include/linux/mm_types.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_MM_TYPES_H
   3 #define _LINUX_MM_TYPES_H
   4
   5 #include <linux/mm_types_task.h>
   6
   7 #include <linux/auxvec.h>
   8 #include <linux/list.h>
   9 #include <linux/spinlock.h>
  10 #include <linux/rbtree.h>
  11 #include <linux/rwsem.h>
  12 #include <linux/completion.h>
  13 #include <linux/cpumask.h>
  14 #include <linux/uprobes.h>
  15 #include <linux/page-flags-layout.h>
  16 #include <linux/workqueue.h>
  17
  18 #include <asm/mmu.h>
  19
  20 #ifndef AT_VECTOR_SIZE_ARCH
  21 #define AT_VECTOR_SIZE_ARCH 0
  22 #endif
  23 #define AT_VECTOR_SIZE (2*(AT_VECTOR_SIZE_ARCH + AT_VECTOR_SIZE_BASE + 1))
  24
  25 typedef int vm_fault_t;
  26
  27 struct address_space;
  28 struct mem_cgroup;
  29 struct hmm;
  30
  31 /*
  32  * Each physical page in the system has a struct page associated with
  33  * it to keep track of whatever it is we are using the page for at the
  34  * moment. Note that we have no way to track which tasks are using
  35  * a page, though if it is a pagecache page, rmap structures can tell us
  36  * who is mapping it.
  37  *
  38  * If you allocate the page using alloc_pages(), you can use some of the
  39  * space in struct page for your own purposes.  The five words in the main
  40  * union are available, except for bit 0 of the first word which must be
  41  * kept clear.  Many users use this word to store a pointer to an object
  42  * which is guaranteed to be aligned.  If you use the same storage as
  43  * page->mapping, you must restore it to NULL before freeing the page.
  44  *
  45  * If your page will not be mapped to userspace, you can also use the four
  46  * bytes in the mapcount union, but you must call page_mapcount_reset()
  47  * before freeing it.
  48  *
  49  * If you want to use the refcount field, it must be used in such a way
  50  * that other CPUs temporarily incrementing and then decrementing the
  51  * refcount does not cause problems.  On receiving the page from
  52  * alloc_pages(), the refcount will be positive.
  53  *
  54  * If you allocate pages of order > 0, you can use some of the fields
  55  * in each subpage, but you may need to restore some of their values
  56  * afterwards.
  57  *
  58  * SLUB uses cmpxchg_double() to atomically update its freelist and
  59  * counters.  That requires that freelist & counters be adjacent and
  60  * double-word aligned.  We align all struct pages to double-word
  61  * boundaries, and ensure that 'freelist' is aligned within the
  62  * struct.
  63  */
  64 #ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE
  65 #define _struct_page_alignment  __aligned(2 * sizeof(unsigned long))
  66 #else
  67 #define _struct_page_alignment
  68 #endif
  69
  70 struct page {
  71         unsigned long flags;            /* Atomic flags, some possibly
  72                                          * updated asynchronously */
  73         /*
  74          * Five words (20/40 bytes) are available in this union.
  75          * WARNING: bit 0 of the first word is used for PageTail(). That
  76          * means the other users of this union MUST NOT use the bit to
  77          * avoid collision and false-positive PageTail().
  78          */
  79         union {
  80                 struct {        /* Page cache and anonymous pages */
  81                         /**
  82                          * @lru: Pageout list, eg. active_list protected by
  83                          * zone_lru_lock.  Sometimes used as a generic list
  84                          * by the page owner.
  85                          */
  86                         struct list_head lru;
  87                         /* See page-flags.h for PAGE_MAPPING_FLAGS */
  88                         struct address_space *mapping;
  89                         pgoff_t index;          /* Our offset within mapping. */
  90                         /**
  91                          * @private: Mapping-private opaque data.
  92                          * Usually used for buffer_heads if PagePrivate.
  93                          * Used for swp_entry_t if PageSwapCache.
  94                          * Indicates order in the buddy system if PageBuddy.
  95                          */
  96                         unsigned long private;
  97                 };
  98                 struct {        /* slab, slob and slub */
  99                         union {
 100                                 struct list_head slab_list;     /* uses lru */
 101                                 struct {        /* Partial pages */
 102                                         struct page *next;
 103 #ifdef CONFIG_64BIT
 104                                         int pages;      /* Nr of pages left */
 105                                         int pobjects;   /* Approximate count */
 106 #else
 107                                         short int pages;
 108                                         short int pobjects;
 109 #endif
 110                                 };
 111                         };
 112                         struct kmem_cache *slab_cache; /* not slob */
 113                         /* Double-word boundary */
 114                         void *freelist;         /* first free object */
 115                         union {
 116                                 void *s_mem;    /* slab: first object */
 117                                 unsigned long counters;         /* SLUB */
 118                                 struct {                        /* SLUB */
 119                                         unsigned inuse:16;
 120                                         unsigned objects:15;
 121                                         unsigned frozen:1;
 122                                 };
 123                         };
 124                 };
 125                 struct {        /* Tail pages of compound page */
 126                         unsigned long compound_head;    /* Bit zero is set */
 127
 128                         /* First tail page only */
 129                         unsigned char compound_dtor;
 130                         unsigned char compound_order;
 131                         atomic_t compound_mapcount;
 132                 };
 133                 struct {        /* Second tail page of compound page */
 134                         unsigned long _compound_pad_1;  /* compound_head */
 135                         unsigned long _compound_pad_2;
 136                         struct list_head deferred_list;
 137                 };
 138                 struct {        /* Page table pages */
 139                         unsigned long _pt_pad_1;        /* compound_head */
 140                         pgtable_t pmd_huge_pte; /* protected by page->ptl */
 141                         unsigned long _pt_pad_2;        /* mapping */
 142                         struct mm_struct *pt_mm;        /* x86 pgds only */
 143 #if ALLOC_SPLIT_PTLOCKS
 144                         spinlock_t *ptl;
 145 #else
 146                         spinlock_t ptl;
 147 #endif
 148                 };
 149                 struct {        /* ZONE_DEVICE pages */
 150                         /** @pgmap: Points to the hosting device page map. */
 151                         struct dev_pagemap *pgmap;
 152                         unsigned long hmm_data;
 153                         unsigned long _zd_pad_1;        /* uses mapping */
 154                 };
 155
 156                 /** @rcu_head: You can use this to free a page by RCU. */
 157                 struct rcu_head rcu_head;
 158         };
 159
 160         union {         /* This union is 4 bytes in size. */
 161                 /*
 162                  * If the page can be mapped to userspace, encodes the number
 163                  * of times this page is referenced by a page table.
 164                  */
 165                 atomic_t _mapcount;
 166
 167                 /*
 168                  * If the page is neither PageSlab nor mappable to userspace,
 169                  * the value stored here may help determine what this page
 170                  * is used for.  See page-flags.h for a list of page types
 171                  * which are currently stored here.
 172                  */
 173                 unsigned int page_type;
 174
 175                 unsigned int active;            /* SLAB */
 176                 int units;                      /* SLOB */
 177         };
 178
 179         /* Usage count. *DO NOT USE DIRECTLY*. See page_ref.h */
 180         atomic_t _refcount;
 181
 182 #ifdef CONFIG_MEMCG
 183         struct mem_cgroup *mem_cgroup;
 184 #endif
 185
 186         /*
 187          * On machines where all RAM is mapped into kernel address space,
 188          * we can simply calculate the virtual address. On machines with
 189          * highmem some memory is mapped into kernel virtual memory
 190          * dynamically, so we need a place to store that address.
 191          * Note that this field could be 16 bits on x86 ... ;)
 192          *
 193          * Architectures with slow multiplication can define
 194          * WANT_PAGE_VIRTUAL in asm/page.h
 195          */
 196 #if defined(WANT_PAGE_VIRTUAL)
 197         void *virtual;                  /* Kernel virtual address (NULL if
 198                                            not kmapped, ie. highmem) */
 199 #endif /* WANT_PAGE_VIRTUAL */
 200
 201 #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
 202         int _last_cpupid;
 203 #endif
 204 } _struct_page_alignment;
 205
 206 #define PAGE_FRAG_CACHE_MAX_SIZE        __ALIGN_MASK(32768, ~PAGE_MASK)
 207 #define PAGE_FRAG_CACHE_MAX_ORDER       get_order(PAGE_FRAG_CACHE_MAX_SIZE)
 208
 209 struct page_frag_cache {
 210         void * va;
 211 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
 212         __u16 offset;
 213         __u16 size;
 214 #else
 215         __u32 offset;
 216 #endif
 217         /* we maintain a pagecount bias, so that we dont dirty cache line
 218          * containing page->_refcount every time we allocate a fragment.
 219          */
 220         unsigned int            pagecnt_bias;
 221         bool pfmemalloc;
 222 };
 223
 224 typedef unsigned long vm_flags_t;
 225
 226 /*
 227  * A region containing a mapping of a non-memory backed file under NOMMU
 228  * conditions.  These are held in a global tree and are pinned by the VMAs that
 229  * map parts of them.
 230  */
 231 struct vm_region {
 232         struct rb_node  vm_rb;          /* link in global region tree */
 233         vm_flags_t      vm_flags;       /* VMA vm_flags */
 234         unsigned long   vm_start;       /* start address of region */
 235         unsigned long   vm_end;         /* region initialised to here */
 236         unsigned long   vm_top;         /* region allocated to here */
 237         unsigned long   vm_pgoff;       /* the offset in vm_file corresponding to vm_start */
 238         struct file     *vm_file;       /* the backing file or NULL */
 239
 240         int             vm_usage;       /* region usage count (access under nommu_region_sem) */
 241         bool            vm_icache_flushed : 1; /* true if the icache has been flushed for
 242                                                 * this region */
 243 };
 244
 245 #ifdef CONFIG_USERFAULTFD
 246 #define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) { NULL, })
 247 struct vm_userfaultfd_ctx {
 248         struct userfaultfd_ctx *ctx;
 249 };
 250 #else /* CONFIG_USERFAULTFD */
 251 #define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) {})
 252 struct vm_userfaultfd_ctx {};
 253 #endif /* CONFIG_USERFAULTFD */
 254
 255 /*
 256  * This struct defines a memory VMM memory area. There is one of these
 257  * per VM-area/task.  A VM area is any part of the process virtual memory
 258  * space that has a special rule for the page-fault handlers (ie a shared
 259  * library, the executable area etc).
 260  */
 261 struct vm_area_struct {
 262         /* The first cache line has the info for VMA tree walking. */
 263
 264         unsigned long vm_start;         /* Our start address within vm_mm. */
 265         unsigned long vm_end;           /* The first byte after our end address
 266                                            within vm_mm. */
 267
 268         /* linked list of VM areas per task, sorted by address */
 269         struct vm_area_struct *vm_next, *vm_prev;
 270
 271         struct rb_node vm_rb;
 272
 273         /*
 274          * Largest free memory gap in bytes to the left of this VMA.
 275          * Either between this VMA and vma->vm_prev, or between one of the
 276          * VMAs below us in the VMA rbtree and its ->vm_prev. This helps
 277          * get_unmapped_area find a free area of the right size.
 278          */
 279         unsigned long rb_subtree_gap;
 280
 281         /* Second cache line starts here. */
 282
 283         struct mm_struct *vm_mm;        /* The address space we belong to. */
 284         pgprot_t vm_page_prot;          /* Access permissions of this VMA. */
 285         unsigned long vm_flags;         /* Flags, see mm.h. */
 286
 287         /*
 288          * For areas with an address space and backing store,
 289          * linkage into the address_space->i_mmap interval tree.
 290          */
 291         struct {
 292                 struct rb_node rb;
 293                 unsigned long rb_subtree_last;
 294         } shared;
 295
 296         /*
 297          * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
 298          * list, after a COW of one of the file pages.  A MAP_SHARED vma
 299          * can only be in the i_mmap tree.  An anonymous MAP_PRIVATE, stack
 300          * or brk vma (with NULL file) can only be in an anon_vma list.
 301          */
 302         struct list_head anon_vma_chain; /* Serialized by mmap_sem &
 303                                           * page_table_lock */
 304         struct anon_vma *anon_vma;      /* Serialized by page_table_lock */
 305
 306         /* Function pointers to deal with this struct. */
 307         const struct vm_operations_struct *vm_ops;
 308
 309         /* Information about our backing store: */
 310         unsigned long vm_pgoff;         /* Offset (within vm_file) in PAGE_SIZE
 311                                            units */
 312         struct file * vm_file;          /* File we map to (can be NULL). */
 313         void * vm_private_data;         /* was vm_pte (shared mem) */
 314
 315         atomic_long_t swap_readahead_info;
 316 #ifndef CONFIG_MMU
 317         struct vm_region *vm_region;    /* NOMMU mapping region */
 318 #endif
 319 #ifdef CONFIG_NUMA
 320         struct mempolicy *vm_policy;    /* NUMA policy for the VMA */
 321 #endif
 322         struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
 323 } __randomize_layout;
 324
 325 struct core_thread {
 326         struct task_struct *task;
 327         struct core_thread *next;
 328 };
 329
 330 struct core_state {
 331         atomic_t nr_threads;
 332         struct core_thread dumper;
 333         struct completion startup;
 334 };
 335
 336 struct kioctx_table;
 337 struct mm_struct {
 338         struct vm_area_struct *mmap;            /* list of VMAs */
 339         struct rb_root mm_rb;
 340         u32 vmacache_seqnum;                   /* per-thread vmacache */
 341 #ifdef CONFIG_MMU
 342         unsigned long (*get_unmapped_area) (struct file *filp,
 343                                 unsigned long addr, unsigned long len,
 344                                 unsigned long pgoff, unsigned long flags);
 345 #endif
 346         unsigned long mmap_base;                /* base of mmap area */
 347         unsigned long mmap_legacy_base;         /* base of mmap area in bottom-up allocations */
 348 #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
 349         /* Base adresses for compatible mmap() */
 350         unsigned long mmap_compat_base;
 351         unsigned long mmap_compat_legacy_base;
 352 #endif
 353         unsigned long task_size;                /* size of task vm space */
 354         unsigned long highest_vm_end;           /* highest vma end address */
 355         pgd_t * pgd;
 356
 357         /**
 358          * @mm_users: The number of users including userspace.
 359          *
 360          * Use mmget()/mmget_not_zero()/mmput() to modify. When this drops
 361          * to 0 (i.e. when the task exits and there are no other temporary
 362          * reference holders), we also release a reference on @mm_count
 363          * (which may then free the &struct mm_struct if @mm_count also
 364          * drops to 0).
 365          */
 366         atomic_t mm_users;
 367
 368         /**
 369          * @mm_count: The number of references to &struct mm_struct
 370          * (@mm_users count as 1).
 371          *
 372          * Use mmgrab()/mmdrop() to modify. When this drops to 0, the
 373          * &struct mm_struct is freed.
 374          */
 375         atomic_t mm_count;
 376
 377 #ifdef CONFIG_MMU
 378         atomic_long_t pgtables_bytes;           /* PTE page table pages */
 379 #endif
 380         int map_count;                          /* number of VMAs */
 381
 382         spinlock_t page_table_lock;             /* Protects page tables and some counters */
 383         struct rw_semaphore mmap_sem;
 384
 385         struct list_head mmlist;                /* List of maybe swapped mm's.  These are globally strung
 386                                                  * together off init_mm.mmlist, and are protected
 387                                                  * by mmlist_lock
 388                                                  */
 389
 390
 391         unsigned long hiwater_rss;      /* High-watermark of RSS usage */
 392         unsigned long hiwater_vm;       /* High-water virtual memory usage */
 393
 394         unsigned long total_vm;         /* Total pages mapped */
 395         unsigned long locked_vm;        /* Pages that have PG_mlocked set */
 396         unsigned long pinned_vm;        /* Refcount permanently increased */
 397         unsigned long data_vm;          /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
 398         unsigned long exec_vm;          /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
 399         unsigned long stack_vm;         /* VM_STACK */
 400         unsigned long def_flags;
 401
 402         spinlock_t arg_lock; /* protect the below fields */
 403         unsigned long start_code, end_code, start_data, end_data;
 404         unsigned long start_brk, brk, start_stack;
 405         unsigned long arg_start, arg_end, env_start, env_end;
 406
 407         unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
 408
 409         /*
 410          * Special counters, in some configurations protected by the
 411          * page_table_lock, in other configurations by being atomic.
 412          */
 413         struct mm_rss_stat rss_stat;
 414
 415         struct linux_binfmt *binfmt;
 416
 417         cpumask_var_t cpu_vm_mask_var;
 418
 419         /* Architecture-specific MM context */
 420         mm_context_t context;
 421
 422         unsigned long flags; /* Must use atomic bitops to access the bits */
 423
 424         struct core_state *core_state; /* coredumping support */
 425 #ifdef CONFIG_MEMBARRIER
 426         atomic_t membarrier_state;
 427 #endif
 428 #ifdef CONFIG_AIO
 429         spinlock_t                      ioctx_lock;
 430         struct kioctx_table __rcu       *ioctx_table;
 431 #endif
 432 #ifdef CONFIG_MEMCG
 433         /*
 434          * "owner" points to a task that is regarded as the canonical
 435          * user/owner of this mm. All of the following must be true in
 436          * order for it to be changed:
 437          *
 438          * current == mm->owner
 439          * current->mm != mm
 440          * new_owner->mm == mm
 441          * new_owner->alloc_lock is held
 442          */
 443         struct task_struct __rcu *owner;
 444 #endif
 445         struct user_namespace *user_ns;
 446
 447         /* store ref to file /proc/<pid>/exe symlink points to */
 448         struct file __rcu *exe_file;
 449 #ifdef CONFIG_MMU_NOTIFIER
 450         struct mmu_notifier_mm *mmu_notifier_mm;
 451 #endif
 452 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 453         pgtable_t pmd_huge_pte; /* protected by page_table_lock */
 454 #endif
 455 #ifdef CONFIG_CPUMASK_OFFSTACK
 456         struct cpumask cpumask_allocation;
 457 #endif
 458 #ifdef CONFIG_NUMA_BALANCING
 459         /*
 460          * numa_next_scan is the next time that the PTEs will be marked
 461          * pte_numa. NUMA hinting faults will gather statistics and migrate
 462          * pages to new nodes if necessary.
 463          */
 464         unsigned long numa_next_scan;
 465
 466         /* Restart point for scanning and setting pte_numa */
 467         unsigned long numa_scan_offset;
 468
 469         /* numa_scan_seq prevents two threads setting pte_numa */
 470         int numa_scan_seq;
 471 #endif
 472         /*
 473          * An operation with batched TLB flushing is going on. Anything that
 474          * can move process memory needs to flush the TLB when moving a
 475          * PROT_NONE or PROT_NUMA mapped page.
 476          */
 477         atomic_t tlb_flush_pending;
 478 #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
 479         /* See flush_tlb_batched_pending() */
 480         bool tlb_flush_batched;
 481 #endif
 482         struct uprobes_state uprobes_state;
 483 #ifdef CONFIG_HUGETLB_PAGE
 484         atomic_long_t hugetlb_usage;
 485 #endif
 486         struct work_struct async_put_work;
 487
 488 #if IS_ENABLED(CONFIG_HMM)
 489         /* HMM needs to track a few things per mm */
 490         struct hmm *hmm;
 491 #endif
 492 } __randomize_layout;
 493
 494 extern struct mm_struct init_mm;
 495
 496 static inline void mm_init_cpumask(struct mm_struct *mm)
 497 {
 498 #ifdef CONFIG_CPUMASK_OFFSTACK
 499         mm->cpu_vm_mask_var = &mm->cpumask_allocation;
 500 #endif
 501         cpumask_clear(mm->cpu_vm_mask_var);
 502 }
 503
 504 /* Future-safe accessor for struct mm_struct's cpu_vm_mask. */
 505 static inline cpumask_t *mm_cpumask(struct mm_struct *mm)
 506 {
 507         return mm->cpu_vm_mask_var;
 508 }
 509
 510 struct mmu_gather;
 511 extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
 512                                 unsigned long start, unsigned long end);
 513 extern void tlb_finish_mmu(struct mmu_gather *tlb,
 514                                 unsigned long start, unsigned long end);
 515
 516 static inline void init_tlb_flush_pending(struct mm_struct *mm)
 517 {
 518         atomic_set(&mm->tlb_flush_pending, 0);
 519 }
 520
 521 static inline void inc_tlb_flush_pending(struct mm_struct *mm)
 522 {
 523         atomic_inc(&mm->tlb_flush_pending);
 524         /*
 525          * The only time this value is relevant is when there are indeed pages
 526          * to flush. And we'll only flush pages after changing them, which
 527          * requires the PTL.
 528          *
 529          * So the ordering here is:
 530          *
 531          *      atomic_inc(&mm->tlb_flush_pending);
 532          *      spin_lock(&ptl);
 533          *      ...
 534          *      set_pte_at();
 535          *      spin_unlock(&ptl);
 536          *
 537          *                              spin_lock(&ptl)
 538          *                              mm_tlb_flush_pending();
 539          *                              ....
 540          *                              spin_unlock(&ptl);
 541          *
 542          *      flush_tlb_range();
 543          *      atomic_dec(&mm->tlb_flush_pending);
 544          *
 545          * Where the increment if constrained by the PTL unlock, it thus
 546          * ensures that the increment is visible if the PTE modification is
 547          * visible. After all, if there is no PTE modification, nobody cares
 548          * about TLB flushes either.
 549          *
 550          * This very much relies on users (mm_tlb_flush_pending() and
 551          * mm_tlb_flush_nested()) only caring about _specific_ PTEs (and
 552          * therefore specific PTLs), because with SPLIT_PTE_PTLOCKS and RCpc
 553          * locks (PPC) the unlock of one doesn't order against the lock of
 554          * another PTL.
 555          *
 556          * The decrement is ordered by the flush_tlb_range(), such that
 557          * mm_tlb_flush_pending() will not return false unless all flushes have
 558          * completed.
 559          */
 560 }
 561
 562 static inline void dec_tlb_flush_pending(struct mm_struct *mm)
 563 {
 564         /*
 565          * See inc_tlb_flush_pending().
 566          *
 567          * This cannot be smp_mb__before_atomic() because smp_mb() simply does
 568          * not order against TLB invalidate completion, which is what we need.
 569          *
 570          * Therefore we must rely on tlb_flush_*() to guarantee order.
 571          */
 572         atomic_dec(&mm->tlb_flush_pending);
 573 }
 574
 575 static inline bool mm_tlb_flush_pending(struct mm_struct *mm)
 576 {
 577         /*
 578          * Must be called after having acquired the PTL; orders against that
 579          * PTLs release and therefore ensures that if we observe the modified
 580          * PTE we must also observe the increment from inc_tlb_flush_pending().
 581          *
 582          * That is, it only guarantees to return true if there is a flush
 583          * pending for _this_ PTL.
 584          */
 585         return atomic_read(&mm->tlb_flush_pending);
 586 }
 587
 588 static inline bool mm_tlb_flush_nested(struct mm_struct *mm)
 589 {
 590         /*
 591          * Similar to mm_tlb_flush_pending(), we must have acquired the PTL
 592          * for which there is a TLB flush pending in order to guarantee
 593          * we've seen both that PTE modification and the increment.
 594          *
 595          * (no requirement on actually still holding the PTL, that is irrelevant)
 596          */
 597         return atomic_read(&mm->tlb_flush_pending) > 1;
 598 }
 599
 600 struct vm_fault;
 601
 602 struct vm_special_mapping {
 603         const char *name;       /* The name, e.g. "[vdso]". */
 604
 605         /*
 606          * If .fault is not provided, this points to a
 607          * NULL-terminated array of pages that back the special mapping.
 608          *
 609          * This must not be NULL unless .fault is provided.
 610          */
 611         struct page **pages;
 612
 613         /*
 614          * If non-NULL, then this is called to resolve page faults
 615          * on the special mapping.  If used, .pages is not checked.
 616          */
 617         vm_fault_t (*fault)(const struct vm_special_mapping *sm,
 618                                 struct vm_area_struct *vma,
 619                                 struct vm_fault *vmf);
 620
 621         int (*mremap)(const struct vm_special_mapping *sm,
 622                      struct vm_area_struct *new_vma);
 623 };
 624
 625 enum tlb_flush_reason {
 626         TLB_FLUSH_ON_TASK_SWITCH,
 627         TLB_REMOTE_SHOOTDOWN,
 628         TLB_LOCAL_SHOOTDOWN,
 629         TLB_LOCAL_MM_SHOOTDOWN,
 630         TLB_REMOTE_SEND_IPI,
 631         NR_TLB_FLUSH_REASONS,
 632 };
 633
 634  /*
 635   * A swap entry has to fit into a "unsigned long", as the entry is hidden
 636   * in the "index" field of the swapper address space.
 637   */
 638 typedef struct {
 639         unsigned long val;
 640 } swp_entry_t;
 641
 642 #endif /* _LINUX_MM_TYPES_H */