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