Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
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}
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/*
46 * Convert the arch-dependent pte representation of a swp_entry_t into an
47 * arch-independent swp_entry_t.
48 */
49static 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 */
62static 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}