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 * All callers that get here will already hold the
173 * i_mmap_rwsem. Therefore, no additional locks need to be
174 * taken before calling hugetlb_walk().
175 */
176 pvmw->pte = hugetlb_walk(vma, pvmw->address, size);
177 if (!pvmw->pte)
178 return false;
179
180 pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte);
181 if (!check_pte(pvmw))
182 return not_found(pvmw);
183 return true;
184 }
185
186 end = vma_address_end(pvmw);
187 if (pvmw->pte)
188 goto next_pte;
189 restart:
190 do {
191 pgd = pgd_offset(mm, pvmw->address);
192 if (!pgd_present(*pgd)) {
193 step_forward(pvmw, PGDIR_SIZE);
194 continue;
195 }
196 p4d = p4d_offset(pgd, pvmw->address);
197 if (!p4d_present(*p4d)) {
198 step_forward(pvmw, P4D_SIZE);
199 continue;
200 }
201 pud = pud_offset(p4d, pvmw->address);
202 if (!pud_present(*pud)) {
203 step_forward(pvmw, PUD_SIZE);
204 continue;
205 }
206
207 pvmw->pmd = pmd_offset(pud, pvmw->address);
208 /*
209 * Make sure the pmd value isn't cached in a register by the
210 * compiler and used as a stale value after we've observed a
211 * subsequent update.
212 */
213 pmde = READ_ONCE(*pvmw->pmd);
214
215 if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) ||
216 (pmd_present(pmde) && pmd_devmap(pmde))) {
217 pvmw->ptl = pmd_lock(mm, pvmw->pmd);
218 pmde = *pvmw->pmd;
219 if (!pmd_present(pmde)) {
220 swp_entry_t entry;
221
222 if (!thp_migration_supported() ||
223 !(pvmw->flags & PVMW_MIGRATION))
224 return not_found(pvmw);
225 entry = pmd_to_swp_entry(pmde);
226 if (!is_migration_entry(entry) ||
227 !check_pmd(swp_offset_pfn(entry), pvmw))
228 return not_found(pvmw);
229 return true;
230 }
231 if (likely(pmd_trans_huge(pmde) || pmd_devmap(pmde))) {
232 if (pvmw->flags & PVMW_MIGRATION)
233 return not_found(pvmw);
234 if (!check_pmd(pmd_pfn(pmde), pvmw))
235 return not_found(pvmw);
236 return true;
237 }
238 /* THP pmd was split under us: handle on pte level */
239 spin_unlock(pvmw->ptl);
240 pvmw->ptl = NULL;
241 } else if (!pmd_present(pmde)) {
242 /*
243 * If PVMW_SYNC, take and drop THP pmd lock so that we
244 * cannot return prematurely, while zap_huge_pmd() has
245 * cleared *pmd but not decremented compound_mapcount().
246 */
247 if ((pvmw->flags & PVMW_SYNC) &&
248 transhuge_vma_suitable(vma, pvmw->address) &&
249 (pvmw->nr_pages >= HPAGE_PMD_NR)) {
250 spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
251
252 spin_unlock(ptl);
253 }
254 step_forward(pvmw, PMD_SIZE);
255 continue;
256 }
257 if (!map_pte(pvmw))
258 goto next_pte;
259 this_pte:
260 if (check_pte(pvmw))
261 return true;
262 next_pte:
263 do {
264 pvmw->address += PAGE_SIZE;
265 if (pvmw->address >= end)
266 return not_found(pvmw);
267 /* Did we cross page table boundary? */
268 if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
269 if (pvmw->ptl) {
270 spin_unlock(pvmw->ptl);
271 pvmw->ptl = NULL;
272 }
273 pte_unmap(pvmw->pte);
274 pvmw->pte = NULL;
275 goto restart;
276 }
277 pvmw->pte++;
278 if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) {
279 pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
280 spin_lock(pvmw->ptl);
281 }
282 } while (pte_none(*pvmw->pte));
283
284 if (!pvmw->ptl) {
285 pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
286 spin_lock(pvmw->ptl);
287 }
288 goto this_pte;
289 } while (pvmw->address < end);
290
291 return false;
292 }
293
294 /**
295 * page_mapped_in_vma - check whether a page is really mapped in a VMA
296 * @page: the page to test
297 * @vma: the VMA to test
298 *
299 * Returns 1 if the page is mapped into the page tables of the VMA, 0
300 * if the page is not mapped into the page tables of this VMA. Only
301 * valid for normal file or anonymous VMAs.
302 */
page_mapped_in_vma(struct page * page,struct vm_area_struct * vma)303 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
304 {
305 struct page_vma_mapped_walk pvmw = {
306 .pfn = page_to_pfn(page),
307 .nr_pages = 1,
308 .vma = vma,
309 .flags = PVMW_SYNC,
310 };
311
312 pvmw.address = vma_address(page, vma);
313 if (pvmw.address == -EFAULT)
314 return 0;
315 if (!page_vma_mapped_walk(&pvmw))
316 return 0;
317 page_vma_mapped_walk_done(&pvmw);
318 return 1;
319 }
320