Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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) && !pte_file(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 BUG_ON(pte_file(pte));
70 arch_entry = __pte_to_swp_entry(pte);
71 return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
72}
73
74/*
75 * Convert the arch-independent representation of a swp_entry_t into the
76 * arch-dependent pte representation.
77 */
78static inline pte_t swp_entry_to_pte(swp_entry_t entry)
79{
80 swp_entry_t arch_entry;
81
82 arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
83 BUG_ON(pte_file(__swp_entry_to_pte(arch_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, pmd_t *pmd,
139 unsigned long address);
140#else
141
142#define make_migration_entry(page, write) swp_entry(0, 0)
143static inline int is_migration_entry(swp_entry_t swp)
144{
145 return 0;
146}
147#define migration_entry_to_page(swp) NULL
148static inline void make_migration_entry_read(swp_entry_t *entryp) { }
149static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
150 unsigned long address) { }
151static inline int is_write_migration_entry(swp_entry_t entry)
152{
153 return 0;
154}
155
156#endif
157
158#ifdef CONFIG_MEMORY_FAILURE
159/*
160 * Support for hardware poisoned pages
161 */
162static inline swp_entry_t make_hwpoison_entry(struct page *page)
163{
164 BUG_ON(!PageLocked(page));
165 return swp_entry(SWP_HWPOISON, page_to_pfn(page));
166}
167
168static inline int is_hwpoison_entry(swp_entry_t entry)
169{
170 return swp_type(entry) == SWP_HWPOISON;
171}
172#else
173
174static inline swp_entry_t make_hwpoison_entry(struct page *page)
175{
176 return swp_entry(0, 0);
177}
178
179static inline int is_hwpoison_entry(swp_entry_t swp)
180{
181 return 0;
182}
183#endif
184
185#if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION)
186static inline int non_swap_entry(swp_entry_t entry)
187{
188 return swp_type(entry) >= MAX_SWAPFILES;
189}
190#else
191static inline int non_swap_entry(swp_entry_t entry)
192{
193 return 0;
194}
195#endif
196
197#endif /* _LINUX_SWAPOPS_H */