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70 lines
1.9 KiB
70 lines
1.9 KiB
20 years ago
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/*
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* swapcache pages are stored in the swapper_space radix tree. We want to
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* get good packing density in that tree, so the index should be dense in
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* the low-order bits.
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*
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* We arrange the `type' and `offset' fields so that `type' is at the five
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* high-order bits of the smp_entry_t and `offset' is right-aligned in the
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* remaining bits.
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*
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* swp_entry_t's are *never* stored anywhere in their arch-dependent format.
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*/
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#define SWP_TYPE_SHIFT(e) (sizeof(e.val) * 8 - MAX_SWAPFILES_SHIFT)
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#define SWP_OFFSET_MASK(e) ((1UL << SWP_TYPE_SHIFT(e)) - 1)
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/*
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* Store a type+offset into a swp_entry_t in an arch-independent format
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*/
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static inline swp_entry_t swp_entry(unsigned long type, pgoff_t offset)
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{
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swp_entry_t ret;
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ret.val = (type << SWP_TYPE_SHIFT(ret)) |
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(offset & SWP_OFFSET_MASK(ret));
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return ret;
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}
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/*
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* Extract the `type' field from a swp_entry_t. The swp_entry_t is in
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* arch-independent format
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*/
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static inline unsigned swp_type(swp_entry_t entry)
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{
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return (entry.val >> SWP_TYPE_SHIFT(entry));
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}
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/*
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* Extract the `offset' field from a swp_entry_t. The swp_entry_t is in
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* arch-independent format
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*/
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static inline pgoff_t swp_offset(swp_entry_t entry)
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{
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return entry.val & SWP_OFFSET_MASK(entry);
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}
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/*
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* Convert the arch-dependent pte representation of a swp_entry_t into an
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* arch-independent swp_entry_t.
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*/
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static inline swp_entry_t pte_to_swp_entry(pte_t pte)
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{
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swp_entry_t arch_entry;
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BUG_ON(pte_file(pte));
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arch_entry = __pte_to_swp_entry(pte);
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return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
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}
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/*
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* Convert the arch-independent representation of a swp_entry_t into the
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* arch-dependent pte representation.
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*/
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static inline pte_t swp_entry_to_pte(swp_entry_t entry)
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{
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swp_entry_t arch_entry;
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arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
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BUG_ON(pte_file(__swp_entry_to_pte(arch_entry)));
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return __swp_entry_to_pte(arch_entry);
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}
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