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

     /*-
      * 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.
     * 4. 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/10.0/sys/vm/vm_page.h 255626 2013-09-17 07:35:26Z kib $
     */
    
    /*
     *      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 pool lock for the page (P),
     *      or the lock for either the free or paging queue (Q).  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.
     *
    *      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().
    */
   
   #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 */
           struct md_page md;              /* machine dependant 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 (P,Q) */
           int8_t segind;
           uint8_t order;                  /* index of the buddy queue */
           uint8_t pool;
           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_UNUSED01    0x01            /* --available-- */
   #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_COUNT        2
   
   TAILQ_HEAD(pglist, vm_page);
   SLIST_HEAD(spglist, vm_page);
   
   struct vm_pagequeue {
           struct mtx      pq_mutex;
           struct pglist   pq_pl;
           int             pq_cnt;
           int             * const pq_vcnt;
           const char      * const pq_name;
   } __aligned(CACHE_LINE_SIZE);
   
   
   struct vm_domain {
           struct vm_pagequeue vmd_pagequeues[PQ_COUNT];
           u_int vmd_page_count;
           u_int vmd_free_count;
           long vmd_segs;  /* bitmask of the segments */
           boolean_t vmd_oom;
           int vmd_pass;   /* local pagedaemon pass */
           struct vm_page vmd_marker; /* marker for pagedaemon private use */
   };
   
   extern struct vm_domain vm_dom[MAXMEMDOM];
   
   #define vm_pagequeue_assert_locked(pq)  mtx_assert(&(pq)->pq_mutex, MA_OWNED)
   #define vm_pagequeue_lock(pq)           mtx_lock(&(pq)->pq_mutex)
   #define vm_pagequeue_unlock(pq)         mtx_unlock(&(pq)->pq_mutex)
   
   #ifdef _KERNEL
   static __inline void
   vm_pagequeue_cnt_add(struct vm_pagequeue *pq, int addend)
   {
   
   #ifdef notyet
           vm_pagequeue_assert_locked(pq);
   #endif
           pq->pq_cnt += addend;
           atomic_add_int(pq->pq_vcnt, addend);
   }
   #define vm_pagequeue_cnt_inc(pq)        vm_pagequeue_cnt_add((pq), 1)
   #define vm_pagequeue_cnt_dec(pq)        vm_pagequeue_cnt_add((pq), -1)
   #endif  /* _KERNEL */
   
   extern struct mtx_padalign vm_page_queue_free_mtx;
   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))
   
   #ifdef KLD_MODULE
   #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 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.
    */
   #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 */
   
   /*
    * 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_CACHED       0x0001          /* page is cached */
   #define PG_FREE         0x0002          /* page is free */
   #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_WINATCFLS    0x0040          /* flush dirty page on inactive q */
   #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 four lists:
    *
    *      free
    *              Available for allocation now.
    *
    *      cache
    *              Almost available for allocation. Still associated with
    *              an object, but clean and immediately freeable.
    *
    * The following lists are LRU sorted:
    *
    *      inactive
    *              Low activity, candidates for reclamation.
    *              This is the list of pages that should be
    *              paged out next.
    *
    *      active
    *              Pages that are "active" i.e. they have been
    *              recently referenced.
    *
    */
   
   extern int vm_page_zero_count;
   
   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_IS_FREE(m)      (((m)->flags & PG_FREE) != 0)
   
   #define VM_PAGE_TO_PHYS(entry)  ((entry)->phys_addr)
   
   vm_page_t PHYS_TO_VM_PAGE(vm_paddr_t pa);
   
   /* page allocation classes: */
   #define VM_ALLOC_NORMAL         0
   #define VM_ALLOC_INTERRUPT      1
   #define VM_ALLOC_SYSTEM         2
   #define VM_ALLOC_CLASS_MASK     3
   /* page allocation flags: */
   #define VM_ALLOC_WIRED          0x0020  /* non pageable */
   #define VM_ALLOC_ZERO           0x0040  /* Try to obtain a zeroed page */
   #define VM_ALLOC_NOOBJ          0x0100  /* No associated object */
   #define VM_ALLOC_NOBUSY         0x0200  /* Do not busy the page */
   #define VM_ALLOC_IFCACHED       0x0400  /* Fail if the page is not cached */
   #define VM_ALLOC_IFNOTCACHED    0x0800  /* Fail if the page is cached */
   #define VM_ALLOC_IGN_SBUSY      0x1000  /* vm_page_grab() only */
   #define VM_ALLOC_NODUMP         0x2000  /* don't include in dump */
   #define VM_ALLOC_SBUSY          0x4000  /* Shared busy the page */
   
   #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;
           return (pflags);
   }
   #endif
   
   void vm_page_busy_downgrade(vm_page_t m);
   void vm_page_busy_sleep(vm_page_t m, const char *msg);
   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_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_freelist(int, int);
   vm_page_t vm_page_grab (vm_object_t, vm_pindex_t, int);
   void vm_page_cache(vm_page_t);
   void vm_page_cache_free(vm_object_t, vm_pindex_t, vm_pindex_t);
   void vm_page_cache_transfer(vm_object_t, vm_pindex_t, vm_object_t);
   int vm_page_try_to_cache (vm_page_t);
   int vm_page_try_to_free (vm_page_t);
   void vm_page_deactivate (vm_page_t);
   void vm_page_dequeue(vm_page_t m);
   void vm_page_dequeue_locked(vm_page_t m);
   vm_page_t vm_page_find_least(vm_object_t, vm_pindex_t);
   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);
   boolean_t vm_page_is_cached(vm_object_t object, vm_pindex_t pindex);
   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);
   void vm_page_putfake(vm_page_t m);
   void vm_page_readahead_finish(vm_page_t m);
   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);
   void vm_page_requeue_locked(vm_page_t m);
   int vm_page_sbusied(vm_page_t m);
   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);
   int vm_page_trysbusy(vm_page_t m);
   void vm_page_unhold_pages(vm_page_t *ma, int count);
   void vm_page_unwire (vm_page_t, int);
   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_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_zero_idle_wakeup(void);
   
   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", \
               (void *)m, __FILE__, __LINE__));
   
   #define vm_page_assert_unbusied(m)                                      \
           KASSERT(!vm_page_busied(m),                                     \
               ("vm_page_assert_unbusied: page %p busy @ %s:%d",           \
               (void *)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", \
               (void *)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 busing", __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 busing", __func__,  \
                       m);                                                 \
   } while (0)
   
   #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)
   #else
   #define VM_PAGE_OBJECT_LOCK_ASSERT(m)   (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;
   
           /*
            * The PGA_WRITEABLE flag can only be set if the page is managed and
            * exclusive busied.  Currently, this flag is only set by pmap_enter().
            */
           KASSERT((bits & PGA_WRITEABLE) == 0 ||
               ((m->oflags & VPO_UNMANAGED) == 0 && vm_page_xbusied(m)),
               ("vm_page_aflag_set: PGA_WRITEABLE and not exclusive busy"));
   
           /*
            * 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(INVARIANTS)
           vm_page_dirty_KBI(m);
   #else
           m->dirty = VM_PAGE_BITS_ALL;
   #endif
   }
   
   /*
    *      vm_page_remque:
    *
    *      If the given page is in a page queue, then remove it from that page
    *      queue.
    *
    *      The page must be locked.
    */
   static inline void
   vm_page_remque(vm_page_t m)
   {
   
           if (m->queue != PQ_NONE)
                   vm_page_dequeue(m);
   }
   
   /*
    *      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;
   }
   
   #endif                          /* _KERNEL */
   #endif                          /* !_VM_PAGE_ */

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