Linux kernel mirror (for testing)
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linux
1#ifndef __LINUX_KSM_H
2#define __LINUX_KSM_H
3/*
4 * Memory merging support.
5 *
6 * This code enables dynamic sharing of identical pages found in different
7 * memory areas, even if they are not shared by fork().
8 */
9
10#include <linux/bitops.h>
11#include <linux/mm.h>
12#include <linux/pagemap.h>
13#include <linux/rmap.h>
14#include <linux/sched.h>
15
16struct stable_node;
17struct mem_cgroup;
18
19#ifdef CONFIG_KSM
20int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
21 unsigned long end, int advice, unsigned long *vm_flags);
22int __ksm_enter(struct mm_struct *mm);
23void __ksm_exit(struct mm_struct *mm);
24
25static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
26{
27 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
28 return __ksm_enter(mm);
29 return 0;
30}
31
32static inline void ksm_exit(struct mm_struct *mm)
33{
34 if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
35 __ksm_exit(mm);
36}
37
38/*
39 * A KSM page is one of those write-protected "shared pages" or "merged pages"
40 * which KSM maps into multiple mms, wherever identical anonymous page content
41 * is found in VM_MERGEABLE vmas. It's a PageAnon page, pointing not to any
42 * anon_vma, but to that page's node of the stable tree.
43 */
44static inline int PageKsm(struct page *page)
45{
46 return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
47 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
48}
49
50static inline struct stable_node *page_stable_node(struct page *page)
51{
52 return PageKsm(page) ? page_rmapping(page) : NULL;
53}
54
55static inline void set_page_stable_node(struct page *page,
56 struct stable_node *stable_node)
57{
58 page->mapping = (void *)stable_node +
59 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
60}
61
62/*
63 * When do_swap_page() first faults in from swap what used to be a KSM page,
64 * no problem, it will be assigned to this vma's anon_vma; but thereafter,
65 * it might be faulted into a different anon_vma (or perhaps to a different
66 * offset in the same anon_vma). do_swap_page() cannot do all the locking
67 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
68 * a copy, and leave remerging the pages to a later pass of ksmd.
69 *
70 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
71 * but what if the vma was unmerged while the page was swapped out?
72 */
73struct page *ksm_does_need_to_copy(struct page *page,
74 struct vm_area_struct *vma, unsigned long address);
75static inline struct page *ksm_might_need_to_copy(struct page *page,
76 struct vm_area_struct *vma, unsigned long address)
77{
78 struct anon_vma *anon_vma = page_anon_vma(page);
79
80 if (!anon_vma ||
81 (anon_vma == vma->anon_vma &&
82 page->index == linear_page_index(vma, address)))
83 return page;
84
85 return ksm_does_need_to_copy(page, vma, address);
86}
87
88int page_referenced_ksm(struct page *page,
89 struct mem_cgroup *memcg, unsigned long *vm_flags);
90int try_to_unmap_ksm(struct page *page, enum ttu_flags flags);
91int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page *,
92 struct vm_area_struct *, unsigned long, void *), void *arg);
93void ksm_migrate_page(struct page *newpage, struct page *oldpage);
94
95#else /* !CONFIG_KSM */
96
97static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
98{
99 return 0;
100}
101
102static inline void ksm_exit(struct mm_struct *mm)
103{
104}
105
106static inline int PageKsm(struct page *page)
107{
108 return 0;
109}
110
111#ifdef CONFIG_MMU
112static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
113 unsigned long end, int advice, unsigned long *vm_flags)
114{
115 return 0;
116}
117
118static inline struct page *ksm_might_need_to_copy(struct page *page,
119 struct vm_area_struct *vma, unsigned long address)
120{
121 return page;
122}
123
124static inline int page_referenced_ksm(struct page *page,
125 struct mem_cgroup *memcg, unsigned long *vm_flags)
126{
127 return 0;
128}
129
130static inline int try_to_unmap_ksm(struct page *page, enum ttu_flags flags)
131{
132 return 0;
133}
134
135static inline int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page*,
136 struct vm_area_struct *, unsigned long, void *), void *arg)
137{
138 return 0;
139}
140
141static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
142{
143}
144#endif /* CONFIG_MMU */
145#endif /* !CONFIG_KSM */
146
147#endif /* __LINUX_KSM_H */