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 unsigned long ksm_zero_pages;
37
ksm_might_unmap_zero_page(struct mm_struct * mm,pte_t pte)38 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
39 {
40 if (is_ksm_zero_pte(pte)) {
41 ksm_zero_pages--;
42 mm->ksm_zero_pages--;
43 }
44 }
45
ksm_fork(struct mm_struct * mm,struct mm_struct * oldmm)46 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
47 {
48 int ret;
49
50 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags)) {
51 ret = __ksm_enter(mm);
52 if (ret)
53 return ret;
54 }
55
56 if (test_bit(MMF_VM_MERGE_ANY, &oldmm->flags))
57 set_bit(MMF_VM_MERGE_ANY, &mm->flags);
58
59 return 0;
60 }
61
ksm_exit(struct mm_struct * mm)62 static inline void ksm_exit(struct mm_struct *mm)
63 {
64 if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
65 __ksm_exit(mm);
66 }
67
68 /*
69 * When do_swap_page() first faults in from swap what used to be a KSM page,
70 * no problem, it will be assigned to this vma's anon_vma; but thereafter,
71 * it might be faulted into a different anon_vma (or perhaps to a different
72 * offset in the same anon_vma). do_swap_page() cannot do all the locking
73 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
74 * a copy, and leave remerging the pages to a later pass of ksmd.
75 *
76 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
77 * but what if the vma was unmerged while the page was swapped out?
78 */
79 struct page *ksm_might_need_to_copy(struct page *page,
80 struct vm_area_struct *vma, unsigned long address);
81
82 void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc);
83 void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);
84
85 #ifdef CONFIG_MEMORY_FAILURE
86 void collect_procs_ksm(struct page *page, struct list_head *to_kill,
87 int force_early);
88 #endif
89
90 #ifdef CONFIG_PROC_FS
91 long ksm_process_profit(struct mm_struct *);
92 #endif /* CONFIG_PROC_FS */
93
94 #else /* !CONFIG_KSM */
95
ksm_add_vma(struct vm_area_struct * vma)96 static inline void ksm_add_vma(struct vm_area_struct *vma)
97 {
98 }
99
ksm_disable(struct mm_struct * mm)100 static inline int ksm_disable(struct mm_struct *mm)
101 {
102 return 0;
103 }
104
ksm_fork(struct mm_struct * mm,struct mm_struct * oldmm)105 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
106 {
107 return 0;
108 }
109
ksm_exit(struct mm_struct * mm)110 static inline void ksm_exit(struct mm_struct *mm)
111 {
112 }
113
ksm_might_unmap_zero_page(struct mm_struct * mm,pte_t pte)114 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
115 {
116 }
117
118 #ifdef CONFIG_MEMORY_FAILURE
collect_procs_ksm(struct page * page,struct list_head * to_kill,int force_early)119 static inline void collect_procs_ksm(struct page *page,
120 struct list_head *to_kill, int force_early)
121 {
122 }
123 #endif
124
125 #ifdef CONFIG_MMU
ksm_madvise(struct vm_area_struct * vma,unsigned long start,unsigned long end,int advice,unsigned long * vm_flags)126 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
127 unsigned long end, int advice, unsigned long *vm_flags)
128 {
129 return 0;
130 }
131
ksm_might_need_to_copy(struct page * page,struct vm_area_struct * vma,unsigned long address)132 static inline struct page *ksm_might_need_to_copy(struct page *page,
133 struct vm_area_struct *vma, unsigned long address)
134 {
135 return page;
136 }
137
rmap_walk_ksm(struct folio * folio,struct rmap_walk_control * rwc)138 static inline void rmap_walk_ksm(struct folio *folio,
139 struct rmap_walk_control *rwc)
140 {
141 }
142
folio_migrate_ksm(struct folio * newfolio,struct folio * old)143 static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old)
144 {
145 }
146 #endif /* CONFIG_MMU */
147 #endif /* !CONFIG_KSM */
148
149 #endif /* __LINUX_KSM_H */
150