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 struct address_space;
  26 struct mem_cgroup;
  27 struct hmm;
  28
  29 /*
  30  * Each physical page in the system has a struct page associated with
  31  * it to keep track of whatever it is we are using the page for at the
  32  * moment. Note that we have no way to track which tasks are using
  33  * a page, though if it is a pagecache page, rmap structures can tell us
  34  * who is mapping it.
  35  *
  36  * The objects in struct page are organized in double word blocks in
  37  * order to allows us to use atomic double word operations on portions
  38  * of struct page. That is currently only used by slub but the arrangement
  39  * allows the use of atomic double word operations on the flags/mapping
  40  * and lru list pointers also.
  41  */
  42 struct page {
  43         /* First double word block */
  44         unsigned long flags;            /* Atomic flags, some possibly
  45                                          * updated asynchronously */
  46         union {
  47                 struct address_space *mapping;  /* If low bit clear, points to
  48                                                  * inode address_space, or NULL.
  49                                                  * If page mapped as anonymous
  50                                                  * memory, low bit is set, and
  51                                                  * it points to anon_vma object:
  52                                                  * see PAGE_MAPPING_ANON below.
  53                                                  */
  54                 void *s_mem;                    /* slab first object */
  55                 atomic_t compound_mapcount;     /* first tail page */
  56                 /* page_deferred_list().next     -- second tail page */
  57         };
  58
  59         /* Second double word */
  60         union {
  61                 pgoff_t index;          /* Our offset within mapping. */
  62                 void *freelist;         /* sl[aou]b first free object */
  63                 /* page_deferred_list().prev    -- second tail page */
  64         };
  65
  66         union {
  67 #if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
  68         defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
  69                 /* Used for cmpxchg_double in slub */
  70                 unsigned long counters;
  71 #else
  72                 /*
  73                  * Keep _refcount separate from slub cmpxchg_double data.
  74                  * As the rest of the double word is protected by slab_lock
  75                  * but _refcount is not.
  76                  */
  77                 unsigned counters;
  78 #endif
  79                 struct {
  80
  81                         union {
  82                                 /*
  83                                  * Count of ptes mapped in mms, to show when
  84                                  * page is mapped & limit reverse map searches.
  85                                  *
  86                                  * Extra information about page type may be
  87                                  * stored here for pages that are never mapped,
  88                                  * in which case the value MUST BE <= -2.
  89                                  * See page-flags.h for more details.
  90                                  */
  91                                 atomic_t _mapcount;
  92
  93                                 unsigned int active;            /* SLAB */
  94                                 struct {                        /* SLUB */
  95                                         unsigned inuse:16;
  96                                         unsigned objects:15;
  97                                         unsigned frozen:1;
  98                                 };
  99                                 int units;                      /* SLOB */
 100                         };
 101                         /*
 102                          * Usage count, *USE WRAPPER FUNCTION* when manual
 103                          * accounting. See page_ref.h
 104                          */
 105                         atomic_t _refcount;
 106                 };
 107         };
 108
 109         /*
 110          * Third double word block
 111          *
 112          * WARNING: bit 0 of the first word encode PageTail(). That means
 113          * the rest users of the storage space MUST NOT use the bit to
 114          * avoid collision and false-positive PageTail().
 115          */
 116         union {
 117                 struct list_head lru;   /* Pageout list, eg. active_list
 118                                          * protected by zone_lru_lock !
 119                                          * Can be used as a generic list
 120                                          * by the page owner.
 121                                          */
 122                 struct dev_pagemap *pgmap; /* ZONE_DEVICE pages are never on an
 123                                             * lru or handled by a slab
 124                                             * allocator, this points to the
 125                                             * hosting device page map.
 126                                             */
 127                 struct {                /* slub per cpu partial pages */
 128                         struct page *next;      /* Next partial slab */
 129 #ifdef CONFIG_64BIT
 130                         int pages;      /* Nr of partial slabs left */
 131                         int pobjects;   /* Approximate # of objects */
 132 #else
 133                         short int pages;
 134                         short int pobjects;
 135 #endif
 136                 };
 137
 138                 struct rcu_head rcu_head;       /* Used by SLAB
 139                                                  * when destroying via RCU
 140                                                  */
 141                 /* Tail pages of compound page */
 142                 struct {
 143                         unsigned long compound_head; /* If bit zero is set */
 144
 145                         /* First tail page only */
 146 #ifdef CONFIG_64BIT
 147                         /*
 148                          * On 64 bit system we have enough space in struct page
 149                          * to encode compound_dtor and compound_order with
 150                          * unsigned int. It can help compiler generate better or
 151                          * smaller code on some archtectures.
 152                          */
 153                         unsigned int compound_dtor;
 154                         unsigned int compound_order;
 155 #else
 156                         unsigned short int compound_dtor;
 157                         unsigned short int compound_order;
 158 #endif
 159                 };
 160
 161 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS
 162                 struct {
 163                         unsigned long __pad;    /* do not overlay pmd_huge_pte
 164                                                  * with compound_head to avoid
 165                                                  * possible bit 0 collision.
 166                                                  */
 167                         pgtable_t pmd_huge_pte; /* protected by page->ptl */
 168                 };
 169 #endif
 170         };
 171
 172         /* Remainder is not double word aligned */
 173         union {
 174                 unsigned long private;          /* Mapping-private opaque data:
 175                                                  * usually used for buffer_heads
 176                                                  * if PagePrivate set; used for
 177                                                  * swp_entry_t if PageSwapCache;
 178                                                  * indicates order in the buddy
 179                                                  * system if PG_buddy is set.
 180                                                  */
 181 #if USE_SPLIT_PTE_PTLOCKS
 182 #if ALLOC_SPLIT_PTLOCKS
 183                 spinlock_t *ptl;
 184 #else
 185                 spinlock_t ptl;
 186 #endif
 187 #endif
 188                 struct kmem_cache *slab_cache;  /* SL[AU]B: Pointer to slab */
 189         };
 190
 191 #ifdef CONFIG_MEMCG
 192         struct mem_cgroup *mem_cgroup;
 193 #endif
 194
 195         /*
 196          * On machines where all RAM is mapped into kernel address space,
 197          * we can simply calculate the virtual address. On machines with
 198          * highmem some memory is mapped into kernel virtual memory
 199          * dynamically, so we need a place to store that address.
 200          * Note that this field could be 16 bits on x86 ... ;)
 201          *
 202          * Architectures with slow multiplication can define
 203          * WANT_PAGE_VIRTUAL in asm/page.h
 204          */
 205 #if defined(WANT_PAGE_VIRTUAL)
 206         void *virtual;                  /* Kernel virtual address (NULL if
 207                                            not kmapped, ie. highmem) */
 208 #endif /* WANT_PAGE_VIRTUAL */
 209
 210 #ifdef CONFIG_KMEMCHECK
 211         /*
 212          * kmemcheck wants to track the status of each byte in a page; this
 213          * is a pointer to such a status block. NULL if not tracked.
 214          */
 215         void *shadow;
 216 #endif
 217
 218 #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
 219         int _last_cpupid;
 220 #endif
 221 }
 222 /*
 223  * The struct page can be forced to be double word aligned so that atomic ops
 224  * on double words work. The SLUB allocator can make use of such a feature.
 225  */
 226 #ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE
 227         __aligned(2 * sizeof(unsigned long))
 228 #endif
 229 ;
 230
 231 #define PAGE_FRAG_CACHE_MAX_SIZE        __ALIGN_MASK(32768, ~PAGE_MASK)
 232 #define PAGE_FRAG_CACHE_MAX_ORDER       get_order(PAGE_FRAG_CACHE_MAX_SIZE)
 233
 234 struct page_frag_cache {
 235         void * va;
 236 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
 237         __u16 offset;
 238         __u16 size;
 239 #else
 240         __u32 offset;
 241 #endif
 242         /* we maintain a pagecount bias, so that we dont dirty cache line
 243          * containing page->_refcount every time we allocate a fragment.
 244          */
 245         unsigned int            pagecnt_bias;
 246         bool pfmemalloc;
 247 };
 248
 249 typedef unsigned long vm_flags_t;
 250
 251 /*
 252  * A region containing a mapping of a non-memory backed file under NOMMU
 253  * conditions.  These are held in a global tree and are pinned by the VMAs that
 254  * map parts of them.
 255  */
 256 struct vm_region {
 257         struct rb_node  vm_rb;          /* link in global region tree */
 258         vm_flags_t      vm_flags;       /* VMA vm_flags */
 259         unsigned long   vm_start;       /* start address of region */
 260         unsigned long   vm_end;         /* region initialised to here */
 261         unsigned long   vm_top;         /* region allocated to here */
 262         unsigned long   vm_pgoff;       /* the offset in vm_file corresponding to vm_start */
 263         struct file     *vm_file;       /* the backing file or NULL */
 264
 265         int             vm_usage;       /* region usage count (access under nommu_region_sem) */
 266         bool            vm_icache_flushed : 1; /* true if the icache has been flushed for
 267                                                 * this region */
 268 };
 269
 270 #ifdef CONFIG_USERFAULTFD
 271 #define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) { NULL, })
 272 struct vm_userfaultfd_ctx {
 273         struct userfaultfd_ctx *ctx;
 274 };
 275 #else /* CONFIG_USERFAULTFD */
 276 #define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) {})
 277 struct vm_userfaultfd_ctx {};
 278 #endif /* CONFIG_USERFAULTFD */
 279
 280 /*
 281  * This struct defines a memory VMM memory area. There is one of these
 282  * per VM-area/task.  A VM area is any part of the process virtual memory
 283  * space that has a special rule for the page-fault handlers (ie a shared
 284  * library, the executable area etc).
 285  */
 286 struct vm_area_struct {
 287         /* The first cache line has the info for VMA tree walking. */
 288
 289         unsigned long vm_start;         /* Our start address within vm_mm. */
 290         unsigned long vm_end;           /* The first byte after our end address
 291                                            within vm_mm. */
 292
 293         /* linked list of VM areas per task, sorted by address */
 294         struct vm_area_struct *vm_next, *vm_prev;
 295
 296         struct rb_node vm_rb;
 297
 298         /*
 299          * Largest free memory gap in bytes to the left of this VMA.
 300          * Either between this VMA and vma->vm_prev, or between one of the
 301          * VMAs below us in the VMA rbtree and its ->vm_prev. This helps
 302          * get_unmapped_area find a free area of the right size.
 303          */
 304         unsigned long rb_subtree_gap;
 305
 306         /* Second cache line starts here. */
 307
 308         struct mm_struct *vm_mm;        /* The address space we belong to. */
 309         pgprot_t vm_page_prot;          /* Access permissions of this VMA. */
 310         unsigned long vm_flags;         /* Flags, see mm.h. */
 311
 312         /*
 313          * For areas with an address space and backing store,
 314          * linkage into the address_space->i_mmap interval tree.
 315          */
 316         struct {
 317                 struct rb_node rb;
 318                 unsigned long rb_subtree_last;
 319         } shared;
 320
 321         /*
 322          * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
 323          * list, after a COW of one of the file pages.  A MAP_SHARED vma
 324          * can only be in the i_mmap tree.  An anonymous MAP_PRIVATE, stack
 325          * or brk vma (with NULL file) can only be in an anon_vma list.
 326          */
 327         struct list_head anon_vma_chain; /* Serialized by mmap_sem &
 328                                           * page_table_lock */
 329         struct anon_vma *anon_vma;      /* Serialized by page_table_lock */
 330
 331         /* Function pointers to deal with this struct. */
 332         const struct vm_operations_struct *vm_ops;
 333
 334         /* Information about our backing store: */
 335         unsigned long vm_pgoff;         /* Offset (within vm_file) in PAGE_SIZE
 336                                            units */
 337         struct file * vm_file;          /* File we map to (can be NULL). */
 338         void * vm_private_data;         /* was vm_pte (shared mem) */
 339
 340         atomic_long_t swap_readahead_info;
 341 #ifndef CONFIG_MMU
 342         struct vm_region *vm_region;    /* NOMMU mapping region */
 343 #endif
 344 #ifdef CONFIG_NUMA
 345         struct mempolicy *vm_policy;    /* NUMA policy for the VMA */
 346 #endif
 347         struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
 348 } __randomize_layout;
 349
 350 struct core_thread {
 351         struct task_struct *task;
 352         struct core_thread *next;
 353 };
 354
 355 struct core_state {
 356         atomic_t nr_threads;
 357         struct core_thread dumper;
 358         struct completion startup;
 359 };
 360
 361 struct kioctx_table;
 362 struct mm_struct {
 363         struct vm_area_struct *mmap;            /* list of VMAs */
 364         struct rb_root mm_rb;
 365         u32 vmacache_seqnum;                   /* per-thread vmacache */
 366 #ifdef CONFIG_MMU
 367         unsigned long (*get_unmapped_area) (struct file *filp,
 368                                 unsigned long addr, unsigned long len,
 369                                 unsigned long pgoff, unsigned long flags);
 370 #endif
 371         unsigned long mmap_base;                /* base of mmap area */
 372         unsigned long mmap_legacy_base;         /* base of mmap area in bottom-up allocations */
 373 #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
 374         /* Base adresses for compatible mmap() */
 375         unsigned long mmap_compat_base;
 376         unsigned long mmap_compat_legacy_base;
 377 #endif
 378         unsigned long task_size;                /* size of task vm space */
 379         unsigned long highest_vm_end;           /* highest vma end address */
 380         pgd_t * pgd;
 381
 382         /**
 383          * @mm_users: The number of users including userspace.
 384          *
 385          * Use mmget()/mmget_not_zero()/mmput() to modify. When this drops
 386          * to 0 (i.e. when the task exits and there are no other temporary
 387          * reference holders), we also release a reference on @mm_count
 388          * (which may then free the &struct mm_struct if @mm_count also
 389          * drops to 0).
 390          */
 391         atomic_t mm_users;
 392
 393         /**
 394          * @mm_count: The number of references to &struct mm_struct
 395          * (@mm_users count as 1).
 396          *
 397          * Use mmgrab()/mmdrop() to modify. When this drops to 0, the
 398          * &struct mm_struct is freed.
 399          */
 400         atomic_t mm_count;
 401
 402         atomic_long_t nr_ptes;                  /* PTE page table pages */
 403 #if CONFIG_PGTABLE_LEVELS > 2
 404         atomic_long_t nr_pmds;                  /* PMD page table pages */
 405 #endif
 406         int map_count;                          /* number of VMAs */
 407
 408         spinlock_t page_table_lock;             /* Protects page tables and some counters */
 409         struct rw_semaphore mmap_sem;
 410
 411         struct list_head mmlist;                /* List of maybe swapped mm's.  These are globally strung
 412                                                  * together off init_mm.mmlist, and are protected
 413                                                  * by mmlist_lock
 414                                                  */
 415
 416
 417         unsigned long hiwater_rss;      /* High-watermark of RSS usage */
 418         unsigned long hiwater_vm;       /* High-water virtual memory usage */
 419
 420         unsigned long total_vm;         /* Total pages mapped */
 421         unsigned long locked_vm;        /* Pages that have PG_mlocked set */
 422         unsigned long pinned_vm;        /* Refcount permanently increased */
 423         unsigned long data_vm;          /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
 424         unsigned long exec_vm;          /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
 425         unsigned long stack_vm;         /* VM_STACK */
 426         unsigned long def_flags;
 427         unsigned long start_code, end_code, start_data, end_data;
 428         unsigned long start_brk, brk, start_stack;
 429         unsigned long arg_start, arg_end, env_start, env_end;
 430
 431         unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
 432
 433         /*
 434          * Special counters, in some configurations protected by the
 435          * page_table_lock, in other configurations by being atomic.
 436          */
 437         struct mm_rss_stat rss_stat;
 438
 439         struct linux_binfmt *binfmt;
 440
 441         cpumask_var_t cpu_vm_mask_var;
 442
 443         /* Architecture-specific MM context */
 444         mm_context_t context;
 445
 446         unsigned long flags; /* Must use atomic bitops to access the bits */
 447
 448         struct core_state *core_state; /* coredumping support */
 449 #ifdef CONFIG_MEMBARRIER
 450         atomic_t membarrier_state;
 451 #endif
 452 #ifdef CONFIG_AIO
 453         spinlock_t                      ioctx_lock;
 454         struct kioctx_table __rcu       *ioctx_table;
 455 #endif
 456 #ifdef CONFIG_MEMCG
 457         /*
 458          * "owner" points to a task that is regarded as the canonical
 459          * user/owner of this mm. All of the following must be true in
 460          * order for it to be changed:
 461          *
 462          * current == mm->owner
 463          * current->mm != mm
 464          * new_owner->mm == mm
 465          * new_owner->alloc_lock is held
 466          */
 467         struct task_struct __rcu *owner;
 468 #endif
 469         struct user_namespace *user_ns;
 470
 471         /* store ref to file /proc/<pid>/exe symlink points to */
 472         struct file __rcu *exe_file;
 473 #ifdef CONFIG_MMU_NOTIFIER
 474         struct mmu_notifier_mm *mmu_notifier_mm;
 475 #endif
 476 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 477         pgtable_t pmd_huge_pte; /* protected by page_table_lock */
 478 #endif
 479 #ifdef CONFIG_CPUMASK_OFFSTACK
 480         struct cpumask cpumask_allocation;
 481 #endif
 482 #ifdef CONFIG_NUMA_BALANCING
 483         /*
 484          * numa_next_scan is the next time that the PTEs will be marked
 485          * pte_numa. NUMA hinting faults will gather statistics and migrate
 486          * pages to new nodes if necessary.
 487          */
 488         unsigned long numa_next_scan;
 489
 490         /* Restart point for scanning and setting pte_numa */
 491         unsigned long numa_scan_offset;
 492
 493         /* numa_scan_seq prevents two threads setting pte_numa */
 494         int numa_scan_seq;
 495 #endif
 496         /*
 497          * An operation with batched TLB flushing is going on. Anything that
 498          * can move process memory needs to flush the TLB when moving a
 499          * PROT_NONE or PROT_NUMA mapped page.
 500          */
 501         atomic_t tlb_flush_pending;
 502 #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
 503         /* See flush_tlb_batched_pending() */
 504         bool tlb_flush_batched;
 505 #endif
 506         struct uprobes_state uprobes_state;
 507 #ifdef CONFIG_HUGETLB_PAGE
 508         atomic_long_t hugetlb_usage;
 509 #endif
 510         struct work_struct async_put_work;
 511
 512 #if IS_ENABLED(CONFIG_HMM)
 513         /* HMM needs to track a few things per mm */
 514         struct hmm *hmm;
 515 #endif
 516 } __randomize_layout;
 517
 518 extern struct mm_struct init_mm;
 519
 520 static inline void mm_init_cpumask(struct mm_struct *mm)
 521 {
 522 #ifdef CONFIG_CPUMASK_OFFSTACK
 523         mm->cpu_vm_mask_var = &mm->cpumask_allocation;
 524 #endif
 525         cpumask_clear(mm->cpu_vm_mask_var);
 526 }
 527
 528 /* Future-safe accessor for struct mm_struct's cpu_vm_mask. */
 529 static inline cpumask_t *mm_cpumask(struct mm_struct *mm)
 530 {
 531         return mm->cpu_vm_mask_var;
 532 }
 533
 534 struct mmu_gather;
 535 extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
 536                                 unsigned long start, unsigned long end);
 537 extern void tlb_finish_mmu(struct mmu_gather *tlb,
 538                                 unsigned long start, unsigned long end);
 539
 540 static inline void init_tlb_flush_pending(struct mm_struct *mm)
 541 {
 542         atomic_set(&mm->tlb_flush_pending, 0);
 543 }
 544
 545 static inline void inc_tlb_flush_pending(struct mm_struct *mm)
 546 {
 547         atomic_inc(&mm->tlb_flush_pending);
 548         /*
 549          * The only time this value is relevant is when there are indeed pages
 550          * to flush. And we'll only flush pages after changing them, which
 551          * requires the PTL.
 552          *
 553          * So the ordering here is:
 554          *
 555          *      atomic_inc(&mm->tlb_flush_pending);
 556          *      spin_lock(&ptl);
 557          *      ...
 558          *      set_pte_at();
 559          *      spin_unlock(&ptl);
 560          *
 561          *                              spin_lock(&ptl)
 562          *                              mm_tlb_flush_pending();
 563          *                              ....
 564          *                              spin_unlock(&ptl);
 565          *
 566          *      flush_tlb_range();
 567          *      atomic_dec(&mm->tlb_flush_pending);
 568          *
 569          * Where the increment if constrained by the PTL unlock, it thus
 570          * ensures that the increment is visible if the PTE modification is
 571          * visible. After all, if there is no PTE modification, nobody cares
 572          * about TLB flushes either.
 573          *
 574          * This very much relies on users (mm_tlb_flush_pending() and
 575          * mm_tlb_flush_nested()) only caring about _specific_ PTEs (and
 576          * therefore specific PTLs), because with SPLIT_PTE_PTLOCKS and RCpc
 577          * locks (PPC) the unlock of one doesn't order against the lock of
 578          * another PTL.
 579          *
 580          * The decrement is ordered by the flush_tlb_range(), such that
 581          * mm_tlb_flush_pending() will not return false unless all flushes have
 582          * completed.
 583          */
 584 }
 585
 586 static inline void dec_tlb_flush_pending(struct mm_struct *mm)
 587 {
 588         /*
 589          * See inc_tlb_flush_pending().
 590          *
 591          * This cannot be smp_mb__before_atomic() because smp_mb() simply does
 592          * not order against TLB invalidate completion, which is what we need.
 593          *
 594          * Therefore we must rely on tlb_flush_*() to guarantee order.
 595          */
 596         atomic_dec(&mm->tlb_flush_pending);
 597 }
 598
 599 static inline bool mm_tlb_flush_pending(struct mm_struct *mm)
 600 {
 601         /*
 602          * Must be called after having acquired the PTL; orders against that
 603          * PTLs release and therefore ensures that if we observe the modified
 604          * PTE we must also observe the increment from inc_tlb_flush_pending().
 605          *
 606          * That is, it only guarantees to return true if there is a flush
 607          * pending for _this_ PTL.
 608          */
 609         return atomic_read(&mm->tlb_flush_pending);
 610 }
 611
 612 static inline bool mm_tlb_flush_nested(struct mm_struct *mm)
 613 {
 614         /*
 615          * Similar to mm_tlb_flush_pending(), we must have acquired the PTL
 616          * for which there is a TLB flush pending in order to guarantee
 617          * we've seen both that PTE modification and the increment.
 618          *
 619          * (no requirement on actually still holding the PTL, that is irrelevant)
 620          */
 621         return atomic_read(&mm->tlb_flush_pending) > 1;
 622 }
 623
 624 struct vm_fault;
 625
 626 struct vm_special_mapping {
 627         const char *name;       /* The name, e.g. "[vdso]". */
 628
 629         /*
 630          * If .fault is not provided, this points to a
 631          * NULL-terminated array of pages that back the special mapping.
 632          *
 633          * This must not be NULL unless .fault is provided.
 634          */
 635         struct page **pages;
 636
 637         /*
 638          * If non-NULL, then this is called to resolve page faults
 639          * on the special mapping.  If used, .pages is not checked.
 640          */
 641         int (*fault)(const struct vm_special_mapping *sm,
 642                      struct vm_area_struct *vma,
 643                      struct vm_fault *vmf);
 644
 645         int (*mremap)(const struct vm_special_mapping *sm,
 646                      struct vm_area_struct *new_vma);
 647 };
 648
 649 enum tlb_flush_reason {
 650         TLB_FLUSH_ON_TASK_SWITCH,
 651         TLB_REMOTE_SHOOTDOWN,
 652         TLB_LOCAL_SHOOTDOWN,
 653         TLB_LOCAL_MM_SHOOTDOWN,
 654         TLB_REMOTE_SEND_IPI,
 655         NR_TLB_FLUSH_REASONS,
 656 };
 657
 658  /*
 659   * A swap entry has to fit into a "unsigned long", as the entry is hidden
 660   * in the "index" field of the swapper address space.
 661   */
 662 typedef struct {
 663         unsigned long val;
 664 } swp_entry_t;
 665
 666 #endif /* _LINUX_MM_TYPES_H */