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 17 #ifdef CONFIG_KSM 18 int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 19 unsigned long end, int advice, vm_flags_t *vm_flags); 20 vm_flags_t ksm_vma_flags(const struct mm_struct *mm, const struct file *file, 21 vm_flags_t vm_flags); 22 int ksm_enable_merge_any(struct mm_struct *mm); 23 int ksm_disable_merge_any(struct mm_struct *mm); 24 int ksm_disable(struct mm_struct *mm); 25 26 int __ksm_enter(struct mm_struct *mm); 27 void __ksm_exit(struct mm_struct *mm); 28 /* 29 * To identify zeropages that were mapped by KSM, we reuse the dirty bit 30 * in the PTE. If the PTE is dirty, the zeropage was mapped by KSM when 31 * deduplicating memory. 32 */ 33 #define is_ksm_zero_pte(pte) (is_zero_pfn(pte_pfn(pte)) && pte_dirty(pte)) 34 35 extern atomic_long_t ksm_zero_pages; 36 37 static inline void ksm_map_zero_page(struct mm_struct *mm) 38 { 39 atomic_long_inc(&ksm_zero_pages); 40 atomic_long_inc(&mm->ksm_zero_pages); 41 } 42 43 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte) 44 { 45 if (is_ksm_zero_pte(pte)) { 46 atomic_long_dec(&ksm_zero_pages); 47 atomic_long_dec(&mm->ksm_zero_pages); 48 } 49 } 50 51 static inline long mm_ksm_zero_pages(struct mm_struct *mm) 52 { 53 return atomic_long_read(&mm->ksm_zero_pages); 54 } 55 56 static inline void ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 57 { 58 /* Adding mm to ksm is best effort on fork. */ 59 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags)) 60 __ksm_enter(mm); 61 } 62 63 static inline int ksm_execve(struct mm_struct *mm) 64 { 65 if (test_bit(MMF_VM_MERGE_ANY, &mm->flags)) 66 return __ksm_enter(mm); 67 68 return 0; 69 } 70 71 static inline void ksm_exit(struct mm_struct *mm) 72 { 73 if (test_bit(MMF_VM_MERGEABLE, &mm->flags)) 74 __ksm_exit(mm); 75 } 76 77 /* 78 * When do_swap_page() first faults in from swap what used to be a KSM page, 79 * no problem, it will be assigned to this vma's anon_vma; but thereafter, 80 * it might be faulted into a different anon_vma (or perhaps to a different 81 * offset in the same anon_vma). do_swap_page() cannot do all the locking 82 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make 83 * a copy, and leave remerging the pages to a later pass of ksmd. 84 * 85 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE, 86 * but what if the vma was unmerged while the page was swapped out? 87 */ 88 struct folio *ksm_might_need_to_copy(struct folio *folio, 89 struct vm_area_struct *vma, unsigned long addr); 90 91 void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc); 92 void folio_migrate_ksm(struct folio *newfolio, struct folio *folio); 93 void collect_procs_ksm(const struct folio *folio, const struct page *page, 94 struct list_head *to_kill, int force_early); 95 long ksm_process_profit(struct mm_struct *); 96 bool ksm_process_mergeable(struct mm_struct *mm); 97 98 #else /* !CONFIG_KSM */ 99 100 static inline vm_flags_t ksm_vma_flags(const struct mm_struct *mm, 101 const struct file *file, vm_flags_t vm_flags) 102 { 103 return vm_flags; 104 } 105 106 static inline int ksm_disable(struct mm_struct *mm) 107 { 108 return 0; 109 } 110 111 static inline void ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 112 { 113 } 114 115 static inline int ksm_execve(struct mm_struct *mm) 116 { 117 return 0; 118 } 119 120 static inline void ksm_exit(struct mm_struct *mm) 121 { 122 } 123 124 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte) 125 { 126 } 127 128 static inline void collect_procs_ksm(const struct folio *folio, 129 const struct page *page, struct list_head *to_kill, 130 int force_early) 131 { 132 } 133 134 #ifdef CONFIG_MMU 135 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 136 unsigned long end, int advice, vm_flags_t *vm_flags) 137 { 138 return 0; 139 } 140 141 static inline struct folio *ksm_might_need_to_copy(struct folio *folio, 142 struct vm_area_struct *vma, unsigned long addr) 143 { 144 return folio; 145 } 146 147 static inline void rmap_walk_ksm(struct folio *folio, 148 struct rmap_walk_control *rwc) 149 { 150 } 151 152 static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old) 153 { 154 } 155 #endif /* CONFIG_MMU */ 156 #endif /* !CONFIG_KSM */ 157 158 #endif /* __LINUX_KSM_H */ 159