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
  19struct page *ksm_does_need_to_copy(struct page *page,
  20                        struct vm_area_struct *vma, unsigned long address);
  21
  22#ifdef CONFIG_KSM
  23int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  24                unsigned long end, int advice, unsigned long *vm_flags);
  25int __ksm_enter(struct mm_struct *mm);
  26void __ksm_exit(struct mm_struct *mm);
  27
  28static 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
  35static 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 */
  47static 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
  53static inline struct stable_node *page_stable_node(struct page *page)
  54{
  55        return PageKsm(page) ? page_rmapping(page) : NULL;
  56}
  57
  58static 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 */
  76static 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
  86int page_referenced_ksm(struct page *page,
  87                        struct mem_cgroup *memcg, unsigned long *vm_flags);
  88int try_to_unmap_ksm(struct page *page, enum ttu_flags flags);
  89int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page *,
  90                  struct vm_area_struct *, unsigned long, void *), void *arg);
  91void ksm_migrate_page(struct page *newpage, struct page *oldpage);
  92
  93#else  /* !CONFIG_KSM */
  94
  95static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  96{
  97        return 0;
  98}
  99
 100static inline void ksm_exit(struct mm_struct *mm)
 101{
 102}
 103
 104static inline int PageKsm(struct page *page)
 105{
 106        return 0;
 107}
 108
 109#ifdef CONFIG_MMU
 110static 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
 116static 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
 122static inline int page_referenced_ksm(struct page *page,
 123                        struct mem_cgroup *memcg, unsigned long *vm_flags)
 124{
 125        return 0;
 126}
 127
 128static inline int try_to_unmap_ksm(struct page *page, enum ttu_flags flags)
 129{
 130        return 0;
 131}
 132
 133static 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
 139static 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 */
 146