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