include/linux/swapops.h

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