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>
19 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
20 unsigned long end, int advice, unsigned long *vm_flags);
21 int __ksm_enter(struct mm_struct *mm);
22 void __ksm_exit(struct mm_struct *mm);
24 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
26 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
27 return __ksm_enter(mm);
31 static inline void ksm_exit(struct mm_struct *mm)
33 if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
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.
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?
48 struct page *ksm_might_need_to_copy(struct page *page,
49 struct vm_area_struct *vma, unsigned long address);
51 void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc);
52 void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);
54 #else /* !CONFIG_KSM */
56 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
61 static inline void ksm_exit(struct mm_struct *mm)
66 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
67 unsigned long end, int advice, unsigned long *vm_flags)
72 static inline struct page *ksm_might_need_to_copy(struct page *page,
73 struct vm_area_struct *vma, unsigned long address)
78 static inline void rmap_walk_ksm(struct folio *folio,
79 struct rmap_walk_control *rwc)
83 static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old)
86 #endif /* CONFIG_MMU */
87 #endif /* !CONFIG_KSM */
89 #endif /* __LINUX_KSM_H */