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, vm_flags_t *vm_flags);
20 vm_flags_t ksm_vma_flags(const struct mm_struct *mm, const struct file *file,
21 vm_flags_t vm_flags);
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
ksm_map_zero_page(struct mm_struct * mm)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
ksm_might_unmap_zero_page(struct mm_struct * mm,pte_t pte)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
mm_ksm_zero_pages(struct mm_struct * mm)51 static inline long mm_ksm_zero_pages(struct mm_struct *mm)
52 {
53 return atomic_long_read(&mm->ksm_zero_pages);
54 }
55
ksm_fork(struct mm_struct * mm,struct mm_struct * oldmm)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 (mm_flags_test(MMF_VM_MERGEABLE, oldmm)) {
60 long nr_ksm_zero_pages = atomic_long_read(&mm->ksm_zero_pages);
61
62 mm->ksm_merging_pages = 0;
63 mm->ksm_rmap_items = 0;
64 atomic_long_add(nr_ksm_zero_pages, &ksm_zero_pages);
65 __ksm_enter(mm);
66 }
67 }
68
ksm_execve(struct mm_struct * mm)69 static inline int ksm_execve(struct mm_struct *mm)
70 {
71 if (mm_flags_test(MMF_VM_MERGE_ANY, mm))
72 return __ksm_enter(mm);
73
74 return 0;
75 }
76
ksm_exit(struct mm_struct * mm)77 static inline void ksm_exit(struct mm_struct *mm)
78 {
79 if (mm_flags_test(MMF_VM_MERGEABLE, mm))
80 __ksm_exit(mm);
81 }
82
83 /*
84 * When do_swap_page() first faults in from swap what used to be a KSM page,
85 * no problem, it will be assigned to this vma's anon_vma; but thereafter,
86 * it might be faulted into a different anon_vma (or perhaps to a different
87 * offset in the same anon_vma). do_swap_page() cannot do all the locking
88 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
89 * a copy, and leave remerging the pages to a later pass of ksmd.
90 *
91 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
92 * but what if the vma was unmerged while the page was swapped out?
93 */
94 struct folio *ksm_might_need_to_copy(struct folio *folio,
95 struct vm_area_struct *vma, unsigned long addr);
96
97 void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc);
98 void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);
99 void collect_procs_ksm(const struct folio *folio, const struct page *page,
100 struct list_head *to_kill, int force_early);
101 long ksm_process_profit(struct mm_struct *);
102 bool ksm_process_mergeable(struct mm_struct *mm);
103
104 #else /* !CONFIG_KSM */
105
ksm_vma_flags(const struct mm_struct * mm,const struct file * file,vm_flags_t vm_flags)106 static inline vm_flags_t ksm_vma_flags(const struct mm_struct *mm,
107 const struct file *file, vm_flags_t vm_flags)
108 {
109 return vm_flags;
110 }
111
ksm_disable(struct mm_struct * mm)112 static inline int ksm_disable(struct mm_struct *mm)
113 {
114 return 0;
115 }
116
ksm_fork(struct mm_struct * mm,struct mm_struct * oldmm)117 static inline void ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
118 {
119 }
120
ksm_execve(struct mm_struct * mm)121 static inline int ksm_execve(struct mm_struct *mm)
122 {
123 return 0;
124 }
125
ksm_exit(struct mm_struct * mm)126 static inline void ksm_exit(struct mm_struct *mm)
127 {
128 }
129
ksm_might_unmap_zero_page(struct mm_struct * mm,pte_t pte)130 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
131 {
132 }
133
collect_procs_ksm(const struct folio * folio,const struct page * page,struct list_head * to_kill,int force_early)134 static inline void collect_procs_ksm(const struct folio *folio,
135 const struct page *page, struct list_head *to_kill,
136 int force_early)
137 {
138 }
139
140 #ifdef CONFIG_MMU
ksm_madvise(struct vm_area_struct * vma,unsigned long start,unsigned long end,int advice,vm_flags_t * vm_flags)141 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
142 unsigned long end, int advice, vm_flags_t *vm_flags)
143 {
144 return 0;
145 }
146
ksm_might_need_to_copy(struct folio * folio,struct vm_area_struct * vma,unsigned long addr)147 static inline struct folio *ksm_might_need_to_copy(struct folio *folio,
148 struct vm_area_struct *vma, unsigned long addr)
149 {
150 return folio;
151 }
152
rmap_walk_ksm(struct folio * folio,struct rmap_walk_control * rwc)153 static inline void rmap_walk_ksm(struct folio *folio,
154 struct rmap_walk_control *rwc)
155 {
156 }
157
folio_migrate_ksm(struct folio * newfolio,struct folio * old)158 static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old)
159 {
160 }
161 #endif /* CONFIG_MMU */
162 #endif /* !CONFIG_KSM */
163
164 #endif /* __LINUX_KSM_H */
165