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