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 atomic_long_t ksm_zero_pages;
37
38 static 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
44 static 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
52 static inline long mm_ksm_zero_pages(struct mm_struct *mm)
53 {
54 return atomic_long_read(&mm->ksm_zero_pages);
55 }
56
57 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
58 {
59 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
60 return __ksm_enter(mm);
61
62 return 0;
63 }
64
65 static inline int ksm_execve(struct mm_struct *mm)
66 {
67 if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
68 return __ksm_enter(mm);
69
70 return 0;
71 }
72
73 static inline void ksm_exit(struct mm_struct *mm)
74 {
75 if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
76 __ksm_exit(mm);
77 }
78
79 /*
80 * When do_swap_page() first faults in from swap what used to be a KSM page,
81 * no problem, it will be assigned to this vma's anon_vma; but thereafter,
82 * it might be faulted into a different anon_vma (or perhaps to a different
83 * offset in the same anon_vma). do_swap_page() cannot do all the locking
84 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
85 * a copy, and leave remerging the pages to a later pass of ksmd.
86 *
87 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
88 * but what if the vma was unmerged while the page was swapped out?
89 */
90 struct folio *ksm_might_need_to_copy(struct folio *folio,
91 struct vm_area_struct *vma, unsigned long addr);
92
93 void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc);
94 void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);
95 void collect_procs_ksm(struct folio *folio, struct page *page,
96 struct list_head *to_kill, int force_early);
97 long ksm_process_profit(struct mm_struct *);
98
99 #else /* !CONFIG_KSM */
100
101 static inline void ksm_add_vma(struct vm_area_struct *vma)
102 {
103 }
104
105 static inline int ksm_disable(struct mm_struct *mm)
106 {
107 return 0;
108 }
109
110 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
111 {
112 return 0;
113 }
114
115 static inline int ksm_execve(struct mm_struct *mm)
116 {
117 return 0;
118 }
119
120 static inline void ksm_exit(struct mm_struct *mm)
121 {
122 }
123
124 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
125 {
126 }
127
128 static inline void collect_procs_ksm(struct folio *folio, struct page *page,
129 struct list_head *to_kill, int force_early)
130 {
131 }
132
133 #ifdef CONFIG_MMU
134 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
135 unsigned long end, int advice, unsigned long *vm_flags)
136 {
137 return 0;
138 }
139
140 static inline struct folio *ksm_might_need_to_copy(struct folio *folio,
141 struct vm_area_struct *vma, unsigned long addr)
142 {
143 return folio;
144 }
145
146 static inline void rmap_walk_ksm(struct folio *folio,
147 struct rmap_walk_control *rwc)
148 {
149 }
150
151 static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old)
152 {
153 }
154 #endif /* CONFIG_MMU */
155 #endif /* !CONFIG_KSM */
156
157 #endif /* __LINUX_KSM_H */
158
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