sys/vm/vm_fault.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  * Copyright (c) 1994 John S. Dyson
   5  * All rights reserved.
   6  * Copyright (c) 1994 David Greenman
   7  * All rights reserved.
   8  *
   9  *
  10  * This code is derived from software contributed to Berkeley by
  11  * The Mach Operating System project at Carnegie-Mellon University.
  12  *
  13  * Redistribution and use in source and binary forms, with or without
  14  * modification, are permitted provided that the following conditions
  15  * are met:
  16  * 1. Redistributions of source code must retain the above copyright
  17  *    notice, this list of conditions and the following disclaimer.
  18  * 2. Redistributions in binary form must reproduce the above copyright
  19  *    notice, this list of conditions and the following disclaimer in the
  20  *    documentation and/or other materials provided with the distribution.
  21  * 3. All advertising materials mentioning features or use of this software
  22  *    must display the following acknowledgement:
  23  *      This product includes software developed by the University of
  24  *      California, Berkeley and its contributors.
  25  * 4. Neither the name of the University nor the names of its contributors
  26  *    may be used to endorse or promote products derived from this software
  27  *    without specific prior written permission.
  28  *
  29  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  30  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  31  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  32  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  33  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  34  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  35  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  36  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  37  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  38  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  39  * SUCH DAMAGE.
  40  *
  41  *      from: @(#)vm_fault.c    8.4 (Berkeley) 1/12/94
  42  *
  43  *
  44  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
  45  * All rights reserved.
  46  *
  47  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
  48  *
  49  * Permission to use, copy, modify and distribute this software and
  50  * its documentation is hereby granted, provided that both the copyright
  51  * notice and this permission notice appear in all copies of the
  52  * software, derivative works or modified versions, and any portions
  53  * thereof, and that both notices appear in supporting documentation.
  54  *
  55  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  56  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
  57  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  58  *
  59  * Carnegie Mellon requests users of this software to return to
  60  *
  61  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  62  *  School of Computer Science
  63  *  Carnegie Mellon University
  64  *  Pittsburgh PA 15213-3890
  65  *
  66  * any improvements or extensions that they make and grant Carnegie the
  67  * rights to redistribute these changes.
  68  */
  69
  70 /*
  71  *      Page fault handling module.
  72  */
  73
  74 #include <sys/cdefs.h>
  75 __FBSDID("$FreeBSD$");
  76
  77 #include "opt_vm.h"
  78
  79 #include <sys/param.h>
  80 #include <sys/systm.h>
  81 #include <sys/kernel.h>
  82 #include <sys/lock.h>
  83 #include <sys/mutex.h>
  84 #include <sys/proc.h>
  85 #include <sys/resourcevar.h>
  86 #include <sys/sysctl.h>
  87 #include <sys/vmmeter.h>
  88 #include <sys/vnode.h>
  89
  90 #include <vm/vm.h>
  91 #include <vm/vm_param.h>
  92 #include <vm/pmap.h>
  93 #include <vm/vm_map.h>
  94 #include <vm/vm_object.h>
  95 #include <vm/vm_page.h>
  96 #include <vm/vm_pageout.h>
  97 #include <vm/vm_kern.h>
  98 #include <vm/vm_pager.h>
  99 #include <vm/vm_extern.h>
 100
 101 #include <sys/mount.h>  /* XXX Temporary for VFS_LOCK_GIANT() */
 102
 103 #define PFBAK 4
 104 #define PFFOR 4
 105 #define PAGEORDER_SIZE (PFBAK+PFFOR)
 106
 107 static int prefault_pageorder[] = {
 108         -1 * PAGE_SIZE, 1 * PAGE_SIZE,
 109         -2 * PAGE_SIZE, 2 * PAGE_SIZE,
 110         -3 * PAGE_SIZE, 3 * PAGE_SIZE,
 111         -4 * PAGE_SIZE, 4 * PAGE_SIZE
 112 };
 113
 114 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
 115 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t);
 116
 117 #define VM_FAULT_READ_AHEAD 8
 118 #define VM_FAULT_READ_BEHIND 7
 119 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1)
 120
 121 struct faultstate {
 122         vm_page_t m;
 123         vm_object_t object;
 124         vm_pindex_t pindex;
 125         vm_page_t first_m;
 126         vm_object_t     first_object;
 127         vm_pindex_t first_pindex;
 128         vm_map_t map;
 129         vm_map_entry_t entry;
 130         int lookup_still_valid;
 131         struct vnode *vp;
 132         int vfslocked;
 133 };
 134
 135 static inline void
 136 release_page(struct faultstate *fs)
 137 {
 138
 139         vm_page_wakeup(fs->m);
 140         vm_page_lock(fs->m);
 141         vm_page_deactivate(fs->m);
 142         vm_page_unlock(fs->m);
 143         fs->m = NULL;
 144 }
 145
 146 static inline void
 147 unlock_map(struct faultstate *fs)
 148 {
 149
 150         if (fs->lookup_still_valid) {
 151                 vm_map_lookup_done(fs->map, fs->entry);
 152                 fs->lookup_still_valid = FALSE;
 153         }
 154 }
 155
 156 static void
 157 unlock_and_deallocate(struct faultstate *fs)
 158 {
 159
 160         vm_object_pip_wakeup(fs->object);
 161         VM_OBJECT_UNLOCK(fs->object);
 162         if (fs->object != fs->first_object) {
 163                 VM_OBJECT_LOCK(fs->first_object);
 164                 vm_page_lock(fs->first_m);
 165                 vm_page_free(fs->first_m);
 166                 vm_page_unlock(fs->first_m);
 167                 vm_object_pip_wakeup(fs->first_object);
 168                 VM_OBJECT_UNLOCK(fs->first_object);
 169                 fs->first_m = NULL;
 170         }
 171         vm_object_deallocate(fs->first_object);
 172         unlock_map(fs);
 173         if (fs->vp != NULL) {
 174                 vput(fs->vp);
 175                 fs->vp = NULL;
 176         }
 177         VFS_UNLOCK_GIANT(fs->vfslocked);
 178         fs->vfslocked = 0;
 179 }
 180
 181 /*
 182  * TRYPAGER - used by vm_fault to calculate whether the pager for the
 183  *            current object *might* contain the page.
 184  *
 185  *            default objects are zero-fill, there is no real pager.
 186  */
 187 #define TRYPAGER        (fs.object->type != OBJT_DEFAULT && \
 188                         ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 || wired))
 189
 190 /*
 191  *      vm_fault:
 192  *
 193  *      Handle a page fault occurring at the given address,
 194  *      requiring the given permissions, in the map specified.
 195  *      If successful, the page is inserted into the
 196  *      associated physical map.
 197  *
 198  *      NOTE: the given address should be truncated to the
 199  *      proper page address.
 200  *
 201  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 202  *      a standard error specifying why the fault is fatal is returned.
 203  *
 204  *
 205  *      The map in question must be referenced, and remains so.
 206  *      Caller may hold no locks.
 207  */
 208 int
 209 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 210          int fault_flags)
 211 {
 212         vm_prot_t prot;
 213         int is_first_object_locked, result;
 214         boolean_t growstack, wired;
 215         int map_generation;
 216         vm_object_t next_object;
 217         vm_page_t marray[VM_FAULT_READ], mt, mt_prev;
 218         int hardfault;
 219         int faultcount, ahead, behind, alloc_req;
 220         struct faultstate fs;
 221         struct vnode *vp;
 222         int locked, error;
 223
 224         hardfault = 0;
 225         growstack = TRUE;
 226         PCPU_INC(cnt.v_vm_faults);
 227         fs.vp = NULL;
 228         fs.vfslocked = 0;
 229         faultcount = behind = 0;
 230
 231 RetryFault:;
 232
 233         /*
 234          * Find the backing store object and offset into it to begin the
 235          * search.
 236          */
 237         fs.map = map;
 238         result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
 239             &fs.first_object, &fs.first_pindex, &prot, &wired);
 240         if (result != KERN_SUCCESS) {
 241                 if (growstack && result == KERN_INVALID_ADDRESS &&
 242                     map != kernel_map) {
 243                         result = vm_map_growstack(curproc, vaddr);
 244                         if (result != KERN_SUCCESS)
 245                                 return (KERN_FAILURE);
 246                         growstack = FALSE;
 247                         goto RetryFault;
 248                 }
 249                 return (result);
 250         }
 251
 252         map_generation = fs.map->timestamp;
 253
 254         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 255                 panic("vm_fault: fault on nofault entry, addr: %lx",
 256                     (u_long)vaddr);
 257         }
 258
 259         /*
 260          * Make a reference to this object to prevent its disposal while we
 261          * are messing with it.  Once we have the reference, the map is free
 262          * to be diddled.  Since objects reference their shadows (and copies),
 263          * they will stay around as well.
 264          *
 265          * Bump the paging-in-progress count to prevent size changes (e.g.
 266          * truncation operations) during I/O.  This must be done after
 267          * obtaining the vnode lock in order to avoid possible deadlocks.
 268          */
 269         VM_OBJECT_LOCK(fs.first_object);
 270         vm_object_reference_locked(fs.first_object);
 271         vm_object_pip_add(fs.first_object, 1);
 272
 273         fs.lookup_still_valid = TRUE;
 274
 275         if (wired)
 276                 fault_type = prot | (fault_type & VM_PROT_COPY);
 277
 278         fs.first_m = NULL;
 279
 280         /*
 281          * Search for the page at object/offset.
 282          */
 283         fs.object = fs.first_object;
 284         fs.pindex = fs.first_pindex;
 285         while (TRUE) {
 286                 /*
 287                  * If the object is dead, we stop here
 288                  */
 289                 if (fs.object->flags & OBJ_DEAD) {
 290                         unlock_and_deallocate(&fs);
 291                         return (KERN_PROTECTION_FAILURE);
 292                 }
 293
 294                 /*
 295                  * See if page is resident
 296                  */
 297                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 298                 if (fs.m != NULL) {
 299                         /*
 300                          * check for page-based copy on write.
 301                          * We check fs.object == fs.first_object so
 302                          * as to ensure the legacy COW mechanism is
 303                          * used when the page in question is part of
 304                          * a shadow object.  Otherwise, vm_page_cowfault()
 305                          * removes the page from the backing object,
 306                          * which is not what we want.
 307                          */
 308                         vm_page_lock(fs.m);
 309                         if ((fs.m->cow) &&
 310                             (fault_type & VM_PROT_WRITE) &&
 311                             (fs.object == fs.first_object)) {
 312                                 vm_page_cowfault(fs.m);
 313                                 unlock_and_deallocate(&fs);
 314                                 goto RetryFault;
 315                         }
 316
 317                         /*
 318                          * Wait/Retry if the page is busy.  We have to do this
 319                          * if the page is busy via either VPO_BUSY or
 320                          * vm_page_t->busy because the vm_pager may be using
 321                          * vm_page_t->busy for pageouts ( and even pageins if
 322                          * it is the vnode pager ), and we could end up trying
 323                          * to pagein and pageout the same page simultaneously.
 324                          *
 325                          * We can theoretically allow the busy case on a read
 326                          * fault if the page is marked valid, but since such
 327                          * pages are typically already pmap'd, putting that
 328                          * special case in might be more effort then it is
 329                          * worth.  We cannot under any circumstances mess
 330                          * around with a vm_page_t->busy page except, perhaps,
 331                          * to pmap it.
 332                          */
 333                         if ((fs.m->oflags & VPO_BUSY) || fs.m->busy) {
 334                                 /*
 335                                  * Reference the page before unlocking and
 336                                  * sleeping so that the page daemon is less
 337                                  * likely to reclaim it.
 338                                  */
 339                                 vm_page_lock_queues();
 340                                 vm_page_flag_set(fs.m, PG_REFERENCED);
 341                                 vm_page_unlock_queues();
 342                                 vm_page_unlock(fs.m);
 343                                 if (fs.object != fs.first_object) {
 344                                         if (!VM_OBJECT_TRYLOCK(
 345                                             fs.first_object)) {
 346                                                 VM_OBJECT_UNLOCK(fs.object);
 347                                                 VM_OBJECT_LOCK(fs.first_object);
 348                                                 VM_OBJECT_LOCK(fs.object);
 349                                         }
 350                                         vm_page_lock(fs.first_m);
 351                                         vm_page_free(fs.first_m);
 352                                         vm_page_unlock(fs.first_m);
 353                                         vm_object_pip_wakeup(fs.first_object);
 354                                         VM_OBJECT_UNLOCK(fs.first_object);
 355                                         fs.first_m = NULL;
 356                                 }
 357                                 unlock_map(&fs);
 358                                 if (fs.m == vm_page_lookup(fs.object,
 359                                     fs.pindex)) {
 360                                         vm_page_sleep_if_busy(fs.m, TRUE,
 361                                             "vmpfw");
 362                                 }
 363                                 vm_object_pip_wakeup(fs.object);
 364                                 VM_OBJECT_UNLOCK(fs.object);
 365                                 PCPU_INC(cnt.v_intrans);
 366                                 vm_object_deallocate(fs.first_object);
 367                                 goto RetryFault;
 368                         }
 369                         vm_pageq_remove(fs.m);
 370                         vm_page_unlock(fs.m);
 371
 372                         /*
 373                          * Mark page busy for other processes, and the
 374                          * pagedaemon.  If it still isn't completely valid
 375                          * (readable), jump to readrest, else break-out ( we
 376                          * found the page ).
 377                          */
 378                         vm_page_busy(fs.m);
 379                         if (fs.m->valid != VM_PAGE_BITS_ALL &&
 380                                 fs.m->object != kernel_object && fs.m->object != kmem_object) {
 381                                 goto readrest;
 382                         }
 383
 384                         break;
 385                 }
 386
 387                 /*
 388                  * Page is not resident, If this is the search termination
 389                  * or the pager might contain the page, allocate a new page.
 390                  */
 391                 if (TRYPAGER || fs.object == fs.first_object) {
 392                         if (fs.pindex >= fs.object->size) {
 393                                 unlock_and_deallocate(&fs);
 394                                 return (KERN_PROTECTION_FAILURE);
 395                         }
 396
 397                         /*
 398                          * Allocate a new page for this object/offset pair.
 399                          *
 400                          * Unlocked read of the p_flag is harmless. At
 401                          * worst, the P_KILLED might be not observed
 402                          * there, and allocation can fail, causing
 403                          * restart and new reading of the p_flag.
 404                          */
 405                         fs.m = NULL;
 406                         if (!vm_page_count_severe() || P_KILLED(curproc)) {
 407 #if VM_NRESERVLEVEL > 0
 408                                 if ((fs.object->flags & OBJ_COLORED) == 0) {
 409                                         fs.object->flags |= OBJ_COLORED;
 410                                         fs.object->pg_color = atop(vaddr) -
 411                                             fs.pindex;
 412                                 }
 413 #endif
 414                                 alloc_req = P_KILLED(curproc) ?
 415                                     VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
 416                                 if (fs.object->type != OBJT_VNODE &&
 417                                     fs.object->backing_object == NULL)
 418                                         alloc_req |= VM_ALLOC_ZERO;
 419                                 fs.m = vm_page_alloc(fs.object, fs.pindex,
 420                                     alloc_req);
 421                         }
 422                         if (fs.m == NULL) {
 423                                 unlock_and_deallocate(&fs);
 424                                 VM_WAITPFAULT;
 425                                 goto RetryFault;
 426                         } else if (fs.m->valid == VM_PAGE_BITS_ALL)
 427                                 break;
 428                 }
 429
 430 readrest:
 431                 /*
 432                  * We have found a valid page or we have allocated a new page.
 433                  * The page thus may not be valid or may not be entirely
 434                  * valid.
 435                  *
 436                  * Attempt to fault-in the page if there is a chance that the
 437                  * pager has it, and potentially fault in additional pages
 438                  * at the same time.
 439                  */
 440                 if (TRYPAGER) {
 441                         int rv;
 442                         int reqpage = 0;
 443                         u_char behavior = vm_map_entry_behavior(fs.entry);
 444
 445                         if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
 446                             P_KILLED(curproc)) {
 447                                 ahead = 0;
 448                                 behind = 0;
 449                         } else {
 450                                 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT;
 451                                 if (behind > VM_FAULT_READ_BEHIND)
 452                                         behind = VM_FAULT_READ_BEHIND;
 453
 454                                 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1;
 455                                 if (ahead > VM_FAULT_READ_AHEAD)
 456                                         ahead = VM_FAULT_READ_AHEAD;
 457                         }
 458                         is_first_object_locked = FALSE;
 459                         if ((behavior == MAP_ENTRY_BEHAV_SEQUENTIAL ||
 460                              (behavior != MAP_ENTRY_BEHAV_RANDOM &&
 461                               fs.pindex >= fs.entry->lastr &&
 462                               fs.pindex < fs.entry->lastr + VM_FAULT_READ)) &&
 463                             (fs.first_object == fs.object ||
 464                              (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object))) &&
 465                             fs.first_object->type != OBJT_DEVICE &&
 466                             fs.first_object->type != OBJT_PHYS &&
 467                             fs.first_object->type != OBJT_SG) {
 468                                 vm_pindex_t firstpindex;
 469
 470                                 if (fs.first_pindex < 2 * VM_FAULT_READ)
 471                                         firstpindex = 0;
 472                                 else
 473                                         firstpindex = fs.first_pindex - 2 * VM_FAULT_READ;
 474                                 mt = fs.first_object != fs.object ?
 475                                     fs.first_m : fs.m;
 476                                 KASSERT(mt != NULL, ("vm_fault: missing mt"));
 477                                 KASSERT((mt->oflags & VPO_BUSY) != 0,
 478                                     ("vm_fault: mt %p not busy", mt));
 479                                 mt_prev = vm_page_prev(mt);
 480
 481                                 /*
 482                                  * note: partially valid pages cannot be
 483                                  * included in the lookahead - NFS piecemeal
 484                                  * writes will barf on it badly.
 485                                  */
 486                                 while ((mt = mt_prev) != NULL &&
 487                                     mt->pindex >= firstpindex &&
 488                                     mt->valid == VM_PAGE_BITS_ALL) {
 489                                         mt_prev = vm_page_prev(mt);
 490                                         if (mt->busy ||
 491                                             (mt->oflags & VPO_BUSY))
 492                                                 continue;
 493                                         vm_page_lock(mt);
 494                                         if (mt->hold_count ||
 495                                             mt->wire_count) {
 496                                                 vm_page_unlock(mt);
 497                                                 continue;
 498                                         }
 499                                         pmap_remove_all(mt);
 500                                         if (mt->dirty != 0)
 501                                                 vm_page_deactivate(mt);
 502                                         else
 503                                                 vm_page_cache(mt);
 504                                         vm_page_unlock(mt);
 505                                 }
 506                                 ahead += behind;
 507                                 behind = 0;
 508                         }
 509                         if (is_first_object_locked)
 510                                 VM_OBJECT_UNLOCK(fs.first_object);
 511
 512                         /*
 513                          * Call the pager to retrieve the data, if any, after
 514                          * releasing the lock on the map.  We hold a ref on
 515                          * fs.object and the pages are VPO_BUSY'd.
 516                          */
 517                         unlock_map(&fs);
 518
 519 vnode_lock:
 520                         if (fs.object->type == OBJT_VNODE) {
 521                                 vp = fs.object->handle;
 522                                 if (vp == fs.vp)
 523                                         goto vnode_locked;
 524                                 else if (fs.vp != NULL) {
 525                                         vput(fs.vp);
 526                                         fs.vp = NULL;
 527                                 }
 528                                 locked = VOP_ISLOCKED(vp);
 529
 530                                 if (VFS_NEEDSGIANT(vp->v_mount) && !fs.vfslocked) {
 531                                         fs.vfslocked = 1;
 532                                         if (!mtx_trylock(&Giant)) {
 533                                                 VM_OBJECT_UNLOCK(fs.object);
 534                                                 mtx_lock(&Giant);
 535                                                 VM_OBJECT_LOCK(fs.object);
 536                                                 goto vnode_lock;
 537                                         }
 538                                 }
 539                                 if (locked != LK_EXCLUSIVE)
 540                                         locked = LK_SHARED;
 541                                 /* Do not sleep for vnode lock while fs.m is busy */
 542                                 error = vget(vp, locked | LK_CANRECURSE |
 543                                     LK_NOWAIT, curthread);
 544                                 if (error != 0) {
 545                                         int vfslocked;
 546
 547                                         vfslocked = fs.vfslocked;
 548                                         fs.vfslocked = 0; /* Keep Giant */
 549                                         vhold(vp);
 550                                         release_page(&fs);
 551                                         unlock_and_deallocate(&fs);
 552                                         error = vget(vp, locked | LK_RETRY |
 553                                             LK_CANRECURSE, curthread);
 554                                         vdrop(vp);
 555                                         fs.vp = vp;
 556                                         fs.vfslocked = vfslocked;
 557                                         KASSERT(error == 0,
 558                                             ("vm_fault: vget failed"));
 559                                         goto RetryFault;
 560                                 }
 561                                 fs.vp = vp;
 562                         }
 563 vnode_locked:
 564                         KASSERT(fs.vp == NULL || !fs.map->system_map,
 565                             ("vm_fault: vnode-backed object mapped by system map"));
 566
 567                         /*
 568                          * now we find out if any other pages should be paged
 569                          * in at this time this routine checks to see if the
 570                          * pages surrounding this fault reside in the same
 571                          * object as the page for this fault.  If they do,
 572                          * then they are faulted in also into the object.  The
 573                          * array "marray" returned contains an array of
 574                          * vm_page_t structs where one of them is the
 575                          * vm_page_t passed to the routine.  The reqpage
 576                          * return value is the index into the marray for the
 577                          * vm_page_t passed to the routine.
 578                          *
 579                          * fs.m plus the additional pages are VPO_BUSY'd.
 580                          */
 581                         faultcount = vm_fault_additional_pages(
 582                             fs.m, behind, ahead, marray, &reqpage);
 583
 584                         rv = faultcount ?
 585                             vm_pager_get_pages(fs.object, marray, faultcount,
 586                                 reqpage) : VM_PAGER_FAIL;
 587
 588                         if (rv == VM_PAGER_OK) {
 589                                 /*
 590                                  * Found the page. Leave it busy while we play
 591                                  * with it.
 592                                  */
 593
 594                                 /*
 595                                  * Relookup in case pager changed page. Pager
 596                                  * is responsible for disposition of old page
 597                                  * if moved.
 598                                  */
 599                                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 600                                 if (!fs.m) {
 601                                         unlock_and_deallocate(&fs);
 602                                         goto RetryFault;
 603                                 }
 604
 605                                 hardfault++;
 606                                 break; /* break to PAGE HAS BEEN FOUND */
 607                         }
 608                         /*
 609                          * Remove the bogus page (which does not exist at this
 610                          * object/offset); before doing so, we must get back
 611                          * our object lock to preserve our invariant.
 612                          *
 613                          * Also wake up any other process that may want to bring
 614                          * in this page.
 615                          *
 616                          * If this is the top-level object, we must leave the
 617                          * busy page to prevent another process from rushing
 618                          * past us, and inserting the page in that object at
 619                          * the same time that we are.
 620                          */
 621                         if (rv == VM_PAGER_ERROR)
 622                                 printf("vm_fault: pager read error, pid %d (%s)\n",
 623                                     curproc->p_pid, curproc->p_comm);
 624                         /*
 625                          * Data outside the range of the pager or an I/O error
 626                          */
 627                         /*
 628                          * XXX - the check for kernel_map is a kludge to work
 629                          * around having the machine panic on a kernel space
 630                          * fault w/ I/O error.
 631                          */
 632                         if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
 633                                 (rv == VM_PAGER_BAD)) {
 634                                 vm_page_lock(fs.m);
 635                                 vm_page_free(fs.m);
 636                                 vm_page_unlock(fs.m);
 637                                 fs.m = NULL;
 638                                 unlock_and_deallocate(&fs);
 639                                 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
 640                         }
 641                         if (fs.object != fs.first_object) {
 642                                 vm_page_lock(fs.m);
 643                                 vm_page_free(fs.m);
 644                                 vm_page_unlock(fs.m);
 645                                 fs.m = NULL;
 646                                 /*
 647                                  * XXX - we cannot just fall out at this
 648                                  * point, m has been freed and is invalid!
 649                                  */
 650                         }
 651                 }
 652
 653                 /*
 654                  * We get here if the object has default pager (or unwiring)
 655                  * or the pager doesn't have the page.
 656                  */
 657                 if (fs.object == fs.first_object)
 658                         fs.first_m = fs.m;
 659
 660                 /*
 661                  * Move on to the next object.  Lock the next object before
 662                  * unlocking the current one.
 663                  */
 664                 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
 665                 next_object = fs.object->backing_object;
 666                 if (next_object == NULL) {
 667                         /*
 668                          * If there's no object left, fill the page in the top
 669                          * object with zeros.
 670                          */
 671                         if (fs.object != fs.first_object) {
 672                                 vm_object_pip_wakeup(fs.object);
 673                                 VM_OBJECT_UNLOCK(fs.object);
 674
 675                                 fs.object = fs.first_object;
 676                                 fs.pindex = fs.first_pindex;
 677                                 fs.m = fs.first_m;
 678                                 VM_OBJECT_LOCK(fs.object);
 679                         }
 680                         fs.first_m = NULL;
 681
 682                         /*
 683                          * Zero the page if necessary and mark it valid.
 684                          */
 685                         if ((fs.m->flags & PG_ZERO) == 0) {
 686                                 pmap_zero_page(fs.m);
 687                         } else {
 688                                 PCPU_INC(cnt.v_ozfod);
 689                         }
 690                         PCPU_INC(cnt.v_zfod);
 691                         fs.m->valid = VM_PAGE_BITS_ALL;
 692                         break;  /* break to PAGE HAS BEEN FOUND */
 693                 } else {
 694                         KASSERT(fs.object != next_object,
 695                             ("object loop %p", next_object));
 696                         VM_OBJECT_LOCK(next_object);
 697                         vm_object_pip_add(next_object, 1);
 698                         if (fs.object != fs.first_object)
 699                                 vm_object_pip_wakeup(fs.object);
 700                         VM_OBJECT_UNLOCK(fs.object);
 701                         fs.object = next_object;
 702                 }
 703         }
 704
 705         KASSERT((fs.m->oflags & VPO_BUSY) != 0,
 706             ("vm_fault: not busy after main loop"));
 707
 708         /*
 709          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
 710          * is held.]
 711          */
 712
 713         /*
 714          * If the page is being written, but isn't already owned by the
 715          * top-level object, we have to copy it into a new page owned by the
 716          * top-level object.
 717          */
 718         if (fs.object != fs.first_object) {
 719                 /*
 720                  * We only really need to copy if we want to write it.
 721                  */
 722                 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
 723                         /*
 724                          * This allows pages to be virtually copied from a
 725                          * backing_object into the first_object, where the
 726                          * backing object has no other refs to it, and cannot
 727                          * gain any more refs.  Instead of a bcopy, we just
 728                          * move the page from the backing object to the
 729                          * first object.  Note that we must mark the page
 730                          * dirty in the first object so that it will go out
 731                          * to swap when needed.
 732                          */
 733                         is_first_object_locked = FALSE;
 734                         if (
 735                                 /*
 736                                  * Only one shadow object
 737                                  */
 738                                 (fs.object->shadow_count == 1) &&
 739                                 /*
 740                                  * No COW refs, except us
 741                                  */
 742                                 (fs.object->ref_count == 1) &&
 743                                 /*
 744                                  * No one else can look this object up
 745                                  */
 746                                 (fs.object->handle == NULL) &&
 747                                 /*
 748                                  * No other ways to look the object up
 749                                  */
 750                                 ((fs.object->type == OBJT_DEFAULT) ||
 751                                  (fs.object->type == OBJT_SWAP)) &&
 752                             (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) &&
 753                                 /*
 754                                  * We don't chase down the shadow chain
 755                                  */
 756                             fs.object == fs.first_object->backing_object) {
 757                                 /*
 758                                  * get rid of the unnecessary page
 759                                  */
 760                                 vm_page_lock(fs.first_m);
 761                                 vm_page_free(fs.first_m);
 762                                 vm_page_unlock(fs.first_m);
 763                                 /*
 764                                  * grab the page and put it into the
 765                                  * process'es object.  The page is
 766                                  * automatically made dirty.
 767                                  */
 768                                 vm_page_lock(fs.m);
 769                                 vm_page_rename(fs.m, fs.first_object, fs.first_pindex);
 770                                 vm_page_unlock(fs.m);
 771                                 vm_page_busy(fs.m);
 772                                 fs.first_m = fs.m;
 773                                 fs.m = NULL;
 774                                 PCPU_INC(cnt.v_cow_optim);
 775                         } else {
 776                                 /*
 777                                  * Oh, well, lets copy it.
 778                                  */
 779                                 pmap_copy_page(fs.m, fs.first_m);
 780                                 fs.first_m->valid = VM_PAGE_BITS_ALL;
 781                                 if (wired && (fault_flags &
 782                                     VM_FAULT_CHANGE_WIRING) == 0) {
 783                                         vm_page_lock(fs.first_m);
 784                                         vm_page_wire(fs.first_m);
 785                                         vm_page_unlock(fs.first_m);
 786
 787                                         vm_page_lock(fs.m);
 788                                         vm_page_unwire(fs.m, FALSE);
 789                                         vm_page_unlock(fs.m);
 790                                 }
 791                                 /*
 792                                  * We no longer need the old page or object.
 793                                  */
 794                                 release_page(&fs);
 795                         }
 796                         /*
 797                          * fs.object != fs.first_object due to above
 798                          * conditional
 799                          */
 800                         vm_object_pip_wakeup(fs.object);
 801                         VM_OBJECT_UNLOCK(fs.object);
 802                         /*
 803                          * Only use the new page below...
 804                          */
 805                         fs.object = fs.first_object;
 806                         fs.pindex = fs.first_pindex;
 807                         fs.m = fs.first_m;
 808                         if (!is_first_object_locked)
 809                                 VM_OBJECT_LOCK(fs.object);
 810                         PCPU_INC(cnt.v_cow_faults);
 811                 } else {
 812                         prot &= ~VM_PROT_WRITE;
 813                 }
 814         }
 815
 816         /*
 817          * We must verify that the maps have not changed since our last
 818          * lookup.
 819          */
 820         if (!fs.lookup_still_valid) {
 821                 vm_object_t retry_object;
 822                 vm_pindex_t retry_pindex;
 823                 vm_prot_t retry_prot;
 824
 825                 if (!vm_map_trylock_read(fs.map)) {
 826                         release_page(&fs);
 827                         unlock_and_deallocate(&fs);
 828                         goto RetryFault;
 829                 }
 830                 fs.lookup_still_valid = TRUE;
 831                 if (fs.map->timestamp != map_generation) {
 832                         result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
 833                             &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
 834
 835                         /*
 836                          * If we don't need the page any longer, put it on the inactive
 837                          * list (the easiest thing to do here).  If no one needs it,
 838                          * pageout will grab it eventually.
 839                          */
 840                         if (result != KERN_SUCCESS) {
 841                                 release_page(&fs);
 842                                 unlock_and_deallocate(&fs);
 843
 844                                 /*
 845                                  * If retry of map lookup would have blocked then
 846                                  * retry fault from start.
 847                                  */
 848                                 if (result == KERN_FAILURE)
 849                                         goto RetryFault;
 850                                 return (result);
 851                         }
 852                         if ((retry_object != fs.first_object) ||
 853                             (retry_pindex != fs.first_pindex)) {
 854                                 release_page(&fs);
 855                                 unlock_and_deallocate(&fs);
 856                                 goto RetryFault;
 857                         }
 858
 859                         /*
 860                          * Check whether the protection has changed or the object has
 861                          * been copied while we left the map unlocked. Changing from
 862                          * read to write permission is OK - we leave the page
 863                          * write-protected, and catch the write fault. Changing from
 864                          * write to read permission means that we can't mark the page
 865                          * write-enabled after all.
 866                          */
 867                         prot &= retry_prot;
 868                 }
 869         }
 870         /*
 871          * If the page was filled by a pager, update the map entry's
 872          * last read offset.  Since the pager does not return the
 873          * actual set of pages that it read, this update is based on
 874          * the requested set.  Typically, the requested and actual
 875          * sets are the same.
 876          *
 877          * XXX The following assignment modifies the map
 878          * without holding a write lock on it.
 879          */
 880         if (hardfault)
 881                 fs.entry->lastr = fs.pindex + faultcount - behind;
 882
 883         if (prot & VM_PROT_WRITE) {
 884                 vm_object_set_writeable_dirty(fs.object);
 885
 886                 /*
 887                  * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
 888                  * if the page is already dirty to prevent data written with
 889                  * the expectation of being synced from not being synced.
 890                  * Likewise if this entry does not request NOSYNC then make
 891                  * sure the page isn't marked NOSYNC.  Applications sharing
 892                  * data should use the same flags to avoid ping ponging.
 893                  */
 894                 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) {
 895                         if (fs.m->dirty == 0)
 896                                 fs.m->oflags |= VPO_NOSYNC;
 897                 } else {
 898                         fs.m->oflags &= ~VPO_NOSYNC;
 899                 }
 900
 901                 /*
 902                  * If the fault is a write, we know that this page is being
 903                  * written NOW so dirty it explicitly to save on
 904                  * pmap_is_modified() calls later.
 905                  *
 906                  * Also tell the backing pager, if any, that it should remove
 907                  * any swap backing since the page is now dirty.
 908                  */
 909                 if ((fault_type & VM_PROT_WRITE) != 0 &&
 910                     (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) {
 911                         vm_page_dirty(fs.m);
 912                         vm_pager_page_unswapped(fs.m);
 913                 }
 914         }
 915
 916         /*
 917          * Page had better still be busy
 918          */
 919         KASSERT(fs.m->oflags & VPO_BUSY,
 920                 ("vm_fault: page %p not busy!", fs.m));
 921         /*
 922          * Page must be completely valid or it is not fit to
 923          * map into user space.  vm_pager_get_pages() ensures this.
 924          */
 925         KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
 926             ("vm_fault: page %p partially invalid", fs.m));
 927         VM_OBJECT_UNLOCK(fs.object);
 928
 929         /*
 930          * Put this page into the physical map.  We had to do the unlock above
 931          * because pmap_enter() may sleep.  We don't put the page
 932          * back on the active queue until later so that the pageout daemon
 933          * won't find it (yet).
 934          */
 935         pmap_enter(fs.map->pmap, vaddr, fault_type, fs.m, prot, wired);
 936         if ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 && wired == 0)
 937                 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry);
 938         VM_OBJECT_LOCK(fs.object);
 939         vm_page_lock(fs.m);
 940
 941         /*
 942          * If the page is not wired down, then put it where the pageout daemon
 943          * can find it.
 944          */
 945         if (fault_flags & VM_FAULT_CHANGE_WIRING) {
 946                 if (wired)
 947                         vm_page_wire(fs.m);
 948                 else
 949                         vm_page_unwire(fs.m, 1);
 950         } else
 951                 vm_page_activate(fs.m);
 952         vm_page_unlock(fs.m);
 953         vm_page_wakeup(fs.m);
 954
 955         /*
 956          * Unlock everything, and return
 957          */
 958         unlock_and_deallocate(&fs);
 959         if (hardfault)
 960                 curthread->td_ru.ru_majflt++;
 961         else
 962                 curthread->td_ru.ru_minflt++;
 963
 964         return (KERN_SUCCESS);
 965 }
 966
 967 /*
 968  * vm_fault_prefault provides a quick way of clustering
 969  * pagefaults into a processes address space.  It is a "cousin"
 970  * of vm_map_pmap_enter, except it runs at page fault time instead
 971  * of mmap time.
 972  */
 973 static void
 974 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry)
 975 {
 976         int i;
 977         vm_offset_t addr, starta;
 978         vm_pindex_t pindex;
 979         vm_page_t m;
 980         vm_object_t object;
 981
 982         if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
 983                 return;
 984
 985         object = entry->object.vm_object;
 986
 987         starta = addra - PFBAK * PAGE_SIZE;
 988         if (starta < entry->start) {
 989                 starta = entry->start;
 990         } else if (starta > addra) {
 991                 starta = 0;
 992         }
 993
 994         for (i = 0; i < PAGEORDER_SIZE; i++) {
 995                 vm_object_t backing_object, lobject;
 996
 997                 addr = addra + prefault_pageorder[i];
 998                 if (addr > addra + (PFFOR * PAGE_SIZE))
 999                         addr = 0;
1000
1001                 if (addr < starta || addr >= entry->end)
1002                         continue;
1003
1004                 if (!pmap_is_prefaultable(pmap, addr))
1005                         continue;
1006
1007                 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1008                 lobject = object;
1009                 VM_OBJECT_LOCK(lobject);
1010                 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1011                     lobject->type == OBJT_DEFAULT &&
1012                     (backing_object = lobject->backing_object) != NULL) {
1013                         KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1014                             0, ("vm_fault_prefault: unaligned object offset"));
1015                         pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1016                         VM_OBJECT_LOCK(backing_object);
1017                         VM_OBJECT_UNLOCK(lobject);
1018                         lobject = backing_object;
1019                 }
1020                 /*
1021                  * give-up when a page is not in memory
1022                  */
1023                 if (m == NULL) {
1024                         VM_OBJECT_UNLOCK(lobject);
1025                         break;
1026                 }
1027                 if (m->valid == VM_PAGE_BITS_ALL &&
1028                     (m->flags & PG_FICTITIOUS) == 0)
1029                         pmap_enter_quick(pmap, addr, m, entry->protection);
1030                 VM_OBJECT_UNLOCK(lobject);
1031         }
1032 }
1033
1034 /*
1035  *      vm_fault_quick:
1036  *
1037  *      Ensure that the requested virtual address, which may be in userland,
1038  *      is valid.  Fault-in the page if necessary.  Return -1 on failure.
1039  */
1040 int
1041 vm_fault_quick(caddr_t v, int prot)
1042 {
1043         int r;
1044
1045         if (prot & VM_PROT_WRITE)
1046                 r = subyte(v, fubyte(v));
1047         else
1048                 r = fubyte(v);
1049         return(r);
1050 }
1051
1052 /*
1053  *      vm_fault_wire:
1054  *
1055  *      Wire down a range of virtual addresses in a map.
1056  */
1057 int
1058 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1059     boolean_t fictitious)
1060 {
1061         vm_offset_t va;
1062         int rv;
1063
1064         /*
1065          * We simulate a fault to get the page and enter it in the physical
1066          * map.  For user wiring, we only ask for read access on currently
1067          * read-only sections.
1068          */
1069         for (va = start; va < end; va += PAGE_SIZE) {
1070                 rv = vm_fault(map, va, VM_PROT_NONE, VM_FAULT_CHANGE_WIRING);
1071                 if (rv) {
1072                         if (va != start)
1073                                 vm_fault_unwire(map, start, va, fictitious);
1074                         return (rv);
1075                 }
1076         }
1077         return (KERN_SUCCESS);
1078 }
1079
1080 /*
1081  *      vm_fault_unwire:
1082  *
1083  *      Unwire a range of virtual addresses in a map.
1084  */
1085 void
1086 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1087     boolean_t fictitious)
1088 {
1089         vm_paddr_t pa;
1090         vm_offset_t va;
1091         vm_page_t m;
1092         pmap_t pmap;
1093
1094         pmap = vm_map_pmap(map);
1095
1096         /*
1097          * Since the pages are wired down, we must be able to get their
1098          * mappings from the physical map system.
1099          */
1100         for (va = start; va < end; va += PAGE_SIZE) {
1101                 pa = pmap_extract(pmap, va);
1102                 if (pa != 0) {
1103                         pmap_change_wiring(pmap, va, FALSE);
1104                         if (!fictitious) {
1105                                 m = PHYS_TO_VM_PAGE(pa);
1106                                 vm_page_lock(m);
1107                                 vm_page_unwire(m, TRUE);
1108                                 vm_page_unlock(m);
1109                         }
1110                 }
1111         }
1112 }
1113
1114 /*
1115  *      Routine:
1116  *              vm_fault_copy_entry
1117  *      Function:
1118  *              Create new shadow object backing dst_entry with private copy of
1119  *              all underlying pages. When src_entry is equal to dst_entry,
1120  *              function implements COW for wired-down map entry. Otherwise,
1121  *              it forks wired entry into dst_map.
1122  *
1123  *      In/out conditions:
1124  *              The source and destination maps must be locked for write.
1125  *              The source map entry must be wired down (or be a sharing map
1126  *              entry corresponding to a main map entry that is wired down).
1127  */
1128 void
1129 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1130     vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1131     vm_ooffset_t *fork_charge)
1132 {
1133         vm_object_t backing_object, dst_object, object, src_object;
1134         vm_pindex_t dst_pindex, pindex, src_pindex;
1135         vm_prot_t access, prot;
1136         vm_offset_t vaddr;
1137         vm_page_t dst_m;
1138         vm_page_t src_m;
1139         boolean_t src_readonly, upgrade;
1140
1141 #ifdef  lint
1142         src_map++;
1143 #endif  /* lint */
1144
1145         upgrade = src_entry == dst_entry;
1146
1147         src_object = src_entry->object.vm_object;
1148         src_pindex = OFF_TO_IDX(src_entry->offset);
1149         src_readonly = (src_entry->protection & VM_PROT_WRITE) == 0;
1150
1151         /*
1152          * Create the top-level object for the destination entry. (Doesn't
1153          * actually shadow anything - we copy the pages directly.)
1154          */
1155         dst_object = vm_object_allocate(OBJT_DEFAULT,
1156             OFF_TO_IDX(dst_entry->end - dst_entry->start));
1157 #if VM_NRESERVLEVEL > 0
1158         dst_object->flags |= OBJ_COLORED;
1159         dst_object->pg_color = atop(dst_entry->start);
1160 #endif
1161
1162         VM_OBJECT_LOCK(dst_object);
1163         KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1164             ("vm_fault_copy_entry: vm_object not NULL"));
1165         dst_entry->object.vm_object = dst_object;
1166         dst_entry->offset = 0;
1167         dst_object->charge = dst_entry->end - dst_entry->start;
1168         if (fork_charge != NULL) {
1169                 KASSERT(dst_entry->uip == NULL,
1170                     ("vm_fault_copy_entry: leaked swp charge"));
1171                 dst_object->uip = curthread->td_ucred->cr_ruidinfo;
1172                 uihold(dst_object->uip);
1173                 *fork_charge += dst_object->charge;
1174         } else {
1175                 dst_object->uip = dst_entry->uip;
1176                 dst_entry->uip = NULL;
1177         }
1178         access = prot = dst_entry->protection;
1179         /*
1180          * If not an upgrade, then enter the mappings in the pmap as
1181          * read and/or execute accesses.  Otherwise, enter them as
1182          * write accesses.
1183          *
1184          * A writeable large page mapping is only created if all of
1185          * the constituent small page mappings are modified. Marking
1186          * PTEs as modified on inception allows promotion to happen
1187          * without taking potentially large number of soft faults.
1188          */
1189         if (!upgrade)
1190                 access &= ~VM_PROT_WRITE;
1191
1192         /*
1193          * Loop through all of the pages in the entry's range, copying each
1194          * one from the source object (it should be there) to the destination
1195          * object.
1196          */
1197         for (vaddr = dst_entry->start, dst_pindex = 0;
1198             vaddr < dst_entry->end;
1199             vaddr += PAGE_SIZE, dst_pindex++) {
1200
1201                 /*
1202                  * Allocate a page in the destination object.
1203                  */
1204                 do {
1205                         dst_m = vm_page_alloc(dst_object, dst_pindex,
1206                             VM_ALLOC_NORMAL);
1207                         if (dst_m == NULL) {
1208                                 VM_OBJECT_UNLOCK(dst_object);
1209                                 VM_WAIT;
1210                                 VM_OBJECT_LOCK(dst_object);
1211                         }
1212                 } while (dst_m == NULL);
1213
1214                 /*
1215                  * Find the page in the source object, and copy it in.
1216                  * (Because the source is wired down, the page will be in
1217                  * memory.)
1218                  */
1219                 VM_OBJECT_LOCK(src_object);
1220                 object = src_object;
1221                 pindex = src_pindex + dst_pindex;
1222                 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1223                     src_readonly &&
1224                     (backing_object = object->backing_object) != NULL) {
1225                         /*
1226                          * Allow fallback to backing objects if we are reading.
1227                          */
1228                         VM_OBJECT_LOCK(backing_object);
1229                         pindex += OFF_TO_IDX(object->backing_object_offset);
1230                         VM_OBJECT_UNLOCK(object);
1231                         object = backing_object;
1232                 }
1233                 if (src_m == NULL)
1234                         panic("vm_fault_copy_wired: page missing");
1235                 pmap_copy_page(src_m, dst_m);
1236                 VM_OBJECT_UNLOCK(object);
1237                 dst_m->valid = VM_PAGE_BITS_ALL;
1238                 VM_OBJECT_UNLOCK(dst_object);
1239
1240                 /*
1241                  * Enter it in the pmap. If a wired, copy-on-write
1242                  * mapping is being replaced by a write-enabled
1243                  * mapping, then wire that new mapping.
1244                  */
1245                 pmap_enter(dst_map->pmap, vaddr, access, dst_m, prot, upgrade);
1246
1247                 /*
1248                  * Mark it no longer busy, and put it on the active list.
1249                  */
1250                 VM_OBJECT_LOCK(dst_object);
1251
1252                 if (upgrade) {
1253                         vm_page_lock(src_m);
1254                         vm_page_unwire(src_m, 0);
1255                         vm_page_unlock(src_m);
1256
1257                         vm_page_lock(dst_m);
1258                         vm_page_wire(dst_m);
1259                         vm_page_unlock(dst_m);
1260                 } else {
1261                         vm_page_lock(dst_m);
1262                         vm_page_activate(dst_m);
1263                         vm_page_unlock(dst_m);
1264                 }
1265                 vm_page_wakeup(dst_m);
1266         }
1267         VM_OBJECT_UNLOCK(dst_object);
1268         if (upgrade) {
1269                 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1270                 vm_object_deallocate(src_object);
1271         }
1272 }
1273
1274
1275 /*
1276  * This routine checks around the requested page for other pages that
1277  * might be able to be faulted in.  This routine brackets the viable
1278  * pages for the pages to be paged in.
1279  *
1280  * Inputs:
1281  *      m, rbehind, rahead
1282  *
1283  * Outputs:
1284  *  marray (array of vm_page_t), reqpage (index of requested page)
1285  *
1286  * Return value:
1287  *  number of pages in marray
1288  */
1289 static int
1290 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1291         vm_page_t m;
1292         int rbehind;
1293         int rahead;
1294         vm_page_t *marray;
1295         int *reqpage;
1296 {
1297         int i,j;
1298         vm_object_t object;
1299         vm_pindex_t pindex, startpindex, endpindex, tpindex;
1300         vm_page_t rtm;
1301         int cbehind, cahead;
1302
1303         VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
1304
1305         object = m->object;
1306         pindex = m->pindex;
1307         cbehind = cahead = 0;
1308
1309         /*
1310          * if the requested page is not available, then give up now
1311          */
1312         if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1313                 return 0;
1314         }
1315
1316         if ((cbehind == 0) && (cahead == 0)) {
1317                 *reqpage = 0;
1318                 marray[0] = m;
1319                 return 1;
1320         }
1321
1322         if (rahead > cahead) {
1323                 rahead = cahead;
1324         }
1325
1326         if (rbehind > cbehind) {
1327                 rbehind = cbehind;
1328         }
1329
1330         /*
1331          * scan backward for the read behind pages -- in memory
1332          */
1333         if (pindex > 0) {
1334                 if (rbehind > pindex) {
1335                         rbehind = pindex;
1336                         startpindex = 0;
1337                 } else {
1338                         startpindex = pindex - rbehind;
1339                 }
1340
1341                 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL &&
1342                     rtm->pindex >= startpindex)
1343                         startpindex = rtm->pindex + 1;
1344
1345                 /* tpindex is unsigned; beware of numeric underflow. */
1346                 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex &&
1347                     tpindex < pindex; i++, tpindex--) {
1348
1349                         rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1350                             VM_ALLOC_IFNOTCACHED);
1351                         if (rtm == NULL) {
1352                                 /*
1353                                  * Shift the allocated pages to the
1354                                  * beginning of the array.
1355                                  */
1356                                 for (j = 0; j < i; j++) {
1357                                         marray[j] = marray[j + tpindex + 1 -
1358                                             startpindex];
1359                                 }
1360                                 break;
1361                         }
1362
1363                         marray[tpindex - startpindex] = rtm;
1364                 }
1365         } else {
1366                 startpindex = 0;
1367                 i = 0;
1368         }
1369
1370         marray[i] = m;
1371         /* page offset of the required page */
1372         *reqpage = i;
1373
1374         tpindex = pindex + 1;
1375         i++;
1376
1377         /*
1378          * scan forward for the read ahead pages
1379          */
1380         endpindex = tpindex + rahead;
1381         if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex)
1382                 endpindex = rtm->pindex;
1383         if (endpindex > object->size)
1384                 endpindex = object->size;
1385
1386         for (; tpindex < endpindex; i++, tpindex++) {
1387
1388                 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1389                     VM_ALLOC_IFNOTCACHED);
1390                 if (rtm == NULL) {
1391                         break;
1392                 }
1393
1394                 marray[i] = rtm;
1395         }
1396
1397         /* return number of pages */
1398         return i;
1399 }