma,
356 .flags = PVMW_SYNC,
357 };
358
359 pvmw.address = vma_address(vma, pgoff: page_pgoff(folio, page), nr_pages: 1);
360 if (pvmw.address == -EFAULT)
361 goto out;
362 if (!page_vma_mapped_walk(pvmw: &pvmw))
363 return -EFAULT;
364 page_vma_mapped_walk_done(pvmw: &pvmw);
365out:
366 return pvmw.address;
367}
368#endif
369

source code of linux/mm/page_vma_mapped.c