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/vnode_pager.h>
 100 #include <vm/vm_extern.h>
 101
 102 #include <sys/mount.h>  /* XXX Temporary for VFS_LOCK_GIANT() */
 103
 104 #define PFBAK 4
 105 #define PFFOR 4
 106 #define PAGEORDER_SIZE (PFBAK+PFFOR)
 107
 108 static int prefault_pageorder[] = {
 109         -1 * PAGE_SIZE, 1 * PAGE_SIZE,
 110         -2 * PAGE_SIZE, 2 * PAGE_SIZE,
 111         -3 * PAGE_SIZE, 3 * PAGE_SIZE,
 112         -4 * PAGE_SIZE, 4 * PAGE_SIZE
 113 };
 114
 115 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
 116 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t);
 117
 118 #define VM_FAULT_READ_AHEAD 8
 119 #define VM_FAULT_READ_BEHIND 7
 120 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1)
 121
 122 struct faultstate {
 123         vm_page_t m;
 124         vm_object_t object;
 125         vm_pindex_t pindex;
 126         vm_page_t first_m;
 127         vm_object_t     first_object;
 128         vm_pindex_t first_pindex;
 129         vm_map_t map;
 130         vm_map_entry_t entry;
 131         int lookup_still_valid;
 132         struct vnode *vp;
 133         int vfslocked;
 134 };
 135
 136 static inline void
 137 release_page(struct faultstate *fs)
 138 {
 139
 140         vm_page_wakeup(fs->m);
 141         vm_page_lock_queues();
 142         vm_page_deactivate(fs->m);
 143         vm_page_unlock_queues();
 144         fs->m = NULL;
 145 }
 146
 147 static inline void
 148 unlock_map(struct faultstate *fs)
 149 {
 150
 151         if (fs->lookup_still_valid) {
 152                 vm_map_lookup_done(fs->map, fs->entry);
 153                 fs->lookup_still_valid = FALSE;
 154         }
 155 }
 156
 157 static void
 158 unlock_and_deallocate(struct faultstate *fs)
 159 {
 160
 161         vm_object_pip_wakeup(fs->object);
 162         VM_OBJECT_UNLOCK(fs->object);
 163         if (fs->object != fs->first_object) {
 164                 VM_OBJECT_LOCK(fs->first_object);
 165                 vm_page_lock_queues();
 166                 vm_page_free(fs->first_m);
 167                 vm_page_unlock_queues();
 168                 vm_object_pip_wakeup(fs->first_object);
 169                 VM_OBJECT_UNLOCK(fs->first_object);
 170                 fs->first_m = NULL;
 171         }
 172         vm_object_deallocate(fs->first_object);
 173         unlock_map(fs);
 174         if (fs->vp != NULL) {
 175                 vput(fs->vp);
 176                 fs->vp = NULL;
 177         }
 178         VFS_UNLOCK_GIANT(fs->vfslocked);
 179         fs->vfslocked = 0;
 180 }
 181
 182 /*
 183  * TRYPAGER - used by vm_fault to calculate whether the pager for the
 184  *            current object *might* contain the page.
 185  *
 186  *            default objects are zero-fill, there is no real pager.
 187  */
 188 #define TRYPAGER        (fs.object->type != OBJT_DEFAULT && \
 189                         (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired))
 190
 191 /*
 192  *      vm_fault:
 193  *
 194  *      Handle a page fault occurring at the given address,
 195  *      requiring the given permissions, in the map specified.
 196  *      If successful, the page is inserted into the
 197  *      associated physical map.
 198  *
 199  *      NOTE: the given address should be truncated to the
 200  *      proper page address.
 201  *
 202  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 203  *      a standard error specifying why the fault is fatal is returned.
 204  *
 205  *
 206  *      The map in question must be referenced, and remains so.
 207  *      Caller may hold no locks.
 208  */
 209 int
 210 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 211          int fault_flags)
 212 {
 213         vm_prot_t prot;
 214         int is_first_object_locked, result;
 215         boolean_t are_queues_locked, growstack, wired;
 216         int map_generation;
 217         vm_object_t next_object;
 218         vm_page_t marray[VM_FAULT_READ];
 219         int hardfault;
 220         int faultcount, ahead, behind, alloc_req;
 221         struct faultstate fs;
 222         struct vnode *vp;
 223         int locked, error;
 224
 225         hardfault = 0;
 226         growstack = TRUE;
 227         PCPU_INC(cnt.v_vm_faults);
 228         fs.vp = NULL;
 229         fs.vfslocked = 0;
 230         faultcount = behind = 0;
 231
 232 RetryFault:;
 233
 234         /*
 235          * Find the backing store object and offset into it to begin the
 236          * search.
 237          */
 238         fs.map = map;
 239         result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
 240             &fs.first_object, &fs.first_pindex, &prot, &wired);
 241         if (result != KERN_SUCCESS) {
 242                 if (result != KERN_PROTECTION_FAILURE ||
 243                     (fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) {
 244                         if (growstack && result == KERN_INVALID_ADDRESS &&
 245                             map != kernel_map && curproc != NULL) {
 246                                 result = vm_map_growstack(curproc, vaddr);
 247                                 if (result != KERN_SUCCESS)
 248                                         return (KERN_FAILURE);
 249                                 growstack = FALSE;
 250                                 goto RetryFault;
 251                         }
 252                         return (result);
 253                 }
 254
 255                 /*
 256                  * If we are user-wiring a r/w segment, and it is COW, then
 257                  * we need to do the COW operation.  Note that we don't COW
 258                  * currently RO sections now, because it is NOT desirable
 259                  * to COW .text.  We simply keep .text from ever being COW'ed
 260                  * and take the heat that one cannot debug wired .text sections.
 261                  */
 262                 result = vm_map_lookup(&fs.map, vaddr,
 263                         VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE,
 264                         &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired);
 265                 if (result != KERN_SUCCESS)
 266                         return (result);
 267
 268                 /*
 269                  * If we don't COW now, on a user wire, the user will never
 270                  * be able to write to the mapping.  If we don't make this
 271                  * restriction, the bookkeeping would be nearly impossible.
 272                  *
 273                  * XXX The following assignment modifies the map without
 274                  * holding a write lock on it.
 275                  */
 276                 if ((fs.entry->protection & VM_PROT_WRITE) == 0)
 277                         fs.entry->max_protection &= ~VM_PROT_WRITE;
 278         }
 279
 280         map_generation = fs.map->timestamp;
 281
 282         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 283                 panic("vm_fault: fault on nofault entry, addr: %lx",
 284                     (u_long)vaddr);
 285         }
 286
 287         /*
 288          * Make a reference to this object to prevent its disposal while we
 289          * are messing with it.  Once we have the reference, the map is free
 290          * to be diddled.  Since objects reference their shadows (and copies),
 291          * they will stay around as well.
 292          *
 293          * Bump the paging-in-progress count to prevent size changes (e.g.
 294          * truncation operations) during I/O.  This must be done after
 295          * obtaining the vnode lock in order to avoid possible deadlocks.
 296          */
 297         VM_OBJECT_LOCK(fs.first_object);
 298         vm_object_reference_locked(fs.first_object);
 299         vm_object_pip_add(fs.first_object, 1);
 300
 301         fs.lookup_still_valid = TRUE;
 302
 303         if (wired)
 304                 fault_type = prot;
 305
 306         fs.first_m = NULL;
 307
 308         /*
 309          * Search for the page at object/offset.
 310          */
 311         fs.object = fs.first_object;
 312         fs.pindex = fs.first_pindex;
 313         while (TRUE) {
 314                 /*
 315                  * If the object is dead, we stop here
 316                  */
 317                 if (fs.object->flags & OBJ_DEAD) {
 318                         unlock_and_deallocate(&fs);
 319                         return (KERN_PROTECTION_FAILURE);
 320                 }
 321
 322                 /*
 323                  * See if page is resident
 324                  */
 325                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 326                 if (fs.m != NULL) {
 327                         /*
 328                          * check for page-based copy on write.
 329                          * We check fs.object == fs.first_object so
 330                          * as to ensure the legacy COW mechanism is
 331                          * used when the page in question is part of
 332                          * a shadow object.  Otherwise, vm_page_cowfault()
 333                          * removes the page from the backing object,
 334                          * which is not what we want.
 335                          */
 336                         vm_page_lock_queues();
 337                         if ((fs.m->cow) &&
 338                             (fault_type & VM_PROT_WRITE) &&
 339                             (fs.object == fs.first_object)) {
 340                                 vm_page_cowfault(fs.m);
 341                                 vm_page_unlock_queues();
 342                                 unlock_and_deallocate(&fs);
 343                                 goto RetryFault;
 344                         }
 345
 346                         /*
 347                          * Wait/Retry if the page is busy.  We have to do this
 348                          * if the page is busy via either VPO_BUSY or
 349                          * vm_page_t->busy because the vm_pager may be using
 350                          * vm_page_t->busy for pageouts ( and even pageins if
 351                          * it is the vnode pager ), and we could end up trying
 352                          * to pagein and pageout the same page simultaneously.
 353                          *
 354                          * We can theoretically allow the busy case on a read
 355                          * fault if the page is marked valid, but since such
 356                          * pages are typically already pmap'd, putting that
 357                          * special case in might be more effort then it is
 358                          * worth.  We cannot under any circumstances mess
 359                          * around with a vm_page_t->busy page except, perhaps,
 360                          * to pmap it.
 361                          */
 362                         if ((fs.m->oflags & VPO_BUSY) || fs.m->busy) {
 363                                 vm_page_unlock_queues();
 364                                 if (fs.object != fs.first_object) {
 365                                         if (!VM_OBJECT_TRYLOCK(
 366                                             fs.first_object)) {
 367                                                 VM_OBJECT_UNLOCK(fs.object);
 368                                                 VM_OBJECT_LOCK(fs.first_object);
 369                                                 VM_OBJECT_LOCK(fs.object);
 370                                         }
 371                                         vm_page_lock_queues();
 372                                         vm_page_free(fs.first_m);
 373                                         vm_page_unlock_queues();
 374                                         vm_object_pip_wakeup(fs.first_object);
 375                                         VM_OBJECT_UNLOCK(fs.first_object);
 376                                         fs.first_m = NULL;
 377                                 }
 378                                 unlock_map(&fs);
 379                                 if (fs.m == vm_page_lookup(fs.object,
 380                                     fs.pindex)) {
 381                                         vm_page_sleep_if_busy(fs.m, TRUE,
 382                                             "vmpfw");
 383                                 }
 384                                 vm_object_pip_wakeup(fs.object);
 385                                 VM_OBJECT_UNLOCK(fs.object);
 386                                 PCPU_INC(cnt.v_intrans);
 387                                 vm_object_deallocate(fs.first_object);
 388                                 goto RetryFault;
 389                         }
 390                         vm_pageq_remove(fs.m);
 391                         vm_page_unlock_queues();
 392
 393                         /*
 394                          * Mark page busy for other processes, and the
 395                          * pagedaemon.  If it still isn't completely valid
 396                          * (readable), jump to readrest, else break-out ( we
 397                          * found the page ).
 398                          */
 399                         vm_page_busy(fs.m);
 400                         if (fs.m->valid != VM_PAGE_BITS_ALL &&
 401                                 fs.m->object != kernel_object && fs.m->object != kmem_object) {
 402                                 goto readrest;
 403                         }
 404
 405                         break;
 406                 }
 407
 408                 /*
 409                  * Page is not resident, If this is the search termination
 410                  * or the pager might contain the page, allocate a new page.
 411                  */
 412                 if (TRYPAGER || fs.object == fs.first_object) {
 413                         if (fs.pindex >= fs.object->size) {
 414                                 unlock_and_deallocate(&fs);
 415                                 return (KERN_PROTECTION_FAILURE);
 416                         }
 417
 418                         /*
 419                          * Allocate a new page for this object/offset pair.
 420                          *
 421                          * Unlocked read of the p_flag is harmless. At
 422                          * worst, the P_KILLED might be not observed
 423                          * there, and allocation can fail, causing
 424                          * restart and new reading of the p_flag.
 425                          */
 426                         fs.m = NULL;
 427                         if (!vm_page_count_severe() || P_KILLED(curproc)) {
 428 #if VM_NRESERVLEVEL > 0
 429                                 if ((fs.object->flags & OBJ_COLORED) == 0) {
 430                                         fs.object->flags |= OBJ_COLORED;
 431                                         fs.object->pg_color = atop(vaddr) -
 432                                             fs.pindex;
 433                                 }
 434 #endif
 435                                 alloc_req = P_KILLED(curproc) ?
 436                                     VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
 437                                 if (fs.object->type != OBJT_VNODE &&
 438                                     fs.object->backing_object == NULL)
 439                                         alloc_req |= VM_ALLOC_ZERO;
 440                                 fs.m = vm_page_alloc(fs.object, fs.pindex,
 441                                     alloc_req);
 442                         }
 443                         if (fs.m == NULL) {
 444                                 unlock_and_deallocate(&fs);
 445                                 VM_WAITPFAULT;
 446                                 goto RetryFault;
 447                         } else if (fs.m->valid == VM_PAGE_BITS_ALL)
 448                                 break;
 449                 }
 450
 451 readrest:
 452                 /*
 453                  * We have found a valid page or we have allocated a new page.
 454                  * The page thus may not be valid or may not be entirely
 455                  * valid.
 456                  *
 457                  * Attempt to fault-in the page if there is a chance that the
 458                  * pager has it, and potentially fault in additional pages
 459                  * at the same time.
 460                  */
 461                 if (TRYPAGER) {
 462                         int rv;
 463                         int reqpage = 0;
 464                         u_char behavior = vm_map_entry_behavior(fs.entry);
 465
 466                         if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
 467                             P_KILLED(curproc)) {
 468                                 ahead = 0;
 469                                 behind = 0;
 470                         } else {
 471                                 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT;
 472                                 if (behind > VM_FAULT_READ_BEHIND)
 473                                         behind = VM_FAULT_READ_BEHIND;
 474
 475                                 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1;
 476                                 if (ahead > VM_FAULT_READ_AHEAD)
 477                                         ahead = VM_FAULT_READ_AHEAD;
 478                         }
 479                         is_first_object_locked = FALSE;
 480                         if ((behavior == MAP_ENTRY_BEHAV_SEQUENTIAL ||
 481                              (behavior != MAP_ENTRY_BEHAV_RANDOM &&
 482                               fs.pindex >= fs.entry->lastr &&
 483                               fs.pindex < fs.entry->lastr + VM_FAULT_READ)) &&
 484                             (fs.first_object == fs.object ||
 485                              (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object))) &&
 486                             fs.first_object->type != OBJT_DEVICE &&
 487                             fs.first_object->type != OBJT_PHYS &&
 488                             fs.first_object->type != OBJT_SG) {
 489                                 vm_pindex_t firstpindex, tmppindex;
 490
 491                                 if (fs.first_pindex < 2 * VM_FAULT_READ)
 492                                         firstpindex = 0;
 493                                 else
 494                                         firstpindex = fs.first_pindex - 2 * VM_FAULT_READ;
 495
 496                                 are_queues_locked = FALSE;
 497                                 /*
 498                                  * note: partially valid pages cannot be
 499                                  * included in the lookahead - NFS piecemeal
 500                                  * writes will barf on it badly.
 501                                  */
 502                                 for (tmppindex = fs.first_pindex - 1;
 503                                         tmppindex >= firstpindex;
 504                                         --tmppindex) {
 505                                         vm_page_t mt;
 506
 507                                         mt = vm_page_lookup(fs.first_object, tmppindex);
 508                                         if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL))
 509                                                 break;
 510                                         if (mt->busy ||
 511                                             (mt->oflags & VPO_BUSY))
 512                                                 continue;
 513                                         if (!are_queues_locked) {
 514                                                 are_queues_locked = TRUE;
 515                                                 vm_page_lock_queues();
 516                                         }
 517                                         if (mt->hold_count ||
 518                                                 mt->wire_count)
 519                                                 continue;
 520                                         pmap_remove_all(mt);
 521                                         if (mt->dirty) {
 522                                                 vm_page_deactivate(mt);
 523                                         } else {
 524                                                 vm_page_cache(mt);
 525                                         }
 526                                 }
 527                                 if (are_queues_locked)
 528                                         vm_page_unlock_queues();
 529                                 ahead += behind;
 530                                 behind = 0;
 531                         }
 532                         if (is_first_object_locked)
 533                                 VM_OBJECT_UNLOCK(fs.first_object);
 534
 535                         /*
 536                          * Call the pager to retrieve the data, if any, after
 537                          * releasing the lock on the map.  We hold a ref on
 538                          * fs.object and the pages are VPO_BUSY'd.
 539                          */
 540                         unlock_map(&fs);
 541
 542 vnode_lock:
 543                         if (fs.object->type == OBJT_VNODE) {
 544                                 vp = fs.object->handle;
 545                                 if (vp == fs.vp)
 546                                         goto vnode_locked;
 547                                 else if (fs.vp != NULL) {
 548                                         vput(fs.vp);
 549                                         fs.vp = NULL;
 550                                 }
 551                                 locked = VOP_ISLOCKED(vp);
 552
 553                                 if (VFS_NEEDSGIANT(vp->v_mount) && !fs.vfslocked) {
 554                                         fs.vfslocked = 1;
 555                                         if (!mtx_trylock(&Giant)) {
 556                                                 VM_OBJECT_UNLOCK(fs.object);
 557                                                 mtx_lock(&Giant);
 558                                                 VM_OBJECT_LOCK(fs.object);
 559                                                 goto vnode_lock;
 560                                         }
 561                                 }
 562                                 if (locked != LK_EXCLUSIVE)
 563                                         locked = LK_SHARED;
 564                                 /* Do not sleep for vnode lock while fs.m is busy */
 565                                 error = vget(vp, locked | LK_CANRECURSE |
 566                                     LK_NOWAIT, curthread);
 567                                 if (error != 0) {
 568                                         int vfslocked;
 569
 570                                         vfslocked = fs.vfslocked;
 571                                         fs.vfslocked = 0; /* Keep Giant */
 572                                         vhold(vp);
 573                                         release_page(&fs);
 574                                         unlock_and_deallocate(&fs);
 575                                         error = vget(vp, locked | LK_RETRY |
 576                                             LK_CANRECURSE, curthread);
 577                                         vdrop(vp);
 578                                         fs.vp = vp;
 579                                         fs.vfslocked = vfslocked;
 580                                         KASSERT(error == 0,
 581                                             ("vm_fault: vget failed"));
 582                                         goto RetryFault;
 583                                 }
 584                                 fs.vp = vp;
 585                         }
 586 vnode_locked:
 587                         KASSERT(fs.vp == NULL || !fs.map->system_map,
 588                             ("vm_fault: vnode-backed object mapped by system map"));
 589
 590                         /*
 591                          * now we find out if any other pages should be paged
 592                          * in at this time this routine checks to see if the
 593                          * pages surrounding this fault reside in the same
 594                          * object as the page for this fault.  If they do,
 595                          * then they are faulted in also into the object.  The
 596                          * array "marray" returned contains an array of
 597                          * vm_page_t structs where one of them is the
 598                          * vm_page_t passed to the routine.  The reqpage
 599                          * return value is the index into the marray for the
 600                          * vm_page_t passed to the routine.
 601                          *
 602                          * fs.m plus the additional pages are VPO_BUSY'd.
 603                          */
 604                         faultcount = vm_fault_additional_pages(
 605                             fs.m, behind, ahead, marray, &reqpage);
 606
 607                         rv = faultcount ?
 608                             vm_pager_get_pages(fs.object, marray, faultcount,
 609                                 reqpage) : VM_PAGER_FAIL;
 610
 611                         if (rv == VM_PAGER_OK) {
 612                                 /*
 613                                  * Found the page. Leave it busy while we play
 614                                  * with it.
 615                                  */
 616
 617                                 /*
 618                                  * Relookup in case pager changed page. Pager
 619                                  * is responsible for disposition of old page
 620                                  * if moved.
 621                                  */
 622                                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 623                                 if (!fs.m) {
 624                                         unlock_and_deallocate(&fs);
 625                                         goto RetryFault;
 626                                 }
 627
 628                                 hardfault++;
 629                                 break; /* break to PAGE HAS BEEN FOUND */
 630                         }
 631                         /*
 632                          * Remove the bogus page (which does not exist at this
 633                          * object/offset); before doing so, we must get back
 634                          * our object lock to preserve our invariant.
 635                          *
 636                          * Also wake up any other process that may want to bring
 637                          * in this page.
 638                          *
 639                          * If this is the top-level object, we must leave the
 640                          * busy page to prevent another process from rushing
 641                          * past us, and inserting the page in that object at
 642                          * the same time that we are.
 643                          */
 644                         if (rv == VM_PAGER_ERROR)
 645                                 printf("vm_fault: pager read error, pid %d (%s)\n",
 646                                     curproc->p_pid, curproc->p_comm);
 647                         /*
 648                          * Data outside the range of the pager or an I/O error
 649                          */
 650                         /*
 651                          * XXX - the check for kernel_map is a kludge to work
 652                          * around having the machine panic on a kernel space
 653                          * fault w/ I/O error.
 654                          */
 655                         if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
 656                                 (rv == VM_PAGER_BAD)) {
 657                                 vm_page_lock_queues();
 658                                 vm_page_free(fs.m);
 659                                 vm_page_unlock_queues();
 660                                 fs.m = NULL;
 661                                 unlock_and_deallocate(&fs);
 662                                 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
 663                         }
 664                         if (fs.object != fs.first_object) {
 665                                 vm_page_lock_queues();
 666                                 vm_page_free(fs.m);
 667                                 vm_page_unlock_queues();
 668                                 fs.m = NULL;
 669                                 /*
 670                                  * XXX - we cannot just fall out at this
 671                                  * point, m has been freed and is invalid!
 672                                  */
 673                         }
 674                 }
 675
 676                 /*
 677                  * We get here if the object has default pager (or unwiring)
 678                  * or the pager doesn't have the page.
 679                  */
 680                 if (fs.object == fs.first_object)
 681                         fs.first_m = fs.m;
 682
 683                 /*
 684                  * Move on to the next object.  Lock the next object before
 685                  * unlocking the current one.
 686                  */
 687                 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
 688                 next_object = fs.object->backing_object;
 689                 if (next_object == NULL) {
 690                         /*
 691                          * If there's no object left, fill the page in the top
 692                          * object with zeros.
 693                          */
 694                         if (fs.object != fs.first_object) {
 695                                 vm_object_pip_wakeup(fs.object);
 696                                 VM_OBJECT_UNLOCK(fs.object);
 697
 698                                 fs.object = fs.first_object;
 699                                 fs.pindex = fs.first_pindex;
 700                                 fs.m = fs.first_m;
 701                                 VM_OBJECT_LOCK(fs.object);
 702                         }
 703                         fs.first_m = NULL;
 704
 705                         /*
 706                          * Zero the page if necessary and mark it valid.
 707                          */
 708                         if ((fs.m->flags & PG_ZERO) == 0) {
 709                                 pmap_zero_page(fs.m);
 710                         } else {
 711                                 PCPU_INC(cnt.v_ozfod);
 712                         }
 713                         PCPU_INC(cnt.v_zfod);
 714                         fs.m->valid = VM_PAGE_BITS_ALL;
 715                         break;  /* break to PAGE HAS BEEN FOUND */
 716                 } else {
 717                         KASSERT(fs.object != next_object,
 718                             ("object loop %p", next_object));
 719                         VM_OBJECT_LOCK(next_object);
 720                         vm_object_pip_add(next_object, 1);
 721                         if (fs.object != fs.first_object)
 722                                 vm_object_pip_wakeup(fs.object);
 723                         VM_OBJECT_UNLOCK(fs.object);
 724                         fs.object = next_object;
 725                 }
 726         }
 727
 728         KASSERT((fs.m->oflags & VPO_BUSY) != 0,
 729             ("vm_fault: not busy after main loop"));
 730
 731         /*
 732          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
 733          * is held.]
 734          */
 735
 736         /*
 737          * If the page is being written, but isn't already owned by the
 738          * top-level object, we have to copy it into a new page owned by the
 739          * top-level object.
 740          */
 741         if (fs.object != fs.first_object) {
 742                 /*
 743                  * We only really need to copy if we want to write it.
 744                  */
 745                 if (fault_type & VM_PROT_WRITE) {
 746                         /*
 747                          * This allows pages to be virtually copied from a
 748                          * backing_object into the first_object, where the
 749                          * backing object has no other refs to it, and cannot
 750                          * gain any more refs.  Instead of a bcopy, we just
 751                          * move the page from the backing object to the
 752                          * first object.  Note that we must mark the page
 753                          * dirty in the first object so that it will go out
 754                          * to swap when needed.
 755                          */
 756                         is_first_object_locked = FALSE;
 757                         if (
 758                                 /*
 759                                  * Only one shadow object
 760                                  */
 761                                 (fs.object->shadow_count == 1) &&
 762                                 /*
 763                                  * No COW refs, except us
 764                                  */
 765                                 (fs.object->ref_count == 1) &&
 766                                 /*
 767                                  * No one else can look this object up
 768                                  */
 769                                 (fs.object->handle == NULL) &&
 770                                 /*
 771                                  * No other ways to look the object up
 772                                  */
 773                                 ((fs.object->type == OBJT_DEFAULT) ||
 774                                  (fs.object->type == OBJT_SWAP)) &&
 775                             (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) &&
 776                                 /*
 777                                  * We don't chase down the shadow chain
 778                                  */
 779                             fs.object == fs.first_object->backing_object) {
 780                                 vm_page_lock_queues();
 781                                 /*
 782                                  * get rid of the unnecessary page
 783                                  */
 784                                 vm_page_free(fs.first_m);
 785                                 /*
 786                                  * grab the page and put it into the
 787                                  * process'es object.  The page is
 788                                  * automatically made dirty.
 789                                  */
 790                                 vm_page_rename(fs.m, fs.first_object, fs.first_pindex);
 791                                 vm_page_unlock_queues();
 792                                 vm_page_busy(fs.m);
 793                                 fs.first_m = fs.m;
 794                                 fs.m = NULL;
 795                                 PCPU_INC(cnt.v_cow_optim);
 796                         } else {
 797                                 /*
 798                                  * Oh, well, lets copy it.
 799                                  */
 800                                 pmap_copy_page(fs.m, fs.first_m);
 801                                 fs.first_m->valid = VM_PAGE_BITS_ALL;
 802                         }
 803                         if (fs.m) {
 804                                 /*
 805                                  * We no longer need the old page or object.
 806                                  */
 807                                 release_page(&fs);
 808                         }
 809                         /*
 810                          * fs.object != fs.first_object due to above
 811                          * conditional
 812                          */
 813                         vm_object_pip_wakeup(fs.object);
 814                         VM_OBJECT_UNLOCK(fs.object);
 815                         /*
 816                          * Only use the new page below...
 817                          */
 818                         fs.object = fs.first_object;
 819                         fs.pindex = fs.first_pindex;
 820                         fs.m = fs.first_m;
 821                         if (!is_first_object_locked)
 822                                 VM_OBJECT_LOCK(fs.object);
 823                         PCPU_INC(cnt.v_cow_faults);
 824                 } else {
 825                         prot &= ~VM_PROT_WRITE;
 826                 }
 827         }
 828
 829         /*
 830          * We must verify that the maps have not changed since our last
 831          * lookup.
 832          */
 833         if (!fs.lookup_still_valid) {
 834                 vm_object_t retry_object;
 835                 vm_pindex_t retry_pindex;
 836                 vm_prot_t retry_prot;
 837
 838                 if (!vm_map_trylock_read(fs.map)) {
 839                         release_page(&fs);
 840                         unlock_and_deallocate(&fs);
 841                         goto RetryFault;
 842                 }
 843                 fs.lookup_still_valid = TRUE;
 844                 if (fs.map->timestamp != map_generation) {
 845                         result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
 846                             &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
 847
 848                         /*
 849                          * If we don't need the page any longer, put it on the inactive
 850                          * list (the easiest thing to do here).  If no one needs it,
 851                          * pageout will grab it eventually.
 852                          */
 853                         if (result != KERN_SUCCESS) {
 854                                 release_page(&fs);
 855                                 unlock_and_deallocate(&fs);
 856
 857                                 /*
 858                                  * If retry of map lookup would have blocked then
 859                                  * retry fault from start.
 860                                  */
 861                                 if (result == KERN_FAILURE)
 862                                         goto RetryFault;
 863                                 return (result);
 864                         }
 865                         if ((retry_object != fs.first_object) ||
 866                             (retry_pindex != fs.first_pindex)) {
 867                                 release_page(&fs);
 868                                 unlock_and_deallocate(&fs);
 869                                 goto RetryFault;
 870                         }
 871
 872                         /*
 873                          * Check whether the protection has changed or the object has
 874                          * been copied while we left the map unlocked. Changing from
 875                          * read to write permission is OK - we leave the page
 876                          * write-protected, and catch the write fault. Changing from
 877                          * write to read permission means that we can't mark the page
 878                          * write-enabled after all.
 879                          */
 880                         prot &= retry_prot;
 881                 }
 882         }
 883         /*
 884          * If the page was filled by a pager, update the map entry's
 885          * last read offset.  Since the pager does not return the
 886          * actual set of pages that it read, this update is based on
 887          * the requested set.  Typically, the requested and actual
 888          * sets are the same.
 889          *
 890          * XXX The following assignment modifies the map
 891          * without holding a write lock on it.
 892          */
 893         if (hardfault)
 894                 fs.entry->lastr = fs.pindex + faultcount - behind;
 895
 896         if (prot & VM_PROT_WRITE) {
 897                 vm_object_set_writeable_dirty(fs.object);
 898
 899                 /*
 900                  * If the fault is a write, we know that this page is being
 901                  * written NOW so dirty it explicitly to save on
 902                  * pmap_is_modified() calls later.
 903                  *
 904                  * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
 905                  * if the page is already dirty to prevent data written with
 906                  * the expectation of being synced from not being synced.
 907                  * Likewise if this entry does not request NOSYNC then make
 908                  * sure the page isn't marked NOSYNC.  Applications sharing
 909                  * data should use the same flags to avoid ping ponging.
 910                  *
 911                  * Also tell the backing pager, if any, that it should remove
 912                  * any swap backing since the page is now dirty.
 913                  */
 914                 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) {
 915                         if (fs.m->dirty == 0)
 916                                 fs.m->oflags |= VPO_NOSYNC;
 917                 } else {
 918                         fs.m->oflags &= ~VPO_NOSYNC;
 919                 }
 920                 if (fault_flags & VM_FAULT_DIRTY) {
 921                         vm_page_dirty(fs.m);
 922                         vm_pager_page_unswapped(fs.m);
 923                 }
 924         }
 925
 926         /*
 927          * Page had better still be busy
 928          */
 929         KASSERT(fs.m->oflags & VPO_BUSY,
 930                 ("vm_fault: page %p not busy!", fs.m));
 931         /*
 932          * Page must be completely valid or it is not fit to
 933          * map into user space.  vm_pager_get_pages() ensures this.
 934          */
 935         KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
 936             ("vm_fault: page %p partially invalid", fs.m));
 937         VM_OBJECT_UNLOCK(fs.object);
 938
 939         /*
 940          * Put this page into the physical map.  We had to do the unlock above
 941          * because pmap_enter() may sleep.  We don't put the page
 942          * back on the active queue until later so that the pageout daemon
 943          * won't find it (yet).
 944          */
 945         pmap_enter(fs.map->pmap, vaddr, fault_type, fs.m, prot, wired);
 946         if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) {
 947                 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry);
 948         }
 949         VM_OBJECT_LOCK(fs.object);
 950         vm_page_lock_queues();
 951         vm_page_flag_set(fs.m, PG_REFERENCED);
 952
 953         /*
 954          * If the page is not wired down, then put it where the pageout daemon
 955          * can find it.
 956          */
 957         if (fault_flags & VM_FAULT_WIRE_MASK) {
 958                 if (wired)
 959                         vm_page_wire(fs.m);
 960                 else
 961                         vm_page_unwire(fs.m, 1);
 962         } else {
 963                 vm_page_activate(fs.m);
 964         }
 965         vm_page_unlock_queues();
 966         vm_page_wakeup(fs.m);
 967
 968         /*
 969          * Unlock everything, and return
 970          */
 971         unlock_and_deallocate(&fs);
 972         if (hardfault)
 973                 curthread->td_ru.ru_majflt++;
 974         else
 975                 curthread->td_ru.ru_minflt++;
 976
 977         return (KERN_SUCCESS);
 978 }
 979
 980 /*
 981  * vm_fault_prefault provides a quick way of clustering
 982  * pagefaults into a processes address space.  It is a "cousin"
 983  * of vm_map_pmap_enter, except it runs at page fault time instead
 984  * of mmap time.
 985  */
 986 static void
 987 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry)
 988 {
 989         int i;
 990         vm_offset_t addr, starta;
 991         vm_pindex_t pindex;
 992         vm_page_t m;
 993         vm_object_t object;
 994
 995         if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
 996                 return;
 997
 998         object = entry->object.vm_object;
 999
1000         starta = addra - PFBAK * PAGE_SIZE;
1001         if (starta < entry->start) {
1002                 starta = entry->start;
1003         } else if (starta > addra) {
1004                 starta = 0;
1005         }
1006
1007         for (i = 0; i < PAGEORDER_SIZE; i++) {
1008                 vm_object_t backing_object, lobject;
1009
1010                 addr = addra + prefault_pageorder[i];
1011                 if (addr > addra + (PFFOR * PAGE_SIZE))
1012                         addr = 0;
1013
1014                 if (addr < starta || addr >= entry->end)
1015                         continue;
1016
1017                 if (!pmap_is_prefaultable(pmap, addr))
1018                         continue;
1019
1020                 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1021                 lobject = object;
1022                 VM_OBJECT_LOCK(lobject);
1023                 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1024                     lobject->type == OBJT_DEFAULT &&
1025                     (backing_object = lobject->backing_object) != NULL) {
1026                         KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1027                             0, ("vm_fault_prefault: unaligned object offset"));
1028                         pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1029                         VM_OBJECT_LOCK(backing_object);
1030                         VM_OBJECT_UNLOCK(lobject);
1031                         lobject = backing_object;
1032                 }
1033                 /*
1034                  * give-up when a page is not in memory
1035                  */
1036                 if (m == NULL) {
1037                         VM_OBJECT_UNLOCK(lobject);
1038                         break;
1039                 }
1040                 if (m->valid == VM_PAGE_BITS_ALL &&
1041                     (m->flags & PG_FICTITIOUS) == 0) {
1042                         vm_page_lock_queues();
1043                         pmap_enter_quick(pmap, addr, m, entry->protection);
1044                         vm_page_unlock_queues();
1045                 }
1046                 VM_OBJECT_UNLOCK(lobject);
1047         }
1048 }
1049
1050 /*
1051  *      vm_fault_quick:
1052  *
1053  *      Ensure that the requested virtual address, which may be in userland,
1054  *      is valid.  Fault-in the page if necessary.  Return -1 on failure.
1055  */
1056 int
1057 vm_fault_quick(caddr_t v, int prot)
1058 {
1059         int r;
1060
1061         if (prot & VM_PROT_WRITE)
1062                 r = subyte(v, fubyte(v));
1063         else
1064                 r = fubyte(v);
1065         return(r);
1066 }
1067
1068 /*
1069  *      vm_fault_wire:
1070  *
1071  *      Wire down a range of virtual addresses in a map.
1072  */
1073 int
1074 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1075     boolean_t user_wire, boolean_t fictitious)
1076 {
1077         vm_offset_t va;
1078         int rv;
1079
1080         /*
1081          * We simulate a fault to get the page and enter it in the physical
1082          * map.  For user wiring, we only ask for read access on currently
1083          * read-only sections.
1084          */
1085         for (va = start; va < end; va += PAGE_SIZE) {
1086                 rv = vm_fault(map, va,
1087                     user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE,
1088                     user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING);
1089                 if (rv) {
1090                         if (va != start)
1091                                 vm_fault_unwire(map, start, va, fictitious);
1092                         return (rv);
1093                 }
1094         }
1095         return (KERN_SUCCESS);
1096 }
1097
1098 /*
1099  *      vm_fault_unwire:
1100  *
1101  *      Unwire a range of virtual addresses in a map.
1102  */
1103 void
1104 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1105     boolean_t fictitious)
1106 {
1107         vm_paddr_t pa;
1108         vm_offset_t va;
1109         pmap_t pmap;
1110
1111         pmap = vm_map_pmap(map);
1112
1113         /*
1114          * Since the pages are wired down, we must be able to get their
1115          * mappings from the physical map system.
1116          */
1117         for (va = start; va < end; va += PAGE_SIZE) {
1118                 pa = pmap_extract(pmap, va);
1119                 if (pa != 0) {
1120                         pmap_change_wiring(pmap, va, FALSE);
1121                         if (!fictitious) {
1122                                 vm_page_lock_queues();
1123                                 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1);
1124                                 vm_page_unlock_queues();
1125                         }
1126                 }
1127         }
1128 }
1129
1130 /*
1131  *      Routine:
1132  *              vm_fault_copy_entry
1133  *      Function:
1134  *              Create new shadow object backing dst_entry with private copy of
1135  *              all underlying pages. When src_entry is equal to dst_entry,
1136  *              function implements COW for wired-down map entry. Otherwise,
1137  *              it forks wired entry into dst_map.
1138  *
1139  *      In/out conditions:
1140  *              The source and destination maps must be locked for write.
1141  *              The source map entry must be wired down (or be a sharing map
1142  *              entry corresponding to a main map entry that is wired down).
1143  */
1144 void
1145 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1146     vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1147     vm_ooffset_t *fork_charge)
1148 {
1149         vm_object_t backing_object, dst_object, object, src_object;
1150         vm_pindex_t dst_pindex, pindex, src_pindex;
1151         vm_prot_t access, prot;
1152         vm_offset_t vaddr;
1153         vm_page_t dst_m;
1154         vm_page_t src_m;
1155         boolean_t src_readonly, upgrade;
1156
1157 #ifdef  lint
1158         src_map++;
1159 #endif  /* lint */
1160
1161         upgrade = src_entry == dst_entry;
1162
1163         src_object = src_entry->object.vm_object;
1164         src_pindex = OFF_TO_IDX(src_entry->offset);
1165         src_readonly = (src_entry->protection & VM_PROT_WRITE) == 0;
1166
1167         /*
1168          * Create the top-level object for the destination entry. (Doesn't
1169          * actually shadow anything - we copy the pages directly.)
1170          */
1171         dst_object = vm_object_allocate(OBJT_DEFAULT,
1172             OFF_TO_IDX(dst_entry->end - dst_entry->start));
1173 #if VM_NRESERVLEVEL > 0
1174         dst_object->flags |= OBJ_COLORED;
1175         dst_object->pg_color = atop(dst_entry->start);
1176 #endif
1177
1178         VM_OBJECT_LOCK(dst_object);
1179         KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1180             ("vm_fault_copy_entry: vm_object not NULL"));
1181         dst_entry->object.vm_object = dst_object;
1182         dst_entry->offset = 0;
1183         dst_object->charge = dst_entry->end - dst_entry->start;
1184         if (fork_charge != NULL) {
1185                 KASSERT(dst_entry->uip == NULL,
1186                     ("vm_fault_copy_entry: leaked swp charge"));
1187                 dst_object->uip = curthread->td_ucred->cr_ruidinfo;
1188                 uihold(dst_object->uip);
1189                 *fork_charge += dst_object->charge;
1190         } else {
1191                 dst_object->uip = dst_entry->uip;
1192                 dst_entry->uip = NULL;
1193         }
1194         access = prot = dst_entry->max_protection;
1195         /*
1196          * If not an upgrade, then enter the mappings in the pmap as
1197          * read and/or execute accesses.  Otherwise, enter them as
1198          * write accesses.
1199          *
1200          * A writeable large page mapping is only created if all of
1201          * the constituent small page mappings are modified. Marking
1202          * PTEs as modified on inception allows promotion to happen
1203          * without taking potentially large number of soft faults.
1204          */
1205         if (!upgrade)
1206                 access &= ~VM_PROT_WRITE;
1207
1208         /*
1209          * Loop through all of the pages in the entry's range, copying each
1210          * one from the source object (it should be there) to the destination
1211          * object.
1212          */
1213         for (vaddr = dst_entry->start, dst_pindex = 0;
1214             vaddr < dst_entry->end;
1215             vaddr += PAGE_SIZE, dst_pindex++) {
1216
1217                 /*
1218                  * Allocate a page in the destination object.
1219                  */
1220                 do {
1221                         dst_m = vm_page_alloc(dst_object, dst_pindex,
1222                             VM_ALLOC_NORMAL);
1223                         if (dst_m == NULL) {
1224                                 VM_OBJECT_UNLOCK(dst_object);
1225                                 VM_WAIT;
1226                                 VM_OBJECT_LOCK(dst_object);
1227                         }
1228                 } while (dst_m == NULL);
1229
1230                 /*
1231                  * Find the page in the source object, and copy it in.
1232                  * (Because the source is wired down, the page will be in
1233                  * memory.)
1234                  */
1235                 VM_OBJECT_LOCK(src_object);
1236                 object = src_object;
1237                 pindex = src_pindex + dst_pindex;
1238                 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1239                     src_readonly &&
1240                     (backing_object = object->backing_object) != NULL) {
1241                         /*
1242                          * Allow fallback to backing objects if we are reading.
1243                          */
1244                         VM_OBJECT_LOCK(backing_object);
1245                         pindex += OFF_TO_IDX(object->backing_object_offset);
1246                         VM_OBJECT_UNLOCK(object);
1247                         object = backing_object;
1248                 }
1249                 if (src_m == NULL)
1250                         panic("vm_fault_copy_wired: page missing");
1251                 pmap_copy_page(src_m, dst_m);
1252                 VM_OBJECT_UNLOCK(object);
1253                 dst_m->valid = VM_PAGE_BITS_ALL;
1254                 VM_OBJECT_UNLOCK(dst_object);
1255
1256                 /*
1257                  * Enter it in the pmap. If a wired, copy-on-write
1258                  * mapping is being replaced by a write-enabled
1259                  * mapping, then wire that new mapping.
1260                  */
1261                 pmap_enter(dst_map->pmap, vaddr, access, dst_m, prot, upgrade);
1262
1263                 /*
1264                  * Mark it no longer busy, and put it on the active list.
1265                  */
1266                 VM_OBJECT_LOCK(dst_object);
1267                 vm_page_lock_queues();
1268                 if (upgrade) {
1269                         vm_page_unwire(src_m, 0);
1270                         vm_page_wire(dst_m);
1271                 } else
1272                         vm_page_activate(dst_m);
1273                 vm_page_unlock_queues();
1274                 vm_page_wakeup(dst_m);
1275         }
1276         VM_OBJECT_UNLOCK(dst_object);
1277         if (upgrade) {
1278                 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1279                 vm_object_deallocate(src_object);
1280         }
1281 }
1282
1283
1284 /*
1285  * This routine checks around the requested page for other pages that
1286  * might be able to be faulted in.  This routine brackets the viable
1287  * pages for the pages to be paged in.
1288  *
1289  * Inputs:
1290  *      m, rbehind, rahead
1291  *
1292  * Outputs:
1293  *  marray (array of vm_page_t), reqpage (index of requested page)
1294  *
1295  * Return value:
1296  *  number of pages in marray
1297  */
1298 static int
1299 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1300         vm_page_t m;
1301         int rbehind;
1302         int rahead;
1303         vm_page_t *marray;
1304         int *reqpage;
1305 {
1306         int i,j;
1307         vm_object_t object;
1308         vm_pindex_t pindex, startpindex, endpindex, tpindex;
1309         vm_page_t rtm;
1310         int cbehind, cahead;
1311
1312         VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
1313
1314         object = m->object;
1315         pindex = m->pindex;
1316         cbehind = cahead = 0;
1317
1318         /*
1319          * if the requested page is not available, then give up now
1320          */
1321         if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1322                 return 0;
1323         }
1324
1325         if ((cbehind == 0) && (cahead == 0)) {
1326                 *reqpage = 0;
1327                 marray[0] = m;
1328                 return 1;
1329         }
1330
1331         if (rahead > cahead) {
1332                 rahead = cahead;
1333         }
1334
1335         if (rbehind > cbehind) {
1336                 rbehind = cbehind;
1337         }
1338
1339         /*
1340          * scan backward for the read behind pages -- in memory
1341          */
1342         if (pindex > 0) {
1343                 if (rbehind > pindex) {
1344                         rbehind = pindex;
1345                         startpindex = 0;
1346                 } else {
1347                         startpindex = pindex - rbehind;
1348                 }
1349
1350                 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL &&
1351                     rtm->pindex >= startpindex)
1352                         startpindex = rtm->pindex + 1;
1353
1354                 /* tpindex is unsigned; beware of numeric underflow. */
1355                 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex &&
1356                     tpindex < pindex; i++, tpindex--) {
1357
1358                         rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1359                             VM_ALLOC_IFNOTCACHED);
1360                         if (rtm == NULL) {
1361                                 /*
1362                                  * Shift the allocated pages to the
1363                                  * beginning of the array.
1364                                  */
1365                                 for (j = 0; j < i; j++) {
1366                                         marray[j] = marray[j + tpindex + 1 -
1367                                             startpindex];
1368                                 }
1369                                 break;
1370                         }
1371
1372                         marray[tpindex - startpindex] = rtm;
1373                 }
1374         } else {
1375                 startpindex = 0;
1376                 i = 0;
1377         }
1378
1379         marray[i] = m;
1380         /* page offset of the required page */
1381         *reqpage = i;
1382
1383         tpindex = pindex + 1;
1384         i++;
1385
1386         /*
1387          * scan forward for the read ahead pages
1388          */
1389         endpindex = tpindex + rahead;
1390         if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex)
1391                 endpindex = rtm->pindex;
1392         if (endpindex > object->size)
1393                 endpindex = object->size;
1394
1395         for (; tpindex < endpindex; i++, tpindex++) {
1396
1397                 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1398                     VM_ALLOC_IFNOTCACHED);
1399                 if (rtm == NULL) {
1400                         break;
1401                 }
1402
1403                 marray[i] = rtm;
1404         }
1405
1406         /* return number of pages */
1407         return i;
1408 }