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 swp_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}
70
71#ifdef CONFIG_MIGRATION
72static inline swp_entry_t make_migration_entry(struct page *page, int write)
73{
74	BUG_ON(!PageLocked(page));
75	return swp_entry(write ? SWP_MIGRATION_WRITE : SWP_MIGRATION_READ,
76			page_to_pfn(page));
77}
78
79static inline int is_migration_entry(swp_entry_t entry)
80{
81	return unlikely(swp_type(entry) == SWP_MIGRATION_READ ||
82			swp_type(entry) == SWP_MIGRATION_WRITE);
83}
84
85static inline int is_write_migration_entry(swp_entry_t entry)
86{
87	return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE);
88}
89
90static inline struct page *migration_entry_to_page(swp_entry_t entry)
91{
92	struct page *p = pfn_to_page(swp_offset(entry));
93	/*
94	 * Any use of migration entries may only occur while the
95	 * corresponding page is locked
96	 */
97	BUG_ON(!PageLocked(p));
98	return p;
99}
100
101static inline void make_migration_entry_read(swp_entry_t *entry)
102{
103	*entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry));
104}
105
106extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
107					unsigned long address);
108#else
109
110#define make_migration_entry(page, write) swp_entry(0, 0)
111static inline int is_migration_entry(swp_entry_t swp)
112{
113	return 0;
114}
115#define migration_entry_to_page(swp) NULL
116static inline void make_migration_entry_read(swp_entry_t *entryp) { }
117static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
118					 unsigned long address) { }
119static inline int is_write_migration_entry(swp_entry_t entry)
120{
121	return 0;
122}
123
124#endif
125