LXR linux/include/linux/ksm.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2#ifndef __LINUX_KSM_H
   3#define __LINUX_KSM_H
   4/*
   5 * Memory merging support.
   6 *
   7 * This code enables dynamic sharing of identical pages found in different
   8 * memory areas, even if they are not shared by fork().
   9 */
  10
  11#include <linux/bitops.h>
  12#include <linux/mm.h>
  13#include <linux/pagemap.h>
  14#include <linux/rmap.h>
  15#include <linux/sched.h>
  16#include <linux/sched/coredump.h>
  17
  18struct stable_node;
  19struct mem_cgroup;
  20
  21#ifdef CONFIG_KSM
  22int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  23                unsigned long end, int advice, unsigned long *vm_flags);
  24int __ksm_enter(struct mm_struct *mm);
  25void __ksm_exit(struct mm_struct *mm);
  26
  27static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  28{
  29        if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
  30                return __ksm_enter(mm);
  31        return 0;
  32}
  33
  34static inline void ksm_exit(struct mm_struct *mm)
  35{
  36        if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
  37                __ksm_exit(mm);
  38}
  39
  40/*
  41 * When do_swap_page() first faults in from swap what used to be a KSM page,
  42 * no problem, it will be assigned to this vma's anon_vma; but thereafter,
  43 * it might be faulted into a different anon_vma (or perhaps to a different
  44 * offset in the same anon_vma).  do_swap_page() cannot do all the locking
  45 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
  46 * a copy, and leave remerging the pages to a later pass of ksmd.
  47 *
  48 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
  49 * but what if the vma was unmerged while the page was swapped out?
  50 */
  51struct page *ksm_might_need_to_copy(struct page *page,
  52                        struct vm_area_struct *vma, unsigned long address);
  53
  54void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc);
  55void ksm_migrate_page(struct page *newpage, struct page *oldpage);
  56
  57#else  /* !CONFIG_KSM */
  58
  59static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  60{
  61        return 0;
  62}
  63
  64static inline void ksm_exit(struct mm_struct *mm)
  65{
  66}
  67
  68#ifdef CONFIG_MMU
  69static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  70                unsigned long end, int advice, unsigned long *vm_flags)
  71{
  72        return 0;
  73}
  74
  75static inline struct page *ksm_might_need_to_copy(struct page *page,
  76                        struct vm_area_struct *vma, unsigned long address)
  77{
  78        return page;
  79}
  80
  81static inline void rmap_walk_ksm(struct page *page,
  82                        struct rmap_walk_control *rwc)
  83{
  84}
  85
  86static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
  87{
  88}
  89#endif /* CONFIG_MMU */
  90#endif /* !CONFIG_KSM */
  91
  92#endif /* __LINUX_KSM_H */
  93