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 * @pte_nr: the number of small pages described by @pvmw->pte.
81 *
82 * page_vma_mapped_walk() found a place where pfn range is *potentially*
83 * mapped. check_pte() has to validate this.
84 *
85 * pvmw->pte may point to empty PTE, swap PTE or PTE pointing to
86 * arbitrary page.
87 *
88 * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration
89 * entry that points to [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages)
90 *
91 * If PVMW_MIGRATION flag is not set, returns true if pvmw->pte points to
92 * [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages)
93 *
94 * Otherwise, return false.
95 *
96 */
check_pte(struct page_vma_mapped_walk * pvmw,unsigned long pte_nr)97 static bool check_pte(struct page_vma_mapped_walk *pvmw, unsigned long pte_nr)
98 {
99 unsigned long pfn;
100 pte_t ptent = ptep_get(pvmw->pte);
101
102 if (pvmw->flags & PVMW_MIGRATION) {
103 swp_entry_t entry;
104 if (!is_swap_pte(ptent))
105 return false;
106 entry = pte_to_swp_entry(ptent);
107
108 if (!is_migration_entry(entry) &&
109 !is_device_exclusive_entry(entry))
110 return false;
111
112 pfn = swp_offset_pfn(entry);
113 } else if (is_swap_pte(ptent)) {
114 swp_entry_t entry;
115
116 /* Handle un-addressable ZONE_DEVICE memory */
117 entry = pte_to_swp_entry(ptent);
118 if (!is_device_private_entry(entry) &&
119 !is_device_exclusive_entry(entry))
120 return false;
121
122 pfn = swp_offset_pfn(entry);
123 } else {
124 if (!pte_present(ptent))
125 return false;
126
127 pfn = pte_pfn(ptent);
128 }
129
130 if ((pfn + pte_nr - 1) < pvmw->pfn)
131 return false;
132 if (pfn > (pvmw->pfn + pvmw->nr_pages - 1))
133 return false;
134 return true;
135 }
136
137 /* Returns true if the two ranges overlap. Careful to not overflow. */
check_pmd(unsigned long pfn,struct page_vma_mapped_walk * pvmw)138 static bool check_pmd(unsigned long pfn, struct page_vma_mapped_walk *pvmw)
139 {
140 if ((pfn + HPAGE_PMD_NR - 1) < pvmw->pfn)
141 return false;
142 if (pfn > pvmw->pfn + pvmw->nr_pages - 1)
143 return false;
144 return true;
145 }
146
step_forward(struct page_vma_mapped_walk * pvmw,unsigned long size)147 static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size)
148 {
149 pvmw->address = (pvmw->address + size) & ~(size - 1);
150 if (!pvmw->address)
151 pvmw->address = ULONG_MAX;
152 }
153
154 /**
155 * page_vma_mapped_walk - check if @pvmw->pfn is mapped in @pvmw->vma at
156 * @pvmw->address
157 * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
158 * must be set. pmd, pte and ptl must be NULL.
159 *
160 * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
161 * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
162 * adjusted if needed (for PTE-mapped THPs).
163 *
164 * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
165 * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
166 * a loop to find all PTEs that map the THP.
167 *
168 * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
169 * regardless of which page table level the page is mapped at. @pvmw->pmd is
170 * NULL.
171 *
172 * Returns false if there are no more page table entries for the page in
173 * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
174 *
175 * If you need to stop the walk before page_vma_mapped_walk() returned false,
176 * use page_vma_mapped_walk_done(). It will do the housekeeping.
177 */
page_vma_mapped_walk(struct page_vma_mapped_walk * pvmw)178 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
179 {
180 struct vm_area_struct *vma = pvmw->vma;
181 struct mm_struct *mm = vma->vm_mm;
182 unsigned long end;
183 spinlock_t *ptl;
184 pgd_t *pgd;
185 p4d_t *p4d;
186 pud_t *pud;
187 pmd_t pmde;
188
189 /* The only possible pmd mapping has been handled on last iteration */
190 if (pvmw->pmd && !pvmw->pte)
191 return not_found(pvmw);
192
193 if (unlikely(is_vm_hugetlb_page(vma))) {
194 struct hstate *hstate = hstate_vma(vma);
195 unsigned long size = huge_page_size(hstate);
196 /* The only possible mapping was handled on last iteration */
197 if (pvmw->pte)
198 return not_found(pvmw);
199 /*
200 * All callers that get here will already hold the
201 * i_mmap_rwsem. Therefore, no additional locks need to be
202 * taken before calling hugetlb_walk().
203 */
204 pvmw->pte = hugetlb_walk(vma, pvmw->address, size);
205 if (!pvmw->pte)
206 return false;
207
208 pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte);
209 if (!check_pte(pvmw, pages_per_huge_page(hstate)))
210 return not_found(pvmw);
211 return true;
212 }
213
214 end = vma_address_end(pvmw);
215 if (pvmw->pte)
216 goto next_pte;
217 restart:
218 do {
219 pgd = pgd_offset(mm, pvmw->address);
220 if (!pgd_present(*pgd)) {
221 step_forward(pvmw, PGDIR_SIZE);
222 continue;
223 }
224 p4d = p4d_offset(pgd, pvmw->address);
225 if (!p4d_present(*p4d)) {
226 step_forward(pvmw, P4D_SIZE);
227 continue;
228 }
229 pud = pud_offset(p4d, pvmw->address);
230 if (!pud_present(*pud)) {
231 step_forward(pvmw, PUD_SIZE);
232 continue;
233 }
234
235 pvmw->pmd = pmd_offset(pud, pvmw->address);
236 /*
237 * Make sure the pmd value isn't cached in a register by the
238 * compiler and used as a stale value after we've observed a
239 * subsequent update.
240 */
241 pmde = pmdp_get_lockless(pvmw->pmd);
242
243 if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) ||
244 (pmd_present(pmde) && pmd_devmap(pmde))) {
245 pvmw->ptl = pmd_lock(mm, pvmw->pmd);
246 pmde = *pvmw->pmd;
247 if (!pmd_present(pmde)) {
248 swp_entry_t entry;
249
250 if (!thp_migration_supported() ||
251 !(pvmw->flags & PVMW_MIGRATION))
252 return not_found(pvmw);
253 entry = pmd_to_swp_entry(pmde);
254 if (!is_migration_entry(entry) ||
255 !check_pmd(swp_offset_pfn(entry), pvmw))
256 return not_found(pvmw);
257 return true;
258 }
259 if (likely(pmd_trans_huge(pmde) || pmd_devmap(pmde))) {
260 if (pvmw->flags & PVMW_MIGRATION)
261 return not_found(pvmw);
262 if (!check_pmd(pmd_pfn(pmde), pvmw))
263 return not_found(pvmw);
264 return true;
265 }
266 /* THP pmd was split under us: handle on pte level */
267 spin_unlock(pvmw->ptl);
268 pvmw->ptl = NULL;
269 } else if (!pmd_present(pmde)) {
270 /*
271 * If PVMW_SYNC, take and drop THP pmd lock so that we
272 * cannot return prematurely, while zap_huge_pmd() has
273 * cleared *pmd but not decremented compound_mapcount().
274 */
275 if ((pvmw->flags & PVMW_SYNC) &&
276 transhuge_vma_suitable(vma, pvmw->address) &&
277 (pvmw->nr_pages >= HPAGE_PMD_NR)) {
278 spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
279
280 spin_unlock(ptl);
281 }
282 step_forward(pvmw, PMD_SIZE);
283 continue;
284 }
285 if (!map_pte(pvmw, &ptl)) {
286 if (!pvmw->pte)
287 goto restart;
288 goto next_pte;
289 }
290 this_pte:
291 if (check_pte(pvmw, 1))
292 return true;
293 next_pte:
294 do {
295 pvmw->address += PAGE_SIZE;
296 if (pvmw->address >= end)
297 return not_found(pvmw);
298 /* Did we cross page table boundary? */
299 if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
300 if (pvmw->ptl) {
301 spin_unlock(pvmw->ptl);
302 pvmw->ptl = NULL;
303 }
304 pte_unmap(pvmw->pte);
305 pvmw->pte = NULL;
306 goto restart;
307 }
308 pvmw->pte++;
309 } while (pte_none(ptep_get(pvmw->pte)));
310
311 if (!pvmw->ptl) {
312 pvmw->ptl = ptl;
313 spin_lock(pvmw->ptl);
314 }
315 goto this_pte;
316 } while (pvmw->address < end);
317
318 return false;
319 }
320
321 /**
322 * page_mapped_in_vma - check whether a page is really mapped in a VMA
323 * @page: the page to test
324 * @vma: the VMA to test
325 *
326 * Returns 1 if the page is mapped into the page tables of the VMA, 0
327 * if the page is not mapped into the page tables of this VMA. Only
328 * valid for normal file or anonymous VMAs.
329 */
page_mapped_in_vma(struct page * page,struct vm_area_struct * vma)330 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
331 {
332 struct page_vma_mapped_walk pvmw = {
333 .pfn = page_to_pfn(page),
334 .nr_pages = 1,
335 .vma = vma,
336 .flags = PVMW_SYNC,
337 };
338
339 pvmw.address = vma_address(page, vma);
340 if (pvmw.address == -EFAULT)
341 return 0;
342 if (!page_vma_mapped_walk(&pvmw))
343 return 0;
344 page_vma_mapped_walk_done(&pvmw);
345 return 1;
346 }
347