swapops.h 3.3 KB

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  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. * Store a type+offset into a swp_entry_t in an arch-independent format
  16. */
  17. static inline swp_entry_t swp_entry(unsigned long type, pgoff_t offset)
  18. {
  19. swp_entry_t ret;
  20. ret.val = (type << SWP_TYPE_SHIFT(ret)) |
  21. (offset & SWP_OFFSET_MASK(ret));
  22. return ret;
  23. }
  24. /*
  25. * Extract the `type' field from a swp_entry_t. The swp_entry_t is in
  26. * arch-independent format
  27. */
  28. static inline unsigned swp_type(swp_entry_t entry)
  29. {
  30. return (entry.val >> SWP_TYPE_SHIFT(entry));
  31. }
  32. /*
  33. * Extract the `offset' field from a swp_entry_t. The swp_entry_t is in
  34. * arch-independent format
  35. */
  36. static inline pgoff_t swp_offset(swp_entry_t entry)
  37. {
  38. return entry.val & SWP_OFFSET_MASK(entry);
  39. }
  40. /*
  41. * Convert the arch-dependent pte representation of a swp_entry_t into an
  42. * arch-independent swp_entry_t.
  43. */
  44. static inline swp_entry_t pte_to_swp_entry(pte_t pte)
  45. {
  46. swp_entry_t arch_entry;
  47. BUG_ON(pte_file(pte));
  48. arch_entry = __pte_to_swp_entry(pte);
  49. return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
  50. }
  51. /*
  52. * Convert the arch-independent representation of a swp_entry_t into the
  53. * arch-dependent pte representation.
  54. */
  55. static inline pte_t swp_entry_to_pte(swp_entry_t entry)
  56. {
  57. swp_entry_t arch_entry;
  58. arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
  59. BUG_ON(pte_file(__swp_entry_to_pte(arch_entry)));
  60. return __swp_entry_to_pte(arch_entry);
  61. }
  62. #ifdef CONFIG_MIGRATION
  63. static inline swp_entry_t make_migration_entry(struct page *page, int write)
  64. {
  65. BUG_ON(!PageLocked(page));
  66. return swp_entry(write ? SWP_MIGRATION_WRITE : SWP_MIGRATION_READ,
  67. page_to_pfn(page));
  68. }
  69. static inline int is_migration_entry(swp_entry_t entry)
  70. {
  71. return unlikely(swp_type(entry) == SWP_MIGRATION_READ ||
  72. swp_type(entry) == SWP_MIGRATION_WRITE);
  73. }
  74. static inline int is_write_migration_entry(swp_entry_t entry)
  75. {
  76. return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE);
  77. }
  78. static inline struct page *migration_entry_to_page(swp_entry_t entry)
  79. {
  80. struct page *p = pfn_to_page(swp_offset(entry));
  81. /*
  82. * Any use of migration entries may only occur while the
  83. * corresponding page is locked
  84. */
  85. BUG_ON(!PageLocked(p));
  86. return p;
  87. }
  88. static inline void make_migration_entry_read(swp_entry_t *entry)
  89. {
  90. *entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry));
  91. }
  92. extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
  93. unsigned long address);
  94. #else
  95. #define make_migration_entry(page, write) swp_entry(0, 0)
  96. static inline int is_migration_entry(swp_entry_t swp)
  97. {
  98. return 0;
  99. }
  100. #define migration_entry_to_page(swp) NULL
  101. static inline void make_migration_entry_read(swp_entry_t *entryp) { }
  102. static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
  103. unsigned long address) { }
  104. static inline int is_write_migration_entry(swp_entry_t entry)
  105. {
  106. return 0;
  107. }
  108. #endif