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ace71a19 KS |
1 | #include <linux/mm.h> |
2 | #include <linux/rmap.h> | |
3 | #include <linux/hugetlb.h> | |
4 | #include <linux/swap.h> | |
5 | #include <linux/swapops.h> | |
6 | ||
7 | #include "internal.h" | |
8 | ||
9 | static inline bool check_pmd(struct page_vma_mapped_walk *pvmw) | |
10 | { | |
11 | pmd_t pmde; | |
12 | /* | |
13 | * Make sure we don't re-load pmd between present and !trans_huge check. | |
14 | * We need a consistent view. | |
15 | */ | |
16 | pmde = READ_ONCE(*pvmw->pmd); | |
17 | return pmd_present(pmde) && !pmd_trans_huge(pmde); | |
18 | } | |
19 | ||
20 | static inline bool not_found(struct page_vma_mapped_walk *pvmw) | |
21 | { | |
22 | page_vma_mapped_walk_done(pvmw); | |
23 | return false; | |
24 | } | |
25 | ||
26 | static bool map_pte(struct page_vma_mapped_walk *pvmw) | |
27 | { | |
28 | pvmw->pte = pte_offset_map(pvmw->pmd, pvmw->address); | |
29 | if (!(pvmw->flags & PVMW_SYNC)) { | |
30 | if (pvmw->flags & PVMW_MIGRATION) { | |
31 | if (!is_swap_pte(*pvmw->pte)) | |
32 | return false; | |
33 | } else { | |
34 | if (!pte_present(*pvmw->pte)) | |
35 | return false; | |
36 | } | |
37 | } | |
38 | pvmw->ptl = pte_lockptr(pvmw->vma->vm_mm, pvmw->pmd); | |
39 | spin_lock(pvmw->ptl); | |
40 | return true; | |
41 | } | |
42 | ||
43 | static bool check_pte(struct page_vma_mapped_walk *pvmw) | |
44 | { | |
45 | if (pvmw->flags & PVMW_MIGRATION) { | |
46 | #ifdef CONFIG_MIGRATION | |
47 | swp_entry_t entry; | |
48 | if (!is_swap_pte(*pvmw->pte)) | |
49 | return false; | |
50 | entry = pte_to_swp_entry(*pvmw->pte); | |
51 | if (!is_migration_entry(entry)) | |
52 | return false; | |
53 | if (migration_entry_to_page(entry) - pvmw->page >= | |
54 | hpage_nr_pages(pvmw->page)) { | |
55 | return false; | |
56 | } | |
57 | if (migration_entry_to_page(entry) < pvmw->page) | |
58 | return false; | |
59 | #else | |
60 | WARN_ON_ONCE(1); | |
61 | #endif | |
62 | } else { | |
63 | if (!pte_present(*pvmw->pte)) | |
64 | return false; | |
65 | ||
66 | /* THP can be referenced by any subpage */ | |
67 | if (pte_page(*pvmw->pte) - pvmw->page >= | |
68 | hpage_nr_pages(pvmw->page)) { | |
69 | return false; | |
70 | } | |
71 | if (pte_page(*pvmw->pte) < pvmw->page) | |
72 | return false; | |
73 | } | |
74 | ||
75 | return true; | |
76 | } | |
77 | ||
78 | /** | |
79 | * page_vma_mapped_walk - check if @pvmw->page is mapped in @pvmw->vma at | |
80 | * @pvmw->address | |
81 | * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags | |
82 | * must be set. pmd, pte and ptl must be NULL. | |
83 | * | |
84 | * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point | |
85 | * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is | |
86 | * adjusted if needed (for PTE-mapped THPs). | |
87 | * | |
88 | * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page | |
89 | * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in | |
90 | * a loop to find all PTEs that map the THP. | |
91 | * | |
92 | * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry | |
93 | * regardless of which page table level the page is mapped at. @pvmw->pmd is | |
94 | * NULL. | |
95 | * | |
96 | * Retruns false if there are no more page table entries for the page in | |
97 | * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped. | |
98 | * | |
99 | * If you need to stop the walk before page_vma_mapped_walk() returned false, | |
100 | * use page_vma_mapped_walk_done(). It will do the housekeeping. | |
101 | */ | |
102 | bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) | |
103 | { | |
104 | struct mm_struct *mm = pvmw->vma->vm_mm; | |
105 | struct page *page = pvmw->page; | |
106 | pgd_t *pgd; | |
107 | pud_t *pud; | |
108 | ||
109 | /* The only possible pmd mapping has been handled on last iteration */ | |
110 | if (pvmw->pmd && !pvmw->pte) | |
111 | return not_found(pvmw); | |
112 | ||
113 | /* Only for THP, seek to next pte entry makes sense */ | |
114 | if (pvmw->pte) { | |
115 | if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page)) | |
116 | return not_found(pvmw); | |
117 | goto next_pte; | |
118 | } | |
119 | ||
120 | if (unlikely(PageHuge(pvmw->page))) { | |
121 | /* when pud is not present, pte will be NULL */ | |
122 | pvmw->pte = huge_pte_offset(mm, pvmw->address); | |
123 | if (!pvmw->pte) | |
124 | return false; | |
125 | ||
126 | pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte); | |
127 | spin_lock(pvmw->ptl); | |
128 | if (!check_pte(pvmw)) | |
129 | return not_found(pvmw); | |
130 | return true; | |
131 | } | |
132 | restart: | |
133 | pgd = pgd_offset(mm, pvmw->address); | |
134 | if (!pgd_present(*pgd)) | |
135 | return false; | |
136 | pud = pud_offset(pgd, pvmw->address); | |
137 | if (!pud_present(*pud)) | |
138 | return false; | |
139 | pvmw->pmd = pmd_offset(pud, pvmw->address); | |
140 | if (pmd_trans_huge(*pvmw->pmd)) { | |
141 | pvmw->ptl = pmd_lock(mm, pvmw->pmd); | |
142 | if (!pmd_present(*pvmw->pmd)) | |
143 | return not_found(pvmw); | |
144 | if (likely(pmd_trans_huge(*pvmw->pmd))) { | |
145 | if (pvmw->flags & PVMW_MIGRATION) | |
146 | return not_found(pvmw); | |
147 | if (pmd_page(*pvmw->pmd) != page) | |
148 | return not_found(pvmw); | |
149 | return true; | |
150 | } else { | |
151 | /* THP pmd was split under us: handle on pte level */ | |
152 | spin_unlock(pvmw->ptl); | |
153 | pvmw->ptl = NULL; | |
154 | } | |
155 | } else { | |
156 | if (!check_pmd(pvmw)) | |
157 | return false; | |
158 | } | |
159 | if (!map_pte(pvmw)) | |
160 | goto next_pte; | |
161 | while (1) { | |
162 | if (check_pte(pvmw)) | |
163 | return true; | |
164 | next_pte: do { | |
165 | pvmw->address += PAGE_SIZE; | |
166 | if (pvmw->address >= | |
167 | __vma_address(pvmw->page, pvmw->vma) + | |
168 | hpage_nr_pages(pvmw->page) * PAGE_SIZE) | |
169 | return not_found(pvmw); | |
170 | /* Did we cross page table boundary? */ | |
171 | if (pvmw->address % PMD_SIZE == 0) { | |
172 | pte_unmap(pvmw->pte); | |
173 | if (pvmw->ptl) { | |
174 | spin_unlock(pvmw->ptl); | |
175 | pvmw->ptl = NULL; | |
176 | } | |
177 | goto restart; | |
178 | } else { | |
179 | pvmw->pte++; | |
180 | } | |
181 | } while (pte_none(*pvmw->pte)); | |
182 | ||
183 | if (!pvmw->ptl) { | |
184 | pvmw->ptl = pte_lockptr(mm, pvmw->pmd); | |
185 | spin_lock(pvmw->ptl); | |
186 | } | |
187 | } | |
188 | } |