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Linux/mm/pagewalk.c

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  1 #include <linux/mm.h>
  2 #include <linux/highmem.h>
  3 #include <linux/sched.h>
  4 #include <linux/hugetlb.h>
  5 
  6 static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
  7                           struct mm_walk *walk)
  8 {
  9         pte_t *pte;
 10         int err = 0;
 11 
 12         pte = pte_offset_map(pmd, addr);
 13         for (;;) {
 14                 err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
 15                 if (err)
 16                        break;
 17                 addr += PAGE_SIZE;
 18                 if (addr == end)
 19                         break;
 20                 pte++;
 21         }
 22 
 23         pte_unmap(pte);
 24         return err;
 25 }
 26 
 27 static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 28                           struct mm_walk *walk)
 29 {
 30         pmd_t *pmd;
 31         unsigned long next;
 32         int err = 0;
 33 
 34         pmd = pmd_offset(pud, addr);
 35         do {
 36 again:
 37                 next = pmd_addr_end(addr, end);
 38                 if (pmd_none(*pmd)) {
 39                         if (walk->pte_hole)
 40                                 err = walk->pte_hole(addr, next, walk);
 41                         if (err)
 42                                 break;
 43                         continue;
 44                 }
 45                 /*
 46                  * This implies that each ->pmd_entry() handler
 47                  * needs to know about pmd_trans_huge() pmds
 48                  */
 49                 if (walk->pmd_entry)
 50                         err = walk->pmd_entry(pmd, addr, next, walk);
 51                 if (err)
 52                         break;
 53 
 54                 /*
 55                  * Check this here so we only break down trans_huge
 56                  * pages when we _need_ to
 57                  */
 58                 if (!walk->pte_entry)
 59                         continue;
 60 
 61                 split_huge_page_pmd_mm(walk->mm, addr, pmd);
 62                 if (pmd_none_or_trans_huge_or_clear_bad(pmd))
 63                         goto again;
 64                 err = walk_pte_range(pmd, addr, next, walk);
 65                 if (err)
 66                         break;
 67         } while (pmd++, addr = next, addr != end);
 68 
 69         return err;
 70 }
 71 
 72 static int walk_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end,
 73                           struct mm_walk *walk)
 74 {
 75         pud_t *pud;
 76         unsigned long next;
 77         int err = 0;
 78 
 79         pud = pud_offset(pgd, addr);
 80         do {
 81                 next = pud_addr_end(addr, end);
 82                 if (pud_none_or_clear_bad(pud)) {
 83                         if (walk->pte_hole)
 84                                 err = walk->pte_hole(addr, next, walk);
 85                         if (err)
 86                                 break;
 87                         continue;
 88                 }
 89                 if (walk->pud_entry)
 90                         err = walk->pud_entry(pud, addr, next, walk);
 91                 if (!err && (walk->pmd_entry || walk->pte_entry))
 92                         err = walk_pmd_range(pud, addr, next, walk);
 93                 if (err)
 94                         break;
 95         } while (pud++, addr = next, addr != end);
 96 
 97         return err;
 98 }
 99 
100 #ifdef CONFIG_HUGETLB_PAGE
101 static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
102                                        unsigned long end)
103 {
104         unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
105         return boundary < end ? boundary : end;
106 }
107 
108 static int walk_hugetlb_range(struct vm_area_struct *vma,
109                               unsigned long addr, unsigned long end,
110                               struct mm_walk *walk)
111 {
112         struct hstate *h = hstate_vma(vma);
113         unsigned long next;
114         unsigned long hmask = huge_page_mask(h);
115         pte_t *pte;
116         int err = 0;
117 
118         do {
119                 next = hugetlb_entry_end(h, addr, end);
120                 pte = huge_pte_offset(walk->mm, addr & hmask);
121                 if (pte && walk->hugetlb_entry)
122                         err = walk->hugetlb_entry(pte, hmask, addr, next, walk);
123                 if (err)
124                         return err;
125         } while (addr = next, addr != end);
126 
127         return 0;
128 }
129 
130 #else /* CONFIG_HUGETLB_PAGE */
131 static int walk_hugetlb_range(struct vm_area_struct *vma,
132                               unsigned long addr, unsigned long end,
133                               struct mm_walk *walk)
134 {
135         return 0;
136 }
137 
138 #endif /* CONFIG_HUGETLB_PAGE */
139 
140 
141 
142 /**
143  * walk_page_range - walk a memory map's page tables with a callback
144  * @addr: starting address
145  * @end: ending address
146  * @walk: set of callbacks to invoke for each level of the tree
147  *
148  * Recursively walk the page table for the memory area in a VMA,
149  * calling supplied callbacks. Callbacks are called in-order (first
150  * PGD, first PUD, first PMD, first PTE, second PTE... second PMD,
151  * etc.). If lower-level callbacks are omitted, walking depth is reduced.
152  *
153  * Each callback receives an entry pointer and the start and end of the
154  * associated range, and a copy of the original mm_walk for access to
155  * the ->private or ->mm fields.
156  *
157  * Usually no locks are taken, but splitting transparent huge page may
158  * take page table lock. And the bottom level iterator will map PTE
159  * directories from highmem if necessary.
160  *
161  * If any callback returns a non-zero value, the walk is aborted and
162  * the return value is propagated back to the caller. Otherwise 0 is returned.
163  *
164  * walk->mm->mmap_sem must be held for at least read if walk->hugetlb_entry
165  * is !NULL.
166  */
167 int walk_page_range(unsigned long addr, unsigned long end,
168                     struct mm_walk *walk)
169 {
170         pgd_t *pgd;
171         unsigned long next;
172         int err = 0;
173 
174         if (addr >= end)
175                 return err;
176 
177         if (!walk->mm)
178                 return -EINVAL;
179 
180         VM_BUG_ON_MM(!rwsem_is_locked(&walk->mm->mmap_sem), walk->mm);
181 
182         pgd = pgd_offset(walk->mm, addr);
183         do {
184                 struct vm_area_struct *vma = NULL;
185 
186                 next = pgd_addr_end(addr, end);
187 
188                 /*
189                  * This function was not intended to be vma based.
190                  * But there are vma special cases to be handled:
191                  * - hugetlb vma's
192                  * - VM_PFNMAP vma's
193                  */
194                 vma = find_vma(walk->mm, addr);
195                 if (vma) {
196                         /*
197                          * There are no page structures backing a VM_PFNMAP
198                          * range, so do not allow split_huge_page_pmd().
199                          */
200                         if ((vma->vm_start <= addr) &&
201                             (vma->vm_flags & VM_PFNMAP)) {
202                                 if (walk->pte_hole)
203                                         err = walk->pte_hole(addr, next, walk);
204                                 if (err)
205                                         break;
206                                 pgd = pgd_offset(walk->mm, next);
207                                 continue;
208                         }
209                         /*
210                          * Handle hugetlb vma individually because pagetable
211                          * walk for the hugetlb page is dependent on the
212                          * architecture and we can't handled it in the same
213                          * manner as non-huge pages.
214                          */
215                         if (walk->hugetlb_entry && (vma->vm_start <= addr) &&
216                             is_vm_hugetlb_page(vma)) {
217                                 if (vma->vm_end < next)
218                                         next = vma->vm_end;
219                                 /*
220                                  * Hugepage is very tightly coupled with vma,
221                                  * so walk through hugetlb entries within a
222                                  * given vma.
223                                  */
224                                 err = walk_hugetlb_range(vma, addr, next, walk);
225                                 if (err)
226                                         break;
227                                 pgd = pgd_offset(walk->mm, next);
228                                 continue;
229                         }
230                 }
231 
232                 if (pgd_none_or_clear_bad(pgd)) {
233                         if (walk->pte_hole)
234                                 err = walk->pte_hole(addr, next, walk);
235                         if (err)
236                                 break;
237                         pgd++;
238                         continue;
239                 }
240                 if (walk->pgd_entry)
241                         err = walk->pgd_entry(pgd, addr, next, walk);
242                 if (!err &&
243                     (walk->pud_entry || walk->pmd_entry || walk->pte_entry))
244                         err = walk_pud_range(pgd, addr, next, walk);
245                 if (err)
246                         break;
247                 pgd++;
248         } while (addr = next, addr < end);
249 
250         return err;
251 }
252 

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