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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 422 | giacomo | 1 | /* |
| 2 | * swapcache pages are stored in the swapper_space radix tree. We want to |
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| 3 | * get good packing density in that tree, so the index should be dense in |
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| 4 | * the low-order bits. |
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| 5 | * |
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| 6 | * We arrange the `type' and `offset' fields so that `type' is at the five |
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| 7 | * high-order bits of the smp_entry_t and `offset' is right-aligned in the |
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| 8 | * remaining bits. |
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| 9 | * |
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| 10 | * swp_entry_t's are *never* stored anywhere in their arch-dependent format. |
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| 11 | */ |
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| 12 | #define SWP_TYPE_SHIFT(e) (sizeof(e.val) * 8 - MAX_SWAPFILES_SHIFT) |
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| 13 | #define SWP_OFFSET_MASK(e) ((1UL << SWP_TYPE_SHIFT(e)) - 1) |
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| 14 | |||
| 15 | /* |
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| 16 | * Store a type+offset into a swp_entry_t in an arch-independent format |
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| 17 | */ |
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| 18 | static inline swp_entry_t swp_entry(unsigned type, pgoff_t offset) |
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| 19 | { |
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| 20 | swp_entry_t ret; |
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| 21 | |||
| 22 | ret.val = ((unsigned long)type << SWP_TYPE_SHIFT(ret)) | |
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| 23 | (offset & SWP_OFFSET_MASK(ret)); |
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| 24 | return ret; |
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| 25 | } |
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| 26 | |||
| 27 | /* |
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| 28 | * Extract the `type' field from a swp_entry_t. The swp_entry_t is in |
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| 29 | * arch-independent format |
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| 30 | */ |
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| 31 | static inline unsigned swp_type(swp_entry_t entry) |
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| 32 | { |
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| 33 | return (entry.val >> SWP_TYPE_SHIFT(entry)) & |
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| 34 | ((1 << MAX_SWAPFILES_SHIFT) - 1); |
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| 35 | } |
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| 36 | |||
| 37 | /* |
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| 38 | * Extract the `offset' field from a swp_entry_t. The swp_entry_t is in |
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| 39 | * arch-independent format |
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| 40 | */ |
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| 41 | static inline pgoff_t swp_offset(swp_entry_t entry) |
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| 42 | { |
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| 43 | return entry.val & SWP_OFFSET_MASK(entry); |
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| 44 | } |
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| 45 | |||
| 46 | /* |
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| 47 | * Convert the arch-dependent pte representation of a swp_entry_t into an |
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| 48 | * arch-independent swp_entry_t. |
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| 49 | */ |
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| 50 | static inline swp_entry_t pte_to_swp_entry(pte_t pte) |
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| 51 | { |
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| 52 | swp_entry_t arch_entry; |
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| 53 | |||
| 54 | BUG_ON(pte_file(pte)); |
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| 55 | arch_entry = __pte_to_swp_entry(pte); |
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| 56 | return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry)); |
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| 57 | } |
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| 58 | |||
| 59 | /* |
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| 60 | * Convert the arch-independent representation of a swp_entry_t into the |
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| 61 | * arch-dependent pte representation. |
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| 62 | */ |
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| 63 | static inline pte_t swp_entry_to_pte(swp_entry_t entry) |
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| 64 | { |
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| 65 | swp_entry_t arch_entry; |
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| 66 | |||
| 67 | arch_entry = __swp_entry(swp_type(entry), swp_offset(entry)); |
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| 68 | BUG_ON(pte_file(__swp_entry_to_pte(arch_entry))); |
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| 69 | return __swp_entry_to_pte(arch_entry); |
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| 70 | } |