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 struct stable_node;
19 struct mem_cgroup;
20
21 #ifdef CONFIG_KSM
22 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
23 unsigned long end, int advice, unsigned long *vm_flags);
24 int __ksm_enter(struct mm_struct *mm);
25 void __ksm_exit(struct mm_struct *mm);
26
ksm_fork(struct mm_struct * mm,struct mm_struct * oldmm)27 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
28 {
29 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
30 return __ksm_enter(mm);
31 return 0;
32 }
33
ksm_exit(struct mm_struct * mm)34 static inline void ksm_exit(struct mm_struct *mm)
35 {
36 if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
37 __ksm_exit(mm);
38 }
39
40 /*
41 * When do_swap_page() first faults in from swap what used to be a KSM page,
42 * no problem, it will be assigned to this vma's anon_vma; but thereafter,
43 * it might be faulted into a different anon_vma (or perhaps to a different
44 * offset in the same anon_vma). do_swap_page() cannot do all the locking
45 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
46 * a copy, and leave remerging the pages to a later pass of ksmd.
47 *
48 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
49 * but what if the vma was unmerged while the page was swapped out?
50 */
51 struct page *ksm_might_need_to_copy(struct page *page,
52 struct vm_area_struct *vma, unsigned long address);
53
54 void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc);
55 void ksm_migrate_page(struct page *newpage, struct page *oldpage);
56
57 #else /* !CONFIG_KSM */
58
ksm_fork(struct mm_struct * mm,struct mm_struct * oldmm)59 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
60 {
61 return 0;
62 }
63
ksm_exit(struct mm_struct * mm)64 static inline void ksm_exit(struct mm_struct *mm)
65 {
66 }
67
68 #ifdef CONFIG_MMU
ksm_madvise(struct vm_area_struct * vma,unsigned long start,unsigned long end,int advice,unsigned long * vm_flags)69 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
70 unsigned long end, int advice, unsigned long *vm_flags)
71 {
72 return 0;
73 }
74
ksm_might_need_to_copy(struct page * page,struct vm_area_struct * vma,unsigned long address)75 static inline struct page *ksm_might_need_to_copy(struct page *page,
76 struct vm_area_struct *vma, unsigned long address)
77 {
78 return page;
79 }
80
rmap_walk_ksm(struct page * page,struct rmap_walk_control * rwc)81 static inline void rmap_walk_ksm(struct page *page,
82 struct rmap_walk_control *rwc)
83 {
84 }
85
ksm_migrate_page(struct page * newpage,struct page * oldpage)86 static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
87 {
88 }
89 #endif /* CONFIG_MMU */
90 #endif /* !CONFIG_KSM */
91
92 #endif /* __LINUX_KSM_H */
93