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 #ifdef CONFIG_MMU 46 /* check whether a pte points to a swap entry */ 47 static inline int is_swap_pte(pte_t pte) 48 { 49 return !pte_none(pte) && !pte_present(pte) && !pte_file(pte); 50 } 51 #endif 52 53 /* 54 * Convert the arch-dependent pte representation of a swp_entry_t into an 55 * arch-independent swp_entry_t. 56 */ 57 static inline swp_entry_t pte_to_swp_entry(pte_t pte) 58 { 59 swp_entry_t arch_entry; 60 61 BUG_ON(pte_file(pte)); 62 arch_entry = __pte_to_swp_entry(pte); 63 return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry)); 64 } 65 66 /* 67 * Convert the arch-independent representation of a swp_entry_t into the 68 * arch-dependent pte representation. 69 */ 70 static inline pte_t swp_entry_to_pte(swp_entry_t entry) 71 { 72 swp_entry_t arch_entry; 73 74 arch_entry = __swp_entry(swp_type(entry), swp_offset(entry)); 75 BUG_ON(pte_file(__swp_entry_to_pte(arch_entry))); 76 return __swp_entry_to_pte(arch_entry); 77 } 78 79 #ifdef CONFIG_MIGRATION 80 static inline swp_entry_t make_migration_entry(struct page *page, int write) 81 { 82 BUG_ON(!PageLocked(page)); 83 return swp_entry(write ? SWP_MIGRATION_WRITE : SWP_MIGRATION_READ, 84 page_to_pfn(page)); 85 } 86 87 static inline int is_migration_entry(swp_entry_t entry) 88 { 89 return unlikely(swp_type(entry) == SWP_MIGRATION_READ || 90 swp_type(entry) == SWP_MIGRATION_WRITE); 91 } 92 93 static inline int is_write_migration_entry(swp_entry_t entry) 94 { 95 return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE); 96 } 97 98 static inline struct page *migration_entry_to_page(swp_entry_t entry) 99 { 100 struct page *p = pfn_to_page(swp_offset(entry)); 101 /* 102 * Any use of migration entries may only occur while the 103 * corresponding page is locked 104 */ 105 BUG_ON(!PageLocked(p)); 106 return p; 107 } 108 109 static inline void make_migration_entry_read(swp_entry_t *entry) 110 { 111 *entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry)); 112 } 113 114 extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, 115 unsigned long address); 116 #else 117 118 #define make_migration_entry(page, write) swp_entry(0, 0) 119 static inline int is_migration_entry(swp_entry_t swp) 120 { 121 return 0; 122 } 123 #define migration_entry_to_page(swp) NULL 124 static inline void make_migration_entry_read(swp_entry_t *entryp) { } 125 static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, 126 unsigned long address) { } 127 static inline int is_write_migration_entry(swp_entry_t entry) 128 { 129 return 0; 130 } 131 132 #endif 133 134 #ifdef CONFIG_MEMORY_FAILURE 135 /* 136 * Support for hardware poisoned pages 137 */ 138 static inline swp_entry_t make_hwpoison_entry(struct page *page) 139 { 140 BUG_ON(!PageLocked(page)); 141 return swp_entry(SWP_HWPOISON, page_to_pfn(page)); 142 } 143 144 static inline int is_hwpoison_entry(swp_entry_t entry) 145 { 146 return swp_type(entry) == SWP_HWPOISON; 147 } 148 #else 149 150 static inline swp_entry_t make_hwpoison_entry(struct page *page) 151 { 152 return swp_entry(0, 0); 153 } 154 155 static inline int is_hwpoison_entry(swp_entry_t swp) 156 { 157 return 0; 158 } 159 #endif 160 161 #if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION) 162 static inline int non_swap_entry(swp_entry_t entry) 163 { 164 return swp_type(entry) >= MAX_SWAPFILES; 165 } 166 #else 167 static inline int non_swap_entry(swp_entry_t entry) 168 { 169 return 0; 170 } 171 #endif 172