1 // SPDX-License-Identifier: GPL-2.0
3 #include <linux/rmap.h>
4 #include <linux/hugetlb.h>
5 #include <linux/swap.h>
6 #include <linux/swapops.h>
10 static inline bool not_found(struct page_vma_mapped_walk *pvmw)
12 page_vma_mapped_walk_done(pvmw);
16 static bool map_pte(struct page_vma_mapped_walk *pvmw)
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))
24 if (!pte_present(*pvmw->pte))
28 pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd);
34 * check_pte - check if @pvmw->page is mapped at the @pvmw->pte
36 * page_vma_mapped_walk() found a place where @pvmw->page is *potentially*
37 * mapped. check_pte() has to validate this.
39 * @pvmw->pte may point to empty PTE, swap PTE or PTE pointing to arbitrary
42 * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration
43 * entry that points to @pvmw->page or any subpage in case of THP.
45 * If PVMW_MIGRATION flag is not set, returns true if @pvmw->pte points to
46 * @pvmw->page or any subpage in case of THP.
48 * Otherwise, return false.
51 static bool check_pte(struct page_vma_mapped_walk *pvmw)
55 if (pvmw->flags & PVMW_MIGRATION) {
57 if (!is_swap_pte(*pvmw->pte))
59 entry = pte_to_swp_entry(*pvmw->pte);
61 if (!is_migration_entry(entry))
64 pfn = migration_entry_to_pfn(entry);
65 } else if (is_swap_pte(*pvmw->pte)) {
68 /* Handle un-addressable ZONE_DEVICE memory */
69 entry = pte_to_swp_entry(*pvmw->pte);
70 if (!is_device_private_entry(entry))
73 pfn = device_private_entry_to_pfn(entry);
75 if (!pte_present(*pvmw->pte))
78 pfn = pte_pfn(*pvmw->pte);
81 if (pfn < page_to_pfn(pvmw->page))
84 /* THP can be referenced by any subpage */
85 if (pfn - page_to_pfn(pvmw->page) >= hpage_nr_pages(pvmw->page))
92 * page_vma_mapped_walk - check if @pvmw->page is mapped in @pvmw->vma at
94 * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
95 * must be set. pmd, pte and ptl must be NULL.
97 * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
98 * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
99 * adjusted if needed (for PTE-mapped THPs).
101 * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
102 * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
103 * a loop to find all PTEs that map the THP.
105 * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
106 * regardless of which page table level the page is mapped at. @pvmw->pmd is
109 * Retruns false if there are no more page table entries for the page in
110 * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
112 * If you need to stop the walk before page_vma_mapped_walk() returned false,
113 * use page_vma_mapped_walk_done(). It will do the housekeeping.
115 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
117 struct mm_struct *mm = pvmw->vma->vm_mm;
118 struct page *page = pvmw->page;
124 /* The only possible pmd mapping has been handled on last iteration */
125 if (pvmw->pmd && !pvmw->pte)
126 return not_found(pvmw);
131 if (unlikely(PageHuge(pvmw->page))) {
132 /* when pud is not present, pte will be NULL */
133 pvmw->pte = huge_pte_offset(mm, pvmw->address,
134 PAGE_SIZE << compound_order(page));
138 pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte);
139 spin_lock(pvmw->ptl);
140 if (!check_pte(pvmw))
141 return not_found(pvmw);
145 pgd = pgd_offset(mm, pvmw->address);
146 if (!pgd_present(*pgd))
148 p4d = p4d_offset(pgd, pvmw->address);
149 if (!p4d_present(*p4d))
151 pud = pud_offset(p4d, pvmw->address);
152 if (!pud_present(*pud))
154 pvmw->pmd = pmd_offset(pud, pvmw->address);
156 * Make sure the pmd value isn't cached in a register by the
157 * compiler and used as a stale value after we've observed a
160 pmde = READ_ONCE(*pvmw->pmd);
161 if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde)) {
162 pvmw->ptl = pmd_lock(mm, pvmw->pmd);
163 if (likely(pmd_trans_huge(*pvmw->pmd))) {
164 if (pvmw->flags & PVMW_MIGRATION)
165 return not_found(pvmw);
166 if (pmd_page(*pvmw->pmd) != page)
167 return not_found(pvmw);
169 } else if (!pmd_present(*pvmw->pmd)) {
170 if (thp_migration_supported()) {
171 if (!(pvmw->flags & PVMW_MIGRATION))
172 return not_found(pvmw);
173 if (is_migration_entry(pmd_to_swp_entry(*pvmw->pmd))) {
174 swp_entry_t entry = pmd_to_swp_entry(*pvmw->pmd);
176 if (migration_entry_to_page(entry) != page)
177 return not_found(pvmw);
181 return not_found(pvmw);
183 /* THP pmd was split under us: handle on pte level */
184 spin_unlock(pvmw->ptl);
187 } else if (!pmd_present(pmde)) {
196 /* Seek to next pte only makes sense for THP */
197 if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page))
198 return not_found(pvmw);
200 pvmw->address += PAGE_SIZE;
201 if (pvmw->address >= pvmw->vma->vm_end ||
203 __vma_address(pvmw->page, pvmw->vma) +
204 hpage_nr_pages(pvmw->page) * PAGE_SIZE)
205 return not_found(pvmw);
206 /* Did we cross page table boundary? */
207 if (pvmw->address % PMD_SIZE == 0) {
208 pte_unmap(pvmw->pte);
210 spin_unlock(pvmw->ptl);
217 } while (pte_none(*pvmw->pte));
220 pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
221 spin_lock(pvmw->ptl);
227 * page_mapped_in_vma - check whether a page is really mapped in a VMA
228 * @page: the page to test
229 * @vma: the VMA to test
231 * Returns 1 if the page is mapped into the page tables of the VMA, 0
232 * if the page is not mapped into the page tables of this VMA. Only
233 * valid for normal file or anonymous VMAs.
235 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
237 struct page_vma_mapped_walk pvmw = {
242 unsigned long start, end;
244 start = __vma_address(page, vma);
245 end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1);
247 if (unlikely(end < vma->vm_start || start >= vma->vm_end))
249 pvmw.address = max(start, vma->vm_start);
250 if (!page_vma_mapped_walk(&pvmw))
252 page_vma_mapped_walk_done(&pvmw);