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 void ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 58 { 59 /* Adding mm to ksm is best effort on fork. */ 60 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags)) 61 __ksm_enter(mm); 62 } 63 64 static inline int ksm_execve(struct mm_struct *mm) 65 { 66 if (test_bit(MMF_VM_MERGE_ANY, &mm->flags)) 67 return __ksm_enter(mm); 68 69 return 0; 70 } 71 72 static inline void ksm_exit(struct mm_struct *mm) 73 { 74 if (test_bit(MMF_VM_MERGEABLE, &mm->flags)) 75 __ksm_exit(mm); 76 } 77 78 /* 79 * When do_swap_page() first faults in from swap what used to be a KSM page, 80 * no problem, it will be assigned to this vma's anon_vma; but thereafter, 81 * it might be faulted into a different anon_vma (or perhaps to a different 82 * offset in the same anon_vma). do_swap_page() cannot do all the locking 83 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make 84 * a copy, and leave remerging the pages to a later pass of ksmd. 85 * 86 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE, 87 * but what if the vma was unmerged while the page was swapped out? 88 */ 89 struct folio *ksm_might_need_to_copy(struct folio *folio, 90 struct vm_area_struct *vma, unsigned long addr); 91 92 void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc); 93 void folio_migrate_ksm(struct folio *newfolio, struct folio *folio); 94 void collect_procs_ksm(struct folio *folio, struct page *page, 95 struct list_head *to_kill, int force_early); 96 long ksm_process_profit(struct mm_struct *); 97 98 #else /* !CONFIG_KSM */ 99 100 static inline void ksm_add_vma(struct vm_area_struct *vma) 101 { 102 } 103 104 static inline int ksm_disable(struct mm_struct *mm) 105 { 106 return 0; 107 } 108 109 static inline void ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 110 { 111 } 112 113 static inline int ksm_execve(struct mm_struct *mm) 114 { 115 return 0; 116 } 117 118 static inline void ksm_exit(struct mm_struct *mm) 119 { 120 } 121 122 static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte) 123 { 124 } 125 126 static inline void collect_procs_ksm(struct folio *folio, struct page *page, 127 struct list_head *to_kill, int force_early) 128 { 129 } 130 131 #ifdef CONFIG_MMU 132 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 133 unsigned long end, int advice, unsigned long *vm_flags) 134 { 135 return 0; 136 } 137 138 static inline struct folio *ksm_might_need_to_copy(struct folio *folio, 139 struct vm_area_struct *vma, unsigned long addr) 140 { 141 return folio; 142 } 143 144 static inline void rmap_walk_ksm(struct folio *folio, 145 struct rmap_walk_control *rwc) 146 { 147 } 148 149 static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old) 150 { 151 } 152 #endif /* CONFIG_MMU */ 153 #endif /* !CONFIG_KSM */ 154 155 #endif /* __LINUX_KSM_H */ 156