Commit | Line | Data |
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1da177e4 LT |
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 | |
e83a9596 | 7 | * high-order bits of the swp_entry_t and `offset' is right-aligned in the |
1da177e4 LT |
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 | */ | |
18 | static 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 | */ | |
31 | static 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 | */ | |
40 | static inline pgoff_t swp_offset(swp_entry_t entry) | |
41 | { | |
42 | return entry.val & SWP_OFFSET_MASK(entry); | |
43 | } | |
44 | ||
45 | /* | |
46 | * Convert the arch-dependent pte representation of a swp_entry_t into an | |
47 | * arch-independent swp_entry_t. | |
48 | */ | |
49 | static inline swp_entry_t pte_to_swp_entry(pte_t pte) | |
50 | { | |
51 | swp_entry_t arch_entry; | |
52 | ||
53 | BUG_ON(pte_file(pte)); | |
54 | arch_entry = __pte_to_swp_entry(pte); | |
55 | return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry)); | |
56 | } | |
57 | ||
58 | /* | |
59 | * Convert the arch-independent representation of a swp_entry_t into the | |
60 | * arch-dependent pte representation. | |
61 | */ | |
62 | static inline pte_t swp_entry_to_pte(swp_entry_t entry) | |
63 | { | |
64 | swp_entry_t arch_entry; | |
65 | ||
66 | arch_entry = __swp_entry(swp_type(entry), swp_offset(entry)); | |
67 | BUG_ON(pte_file(__swp_entry_to_pte(arch_entry))); | |
68 | return __swp_entry_to_pte(arch_entry); | |
69 | } |