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