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 19int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 20 unsigned long end, int advice, unsigned long *vm_flags); 21 22void ksm_add_vma(struct vm_area_struct *vma); 23int ksm_enable_merge_any(struct mm_struct *mm); 24int ksm_disable_merge_any(struct mm_struct *mm); 25int ksm_disable(struct mm_struct *mm); 26 27int __ksm_enter(struct mm_struct *mm); 28void __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 36extern unsigned long ksm_zero_pages; 37 38static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte) 39{ 40 if (is_ksm_zero_pte(pte)) { 41 ksm_zero_pages--; 42 mm->ksm_zero_pages--; 43 } 44} 45 46static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 47{ 48 int ret; 49 50 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags)) { 51 ret = __ksm_enter(mm); 52 if (ret) 53 return ret; 54 } 55 56 if (test_bit(MMF_VM_MERGE_ANY, &oldmm->flags)) 57 set_bit(MMF_VM_MERGE_ANY, &mm->flags); 58 59 return 0; 60} 61 62static inline void ksm_exit(struct mm_struct *mm) 63{ 64 if (test_bit(MMF_VM_MERGEABLE, &mm->flags)) 65 __ksm_exit(mm); 66} 67 68/* 69 * When do_swap_page() first faults in from swap what used to be a KSM page, 70 * no problem, it will be assigned to this vma's anon_vma; but thereafter, 71 * it might be faulted into a different anon_vma (or perhaps to a different 72 * offset in the same anon_vma). do_swap_page() cannot do all the locking 73 * needed to reconstitute a cross-anon_vma KSM page: for now it has to make 74 * a copy, and leave remerging the pages to a later pass of ksmd. 75 * 76 * We'd like to make this conditional on vma->vm_flags & VM_MERGEABLE, 77 * but what if the vma was unmerged while the page was swapped out? 78 */ 79struct folio *ksm_might_need_to_copy(struct folio *folio, 80 struct vm_area_struct *vma, unsigned long addr); 81 82void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc); 83void folio_migrate_ksm(struct folio *newfolio, struct folio *folio); 84 85#ifdef CONFIG_MEMORY_FAILURE 86void collect_procs_ksm(struct page *page, struct list_head *to_kill, 87 int force_early); 88#endif 89 90#ifdef CONFIG_PROC_FS 91long ksm_process_profit(struct mm_struct *); 92#endif /* CONFIG_PROC_FS */ 93 94#else /* !CONFIG_KSM */ 95 96static inline void ksm_add_vma(struct vm_area_struct *vma) 97{ 98} 99 100static inline int ksm_disable(struct mm_struct *mm) 101{ 102 return 0; 103} 104 105static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 106{ 107 return 0; 108} 109 110static inline void ksm_exit(struct mm_struct *mm) 111{ 112} 113 114static inline void ksm_might_unmap_zero_page(struct mm_struct *mm, pte_t pte) 115{ 116} 117 118#ifdef CONFIG_MEMORY_FAILURE 119static inline void collect_procs_ksm(struct page *page, 120 struct list_head *to_kill, int force_early) 121{ 122} 123#endif 124 125#ifdef CONFIG_MMU 126static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 127 unsigned long end, int advice, unsigned long *vm_flags) 128{ 129 return 0; 130} 131 132static inline struct folio *ksm_might_need_to_copy(struct folio *folio, 133 struct vm_area_struct *vma, unsigned long addr) 134{ 135 return folio; 136} 137 138static inline void rmap_walk_ksm(struct folio *folio, 139 struct rmap_walk_control *rwc) 140{ 141} 142 143static inline void folio_migrate_ksm(struct folio *newfolio, struct folio *old) 144{ 145} 146#endif /* CONFIG_MMU */ 147#endif /* !CONFIG_KSM */ 148 149#endif /* __LINUX_KSM_H */ 150