1 #ifndef __LINUX_KSM_H 2 #define __LINUX_KSM_H 3 /* 4 * Memory merging support. 5 * 6 * This code enables dynamic sharing of identical pages found in different 7 * memory areas, even if they are not shared by fork(). 8 */ 9 10 #include <linux/bitops.h> 11 #include <linux/mm.h> 12 #include <linux/pagemap.h> 13 #include <linux/rmap.h> 14 #include <linux/sched.h> 15 16 struct stable_node; 17 struct mem_cgroup; 18 19 struct page *ksm_does_need_to_copy(struct page *page, 20 struct vm_area_struct *vma, unsigned long address); 21 22 #ifdef CONFIG_KSM 23 int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 24 unsigned long end, int advice, unsigned long *vm_flags); 25 int __ksm_enter(struct mm_struct *mm); 26 void __ksm_exit(struct mm_struct *mm); 27 28 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 29 { 30 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags)) 31 return __ksm_enter(mm); 32 return 0; 33 } 34 35 static inline void ksm_exit(struct mm_struct *mm) 36 { 37 if (test_bit(MMF_VM_MERGEABLE, &mm->flags)) 38 __ksm_exit(mm); 39 } 40 41 /* 42 * A KSM page is one of those write-protected "shared pages" or "merged pages" 43 * which KSM maps into multiple mms, wherever identical anonymous page content 44 * is found in VM_MERGEABLE vmas. It's a PageAnon page, pointing not to any 45 * anon_vma, but to that page's node of the stable tree. 46 */ 47 static inline int PageKsm(struct page *page) 48 { 49 return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) == 50 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); 51 } 52 53 static inline struct stable_node *page_stable_node(struct page *page) 54 { 55 return PageKsm(page) ? page_rmapping(page) : NULL; 56 } 57 58 static inline void set_page_stable_node(struct page *page, 59 struct stable_node *stable_node) 60 { 61 page->mapping = (void *)stable_node + 62 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM); 63 } 64 65 /* 66 * When do_swap_page() first faults in from swap what used to be a KSM page, 67 * no problem, it will be assigned to this vma's anon_vma; but thereafter, 68 * it might be faulted into a different anon_vma (or perhaps to a different 69 * offset in the same anon_vma). do_swap_page() cannot do all the locking 70 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make 71 * a copy, and leave remerging the pages to a later pass of ksmd. 72 * 73 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE, 74 * but what if the vma was unmerged while the page was swapped out? 75 */ 76 static inline int ksm_might_need_to_copy(struct page *page, 77 struct vm_area_struct *vma, unsigned long address) 78 { 79 struct anon_vma *anon_vma = page_anon_vma(page); 80 81 return anon_vma && 82 (anon_vma->root != vma->anon_vma->root || 83 page->index != linear_page_index(vma, address)); 84 } 85 86 int page_referenced_ksm(struct page *page, 87 struct mem_cgroup *memcg, unsigned long *vm_flags); 88 int try_to_unmap_ksm(struct page *page, enum ttu_flags flags); 89 int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page *, 90 struct vm_area_struct *, unsigned long, void *), void *arg); 91 void ksm_migrate_page(struct page *newpage, struct page *oldpage); 92 93 #else /* !CONFIG_KSM */ 94 95 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 96 { 97 return 0; 98 } 99 100 static inline void ksm_exit(struct mm_struct *mm) 101 { 102 } 103 104 static inline int PageKsm(struct page *page) 105 { 106 return 0; 107 } 108 109 #ifdef CONFIG_MMU 110 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 111 unsigned long end, int advice, unsigned long *vm_flags) 112 { 113 return 0; 114 } 115 116 static inline int ksm_might_need_to_copy(struct page *page, 117 struct vm_area_struct *vma, unsigned long address) 118 { 119 return 0; 120 } 121 122 static inline int page_referenced_ksm(struct page *page, 123 struct mem_cgroup *memcg, unsigned long *vm_flags) 124 { 125 return 0; 126 } 127 128 static inline int try_to_unmap_ksm(struct page *page, enum ttu_flags flags) 129 { 130 return 0; 131 } 132 133 static inline int rmap_walk_ksm(struct page *page, int (*rmap_one)(struct page*, 134 struct vm_area_struct *, unsigned long, void *), void *arg) 135 { 136 return 0; 137 } 138 139 static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage) 140 { 141 } 142 #endif /* CONFIG_MMU */ 143 #endif /* !CONFIG_KSM */ 144 145 #endif /* __LINUX_KSM_H */ 146