linux/include/linux/swapops.h
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   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 */
 198
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