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
  18 struct stable_node;
  19 struct mem_cgroup;
  20
  21 #ifdef CONFIG_KSM
  22 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  23                 unsigned long end, int advice, unsigned long *vm_flags);
  24 int __ksm_enter(struct mm_struct *mm);
  25 void __ksm_exit(struct mm_struct *mm);
  26
  27 static 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
  34 static 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  */
  51 struct page *ksm_might_need_to_copy(struct page *page,
  52                         struct vm_area_struct *vma, unsigned long address);
  53
  54 void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc);
  55 void ksm_migrate_page(struct page *newpage, struct page *oldpage);
  56 bool reuse_ksm_page(struct page *page,
  57                         struct vm_area_struct *vma, unsigned long address);
  58
  59 #else  /* !CONFIG_KSM */
  60
  61 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  62 {
  63         return 0;
  64 }
  65
  66 static inline void ksm_exit(struct mm_struct *mm)
  67 {
  68 }
  69
  70 #ifdef CONFIG_MMU
  71 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  72                 unsigned long end, int advice, unsigned long *vm_flags)
  73 {
  74         return 0;
  75 }
  76
  77 static inline struct page *ksm_might_need_to_copy(struct page *page,
  78                         struct vm_area_struct *vma, unsigned long address)
  79 {
  80         return page;
  81 }
  82
  83 static inline void rmap_walk_ksm(struct page *page,
  84                         struct rmap_walk_control *rwc)
  85 {
  86 }
  87
  88 static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
  89 {
  90 }
  91 static inline bool reuse_ksm_page(struct page *page,
  92                         struct vm_area_struct *vma, unsigned long address)
  93 {
  94         return false;
  95 }
  96 #endif /* CONFIG_MMU */
  97 #endif /* !CONFIG_KSM */
  98
  99 #endif /* __LINUX_KSM_H */