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       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 page *page, struct rmap_walk_control *rwc);
      55                 :            : void ksm_migrate_page(struct page *newpage, struct page *oldpage);
      56                 :            : bool reuse_ksm_page(struct page *page,
      57                 :            :                         struct vm_area_struct *vma, unsigned long address);
      58                 :            : 
      59                 :            : #else  /* !CONFIG_KSM */
      60                 :            : 
      61                 :       3960 : static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
      62                 :            : {
      63                 :       3960 :         return 0;
      64                 :            : }
      65                 :            : 
      66                 :       7568 : static inline void ksm_exit(struct mm_struct *mm)
      67                 :            : {
      68                 :       7568 : }
      69                 :            : 
      70                 :            : #ifdef CONFIG_MMU
      71                 :            : static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
      72                 :            :                 unsigned long end, int advice, unsigned long *vm_flags)
      73                 :            : {
      74                 :            :         return 0;
      75                 :            : }
      76                 :            : 
      77                 :          0 : static inline struct page *ksm_might_need_to_copy(struct page *page,
      78                 :            :                         struct vm_area_struct *vma, unsigned long address)
      79                 :            : {
      80         [ #  # ]:          0 :         return page;
      81                 :            : }
      82                 :            : 
      83                 :            : static inline void rmap_walk_ksm(struct page *page,
      84                 :            :                         struct rmap_walk_control *rwc)
      85                 :            : {
      86                 :            : }
      87                 :            : 
      88                 :          0 : static inline void ksm_migrate_page(struct page *newpage, struct page *oldpage)
      89                 :            : {
      90         [ #  # ]:          0 : }
      91                 :            : static inline bool reuse_ksm_page(struct page *page,
      92                 :            :                         struct vm_area_struct *vma, unsigned long address)
      93                 :            : {
      94                 :            :         return false;
      95                 :            : }
      96                 :            : #endif /* CONFIG_MMU */
      97                 :            : #endif /* !CONFIG_KSM */
      98                 :            : 
      99                 :            : #endif /* __LINUX_KSM_H */