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 static inline struct stable_node *page_stable_node(struct page *page)
  41 {
  42         return PageKsm(page) ? page_rmapping(page) : NULL;
  43 }
  44
  45 static inline void set_page_stable_node(struct page *page,
  46                                         struct stable_node *stable_node)
  47 {
  48         page->mapping = (void *)((unsigned long)stable_node | PAGE_MAPPING_KSM);
  49 }
  50
  51 /*
  52  * When do_swap_page() first faults in from swap what used to be a KSM page,
  53  * no problem, it will be assigned to this vma's anon_vma; but thereafter,
  54  * it might be faulted into a different anon_vma (or perhaps to a different
  55  * offset in the same anon_vma).  do_swap_page() cannot do all the locking
  56  * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
  57  * a copy, and leave remerging the pages to a later pass of ksmd.
  58  *
  59  * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
  60  * but what if the vma was unmerged while the page was swapped out?
  61  */
  62 struct page *ksm_might_need_to_copy(struct page *page,
  63                         struct vm_area_struct *vma, unsigned long address);
  64
  65 void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc);
  66 void ksm_migrate_page(struct page *newpage, struct page *oldpage);
  67
  68 #else  /* !CONFIG_KSM */
  69
  70 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  71 {
  72         return 0;
  73 }
  74
  75 static inline void ksm_exit(struct mm_struct *mm)
  76 {
  77 }
  78
  79 #ifdef CONFIG_MMU
  80 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  81                 unsigned long end, int advice, unsigned long *vm_flags)
  82 {
  83         return 0;
  84 }
  85
  86 static inline struct page *ksm_might_need_to_copy(struct page *page,
  87                         struct vm_area_struct *vma, unsigned long address)
  88 {
  89         return page;
  90 }
  91
  92 static inline int page_referenced_ksm(struct page *page,
  93                         struct mem_cgroup *memcg, unsigned long *vm_flags)
  94 {
  95         return 0;
  96 }
  97
  98 static inline void rmap_walk_ksm(struct page *page,
  99                         struct rmap_walk_control *rwc)
 100 {
 101 }
 102
 103 static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
 104 {
 105 }
 106 #endif /* CONFIG_MMU */
 107 #endif /* !CONFIG_KSM */
 108
 109 #endif /* __LINUX_KSM_H */