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 #ifdef CONFIG_KSM
  20 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  21                 unsigned long end, int advice, unsigned long *vm_flags);
  22 int __ksm_enter(struct mm_struct *mm);
  23 void __ksm_exit(struct mm_struct *mm);
  24
  25 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  26 {
  27         if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
  28                 return __ksm_enter(mm);
  29         return 0;
  30 }
  31
  32 static inline void ksm_exit(struct mm_struct *mm)
  33 {
  34         if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
  35                 __ksm_exit(mm);
  36 }
  37
  38 static inline struct stable_node *page_stable_node(struct page *page)
  39 {
  40         return PageKsm(page) ? page_rmapping(page) : NULL;
  41 }
  42
  43 static inline void set_page_stable_node(struct page *page,
  44                                         struct stable_node *stable_node)
  45 {
  46         page->mapping = (void *)stable_node +
  47                                 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
  48 }
  49
  50 /*
  51  * When do_swap_page() first faults in from swap what used to be a KSM page,
  52  * no problem, it will be assigned to this vma's anon_vma; but thereafter,
  53  * it might be faulted into a different anon_vma (or perhaps to a different
  54  * offset in the same anon_vma).  do_swap_page() cannot do all the locking
  55  * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
  56  * a copy, and leave remerging the pages to a later pass of ksmd.
  57  *
  58  * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
  59  * but what if the vma was unmerged while the page was swapped out?
  60  */
  61 struct page *ksm_might_need_to_copy(struct page *page,
  62                         struct vm_area_struct *vma, unsigned long address);
  63
  64 int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc);
  65 void ksm_migrate_page(struct page *newpage, struct page *oldpage);
  66
  67 #else  /* !CONFIG_KSM */
  68
  69 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  70 {
  71         return 0;
  72 }
  73
  74 static inline void ksm_exit(struct mm_struct *mm)
  75 {
  76 }
  77
  78 #ifdef CONFIG_MMU
  79 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  80                 unsigned long end, int advice, unsigned long *vm_flags)
  81 {
  82         return 0;
  83 }
  84
  85 static inline struct page *ksm_might_need_to_copy(struct page *page,
  86                         struct vm_area_struct *vma, unsigned long address)
  87 {
  88         return page;
  89 }
  90
  91 static inline int page_referenced_ksm(struct page *page,
  92                         struct mem_cgroup *memcg, unsigned long *vm_flags)
  93 {
  94         return 0;
  95 }
  96
  97 static inline int rmap_walk_ksm(struct page *page,
  98                         struct rmap_walk_control *rwc)
  99 {
 100         return 0;
 101 }
 102
 103 static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
 104 {
 105 }
 106 #endif /* CONFIG_MMU */
 107 #endif /* !CONFIG_KSM */
 108
 109 #endif /* __LINUX_KSM_H */