4 * Memory merging support.
6 * This code enables dynamic sharing of identical pages found in different
7 * memory areas, even if they are not shared by fork().
10 #include <linux/bitops.h>
12 #include <linux/sched.h>
13 #include <linux/vmstat.h>
18 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
19 unsigned long end, int advice, unsigned long *vm_flags);
20 int __ksm_enter(struct mm_struct *mm);
21 void __ksm_exit(struct mm_struct *mm);
23 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
25 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
26 return __ksm_enter(mm);
30 static inline void ksm_exit(struct mm_struct *mm)
32 if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
37 * A KSM page is one of those write-protected "shared pages" or "merged pages"
38 * which KSM maps into multiple mms, wherever identical anonymous page content
39 * is found in VM_MERGEABLE vmas. It's a PageAnon page, pointing not to any
40 * anon_vma, but to that page's node of the stable tree.
42 static inline int PageKsm(struct page *page)
44 return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
45 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
48 static inline struct stable_node *page_stable_node(struct page *page)
50 return PageKsm(page) ? page_rmapping(page) : NULL;
53 static inline void set_page_stable_node(struct page *page,
54 struct stable_node *stable_node)
56 page->mapping = (void *)stable_node +
57 (PAGE_MAPPING_ANON | PAGE_MAPPING_KSM);
60 static inline void page_add_ksm_rmap(struct page *page)
62 if (atomic_inc_and_test(&page->_mapcount))
63 __inc_zone_page_state(page, NR_ANON_PAGES);
65 #else /* !CONFIG_KSM */
67 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
68 unsigned long end, int advice, unsigned long *vm_flags)
73 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
78 static inline void ksm_exit(struct mm_struct *mm)
82 static inline int PageKsm(struct page *page)
87 /* No stub required for page_add_ksm_rmap(page) */
88 #endif /* !CONFIG_KSM */