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