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
  17 #ifdef CONFIG_KSM
  18 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
  19                 unsigned long end, int advice, unsigned long *vm_flags);
  20
  21 void ksm_add_vma(struct vm_area_struct *vma);
  22 int ksm_enable_merge_any(struct mm_struct *mm);
  23 int ksm_disable_merge_any(struct mm_struct *mm);
  24 int ksm_disable(struct mm_struct *mm);
  25
  26 int __ksm_enter(struct mm_struct *mm);
  27 void __ksm_exit(struct mm_struct *mm);
  28 /*
  29  * To identify zeropages that were mapped by KSM, we reuse the dirty bit
  30  * in the PTE. If the PTE is dirty, the zeropage was mapped by KSM when
  31  * deduplicating memory.
  32  */
  33 #define is_ksm_zero_pte(pte)    (is_zero_pfn(pte_pfn(pte)) && pte_dirty(pte))
  34
  35 extern atomic_long_t ksm_zero_pages;
  36
  37 static inline void ksm_map_zero_page(struct mm_struct *mm)
  38 {
  39         atomic_long_inc(&ksm_zero_pages);
  40         atomic_long_inc(&mm->ksm_zero_pages);
  41 }
  42
  43 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
  44 {
  45         if (is_ksm_zero_pte(pte)) {
  46                 atomic_long_dec(&ksm_zero_pages);
  47                 atomic_long_dec(&mm->ksm_zero_pages);
  48         }
  49 }
  50
  51 static inline long mm_ksm_zero_pages(struct mm_struct *mm)
  52 {
  53         return atomic_long_read(&mm->ksm_zero_pages);
  54 }
  55
  56 static inline void ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
  57 {
  58         /* Adding mm to ksm is best effort on fork. */
  59         if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
  60                 __ksm_enter(mm);
  61 }
  62
  63 static inline int ksm_execve(struct mm_struct *mm)
  64 {
  65         if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
  66                 return __ksm_enter(mm);
  67
  68         return 0;
  69 }
  70
  71 static inline void ksm_exit(struct mm_struct *mm)
  72 {
  73         if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
  74                 __ksm_exit(mm);
  75 }
  76
  77 /*
  78  * When do_swap_page() first faults in from swap what used to be a KSM page,
  79  * no problem, it will be assigned to this vma's anon_vma; but thereafter,
  80  * it might be faulted into a different anon_vma (or perhaps to a different
  81  * offset in the same anon_vma).  do_swap_page() cannot do all the locking
  82  * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
  83  * a copy, and leave remerging the pages to a later pass of ksmd.
  84  *
  85  * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
  86  * but what if the vma was unmerged while the page was swapped out?
  87  */
  88 struct folio *ksm_might_need_to_copy(struct folio *folio,
  89                         struct vm_area_struct *vma, unsigned long addr);
  90
  91 void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc);
  92 void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);
  93 void collect_procs_ksm(const struct folio *folio, const struct page *page,
  94                 struct list_head *to_kill, int force_early);
  95 long ksm_process_profit(struct mm_struct *);
  96
  97 #else  /* !CONFIG_KSM */
  98
  99 static inline void ksm_add_vma(struct vm_area_struct *vma)
 100 {
 101 }
 102
 103 static inline int ksm_disable(struct mm_struct *mm)
 104 {
 105         return 0;
 106 }
 107
 108 static inline void ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 109 {
 110 }
 111
 112 static inline int ksm_execve(struct mm_struct *mm)
 113 {
 114         return 0;
 115 }
 116
 117 static inline void ksm_exit(struct mm_struct *mm)
 118 {
 119 }
 120
 121 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
 122 {
 123 }
 124
 125 static inline void collect_procs_ksm(const struct folio *folio,
 126                 const struct page *page, struct list_head *to_kill,
 127                 int force_early)
 128 {
 129 }
 130
 131 #ifdef CONFIG_MMU
 132 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 133                 unsigned long end, int advice, unsigned long *vm_flags)
 134 {
 135         return 0;
 136 }
 137
 138 static inline struct folio *ksm_might_need_to_copy(struct folio *folio,
 139                         struct vm_area_struct *vma, unsigned long addr)
 140 {
 141         return folio;
 142 }
 143
 144 static inline void rmap_walk_ksm(struct folio *folio,
 145                         struct rmap_walk_control *rwc)
 146 {
 147 }
 148
 149 static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old)
 150 {
 151 }
 152 #endif /* CONFIG_MMU */
 153 #endif /* !CONFIG_KSM */
 154
 155 #endif /* __LINUX_KSM_H */