kernel - Fix auto port assignment collision in network code

[dragonfly.git] / sys / vm / vm_object.c

/*
 * Copyright (c) 1991, 1993, 2013
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * The Mach Operating System project at Carnegie-Mellon University.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      from: @(#)vm_object.c   8.5 (Berkeley) 3/22/94
 *
 *
 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
 * All rights reserved.
 *
 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
 *
 * Permission to use, copy, modify and distribute this software and
 * its documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 *
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 *
 * Carnegie Mellon requests users of this software to return to
 *
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie the
 * rights to redistribute these changes.
 *
 * $FreeBSD: src/sys/vm/vm_object.c,v 1.171.2.8 2003/05/26 19:17:56 alc Exp $
 */

/*
 *      Virtual memory object module.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>           /* for curproc, pageproc */
#include <sys/thread.h>
#include <sys/vnode.h>
#include <sys/vmmeter.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/sysctl.h>
#include <sys/refcount.h>

#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_pager.h>
#include <vm/swap_pager.h>
#include <vm/vm_kern.h>
#include <vm/vm_extern.h>
#include <vm/vm_zone.h>

#include <vm/vm_page2.h>

#include <machine/specialreg.h>

#define EASY_SCAN_FACTOR        8

static void     vm_object_page_collect_flush(vm_object_t object, vm_page_t p,
                                             int pagerflags);
static void     vm_object_lock_init(vm_object_t);

/*
 *      Virtual memory objects maintain the actual data
 *      associated with allocated virtual memory.  A given
 *      page of memory exists within exactly one object.
 *
 *      An object is only deallocated when all "references"
 *      are given up.  Only one "reference" to a given
 *      region of an object should be writeable.
 *
 *      Associated with each object is a list of all resident
 *      memory pages belonging to that object; this list is
 *      maintained by the "vm_page" module, and locked by the object's
 *      lock.
 *
 *      Each object also records a "pager" routine which is
 *      used to retrieve (and store) pages to the proper backing
 *      storage.  In addition, objects may be backed by other
 *      objects from which they were virtual-copied.
 *
 *      The only items within the object structure which are
 *      modified after time of creation are:
 *              reference count         locked by object's lock
 *              pager routine           locked by object's lock
 *
 */

static struct vm_object kernel_object_store;
struct vm_object *kernel_object = &kernel_object_store;

struct vm_object_hash vm_object_hash[VMOBJ_HSIZE];

static MALLOC_DEFINE_OBJ(M_VM_OBJECT, sizeof(struct vm_object),
                "vm_object", "vm_object structures");

#define VMOBJ_HASH_PRIME1       66555444443333333ULL
#define VMOBJ_HASH_PRIME2       989042931893ULL

int vm_object_debug;
SYSCTL_INT(_vm, OID_AUTO, object_debug, CTLFLAG_RW, &vm_object_debug, 0, "");

static __inline
struct vm_object_hash *
vmobj_hash(vm_object_t obj)
{
        uintptr_t hash1;
        uintptr_t hash2;

        hash1 = (uintptr_t)obj + ((uintptr_t)obj >> 18);
        hash1 %= VMOBJ_HASH_PRIME1;
        hash2 = ((uintptr_t)obj >> 8) + ((uintptr_t)obj >> 24);
        hash2 %= VMOBJ_HASH_PRIME2;
        return (&vm_object_hash[(hash1 ^ hash2) & VMOBJ_HMASK]);
}

#if defined(DEBUG_LOCKS)

#define vm_object_vndeallocate(obj, vpp)        \
                debugvm_object_vndeallocate(obj, vpp, __FILE__, __LINE__)

/*
 * Debug helper to track hold/drop/ref/deallocate calls.
 */
static void
debugvm_object_add(vm_object_t obj, char *file, int line, int addrem)
{
        int i;

        i = atomic_fetchadd_int(&obj->debug_index, 1);
        i = i & (VMOBJ_DEBUG_ARRAY_SIZE - 1);
        ksnprintf(obj->debug_hold_thrs[i],
                  sizeof(obj->debug_hold_thrs[i]),
                  "%c%d:(%d):%s",
                  (addrem == -1 ? '-' : (addrem == 1 ? '+' : '=')),
                  (curthread->td_proc ? curthread->td_proc->p_pid : -1),
                  obj->ref_count,
                  curthread->td_comm);
        obj->debug_hold_file[i] = file;
        obj->debug_hold_line[i] = line;
#if 0
        /* Uncomment for debugging obj refs/derefs in reproducable cases */
        if (strcmp(curthread->td_comm, "sshd") == 0) {
                kprintf("%d %p refs=%d ar=%d file: %s/%d\n",
                        (curthread->td_proc ? curthread->td_proc->p_pid : -1),
                        obj, obj->ref_count, addrem, file, line);
        }
#endif
}

#endif

/*
 * Misc low level routines
 */
static void
vm_object_lock_init(vm_object_t obj)
{
#if defined(DEBUG_LOCKS)
        int i;

        obj->debug_index = 0;
        for (i = 0; i < VMOBJ_DEBUG_ARRAY_SIZE; i++) {
                obj->debug_hold_thrs[i][0] = 0;
                obj->debug_hold_file[i] = NULL;
                obj->debug_hold_line[i] = 0;
        }
#endif
}

void
vm_object_lock_swap(void)
{
        lwkt_token_swap();
}

void
vm_object_lock(vm_object_t obj)
{
        lwkt_gettoken(&obj->token);
}

/*
 * Returns TRUE on sucesss
 */
static int
vm_object_lock_try(vm_object_t obj)
{
        return(lwkt_trytoken(&obj->token));
}

void
vm_object_lock_shared(vm_object_t obj)
{
        lwkt_gettoken_shared(&obj->token);
}

void
vm_object_unlock(vm_object_t obj)
{
        lwkt_reltoken(&obj->token);
}

void
vm_object_upgrade(vm_object_t obj)
{
        lwkt_reltoken(&obj->token);
        lwkt_gettoken(&obj->token);
}

void
vm_object_downgrade(vm_object_t obj)
{
        lwkt_reltoken(&obj->token);
        lwkt_gettoken_shared(&obj->token);
}

static __inline void
vm_object_assert_held(vm_object_t obj)
{
        ASSERT_LWKT_TOKEN_HELD(&obj->token);
}

/*
 * Aquire a semi-random base page color for a new object.  Our main concern
 * is that the color be spread out a bit.  Further spreading out occurs in
 * bio_page_alloc().
 */
int
vm_quickcolor(void)
{
        globaldata_t gd = mycpu;
        int pg_color;

        pg_color = (int)(intptr_t)gd->gd_curthread >> 10;
        pg_color += gd->gd_quick_color;
        gd->gd_quick_color += PQ_PRIME2;

        return pg_color;
}

void
VMOBJDEBUG(vm_object_hold)(vm_object_t obj VMOBJDBARGS)
{
        KKASSERT(obj != NULL);

        /*
         * Object must be held (object allocation is stable due to callers
         * context, typically already holding the token on a parent object)
         * prior to potentially blocking on the lock, otherwise the object
         * can get ripped away from us.
         */
        refcount_acquire(&obj->hold_count);
        vm_object_lock(obj);

#if defined(DEBUG_LOCKS)
        debugvm_object_add(obj, file, line, 1);
#endif
}

int
VMOBJDEBUG(vm_object_hold_try)(vm_object_t obj VMOBJDBARGS)
{
        KKASSERT(obj != NULL);

        /*
         * Object must be held (object allocation is stable due to callers
         * context, typically already holding the token on a parent object)
         * prior to potentially blocking on the lock, otherwise the object
         * can get ripped away from us.
         */
        refcount_acquire(&obj->hold_count);
        if (vm_object_lock_try(obj) == 0) {
                if (refcount_release(&obj->hold_count)) {
                        if (obj->ref_count == 0 && (obj->flags & OBJ_DEAD))
                                kfree_obj(obj, M_VM_OBJECT);
                }
                return(0);
        }

#if defined(DEBUG_LOCKS)
        debugvm_object_add(obj, file, line, 1);
#endif
        return(1);
}

void
VMOBJDEBUG(vm_object_hold_shared)(vm_object_t obj VMOBJDBARGS)
{
        KKASSERT(obj != NULL);

        /*
         * Object must be held (object allocation is stable due to callers
         * context, typically already holding the token on a parent object)
         * prior to potentially blocking on the lock, otherwise the object
         * can get ripped away from us.
         */
        refcount_acquire(&obj->hold_count);
        vm_object_lock_shared(obj);

#if defined(DEBUG_LOCKS)
        debugvm_object_add(obj, file, line, 1);
#endif
}

/*
 * Drop the token and hold_count on the object.
 *
 * WARNING! Token might be shared.
 */
void
VMOBJDEBUG(vm_object_drop)(vm_object_t obj VMOBJDBARGS)
{
        if (obj == NULL)
                return;

        /*
         * No new holders should be possible once we drop hold_count 1->0 as
         * there is no longer any way to reference the object.
         */
        KKASSERT(obj->hold_count > 0);
        if (refcount_release(&obj->hold_count)) {
#if defined(DEBUG_LOCKS)
                debugvm_object_add(obj, file, line, -1);
#endif

                if (obj->ref_count == 0 && (obj->flags & OBJ_DEAD)) {
                        vm_object_unlock(obj);
                        kfree_obj(obj, M_VM_OBJECT);
                } else {
                        vm_object_unlock(obj);
                }
        } else {
#if defined(DEBUG_LOCKS)
                debugvm_object_add(obj, file, line, -1);
#endif
                vm_object_unlock(obj);
        }
}

/*
 * Initialize a freshly allocated object, returning a held object.
 *
 * Used only by vm_object_allocate(), zinitna() and vm_object_init().
 *
 * No requirements.
 */
void
_vm_object_allocate(objtype_t type, vm_pindex_t size, vm_object_t object,
                    const char *ident)
{
        struct vm_object_hash *hash;

        RB_INIT(&object->rb_memq);
        lwkt_token_init(&object->token, ident);

        TAILQ_INIT(&object->backing_list);
        lockinit(&object->backing_lk, "baclk", 0, 0);

        object->type = type;
        object->size = size;
        object->ref_count = 1;
        object->memattr = VM_MEMATTR_DEFAULT;
        object->hold_count = 0;
        object->flags = 0;
        if ((object->type == OBJT_DEFAULT) || (object->type == OBJT_SWAP))
                vm_object_set_flag(object, OBJ_ONEMAPPING);
        object->paging_in_progress = 0;
        object->resident_page_count = 0;
        /* cpu localization twist */
        object->pg_color = vm_quickcolor();
        object->handle = NULL;

        atomic_add_int(&object->generation, 1);
        object->swblock_count = 0;
        RB_INIT(&object->swblock_root);
        vm_object_lock_init(object);
        pmap_object_init(object);

        vm_object_hold(object);

        hash = vmobj_hash(object);
        lwkt_gettoken(&hash->token);
        TAILQ_INSERT_TAIL(&hash->list, object, object_entry);
        lwkt_reltoken(&hash->token);
}

/*
 * Initialize a VM object.
 */
void
vm_object_init(vm_object_t object, vm_pindex_t size)
{
        _vm_object_allocate(OBJT_DEFAULT, size, object, "vmobj");
        vm_object_drop(object);
}

/*
 * Initialize the VM objects module.
 *
 * Called from the low level boot code only.  Note that this occurs before
 * kmalloc is initialized so we cannot allocate any VM objects.
 */
void
vm_object_init1(void)
{
        int i;

        for (i = 0; i < VMOBJ_HSIZE; ++i) {
                TAILQ_INIT(&vm_object_hash[i].list);
                lwkt_token_init(&vm_object_hash[i].token, "vmobjlst");
        }

        _vm_object_allocate(OBJT_DEFAULT, OFF_TO_IDX(KvaEnd),
                            kernel_object, "kobj");
        vm_object_drop(kernel_object);
}

void
vm_object_init2(void)
{
        kmalloc_obj_set_unlimited(M_VM_OBJECT);
}

/*
 * Allocate and return a new object of the specified type and size.
 *
 * No requirements.
 */
vm_object_t
vm_object_allocate(objtype_t type, vm_pindex_t size)
{
        vm_object_t obj;

        obj = kmalloc_obj(sizeof(*obj), M_VM_OBJECT, M_INTWAIT|M_ZERO);
        _vm_object_allocate(type, size, obj, "vmobj");
        vm_object_drop(obj);

        return (obj);
}

/*
 * This version returns a held object, allowing further atomic initialization
 * of the object.
 */
vm_object_t
vm_object_allocate_hold(objtype_t type, vm_pindex_t size)
{
        vm_object_t obj;

        obj = kmalloc_obj(sizeof(*obj), M_VM_OBJECT, M_INTWAIT|M_ZERO);
        _vm_object_allocate(type, size, obj, "vmobj");

        return (obj);
}

/*
 * Add an additional reference to a vm_object.  The object must already be
 * held.  The original non-lock version is no longer supported.  The object
 * must NOT be chain locked by anyone at the time the reference is added.
 *
 * The object must be held, but may be held shared if desired (hence why
 * we use an atomic op).
 */
void
VMOBJDEBUG(vm_object_reference_locked)(vm_object_t object VMOBJDBARGS)
{
        KKASSERT(object != NULL);
        ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
        atomic_add_int(&object->ref_count, 1);
        if (object->type == OBJT_VNODE) {
                vref(object->handle);
                /* XXX what if the vnode is being destroyed? */
        }
#if defined(DEBUG_LOCKS)
        debugvm_object_add(object, file, line, 1);
#endif
}

/*
 * This version is only allowed in situations where the caller
 * already knows that the object is deterministically referenced
 * (usually because its taken from a ref'd vnode, or during a map_entry
 * replication).
 */
void
VMOBJDEBUG(vm_object_reference_quick)(vm_object_t object VMOBJDBARGS)
{
        KKASSERT(object->type == OBJT_VNODE || object->ref_count > 0);
        atomic_add_int(&object->ref_count, 1);
        if (object->type == OBJT_VNODE)
                vref(object->handle);
#if defined(DEBUG_LOCKS)
        debugvm_object_add(object, file, line, 1);
#endif
}

/*
 * Dereference an object and its underlying vnode.  The object may be
 * held shared.  On return the object will remain held.
 *
 * This function may return a vnode in *vpp which the caller must release
 * after the caller drops its own lock.  If vpp is NULL, we assume that
 * the caller was holding an exclusive lock on the object and we vrele()
 * the vp ourselves.
 */
static void
VMOBJDEBUG(vm_object_vndeallocate)(vm_object_t object, struct vnode **vpp
                                   VMOBJDBARGS)
{
        struct vnode *vp = (struct vnode *) object->handle;
        int count;

        KASSERT(object->type == OBJT_VNODE,
            ("vm_object_vndeallocate: not a vnode object"));
        KASSERT(vp != NULL, ("vm_object_vndeallocate: missing vp"));
        ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
#ifdef INVARIANTS
        if (object->ref_count == 0) {
                vprint("vm_object_vndeallocate", vp);
                panic("vm_object_vndeallocate: bad object reference count");
        }
#endif
        count = object->ref_count;
        cpu_ccfence();
        for (;;) {
                if (count == 1) {
                        vm_object_upgrade(object);
                        if (atomic_fcmpset_int(&object->ref_count, &count, 0)) {
                                vclrflags(vp, VTEXT);
                                break;
                        }
                } else {
                        if (atomic_fcmpset_int(&object->ref_count,
                                               &count, count - 1)) {
                                break;
                        }
                }
                cpu_pause();
                /* retry */
        }
#if defined(DEBUG_LOCKS)
        debugvm_object_add(object, file, line, -1);
#endif

        /*
         * vrele or return the vp to vrele.  We can only safely vrele(vp)
         * if the object was locked exclusively.  But there are two races
         * here.
         *
         * We had to upgrade the object above to safely clear VTEXT
         * but the alternative path where the shared lock is retained
         * can STILL race to 0 in other paths and cause our own vrele()
         * to terminate the vnode.  We can't allow that if the VM object
         * is still locked shared.
         */
        if (vpp)
                *vpp = vp;
        else
                vrele(vp);
}

/*
 * Release a reference to the specified object, gained either through a
 * vm_object_allocate or a vm_object_reference call.  When all references
 * are gone, storage associated with this object may be relinquished.
 *
 * The caller does not have to hold the object locked but must have control
 * over the reference in question in order to guarantee that the object
 * does not get ripped out from under us.
 *
 * XXX Currently all deallocations require an exclusive lock.
 */
void
VMOBJDEBUG(vm_object_deallocate)(vm_object_t object VMOBJDBARGS)
{
        struct vnode *vp;
        int count;

        if (object == NULL)
                return;

        count = object->ref_count;
        cpu_ccfence();
        for (;;) {
                /*
                 * If decrementing the count enters into special handling
                 * territory (0, 1, or 2) we have to do it the hard way.
                 * Fortunate though, objects with only a few refs like this
                 * are not likely to be heavily contended anyway.
                 *
                 * For vnode objects we only care about 1->0 transitions.
                 */
                if (count <= 3 || (object->type == OBJT_VNODE && count <= 1)) {
#if defined(DEBUG_LOCKS)
                        debugvm_object_add(object, file, line, 0);
#endif
                        vm_object_hold(object);
                        vm_object_deallocate_locked(object);
                        vm_object_drop(object);
                        break;
                }

                /*
                 * Try to decrement ref_count without acquiring a hold on
                 * the object.  This is particularly important for the exec*()
                 * and exit*() code paths because the program binary may
                 * have a great deal of sharing and an exclusive lock will
                 * crowbar performance in those circumstances.
                 */
                if (object->type == OBJT_VNODE) {
                        vp = (struct vnode *)object->handle;
                        if (atomic_fcmpset_int(&object->ref_count,
                                               &count, count - 1)) {
#if defined(DEBUG_LOCKS)
                                debugvm_object_add(object, file, line, -1);
#endif

                                vrele(vp);
                                break;
                        }
                        /* retry */
                } else {
                        if (atomic_fcmpset_int(&object->ref_count,
                                               &count, count - 1)) {
#if defined(DEBUG_LOCKS)
                                debugvm_object_add(object, file, line, -1);
#endif
                                break;
                        }
                        /* retry */
                }
                cpu_pause();
                /* retry */
        }
}

void
VMOBJDEBUG(vm_object_deallocate_locked)(vm_object_t object VMOBJDBARGS)
{
        /*
         * Degenerate case
         */
        if (object == NULL)
                return;

        /*
         * vnode case, caller either locked the object exclusively
         * or this is a recursion with must_drop != 0 and the vnode
         * object will be locked shared.
         *
         * If locked shared we have to drop the object before we can
         * call vrele() or risk a shared/exclusive livelock.
         */
        if (object->type == OBJT_VNODE) {
                ASSERT_LWKT_TOKEN_HELD(&object->token);
                vm_object_vndeallocate(object, NULL);
                return;
        }
        ASSERT_LWKT_TOKEN_HELD_EXCL(&object->token);

        /*
         * Normal case (object is locked exclusively)
         */
        if (object->ref_count == 0) {
                panic("vm_object_deallocate: object deallocated "
                      "too many times: %d", object->type);
        }
        if (object->ref_count > 2) {
                atomic_add_int(&object->ref_count, -1);
#if defined(DEBUG_LOCKS)
                debugvm_object_add(object, file, line, -1);
#endif
                return;
        }

        /*
         * Drop the ref and handle termination on the 1->0 transition.
         * We may have blocked above so we have to recheck.
         */
        KKASSERT(object->ref_count != 0);
        if (object->ref_count >= 2) {
                atomic_add_int(&object->ref_count, -1);
#if defined(DEBUG_LOCKS)
                debugvm_object_add(object, file, line, -1);
#endif
                return;
        }

        atomic_add_int(&object->ref_count, -1);
        if ((object->flags & OBJ_DEAD) == 0)
                vm_object_terminate(object);
}

/*
 * Destroy the specified object, freeing up related resources.
 *
 * The object must have zero references.
 *
 * The object must held.  The caller is responsible for dropping the object
 * after terminate returns.  Terminate does NOT drop the object.
 */
static int vm_object_terminate_callback(vm_page_t p, void *data);

void
vm_object_terminate(vm_object_t object)
{
        struct rb_vm_page_scan_info info;
        struct vm_object_hash *hash;

        /*
         * Make sure no one uses us.  Once we set OBJ_DEAD we should be
         * able to safely block.
         */
        ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));
        KKASSERT((object->flags & OBJ_DEAD) == 0);
        vm_object_set_flag(object, OBJ_DEAD);

        /*
         * Wait for the pageout daemon to be done with the object
         */
        vm_object_pip_wait(object, "objtrm1");

        KASSERT(!object->paging_in_progress,
                ("vm_object_terminate: pageout in progress"));

        /*
         * Clean and free the pages, as appropriate. All references to the
         * object are gone, so we don't need to lock it.
         */
        if (object->type == OBJT_VNODE) {
                struct vnode *vp;

                /*
                 * Clean pages and flush buffers.
                 *
                 * NOTE!  TMPFS buffer flushes do not typically flush the
                 *        actual page to swap as this would be highly
                 *        inefficient, and normal filesystems usually wrap
                 *        page flushes with buffer cache buffers.
                 *
                 *        To deal with this we have to call vinvalbuf() both
                 *        before and after the vm_object_page_clean().
                 */
                vp = (struct vnode *) object->handle;
                vinvalbuf(vp, V_SAVE, 0, 0);
                vm_object_page_clean(object, 0, 0, OBJPC_SYNC);
                vinvalbuf(vp, V_SAVE, 0, 0);
        }

        /*
         * Wait for any I/O to complete, after which there had better not
         * be any references left on the object.
         */
        vm_object_pip_wait(object, "objtrm2");

        if (object->ref_count != 0) {
                panic("vm_object_terminate: object with references, "
                      "ref_count=%d", object->ref_count);
        }

        /*
         * Cleanup any shared pmaps associated with this object.
         */
        pmap_object_free(object);

        /*
         * Now free any remaining pages. For internal objects, this also
         * removes them from paging queues. Don't free wired pages, just
         * remove them from the object.
         */
        info.count = 0;
        info.object = object;
        do {
                info.error = 0;
                vm_page_rb_tree_RB_SCAN(&object->rb_memq, NULL,
                                        vm_object_terminate_callback, &info);
        } while (info.error);

        /*
         * Let the pager know object is dead.
         */
        vm_pager_deallocate(object);

        /*
         * Wait for the object hold count to hit 1, clean out pages as
         * we go.  vmobj_token interlocks any race conditions that might
         * pick the object up from the vm_object_list after we have cleared
         * rb_memq.
         */
        for (;;) {
                if (RB_ROOT(&object->rb_memq) == NULL)
                        break;
                kprintf("vm_object_terminate: Warning, object %p "
                        "still has %ld pages\n",
                        object, object->resident_page_count);
                vm_page_rb_tree_RB_SCAN(&object->rb_memq, NULL,
                                        vm_object_terminate_callback, &info);
        }

        /*
         * There had better not be any pages left
         */
        KKASSERT(object->resident_page_count == 0);

        /*
         * Remove the object from the global object list.
         */
        hash = vmobj_hash(object);
        lwkt_gettoken(&hash->token);
        TAILQ_REMOVE(&hash->list, object, object_entry);
        lwkt_reltoken(&hash->token);

        if (object->ref_count != 0) {
                panic("vm_object_terminate2: object with references, "
                      "ref_count=%d", object->ref_count);
        }

        /*
         * NOTE: The object hold_count is at least 1, so we cannot kfree()
         *       the object here.  See vm_object_drop().
         */
}

/*
 * The caller must hold the object.
 *
 * NOTE: It is possible for vm_page's to remain flagged PG_MAPPED
 *       or PG_MAPPED|PG_WRITEABLE, even after pmap_mapped_sync()
 *       is called, due to normal pmap operations.  This is because only
 *       global pmap operations on the vm_page can clear the bits and not
 *       just local operations on individual pmaps.
 *
 *       Most interactions that necessitate the clearing of these bits
 *       proactively call vm_page_protect(), and we must do so here as well.
 */
static int
vm_object_terminate_callback(vm_page_t p, void *data)
{
        struct rb_vm_page_scan_info *info = data;
        vm_object_t object;

        object = p->object;
        KKASSERT(object == info->object);
        if (vm_page_busy_try(p, TRUE)) {
                vm_page_sleep_busy(p, TRUE, "vmotrm");
                info->error = 1;
                return 0;
        }
        if (object != p->object) {
                /* XXX remove once we determine it can't happen */
                kprintf("vm_object_terminate: Warning: Encountered "
                        "busied page %p on queue %d\n", p, p->queue);
                vm_page_wakeup(p);
                info->error = 1;
        } else if (p->wire_count == 0) {
                /*
                 * NOTE: p->dirty and PG_NEED_COMMIT are ignored.
                 */
                if (pmap_mapped_sync(p) & (PG_MAPPED | PG_WRITEABLE))
                        vm_page_protect(p, VM_PROT_NONE);
                vm_page_free(p);
                mycpu->gd_cnt.v_pfree++;
        } else {
                if (p->queue != PQ_NONE) {
                        kprintf("vm_object_terminate: Warning: Encountered "
                                "wired page %p on queue %d\n", p, p->queue);
                        if (vm_object_debug > 0) {
                                --vm_object_debug;
                                print_backtrace(10);
                        }
                }
                if (pmap_mapped_sync(p) & (PG_MAPPED | PG_WRITEABLE))
                        vm_page_protect(p, VM_PROT_NONE);
                vm_page_remove(p);
                vm_page_wakeup(p);
        }

        /*
         * Must be at end to avoid SMP races, caller holds object token
         */
        if ((++info->count & 63) == 0)
                lwkt_user_yield();
        return(0);
}

/*
 * Clean all dirty pages in the specified range of object.  Leaves page
 * on whatever queue it is currently on.   If NOSYNC is set then do not
 * write out pages with PG_NOSYNC set (originally comes from MAP_NOSYNC),
 * leaving the object dirty.
 *
 * When stuffing pages asynchronously, allow clustering.  XXX we need a
 * synchronous clustering mode implementation.
 *
 * Odd semantics: if start == end, we clean everything.
 *
 * The object must be locked? XXX
 */
static int vm_object_page_clean_pass1(struct vm_page *p, void *data);
static int vm_object_page_clean_pass2(struct vm_page *p, void *data);

void
vm_object_page_clean(vm_object_t object, vm_pindex_t start, vm_pindex_t end,
                     int flags)
{
        struct rb_vm_page_scan_info info;
        struct vnode *vp;
        int wholescan;
        int pagerflags;
        int generation;

        vm_object_hold(object);
        if (object->type != OBJT_VNODE ||
            (object->flags & OBJ_MIGHTBEDIRTY) == 0) {
                vm_object_drop(object);
                return;
        }

        pagerflags = (flags & (OBJPC_SYNC | OBJPC_INVAL)) ?
                        OBJPC_SYNC : OBJPC_CLUSTER_OK;
        pagerflags |= (flags & OBJPC_INVAL) ? OBJPC_INVAL : 0;

        vp = object->handle;

        /*
         * Interlock other major object operations.  This allows us to
         * temporarily clear OBJ_WRITEABLE and OBJ_MIGHTBEDIRTY.
         */
        vm_object_set_flag(object, OBJ_CLEANING);

        /*
         * Handle 'entire object' case
         */
        info.start_pindex = start;
        if (end == 0) {
                info.end_pindex = object->size - 1;
        } else {
                info.end_pindex = end - 1;
        }
        wholescan = (start == 0 && info.end_pindex == object->size - 1);
        info.limit = flags;
        info.pagerflags = pagerflags;
        info.object = object;

        /*
         * If cleaning the entire object do a pass to mark the pages read-only.
         * If everything worked out ok, clear OBJ_WRITEABLE and
         * OBJ_MIGHTBEDIRTY.
         */
        if (wholescan) {
                info.error = 0;
                info.count = 0;
                vm_page_rb_tree_RB_SCAN(&object->rb_memq, rb_vm_page_scancmp,
                                        vm_object_page_clean_pass1, &info);
                if (info.error == 0) {
                        vm_object_clear_flag(object,
                                             OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
                        if (object->type == OBJT_VNODE &&
                            (vp = (struct vnode *)object->handle) != NULL) {
                                /*
                                 * Use new-style interface to clear VISDIRTY
                                 * because the vnode is not necessarily removed
                                 * from the syncer list(s) as often as it was
                                 * under the old interface, which can leave
                                 * the vnode on the syncer list after reclaim.
                                 */
                                vclrobjdirty(vp);
                        }
                }
        }

        /*
         * Do a pass to clean all the dirty pages we find.
         */
        do {
                info.error = 0;
                info.count = 0;
                generation = object->generation;
                vm_page_rb_tree_RB_SCAN(&object->rb_memq, rb_vm_page_scancmp,
                                        vm_object_page_clean_pass2, &info);
        } while (info.error || generation != object->generation);

        vm_object_clear_flag(object, OBJ_CLEANING);
        vm_object_drop(object);
}

/*
 * The caller must hold the object.
 */
static
int
vm_object_page_clean_pass1(struct vm_page *p, void *data)
{
        struct rb_vm_page_scan_info *info = data;

        KKASSERT(p->object == info->object);

        vm_page_flag_set(p, PG_CLEANCHK);
        if ((info->limit & OBJPC_NOSYNC) && (p->flags & PG_NOSYNC)) {
                info->error = 1;
        } else if (vm_page_busy_try(p, FALSE)) {
                info->error = 1;
        } else {
                KKASSERT(p->object == info->object);
                vm_page_protect(p, VM_PROT_READ);
                vm_page_wakeup(p);
        }

        /*
         * Must be at end to avoid SMP races, caller holds object token
         */
        if ((++info->count & 63) == 0)
                lwkt_user_yield();
        return(0);
}

/*
 * The caller must hold the object
 */
static
int
vm_object_page_clean_pass2(struct vm_page *p, void *data)
{
        struct rb_vm_page_scan_info *info = data;
        int generation;

        KKASSERT(p->object == info->object);

        /*
         * Do not mess with pages that were inserted after we started
         * the cleaning pass.
         */
        if ((p->flags & PG_CLEANCHK) == 0)
                goto done;

        generation = info->object->generation;

        if (vm_page_busy_try(p, TRUE)) {
                vm_page_sleep_busy(p, TRUE, "vpcwai");
                info->error = 1;
                goto done;
        }

        KKASSERT(p->object == info->object &&
                 info->object->generation == generation);

        /*
         * Before wasting time traversing the pmaps, check for trivial
         * cases where the page cannot be dirty.
         */
        if (p->valid == 0 || (p->queue - p->pc) == PQ_CACHE) {
                KKASSERT((p->dirty & p->valid) == 0 &&
                         (p->flags & PG_NEED_COMMIT) == 0);
                vm_page_wakeup(p);
                goto done;
        }

        /*
         * Check whether the page is dirty or not.  The page has been set
         * to be read-only so the check will not race a user dirtying the
         * page.
         */
        vm_page_test_dirty(p);
        if ((p->dirty & p->valid) == 0 && (p->flags & PG_NEED_COMMIT) == 0) {
                vm_page_flag_clear(p, PG_CLEANCHK);
                vm_page_wakeup(p);
                goto done;
        }

        /*
         * If we have been asked to skip nosync pages and this is a
         * nosync page, skip it.  Note that the object flags were
         * not cleared in this case (because pass1 will have returned an
         * error), so we do not have to set them.
         */
        if ((info->limit & OBJPC_NOSYNC) && (p->flags & PG_NOSYNC)) {
                vm_page_flag_clear(p, PG_CLEANCHK);
                vm_page_wakeup(p);
                goto done;
        }

        /*
         * Flush as many pages as we can.  PG_CLEANCHK will be cleared on
         * the pages that get successfully flushed.  Set info->error if
         * we raced an object modification.
         */
        vm_object_page_collect_flush(info->object, p, info->pagerflags);
        /* vm_wait_nominal(); this can deadlock the system in syncer/pageout */

        /*
         * Must be at end to avoid SMP races, caller holds object token
         */
done:
        if ((++info->count & 63) == 0)
                lwkt_user_yield();
        return(0);
}

/*
 * Collect the specified page and nearby pages and flush them out.
 * The number of pages flushed is returned.  The passed page is busied
 * by the caller and we are responsible for its disposition.
 *
 * The caller must hold the object.
 */
static void
vm_object_page_collect_flush(vm_object_t object, vm_page_t p, int pagerflags)
{
        int error;
        int is;
        int ib;
        int i;
        int page_base;
        vm_pindex_t pi;
        vm_page_t ma[BLIST_MAX_ALLOC];

        ASSERT_LWKT_TOKEN_HELD(vm_object_token(object));

        pi = p->pindex;
        page_base = pi % BLIST_MAX_ALLOC;
        ma[page_base] = p;
        ib = page_base - 1;
        is = page_base + 1;

        while (ib >= 0) {
                vm_page_t tp;

                tp = vm_page_lookup_busy_try(object, pi - page_base + ib,
                                             TRUE, &error);
                if (error)
                        break;
                if (tp == NULL)
                        break;
                if ((pagerflags & OBJPC_IGNORE_CLEANCHK) == 0 &&
                    (tp->flags & PG_CLEANCHK) == 0) {
                        vm_page_wakeup(tp);
                        break;
                }
                if ((tp->queue - tp->pc) == PQ_CACHE) {
                        vm_page_flag_clear(tp, PG_CLEANCHK);
                        vm_page_wakeup(tp);
                        break;
                }
                vm_page_test_dirty(tp);
                if ((tp->dirty & tp->valid) == 0 &&
                    (tp->flags & PG_NEED_COMMIT) == 0) {
                        vm_page_flag_clear(tp, PG_CLEANCHK);
                        vm_page_wakeup(tp);
                        break;
                }
                ma[ib] = tp;
                --ib;
        }
        ++ib;   /* fixup */

        while (is < BLIST_MAX_ALLOC &&
               pi - page_base + is < object->size) {
                vm_page_t tp;

                tp = vm_page_lookup_busy_try(object, pi - page_base + is,
                                             TRUE, &error);
                if (error)
                        break;
                if (tp == NULL)
                        break;
                if ((pagerflags & OBJPC_IGNORE_CLEANCHK) == 0 &&
                    (tp->flags & PG_CLEANCHK) == 0) {
                        vm_page_wakeup(tp);
                        break;
                }
                if ((tp->queue - tp->pc) == PQ_CACHE) {
                        vm_page_flag_clear(tp, PG_CLEANCHK);
                        vm_page_wakeup(tp);
                        break;
                }
                vm_page_test_dirty(tp);
                if ((tp->dirty & tp->valid) == 0 &&
                    (tp->flags & PG_NEED_COMMIT) == 0) {
                        vm_page_flag_clear(tp, PG_CLEANCHK);
                        vm_page_wakeup(tp);
                        break;
                }
                ma[is] = tp;
                ++is;
        }

        /*
         * All pages in the ma[] array are busied now
         */
        for (i = ib; i < is; ++i) {
                vm_page_flag_clear(ma[i], PG_CLEANCHK);
                vm_page_hold(ma[i]);    /* XXX need this any more? */
        }
        vm_pageout_flush(&ma[ib], is - ib, pagerflags);
        for (i = ib; i < is; ++i)       /* XXX need this any more? */
                vm_page_unhold(ma[i]);
}

/*
 * Implements the madvise function at the object/page level.
 *
 * MADV_WILLNEED        (any object)
 *
 *      Activate the specified pages if they are resident.
 *
 * MADV_DONTNEED        (any object)
 *
 *      Deactivate the specified pages if they are resident.
 *
 * MADV_FREE    (OBJT_DEFAULT/OBJT_SWAP objects, OBJ_ONEMAPPING only)
 *
 *      Deactivate and clean the specified pages if they are
 *      resident.  This permits the process to reuse the pages
 *      without faulting or the kernel to reclaim the pages
 *      without I/O.
 *
 * No requirements.
 */
void
vm_object_madvise(vm_object_t object, vm_pindex_t pindex,
                  vm_pindex_t count, int advise)
{
        vm_pindex_t end;
        vm_page_t m;
        int error;

        if (object == NULL)
                return;

        end = pindex + count;

        vm_object_hold(object);

        /*
         * Locate and adjust resident pages.  This only applies to the
         * primary object in the mapping.
         */
        for (; pindex < end; pindex += 1) {
relookup:
                /*
                 * MADV_FREE only operates on OBJT_DEFAULT or OBJT_SWAP pages
                 * and those pages must be OBJ_ONEMAPPING.
                 */
                if (advise == MADV_FREE) {
                        if ((object->type != OBJT_DEFAULT &&
                             object->type != OBJT_SWAP) ||
                            (object->flags & OBJ_ONEMAPPING) == 0) {
                                continue;
                        }
                }

                m = vm_page_lookup_busy_try(object, pindex, TRUE, &error);

                if (error) {
                        vm_page_sleep_busy(m, TRUE, "madvpo");
                        goto relookup;
                }
                if (m == NULL) {
                        /*
                         * There may be swap even if there is no backing page
                         */
                        if (advise == MADV_FREE && object->type == OBJT_SWAP)
                                swap_pager_freespace(object, pindex, 1);
                        continue;
                }

                /*
                 * If the page is not in a normal active state, we skip it.
                 * If the page is not managed there are no page queues to
                 * mess with.  Things can break if we mess with pages in
                 * any of the below states.
                 */
                if (m->wire_count ||
                    (m->flags & (PG_FICTITIOUS | PG_UNQUEUED |
                                 PG_NEED_COMMIT)) ||
                    m->valid != VM_PAGE_BITS_ALL
                ) {
                        vm_page_wakeup(m);
                        continue;
                }

                /*
                 * Theoretically once a page is known not to be busy, an
                 * interrupt cannot come along and rip it out from under us.
                 */
                if (advise == MADV_WILLNEED) {
                        vm_page_activate(m);
                } else if (advise == MADV_DONTNEED) {
                        vm_page_dontneed(m);
                } else if (advise == MADV_FREE) {
                        /*
                         * Mark the page clean.  This will allow the page
                         * to be freed up by the system.  However, such pages
                         * are often reused quickly by malloc()/free()
                         * so we do not do anything that would cause
                         * a page fault if we can help it.
                         *
                         * Specifically, we do not try to actually free
                         * the page now nor do we try to put it in the
                         * cache (which would cause a page fault on reuse).
                         *
                         * But we do make the page is freeable as we
                         * can without actually taking the step of unmapping
                         * it.
                         */
                        pmap_clear_modify(m);
                        m->dirty = 0;
                        m->act_count = 0;
                        vm_page_dontneed(m);
                        if (object->type == OBJT_SWAP)
                                swap_pager_freespace(object, pindex, 1);
                }
                vm_page_wakeup(m);
        }
        vm_object_drop(object);
}

/*
 * Removes all physical pages in the specified object range from the
 * object's list of pages.
 *
 * No requirements.
 */
static int vm_object_page_remove_callback(vm_page_t p, void *data);

void
vm_object_page_remove(vm_object_t object, vm_pindex_t start, vm_pindex_t end,
                      boolean_t clean_only)
{
        struct rb_vm_page_scan_info info;
        int all;

        /*
         * Degenerate cases and assertions.
         *
         * NOTE: Don't shortcut on resident_page_count for MGTDEVICE objects.
         *       These objects do not have to have their pages entered into
         *       them and are handled via their vm_map_backing lists.
         */
        vm_object_hold(object);
        if (object == NULL ||
            (object->type != OBJT_MGTDEVICE &&
             object->resident_page_count == 0 && object->swblock_count == 0)) {
                vm_object_drop(object);
                return;
        }
        KASSERT(object->type != OBJT_PHYS,
                ("attempt to remove pages from a physical object"));

        /*
         * Indicate that paging is occuring on the object
         */
        vm_object_pip_add(object, 1);

        /*
         * Figure out the actual removal range and whether we are removing
         * the entire contents of the object or not.  If removing the entire
         * contents, be sure to get all pages, even those that might be
         * beyond the end of the object.
         *
         * NOTE: end is non-inclusive, but info.end_pindex is inclusive.
         */
        info.object = object;
        info.start_pindex = start;
        if (end == 0 || end == (vm_pindex_t)-1) {
                info.end_pindex = (vm_pindex_t)-1;
                end = object->size;
        } else {
                info.end_pindex = end - 1;
        }
        info.limit = clean_only;
        info.count = 0;
        all = (start == 0 && info.end_pindex >= object->size - 1);

        /*
         * Efficiently remove pages from the pmap via a backing scan.
         *
         * NOTE: This is the only way pages can be removed and unwired
         *       from OBJT_MGTDEVICE devices which typically do not enter
         *       their pages into the vm_object's RB tree.  And possibly
         *       other OBJT_* types in the future.
         */
        {
                vm_map_backing_t ba;
                vm_pindex_t sba, eba;
                vm_offset_t sva, eva;

                lockmgr(&object->backing_lk, LK_EXCLUSIVE);
                TAILQ_FOREACH(ba, &object->backing_list, entry) {
                        /*
                         * object offset range within the ba, intersectioned
                         * with the page range specified for the object
                         */
                        sba = OFF_TO_IDX(ba->offset);
                        eba = sba + OFF_TO_IDX(ba->end - ba->start);
                        if (sba < start)
                                sba = start;
                        if (eba > end)
                                eba = end;

                        /*
                         * If the intersection is valid, remove the related
                         * pages.
                         *
                         * NOTE! This may also remove other incidental pages
                         *       in the pmap, as the backing area may be
                         *       overloaded.
                         *
                         * NOTE! pages for MGTDEVICE objects are only removed
                         *       here, they aren't entered into rb_memq, so
                         *       we must use pmap_remove() instead of
                         *       the non-TLB-invalidating pmap_remove_pages().
                         */
                        if (sba < eba) {
                                sva = ba->start + IDX_TO_OFF(sba) - ba->offset;
                                eva = sva + IDX_TO_OFF(eba - sba);
#if 0
                                kprintf("VM_OBJECT_PAGE_REMOVE "
                                        "%p[%016jx] %016jx-%016jx\n",
                                        ba->pmap, ba->start, sva, eva);
#endif
                                pmap_remove(ba->pmap, sva, eva);
                        }
                }
                lockmgr(&object->backing_lk, LK_RELEASE);
        }

        /*
         * Remove and free pages entered onto the object list.  Note that
         * for OBJT_MGTDEVICE objects, there are typically no pages entered.
         *
         * Loop until we are sure we have gotten them all.
         */
        do {
                info.error = 0;
                vm_page_rb_tree_RB_SCAN(&object->rb_memq, rb_vm_page_scancmp,
                                        vm_object_page_remove_callback, &info);
        } while (info.error);

        /*
         * Remove any related swap if throwing away pages, or for
         * non-swap objects (the swap is a clean copy in that case).
         */
        if (object->type != OBJT_SWAP || clean_only == FALSE) {
                if (all)
                        swap_pager_freespace_all(object);
                else
                        swap_pager_freespace(object, info.start_pindex,
                             info.end_pindex - info.start_pindex + 1);
        }

        /*
         * Cleanup
         */
        vm_object_pip_wakeup(object);
        vm_object_drop(object);
}

/*
 * The caller must hold the object.
 *
 * NOTE: User yields are allowed when removing more than one page, but not
 *       allowed if only removing one page (the path for single page removals
 *       might hold a spinlock).
 */
static int
vm_object_page_remove_callback(vm_page_t p, void *data)
{
        struct rb_vm_page_scan_info *info = data;

        if (info->object != p->object ||
            p->pindex < info->start_pindex ||
            p->pindex > info->end_pindex) {
                kprintf("vm_object_page_remove_callbackA: obj/pg race %p/%p\n",
                        info->object, p);
                return(0);
        }
        if (vm_page_busy_try(p, TRUE)) {
                vm_page_sleep_busy(p, TRUE, "vmopar");
                info->error = 1;
                return(0);
        }
        if (info->object != p->object) {
                /* this should never happen */
                kprintf("vm_object_page_remove_callbackB: obj/pg race %p/%p\n",
                        info->object, p);
                vm_page_wakeup(p);
                return(0);
        }

        /*
         * Wired pages cannot be destroyed, but they can be invalidated
         * and we do so if clean_only (limit) is not set.
         *
         * WARNING!  The page may be wired due to being part of a buffer
         *           cache buffer, and the buffer might be marked B_CACHE.
         *           This is fine as part of a truncation but VFSs must be
         *           sure to fix the buffer up when re-extending the file.
         *
         * NOTE!     PG_NEED_COMMIT is ignored.
         */
        if (p->wire_count != 0) {
                vm_page_protect(p, VM_PROT_NONE);
                if (info->limit == 0)
                        p->valid = 0;
                vm_page_wakeup(p);
                goto done;
        }

        /*
         * limit is our clean_only flag.  If set and the page is dirty or
         * requires a commit, do not free it.  If set and the page is being
         * held by someone, do not free it.
         */
        if (info->limit && p->valid) {
                vm_page_test_dirty(p);
                if ((p->valid & p->dirty) || (p->flags & PG_NEED_COMMIT)) {
                        vm_page_wakeup(p);
                        goto done;
                }
        }

        /*
         * Destroy the page.  But we have to re-test whether its dirty after
         * removing it from its pmaps.
         */
        vm_page_protect(p, VM_PROT_NONE);
        if (info->limit && p->valid) {
                vm_page_test_dirty(p);
                if ((p->valid & p->dirty) || (p->flags & PG_NEED_COMMIT)) {
                        vm_page_wakeup(p);
                        goto done;
                }
        }
        vm_page_free(p);

        /*
         * Must be at end to avoid SMP races, caller holds object token
         */
done:
        if ((++info->count & 63) == 0)
                lwkt_user_yield();

        return(0);
}

/*
 * Try to extend prev_object into an adjoining region of virtual
 * memory, return TRUE on success.
 *
 * The caller does not need to hold (prev_object) but must have a stable
 * pointer to it (typically by holding the vm_map locked).
 *
 * This function only works for anonymous memory objects which either
 * have (a) one reference or (b) we are extending the object's size.
 * Otherwise the related VM pages we want to use for the object might
 * be in use by another mapping.
 */
boolean_t
vm_object_coalesce(vm_object_t prev_object, vm_pindex_t prev_pindex,
                   vm_size_t prev_size, vm_size_t next_size)
{
        vm_pindex_t next_pindex;

        if (prev_object == NULL)
                return (TRUE);

        vm_object_hold(prev_object);

        if (prev_object->type != OBJT_DEFAULT &&
            prev_object->type != OBJT_SWAP) {
                vm_object_drop(prev_object);
                return (FALSE);
        }

#if 0
        /* caller now checks this */
        /*
         * Try to collapse the object first
         */
        vm_object_collapse(prev_object, NULL);
#endif

#if 0
        /* caller now checks this */
        /*
         * We can't coalesce if we shadow another object (figuring out the
         * relationships become too complex).
         */
        if (prev_object->backing_object != NULL) {
                vm_object_chain_release(prev_object);
                vm_object_drop(prev_object);
                return (FALSE);
        }
#endif

        prev_size >>= PAGE_SHIFT;
        next_size >>= PAGE_SHIFT;
        next_pindex = prev_pindex + prev_size;

        /*
         * We can't if the object has more than one ref count unless we
         * are extending it into newly minted space.
         */
        if (prev_object->ref_count > 1 &&
            prev_object->size != next_pindex) {
                vm_object_drop(prev_object);
                return (FALSE);
        }

        /*
         * Remove any pages that may still be in the object from a previous
         * deallocation.
         */
        if (next_pindex < prev_object->size) {
                vm_object_page_remove(prev_object,
                                      next_pindex,
                                      next_pindex + next_size, FALSE);
                if (prev_object->type == OBJT_SWAP)
                        swap_pager_freespace(prev_object,
                                             next_pindex, next_size);
        }

        /*
         * Extend the object if necessary.
         */
        if (next_pindex + next_size > prev_object->size)
                prev_object->size = next_pindex + next_size;
        vm_object_drop(prev_object);

        return (TRUE);
}

/*
 * Make the object writable and flag is being possibly dirty.
 *
 * The object might not be held (or might be held but held shared),
 * the related vnode is probably not held either.  Object and vnode are
 * stable by virtue of the vm_page busied by the caller preventing
 * destruction.
 *
 * If the related mount is flagged MNTK_THR_SYNC we need to call
 * vsetobjdirty().  Filesystems using this option usually shortcut
 * synchronization by only scanning the syncer list.
 */
void
vm_object_set_writeable_dirty(vm_object_t object)
{
        struct vnode *vp;

        /*vm_object_assert_held(object);*/
        /*
         * Avoid contention in vm fault path by checking the state before
         * issuing an atomic op on it.
         */
        if ((object->flags & (OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY)) !=
            (OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY)) {
                vm_object_set_flag(object, OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
        }
        if (object->type == OBJT_VNODE &&
            (vp = (struct vnode *)object->handle) != NULL) {
                if ((vp->v_flag & VOBJDIRTY) == 0) {
                        if (vp->v_mount &&
                            (vp->v_mount->mnt_kern_flag & MNTK_THR_SYNC)) {
                                /*
                                 * New style THR_SYNC places vnodes on the
                                 * syncer list more deterministically.
                                 */
                                vsetobjdirty(vp);
                        } else {
                                /*
                                 * Old style scan would not necessarily place
                                 * a vnode on the syncer list when possibly
                                 * modified via mmap.
                                 */
                                vsetflags(vp, VOBJDIRTY);
                        }
                }
        }
}

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

#include <ddb/ddb.h>

static int      _vm_object_in_map (vm_map_t map, vm_object_t object,
                                       vm_map_entry_t entry);
static int      vm_object_in_map (vm_object_t object);

/*
 * The caller must hold the object.
 */
static int
_vm_object_in_map(vm_map_t map, vm_object_t object, vm_map_entry_t entry)
{
        vm_map_backing_t ba;
        vm_map_t tmpm;
        vm_map_entry_t tmpe;
        int entcount;

        if (map == NULL)
                return 0;
        if (entry == NULL) {
                tmpe = RB_MIN(vm_map_rb_tree, &map->rb_root);
                entcount = map->nentries;
                while (entcount-- && tmpe) {
                        if( _vm_object_in_map(map, object, tmpe)) {
                                return 1;
                        }
                        tmpe = vm_map_rb_tree_RB_NEXT(tmpe);
                }
                return (0);
        }
        switch(entry->maptype) {
        case VM_MAPTYPE_SUBMAP:
                tmpm = entry->ba.sub_map;
                tmpe = RB_MIN(vm_map_rb_tree, &tmpm->rb_root);
                entcount = tmpm->nentries;
                while (entcount-- && tmpe) {
                        if( _vm_object_in_map(tmpm, object, tmpe)) {
                                return 1;
                        }
                        tmpe = vm_map_rb_tree_RB_NEXT(tmpe);
                }
                break;
        case VM_MAPTYPE_NORMAL:
                ba = &entry->ba;
                while (ba) {
                        if (ba->object == object)
                                return TRUE;
                        ba = ba->backing_ba;
                }
                break;
        default:
                break;
        }
        return 0;
}

static int vm_object_in_map_callback(struct proc *p, void *data);

struct vm_object_in_map_info {
        vm_object_t object;
        int rv;
};

/*
 * Debugging only
 */
static int
vm_object_in_map(vm_object_t object)
{
        struct vm_object_in_map_info info;

        info.rv = 0;
        info.object = object;

        allproc_scan(vm_object_in_map_callback, &info, 0);
        if (info.rv)
                return 1;
        if( _vm_object_in_map(kernel_map, object, 0))
                return 1;
        if( _vm_object_in_map(pager_map, object, 0))
                return 1;
        if( _vm_object_in_map(buffer_map, object, 0))
                return 1;
        return 0;
}

/*
 * Debugging only
 */
static int
vm_object_in_map_callback(struct proc *p, void *data)
{
        struct vm_object_in_map_info *info = data;

        if (p->p_vmspace) {
                if (_vm_object_in_map(&p->p_vmspace->vm_map, info->object, 0)) {
                        info->rv = 1;
                        return -1;
                }
        }
        return (0);
}

DB_SHOW_COMMAND(vmochk, vm_object_check)
{
        struct vm_object_hash *hash;
        vm_object_t object;
        int n;

        /*
         * make sure that internal objs are in a map somewhere
         * and none have zero ref counts.
         */
        for (n = 0; n < VMOBJ_HSIZE; ++n) {
                hash = &vm_object_hash[n];
                for (object = TAILQ_FIRST(&hash->list);
                                object != NULL;
                                object = TAILQ_NEXT(object, object_entry)) {
                        if (object->type == OBJT_MARKER)
                                continue;
                        if (object->handle != NULL ||
                            (object->type != OBJT_DEFAULT &&
                             object->type != OBJT_SWAP)) {
                                continue;
                        }
                        if (object->ref_count == 0) {
                                db_printf("vmochk: internal obj has "
                                          "zero ref count: %ld\n",
                                          (long)object->size);
                        }
                        if (vm_object_in_map(object))
                                continue;
                        db_printf("vmochk: internal obj is not in a map: "
                                  "ref: %d, size: %lu: 0x%lx\n",
                                  object->ref_count, (u_long)object->size,
                                  (u_long)object->size);
                }
        }
}

/*
 * Debugging only
 */
DB_SHOW_COMMAND(object, vm_object_print_static)
{
        /* XXX convert args. */
        vm_object_t object = (vm_object_t)addr;
        boolean_t full = have_addr;

        vm_page_t p;

        /* XXX count is an (unused) arg.  Avoid shadowing it. */
#define count   was_count

        int count;

        if (object == NULL)
                return;

        db_iprintf(
            "Object %p: type=%d, size=0x%lx, res=%ld, ref=%d, flags=0x%x\n",
            object, (int)object->type, (u_long)object->size,
            object->resident_page_count, object->ref_count, object->flags);
        /*
         * XXX no %qd in kernel.  Truncate object->backing_object_offset.
         */
        db_iprintf("\n");

        if (!full)
                return;

        db_indent += 2;
        count = 0;
        RB_FOREACH(p, vm_page_rb_tree, &object->rb_memq) {
                if (count == 0)
                        db_iprintf("memory:=");
                else if (count == 6) {
                        db_printf("\n");
                        db_iprintf(" ...");
                        count = 0;
                } else
                        db_printf(",");
                count++;

                db_printf("(off=0x%lx,page=0x%lx)",
                    (u_long) p->pindex, (u_long) VM_PAGE_TO_PHYS(p));
        }
        if (count != 0)
                db_printf("\n");
        db_indent -= 2;
}

/* XXX. */
#undef count

/*
 * XXX need this non-static entry for calling from vm_map_print.
 *
 * Debugging only
 */
void
vm_object_print(/* db_expr_t */ long addr,
                boolean_t have_addr,
                /* db_expr_t */ long count,
                char *modif)
{
        vm_object_print_static(addr, have_addr, count, modif);
}

/*
 * Debugging only
 */
DB_SHOW_COMMAND(vmopag, vm_object_print_pages)
{
        struct vm_object_hash *hash;
        vm_object_t object;
        int nl = 0;
        int c;
        int n;

        for (n = 0; n < VMOBJ_HSIZE; ++n) {
                hash = &vm_object_hash[n];
                for (object = TAILQ_FIRST(&hash->list);
                                object != NULL;
                                object = TAILQ_NEXT(object, object_entry)) {
                        vm_pindex_t idx, fidx;
                        vm_pindex_t osize;
                        vm_paddr_t pa = -1, padiff;
                        int rcount;
                        vm_page_t m;

                        if (object->type == OBJT_MARKER)
                                continue;
                        db_printf("new object: %p\n", (void *)object);
                        if ( nl > 18) {
                                c = cngetc();
                                if (c != ' ')
                                        return;
                                nl = 0;
                        }
                        nl++;
                        rcount = 0;
                        fidx = 0;
                        osize = object->size;
                        if (osize > 128)
                                osize = 128;
                        for (idx = 0; idx < osize; idx++) {
                                m = vm_page_lookup(object, idx);
                                if (m == NULL) {
                                        if (rcount) {
                                                db_printf(" index(%ld)run(%d)pa(0x%lx)\n",
                                                        (long)fidx, rcount, (long)pa);
                                                if ( nl > 18) {
                                                        c = cngetc();
                                                        if (c != ' ')
                                                                return;
                                                        nl = 0;
                                                }
                                                nl++;
                                                rcount = 0;
                                        }
                                        continue;
                                }

                                if (rcount &&
                                        (VM_PAGE_TO_PHYS(m) == pa + rcount * PAGE_SIZE)) {
                                        ++rcount;
                                        continue;
                                }
                                if (rcount) {
                                        padiff = pa + rcount * PAGE_SIZE - VM_PAGE_TO_PHYS(m);
                                        padiff >>= PAGE_SHIFT;
                                        padiff &= PQ_L2_MASK;
                                        if (padiff == 0) {
                                                pa = VM_PAGE_TO_PHYS(m) - rcount * PAGE_SIZE;
                                                ++rcount;
                                                continue;
                                        }
                                        db_printf(" index(%ld)run(%d)pa(0x%lx)",
                                                (long)fidx, rcount, (long)pa);
                                        db_printf("pd(%ld)\n", (long)padiff);
                                        if ( nl > 18) {
                                                c = cngetc();
                                                if (c != ' ')
                                                        return;
                                                nl = 0;
                                        }
                                        nl++;
                                }
                                fidx = idx;
                                pa = VM_PAGE_TO_PHYS(m);
                                rcount = 1;
                        }
                        if (rcount) {
                                db_printf(" index(%ld)run(%d)pa(0x%lx)\n",
                                        (long)fidx, rcount, (long)pa);
                                if ( nl > 18) {
                                        c = cngetc();
                                        if (c != ' ')
                                                return;
                                        nl = 0;
                                }
                                nl++;
                        }
                }
        }
}
#endif /* DDB */