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
ksm_map_zero_page(struct mm_struct * mm)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
ksm_might_unmap_zero_page(struct mm_struct * mm,pte_t pte)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
mm_ksm_zero_pages(struct mm_struct * mm)52 static inline long mm_ksm_zero_pages(struct mm_struct *mm)
53 {
54 return atomic_long_read(&mm->ksm_zero_pages);
55 }
56
ksm_fork(struct mm_struct * mm,struct mm_struct * oldmm)57 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
58 {
59 int ret;
60
61 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags)) {
62 ret = __ksm_enter(mm);
63 if (ret)
64 return ret;
65 }
66
67 if (test_bit(MMF_VM_MERGE_ANY, &oldmm->flags))
68 set_bit(MMF_VM_MERGE_ANY, &mm->flags);
69
70 return 0;
71 }
72
ksm_exit(struct mm_struct * mm)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 page *ksm_might_need_to_copy(struct page *page,
91 struct vm_area_struct *vma, unsigned long address);
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
96 #ifdef CONFIG_MEMORY_FAILURE
97 void collect_procs_ksm(struct page *page, struct list_head *to_kill,
98 int force_early);
99 #endif
100
101 #ifdef CONFIG_PROC_FS
102 long ksm_process_profit(struct mm_struct *);
103 #endif /* CONFIG_PROC_FS */
104
105 #else /* !CONFIG_KSM */
106
ksm_add_vma(struct vm_area_struct * vma)107 static inline void ksm_add_vma(struct vm_area_struct *vma)
108 {
109 }
110
ksm_disable(struct mm_struct * mm)111 static inline int ksm_disable(struct mm_struct *mm)
112 {
113 return 0;
114 }
115
ksm_fork(struct mm_struct * mm,struct mm_struct * oldmm)116 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
117 {
118 return 0;
119 }
120
ksm_exit(struct mm_struct * mm)121 static inline void ksm_exit(struct mm_struct *mm)
122 {
123 }
124
ksm_might_unmap_zero_page(struct mm_struct * mm,pte_t pte)125 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
126 {
127 }
128
129 #ifdef CONFIG_MEMORY_FAILURE
collect_procs_ksm(struct page * page,struct list_head * to_kill,int force_early)130 static inline void collect_procs_ksm(struct page *page,
131 struct list_head *to_kill, int force_early)
132 {
133 }
134 #endif
135
136 #ifdef CONFIG_MMU
ksm_madvise(struct vm_area_struct * vma,unsigned long start,unsigned long end,int advice,unsigned long * vm_flags)137 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
138 unsigned long end, int advice, unsigned long *vm_flags)
139 {
140 return 0;
141 }
142
ksm_might_need_to_copy(struct page * page,struct vm_area_struct * vma,unsigned long address)143 static inline struct page *ksm_might_need_to_copy(struct page *page,
144 struct vm_area_struct *vma, unsigned long address)
145 {
146 return page;
147 }
148
rmap_walk_ksm(struct folio * folio,struct rmap_walk_control * rwc)149 static inline void rmap_walk_ksm(struct folio *folio,
150 struct rmap_walk_control *rwc)
151 {
152 }
153
folio_migrate_ksm(struct folio * newfolio,struct folio * old)154 static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old)
155 {
156 }
157 #endif /* CONFIG_MMU */
158 #endif /* !CONFIG_KSM */
159
160 #endif /* __LINUX_KSM_H */
161