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. If you allocate the page using alloc_pages(), you
  35  * can use some of the space in struct page for your own purposes.
  36  *
  37  * Pages that were once in the page cache may be found under the RCU lock
  38  * even after they have been recycled to a different purpose.  The page
  39  * cache reads and writes some of the fields in struct page to pin the
  40  * page before checking that it's still in the page cache.  It is vital
  41  * that all users of struct page:
  42  * 1. Use the first word as PageFlags.
  43  * 2. Clear or preserve bit 0 of page->compound_head.  It is used as
  44  *    PageTail for compound pages, and the page cache must not see false
  45  *    positives.  Some users put a pointer here (guaranteed to be at least
  46  *    4-byte aligned), other users avoid using the field altogether.
  47  * 3. page->_refcount must either not be used, or must be used in such a
  48  *    way that other CPUs temporarily incrementing and then decrementing the
  49  *    refcount does not cause problems.  On receiving the page from
  50  *    alloc_pages(), the refcount will be positive.
  51  * 4. Either preserve page->_mapcount or restore it to -1 before freeing it.
  52  *
  53  * If you allocate pages of order > 0, you can use the fields in the struct
  54  * page associated with each page, but bear in mind that the pages may have
  55  * been inserted individually into the page cache, so you must use the above
  56  * four fields in a compatible way for each struct page.
  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 #if defined(CONFIG_HAVE_CMPXCHG_DOUBLE)
  67 #define _slub_counter_t         unsigned long
  68 #else
  69 #define _slub_counter_t         unsigned int
  70 #endif
  71 #else /* !CONFIG_HAVE_ALIGNED_STRUCT_PAGE */
  72 #define _struct_page_alignment
  73 #define _slub_counter_t         unsigned int
  74 #endif /* !CONFIG_HAVE_ALIGNED_STRUCT_PAGE */
  75
  76 struct page {
  77         /* First double word block */
  78         unsigned long flags;            /* Atomic flags, some possibly
  79                                          * updated asynchronously */
  80         union {
  81                 /* See page-flags.h for the definition of PAGE_MAPPING_FLAGS */
  82                 struct address_space *mapping;
  83
  84                 void *s_mem;                    /* slab first object */
  85                 atomic_t compound_mapcount;     /* first tail page */
  86                 /* page_deferred_list().next     -- second tail page */
  87         };
  88
  89         /* Second double word */
  90         union {
  91                 pgoff_t index;          /* Our offset within mapping. */
  92                 void *freelist;         /* sl[aou]b first free object */
  93                 /* page_deferred_list().prev    -- second tail page */
  94         };
  95
  96         union {
  97                 _slub_counter_t counters;
  98                 unsigned int active;            /* SLAB */
  99                 struct {                        /* SLUB */
 100                         unsigned inuse:16;
 101                         unsigned objects:15;
 102                         unsigned frozen:1;
 103                 };
 104                 int units;                      /* SLOB */
 105
 106                 struct {                        /* Page cache */
 107                         /*
 108                          * Count of ptes mapped in mms, to show when
 109                          * page is mapped & limit reverse map searches.
 110                          *
 111                          * Extra information about page type may be
 112                          * stored here for pages that are never mapped,
 113                          * in which case the value MUST BE <= -2.
 114                          * See page-flags.h for more details.
 115                          */
 116                         atomic_t _mapcount;
 117
 118                         /*
 119                          * Usage count, *USE WRAPPER FUNCTION* when manual
 120                          * accounting. See page_ref.h
 121                          */
 122                         atomic_t _refcount;
 123                 };
 124         };
 125
 126         /*
 127          * WARNING: bit 0 of the first word encode PageTail(). That means
 128          * the rest users of the storage space MUST NOT use the bit to
 129          * avoid collision and false-positive PageTail().
 130          */
 131         union {
 132                 struct list_head lru;   /* Pageout list, eg. active_list
 133                                          * protected by zone_lru_lock !
 134                                          * Can be used as a generic list
 135                                          * by the page owner.
 136                                          */
 137                 struct dev_pagemap *pgmap; /* ZONE_DEVICE pages are never on an
 138                                             * lru or handled by a slab
 139                                             * allocator, this points to the
 140                                             * hosting device page map.
 141                                             */
 142                 struct {                /* slub per cpu partial pages */
 143                         struct page *next;      /* Next partial slab */
 144 #ifdef CONFIG_64BIT
 145                         int pages;      /* Nr of partial slabs left */
 146                         int pobjects;   /* Approximate # of objects */
 147 #else
 148                         short int pages;
 149                         short int pobjects;
 150 #endif
 151                 };
 152
 153                 struct rcu_head rcu_head;       /* Used by SLAB
 154                                                  * when destroying via RCU
 155                                                  */
 156                 /* Tail pages of compound page */
 157                 struct {
 158                         unsigned long compound_head; /* If bit zero is set */
 159
 160                         /* First tail page only */
 161                         unsigned char compound_dtor;
 162                         unsigned char compound_order;
 163                         /* two/six bytes available here */
 164                 };
 165
 166 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS
 167                 struct {
 168                         unsigned long __pad;    /* do not overlay pmd_huge_pte
 169                                                  * with compound_head to avoid
 170                                                  * possible bit 0 collision.
 171                                                  */
 172                         pgtable_t pmd_huge_pte; /* protected by page->ptl */
 173                 };
 174 #endif
 175         };
 176
 177         union {
 178                 /*
 179                  * Mapping-private opaque data:
 180                  * Usually used for buffer_heads if PagePrivate
 181                  * Used for swp_entry_t if PageSwapCache
 182                  * Indicates order in the buddy system if PageBuddy
 183                  */
 184                 unsigned long private;
 185 #if USE_SPLIT_PTE_PTLOCKS
 186 #if ALLOC_SPLIT_PTLOCKS
 187                 spinlock_t *ptl;
 188 #else
 189                 spinlock_t ptl;
 190 #endif
 191 #endif
 192                 struct kmem_cache *slab_cache;  /* SL[AU]B: Pointer to slab */
 193         };
 194
 195 #ifdef CONFIG_MEMCG
 196         struct mem_cgroup *mem_cgroup;
 197 #endif
 198
 199         /*
 200          * On machines where all RAM is mapped into kernel address space,
 201          * we can simply calculate the virtual address. On machines with
 202          * highmem some memory is mapped into kernel virtual memory
 203          * dynamically, so we need a place to store that address.
 204          * Note that this field could be 16 bits on x86 ... ;)
 205          *
 206          * Architectures with slow multiplication can define
 207          * WANT_PAGE_VIRTUAL in asm/page.h
 208          */
 209 #if defined(WANT_PAGE_VIRTUAL)
 210         void *virtual;                  /* Kernel virtual address (NULL if
 211                                            not kmapped, ie. highmem) */
 212 #endif /* WANT_PAGE_VIRTUAL */
 213
 214 #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
 215         int _last_cpupid;
 216 #endif
 217 } _struct_page_alignment;
 218
 219 #define PAGE_FRAG_CACHE_MAX_SIZE        __ALIGN_MASK(32768, ~PAGE_MASK)
 220 #define PAGE_FRAG_CACHE_MAX_ORDER       get_order(PAGE_FRAG_CACHE_MAX_SIZE)
 221
 222 struct page_frag_cache {
 223         void * va;
 224 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
 225         __u16 offset;
 226         __u16 size;
 227 #else
 228         __u32 offset;
 229 #endif
 230         /* we maintain a pagecount bias, so that we dont dirty cache line
 231          * containing page->_refcount every time we allocate a fragment.
 232          */
 233         unsigned int            pagecnt_bias;
 234         bool pfmemalloc;
 235 };
 236
 237 typedef unsigned long vm_flags_t;
 238
 239 /*
 240  * A region containing a mapping of a non-memory backed file under NOMMU
 241  * conditions.  These are held in a global tree and are pinned by the VMAs that
 242  * map parts of them.
 243  */
 244 struct vm_region {
 245         struct rb_node  vm_rb;          /* link in global region tree */
 246         vm_flags_t      vm_flags;       /* VMA vm_flags */
 247         unsigned long   vm_start;       /* start address of region */
 248         unsigned long   vm_end;         /* region initialised to here */
 249         unsigned long   vm_top;         /* region allocated to here */
 250         unsigned long   vm_pgoff;       /* the offset in vm_file corresponding to vm_start */
 251         struct file     *vm_file;       /* the backing file or NULL */
 252
 253         int             vm_usage;       /* region usage count (access under nommu_region_sem) */
 254         bool            vm_icache_flushed : 1; /* true if the icache has been flushed for
 255                                                 * this region */
 256 };
 257
 258 #ifdef CONFIG_USERFAULTFD
 259 #define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) { NULL, })
 260 struct vm_userfaultfd_ctx {
 261         struct userfaultfd_ctx *ctx;
 262 };
 263 #else /* CONFIG_USERFAULTFD */
 264 #define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) {})
 265 struct vm_userfaultfd_ctx {};
 266 #endif /* CONFIG_USERFAULTFD */
 267
 268 /*
 269  * This struct defines a memory VMM memory area. There is one of these
 270  * per VM-area/task.  A VM area is any part of the process virtual memory
 271  * space that has a special rule for the page-fault handlers (ie a shared
 272  * library, the executable area etc).
 273  */
 274 struct vm_area_struct {
 275         /* The first cache line has the info for VMA tree walking. */
 276
 277         unsigned long vm_start;         /* Our start address within vm_mm. */
 278         unsigned long vm_end;           /* The first byte after our end address
 279                                            within vm_mm. */
 280
 281         /* linked list of VM areas per task, sorted by address */
 282         struct vm_area_struct *vm_next, *vm_prev;
 283
 284         struct rb_node vm_rb;
 285
 286         /*
 287          * Largest free memory gap in bytes to the left of this VMA.
 288          * Either between this VMA and vma->vm_prev, or between one of the
 289          * VMAs below us in the VMA rbtree and its ->vm_prev. This helps
 290          * get_unmapped_area find a free area of the right size.
 291          */
 292         unsigned long rb_subtree_gap;
 293
 294         /* Second cache line starts here. */
 295
 296         struct mm_struct *vm_mm;        /* The address space we belong to. */
 297         pgprot_t vm_page_prot;          /* Access permissions of this VMA. */
 298         unsigned long vm_flags;         /* Flags, see mm.h. */
 299
 300         /*
 301          * For areas with an address space and backing store,
 302          * linkage into the address_space->i_mmap interval tree.
 303          */
 304         struct {
 305                 struct rb_node rb;
 306                 unsigned long rb_subtree_last;
 307         } shared;
 308
 309         /*
 310          * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
 311          * list, after a COW of one of the file pages.  A MAP_SHARED vma
 312          * can only be in the i_mmap tree.  An anonymous MAP_PRIVATE, stack
 313          * or brk vma (with NULL file) can only be in an anon_vma list.
 314          */
 315         struct list_head anon_vma_chain; /* Serialized by mmap_sem &
 316                                           * page_table_lock */
 317         struct anon_vma *anon_vma;      /* Serialized by page_table_lock */
 318
 319         /* Function pointers to deal with this struct. */
 320         const struct vm_operations_struct *vm_ops;
 321
 322         /* Information about our backing store: */
 323         unsigned long vm_pgoff;         /* Offset (within vm_file) in PAGE_SIZE
 324                                            units */
 325         struct file * vm_file;          /* File we map to (can be NULL). */
 326         void * vm_private_data;         /* was vm_pte (shared mem) */
 327
 328         atomic_long_t swap_readahead_info;
 329 #ifndef CONFIG_MMU
 330         struct vm_region *vm_region;    /* NOMMU mapping region */
 331 #endif
 332 #ifdef CONFIG_NUMA
 333         struct mempolicy *vm_policy;    /* NUMA policy for the VMA */
 334 #endif
 335         struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
 336 } __randomize_layout;
 337
 338 struct core_thread {
 339         struct task_struct *task;
 340         struct core_thread *next;
 341 };
 342
 343 struct core_state {
 344         atomic_t nr_threads;
 345         struct core_thread dumper;
 346         struct completion startup;
 347 };
 348
 349 struct kioctx_table;
 350 struct mm_struct {
 351         struct vm_area_struct *mmap;            /* list of VMAs */
 352         struct rb_root mm_rb;
 353         u32 vmacache_seqnum;                   /* per-thread vmacache */
 354 #ifdef CONFIG_MMU
 355         unsigned long (*get_unmapped_area) (struct file *filp,
 356                                 unsigned long addr, unsigned long len,
 357                                 unsigned long pgoff, unsigned long flags);
 358 #endif
 359         unsigned long mmap_base;                /* base of mmap area */
 360         unsigned long mmap_legacy_base;         /* base of mmap area in bottom-up allocations */
 361 #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
 362         /* Base adresses for compatible mmap() */
 363         unsigned long mmap_compat_base;
 364         unsigned long mmap_compat_legacy_base;
 365 #endif
 366         unsigned long task_size;                /* size of task vm space */
 367         unsigned long highest_vm_end;           /* highest vma end address */
 368         pgd_t * pgd;
 369
 370         /**
 371          * @mm_users: The number of users including userspace.
 372          *
 373          * Use mmget()/mmget_not_zero()/mmput() to modify. When this drops
 374          * to 0 (i.e. when the task exits and there are no other temporary
 375          * reference holders), we also release a reference on @mm_count
 376          * (which may then free the &struct mm_struct if @mm_count also
 377          * drops to 0).
 378          */
 379         atomic_t mm_users;
 380
 381         /**
 382          * @mm_count: The number of references to &struct mm_struct
 383          * (@mm_users count as 1).
 384          *
 385          * Use mmgrab()/mmdrop() to modify. When this drops to 0, the
 386          * &struct mm_struct is freed.
 387          */
 388         atomic_t mm_count;
 389
 390 #ifdef CONFIG_MMU
 391         atomic_long_t pgtables_bytes;           /* PTE page table pages */
 392 #endif
 393         int map_count;                          /* number of VMAs */
 394
 395         spinlock_t page_table_lock;             /* Protects page tables and some counters */
 396         struct rw_semaphore mmap_sem;
 397
 398         struct list_head mmlist;                /* List of maybe swapped mm's.  These are globally strung
 399                                                  * together off init_mm.mmlist, and are protected
 400                                                  * by mmlist_lock
 401                                                  */
 402
 403
 404         unsigned long hiwater_rss;      /* High-watermark of RSS usage */
 405         unsigned long hiwater_vm;       /* High-water virtual memory usage */
 406
 407         unsigned long total_vm;         /* Total pages mapped */
 408         unsigned long locked_vm;        /* Pages that have PG_mlocked set */
 409         unsigned long pinned_vm;        /* Refcount permanently increased */
 410         unsigned long data_vm;          /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
 411         unsigned long exec_vm;          /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
 412         unsigned long stack_vm;         /* VM_STACK */
 413         unsigned long def_flags;
 414         unsigned long start_code, end_code, start_data, end_data;
 415         unsigned long start_brk, brk, start_stack;
 416         unsigned long arg_start, arg_end, env_start, env_end;
 417
 418         unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
 419
 420         /*
 421          * Special counters, in some configurations protected by the
 422          * page_table_lock, in other configurations by being atomic.
 423          */
 424         struct mm_rss_stat rss_stat;
 425
 426         struct linux_binfmt *binfmt;
 427
 428         cpumask_var_t cpu_vm_mask_var;
 429
 430         /* Architecture-specific MM context */
 431         mm_context_t context;
 432
 433         unsigned long flags; /* Must use atomic bitops to access the bits */
 434
 435         struct core_state *core_state; /* coredumping support */
 436 #ifdef CONFIG_MEMBARRIER
 437         atomic_t membarrier_state;
 438 #endif
 439 #ifdef CONFIG_AIO
 440         spinlock_t                      ioctx_lock;
 441         struct kioctx_table __rcu       *ioctx_table;
 442 #endif
 443 #ifdef CONFIG_MEMCG
 444         /*
 445          * "owner" points to a task that is regarded as the canonical
 446          * user/owner of this mm. All of the following must be true in
 447          * order for it to be changed:
 448          *
 449          * current == mm->owner
 450          * current->mm != mm
 451          * new_owner->mm == mm
 452          * new_owner->alloc_lock is held
 453          */
 454         struct task_struct __rcu *owner;
 455 #endif
 456         struct user_namespace *user_ns;
 457
 458         /* store ref to file /proc/<pid>/exe symlink points to */
 459         struct file __rcu *exe_file;
 460 #ifdef CONFIG_MMU_NOTIFIER
 461         struct mmu_notifier_mm *mmu_notifier_mm;
 462 #endif
 463 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
 464         pgtable_t pmd_huge_pte; /* protected by page_table_lock */
 465 #endif
 466 #ifdef CONFIG_CPUMASK_OFFSTACK
 467         struct cpumask cpumask_allocation;
 468 #endif
 469 #ifdef CONFIG_NUMA_BALANCING
 470         /*
 471          * numa_next_scan is the next time that the PTEs will be marked
 472          * pte_numa. NUMA hinting faults will gather statistics and migrate
 473          * pages to new nodes if necessary.
 474          */
 475         unsigned long numa_next_scan;
 476
 477         /* Restart point for scanning and setting pte_numa */
 478         unsigned long numa_scan_offset;
 479
 480         /* numa_scan_seq prevents two threads setting pte_numa */
 481         int numa_scan_seq;
 482 #endif
 483         /*
 484          * An operation with batched TLB flushing is going on. Anything that
 485          * can move process memory needs to flush the TLB when moving a
 486          * PROT_NONE or PROT_NUMA mapped page.
 487          */
 488         atomic_t tlb_flush_pending;
 489 #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
 490         /* See flush_tlb_batched_pending() */
 491         bool tlb_flush_batched;
 492 #endif
 493         struct uprobes_state uprobes_state;
 494 #ifdef CONFIG_HUGETLB_PAGE
 495         atomic_long_t hugetlb_usage;
 496 #endif
 497         struct work_struct async_put_work;
 498
 499 #if IS_ENABLED(CONFIG_HMM)
 500         /* HMM needs to track a few things per mm */
 501         struct hmm *hmm;
 502 #endif
 503 } __randomize_layout;
 504
 505 extern struct mm_struct init_mm;
 506
 507 static inline void mm_init_cpumask(struct mm_struct *mm)
 508 {
 509 #ifdef CONFIG_CPUMASK_OFFSTACK
 510         mm->cpu_vm_mask_var = &mm->cpumask_allocation;
 511 #endif
 512         cpumask_clear(mm->cpu_vm_mask_var);
 513 }
 514
 515 /* Future-safe accessor for struct mm_struct's cpu_vm_mask. */
 516 static inline cpumask_t *mm_cpumask(struct mm_struct *mm)
 517 {
 518         return mm->cpu_vm_mask_var;
 519 }
 520
 521 struct mmu_gather;
 522 extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
 523                                 unsigned long start, unsigned long end);
 524 extern void tlb_finish_mmu(struct mmu_gather *tlb,
 525                                 unsigned long start, unsigned long end);
 526
 527 static inline void init_tlb_flush_pending(struct mm_struct *mm)
 528 {
 529         atomic_set(&mm->tlb_flush_pending, 0);
 530 }
 531
 532 static inline void inc_tlb_flush_pending(struct mm_struct *mm)
 533 {
 534         atomic_inc(&mm->tlb_flush_pending);
 535         /*
 536          * The only time this value is relevant is when there are indeed pages
 537          * to flush. And we'll only flush pages after changing them, which
 538          * requires the PTL.
 539          *
 540          * So the ordering here is:
 541          *
 542          *      atomic_inc(&mm->tlb_flush_pending);
 543          *      spin_lock(&ptl);
 544          *      ...
 545          *      set_pte_at();
 546          *      spin_unlock(&ptl);
 547          *
 548          *                              spin_lock(&ptl)
 549          *                              mm_tlb_flush_pending();
 550          *                              ....
 551          *                              spin_unlock(&ptl);
 552          *
 553          *      flush_tlb_range();
 554          *      atomic_dec(&mm->tlb_flush_pending);
 555          *
 556          * Where the increment if constrained by the PTL unlock, it thus
 557          * ensures that the increment is visible if the PTE modification is
 558          * visible. After all, if there is no PTE modification, nobody cares
 559          * about TLB flushes either.
 560          *
 561          * This very much relies on users (mm_tlb_flush_pending() and
 562          * mm_tlb_flush_nested()) only caring about _specific_ PTEs (and
 563          * therefore specific PTLs), because with SPLIT_PTE_PTLOCKS and RCpc
 564          * locks (PPC) the unlock of one doesn't order against the lock of
 565          * another PTL.
 566          *
 567          * The decrement is ordered by the flush_tlb_range(), such that
 568          * mm_tlb_flush_pending() will not return false unless all flushes have
 569          * completed.
 570          */
 571 }
 572
 573 static inline void dec_tlb_flush_pending(struct mm_struct *mm)
 574 {
 575         /*
 576          * See inc_tlb_flush_pending().
 577          *
 578          * This cannot be smp_mb__before_atomic() because smp_mb() simply does
 579          * not order against TLB invalidate completion, which is what we need.
 580          *
 581          * Therefore we must rely on tlb_flush_*() to guarantee order.
 582          */
 583         atomic_dec(&mm->tlb_flush_pending);
 584 }
 585
 586 static inline bool mm_tlb_flush_pending(struct mm_struct *mm)
 587 {
 588         /*
 589          * Must be called after having acquired the PTL; orders against that
 590          * PTLs release and therefore ensures that if we observe the modified
 591          * PTE we must also observe the increment from inc_tlb_flush_pending().
 592          *
 593          * That is, it only guarantees to return true if there is a flush
 594          * pending for _this_ PTL.
 595          */
 596         return atomic_read(&mm->tlb_flush_pending);
 597 }
 598
 599 static inline bool mm_tlb_flush_nested(struct mm_struct *mm)
 600 {
 601         /*
 602          * Similar to mm_tlb_flush_pending(), we must have acquired the PTL
 603          * for which there is a TLB flush pending in order to guarantee
 604          * we've seen both that PTE modification and the increment.
 605          *
 606          * (no requirement on actually still holding the PTL, that is irrelevant)
 607          */
 608         return atomic_read(&mm->tlb_flush_pending) > 1;
 609 }
 610
 611 struct vm_fault;
 612
 613 struct vm_special_mapping {
 614         const char *name;       /* The name, e.g. "[vdso]". */
 615
 616         /*
 617          * If .fault is not provided, this points to a
 618          * NULL-terminated array of pages that back the special mapping.
 619          *
 620          * This must not be NULL unless .fault is provided.
 621          */
 622         struct page **pages;
 623
 624         /*
 625          * If non-NULL, then this is called to resolve page faults
 626          * on the special mapping.  If used, .pages is not checked.
 627          */
 628         int (*fault)(const struct vm_special_mapping *sm,
 629                      struct vm_area_struct *vma,
 630                      struct vm_fault *vmf);
 631
 632         int (*mremap)(const struct vm_special_mapping *sm,
 633                      struct vm_area_struct *new_vma);
 634 };
 635
 636 enum tlb_flush_reason {
 637         TLB_FLUSH_ON_TASK_SWITCH,
 638         TLB_REMOTE_SHOOTDOWN,
 639         TLB_LOCAL_SHOOTDOWN,
 640         TLB_LOCAL_MM_SHOOTDOWN,
 641         TLB_REMOTE_SEND_IPI,
 642         NR_TLB_FLUSH_REASONS,
 643 };
 644
 645  /*
 646   * A swap entry has to fit into a "unsigned long", as the entry is hidden
 647   * in the "index" field of the swapper address space.
 648   */
 649 typedef struct {
 650         unsigned long val;
 651 } swp_entry_t;
 652
 653 #endif /* _LINUX_MM_TYPES_H */