blob: 6a03946469a99eb535851194f519893a5e8a2d11 [file] [log] [blame]
Kirill A. Shutemovace71a12017-02-24 14:57:45 -08001#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
9static 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
20static inline bool not_found(struct page_vma_mapped_walk *pvmw)
21{
22 page_vma_mapped_walk_done(pvmw);
23 return false;
24}
25
26static 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
43static 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);
Jérôme Glissea5430dd2017-09-08 16:12:17 -070051
Kirill A. Shutemovace71a12017-02-24 14:57:45 -080052 if (!is_migration_entry(entry))
53 return false;
54 if (migration_entry_to_page(entry) - pvmw->page >=
55 hpage_nr_pages(pvmw->page)) {
56 return false;
57 }
58 if (migration_entry_to_page(entry) < pvmw->page)
59 return false;
60#else
61 WARN_ON_ONCE(1);
62#endif
63 } else {
Jérôme Glissea5430dd2017-09-08 16:12:17 -070064 if (is_swap_pte(*pvmw->pte)) {
65 swp_entry_t entry;
66
67 entry = pte_to_swp_entry(*pvmw->pte);
68 if (is_device_private_entry(entry) &&
69 device_private_entry_to_page(entry) == pvmw->page)
70 return true;
71 }
72
Kirill A. Shutemovace71a12017-02-24 14:57:45 -080073 if (!pte_present(*pvmw->pte))
74 return false;
75
76 /* THP can be referenced by any subpage */
77 if (pte_page(*pvmw->pte) - pvmw->page >=
78 hpage_nr_pages(pvmw->page)) {
79 return false;
80 }
81 if (pte_page(*pvmw->pte) < pvmw->page)
82 return false;
83 }
84
85 return true;
86}
87
88/**
89 * page_vma_mapped_walk - check if @pvmw->page is mapped in @pvmw->vma at
90 * @pvmw->address
91 * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
92 * must be set. pmd, pte and ptl must be NULL.
93 *
94 * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
95 * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
96 * adjusted if needed (for PTE-mapped THPs).
97 *
98 * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
99 * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
100 * a loop to find all PTEs that map the THP.
101 *
102 * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
103 * regardless of which page table level the page is mapped at. @pvmw->pmd is
104 * NULL.
105 *
106 * Retruns false if there are no more page table entries for the page in
107 * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
108 *
109 * If you need to stop the walk before page_vma_mapped_walk() returned false,
110 * use page_vma_mapped_walk_done(). It will do the housekeeping.
111 */
112bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
113{
114 struct mm_struct *mm = pvmw->vma->vm_mm;
115 struct page *page = pvmw->page;
116 pgd_t *pgd;
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +0300117 p4d_t *p4d;
Kirill A. Shutemovace71a12017-02-24 14:57:45 -0800118 pud_t *pud;
119
120 /* The only possible pmd mapping has been handled on last iteration */
121 if (pvmw->pmd && !pvmw->pte)
122 return not_found(pvmw);
123
Hugh Dickinsd75450f2017-04-07 16:04:39 -0700124 if (pvmw->pte)
Kirill A. Shutemovace71a12017-02-24 14:57:45 -0800125 goto next_pte;
Kirill A. Shutemovace71a12017-02-24 14:57:45 -0800126
127 if (unlikely(PageHuge(pvmw->page))) {
128 /* when pud is not present, pte will be NULL */
Punit Agrawal7868a202017-07-06 15:39:42 -0700129 pvmw->pte = huge_pte_offset(mm, pvmw->address,
130 PAGE_SIZE << compound_order(page));
Kirill A. Shutemovace71a12017-02-24 14:57:45 -0800131 if (!pvmw->pte)
132 return false;
133
134 pvmw->ptl = huge_pte_lockptr(page_hstate(page), mm, pvmw->pte);
135 spin_lock(pvmw->ptl);
136 if (!check_pte(pvmw))
137 return not_found(pvmw);
138 return true;
139 }
140restart:
141 pgd = pgd_offset(mm, pvmw->address);
142 if (!pgd_present(*pgd))
143 return false;
Kirill A. Shutemovc2febaf2017-03-09 17:24:07 +0300144 p4d = p4d_offset(pgd, pvmw->address);
145 if (!p4d_present(*p4d))
146 return false;
147 pud = pud_offset(p4d, pvmw->address);
Kirill A. Shutemovace71a12017-02-24 14:57:45 -0800148 if (!pud_present(*pud))
149 return false;
150 pvmw->pmd = pmd_offset(pud, pvmw->address);
Zi Yan616b8372017-09-08 16:10:57 -0700151 if (pmd_trans_huge(*pvmw->pmd) || is_pmd_migration_entry(*pvmw->pmd)) {
Kirill A. Shutemovace71a12017-02-24 14:57:45 -0800152 pvmw->ptl = pmd_lock(mm, pvmw->pmd);
Kirill A. Shutemovace71a12017-02-24 14:57:45 -0800153 if (likely(pmd_trans_huge(*pvmw->pmd))) {
154 if (pvmw->flags & PVMW_MIGRATION)
155 return not_found(pvmw);
156 if (pmd_page(*pvmw->pmd) != page)
157 return not_found(pvmw);
158 return true;
Zi Yan616b8372017-09-08 16:10:57 -0700159 } else if (!pmd_present(*pvmw->pmd)) {
160 if (thp_migration_supported()) {
161 if (!(pvmw->flags & PVMW_MIGRATION))
162 return not_found(pvmw);
163 if (is_migration_entry(pmd_to_swp_entry(*pvmw->pmd))) {
164 swp_entry_t entry = pmd_to_swp_entry(*pvmw->pmd);
165
166 if (migration_entry_to_page(entry) != page)
167 return not_found(pvmw);
168 return true;
169 }
170 } else
171 WARN_ONCE(1, "Non present huge pmd without pmd migration enabled!");
172 return not_found(pvmw);
Kirill A. Shutemovace71a12017-02-24 14:57:45 -0800173 } else {
174 /* THP pmd was split under us: handle on pte level */
175 spin_unlock(pvmw->ptl);
176 pvmw->ptl = NULL;
177 }
178 } else {
179 if (!check_pmd(pvmw))
180 return false;
181 }
182 if (!map_pte(pvmw))
183 goto next_pte;
184 while (1) {
185 if (check_pte(pvmw))
186 return true;
Hugh Dickinsd75450f2017-04-07 16:04:39 -0700187next_pte:
188 /* Seek to next pte only makes sense for THP */
189 if (!PageTransHuge(pvmw->page) || PageHuge(pvmw->page))
190 return not_found(pvmw);
191 do {
Kirill A. Shutemovace71a12017-02-24 14:57:45 -0800192 pvmw->address += PAGE_SIZE;
Hugh Dickinsd75450f2017-04-07 16:04:39 -0700193 if (pvmw->address >= pvmw->vma->vm_end ||
194 pvmw->address >=
Kirill A. Shutemovace71a12017-02-24 14:57:45 -0800195 __vma_address(pvmw->page, pvmw->vma) +
196 hpage_nr_pages(pvmw->page) * PAGE_SIZE)
197 return not_found(pvmw);
198 /* Did we cross page table boundary? */
199 if (pvmw->address % PMD_SIZE == 0) {
200 pte_unmap(pvmw->pte);
201 if (pvmw->ptl) {
202 spin_unlock(pvmw->ptl);
203 pvmw->ptl = NULL;
204 }
205 goto restart;
206 } else {
207 pvmw->pte++;
208 }
209 } while (pte_none(*pvmw->pte));
210
211 if (!pvmw->ptl) {
212 pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
213 spin_lock(pvmw->ptl);
214 }
215 }
216}
Kirill A. Shutemov6a328a62017-02-24 14:58:10 -0800217
218/**
219 * page_mapped_in_vma - check whether a page is really mapped in a VMA
220 * @page: the page to test
221 * @vma: the VMA to test
222 *
223 * Returns 1 if the page is mapped into the page tables of the VMA, 0
224 * if the page is not mapped into the page tables of this VMA. Only
225 * valid for normal file or anonymous VMAs.
226 */
227int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
228{
229 struct page_vma_mapped_walk pvmw = {
230 .page = page,
231 .vma = vma,
232 .flags = PVMW_SYNC,
233 };
234 unsigned long start, end;
235
236 start = __vma_address(page, vma);
237 end = start + PAGE_SIZE * (hpage_nr_pages(page) - 1);
238
239 if (unlikely(end < vma->vm_start || start >= vma->vm_end))
240 return 0;
241 pvmw.address = max(start, vma->vm_start);
242 if (!page_vma_mapped_walk(&pvmw))
243 return 0;
244 page_vma_mapped_walk_done(&pvmw);
245 return 1;
246}