Add 'contrib/bsddialog/' from commit '857c66bb5f3c5651b012beb1b5ea6ba39354ea94'

[FreeBSD/FreeBSD.git] / sys / vm / vm_page.c

/*-
 * SPDX-License-Identifier: (BSD-3-Clause AND MIT-CMU)
 *
 * Copyright (c) 1991 Regents of the University of California.
 * All rights reserved.
 * Copyright (c) 1998 Matthew Dillon.  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.c     7.4 (Berkeley) 5/7/91
 */

/*-
 * 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.
 */

/*
 *      Resident memory management module.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_vm.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/counter.h>
#include <sys/domainset.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/linker.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/msgbuf.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/rwlock.h>
#include <sys/sleepqueue.h>
#include <sys/sbuf.h>
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>

#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_param.h>
#include <vm/vm_domainset.h>
#include <vm/vm_kern.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_phys.h>
#include <vm/vm_pagequeue.h>
#include <vm/vm_pager.h>
#include <vm/vm_radix.h>
#include <vm/vm_reserv.h>
#include <vm/vm_extern.h>
#include <vm/vm_dumpset.h>
#include <vm/uma.h>
#include <vm/uma_int.h>

#include <machine/md_var.h>

struct vm_domain vm_dom[MAXMEMDOM];

DPCPU_DEFINE_STATIC(struct vm_batchqueue, pqbatch[MAXMEMDOM][PQ_COUNT]);

struct mtx_padalign __exclusive_cache_line pa_lock[PA_LOCK_COUNT];

struct mtx_padalign __exclusive_cache_line vm_domainset_lock;
/* The following fields are protected by the domainset lock. */
domainset_t __exclusive_cache_line vm_min_domains;
domainset_t __exclusive_cache_line vm_severe_domains;
static int vm_min_waiters;
static int vm_severe_waiters;
static int vm_pageproc_waiters;

static SYSCTL_NODE(_vm_stats, OID_AUTO, page, CTLFLAG_RD | CTLFLAG_MPSAFE, 0,
    "VM page statistics");

static COUNTER_U64_DEFINE_EARLY(pqstate_commit_retries);
SYSCTL_COUNTER_U64(_vm_stats_page, OID_AUTO, pqstate_commit_retries,
    CTLFLAG_RD, &pqstate_commit_retries,
    "Number of failed per-page atomic queue state updates");

static COUNTER_U64_DEFINE_EARLY(queue_ops);
SYSCTL_COUNTER_U64(_vm_stats_page, OID_AUTO, queue_ops,
    CTLFLAG_RD, &queue_ops,
    "Number of batched queue operations");

static COUNTER_U64_DEFINE_EARLY(queue_nops);
SYSCTL_COUNTER_U64(_vm_stats_page, OID_AUTO, queue_nops,
    CTLFLAG_RD, &queue_nops,
    "Number of batched queue operations with no effects");

/*
 * bogus page -- for I/O to/from partially complete buffers,
 * or for paging into sparsely invalid regions.
 */
vm_page_t bogus_page;

vm_page_t vm_page_array;
long vm_page_array_size;
long first_page;

struct bitset *vm_page_dump;
long vm_page_dump_pages;

static TAILQ_HEAD(, vm_page) blacklist_head;
static int sysctl_vm_page_blacklist(SYSCTL_HANDLER_ARGS);
SYSCTL_PROC(_vm, OID_AUTO, page_blacklist, CTLTYPE_STRING | CTLFLAG_RD |
    CTLFLAG_MPSAFE, NULL, 0, sysctl_vm_page_blacklist, "A", "Blacklist pages");

static uma_zone_t fakepg_zone;

static void vm_page_alloc_check(vm_page_t m);
static bool _vm_page_busy_sleep(vm_object_t obj, vm_page_t m,
    vm_pindex_t pindex, const char *wmesg, int allocflags, bool locked);
static void vm_page_clear_dirty_mask(vm_page_t m, vm_page_bits_t pagebits);
static void vm_page_enqueue(vm_page_t m, uint8_t queue);
static bool vm_page_free_prep(vm_page_t m);
static void vm_page_free_toq(vm_page_t m);
static void vm_page_init(void *dummy);
static int vm_page_insert_after(vm_page_t m, vm_object_t object,
    vm_pindex_t pindex, vm_page_t mpred);
static void vm_page_insert_radixdone(vm_page_t m, vm_object_t object,
    vm_page_t mpred);
static void vm_page_mvqueue(vm_page_t m, const uint8_t queue,
    const uint16_t nflag);
static int vm_page_reclaim_run(int req_class, int domain, u_long npages,
    vm_page_t m_run, vm_paddr_t high);
static void vm_page_release_toq(vm_page_t m, uint8_t nqueue, bool noreuse);
static int vm_domain_alloc_fail(struct vm_domain *vmd, vm_object_t object,
    int req);
static int vm_page_zone_import(void *arg, void **store, int cnt, int domain,
    int flags);
static void vm_page_zone_release(void *arg, void **store, int cnt);

SYSINIT(vm_page, SI_SUB_VM, SI_ORDER_SECOND, vm_page_init, NULL);

static void
vm_page_init(void *dummy)
{

        fakepg_zone = uma_zcreate("fakepg", sizeof(struct vm_page), NULL, NULL,
            NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
        bogus_page = vm_page_alloc_noobj(VM_ALLOC_WIRED);
}

/*
 * The cache page zone is initialized later since we need to be able to allocate
 * pages before UMA is fully initialized.
 */
static void
vm_page_init_cache_zones(void *dummy __unused)
{
        struct vm_domain *vmd;
        struct vm_pgcache *pgcache;
        int cache, domain, maxcache, pool;

        maxcache = 0;
        TUNABLE_INT_FETCH("vm.pgcache_zone_max_pcpu", &maxcache);
        maxcache *= mp_ncpus;
        for (domain = 0; domain < vm_ndomains; domain++) {
                vmd = VM_DOMAIN(domain);
                for (pool = 0; pool < VM_NFREEPOOL; pool++) {
                        pgcache = &vmd->vmd_pgcache[pool];
                        pgcache->domain = domain;
                        pgcache->pool = pool;
                        pgcache->zone = uma_zcache_create("vm pgcache",
                            PAGE_SIZE, NULL, NULL, NULL, NULL,
                            vm_page_zone_import, vm_page_zone_release, pgcache,
                            UMA_ZONE_VM);

                        /*
                         * Limit each pool's zone to 0.1% of the pages in the
                         * domain.
                         */
                        cache = maxcache != 0 ? maxcache :
                            vmd->vmd_page_count / 1000;
                        uma_zone_set_maxcache(pgcache->zone, cache);
                }
        }
}
SYSINIT(vm_page2, SI_SUB_VM_CONF, SI_ORDER_ANY, vm_page_init_cache_zones, NULL);

/* Make sure that u_long is at least 64 bits when PAGE_SIZE is 32K. */
#if PAGE_SIZE == 32768
#ifdef CTASSERT
CTASSERT(sizeof(u_long) >= 8);
#endif
#endif

/*
 *      vm_set_page_size:
 *
 *      Sets the page size, perhaps based upon the memory
 *      size.  Must be called before any use of page-size
 *      dependent functions.
 */
void
vm_set_page_size(void)
{
        if (vm_cnt.v_page_size == 0)
                vm_cnt.v_page_size = PAGE_SIZE;
        if (((vm_cnt.v_page_size - 1) & vm_cnt.v_page_size) != 0)
                panic("vm_set_page_size: page size not a power of two");
}

/*
 *      vm_page_blacklist_next:
 *
 *      Find the next entry in the provided string of blacklist
 *      addresses.  Entries are separated by space, comma, or newline.
 *      If an invalid integer is encountered then the rest of the
 *      string is skipped.  Updates the list pointer to the next
 *      character, or NULL if the string is exhausted or invalid.
 */
static vm_paddr_t
vm_page_blacklist_next(char **list, char *end)
{
        vm_paddr_t bad;
        char *cp, *pos;

        if (list == NULL || *list == NULL)
                return (0);
        if (**list =='\0') {
                *list = NULL;
                return (0);
        }

        /*
         * If there's no end pointer then the buffer is coming from
         * the kenv and we know it's null-terminated.
         */
        if (end == NULL)
                end = *list + strlen(*list);

        /* Ensure that strtoq() won't walk off the end */
        if (*end != '\0') {
                if (*end == '\n' || *end == ' ' || *end  == ',')
                        *end = '\0';
                else {
                        printf("Blacklist not terminated, skipping\n");
                        *list = NULL;
                        return (0);
                }
        }

        for (pos = *list; *pos != '\0'; pos = cp) {
                bad = strtoq(pos, &cp, 0);
                if (*cp == '\0' || *cp == ' ' || *cp == ',' || *cp == '\n') {
                        if (bad == 0) {
                                if (++cp < end)
                                        continue;
                                else
                                        break;
                        }
                } else
                        break;
                if (*cp == '\0' || ++cp >= end)
                        *list = NULL;
                else
                        *list = cp;
                return (trunc_page(bad));
        }
        printf("Garbage in RAM blacklist, skipping\n");
        *list = NULL;
        return (0);
}

bool
vm_page_blacklist_add(vm_paddr_t pa, bool verbose)
{
        struct vm_domain *vmd;
        vm_page_t m;
        int ret;

        m = vm_phys_paddr_to_vm_page(pa);
        if (m == NULL)
                return (true); /* page does not exist, no failure */

        vmd = vm_pagequeue_domain(m);
        vm_domain_free_lock(vmd);
        ret = vm_phys_unfree_page(m);
        vm_domain_free_unlock(vmd);
        if (ret != 0) {
                vm_domain_freecnt_inc(vmd, -1);
                TAILQ_INSERT_TAIL(&blacklist_head, m, listq);
                if (verbose)
                        printf("Skipping page with pa 0x%jx\n", (uintmax_t)pa);
        }
        return (ret);
}

/*
 *      vm_page_blacklist_check:
 *
 *      Iterate through the provided string of blacklist addresses, pulling
 *      each entry out of the physical allocator free list and putting it
 *      onto a list for reporting via the vm.page_blacklist sysctl.
 */
static void
vm_page_blacklist_check(char *list, char *end)
{
        vm_paddr_t pa;
        char *next;

        next = list;
        while (next != NULL) {
                if ((pa = vm_page_blacklist_next(&next, end)) == 0)
                        continue;
                vm_page_blacklist_add(pa, bootverbose);
        }
}

/*
 *      vm_page_blacklist_load:
 *
 *      Search for a special module named "ram_blacklist".  It'll be a
 *      plain text file provided by the user via the loader directive
 *      of the same name.
 */
static void
vm_page_blacklist_load(char **list, char **end)
{
        void *mod;
        u_char *ptr;
        u_int len;

        mod = NULL;
        ptr = NULL;

        mod = preload_search_by_type("ram_blacklist");
        if (mod != NULL) {
                ptr = preload_fetch_addr(mod);
                len = preload_fetch_size(mod);
        }
        *list = ptr;
        if (ptr != NULL)
                *end = ptr + len;
        else
                *end = NULL;
        return;
}

static int
sysctl_vm_page_blacklist(SYSCTL_HANDLER_ARGS)
{
        vm_page_t m;
        struct sbuf sbuf;
        int error, first;

        first = 1;
        error = sysctl_wire_old_buffer(req, 0);
        if (error != 0)
                return (error);
        sbuf_new_for_sysctl(&sbuf, NULL, 128, req);
        TAILQ_FOREACH(m, &blacklist_head, listq) {
                sbuf_printf(&sbuf, "%s%#jx", first ? "" : ",",
                    (uintmax_t)m->phys_addr);
                first = 0;
        }
        error = sbuf_finish(&sbuf);
        sbuf_delete(&sbuf);
        return (error);
}

/*
 * Initialize a dummy page for use in scans of the specified paging queue.
 * In principle, this function only needs to set the flag PG_MARKER.
 * Nonetheless, it write busies the page as a safety precaution.
 */
void
vm_page_init_marker(vm_page_t marker, int queue, uint16_t aflags)
{

        bzero(marker, sizeof(*marker));
        marker->flags = PG_MARKER;
        marker->a.flags = aflags;
        marker->busy_lock = VPB_CURTHREAD_EXCLUSIVE;
        marker->a.queue = queue;
}

static void
vm_page_domain_init(int domain)
{
        struct vm_domain *vmd;
        struct vm_pagequeue *pq;
        int i;

        vmd = VM_DOMAIN(domain);
        bzero(vmd, sizeof(*vmd));
        *__DECONST(const char **, &vmd->vmd_pagequeues[PQ_INACTIVE].pq_name) =
            "vm inactive pagequeue";
        *__DECONST(const char **, &vmd->vmd_pagequeues[PQ_ACTIVE].pq_name) =
            "vm active pagequeue";
        *__DECONST(const char **, &vmd->vmd_pagequeues[PQ_LAUNDRY].pq_name) =
            "vm laundry pagequeue";
        *__DECONST(const char **,
            &vmd->vmd_pagequeues[PQ_UNSWAPPABLE].pq_name) =
            "vm unswappable pagequeue";
        vmd->vmd_domain = domain;
        vmd->vmd_page_count = 0;
        vmd->vmd_free_count = 0;
        vmd->vmd_segs = 0;
        vmd->vmd_oom = FALSE;
        for (i = 0; i < PQ_COUNT; i++) {
                pq = &vmd->vmd_pagequeues[i];
                TAILQ_INIT(&pq->pq_pl);
                mtx_init(&pq->pq_mutex, pq->pq_name, "vm pagequeue",
                    MTX_DEF | MTX_DUPOK);
                pq->pq_pdpages = 0;
                vm_page_init_marker(&vmd->vmd_markers[i], i, 0);
        }
        mtx_init(&vmd->vmd_free_mtx, "vm page free queue", NULL, MTX_DEF);
        mtx_init(&vmd->vmd_pageout_mtx, "vm pageout lock", NULL, MTX_DEF);
        snprintf(vmd->vmd_name, sizeof(vmd->vmd_name), "%d", domain);

        /*
         * inacthead is used to provide FIFO ordering for LRU-bypassing
         * insertions.
         */
        vm_page_init_marker(&vmd->vmd_inacthead, PQ_INACTIVE, PGA_ENQUEUED);
        TAILQ_INSERT_HEAD(&vmd->vmd_pagequeues[PQ_INACTIVE].pq_pl,
            &vmd->vmd_inacthead, plinks.q);

        /*
         * The clock pages are used to implement active queue scanning without
         * requeues.  Scans start at clock[0], which is advanced after the scan
         * ends.  When the two clock hands meet, they are reset and scanning
         * resumes from the head of the queue.
         */
        vm_page_init_marker(&vmd->vmd_clock[0], PQ_ACTIVE, PGA_ENQUEUED);
        vm_page_init_marker(&vmd->vmd_clock[1], PQ_ACTIVE, PGA_ENQUEUED);
        TAILQ_INSERT_HEAD(&vmd->vmd_pagequeues[PQ_ACTIVE].pq_pl,
            &vmd->vmd_clock[0], plinks.q);
        TAILQ_INSERT_TAIL(&vmd->vmd_pagequeues[PQ_ACTIVE].pq_pl,
            &vmd->vmd_clock[1], plinks.q);
}

/*
 * Initialize a physical page in preparation for adding it to the free
 * lists.
 */
void
vm_page_init_page(vm_page_t m, vm_paddr_t pa, int segind)
{

        m->object = NULL;
        m->ref_count = 0;
        m->busy_lock = VPB_FREED;
        m->flags = m->a.flags = 0;
        m->phys_addr = pa;
        m->a.queue = PQ_NONE;
        m->psind = 0;
        m->segind = segind;
        m->order = VM_NFREEORDER;
        m->pool = VM_FREEPOOL_DEFAULT;
        m->valid = m->dirty = 0;
        pmap_page_init(m);
}

#ifndef PMAP_HAS_PAGE_ARRAY
static vm_paddr_t
vm_page_array_alloc(vm_offset_t *vaddr, vm_paddr_t end, vm_paddr_t page_range)
{
        vm_paddr_t new_end;

        /*
         * Reserve an unmapped guard page to trap access to vm_page_array[-1].
         * However, because this page is allocated from KVM, out-of-bounds
         * accesses using the direct map will not be trapped.
         */
        *vaddr += PAGE_SIZE;

        /*
         * Allocate physical memory for the page structures, and map it.
         */
        new_end = trunc_page(end - page_range * sizeof(struct vm_page));
        vm_page_array = (vm_page_t)pmap_map(vaddr, new_end, end,
            VM_PROT_READ | VM_PROT_WRITE);
        vm_page_array_size = page_range;

        return (new_end);
}
#endif

/*
 *      vm_page_startup:
 *
 *      Initializes the resident memory module.  Allocates physical memory for
 *      bootstrapping UMA and some data structures that are used to manage
 *      physical pages.  Initializes these structures, and populates the free
 *      page queues.
 */
vm_offset_t
vm_page_startup(vm_offset_t vaddr)
{
        struct vm_phys_seg *seg;
        struct vm_domain *vmd;
        vm_page_t m;
        char *list, *listend;
        vm_paddr_t end, high_avail, low_avail, new_end, size;
        vm_paddr_t page_range __unused;
        vm_paddr_t last_pa, pa, startp, endp;
        u_long pagecount;
#if MINIDUMP_PAGE_TRACKING
        u_long vm_page_dump_size;
#endif
        int biggestone, i, segind;
#ifdef WITNESS
        vm_offset_t mapped;
        int witness_size;
#endif
#if defined(__i386__) && defined(VM_PHYSSEG_DENSE)
        long ii;
#endif

        vaddr = round_page(vaddr);

        vm_phys_early_startup();
        biggestone = vm_phys_avail_largest();
        end = phys_avail[biggestone+1];

        /*
         * Initialize the page and queue locks.
         */
        mtx_init(&vm_domainset_lock, "vm domainset lock", NULL, MTX_DEF);
        for (i = 0; i < PA_LOCK_COUNT; i++)
                mtx_init(&pa_lock[i], "vm page", NULL, MTX_DEF);
        for (i = 0; i < vm_ndomains; i++)
                vm_page_domain_init(i);

        new_end = end;
#ifdef WITNESS
        witness_size = round_page(witness_startup_count());
        new_end -= witness_size;
        mapped = pmap_map(&vaddr, new_end, new_end + witness_size,
            VM_PROT_READ | VM_PROT_WRITE);
        bzero((void *)mapped, witness_size);
        witness_startup((void *)mapped);
#endif

#if MINIDUMP_PAGE_TRACKING
        /*
         * Allocate a bitmap to indicate that a random physical page
         * needs to be included in a minidump.
         *
         * The amd64 port needs this to indicate which direct map pages
         * need to be dumped, via calls to dump_add_page()/dump_drop_page().
         *
         * However, i386 still needs this workspace internally within the
         * minidump code.  In theory, they are not needed on i386, but are
         * included should the sf_buf code decide to use them.
         */
        last_pa = 0;
        vm_page_dump_pages = 0;
        for (i = 0; dump_avail[i + 1] != 0; i += 2) {
                vm_page_dump_pages += howmany(dump_avail[i + 1], PAGE_SIZE) -
                    dump_avail[i] / PAGE_SIZE;
                if (dump_avail[i + 1] > last_pa)
                        last_pa = dump_avail[i + 1];
        }
        vm_page_dump_size = round_page(BITSET_SIZE(vm_page_dump_pages));
        new_end -= vm_page_dump_size;
        vm_page_dump = (void *)(uintptr_t)pmap_map(&vaddr, new_end,
            new_end + vm_page_dump_size, VM_PROT_READ | VM_PROT_WRITE);
        bzero((void *)vm_page_dump, vm_page_dump_size);
#else
        (void)last_pa;
#endif
#if defined(__aarch64__) || defined(__amd64__) || defined(__mips__) || \
    defined(__riscv) || defined(__powerpc64__)
        /*
         * Include the UMA bootstrap pages, witness pages and vm_page_dump
         * in a crash dump.  When pmap_map() uses the direct map, they are
         * not automatically included.
         */
        for (pa = new_end; pa < end; pa += PAGE_SIZE)
                dump_add_page(pa);
#endif
        phys_avail[biggestone + 1] = new_end;
#ifdef __amd64__
        /*
         * Request that the physical pages underlying the message buffer be
         * included in a crash dump.  Since the message buffer is accessed
         * through the direct map, they are not automatically included.
         */
        pa = DMAP_TO_PHYS((vm_offset_t)msgbufp->msg_ptr);
        last_pa = pa + round_page(msgbufsize);
        while (pa < last_pa) {
                dump_add_page(pa);
                pa += PAGE_SIZE;
        }
#endif
        /*
         * Compute the number of pages of memory that will be available for
         * use, taking into account the overhead of a page structure per page.
         * In other words, solve
         *      "available physical memory" - round_page(page_range *
         *          sizeof(struct vm_page)) = page_range * PAGE_SIZE 
         * for page_range.  
         */
        low_avail = phys_avail[0];
        high_avail = phys_avail[1];
        for (i = 0; i < vm_phys_nsegs; i++) {
                if (vm_phys_segs[i].start < low_avail)
                        low_avail = vm_phys_segs[i].start;
                if (vm_phys_segs[i].end > high_avail)
                        high_avail = vm_phys_segs[i].end;
        }
        /* Skip the first chunk.  It is already accounted for. */
        for (i = 2; phys_avail[i + 1] != 0; i += 2) {
                if (phys_avail[i] < low_avail)
                        low_avail = phys_avail[i];
                if (phys_avail[i + 1] > high_avail)
                        high_avail = phys_avail[i + 1];
        }
        first_page = low_avail / PAGE_SIZE;
#ifdef VM_PHYSSEG_SPARSE
        size = 0;
        for (i = 0; i < vm_phys_nsegs; i++)
                size += vm_phys_segs[i].end - vm_phys_segs[i].start;
        for (i = 0; phys_avail[i + 1] != 0; i += 2)
                size += phys_avail[i + 1] - phys_avail[i];
#elif defined(VM_PHYSSEG_DENSE)
        size = high_avail - low_avail;
#else
#error "Either VM_PHYSSEG_DENSE or VM_PHYSSEG_SPARSE must be defined."
#endif

#ifdef PMAP_HAS_PAGE_ARRAY
        pmap_page_array_startup(size / PAGE_SIZE);
        biggestone = vm_phys_avail_largest();
        end = new_end = phys_avail[biggestone + 1];
#else
#ifdef VM_PHYSSEG_DENSE
        /*
         * In the VM_PHYSSEG_DENSE case, the number of pages can account for
         * the overhead of a page structure per page only if vm_page_array is
         * allocated from the last physical memory chunk.  Otherwise, we must
         * allocate page structures representing the physical memory
         * underlying vm_page_array, even though they will not be used.
         */
        if (new_end != high_avail)
                page_range = size / PAGE_SIZE;
        else
#endif
        {
                page_range = size / (PAGE_SIZE + sizeof(struct vm_page));

                /*
                 * If the partial bytes remaining are large enough for
                 * a page (PAGE_SIZE) without a corresponding
                 * 'struct vm_page', then new_end will contain an
                 * extra page after subtracting the length of the VM
                 * page array.  Compensate by subtracting an extra
                 * page from new_end.
                 */
                if (size % (PAGE_SIZE + sizeof(struct vm_page)) >= PAGE_SIZE) {
                        if (new_end == high_avail)
                                high_avail -= PAGE_SIZE;
                        new_end -= PAGE_SIZE;
                }
        }
        end = new_end;
        new_end = vm_page_array_alloc(&vaddr, end, page_range);
#endif

#if VM_NRESERVLEVEL > 0
        /*
         * Allocate physical memory for the reservation management system's
         * data structures, and map it.
         */
        new_end = vm_reserv_startup(&vaddr, new_end);
#endif
#if defined(__aarch64__) || defined(__amd64__) || defined(__mips__) || \
    defined(__riscv) || defined(__powerpc64__)
        /*
         * Include vm_page_array and vm_reserv_array in a crash dump.
         */
        for (pa = new_end; pa < end; pa += PAGE_SIZE)
                dump_add_page(pa);
#endif
        phys_avail[biggestone + 1] = new_end;

        /*
         * Add physical memory segments corresponding to the available
         * physical pages.
         */
        for (i = 0; phys_avail[i + 1] != 0; i += 2)
                if (vm_phys_avail_size(i) != 0)
                        vm_phys_add_seg(phys_avail[i], phys_avail[i + 1]);

        /*
         * Initialize the physical memory allocator.
         */
        vm_phys_init();

        /*
         * Initialize the page structures and add every available page to the
         * physical memory allocator's free lists.
         */
#if defined(__i386__) && defined(VM_PHYSSEG_DENSE)
        for (ii = 0; ii < vm_page_array_size; ii++) {
                m = &vm_page_array[ii];
                vm_page_init_page(m, (first_page + ii) << PAGE_SHIFT, 0);
                m->flags = PG_FICTITIOUS;
        }
#endif
        vm_cnt.v_page_count = 0;
        for (segind = 0; segind < vm_phys_nsegs; segind++) {
                seg = &vm_phys_segs[segind];
                for (m = seg->first_page, pa = seg->start; pa < seg->end;
                    m++, pa += PAGE_SIZE)
                        vm_page_init_page(m, pa, segind);

                /*
                 * Add the segment's pages that are covered by one of
                 * phys_avail's ranges to the free lists.
                 */
                for (i = 0; phys_avail[i + 1] != 0; i += 2) {
                        if (seg->end <= phys_avail[i] ||
                            seg->start >= phys_avail[i + 1])
                                continue;

                        startp = MAX(seg->start, phys_avail[i]);
                        endp = MIN(seg->end, phys_avail[i + 1]);
                        pagecount = (u_long)atop(endp - startp);
                        if (pagecount == 0)
                                continue;

                        m = seg->first_page + atop(startp - seg->start);
                        vmd = VM_DOMAIN(seg->domain);
                        vm_domain_free_lock(vmd);
                        vm_phys_enqueue_contig(m, pagecount);
                        vm_domain_free_unlock(vmd);
                        vm_domain_freecnt_inc(vmd, pagecount);
                        vm_cnt.v_page_count += (u_int)pagecount;
                        vmd->vmd_page_count += (u_int)pagecount;
                        vmd->vmd_segs |= 1UL << segind;
                }
        }

        /*
         * Remove blacklisted pages from the physical memory allocator.
         */
        TAILQ_INIT(&blacklist_head);
        vm_page_blacklist_load(&list, &listend);
        vm_page_blacklist_check(list, listend);

        list = kern_getenv("vm.blacklist");
        vm_page_blacklist_check(list, NULL);

        freeenv(list);
#if VM_NRESERVLEVEL > 0
        /*
         * Initialize the reservation management system.
         */
        vm_reserv_init();
#endif

        return (vaddr);
}

void
vm_page_reference(vm_page_t m)
{

        vm_page_aflag_set(m, PGA_REFERENCED);
}

/*
 *      vm_page_trybusy
 *
 *      Helper routine for grab functions to trylock busy.
 *
 *      Returns true on success and false on failure.
 */
static bool
vm_page_trybusy(vm_page_t m, int allocflags)
{

        if ((allocflags & (VM_ALLOC_SBUSY | VM_ALLOC_IGN_SBUSY)) != 0)
                return (vm_page_trysbusy(m));
        else
                return (vm_page_tryxbusy(m));
}

/*
 *      vm_page_tryacquire
 *
 *      Helper routine for grab functions to trylock busy and wire.
 *
 *      Returns true on success and false on failure.
 */
static inline bool
vm_page_tryacquire(vm_page_t m, int allocflags)
{
        bool locked;

        locked = vm_page_trybusy(m, allocflags);
        if (locked && (allocflags & VM_ALLOC_WIRED) != 0)
                vm_page_wire(m);
        return (locked);
}

/*
 *      vm_page_busy_acquire:
 *
 *      Acquire the busy lock as described by VM_ALLOC_* flags.  Will loop
 *      and drop the object lock if necessary.
 */
bool
vm_page_busy_acquire(vm_page_t m, int allocflags)
{
        vm_object_t obj;
        bool locked;

        /*
         * The page-specific object must be cached because page
         * identity can change during the sleep, causing the
         * re-lock of a different object.
         * It is assumed that a reference to the object is already
         * held by the callers.
         */
        obj = atomic_load_ptr(&m->object);
        for (;;) {
                if (vm_page_tryacquire(m, allocflags))
                        return (true);
                if ((allocflags & VM_ALLOC_NOWAIT) != 0)
                        return (false);
                if (obj != NULL)
                        locked = VM_OBJECT_WOWNED(obj);
                else
                        locked = false;
                MPASS(locked || vm_page_wired(m));
                if (_vm_page_busy_sleep(obj, m, m->pindex, "vmpba", allocflags,
                    locked) && locked)
                        VM_OBJECT_WLOCK(obj);
                if ((allocflags & VM_ALLOC_WAITFAIL) != 0)
                        return (false);
                KASSERT(m->object == obj || m->object == NULL,
                    ("vm_page_busy_acquire: page %p does not belong to %p",
                    m, obj));
        }
}

/*
 *      vm_page_busy_downgrade:
 *
 *      Downgrade an exclusive busy page into a single shared busy page.
 */
void
vm_page_busy_downgrade(vm_page_t m)
{
        u_int x;

        vm_page_assert_xbusied(m);

        x = vm_page_busy_fetch(m);
        for (;;) {
                if (atomic_fcmpset_rel_int(&m->busy_lock,
                    &x, VPB_SHARERS_WORD(1)))
                        break;
        }
        if ((x & VPB_BIT_WAITERS) != 0)
                wakeup(m);
}

/*
 *
 *      vm_page_busy_tryupgrade:
 *
 *      Attempt to upgrade a single shared busy into an exclusive busy.
 */
int
vm_page_busy_tryupgrade(vm_page_t m)
{
        u_int ce, x;

        vm_page_assert_sbusied(m);

        x = vm_page_busy_fetch(m);
        ce = VPB_CURTHREAD_EXCLUSIVE;
        for (;;) {
                if (VPB_SHARERS(x) > 1)
                        return (0);
                KASSERT((x & ~VPB_BIT_WAITERS) == VPB_SHARERS_WORD(1),
                    ("vm_page_busy_tryupgrade: invalid lock state"));
                if (!atomic_fcmpset_acq_int(&m->busy_lock, &x,
                    ce | (x & VPB_BIT_WAITERS)))
                        continue;
                return (1);
        }
}

/*
 *      vm_page_sbusied:
 *
 *      Return a positive value if the page is shared busied, 0 otherwise.
 */
int
vm_page_sbusied(vm_page_t m)
{
        u_int x;

        x = vm_page_busy_fetch(m);
        return ((x & VPB_BIT_SHARED) != 0 && x != VPB_UNBUSIED);
}

/*
 *      vm_page_sunbusy:
 *
 *      Shared unbusy a page.
 */
void
vm_page_sunbusy(vm_page_t m)
{
        u_int x;

        vm_page_assert_sbusied(m);

        x = vm_page_busy_fetch(m);
        for (;;) {
                KASSERT(x != VPB_FREED,
                    ("vm_page_sunbusy: Unlocking freed page."));
                if (VPB_SHARERS(x) > 1) {
                        if (atomic_fcmpset_int(&m->busy_lock, &x,
                            x - VPB_ONE_SHARER))
                                break;
                        continue;
                }
                KASSERT((x & ~VPB_BIT_WAITERS) == VPB_SHARERS_WORD(1),
                    ("vm_page_sunbusy: invalid lock state"));
                if (!atomic_fcmpset_rel_int(&m->busy_lock, &x, VPB_UNBUSIED))
                        continue;
                if ((x & VPB_BIT_WAITERS) == 0)
                        break;
                wakeup(m);
                break;
        }
}

/*
 *      vm_page_busy_sleep:
 *
 *      Sleep if the page is busy, using the page pointer as wchan.
 *      This is used to implement the hard-path of the busying mechanism.
 *
 *      If VM_ALLOC_IGN_SBUSY is specified in allocflags, the function
 *      will not sleep if the page is shared-busy.
 *
 *      The object lock must be held on entry.
 *
 *      Returns true if it slept and dropped the object lock, or false
 *      if there was no sleep and the lock is still held.
 */
bool
vm_page_busy_sleep(vm_page_t m, const char *wmesg, int allocflags)
{
        vm_object_t obj;

        obj = m->object;
        VM_OBJECT_ASSERT_LOCKED(obj);

        return (_vm_page_busy_sleep(obj, m, m->pindex, wmesg, allocflags,
            true));
}

/*
 *      vm_page_busy_sleep_unlocked:
 *
 *      Sleep if the page is busy, using the page pointer as wchan.
 *      This is used to implement the hard-path of busying mechanism.
 *
 *      If VM_ALLOC_IGN_SBUSY is specified in allocflags, the function
 *      will not sleep if the page is shared-busy.
 *
 *      The object lock must not be held on entry.  The operation will
 *      return if the page changes identity.
 */
void
vm_page_busy_sleep_unlocked(vm_object_t obj, vm_page_t m, vm_pindex_t pindex,
    const char *wmesg, int allocflags)
{
        VM_OBJECT_ASSERT_UNLOCKED(obj);

        (void)_vm_page_busy_sleep(obj, m, pindex, wmesg, allocflags, false);
}

/*
 *      _vm_page_busy_sleep:
 *
 *      Internal busy sleep function.  Verifies the page identity and
 *      lockstate against parameters.  Returns true if it sleeps and
 *      false otherwise.
 *
 *      allocflags uses VM_ALLOC_* flags to specify the lock required.
 *
 *      If locked is true the lock will be dropped for any true returns
 *      and held for any false returns.
 */
static bool
_vm_page_busy_sleep(vm_object_t obj, vm_page_t m, vm_pindex_t pindex,
    const char *wmesg, int allocflags, bool locked)
{
        bool xsleep;
        u_int x;

        /*
         * If the object is busy we must wait for that to drain to zero
         * before trying the page again.
         */
        if (obj != NULL && vm_object_busied(obj)) {
                if (locked)
                        VM_OBJECT_DROP(obj);
                vm_object_busy_wait(obj, wmesg);
                return (true);
        }

        if (!vm_page_busied(m))
                return (false);

        xsleep = (allocflags & (VM_ALLOC_SBUSY | VM_ALLOC_IGN_SBUSY)) != 0;
        sleepq_lock(m);
        x = vm_page_busy_fetch(m);
        do {
                /*
                 * If the page changes objects or becomes unlocked we can
                 * simply return.
                 */
                if (x == VPB_UNBUSIED ||
                    (xsleep && (x & VPB_BIT_SHARED) != 0) ||
                    m->object != obj || m->pindex != pindex) {
                        sleepq_release(m);
                        return (false);
                }
                if ((x & VPB_BIT_WAITERS) != 0)
                        break;
        } while (!atomic_fcmpset_int(&m->busy_lock, &x, x | VPB_BIT_WAITERS));
        if (locked)
                VM_OBJECT_DROP(obj);
        DROP_GIANT();
        sleepq_add(m, NULL, wmesg, 0, 0);
        sleepq_wait(m, PVM);
        PICKUP_GIANT();
        return (true);
}

/*
 *      vm_page_trysbusy:
 *
 *      Try to shared busy a page.
 *      If the operation succeeds 1 is returned otherwise 0.
 *      The operation never sleeps.
 */
int
vm_page_trysbusy(vm_page_t m)
{
        vm_object_t obj;
        u_int x;

        obj = m->object;
        x = vm_page_busy_fetch(m);
        for (;;) {
                if ((x & VPB_BIT_SHARED) == 0)
                        return (0);
                /*
                 * Reduce the window for transient busies that will trigger
                 * false negatives in vm_page_ps_test().
                 */
                if (obj != NULL && vm_object_busied(obj))
                        return (0);
                if (atomic_fcmpset_acq_int(&m->busy_lock, &x,
                    x + VPB_ONE_SHARER))
                        break;
        }

        /* Refetch the object now that we're guaranteed that it is stable. */
        obj = m->object;
        if (obj != NULL && vm_object_busied(obj)) {
                vm_page_sunbusy(m);
                return (0);
        }
        return (1);
}

/*
 *      vm_page_tryxbusy:
 *
 *      Try to exclusive busy a page.
 *      If the operation succeeds 1 is returned otherwise 0.
 *      The operation never sleeps.
 */
int
vm_page_tryxbusy(vm_page_t m)
{
        vm_object_t obj;

        if (atomic_cmpset_acq_int(&m->busy_lock, VPB_UNBUSIED,
            VPB_CURTHREAD_EXCLUSIVE) == 0)
                return (0);

        obj = m->object;
        if (obj != NULL && vm_object_busied(obj)) {
                vm_page_xunbusy(m);
                return (0);
        }
        return (1);
}

static void
vm_page_xunbusy_hard_tail(vm_page_t m)
{
        atomic_store_rel_int(&m->busy_lock, VPB_UNBUSIED);
        /* Wake the waiter. */
        wakeup(m);
}

/*
 *      vm_page_xunbusy_hard:
 *
 *      Called when unbusy has failed because there is a waiter.
 */
void
vm_page_xunbusy_hard(vm_page_t m)
{
        vm_page_assert_xbusied(m);
        vm_page_xunbusy_hard_tail(m);
}

void
vm_page_xunbusy_hard_unchecked(vm_page_t m)
{
        vm_page_assert_xbusied_unchecked(m);
        vm_page_xunbusy_hard_tail(m);
}

static void
vm_page_busy_free(vm_page_t m)
{
        u_int x;

        atomic_thread_fence_rel();
        x = atomic_swap_int(&m->busy_lock, VPB_FREED);
        if ((x & VPB_BIT_WAITERS) != 0)
                wakeup(m);
}

/*
 *      vm_page_unhold_pages:
 *
 *      Unhold each of the pages that is referenced by the given array.
 */
void
vm_page_unhold_pages(vm_page_t *ma, int count)
{

        for (; count != 0; count--) {
                vm_page_unwire(*ma, PQ_ACTIVE);
                ma++;
        }
}

vm_page_t
PHYS_TO_VM_PAGE(vm_paddr_t pa)
{
        vm_page_t m;

#ifdef VM_PHYSSEG_SPARSE
        m = vm_phys_paddr_to_vm_page(pa);
        if (m == NULL)
                m = vm_phys_fictitious_to_vm_page(pa);
        return (m);
#elif defined(VM_PHYSSEG_DENSE)
        long pi;

        pi = atop(pa);
        if (pi >= first_page && (pi - first_page) < vm_page_array_size) {
                m = &vm_page_array[pi - first_page];
                return (m);
        }
        return (vm_phys_fictitious_to_vm_page(pa));
#else
#error "Either VM_PHYSSEG_DENSE or VM_PHYSSEG_SPARSE must be defined."
#endif
}

/*
 *      vm_page_getfake:
 *
 *      Create a fictitious page with the specified physical address and
 *      memory attribute.  The memory attribute is the only the machine-
 *      dependent aspect of a fictitious page that must be initialized.
 */
vm_page_t
vm_page_getfake(vm_paddr_t paddr, vm_memattr_t memattr)
{
        vm_page_t m;

        m = uma_zalloc(fakepg_zone, M_WAITOK | M_ZERO);
        vm_page_initfake(m, paddr, memattr);
        return (m);
}

void
vm_page_initfake(vm_page_t m, vm_paddr_t paddr, vm_memattr_t memattr)
{

        if ((m->flags & PG_FICTITIOUS) != 0) {
                /*
                 * The page's memattr might have changed since the
                 * previous initialization.  Update the pmap to the
                 * new memattr.
                 */
                goto memattr;
        }
        m->phys_addr = paddr;
        m->a.queue = PQ_NONE;
        /* Fictitious pages don't use "segind". */
        m->flags = PG_FICTITIOUS;
        /* Fictitious pages don't use "order" or "pool". */
        m->oflags = VPO_UNMANAGED;
        m->busy_lock = VPB_CURTHREAD_EXCLUSIVE;
        /* Fictitious pages are unevictable. */
        m->ref_count = 1;
        pmap_page_init(m);
memattr:
        pmap_page_set_memattr(m, memattr);
}

/*
 *      vm_page_putfake:
 *
 *      Release a fictitious page.
 */
void
vm_page_putfake(vm_page_t m)
{

        KASSERT((m->oflags & VPO_UNMANAGED) != 0, ("managed %p", m));
        KASSERT((m->flags & PG_FICTITIOUS) != 0,
            ("vm_page_putfake: bad page %p", m));
        vm_page_assert_xbusied(m);
        vm_page_busy_free(m);
        uma_zfree(fakepg_zone, m);
}

/*
 *      vm_page_updatefake:
 *
 *      Update the given fictitious page to the specified physical address and
 *      memory attribute.
 */
void
vm_page_updatefake(vm_page_t m, vm_paddr_t paddr, vm_memattr_t memattr)
{

        KASSERT((m->flags & PG_FICTITIOUS) != 0,
            ("vm_page_updatefake: bad page %p", m));
        m->phys_addr = paddr;
        pmap_page_set_memattr(m, memattr);
}

/*
 *      vm_page_free:
 *
 *      Free a page.
 */
void
vm_page_free(vm_page_t m)
{

        m->flags &= ~PG_ZERO;
        vm_page_free_toq(m);
}

/*
 *      vm_page_free_zero:
 *
 *      Free a page to the zerod-pages queue
 */
void
vm_page_free_zero(vm_page_t m)
{

        m->flags |= PG_ZERO;
        vm_page_free_toq(m);
}

/*
 * Unbusy and handle the page queueing for a page from a getpages request that
 * was optionally read ahead or behind.
 */
void
vm_page_readahead_finish(vm_page_t m)
{

        /* We shouldn't put invalid pages on queues. */
        KASSERT(!vm_page_none_valid(m), ("%s: %p is invalid", __func__, m));

        /*
         * Since the page is not the actually needed one, whether it should
         * be activated or deactivated is not obvious.  Empirical results
         * have shown that deactivating the page is usually the best choice,
         * unless the page is wanted by another thread.
         */
        if ((vm_page_busy_fetch(m) & VPB_BIT_WAITERS) != 0)
                vm_page_activate(m);
        else
                vm_page_deactivate(m);
        vm_page_xunbusy_unchecked(m);
}

/*
 * Destroy the identity of an invalid page and free it if possible.
 * This is intended to be used when reading a page from backing store fails.
 */
void
vm_page_free_invalid(vm_page_t m)
{

        KASSERT(vm_page_none_valid(m), ("page %p is valid", m));
        KASSERT(!pmap_page_is_mapped(m), ("page %p is mapped", m));
        KASSERT(m->object != NULL, ("page %p has no object", m));
        VM_OBJECT_ASSERT_WLOCKED(m->object);

        /*
         * We may be attempting to free the page as part of the handling for an
         * I/O error, in which case the page was xbusied by a different thread.
         */
        vm_page_xbusy_claim(m);

        /*
         * If someone has wired this page while the object lock
         * was not held, then the thread that unwires is responsible
         * for freeing the page.  Otherwise just free the page now.
         * The wire count of this unmapped page cannot change while
         * we have the page xbusy and the page's object wlocked.
         */
        if (vm_page_remove(m))
                vm_page_free(m);
}

/*
 *      vm_page_dirty_KBI:              [ internal use only ]
 *
 *      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().
 *
 *      This function should only be called by vm_page_dirty().
 */
void
vm_page_dirty_KBI(vm_page_t m)
{

        /* Refer to this operation by its public name. */
        KASSERT(vm_page_all_valid(m), ("vm_page_dirty: page is invalid!"));
        m->dirty = VM_PAGE_BITS_ALL;
}

/*
 *      vm_page_insert:         [ internal use only ]
 *
 *      Inserts the given mem entry into the object and object list.
 *
 *      The object must be locked.
 */
int
vm_page_insert(vm_page_t m, vm_object_t object, vm_pindex_t pindex)
{
        vm_page_t mpred;

        VM_OBJECT_ASSERT_WLOCKED(object);
        mpred = vm_radix_lookup_le(&object->rtree, pindex);
        return (vm_page_insert_after(m, object, pindex, mpred));
}

/*
 *      vm_page_insert_after:
 *
 *      Inserts the page "m" into the specified object at offset "pindex".
 *
 *      The page "mpred" must immediately precede the offset "pindex" within
 *      the specified object.
 *
 *      The object must be locked.
 */
static int
vm_page_insert_after(vm_page_t m, vm_object_t object, vm_pindex_t pindex,
    vm_page_t mpred)
{
        vm_page_t msucc;

        VM_OBJECT_ASSERT_WLOCKED(object);
        KASSERT(m->object == NULL,
            ("vm_page_insert_after: page already inserted"));
        if (mpred != NULL) {
                KASSERT(mpred->object == object,
                    ("vm_page_insert_after: object doesn't contain mpred"));
                KASSERT(mpred->pindex < pindex,
                    ("vm_page_insert_after: mpred doesn't precede pindex"));
                msucc = TAILQ_NEXT(mpred, listq);
        } else
                msucc = TAILQ_FIRST(&object->memq);
        if (msucc != NULL)
                KASSERT(msucc->pindex > pindex,
                    ("vm_page_insert_after: msucc doesn't succeed pindex"));

        /*
         * Record the object/offset pair in this page.
         */
        m->object = object;
        m->pindex = pindex;
        m->ref_count |= VPRC_OBJREF;

        /*
         * Now link into the object's ordered list of backed pages.
         */
        if (vm_radix_insert(&object->rtree, m)) {
                m->object = NULL;
                m->pindex = 0;
                m->ref_count &= ~VPRC_OBJREF;
                return (1);
        }
        vm_page_insert_radixdone(m, object, mpred);
        return (0);
}

/*
 *      vm_page_insert_radixdone:
 *
 *      Complete page "m" insertion into the specified object after the
 *      radix trie hooking.
 *
 *      The page "mpred" must precede the offset "m->pindex" within the
 *      specified object.
 *
 *      The object must be locked.
 */
static void
vm_page_insert_radixdone(vm_page_t m, vm_object_t object, vm_page_t mpred)
{

        VM_OBJECT_ASSERT_WLOCKED(object);
        KASSERT(object != NULL && m->object == object,
            ("vm_page_insert_radixdone: page %p has inconsistent object", m));
        KASSERT((m->ref_count & VPRC_OBJREF) != 0,
            ("vm_page_insert_radixdone: page %p is missing object ref", m));
        if (mpred != NULL) {
                KASSERT(mpred->object == object,
                    ("vm_page_insert_radixdone: object doesn't contain mpred"));
                KASSERT(mpred->pindex < m->pindex,
                    ("vm_page_insert_radixdone: mpred doesn't precede pindex"));
        }

        if (mpred != NULL)
                TAILQ_INSERT_AFTER(&object->memq, mpred, m, listq);
        else
                TAILQ_INSERT_HEAD(&object->memq, m, listq);

        /*
         * Show that the object has one more resident page.
         */
        object->resident_page_count++;

        /*
         * Hold the vnode until the last page is released.
         */
        if (object->resident_page_count == 1 && object->type == OBJT_VNODE)
                vhold(object->handle);

        /*
         * Since we are inserting a new and possibly dirty page,
         * update the object's generation count.
         */
        if (pmap_page_is_write_mapped(m))
                vm_object_set_writeable_dirty(object);
}

/*
 * Do the work to remove a page from its object.  The caller is responsible for
 * updating the page's fields to reflect this removal.
 */
static void
vm_page_object_remove(vm_page_t m)
{
        vm_object_t object;
        vm_page_t mrem;

        vm_page_assert_xbusied(m);
        object = m->object;
        VM_OBJECT_ASSERT_WLOCKED(object);
        KASSERT((m->ref_count & VPRC_OBJREF) != 0,
            ("page %p is missing its object ref", m));

        /* Deferred free of swap space. */
        if ((m->a.flags & PGA_SWAP_FREE) != 0)
                vm_pager_page_unswapped(m);

        m->object = NULL;
        mrem = vm_radix_remove(&object->rtree, m->pindex);
        KASSERT(mrem == m, ("removed page %p, expected page %p", mrem, m));

        /*
         * Now remove from the object's list of backed pages.
         */
        TAILQ_REMOVE(&object->memq, m, listq);

        /*
         * And show that the object has one fewer resident page.
         */
        object->resident_page_count--;

        /*
         * The vnode may now be recycled.
         */
        if (object->resident_page_count == 0 && object->type == OBJT_VNODE)
                vdrop(object->handle);
}

/*
 *      vm_page_remove:
 *
 *      Removes the specified page from its containing object, but does not
 *      invalidate any backing storage.  Returns true if the object's reference
 *      was the last reference to the page, and false otherwise.
 *
 *      The object must be locked and the page must be exclusively busied.
 *      The exclusive busy will be released on return.  If this is not the
 *      final ref and the caller does not hold a wire reference it may not
 *      continue to access the page.
 */
bool
vm_page_remove(vm_page_t m)
{
        bool dropped;

        dropped = vm_page_remove_xbusy(m);
        vm_page_xunbusy(m);

        return (dropped);
}

/*
 *      vm_page_remove_xbusy
 *
 *      Removes the page but leaves the xbusy held.  Returns true if this
 *      removed the final ref and false otherwise.
 */
bool
vm_page_remove_xbusy(vm_page_t m)
{

        vm_page_object_remove(m);
        return (vm_page_drop(m, VPRC_OBJREF) == VPRC_OBJREF);
}

/*
 *      vm_page_lookup:
 *
 *      Returns the page associated with the object/offset
 *      pair specified; if none is found, NULL is returned.
 *
 *      The object must be locked.
 */
vm_page_t
vm_page_lookup(vm_object_t object, vm_pindex_t pindex)
{

        VM_OBJECT_ASSERT_LOCKED(object);
        return (vm_radix_lookup(&object->rtree, pindex));
}

/*
 *      vm_page_lookup_unlocked:
 *
 *      Returns the page associated with the object/offset pair specified;
 *      if none is found, NULL is returned.  The page may be no longer be
 *      present in the object at the time that this function returns.  Only
 *      useful for opportunistic checks such as inmem().
 */
vm_page_t
vm_page_lookup_unlocked(vm_object_t object, vm_pindex_t pindex)
{

        return (vm_radix_lookup_unlocked(&object->rtree, pindex));
}

/*
 *      vm_page_relookup:
 *
 *      Returns a page that must already have been busied by
 *      the caller.  Used for bogus page replacement.
 */
vm_page_t
vm_page_relookup(vm_object_t object, vm_pindex_t pindex)
{
        vm_page_t m;

        m = vm_radix_lookup_unlocked(&object->rtree, pindex);
        KASSERT(m != NULL && (vm_page_busied(m) || vm_page_wired(m)) &&
            m->object == object && m->pindex == pindex,
            ("vm_page_relookup: Invalid page %p", m));
        return (m);
}

/*
 * This should only be used by lockless functions for releasing transient
 * incorrect acquires.  The page may have been freed after we acquired a
 * busy lock.  In this case busy_lock == VPB_FREED and we have nothing
 * further to do.
 */
static void
vm_page_busy_release(vm_page_t m)
{
        u_int x;

        x = vm_page_busy_fetch(m);
        for (;;) {
                if (x == VPB_FREED)
                        break;
                if ((x & VPB_BIT_SHARED) != 0 && VPB_SHARERS(x) > 1) {
                        if (atomic_fcmpset_int(&m->busy_lock, &x,
                            x - VPB_ONE_SHARER))
                                break;
                        continue;
                }
                KASSERT((x & VPB_BIT_SHARED) != 0 ||
                    (x & ~VPB_BIT_WAITERS) == VPB_CURTHREAD_EXCLUSIVE,
                    ("vm_page_busy_release: %p xbusy not owned.", m));
                if (!atomic_fcmpset_rel_int(&m->busy_lock, &x, VPB_UNBUSIED))
                        continue;
                if ((x & VPB_BIT_WAITERS) != 0)
                        wakeup(m);
                break;
        }
}

/*
 *      vm_page_find_least:
 *
 *      Returns the page associated with the object with least pindex
 *      greater than or equal to the parameter pindex, or NULL.
 *
 *      The object must be locked.
 */
vm_page_t
vm_page_find_least(vm_object_t object, vm_pindex_t pindex)
{
        vm_page_t m;

        VM_OBJECT_ASSERT_LOCKED(object);
        if ((m = TAILQ_FIRST(&object->memq)) != NULL && m->pindex < pindex)
                m = vm_radix_lookup_ge(&object->rtree, pindex);
        return (m);
}

/*
 * Returns the given page's successor (by pindex) within the object if it is
 * resident; if none is found, NULL is returned.
 *
 * The object must be locked.
 */
vm_page_t
vm_page_next(vm_page_t m)
{
        vm_page_t next;

        VM_OBJECT_ASSERT_LOCKED(m->object);
        if ((next = TAILQ_NEXT(m, listq)) != NULL) {
                MPASS(next->object == m->object);
                if (next->pindex != m->pindex + 1)
                        next = NULL;
        }
        return (next);
}

/*
 * Returns the given page's predecessor (by pindex) within the object if it is
 * resident; if none is found, NULL is returned.
 *
 * The object must be locked.
 */
vm_page_t
vm_page_prev(vm_page_t m)
{
        vm_page_t prev;

        VM_OBJECT_ASSERT_LOCKED(m->object);
        if ((prev = TAILQ_PREV(m, pglist, listq)) != NULL) {
                MPASS(prev->object == m->object);
                if (prev->pindex != m->pindex - 1)
                        prev = NULL;
        }
        return (prev);
}

/*
 * Uses the page mnew as a replacement for an existing page at index
 * pindex which must be already present in the object.
 *
 * Both pages must be exclusively busied on enter.  The old page is
 * unbusied on exit.
 *
 * A return value of true means mold is now free.  If this is not the
 * final ref and the caller does not hold a wire reference it may not
 * continue to access the page.
 */
static bool
vm_page_replace_hold(vm_page_t mnew, vm_object_t object, vm_pindex_t pindex,
    vm_page_t mold)
{
        vm_page_t mret;
        bool dropped;

        VM_OBJECT_ASSERT_WLOCKED(object);
        vm_page_assert_xbusied(mold);
        KASSERT(mnew->object == NULL && (mnew->ref_count & VPRC_OBJREF) == 0,
            ("vm_page_replace: page %p already in object", mnew));

        /*
         * This function mostly follows vm_page_insert() and
         * vm_page_remove() without the radix, object count and vnode
         * dance.  Double check such functions for more comments.
         */

        mnew->object = object;
        mnew->pindex = pindex;
        atomic_set_int(&mnew->ref_count, VPRC_OBJREF);
        mret = vm_radix_replace(&object->rtree, mnew);
        KASSERT(mret == mold,
            ("invalid page replacement, mold=%p, mret=%p", mold, mret));
        KASSERT((mold->oflags & VPO_UNMANAGED) ==
            (mnew->oflags & VPO_UNMANAGED),
            ("vm_page_replace: mismatched VPO_UNMANAGED"));

        /* Keep the resident page list in sorted order. */
        TAILQ_INSERT_AFTER(&object->memq, mold, mnew, listq);
        TAILQ_REMOVE(&object->memq, mold, listq);
        mold->object = NULL;

        /*
         * The object's resident_page_count does not change because we have
         * swapped one page for another, but the generation count should
         * change if the page is dirty.
         */
        if (pmap_page_is_write_mapped(mnew))
                vm_object_set_writeable_dirty(object);
        dropped = vm_page_drop(mold, VPRC_OBJREF) == VPRC_OBJREF;
        vm_page_xunbusy(mold);

        return (dropped);
}

void
vm_page_replace(vm_page_t mnew, vm_object_t object, vm_pindex_t pindex,
    vm_page_t mold)
{

        vm_page_assert_xbusied(mnew);

        if (vm_page_replace_hold(mnew, object, pindex, mold))
                vm_page_free(mold);
}

/*
 *      vm_page_rename:
 *
 *      Move the given memory entry from its
 *      current object to the specified target object/offset.
 *
 *      Note: swap associated with the page must be invalidated by the move.  We
 *            have to do this for several reasons:  (1) we aren't freeing the
 *            page, (2) we are dirtying the page, (3) the VM system is probably
 *            moving the page from object A to B, and will then later move
 *            the backing store from A to B and we can't have a conflict.
 *
 *      Note: we *always* dirty the page.  It is necessary both for the
 *            fact that we moved it, and because we may be invalidating
 *            swap.
 *
 *      The objects must be locked.
 */
int
vm_page_rename(vm_page_t m, vm_object_t new_object, vm_pindex_t new_pindex)
{
        vm_page_t mpred;
        vm_pindex_t opidx;

        VM_OBJECT_ASSERT_WLOCKED(new_object);

        KASSERT(m->ref_count != 0, ("vm_page_rename: page %p has no refs", m));
        mpred = vm_radix_lookup_le(&new_object->rtree, new_pindex);
        KASSERT(mpred == NULL || mpred->pindex != new_pindex,
            ("vm_page_rename: pindex already renamed"));

        /*
         * Create a custom version of vm_page_insert() which does not depend
         * by m_prev and can cheat on the implementation aspects of the
         * function.
         */
        opidx = m->pindex;
        m->pindex = new_pindex;
        if (vm_radix_insert(&new_object->rtree, m)) {
                m->pindex = opidx;
                return (1);
        }

        /*
         * The operation cannot fail anymore.  The removal must happen before
         * the listq iterator is tainted.
         */
        m->pindex = opidx;
        vm_page_object_remove(m);

        /* Return back to the new pindex to complete vm_page_insert(). */
        m->pindex = new_pindex;
        m->object = new_object;

        vm_page_insert_radixdone(m, new_object, mpred);
        vm_page_dirty(m);
        return (0);
}

/*
 *      vm_page_alloc:
 *
 *      Allocate and return a page that is associated with the specified
 *      object and offset pair.  By default, this page is exclusive busied.
 *
 *      The caller must always specify an allocation class.
 *
 *      allocation classes:
 *      VM_ALLOC_NORMAL         normal process request
 *      VM_ALLOC_SYSTEM         system *really* needs a page
 *      VM_ALLOC_INTERRUPT      interrupt time request
 *
 *      optional allocation flags:
 *      VM_ALLOC_COUNT(number)  the number of additional pages that the caller
 *                              intends to allocate
 *      VM_ALLOC_NOBUSY         do not exclusive busy the page
 *      VM_ALLOC_NODUMP         do not include the page in a kernel core dump
 *      VM_ALLOC_SBUSY          shared busy the allocated page
 *      VM_ALLOC_WIRED          wire the allocated page
 *      VM_ALLOC_ZERO           prefer a zeroed page
 */
vm_page_t
vm_page_alloc(vm_object_t object, vm_pindex_t pindex, int req)
{

        return (vm_page_alloc_after(object, pindex, req,
            vm_radix_lookup_le(&object->rtree, pindex)));
}

vm_page_t
vm_page_alloc_domain(vm_object_t object, vm_pindex_t pindex, int domain,
    int req)
{

        return (vm_page_alloc_domain_after(object, pindex, domain, req,
            vm_radix_lookup_le(&object->rtree, pindex)));
}

/*
 * Allocate a page in the specified object with the given page index.  To
 * optimize insertion of the page into the object, the caller must also specifiy
 * the resident page in the object with largest index smaller than the given
 * page index, or NULL if no such page exists.
 */
vm_page_t
vm_page_alloc_after(vm_object_t object, vm_pindex_t pindex,
    int req, vm_page_t mpred)
{
        struct vm_domainset_iter di;
        vm_page_t m;
        int domain;

        vm_domainset_iter_page_init(&di, object, pindex, &domain, &req);
        do {
                m = vm_page_alloc_domain_after(object, pindex, domain, req,
                    mpred);
                if (m != NULL)
                        break;
        } while (vm_domainset_iter_page(&di, object, &domain) == 0);

        return (m);
}

/*
 * Returns true if the number of free pages exceeds the minimum
 * for the request class and false otherwise.
 */
static int
_vm_domain_allocate(struct vm_domain *vmd, int req_class, int npages)
{
        u_int limit, old, new;

        if (req_class == VM_ALLOC_INTERRUPT)
                limit = 0;
        else if (req_class == VM_ALLOC_SYSTEM)
                limit = vmd->vmd_interrupt_free_min;
        else
                limit = vmd->vmd_free_reserved;

        /*
         * Attempt to reserve the pages.  Fail if we're below the limit.
         */
        limit += npages;
        old = vmd->vmd_free_count;
        do {
                if (old < limit)
                        return (0);
                new = old - npages;
        } while (atomic_fcmpset_int(&vmd->vmd_free_count, &old, new) == 0);

        /* Wake the page daemon if we've crossed the threshold. */
        if (vm_paging_needed(vmd, new) && !vm_paging_needed(vmd, old))
                pagedaemon_wakeup(vmd->vmd_domain);

        /* Only update bitsets on transitions. */
        if ((old >= vmd->vmd_free_min && new < vmd->vmd_free_min) ||
            (old >= vmd->vmd_free_severe && new < vmd->vmd_free_severe))
                vm_domain_set(vmd);

        return (1);
}

int
vm_domain_allocate(struct vm_domain *vmd, int req, int npages)
{
        int req_class;

        /*
         * The page daemon is allowed to dig deeper into the free page list.
         */
        req_class = req & VM_ALLOC_CLASS_MASK;
        if (curproc == pageproc && req_class != VM_ALLOC_INTERRUPT)
                req_class = VM_ALLOC_SYSTEM;
        return (_vm_domain_allocate(vmd, req_class, npages));
}

vm_page_t
vm_page_alloc_domain_after(vm_object_t object, vm_pindex_t pindex, int domain,
    int req, vm_page_t mpred)
{
        struct vm_domain *vmd;
        vm_page_t m;
        int flags;

#define VPA_FLAGS       (VM_ALLOC_CLASS_MASK | VM_ALLOC_WAITFAIL |      \
                         VM_ALLOC_NOWAIT | VM_ALLOC_NOBUSY |            \
                         VM_ALLOC_SBUSY | VM_ALLOC_WIRED |              \
                         VM_ALLOC_NODUMP | VM_ALLOC_ZERO | VM_ALLOC_COUNT_MASK)
        KASSERT((req & ~VPA_FLAGS) == 0,
            ("invalid request %#x", req));
        KASSERT(((req & (VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY)) !=
            (VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY)),
            ("invalid request %#x", req));
        KASSERT(mpred == NULL || mpred->pindex < pindex,
            ("mpred %p doesn't precede pindex 0x%jx", mpred,
            (uintmax_t)pindex));
        VM_OBJECT_ASSERT_WLOCKED(object);

        flags = 0;
        m = NULL;
again:
#if VM_NRESERVLEVEL > 0
        /*
         * Can we allocate the page from a reservation?
         */
        if (vm_object_reserv(object) &&
            (m = vm_reserv_alloc_page(object, pindex, domain, req, mpred)) !=
            NULL) {
                goto found;
        }
#endif
        vmd = VM_DOMAIN(domain);
        if (vmd->vmd_pgcache[VM_FREEPOOL_DEFAULT].zone != NULL) {
                m = uma_zalloc(vmd->vmd_pgcache[VM_FREEPOOL_DEFAULT].zone,
                    M_NOWAIT | M_NOVM);
                if (m != NULL) {
                        flags |= PG_PCPU_CACHE;
                        goto found;
                }
        }
        if (vm_domain_allocate(vmd, req, 1)) {
                /*
                 * If not, allocate it from the free page queues.
                 */
                vm_domain_free_lock(vmd);
                m = vm_phys_alloc_pages(domain, VM_FREEPOOL_DEFAULT, 0);
                vm_domain_free_unlock(vmd);
                if (m == NULL) {
                        vm_domain_freecnt_inc(vmd, 1);
#if VM_NRESERVLEVEL > 0
                        if (vm_reserv_reclaim_inactive(domain))
                                goto again;
#endif
                }
        }
        if (m == NULL) {
                /*
                 * Not allocatable, give up.
                 */
                if (vm_domain_alloc_fail(vmd, object, req))
                        goto again;
                return (NULL);
        }

        /*
         * At this point we had better have found a good page.
         */
found:
        vm_page_dequeue(m);
        vm_page_alloc_check(m);

        /*
         * Initialize the page.  Only the PG_ZERO flag is inherited.
         */
        flags |= m->flags & PG_ZERO;
        if ((req & VM_ALLOC_NODUMP) != 0)
                flags |= PG_NODUMP;
        m->flags = flags;
        m->a.flags = 0;
        m->oflags = (object->flags & OBJ_UNMANAGED) != 0 ? VPO_UNMANAGED : 0;
        if ((req & (VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY)) == 0)
                m->busy_lock = VPB_CURTHREAD_EXCLUSIVE;
        else if ((req & VM_ALLOC_SBUSY) != 0)
                m->busy_lock = VPB_SHARERS_WORD(1);
        else
                m->busy_lock = VPB_UNBUSIED;
        if (req & VM_ALLOC_WIRED) {
                vm_wire_add(1);
                m->ref_count = 1;
        }
        m->a.act_count = 0;

        if (vm_page_insert_after(m, object, pindex, mpred)) {
                if (req & VM_ALLOC_WIRED) {
                        vm_wire_sub(1);
                        m->ref_count = 0;
                }
                KASSERT(m->object == NULL, ("page %p has object", m));
                m->oflags = VPO_UNMANAGED;
                m->busy_lock = VPB_UNBUSIED;
                /* Don't change PG_ZERO. */
                vm_page_free_toq(m);
                if (req & VM_ALLOC_WAITFAIL) {
                        VM_OBJECT_WUNLOCK(object);
                        vm_radix_wait();
                        VM_OBJECT_WLOCK(object);
                }
                return (NULL);
        }

        /* Ignore device objects; the pager sets "memattr" for them. */
        if (object->memattr != VM_MEMATTR_DEFAULT &&
            (object->flags & OBJ_FICTITIOUS) == 0)
                pmap_page_set_memattr(m, object->memattr);

        return (m);
}

/*
 *      vm_page_alloc_contig:
 *
 *      Allocate a contiguous set of physical pages of the given size "npages"
 *      from the free lists.  All of the physical pages must be at or above
 *      the given physical address "low" and below the given physical address
 *      "high".  The given value "alignment" determines the alignment of the
 *      first physical page in the set.  If the given value "boundary" is
 *      non-zero, then the set of physical pages cannot cross any physical
 *      address boundary that is a multiple of that value.  Both "alignment"
 *      and "boundary" must be a power of two.
 *
 *      If the specified memory attribute, "memattr", is VM_MEMATTR_DEFAULT,
 *      then the memory attribute setting for the physical pages is configured
 *      to the object's memory attribute setting.  Otherwise, the memory
 *      attribute setting for the physical pages is configured to "memattr",
 *      overriding the object's memory attribute setting.  However, if the
 *      object's memory attribute setting is not VM_MEMATTR_DEFAULT, then the
 *      memory attribute setting for the physical pages cannot be configured
 *      to VM_MEMATTR_DEFAULT.
 *
 *      The specified object may not contain fictitious pages.
 *
 *      The caller must always specify an allocation class.
 *
 *      allocation classes:
 *      VM_ALLOC_NORMAL         normal process request
 *      VM_ALLOC_SYSTEM         system *really* needs a page
 *      VM_ALLOC_INTERRUPT      interrupt time request
 *
 *      optional allocation flags:
 *      VM_ALLOC_NOBUSY         do not exclusive busy the page
 *      VM_ALLOC_NODUMP         do not include the page in a kernel core dump
 *      VM_ALLOC_SBUSY          shared busy the allocated page
 *      VM_ALLOC_WIRED          wire the allocated page
 *      VM_ALLOC_ZERO           prefer a zeroed page
 */
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)
{
        struct vm_domainset_iter di;
        vm_page_t m;
        int domain;

        vm_domainset_iter_page_init(&di, object, pindex, &domain, &req);
        do {
                m = vm_page_alloc_contig_domain(object, pindex, domain, req,
                    npages, low, high, alignment, boundary, memattr);
                if (m != NULL)
                        break;
        } while (vm_domainset_iter_page(&di, object, &domain) == 0);

        return (m);
}

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)
{
        struct vm_domain *vmd;
        vm_page_t m, m_ret, mpred;
        u_int busy_lock, flags, oflags;

#define VPAC_FLAGS      (VPA_FLAGS | VM_ALLOC_NORECLAIM)
        KASSERT((req & ~VPAC_FLAGS) == 0,
            ("invalid request %#x", req));
        KASSERT(((req & (VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY)) !=
            (VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY)),
            ("invalid request %#x", req));
        KASSERT((req & (VM_ALLOC_WAITOK | VM_ALLOC_NORECLAIM)) !=
            (VM_ALLOC_WAITOK | VM_ALLOC_NORECLAIM),
            ("invalid request %#x", req));
        VM_OBJECT_ASSERT_WLOCKED(object);
        KASSERT((object->flags & OBJ_FICTITIOUS) == 0,
            ("vm_page_alloc_contig: object %p has fictitious pages",
            object));
        KASSERT(npages > 0, ("vm_page_alloc_contig: npages is zero"));

        mpred = vm_radix_lookup_le(&object->rtree, pindex);
        KASSERT(mpred == NULL || mpred->pindex != pindex,
            ("vm_page_alloc_contig: pindex already allocated"));

        /*
         * Can we allocate the pages without the number of free pages falling
         * below the lower bound for the allocation class?
         */
        m_ret = NULL;
again:
#if VM_NRESERVLEVEL > 0
        /*
         * Can we allocate the pages from a reservation?
         */
        if (vm_object_reserv(object) &&
            (m_ret = vm_reserv_alloc_contig(object, pindex, domain, req,
            mpred, npages, low, high, alignment, boundary)) != NULL) {
                goto found;
        }
#endif
        vmd = VM_DOMAIN(domain);
        if (vm_domain_allocate(vmd, req, npages)) {
                /*
                 * allocate them from the free page queues.
                 */
                vm_domain_free_lock(vmd);
                m_ret = vm_phys_alloc_contig(domain, npages, low, high,
                    alignment, boundary);
                vm_domain_free_unlock(vmd);
                if (m_ret == NULL) {
                        vm_domain_freecnt_inc(vmd, npages);
#if VM_NRESERVLEVEL > 0
                        if ((req & VM_ALLOC_NORECLAIM) == 0 &&
                            vm_reserv_reclaim_contig(domain, npages, low,
                            high, alignment, boundary))
                                goto again;
#endif
                }
        }
        if (m_ret == NULL) {
                if (vm_domain_alloc_fail(vmd, object, req))
                        goto again;
                return (NULL);
        }
#if VM_NRESERVLEVEL > 0
found:
#endif
        for (m = m_ret; m < &m_ret[npages]; m++) {
                vm_page_dequeue(m);
                vm_page_alloc_check(m);
        }

        /*
         * Initialize the pages.  Only the PG_ZERO flag is inherited.
         */
        flags = PG_ZERO;
        if ((req & VM_ALLOC_NODUMP) != 0)
                flags |= PG_NODUMP;
        oflags = (object->flags & OBJ_UNMANAGED) != 0 ? VPO_UNMANAGED : 0;
        if ((req & (VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY)) == 0)
                busy_lock = VPB_CURTHREAD_EXCLUSIVE;
        else if ((req & VM_ALLOC_SBUSY) != 0)
                busy_lock = VPB_SHARERS_WORD(1);
        else
                busy_lock = VPB_UNBUSIED;
        if ((req & VM_ALLOC_WIRED) != 0)
                vm_wire_add(npages);
        if (object->memattr != VM_MEMATTR_DEFAULT &&
            memattr == VM_MEMATTR_DEFAULT)
                memattr = object->memattr;
        for (m = m_ret; m < &m_ret[npages]; m++) {
                m->a.flags = 0;
                m->flags = (m->flags | PG_NODUMP) & flags;
                m->busy_lock = busy_lock;
                if ((req & VM_ALLOC_WIRED) != 0)
                        m->ref_count = 1;
                m->a.act_count = 0;
                m->oflags = oflags;
                if (vm_page_insert_after(m, object, pindex, mpred)) {
                        if ((req & VM_ALLOC_WIRED) != 0)
                                vm_wire_sub(npages);
                        KASSERT(m->object == NULL,
                            ("page %p has object", m));
                        mpred = m;
                        for (m = m_ret; m < &m_ret[npages]; m++) {
                                if (m <= mpred &&
                                    (req & VM_ALLOC_WIRED) != 0)
                                        m->ref_count = 0;
                                m->oflags = VPO_UNMANAGED;
                                m->busy_lock = VPB_UNBUSIED;
                                /* Don't change PG_ZERO. */
                                vm_page_free_toq(m);
                        }
                        if (req & VM_ALLOC_WAITFAIL) {
                                VM_OBJECT_WUNLOCK(object);
                                vm_radix_wait();
                                VM_OBJECT_WLOCK(object);
                        }
                        return (NULL);
                }
                mpred = m;
                if (memattr != VM_MEMATTR_DEFAULT)
                        pmap_page_set_memattr(m, memattr);
                pindex++;
        }
        return (m_ret);
}

/*
 * Allocate a physical page that is not intended to be inserted into a VM
 * object.  If the "freelist" parameter is not equal to VM_NFREELIST, then only
 * pages from the specified vm_phys freelist will be returned.
 */
static __always_inline vm_page_t
_vm_page_alloc_noobj_domain(int domain, const int freelist, int req)
{
        struct vm_domain *vmd;
        vm_page_t m;
        int flags;

#define VPAN_FLAGS      (VM_ALLOC_CLASS_MASK | VM_ALLOC_WAITFAIL |      \
                         VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK |            \
                         VM_ALLOC_NOBUSY | VM_ALLOC_WIRED |             \
                         VM_ALLOC_NODUMP | VM_ALLOC_ZERO | VM_ALLOC_COUNT_MASK)
        KASSERT((req & ~VPAN_FLAGS) == 0,
            ("invalid request %#x", req));

        flags = (req & VM_ALLOC_NODUMP) != 0 ? PG_NODUMP : 0;
        vmd = VM_DOMAIN(domain);
again:
        if (freelist == VM_NFREELIST &&
            vmd->vmd_pgcache[VM_FREEPOOL_DIRECT].zone != NULL) {
                m = uma_zalloc(vmd->vmd_pgcache[VM_FREEPOOL_DIRECT].zone,
                    M_NOWAIT | M_NOVM);
                if (m != NULL) {
                        flags |= PG_PCPU_CACHE;
                        goto found;
                }
        }

        if (vm_domain_allocate(vmd, req, 1)) {
                vm_domain_free_lock(vmd);
                if (freelist == VM_NFREELIST)
                        m = vm_phys_alloc_pages(domain, VM_FREEPOOL_DIRECT, 0);
                else
                        m = vm_phys_alloc_freelist_pages(domain, freelist,
                            VM_FREEPOOL_DIRECT, 0);
                vm_domain_free_unlock(vmd);
                if (m == NULL) {
                        vm_domain_freecnt_inc(vmd, 1);
#if VM_NRESERVLEVEL > 0
                        if (freelist == VM_NFREELIST &&
                            vm_reserv_reclaim_inactive(domain))
                                goto again;
#endif
                }
        }
        if (m == NULL) {
                if (vm_domain_alloc_fail(vmd, NULL, req))
                        goto again;
                return (NULL);
        }

found:
        vm_page_dequeue(m);
        vm_page_alloc_check(m);

        /*
         * Consumers should not rely on a useful default pindex value.
         */
        m->pindex = 0xdeadc0dedeadc0de;
        m->flags = (m->flags & PG_ZERO) | flags;
        m->a.flags = 0;
        m->oflags = VPO_UNMANAGED;
        m->busy_lock = VPB_UNBUSIED;
        if ((req & VM_ALLOC_WIRED) != 0) {
                vm_wire_add(1);
                m->ref_count = 1;
        }

        if ((req & VM_ALLOC_ZERO) != 0 && (m->flags & PG_ZERO) == 0)
                pmap_zero_page(m);

        return (m);
}

vm_page_t
vm_page_alloc_freelist(int freelist, int req)
{
        struct vm_domainset_iter di;
        vm_page_t m;
        int domain;

        vm_domainset_iter_page_init(&di, NULL, 0, &domain, &req);
        do {
                m = vm_page_alloc_freelist_domain(domain, freelist, req);
                if (m != NULL)
                        break;
        } while (vm_domainset_iter_page(&di, NULL, &domain) == 0);

        return (m);
}

vm_page_t
vm_page_alloc_freelist_domain(int domain, int freelist, int req)
{
        KASSERT(freelist >= 0 && freelist < VM_NFREELIST,
            ("%s: invalid freelist %d", __func__, freelist));

        return (_vm_page_alloc_noobj_domain(domain, freelist, req));
}

vm_page_t
vm_page_alloc_noobj(int req)
{
        struct vm_domainset_iter di;
        vm_page_t m;
        int domain;

        vm_domainset_iter_page_init(&di, NULL, 0, &domain, &req);
        do {
                m = vm_page_alloc_noobj_domain(domain, req);
                if (m != NULL)
                        break;
        } while (vm_domainset_iter_page(&di, NULL, &domain) == 0);

        return (m);
}

vm_page_t
vm_page_alloc_noobj_domain(int domain, int req)
{
        return (_vm_page_alloc_noobj_domain(domain, VM_NFREELIST, req));
}

vm_page_t
vm_page_alloc_noobj_contig(int req, u_long npages, vm_paddr_t low,
    vm_paddr_t high, u_long alignment, vm_paddr_t boundary,
    vm_memattr_t memattr)
{
        struct vm_domainset_iter di;
        vm_page_t m;
        int domain;

        vm_domainset_iter_page_init(&di, NULL, 0, &domain, &req);
        do {
                m = vm_page_alloc_noobj_contig_domain(domain, req, npages, low,
                    high, alignment, boundary, memattr);
                if (m != NULL)
                        break;
        } while (vm_domainset_iter_page(&di, NULL, &domain) == 0);

        return (m);
}

vm_page_t
vm_page_alloc_noobj_contig_domain(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)
{
        struct vm_domain *vmd;
        vm_page_t m, m_ret;
        u_int flags;

#define VPANC_FLAGS     (VPAN_FLAGS | VM_ALLOC_NORECLAIM)
        KASSERT((req & ~VPANC_FLAGS) == 0,
            ("invalid request %#x", req));
        KASSERT((req & (VM_ALLOC_WAITOK | VM_ALLOC_NORECLAIM)) !=
            (VM_ALLOC_WAITOK | VM_ALLOC_NORECLAIM),
            ("invalid request %#x", req));
        KASSERT(((req & (VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY)) !=
            (VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY)),
            ("invalid request %#x", req));
        KASSERT(npages > 0, ("vm_page_alloc_contig: npages is zero"));

        m_ret = NULL;
again:
        vmd = VM_DOMAIN(domain);
        if (vm_domain_allocate(vmd, req, npages)) {
                /*
                 * allocate them from the free page queues.
                 */
                vm_domain_free_lock(vmd);
                m_ret = vm_phys_alloc_contig(domain, npages, low, high,
                    alignment, boundary);
                vm_domain_free_unlock(vmd);
                if (m_ret == NULL) {
                        vm_domain_freecnt_inc(vmd, npages);
#if VM_NRESERVLEVEL > 0
                        if ((req & VM_ALLOC_NORECLAIM) == 0 &&
                            vm_reserv_reclaim_contig(domain, npages, low,
                            high, alignment, boundary))
                                goto again;
#endif
                }
        }
        if (m_ret == NULL) {
                if (vm_domain_alloc_fail(vmd, NULL, req))
                        goto again;
                return (NULL);
        }

        /*
         * Initialize the pages.  Only the PG_ZERO flag is inherited.
         */
        flags = PG_ZERO;
        if ((req & VM_ALLOC_NODUMP) != 0)
                flags |= PG_NODUMP;
        if ((req & VM_ALLOC_WIRED) != 0)
                vm_wire_add(npages);
        for (m = m_ret; m < &m_ret[npages]; m++) {
                vm_page_dequeue(m);
                vm_page_alloc_check(m);

                /*
                 * Consumers should not rely on a useful default pindex value.
                 */
                m->pindex = 0xdeadc0dedeadc0de;
                m->a.flags = 0;
                m->flags = (m->flags | PG_NODUMP) & flags;
                m->busy_lock = VPB_UNBUSIED;
                if ((req & VM_ALLOC_WIRED) != 0)
                        m->ref_count = 1;
                m->a.act_count = 0;
                m->oflags = VPO_UNMANAGED;

                /*
                 * Zero the page before updating any mappings since the page is
                 * not yet shared with any devices which might require the
                 * non-default memory attribute.  pmap_page_set_memattr()
                 * flushes data caches before returning.
                 */
                if ((req & VM_ALLOC_ZERO) != 0 && (m->flags & PG_ZERO) == 0)
                        pmap_zero_page(m);
                if (memattr != VM_MEMATTR_DEFAULT)
                        pmap_page_set_memattr(m, memattr);
        }
        return (m_ret);
}

/*
 * Check a page that has been freshly dequeued from a freelist.
 */
static void
vm_page_alloc_check(vm_page_t m)
{

        KASSERT(m->object == NULL, ("page %p has object", m));
        KASSERT(m->a.queue == PQ_NONE &&
            (m->a.flags & PGA_QUEUE_STATE_MASK) == 0,
            ("page %p has unexpected queue %d, flags %#x",
            m, m->a.queue, (m->a.flags & PGA_QUEUE_STATE_MASK)));
        KASSERT(m->ref_count == 0, ("page %p has references", m));
        KASSERT(vm_page_busy_freed(m), ("page %p is not freed", m));
        KASSERT(m->dirty == 0, ("page %p is dirty", m));
        KASSERT(pmap_page_get_memattr(m) == VM_MEMATTR_DEFAULT,
            ("page %p has unexpected memattr %d",
            m, pmap_page_get_memattr(m)));
        KASSERT(m->valid == 0, ("free page %p is valid", m));
        pmap_vm_page_alloc_check(m);
}

static int
vm_page_zone_import(void *arg, void **store, int cnt, int domain, int flags)
{
        struct vm_domain *vmd;
        struct vm_pgcache *pgcache;
        int i;

        pgcache = arg;
        vmd = VM_DOMAIN(pgcache->domain);

        /*
         * The page daemon should avoid creating extra memory pressure since its
         * main purpose is to replenish the store of free pages.
         */
        if (vmd->vmd_severeset || curproc == pageproc ||
            !_vm_domain_allocate(vmd, VM_ALLOC_NORMAL, cnt))
                return (0);
        domain = vmd->vmd_domain;
        vm_domain_free_lock(vmd);
        i = vm_phys_alloc_npages(domain, pgcache->pool, cnt,
            (vm_page_t *)store);
        vm_domain_free_unlock(vmd);
        if (cnt != i)
                vm_domain_freecnt_inc(vmd, cnt - i);

        return (i);
}

static void
vm_page_zone_release(void *arg, void **store, int cnt)
{
        struct vm_domain *vmd;
        struct vm_pgcache *pgcache;
        vm_page_t m;
        int i;

        pgcache = arg;
        vmd = VM_DOMAIN(pgcache->domain);
        vm_domain_free_lock(vmd);
        for (i = 0; i < cnt; i++) {
                m = (vm_page_t)store[i];
                vm_phys_free_pages(m, 0);
        }
        vm_domain_free_unlock(vmd);
        vm_domain_freecnt_inc(vmd, cnt);
}

#define VPSC_ANY        0       /* No restrictions. */
#define VPSC_NORESERV   1       /* Skip reservations; implies VPSC_NOSUPER. */
#define VPSC_NOSUPER    2       /* Skip superpages. */

/*
 *      vm_page_scan_contig:
 *
 *      Scan vm_page_array[] between the specified entries "m_start" and
 *      "m_end" for a run of contiguous physical pages that satisfy the
 *      specified conditions, and return the lowest page in the run.  The
 *      specified "alignment" determines the alignment of the lowest physical
 *      page in the run.  If the specified "boundary" is non-zero, then the
 *      run of physical pages cannot span a physical address that is a
 *      multiple of "boundary".
 *
 *      "m_end" is never dereferenced, so it need not point to a vm_page
 *      structure within vm_page_array[].
 *
 *      "npages" must be greater than zero.  "m_start" and "m_end" must not
 *      span a hole (or discontiguity) in the physical address space.  Both
 *      "alignment" and "boundary" must be a power of two.
 */
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_object_t object;
        vm_paddr_t pa;
        vm_page_t m, m_run;
#if VM_NRESERVLEVEL > 0
        int level;
#endif
        int m_inc, order, run_ext, run_len;

        KASSERT(npages > 0, ("npages is 0"));
        KASSERT(powerof2(alignment), ("alignment is not a power of 2"));
        KASSERT(powerof2(boundary), ("boundary is not a power of 2"));
        m_run = NULL;
        run_len = 0;
        for (m = m_start; m < m_end && run_len < npages; m += m_inc) {
                KASSERT((m->flags & PG_MARKER) == 0,
                    ("page %p is PG_MARKER", m));
                KASSERT((m->flags & PG_FICTITIOUS) == 0 || m->ref_count >= 1,
                    ("fictitious page %p has invalid ref count", m));

                /*
                 * If the current page would be the start of a run, check its
                 * physical address against the end, alignment, and boundary
                 * conditions.  If it doesn't satisfy these conditions, either
                 * terminate the scan or advance to the next page that
                 * satisfies the failed condition.
                 */
                if (run_len == 0) {
                        KASSERT(m_run == NULL, ("m_run != NULL"));
                        if (m + npages > m_end)
                                break;
                        pa = VM_PAGE_TO_PHYS(m);
                        if ((pa & (alignment - 1)) != 0) {
                                m_inc = atop(roundup2(pa, alignment) - pa);
                                continue;
                        }
                        if (rounddown2(pa ^ (pa + ptoa(npages) - 1),
                            boundary) != 0) {
                                m_inc = atop(roundup2(pa, boundary) - pa);
                                continue;
                        }
                } else
                        KASSERT(m_run != NULL, ("m_run == NULL"));

retry:
                m_inc = 1;
                if (vm_page_wired(m))
                        run_ext = 0;
#if VM_NRESERVLEVEL > 0
                else if ((level = vm_reserv_level(m)) >= 0 &&
                    (options & VPSC_NORESERV) != 0) {
                        run_ext = 0;
                        /* Advance to the end of the reservation. */
                        pa = VM_PAGE_TO_PHYS(m);
                        m_inc = atop(roundup2(pa + 1, vm_reserv_size(level)) -
                            pa);
                }
#endif
                else if ((object = atomic_load_ptr(&m->object)) != NULL) {
                        /*
                         * The page is considered eligible for relocation if
                         * and only if it could be laundered or reclaimed by
                         * the page daemon.
                         */
                        VM_OBJECT_RLOCK(object);
                        if (object != m->object) {
                                VM_OBJECT_RUNLOCK(object);
                                goto retry;
                        }
                        /* Don't care: PG_NODUMP, PG_ZERO. */
                        if (object->type != OBJT_DEFAULT &&
                            (object->flags & OBJ_SWAP) == 0 &&
                            object->type != OBJT_VNODE) {
                                run_ext = 0;
#if VM_NRESERVLEVEL > 0
                        } else if ((options & VPSC_NOSUPER) != 0 &&
                            (level = vm_reserv_level_iffullpop(m)) >= 0) {
                                run_ext = 0;
                                /* Advance to the end of the superpage. */
                                pa = VM_PAGE_TO_PHYS(m);
                                m_inc = atop(roundup2(pa + 1,
                                    vm_reserv_size(level)) - pa);
#endif
                        } else if (object->memattr == VM_MEMATTR_DEFAULT &&
                            vm_page_queue(m) != PQ_NONE && !vm_page_busied(m)) {
                                /*
                                 * The page is allocated but eligible for
                                 * relocation.  Extend the current run by one
                                 * page.
                                 */
                                KASSERT(pmap_page_get_memattr(m) ==
                                    VM_MEMATTR_DEFAULT,
                                    ("page %p has an unexpected memattr", m));
                                KASSERT((m->oflags & (VPO_SWAPINPROG |
                                    VPO_SWAPSLEEP | VPO_UNMANAGED)) == 0,
                                    ("page %p has unexpected oflags", m));
                                /* Don't care: PGA_NOSYNC. */
                                run_ext = 1;
                        } else
                                run_ext = 0;
                        VM_OBJECT_RUNLOCK(object);
#if VM_NRESERVLEVEL > 0
                } else if (level >= 0) {
                        /*
                         * The page is reserved but not yet allocated.  In
                         * other words, it is still free.  Extend the current
                         * run by one page.
                         */
                        run_ext = 1;
#endif
                } else if ((order = m->order) < VM_NFREEORDER) {
                        /*
                         * The page is enqueued in the physical memory
                         * allocator's free page queues.  Moreover, it is the
                         * first page in a power-of-two-sized run of
                         * contiguous free pages.  Add these pages to the end
                         * of the current run, and jump ahead.
                         */
                        run_ext = 1 << order;
                        m_inc = 1 << order;
                } else {
                        /*
                         * Skip the page for one of the following reasons: (1)
                         * It is enqueued in the physical memory allocator's
                         * free page queues.  However, it is not the first
                         * page in a run of contiguous free pages.  (This case
                         * rarely occurs because the scan is performed in
                         * ascending order.) (2) It is not reserved, and it is
                         * transitioning from free to allocated.  (Conversely,
                         * the transition from allocated to free for managed
                         * pages is blocked by the page busy lock.) (3) It is
                         * allocated but not contained by an object and not
                         * wired, e.g., allocated by Xen's balloon driver.
                         */
                        run_ext = 0;
                }

                /*
                 * Extend or reset the current run of pages.
                 */
                if (run_ext > 0) {
                        if (run_len == 0)
                                m_run = m;
                        run_len += run_ext;
                } else {
                        if (run_len > 0) {
                                m_run = NULL;
                                run_len = 0;
                        }
                }
        }
        if (run_len >= npages)
                return (m_run);
        return (NULL);
}

/*
 *      vm_page_reclaim_run:
 *
 *      Try to relocate each of the allocated virtual pages within the
 *      specified run of physical pages to a new physical address.  Free the
 *      physical pages underlying the relocated virtual pages.  A virtual page
 *      is relocatable if and only if it could be laundered or reclaimed by
 *      the page daemon.  Whenever possible, a virtual page is relocated to a
 *      physical address above "high".
 *
 *      Returns 0 if every physical page within the run was already free or
 *      just freed by a successful relocation.  Otherwise, returns a non-zero
 *      value indicating why the last attempt to relocate a virtual page was
 *      unsuccessful.
 *
 *      "req_class" must be an allocation class.
 */
static int
vm_page_reclaim_run(int req_class, int domain, u_long npages, vm_page_t m_run,
    vm_paddr_t high)
{
        struct vm_domain *vmd;
        struct spglist free;
        vm_object_t object;
        vm_paddr_t pa;
        vm_page_t m, m_end, m_new;
        int error, order, req;

        KASSERT((req_class & VM_ALLOC_CLASS_MASK) == req_class,
            ("req_class is not an allocation class"));
        SLIST_INIT(&free);
        error = 0;
        m = m_run;
        m_end = m_run + npages;
        for (; error == 0 && m < m_end; m++) {
                KASSERT((m->flags & (PG_FICTITIOUS | PG_MARKER)) == 0,
                    ("page %p is PG_FICTITIOUS or PG_MARKER", m));

                /*
                 * Racily check for wirings.  Races are handled once the object
                 * lock is held and the page is unmapped.
                 */
                if (vm_page_wired(m))
                        error = EBUSY;
                else if ((object = atomic_load_ptr(&m->object)) != NULL) {
                        /*
                         * The page is relocated if and only if it could be
                         * laundered or reclaimed by the page daemon.
                         */
                        VM_OBJECT_WLOCK(object);
                        /* Don't care: PG_NODUMP, PG_ZERO. */
                        if (m->object != object ||
                            (object->type != OBJT_DEFAULT &&
                            (object->flags & OBJ_SWAP) == 0 &&
                            object->type != OBJT_VNODE))
                                error = EINVAL;
                        else if (object->memattr != VM_MEMATTR_DEFAULT)
                                error = EINVAL;
                        else if (vm_page_queue(m) != PQ_NONE &&
                            vm_page_tryxbusy(m) != 0) {
                                if (vm_page_wired(m)) {
                                        vm_page_xunbusy(m);
                                        error = EBUSY;
                                        goto unlock;
                                }
                                KASSERT(pmap_page_get_memattr(m) ==
                                    VM_MEMATTR_DEFAULT,
                                    ("page %p has an unexpected memattr", m));
                                KASSERT(m->oflags == 0,
                                    ("page %p has unexpected oflags", m));
                                /* Don't care: PGA_NOSYNC. */
                                if (!vm_page_none_valid(m)) {
                                        /*
                                         * First, try to allocate a new page
                                         * that is above "high".  Failing
                                         * that, try to allocate a new page
                                         * that is below "m_run".  Allocate
                                         * the new page between the end of
                                         * "m_run" and "high" only as a last
                                         * resort.
                                         */
                                        req = req_class;
                                        if ((m->flags & PG_NODUMP) != 0)
                                                req |= VM_ALLOC_NODUMP;
                                        if (trunc_page(high) !=
                                            ~(vm_paddr_t)PAGE_MASK) {
                                                m_new =
                                                    vm_page_alloc_noobj_contig(
                                                    req, 1, round_page(high),
                                                    ~(vm_paddr_t)0, PAGE_SIZE,
                                                    0, VM_MEMATTR_DEFAULT);
                                        } else
                                                m_new = NULL;
                                        if (m_new == NULL) {
                                                pa = VM_PAGE_TO_PHYS(m_run);
                                                m_new =
                                                    vm_page_alloc_noobj_contig(
                                                    req, 1, 0, pa - 1,
                                                    PAGE_SIZE, 0,
                                                    VM_MEMATTR_DEFAULT);
                                        }
                                        if (m_new == NULL) {
                                                pa += ptoa(npages);
                                                m_new =
                                                    vm_page_alloc_noobj_contig(
                                                    req, 1, pa, high, PAGE_SIZE,
                                                    0, VM_MEMATTR_DEFAULT);
                                        }
                                        if (m_new == NULL) {
                                                vm_page_xunbusy(m);
                                                error = ENOMEM;
                                                goto unlock;
                                        }

                                        /*
                                         * Unmap the page and check for new
                                         * wirings that may have been acquired
                                         * through a pmap lookup.
                                         */
                                        if (object->ref_count != 0 &&
                                            !vm_page_try_remove_all(m)) {
                                                vm_page_xunbusy(m);
                                                vm_page_free(m_new);
                                                error = EBUSY;
                                                goto unlock;
                                        }

                                        /*
                                         * Replace "m" with the new page.  For
                                         * vm_page_replace(), "m" must be busy
                                         * and dequeued.  Finally, change "m"
                                         * as if vm_page_free() was called.
                                         */
                                        m_new->a.flags = m->a.flags &
                                            ~PGA_QUEUE_STATE_MASK;
                                        KASSERT(m_new->oflags == VPO_UNMANAGED,
                                            ("page %p is managed", m_new));
                                        m_new->oflags = 0;
                                        pmap_copy_page(m, m_new);
                                        m_new->valid = m->valid;
                                        m_new->dirty = m->dirty;
                                        m->flags &= ~PG_ZERO;
                                        vm_page_dequeue(m);
                                        if (vm_page_replace_hold(m_new, object,
                                            m->pindex, m) &&
                                            vm_page_free_prep(m))
                                                SLIST_INSERT_HEAD(&free, m,
                                                    plinks.s.ss);

                                        /*
                                         * The new page must be deactivated
                                         * before the object is unlocked.
                                         */
                                        vm_page_deactivate(m_new);
                                } else {
                                        m->flags &= ~PG_ZERO;
                                        vm_page_dequeue(m);
                                        if (vm_page_free_prep(m))
                                                SLIST_INSERT_HEAD(&free, m,
                                                    plinks.s.ss);
                                        KASSERT(m->dirty == 0,
                                            ("page %p is dirty", m));
                                }
                        } else
                                error = EBUSY;
unlock:
                        VM_OBJECT_WUNLOCK(object);
                } else {
                        MPASS(vm_page_domain(m) == domain);
                        vmd = VM_DOMAIN(domain);
                        vm_domain_free_lock(vmd);
                        order = m->order;
                        if (order < VM_NFREEORDER) {
                                /*
                                 * The page is enqueued in the physical memory
                                 * allocator's free page queues.  Moreover, it
                                 * is the first page in a power-of-two-sized
                                 * run of contiguous free pages.  Jump ahead
                                 * to the last page within that run, and
                                 * continue from there.
                                 */
                                m += (1 << order) - 1;
                        }
#if VM_NRESERVLEVEL > 0
                        else if (vm_reserv_is_page_free(m))
                                order = 0;
#endif
                        vm_domain_free_unlock(vmd);
                        if (order == VM_NFREEORDER)
                                error = EINVAL;
                }
        }
        if ((m = SLIST_FIRST(&free)) != NULL) {
                int cnt;

                vmd = VM_DOMAIN(domain);
                cnt = 0;
                vm_domain_free_lock(vmd);
                do {
                        MPASS(vm_page_domain(m) == domain);
                        SLIST_REMOVE_HEAD(&free, plinks.s.ss);
                        vm_phys_free_pages(m, 0);
                        cnt++;
                } while ((m = SLIST_FIRST(&free)) != NULL);
                vm_domain_free_unlock(vmd);
                vm_domain_freecnt_inc(vmd, cnt);
        }
        return (error);
}

#define NRUNS   16

CTASSERT(powerof2(NRUNS));

#define RUN_INDEX(count)        ((count) & (NRUNS - 1))

#define MIN_RECLAIM     8

/*
 *      vm_page_reclaim_contig:
 *
 *      Reclaim allocated, contiguous physical memory satisfying the specified
 *      conditions by relocating the virtual pages using that physical memory.
 *      Returns true if reclamation is successful and false otherwise.  Since
 *      relocation requires the allocation of physical pages, reclamation may
 *      fail due to a shortage of free pages.  When reclamation fails, callers
 *      are expected to perform vm_wait() before retrying a failed allocation
 *      operation, e.g., vm_page_alloc_contig().
 *
 *      The caller must always specify an allocation class through "req".
 *
 *      allocation classes:
 *      VM_ALLOC_NORMAL         normal process request
 *      VM_ALLOC_SYSTEM         system *really* needs a page
 *      VM_ALLOC_INTERRUPT      interrupt time request
 *
 *      The optional allocation flags are ignored.
 *
 *      "npages" must be greater than zero.  Both "alignment" and "boundary"
 *      must be a power of two.
 */
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)
{
        struct vm_domain *vmd;
        vm_paddr_t curr_low;
        vm_page_t m_run, m_runs[NRUNS];
        u_long count, minalign, reclaimed;
        int error, i, options, req_class;

        KASSERT(npages > 0, ("npages is 0"));
        KASSERT(powerof2(alignment), ("alignment is not a power of 2"));
        KASSERT(powerof2(boundary), ("boundary is not a power of 2"));

        /*
         * The caller will attempt an allocation after some runs have been
         * reclaimed and added to the vm_phys buddy lists.  Due to limitations
         * of vm_phys_alloc_contig(), round up the requested length to the next
         * power of two or maximum chunk size, and ensure that each run is
         * suitably aligned.
         */
        minalign = 1ul << imin(flsl(npages - 1), VM_NFREEORDER - 1);
        npages = roundup2(npages, minalign);
        if (alignment < ptoa(minalign))
                alignment = ptoa(minalign);

        /*
         * The page daemon is allowed to dig deeper into the free page list.
         */
        req_class = req & VM_ALLOC_CLASS_MASK;
        if (curproc == pageproc && req_class != VM_ALLOC_INTERRUPT)
                req_class = VM_ALLOC_SYSTEM;

        /*
         * Return if the number of free pages cannot satisfy the requested
         * allocation.
         */
        vmd = VM_DOMAIN(domain);
        count = vmd->vmd_free_count;
        if (count < npages + vmd->vmd_free_reserved || (count < npages +
            vmd->vmd_interrupt_free_min && req_class == VM_ALLOC_SYSTEM) ||
            (count < npages && req_class == VM_ALLOC_INTERRUPT))
                return (false);

        /*
         * Scan up to three times, relaxing the restrictions ("options") on
         * the reclamation of reservations and superpages each time.
         */
        for (options = VPSC_NORESERV;;) {
                /*
                 * Find the highest runs that satisfy the given constraints
                 * and restrictions, and record them in "m_runs".
                 */
                curr_low = low;
                count = 0;
                for (;;) {
                        m_run = vm_phys_scan_contig(domain, npages, curr_low,
                            high, alignment, boundary, options);
                        if (m_run == NULL)
                                break;
                        curr_low = VM_PAGE_TO_PHYS(m_run) + ptoa(npages);
                        m_runs[RUN_INDEX(count)] = m_run;
                        count++;
                }

                /*
                 * Reclaim the highest runs in LIFO (descending) order until
                 * the number of reclaimed pages, "reclaimed", is at least
                 * MIN_RECLAIM.  Reset "reclaimed" each time because each
                 * reclamation is idempotent, and runs will (likely) recur
                 * from one scan to the next as restrictions are relaxed.
                 */
                reclaimed = 0;
                for (i = 0; count > 0 && i < NRUNS; i++) {
                        count--;
                        m_run = m_runs[RUN_INDEX(count)];
                        error = vm_page_reclaim_run(req_class, domain, npages,
                            m_run, high);
                        if (error == 0) {
                                reclaimed += npages;
                                if (reclaimed >= MIN_RECLAIM)
                                        return (true);
                        }
                }

                /*
                 * Either relax the restrictions on the next scan or return if
                 * the last scan had no restrictions.
                 */
                if (options == VPSC_NORESERV)
                        options = VPSC_NOSUPER;
                else if (options == VPSC_NOSUPER)
                        options = VPSC_ANY;
                else if (options == VPSC_ANY)
                        return (reclaimed != 0);
        }
}

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)
{
        struct vm_domainset_iter di;
        int domain;
        bool ret;

        vm_domainset_iter_page_init(&di, NULL, 0, &domain, &req);
        do {
                ret = vm_page_reclaim_contig_domain(domain, req, npages, low,
                    high, alignment, boundary);
                if (ret)
                        break;
        } while (vm_domainset_iter_page(&di, NULL, &domain) == 0);

        return (ret);
}

/*
 * Set the domain in the appropriate page level domainset.
 */
void
vm_domain_set(struct vm_domain *vmd)
{

        mtx_lock(&vm_domainset_lock);
        if (!vmd->vmd_minset && vm_paging_min(vmd)) {
                vmd->vmd_minset = 1;
                DOMAINSET_SET(vmd->vmd_domain, &vm_min_domains);
        }
        if (!vmd->vmd_severeset && vm_paging_severe(vmd)) {
                vmd->vmd_severeset = 1;
                DOMAINSET_SET(vmd->vmd_domain, &vm_severe_domains);
        }
        mtx_unlock(&vm_domainset_lock);
}

/*
 * Clear the domain from the appropriate page level domainset.
 */
void
vm_domain_clear(struct vm_domain *vmd)
{

        mtx_lock(&vm_domainset_lock);
        if (vmd->vmd_minset && !vm_paging_min(vmd)) {
                vmd->vmd_minset = 0;
                DOMAINSET_CLR(vmd->vmd_domain, &vm_min_domains);
                if (vm_min_waiters != 0) {
                        vm_min_waiters = 0;
                        wakeup(&vm_min_domains);
                }
        }
        if (vmd->vmd_severeset && !vm_paging_severe(vmd)) {
                vmd->vmd_severeset = 0;
                DOMAINSET_CLR(vmd->vmd_domain, &vm_severe_domains);
                if (vm_severe_waiters != 0) {
                        vm_severe_waiters = 0;
                        wakeup(&vm_severe_domains);
                }
        }

        /*
         * If pageout daemon needs pages, then tell it that there are
         * some free.
         */
        if (vmd->vmd_pageout_pages_needed &&
            vmd->vmd_free_count >= vmd->vmd_pageout_free_min) {
                wakeup(&vmd->vmd_pageout_pages_needed);
                vmd->vmd_pageout_pages_needed = 0;
        }

        /* See comments in vm_wait_doms(). */
        if (vm_pageproc_waiters) {
                vm_pageproc_waiters = 0;
                wakeup(&vm_pageproc_waiters);
        }
        mtx_unlock(&vm_domainset_lock);
}

/*
 * Wait for free pages to exceed the min threshold globally.
 */
void
vm_wait_min(void)
{

        mtx_lock(&vm_domainset_lock);
        while (vm_page_count_min()) {
                vm_min_waiters++;
                msleep(&vm_min_domains, &vm_domainset_lock, PVM, "vmwait", 0);
        }
        mtx_unlock(&vm_domainset_lock);
}

/*
 * Wait for free pages to exceed the severe threshold globally.
 */
void
vm_wait_severe(void)
{

        mtx_lock(&vm_domainset_lock);
        while (vm_page_count_severe()) {
                vm_severe_waiters++;
                msleep(&vm_severe_domains, &vm_domainset_lock, PVM,
                    "vmwait", 0);
        }
        mtx_unlock(&vm_domainset_lock);
}

u_int
vm_wait_count(void)
{

        return (vm_severe_waiters + vm_min_waiters + vm_pageproc_waiters);
}

int
vm_wait_doms(const domainset_t *wdoms, int mflags)
{
        int error;

        error = 0;

        /*
         * We use racey wakeup synchronization to avoid expensive global
         * locking for the pageproc when sleeping with a non-specific vm_wait.
         * To handle this, we only sleep for one tick in this instance.  It
         * is expected that most allocations for the pageproc will come from
         * kmem or vm_page_grab* which will use the more specific and
         * race-free vm_wait_domain().
         */
        if (curproc == pageproc) {
                mtx_lock(&vm_domainset_lock);
                vm_pageproc_waiters++;
                error = msleep(&vm_pageproc_waiters, &vm_domainset_lock,
                    PVM | PDROP | mflags, "pageprocwait", 1);
        } else {
                /*
                 * XXX Ideally we would wait only until the allocation could
                 * be satisfied.  This condition can cause new allocators to
                 * consume all freed pages while old allocators wait.
                 */
                mtx_lock(&vm_domainset_lock);
                if (vm_page_count_min_set(wdoms)) {
                        vm_min_waiters++;
                        error = msleep(&vm_min_domains, &vm_domainset_lock,
                            PVM | PDROP | mflags, "vmwait", 0);
                } else
                        mtx_unlock(&vm_domainset_lock);
        }
        return (error);
}

/*
 *      vm_wait_domain:
 *
 *      Sleep until free pages are available for allocation.
 *      - Called in various places after failed memory allocations.
 */
void
vm_wait_domain(int domain)
{
        struct vm_domain *vmd;
        domainset_t wdom;

        vmd = VM_DOMAIN(domain);
        vm_domain_free_assert_unlocked(vmd);

        if (curproc == pageproc) {
                mtx_lock(&vm_domainset_lock);
                if (vmd->vmd_free_count < vmd->vmd_pageout_free_min) {
                        vmd->vmd_pageout_pages_needed = 1;
                        msleep(&vmd->vmd_pageout_pages_needed,
                            &vm_domainset_lock, PDROP | PSWP, "VMWait", 0);
                } else
                        mtx_unlock(&vm_domainset_lock);
        } else {
                if (pageproc == NULL)
                        panic("vm_wait in early boot");
                DOMAINSET_ZERO(&wdom);
                DOMAINSET_SET(vmd->vmd_domain, &wdom);
                vm_wait_doms(&wdom, 0);
        }
}

static int
vm_wait_flags(vm_object_t obj, int mflags)
{
        struct domainset *d;

        d = NULL;

        /*
         * Carefully fetch pointers only once: the struct domainset
         * itself is ummutable but the pointer might change.
         */
        if (obj != NULL)
                d = obj->domain.dr_policy;
        if (d == NULL)
                d = curthread->td_domain.dr_policy;

        return (vm_wait_doms(&d->ds_mask, mflags));
}

/*
 *      vm_wait:
 *
 *      Sleep until free pages are available for allocation in the
 *      affinity domains of the obj.  If obj is NULL, the domain set
 *      for the calling thread is used.
 *      Called in various places after failed memory allocations.
 */
void
vm_wait(vm_object_t obj)
{
        (void)vm_wait_flags(obj, 0);
}

int
vm_wait_intr(vm_object_t obj)
{
        return (vm_wait_flags(obj, PCATCH));
}

/*
 *      vm_domain_alloc_fail:
 *
 *      Called when a page allocation function fails.  Informs the
 *      pagedaemon and performs the requested wait.  Requires the
 *      domain_free and object lock on entry.  Returns with the
 *      object lock held and free lock released.  Returns an error when
 *      retry is necessary.
 *
 */
static int
vm_domain_alloc_fail(struct vm_domain *vmd, vm_object_t object, int req)
{

        vm_domain_free_assert_unlocked(vmd);

        atomic_add_int(&vmd->vmd_pageout_deficit,
            max((u_int)req >> VM_ALLOC_COUNT_SHIFT, 1));
        if (req & (VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL)) {
                if (object != NULL) 
                        VM_OBJECT_WUNLOCK(object);
                vm_wait_domain(vmd->vmd_domain);
                if (object != NULL) 
                        VM_OBJECT_WLOCK(object);
                if (req & VM_ALLOC_WAITOK)
                        return (EAGAIN);
        }

        return (0);
}

/*
 *      vm_waitpfault:
 *
 *      Sleep until free pages are available for allocation.
 *      - Called only in vm_fault so that processes page faulting
 *        can be easily tracked.
 *      - Sleeps at a lower priority than vm_wait() so that vm_wait()ing
 *        processes will be able to grab memory first.  Do not change
 *        this balance without careful testing first.
 */
void
vm_waitpfault(struct domainset *dset, int timo)
{

        /*
         * XXX Ideally we would wait only until the allocation could
         * be satisfied.  This condition can cause new allocators to
         * consume all freed pages while old allocators wait.
         */
        mtx_lock(&vm_domainset_lock);
        if (vm_page_count_min_set(&dset->ds_mask)) {
                vm_min_waiters++;
                msleep(&vm_min_domains, &vm_domainset_lock, PUSER | PDROP,
                    "pfault", timo);
        } else
                mtx_unlock(&vm_domainset_lock);
}

static struct vm_pagequeue *
_vm_page_pagequeue(vm_page_t m, uint8_t queue)
{

        return (&vm_pagequeue_domain(m)->vmd_pagequeues[queue]);
}

#ifdef INVARIANTS
static struct vm_pagequeue *
vm_page_pagequeue(vm_page_t m)
{

        return (_vm_page_pagequeue(m, vm_page_astate_load(m).queue));
}
#endif

static __always_inline bool
vm_page_pqstate_fcmpset(vm_page_t m, vm_page_astate_t *old, vm_page_astate_t new)
{
        vm_page_astate_t tmp;

        tmp = *old;
        do {
                if (__predict_true(vm_page_astate_fcmpset(m, old, new)))
                        return (true);
                counter_u64_add(pqstate_commit_retries, 1);
        } while (old->_bits == tmp._bits);

        return (false);
}

/*
 * Do the work of committing a queue state update that moves the page out of
 * its current queue.
 */
static bool
_vm_page_pqstate_commit_dequeue(struct vm_pagequeue *pq, vm_page_t m,
    vm_page_astate_t *old, vm_page_astate_t new)
{
        vm_page_t next;

        vm_pagequeue_assert_locked(pq);
        KASSERT(vm_page_pagequeue(m) == pq,
            ("%s: queue %p does not match page %p", __func__, pq, m));
        KASSERT(old->queue != PQ_NONE && new.queue != old->queue,
            ("%s: invalid queue indices %d %d",
            __func__, old->queue, new.queue));

        /*
         * Once the queue index of the page changes there is nothing
         * synchronizing with further updates to the page's physical
         * queue state.  Therefore we must speculatively remove the page
         * from the queue now and be prepared to roll back if the queue
         * state update fails.  If the page is not physically enqueued then
         * we just update its queue index.
         */
        if ((old->flags & PGA_ENQUEUED) != 0) {
                new.flags &= ~PGA_ENQUEUED;
                next = TAILQ_NEXT(m, plinks.q);
                TAILQ_REMOVE(&pq->pq_pl, m, plinks.q);
                vm_pagequeue_cnt_dec(pq);
                if (!vm_page_pqstate_fcmpset(m, old, new)) {
                        if (next == NULL)
                                TAILQ_INSERT_TAIL(&pq->pq_pl, m, plinks.q);
                        else
                                TAILQ_INSERT_BEFORE(next, m, plinks.q);
                        vm_pagequeue_cnt_inc(pq);
                        return (false);
                } else {
                        return (true);
                }
        } else {
                return (vm_page_pqstate_fcmpset(m, old, new));
        }
}

static bool
vm_page_pqstate_commit_dequeue(vm_page_t m, vm_page_astate_t *old,
    vm_page_astate_t new)
{
        struct vm_pagequeue *pq;
        vm_page_astate_t as;
        bool ret;

        pq = _vm_page_pagequeue(m, old->queue);

        /*
         * The queue field and PGA_ENQUEUED flag are stable only so long as the
         * corresponding page queue lock is held.
         */
        vm_pagequeue_lock(pq);
        as = vm_page_astate_load(m);
        if (__predict_false(as._bits != old->_bits)) {
                *old = as;
                ret = false;
        } else {
                ret = _vm_page_pqstate_commit_dequeue(pq, m, old, new);
        }
        vm_pagequeue_unlock(pq);
        return (ret);
}

/*
 * Commit a queue state update that enqueues or requeues a page.
 */
static bool
_vm_page_pqstate_commit_requeue(struct vm_pagequeue *pq, vm_page_t m,
    vm_page_astate_t *old, vm_page_astate_t new)
{
        struct vm_domain *vmd;

        vm_pagequeue_assert_locked(pq);
        KASSERT(old->queue != PQ_NONE && new.queue == old->queue,
            ("%s: invalid queue indices %d %d",
            __func__, old->queue, new.queue));

        new.flags |= PGA_ENQUEUED;
        if (!vm_page_pqstate_fcmpset(m, old, new))
                return (false);

        if ((old->flags & PGA_ENQUEUED) != 0)
                TAILQ_REMOVE(&pq->pq_pl, m, plinks.q);
        else
                vm_pagequeue_cnt_inc(pq);

        /*
         * Give PGA_REQUEUE_HEAD precedence over PGA_REQUEUE.  In particular, if
         * both flags are set in close succession, only PGA_REQUEUE_HEAD will be
         * applied, even if it was set first.
         */
        if ((old->flags & PGA_REQUEUE_HEAD) != 0) {
                vmd = vm_pagequeue_domain(m);
                KASSERT(pq == &vmd->vmd_pagequeues[PQ_INACTIVE],
                    ("%s: invalid page queue for page %p", __func__, m));
                TAILQ_INSERT_BEFORE(&vmd->vmd_inacthead, m, plinks.q);
        } else {
                TAILQ_INSERT_TAIL(&pq->pq_pl, m, plinks.q);
        }
        return (true);
}

/*
 * Commit a queue state update that encodes a request for a deferred queue
 * operation.
 */
static bool
vm_page_pqstate_commit_request(vm_page_t m, vm_page_astate_t *old,
    vm_page_astate_t new)
{

        KASSERT(old->queue == new.queue || new.queue != PQ_NONE,
            ("%s: invalid state, queue %d flags %x",
            __func__, new.queue, new.flags));

        if (old->_bits != new._bits &&
            !vm_page_pqstate_fcmpset(m, old, new))
                return (false);
        vm_page_pqbatch_submit(m, new.queue);
        return (true);
}

/*
 * A generic queue state update function.  This handles more cases than the
 * specialized functions above.
 */
bool
vm_page_pqstate_commit(vm_page_t m, vm_page_astate_t *old, vm_page_astate_t new)
{

        if (old->_bits == new._bits)
                return (true);

        if (old->queue != PQ_NONE && new.queue != old->queue) {
                if (!vm_page_pqstate_commit_dequeue(m, old, new))
                        return (false);
                if (new.queue != PQ_NONE)
                        vm_page_pqbatch_submit(m, new.queue);
        } else {
                if (!vm_page_pqstate_fcmpset(m, old, new))
                        return (false);
                if (new.queue != PQ_NONE &&
                    ((new.flags & ~old->flags) & PGA_QUEUE_OP_MASK) != 0)
                        vm_page_pqbatch_submit(m, new.queue);
        }
        return (true);
}

/*
 * Apply deferred queue state updates to a page.
 */
static inline void
vm_pqbatch_process_page(struct vm_pagequeue *pq, vm_page_t m, uint8_t queue)
{
        vm_page_astate_t new, old;

        CRITICAL_ASSERT(curthread);
        vm_pagequeue_assert_locked(pq);
        KASSERT(queue < PQ_COUNT,
            ("%s: invalid queue index %d", __func__, queue));
        KASSERT(pq == _vm_page_pagequeue(m, queue),
            ("%s: page %p does not belong to queue %p", __func__, m, pq));

        for (old = vm_page_astate_load(m);;) {
                if (__predict_false(old.queue != queue ||
                    (old.flags & PGA_QUEUE_OP_MASK) == 0)) {
                        counter_u64_add(queue_nops, 1);
                        break;
                }
                KASSERT((m->oflags & VPO_UNMANAGED) == 0,
                    ("%s: page %p is unmanaged", __func__, m));

                new = old;
                if ((old.flags & PGA_DEQUEUE) != 0) {
                        new.flags &= ~PGA_QUEUE_OP_MASK;
                        new.queue = PQ_NONE;
                        if (__predict_true(_vm_page_pqstate_commit_dequeue(pq,
                            m, &old, new))) {
                                counter_u64_add(queue_ops, 1);
                                break;
                        }
                } else {
                        new.flags &= ~(PGA_REQUEUE | PGA_REQUEUE_HEAD);
                        if (__predict_true(_vm_page_pqstate_commit_requeue(pq,
                            m, &old, new))) {
                                counter_u64_add(queue_ops, 1);
                                break;
                        }
                }
        }
}

static void
vm_pqbatch_process(struct vm_pagequeue *pq, struct vm_batchqueue *bq,
    uint8_t queue)
{
        int i;

        for (i = 0; i < bq->bq_cnt; i++)
                vm_pqbatch_process_page(pq, bq->bq_pa[i], queue);
        vm_batchqueue_init(bq);
}

/*
 *      vm_page_pqbatch_submit:         [ internal use only ]
 *
 *      Enqueue a page in the specified page queue's batched work queue.
 *      The caller must have encoded the requested operation in the page
 *      structure's a.flags field.
 */
void
vm_page_pqbatch_submit(vm_page_t m, uint8_t queue)
{
        struct vm_batchqueue *bq;
        struct vm_pagequeue *pq;
        int domain;

        KASSERT(queue < PQ_COUNT, ("invalid queue %d", queue));

        domain = vm_page_domain(m);
        critical_enter();
        bq = DPCPU_PTR(pqbatch[domain][queue]);
        if (vm_batchqueue_insert(bq, m)) {
                critical_exit();
                return;
        }
        critical_exit();

        pq = &VM_DOMAIN(domain)->vmd_pagequeues[queue];
        vm_pagequeue_lock(pq);
        critical_enter();
        bq = DPCPU_PTR(pqbatch[domain][queue]);
        vm_pqbatch_process(pq, bq, queue);
        vm_pqbatch_process_page(pq, m, queue);
        vm_pagequeue_unlock(pq);
        critical_exit();
}

/*
 *      vm_page_pqbatch_drain:          [ internal use only ]
 *
 *      Force all per-CPU page queue batch queues to be drained.  This is
 *      intended for use in severe memory shortages, to ensure that pages
 *      do not remain stuck in the batch queues.
 */
void
vm_page_pqbatch_drain(void)
{
        struct thread *td;
        struct vm_domain *vmd;
        struct vm_pagequeue *pq;
        int cpu, domain, queue;

        td = curthread;
        CPU_FOREACH(cpu) {
                thread_lock(td);
                sched_bind(td, cpu);
                thread_unlock(td);

                for (domain = 0; domain < vm_ndomains; domain++) {
                        vmd = VM_DOMAIN(domain);
                        for (queue = 0; queue < PQ_COUNT; queue++) {
                                pq = &vmd->vmd_pagequeues[queue];
                                vm_pagequeue_lock(pq);
                                critical_enter();
                                vm_pqbatch_process(pq,
                                    DPCPU_PTR(pqbatch[domain][queue]), queue);
                                critical_exit();
                                vm_pagequeue_unlock(pq);
                        }
                }
        }
        thread_lock(td);
        sched_unbind(td);
        thread_unlock(td);
}

/*
 *      vm_page_dequeue_deferred:       [ internal use only ]
 *
 *      Request removal of the given page from its current page
 *      queue.  Physical removal from the queue may be deferred
 *      indefinitely.
 */
void
vm_page_dequeue_deferred(vm_page_t m)
{
        vm_page_astate_t new, old;

        old = vm_page_astate_load(m);
        do {
                if (old.queue == PQ_NONE) {
                        KASSERT((old.flags & PGA_QUEUE_STATE_MASK) == 0,
                            ("%s: page %p has unexpected queue state",
                            __func__, m));
                        break;
                }
                new = old;
                new.flags |= PGA_DEQUEUE;
        } while (!vm_page_pqstate_commit_request(m, &old, new));
}

/*
 *      vm_page_dequeue:
 *
 *      Remove the page from whichever page queue it's in, if any, before
 *      returning.
 */
void
vm_page_dequeue(vm_page_t m)
{
        vm_page_astate_t new, old;

        old = vm_page_astate_load(m);
        do {
                if (old.queue == PQ_NONE) {
                        KASSERT((old.flags & PGA_QUEUE_STATE_MASK) == 0,
                            ("%s: page %p has unexpected queue state",
                            __func__, m));
                        break;
                }
                new = old;
                new.flags &= ~PGA_QUEUE_OP_MASK;
                new.queue = PQ_NONE;
        } while (!vm_page_pqstate_commit_dequeue(m, &old, new));

}

/*
 * Schedule the given page for insertion into the specified page queue.
 * Physical insertion of the page may be deferred indefinitely.
 */
static void
vm_page_enqueue(vm_page_t m, uint8_t queue)
{

        KASSERT(m->a.queue == PQ_NONE &&
            (m->a.flags & PGA_QUEUE_STATE_MASK) == 0,
            ("%s: page %p is already enqueued", __func__, m));
        KASSERT(m->ref_count > 0,
            ("%s: page %p does not carry any references", __func__, m));

        m->a.queue = queue;
        if ((m->a.flags & PGA_REQUEUE) == 0)
                vm_page_aflag_set(m, PGA_REQUEUE);
        vm_page_pqbatch_submit(m, queue);
}

/*
 *      vm_page_free_prep:
 *
 *      Prepares the given page to be put on the free list,
 *      disassociating it from any VM object. The caller may return
 *      the page to the free list only if this function returns true.
 *
 *      The object, if it exists, must be locked, and then the page must
 *      be xbusy.  Otherwise the page must be not busied.  A managed
 *      page must be unmapped.
 */
static bool
vm_page_free_prep(vm_page_t m)
{

        /*
         * Synchronize with threads that have dropped a reference to this
         * page.
         */
        atomic_thread_fence_acq();

#if defined(DIAGNOSTIC) && defined(PHYS_TO_DMAP)
        if (PMAP_HAS_DMAP && (m->flags & PG_ZERO) != 0) {
                uint64_t *p;
                int i;
                p = (uint64_t *)PHYS_TO_DMAP(VM_PAGE_TO_PHYS(m));
                for (i = 0; i < PAGE_SIZE / sizeof(uint64_t); i++, p++)
                        KASSERT(*p == 0, ("vm_page_free_prep %p PG_ZERO %d %jx",
                            m, i, (uintmax_t)*p));
        }
#endif
        if ((m->oflags & VPO_UNMANAGED) == 0) {
                KASSERT(!pmap_page_is_mapped(m),
                    ("vm_page_free_prep: freeing mapped page %p", m));
                KASSERT((m->a.flags & (PGA_EXECUTABLE | PGA_WRITEABLE)) == 0,
                    ("vm_page_free_prep: mapping flags set in page %p", m));
        } else {
                KASSERT(m->a.queue == PQ_NONE,
                    ("vm_page_free_prep: unmanaged page %p is queued", m));
        }
        VM_CNT_INC(v_tfree);

        if (m->object != NULL) {
                KASSERT(((m->oflags & VPO_UNMANAGED) != 0) ==
                    ((m->object->flags & OBJ_UNMANAGED) != 0),
                    ("vm_page_free_prep: managed flag mismatch for page %p",
                    m));
                vm_page_assert_xbusied(m);

                /*
                 * The object reference can be released without an atomic
                 * operation.
                 */
                KASSERT((m->flags & PG_FICTITIOUS) != 0 ||
                    m->ref_count == VPRC_OBJREF,
                    ("vm_page_free_prep: page %p has unexpected ref_count %u",
                    m, m->ref_count));
                vm_page_object_remove(m);
                m->ref_count -= VPRC_OBJREF;
        } else
                vm_page_assert_unbusied(m);

        vm_page_busy_free(m);

        /*
         * If fictitious remove object association and
         * return.
         */
        if ((m->flags & PG_FICTITIOUS) != 0) {
                KASSERT(m->ref_count == 1,
                    ("fictitious page %p is referenced", m));
                KASSERT(m->a.queue == PQ_NONE,
                    ("fictitious page %p is queued", m));
                return (false);
        }

        /*
         * Pages need not be dequeued before they are returned to the physical
         * memory allocator, but they must at least be marked for a deferred
         * dequeue.
         */
        if ((m->oflags & VPO_UNMANAGED) == 0)
                vm_page_dequeue_deferred(m);

        m->valid = 0;
        vm_page_undirty(m);

        if (m->ref_count != 0)
                panic("vm_page_free_prep: page %p has references", m);

        /*
         * Restore the default memory attribute to the page.
         */
        if (pmap_page_get_memattr(m) != VM_MEMATTR_DEFAULT)
                pmap_page_set_memattr(m, VM_MEMATTR_DEFAULT);

#if VM_NRESERVLEVEL > 0
        /*
         * Determine whether the page belongs to a reservation.  If the page was
         * allocated from a per-CPU cache, it cannot belong to a reservation, so
         * as an optimization, we avoid the check in that case.
         */
        if ((m->flags & PG_PCPU_CACHE) == 0 && vm_reserv_free_page(m))
                return (false);
#endif

        return (true);
}

/*
 *      vm_page_free_toq:
 *
 *      Returns the given page to the free list, disassociating it
 *      from any VM object.
 *
 *      The object must be locked.  The page must be exclusively busied if it
 *      belongs to an object.
 */
static void
vm_page_free_toq(vm_page_t m)
{
        struct vm_domain *vmd;
        uma_zone_t zone;

        if (!vm_page_free_prep(m))
                return;

        vmd = vm_pagequeue_domain(m);
        zone = vmd->vmd_pgcache[m->pool].zone;
        if ((m->flags & PG_PCPU_CACHE) != 0 && zone != NULL) {
                uma_zfree(zone, m);
                return;
        }
        vm_domain_free_lock(vmd);
        vm_phys_free_pages(m, 0);
        vm_domain_free_unlock(vmd);
        vm_domain_freecnt_inc(vmd, 1);
}

/*
 *      vm_page_free_pages_toq:
 *
 *      Returns a list of pages to the free list, disassociating it
 *      from any VM object.  In other words, this is equivalent to
 *      calling vm_page_free_toq() for each page of a list of VM objects.
 */
void
vm_page_free_pages_toq(struct spglist *free, bool update_wire_count)
{
        vm_page_t m;
        int count;

        if (SLIST_EMPTY(free))
                return;

        count = 0;
        while ((m = SLIST_FIRST(free)) != NULL) {
                count++;
                SLIST_REMOVE_HEAD(free, plinks.s.ss);
                vm_page_free_toq(m);
        }

        if (update_wire_count)
                vm_wire_sub(count);
}

/*
 * Mark this page as wired down.  For managed pages, this prevents reclamation
 * by the page daemon, or when the containing object, if any, is destroyed.
 */
void
vm_page_wire(vm_page_t m)
{
        u_int old;

#ifdef INVARIANTS
        if (m->object != NULL && !vm_page_busied(m) &&
            !vm_object_busied(m->object))
                VM_OBJECT_ASSERT_LOCKED(m->object);
#endif
        KASSERT((m->flags & PG_FICTITIOUS) == 0 ||
            VPRC_WIRE_COUNT(m->ref_count) >= 1,
            ("vm_page_wire: fictitious page %p has zero wirings", m));

        old = atomic_fetchadd_int(&m->ref_count, 1);
        KASSERT(VPRC_WIRE_COUNT(old) != VPRC_WIRE_COUNT_MAX,
            ("vm_page_wire: counter overflow for page %p", m));
        if (VPRC_WIRE_COUNT(old) == 0) {
                if ((m->oflags & VPO_UNMANAGED) == 0)
                        vm_page_aflag_set(m, PGA_DEQUEUE);
                vm_wire_add(1);
        }
}

/*
 * Attempt to wire a mapped page following a pmap lookup of that page.
 * This may fail if a thread is concurrently tearing down mappings of the page.
 * The transient failure is acceptable because it translates to the
 * failure of the caller pmap_extract_and_hold(), which should be then
 * followed by the vm_fault() fallback, see e.g. vm_fault_quick_hold_pages().
 */
bool
vm_page_wire_mapped(vm_page_t m)
{
        u_int old;

        old = m->ref_count;
        do {
                KASSERT(old > 0,
                    ("vm_page_wire_mapped: wiring unreferenced page %p", m));
                if ((old & VPRC_BLOCKED) != 0)
                        return (false);
        } while (!atomic_fcmpset_int(&m->ref_count, &old, old + 1));

        if (VPRC_WIRE_COUNT(old) == 0) {
                if ((m->oflags & VPO_UNMANAGED) == 0)
                        vm_page_aflag_set(m, PGA_DEQUEUE);
                vm_wire_add(1);
        }
        return (true);
}

/*
 * Release a wiring reference to a managed page.  If the page still belongs to
 * an object, update its position in the page queues to reflect the reference.
 * If the wiring was the last reference to the page, free the page.
 */
static void
vm_page_unwire_managed(vm_page_t m, uint8_t nqueue, bool noreuse)
{
        u_int old;

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("%s: page %p is unmanaged", __func__, m));

        /*
         * Update LRU state before releasing the wiring reference.
         * Use a release store when updating the reference count to
         * synchronize with vm_page_free_prep().
         */
        old = m->ref_count;
        do {
                KASSERT(VPRC_WIRE_COUNT(old) > 0,
                    ("vm_page_unwire: wire count underflow for page %p", m));

                if (old > VPRC_OBJREF + 1) {
                        /*
                         * The page has at least one other wiring reference.  An
                         * earlier iteration of this loop may have called
                         * vm_page_release_toq() and cleared PGA_DEQUEUE, so
                         * re-set it if necessary.
                         */
                        if ((vm_page_astate_load(m).flags & PGA_DEQUEUE) == 0)
                                vm_page_aflag_set(m, PGA_DEQUEUE);
                } else if (old == VPRC_OBJREF + 1) {
                        /*
                         * This is the last wiring.  Clear PGA_DEQUEUE and
                         * update the page's queue state to reflect the
                         * reference.  If the page does not belong to an object
                         * (i.e., the VPRC_OBJREF bit is clear), we only need to
                         * clear leftover queue state.
                         */
                        vm_page_release_toq(m, nqueue, noreuse);
                } else if (old == 1) {
                        vm_page_aflag_clear(m, PGA_DEQUEUE);
                }
        } while (!atomic_fcmpset_rel_int(&m->ref_count, &old, old - 1));

        if (VPRC_WIRE_COUNT(old) == 1) {
                vm_wire_sub(1);
                if (old == 1)
                        vm_page_free(m);
        }
}

/*
 * Release one wiring of the specified page, potentially allowing it to be
 * paged out.
 *
 * Only managed pages belonging to an object can be paged out.  If the number
 * of wirings transitions to zero and the page is eligible for page out, then
 * the page is added to the specified paging queue.  If the released wiring
 * represented the last reference to the page, the page is freed.
 */
void
vm_page_unwire(vm_page_t m, uint8_t nqueue)
{

        KASSERT(nqueue < PQ_COUNT,
            ("vm_page_unwire: invalid queue %u request for page %p",
            nqueue, m));

        if ((m->oflags & VPO_UNMANAGED) != 0) {
                if (vm_page_unwire_noq(m) && m->ref_count == 0)
                        vm_page_free(m);
                return;
        }
        vm_page_unwire_managed(m, nqueue, false);
}

/*
 * Unwire a page without (re-)inserting it into a page queue.  It is up
 * to the caller to enqueue, requeue, or free the page as appropriate.
 * In most cases involving managed pages, vm_page_unwire() should be used
 * instead.
 */
bool
vm_page_unwire_noq(vm_page_t m)
{
        u_int old;

        old = vm_page_drop(m, 1);
        KASSERT(VPRC_WIRE_COUNT(old) != 0,
            ("%s: counter underflow for page %p", __func__,  m));
        KASSERT((m->flags & PG_FICTITIOUS) == 0 || VPRC_WIRE_COUNT(old) > 1,
            ("%s: missing ref on fictitious page %p", __func__, m));

        if (VPRC_WIRE_COUNT(old) > 1)
                return (false);
        if ((m->oflags & VPO_UNMANAGED) == 0)
                vm_page_aflag_clear(m, PGA_DEQUEUE);
        vm_wire_sub(1);
        return (true);
}

/*
 * Ensure that the page ends up in the specified page queue.  If the page is
 * active or being moved to the active queue, ensure that its act_count is
 * at least ACT_INIT but do not otherwise mess with it.
 */
static __always_inline void
vm_page_mvqueue(vm_page_t m, const uint8_t nqueue, const uint16_t nflag)
{
        vm_page_astate_t old, new;

        KASSERT(m->ref_count > 0,
            ("%s: page %p does not carry any references", __func__, m));
        KASSERT(nflag == PGA_REQUEUE || nflag == PGA_REQUEUE_HEAD,
            ("%s: invalid flags %x", __func__, nflag));

        if ((m->oflags & VPO_UNMANAGED) != 0 || vm_page_wired(m))
                return;

        old = vm_page_astate_load(m);
        do {
                if ((old.flags & PGA_DEQUEUE) != 0)
                        break;
                new = old;
                new.flags &= ~PGA_QUEUE_OP_MASK;
                if (nqueue == PQ_ACTIVE)
                        new.act_count = max(old.act_count, ACT_INIT);
                if (old.queue == nqueue) {
                        if (nqueue != PQ_ACTIVE)
                                new.flags |= nflag;
                } else {
                        new.flags |= nflag;
                        new.queue = nqueue;
                }
        } while (!vm_page_pqstate_commit(m, &old, new));
}

/*
 * Put the specified page on the active list (if appropriate).
 */
void
vm_page_activate(vm_page_t m)
{

        vm_page_mvqueue(m, PQ_ACTIVE, PGA_REQUEUE);
}

/*
 * Move the specified page to the tail of the inactive queue, or requeue
 * the page if it is already in the inactive queue.
 */
void
vm_page_deactivate(vm_page_t m)
{

        vm_page_mvqueue(m, PQ_INACTIVE, PGA_REQUEUE);
}

void
vm_page_deactivate_noreuse(vm_page_t m)
{

        vm_page_mvqueue(m, PQ_INACTIVE, PGA_REQUEUE_HEAD);
}

/*
 * Put a page in the laundry, or requeue it if it is already there.
 */
void
vm_page_launder(vm_page_t m)
{

        vm_page_mvqueue(m, PQ_LAUNDRY, PGA_REQUEUE);
}

/*
 * Put a page in the PQ_UNSWAPPABLE holding queue.
 */
void
vm_page_unswappable(vm_page_t m)
{

        KASSERT(!vm_page_wired(m) && (m->oflags & VPO_UNMANAGED) == 0,
            ("page %p already unswappable", m));

        vm_page_dequeue(m);
        vm_page_enqueue(m, PQ_UNSWAPPABLE);
}

/*
 * Release a page back to the page queues in preparation for unwiring.
 */
static void
vm_page_release_toq(vm_page_t m, uint8_t nqueue, const bool noreuse)
{
        vm_page_astate_t old, new;
        uint16_t nflag;

        /*
         * Use a check of the valid bits to determine whether we should
         * accelerate reclamation of the page.  The object lock might not be
         * held here, in which case the check is racy.  At worst we will either
         * accelerate reclamation of a valid page and violate LRU, or
         * unnecessarily defer reclamation of an invalid page.
         *
         * If we were asked to not cache the page, place it near the head of the
         * inactive queue so that is reclaimed sooner.
         */
        if (noreuse || m->valid == 0) {
                nqueue = PQ_INACTIVE;
                nflag = PGA_REQUEUE_HEAD;
        } else {
                nflag = PGA_REQUEUE;
        }

        old = vm_page_astate_load(m);
        do {
                new = old;

                /*
                 * If the page is already in the active queue and we are not
                 * trying to accelerate reclamation, simply mark it as
                 * referenced and avoid any queue operations.
                 */
                new.flags &= ~PGA_QUEUE_OP_MASK;
                if (nflag != PGA_REQUEUE_HEAD && old.queue == PQ_ACTIVE)
                        new.flags |= PGA_REFERENCED;
                else {
                        new.flags |= nflag;
                        new.queue = nqueue;
                }
        } while (!vm_page_pqstate_commit(m, &old, new));
}

/*
 * Unwire a page and either attempt to free it or re-add it to the page queues.
 */
void
vm_page_release(vm_page_t m, int flags)
{
        vm_object_t object;

        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("vm_page_release: page %p is unmanaged", m));

        if ((flags & VPR_TRYFREE) != 0) {
                for (;;) {
                        object = atomic_load_ptr(&m->object);
                        if (object == NULL)
                                break;
                        /* Depends on type-stability. */
                        if (vm_page_busied(m) || !VM_OBJECT_TRYWLOCK(object))
                                break;
                        if (object == m->object) {
                                vm_page_release_locked(m, flags);
                                VM_OBJECT_WUNLOCK(object);
                                return;
                        }
                        VM_OBJECT_WUNLOCK(object);
                }
        }
        vm_page_unwire_managed(m, PQ_INACTIVE, flags != 0);
}

/* See vm_page_release(). */
void
vm_page_release_locked(vm_page_t m, int flags)
{

        VM_OBJECT_ASSERT_WLOCKED(m->object);
        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("vm_page_release_locked: page %p is unmanaged", m));

        if (vm_page_unwire_noq(m)) {
                if ((flags & VPR_TRYFREE) != 0 &&
                    (m->object->ref_count == 0 || !pmap_page_is_mapped(m)) &&
                    m->dirty == 0 && vm_page_tryxbusy(m)) {
                        /*
                         * An unlocked lookup may have wired the page before the
                         * busy lock was acquired, in which case the page must
                         * not be freed.
                         */
                        if (__predict_true(!vm_page_wired(m))) {
                                vm_page_free(m);
                                return;
                        }
                        vm_page_xunbusy(m);
                } else {
                        vm_page_release_toq(m, PQ_INACTIVE, flags != 0);
                }
        }
}

static bool
vm_page_try_blocked_op(vm_page_t m, void (*op)(vm_page_t))
{
        u_int old;

        KASSERT(m->object != NULL && (m->oflags & VPO_UNMANAGED) == 0,
            ("vm_page_try_blocked_op: page %p has no object", m));
        KASSERT(vm_page_busied(m),
            ("vm_page_try_blocked_op: page %p is not busy", m));
        VM_OBJECT_ASSERT_LOCKED(m->object);

        old = m->ref_count;
        do {
                KASSERT(old != 0,
                    ("vm_page_try_blocked_op: page %p has no references", m));
                if (VPRC_WIRE_COUNT(old) != 0)
                        return (false);
        } while (!atomic_fcmpset_int(&m->ref_count, &old, old | VPRC_BLOCKED));

        (op)(m);

        /*
         * If the object is read-locked, new wirings may be created via an
         * object lookup.
         */
        old = vm_page_drop(m, VPRC_BLOCKED);
        KASSERT(!VM_OBJECT_WOWNED(m->object) ||
            old == (VPRC_BLOCKED | VPRC_OBJREF),
            ("vm_page_try_blocked_op: unexpected refcount value %u for %p",
            old, m));
        return (true);
}

/*
 * Atomically check for wirings and remove all mappings of the page.
 */
bool
vm_page_try_remove_all(vm_page_t m)
{

        return (vm_page_try_blocked_op(m, pmap_remove_all));
}

/*
 * Atomically check for wirings and remove all writeable mappings of the page.
 */
bool
vm_page_try_remove_write(vm_page_t m)
{

        return (vm_page_try_blocked_op(m, pmap_remove_write));
}

/*
 * vm_page_advise
 *
 *      Apply the specified advice to the given page.
 */
void
vm_page_advise(vm_page_t m, int advice)
{

        VM_OBJECT_ASSERT_WLOCKED(m->object);
        vm_page_assert_xbusied(m);

        if (advice == MADV_FREE)
                /*
                 * Mark the page clean.  This will allow the page to be freed
                 * without first paging it out.  MADV_FREE pages are often
                 * quickly reused by malloc(3), so we do not do anything that
                 * would result in a page fault on a later access.
                 */
                vm_page_undirty(m);
        else if (advice != MADV_DONTNEED) {
                if (advice == MADV_WILLNEED)
                        vm_page_activate(m);
                return;
        }

        if (advice != MADV_FREE && m->dirty == 0 && pmap_is_modified(m))
                vm_page_dirty(m);

        /*
         * Clear any references to the page.  Otherwise, the page daemon will
         * immediately reactivate the page.
         */
        vm_page_aflag_clear(m, PGA_REFERENCED);

        /*
         * Place clean pages near the head of the inactive queue rather than
         * the tail, thus defeating the queue's LRU operation and ensuring that
         * the page will be reused quickly.  Dirty pages not already in the
         * laundry are moved there.
         */
        if (m->dirty == 0)
                vm_page_deactivate_noreuse(m);
        else if (!vm_page_in_laundry(m))
                vm_page_launder(m);
}

/*
 *      vm_page_grab_release
 *
 *      Helper routine for grab functions to release busy on return.
 */
static inline void
vm_page_grab_release(vm_page_t m, int allocflags)
{

        if ((allocflags & VM_ALLOC_NOBUSY) != 0) {
                if ((allocflags & VM_ALLOC_IGN_SBUSY) != 0)
                        vm_page_sunbusy(m);
                else
                        vm_page_xunbusy(m);
        }
}

/*
 *      vm_page_grab_sleep
 *
 *      Sleep for busy according to VM_ALLOC_ parameters.  Returns true
 *      if the caller should retry and false otherwise.
 *
 *      If the object is locked on entry the object will be unlocked with
 *      false returns and still locked but possibly having been dropped
 *      with true returns.
 */
static bool
vm_page_grab_sleep(vm_object_t object, vm_page_t m, vm_pindex_t pindex,
    const char *wmesg, int allocflags, bool locked)
{

        if ((allocflags & VM_ALLOC_NOWAIT) != 0)
                return (false);

        /*
         * Reference the page before unlocking and sleeping so that
         * the page daemon is less likely to reclaim it.
         */
        if (locked && (allocflags & VM_ALLOC_NOCREAT) == 0)
                vm_page_reference(m);

        if (_vm_page_busy_sleep(object, m, pindex, wmesg, allocflags, locked) &&
            locked)
                VM_OBJECT_WLOCK(object);
        if ((allocflags & VM_ALLOC_WAITFAIL) != 0)
                return (false);

        return (true);
}

/*
 * Assert that the grab flags are valid.
 */
static inline void
vm_page_grab_check(int allocflags)
{

        KASSERT((allocflags & VM_ALLOC_NOBUSY) == 0 ||
            (allocflags & VM_ALLOC_WIRED) != 0,
            ("vm_page_grab*: the pages must be busied or wired"));

        KASSERT((allocflags & VM_ALLOC_SBUSY) == 0 ||
            (allocflags & VM_ALLOC_IGN_SBUSY) != 0,
            ("vm_page_grab*: VM_ALLOC_SBUSY/VM_ALLOC_IGN_SBUSY mismatch"));
}

/*
 * Calculate the page allocation flags for grab.
 */
static inline int
vm_page_grab_pflags(int allocflags)
{
        int pflags;

        pflags = allocflags &
            ~(VM_ALLOC_NOWAIT | VM_ALLOC_WAITOK | VM_ALLOC_WAITFAIL |
            VM_ALLOC_NOBUSY | VM_ALLOC_IGN_SBUSY);
        if ((allocflags & VM_ALLOC_NOWAIT) == 0)
                pflags |= VM_ALLOC_WAITFAIL;
        if ((allocflags & VM_ALLOC_IGN_SBUSY) != 0)
                pflags |= VM_ALLOC_SBUSY;

        return (pflags);
}

/*
 * Grab a page, waiting until we are waken up due to the page
 * changing state.  We keep on waiting, if the page continues
 * to be in the object.  If the page doesn't exist, first allocate it
 * and then conditionally zero it.
 *
 * This routine may sleep.
 *
 * The object must be locked on entry.  The lock will, however, be released
 * and reacquired if the routine sleeps.
 */
vm_page_t
vm_page_grab(vm_object_t object, vm_pindex_t pindex, int allocflags)
{
        vm_page_t m;

        VM_OBJECT_ASSERT_WLOCKED(object);
        vm_page_grab_check(allocflags);

retrylookup:
        if ((m = vm_page_lookup(object, pindex)) != NULL) {
                if (!vm_page_tryacquire(m, allocflags)) {
                        if (vm_page_grab_sleep(object, m, pindex, "pgrbwt",
                            allocflags, true))
                                goto retrylookup;
                        return (NULL);
                }
                goto out;
        }
        if ((allocflags & VM_ALLOC_NOCREAT) != 0)
                return (NULL);
        m = vm_page_alloc(object, pindex, vm_page_grab_pflags(allocflags));
        if (m == NULL) {
                if ((allocflags & (VM_ALLOC_NOWAIT | VM_ALLOC_WAITFAIL)) != 0)
                        return (NULL);
                goto retrylookup;
        }
        if (allocflags & VM_ALLOC_ZERO && (m->flags & PG_ZERO) == 0)
                pmap_zero_page(m);

out:
        vm_page_grab_release(m, allocflags);

        return (m);
}

/*
 * Locklessly attempt to acquire a page given a (object, pindex) tuple
 * and an optional previous page to avoid the radix lookup.  The resulting
 * page will be validated against the identity tuple and busied or wired
 * as requested.  A NULL *mp return guarantees that the page was not in
 * radix at the time of the call but callers must perform higher level
 * synchronization or retry the operation under a lock if they require
 * an atomic answer.  This is the only lock free validation routine,
 * other routines can depend on the resulting page state.
 *
 * The return value indicates whether the operation failed due to caller
 * flags.  The return is tri-state with mp:
 *
 * (true, *mp != NULL) - The operation was successful.
 * (true, *mp == NULL) - The page was not found in tree.
 * (false, *mp == NULL) - WAITFAIL or NOWAIT prevented acquisition.
 */
static bool
vm_page_acquire_unlocked(vm_object_t object, vm_pindex_t pindex,
    vm_page_t prev, vm_page_t *mp, int allocflags)
{
        vm_page_t m;

        vm_page_grab_check(allocflags);
        MPASS(prev == NULL || vm_page_busied(prev) || vm_page_wired(prev));

        *mp = NULL;
        for (;;) {
                /*
                 * We may see a false NULL here because the previous page
                 * has been removed or just inserted and the list is loaded
                 * without barriers.  Switch to radix to verify.
                 */
                if (prev == NULL || (m = TAILQ_NEXT(prev, listq)) == NULL ||
                    QMD_IS_TRASHED(m) || m->pindex != pindex ||
                    atomic_load_ptr(&m->object) != object) {
                        prev = NULL;
                        /*
                         * This guarantees the result is instantaneously
                         * correct.
                         */
                        m = vm_radix_lookup_unlocked(&object->rtree, pindex);
                }
                if (m == NULL)
                        return (true);
                if (vm_page_trybusy(m, allocflags)) {
                        if (m->object == object && m->pindex == pindex)
                                break;
                        /* relookup. */
                        vm_page_busy_release(m);
                        cpu_spinwait();
                        continue;
                }
                if (!vm_page_grab_sleep(object, m, pindex, "pgnslp",
                    allocflags, false))
                        return (false);
        }
        if ((allocflags & VM_ALLOC_WIRED) != 0)
                vm_page_wire(m);
        vm_page_grab_release(m, allocflags);
        *mp = m;
        return (true);
}

/*
 * Try to locklessly grab a page and fall back to the object lock if NOCREAT
 * is not set.
 */
vm_page_t
vm_page_grab_unlocked(vm_object_t object, vm_pindex_t pindex, int allocflags)
{
        vm_page_t m;

        vm_page_grab_check(allocflags);

        if (!vm_page_acquire_unlocked(object, pindex, NULL, &m, allocflags))
                return (NULL);
        if (m != NULL)
                return (m);

        /*
         * The radix lockless lookup should never return a false negative
         * errors.  If the user specifies NOCREAT they are guaranteed there
         * was no page present at the instant of the call.  A NOCREAT caller
         * must handle create races gracefully.
         */
        if ((allocflags & VM_ALLOC_NOCREAT) != 0)
                return (NULL);

        VM_OBJECT_WLOCK(object);
        m = vm_page_grab(object, pindex, allocflags);
        VM_OBJECT_WUNLOCK(object);

        return (m);
}

/*
 * Grab a page and make it valid, paging in if necessary.  Pages missing from
 * their pager are zero filled and validated.  If a VM_ALLOC_COUNT is supplied
 * and the page is not valid as many as VM_INITIAL_PAGEIN pages can be brought
 * in simultaneously.  Additional pages will be left on a paging queue but
 * will neither be wired nor busy regardless of allocflags.
 */
int
vm_page_grab_valid(vm_page_t *mp, vm_object_t object, vm_pindex_t pindex, int allocflags)
{
        vm_page_t m;
        vm_page_t ma[VM_INITIAL_PAGEIN];
        int after, i, pflags, rv;

        KASSERT((allocflags & VM_ALLOC_SBUSY) == 0 ||
            (allocflags & VM_ALLOC_IGN_SBUSY) != 0,
            ("vm_page_grab_valid: VM_ALLOC_SBUSY/VM_ALLOC_IGN_SBUSY mismatch"));
        KASSERT((allocflags &
            (VM_ALLOC_NOWAIT | VM_ALLOC_WAITFAIL | VM_ALLOC_ZERO)) == 0,
            ("vm_page_grab_valid: Invalid flags 0x%X", allocflags));
        VM_OBJECT_ASSERT_WLOCKED(object);
        pflags = allocflags & ~(VM_ALLOC_NOBUSY | VM_ALLOC_SBUSY |
            VM_ALLOC_WIRED | VM_ALLOC_IGN_SBUSY);
        pflags |= VM_ALLOC_WAITFAIL;

retrylookup:
        if ((m = vm_page_lookup(object, pindex)) != NULL) {
                /*
                 * If the page is fully valid it can only become invalid
                 * with the object lock held.  If it is not valid it can
                 * become valid with the busy lock held.  Therefore, we
                 * may unnecessarily lock the exclusive busy here if we
                 * race with I/O completion not using the object lock.
                 * However, we will not end up with an invalid page and a
                 * shared lock.
                 */
                if (!vm_page_trybusy(m,
                    vm_page_all_valid(m) ? allocflags : 0)) {
                        (void)vm_page_grab_sleep(object, m, pindex, "pgrbwt",
                            allocflags, true);
                        goto retrylookup;
                }
                if (vm_page_all_valid(m))
                        goto out;
                if ((allocflags & VM_ALLOC_NOCREAT) != 0) {
                        vm_page_busy_release(m);
                        *mp = NULL;
                        return (VM_PAGER_FAIL);
                }
        } else if ((allocflags & VM_ALLOC_NOCREAT) != 0) {
                *mp = NULL;
                return (VM_PAGER_FAIL);
        } else if ((m = vm_page_alloc(object, pindex, pflags)) == NULL) {
                goto retrylookup;
        }

        vm_page_assert_xbusied(m);
        if (vm_pager_has_page(object, pindex, NULL, &after)) {
                after = MIN(after, VM_INITIAL_PAGEIN);
                after = MIN(after, allocflags >> VM_ALLOC_COUNT_SHIFT);
                after = MAX(after, 1);
                ma[0] = m;
                for (i = 1; i < after; i++) {
                        if ((ma[i] = vm_page_next(ma[i - 1])) != NULL) {
                                if (ma[i]->valid || !vm_page_tryxbusy(ma[i]))
                                        break;
                        } else {
                                ma[i] = vm_page_alloc(object, m->pindex + i,
                                    VM_ALLOC_NORMAL);
                                if (ma[i] == NULL)
                                        break;
                        }
                }
                after = i;
                vm_object_pip_add(object, after);
                VM_OBJECT_WUNLOCK(object);
                rv = vm_pager_get_pages(object, ma, after, NULL, NULL);
                VM_OBJECT_WLOCK(object);
                vm_object_pip_wakeupn(object, after);
                /* Pager may have replaced a page. */
                m = ma[0];
                if (rv != VM_PAGER_OK) {
                        for (i = 0; i < after; i++) {
                                if (!vm_page_wired(ma[i]))
                                        vm_page_free(ma[i]);
                                else
                                        vm_page_xunbusy(ma[i]);
                        }
                        *mp = NULL;
                        return (rv);
                }
                for (i = 1; i < after; i++)
                        vm_page_readahead_finish(ma[i]);
                MPASS(vm_page_all_valid(m));
        } else {
                vm_page_zero_invalid(m, TRUE);
        }
out:
        if ((allocflags & VM_ALLOC_WIRED) != 0)
                vm_page_wire(m);
        if ((allocflags & VM_ALLOC_SBUSY) != 0 && vm_page_xbusied(m))
                vm_page_busy_downgrade(m);
        else if ((allocflags & VM_ALLOC_NOBUSY) != 0)
                vm_page_busy_release(m);
        *mp = m;
        return (VM_PAGER_OK);
}

/*
 * Locklessly grab a valid page.  If the page is not valid or not yet
 * allocated this will fall back to the object lock method.
 */
int
vm_page_grab_valid_unlocked(vm_page_t *mp, vm_object_t object,
    vm_pindex_t pindex, int allocflags)
{
        vm_page_t m;
        int flags;
        int error;

        KASSERT((allocflags & VM_ALLOC_SBUSY) == 0 ||
            (allocflags & VM_ALLOC_IGN_SBUSY) != 0,
            ("vm_page_grab_valid_unlocked: VM_ALLOC_SBUSY/VM_ALLOC_IGN_SBUSY "
            "mismatch"));
        KASSERT((allocflags &
            (VM_ALLOC_NOWAIT | VM_ALLOC_WAITFAIL | VM_ALLOC_ZERO)) == 0,
            ("vm_page_grab_valid_unlocked: Invalid flags 0x%X", allocflags));

        /*
         * Attempt a lockless lookup and busy.  We need at least an sbusy
         * before we can inspect the valid field and return a wired page.
         */
        flags = allocflags & ~(VM_ALLOC_NOBUSY | VM_ALLOC_WIRED);
        if (!vm_page_acquire_unlocked(object, pindex, NULL, mp, flags))
                return (VM_PAGER_FAIL);
        if ((m = *mp) != NULL) {
                if (vm_page_all_valid(m)) {
                        if ((allocflags & VM_ALLOC_WIRED) != 0)
                                vm_page_wire(m);
                        vm_page_grab_release(m, allocflags);
                        return (VM_PAGER_OK);
                }
                vm_page_busy_release(m);
        }
        if ((allocflags & VM_ALLOC_NOCREAT) != 0) {
                *mp = NULL;
                return (VM_PAGER_FAIL);
        }
        VM_OBJECT_WLOCK(object);
        error = vm_page_grab_valid(mp, object, pindex, allocflags);
        VM_OBJECT_WUNLOCK(object);

        return (error);
}

/*
 * Return the specified range of pages from the given object.  For each
 * page offset within the range, if a page already exists within the object
 * at that offset and it is busy, then wait for it to change state.  If,
 * instead, the page doesn't exist, then allocate it.
 *
 * The caller must always specify an allocation class.
 *
 * allocation classes:
 *      VM_ALLOC_NORMAL         normal process request
 *      VM_ALLOC_SYSTEM         system *really* needs the pages
 *
 * The caller must always specify that the pages are to be busied and/or
 * wired.
 *
 * optional allocation flags:
 *      VM_ALLOC_IGN_SBUSY      do not sleep on soft busy pages
 *      VM_ALLOC_NOBUSY         do not exclusive busy the page
 *      VM_ALLOC_NOWAIT         do not sleep
 *      VM_ALLOC_SBUSY          set page to sbusy state
 *      VM_ALLOC_WIRED          wire the pages
 *      VM_ALLOC_ZERO           zero and validate any invalid pages
 *
 * If VM_ALLOC_NOWAIT is not specified, this routine may sleep.  Otherwise, it
 * may return a partial prefix of the requested range.
 */
int
vm_page_grab_pages(vm_object_t object, vm_pindex_t pindex, int allocflags,
    vm_page_t *ma, int count)
{
        vm_page_t m, mpred;
        int pflags;
        int i;

        VM_OBJECT_ASSERT_WLOCKED(object);
        KASSERT(((u_int)allocflags >> VM_ALLOC_COUNT_SHIFT) == 0,
            ("vm_page_grap_pages: VM_ALLOC_COUNT() is not allowed"));
        KASSERT(count > 0,
            ("vm_page_grab_pages: invalid page count %d", count));
        vm_page_grab_check(allocflags);

        pflags = vm_page_grab_pflags(allocflags);
        i = 0;
retrylookup:
        m = vm_radix_lookup_le(&object->rtree, pindex + i);
        if (m == NULL || m->pindex != pindex + i) {
                mpred = m;
                m = NULL;
        } else
                mpred = TAILQ_PREV(m, pglist, listq);
        for (; i < count; i++) {
                if (m != NULL) {
                        if (!vm_page_tryacquire(m, allocflags)) {
                                if (vm_page_grab_sleep(object, m, pindex + i,
                                    "grbmaw", allocflags, true))
                                        goto retrylookup;
                                break;
                        }
                } else {
                        if ((allocflags & VM_ALLOC_NOCREAT) != 0)
                                break;
                        m = vm_page_alloc_after(object, pindex + i,
                            pflags | VM_ALLOC_COUNT(count - i), mpred);
                        if (m == NULL) {
                                if ((allocflags & (VM_ALLOC_NOWAIT |
                                    VM_ALLOC_WAITFAIL)) != 0)
                                        break;
                                goto retrylookup;
                        }
                }
                if (vm_page_none_valid(m) &&
                    (allocflags & VM_ALLOC_ZERO) != 0) {
                        if ((m->flags & PG_ZERO) == 0)
                                pmap_zero_page(m);
                        vm_page_valid(m);
                }
                vm_page_grab_release(m, allocflags);
                ma[i] = mpred = m;
                m = vm_page_next(m);
        }
        return (i);
}

/*
 * Unlocked variant of vm_page_grab_pages().  This accepts the same flags
 * and will fall back to the locked variant to handle allocation.
 */
int
vm_page_grab_pages_unlocked(vm_object_t object, vm_pindex_t pindex,
    int allocflags, vm_page_t *ma, int count)
{
        vm_page_t m, pred;
        int flags;
        int i;

        KASSERT(count > 0,
            ("vm_page_grab_pages_unlocked: invalid page count %d", count));
        vm_page_grab_check(allocflags);

        /*
         * Modify flags for lockless acquire to hold the page until we
         * set it valid if necessary.
         */
        flags = allocflags & ~VM_ALLOC_NOBUSY;
        pred = NULL;
        for (i = 0; i < count; i++, pindex++) {
                if (!vm_page_acquire_unlocked(object, pindex, pred, &m, flags))
                        return (i);
                if (m == NULL)
                        break;
                if ((flags & VM_ALLOC_ZERO) != 0 && vm_page_none_valid(m)) {
                        if ((m->flags & PG_ZERO) == 0)
                                pmap_zero_page(m);
                        vm_page_valid(m);
                }
                /* m will still be wired or busy according to flags. */
                vm_page_grab_release(m, allocflags);
                pred = ma[i] = m;
        }
        if (i == count || (allocflags & VM_ALLOC_NOCREAT) != 0)
                return (i);
        count -= i;
        VM_OBJECT_WLOCK(object);
        i += vm_page_grab_pages(object, pindex, allocflags, &ma[i], count);
        VM_OBJECT_WUNLOCK(object);

        return (i);
}

/*
 * Mapping function for valid or dirty bits in a page.
 *
 * Inputs are required to range within a page.
 */
vm_page_bits_t
vm_page_bits(int base, int size)
{
        int first_bit;
        int last_bit;

        KASSERT(
            base + size <= PAGE_SIZE,
            ("vm_page_bits: illegal base/size %d/%d", base, size)
        );

        if (size == 0)          /* handle degenerate case */
                return (0);

        first_bit = base >> DEV_BSHIFT;
        last_bit = (base + size - 1) >> DEV_BSHIFT;

        return (((vm_page_bits_t)2 << last_bit) -
            ((vm_page_bits_t)1 << first_bit));
}

void
vm_page_bits_set(vm_page_t m, vm_page_bits_t *bits, vm_page_bits_t set)
{

#if PAGE_SIZE == 32768
        atomic_set_64((uint64_t *)bits, set);
#elif PAGE_SIZE == 16384
        atomic_set_32((uint32_t *)bits, set);
#elif (PAGE_SIZE == 8192) && defined(atomic_set_16)
        atomic_set_16((uint16_t *)bits, set);
#elif (PAGE_SIZE == 4096) && defined(atomic_set_8)
        atomic_set_8((uint8_t *)bits, set);
#else           /* PAGE_SIZE <= 8192 */
        uintptr_t addr;
        int shift;

        addr = (uintptr_t)bits;
        /*
         * Use a trick to perform a 32-bit atomic on the
         * containing aligned word, to not depend on the existence
         * of atomic_{set, clear}_{8, 16}.
         */
        shift = addr & (sizeof(uint32_t) - 1);
#if BYTE_ORDER == BIG_ENDIAN
        shift = (sizeof(uint32_t) - sizeof(vm_page_bits_t) - shift) * NBBY;
#else
        shift *= NBBY;
#endif
        addr &= ~(sizeof(uint32_t) - 1);
        atomic_set_32((uint32_t *)addr, set << shift);
#endif          /* PAGE_SIZE */
}

static inline void
vm_page_bits_clear(vm_page_t m, vm_page_bits_t *bits, vm_page_bits_t clear)
{

#if PAGE_SIZE == 32768
        atomic_clear_64((uint64_t *)bits, clear);
#elif PAGE_SIZE == 16384
        atomic_clear_32((uint32_t *)bits, clear);
#elif (PAGE_SIZE == 8192) && defined(atomic_clear_16)
        atomic_clear_16((uint16_t *)bits, clear);
#elif (PAGE_SIZE == 4096) && defined(atomic_clear_8)
        atomic_clear_8((uint8_t *)bits, clear);
#else           /* PAGE_SIZE <= 8192 */
        uintptr_t addr;
        int shift;

        addr = (uintptr_t)bits;
        /*
         * Use a trick to perform a 32-bit atomic on the
         * containing aligned word, to not depend on the existence
         * of atomic_{set, clear}_{8, 16}.
         */
        shift = addr & (sizeof(uint32_t) - 1);
#if BYTE_ORDER == BIG_ENDIAN
        shift = (sizeof(uint32_t) - sizeof(vm_page_bits_t) - shift) * NBBY;
#else
        shift *= NBBY;
#endif
        addr &= ~(sizeof(uint32_t) - 1);
        atomic_clear_32((uint32_t *)addr, clear << shift);
#endif          /* PAGE_SIZE */
}

static inline vm_page_bits_t
vm_page_bits_swap(vm_page_t m, vm_page_bits_t *bits, vm_page_bits_t newbits)
{
#if PAGE_SIZE == 32768
        uint64_t old;

        old = *bits;
        while (atomic_fcmpset_64(bits, &old, newbits) == 0);
        return (old);
#elif PAGE_SIZE == 16384
        uint32_t old;

        old = *bits;
        while (atomic_fcmpset_32(bits, &old, newbits) == 0);
        return (old);
#elif (PAGE_SIZE == 8192) && defined(atomic_fcmpset_16)
        uint16_t old;

        old = *bits;
        while (atomic_fcmpset_16(bits, &old, newbits) == 0);
        return (old);
#elif (PAGE_SIZE == 4096) && defined(atomic_fcmpset_8)
        uint8_t old;

        old = *bits;
        while (atomic_fcmpset_8(bits, &old, newbits) == 0);
        return (old);
#else           /* PAGE_SIZE <= 4096*/
        uintptr_t addr;
        uint32_t old, new, mask;
        int shift;

        addr = (uintptr_t)bits;
        /*
         * Use a trick to perform a 32-bit atomic on the
         * containing aligned word, to not depend on the existence
         * of atomic_{set, swap, clear}_{8, 16}.
         */
        shift = addr & (sizeof(uint32_t) - 1);
#if BYTE_ORDER == BIG_ENDIAN
        shift = (sizeof(uint32_t) - sizeof(vm_page_bits_t) - shift) * NBBY;
#else
        shift *= NBBY;
#endif
        addr &= ~(sizeof(uint32_t) - 1);
        mask = VM_PAGE_BITS_ALL << shift;

        old = *bits;
        do {
                new = old & ~mask;
                new |= newbits << shift;
        } while (atomic_fcmpset_32((uint32_t *)addr, &old, new) == 0);
        return (old >> shift);
#endif          /* PAGE_SIZE */
}

/*
 *      vm_page_set_valid_range:
 *
 *      Sets portions of a page valid.  The arguments are expected
 *      to be DEV_BSIZE aligned but if they aren't the bitmap is inclusive
 *      of any partial chunks touched by the range.  The invalid portion of
 *      such chunks will be zeroed.
 *
 *      (base + size) must be less then or equal to PAGE_SIZE.
 */
void
vm_page_set_valid_range(vm_page_t m, int base, int size)
{
        int endoff, frag;
        vm_page_bits_t pagebits;

        vm_page_assert_busied(m);
        if (size == 0)  /* handle degenerate case */
                return;

        /*
         * If the base is not DEV_BSIZE aligned and the valid
         * bit is clear, we have to zero out a portion of the
         * first block.
         */
        if ((frag = rounddown2(base, DEV_BSIZE)) != base &&
            (m->valid & (1 << (base >> DEV_BSHIFT))) == 0)
                pmap_zero_page_area(m, frag, base - frag);

        /*
         * If the ending offset is not DEV_BSIZE aligned and the
         * valid bit is clear, we have to zero out a portion of
         * the last block.
         */
        endoff = base + size;
        if ((frag = rounddown2(endoff, DEV_BSIZE)) != endoff &&
            (m->valid & (1 << (endoff >> DEV_BSHIFT))) == 0)
                pmap_zero_page_area(m, endoff,
                    DEV_BSIZE - (endoff & (DEV_BSIZE - 1)));

        /*
         * Assert that no previously invalid block that is now being validated
         * is already dirty.
         */
        KASSERT((~m->valid & vm_page_bits(base, size) & m->dirty) == 0,
            ("vm_page_set_valid_range: page %p is dirty", m));

        /*
         * Set valid bits inclusive of any overlap.
         */
        pagebits = vm_page_bits(base, size);
        if (vm_page_xbusied(m))
                m->valid |= pagebits;
        else
                vm_page_bits_set(m, &m->valid, pagebits);
}

/*
 * Set the page dirty bits and free the invalid swap space if
 * present.  Returns the previous dirty bits.
 */
vm_page_bits_t
vm_page_set_dirty(vm_page_t m)
{
        vm_page_bits_t old;

        VM_PAGE_OBJECT_BUSY_ASSERT(m);

        if (vm_page_xbusied(m) && !pmap_page_is_write_mapped(m)) {
                old = m->dirty;
                m->dirty = VM_PAGE_BITS_ALL;
        } else
                old = vm_page_bits_swap(m, &m->dirty, VM_PAGE_BITS_ALL);
        if (old == 0 && (m->a.flags & PGA_SWAP_SPACE) != 0)
                vm_pager_page_unswapped(m);

        return (old);
}

/*
 * Clear the given bits from the specified page's dirty field.
 */
static __inline void
vm_page_clear_dirty_mask(vm_page_t m, vm_page_bits_t pagebits)
{

        vm_page_assert_busied(m);

        /*
         * If the page is xbusied and not write mapped we are the
         * only thread that can modify dirty bits.  Otherwise, The pmap
         * layer can call vm_page_dirty() without holding a distinguished
         * lock.  The combination of page busy and atomic operations
         * suffice to guarantee consistency of the page dirty field.
         */
        if (vm_page_xbusied(m) && !pmap_page_is_write_mapped(m))
                m->dirty &= ~pagebits;
        else
                vm_page_bits_clear(m, &m->dirty, pagebits);
}

/*
 *      vm_page_set_validclean:
 *
 *      Sets portions of a page valid and clean.  The arguments are expected
 *      to be DEV_BSIZE aligned but if they aren't the bitmap is inclusive
 *      of any partial chunks touched by the range.  The invalid portion of
 *      such chunks will be zero'd.
 *
 *      (base + size) must be less then or equal to PAGE_SIZE.
 */
void
vm_page_set_validclean(vm_page_t m, int base, int size)
{
        vm_page_bits_t oldvalid, pagebits;
        int endoff, frag;

        vm_page_assert_busied(m);
        if (size == 0)  /* handle degenerate case */
                return;

        /*
         * If the base is not DEV_BSIZE aligned and the valid
         * bit is clear, we have to zero out a portion of the
         * first block.
         */
        if ((frag = rounddown2(base, DEV_BSIZE)) != base &&
            (m->valid & ((vm_page_bits_t)1 << (base >> DEV_BSHIFT))) == 0)
                pmap_zero_page_area(m, frag, base - frag);

        /*
         * If the ending offset is not DEV_BSIZE aligned and the
         * valid bit is clear, we have to zero out a portion of
         * the last block.
         */
        endoff = base + size;
        if ((frag = rounddown2(endoff, DEV_BSIZE)) != endoff &&
            (m->valid & ((vm_page_bits_t)1 << (endoff >> DEV_BSHIFT))) == 0)
                pmap_zero_page_area(m, endoff,
                    DEV_BSIZE - (endoff & (DEV_BSIZE - 1)));

        /*
         * Set valid, clear dirty bits.  If validating the entire
         * page we can safely clear the pmap modify bit.  We also
         * use this opportunity to clear the PGA_NOSYNC flag.  If a process
         * takes a write fault on a MAP_NOSYNC memory area the flag will
         * be set again.
         *
         * We set valid bits inclusive of any overlap, but we can only
         * clear dirty bits for DEV_BSIZE chunks that are fully within
         * the range.
         */
        oldvalid = m->valid;
        pagebits = vm_page_bits(base, size);
        if (vm_page_xbusied(m))
                m->valid |= pagebits;
        else
                vm_page_bits_set(m, &m->valid, pagebits);
#if 0   /* NOT YET */
        if ((frag = base & (DEV_BSIZE - 1)) != 0) {
                frag = DEV_BSIZE - frag;
                base += frag;
                size -= frag;
                if (size < 0)
                        size = 0;
        }
        pagebits = vm_page_bits(base, size & (DEV_BSIZE - 1));
#endif
        if (base == 0 && size == PAGE_SIZE) {
                /*
                 * The page can only be modified within the pmap if it is
                 * mapped, and it can only be mapped if it was previously
                 * fully valid.
                 */
                if (oldvalid == VM_PAGE_BITS_ALL)
                        /*
                         * Perform the pmap_clear_modify() first.  Otherwise,
                         * a concurrent pmap operation, such as
                         * pmap_protect(), could clear a modification in the
                         * pmap and set the dirty field on the page before
                         * pmap_clear_modify() had begun and after the dirty
                         * field was cleared here.
                         */
                        pmap_clear_modify(m);
                m->dirty = 0;
                vm_page_aflag_clear(m, PGA_NOSYNC);
        } else if (oldvalid != VM_PAGE_BITS_ALL && vm_page_xbusied(m))
                m->dirty &= ~pagebits;
        else
                vm_page_clear_dirty_mask(m, pagebits);
}

void
vm_page_clear_dirty(vm_page_t m, int base, int size)
{

        vm_page_clear_dirty_mask(m, vm_page_bits(base, size));
}

/*
 *      vm_page_set_invalid:
 *
 *      Invalidates DEV_BSIZE'd chunks within a page.  Both the
 *      valid and dirty bits for the effected areas are cleared.
 */
void
vm_page_set_invalid(vm_page_t m, int base, int size)
{
        vm_page_bits_t bits;
        vm_object_t object;

        /*
         * The object lock is required so that pages can't be mapped
         * read-only while we're in the process of invalidating them.
         */
        object = m->object;
        VM_OBJECT_ASSERT_WLOCKED(object);
        vm_page_assert_busied(m);

        if (object->type == OBJT_VNODE && base == 0 && IDX_TO_OFF(m->pindex) +
            size >= object->un_pager.vnp.vnp_size)
                bits = VM_PAGE_BITS_ALL;
        else
                bits = vm_page_bits(base, size);
        if (object->ref_count != 0 && vm_page_all_valid(m) && bits != 0)
                pmap_remove_all(m);
        KASSERT((bits == 0 && vm_page_all_valid(m)) ||
            !pmap_page_is_mapped(m),
            ("vm_page_set_invalid: page %p is mapped", m));
        if (vm_page_xbusied(m)) {
                m->valid &= ~bits;
                m->dirty &= ~bits;
        } else {
                vm_page_bits_clear(m, &m->valid, bits);
                vm_page_bits_clear(m, &m->dirty, bits);
        }
}

/*
 *      vm_page_invalid:
 *
 *      Invalidates the entire page.  The page must be busy, unmapped, and
 *      the enclosing object must be locked.  The object locks protects
 *      against concurrent read-only pmap enter which is done without
 *      busy.
 */
void
vm_page_invalid(vm_page_t m)
{

        vm_page_assert_busied(m);
        VM_OBJECT_ASSERT_LOCKED(m->object);
        MPASS(!pmap_page_is_mapped(m));

        if (vm_page_xbusied(m))
                m->valid = 0;
        else
                vm_page_bits_clear(m, &m->valid, VM_PAGE_BITS_ALL);
}

/*
 * vm_page_zero_invalid()
 *
 *      The kernel assumes that the invalid portions of a page contain
 *      garbage, but such pages can be mapped into memory by user code.
 *      When this occurs, we must zero out the non-valid portions of the
 *      page so user code sees what it expects.
 *
 *      Pages are most often semi-valid when the end of a file is mapped
 *      into memory and the file's size is not page aligned.
 */
void
vm_page_zero_invalid(vm_page_t m, boolean_t setvalid)
{
        int b;
        int i;

        /*
         * Scan the valid bits looking for invalid sections that
         * must be zeroed.  Invalid sub-DEV_BSIZE'd areas ( where the
         * valid bit may be set ) have already been zeroed by
         * vm_page_set_validclean().
         */
        for (b = i = 0; i <= PAGE_SIZE / DEV_BSIZE; ++i) {
                if (i == (PAGE_SIZE / DEV_BSIZE) ||
                    (m->valid & ((vm_page_bits_t)1 << i))) {
                        if (i > b) {
                                pmap_zero_page_area(m,
                                    b << DEV_BSHIFT, (i - b) << DEV_BSHIFT);
                        }
                        b = i + 1;
                }
        }

        /*
         * setvalid is TRUE when we can safely set the zero'd areas
         * as being valid.  We can do this if there are no cache consistancy
         * issues.  e.g. it is ok to do with UFS, but not ok to do with NFS.
         */
        if (setvalid)
                vm_page_valid(m);
}

/*
 *      vm_page_is_valid:
 *
 *      Is (partial) page valid?  Note that the case where size == 0
 *      will return FALSE in the degenerate case where the page is
 *      entirely invalid, and TRUE otherwise.
 *
 *      Some callers envoke this routine without the busy lock held and
 *      handle races via higher level locks.  Typical callers should
 *      hold a busy lock to prevent invalidation.
 */
int
vm_page_is_valid(vm_page_t m, int base, int size)
{
        vm_page_bits_t bits;

        bits = vm_page_bits(base, size);
        return (m->valid != 0 && (m->valid & bits) == bits);
}

/*
 * Returns true if all of the specified predicates are true for the entire
 * (super)page and false otherwise.
 */
bool
vm_page_ps_test(vm_page_t m, int flags, vm_page_t skip_m)
{
        vm_object_t object;
        int i, npages;

        object = m->object;
        if (skip_m != NULL && skip_m->object != object)
                return (false);
        VM_OBJECT_ASSERT_LOCKED(object);
        npages = atop(pagesizes[m->psind]);

        /*
         * The physically contiguous pages that make up a superpage, i.e., a
         * page with a page size index ("psind") greater than zero, will
         * occupy adjacent entries in vm_page_array[].
         */
        for (i = 0; i < npages; i++) {
                /* Always test object consistency, including "skip_m". */
                if (m[i].object != object)
                        return (false);
                if (&m[i] == skip_m)
                        continue;
                if ((flags & PS_NONE_BUSY) != 0 && vm_page_busied(&m[i]))
                        return (false);
                if ((flags & PS_ALL_DIRTY) != 0) {
                        /*
                         * Calling vm_page_test_dirty() or pmap_is_modified()
                         * might stop this case from spuriously returning
                         * "false".  However, that would require a write lock
                         * on the object containing "m[i]".
                         */
                        if (m[i].dirty != VM_PAGE_BITS_ALL)
                                return (false);
                }
                if ((flags & PS_ALL_VALID) != 0 &&
                    m[i].valid != VM_PAGE_BITS_ALL)
                        return (false);
        }
        return (true);
}

/*
 * Set the page's dirty bits if the page is modified.
 */
void
vm_page_test_dirty(vm_page_t m)
{

        vm_page_assert_busied(m);
        if (m->dirty != VM_PAGE_BITS_ALL && pmap_is_modified(m))
                vm_page_dirty(m);
}

void
vm_page_valid(vm_page_t m)
{

        vm_page_assert_busied(m);
        if (vm_page_xbusied(m))
                m->valid = VM_PAGE_BITS_ALL;
        else
                vm_page_bits_set(m, &m->valid, VM_PAGE_BITS_ALL);
}

void
vm_page_lock_KBI(vm_page_t m, const char *file, int line)
{

        mtx_lock_flags_(vm_page_lockptr(m), 0, file, line);
}

void
vm_page_unlock_KBI(vm_page_t m, const char *file, int line)
{

        mtx_unlock_flags_(vm_page_lockptr(m), 0, file, line);
}

int
vm_page_trylock_KBI(vm_page_t m, const char *file, int line)
{

        return (mtx_trylock_flags_(vm_page_lockptr(m), 0, file, line));
}

#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
void
vm_page_assert_locked_KBI(vm_page_t m, const char *file, int line)
{

        vm_page_lock_assert_KBI(m, MA_OWNED, file, line);
}

void
vm_page_lock_assert_KBI(vm_page_t m, int a, const char *file, int line)
{

        mtx_assert_(vm_page_lockptr(m), a, file, line);
}
#endif

#ifdef INVARIANTS
void
vm_page_object_busy_assert(vm_page_t m)
{

        /*
         * Certain of the page's fields may only be modified by the
         * holder of a page or object busy.
         */
        if (m->object != NULL && !vm_page_busied(m))
                VM_OBJECT_ASSERT_BUSY(m->object);
}

void
vm_page_assert_pga_writeable(vm_page_t m, uint16_t bits)
{

        if ((bits & PGA_WRITEABLE) == 0)
                return;

        /*
         * The PGA_WRITEABLE flag can only be set if the page is
         * managed, is exclusively busied or the object is locked.
         * Currently, this flag is only set by pmap_enter().
         */
        KASSERT((m->oflags & VPO_UNMANAGED) == 0,
            ("PGA_WRITEABLE on unmanaged page"));
        if (!vm_page_xbusied(m))
                VM_OBJECT_ASSERT_BUSY(m->object);
}
#endif

#include "opt_ddb.h"
#ifdef DDB
#include <sys/kernel.h>

#include <ddb/ddb.h>

DB_SHOW_COMMAND(page, vm_page_print_page_info)
{

        db_printf("vm_cnt.v_free_count: %d\n", vm_free_count());
        db_printf("vm_cnt.v_inactive_count: %d\n", vm_inactive_count());
        db_printf("vm_cnt.v_active_count: %d\n", vm_active_count());
        db_printf("vm_cnt.v_laundry_count: %d\n", vm_laundry_count());
        db_printf("vm_cnt.v_wire_count: %d\n", vm_wire_count());
        db_printf("vm_cnt.v_free_reserved: %d\n", vm_cnt.v_free_reserved);
        db_printf("vm_cnt.v_free_min: %d\n", vm_cnt.v_free_min);
        db_printf("vm_cnt.v_free_target: %d\n", vm_cnt.v_free_target);
        db_printf("vm_cnt.v_inactive_target: %d\n", vm_cnt.v_inactive_target);
}

DB_SHOW_COMMAND(pageq, vm_page_print_pageq_info)
{
        int dom;

        db_printf("pq_free %d\n", vm_free_count());
        for (dom = 0; dom < vm_ndomains; dom++) {
                db_printf(
    "dom %d page_cnt %d free %d pq_act %d pq_inact %d pq_laund %d pq_unsw %d\n",
                    dom,
                    vm_dom[dom].vmd_page_count,
                    vm_dom[dom].vmd_free_count,
                    vm_dom[dom].vmd_pagequeues[PQ_ACTIVE].pq_cnt,
                    vm_dom[dom].vmd_pagequeues[PQ_INACTIVE].pq_cnt,
                    vm_dom[dom].vmd_pagequeues[PQ_LAUNDRY].pq_cnt,
                    vm_dom[dom].vmd_pagequeues[PQ_UNSWAPPABLE].pq_cnt);
        }
}

DB_SHOW_COMMAND(pginfo, vm_page_print_pginfo)
{
        vm_page_t m;
        boolean_t phys, virt;

        if (!have_addr) {
                db_printf("show pginfo addr\n");
                return;
        }

        phys = strchr(modif, 'p') != NULL;
        virt = strchr(modif, 'v') != NULL;
        if (virt)
                m = PHYS_TO_VM_PAGE(pmap_kextract(addr));
        else if (phys)
                m = PHYS_TO_VM_PAGE(addr);
        else
                m = (vm_page_t)addr;
        db_printf(
    "page %p obj %p pidx 0x%jx phys 0x%jx q %d ref 0x%x\n"
    "  af 0x%x of 0x%x f 0x%x act %d busy %x valid 0x%x dirty 0x%x\n",
            m, m->object, (uintmax_t)m->pindex, (uintmax_t)m->phys_addr,
            m->a.queue, m->ref_count, m->a.flags, m->oflags,
            m->flags, m->a.act_count, m->busy_lock, m->valid, m->dirty);
}
#endif /* DDB */