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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 | ||
5b8d6e37 | 55 | static inline bool pfn_is_match(struct page *page, unsigned long pfn) |
7222708e | 56 | { |
5b8d6e37 LX |
57 | unsigned long page_pfn = page_to_pfn(page); |
58 | ||
59 | /* normal page and hugetlbfs page */ | |
60 | if (!PageTransCompound(page) || PageHuge(page)) | |
61 | return page_pfn == pfn; | |
7222708e KS |
62 | |
63 | /* THP can be referenced by any subpage */ | |
6c357848 | 64 | return pfn >= page_pfn && pfn - page_pfn < thp_nr_pages(page); |
7222708e KS |
65 | } |
66 | ||
0d665e7b KS |
67 | /** |
68 | * check_pte - check if @pvmw->page is mapped at the @pvmw->pte | |
69 | * | |
70 | * page_vma_mapped_walk() found a place where @pvmw->page is *potentially* | |
71 | * mapped. check_pte() has to validate this. | |
72 | * | |
73 | * @pvmw->pte may point to empty PTE, swap PTE or PTE pointing to arbitrary | |
74 | * page. | |
75 | * | |
76 | * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration | |
77 | * entry that points to @pvmw->page or any subpage in case of THP. | |
78 | * | |
79 | * If PVMW_MIGRATION flag is not set, returns true if @pvmw->pte points to | |
80 | * @pvmw->page or any subpage in case of THP. | |
81 | * | |
82 | * Otherwise, return false. | |
83 | * | |
84 | */ | |
ace71a19 KS |
85 | static bool check_pte(struct page_vma_mapped_walk *pvmw) |
86 | { | |
0d665e7b KS |
87 | unsigned long pfn; |
88 | ||
ace71a19 | 89 | if (pvmw->flags & PVMW_MIGRATION) { |
ace71a19 KS |
90 | swp_entry_t entry; |
91 | if (!is_swap_pte(*pvmw->pte)) | |
92 | return false; | |
93 | entry = pte_to_swp_entry(*pvmw->pte); | |
a5430dda | 94 | |
ace71a19 KS |
95 | if (!is_migration_entry(entry)) |
96 | return false; | |
a5430dda | 97 | |
0d665e7b KS |
98 | pfn = migration_entry_to_pfn(entry); |
99 | } else if (is_swap_pte(*pvmw->pte)) { | |
100 | swp_entry_t entry; | |
a5430dda | 101 | |
0d665e7b KS |
102 | /* Handle un-addressable ZONE_DEVICE memory */ |
103 | entry = pte_to_swp_entry(*pvmw->pte); | |
104 | if (!is_device_private_entry(entry)) | |
ace71a19 KS |
105 | return false; |
106 | ||
0d665e7b KS |
107 | pfn = device_private_entry_to_pfn(entry); |
108 | } else { | |
109 | if (!pte_present(*pvmw->pte)) | |
ace71a19 | 110 | return false; |
0d665e7b KS |
111 | |
112 | pfn = pte_pfn(*pvmw->pte); | |
ace71a19 KS |
113 | } |
114 | ||
5b8d6e37 | 115 | return pfn_is_match(pvmw->page, pfn); |
ace71a19 KS |
116 | } |
117 | ||
118 | /** | |
119 | * page_vma_mapped_walk - check if @pvmw->page is mapped in @pvmw->vma at | |
120 | * @pvmw->address | |
121 | * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags | |
122 | * must be set. pmd, pte and ptl must be NULL. | |
123 | * | |
124 | * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point | |
125 | * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is | |
126 | * adjusted if needed (for PTE-mapped THPs). | |
127 | * | |
128 | * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page | |
129 | * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in | |
130 | * a loop to find all PTEs that map the THP. | |
131 | * | |
132 | * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry | |
133 | * regardless of which page table level the page is mapped at. @pvmw->pmd is | |
134 | * NULL. | |
135 | * | |
136 | * Retruns false if there are no more page table entries for the page in | |
137 | * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped. | |
138 | * | |
139 | * If you need to stop the walk before page_vma_mapped_walk() returned false, | |
140 | * use page_vma_mapped_walk_done(). It will do the housekeeping. | |
141 | */ | |
142 | bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) | |
143 | { | |
144 | struct mm_struct *mm = pvmw->vma->vm_mm; | |
145 | struct page *page = pvmw->page; | |
146 | pgd_t *pgd; | |
c2febafc | 147 | p4d_t *p4d; |
ace71a19 | 148 | pud_t *pud; |
a7b10095 | 149 | pmd_t pmde; |
ace71a19 KS |
150 | |
151 | /* The only possible pmd mapping has been handled on last iteration */ | |
152 | if (pvmw->pmd && !pvmw->pte) | |
153 | return not_found(pvmw); | |
154 | ||
d75450ff | 155 | if (pvmw->pte) |
ace71a19 | 156 | goto next_pte; |
ace71a19 KS |
157 | |
158 | if (unlikely(PageHuge(pvmw->page))) { | |
159 | /* when pud is not present, pte will be NULL */ | |
a50b854e | 160 | pvmw->pte = huge_pte_offset(mm, pvmw->address, page_size(page)); |
ace71a19 KS |
161 | if (!pvmw->pte) |
162 | return false; | |
163 | ||
164 | pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte); | |
165 | spin_lock(pvmw->ptl); | |
166 | if (!check_pte(pvmw)) | |
167 | return not_found(pvmw); | |
168 | return true; | |
169 | } | |
170 | restart: | |
171 | pgd = pgd_offset(mm, pvmw->address); | |
172 | if (!pgd_present(*pgd)) | |
173 | return false; | |
c2febafc KS |
174 | p4d = p4d_offset(pgd, pvmw->address); |
175 | if (!p4d_present(*p4d)) | |
176 | return false; | |
177 | pud = pud_offset(p4d, pvmw->address); | |
ace71a19 KS |
178 | if (!pud_present(*pud)) |
179 | return false; | |
180 | pvmw->pmd = pmd_offset(pud, pvmw->address); | |
a7b10095 WD |
181 | /* |
182 | * Make sure the pmd value isn't cached in a register by the | |
183 | * compiler and used as a stale value after we've observed a | |
184 | * subsequent update. | |
185 | */ | |
186 | pmde = READ_ONCE(*pvmw->pmd); | |
187 | if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) { | |
ace71a19 | 188 | pvmw->ptl = pmd_lock(mm, pvmw->pmd); |
ace71a19 KS |
189 | if (likely(pmd_trans_huge(*pvmw->pmd))) { |
190 | if (pvmw->flags & PVMW_MIGRATION) | |
191 | return not_found(pvmw); | |
192 | if (pmd_page(*pvmw->pmd) != page) | |
193 | return not_found(pvmw); | |
194 | return true; | |
616b8371 ZY |
195 | } else if (!pmd_present(*pvmw->pmd)) { |
196 | if (thp_migration_supported()) { | |
197 | if (!(pvmw->flags & PVMW_MIGRATION)) | |
198 | return not_found(pvmw); | |
199 | if (is_migration_entry(pmd_to_swp_entry(*pvmw->pmd))) { | |
200 | swp_entry_t entry = pmd_to_swp_entry(*pvmw->pmd); | |
201 | ||
202 | if (migration_entry_to_page(entry) != page) | |
203 | return not_found(pvmw); | |
204 | return true; | |
205 | } | |
af0db981 | 206 | } |
616b8371 | 207 | return not_found(pvmw); |
ace71a19 KS |
208 | } else { |
209 | /* THP pmd was split under us: handle on pte level */ | |
210 | spin_unlock(pvmw->ptl); | |
211 | pvmw->ptl = NULL; | |
212 | } | |
a7b10095 WD |
213 | } else if (!pmd_present(pmde)) { |
214 | return false; | |
ace71a19 KS |
215 | } |
216 | if (!map_pte(pvmw)) | |
217 | goto next_pte; | |
218 | while (1) { | |
219 | if (check_pte(pvmw)) | |
220 | return true; | |
d75450ff HD |
221 | next_pte: |
222 | /* Seek to next pte only makes sense for THP */ | |
223 | if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page)) | |
224 | return not_found(pvmw); | |
225 | do { | |
ace71a19 | 226 | pvmw->address += PAGE_SIZE; |
d75450ff HD |
227 | if (pvmw->address >= pvmw->vma->vm_end || |
228 | pvmw->address >= | |
ace71a19 | 229 | __vma_address(pvmw->page, pvmw->vma) + |
af3bbc12 | 230 | thp_size(pvmw->page)) |
ace71a19 KS |
231 | return not_found(pvmw); |
232 | /* Did we cross page table boundary? */ | |
233 | if (pvmw->address % PMD_SIZE == 0) { | |
234 | pte_unmap(pvmw->pte); | |
235 | if (pvmw->ptl) { | |
236 | spin_unlock(pvmw->ptl); | |
237 | pvmw->ptl = NULL; | |
238 | } | |
239 | goto restart; | |
240 | } else { | |
241 | pvmw->pte++; | |
242 | } | |
243 | } while (pte_none(*pvmw->pte)); | |
244 | ||
245 | if (!pvmw->ptl) { | |
246 | pvmw->ptl = pte_lockptr(mm, pvmw->pmd); | |
247 | spin_lock(pvmw->ptl); | |
248 | } | |
249 | } | |
250 | } | |
6a328a62 KS |
251 | |
252 | /** | |
253 | * page_mapped_in_vma - check whether a page is really mapped in a VMA | |
254 | * @page: the page to test | |
255 | * @vma: the VMA to test | |
256 | * | |
257 | * Returns 1 if the page is mapped into the page tables of the VMA, 0 | |
258 | * if the page is not mapped into the page tables of this VMA. Only | |
259 | * valid for normal file or anonymous VMAs. | |
260 | */ | |
261 | int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) | |
262 | { | |
263 | struct page_vma_mapped_walk pvmw = { | |
264 | .page = page, | |
265 | .vma = vma, | |
266 | .flags = PVMW_SYNC, | |
267 | }; | |
268 | unsigned long start, end; | |
269 | ||
270 | start = __vma_address(page, vma); | |
af3bbc12 | 271 | end = start + thp_size(page) - PAGE_SIZE; |
6a328a62 KS |
272 | |
273 | if (unlikely(end < vma->vm_start || start >= vma->vm_end)) | |
274 | return 0; | |
275 | pvmw.address = max(start, vma->vm_start); | |
276 | if (!page_vma_mapped_walk(&pvmw)) | |
277 | return 0; | |
278 | page_vma_mapped_walk_done(&pvmw); | |
279 | return 1; | |
280 | } |