include/linux/swapops.h

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