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);
22 void ksm_add_vma(struct vm_area_struct *vma);
23 int ksm_enable_merge_any(struct mm_struct *mm);
24 int ksm_disable_merge_any(struct mm_struct *mm);
25 int ksm_disable(struct mm_struct *mm);
27 int __ksm_enter(struct mm_struct *mm);
28 void __ksm_exit(struct mm_struct *mm);
30 * To identify zeropages that were mapped by KSM, we reuse the dirty bit
31 * in the PTE. If the PTE is dirty, the zeropage was mapped by KSM when
32 * deduplicating memory.
34 #define is_ksm_zero_pte(pte) (is_zero_pfn(pte_pfn(pte)) && pte_dirty(pte))
36 extern unsigned long ksm_zero_pages;
38 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
40 if (is_ksm_zero_pte(pte)) {
46 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
48 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
49 return __ksm_enter(mm);
54 static inline int ksm_execve(struct mm_struct *mm)
56 if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
57 return __ksm_enter(mm);
62 static inline void ksm_exit(struct mm_struct *mm)
64 if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
69 * When do_swap_page() first faults in from swap what used to be a KSM page,
70 * no problem, it will be assigned to this vma's anon_vma; but thereafter,
71 * it might be faulted into a different anon_vma (or perhaps to a different
72 * offset in the same anon_vma). do_swap_page() cannot do all the locking
73 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make
74 * a copy, and leave remerging the pages to a later pass of ksmd.
76 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE,
77 * but what if the vma was unmerged while the page was swapped out?
79 struct folio *ksm_might_need_to_copy(struct folio *folio,
80 struct vm_area_struct *vma, unsigned long addr);
82 void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc);
83 void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);
84 void collect_procs_ksm(struct folio *folio, struct page *page,
85 struct list_head *to_kill, int force_early);
86 long ksm_process_profit(struct mm_struct *);
88 #else /* !CONFIG_KSM */
90 static inline void ksm_add_vma(struct vm_area_struct *vma)
94 static inline int ksm_disable(struct mm_struct *mm)
99 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
104 static inline int ksm_execve(struct mm_struct *mm)
109 static inline void ksm_exit(struct mm_struct *mm)
113 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte)
117 static inline void collect_procs_ksm(struct folio *folio, struct page *page,
118 struct list_head *to_kill, int force_early)
123 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
124 unsigned long end, int advice, unsigned long *vm_flags)
129 static inline struct folio *ksm_might_need_to_copy(struct folio *folio,
130 struct vm_area_struct *vma, unsigned long addr)
135 static inline void rmap_walk_ksm(struct folio *folio,
136 struct rmap_walk_control *rwc)
140 static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old)
143 #endif /* CONFIG_MMU */
144 #endif /* !CONFIG_KSM */
146 #endif /* __LINUX_KSM_H */