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 smp_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