1 /* SPDX-License-Identifier: GPL-2.0 */
5 * Memory merging support.
7 * This code enables dynamic sharing of identical pages found in different
8 * memory areas, even if they are not shared by fork().
11 #include <linux/bitops.h>
13 #include <linux/pagemap.h>
14 #include <linux/rmap.h>
15 #include <linux/sched.h>
16 #include <linux/sched/coredump.h>
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);
27 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
29 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
30 return __ksm_enter(mm);
34 static inline void ksm_exit(struct mm_struct *mm)
36 if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
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.
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?
51 struct page *ksm_might_need_to_copy(struct page *page,
52 struct vm_area_struct *vma, unsigned long address);
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 bool reuse_ksm_page(struct page *page,
57 struct vm_area_struct *vma, unsigned long address);
59 #else /* !CONFIG_KSM */
61 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
66 static inline void ksm_exit(struct mm_struct *mm)
71 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
72 unsigned long end, int advice, unsigned long *vm_flags)
77 static inline struct page *ksm_might_need_to_copy(struct page *page,
78 struct vm_area_struct *vma, unsigned long address)
83 static inline void rmap_walk_ksm(struct page *page,
84 struct rmap_walk_control *rwc)
88 static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
91 static inline bool reuse_ksm_page(struct page *page,
92 struct vm_area_struct *vma, unsigned long address)
96 #endif /* CONFIG_MMU */
97 #endif /* !CONFIG_KSM */
99 #endif /* __LINUX_KSM_H */