LXR linux/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
  16struct stable_node;
  17struct mem_cgroup;
  18
  19#ifdef CONFIG_KSM
  20int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  21                unsigned long end, int advice, unsigned long *vm_flags);
  22int __ksm_enter(struct mm_struct *mm);
  23void __ksm_exit(struct mm_struct *mm);
  24
  25static 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
  32static 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/*
  39 * A KSM page is one of those write-protected "shared pages" or "merged pages"
  40 * which KSM maps into multiple mms, wherever identical anonymous page content
  41 * is found in VM_MERGEABLE vmas.  It's a PageAnon page, pointing not to any
  42 * anon_vma, but to that page's node of the stable tree.
  43 */
  44static inline int PageKsm(struct page *page)
  45{
  46        return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
  47                                (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
  48}
  49
  50static inline struct stable_node *page_stable_node(struct page *page)
  51{
  52        return PageKsm(page) ? page_rmapping(page) : NULL;
  53}
  54
  55static inline void set_page_stable_node(struct page *page,
  56                                        struct stable_node *stable_node)
  57{
  58        page->mapping = (void *)stable_node +
  59                                (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
  60}
  61
  62/*
  63 * When do_swap_page() first faults in from swap what used to be a KSM page,
  64 * no problem, it will be assigned to this vma's anon_vma; but thereafter,
  65 * it might be faulted into a different anon_vma (or perhaps to a different
  66 * offset in the same anon_vma).  do_swap_page() cannot do all the locking
  67 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
  68 * a copy, and leave remerging the pages to a later pass of ksmd.
  69 *
  70 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
  71 * but what if the vma was unmerged while the page was swapped out?
  72 */
  73struct page *ksm_might_need_to_copy(struct page *page,
  74                        struct vm_area_struct *vma, unsigned long address);
  75
  76int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc);
  77void ksm_migrate_page(struct page *newpage, struct page *oldpage);
  78
  79#else  /* !CONFIG_KSM */
  80
  81static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  82{
  83        return 0;
  84}
  85
  86static inline void ksm_exit(struct mm_struct *mm)
  87{
  88}
  89
  90static inline int PageKsm(struct page *page)
  91{
  92        return 0;
  93}
  94
  95#ifdef CONFIG_MMU
  96static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  97                unsigned long end, int advice, unsigned long *vm_flags)
  98{
  99        return 0;
 100}
 101
 102static inline struct page *ksm_might_need_to_copy(struct page *page,
 103                        struct vm_area_struct *vma, unsigned long address)
 104{
 105        return page;
 106}
 107
 108static inline int page_referenced_ksm(struct page *page,
 109                        struct mem_cgroup *memcg, unsigned long *vm_flags)
 110{
 111        return 0;
 112}
 113
 114static inline int rmap_walk_ksm(struct page *page,
 115                        struct rmap_walk_control *rwc)
 116{
 117        return 0;
 118}
 119
 120static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
 121{
 122}
 123#endif /* CONFIG_MMU */
 124#endif /* !CONFIG_KSM */
 125
 126#endif /* __LINUX_KSM_H */
 127