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 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  */
  26 static 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  */
  39 static 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  */
  48 static 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 */
  55 static 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  */
  65 static 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         if (pte_swp_soft_dirty(pte))
  71                 pte = pte_swp_clear_soft_dirty(pte);
  72         arch_entry = __pte_to_swp_entry(pte);
  73         return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
  74 }
  75
  76 /*
  77  * Convert the arch-independent representation of a swp_entry_t into the
  78  * arch-dependent pte representation.
  79  */
  80 static inline pte_t swp_entry_to_pte(swp_entry_t entry)
  81 {
  82         swp_entry_t arch_entry;
  83
  84         arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
  85         BUG_ON(pte_file(__swp_entry_to_pte(arch_entry)));
  86         return __swp_entry_to_pte(arch_entry);
  87 }
  88
  89 static inline swp_entry_t radix_to_swp_entry(void *arg)
  90 {
  91         swp_entry_t entry;
  92
  93         entry.val = (unsigned long)arg >> RADIX_TREE_EXCEPTIONAL_SHIFT;
  94         return entry;
  95 }
  96
  97 static inline void *swp_to_radix_entry(swp_entry_t entry)
  98 {
  99         unsigned long value;
 100
 101         value = entry.val << RADIX_TREE_EXCEPTIONAL_SHIFT;
 102         return (void *)(value | RADIX_TREE_EXCEPTIONAL_ENTRY);
 103 }
 104
 105 #ifdef CONFIG_MIGRATION
 106 static inline swp_entry_t make_migration_entry(struct page *page, int write)
 107 {
 108         BUG_ON(!PageLocked(page));
 109         return swp_entry(write ? SWP_MIGRATION_WRITE : SWP_MIGRATION_READ,
 110                         page_to_pfn(page));
 111 }
 112
 113 static inline int is_migration_entry(swp_entry_t entry)
 114 {
 115         return unlikely(swp_type(entry) == SWP_MIGRATION_READ ||
 116                         swp_type(entry) == SWP_MIGRATION_WRITE);
 117 }
 118
 119 static inline int is_write_migration_entry(swp_entry_t entry)
 120 {
 121         return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE);
 122 }
 123
 124 static inline struct page *migration_entry_to_page(swp_entry_t entry)
 125 {
 126         struct page *p = pfn_to_page(swp_offset(entry));
 127         /*
 128          * Any use of migration entries may only occur while the
 129          * corresponding page is locked
 130          */
 131         BUG_ON(!PageLocked(p));
 132         return p;
 133 }
 134
 135 static inline void make_migration_entry_read(swp_entry_t *entry)
 136 {
 137         *entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry));
 138 }
 139
 140 extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
 141                                         unsigned long address);
 142 extern 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)
 147 static inline int is_migration_entry(swp_entry_t swp)
 148 {
 149         return 0;
 150 }
 151 #define migration_entry_to_page(swp) NULL
 152 static inline void make_migration_entry_read(swp_entry_t *entryp) { }
 153 static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
 154                                          unsigned long address) { }
 155 static inline void migration_entry_wait_huge(struct vm_area_struct *vma,
 156                 struct mm_struct *mm, pte_t *pte) { }
 157 static inline int is_write_migration_entry(swp_entry_t entry)
 158 {
 159         return 0;
 160 }
 161
 162 #endif
 163
 164 #ifdef CONFIG_MEMORY_FAILURE
 165 /*
 166  * Support for hardware poisoned pages
 167  */
 168 static inline swp_entry_t make_hwpoison_entry(struct page *page)
 169 {
 170         BUG_ON(!PageLocked(page));
 171         return swp_entry(SWP_HWPOISON, page_to_pfn(page));
 172 }
 173
 174 static inline int is_hwpoison_entry(swp_entry_t entry)
 175 {
 176         return swp_type(entry) == SWP_HWPOISON;
 177 }
 178 #else
 179
 180 static inline swp_entry_t make_hwpoison_entry(struct page *page)
 181 {
 182         return swp_entry(0, 0);
 183 }
 184
 185 static inline int is_hwpoison_entry(swp_entry_t swp)
 186 {
 187         return 0;
 188 }
 189 #endif
 190
 191 #if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION)
 192 static inline int non_swap_entry(swp_entry_t entry)
 193 {
 194         return swp_type(entry) >= MAX_SWAPFILES;
 195 }
 196 #else
 197 static inline int non_swap_entry(swp_entry_t entry)
 198 {
 199         return 0;
 200 }
 201 #endif
 202
 203 #endif /* _LINUX_SWAPOPS_H */