Merge tag 'ntb-6.6' of https://github.com/jonmason/ntb
[platform/kernel/linux-starfive.git] / mm / page_vma_mapped.c
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
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
16 static bool map_pte(struct page_vma_mapped_walk *pvmw, spinlock_t **ptlp)
17 {
18         pte_t ptent;
19
20         if (pvmw->flags & PVMW_SYNC) {
21                 /* Use the stricter lookup */
22                 pvmw->pte = pte_offset_map_lock(pvmw->vma->vm_mm, pvmw->pmd,
23                                                 pvmw->address, &pvmw->ptl);
24                 *ptlp = pvmw->ptl;
25                 return !!pvmw->pte;
26         }
27
28         /*
29          * It is important to return the ptl corresponding to pte,
30          * in case *pvmw->pmd changes underneath us; so we need to
31          * return it even when choosing not to lock, in case caller
32          * proceeds to loop over next ptes, and finds a match later.
33          * Though, in most cases, page lock already protects this.
34          */
35         pvmw->pte = pte_offset_map_nolock(pvmw->vma->vm_mm, pvmw->pmd,
36                                           pvmw->address, ptlp);
37         if (!pvmw->pte)
38                 return false;
39
40         ptent = ptep_get(pvmw->pte);
41
42         if (pvmw->flags & PVMW_MIGRATION) {
43                 if (!is_swap_pte(ptent))
44                         return false;
45         } else if (is_swap_pte(ptent)) {
46                 swp_entry_t entry;
47                 /*
48                  * Handle un-addressable ZONE_DEVICE memory.
49                  *
50                  * We get here when we are trying to unmap a private
51                  * device page from the process address space. Such
52                  * page is not CPU accessible and thus is mapped as
53                  * a special swap entry, nonetheless it still does
54                  * count as a valid regular mapping for the page
55                  * (and is accounted as such in page maps count).
56                  *
57                  * So handle this special case as if it was a normal
58                  * page mapping ie lock CPU page table and return true.
59                  *
60                  * For more details on device private memory see HMM
61                  * (include/linux/hmm.h or mm/hmm.c).
62                  */
63                 entry = pte_to_swp_entry(ptent);
64                 if (!is_device_private_entry(entry) &&
65                     !is_device_exclusive_entry(entry))
66                         return false;
67         } else if (!pte_present(ptent)) {
68                 return false;
69         }
70         pvmw->ptl = *ptlp;
71         spin_lock(pvmw->ptl);
72         return true;
73 }
74
75 /**
76  * check_pte - check if [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages) is
77  * mapped at the @pvmw->pte
78  * @pvmw: page_vma_mapped_walk struct, includes a pair pte and pfn range
79  * for checking
80  *
81  * page_vma_mapped_walk() found a place where pfn range is *potentially*
82  * mapped. check_pte() has to validate this.
83  *
84  * pvmw->pte may point to empty PTE, swap PTE or PTE pointing to
85  * arbitrary page.
86  *
87  * If PVMW_MIGRATION flag is set, returns true if @pvmw->pte contains migration
88  * entry that points to [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages)
89  *
90  * If PVMW_MIGRATION flag is not set, returns true if pvmw->pte points to
91  * [pvmw->pfn, @pvmw->pfn + @pvmw->nr_pages)
92  *
93  * Otherwise, return false.
94  *
95  */
96 static bool check_pte(struct page_vma_mapped_walk *pvmw)
97 {
98         unsigned long pfn;
99         pte_t ptent = ptep_get(pvmw->pte);
100
101         if (pvmw->flags & PVMW_MIGRATION) {
102                 swp_entry_t entry;
103                 if (!is_swap_pte(ptent))
104                         return false;
105                 entry = pte_to_swp_entry(ptent);
106
107                 if (!is_migration_entry(entry) &&
108                     !is_device_exclusive_entry(entry))
109                         return false;
110
111                 pfn = swp_offset_pfn(entry);
112         } else if (is_swap_pte(ptent)) {
113                 swp_entry_t entry;
114
115                 /* Handle un-addressable ZONE_DEVICE memory */
116                 entry = pte_to_swp_entry(ptent);
117                 if (!is_device_private_entry(entry) &&
118                     !is_device_exclusive_entry(entry))
119                         return false;
120
121                 pfn = swp_offset_pfn(entry);
122         } else {
123                 if (!pte_present(ptent))
124                         return false;
125
126                 pfn = pte_pfn(ptent);
127         }
128
129         return (pfn - pvmw->pfn) < pvmw->nr_pages;
130 }
131
132 /* Returns true if the two ranges overlap.  Careful to not overflow. */
133 static bool check_pmd(unsigned long pfn, struct page_vma_mapped_walk *pvmw)
134 {
135         if ((pfn + HPAGE_PMD_NR - 1) < pvmw->pfn)
136                 return false;
137         if (pfn > pvmw->pfn + pvmw->nr_pages - 1)
138                 return false;
139         return true;
140 }
141
142 static void step_forward(struct page_vma_mapped_walk *pvmw, unsigned long size)
143 {
144         pvmw->address = (pvmw->address + size) & ~(size - 1);
145         if (!pvmw->address)
146                 pvmw->address = ULONG_MAX;
147 }
148
149 /**
150  * page_vma_mapped_walk - check if @pvmw->pfn is mapped in @pvmw->vma at
151  * @pvmw->address
152  * @pvmw: pointer to struct page_vma_mapped_walk. page, vma, address and flags
153  * must be set. pmd, pte and ptl must be NULL.
154  *
155  * Returns true if the page is mapped in the vma. @pvmw->pmd and @pvmw->pte point
156  * to relevant page table entries. @pvmw->ptl is locked. @pvmw->address is
157  * adjusted if needed (for PTE-mapped THPs).
158  *
159  * If @pvmw->pmd is set but @pvmw->pte is not, you have found PMD-mapped page
160  * (usually THP). For PTE-mapped THP, you should run page_vma_mapped_walk() in
161  * a loop to find all PTEs that map the THP.
162  *
163  * For HugeTLB pages, @pvmw->pte is set to the relevant page table entry
164  * regardless of which page table level the page is mapped at. @pvmw->pmd is
165  * NULL.
166  *
167  * Returns false if there are no more page table entries for the page in
168  * the vma. @pvmw->ptl is unlocked and @pvmw->pte is unmapped.
169  *
170  * If you need to stop the walk before page_vma_mapped_walk() returned false,
171  * use page_vma_mapped_walk_done(). It will do the housekeeping.
172  */
173 bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
174 {
175         struct vm_area_struct *vma = pvmw->vma;
176         struct mm_struct *mm = vma->vm_mm;
177         unsigned long end;
178         spinlock_t *ptl;
179         pgd_t *pgd;
180         p4d_t *p4d;
181         pud_t *pud;
182         pmd_t pmde;
183
184         /* The only possible pmd mapping has been handled on last iteration */
185         if (pvmw->pmd && !pvmw->pte)
186                 return not_found(pvmw);
187
188         if (unlikely(is_vm_hugetlb_page(vma))) {
189                 struct hstate *hstate = hstate_vma(vma);
190                 unsigned long size = huge_page_size(hstate);
191                 /* The only possible mapping was handled on last iteration */
192                 if (pvmw->pte)
193                         return not_found(pvmw);
194                 /*
195                  * All callers that get here will already hold the
196                  * i_mmap_rwsem.  Therefore, no additional locks need to be
197                  * taken before calling hugetlb_walk().
198                  */
199                 pvmw->pte = hugetlb_walk(vma, pvmw->address, size);
200                 if (!pvmw->pte)
201                         return false;
202
203                 pvmw->ptl = huge_pte_lock(hstate, mm, pvmw->pte);
204                 if (!check_pte(pvmw))
205                         return not_found(pvmw);
206                 return true;
207         }
208
209         end = vma_address_end(pvmw);
210         if (pvmw->pte)
211                 goto next_pte;
212 restart:
213         do {
214                 pgd = pgd_offset(mm, pvmw->address);
215                 if (!pgd_present(*pgd)) {
216                         step_forward(pvmw, PGDIR_SIZE);
217                         continue;
218                 }
219                 p4d = p4d_offset(pgd, pvmw->address);
220                 if (!p4d_present(*p4d)) {
221                         step_forward(pvmw, P4D_SIZE);
222                         continue;
223                 }
224                 pud = pud_offset(p4d, pvmw->address);
225                 if (!pud_present(*pud)) {
226                         step_forward(pvmw, PUD_SIZE);
227                         continue;
228                 }
229
230                 pvmw->pmd = pmd_offset(pud, pvmw->address);
231                 /*
232                  * Make sure the pmd value isn't cached in a register by the
233                  * compiler and used as a stale value after we've observed a
234                  * subsequent update.
235                  */
236                 pmde = pmdp_get_lockless(pvmw->pmd);
237
238                 if (pmd_trans_huge(pmde) || is_pmd_migration_entry(pmde) ||
239                     (pmd_present(pmde) && pmd_devmap(pmde))) {
240                         pvmw->ptl = pmd_lock(mm, pvmw->pmd);
241                         pmde = *pvmw->pmd;
242                         if (!pmd_present(pmde)) {
243                                 swp_entry_t entry;
244
245                                 if (!thp_migration_supported() ||
246                                     !(pvmw->flags & PVMW_MIGRATION))
247                                         return not_found(pvmw);
248                                 entry = pmd_to_swp_entry(pmde);
249                                 if (!is_migration_entry(entry) ||
250                                     !check_pmd(swp_offset_pfn(entry), pvmw))
251                                         return not_found(pvmw);
252                                 return true;
253                         }
254                         if (likely(pmd_trans_huge(pmde) || pmd_devmap(pmde))) {
255                                 if (pvmw->flags & PVMW_MIGRATION)
256                                         return not_found(pvmw);
257                                 if (!check_pmd(pmd_pfn(pmde), pvmw))
258                                         return not_found(pvmw);
259                                 return true;
260                         }
261                         /* THP pmd was split under us: handle on pte level */
262                         spin_unlock(pvmw->ptl);
263                         pvmw->ptl = NULL;
264                 } else if (!pmd_present(pmde)) {
265                         /*
266                          * If PVMW_SYNC, take and drop THP pmd lock so that we
267                          * cannot return prematurely, while zap_huge_pmd() has
268                          * cleared *pmd but not decremented compound_mapcount().
269                          */
270                         if ((pvmw->flags & PVMW_SYNC) &&
271                             transhuge_vma_suitable(vma, pvmw->address) &&
272                             (pvmw->nr_pages >= HPAGE_PMD_NR)) {
273                                 spinlock_t *ptl = pmd_lock(mm, pvmw->pmd);
274
275                                 spin_unlock(ptl);
276                         }
277                         step_forward(pvmw, PMD_SIZE);
278                         continue;
279                 }
280                 if (!map_pte(pvmw, &ptl)) {
281                         if (!pvmw->pte)
282                                 goto restart;
283                         goto next_pte;
284                 }
285 this_pte:
286                 if (check_pte(pvmw))
287                         return true;
288 next_pte:
289                 do {
290                         pvmw->address += PAGE_SIZE;
291                         if (pvmw->address >= end)
292                                 return not_found(pvmw);
293                         /* Did we cross page table boundary? */
294                         if ((pvmw->address & (PMD_SIZE - PAGE_SIZE)) == 0) {
295                                 if (pvmw->ptl) {
296                                         spin_unlock(pvmw->ptl);
297                                         pvmw->ptl = NULL;
298                                 }
299                                 pte_unmap(pvmw->pte);
300                                 pvmw->pte = NULL;
301                                 goto restart;
302                         }
303                         pvmw->pte++;
304                 } while (pte_none(ptep_get(pvmw->pte)));
305
306                 if (!pvmw->ptl) {
307                         pvmw->ptl = ptl;
308                         spin_lock(pvmw->ptl);
309                 }
310                 goto this_pte;
311         } while (pvmw->address < end);
312
313         return false;
314 }
315
316 /**
317  * page_mapped_in_vma - check whether a page is really mapped in a VMA
318  * @page: the page to test
319  * @vma: the VMA to test
320  *
321  * Returns 1 if the page is mapped into the page tables of the VMA, 0
322  * if the page is not mapped into the page tables of this VMA.  Only
323  * valid for normal file or anonymous VMAs.
324  */
325 int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
326 {
327         struct page_vma_mapped_walk pvmw = {
328                 .pfn = page_to_pfn(page),
329                 .nr_pages = 1,
330                 .vma = vma,
331                 .flags = PVMW_SYNC,
332         };
333
334         pvmw.address = vma_address(page, vma);
335         if (pvmw.address == -EFAULT)
336                 return 0;
337         if (!page_vma_mapped_walk(&pvmw))
338                 return 0;
339         page_vma_mapped_walk_done(&pvmw);
340         return 1;
341 }