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 /* 41 * When do_swap_page() first faults in from swap what used to be a KSM page, 42 * no problem, it will be assigned to this vma's anon_vma; but thereafter, 43 * it might be faulted into a different anon_vma (or perhaps to a different 44 * offset in the same anon_vma). do_swap_page() cannot do all the locking 45 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make 46 * a copy, and leave remerging the pages to a later pass of ksmd. 47 * 48 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE, 49 * but what if the vma was unmerged while the page was swapped out? 50 */ 51 struct page *ksm_might_need_to_copy(struct page *page, 52 struct vm_area_struct *vma, unsigned long address); 53 54 void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc); 55 void folio_migrate_ksm(struct folio *newfolio, struct folio *folio); 56 57 #else /* !CONFIG_KSM */ 58 59 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 60 { 61 return 0; 62 } 63 64 static inline void ksm_exit(struct mm_struct *mm) 65 { 66 } 67 68 #ifdef CONFIG_MMU 69 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 70 unsigned long end, int advice, unsigned long *vm_flags) 71 { 72 return 0; 73 } 74 75 static inline struct page *ksm_might_need_to_copy(struct page *page, 76 struct vm_area_struct *vma, unsigned long address) 77 { 78 return page; 79 } 80 81 static inline void rmap_walk_ksm(struct folio *folio, 82 struct rmap_walk_control *rwc) 83 { 84 } 85 86 static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old) 87 { 88 } 89 #endif /* CONFIG_MMU */ 90 #endif /* !CONFIG_KSM */ 91 92 #endif /* __LINUX_KSM_H */ 93