MFH

[FreeBSD/FreeBSD.git] / 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.
 *
 * $FreeBSD$
 */

/*
 *      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 locks.  If a
 *      field is annotated with two of these locks then holding either is
 *      sufficient for read access but both are required for write access.
 *      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 is described in detail below.
 *
 *      The following annotations are possible:
 *      (A) the field must be accessed using atomic(9) and may require
 *          additional synchronization.
 *      (B) the page busy lock.
 *      (C) the field is immutable.
 *      (F) the per-domain lock for the free queues
 *      (M) Machine dependent, defined by pmap layer.
 *      (O) the object that the page belongs to.
 *      (P) the page lock.
 *      (Q) the page's queue lock.
 *
 *      The busy lock is an embedded reader-writer lock that protects the
 *      page's contents and identity (i.e., its <object, pindex> tuple) as
 *      well as certain valid/dirty modifications.  To avoid bloating the
 *      the page structure, the busy lock lacks some of the features available
 *      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.  vm_page_busy_acquire() will block until
 *      the lock is acquired.
 *
 *      The valid field is protected by the page busy lock (B) and object
 *      lock (O).  Transitions from invalid to valid are generally done
 *      via I/O or zero filling and do not require the object lock.
 *      These must be protected with the busy lock to prevent page-in or
 *      creation races.  Page invalidation generally happens as a result
 *      of truncate or msync.  When invalidated, pages must not be present
 *      in pmap and must hold the object lock to prevent concurrent
 *      speculative read-only mappings that do not require busy.  I/O
 *      routines may check for validity without a lock if they are prepared
 *      to handle invalidation races with higher level locks (vnode) or are
 *      unconcerned with races so long as they hold a reference to prevent
 *      recycling.  When a valid bit is set while holding a shared busy
 *      lock (A) atomic operations are used to protect against concurrent
 *      modification.
 *
 *      In contrast, the synchronization of accesses to the page's
 *      dirty field is a mix of machine dependent (M) and busy (B).  In
 *      the machine-independent layer, the page busy must be held 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().  An
 *      exclusive busy lock combined with pmap_remove_{write/all}() is the
 *      only way to ensure a page can not become dirty.  I/O generally
 *      removes the page from pmap to ensure exclusive access and atomic
 *      writes.
 *
 *      The ref_count field tracks references to the page.  References that
 *      prevent the page from being reclaimable are called wirings and are
 *      counted in the low bits of ref_count.  The containing object's
 *      reference, if one exists, is counted using the VPRC_OBJREF bit in the
 *      ref_count field.  Additionally, the VPRC_BLOCKED bit is used to
 *      atomically check for wirings and prevent new wirings via
 *      pmap_extract_and_hold().  When a page belongs to an object, it may be
 *      wired only when the object is locked, or the page is busy, or by
 *      pmap_extract_and_hold().  As a result, if the object is locked and the
 *      page is not busy (or is exclusively busied by the current thread), and
 *      the page is unmapped, its wire count will not increase.  The ref_count
 *      field is updated using atomic operations in most cases, except when it
 *      is known that no other references to the page exist, such as in the page
 *      allocator.  A page may be present in the page queues, or even actively
 *      scanned by the page daemon, without an explicitly counted referenced.
 *      The page daemon must therefore handle the possibility of a concurrent
 *      free of the page.
 *
 *      The queue state of a page consists of the queue and act_count fields of
 *      its atomically updated state, and the subset of atomic flags specified
 *      by PGA_QUEUE_STATE_MASK.  The queue field contains the page's page queue
 *      index, or PQ_NONE if it does not belong to a page queue.  To modify the
 *      queue field, the page queue lock corresponding to the old value must be
 *      held, unless that value is PQ_NONE, in which case the queue index must
 *      be updated using an atomic RMW operation.  There is one exception to
 *      this rule: the page daemon may transition the queue field from
 *      PQ_INACTIVE to PQ_NONE immediately prior to freeing the page during an
 *      inactive queue scan.  At that point the page is already dequeued and no
 *      other references to that vm_page structure can exist.  The PGA_ENQUEUED
 *      flag, when set, indicates that the page structure is physically inserted
 *      into the queue corresponding to the page's queue index, and may only be
 *      set or cleared with the corresponding page queue lock held.
 *
 *      To avoid contention on page queue locks, page queue operations (enqueue,
 *      dequeue, requeue) are batched using fixed-size per-CPU queues.  A
 *      deferred operation is requested by setting one of the flags in
 *      PGA_QUEUE_OP_MASK and inserting an entry into a batch queue.  When a
 *      queue is full, an attempt to insert a new entry will lock the page
 *      queues and trigger processing of the pending entries.  The
 *      type-stability of vm_page structures 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 with pending batch
 *      queue entries.  The page queue operation flags must be set using atomic
 *      RWM operations.
 */

#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

typedef union vm_page_astate {
        struct {
                uint16_t flags;
                uint8_t queue;
                uint8_t act_count;
        };
        uint32_t _bits;
} vm_page_astate_t;

struct vm_page {
        union {
                TAILQ_ENTRY(vm_page) q; /* page queue or free list (Q) */
                struct {
                        SLIST_ENTRY(vm_page) ss; /* private slists */
                } s;
                struct {
                        u_long p;
                        u_long v;
                } memguard;
                struct {
                        void *slab;
                        void *zone;
                } uma;
        } plinks;
        TAILQ_ENTRY(vm_page) listq;     /* pages in same object (O) */
        vm_object_t object;             /* which object am I in (O) */
        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 ref_count;                /* page references (A) */
        u_int busy_lock;                /* busy owners lock (A) */
        union vm_page_astate a;         /* state accessed atomically (A) */
        uint8_t order;                  /* index of the buddy queue (F) */
        uint8_t pool;                   /* vm_phys freepool index (F) */
        uint8_t flags;                  /* page PG_* flags (P) */
        uint8_t oflags;                 /* page VPO_* flags (O) */
        int8_t psind;                   /* pagesizes[] index (O) */
        int8_t segind;                  /* vm_phys segment index (C) */
        /* 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;           /* valid DEV_BSIZE chunk map (O,B) */
        vm_page_bits_t dirty;           /* dirty DEV_BSIZE chunk map (M,B) */
};

/*
 * Special bits used in the ref_count field.
 *
 * ref_count is normally used to count wirings that prevent the page from being
 * reclaimed, but also supports several special types of references that do not
 * prevent reclamation.  Accesses to the ref_count field must be atomic unless
 * the page is unallocated.
 *
 * VPRC_OBJREF is the reference held by the containing object.  It can set or
 * cleared only when the corresponding object's write lock is held.
 *
 * VPRC_BLOCKED is used to atomically block wirings via pmap lookups while
 * attempting to tear down all mappings of a given page.  The page lock and
 * object write lock must both be held in order to set or clear this bit.
 */
#define VPRC_BLOCKED    0x40000000u     /* mappings are being removed */
#define VPRC_OBJREF     0x80000000u     /* object reference, cleared with (O) */
#define VPRC_WIRE_COUNT(c)      ((c) & ~(VPRC_BLOCKED | VPRC_OBJREF))
#define VPRC_WIRE_COUNT_MAX     (~(VPRC_BLOCKED | VPRC_OBJREF))

/*
 * 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 */

/*
 * 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_EXCLUSIVE    VPB_BIT_EXCLUSIVE
#ifdef INVARIANTS
#define VPB_CURTHREAD_EXCLUSIVE                                         \
        (VPB_BIT_EXCLUSIVE | ((u_int)(uintptr_t)curthread & ~VPB_BIT_FLAGMASK))
#else
#define VPB_CURTHREAD_EXCLUSIVE VPB_SINGLE_EXCLUSIVE
#endif

#define VPB_UNBUSIED            VPB_SHARERS_WORD(0)

/* Freed lock blocks both shared and exclusive. */
#define VPB_FREED               (0xffffffff - VPB_BIT_SHARED)

#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_NOSYNC must be set and cleared with the page busy lock held.
 *
 * 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.  For allocated pages, the page lock
 * must be held to set this flag, but it may be set by vm_page_free_prep()
 * without the page lock held.  The page queue lock must be held to clear the
 * PGA_DEQUEUE flag.
 *
 * 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.
 *
 * PGA_SWAP_FREE is used to defer freeing swap space to the pageout daemon
 * when the context that dirties the page does not have the object write lock
 * held.
 */
#define PGA_WRITEABLE   0x0001          /* page may be mapped writeable */
#define PGA_REFERENCED  0x0002          /* page has been referenced */
#define PGA_EXECUTABLE  0x0004          /* page may be mapped executable */
#define PGA_ENQUEUED    0x0008          /* page is enqueued in a page queue */
#define PGA_DEQUEUE     0x0010          /* page is due to be dequeued */
#define PGA_REQUEUE     0x0020          /* page is due to be requeued */
#define PGA_REQUEUE_HEAD 0x0040         /* page requeue should bypass LRU */
#define PGA_NOSYNC      0x0080          /* do not collect for syncer */
#define PGA_SWAP_FREE   0x0100          /* page with swap space was dirtied */
#define PGA_SWAP_SPACE  0x0200          /* page has allocated swap space */

#define PGA_QUEUE_OP_MASK       (PGA_DEQUEUE | PGA_REQUEUE | PGA_REQUEUE_HEAD)
#define PGA_QUEUE_STATE_MASK    (PGA_ENQUEUED | PGA_QUEUE_OP_MASK)

/*
 * Page flags.  If changed at any other time than page allocation or
 * freeing, the modification must be protected by the vm_page lock.
 *
 * The PG_PCPU_CACHE flag is set at allocation time if the page was
 * allocated from a per-CPU cache.  It is cleared the next time that the
 * page is allocated from the physical memory allocator.
 */
#define PG_PCPU_CACHE   0x01            /* was allocated from per-CPU caches */
#define PG_FICTITIOUS   0x02            /* physical page doesn't exist */
#define PG_ZERO         0x04            /* page is zeroed */
#define PG_MARKER       0x08            /* special queue marker page */
#define PG_NODUMP       0x10            /* don't include this page in a dump */

/*
 * 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_NOCREAT        0x0400  /* (gp) Don't create a 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

bool vm_page_busy_acquire(vm_page_t m, int allocflags);
void vm_page_busy_downgrade(vm_page_t m);
int vm_page_busy_tryupgrade(vm_page_t m);
void vm_page_busy_sleep(vm_page_t m, const char *msg, bool nonshared);
void vm_page_busy_sleep_unlocked(vm_object_t obj, vm_page_t m,
    vm_pindex_t pindex, const char *wmesg, bool nonshared);
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);
void vm_page_bits_set(vm_page_t m, vm_page_bits_t *bits, vm_page_bits_t set);
bool vm_page_blacklist_add(vm_paddr_t pa, bool verbose);
vm_page_t vm_page_grab(vm_object_t, vm_pindex_t, int);
vm_page_t vm_page_grab_unlocked(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);
int vm_page_grab_pages_unlocked(vm_object_t object, vm_pindex_t pindex,
    int allocflags, vm_page_t *ma, int count);
int vm_page_grab_valid(vm_page_t *mp, vm_object_t object, vm_pindex_t pindex,
    int allocflags);
int vm_page_grab_valid_unlocked(vm_page_t *mp, vm_object_t object,
    vm_pindex_t pindex, int allocflags);
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);
vm_page_t vm_page_find_least(vm_object_t, vm_pindex_t);
void vm_page_free_invalid(vm_page_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);
void vm_page_invalid(vm_page_t m);
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);
void vm_page_pqbatch_drain(void);
void vm_page_pqbatch_submit(vm_page_t m, uint8_t queue);
bool vm_page_pqstate_commit(vm_page_t m, vm_page_astate_t *old,
    vm_page_astate_t new);
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);
#define VPR_TRYFREE     0x01
#define VPR_NOREUSE     0x02
void vm_page_release(vm_page_t m, int flags);
void vm_page_release_locked(vm_page_t m, int flags);
vm_page_t vm_page_relookup(vm_object_t, vm_pindex_t);
bool vm_page_remove(vm_page_t);
bool vm_page_remove_xbusy(vm_page_t);
int vm_page_rename(vm_page_t, vm_object_t, vm_pindex_t);
void vm_page_replace(vm_page_t mnew, vm_object_t object,
    vm_pindex_t pindex, vm_page_t mold);
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);
vm_page_bits_t vm_page_set_dirty(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);
int vm_page_sleep_if_xbusy(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_remove_all(vm_page_t m);
bool vm_page_try_remove_write(vm_page_t m);
int vm_page_trysbusy(vm_page_t m);
int vm_page_tryxbusy(vm_page_t m);
void vm_page_unhold_pages(vm_page_t *ma, int count);
void vm_page_unswappable(vm_page_t m);
void 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);
bool vm_page_wire_mapped(vm_page_t m);
void vm_page_xunbusy_hard(vm_page_t m);
void vm_page_xunbusy_hard_unchecked(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);
void vm_page_valid(vm_page_t m);
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_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_busy_fetch(m)   atomic_load_int(&(m)->busy_lock)

#define vm_page_assert_busied(m)                                        \
        KASSERT(vm_page_busied(m),                                      \
            ("vm_page_assert_busied: page %p not busy @ %s:%d", \
            (m), __FILE__, __LINE__))

#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_busy_fetch(m) & ~VPB_BIT_WAITERS) !=           \
            VPB_CURTHREAD_EXCLUSIVE,                                    \
            ("vm_page_assert_xbusied: page %p busy_lock %#x owned"      \
            " by me @ %s:%d",                                           \
            (m), (m)->busy_lock, __FILE__, __LINE__));                  \

#define vm_page_assert_xbusied_unchecked(m) do {                        \
        KASSERT(vm_page_xbusied(m),                                     \
            ("vm_page_assert_xbusied: page %p not exclusive busy @ %s:%d", \
            (m), __FILE__, __LINE__));                                  \
} while (0)
#define vm_page_assert_xbusied(m) do {                                  \
        vm_page_assert_xbusied_unchecked(m);                            \
        KASSERT((vm_page_busy_fetch(m) & ~VPB_BIT_WAITERS) ==           \
            VPB_CURTHREAD_EXCLUSIVE,                                    \
            ("vm_page_assert_xbusied: page %p busy_lock %#x not owned"  \
            " by me @ %s:%d",                                           \
            (m), (m)->busy_lock, __FILE__, __LINE__));                  \
} while (0)

#define vm_page_busied(m)                                               \
        (vm_page_busy_fetch(m) != 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_xbusied(m)                                              \
        ((vm_page_busy_fetch(m) & VPB_SINGLE_EXCLUSIVE) != 0)

#define vm_page_busy_freed(m)                                           \
        (vm_page_busy_fetch(m) == VPB_FREED)

#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_CURTHREAD_EXCLUSIVE, VPB_UNBUSIED))                     \
                vm_page_xunbusy_hard(m);                                \
} while (0)
#define vm_page_xunbusy_unchecked(m) do {                               \
        if (!atomic_cmpset_rel_int(&(m)->busy_lock,                     \
            VPB_CURTHREAD_EXCLUSIVE, VPB_UNBUSIED))                     \
                vm_page_xunbusy_hard_unchecked(m);                      \
} while (0)

#ifdef INVARIANTS
void vm_page_object_busy_assert(vm_page_t m);
#define VM_PAGE_OBJECT_BUSY_ASSERT(m)   vm_page_object_busy_assert(m)
void vm_page_assert_pga_writeable(vm_page_t m, uint16_t bits);
#define VM_PAGE_ASSERT_PGA_WRITEABLE(m, bits)                           \
        vm_page_assert_pga_writeable(m, bits)
/*
 * Claim ownership of a page's xbusy state.  In non-INVARIANTS kernels this
 * operation is a no-op since ownership is not tracked.  In particular
 * this macro does not provide any synchronization with the previous owner.
 */
#define vm_page_xbusy_claim(m) do {                                     \
        u_int _busy_lock;                                               \
                                                                        \
        vm_page_assert_xbusied_unchecked((m));                          \
        do {                                                            \
                _busy_lock = vm_page_busy_fetch(m);                     \
        } while (!atomic_cmpset_int(&(m)->busy_lock, _busy_lock,        \
            (_busy_lock & VPB_BIT_FLAGMASK) | VPB_CURTHREAD_EXCLUSIVE)); \
} while (0)
#else
#define VM_PAGE_OBJECT_BUSY_ASSERT(m)   (void)0
#define VM_PAGE_ASSERT_PGA_WRITEABLE(m, bits)   (void)0
#define vm_page_xbusy_claim(m)
#endif

#if BYTE_ORDER == BIG_ENDIAN
#define VM_PAGE_AFLAG_SHIFT     16
#else
#define VM_PAGE_AFLAG_SHIFT     0
#endif

/*
 *      Load a snapshot of a page's 32-bit atomic state.
 */
static inline vm_page_astate_t
vm_page_astate_load(vm_page_t m)
{
        vm_page_astate_t a;

        a._bits = atomic_load_32(&m->a._bits);
        return (a);
}

/*
 *      Atomically compare and set a page's atomic state.
 */
static inline bool
vm_page_astate_fcmpset(vm_page_t m, vm_page_astate_t *old, vm_page_astate_t new)
{

        KASSERT(new.queue == PQ_INACTIVE || (new.flags & PGA_REQUEUE_HEAD) == 0,
            ("%s: invalid head requeue request for page %p", __func__, m));
        KASSERT((new.flags & PGA_ENQUEUED) == 0 || new.queue != PQ_NONE,
            ("%s: setting PGA_ENQUEUED with PQ_NONE in page %p", __func__, m));
        KASSERT(new._bits != old->_bits,
            ("%s: bits are unchanged", __func__));

        return (atomic_fcmpset_32(&m->a._bits, &old->_bits, new._bits) != 0);
}

/*
 *      Clear the given bits in the specified page.
 */
static inline void
vm_page_aflag_clear(vm_page_t m, uint16_t bits)
{
        uint32_t *addr, val;

        /*
         * 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->a;
        val = bits << VM_PAGE_AFLAG_SHIFT;
        atomic_clear_32(addr, val);
}

/*
 *      Set the given bits in the specified page.
 */
static inline void
vm_page_aflag_set(vm_page_t m, uint16_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->a;
        val = bits << VM_PAGE_AFLAG_SHIFT;
        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_BUSY_ASSERT(m);
        m->dirty = 0;
}

static inline uint8_t
_vm_page_queue(vm_page_astate_t as)
{

        if ((as.flags & PGA_DEQUEUE) != 0)
                return (PQ_NONE);
        return (as.queue);
}

/*
 *      vm_page_queue:
 *
 *      Return the index of the queue containing m.
 */
static inline uint8_t
vm_page_queue(vm_page_t m)
{

        return (_vm_page_queue(vm_page_astate_load(m)));
}

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_drop:
 *
 *      Release a reference to a page and return the old reference count.
 */
static inline u_int
vm_page_drop(vm_page_t m, u_int val)
{
        u_int old;

        /*
         * Synchronize with vm_page_free_prep(): ensure that all updates to the
         * page structure are visible before it is freed.
         */
        atomic_thread_fence_rel();
        old = atomic_fetchadd_int(&m->ref_count, -val);
        KASSERT(old != VPRC_BLOCKED,
            ("vm_page_drop: page %p has an invalid refcount value", m));
        return (old);
}

/*
 *      vm_page_wired:
 *
 *      Perform a racy check to determine whether a reference prevents the page
 *      from being reclaimable.  If the page's object is locked, and the page is
 *      unmapped and exclusively busied by the current thread, no new wirings
 *      may be created.
 */
static inline bool
vm_page_wired(vm_page_t m)
{

        return (VPRC_WIRE_COUNT(m->ref_count) > 0);
}

static inline bool
vm_page_all_valid(vm_page_t m)
{

        return (m->valid == VM_PAGE_BITS_ALL);
}

static inline bool
vm_page_none_valid(vm_page_t m)
{

        return (m->valid == 0);
}

#endif                          /* _KERNEL */
#endif                          /* !_VM_PAGE_ */