1 #ifndef __LINUX_KSM_H 2 #define __LINUX_KSM_H 3 /* 4 * Memory merging support. 5 * 6 * This code enables dynamic sharing of identical pages found in different 7 * memory areas, even if they are not shared by fork(). 8 */ 9 10 #include <linux/bitops.h> 11 #include <linux/mm.h> 12 #include <linux/sched.h> 13 #include <linux/vmstat.h> 14 15 #ifdef CONFIG_KSM 16 int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 17 unsigned long end, int advice, unsigned long *vm_flags); 18 int __ksm_enter(struct mm_struct *mm); 19 void __ksm_exit(struct mm_struct *mm); 20 21 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 22 { 23 if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags)) 24 return __ksm_enter(mm); 25 return 0; 26 } 27 28 static inline void ksm_exit(struct mm_struct *mm) 29 { 30 if (test_bit(MMF_VM_MERGEABLE, &mm->flags)) 31 __ksm_exit(mm); 32 } 33 34 /* 35 * A KSM page is one of those write-protected "shared pages" or "merged pages" 36 * which KSM maps into multiple mms, wherever identical anonymous page content 37 * is found in VM_MERGEABLE vmas. It's a PageAnon page, with NULL anon_vma. 38 */ 39 static inline int PageKsm(struct page *page) 40 { 41 return ((unsigned long)page->mapping == PAGE_MAPPING_ANON); 42 } 43 44 /* 45 * But we have to avoid the checking which page_add_anon_rmap() performs. 46 */ 47 static inline void page_add_ksm_rmap(struct page *page) 48 { 49 if (atomic_inc_and_test(&page->_mapcount)) { 50 page->mapping = (void *) PAGE_MAPPING_ANON; 51 __inc_zone_page_state(page, NR_ANON_PAGES); 52 } 53 } 54 #else /* !CONFIG_KSM */ 55 56 static inline int ksm_madvise(struct vm_area_struct *vma, unsigned long start, 57 unsigned long end, int advice, unsigned long *vm_flags) 58 { 59 return 0; 60 } 61 62 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm) 63 { 64 return 0; 65 } 66 67 static inline void ksm_exit(struct mm_struct *mm) 68 { 69 } 70 71 static inline int PageKsm(struct page *page) 72 { 73 return 0; 74 } 75 76 /* No stub required for page_add_ksm_rmap(page) */ 77 #endif /* !CONFIG_KSM */ 78 79 #endif 80