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
not_found(struct page_vma_mapped_walk * pvmw)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
map_pte(struct page_vma_mapped_walk * pvmw,spinlock_t ** ptlp)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 */
check_pte(struct page_vma_mapped_walk * pvmw)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. */
check_pmd(unsigned long pfn,struct page_vma_mapped_walk * pvmw)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
step_forward(struct page_vma_mapped_walk * pvmw,unsigned long size)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 */
page_vma_mapped_walk(struct page_vma_mapped_walk * pvmw)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 */
page_mapped_in_vma(struct page * page,struct vm_area_struct * vma)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