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