include/linux/ksm.h

   1 #ifndef __LINUX_KSM_H
   2 #define __LINUX_KSM_H
   3 /*
   4  * Memory merging support.
   5  *
   6  * This code enables dynamic sharing of identical pages found in different
   7  * memory areas, even if they are not shared by fork().
   8  */
   9
  10 #include <linux/bitops.h>
  11 #include <linux/mm.h>
  12 #include <linux/pagemap.h>
  13 #include <linux/rmap.h>
  14 #include <linux/sched.h>
  15
  16 struct stable_node;
  17 struct mem_cgroup;
  18
  19 struct page *ksm_does_need_to_copy(struct page *page,
  20                         struct vm_area_struct *vma, unsigned long address);
  21
  22 #ifdef CONFIG_KSM
  23 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  24                 unsigned long end, int advice, unsigned long *vm_flags);
  25 int __ksm_enter(struct mm_struct *mm);
  26 void __ksm_exit(struct mm_struct *mm);
  27
  28 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  29 {
  30         if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
  31                 return __ksm_enter(mm);
  32         return 0;
  33 }
  34
  35 static inline void ksm_exit(struct mm_struct *mm)
  36 {
  37         if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
  38                 __ksm_exit(mm);
  39 }
  40
  41 /*
  42  * A KSM page is one of those write-protected "shared pages" or "merged pages"
  43  * which KSM maps into multiple mms, wherever identical anonymous page content
  44  * is found in VM_MERGEABLE vmas.  It's a PageAnon page, pointing not to any
  45  * anon_vma, but to that page's node of the stable tree.
  46  */
  47 static inline int PageKsm(struct page *page)
  48 {
  49         return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
  50                                 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
  51 }
  52
  53 static inline struct stable_node *page_stable_node(struct page *page)
  54 {
  55         return PageKsm(page) ? page_rmapping(page) : NULL;
  56 }
  57
  58 static inline void set_page_stable_node(struct page *page,
  59                                         struct stable_node *stable_node)
  60 {
  61         page->mapping = (void *)stable_node +
  62                                 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
  63 }
  64
  65 /*
  66  * When do_swap_page() first faults in from swap what used to be a KSM page,
  67  * no problem, it will be assigned to this vma's anon_vma; but thereafter,
  68  * it might be faulted into a different anon_vma (or perhaps to a different
  69  * offset in the same anon_vma).  do_swap_page() cannot do all the locking
  70  * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
  71  * a copy, and leave remerging the pages to a later pass of ksmd.
  72  *
  73  * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
  74  * but what if the vma was unmerged while the page was swapped out?
  75  */
  76 static inline int ksm_might_need_to_copy(struct page *page,
  77                         struct vm_area_struct *vma, unsigned long address)
  78 {
  79         struct anon_vma *anon_vma = page_anon_vma(page);
  80
  81         return anon_vma &&
  82                 (anon_vma->root != vma->anon_vma->root ||
  83                  page->index != linear_page_index(vma, address));
  84 }
  85
  86 int page_referenced_ksm(struct page *page,
  87                         struct mem_cgroup *memcg, unsigned long *vm_flags);
  88 int try_to_unmap_ksm(struct page *page, enum ttu_flags flags);
  89 int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page *,
  90                   struct vm_area_struct *, unsigned long, void *), void *arg);
  91 void ksm_migrate_page(struct page *newpage, struct page *oldpage);
  92
  93 #else  /* !CONFIG_KSM */
  94
  95 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  96 {
  97         return 0;
  98 }
  99
 100 static inline void ksm_exit(struct mm_struct *mm)
 101 {
 102 }
 103
 104 static inline int PageKsm(struct page *page)
 105 {
 106         return 0;
 107 }
 108
 109 #ifdef CONFIG_MMU
 110 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 111                 unsigned long end, int advice, unsigned long *vm_flags)
 112 {
 113         return 0;
 114 }
 115
 116 static inline int ksm_might_need_to_copy(struct page *page,
 117                         struct vm_area_struct *vma, unsigned long address)
 118 {
 119         return 0;
 120 }
 121
 122 static inline int page_referenced_ksm(struct page *page,
 123                         struct mem_cgroup *memcg, unsigned long *vm_flags)
 124 {
 125         return 0;
 126 }
 127
 128 static inline int try_to_unmap_ksm(struct page *page, enum ttu_flags flags)
 129 {
 130         return 0;
 131 }
 132
 133 static inline int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page*,
 134                 struct vm_area_struct *, unsigned long, void *), void *arg)
 135 {
 136         return 0;
 137 }
 138
 139 static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
 140 {
 141 }
 142 #endif /* CONFIG_MMU */
 143 #endif /* !CONFIG_KSM */
 144
 145 #endif /* __LINUX_KSM_H */