LXR linux-bk/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 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 */
  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                        ((1 << MAX_SWAPFILES_SHIFT) - 1);
  35}
  36
  37/*
  38 * Extract the `offset' field from a swp_entry_t.  The swp_entry_t is in
  39 * arch-independent format
  40 */
  41static inline pgoff_t swp_offset(swp_entry_t entry)
  42{
  43        return entry.val & SWP_OFFSET_MASK(entry);
  44}
  45
  46/*
  47 * Convert the arch-dependent pte representation of a swp_entry_t into an
  48 * arch-independent swp_entry_t.
  49 */
  50static inline swp_entry_t pte_to_swp_entry(pte_t pte)
  51{
  52        swp_entry_t arch_entry;
  53
  54        BUG_ON(pte_file(pte));
  55        arch_entry = __pte_to_swp_entry(pte);
  56        return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
  57}
  58
  59/*
  60 * Convert the arch-independent representation of a swp_entry_t into the
  61 * arch-dependent pte representation.
  62 */
  63static inline pte_t swp_entry_to_pte(swp_entry_t entry)
  64{
  65        swp_entry_t arch_entry;
  66
  67        arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
  68        BUG_ON(pte_file(__swp_entry_to_pte(arch_entry)));
  69        return __swp_entry_to_pte(arch_entry);
  70}
  71