FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_page.h

     /*-
      * SPDX-License-Identifier: (BSD-3-Clause AND MIT-CMU)
      *
      * Copyright (c) 1991, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * This code is derived from software contributed to Berkeley by
      * The Mach Operating System project at Carnegie-Mellon University.
      *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      from: @(#)vm_page.h     8.2 (Berkeley) 12/13/93
     *
     *
     * Copyright (c) 1987, 1990 Carnegie-Mellon University.
     * All rights reserved.
     *
     * Authors: Avadis Tevanian, Jr., Michael Wayne Young
     *
     * Permission to use, copy, modify and distribute this software and
     * its documentation is hereby granted, provided that both the copyright
     * notice and this permission notice appear in all copies of the
     * software, derivative works or modified versions, and any portions
     * thereof, and that both notices appear in supporting documentation.
     *
     * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
     * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
     * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
     *
     * Carnegie Mellon requests users of this software to return to
     *
     *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
     *  School of Computer Science
     *  Carnegie Mellon University
     *  Pittsburgh PA 15213-3890
     *
     * any improvements or extensions that they make and grant Carnegie the
     * rights to redistribute these changes.
     *
     * $FreeBSD: releng/12.0/sys/vm/vm_page.h 338499 2018-09-06 16:17:45Z markj $
     */
    
    /*
     *      Resident memory system definitions.
     */
    
    #ifndef _VM_PAGE_
    #define _VM_PAGE_
    
    #include <vm/pmap.h>
    
    /*
     *      Management of resident (logical) pages.
     *
     *      A small structure is kept for each resident
     *      page, indexed by page number.  Each structure
     *      is an element of several collections:
     *
     *              A radix tree used to quickly
     *              perform object/offset lookups
     *
     *              A list of all pages for a given object,
     *              so they can be quickly deactivated at
     *              time of deallocation.
     *
     *              An ordered list of pages due for pageout.
     *
     *      In addition, the structure contains the object
     *      and offset to which this page belongs (for pageout),
     *      and sundry status bits.
     *
     *      In general, operations on this structure's mutable fields are
     *      synchronized using either one of or a combination of the lock on the
     *      object that the page belongs to (O), the page lock (P),
     *      the per-domain lock for the free queues (F), or the page's queue
     *      lock (Q).  The physical address of a page is used to select its page
     *      lock from a pool.  The queue lock for a page depends on the value of
    *      its queue field and described in detail below.  If a field is
    *      annotated below with two of these locks, then holding either lock is
    *      sufficient for read access, but both locks are required for write
    *      access.  An annotation of (C) indicates that the field is immutable.
    *
    *      In contrast, the synchronization of accesses to the page's
    *      dirty field is machine dependent (M).  In the
    *      machine-independent layer, the lock on the object that the
    *      page belongs to must be held in order to operate on the field.
    *      However, the pmap layer is permitted to set all bits within
    *      the field without holding that lock.  If the underlying
    *      architecture does not support atomic read-modify-write
    *      operations on the field's type, then the machine-independent
    *      layer uses a 32-bit atomic on the aligned 32-bit word that
    *      contains the dirty field.  In the machine-independent layer,
    *      the implementation of read-modify-write operations on the
    *      field is encapsulated in vm_page_clear_dirty_mask().
    *
    *      The page structure contains two counters which prevent page reuse.
    *      Both counters are protected by the page lock (P).  The hold
    *      counter counts transient references obtained via a pmap lookup, and
    *      is also used to prevent page reclamation in situations where it is
    *      undesirable to block other accesses to the page.  The wire counter
    *      is used to implement mlock(2) and is non-zero for pages containing
    *      kernel memory.  Pages that are wired or held will not be reclaimed
    *      or laundered by the page daemon, but are treated differently during
    *      a page queue scan: held pages remain at their position in the queue,
    *      while wired pages are removed from the queue and must later be
    *      re-enqueued appropriately by the unwiring thread.  It is legal to
    *      call vm_page_free() on a held page; doing so causes it to be removed
    *      from its object and page queue, and the page is released to the
    *      allocator once the last hold reference is dropped.  In contrast,
    *      wired pages may not be freed.
    *
    *      In some pmap implementations, the wire count of a page table page is
    *      used to track the number of populated entries.
    *
    *      The busy lock is an embedded reader-writer lock which protects the
    *      page's contents and identity (i.e., its <object, pindex> tuple) and
    *      interlocks with the object lock (O).  In particular, a page may be
    *      busied or unbusied only with the object write lock held.  To avoid
    *      bloating the page structure, the busy lock lacks some of the
    *      features available to the kernel's general-purpose synchronization
    *      primitives.  As a result, busy lock ordering rules are not verified,
    *      lock recursion is not detected, and an attempt to xbusy a busy page
    *      or sbusy an xbusy page results will trigger a panic rather than
    *      causing the thread to block.  vm_page_sleep_if_busy() can be used to
    *      sleep until the page's busy state changes, after which the caller
    *      must re-lookup the page and re-evaluate its state.
    *
    *      The queue field is the index of the page queue containing the
    *      page, or PQ_NONE if the page is not enqueued.  The queue lock of a
    *      page is the page queue lock corresponding to the page queue index,
    *      or the page lock (P) for the page if it is not enqueued.  To modify
    *      the queue field, the queue lock for the old value of the field must
    *      be held.  It is invalid for a page's queue field to transition
    *      between two distinct page queue indices.  That is, when updating
    *      the queue field, either the new value or the old value must be
    *      PQ_NONE.
    *
    *      To avoid contention on page queue locks, page queue operations
    *      (enqueue, dequeue, requeue) are batched using per-CPU queues.
    *      A deferred operation is requested by inserting an entry into a
    *      batch queue; the entry is simply a pointer to the page, and the
    *      request type is encoded in the page's aflags field using the values
    *      in PGA_QUEUE_STATE_MASK.  The type-stability of struct vm_pages is
    *      crucial to this scheme since the processing of entries in a given
    *      batch queue may be deferred indefinitely.  In particular, a page
    *      may be freed before its pending batch queue entries have been
    *      processed.  The page lock (P) must be held to schedule a batched
    *      queue operation, and the page queue lock must be held in order to
    *      process batch queue entries for the page queue.
    */
   
   #if PAGE_SIZE == 4096
   #define VM_PAGE_BITS_ALL 0xffu
   typedef uint8_t vm_page_bits_t;
   #elif PAGE_SIZE == 8192
   #define VM_PAGE_BITS_ALL 0xffffu
   typedef uint16_t vm_page_bits_t;
   #elif PAGE_SIZE == 16384
   #define VM_PAGE_BITS_ALL 0xffffffffu
   typedef uint32_t vm_page_bits_t;
   #elif PAGE_SIZE == 32768
   #define VM_PAGE_BITS_ALL 0xfffffffffffffffflu
   typedef uint64_t vm_page_bits_t;
   #endif
   
   struct vm_page {
           union {
                   TAILQ_ENTRY(vm_page) q; /* page queue or free list (Q) */
                   struct {
                           SLIST_ENTRY(vm_page) ss; /* private slists */
                           void *pv;
                   } s;
                   struct {
                           u_long p;
                           u_long v;
                   } memguard;
           } plinks;
           TAILQ_ENTRY(vm_page) listq;     /* pages in same object (O) */
           vm_object_t object;             /* which object am I in (O,P) */
           vm_pindex_t pindex;             /* offset into object (O,P) */
           vm_paddr_t phys_addr;           /* physical address of page (C) */
           struct md_page md;              /* machine dependent stuff */
           u_int wire_count;               /* wired down maps refs (P) */
           volatile u_int busy_lock;       /* busy owners lock */
           uint16_t hold_count;            /* page hold count (P) */
           uint16_t flags;                 /* page PG_* flags (P) */
           uint8_t aflags;                 /* access is atomic */
           uint8_t oflags;                 /* page VPO_* flags (O) */
           uint8_t queue;                  /* page queue index (Q) */
           int8_t psind;                   /* pagesizes[] index (O) */
           int8_t segind;                  /* vm_phys segment index (C) */
           uint8_t order;                  /* index of the buddy queue (F) */
           uint8_t pool;                   /* vm_phys freepool index (F) */
           u_char  act_count;              /* page usage count (P) */
           /* NOTE that these must support one bit per DEV_BSIZE in a page */
           /* so, on normal X86 kernels, they must be at least 8 bits wide */
           vm_page_bits_t valid;           /* map of valid DEV_BSIZE chunks (O) */
           vm_page_bits_t dirty;           /* map of dirty DEV_BSIZE chunks (M) */
   };
   
   /*
    * Page flags stored in oflags:
    *
    * Access to these page flags is synchronized by the lock on the object
    * containing the page (O).
    *
    * Note: VPO_UNMANAGED (used by OBJT_DEVICE, OBJT_PHYS and OBJT_SG)
    *       indicates that the page is not under PV management but
    *       otherwise should be treated as a normal page.  Pages not
    *       under PV management cannot be paged out via the
    *       object/vm_page_t because there is no knowledge of their pte
    *       mappings, and such pages are also not on any PQ queue.
    *
    */
   #define VPO_KMEM_EXEC   0x01            /* kmem mapping allows execution */
   #define VPO_SWAPSLEEP   0x02            /* waiting for swap to finish */
   #define VPO_UNMANAGED   0x04            /* no PV management for page */
   #define VPO_SWAPINPROG  0x08            /* swap I/O in progress on page */
   #define VPO_NOSYNC      0x10            /* do not collect for syncer */
   
   /*
    * Busy page implementation details.
    * The algorithm is taken mostly by rwlock(9) and sx(9) locks implementation,
    * even if the support for owner identity is removed because of size
    * constraints.  Checks on lock recursion are then not possible, while the
    * lock assertions effectiveness is someway reduced.
    */
   #define VPB_BIT_SHARED          0x01
   #define VPB_BIT_EXCLUSIVE       0x02
   #define VPB_BIT_WAITERS         0x04
   #define VPB_BIT_FLAGMASK                                                \
           (VPB_BIT_SHARED | VPB_BIT_EXCLUSIVE | VPB_BIT_WAITERS)
   
   #define VPB_SHARERS_SHIFT       3
   #define VPB_SHARERS(x)                                                  \
           (((x) & ~VPB_BIT_FLAGMASK) >> VPB_SHARERS_SHIFT)
   #define VPB_SHARERS_WORD(x)     ((x) << VPB_SHARERS_SHIFT | VPB_BIT_SHARED)
   #define VPB_ONE_SHARER          (1 << VPB_SHARERS_SHIFT)
   
   #define VPB_SINGLE_EXCLUSIVER   VPB_BIT_EXCLUSIVE
   
   #define VPB_UNBUSIED            VPB_SHARERS_WORD(0)
   
   #define PQ_NONE         255
   #define PQ_INACTIVE     0
   #define PQ_ACTIVE       1
   #define PQ_LAUNDRY      2
   #define PQ_UNSWAPPABLE  3
   #define PQ_COUNT        4
   
   #ifndef VM_PAGE_HAVE_PGLIST
   TAILQ_HEAD(pglist, vm_page);
   #define VM_PAGE_HAVE_PGLIST
   #endif
   SLIST_HEAD(spglist, vm_page);
   
   #ifdef _KERNEL
   extern vm_page_t bogus_page;
   #endif  /* _KERNEL */
   
   extern struct mtx_padalign pa_lock[];
   
   #if defined(__arm__)
   #define PDRSHIFT        PDR_SHIFT
   #elif !defined(PDRSHIFT)
   #define PDRSHIFT        21
   #endif
   
   #define pa_index(pa)    ((pa) >> PDRSHIFT)
   #define PA_LOCKPTR(pa)  ((struct mtx *)(&pa_lock[pa_index(pa) % PA_LOCK_COUNT]))
   #define PA_LOCKOBJPTR(pa)       ((struct lock_object *)PA_LOCKPTR((pa)))
   #define PA_LOCK(pa)     mtx_lock(PA_LOCKPTR(pa))
   #define PA_TRYLOCK(pa)  mtx_trylock(PA_LOCKPTR(pa))
   #define PA_UNLOCK(pa)   mtx_unlock(PA_LOCKPTR(pa))
   #define PA_UNLOCK_COND(pa)                      \
           do {                                    \
                   if ((pa) != 0) {                \
                           PA_UNLOCK((pa));        \
                           (pa) = 0;               \
                   }                               \
           } while (0)
   
   #define PA_LOCK_ASSERT(pa, a)   mtx_assert(PA_LOCKPTR(pa), (a))
   
   #if defined(KLD_MODULE) && !defined(KLD_TIED)
   #define vm_page_lock(m)         vm_page_lock_KBI((m), LOCK_FILE, LOCK_LINE)
   #define vm_page_unlock(m)       vm_page_unlock_KBI((m), LOCK_FILE, LOCK_LINE)
   #define vm_page_trylock(m)      vm_page_trylock_KBI((m), LOCK_FILE, LOCK_LINE)
   #else   /* !KLD_MODULE */
   #define vm_page_lockptr(m)      (PA_LOCKPTR(VM_PAGE_TO_PHYS((m))))
   #define vm_page_lock(m)         mtx_lock(vm_page_lockptr((m)))
   #define vm_page_unlock(m)       mtx_unlock(vm_page_lockptr((m)))
   #define vm_page_trylock(m)      mtx_trylock(vm_page_lockptr((m)))
   #endif
   #if defined(INVARIANTS)
   #define vm_page_assert_locked(m)                \
       vm_page_assert_locked_KBI((m), __FILE__, __LINE__)
   #define vm_page_lock_assert(m, a)               \
       vm_page_lock_assert_KBI((m), (a), __FILE__, __LINE__)
   #else
   #define vm_page_assert_locked(m)
   #define vm_page_lock_assert(m, a)
   #endif
   
   /*
    * The vm_page's aflags are updated using atomic operations.  To set or clear
    * these flags, the functions vm_page_aflag_set() and vm_page_aflag_clear()
    * must be used.  Neither these flags nor these functions are part of the KBI.
    *
    * PGA_REFERENCED may be cleared only if the page is locked.  It is set by
    * both the MI and MD VM layers.  However, kernel loadable modules should not
    * directly set this flag.  They should call vm_page_reference() instead.
    *
    * PGA_WRITEABLE is set exclusively on managed pages by pmap_enter().
    * When it does so, the object must be locked, or the page must be
    * exclusive busied.  The MI VM layer must never access this flag
    * directly.  Instead, it should call pmap_page_is_write_mapped().
    *
    * PGA_EXECUTABLE may be set by pmap routines, and indicates that a page has
    * at least one executable mapping.  It is not consumed by the MI VM layer.
    *
    * PGA_ENQUEUED is set and cleared when a page is inserted into or removed
    * from a page queue, respectively.  It determines whether the plinks.q field
    * of the page is valid.  To set or clear this flag, the queue lock for the
    * page must be held: the page queue lock corresponding to the page's "queue"
    * field if its value is not PQ_NONE, and the page lock otherwise.
    *
    * PGA_DEQUEUE is set when the page is scheduled to be dequeued from a page
    * queue, and cleared when the dequeue request is processed.  A page may
    * have PGA_DEQUEUE set and PGA_ENQUEUED cleared, for instance if a dequeue
    * is requested after the page is scheduled to be enqueued but before it is
    * actually inserted into the page queue.  The page lock must be held to set
    * this flag, and the queue lock for the page must be held to clear it.
    *
    * PGA_REQUEUE is set when the page is scheduled to be enqueued or requeued
    * in its page queue.  The page lock must be held to set this flag, and the
    * queue lock for the page must be held to clear it.
    *
    * PGA_REQUEUE_HEAD is a special flag for enqueuing pages near the head of
    * the inactive queue, thus bypassing LRU.  The page lock must be held to
    * set this flag, and the queue lock for the page must be held to clear it.
    */
   #define PGA_WRITEABLE   0x01            /* page may be mapped writeable */
   #define PGA_REFERENCED  0x02            /* page has been referenced */
   #define PGA_EXECUTABLE  0x04            /* page may be mapped executable */
   #define PGA_ENQUEUED    0x08            /* page is enqueued in a page queue */
   #define PGA_DEQUEUE     0x10            /* page is due to be dequeued */
   #define PGA_REQUEUE     0x20            /* page is due to be requeued */
   #define PGA_REQUEUE_HEAD 0x40           /* page requeue should bypass LRU */
   
   #define PGA_QUEUE_STATE_MASK    (PGA_ENQUEUED | PGA_DEQUEUE | PGA_REQUEUE | \
                                   PGA_REQUEUE_HEAD)
   
   /*
    * Page flags.  If changed at any other time than page allocation or
    * freeing, the modification must be protected by the vm_page lock.
    */
   #define PG_FICTITIOUS   0x0004          /* physical page doesn't exist */
   #define PG_ZERO         0x0008          /* page is zeroed */
   #define PG_MARKER       0x0010          /* special queue marker page */
   #define PG_NODUMP       0x0080          /* don't include this page in a dump */
   #define PG_UNHOLDFREE   0x0100          /* delayed free of a held page */
   
   /*
    * Misc constants.
    */
   #define ACT_DECLINE             1
   #define ACT_ADVANCE             3
   #define ACT_INIT                5
   #define ACT_MAX                 64
   
   #ifdef _KERNEL
   
   #include <sys/systm.h>
   
   #include <machine/atomic.h>
   
   /*
    * Each pageable resident page falls into one of five lists:
    *
    *      free
    *              Available for allocation now.
    *
    *      inactive
    *              Low activity, candidates for reclamation.
    *              This list is approximately LRU ordered.
    *
    *      laundry
    *              This is the list of pages that should be
    *              paged out next.
    *
    *      unswappable
    *              Dirty anonymous pages that cannot be paged
    *              out because no swap device is configured.
    *
    *      active
    *              Pages that are "active", i.e., they have been
    *              recently referenced.
    *
    */
   
   extern vm_page_t vm_page_array;         /* First resident page in table */
   extern long vm_page_array_size;         /* number of vm_page_t's */
   extern long first_page;                 /* first physical page number */
   
   #define VM_PAGE_TO_PHYS(entry)  ((entry)->phys_addr)
   
   /*
    * PHYS_TO_VM_PAGE() returns the vm_page_t object that represents a memory
    * page to which the given physical address belongs. The correct vm_page_t
    * object is returned for addresses that are not page-aligned.
    */
   vm_page_t PHYS_TO_VM_PAGE(vm_paddr_t pa);
   
   /*
    * Page allocation parameters for vm_page for the functions
    * vm_page_alloc(), vm_page_grab(), vm_page_alloc_contig() and
    * vm_page_alloc_freelist().  Some functions support only a subset
    * of the flags, and ignore others, see the flags legend.
    *
    * The meaning of VM_ALLOC_ZERO differs slightly between the vm_page_alloc*()
    * and the vm_page_grab*() functions.  See these functions for details.
    *
    * Bits 0 - 1 define class.
    * Bits 2 - 15 dedicated for flags.
    * Legend:
    * (a) - vm_page_alloc() supports the flag.
    * (c) - vm_page_alloc_contig() supports the flag.
    * (f) - vm_page_alloc_freelist() supports the flag.
    * (g) - vm_page_grab() supports the flag.
    * (p) - vm_page_grab_pages() supports the flag.
    * Bits above 15 define the count of additional pages that the caller
    * intends to allocate.
    */
   #define VM_ALLOC_NORMAL         0
   #define VM_ALLOC_INTERRUPT      1
   #define VM_ALLOC_SYSTEM         2
   #define VM_ALLOC_CLASS_MASK     3
   #define VM_ALLOC_WAITOK         0x0008  /* (acf) Sleep and retry */
   #define VM_ALLOC_WAITFAIL       0x0010  /* (acf) Sleep and return error */
   #define VM_ALLOC_WIRED          0x0020  /* (acfgp) Allocate a wired page */
   #define VM_ALLOC_ZERO           0x0040  /* (acfgp) Allocate a prezeroed page */
   #define VM_ALLOC_NOOBJ          0x0100  /* (acg) No associated object */
   #define VM_ALLOC_NOBUSY         0x0200  /* (acgp) Do not excl busy the page */
   #define VM_ALLOC_IGN_SBUSY      0x1000  /* (gp) Ignore shared busy flag */
   #define VM_ALLOC_NODUMP         0x2000  /* (ag) don't include in dump */
   #define VM_ALLOC_SBUSY          0x4000  /* (acgp) Shared busy the page */
   #define VM_ALLOC_NOWAIT         0x8000  /* (acfgp) Do not sleep */
   #define VM_ALLOC_COUNT_SHIFT    16
   #define VM_ALLOC_COUNT(count)   ((count) << VM_ALLOC_COUNT_SHIFT)
   
   #ifdef M_NOWAIT
   static inline int
   malloc2vm_flags(int malloc_flags)
   {
           int pflags;
   
           KASSERT((malloc_flags & M_USE_RESERVE) == 0 ||
               (malloc_flags & M_NOWAIT) != 0,
               ("M_USE_RESERVE requires M_NOWAIT"));
           pflags = (malloc_flags & M_USE_RESERVE) != 0 ? VM_ALLOC_INTERRUPT :
               VM_ALLOC_SYSTEM;
           if ((malloc_flags & M_ZERO) != 0)
                   pflags |= VM_ALLOC_ZERO;
           if ((malloc_flags & M_NODUMP) != 0)
                   pflags |= VM_ALLOC_NODUMP;
           if ((malloc_flags & M_NOWAIT))
                   pflags |= VM_ALLOC_NOWAIT;
           if ((malloc_flags & M_WAITOK))
                   pflags |= VM_ALLOC_WAITOK;
           return (pflags);
   }
   #endif
   
   /*
    * Predicates supported by vm_page_ps_test():
    *
    *      PS_ALL_DIRTY is true only if the entire (super)page is dirty.
    *      However, it can be spuriously false when the (super)page has become
    *      dirty in the pmap but that information has not been propagated to the
    *      machine-independent layer.
    */
   #define PS_ALL_DIRTY    0x1
   #define PS_ALL_VALID    0x2
   #define PS_NONE_BUSY    0x4
   
   void vm_page_busy_downgrade(vm_page_t m);
   void vm_page_busy_sleep(vm_page_t m, const char *msg, bool nonshared);
   void vm_page_flash(vm_page_t m);
   void vm_page_hold(vm_page_t mem);
   void vm_page_unhold(vm_page_t mem);
   void vm_page_free(vm_page_t m);
   void vm_page_free_zero(vm_page_t m);
   
   void vm_page_activate (vm_page_t);
   void vm_page_advise(vm_page_t m, int advice);
   vm_page_t vm_page_alloc(vm_object_t, vm_pindex_t, int);
   vm_page_t vm_page_alloc_domain(vm_object_t, vm_pindex_t, int, int);
   vm_page_t vm_page_alloc_after(vm_object_t, vm_pindex_t, int, vm_page_t);
   vm_page_t vm_page_alloc_domain_after(vm_object_t, vm_pindex_t, int, int,
       vm_page_t);
   vm_page_t vm_page_alloc_contig(vm_object_t object, vm_pindex_t pindex, int req,
       u_long npages, vm_paddr_t low, vm_paddr_t high, u_long alignment,
       vm_paddr_t boundary, vm_memattr_t memattr);
   vm_page_t vm_page_alloc_contig_domain(vm_object_t object,
       vm_pindex_t pindex, int domain, int req, u_long npages, vm_paddr_t low,
       vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
       vm_memattr_t memattr);
   vm_page_t vm_page_alloc_freelist(int, int);
   vm_page_t vm_page_alloc_freelist_domain(int, int, int);
   bool vm_page_blacklist_add(vm_paddr_t pa, bool verbose);
   void vm_page_change_lock(vm_page_t m, struct mtx **mtx);
   vm_page_t vm_page_grab (vm_object_t, vm_pindex_t, int);
   int vm_page_grab_pages(vm_object_t object, vm_pindex_t pindex, int allocflags,
       vm_page_t *ma, int count);
   void vm_page_deactivate(vm_page_t);
   void vm_page_deactivate_noreuse(vm_page_t);
   void vm_page_dequeue(vm_page_t m);
   void vm_page_dequeue_deferred(vm_page_t m);
   void vm_page_drain_pqbatch(void);
   vm_page_t vm_page_find_least(vm_object_t, vm_pindex_t);
   bool vm_page_free_prep(vm_page_t m);
   vm_page_t vm_page_getfake(vm_paddr_t paddr, vm_memattr_t memattr);
   void vm_page_initfake(vm_page_t m, vm_paddr_t paddr, vm_memattr_t memattr);
   int vm_page_insert (vm_page_t, vm_object_t, vm_pindex_t);
   void vm_page_launder(vm_page_t m);
   vm_page_t vm_page_lookup (vm_object_t, vm_pindex_t);
   vm_page_t vm_page_next(vm_page_t m);
   int vm_page_pa_tryrelock(pmap_t, vm_paddr_t, vm_paddr_t *);
   struct vm_pagequeue *vm_page_pagequeue(vm_page_t m);
   vm_page_t vm_page_prev(vm_page_t m);
   bool vm_page_ps_test(vm_page_t m, int flags, vm_page_t skip_m);
   void vm_page_putfake(vm_page_t m);
   void vm_page_readahead_finish(vm_page_t m);
   bool vm_page_reclaim_contig(int req, u_long npages, vm_paddr_t low,
       vm_paddr_t high, u_long alignment, vm_paddr_t boundary);
   bool vm_page_reclaim_contig_domain(int domain, int req, u_long npages,
       vm_paddr_t low, vm_paddr_t high, u_long alignment, vm_paddr_t boundary);
   void vm_page_reference(vm_page_t m);
   void vm_page_remove (vm_page_t);
   int vm_page_rename (vm_page_t, vm_object_t, vm_pindex_t);
   vm_page_t vm_page_replace(vm_page_t mnew, vm_object_t object,
       vm_pindex_t pindex);
   void vm_page_requeue(vm_page_t m);
   int vm_page_sbusied(vm_page_t m);
   vm_page_t vm_page_scan_contig(u_long npages, vm_page_t m_start,
       vm_page_t m_end, u_long alignment, vm_paddr_t boundary, int options);
   void vm_page_set_valid_range(vm_page_t m, int base, int size);
   int vm_page_sleep_if_busy(vm_page_t m, const char *msg);
   vm_offset_t vm_page_startup(vm_offset_t vaddr);
   void vm_page_sunbusy(vm_page_t m);
   bool vm_page_try_to_free(vm_page_t m);
   int vm_page_trysbusy(vm_page_t m);
   void vm_page_unhold_pages(vm_page_t *ma, int count);
   void vm_page_unswappable(vm_page_t m);
   bool vm_page_unwire(vm_page_t m, uint8_t queue);
   bool vm_page_unwire_noq(vm_page_t m);
   void vm_page_updatefake(vm_page_t m, vm_paddr_t paddr, vm_memattr_t memattr);
   void vm_page_wire (vm_page_t);
   void vm_page_xunbusy_hard(vm_page_t m);
   void vm_page_xunbusy_maybelocked(vm_page_t m);
   void vm_page_set_validclean (vm_page_t, int, int);
   void vm_page_clear_dirty (vm_page_t, int, int);
   void vm_page_set_invalid (vm_page_t, int, int);
   int vm_page_is_valid (vm_page_t, int, int);
   void vm_page_test_dirty (vm_page_t);
   vm_page_bits_t vm_page_bits(int base, int size);
   void vm_page_zero_invalid(vm_page_t m, boolean_t setvalid);
   void vm_page_free_toq(vm_page_t m);
   void vm_page_free_pages_toq(struct spglist *free, bool update_wire_count);
   
   void vm_page_dirty_KBI(vm_page_t m);
   void vm_page_lock_KBI(vm_page_t m, const char *file, int line);
   void vm_page_unlock_KBI(vm_page_t m, const char *file, int line);
   int vm_page_trylock_KBI(vm_page_t m, const char *file, int line);
   #if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
   void vm_page_assert_locked_KBI(vm_page_t m, const char *file, int line);
   void vm_page_lock_assert_KBI(vm_page_t m, int a, const char *file, int line);
   #endif
   
   #define vm_page_assert_sbusied(m)                                       \
           KASSERT(vm_page_sbusied(m),                                     \
               ("vm_page_assert_sbusied: page %p not shared busy @ %s:%d", \
               (m), __FILE__, __LINE__))
   
   #define vm_page_assert_unbusied(m)                                      \
           KASSERT(!vm_page_busied(m),                                     \
               ("vm_page_assert_unbusied: page %p busy @ %s:%d",           \
               (m), __FILE__, __LINE__))
   
   #define vm_page_assert_xbusied(m)                                       \
           KASSERT(vm_page_xbusied(m),                                     \
               ("vm_page_assert_xbusied: page %p not exclusive busy @ %s:%d", \
               (m), __FILE__, __LINE__))
   
   #define vm_page_busied(m)                                               \
           ((m)->busy_lock != VPB_UNBUSIED)
   
   #define vm_page_sbusy(m) do {                                           \
           if (!vm_page_trysbusy(m))                                       \
                   panic("%s: page %p failed shared busying", __func__,    \
                       (m));                                               \
   } while (0)
   
   #define vm_page_tryxbusy(m)                                             \
           (atomic_cmpset_acq_int(&(m)->busy_lock, VPB_UNBUSIED,           \
               VPB_SINGLE_EXCLUSIVER))
   
   #define vm_page_xbusied(m)                                              \
           (((m)->busy_lock & VPB_SINGLE_EXCLUSIVER) != 0)
   
   #define vm_page_xbusy(m) do {                                           \
           if (!vm_page_tryxbusy(m))                                       \
                   panic("%s: page %p failed exclusive busying", __func__, \
                       (m));                                               \
   } while (0)
   
   /* Note: page m's lock must not be owned by the caller. */
   #define vm_page_xunbusy(m) do {                                         \
           if (!atomic_cmpset_rel_int(&(m)->busy_lock,                     \
               VPB_SINGLE_EXCLUSIVER, VPB_UNBUSIED))                       \
                   vm_page_xunbusy_hard(m);                                \
   } while (0)
   
   #ifdef INVARIANTS
   void vm_page_object_lock_assert(vm_page_t m);
   #define VM_PAGE_OBJECT_LOCK_ASSERT(m)   vm_page_object_lock_assert(m)
   void vm_page_assert_pga_writeable(vm_page_t m, uint8_t bits);
   #define VM_PAGE_ASSERT_PGA_WRITEABLE(m, bits)                           \
           vm_page_assert_pga_writeable(m, bits)
   #else
   #define VM_PAGE_OBJECT_LOCK_ASSERT(m)   (void)0
   #define VM_PAGE_ASSERT_PGA_WRITEABLE(m, bits)   (void)0
   #endif
   
   /*
    * We want to use atomic updates for the aflags field, which is 8 bits wide.
    * However, not all architectures support atomic operations on 8-bit
    * destinations.  In order that we can easily use a 32-bit operation, we
    * require that the aflags field be 32-bit aligned.
    */
   CTASSERT(offsetof(struct vm_page, aflags) % sizeof(uint32_t) == 0);
   
   /*
    *      Clear the given bits in the specified page.
    */
   static inline void
   vm_page_aflag_clear(vm_page_t m, uint8_t bits)
   {
           uint32_t *addr, val;
   
           /*
            * The PGA_REFERENCED flag can only be cleared if the page is locked.
            */
           if ((bits & PGA_REFERENCED) != 0)
                   vm_page_assert_locked(m);
   
           /*
            * Access the whole 32-bit word containing the aflags field with an
            * atomic update.  Parallel non-atomic updates to the other fields
            * within this word are handled properly by the atomic update.
            */
           addr = (void *)&m->aflags;
           KASSERT(((uintptr_t)addr & (sizeof(uint32_t) - 1)) == 0,
               ("vm_page_aflag_clear: aflags is misaligned"));
           val = bits;
   #if BYTE_ORDER == BIG_ENDIAN
           val <<= 24;
   #endif
           atomic_clear_32(addr, val);
   }
   
   /*
    *      Set the given bits in the specified page.
    */
   static inline void
   vm_page_aflag_set(vm_page_t m, uint8_t bits)
   {
           uint32_t *addr, val;
   
           VM_PAGE_ASSERT_PGA_WRITEABLE(m, bits);
   
           /*
            * Access the whole 32-bit word containing the aflags field with an
            * atomic update.  Parallel non-atomic updates to the other fields
            * within this word are handled properly by the atomic update.
            */
           addr = (void *)&m->aflags;
           KASSERT(((uintptr_t)addr & (sizeof(uint32_t) - 1)) == 0,
               ("vm_page_aflag_set: aflags is misaligned"));
           val = bits;
   #if BYTE_ORDER == BIG_ENDIAN
           val <<= 24;
   #endif
           atomic_set_32(addr, val);
   } 
   
   /*
    *      vm_page_dirty:
    *
    *      Set all bits in the page's dirty field.
    *
    *      The object containing the specified page must be locked if the
    *      call is made from the machine-independent layer.
    *
    *      See vm_page_clear_dirty_mask().
    */
   static __inline void
   vm_page_dirty(vm_page_t m)
   {
   
           /* Use vm_page_dirty_KBI() under INVARIANTS to save memory. */
   #if (defined(KLD_MODULE) && !defined(KLD_TIED)) || defined(INVARIANTS)
           vm_page_dirty_KBI(m);
   #else
           m->dirty = VM_PAGE_BITS_ALL;
   #endif
   }
   
   /*
    *      vm_page_undirty:
    *
    *      Set page to not be dirty.  Note: does not clear pmap modify bits
    */
   static __inline void
   vm_page_undirty(vm_page_t m)
   {
   
           VM_PAGE_OBJECT_LOCK_ASSERT(m);
           m->dirty = 0;
   }
   
   static inline void
   vm_page_replace_checked(vm_page_t mnew, vm_object_t object, vm_pindex_t pindex,
       vm_page_t mold)
   {
           vm_page_t mret;
   
           mret = vm_page_replace(mnew, object, pindex);
           KASSERT(mret == mold,
               ("invalid page replacement, mold=%p, mret=%p", mold, mret));
   
           /* Unused if !INVARIANTS. */
           (void)mold;
           (void)mret;
   }
   
   /*
    *      vm_page_queue:
    *
    *      Return the index of the queue containing m.  This index is guaranteed
    *      not to change while the page lock is held.
    */
   static inline uint8_t
   vm_page_queue(vm_page_t m)
   {
   
           vm_page_assert_locked(m);
   
           if ((m->aflags & PGA_DEQUEUE) != 0)
                   return (PQ_NONE);
           atomic_thread_fence_acq();
           return (m->queue);
   }
   
   static inline bool
   vm_page_active(vm_page_t m)
   {
   
           return (vm_page_queue(m) == PQ_ACTIVE);
   }
   
   static inline bool
   vm_page_inactive(vm_page_t m)
   {
   
           return (vm_page_queue(m) == PQ_INACTIVE);
   }
   
   static inline bool
   vm_page_in_laundry(vm_page_t m)
   {
           uint8_t queue;
   
           queue = vm_page_queue(m);
           return (queue == PQ_LAUNDRY || queue == PQ_UNSWAPPABLE);
   }
   
   /*
    *      vm_page_held:
    *
    *      Return true if a reference prevents the page from being reclaimable.
    */
   static inline bool
   vm_page_held(vm_page_t m)
   {
   
           return (m->hold_count > 0 || m->wire_count > 0);
   }
   
   #endif                          /* _KERNEL */
   #endif                          /* !_VM_PAGE_ */

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