include/linux/migrate.h

   1 #ifndef _LINUX_MIGRATE_H
   2 #define _LINUX_MIGRATE_H
   3
   4 #include <linux/mm.h>
   5 #include <linux/mempolicy.h>
   6 #include <linux/migrate_mode.h>
   7 #include <linux/hugetlb.h>
   8
   9 typedef struct page *new_page_t(struct page *page, unsigned long private,
  10                                 int **reason);
  11 typedef void free_page_t(struct page *page, unsigned long private);
  12
  13 /*
  14  * Return values from addresss_space_operations.migratepage():
  15  * - negative errno on page migration failure;
  16  * - zero on page migration success;
  17  */
  18 #define MIGRATEPAGE_SUCCESS             0
  19
  20 enum migrate_reason {
  21         MR_COMPACTION,
  22         MR_MEMORY_FAILURE,
  23         MR_MEMORY_HOTPLUG,
  24         MR_SYSCALL,             /* also applies to cpusets */
  25         MR_MEMPOLICY_MBIND,
  26         MR_NUMA_MISPLACED,
  27         MR_CMA,
  28         MR_TYPES
  29 };
  30
  31 /* In mm/debug.c; also keep sync with include/trace/events/migrate.h */
  32 extern char *migrate_reason_names[MR_TYPES];
  33
  34 static inline struct page *new_page_nodemask(struct page *page,
  35                                 int preferred_nid, nodemask_t *nodemask)
  36 {
  37         gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL;
  38         unsigned int order = 0;
  39         struct page *new_page = NULL;
  40
  41         if (PageHuge(page))
  42                 return alloc_huge_page_nodemask(page_hstate(compound_head(page)),
  43                                 preferred_nid, nodemask);
  44
  45         if (thp_migration_supported() && PageTransHuge(page)) {
  46                 order = HPAGE_PMD_ORDER;
  47                 gfp_mask |= GFP_TRANSHUGE;
  48         }
  49
  50         if (PageHighMem(page) || (zone_idx(page_zone(page)) == ZONE_MOVABLE))
  51                 gfp_mask |= __GFP_HIGHMEM;
  52
  53         new_page = __alloc_pages_nodemask(gfp_mask, order,
  54                                 preferred_nid, nodemask);
  55
  56         if (new_page && PageTransHuge(page))
  57                 prep_transhuge_page(new_page);
  58
  59         return new_page;
  60 }
  61
  62 #ifdef CONFIG_MIGRATION
  63
  64 extern void putback_movable_pages(struct list_head *l);
  65 extern int migrate_page(struct address_space *mapping,
  66                         struct page *newpage, struct page *page,
  67                         enum migrate_mode mode);
  68 extern int migrate_pages(struct list_head *l, new_page_t new, free_page_t free,
  69                 unsigned long private, enum migrate_mode mode, int reason);
  70 extern int isolate_movable_page(struct page *page, isolate_mode_t mode);
  71 extern void putback_movable_page(struct page *page);
  72
  73 extern int migrate_prep(void);
  74 extern int migrate_prep_local(void);
  75 extern void migrate_page_states(struct page *newpage, struct page *page);
  76 extern void migrate_page_copy(struct page *newpage, struct page *page);
  77 extern int migrate_huge_page_move_mapping(struct address_space *mapping,
  78                                   struct page *newpage, struct page *page);
  79 extern int migrate_page_move_mapping(struct address_space *mapping,
  80                 struct page *newpage, struct page *page,
  81                 struct buffer_head *head, enum migrate_mode mode,
  82                 int extra_count);
  83 #else
  84
  85 static inline void putback_movable_pages(struct list_head *l) {}
  86 static inline int migrate_pages(struct list_head *l, new_page_t new,
  87                 free_page_t free, unsigned long private, enum migrate_mode mode,
  88                 int reason)
  89         { return -ENOSYS; }
  90 static inline int isolate_movable_page(struct page *page, isolate_mode_t mode)
  91         { return -EBUSY; }
  92
  93 static inline int migrate_prep(void) { return -ENOSYS; }
  94 static inline int migrate_prep_local(void) { return -ENOSYS; }
  95
  96 static inline void migrate_page_states(struct page *newpage, struct page *page)
  97 {
  98 }
  99
 100 static inline void migrate_page_copy(struct page *newpage,
 101                                      struct page *page) {}
 102
 103 static inline int migrate_huge_page_move_mapping(struct address_space *mapping,
 104                                   struct page *newpage, struct page *page)
 105 {
 106         return -ENOSYS;
 107 }
 108
 109 #endif /* CONFIG_MIGRATION */
 110
 111 #ifdef CONFIG_COMPACTION
 112 extern int PageMovable(struct page *page);
 113 extern void __SetPageMovable(struct page *page, struct address_space *mapping);
 114 extern void __ClearPageMovable(struct page *page);
 115 #else
 116 static inline int PageMovable(struct page *page) { return 0; };
 117 static inline void __SetPageMovable(struct page *page,
 118                                 struct address_space *mapping)
 119 {
 120 }
 121 static inline void __ClearPageMovable(struct page *page)
 122 {
 123 }
 124 #endif
 125
 126 #ifdef CONFIG_NUMA_BALANCING
 127 extern bool pmd_trans_migrating(pmd_t pmd);
 128 extern int migrate_misplaced_page(struct page *page,
 129                                   struct vm_area_struct *vma, int node);
 130 #else
 131 static inline bool pmd_trans_migrating(pmd_t pmd)
 132 {
 133         return false;
 134 }
 135 static inline int migrate_misplaced_page(struct page *page,
 136                                          struct vm_area_struct *vma, int node)
 137 {
 138         return -EAGAIN; /* can't migrate now */
 139 }
 140 #endif /* CONFIG_NUMA_BALANCING */
 141
 142 #if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
 143 extern int migrate_misplaced_transhuge_page(struct mm_struct *mm,
 144                         struct vm_area_struct *vma,
 145                         pmd_t *pmd, pmd_t entry,
 146                         unsigned long address,
 147                         struct page *page, int node);
 148 #else
 149 static inline int migrate_misplaced_transhuge_page(struct mm_struct *mm,
 150                         struct vm_area_struct *vma,
 151                         pmd_t *pmd, pmd_t entry,
 152                         unsigned long address,
 153                         struct page *page, int node)
 154 {
 155         return -EAGAIN;
 156 }
 157 #endif /* CONFIG_NUMA_BALANCING && CONFIG_TRANSPARENT_HUGEPAGE*/
 158
 159
 160 #ifdef CONFIG_MIGRATION
 161
 162 /*
 163  * Watch out for PAE architecture, which has an unsigned long, and might not
 164  * have enough bits to store all physical address and flags. So far we have
 165  * enough room for all our flags.
 166  */
 167 #define MIGRATE_PFN_VALID       (1UL << 0)
 168 #define MIGRATE_PFN_MIGRATE     (1UL << 1)
 169 #define MIGRATE_PFN_LOCKED      (1UL << 2)
 170 #define MIGRATE_PFN_WRITE       (1UL << 3)
 171 #define MIGRATE_PFN_DEVICE      (1UL << 4)
 172 #define MIGRATE_PFN_ERROR       (1UL << 5)
 173 #define MIGRATE_PFN_SHIFT       6
 174
 175 static inline struct page *migrate_pfn_to_page(unsigned long mpfn)
 176 {
 177         if (!(mpfn & MIGRATE_PFN_VALID))
 178                 return NULL;
 179         return pfn_to_page(mpfn >> MIGRATE_PFN_SHIFT);
 180 }
 181
 182 static inline unsigned long migrate_pfn(unsigned long pfn)
 183 {
 184         return (pfn << MIGRATE_PFN_SHIFT) | MIGRATE_PFN_VALID;
 185 }
 186
 187 /*
 188  * struct migrate_vma_ops - migrate operation callback
 189  *
 190  * @alloc_and_copy: alloc destination memory and copy source memory to it
 191  * @finalize_and_map: allow caller to map the successfully migrated pages
 192  *
 193  *
 194  * The alloc_and_copy() callback happens once all source pages have been locked,
 195  * unmapped and checked (checked whether pinned or not). All pages that can be
 196  * migrated will have an entry in the src array set with the pfn value of the
 197  * page and with the MIGRATE_PFN_VALID and MIGRATE_PFN_MIGRATE flag set (other
 198  * flags might be set but should be ignored by the callback).
 199  *
 200  * The alloc_and_copy() callback can then allocate destination memory and copy
 201  * source memory to it for all those entries (ie with MIGRATE_PFN_VALID and
 202  * MIGRATE_PFN_MIGRATE flag set). Once these are allocated and copied, the
 203  * callback must update each corresponding entry in the dst array with the pfn
 204  * value of the destination page and with the MIGRATE_PFN_VALID and
 205  * MIGRATE_PFN_LOCKED flags set (destination pages must have their struct pages
 206  * locked, via lock_page()).
 207  *
 208  * At this point the alloc_and_copy() callback is done and returns.
 209  *
 210  * Note that the callback does not have to migrate all the pages that are
 211  * marked with MIGRATE_PFN_MIGRATE flag in src array unless this is a migration
 212  * from device memory to system memory (ie the MIGRATE_PFN_DEVICE flag is also
 213  * set in the src array entry). If the device driver cannot migrate a device
 214  * page back to system memory, then it must set the corresponding dst array
 215  * entry to MIGRATE_PFN_ERROR. This will trigger a SIGBUS if CPU tries to
 216  * access any of the virtual addresses originally backed by this page. Because
 217  * a SIGBUS is such a severe result for the userspace process, the device
 218  * driver should avoid setting MIGRATE_PFN_ERROR unless it is really in an
 219  * unrecoverable state.
 220  *
 221  * For empty entry inside CPU page table (pte_none() or pmd_none() is true) we
 222  * do set MIGRATE_PFN_MIGRATE flag inside the corresponding source array thus
 223  * allowing device driver to allocate device memory for those unback virtual
 224  * address. For this the device driver simply have to allocate device memory
 225  * and properly set the destination entry like for regular migration. Note that
 226  * this can still fails and thus inside the device driver must check if the
 227  * migration was successful for those entry inside the finalize_and_map()
 228  * callback just like for regular migration.
 229  *
 230  * THE alloc_and_copy() CALLBACK MUST NOT CHANGE ANY OF THE SRC ARRAY ENTRIES
 231  * OR BAD THINGS WILL HAPPEN !
 232  *
 233  *
 234  * The finalize_and_map() callback happens after struct page migration from
 235  * source to destination (destination struct pages are the struct pages for the
 236  * memory allocated by the alloc_and_copy() callback).  Migration can fail, and
 237  * thus the finalize_and_map() allows the driver to inspect which pages were
 238  * successfully migrated, and which were not. Successfully migrated pages will
 239  * have the MIGRATE_PFN_MIGRATE flag set for their src array entry.
 240  *
 241  * It is safe to update device page table from within the finalize_and_map()
 242  * callback because both destination and source page are still locked, and the
 243  * mmap_sem is held in read mode (hence no one can unmap the range being
 244  * migrated).
 245  *
 246  * Once callback is done cleaning up things and updating its page table (if it
 247  * chose to do so, this is not an obligation) then it returns. At this point,
 248  * the HMM core will finish up the final steps, and the migration is complete.
 249  *
 250  * THE finalize_and_map() CALLBACK MUST NOT CHANGE ANY OF THE SRC OR DST ARRAY
 251  * ENTRIES OR BAD THINGS WILL HAPPEN !
 252  */
 253 struct migrate_vma_ops {
 254         void (*alloc_and_copy)(struct vm_area_struct *vma,
 255                                const unsigned long *src,
 256                                unsigned long *dst,
 257                                unsigned long start,
 258                                unsigned long end,
 259                                void *private);
 260         void (*finalize_and_map)(struct vm_area_struct *vma,
 261                                  const unsigned long *src,
 262                                  const unsigned long *dst,
 263                                  unsigned long start,
 264                                  unsigned long end,
 265                                  void *private);
 266 };
 267
 268 #if defined(CONFIG_MIGRATE_VMA_HELPER)
 269 int migrate_vma(const struct migrate_vma_ops *ops,
 270                 struct vm_area_struct *vma,
 271                 unsigned long start,
 272                 unsigned long end,
 273                 unsigned long *src,
 274                 unsigned long *dst,
 275                 void *private);
 276 #else
 277 static inline int migrate_vma(const struct migrate_vma_ops *ops,
 278                               struct vm_area_struct *vma,
 279                               unsigned long start,
 280                               unsigned long end,
 281                               unsigned long *src,
 282                               unsigned long *dst,
 283                               void *private)
 284 {
 285         return -EINVAL;
 286 }
 287 #endif /* IS_ENABLED(CONFIG_MIGRATE_VMA_HELPER) */
 288
 289 #endif /* CONFIG_MIGRATION */
 290
 291 #endif /* _LINUX_MIGRATE_H */