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 static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)
  131 {
  132         struct vm_area_struct *vma;
  133 
  134         /* We don't need vma lookup at all. */
  135         if (!walk->hugetlb_entry)
  136                 return NULL;
  137 
  138         VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
  139         vma = find_vma(walk->mm, addr);
  140         if (vma && vma->vm_start <= addr && is_vm_hugetlb_page(vma))
  141                 return vma;
  142 
  143         return NULL;
  144 }
  145 
  146 #else /* CONFIG_HUGETLB_PAGE */
  147 static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)
  148 {
  149         return NULL;
  150 }
  151 
  152 static int walk_hugetlb_range(struct vm_area_struct *vma,
  153                               unsigned long addr, unsigned long end,
  154                               struct mm_walk *walk)
  155 {
  156         return 0;
  157 }
  158 
  159 #endif /* CONFIG_HUGETLB_PAGE */
  160 
  161 
  162 
  163 /**
  164  * walk_page_range - walk a memory map's page tables with a callback
  165  * @addr: starting address
  166  * @end: ending address
  167  * @walk: set of callbacks to invoke for each level of the tree
  168  *
  169  * Recursively walk the page table for the memory area in a VMA,
  170  * calling supplied callbacks. Callbacks are called in-order (first
  171  * PGD, first PUD, first PMD, first PTE, second PTE... second PMD,
  172  * etc.). If lower-level callbacks are omitted, walking depth is reduced.
  173  *
  174  * Each callback receives an entry pointer and the start and end of the
  175  * associated range, and a copy of the original mm_walk for access to
  176  * the ->private or ->mm fields.
  177  *
  178  * Usually no locks are taken, but splitting transparent huge page may
  179  * take page table lock. And the bottom level iterator will map PTE
  180  * directories from highmem if necessary.
  181  *
  182  * If any callback returns a non-zero value, the walk is aborted and
  183  * the return value is propagated back to the caller. Otherwise 0 is returned.
  184  *
  185  * walk->mm->mmap_sem must be held for at least read if walk->hugetlb_entry
  186  * is !NULL.
  187  */
  188 int walk_page_range(unsigned long addr, unsigned long end,
  189                     struct mm_walk *walk)
  190 {
  191         pgd_t *pgd;
  192         unsigned long next;
  193         int err = 0;
  194 
  195         if (addr >= end)
  196                 return err;
  197 
  198         if (!walk->mm)
  199                 return -EINVAL;
  200 
  201         pgd = pgd_offset(walk->mm, addr);
  202         do {
  203                 struct vm_area_struct *vma;
  204 
  205                 next = pgd_addr_end(addr, end);
  206 
  207                 /*
  208                  * handle hugetlb vma individually because pagetable walk for
  209                  * the hugetlb page is dependent on the architecture and
  210                  * we can't handled it in the same manner as non-huge pages.
  211                  */
  212                 vma = hugetlb_vma(addr, walk);
  213                 if (vma) {
  214                         if (vma->vm_end < next)
  215                                 next = vma->vm_end;
  216                         /*
  217                          * Hugepage is very tightly coupled with vma, so
  218                          * walk through hugetlb entries within a given vma.
  219                          */
  220                         err = walk_hugetlb_range(vma, addr, next, walk);
  221                         if (err)
  222                                 break;
  223                         pgd = pgd_offset(walk->mm, next);
  224                         continue;
  225                 }
  226 
  227                 if (pgd_none_or_clear_bad(pgd)) {
  228                         if (walk->pte_hole)
  229                                 err = walk->pte_hole(addr, next, walk);
  230                         if (err)
  231                                 break;
  232                         pgd++;
  233                         continue;
  234                 }
  235                 if (walk->pgd_entry)
  236                         err = walk->pgd_entry(pgd, addr, next, walk);
  237                 if (!err &&
  238                     (walk->pud_entry || walk->pmd_entry || walk->pte_entry))
  239                         err = walk_pud_range(pgd, addr, next, walk);
  240                 if (err)
  241                         break;
  242                 pgd++;
  243         } while (addr = next, addr != end);
  244 
  245         return err;
  246 }

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FreeBSD/Linux Kernel Cross Reference sys/mm/pagewalk.c

FreeBSD/Linux Kernel Cross Reference
sys/mm/pagewalk.c