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 /* 46 * Convert the arch-dependent pte representation of a swp_entry_t into an 47 * arch-independent swp_entry_t. 48 */ 49 static inline swp_entry_t pte_to_swp_entry(pte_t pte) 50 { 51 swp_entry_t arch_entry; 52 53 BUG_ON(pte_file(pte)); 54 arch_entry = __pte_to_swp_entry(pte); 55 return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry)); 56 } 57 58 /* 59 * Convert the arch-independent representation of a swp_entry_t into the 60 * arch-dependent pte representation. 61 */ 62 static inline pte_t swp_entry_to_pte(swp_entry_t entry) 63 { 64 swp_entry_t arch_entry; 65 66 arch_entry = __swp_entry(swp_type(entry), swp_offset(entry)); 67 BUG_ON(pte_file(__swp_entry_to_pte(arch_entry))); 68 return __swp_entry_to_pte(arch_entry); 69 } 70 71 #ifdef CONFIG_MIGRATION 72 static inline swp_entry_t make_migration_entry(struct page *page, int write) 73 { 74 BUG_ON(!PageLocked(page)); 75 return swp_entry(write ? SWP_MIGRATION_WRITE : SWP_MIGRATION_READ, 76 page_to_pfn(page)); 77 } 78 79 static inline int is_migration_entry(swp_entry_t entry) 80 { 81 return unlikely(swp_type(entry) == SWP_MIGRATION_READ || 82 swp_type(entry) == SWP_MIGRATION_WRITE); 83 } 84 85 static inline int is_write_migration_entry(swp_entry_t entry) 86 { 87 return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE); 88 } 89 90 static inline struct page *migration_entry_to_page(swp_entry_t entry) 91 { 92 struct page *p = pfn_to_page(swp_offset(entry)); 93 /* 94 * Any use of migration entries may only occur while the 95 * corresponding page is locked 96 */ 97 BUG_ON(!PageLocked(p)); 98 return p; 99 } 100 101 static inline void make_migration_entry_read(swp_entry_t *entry) 102 { 103 *entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry)); 104 } 105 106 extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, 107 unsigned long address); 108 #else 109 110 #define make_migration_entry(page, write) swp_entry(0, 0) 111 static inline int is_migration_entry(swp_entry_t swp) 112 { 113 return 0; 114 } 115 #define migration_entry_to_page(swp) NULL 116 static inline void make_migration_entry_read(swp_entry_t *entryp) { } 117 static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, 118 unsigned long address) { } 119 static inline int is_write_migration_entry(swp_entry_t entry) 120 { 121 return 0; 122 } 123 124 #endif 125 126