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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
ace71a19 KS |
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 | ||
ace71a19 KS |
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 | ||
16 | static bool map_pte(struct page_vma_mapped_walk *pvmw) | |
17 | { | |
18 | pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address); | |
19 | if (!(pvmw->flags & PVMW_SYNC)) { | |
20 | if (pvmw->flags & PVMW_MIGRATION) { | |
21 | if (!is_swap_pte(*pvmw->pte)) | |
22 | return false; | |
23 | } else { | |
aab8d052 RC |
24 | /* |
25 | * We get here when we are trying to unmap a private | |
26 | * device page from the process address space. Such | |
27 | * page is not CPU accessible and thus is mapped as | |
28 | * a special swap entry, nonetheless it still does | |
29 | * count as a valid regular mapping for the page (and | |
30 | * is accounted as such in page maps count). | |
31 | * | |
32 | * So handle this special case as if it was a normal | |
33 | * page mapping ie lock CPU page table and returns | |
34 | * true. | |
35 | * | |
36 | * For more details on device private memory see HMM | |
37 | * (include/linux/hmm.h or mm/hmm.c). | |
38 | */ | |
39 | if (is_swap_pte(*pvmw->pte)) { | |
40 | swp_entry_t entry; | |
41 | ||
42 | /* Handle un-addressable ZONE_DEVICE memory */ | |
43 | entry = pte_to_swp_entry(*pvmw->pte); | |
44 | if (!is_device_private_entry(entry)) | |
45 | return false; | |
46 | } else if (!pte_present(*pvmw->pte)) | |
ace71a19 KS |
47 | return false; |
48 | } | |
49 | } | |
50 | pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd); | |
51 | spin_lock(pvmw->ptl); | |
52 | return true; | |
53 | } | |
54 | ||
7222708e KS |
55 | static inline bool pfn_in_hpage(struct page *hpage, unsigned long pfn) |
56 | { | |
57 | unsigned long hpage_pfn = page_to_pfn(hpage); | |
58 | ||
59 | /* THP can be referenced by any subpage */ | |
60 | return pfn >= hpage_pfn && pfn - hpage_pfn < hpage_nr_pages(hpage); | |
61 | } | |
62 | ||
0d665e7b KS |
63 | /** |
64 | * check_pte - check if @pvmw->page is mapped at the @pvmw->pte | |
65 | * | |
66 | * page_vma_mapped_walk() found a place where @pvmw->page is *potentially* | |
67 | * mapped. check_pte() has to validate this. | |
68 | * | |
69 | * @pvmw->pte may point to empty PTE, swap PTE or PTE pointing to arbitrary | |
70 | * page. | |
71 | * | |
72 | * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration | |
73 | * entry that points to @pvmw->page or any subpage in case of THP. | |
74 | * | |
75 | * If PVMW_MIGRATION flag is not set, returns true if @pvmw->pte points to | |
76 | * @pvmw->page or any subpage in case of THP. | |
77 | * | |
78 | * Otherwise, return false. | |
79 | * | |
80 | */ | |
ace71a19 KS |
81 | static bool check_pte(struct page_vma_mapped_walk *pvmw) |
82 | { | |
0d665e7b KS |
83 | unsigned long pfn; |
84 | ||
ace71a19 | 85 | if (pvmw->flags & PVMW_MIGRATION) { |
ace71a19 KS |
86 | swp_entry_t entry; |
87 | if (!is_swap_pte(*pvmw->pte)) | |
88 | return false; | |
89 | entry = pte_to_swp_entry(*pvmw->pte); | |
a5430dda | 90 | |
ace71a19 KS |
91 | if (!is_migration_entry(entry)) |
92 | return false; | |
a5430dda | 93 | |
0d665e7b KS |
94 | pfn = migration_entry_to_pfn(entry); |
95 | } else if (is_swap_pte(*pvmw->pte)) { | |
96 | swp_entry_t entry; | |
a5430dda | 97 | |
0d665e7b KS |
98 | /* Handle un-addressable ZONE_DEVICE memory */ |
99 | entry = pte_to_swp_entry(*pvmw->pte); | |
100 | if (!is_device_private_entry(entry)) | |
ace71a19 KS |
101 | return false; |
102 | ||
0d665e7b KS |
103 | pfn = device_private_entry_to_pfn(entry); |
104 | } else { | |
105 | if (!pte_present(*pvmw->pte)) | |
ace71a19 | 106 | return false; |
0d665e7b KS |
107 | |
108 | pfn = pte_pfn(*pvmw->pte); | |
ace71a19 KS |
109 | } |
110 | ||
7222708e | 111 | return pfn_in_hpage(pvmw->page, pfn); |
ace71a19 KS |
112 | } |
113 | ||
114 | /** | |
115 | * page_vma_mapped_walk - check if @pvmw->page is mapped in @pvmw->vma at | |
116 | * @pvmw->address | |
117 | * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags | |
118 | * must be set. pmd, pte and ptl must be NULL. | |
119 | * | |
120 | * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point | |
121 | * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is | |
122 | * adjusted if needed (for PTE-mapped THPs). | |
123 | * | |
124 | * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page | |
125 | * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in | |
126 | * a loop to find all PTEs that map the THP. | |
127 | * | |
128 | * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry | |
129 | * regardless of which page table level the page is mapped at. @pvmw->pmd is | |
130 | * NULL. | |
131 | * | |
132 | * Retruns false if there are no more page table entries for the page in | |
133 | * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped. | |
134 | * | |
135 | * If you need to stop the walk before page_vma_mapped_walk() returned false, | |
136 | * use page_vma_mapped_walk_done(). It will do the housekeeping. | |
137 | */ | |
138 | bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) | |
139 | { | |
140 | struct mm_struct *mm = pvmw->vma->vm_mm; | |
141 | struct page *page = pvmw->page; | |
142 | pgd_t *pgd; | |
c2febafc | 143 | p4d_t *p4d; |
ace71a19 | 144 | pud_t *pud; |
a7b10095 | 145 | pmd_t pmde; |
ace71a19 KS |
146 | |
147 | /* The only possible pmd mapping has been handled on last iteration */ | |
148 | if (pvmw->pmd && !pvmw->pte) | |
149 | return not_found(pvmw); | |
150 | ||
d75450ff | 151 | if (pvmw->pte) |
ace71a19 | 152 | goto next_pte; |
ace71a19 KS |
153 | |
154 | if (unlikely(PageHuge(pvmw->page))) { | |
155 | /* when pud is not present, pte will be NULL */ | |
7868a208 PA |
156 | pvmw->pte = huge_pte_offset(mm, pvmw->address, |
157 | PAGE_SIZE << compound_order(page)); | |
ace71a19 KS |
158 | if (!pvmw->pte) |
159 | return false; | |
160 | ||
161 | pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte); | |
162 | spin_lock(pvmw->ptl); | |
163 | if (!check_pte(pvmw)) | |
164 | return not_found(pvmw); | |
165 | return true; | |
166 | } | |
167 | restart: | |
168 | pgd = pgd_offset(mm, pvmw->address); | |
169 | if (!pgd_present(*pgd)) | |
170 | return false; | |
c2febafc KS |
171 | p4d = p4d_offset(pgd, pvmw->address); |
172 | if (!p4d_present(*p4d)) | |
173 | return false; | |
174 | pud = pud_offset(p4d, pvmw->address); | |
ace71a19 KS |
175 | if (!pud_present(*pud)) |
176 | return false; | |
177 | pvmw->pmd = pmd_offset(pud, pvmw->address); | |
a7b10095 WD |
178 | /* |
179 | * Make sure the pmd value isn't cached in a register by the | |
180 | * compiler and used as a stale value after we've observed a | |
181 | * subsequent update. | |
182 | */ | |
183 | pmde = READ_ONCE(*pvmw->pmd); | |
184 | if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) { | |
ace71a19 | 185 | pvmw->ptl = pmd_lock(mm, pvmw->pmd); |
ace71a19 KS |
186 | if (likely(pmd_trans_huge(*pvmw->pmd))) { |
187 | if (pvmw->flags & PVMW_MIGRATION) | |
188 | return not_found(pvmw); | |
189 | if (pmd_page(*pvmw->pmd) != page) | |
190 | return not_found(pvmw); | |
191 | return true; | |
616b8371 ZY |
192 | } else if (!pmd_present(*pvmw->pmd)) { |
193 | if (thp_migration_supported()) { | |
194 | if (!(pvmw->flags & PVMW_MIGRATION)) | |
195 | return not_found(pvmw); | |
196 | if (is_migration_entry(pmd_to_swp_entry(*pvmw->pmd))) { | |
197 | swp_entry_t entry = pmd_to_swp_entry(*pvmw->pmd); | |
198 | ||
199 | if (migration_entry_to_page(entry) != page) | |
200 | return not_found(pvmw); | |
201 | return true; | |
202 | } | |
af0db981 | 203 | } |
616b8371 | 204 | return not_found(pvmw); |
ace71a19 KS |
205 | } else { |
206 | /* THP pmd was split under us: handle on pte level */ | |
207 | spin_unlock(pvmw->ptl); | |
208 | pvmw->ptl = NULL; | |
209 | } | |
a7b10095 WD |
210 | } else if (!pmd_present(pmde)) { |
211 | return false; | |
ace71a19 KS |
212 | } |
213 | if (!map_pte(pvmw)) | |
214 | goto next_pte; | |
215 | while (1) { | |
216 | if (check_pte(pvmw)) | |
217 | return true; | |
d75450ff HD |
218 | next_pte: |
219 | /* Seek to next pte only makes sense for THP */ | |
220 | if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page)) | |
221 | return not_found(pvmw); | |
222 | do { | |
ace71a19 | 223 | pvmw->address += PAGE_SIZE; |
d75450ff HD |
224 | if (pvmw->address >= pvmw->vma->vm_end || |
225 | pvmw->address >= | |
ace71a19 KS |
226 | __vma_address(pvmw->page, pvmw->vma) + |
227 | hpage_nr_pages(pvmw->page) * PAGE_SIZE) | |
228 | return not_found(pvmw); | |
229 | /* Did we cross page table boundary? */ | |
230 | if (pvmw->address % PMD_SIZE == 0) { | |
231 | pte_unmap(pvmw->pte); | |
232 | if (pvmw->ptl) { | |
233 | spin_unlock(pvmw->ptl); | |
234 | pvmw->ptl = NULL; | |
235 | } | |
236 | goto restart; | |
237 | } else { | |
238 | pvmw->pte++; | |
239 | } | |
240 | } while (pte_none(*pvmw->pte)); | |
241 | ||
242 | if (!pvmw->ptl) { | |
243 | pvmw->ptl = pte_lockptr(mm, pvmw->pmd); | |
244 | spin_lock(pvmw->ptl); | |
245 | } | |
246 | } | |
247 | } | |
6a328a62 KS |
248 | |
249 | /** | |
250 | * page_mapped_in_vma - check whether a page is really mapped in a VMA | |
251 | * @page: the page to test | |
252 | * @vma: the VMA to test | |
253 | * | |
254 | * Returns 1 if the page is mapped into the page tables of the VMA, 0 | |
255 | * if the page is not mapped into the page tables of this VMA. Only | |
256 | * valid for normal file or anonymous VMAs. | |
257 | */ | |
258 | int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) | |
259 | { | |
260 | struct page_vma_mapped_walk pvmw = { | |
261 | .page = page, | |
262 | .vma = vma, | |
263 | .flags = PVMW_SYNC, | |
264 | }; | |
265 | unsigned long start, end; | |
266 | ||
267 | start = __vma_address(page, vma); | |
268 | end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1); | |
269 | ||
270 | if (unlikely(end < vma->vm_start || start >= vma->vm_end)) | |
271 | return 0; | |
272 | pvmw.address = max(start, vma->vm_start); | |
273 | if (!page_vma_mapped_walk(&pvmw)) | |
274 | return 0; | |
275 | page_vma_mapped_walk_done(&pvmw); | |
276 | return 1; | |
277 | } |