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 struct stable_node; 19 struct mem_cgroup; 20 21 #ifdef CONFIG_KSM 22 int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 23 unsigned long end, int advice, unsigned long *vm_flags); 24 int __ksm_enter(struct mm_struct *mm); 25 void __ksm_exit(struct mm_struct *mm); 26 27 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 28 { 29 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags)) 30 return __ksm_enter(mm); 31 return 0; 32 } 33 34 static inline void ksm_exit(struct mm_struct *mm) 35 { 36 if (test_bit(MMF_VM_MERGEABLE, &mm->flags)) 37 __ksm_exit(mm); 38 } 39 40 static inline struct stable_node *page_stable_node(struct page *page) 41 { 42 return PageKsm(page) ? page_rmapping(page) : NULL; 43 } 44 45 static inline void set_page_stable_node(struct page *page, 46 struct stable_node *stable_node) 47 { 48 page->mapping = (void *)((unsigned long)stable_node | PAGE_MAPPING_KSM); 49 } 50 51 /* 52 * When do_swap_page() first faults in from swap what used to be a KSM page, 53 * no problem, it will be assigned to this vma's anon_vma; but thereafter, 54 * it might be faulted into a different anon_vma (or perhaps to a different 55 * offset in the same anon_vma). do_swap_page() cannot do all the locking 56 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make 57 * a copy, and leave remerging the pages to a later pass of ksmd. 58 * 59 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE, 60 * but what if the vma was unmerged while the page was swapped out? 61 */ 62 struct page *ksm_might_need_to_copy(struct page *page, 63 struct vm_area_struct *vma, unsigned long address); 64 65 void rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc); 66 void ksm_migrate_page(struct page *newpage, struct page *oldpage); 67 68 #else /* !CONFIG_KSM */ 69 70 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 71 { 72 return 0; 73 } 74 75 static inline void ksm_exit(struct mm_struct *mm) 76 { 77 } 78 79 #ifdef CONFIG_MMU 80 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 81 unsigned long end, int advice, unsigned long *vm_flags) 82 { 83 return 0; 84 } 85 86 static inline struct page *ksm_might_need_to_copy(struct page *page, 87 struct vm_area_struct *vma, unsigned long address) 88 { 89 return page; 90 } 91 92 static inline int page_referenced_ksm(struct page *page, 93 struct mem_cgroup *memcg, unsigned long *vm_flags) 94 { 95 return 0; 96 } 97 98 static inline void rmap_walk_ksm(struct page *page, 99 struct rmap_walk_control *rwc) 100 { 101 } 102 103 static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage) 104 { 105 } 106 #endif /* CONFIG_MMU */ 107 #endif /* !CONFIG_KSM */ 108 109 #endif /* __LINUX_KSM_H */ 110