LXR linux/include/linux/swapops.h

   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#ifdef CONFIG_MMU
  46/* check whether a pte points to a swap entry */
  47static 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 */
  57static 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 */
  70static 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
  80static 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
  87static 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
  93static inline int is_write_migration_entry(swp_entry_t entry)
  94{
  95        return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE);
  96}
  97
  98static 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
 109static inline void make_migration_entry_read(swp_entry_t *entry)
 110{
 111        *entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry));
 112}
 113
 114extern 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)
 119static inline int is_migration_entry(swp_entry_t swp)
 120{
 121        return 0;
 122}
 123#define migration_entry_to_page(swp) NULL
 124static inline void make_migration_entry_read(swp_entry_t *entryp) { }
 125static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
 126                                         unsigned long address) { }
 127static 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 */
 138static 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
 144static inline int is_hwpoison_entry(swp_entry_t entry)
 145{
 146        return swp_type(entry) == SWP_HWPOISON;
 147}
 148#else
 149
 150static inline swp_entry_t make_hwpoison_entry(struct page *page)
 151{
 152        return swp_entry(0, 0);
 153}
 154
 155static 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)
 162static inline int non_swap_entry(swp_entry_t entry)
 163{
 164        return swp_type(entry) >= MAX_SWAPFILES;
 165}
 166#else
 167static inline int non_swap_entry(swp_entry_t entry)
 168{
 169        return 0;
 170}
 171#endif
 172