The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_object.c

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    1 /*-
    2  * Copyright (c) 1991, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software contributed to Berkeley by
    6  * The Mach Operating System project at Carnegie-Mellon University.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 4. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  *      from: @(#)vm_object.c   8.5 (Berkeley) 3/22/94
   33  *
   34  *
   35  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
   36  * All rights reserved.
   37  *
   38  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
   39  *
   40  * Permission to use, copy, modify and distribute this software and
   41  * its documentation is hereby granted, provided that both the copyright
   42  * notice and this permission notice appear in all copies of the
   43  * software, derivative works or modified versions, and any portions
   44  * thereof, and that both notices appear in supporting documentation.
   45  *
   46  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
   47  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
   48  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
   49  *
   50  * Carnegie Mellon requests users of this software to return to
   51  *
   52  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
   53  *  School of Computer Science
   54  *  Carnegie Mellon University
   55  *  Pittsburgh PA 15213-3890
   56  *
   57  * any improvements or extensions that they make and grant Carnegie the
   58  * rights to redistribute these changes.
   59  */
   60 
   61 /*
   62  *      Virtual memory object module.
   63  */
   64 
   65 #include <sys/cdefs.h>
   66 __FBSDID("$FreeBSD: releng/10.0/sys/vm/vm_object.c 258037 2013-11-12 08:01:58Z kib $");
   67 
   68 #include "opt_vm.h"
   69 
   70 #include <sys/param.h>
   71 #include <sys/systm.h>
   72 #include <sys/lock.h>
   73 #include <sys/mman.h>
   74 #include <sys/mount.h>
   75 #include <sys/kernel.h>
   76 #include <sys/sysctl.h>
   77 #include <sys/mutex.h>
   78 #include <sys/proc.h>           /* for curproc, pageproc */
   79 #include <sys/socket.h>
   80 #include <sys/resourcevar.h>
   81 #include <sys/rwlock.h>
   82 #include <sys/vnode.h>
   83 #include <sys/vmmeter.h>
   84 #include <sys/sx.h>
   85 
   86 #include <vm/vm.h>
   87 #include <vm/vm_param.h>
   88 #include <vm/pmap.h>
   89 #include <vm/vm_map.h>
   90 #include <vm/vm_object.h>
   91 #include <vm/vm_page.h>
   92 #include <vm/vm_pageout.h>
   93 #include <vm/vm_pager.h>
   94 #include <vm/swap_pager.h>
   95 #include <vm/vm_kern.h>
   96 #include <vm/vm_extern.h>
   97 #include <vm/vm_radix.h>
   98 #include <vm/vm_reserv.h>
   99 #include <vm/uma.h>
  100 
  101 static int old_msync;
  102 SYSCTL_INT(_vm, OID_AUTO, old_msync, CTLFLAG_RW, &old_msync, 0,
  103     "Use old (insecure) msync behavior");
  104 
  105 static int      vm_object_page_collect_flush(vm_object_t object, vm_page_t p,
  106                     int pagerflags, int flags, boolean_t *clearobjflags,
  107                     boolean_t *eio);
  108 static boolean_t vm_object_page_remove_write(vm_page_t p, int flags,
  109                     boolean_t *clearobjflags);
  110 static void     vm_object_qcollapse(vm_object_t object);
  111 static void     vm_object_vndeallocate(vm_object_t object);
  112 
  113 /*
  114  *      Virtual memory objects maintain the actual data
  115  *      associated with allocated virtual memory.  A given
  116  *      page of memory exists within exactly one object.
  117  *
  118  *      An object is only deallocated when all "references"
  119  *      are given up.  Only one "reference" to a given
  120  *      region of an object should be writeable.
  121  *
  122  *      Associated with each object is a list of all resident
  123  *      memory pages belonging to that object; this list is
  124  *      maintained by the "vm_page" module, and locked by the object's
  125  *      lock.
  126  *
  127  *      Each object also records a "pager" routine which is
  128  *      used to retrieve (and store) pages to the proper backing
  129  *      storage.  In addition, objects may be backed by other
  130  *      objects from which they were virtual-copied.
  131  *
  132  *      The only items within the object structure which are
  133  *      modified after time of creation are:
  134  *              reference count         locked by object's lock
  135  *              pager routine           locked by object's lock
  136  *
  137  */
  138 
  139 struct object_q vm_object_list;
  140 struct mtx vm_object_list_mtx;  /* lock for object list and count */
  141 
  142 struct vm_object kernel_object_store;
  143 struct vm_object kmem_object_store;
  144 
  145 static SYSCTL_NODE(_vm_stats, OID_AUTO, object, CTLFLAG_RD, 0,
  146     "VM object stats");
  147 
  148 static long object_collapses;
  149 SYSCTL_LONG(_vm_stats_object, OID_AUTO, collapses, CTLFLAG_RD,
  150     &object_collapses, 0, "VM object collapses");
  151 
  152 static long object_bypasses;
  153 SYSCTL_LONG(_vm_stats_object, OID_AUTO, bypasses, CTLFLAG_RD,
  154     &object_bypasses, 0, "VM object bypasses");
  155 
  156 static uma_zone_t obj_zone;
  157 
  158 static int vm_object_zinit(void *mem, int size, int flags);
  159 
  160 #ifdef INVARIANTS
  161 static void vm_object_zdtor(void *mem, int size, void *arg);
  162 
  163 static void
  164 vm_object_zdtor(void *mem, int size, void *arg)
  165 {
  166         vm_object_t object;
  167 
  168         object = (vm_object_t)mem;
  169         KASSERT(TAILQ_EMPTY(&object->memq),
  170             ("object %p has resident pages in its memq", object));
  171         KASSERT(vm_radix_is_empty(&object->rtree),
  172             ("object %p has resident pages in its trie", object));
  173 #if VM_NRESERVLEVEL > 0
  174         KASSERT(LIST_EMPTY(&object->rvq),
  175             ("object %p has reservations",
  176             object));
  177 #endif
  178         KASSERT(vm_object_cache_is_empty(object),
  179             ("object %p has cached pages",
  180             object));
  181         KASSERT(object->paging_in_progress == 0,
  182             ("object %p paging_in_progress = %d",
  183             object, object->paging_in_progress));
  184         KASSERT(object->resident_page_count == 0,
  185             ("object %p resident_page_count = %d",
  186             object, object->resident_page_count));
  187         KASSERT(object->shadow_count == 0,
  188             ("object %p shadow_count = %d",
  189             object, object->shadow_count));
  190 }
  191 #endif
  192 
  193 static int
  194 vm_object_zinit(void *mem, int size, int flags)
  195 {
  196         vm_object_t object;
  197 
  198         object = (vm_object_t)mem;
  199         bzero(&object->lock, sizeof(object->lock));
  200         rw_init_flags(&object->lock, "vm object", RW_DUPOK);
  201 
  202         /* These are true for any object that has been freed */
  203         object->rtree.rt_root = 0;
  204         object->rtree.rt_flags = 0;
  205         object->paging_in_progress = 0;
  206         object->resident_page_count = 0;
  207         object->shadow_count = 0;
  208         object->cache.rt_root = 0;
  209         object->cache.rt_flags = 0;
  210         return (0);
  211 }
  212 
  213 static void
  214 _vm_object_allocate(objtype_t type, vm_pindex_t size, vm_object_t object)
  215 {
  216 
  217         TAILQ_INIT(&object->memq);
  218         LIST_INIT(&object->shadow_head);
  219 
  220         object->type = type;
  221         switch (type) {
  222         case OBJT_DEAD:
  223                 panic("_vm_object_allocate: can't create OBJT_DEAD");
  224         case OBJT_DEFAULT:
  225         case OBJT_SWAP:
  226                 object->flags = OBJ_ONEMAPPING;
  227                 break;
  228         case OBJT_DEVICE:
  229         case OBJT_SG:
  230                 object->flags = OBJ_FICTITIOUS | OBJ_UNMANAGED;
  231                 break;
  232         case OBJT_MGTDEVICE:
  233                 object->flags = OBJ_FICTITIOUS;
  234                 break;
  235         case OBJT_PHYS:
  236                 object->flags = OBJ_UNMANAGED;
  237                 break;
  238         case OBJT_VNODE:
  239                 object->flags = 0;
  240                 break;
  241         default:
  242                 panic("_vm_object_allocate: type %d is undefined", type);
  243         }
  244         object->size = size;
  245         object->generation = 1;
  246         object->ref_count = 1;
  247         object->memattr = VM_MEMATTR_DEFAULT;
  248         object->cred = NULL;
  249         object->charge = 0;
  250         object->handle = NULL;
  251         object->backing_object = NULL;
  252         object->backing_object_offset = (vm_ooffset_t) 0;
  253 #if VM_NRESERVLEVEL > 0
  254         LIST_INIT(&object->rvq);
  255 #endif
  256 
  257         mtx_lock(&vm_object_list_mtx);
  258         TAILQ_INSERT_TAIL(&vm_object_list, object, object_list);
  259         mtx_unlock(&vm_object_list_mtx);
  260 }
  261 
  262 /*
  263  *      vm_object_init:
  264  *
  265  *      Initialize the VM objects module.
  266  */
  267 void
  268 vm_object_init(void)
  269 {
  270         TAILQ_INIT(&vm_object_list);
  271         mtx_init(&vm_object_list_mtx, "vm object_list", NULL, MTX_DEF);
  272         
  273         rw_init(&kernel_object->lock, "kernel vm object");
  274         _vm_object_allocate(OBJT_PHYS, OFF_TO_IDX(VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS),
  275             kernel_object);
  276 #if VM_NRESERVLEVEL > 0
  277         kernel_object->flags |= OBJ_COLORED;
  278         kernel_object->pg_color = (u_short)atop(VM_MIN_KERNEL_ADDRESS);
  279 #endif
  280 
  281         rw_init(&kmem_object->lock, "kmem vm object");
  282         _vm_object_allocate(OBJT_PHYS, OFF_TO_IDX(VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS),
  283             kmem_object);
  284 #if VM_NRESERVLEVEL > 0
  285         kmem_object->flags |= OBJ_COLORED;
  286         kmem_object->pg_color = (u_short)atop(VM_MIN_KERNEL_ADDRESS);
  287 #endif
  288 
  289         /*
  290          * The lock portion of struct vm_object must be type stable due
  291          * to vm_pageout_fallback_object_lock locking a vm object
  292          * without holding any references to it.
  293          */
  294         obj_zone = uma_zcreate("VM OBJECT", sizeof (struct vm_object), NULL,
  295 #ifdef INVARIANTS
  296             vm_object_zdtor,
  297 #else
  298             NULL,
  299 #endif
  300             vm_object_zinit, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
  301 
  302         vm_radix_init();
  303 }
  304 
  305 void
  306 vm_object_clear_flag(vm_object_t object, u_short bits)
  307 {
  308 
  309         VM_OBJECT_ASSERT_WLOCKED(object);
  310         object->flags &= ~bits;
  311 }
  312 
  313 /*
  314  *      Sets the default memory attribute for the specified object.  Pages
  315  *      that are allocated to this object are by default assigned this memory
  316  *      attribute.
  317  *
  318  *      Presently, this function must be called before any pages are allocated
  319  *      to the object.  In the future, this requirement may be relaxed for
  320  *      "default" and "swap" objects.
  321  */
  322 int
  323 vm_object_set_memattr(vm_object_t object, vm_memattr_t memattr)
  324 {
  325 
  326         VM_OBJECT_ASSERT_WLOCKED(object);
  327         switch (object->type) {
  328         case OBJT_DEFAULT:
  329         case OBJT_DEVICE:
  330         case OBJT_MGTDEVICE:
  331         case OBJT_PHYS:
  332         case OBJT_SG:
  333         case OBJT_SWAP:
  334         case OBJT_VNODE:
  335                 if (!TAILQ_EMPTY(&object->memq))
  336                         return (KERN_FAILURE);
  337                 break;
  338         case OBJT_DEAD:
  339                 return (KERN_INVALID_ARGUMENT);
  340         default:
  341                 panic("vm_object_set_memattr: object %p is of undefined type",
  342                     object);
  343         }
  344         object->memattr = memattr;
  345         return (KERN_SUCCESS);
  346 }
  347 
  348 void
  349 vm_object_pip_add(vm_object_t object, short i)
  350 {
  351 
  352         VM_OBJECT_ASSERT_WLOCKED(object);
  353         object->paging_in_progress += i;
  354 }
  355 
  356 void
  357 vm_object_pip_subtract(vm_object_t object, short i)
  358 {
  359 
  360         VM_OBJECT_ASSERT_WLOCKED(object);
  361         object->paging_in_progress -= i;
  362 }
  363 
  364 void
  365 vm_object_pip_wakeup(vm_object_t object)
  366 {
  367 
  368         VM_OBJECT_ASSERT_WLOCKED(object);
  369         object->paging_in_progress--;
  370         if ((object->flags & OBJ_PIPWNT) && object->paging_in_progress == 0) {
  371                 vm_object_clear_flag(object, OBJ_PIPWNT);
  372                 wakeup(object);
  373         }
  374 }
  375 
  376 void
  377 vm_object_pip_wakeupn(vm_object_t object, short i)
  378 {
  379 
  380         VM_OBJECT_ASSERT_WLOCKED(object);
  381         if (i)
  382                 object->paging_in_progress -= i;
  383         if ((object->flags & OBJ_PIPWNT) && object->paging_in_progress == 0) {
  384                 vm_object_clear_flag(object, OBJ_PIPWNT);
  385                 wakeup(object);
  386         }
  387 }
  388 
  389 void
  390 vm_object_pip_wait(vm_object_t object, char *waitid)
  391 {
  392 
  393         VM_OBJECT_ASSERT_WLOCKED(object);
  394         while (object->paging_in_progress) {
  395                 object->flags |= OBJ_PIPWNT;
  396                 VM_OBJECT_SLEEP(object, object, PVM, waitid, 0);
  397         }
  398 }
  399 
  400 /*
  401  *      vm_object_allocate:
  402  *
  403  *      Returns a new object with the given size.
  404  */
  405 vm_object_t
  406 vm_object_allocate(objtype_t type, vm_pindex_t size)
  407 {
  408         vm_object_t object;
  409 
  410         object = (vm_object_t)uma_zalloc(obj_zone, M_WAITOK);
  411         _vm_object_allocate(type, size, object);
  412         return (object);
  413 }
  414 
  415 
  416 /*
  417  *      vm_object_reference:
  418  *
  419  *      Gets another reference to the given object.  Note: OBJ_DEAD
  420  *      objects can be referenced during final cleaning.
  421  */
  422 void
  423 vm_object_reference(vm_object_t object)
  424 {
  425         if (object == NULL)
  426                 return;
  427         VM_OBJECT_WLOCK(object);
  428         vm_object_reference_locked(object);
  429         VM_OBJECT_WUNLOCK(object);
  430 }
  431 
  432 /*
  433  *      vm_object_reference_locked:
  434  *
  435  *      Gets another reference to the given object.
  436  *
  437  *      The object must be locked.
  438  */
  439 void
  440 vm_object_reference_locked(vm_object_t object)
  441 {
  442         struct vnode *vp;
  443 
  444         VM_OBJECT_ASSERT_WLOCKED(object);
  445         object->ref_count++;
  446         if (object->type == OBJT_VNODE) {
  447                 vp = object->handle;
  448                 vref(vp);
  449         }
  450 }
  451 
  452 /*
  453  * Handle deallocating an object of type OBJT_VNODE.
  454  */
  455 static void
  456 vm_object_vndeallocate(vm_object_t object)
  457 {
  458         struct vnode *vp = (struct vnode *) object->handle;
  459 
  460         VM_OBJECT_ASSERT_WLOCKED(object);
  461         KASSERT(object->type == OBJT_VNODE,
  462             ("vm_object_vndeallocate: not a vnode object"));
  463         KASSERT(vp != NULL, ("vm_object_vndeallocate: missing vp"));
  464 #ifdef INVARIANTS
  465         if (object->ref_count == 0) {
  466                 vprint("vm_object_vndeallocate", vp);
  467                 panic("vm_object_vndeallocate: bad object reference count");
  468         }
  469 #endif
  470 
  471         if (object->ref_count > 1) {
  472                 object->ref_count--;
  473                 VM_OBJECT_WUNLOCK(object);
  474                 /* vrele may need the vnode lock. */
  475                 vrele(vp);
  476         } else {
  477                 vhold(vp);
  478                 VM_OBJECT_WUNLOCK(object);
  479                 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  480                 vdrop(vp);
  481                 VM_OBJECT_WLOCK(object);
  482                 object->ref_count--;
  483                 if (object->type == OBJT_DEAD) {
  484                         VM_OBJECT_WUNLOCK(object);
  485                         VOP_UNLOCK(vp, 0);
  486                 } else {
  487                         if (object->ref_count == 0)
  488                                 VOP_UNSET_TEXT(vp);
  489                         VM_OBJECT_WUNLOCK(object);
  490                         vput(vp);
  491                 }
  492         }
  493 }
  494 
  495 /*
  496  *      vm_object_deallocate:
  497  *
  498  *      Release a reference to the specified object,
  499  *      gained either through a vm_object_allocate
  500  *      or a vm_object_reference call.  When all references
  501  *      are gone, storage associated with this object
  502  *      may be relinquished.
  503  *
  504  *      No object may be locked.
  505  */
  506 void
  507 vm_object_deallocate(vm_object_t object)
  508 {
  509         vm_object_t temp;
  510         struct vnode *vp;
  511 
  512         while (object != NULL) {
  513                 VM_OBJECT_WLOCK(object);
  514                 if (object->type == OBJT_VNODE) {
  515                         vm_object_vndeallocate(object);
  516                         return;
  517                 }
  518 
  519                 KASSERT(object->ref_count != 0,
  520                         ("vm_object_deallocate: object deallocated too many times: %d", object->type));
  521 
  522                 /*
  523                  * If the reference count goes to 0 we start calling
  524                  * vm_object_terminate() on the object chain.
  525                  * A ref count of 1 may be a special case depending on the
  526                  * shadow count being 0 or 1.
  527                  */
  528                 object->ref_count--;
  529                 if (object->ref_count > 1) {
  530                         VM_OBJECT_WUNLOCK(object);
  531                         return;
  532                 } else if (object->ref_count == 1) {
  533                         if (object->type == OBJT_SWAP &&
  534                             (object->flags & OBJ_TMPFS) != 0) {
  535                                 vp = object->un_pager.swp.swp_tmpfs;
  536                                 vhold(vp);
  537                                 VM_OBJECT_WUNLOCK(object);
  538                                 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
  539                                 vdrop(vp);
  540                                 VM_OBJECT_WLOCK(object);
  541                                 if (object->type == OBJT_DEAD ||
  542                                     object->ref_count != 1) {
  543                                         VM_OBJECT_WUNLOCK(object);
  544                                         VOP_UNLOCK(vp, 0);
  545                                         return;
  546                                 }
  547                                 if ((object->flags & OBJ_TMPFS) != 0)
  548                                         VOP_UNSET_TEXT(vp);
  549                                 VOP_UNLOCK(vp, 0);
  550                         }
  551                         if (object->shadow_count == 0 &&
  552                             object->handle == NULL &&
  553                             (object->type == OBJT_DEFAULT ||
  554                             (object->type == OBJT_SWAP &&
  555                             (object->flags & OBJ_TMPFS) == 0))) {
  556                                 vm_object_set_flag(object, OBJ_ONEMAPPING);
  557                         } else if ((object->shadow_count == 1) &&
  558                             (object->handle == NULL) &&
  559                             (object->type == OBJT_DEFAULT ||
  560                              object->type == OBJT_SWAP)) {
  561                                 KASSERT((object->flags & OBJ_TMPFS) == 0,
  562                                     ("shadowed tmpfs v_object %p", object));
  563                                 vm_object_t robject;
  564 
  565                                 robject = LIST_FIRST(&object->shadow_head);
  566                                 KASSERT(robject != NULL,
  567                                     ("vm_object_deallocate: ref_count: %d, shadow_count: %d",
  568                                          object->ref_count,
  569                                          object->shadow_count));
  570                                 if (!VM_OBJECT_TRYWLOCK(robject)) {
  571                                         /*
  572                                          * Avoid a potential deadlock.
  573                                          */
  574                                         object->ref_count++;
  575                                         VM_OBJECT_WUNLOCK(object);
  576                                         /*
  577                                          * More likely than not the thread
  578                                          * holding robject's lock has lower
  579                                          * priority than the current thread.
  580                                          * Let the lower priority thread run.
  581                                          */
  582                                         pause("vmo_de", 1);
  583                                         continue;
  584                                 }
  585                                 /*
  586                                  * Collapse object into its shadow unless its
  587                                  * shadow is dead.  In that case, object will
  588                                  * be deallocated by the thread that is
  589                                  * deallocating its shadow.
  590                                  */
  591                                 if ((robject->flags & OBJ_DEAD) == 0 &&
  592                                     (robject->handle == NULL) &&
  593                                     (robject->type == OBJT_DEFAULT ||
  594                                      robject->type == OBJT_SWAP)) {
  595 
  596                                         robject->ref_count++;
  597 retry:
  598                                         if (robject->paging_in_progress) {
  599                                                 VM_OBJECT_WUNLOCK(object);
  600                                                 vm_object_pip_wait(robject,
  601                                                     "objde1");
  602                                                 temp = robject->backing_object;
  603                                                 if (object == temp) {
  604                                                         VM_OBJECT_WLOCK(object);
  605                                                         goto retry;
  606                                                 }
  607                                         } else if (object->paging_in_progress) {
  608                                                 VM_OBJECT_WUNLOCK(robject);
  609                                                 object->flags |= OBJ_PIPWNT;
  610                                                 VM_OBJECT_SLEEP(object, object,
  611                                                     PDROP | PVM, "objde2", 0);
  612                                                 VM_OBJECT_WLOCK(robject);
  613                                                 temp = robject->backing_object;
  614                                                 if (object == temp) {
  615                                                         VM_OBJECT_WLOCK(object);
  616                                                         goto retry;
  617                                                 }
  618                                         } else
  619                                                 VM_OBJECT_WUNLOCK(object);
  620 
  621                                         if (robject->ref_count == 1) {
  622                                                 robject->ref_count--;
  623                                                 object = robject;
  624                                                 goto doterm;
  625                                         }
  626                                         object = robject;
  627                                         vm_object_collapse(object);
  628                                         VM_OBJECT_WUNLOCK(object);
  629                                         continue;
  630                                 }
  631                                 VM_OBJECT_WUNLOCK(robject);
  632                         }
  633                         VM_OBJECT_WUNLOCK(object);
  634                         return;
  635                 }
  636 doterm:
  637                 temp = object->backing_object;
  638                 if (temp != NULL) {
  639                         VM_OBJECT_WLOCK(temp);
  640                         LIST_REMOVE(object, shadow_list);
  641                         temp->shadow_count--;
  642                         VM_OBJECT_WUNLOCK(temp);
  643                         object->backing_object = NULL;
  644                 }
  645                 /*
  646                  * Don't double-terminate, we could be in a termination
  647                  * recursion due to the terminate having to sync data
  648                  * to disk.
  649                  */
  650                 if ((object->flags & OBJ_DEAD) == 0)
  651                         vm_object_terminate(object);
  652                 else
  653                         VM_OBJECT_WUNLOCK(object);
  654                 object = temp;
  655         }
  656 }
  657 
  658 /*
  659  *      vm_object_destroy removes the object from the global object list
  660  *      and frees the space for the object.
  661  */
  662 void
  663 vm_object_destroy(vm_object_t object)
  664 {
  665 
  666         /*
  667          * Remove the object from the global object list.
  668          */
  669         mtx_lock(&vm_object_list_mtx);
  670         TAILQ_REMOVE(&vm_object_list, object, object_list);
  671         mtx_unlock(&vm_object_list_mtx);
  672 
  673         /*
  674          * Release the allocation charge.
  675          */
  676         if (object->cred != NULL) {
  677                 KASSERT(object->type == OBJT_DEFAULT ||
  678                     object->type == OBJT_SWAP,
  679                     ("vm_object_terminate: non-swap obj %p has cred",
  680                      object));
  681                 swap_release_by_cred(object->charge, object->cred);
  682                 object->charge = 0;
  683                 crfree(object->cred);
  684                 object->cred = NULL;
  685         }
  686 
  687         /*
  688          * Free the space for the object.
  689          */
  690         uma_zfree(obj_zone, object);
  691 }
  692 
  693 /*
  694  *      vm_object_terminate actually destroys the specified object, freeing
  695  *      up all previously used resources.
  696  *
  697  *      The object must be locked.
  698  *      This routine may block.
  699  */
  700 void
  701 vm_object_terminate(vm_object_t object)
  702 {
  703         vm_page_t p, p_next;
  704 
  705         VM_OBJECT_ASSERT_WLOCKED(object);
  706 
  707         /*
  708          * Make sure no one uses us.
  709          */
  710         vm_object_set_flag(object, OBJ_DEAD);
  711 
  712         /*
  713          * wait for the pageout daemon to be done with the object
  714          */
  715         vm_object_pip_wait(object, "objtrm");
  716 
  717         KASSERT(!object->paging_in_progress,
  718                 ("vm_object_terminate: pageout in progress"));
  719 
  720         /*
  721          * Clean and free the pages, as appropriate. All references to the
  722          * object are gone, so we don't need to lock it.
  723          */
  724         if (object->type == OBJT_VNODE) {
  725                 struct vnode *vp = (struct vnode *)object->handle;
  726 
  727                 /*
  728                  * Clean pages and flush buffers.
  729                  */
  730                 vm_object_page_clean(object, 0, 0, OBJPC_SYNC);
  731                 VM_OBJECT_WUNLOCK(object);
  732 
  733                 vinvalbuf(vp, V_SAVE, 0, 0);
  734 
  735                 VM_OBJECT_WLOCK(object);
  736         }
  737 
  738         KASSERT(object->ref_count == 0, 
  739                 ("vm_object_terminate: object with references, ref_count=%d",
  740                 object->ref_count));
  741 
  742         /*
  743          * Free any remaining pageable pages.  This also removes them from the
  744          * paging queues.  However, don't free wired pages, just remove them
  745          * from the object.  Rather than incrementally removing each page from
  746          * the object, the page and object are reset to any empty state. 
  747          */
  748         TAILQ_FOREACH_SAFE(p, &object->memq, listq, p_next) {
  749                 vm_page_assert_unbusied(p);
  750                 vm_page_lock(p);
  751                 /*
  752                  * Optimize the page's removal from the object by resetting
  753                  * its "object" field.  Specifically, if the page is not
  754                  * wired, then the effect of this assignment is that
  755                  * vm_page_free()'s call to vm_page_remove() will return
  756                  * immediately without modifying the page or the object.
  757                  */ 
  758                 p->object = NULL;
  759                 if (p->wire_count == 0) {
  760                         vm_page_free(p);
  761                         PCPU_INC(cnt.v_pfree);
  762                 }
  763                 vm_page_unlock(p);
  764         }
  765         /*
  766          * If the object contained any pages, then reset it to an empty state.
  767          * None of the object's fields, including "resident_page_count", were
  768          * modified by the preceding loop.
  769          */
  770         if (object->resident_page_count != 0) {
  771                 vm_radix_reclaim_allnodes(&object->rtree);
  772                 TAILQ_INIT(&object->memq);
  773                 object->resident_page_count = 0;
  774                 if (object->type == OBJT_VNODE)
  775                         vdrop(object->handle);
  776         }
  777 
  778 #if VM_NRESERVLEVEL > 0
  779         if (__predict_false(!LIST_EMPTY(&object->rvq)))
  780                 vm_reserv_break_all(object);
  781 #endif
  782         if (__predict_false(!vm_object_cache_is_empty(object)))
  783                 vm_page_cache_free(object, 0, 0);
  784 
  785         /*
  786          * Let the pager know object is dead.
  787          */
  788         vm_pager_deallocate(object);
  789         VM_OBJECT_WUNLOCK(object);
  790 
  791         vm_object_destroy(object);
  792 }
  793 
  794 /*
  795  * Make the page read-only so that we can clear the object flags.  However, if
  796  * this is a nosync mmap then the object is likely to stay dirty so do not
  797  * mess with the page and do not clear the object flags.  Returns TRUE if the
  798  * page should be flushed, and FALSE otherwise.
  799  */
  800 static boolean_t
  801 vm_object_page_remove_write(vm_page_t p, int flags, boolean_t *clearobjflags)
  802 {
  803 
  804         /*
  805          * If we have been asked to skip nosync pages and this is a
  806          * nosync page, skip it.  Note that the object flags were not
  807          * cleared in this case so we do not have to set them.
  808          */
  809         if ((flags & OBJPC_NOSYNC) != 0 && (p->oflags & VPO_NOSYNC) != 0) {
  810                 *clearobjflags = FALSE;
  811                 return (FALSE);
  812         } else {
  813                 pmap_remove_write(p);
  814                 return (p->dirty != 0);
  815         }
  816 }
  817 
  818 /*
  819  *      vm_object_page_clean
  820  *
  821  *      Clean all dirty pages in the specified range of object.  Leaves page 
  822  *      on whatever queue it is currently on.   If NOSYNC is set then do not
  823  *      write out pages with VPO_NOSYNC set (originally comes from MAP_NOSYNC),
  824  *      leaving the object dirty.
  825  *
  826  *      When stuffing pages asynchronously, allow clustering.  XXX we need a
  827  *      synchronous clustering mode implementation.
  828  *
  829  *      Odd semantics: if start == end, we clean everything.
  830  *
  831  *      The object must be locked.
  832  *
  833  *      Returns FALSE if some page from the range was not written, as
  834  *      reported by the pager, and TRUE otherwise.
  835  */
  836 boolean_t
  837 vm_object_page_clean(vm_object_t object, vm_ooffset_t start, vm_ooffset_t end,
  838     int flags)
  839 {
  840         vm_page_t np, p;
  841         vm_pindex_t pi, tend, tstart;
  842         int curgeneration, n, pagerflags;
  843         boolean_t clearobjflags, eio, res;
  844 
  845         VM_OBJECT_ASSERT_WLOCKED(object);
  846 
  847         /*
  848          * The OBJ_MIGHTBEDIRTY flag is only set for OBJT_VNODE
  849          * objects.  The check below prevents the function from
  850          * operating on non-vnode objects.
  851          */
  852         if ((object->flags & OBJ_MIGHTBEDIRTY) == 0 ||
  853             object->resident_page_count == 0)
  854                 return (TRUE);
  855 
  856         pagerflags = (flags & (OBJPC_SYNC | OBJPC_INVAL)) != 0 ?
  857             VM_PAGER_PUT_SYNC : VM_PAGER_CLUSTER_OK;
  858         pagerflags |= (flags & OBJPC_INVAL) != 0 ? VM_PAGER_PUT_INVAL : 0;
  859 
  860         tstart = OFF_TO_IDX(start);
  861         tend = (end == 0) ? object->size : OFF_TO_IDX(end + PAGE_MASK);
  862         clearobjflags = tstart == 0 && tend >= object->size;
  863         res = TRUE;
  864 
  865 rescan:
  866         curgeneration = object->generation;
  867 
  868         for (p = vm_page_find_least(object, tstart); p != NULL; p = np) {
  869                 pi = p->pindex;
  870                 if (pi >= tend)
  871                         break;
  872                 np = TAILQ_NEXT(p, listq);
  873                 if (p->valid == 0)
  874                         continue;
  875                 if (vm_page_sleep_if_busy(p, "vpcwai")) {
  876                         if (object->generation != curgeneration) {
  877                                 if ((flags & OBJPC_SYNC) != 0)
  878                                         goto rescan;
  879                                 else
  880                                         clearobjflags = FALSE;
  881                         }
  882                         np = vm_page_find_least(object, pi);
  883                         continue;
  884                 }
  885                 if (!vm_object_page_remove_write(p, flags, &clearobjflags))
  886                         continue;
  887 
  888                 n = vm_object_page_collect_flush(object, p, pagerflags,
  889                     flags, &clearobjflags, &eio);
  890                 if (eio) {
  891                         res = FALSE;
  892                         clearobjflags = FALSE;
  893                 }
  894                 if (object->generation != curgeneration) {
  895                         if ((flags & OBJPC_SYNC) != 0)
  896                                 goto rescan;
  897                         else
  898                                 clearobjflags = FALSE;
  899                 }
  900 
  901                 /*
  902                  * If the VOP_PUTPAGES() did a truncated write, so
  903                  * that even the first page of the run is not fully
  904                  * written, vm_pageout_flush() returns 0 as the run
  905                  * length.  Since the condition that caused truncated
  906                  * write may be permanent, e.g. exhausted free space,
  907                  * accepting n == 0 would cause an infinite loop.
  908                  *
  909                  * Forwarding the iterator leaves the unwritten page
  910                  * behind, but there is not much we can do there if
  911                  * filesystem refuses to write it.
  912                  */
  913                 if (n == 0) {
  914                         n = 1;
  915                         clearobjflags = FALSE;
  916                 }
  917                 np = vm_page_find_least(object, pi + n);
  918         }
  919 #if 0
  920         VOP_FSYNC(vp, (pagerflags & VM_PAGER_PUT_SYNC) ? MNT_WAIT : 0);
  921 #endif
  922 
  923         if (clearobjflags)
  924                 vm_object_clear_flag(object, OBJ_MIGHTBEDIRTY);
  925         return (res);
  926 }
  927 
  928 static int
  929 vm_object_page_collect_flush(vm_object_t object, vm_page_t p, int pagerflags,
  930     int flags, boolean_t *clearobjflags, boolean_t *eio)
  931 {
  932         vm_page_t ma[vm_pageout_page_count], p_first, tp;
  933         int count, i, mreq, runlen;
  934 
  935         vm_page_lock_assert(p, MA_NOTOWNED);
  936         VM_OBJECT_ASSERT_WLOCKED(object);
  937 
  938         count = 1;
  939         mreq = 0;
  940 
  941         for (tp = p; count < vm_pageout_page_count; count++) {
  942                 tp = vm_page_next(tp);
  943                 if (tp == NULL || vm_page_busied(tp))
  944                         break;
  945                 if (!vm_object_page_remove_write(tp, flags, clearobjflags))
  946                         break;
  947         }
  948 
  949         for (p_first = p; count < vm_pageout_page_count; count++) {
  950                 tp = vm_page_prev(p_first);
  951                 if (tp == NULL || vm_page_busied(tp))
  952                         break;
  953                 if (!vm_object_page_remove_write(tp, flags, clearobjflags))
  954                         break;
  955                 p_first = tp;
  956                 mreq++;
  957         }
  958 
  959         for (tp = p_first, i = 0; i < count; tp = TAILQ_NEXT(tp, listq), i++)
  960                 ma[i] = tp;
  961 
  962         vm_pageout_flush(ma, count, pagerflags, mreq, &runlen, eio);
  963         return (runlen);
  964 }
  965 
  966 /*
  967  * Note that there is absolutely no sense in writing out
  968  * anonymous objects, so we track down the vnode object
  969  * to write out.
  970  * We invalidate (remove) all pages from the address space
  971  * for semantic correctness.
  972  *
  973  * If the backing object is a device object with unmanaged pages, then any
  974  * mappings to the specified range of pages must be removed before this
  975  * function is called.
  976  *
  977  * Note: certain anonymous maps, such as MAP_NOSYNC maps,
  978  * may start out with a NULL object.
  979  */
  980 boolean_t
  981 vm_object_sync(vm_object_t object, vm_ooffset_t offset, vm_size_t size,
  982     boolean_t syncio, boolean_t invalidate)
  983 {
  984         vm_object_t backing_object;
  985         struct vnode *vp;
  986         struct mount *mp;
  987         int error, flags, fsync_after;
  988         boolean_t res;
  989 
  990         if (object == NULL)
  991                 return (TRUE);
  992         res = TRUE;
  993         error = 0;
  994         VM_OBJECT_WLOCK(object);
  995         while ((backing_object = object->backing_object) != NULL) {
  996                 VM_OBJECT_WLOCK(backing_object);
  997                 offset += object->backing_object_offset;
  998                 VM_OBJECT_WUNLOCK(object);
  999                 object = backing_object;
 1000                 if (object->size < OFF_TO_IDX(offset + size))
 1001                         size = IDX_TO_OFF(object->size) - offset;
 1002         }
 1003         /*
 1004          * Flush pages if writing is allowed, invalidate them
 1005          * if invalidation requested.  Pages undergoing I/O
 1006          * will be ignored by vm_object_page_remove().
 1007          *
 1008          * We cannot lock the vnode and then wait for paging
 1009          * to complete without deadlocking against vm_fault.
 1010          * Instead we simply call vm_object_page_remove() and
 1011          * allow it to block internally on a page-by-page
 1012          * basis when it encounters pages undergoing async
 1013          * I/O.
 1014          */
 1015         if (object->type == OBJT_VNODE &&
 1016             (object->flags & OBJ_MIGHTBEDIRTY) != 0) {
 1017                 vp = object->handle;
 1018                 VM_OBJECT_WUNLOCK(object);
 1019                 (void) vn_start_write(vp, &mp, V_WAIT);
 1020                 vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 1021                 if (syncio && !invalidate && offset == 0 &&
 1022                     OFF_TO_IDX(size) == object->size) {
 1023                         /*
 1024                          * If syncing the whole mapping of the file,
 1025                          * it is faster to schedule all the writes in
 1026                          * async mode, also allowing the clustering,
 1027                          * and then wait for i/o to complete.
 1028                          */
 1029                         flags = 0;
 1030                         fsync_after = TRUE;
 1031                 } else {
 1032                         flags = (syncio || invalidate) ? OBJPC_SYNC : 0;
 1033                         flags |= invalidate ? (OBJPC_SYNC | OBJPC_INVAL) : 0;
 1034                         fsync_after = FALSE;
 1035                 }
 1036                 VM_OBJECT_WLOCK(object);
 1037                 res = vm_object_page_clean(object, offset, offset + size,
 1038                     flags);
 1039                 VM_OBJECT_WUNLOCK(object);
 1040                 if (fsync_after)
 1041                         error = VOP_FSYNC(vp, MNT_WAIT, curthread);
 1042                 VOP_UNLOCK(vp, 0);
 1043                 vn_finished_write(mp);
 1044                 if (error != 0)
 1045                         res = FALSE;
 1046                 VM_OBJECT_WLOCK(object);
 1047         }
 1048         if ((object->type == OBJT_VNODE ||
 1049              object->type == OBJT_DEVICE) && invalidate) {
 1050                 if (object->type == OBJT_DEVICE)
 1051                         /*
 1052                          * The option OBJPR_NOTMAPPED must be passed here
 1053                          * because vm_object_page_remove() cannot remove
 1054                          * unmanaged mappings.
 1055                          */
 1056                         flags = OBJPR_NOTMAPPED;
 1057                 else if (old_msync)
 1058                         flags = OBJPR_NOTWIRED;
 1059                 else
 1060                         flags = OBJPR_CLEANONLY | OBJPR_NOTWIRED;
 1061                 vm_object_page_remove(object, OFF_TO_IDX(offset),
 1062                     OFF_TO_IDX(offset + size + PAGE_MASK), flags);
 1063         }
 1064         VM_OBJECT_WUNLOCK(object);
 1065         return (res);
 1066 }
 1067 
 1068 /*
 1069  *      vm_object_madvise:
 1070  *
 1071  *      Implements the madvise function at the object/page level.
 1072  *
 1073  *      MADV_WILLNEED   (any object)
 1074  *
 1075  *          Activate the specified pages if they are resident.
 1076  *
 1077  *      MADV_DONTNEED   (any object)
 1078  *
 1079  *          Deactivate the specified pages if they are resident.
 1080  *
 1081  *      MADV_FREE       (OBJT_DEFAULT/OBJT_SWAP objects,
 1082  *                       OBJ_ONEMAPPING only)
 1083  *
 1084  *          Deactivate and clean the specified pages if they are
 1085  *          resident.  This permits the process to reuse the pages
 1086  *          without faulting or the kernel to reclaim the pages
 1087  *          without I/O.
 1088  */
 1089 void
 1090 vm_object_madvise(vm_object_t object, vm_pindex_t pindex, vm_pindex_t end,
 1091     int advise)
 1092 {
 1093         vm_pindex_t tpindex;
 1094         vm_object_t backing_object, tobject;
 1095         vm_page_t m;
 1096 
 1097         if (object == NULL)
 1098                 return;
 1099         VM_OBJECT_WLOCK(object);
 1100         /*
 1101          * Locate and adjust resident pages
 1102          */
 1103         for (; pindex < end; pindex += 1) {
 1104 relookup:
 1105                 tobject = object;
 1106                 tpindex = pindex;
 1107 shadowlookup:
 1108                 /*
 1109                  * MADV_FREE only operates on OBJT_DEFAULT or OBJT_SWAP pages
 1110                  * and those pages must be OBJ_ONEMAPPING.
 1111                  */
 1112                 if (advise == MADV_FREE) {
 1113                         if ((tobject->type != OBJT_DEFAULT &&
 1114                              tobject->type != OBJT_SWAP) ||
 1115                             (tobject->flags & OBJ_ONEMAPPING) == 0) {
 1116                                 goto unlock_tobject;
 1117                         }
 1118                 } else if ((tobject->flags & OBJ_UNMANAGED) != 0)
 1119                         goto unlock_tobject;
 1120                 m = vm_page_lookup(tobject, tpindex);
 1121                 if (m == NULL && advise == MADV_WILLNEED) {
 1122                         /*
 1123                          * If the page is cached, reactivate it.
 1124                          */
 1125                         m = vm_page_alloc(tobject, tpindex, VM_ALLOC_IFCACHED |
 1126                             VM_ALLOC_NOBUSY);
 1127                 }
 1128                 if (m == NULL) {
 1129                         /*
 1130                          * There may be swap even if there is no backing page
 1131                          */
 1132                         if (advise == MADV_FREE && tobject->type == OBJT_SWAP)
 1133                                 swap_pager_freespace(tobject, tpindex, 1);
 1134                         /*
 1135                          * next object
 1136                          */
 1137                         backing_object = tobject->backing_object;
 1138                         if (backing_object == NULL)
 1139                                 goto unlock_tobject;
 1140                         VM_OBJECT_WLOCK(backing_object);
 1141                         tpindex += OFF_TO_IDX(tobject->backing_object_offset);
 1142                         if (tobject != object)
 1143                                 VM_OBJECT_WUNLOCK(tobject);
 1144                         tobject = backing_object;
 1145                         goto shadowlookup;
 1146                 } else if (m->valid != VM_PAGE_BITS_ALL)
 1147                         goto unlock_tobject;
 1148                 /*
 1149                  * If the page is not in a normal state, skip it.
 1150                  */
 1151                 vm_page_lock(m);
 1152                 if (m->hold_count != 0 || m->wire_count != 0) {
 1153                         vm_page_unlock(m);
 1154                         goto unlock_tobject;
 1155                 }
 1156                 KASSERT((m->flags & PG_FICTITIOUS) == 0,
 1157                     ("vm_object_madvise: page %p is fictitious", m));
 1158                 KASSERT((m->oflags & VPO_UNMANAGED) == 0,
 1159                     ("vm_object_madvise: page %p is not managed", m));
 1160                 if (vm_page_busied(m)) {
 1161                         if (advise == MADV_WILLNEED) {
 1162                                 /*
 1163                                  * Reference the page before unlocking and
 1164                                  * sleeping so that the page daemon is less
 1165                                  * likely to reclaim it. 
 1166                                  */
 1167                                 vm_page_aflag_set(m, PGA_REFERENCED);
 1168                         }
 1169                         if (object != tobject)
 1170                                 VM_OBJECT_WUNLOCK(object);
 1171                         VM_OBJECT_WUNLOCK(tobject);
 1172                         vm_page_busy_sleep(m, "madvpo");
 1173                         VM_OBJECT_WLOCK(object);
 1174                         goto relookup;
 1175                 }
 1176                 if (advise == MADV_WILLNEED) {
 1177                         vm_page_activate(m);
 1178                 } else {
 1179                         vm_page_advise(m, advise);
 1180                 }
 1181                 vm_page_unlock(m);
 1182                 if (advise == MADV_FREE && tobject->type == OBJT_SWAP)
 1183                         swap_pager_freespace(tobject, tpindex, 1);
 1184 unlock_tobject:
 1185                 if (tobject != object)
 1186                         VM_OBJECT_WUNLOCK(tobject);
 1187         }       
 1188         VM_OBJECT_WUNLOCK(object);
 1189 }
 1190 
 1191 /*
 1192  *      vm_object_shadow:
 1193  *
 1194  *      Create a new object which is backed by the
 1195  *      specified existing object range.  The source
 1196  *      object reference is deallocated.
 1197  *
 1198  *      The new object and offset into that object
 1199  *      are returned in the source parameters.
 1200  */
 1201 void
 1202 vm_object_shadow(
 1203         vm_object_t *object,    /* IN/OUT */
 1204         vm_ooffset_t *offset,   /* IN/OUT */
 1205         vm_size_t length)
 1206 {
 1207         vm_object_t source;
 1208         vm_object_t result;
 1209 
 1210         source = *object;
 1211 
 1212         /*
 1213          * Don't create the new object if the old object isn't shared.
 1214          */
 1215         if (source != NULL) {
 1216                 VM_OBJECT_WLOCK(source);
 1217                 if (source->ref_count == 1 &&
 1218                     source->handle == NULL &&
 1219                     (source->type == OBJT_DEFAULT ||
 1220                      source->type == OBJT_SWAP)) {
 1221                         VM_OBJECT_WUNLOCK(source);
 1222                         return;
 1223                 }
 1224                 VM_OBJECT_WUNLOCK(source);
 1225         }
 1226 
 1227         /*
 1228          * Allocate a new object with the given length.
 1229          */
 1230         result = vm_object_allocate(OBJT_DEFAULT, atop(length));
 1231 
 1232         /*
 1233          * The new object shadows the source object, adding a reference to it.
 1234          * Our caller changes his reference to point to the new object,
 1235          * removing a reference to the source object.  Net result: no change
 1236          * of reference count.
 1237          *
 1238          * Try to optimize the result object's page color when shadowing
 1239          * in order to maintain page coloring consistency in the combined 
 1240          * shadowed object.
 1241          */
 1242         result->backing_object = source;
 1243         /*
 1244          * Store the offset into the source object, and fix up the offset into
 1245          * the new object.
 1246          */
 1247         result->backing_object_offset = *offset;
 1248         if (source != NULL) {
 1249                 VM_OBJECT_WLOCK(source);
 1250                 LIST_INSERT_HEAD(&source->shadow_head, result, shadow_list);
 1251                 source->shadow_count++;
 1252 #if VM_NRESERVLEVEL > 0
 1253                 result->flags |= source->flags & OBJ_COLORED;
 1254                 result->pg_color = (source->pg_color + OFF_TO_IDX(*offset)) &
 1255                     ((1 << (VM_NFREEORDER - 1)) - 1);
 1256 #endif
 1257                 VM_OBJECT_WUNLOCK(source);
 1258         }
 1259 
 1260 
 1261         /*
 1262          * Return the new things
 1263          */
 1264         *offset = 0;
 1265         *object = result;
 1266 }
 1267 
 1268 /*
 1269  *      vm_object_split:
 1270  *
 1271  * Split the pages in a map entry into a new object.  This affords
 1272  * easier removal of unused pages, and keeps object inheritance from
 1273  * being a negative impact on memory usage.
 1274  */
 1275 void
 1276 vm_object_split(vm_map_entry_t entry)
 1277 {
 1278         vm_page_t m, m_next;
 1279         vm_object_t orig_object, new_object, source;
 1280         vm_pindex_t idx, offidxstart;
 1281         vm_size_t size;
 1282 
 1283         orig_object = entry->object.vm_object;
 1284         if (orig_object->type != OBJT_DEFAULT && orig_object->type != OBJT_SWAP)
 1285                 return;
 1286         if (orig_object->ref_count <= 1)
 1287                 return;
 1288         VM_OBJECT_WUNLOCK(orig_object);
 1289 
 1290         offidxstart = OFF_TO_IDX(entry->offset);
 1291         size = atop(entry->end - entry->start);
 1292 
 1293         /*
 1294          * If swap_pager_copy() is later called, it will convert new_object
 1295          * into a swap object.
 1296          */
 1297         new_object = vm_object_allocate(OBJT_DEFAULT, size);
 1298 
 1299         /*
 1300          * At this point, the new object is still private, so the order in
 1301          * which the original and new objects are locked does not matter.
 1302          */
 1303         VM_OBJECT_WLOCK(new_object);
 1304         VM_OBJECT_WLOCK(orig_object);
 1305         source = orig_object->backing_object;
 1306         if (source != NULL) {
 1307                 VM_OBJECT_WLOCK(source);
 1308                 if ((source->flags & OBJ_DEAD) != 0) {
 1309                         VM_OBJECT_WUNLOCK(source);
 1310                         VM_OBJECT_WUNLOCK(orig_object);
 1311                         VM_OBJECT_WUNLOCK(new_object);
 1312                         vm_object_deallocate(new_object);
 1313                         VM_OBJECT_WLOCK(orig_object);
 1314                         return;
 1315                 }
 1316                 LIST_INSERT_HEAD(&source->shadow_head,
 1317                                   new_object, shadow_list);
 1318                 source->shadow_count++;
 1319                 vm_object_reference_locked(source);     /* for new_object */
 1320                 vm_object_clear_flag(source, OBJ_ONEMAPPING);
 1321                 VM_OBJECT_WUNLOCK(source);
 1322                 new_object->backing_object_offset = 
 1323                         orig_object->backing_object_offset + entry->offset;
 1324                 new_object->backing_object = source;
 1325         }
 1326         if (orig_object->cred != NULL) {
 1327                 new_object->cred = orig_object->cred;
 1328                 crhold(orig_object->cred);
 1329                 new_object->charge = ptoa(size);
 1330                 KASSERT(orig_object->charge >= ptoa(size),
 1331                     ("orig_object->charge < 0"));
 1332                 orig_object->charge -= ptoa(size);
 1333         }
 1334 retry:
 1335         m = vm_page_find_least(orig_object, offidxstart);
 1336         for (; m != NULL && (idx = m->pindex - offidxstart) < size;
 1337             m = m_next) {
 1338                 m_next = TAILQ_NEXT(m, listq);
 1339 
 1340                 /*
 1341                  * We must wait for pending I/O to complete before we can
 1342                  * rename the page.
 1343                  *
 1344                  * We do not have to VM_PROT_NONE the page as mappings should
 1345                  * not be changed by this operation.
 1346                  */
 1347                 if (vm_page_busied(m)) {
 1348                         VM_OBJECT_WUNLOCK(new_object);
 1349                         vm_page_lock(m);
 1350                         VM_OBJECT_WUNLOCK(orig_object);
 1351                         vm_page_busy_sleep(m, "spltwt");
 1352                         VM_OBJECT_WLOCK(orig_object);
 1353                         VM_OBJECT_WLOCK(new_object);
 1354                         goto retry;
 1355                 }
 1356 
 1357                 /* vm_page_rename() will handle dirty and cache. */
 1358                 if (vm_page_rename(m, new_object, idx)) {
 1359                         VM_OBJECT_WUNLOCK(new_object);
 1360                         VM_OBJECT_WUNLOCK(orig_object);
 1361                         VM_WAIT;
 1362                         VM_OBJECT_WLOCK(orig_object);
 1363                         VM_OBJECT_WLOCK(new_object);
 1364                         goto retry;
 1365                 }
 1366 #if VM_NRESERVLEVEL > 0
 1367                 /*
 1368                  * If some of the reservation's allocated pages remain with
 1369                  * the original object, then transferring the reservation to
 1370                  * the new object is neither particularly beneficial nor
 1371                  * particularly harmful as compared to leaving the reservation
 1372                  * with the original object.  If, however, all of the
 1373                  * reservation's allocated pages are transferred to the new
 1374                  * object, then transferring the reservation is typically
 1375                  * beneficial.  Determining which of these two cases applies
 1376                  * would be more costly than unconditionally renaming the
 1377                  * reservation.
 1378                  */
 1379                 vm_reserv_rename(m, new_object, orig_object, offidxstart);
 1380 #endif
 1381                 if (orig_object->type == OBJT_SWAP)
 1382                         vm_page_xbusy(m);
 1383         }
 1384         if (orig_object->type == OBJT_SWAP) {
 1385                 /*
 1386                  * swap_pager_copy() can sleep, in which case the orig_object's
 1387                  * and new_object's locks are released and reacquired. 
 1388                  */
 1389                 swap_pager_copy(orig_object, new_object, offidxstart, 0);
 1390                 TAILQ_FOREACH(m, &new_object->memq, listq)
 1391                         vm_page_xunbusy(m);
 1392 
 1393                 /*
 1394                  * Transfer any cached pages from orig_object to new_object.
 1395                  * If swap_pager_copy() found swapped out pages within the
 1396                  * specified range of orig_object, then it changed
 1397                  * new_object's type to OBJT_SWAP when it transferred those
 1398                  * pages to new_object.  Otherwise, new_object's type
 1399                  * should still be OBJT_DEFAULT and orig_object should not
 1400                  * contain any cached pages within the specified range.
 1401                  */
 1402                 if (__predict_false(!vm_object_cache_is_empty(orig_object)))
 1403                         vm_page_cache_transfer(orig_object, offidxstart,
 1404                             new_object);
 1405         }
 1406         VM_OBJECT_WUNLOCK(orig_object);
 1407         VM_OBJECT_WUNLOCK(new_object);
 1408         entry->object.vm_object = new_object;
 1409         entry->offset = 0LL;
 1410         vm_object_deallocate(orig_object);
 1411         VM_OBJECT_WLOCK(new_object);
 1412 }
 1413 
 1414 #define OBSC_TEST_ALL_SHADOWED  0x0001
 1415 #define OBSC_COLLAPSE_NOWAIT    0x0002
 1416 #define OBSC_COLLAPSE_WAIT      0x0004
 1417 
 1418 static int
 1419 vm_object_backing_scan(vm_object_t object, int op)
 1420 {
 1421         int r = 1;
 1422         vm_page_t p;
 1423         vm_object_t backing_object;
 1424         vm_pindex_t backing_offset_index;
 1425 
 1426         VM_OBJECT_ASSERT_WLOCKED(object);
 1427         VM_OBJECT_ASSERT_WLOCKED(object->backing_object);
 1428 
 1429         backing_object = object->backing_object;
 1430         backing_offset_index = OFF_TO_IDX(object->backing_object_offset);
 1431 
 1432         /*
 1433          * Initial conditions
 1434          */
 1435         if (op & OBSC_TEST_ALL_SHADOWED) {
 1436                 /*
 1437                  * We do not want to have to test for the existence of cache
 1438                  * or swap pages in the backing object.  XXX but with the
 1439                  * new swapper this would be pretty easy to do.
 1440                  *
 1441                  * XXX what about anonymous MAP_SHARED memory that hasn't
 1442                  * been ZFOD faulted yet?  If we do not test for this, the
 1443                  * shadow test may succeed! XXX
 1444                  */
 1445                 if (backing_object->type != OBJT_DEFAULT) {
 1446                         return (0);
 1447                 }
 1448         }
 1449         if (op & OBSC_COLLAPSE_WAIT) {
 1450                 vm_object_set_flag(backing_object, OBJ_DEAD);
 1451         }
 1452 
 1453         /*
 1454          * Our scan
 1455          */
 1456         p = TAILQ_FIRST(&backing_object->memq);
 1457         while (p) {
 1458                 vm_page_t next = TAILQ_NEXT(p, listq);
 1459                 vm_pindex_t new_pindex = p->pindex - backing_offset_index;
 1460 
 1461                 if (op & OBSC_TEST_ALL_SHADOWED) {
 1462                         vm_page_t pp;
 1463 
 1464                         /*
 1465                          * Ignore pages outside the parent object's range
 1466                          * and outside the parent object's mapping of the 
 1467                          * backing object.
 1468                          *
 1469                          * note that we do not busy the backing object's
 1470                          * page.
 1471                          */
 1472                         if (
 1473                             p->pindex < backing_offset_index ||
 1474                             new_pindex >= object->size
 1475                         ) {
 1476                                 p = next;
 1477                                 continue;
 1478                         }
 1479 
 1480                         /*
 1481                          * See if the parent has the page or if the parent's
 1482                          * object pager has the page.  If the parent has the
 1483                          * page but the page is not valid, the parent's
 1484                          * object pager must have the page.
 1485                          *
 1486                          * If this fails, the parent does not completely shadow
 1487                          * the object and we might as well give up now.
 1488                          */
 1489 
 1490                         pp = vm_page_lookup(object, new_pindex);
 1491                         if (
 1492                             (pp == NULL || pp->valid == 0) &&
 1493                             !vm_pager_has_page(object, new_pindex, NULL, NULL)
 1494                         ) {
 1495                                 r = 0;
 1496                                 break;
 1497                         }
 1498                 }
 1499 
 1500                 /*
 1501                  * Check for busy page
 1502                  */
 1503                 if (op & (OBSC_COLLAPSE_WAIT | OBSC_COLLAPSE_NOWAIT)) {
 1504                         vm_page_t pp;
 1505 
 1506                         if (op & OBSC_COLLAPSE_NOWAIT) {
 1507                                 if (!p->valid || vm_page_busied(p)) {
 1508                                         p = next;
 1509                                         continue;
 1510                                 }
 1511                         } else if (op & OBSC_COLLAPSE_WAIT) {
 1512                                 if (vm_page_busied(p)) {
 1513                                         VM_OBJECT_WUNLOCK(object);
 1514                                         vm_page_lock(p);
 1515                                         VM_OBJECT_WUNLOCK(backing_object);
 1516                                         vm_page_busy_sleep(p, "vmocol");
 1517                                         VM_OBJECT_WLOCK(object);
 1518                                         VM_OBJECT_WLOCK(backing_object);
 1519                                         /*
 1520                                          * If we slept, anything could have
 1521                                          * happened.  Since the object is
 1522                                          * marked dead, the backing offset
 1523                                          * should not have changed so we
 1524                                          * just restart our scan.
 1525                                          */
 1526                                         p = TAILQ_FIRST(&backing_object->memq);
 1527                                         continue;
 1528                                 }
 1529                         }
 1530 
 1531                         KASSERT(
 1532                             p->object == backing_object,
 1533                             ("vm_object_backing_scan: object mismatch")
 1534                         );
 1535 
 1536                         if (
 1537                             p->pindex < backing_offset_index ||
 1538                             new_pindex >= object->size
 1539                         ) {
 1540                                 if (backing_object->type == OBJT_SWAP)
 1541                                         swap_pager_freespace(backing_object, 
 1542                                             p->pindex, 1);
 1543 
 1544                                 /*
 1545                                  * Page is out of the parent object's range, we 
 1546                                  * can simply destroy it. 
 1547                                  */
 1548                                 vm_page_lock(p);
 1549                                 KASSERT(!pmap_page_is_mapped(p),
 1550                                     ("freeing mapped page %p", p));
 1551                                 if (p->wire_count == 0)
 1552                                         vm_page_free(p);
 1553                                 else
 1554                                         vm_page_remove(p);
 1555                                 vm_page_unlock(p);
 1556                                 p = next;
 1557                                 continue;
 1558                         }
 1559 
 1560                         pp = vm_page_lookup(object, new_pindex);
 1561                         if (
 1562                             (op & OBSC_COLLAPSE_NOWAIT) != 0 &&
 1563                             (pp != NULL && pp->valid == 0)
 1564                         ) {
 1565                                 if (backing_object->type == OBJT_SWAP)
 1566                                         swap_pager_freespace(backing_object, 
 1567                                             p->pindex, 1);
 1568 
 1569                                 /*
 1570                                  * The page in the parent is not (yet) valid.
 1571                                  * We don't know anything about the state of
 1572                                  * the original page.  It might be mapped,
 1573                                  * so we must avoid the next if here.
 1574                                  *
 1575                                  * This is due to a race in vm_fault() where
 1576                                  * we must unbusy the original (backing_obj)
 1577                                  * page before we can (re)lock the parent.
 1578                                  * Hence we can get here.
 1579                                  */
 1580                                 p = next;
 1581                                 continue;
 1582                         }
 1583                         if (
 1584                             pp != NULL ||
 1585                             vm_pager_has_page(object, new_pindex, NULL, NULL)
 1586                         ) {
 1587                                 if (backing_object->type == OBJT_SWAP)
 1588                                         swap_pager_freespace(backing_object, 
 1589                                             p->pindex, 1);
 1590 
 1591                                 /*
 1592                                  * page already exists in parent OR swap exists
 1593                                  * for this location in the parent.  Destroy 
 1594                                  * the original page from the backing object.
 1595                                  *
 1596                                  * Leave the parent's page alone
 1597                                  */
 1598                                 vm_page_lock(p);
 1599                                 KASSERT(!pmap_page_is_mapped(p),
 1600                                     ("freeing mapped page %p", p));
 1601                                 if (p->wire_count == 0)
 1602                                         vm_page_free(p);
 1603                                 else
 1604                                         vm_page_remove(p);
 1605                                 vm_page_unlock(p);
 1606                                 p = next;
 1607                                 continue;
 1608                         }
 1609 
 1610                         /*
 1611                          * Page does not exist in parent, rename the
 1612                          * page from the backing object to the main object. 
 1613                          *
 1614                          * If the page was mapped to a process, it can remain 
 1615                          * mapped through the rename.
 1616                          * vm_page_rename() will handle dirty and cache.
 1617                          */
 1618                         if (vm_page_rename(p, object, new_pindex)) {
 1619                                 if (op & OBSC_COLLAPSE_NOWAIT) {
 1620                                         p = next;
 1621                                         continue;
 1622                                 }
 1623                                 VM_OBJECT_WLOCK(backing_object);
 1624                                 VM_OBJECT_WUNLOCK(object);
 1625                                 VM_WAIT;
 1626                                 VM_OBJECT_WLOCK(object);
 1627                                 VM_OBJECT_WLOCK(backing_object);
 1628                                 p = TAILQ_FIRST(&backing_object->memq);
 1629                                 continue;
 1630                         }
 1631                         if (backing_object->type == OBJT_SWAP)
 1632                                 swap_pager_freespace(backing_object, p->pindex,
 1633                                     1);
 1634 
 1635 #if VM_NRESERVLEVEL > 0
 1636                         /*
 1637                          * Rename the reservation.
 1638                          */
 1639                         vm_reserv_rename(p, object, backing_object,
 1640                             backing_offset_index);
 1641 #endif
 1642                 }
 1643                 p = next;
 1644         }
 1645         return (r);
 1646 }
 1647 
 1648 
 1649 /*
 1650  * this version of collapse allows the operation to occur earlier and
 1651  * when paging_in_progress is true for an object...  This is not a complete
 1652  * operation, but should plug 99.9% of the rest of the leaks.
 1653  */
 1654 static void
 1655 vm_object_qcollapse(vm_object_t object)
 1656 {
 1657         vm_object_t backing_object = object->backing_object;
 1658 
 1659         VM_OBJECT_ASSERT_WLOCKED(object);
 1660         VM_OBJECT_ASSERT_WLOCKED(backing_object);
 1661 
 1662         if (backing_object->ref_count != 1)
 1663                 return;
 1664 
 1665         vm_object_backing_scan(object, OBSC_COLLAPSE_NOWAIT);
 1666 }
 1667 
 1668 /*
 1669  *      vm_object_collapse:
 1670  *
 1671  *      Collapse an object with the object backing it.
 1672  *      Pages in the backing object are moved into the
 1673  *      parent, and the backing object is deallocated.
 1674  */
 1675 void
 1676 vm_object_collapse(vm_object_t object)
 1677 {
 1678         VM_OBJECT_ASSERT_WLOCKED(object);
 1679         
 1680         while (TRUE) {
 1681                 vm_object_t backing_object;
 1682 
 1683                 /*
 1684                  * Verify that the conditions are right for collapse:
 1685                  *
 1686                  * The object exists and the backing object exists.
 1687                  */
 1688                 if ((backing_object = object->backing_object) == NULL)
 1689                         break;
 1690 
 1691                 /*
 1692                  * we check the backing object first, because it is most likely
 1693                  * not collapsable.
 1694                  */
 1695                 VM_OBJECT_WLOCK(backing_object);
 1696                 if (backing_object->handle != NULL ||
 1697                     (backing_object->type != OBJT_DEFAULT &&
 1698                      backing_object->type != OBJT_SWAP) ||
 1699                     (backing_object->flags & OBJ_DEAD) ||
 1700                     object->handle != NULL ||
 1701                     (object->type != OBJT_DEFAULT &&
 1702                      object->type != OBJT_SWAP) ||
 1703                     (object->flags & OBJ_DEAD)) {
 1704                         VM_OBJECT_WUNLOCK(backing_object);
 1705                         break;
 1706                 }
 1707 
 1708                 if (
 1709                     object->paging_in_progress != 0 ||
 1710                     backing_object->paging_in_progress != 0
 1711                 ) {
 1712                         vm_object_qcollapse(object);
 1713                         VM_OBJECT_WUNLOCK(backing_object);
 1714                         break;
 1715                 }
 1716                 /*
 1717                  * We know that we can either collapse the backing object (if
 1718                  * the parent is the only reference to it) or (perhaps) have
 1719                  * the parent bypass the object if the parent happens to shadow
 1720                  * all the resident pages in the entire backing object.
 1721                  *
 1722                  * This is ignoring pager-backed pages such as swap pages.
 1723                  * vm_object_backing_scan fails the shadowing test in this
 1724                  * case.
 1725                  */
 1726                 if (backing_object->ref_count == 1) {
 1727                         /*
 1728                          * If there is exactly one reference to the backing
 1729                          * object, we can collapse it into the parent.  
 1730                          */
 1731                         vm_object_backing_scan(object, OBSC_COLLAPSE_WAIT);
 1732 
 1733 #if VM_NRESERVLEVEL > 0
 1734                         /*
 1735                          * Break any reservations from backing_object.
 1736                          */
 1737                         if (__predict_false(!LIST_EMPTY(&backing_object->rvq)))
 1738                                 vm_reserv_break_all(backing_object);
 1739 #endif
 1740 
 1741                         /*
 1742                          * Move the pager from backing_object to object.
 1743                          */
 1744                         if (backing_object->type == OBJT_SWAP) {
 1745                                 /*
 1746                                  * swap_pager_copy() can sleep, in which case
 1747                                  * the backing_object's and object's locks are
 1748                                  * released and reacquired.
 1749                                  * Since swap_pager_copy() is being asked to
 1750                                  * destroy the source, it will change the
 1751                                  * backing_object's type to OBJT_DEFAULT.
 1752                                  */
 1753                                 swap_pager_copy(
 1754                                     backing_object,
 1755                                     object,
 1756                                     OFF_TO_IDX(object->backing_object_offset), TRUE);
 1757 
 1758                                 /*
 1759                                  * Free any cached pages from backing_object.
 1760                                  */
 1761                                 if (__predict_false(
 1762                                     !vm_object_cache_is_empty(backing_object)))
 1763                                         vm_page_cache_free(backing_object, 0, 0);
 1764                         }
 1765                         /*
 1766                          * Object now shadows whatever backing_object did.
 1767                          * Note that the reference to 
 1768                          * backing_object->backing_object moves from within 
 1769                          * backing_object to within object.
 1770                          */
 1771                         LIST_REMOVE(object, shadow_list);
 1772                         backing_object->shadow_count--;
 1773                         if (backing_object->backing_object) {
 1774                                 VM_OBJECT_WLOCK(backing_object->backing_object);
 1775                                 LIST_REMOVE(backing_object, shadow_list);
 1776                                 LIST_INSERT_HEAD(
 1777                                     &backing_object->backing_object->shadow_head,
 1778                                     object, shadow_list);
 1779                                 /*
 1780                                  * The shadow_count has not changed.
 1781                                  */
 1782                                 VM_OBJECT_WUNLOCK(backing_object->backing_object);
 1783                         }
 1784                         object->backing_object = backing_object->backing_object;
 1785                         object->backing_object_offset +=
 1786                             backing_object->backing_object_offset;
 1787 
 1788                         /*
 1789                          * Discard backing_object.
 1790                          *
 1791                          * Since the backing object has no pages, no pager left,
 1792                          * and no object references within it, all that is
 1793                          * necessary is to dispose of it.
 1794                          */
 1795                         KASSERT(backing_object->ref_count == 1, (
 1796 "backing_object %p was somehow re-referenced during collapse!",
 1797                             backing_object));
 1798                         VM_OBJECT_WUNLOCK(backing_object);
 1799                         vm_object_destroy(backing_object);
 1800 
 1801                         object_collapses++;
 1802                 } else {
 1803                         vm_object_t new_backing_object;
 1804 
 1805                         /*
 1806                          * If we do not entirely shadow the backing object,
 1807                          * there is nothing we can do so we give up.
 1808                          */
 1809                         if (object->resident_page_count != object->size &&
 1810                             vm_object_backing_scan(object,
 1811                             OBSC_TEST_ALL_SHADOWED) == 0) {
 1812                                 VM_OBJECT_WUNLOCK(backing_object);
 1813                                 break;
 1814                         }
 1815 
 1816                         /*
 1817                          * Make the parent shadow the next object in the
 1818                          * chain.  Deallocating backing_object will not remove
 1819                          * it, since its reference count is at least 2.
 1820                          */
 1821                         LIST_REMOVE(object, shadow_list);
 1822                         backing_object->shadow_count--;
 1823 
 1824                         new_backing_object = backing_object->backing_object;
 1825                         if ((object->backing_object = new_backing_object) != NULL) {
 1826                                 VM_OBJECT_WLOCK(new_backing_object);
 1827                                 LIST_INSERT_HEAD(
 1828                                     &new_backing_object->shadow_head,
 1829                                     object,
 1830                                     shadow_list
 1831                                 );
 1832                                 new_backing_object->shadow_count++;
 1833                                 vm_object_reference_locked(new_backing_object);
 1834                                 VM_OBJECT_WUNLOCK(new_backing_object);
 1835                                 object->backing_object_offset +=
 1836                                         backing_object->backing_object_offset;
 1837                         }
 1838 
 1839                         /*
 1840                          * Drop the reference count on backing_object. Since
 1841                          * its ref_count was at least 2, it will not vanish.
 1842                          */
 1843                         backing_object->ref_count--;
 1844                         VM_OBJECT_WUNLOCK(backing_object);
 1845                         object_bypasses++;
 1846                 }
 1847 
 1848                 /*
 1849                  * Try again with this object's new backing object.
 1850                  */
 1851         }
 1852 }
 1853 
 1854 /*
 1855  *      vm_object_page_remove:
 1856  *
 1857  *      For the given object, either frees or invalidates each of the
 1858  *      specified pages.  In general, a page is freed.  However, if a page is
 1859  *      wired for any reason other than the existence of a managed, wired
 1860  *      mapping, then it may be invalidated but not removed from the object.
 1861  *      Pages are specified by the given range ["start", "end") and the option
 1862  *      OBJPR_CLEANONLY.  As a special case, if "end" is zero, then the range
 1863  *      extends from "start" to the end of the object.  If the option
 1864  *      OBJPR_CLEANONLY is specified, then only the non-dirty pages within the
 1865  *      specified range are affected.  If the option OBJPR_NOTMAPPED is
 1866  *      specified, then the pages within the specified range must have no
 1867  *      mappings.  Otherwise, if this option is not specified, any mappings to
 1868  *      the specified pages are removed before the pages are freed or
 1869  *      invalidated.
 1870  *
 1871  *      In general, this operation should only be performed on objects that
 1872  *      contain managed pages.  There are, however, two exceptions.  First, it
 1873  *      is performed on the kernel and kmem objects by vm_map_entry_delete().
 1874  *      Second, it is used by msync(..., MS_INVALIDATE) to invalidate device-
 1875  *      backed pages.  In both of these cases, the option OBJPR_CLEANONLY must
 1876  *      not be specified and the option OBJPR_NOTMAPPED must be specified.
 1877  *
 1878  *      The object must be locked.
 1879  */
 1880 void
 1881 vm_object_page_remove(vm_object_t object, vm_pindex_t start, vm_pindex_t end,
 1882     int options)
 1883 {
 1884         vm_page_t p, next;
 1885         int wirings;
 1886 
 1887         VM_OBJECT_ASSERT_WLOCKED(object);
 1888         KASSERT((object->flags & OBJ_UNMANAGED) == 0 ||
 1889             (options & (OBJPR_CLEANONLY | OBJPR_NOTMAPPED)) == OBJPR_NOTMAPPED,
 1890             ("vm_object_page_remove: illegal options for object %p", object));
 1891         if (object->resident_page_count == 0)
 1892                 goto skipmemq;
 1893         vm_object_pip_add(object, 1);
 1894 again:
 1895         p = vm_page_find_least(object, start);
 1896 
 1897         /*
 1898          * Here, the variable "p" is either (1) the page with the least pindex
 1899          * greater than or equal to the parameter "start" or (2) NULL. 
 1900          */
 1901         for (; p != NULL && (p->pindex < end || end == 0); p = next) {
 1902                 next = TAILQ_NEXT(p, listq);
 1903 
 1904                 /*
 1905                  * If the page is wired for any reason besides the existence
 1906                  * of managed, wired mappings, then it cannot be freed.  For
 1907                  * example, fictitious pages, which represent device memory,
 1908                  * are inherently wired and cannot be freed.  They can,
 1909                  * however, be invalidated if the option OBJPR_CLEANONLY is
 1910                  * not specified.
 1911                  */
 1912                 vm_page_lock(p);
 1913                 if (vm_page_xbusied(p)) {
 1914                         VM_OBJECT_WUNLOCK(object);
 1915                         vm_page_busy_sleep(p, "vmopax");
 1916                         VM_OBJECT_WLOCK(object);
 1917                         goto again;
 1918                 }
 1919                 if ((wirings = p->wire_count) != 0 &&
 1920                     (wirings = pmap_page_wired_mappings(p)) != p->wire_count) {
 1921                         if ((options & (OBJPR_NOTWIRED | OBJPR_NOTMAPPED)) ==
 1922                             0) {
 1923                                 pmap_remove_all(p);
 1924                                 /* Account for removal of wired mappings. */
 1925                                 if (wirings != 0)
 1926                                         p->wire_count -= wirings;
 1927                         }
 1928                         if ((options & OBJPR_CLEANONLY) == 0) {
 1929                                 p->valid = 0;
 1930                                 vm_page_undirty(p);
 1931                         }
 1932                         goto next;
 1933                 }
 1934                 if (vm_page_busied(p)) {
 1935                         VM_OBJECT_WUNLOCK(object);
 1936                         vm_page_busy_sleep(p, "vmopar");
 1937                         VM_OBJECT_WLOCK(object);
 1938                         goto again;
 1939                 }
 1940                 KASSERT((p->flags & PG_FICTITIOUS) == 0,
 1941                     ("vm_object_page_remove: page %p is fictitious", p));
 1942                 if ((options & OBJPR_CLEANONLY) != 0 && p->valid != 0) {
 1943                         if ((options & OBJPR_NOTMAPPED) == 0)
 1944                                 pmap_remove_write(p);
 1945                         if (p->dirty)
 1946                                 goto next;
 1947                 }
 1948                 if ((options & OBJPR_NOTMAPPED) == 0) {
 1949                         if ((options & OBJPR_NOTWIRED) != 0 && wirings != 0)
 1950                                 goto next;
 1951                         pmap_remove_all(p);
 1952                         /* Account for removal of wired mappings. */
 1953                         if (wirings != 0) {
 1954                                 KASSERT(p->wire_count == wirings,
 1955                                     ("inconsistent wire count %d %d %p",
 1956                                     p->wire_count, wirings, p));
 1957                                 p->wire_count = 0;
 1958                                 atomic_subtract_int(&cnt.v_wire_count, 1);
 1959                         }
 1960                 }
 1961                 vm_page_free(p);
 1962 next:
 1963                 vm_page_unlock(p);
 1964         }
 1965         vm_object_pip_wakeup(object);
 1966 skipmemq:
 1967         if (__predict_false(!vm_object_cache_is_empty(object)))
 1968                 vm_page_cache_free(object, start, end);
 1969 }
 1970 
 1971 /*
 1972  *      vm_object_page_cache:
 1973  *
 1974  *      For the given object, attempt to move the specified clean
 1975  *      pages to the cache queue.  If a page is wired for any reason,
 1976  *      then it will not be changed.  Pages are specified by the given
 1977  *      range ["start", "end").  As a special case, if "end" is zero,
 1978  *      then the range extends from "start" to the end of the object.
 1979  *      Any mappings to the specified pages are removed before the
 1980  *      pages are moved to the cache queue.
 1981  *
 1982  *      This operation should only be performed on objects that
 1983  *      contain non-fictitious, managed pages.
 1984  *
 1985  *      The object must be locked.
 1986  */
 1987 void
 1988 vm_object_page_cache(vm_object_t object, vm_pindex_t start, vm_pindex_t end)
 1989 {
 1990         struct mtx *mtx, *new_mtx;
 1991         vm_page_t p, next;
 1992 
 1993         VM_OBJECT_ASSERT_WLOCKED(object);
 1994         KASSERT((object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0,
 1995             ("vm_object_page_cache: illegal object %p", object));
 1996         if (object->resident_page_count == 0)
 1997                 return;
 1998         p = vm_page_find_least(object, start);
 1999 
 2000         /*
 2001          * Here, the variable "p" is either (1) the page with the least pindex
 2002          * greater than or equal to the parameter "start" or (2) NULL. 
 2003          */
 2004         mtx = NULL;
 2005         for (; p != NULL && (p->pindex < end || end == 0); p = next) {
 2006                 next = TAILQ_NEXT(p, listq);
 2007 
 2008                 /*
 2009                  * Avoid releasing and reacquiring the same page lock.
 2010                  */
 2011                 new_mtx = vm_page_lockptr(p);
 2012                 if (mtx != new_mtx) {
 2013                         if (mtx != NULL)
 2014                                 mtx_unlock(mtx);
 2015                         mtx = new_mtx;
 2016                         mtx_lock(mtx);
 2017                 }
 2018                 vm_page_try_to_cache(p);
 2019         }
 2020         if (mtx != NULL)
 2021                 mtx_unlock(mtx);
 2022 }
 2023 
 2024 /*
 2025  *      Populate the specified range of the object with valid pages.  Returns
 2026  *      TRUE if the range is successfully populated and FALSE otherwise.
 2027  *
 2028  *      Note: This function should be optimized to pass a larger array of
 2029  *      pages to vm_pager_get_pages() before it is applied to a non-
 2030  *      OBJT_DEVICE object.
 2031  *
 2032  *      The object must be locked.
 2033  */
 2034 boolean_t
 2035 vm_object_populate(vm_object_t object, vm_pindex_t start, vm_pindex_t end)
 2036 {
 2037         vm_page_t m, ma[1];
 2038         vm_pindex_t pindex;
 2039         int rv;
 2040 
 2041         VM_OBJECT_ASSERT_WLOCKED(object);
 2042         for (pindex = start; pindex < end; pindex++) {
 2043                 m = vm_page_grab(object, pindex, VM_ALLOC_NORMAL);
 2044                 if (m->valid != VM_PAGE_BITS_ALL) {
 2045                         ma[0] = m;
 2046                         rv = vm_pager_get_pages(object, ma, 1, 0);
 2047                         m = vm_page_lookup(object, pindex);
 2048                         if (m == NULL)
 2049                                 break;
 2050                         if (rv != VM_PAGER_OK) {
 2051                                 vm_page_lock(m);
 2052                                 vm_page_free(m);
 2053                                 vm_page_unlock(m);
 2054                                 break;
 2055                         }
 2056                 }
 2057                 /*
 2058                  * Keep "m" busy because a subsequent iteration may unlock
 2059                  * the object.
 2060                  */
 2061         }
 2062         if (pindex > start) {
 2063                 m = vm_page_lookup(object, start);
 2064                 while (m != NULL && m->pindex < pindex) {
 2065                         vm_page_xunbusy(m);
 2066                         m = TAILQ_NEXT(m, listq);
 2067                 }
 2068         }
 2069         return (pindex == end);
 2070 }
 2071 
 2072 /*
 2073  *      Routine:        vm_object_coalesce
 2074  *      Function:       Coalesces two objects backing up adjoining
 2075  *                      regions of memory into a single object.
 2076  *
 2077  *      returns TRUE if objects were combined.
 2078  *
 2079  *      NOTE:   Only works at the moment if the second object is NULL -
 2080  *              if it's not, which object do we lock first?
 2081  *
 2082  *      Parameters:
 2083  *              prev_object     First object to coalesce
 2084  *              prev_offset     Offset into prev_object
 2085  *              prev_size       Size of reference to prev_object
 2086  *              next_size       Size of reference to the second object
 2087  *              reserved        Indicator that extension region has
 2088  *                              swap accounted for
 2089  *
 2090  *      Conditions:
 2091  *      The object must *not* be locked.
 2092  */
 2093 boolean_t
 2094 vm_object_coalesce(vm_object_t prev_object, vm_ooffset_t prev_offset,
 2095     vm_size_t prev_size, vm_size_t next_size, boolean_t reserved)
 2096 {
 2097         vm_pindex_t next_pindex;
 2098 
 2099         if (prev_object == NULL)
 2100                 return (TRUE);
 2101         VM_OBJECT_WLOCK(prev_object);
 2102         if ((prev_object->type != OBJT_DEFAULT &&
 2103             prev_object->type != OBJT_SWAP) ||
 2104             (prev_object->flags & OBJ_TMPFS) != 0) {
 2105                 VM_OBJECT_WUNLOCK(prev_object);
 2106                 return (FALSE);
 2107         }
 2108 
 2109         /*
 2110          * Try to collapse the object first
 2111          */
 2112         vm_object_collapse(prev_object);
 2113 
 2114         /*
 2115          * Can't coalesce if: . more than one reference . paged out . shadows
 2116          * another object . has a copy elsewhere (any of which mean that the
 2117          * pages not mapped to prev_entry may be in use anyway)
 2118          */
 2119         if (prev_object->backing_object != NULL) {
 2120                 VM_OBJECT_WUNLOCK(prev_object);
 2121                 return (FALSE);
 2122         }
 2123 
 2124         prev_size >>= PAGE_SHIFT;
 2125         next_size >>= PAGE_SHIFT;
 2126         next_pindex = OFF_TO_IDX(prev_offset) + prev_size;
 2127 
 2128         if ((prev_object->ref_count > 1) &&
 2129             (prev_object->size != next_pindex)) {
 2130                 VM_OBJECT_WUNLOCK(prev_object);
 2131                 return (FALSE);
 2132         }
 2133 
 2134         /*
 2135          * Account for the charge.
 2136          */
 2137         if (prev_object->cred != NULL) {
 2138 
 2139                 /*
 2140                  * If prev_object was charged, then this mapping,
 2141                  * althought not charged now, may become writable
 2142                  * later. Non-NULL cred in the object would prevent
 2143                  * swap reservation during enabling of the write
 2144                  * access, so reserve swap now. Failed reservation
 2145                  * cause allocation of the separate object for the map
 2146                  * entry, and swap reservation for this entry is
 2147                  * managed in appropriate time.
 2148                  */
 2149                 if (!reserved && !swap_reserve_by_cred(ptoa(next_size),
 2150                     prev_object->cred)) {
 2151                         return (FALSE);
 2152                 }
 2153                 prev_object->charge += ptoa(next_size);
 2154         }
 2155 
 2156         /*
 2157          * Remove any pages that may still be in the object from a previous
 2158          * deallocation.
 2159          */
 2160         if (next_pindex < prev_object->size) {
 2161                 vm_object_page_remove(prev_object, next_pindex, next_pindex +
 2162                     next_size, 0);
 2163                 if (prev_object->type == OBJT_SWAP)
 2164                         swap_pager_freespace(prev_object,
 2165                                              next_pindex, next_size);
 2166 #if 0
 2167                 if (prev_object->cred != NULL) {
 2168                         KASSERT(prev_object->charge >=
 2169                             ptoa(prev_object->size - next_pindex),
 2170                             ("object %p overcharged 1 %jx %jx", prev_object,
 2171                                 (uintmax_t)next_pindex, (uintmax_t)next_size));
 2172                         prev_object->charge -= ptoa(prev_object->size -
 2173                             next_pindex);
 2174                 }
 2175 #endif
 2176         }
 2177 
 2178         /*
 2179          * Extend the object if necessary.
 2180          */
 2181         if (next_pindex + next_size > prev_object->size)
 2182                 prev_object->size = next_pindex + next_size;
 2183 
 2184         VM_OBJECT_WUNLOCK(prev_object);
 2185         return (TRUE);
 2186 }
 2187 
 2188 void
 2189 vm_object_set_writeable_dirty(vm_object_t object)
 2190 {
 2191 
 2192         VM_OBJECT_ASSERT_WLOCKED(object);
 2193         if (object->type != OBJT_VNODE)
 2194                 return;
 2195         object->generation++;
 2196         if ((object->flags & OBJ_MIGHTBEDIRTY) != 0)
 2197                 return;
 2198         vm_object_set_flag(object, OBJ_MIGHTBEDIRTY);
 2199 }
 2200 
 2201 #include "opt_ddb.h"
 2202 #ifdef DDB
 2203 #include <sys/kernel.h>
 2204 
 2205 #include <sys/cons.h>
 2206 
 2207 #include <ddb/ddb.h>
 2208 
 2209 static int
 2210 _vm_object_in_map(vm_map_t map, vm_object_t object, vm_map_entry_t entry)
 2211 {
 2212         vm_map_t tmpm;
 2213         vm_map_entry_t tmpe;
 2214         vm_object_t obj;
 2215         int entcount;
 2216 
 2217         if (map == 0)
 2218                 return 0;
 2219 
 2220         if (entry == 0) {
 2221                 tmpe = map->header.next;
 2222                 entcount = map->nentries;
 2223                 while (entcount-- && (tmpe != &map->header)) {
 2224                         if (_vm_object_in_map(map, object, tmpe)) {
 2225                                 return 1;
 2226                         }
 2227                         tmpe = tmpe->next;
 2228                 }
 2229         } else if (entry->eflags & MAP_ENTRY_IS_SUB_MAP) {
 2230                 tmpm = entry->object.sub_map;
 2231                 tmpe = tmpm->header.next;
 2232                 entcount = tmpm->nentries;
 2233                 while (entcount-- && tmpe != &tmpm->header) {
 2234                         if (_vm_object_in_map(tmpm, object, tmpe)) {
 2235                                 return 1;
 2236                         }
 2237                         tmpe = tmpe->next;
 2238                 }
 2239         } else if ((obj = entry->object.vm_object) != NULL) {
 2240                 for (; obj; obj = obj->backing_object)
 2241                         if (obj == object) {
 2242                                 return 1;
 2243                         }
 2244         }
 2245         return 0;
 2246 }
 2247 
 2248 static int
 2249 vm_object_in_map(vm_object_t object)
 2250 {
 2251         struct proc *p;
 2252 
 2253         /* sx_slock(&allproc_lock); */
 2254         FOREACH_PROC_IN_SYSTEM(p) {
 2255                 if (!p->p_vmspace /* || (p->p_flag & (P_SYSTEM|P_WEXIT)) */)
 2256                         continue;
 2257                 if (_vm_object_in_map(&p->p_vmspace->vm_map, object, 0)) {
 2258                         /* sx_sunlock(&allproc_lock); */
 2259                         return 1;
 2260                 }
 2261         }
 2262         /* sx_sunlock(&allproc_lock); */
 2263         if (_vm_object_in_map(kernel_map, object, 0))
 2264                 return 1;
 2265         return 0;
 2266 }
 2267 
 2268 DB_SHOW_COMMAND(vmochk, vm_object_check)
 2269 {
 2270         vm_object_t object;
 2271 
 2272         /*
 2273          * make sure that internal objs are in a map somewhere
 2274          * and none have zero ref counts.
 2275          */
 2276         TAILQ_FOREACH(object, &vm_object_list, object_list) {
 2277                 if (object->handle == NULL &&
 2278                     (object->type == OBJT_DEFAULT || object->type == OBJT_SWAP)) {
 2279                         if (object->ref_count == 0) {
 2280                                 db_printf("vmochk: internal obj has zero ref count: %ld\n",
 2281                                         (long)object->size);
 2282                         }
 2283                         if (!vm_object_in_map(object)) {
 2284                                 db_printf(
 2285                         "vmochk: internal obj is not in a map: "
 2286                         "ref: %d, size: %lu: 0x%lx, backing_object: %p\n",
 2287                                     object->ref_count, (u_long)object->size, 
 2288                                     (u_long)object->size,
 2289                                     (void *)object->backing_object);
 2290                         }
 2291                 }
 2292         }
 2293 }
 2294 
 2295 /*
 2296  *      vm_object_print:        [ debug ]
 2297  */
 2298 DB_SHOW_COMMAND(object, vm_object_print_static)
 2299 {
 2300         /* XXX convert args. */
 2301         vm_object_t object = (vm_object_t)addr;
 2302         boolean_t full = have_addr;
 2303 
 2304         vm_page_t p;
 2305 
 2306         /* XXX count is an (unused) arg.  Avoid shadowing it. */
 2307 #define count   was_count
 2308 
 2309         int count;
 2310 
 2311         if (object == NULL)
 2312                 return;
 2313 
 2314         db_iprintf(
 2315             "Object %p: type=%d, size=0x%jx, res=%d, ref=%d, flags=0x%x ruid %d charge %jx\n",
 2316             object, (int)object->type, (uintmax_t)object->size,
 2317             object->resident_page_count, object->ref_count, object->flags,
 2318             object->cred ? object->cred->cr_ruid : -1, (uintmax_t)object->charge);
 2319         db_iprintf(" sref=%d, backing_object(%d)=(%p)+0x%jx\n",
 2320             object->shadow_count, 
 2321             object->backing_object ? object->backing_object->ref_count : 0,
 2322             object->backing_object, (uintmax_t)object->backing_object_offset);
 2323 
 2324         if (!full)
 2325                 return;
 2326 
 2327         db_indent += 2;
 2328         count = 0;
 2329         TAILQ_FOREACH(p, &object->memq, listq) {
 2330                 if (count == 0)
 2331                         db_iprintf("memory:=");
 2332                 else if (count == 6) {
 2333                         db_printf("\n");
 2334                         db_iprintf(" ...");
 2335                         count = 0;
 2336                 } else
 2337                         db_printf(",");
 2338                 count++;
 2339 
 2340                 db_printf("(off=0x%jx,page=0x%jx)",
 2341                     (uintmax_t)p->pindex, (uintmax_t)VM_PAGE_TO_PHYS(p));
 2342         }
 2343         if (count != 0)
 2344                 db_printf("\n");
 2345         db_indent -= 2;
 2346 }
 2347 
 2348 /* XXX. */
 2349 #undef count
 2350 
 2351 /* XXX need this non-static entry for calling from vm_map_print. */
 2352 void
 2353 vm_object_print(
 2354         /* db_expr_t */ long addr,
 2355         boolean_t have_addr,
 2356         /* db_expr_t */ long count,
 2357         char *modif)
 2358 {
 2359         vm_object_print_static(addr, have_addr, count, modif);
 2360 }
 2361 
 2362 DB_SHOW_COMMAND(vmopag, vm_object_print_pages)
 2363 {
 2364         vm_object_t object;
 2365         vm_pindex_t fidx;
 2366         vm_paddr_t pa;
 2367         vm_page_t m, prev_m;
 2368         int rcount, nl, c;
 2369 
 2370         nl = 0;
 2371         TAILQ_FOREACH(object, &vm_object_list, object_list) {
 2372                 db_printf("new object: %p\n", (void *)object);
 2373                 if (nl > 18) {
 2374                         c = cngetc();
 2375                         if (c != ' ')
 2376                                 return;
 2377                         nl = 0;
 2378                 }
 2379                 nl++;
 2380                 rcount = 0;
 2381                 fidx = 0;
 2382                 pa = -1;
 2383                 TAILQ_FOREACH(m, &object->memq, listq) {
 2384                         if (m->pindex > 128)
 2385                                 break;
 2386                         if ((prev_m = TAILQ_PREV(m, pglist, listq)) != NULL &&
 2387                             prev_m->pindex + 1 != m->pindex) {
 2388                                 if (rcount) {
 2389                                         db_printf(" index(%ld)run(%d)pa(0x%lx)\n",
 2390                                                 (long)fidx, rcount, (long)pa);
 2391                                         if (nl > 18) {
 2392                                                 c = cngetc();
 2393                                                 if (c != ' ')
 2394                                                         return;
 2395                                                 nl = 0;
 2396                                         }
 2397                                         nl++;
 2398                                         rcount = 0;
 2399                                 }
 2400                         }                               
 2401                         if (rcount &&
 2402                                 (VM_PAGE_TO_PHYS(m) == pa + rcount * PAGE_SIZE)) {
 2403                                 ++rcount;
 2404                                 continue;
 2405                         }
 2406                         if (rcount) {
 2407                                 db_printf(" index(%ld)run(%d)pa(0x%lx)\n",
 2408                                         (long)fidx, rcount, (long)pa);
 2409                                 if (nl > 18) {
 2410                                         c = cngetc();
 2411                                         if (c != ' ')
 2412                                                 return;
 2413                                         nl = 0;
 2414                                 }
 2415                                 nl++;
 2416                         }
 2417                         fidx = m->pindex;
 2418                         pa = VM_PAGE_TO_PHYS(m);
 2419                         rcount = 1;
 2420                 }
 2421                 if (rcount) {
 2422                         db_printf(" index(%ld)run(%d)pa(0x%lx)\n",
 2423                                 (long)fidx, rcount, (long)pa);
 2424                         if (nl > 18) {
 2425                                 c = cngetc();
 2426                                 if (c != ' ')
 2427                                         return;
 2428                                 nl = 0;
 2429                         }
 2430                         nl++;
 2431                 }
 2432         }
 2433 }
 2434 #endif /* DDB */

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