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 /*
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 !is_device_exclusive_entry(entry))
46 return false;
47 } else if (!pte_present(*pvmw->pte))
48 return false;
49 }
50 }
51 pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd);
52 spin_lock(pvmw->ptl);
53 return true;
54 }
55
56 /**
57 * check_pte - check if @pvmw->page is mapped at the @pvmw->pte
58 * @pvmw: page_vma_mapped_walk struct, includes a pair pte and page for checking
59 *
60 * page_vma_mapped_walk() found a place where @pvmw->page is *potentially*
61 * mapped. check_pte() has to validate this.
62 *
63 * pvmw->pte may point to empty PTE, swap PTE or PTE pointing to
64 * arbitrary page.
65 *
66 * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration
67 * entry that points to @pvmw->page or any subpage in case of THP.
68 *
69 * If PVMW_MIGRATION flag is not set, returns true if pvmw->pte points to
70 * pvmw->page or any subpage in case of THP.
71 *
72 * Otherwise, return false.
73 *
74 */
check_pte(struct page_vma_mapped_walk * pvmw)75 static bool check_pte(struct page_vma_mapped_walk *pvmw)
76 {
77 unsigned long pfn;
78
79 if (pvmw->flags & PVMW_MIGRATION) {
80 swp_entry_t entry;
81 if (!is_swap_pte(*pvmw->pte))
82 return false;
83 entry = pte_to_swp_entry(*pvmw->pte);
84
85 if (!is_migration_entry(entry) &&
86 !is_device_exclusive_entry(entry))
87 return false;
88
89 pfn = swp_offset_pfn(entry);
90 } else if (is_swap_pte(*pvmw->pte)) {
91 swp_entry_t entry;
92
93 /* Handle un-addressable ZONE_DEVICE memory */
94 entry = pte_to_swp_entry(*pvmw->pte);
95 if (!is_device_private_entry(entry) &&
96 !is_device_exclusive_entry(entry))
97 return false;
98
99 pfn = swp_offset_pfn(entry);
100 } else {
101 if (!pte_present(*pvmw->pte))
102 return false;
103
104 pfn = pte_pfn(*pvmw->pte);
105 }
106
107 return (pfn - pvmw->pfn) < pvmw->nr_pages;
108 }
109
110 /* Returns true if the two ranges overlap. Careful to not overflow. */
check_pmd(unsigned long pfn,struct page_vma_mapped_walk * pvmw)111 static bool check_pmd(unsigned long pfn, struct page_vma_mapped_walk *pvmw)
112 {
113 if ((pfn + HPAGE_PMD_NR - 1) < pvmw->pfn)
114 return false;
115 if (pfn > pvmw->pfn + pvmw->nr_pages - 1)
116 return false;
117 return true;
118 }
119
step_forward(struct page_vma_mapped_walk * pvmw,unsigned long size)120 static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size)
121 {
122 pvmw->address = (pvmw->address + size) & ~(size - 1);
123 if (!pvmw->address)
124 pvmw->address = ULONG_MAX;
125 }
126
127 /**
128 * page_vma_mapped_walk - check if @pvmw->pfn is mapped in @pvmw->vma at
129 * @pvmw->address
130 * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
131 * must be set. pmd, pte and ptl must be NULL.
132 *
133 * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
134 * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
135 * adjusted if needed (for PTE-mapped THPs).
136 *
137 * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
138 * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
139 * a loop to find all PTEs that map the THP.
140 *
141 * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
142 * regardless of which page table level the page is mapped at. @pvmw->pmd is
143 * NULL.
144 *
145 * Returns false if there are no more page table entries for the page in
146 * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
147 *
148 * If you need to stop the walk before page_vma_mapped_walk() returned false,
149 * use page_vma_mapped_walk_done(). It will do the housekeeping.
150 */
page_vma_mapped_walk(struct page_vma_mapped_walk * pvmw)151 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
152 {
153 struct vm_area_struct *vma = pvmw->vma;
154 struct mm_struct *mm = vma->vm_mm;
155 unsigned long end;
156 pgd_t *pgd;
157 p4d_t *p4d;
158 pud_t *pud;
159 pmd_t pmde;
160
161 /* The only possible pmd mapping has been handled on last iteration */
162 if (pvmw->pmd && !pvmw->pte)
163 return not_found(pvmw);
164
165 if (unlikely(is_vm_hugetlb_page(vma))) {
166 struct hstate *hstate = hstate_vma(vma);
167 unsigned long size = huge_page_size(hstate);
168 /* The only possible mapping was handled on last iteration */
169 if (pvmw->pte)
170 return not_found(pvmw);
171
172 /* when pud is not present, pte will be NULL */
173 pvmw->pte = huge_pte_offset(mm, pvmw->address, size);
174 if (!pvmw->pte)
175 return false;
176
177 pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte);
178 if (!check_pte(pvmw))
179 return not_found(pvmw);
180 return true;
181 }
182
183 end = vma_address_end(pvmw);
184 if (pvmw->pte)
185 goto next_pte;
186 restart:
187 do {
188 pgd = pgd_offset(mm, pvmw->address);
189 if (!pgd_present(*pgd)) {
190 step_forward(pvmw, PGDIR_SIZE);
191 continue;
192 }
193 p4d = p4d_offset(pgd, pvmw->address);
194 if (!p4d_present(*p4d)) {
195 step_forward(pvmw, P4D_SIZE);
196 continue;
197 }
198 pud = pud_offset(p4d, pvmw->address);
199 if (!pud_present(*pud)) {
200 step_forward(pvmw, PUD_SIZE);
201 continue;
202 }
203
204 pvmw->pmd = pmd_offset(pud, pvmw->address);
205 /*
206 * Make sure the pmd value isn't cached in a register by the
207 * compiler and used as a stale value after we've observed a
208 * subsequent update.
209 */
210 pmde = READ_ONCE(*pvmw->pmd);
211
212 if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) ||
213 (pmd_present(pmde) && pmd_devmap(pmde))) {
214 pvmw->ptl = pmd_lock(mm, pvmw->pmd);
215 pmde = *pvmw->pmd;
216 if (!pmd_present(pmde)) {
217 swp_entry_t entry;
218
219 if (!thp_migration_supported() ||
220 !(pvmw->flags & PVMW_MIGRATION))
221 return not_found(pvmw);
222 entry = pmd_to_swp_entry(pmde);
223 if (!is_migration_entry(entry) ||
224 !check_pmd(swp_offset_pfn(entry), pvmw))
225 return not_found(pvmw);
226 return true;
227 }
228 if (likely(pmd_trans_huge(pmde) || pmd_devmap(pmde))) {
229 if (pvmw->flags & PVMW_MIGRATION)
230 return not_found(pvmw);
231 if (!check_pmd(pmd_pfn(pmde), pvmw))
232 return not_found(pvmw);
233 return true;
234 }
235 /* THP pmd was split under us: handle on pte level */
236 spin_unlock(pvmw->ptl);
237 pvmw->ptl = NULL;
238 } else if (!pmd_present(pmde)) {
239 /*
240 * If PVMW_SYNC, take and drop THP pmd lock so that we
241 * cannot return prematurely, while zap_huge_pmd() has
242 * cleared *pmd but not decremented compound_mapcount().
243 */
244 if ((pvmw->flags & PVMW_SYNC) &&
245 transhuge_vma_suitable(vma, pvmw->address) &&
246 (pvmw->nr_pages >= HPAGE_PMD_NR)) {
247 spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
248
249 spin_unlock(ptl);
250 }
251 step_forward(pvmw, PMD_SIZE);
252 continue;
253 }
254 if (!map_pte(pvmw))
255 goto next_pte;
256 this_pte:
257 if (check_pte(pvmw))
258 return true;
259 next_pte:
260 do {
261 pvmw->address += PAGE_SIZE;
262 if (pvmw->address >= end)
263 return not_found(pvmw);
264 /* Did we cross page table boundary? */
265 if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
266 if (pvmw->ptl) {
267 spin_unlock(pvmw->ptl);
268 pvmw->ptl = NULL;
269 }
270 pte_unmap(pvmw->pte);
271 pvmw->pte = NULL;
272 goto restart;
273 }
274 pvmw->pte++;
275 if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) {
276 pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
277 spin_lock(pvmw->ptl);
278 }
279 } while (pte_none(*pvmw->pte));
280
281 if (!pvmw->ptl) {
282 pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
283 spin_lock(pvmw->ptl);
284 }
285 goto this_pte;
286 } while (pvmw->address < end);
287
288 return false;
289 }
290
291 /**
292 * page_mapped_in_vma - check whether a page is really mapped in a VMA
293 * @page: the page to test
294 * @vma: the VMA to test
295 *
296 * Returns 1 if the page is mapped into the page tables of the VMA, 0
297 * if the page is not mapped into the page tables of this VMA. Only
298 * valid for normal file or anonymous VMAs.
299 */
page_mapped_in_vma(struct page * page,struct vm_area_struct * vma)300 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
301 {
302 struct page_vma_mapped_walk pvmw = {
303 .pfn = page_to_pfn(page),
304 .nr_pages = 1,
305 .vma = vma,
306 .flags = PVMW_SYNC,
307 };
308
309 pvmw.address = vma_address(page, vma);
310 if (pvmw.address == -EFAULT)
311 return 0;
312 if (!page_vma_mapped_walk(&pvmw))
313 return 0;
314 page_vma_mapped_walk_done(&pvmw);
315 return 1;
316 }
317
