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