Line data Source code
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 0 : page_vma_mapped_walk_done(pvmw);
13 : return false;
14 : }
15 :
16 0 : static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
17 : {
18 : pte_t ptent;
19 :
20 0 : if (pvmw->flags & PVMW_SYNC) {
21 : /* Use the stricter lookup */
22 0 : pvmw->pte = pte_offset_map_lock(pvmw->vma->vm_mm, pvmw->pmd,
23 : pvmw->address, &pvmw->ptl);
24 0 : *ptlp = pvmw->ptl;
25 0 : 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 0 : pvmw->pte = pte_offset_map_nolock(pvmw->vma->vm_mm, pvmw->pmd,
36 : pvmw->address, ptlp);
37 0 : if (!pvmw->pte)
38 : return false;
39 :
40 0 : ptent = ptep_get(pvmw->pte);
41 :
42 0 : if (pvmw->flags & PVMW_MIGRATION) {
43 0 : if (!is_swap_pte(ptent))
44 : return false;
45 0 : } 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 0 : entry = pte_to_swp_entry(ptent);
64 0 : if (!is_device_private_entry(entry) &&
65 0 : !is_device_exclusive_entry(entry))
66 : return false;
67 0 : } else if (!pte_present(ptent)) {
68 : return false;
69 : }
70 0 : pvmw->ptl = *ptlp;
71 0 : spin_lock(pvmw->ptl);
72 0 : return true;
73 : }
74 :
75 : /**
76 : * check_pte - check if @pvmw->page is mapped at the @pvmw->pte
77 : * @pvmw: page_vma_mapped_walk struct, includes a pair pte and page for checking
78 : *
79 : * page_vma_mapped_walk() found a place where @pvmw->page is *potentially*
80 : * mapped. check_pte() has to validate this.
81 : *
82 : * pvmw->pte may point to empty PTE, swap PTE or PTE pointing to
83 : * arbitrary page.
84 : *
85 : * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration
86 : * entry that points to @pvmw->page or any subpage in case of THP.
87 : *
88 : * If PVMW_MIGRATION flag is not set, returns true if pvmw->pte points to
89 : * pvmw->page or any subpage in case of THP.
90 : *
91 : * Otherwise, return false.
92 : *
93 : */
94 0 : static bool check_pte(struct page_vma_mapped_walk *pvmw)
95 : {
96 : unsigned long pfn;
97 0 : pte_t ptent = ptep_get(pvmw->pte);
98 :
99 0 : if (pvmw->flags & PVMW_MIGRATION) {
100 : swp_entry_t entry;
101 0 : if (!is_swap_pte(ptent))
102 : return false;
103 0 : entry = pte_to_swp_entry(ptent);
104 :
105 0 : if (!is_migration_entry(entry) &&
106 : !is_device_exclusive_entry(entry))
107 : return false;
108 :
109 0 : pfn = swp_offset_pfn(entry);
110 0 : } else if (is_swap_pte(ptent)) {
111 : swp_entry_t entry;
112 :
113 : /* Handle un-addressable ZONE_DEVICE memory */
114 : entry = pte_to_swp_entry(ptent);
115 : if (!is_device_private_entry(entry) &&
116 : !is_device_exclusive_entry(entry))
117 : return false;
118 :
119 : pfn = swp_offset_pfn(entry);
120 : } else {
121 0 : if (!pte_present(ptent))
122 : return false;
123 :
124 0 : pfn = pte_pfn(ptent);
125 : }
126 :
127 0 : return (pfn - pvmw->pfn) < pvmw->nr_pages;
128 : }
129 :
130 : /* Returns true if the two ranges overlap. Careful to not overflow. */
131 : static bool check_pmd(unsigned long pfn, struct page_vma_mapped_walk *pvmw)
132 : {
133 : if ((pfn + HPAGE_PMD_NR - 1) < pvmw->pfn)
134 : return false;
135 : if (pfn > pvmw->pfn + pvmw->nr_pages - 1)
136 : return false;
137 : return true;
138 : }
139 :
140 : static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size)
141 : {
142 0 : pvmw->address = (pvmw->address + size) & ~(size - 1);
143 0 : if (!pvmw->address)
144 0 : pvmw->address = ULONG_MAX;
145 : }
146 :
147 : /**
148 : * page_vma_mapped_walk - check if @pvmw->pfn is mapped in @pvmw->vma at
149 : * @pvmw->address
150 : * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
151 : * must be set. pmd, pte and ptl must be NULL.
152 : *
153 : * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
154 : * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
155 : * adjusted if needed (for PTE-mapped THPs).
156 : *
157 : * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
158 : * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
159 : * a loop to find all PTEs that map the THP.
160 : *
161 : * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
162 : * regardless of which page table level the page is mapped at. @pvmw->pmd is
163 : * NULL.
164 : *
165 : * Returns false if there are no more page table entries for the page in
166 : * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
167 : *
168 : * If you need to stop the walk before page_vma_mapped_walk() returned false,
169 : * use page_vma_mapped_walk_done(). It will do the housekeeping.
170 : */
171 0 : bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
172 : {
173 0 : struct vm_area_struct *vma = pvmw->vma;
174 0 : struct mm_struct *mm = vma->vm_mm;
175 : unsigned long end;
176 : spinlock_t *ptl;
177 : pgd_t *pgd;
178 : p4d_t *p4d;
179 : pud_t *pud;
180 : pmd_t pmde;
181 :
182 : /* The only possible pmd mapping has been handled on last iteration */
183 0 : if (pvmw->pmd && !pvmw->pte)
184 : return not_found(pvmw);
185 :
186 0 : if (unlikely(is_vm_hugetlb_page(vma))) {
187 : struct hstate *hstate = hstate_vma(vma);
188 : unsigned long size = huge_page_size(hstate);
189 : /* The only possible mapping was handled on last iteration */
190 : if (pvmw->pte)
191 : return not_found(pvmw);
192 : /*
193 : * All callers that get here will already hold the
194 : * i_mmap_rwsem. Therefore, no additional locks need to be
195 : * taken before calling hugetlb_walk().
196 : */
197 : pvmw->pte = hugetlb_walk(vma, pvmw->address, size);
198 : if (!pvmw->pte)
199 : return false;
200 :
201 : pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte);
202 : if (!check_pte(pvmw))
203 : return not_found(pvmw);
204 : return true;
205 : }
206 :
207 0 : end = vma_address_end(pvmw);
208 0 : if (pvmw->pte)
209 : goto next_pte;
210 : restart:
211 : do {
212 0 : pgd = pgd_offset(mm, pvmw->address);
213 : if (!pgd_present(*pgd)) {
214 : step_forward(pvmw, PGDIR_SIZE);
215 : continue;
216 : }
217 0 : p4d = p4d_offset(pgd, pvmw->address);
218 : if (!p4d_present(*p4d)) {
219 : step_forward(pvmw, P4D_SIZE);
220 : continue;
221 : }
222 0 : pud = pud_offset(p4d, pvmw->address);
223 0 : if (!pud_present(*pud)) {
224 0 : step_forward(pvmw, PUD_SIZE);
225 0 : continue;
226 : }
227 :
228 0 : pvmw->pmd = pmd_offset(pud, pvmw->address);
229 : /*
230 : * Make sure the pmd value isn't cached in a register by the
231 : * compiler and used as a stale value after we've observed a
232 : * subsequent update.
233 : */
234 0 : pmde = pmdp_get_lockless(pvmw->pmd);
235 :
236 0 : if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) ||
237 0 : (pmd_present(pmde) && pmd_devmap(pmde))) {
238 : pvmw->ptl = pmd_lock(mm, pvmw->pmd);
239 : pmde = *pvmw->pmd;
240 : if (!pmd_present(pmde)) {
241 : swp_entry_t entry;
242 :
243 : if (!thp_migration_supported() ||
244 : !(pvmw->flags & PVMW_MIGRATION))
245 : return not_found(pvmw);
246 : entry = pmd_to_swp_entry(pmde);
247 : if (!is_migration_entry(entry) ||
248 : !check_pmd(swp_offset_pfn(entry), pvmw))
249 : return not_found(pvmw);
250 : return true;
251 : }
252 : if (likely(pmd_trans_huge(pmde) || pmd_devmap(pmde))) {
253 : if (pvmw->flags & PVMW_MIGRATION)
254 : return not_found(pvmw);
255 : if (!check_pmd(pmd_pfn(pmde), pvmw))
256 : return not_found(pvmw);
257 : return true;
258 : }
259 : /* THP pmd was split under us: handle on pte level */
260 : spin_unlock(pvmw->ptl);
261 : pvmw->ptl = NULL;
262 0 : } else if (!pmd_present(pmde)) {
263 : /*
264 : * If PVMW_SYNC, take and drop THP pmd lock so that we
265 : * cannot return prematurely, while zap_huge_pmd() has
266 : * cleared *pmd but not decremented compound_mapcount().
267 : */
268 : if ((pvmw->flags & PVMW_SYNC) &&
269 : transhuge_vma_suitable(vma, pvmw->address) &&
270 : (pvmw->nr_pages >= HPAGE_PMD_NR)) {
271 : spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
272 :
273 : spin_unlock(ptl);
274 : }
275 0 : step_forward(pvmw, PMD_SIZE);
276 0 : continue;
277 : }
278 0 : if (!map_pte(pvmw, &ptl)) {
279 0 : if (!pvmw->pte)
280 : goto restart;
281 : goto next_pte;
282 : }
283 : this_pte:
284 0 : if (check_pte(pvmw))
285 : return true;
286 : next_pte:
287 : do {
288 0 : pvmw->address += PAGE_SIZE;
289 0 : if (pvmw->address >= end)
290 : return not_found(pvmw);
291 : /* Did we cross page table boundary? */
292 0 : if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
293 0 : if (pvmw->ptl) {
294 0 : spin_unlock(pvmw->ptl);
295 0 : pvmw->ptl = NULL;
296 : }
297 0 : pte_unmap(pvmw->pte);
298 0 : pvmw->pte = NULL;
299 0 : goto restart;
300 : }
301 0 : pvmw->pte++;
302 0 : } while (pte_none(ptep_get(pvmw->pte)));
303 :
304 0 : if (!pvmw->ptl) {
305 0 : pvmw->ptl = ptl;
306 0 : spin_lock(pvmw->ptl);
307 : }
308 : goto this_pte;
309 0 : } while (pvmw->address < end);
310 :
311 : return false;
312 : }
313 :
314 : /**
315 : * page_mapped_in_vma - check whether a page is really mapped in a VMA
316 : * @page: the page to test
317 : * @vma: the VMA to test
318 : *
319 : * Returns 1 if the page is mapped into the page tables of the VMA, 0
320 : * if the page is not mapped into the page tables of this VMA. Only
321 : * valid for normal file or anonymous VMAs.
322 : */
323 0 : int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
324 : {
325 0 : struct page_vma_mapped_walk pvmw = {
326 0 : .pfn = page_to_pfn(page),
327 : .nr_pages = 1,
328 : .vma = vma,
329 : .flags = PVMW_SYNC,
330 : };
331 :
332 0 : pvmw.address = vma_address(page, vma);
333 0 : if (pvmw.address == -EFAULT)
334 : return 0;
335 0 : if (!page_vma_mapped_walk(&pvmw))
336 : return 0;
337 0 : page_vma_mapped_walk_done(&pvmw);
338 : return 1;
339 : }
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