1#ifndef _LINUX_SWAPOPS_H
2#define _LINUX_SWAPOPS_H
3
4#include <linux/radix-tree.h>
5#include <linux/bug.h>
6
7/*
8 * swapcache pages are stored in the swapper_space radix tree.  We want to
9 * get good packing density in that tree, so the index should be dense in
10 * the low-order bits.
11 *
12 * We arrange the `type' and `offset' fields so that `type' is at the seven
13 * high-order bits of the swp_entry_t and `offset' is right-aligned in the
14 * remaining bits.  Although `type' itself needs only five bits, we allow for
15 * shmem/tmpfs to shift it all up a further two bits: see swp_to_radix_entry().
16 *
17 * swp_entry_t's are *never* stored anywhere in their arch-dependent format.
18 */
19#define SWP_TYPE_SHIFT(e)	((sizeof(e.val) * 8) - \
20			(MAX_SWAPFILES_SHIFT + RADIX_TREE_EXCEPTIONAL_SHIFT))
21#define SWP_OFFSET_MASK(e)	((1UL << SWP_TYPE_SHIFT(e)) - 1)
22
23/*
24 * Store a type+offset into a swp_entry_t in an arch-independent format
25 */
26static inline swp_entry_t swp_entry(unsigned long type, pgoff_t offset)
27{
28	swp_entry_t ret;
29
30	ret.val = (type << SWP_TYPE_SHIFT(ret)) |
31			(offset & SWP_OFFSET_MASK(ret));
32	return ret;
33}
34
35/*
36 * Extract the `type' field from a swp_entry_t.  The swp_entry_t is in
37 * arch-independent format
38 */
39static inline unsigned swp_type(swp_entry_t entry)
40{
41	return (entry.val >> SWP_TYPE_SHIFT(entry));
42}
43
44/*
45 * Extract the `offset' field from a swp_entry_t.  The swp_entry_t is in
46 * arch-independent format
47 */
48static inline pgoff_t swp_offset(swp_entry_t entry)
49{
50	return entry.val & SWP_OFFSET_MASK(entry);
51}
52
53#ifdef CONFIG_MMU
54/* check whether a pte points to a swap entry */
55static inline int is_swap_pte(pte_t pte)
56{
57	return !pte_none(pte) && !pte_present(pte);
58}
59#endif
60
61/*
62 * Convert the arch-dependent pte representation of a swp_entry_t into an
63 * arch-independent swp_entry_t.
64 */
65static inline swp_entry_t pte_to_swp_entry(pte_t pte)
66{
67	swp_entry_t arch_entry;
68
69	if (pte_swp_soft_dirty(pte))
70		pte = pte_swp_clear_soft_dirty(pte);
71	arch_entry = __pte_to_swp_entry(pte);
72	return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
73}
74
75/*
76 * Convert the arch-independent representation of a swp_entry_t into the
77 * arch-dependent pte representation.
78 */
79static inline pte_t swp_entry_to_pte(swp_entry_t entry)
80{
81	swp_entry_t arch_entry;
82
83	arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
84	return __swp_entry_to_pte(arch_entry);
85}
86
87static inline swp_entry_t radix_to_swp_entry(void *arg)
88{
89	swp_entry_t entry;
90
91	entry.val = (unsigned long)arg >> RADIX_TREE_EXCEPTIONAL_SHIFT;
92	return entry;
93}
94
95static inline void *swp_to_radix_entry(swp_entry_t entry)
96{
97	unsigned long value;
98
99	value = entry.val << RADIX_TREE_EXCEPTIONAL_SHIFT;
100	return (void *)(value | RADIX_TREE_EXCEPTIONAL_ENTRY);
101}
102
103#ifdef CONFIG_MIGRATION
104static inline swp_entry_t make_migration_entry(struct page *page, int write)
105{
106	BUG_ON(!PageLocked(page));
107	return swp_entry(write ? SWP_MIGRATION_WRITE : SWP_MIGRATION_READ,
108			page_to_pfn(page));
109}
110
111static inline int is_migration_entry(swp_entry_t entry)
112{
113	return unlikely(swp_type(entry) == SWP_MIGRATION_READ ||
114			swp_type(entry) == SWP_MIGRATION_WRITE);
115}
116
117static inline int is_write_migration_entry(swp_entry_t entry)
118{
119	return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE);
120}
121
122static inline struct page *migration_entry_to_page(swp_entry_t entry)
123{
124	struct page *p = pfn_to_page(swp_offset(entry));
125	/*
126	 * Any use of migration entries may only occur while the
127	 * corresponding page is locked
128	 */
129	BUG_ON(!PageLocked(p));
130	return p;
131}
132
133static inline void make_migration_entry_read(swp_entry_t *entry)
134{
135	*entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry));
136}
137
138extern void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
139					spinlock_t *ptl);
140extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
141					unsigned long address);
142extern void migration_entry_wait_huge(struct vm_area_struct *vma,
143		struct mm_struct *mm, pte_t *pte);
144#else
145
146#define make_migration_entry(page, write) swp_entry(0, 0)
147static inline int is_migration_entry(swp_entry_t swp)
148{
149	return 0;
150}
151#define migration_entry_to_page(swp) NULL
152static inline void make_migration_entry_read(swp_entry_t *entryp) { }
153static inline void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
154					spinlock_t *ptl) { }
155static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
156					 unsigned long address) { }
157static inline void migration_entry_wait_huge(struct vm_area_struct *vma,
158		struct mm_struct *mm, pte_t *pte) { }
159static inline int is_write_migration_entry(swp_entry_t entry)
160{
161	return 0;
162}
163
164#endif
165
166#ifdef CONFIG_MEMORY_FAILURE
167/*
168 * Support for hardware poisoned pages
169 */
170static inline swp_entry_t make_hwpoison_entry(struct page *page)
171{
172	BUG_ON(!PageLocked(page));
173	return swp_entry(SWP_HWPOISON, page_to_pfn(page));
174}
175
176static inline int is_hwpoison_entry(swp_entry_t entry)
177{
178	return swp_type(entry) == SWP_HWPOISON;
179}
180#else
181
182static inline swp_entry_t make_hwpoison_entry(struct page *page)
183{
184	return swp_entry(0, 0);
185}
186
187static inline int is_hwpoison_entry(swp_entry_t swp)
188{
189	return 0;
190}
191#endif
192
193#if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION)
194static inline int non_swap_entry(swp_entry_t entry)
195{
196	return swp_type(entry) >= MAX_SWAPFILES;
197}
198#else
199static inline int non_swap_entry(swp_entry_t entry)
200{
201	return 0;
202}
203#endif
204
205#endif /* _LINUX_SWAPOPS_H */
206