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 #include <linux/sched/coredump.h>
  16
  17 struct stable_node;
  18 struct mem_cgroup;
  19
  20 #ifdef CONFIG_KSM
  21 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  22                 unsigned long end, int advice, unsigned long *vm_flags);
  23 int __ksm_enter(struct mm_struct *mm);
  24 void __ksm_exit(struct mm_struct *mm);
  25
  26 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  27 {
  28         if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
  29                 return __ksm_enter(mm);
  30         return 0;
  31 }
  32
  33 static inline void ksm_exit(struct mm_struct *mm)
  34 {
  35         if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
  36                 __ksm_exit(mm);
  37 }
  38
  39 static inline struct stable_node *page_stable_node(struct page *page)
  40 {
  41         return PageKsm(page) ? page_rmapping(page) : NULL;
  42 }
  43
  44 static inline void set_page_stable_node(struct page *page,
  45                                         struct stable_node *stable_node)
  46 {
  47         page->mapping = (void *)((unsigned long)stable_node | 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 void 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 void rmap_walk_ksm(struct page *page,
  98                         struct rmap_walk_control *rwc)
  99 {
 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 */