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 */ 18static 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 */ 31static 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 */ 40static 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 */ 49static 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 */ 62static 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 72static 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 79static 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 85static inline int is_write_migration_entry(swp_entry_t entry) 86{ 87 return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE); 88} 89 90static 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 101static inline void make_migration_entry_read(swp_entry_t *entry) 102{ 103 *entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry)); 104} 105 106extern 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) 111static inline int is_migration_entry(swp_entry_t swp) 112{ 113 return 0; 114} 115#define migration_entry_to_page(swp) NULL 116static inline void make_migration_entry_read(swp_entry_t *entryp) { } 117static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, 118 unsigned long address) { } 119static inline int is_write_migration_entry(swp_entry_t entry) 120{ 121 return 0; 122} 123 124#endif 125