1 /* 2 * swapcache pages are stored in the swapper_space radix tree. We want to 3 * get good packing density in that tree, so the index should be dense in 4 * the low-order bits. 5 * 6 * We arrange the `type' and `offset' fields so that `type' is at the five 7 * high-order bits of the swp_entry_t and `offset' is right-aligned in the 8 * remaining bits. 9 * 10 * swp_entry_t's are *never* stored anywhere in their arch-dependent format. 11 */ 12 #define SWP_TYPE_SHIFT(e) (sizeof(e.val) * 8 - MAX_SWAPFILES_SHIFT) 13 #define SWP_OFFSET_MASK(e) ((1UL << SWP_TYPE_SHIFT(e)) - 1) 14 15 /* 16 * Store a type+offset into a swp_entry_t in an arch-independent format 17 */ 18 static inline swp_entry_t swp_entry(unsigned long type, pgoff_t offset) 19 { 20 swp_entry_t ret; 21 22 ret.val = (type << SWP_TYPE_SHIFT(ret)) | 23 (offset & SWP_OFFSET_MASK(ret)); 24 return ret; 25 } 26 27 /* 28 * Extract the `type' field from a swp_entry_t. The swp_entry_t is in 29 * arch-independent format 30 */ 31 static inline unsigned swp_type(swp_entry_t entry) 32 { 33 return (entry.val >> SWP_TYPE_SHIFT(entry)); 34 } 35 36 /* 37 * Extract the `offset' field from a swp_entry_t. The swp_entry_t is in 38 * arch-independent format 39 */ 40 static inline pgoff_t swp_offset(swp_entry_t entry) 41 { 42 return entry.val & SWP_OFFSET_MASK(entry); 43 } 44 45 /* check whether a pte points to a swap entry */ 46 static inline int is_swap_pte(pte_t pte) 47 { 48 return !pte_none(pte) && !pte_present(pte) && !pte_file(pte); 49 } 50 51 /* 52 * Convert the arch-dependent pte representation of a swp_entry_t into an 53 * arch-independent swp_entry_t. 54 */ 55 static inline swp_entry_t pte_to_swp_entry(pte_t pte) 56 { 57 swp_entry_t arch_entry; 58 59 BUG_ON(pte_file(pte)); 60 arch_entry = __pte_to_swp_entry(pte); 61 return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry)); 62 } 63 64 /* 65 * Convert the arch-independent representation of a swp_entry_t into the 66 * arch-dependent pte representation. 67 */ 68 static inline pte_t swp_entry_to_pte(swp_entry_t entry) 69 { 70 swp_entry_t arch_entry; 71 72 arch_entry = __swp_entry(swp_type(entry), swp_offset(entry)); 73 BUG_ON(pte_file(__swp_entry_to_pte(arch_entry))); 74 return __swp_entry_to_pte(arch_entry); 75 } 76 77 #ifdef CONFIG_MIGRATION 78 static inline swp_entry_t make_migration_entry(struct page *page, int write) 79 { 80 BUG_ON(!PageLocked(page)); 81 return swp_entry(write ? SWP_MIGRATION_WRITE : SWP_MIGRATION_READ, 82 page_to_pfn(page)); 83 } 84 85 static inline int is_migration_entry(swp_entry_t entry) 86 { 87 return unlikely(swp_type(entry) == SWP_MIGRATION_READ || 88 swp_type(entry) == SWP_MIGRATION_WRITE); 89 } 90 91 static inline int is_write_migration_entry(swp_entry_t entry) 92 { 93 return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE); 94 } 95 96 static inline struct page *migration_entry_to_page(swp_entry_t entry) 97 { 98 struct page *p = pfn_to_page(swp_offset(entry)); 99 /* 100 * Any use of migration entries may only occur while the 101 * corresponding page is locked 102 */ 103 BUG_ON(!PageLocked(p)); 104 return p; 105 } 106 107 static inline void make_migration_entry_read(swp_entry_t *entry) 108 { 109 *entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry)); 110 } 111 112 extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, 113 unsigned long address); 114 #else 115 116 #define make_migration_entry(page, write) swp_entry(0, 0) 117 static inline int is_migration_entry(swp_entry_t swp) 118 { 119 return 0; 120 } 121 #define migration_entry_to_page(swp) NULL 122 static inline void make_migration_entry_read(swp_entry_t *entryp) { } 123 static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, 124 unsigned long address) { } 125 static inline int is_write_migration_entry(swp_entry_t entry) 126 { 127 return 0; 128 } 129 130 #endif 131 132