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