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                         union {
 143                                 struct mm_struct *pt_mm; /* x86 pgds only */
 144                                 atomic_t pt_frag_refcount; /* powerpc */
 145                         };
 146 #if ALLOC_SPLIT_PTLOCKS
 147                         spinlock_t *ptl;
 148 #else
 149                         spinlock_t ptl;
 150 #endif
 151                 };
 152                 struct {        /* ZONE_DEVICE pages */
 153                         /** @pgmap: Points to the hosting device page map. */
 154                         struct dev_pagemap *pgmap;
 155                         unsigned long hmm_data;
 156                         unsigned long _zd_pad_1;        /* uses mapping */
 157                 };
 158
 159                 /** @rcu_head: You can use this to free a page by RCU. */
 160                 struct rcu_head rcu_head;
 161         };
 162
 163         union {         /* This union is 4 bytes in size. */
 164                 /*
 165                  * If the page can be mapped to userspace, encodes the number
 166                  * of times this page is referenced by a page table.
 167                  */
 168                 atomic_t _mapcount;
 169
 170                 /*
 171                  * If the page is neither PageSlab nor mappable to userspace,
 172                  * the value stored here may help determine what this page
 173                  * is used for.  See page-flags.h for a list of page types
 174                  * which are currently stored here.
 175                  */
 176                 unsigned int page_type;
 177
 178                 unsigned int active;            /* SLAB */
 179                 int units;                      /* SLOB */
 180         };
 181
 182         /* Usage count. *DO NOT USE DIRECTLY*. See page_ref.h */
 183         atomic_t _refcount;
 184
 185 #ifdef CONFIG_MEMCG
 186         struct mem_cgroup *mem_cgroup;
 187 #endif
 188
 189         /*
 190          * On machines where all RAM is mapped into kernel address space,
 191          * we can simply calculate the virtual address. On machines with
 192          * highmem some memory is mapped into kernel virtual memory
 193          * dynamically, so we need a place to store that address.
 194          * Note that this field could be 16 bits on x86 ... ;)
 195          *
 196          * Architectures with slow multiplication can define
 197          * WANT_PAGE_VIRTUAL in asm/page.h
 198          */
 199 #if defined(WANT_PAGE_VIRTUAL)
 200         void *virtual;                  /* Kernel virtual address (NULL if
 201                                            not kmapped, ie. highmem) */
 202 #endif /* WANT_PAGE_VIRTUAL */
 203
 204 #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
 205         int _last_cpupid;
 206 #endif
 207 } _struct_page_alignment;
 208
 209 #define PAGE_FRAG_CACHE_MAX_SIZE        __ALIGN_MASK(32768, ~PAGE_MASK)
 210 #define PAGE_FRAG_CACHE_MAX_ORDER       get_order(PAGE_FRAG_CACHE_MAX_SIZE)
 211
 212 struct page_frag_cache {
 213         void * va;
 214 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
 215         __u16 offset;
 216         __u16 size;
 217 #else
 218         __u32 offset;
 219 #endif
 220         /* we maintain a pagecount bias, so that we dont dirty cache line
 221          * containing page->_refcount every time we allocate a fragment.
 222          */
 223         unsigned int            pagecnt_bias;
 224         bool pfmemalloc;
 225 };
 226
 227 typedef unsigned long vm_flags_t;
 228
 229 /*
 230  * A region containing a mapping of a non-memory backed file under NOMMU
 231  * conditions.  These are held in a global tree and are pinned by the VMAs that
 232  * map parts of them.
 233  */
 234 struct vm_region {
 235         struct rb_node  vm_rb;          /* link in global region tree */
 236         vm_flags_t      vm_flags;       /* VMA vm_flags */
 237         unsigned long   vm_start;       /* start address of region */
 238         unsigned long   vm_end;         /* region initialised to here */
 239         unsigned long   vm_top;         /* region allocated to here */
 240         unsigned long   vm_pgoff;       /* the offset in vm_file corresponding to vm_start */
 241         struct file     *vm_file;       /* the backing file or NULL */
 242
 243         int             vm_usage;       /* region usage count (access under nommu_region_sem) */
 244         bool            vm_icache_flushed : 1; /* true if the icache has been flushed for
 245                                                 * this region */
 246 };
 247
 248 #ifdef CONFIG_USERFAULTFD
 249 #define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) { NULL, })
 250 struct vm_userfaultfd_ctx {
 251         struct userfaultfd_ctx *ctx;
 252 };
 253 #else /* CONFIG_USERFAULTFD */
 254 #define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) {})
 255 struct vm_userfaultfd_ctx {};
 256 #endif /* CONFIG_USERFAULTFD */
 257
 258 /*
 259  * This struct defines a memory VMM memory area. There is one of these
 260  * per VM-area/task.  A VM area is any part of the process virtual memory
 261  * space that has a special rule for the page-fault handlers (ie a shared
 262  * library, the executable area etc).
 263  */
 264 struct vm_area_struct {
 265         /* The first cache line has the info for VMA tree walking. */
 266
 267         unsigned long vm_start;         /* Our start address within vm_mm. */
 268         unsigned long vm_end;           /* The first byte after our end address
 269                                            within vm_mm. */
 270
 271         /* linked list of VM areas per task, sorted by address */
 272         struct vm_area_struct *vm_next, *vm_prev;
 273
 274         struct rb_node vm_rb;
 275
 276         /*
 277          * Largest free memory gap in bytes to the left of this VMA.
 278          * Either between this VMA and vma->vm_prev, or between one of the
 279          * VMAs below us in the VMA rbtree and its ->vm_prev. This helps
 280          * get_unmapped_area find a free area of the right size.
 281          */
 282         unsigned long rb_subtree_gap;
 283
 284         /* Second cache line starts here. */
 285
 286         struct mm_struct *vm_mm;        /* The address space we belong to. */
 287         pgprot_t vm_page_prot;          /* Access permissions of this VMA. */
 288         unsigned long vm_flags;         /* Flags, see mm.h. */
 289
 290         /*
 291          * For areas with an address space and backing store,
 292          * linkage into the address_space->i_mmap interval tree.
 293          */
 294         struct {
 295                 struct rb_node rb;
 296                 unsigned long rb_subtree_last;
 297         } shared;
 298
 299         /*
 300          * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
 301          * list, after a COW of one of the file pages.  A MAP_SHARED vma
 302          * can only be in the i_mmap tree.  An anonymous MAP_PRIVATE, stack
 303          * or brk vma (with NULL file) can only be in an anon_vma list.
 304          */
 305         struct list_head anon_vma_chain; /* Serialized by mmap_sem &
 306                                           * page_table_lock */
 307         struct anon_vma *anon_vma;      /* Serialized by page_table_lock */
 308
 309         /* Function pointers to deal with this struct. */
 310         const struct vm_operations_struct *vm_ops;
 311
 312         /* Information about our backing store: */
 313         unsigned long vm_pgoff;         /* Offset (within vm_file) in PAGE_SIZE
 314                                            units */
 315         struct file * vm_file;          /* File we map to (can be NULL). */
 316         void * vm_private_data;         /* was vm_pte (shared mem) */
 317
 318         atomic_long_t swap_readahead_info;
 319 #ifndef CONFIG_MMU
 320         struct vm_region *vm_region;    /* NOMMU mapping region */
 321 #endif
 322 #ifdef CONFIG_NUMA
 323         struct mempolicy *vm_policy;    /* NUMA policy for the VMA */
 324 #endif
 325         struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
 326 } __randomize_layout;
 327
 328 struct core_thread {
 329         struct task_struct *task;
 330         struct core_thread *next;
 331 };
 332
 333 struct core_state {
 334         atomic_t nr_threads;
 335         struct core_thread dumper;
 336         struct completion startup;
 337 };
 338
 339 struct kioctx_table;
 340 struct mm_struct {
 341         struct {
 342                 struct vm_area_struct *mmap;            /* list of VMAs */
 343                 struct rb_root mm_rb;
 344                 u64 vmacache_seqnum;                   /* per-thread vmacache */
 345 #ifdef CONFIG_MMU
 346                 unsigned long (*get_unmapped_area) (struct file *filp,
 347                                 unsigned long addr, unsigned long len,
 348                                 unsigned long pgoff, unsigned long flags);
 349 #endif
 350                 unsigned long mmap_base;        /* base of mmap area */
 351                 unsigned long mmap_legacy_base; /* base of mmap area in bottom-up allocations */
 352 #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
 353                 /* Base adresses for compatible mmap() */
 354                 unsigned long mmap_compat_base;
 355                 unsigned long mmap_compat_legacy_base;
 356 #endif
 357                 unsigned long task_size;        /* size of task vm space */
 358                 unsigned long highest_vm_end;   /* highest vma end address */
 359                 pgd_t * pgd;
 360
 361                 /**
 362                  * @mm_users: The number of users including userspace.
 363                  *
 364                  * Use mmget()/mmget_not_zero()/mmput() to modify. When this
 365                  * drops to 0 (i.e. when the task exits and there are no other
 366                  * temporary reference holders), we also release a reference on
 367                  * @mm_count (which may then free the &struct mm_struct if
 368                  * @mm_count also drops to 0).
 369                  */
 370                 atomic_t mm_users;
 371
 372                 /**
 373                  * @mm_count: The number of references to &struct mm_struct
 374                  * (@mm_users count as 1).
 375                  *
 376                  * Use mmgrab()/mmdrop() to modify. When this drops to 0, the
 377                  * &struct mm_struct is freed.
 378                  */
 379                 atomic_t mm_count;
 380
 381 #ifdef CONFIG_MMU
 382                 atomic_long_t pgtables_bytes;   /* PTE page table pages */
 383 #endif
 384                 int map_count;                  /* number of VMAs */
 385
 386                 spinlock_t page_table_lock; /* Protects page tables and some
 387                                              * counters
 388                                              */
 389                 struct rw_semaphore mmap_sem;
 390
 391                 struct list_head mmlist; /* List of maybe swapped mm's. These
 392                                           * are globally strung together off
 393                                           * init_mm.mmlist, and are protected
 394                                           * by mmlist_lock
 395                                           */
 396
 397
 398                 unsigned long hiwater_rss; /* High-watermark of RSS usage */
 399                 unsigned long hiwater_vm;  /* High-water virtual memory usage */
 400
 401                 unsigned long total_vm;    /* Total pages mapped */
 402                 unsigned long locked_vm;   /* Pages that have PG_mlocked set */
 403                 unsigned long pinned_vm;   /* Refcount permanently increased */
 404                 unsigned long data_vm;     /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
 405                 unsigned long exec_vm;     /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
 406                 unsigned long stack_vm;    /* VM_STACK */
 407                 unsigned long def_flags;
 408
 409                 spinlock_t arg_lock; /* protect the below fields */
 410                 unsigned long start_code, end_code, start_data, end_data;
 411                 unsigned long start_brk, brk, start_stack;
 412                 unsigned long arg_start, arg_end, env_start, env_end;
 413
 414                 unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
 415
 416                 /*
 417                  * Special counters, in some configurations protected by the
 418                  * page_table_lock, in other configurations by being atomic.
 419                  */
 420                 struct mm_rss_stat rss_stat;
 421
 422                 struct linux_binfmt *binfmt;
 423
 424                 /* Architecture-specific MM context */
 425                 mm_context_t context;
 426
 427                 unsigned long flags; /* Must use atomic bitops to access */
 428
 429                 struct core_state *core_state; /* coredumping support */
 430 #ifdef CONFIG_MEMBARRIER
 431                 atomic_t membarrier_state;
 432 #endif
 433 #ifdef CONFIG_AIO
 434                 spinlock_t                      ioctx_lock;
 435                 struct kioctx_table __rcu       *ioctx_table;
 436 #endif
 437 #ifdef CONFIG_MEMCG
 438                 /*
 439                  * "owner" points to a task that is regarded as the canonical
 440                  * user/owner of this mm. All of the following must be true in
 441                  * order for it to be changed:
 442                  *
 443                  * current == mm->owner
 444                  * current->mm != mm
 445                  * new_owner->mm == mm
 446                  * new_owner->alloc_lock is held
 447                  */
 448                 struct task_struct __rcu *owner;
 449 #endif
 450                 struct user_namespace *user_ns;
 451
 452                 /* store ref to file /proc/<pid>/exe symlink points to */
 453                 struct file __rcu *exe_file;
 454 #ifdef CONFIG_MMU_NOTIFIER
 455                 struct mmu_notifier_mm *mmu_notifier_mm;
 456 #endif
 457 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 458                 pgtable_t pmd_huge_pte; /* protected by page_table_lock */
 459 #endif
 460 #ifdef CONFIG_NUMA_BALANCING
 461                 /*
 462                  * numa_next_scan is the next time that the PTEs will be marked
 463                  * pte_numa. NUMA hinting faults will gather statistics and
 464                  * migrate pages to new nodes if necessary.
 465                  */
 466                 unsigned long numa_next_scan;
 467
 468                 /* Restart point for scanning and setting pte_numa */
 469                 unsigned long numa_scan_offset;
 470
 471                 /* numa_scan_seq prevents two threads setting pte_numa */
 472                 int numa_scan_seq;
 473 #endif
 474                 /*
 475                  * An operation with batched TLB flushing is going on. Anything
 476                  * that can move process memory needs to flush the TLB when
 477                  * moving a PROT_NONE or PROT_NUMA mapped page.
 478                  */
 479                 atomic_t tlb_flush_pending;
 480 #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
 481                 /* See flush_tlb_batched_pending() */
 482                 bool tlb_flush_batched;
 483 #endif
 484                 struct uprobes_state uprobes_state;
 485 #ifdef CONFIG_HUGETLB_PAGE
 486                 atomic_long_t hugetlb_usage;
 487 #endif
 488                 struct work_struct async_put_work;
 489
 490 #if IS_ENABLED(CONFIG_HMM)
 491                 /* HMM needs to track a few things per mm */
 492                 struct hmm *hmm;
 493 #endif
 494         } __randomize_layout;
 495
 496         /*
 497          * The mm_cpumask needs to be at the end of mm_struct, because it
 498          * is dynamically sized based on nr_cpu_ids.
 499          */
 500         unsigned long cpu_bitmap[];
 501 };
 502
 503 extern struct mm_struct init_mm;
 504
 505 /* Pointer magic because the dynamic array size confuses some compilers. */
 506 static inline void mm_init_cpumask(struct mm_struct *mm)
 507 {
 508         unsigned long cpu_bitmap = (unsigned long)mm;
 509
 510         cpu_bitmap += offsetof(struct mm_struct, cpu_bitmap);
 511         cpumask_clear((struct cpumask *)cpu_bitmap);
 512 }
 513
 514 /* Future-safe accessor for struct mm_struct's cpu_vm_mask. */
 515 static inline cpumask_t *mm_cpumask(struct mm_struct *mm)
 516 {
 517         return (struct cpumask *)&mm->cpu_bitmap;
 518 }
 519
 520 struct mmu_gather;
 521 extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
 522                                 unsigned long start, unsigned long end);
 523 extern void tlb_finish_mmu(struct mmu_gather *tlb,
 524                                 unsigned long start, unsigned long end);
 525
 526 static inline void init_tlb_flush_pending(struct mm_struct *mm)
 527 {
 528         atomic_set(&mm->tlb_flush_pending, 0);
 529 }
 530
 531 static inline void inc_tlb_flush_pending(struct mm_struct *mm)
 532 {
 533         atomic_inc(&mm->tlb_flush_pending);
 534         /*
 535          * The only time this value is relevant is when there are indeed pages
 536          * to flush. And we'll only flush pages after changing them, which
 537          * requires the PTL.
 538          *
 539          * So the ordering here is:
 540          *
 541          *      atomic_inc(&mm->tlb_flush_pending);
 542          *      spin_lock(&ptl);
 543          *      ...
 544          *      set_pte_at();
 545          *      spin_unlock(&ptl);
 546          *
 547          *                              spin_lock(&ptl)
 548          *                              mm_tlb_flush_pending();
 549          *                              ....
 550          *                              spin_unlock(&ptl);
 551          *
 552          *      flush_tlb_range();
 553          *      atomic_dec(&mm->tlb_flush_pending);
 554          *
 555          * Where the increment if constrained by the PTL unlock, it thus
 556          * ensures that the increment is visible if the PTE modification is
 557          * visible. After all, if there is no PTE modification, nobody cares
 558          * about TLB flushes either.
 559          *
 560          * This very much relies on users (mm_tlb_flush_pending() and
 561          * mm_tlb_flush_nested()) only caring about _specific_ PTEs (and
 562          * therefore specific PTLs), because with SPLIT_PTE_PTLOCKS and RCpc
 563          * locks (PPC) the unlock of one doesn't order against the lock of
 564          * another PTL.
 565          *
 566          * The decrement is ordered by the flush_tlb_range(), such that
 567          * mm_tlb_flush_pending() will not return false unless all flushes have
 568          * completed.
 569          */
 570 }
 571
 572 static inline void dec_tlb_flush_pending(struct mm_struct *mm)
 573 {
 574         /*
 575          * See inc_tlb_flush_pending().
 576          *
 577          * This cannot be smp_mb__before_atomic() because smp_mb() simply does
 578          * not order against TLB invalidate completion, which is what we need.
 579          *
 580          * Therefore we must rely on tlb_flush_*() to guarantee order.
 581          */
 582         atomic_dec(&mm->tlb_flush_pending);
 583 }
 584
 585 static inline bool mm_tlb_flush_pending(struct mm_struct *mm)
 586 {
 587         /*
 588          * Must be called after having acquired the PTL; orders against that
 589          * PTLs release and therefore ensures that if we observe the modified
 590          * PTE we must also observe the increment from inc_tlb_flush_pending().
 591          *
 592          * That is, it only guarantees to return true if there is a flush
 593          * pending for _this_ PTL.
 594          */
 595         return atomic_read(&mm->tlb_flush_pending);
 596 }
 597
 598 static inline bool mm_tlb_flush_nested(struct mm_struct *mm)
 599 {
 600         /*
 601          * Similar to mm_tlb_flush_pending(), we must have acquired the PTL
 602          * for which there is a TLB flush pending in order to guarantee
 603          * we've seen both that PTE modification and the increment.
 604          *
 605          * (no requirement on actually still holding the PTL, that is irrelevant)
 606          */
 607         return atomic_read(&mm->tlb_flush_pending) > 1;
 608 }
 609
 610 struct vm_fault;
 611
 612 struct vm_special_mapping {
 613         const char *name;       /* The name, e.g. "[vdso]". */
 614
 615         /*
 616          * If .fault is not provided, this points to a
 617          * NULL-terminated array of pages that back the special mapping.
 618          *
 619          * This must not be NULL unless .fault is provided.
 620          */
 621         struct page **pages;
 622
 623         /*
 624          * If non-NULL, then this is called to resolve page faults
 625          * on the special mapping.  If used, .pages is not checked.
 626          */
 627         vm_fault_t (*fault)(const struct vm_special_mapping *sm,
 628                                 struct vm_area_struct *vma,
 629                                 struct vm_fault *vmf);
 630
 631         int (*mremap)(const struct vm_special_mapping *sm,
 632                      struct vm_area_struct *new_vma);
 633 };
 634
 635 enum tlb_flush_reason {
 636         TLB_FLUSH_ON_TASK_SWITCH,
 637         TLB_REMOTE_SHOOTDOWN,
 638         TLB_LOCAL_SHOOTDOWN,
 639         TLB_LOCAL_MM_SHOOTDOWN,
 640         TLB_REMOTE_SEND_IPI,
 641         NR_TLB_FLUSH_REASONS,
 642 };
 643
 644  /*
 645   * A swap entry has to fit into a "unsigned long", as the entry is hidden
 646   * in the "index" field of the swapper address space.
 647   */
 648 typedef struct {
 649         unsigned long val;
 650 } swp_entry_t;
 651
 652 #endif /* _LINUX_MM_TYPES_H */