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 (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
60 __ksm_enter(mm);
61 }
62
ksm_execve(struct mm_struct * mm)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
ksm_exit(struct mm_struct * mm)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 bool ksm_process_mergeable(struct mm_struct *mm);
97
98 #else /* !CONFIG_KSM */
99
ksm_vma_flags(const struct mm_struct * mm,const struct file * file,vm_flags_t vm_flags)100 static inline vm_flags_t ksm_vma_flags(const struct mm_struct *mm,
101 const struct file *file, vm_flags_t vm_flags)
102 {
103 return vm_flags;
104 }
105
ksm_disable(struct mm_struct * mm)106 static inline int ksm_disable(struct mm_struct *mm)
107 {
108 return 0;
109 }
110
ksm_fork(struct mm_struct * mm,struct mm_struct * oldmm)111 static inline void ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
112 {
113 }
114
ksm_execve(struct mm_struct * mm)115 static inline int ksm_execve(struct mm_struct *mm)
116 {
117 return 0;
118 }
119
ksm_exit(struct mm_struct * mm)120 static inline void ksm_exit(struct mm_struct *mm)
121 {
122 }
123
ksm_might_unmap_zero_page(struct mm_struct * mm,pte_t pte)124 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
125 {
126 }
127
collect_procs_ksm(const struct folio * folio,const struct page * page,struct list_head * to_kill,int force_early)128 static inline void collect_procs_ksm(const struct folio *folio,
129 const struct page *page, struct list_head *to_kill,
130 int force_early)
131 {
132 }
133
134 #ifdef CONFIG_MMU
ksm_madvise(struct vm_area_struct * vma,unsigned long start,unsigned long end,int advice,vm_flags_t * vm_flags)135 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
136 unsigned long end, int advice, vm_flags_t *vm_flags)
137 {
138 return 0;
139 }
140
ksm_might_need_to_copy(struct folio * folio,struct vm_area_struct * vma,unsigned long addr)141 static inline struct folio *ksm_might_need_to_copy(struct folio *folio,
142 struct vm_area_struct *vma, unsigned long addr)
143 {
144 return folio;
145 }
146
rmap_walk_ksm(struct folio * folio,struct rmap_walk_control * rwc)147 static inline void rmap_walk_ksm(struct folio *folio,
148 struct rmap_walk_control *rwc)
149 {
150 }
151
folio_migrate_ksm(struct folio * newfolio,struct folio * old)152 static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old)
153 {
154 }
155 #endif /* CONFIG_MMU */
156 #endif /* !CONFIG_KSM */
157
158 #endif /* __LINUX_KSM_H */
159