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  * $FreeBSD$
  70  */
  71
  72 /*
  73  *      Page fault handling module.
  74  */
  75
  76 #include <sys/param.h>
  77 #include <sys/systm.h>
  78 #include <sys/lock.h>
  79 #include <sys/mutex.h>
  80 #include <sys/proc.h>
  81 #include <sys/vnode.h>
  82 #include <sys/resourcevar.h>
  83 #include <sys/vmmeter.h>
  84
  85 #include <vm/vm.h>
  86 #include <vm/vm_param.h>
  87 #include <vm/pmap.h>
  88 #include <vm/vm_map.h>
  89 #include <vm/vm_object.h>
  90 #include <vm/vm_page.h>
  91 #include <vm/vm_pageout.h>
  92 #include <vm/vm_kern.h>
  93 #include <vm/vm_pager.h>
  94 #include <vm/vnode_pager.h>
  95 #include <vm/vm_extern.h>
  96
  97 static int vm_fault_additional_pages __P((vm_page_t, int,
  98                                           int, vm_page_t *, int *));
  99
 100 #define VM_FAULT_READ_AHEAD 8
 101 #define VM_FAULT_READ_BEHIND 7
 102 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1)
 103
 104 struct faultstate {
 105         vm_page_t m;
 106         vm_object_t object;
 107         vm_pindex_t pindex;
 108         vm_page_t first_m;
 109         vm_object_t     first_object;
 110         vm_pindex_t first_pindex;
 111         vm_map_t map;
 112         vm_map_entry_t entry;
 113         int lookup_still_valid;
 114         struct vnode *vp;
 115 };
 116
 117 static __inline void
 118 release_page(struct faultstate *fs)
 119 {
 120         vm_page_wakeup(fs->m);
 121         vm_page_deactivate(fs->m);
 122         fs->m = NULL;
 123 }
 124
 125 static __inline void
 126 unlock_map(struct faultstate *fs)
 127 {
 128         if (fs->lookup_still_valid) {
 129                 vm_map_lookup_done(fs->map, fs->entry);
 130                 fs->lookup_still_valid = FALSE;
 131         }
 132 }
 133
 134 static void
 135 _unlock_things(struct faultstate *fs, int dealloc)
 136 {
 137         vm_object_pip_wakeup(fs->object);
 138         if (fs->object != fs->first_object) {
 139                 vm_page_free(fs->first_m);
 140                 vm_object_pip_wakeup(fs->first_object);
 141                 fs->first_m = NULL;
 142         }
 143         if (dealloc) {
 144                 vm_object_deallocate(fs->first_object);
 145         }
 146         unlock_map(fs);
 147         if (fs->vp != NULL) {
 148                 vput(fs->vp);
 149                 fs->vp = NULL;
 150         }
 151 }
 152
 153 #define unlock_things(fs) _unlock_things(fs, 0)
 154 #define unlock_and_deallocate(fs) _unlock_things(fs, 1)
 155
 156 /*
 157  * TRYPAGER - used by vm_fault to calculate whether the pager for the
 158  *            current object *might* contain the page.
 159  *
 160  *            default objects are zero-fill, there is no real pager.
 161  */
 162
 163 #define TRYPAGER        (fs.object->type != OBJT_DEFAULT && \
 164                         (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired))
 165
 166 /*
 167  *      vm_fault:
 168  *
 169  *      Handle a page fault occurring at the given address,
 170  *      requiring the given permissions, in the map specified.
 171  *      If successful, the page is inserted into the
 172  *      associated physical map.
 173  *
 174  *      NOTE: the given address should be truncated to the
 175  *      proper page address.
 176  *
 177  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 178  *      a standard error specifying why the fault is fatal is returned.
 179  *
 180  *
 181  *      The map in question must be referenced, and remains so.
 182  *      Caller may hold no locks.
 183  */
 184 int
 185 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, int fault_flags)
 186 {
 187         vm_prot_t prot;
 188         int result;
 189         boolean_t wired;
 190         int map_generation;
 191         vm_object_t next_object;
 192         vm_page_t marray[VM_FAULT_READ];
 193         int hardfault;
 194         int faultcount;
 195         struct faultstate fs;
 196
 197         cnt.v_vm_faults++;      /* needs lock XXX */
 198         hardfault = 0;
 199
 200 RetryFault:;
 201
 202         /*
 203          * Find the backing store object and offset into it to begin the
 204          * search.
 205          */
 206         fs.map = map;
 207         if ((result = vm_map_lookup(&fs.map, vaddr,
 208                 fault_type, &fs.entry, &fs.first_object,
 209                 &fs.first_pindex, &prot, &wired)) != KERN_SUCCESS) {
 210                 if ((result != KERN_PROTECTION_FAILURE) ||
 211                         ((fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE)) {
 212                         return result;
 213                 }
 214
 215                 /*
 216                  * If we are user-wiring a r/w segment, and it is COW, then
 217                  * we need to do the COW operation.  Note that we don't COW
 218                  * currently RO sections now, because it is NOT desirable
 219                  * to COW .text.  We simply keep .text from ever being COW'ed
 220                  * and take the heat that one cannot debug wired .text sections.
 221                  */
 222                 result = vm_map_lookup(&fs.map, vaddr,
 223                         VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE,
 224                         &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired);
 225                 if (result != KERN_SUCCESS) {
 226                         return result;
 227                 }
 228
 229                 /*
 230                  * If we don't COW now, on a user wire, the user will never
 231                  * be able to write to the mapping.  If we don't make this
 232                  * restriction, the bookkeeping would be nearly impossible.
 233                  */
 234                 if ((fs.entry->protection & VM_PROT_WRITE) == 0)
 235                         fs.entry->max_protection &= ~VM_PROT_WRITE;
 236         }
 237
 238         map_generation = fs.map->timestamp;
 239
 240         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 241                 panic("vm_fault: fault on nofault entry, addr: %lx",
 242                     (u_long)vaddr);
 243         }
 244
 245         /*
 246          * Make a reference to this object to prevent its disposal while we
 247          * are messing with it.  Once we have the reference, the map is free
 248          * to be diddled.  Since objects reference their shadows (and copies),
 249          * they will stay around as well.
 250          */
 251         vm_object_reference(fs.first_object);
 252         vm_object_pip_add(fs.first_object, 1);
 253
 254         fs.vp = vnode_pager_lock(fs.first_object);
 255         if ((fault_type & VM_PROT_WRITE) &&
 256                 (fs.first_object->type == OBJT_VNODE)) {
 257                 vm_freeze_copyopts(fs.first_object,
 258                         fs.first_pindex, fs.first_pindex + 1);
 259         }
 260
 261         fs.lookup_still_valid = TRUE;
 262
 263         if (wired)
 264                 fault_type = prot;
 265
 266         fs.first_m = NULL;
 267
 268         /*
 269          * Search for the page at object/offset.
 270          */
 271
 272         fs.object = fs.first_object;
 273         fs.pindex = fs.first_pindex;
 274
 275         while (TRUE) {
 276                 /*
 277                  * If the object is dead, we stop here
 278                  */
 279
 280                 if (fs.object->flags & OBJ_DEAD) {
 281                         unlock_and_deallocate(&fs);
 282                         return (KERN_PROTECTION_FAILURE);
 283                 }
 284
 285                 /*
 286                  * See if page is resident
 287                  */
 288
 289                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 290                 if (fs.m != NULL) {
 291                         int queue, s;
 292                         /*
 293                          * Wait/Retry if the page is busy.  We have to do this
 294                          * if the page is busy via either PG_BUSY or
 295                          * vm_page_t->busy because the vm_pager may be using
 296                          * vm_page_t->busy for pageouts ( and even pageins if
 297                          * it is the vnode pager ), and we could end up trying
 298                          * to pagein and pageout the same page simultaneously.
 299                          *
 300                          * We can theoretically allow the busy case on a read
 301                          * fault if the page is marked valid, but since such
 302                          * pages are typically already pmap'd, putting that
 303                          * special case in might be more effort then it is
 304                          * worth.  We cannot under any circumstances mess
 305                          * around with a vm_page_t->busy page except, perhaps,
 306                          * to pmap it.
 307                          */
 308                         if ((fs.m->flags & PG_BUSY) || fs.m->busy) {
 309                                 unlock_things(&fs);
 310                                 (void)vm_page_sleep_busy(fs.m, TRUE, "vmpfw");
 311                                 cnt.v_intrans++;
 312                                 vm_object_deallocate(fs.first_object);
 313                                 goto RetryFault;
 314                         }
 315
 316                         queue = fs.m->queue;
 317                         s = splvm();
 318                         vm_page_unqueue_nowakeup(fs.m);
 319                         splx(s);
 320
 321                         if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) {
 322                                 vm_page_activate(fs.m);
 323                                 unlock_and_deallocate(&fs);
 324                                 VM_WAIT;
 325                                 goto RetryFault;
 326                         }
 327
 328                         /*
 329                          * Mark page busy for other processes, and the
 330                          * pagedaemon.  If it still isn't completely valid
 331                          * (readable), jump to readrest, else break-out ( we
 332                          * found the page ).
 333                          */
 334
 335                         vm_page_busy(fs.m);
 336                         if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) &&
 337                                 fs.m->object != kernel_object && fs.m->object != kmem_object) {
 338                                 goto readrest;
 339                         }
 340
 341                         break;
 342                 }
 343
 344                 /*
 345                  * Page is not resident, If this is the search termination
 346                  * or the pager might contain the page, allocate a new page.
 347                  */
 348
 349                 if (TRYPAGER || fs.object == fs.first_object) {
 350                         if (fs.pindex >= fs.object->size) {
 351                                 unlock_and_deallocate(&fs);
 352                                 return (KERN_PROTECTION_FAILURE);
 353                         }
 354
 355                         /*
 356                          * Allocate a new page for this object/offset pair.
 357                          */
 358                         fs.m = NULL;
 359                         if (!vm_page_count_severe()) {
 360                                 fs.m = vm_page_alloc(fs.object, fs.pindex,
 361                                     (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO);
 362                         }
 363                         if (fs.m == NULL) {
 364                                 unlock_and_deallocate(&fs);
 365                                 VM_WAIT;
 366                                 goto RetryFault;
 367                         }
 368                 }
 369
 370 readrest:
 371                 /*
 372                  * We have found a valid page or we have allocated a new page.
 373                  * The page thus may not be valid or may not be entirely
 374                  * valid.
 375                  *
 376                  * Attempt to fault-in the page if there is a chance that the
 377                  * pager has it, and potentially fault in additional pages
 378                  * at the same time.
 379                  */
 380
 381                 if (TRYPAGER) {
 382                         int rv;
 383                         int reqpage;
 384                         int ahead, behind;
 385                         u_char behavior = vm_map_entry_behavior(fs.entry);
 386
 387                         if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
 388                                 ahead = 0;
 389                                 behind = 0;
 390                         } else {
 391                                 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT;
 392                                 if (behind > VM_FAULT_READ_BEHIND)
 393                                         behind = VM_FAULT_READ_BEHIND;
 394
 395                                 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1;
 396                                 if (ahead > VM_FAULT_READ_AHEAD)
 397                                         ahead = VM_FAULT_READ_AHEAD;
 398                         }
 399
 400                         if ((fs.first_object->type != OBJT_DEVICE) &&
 401                             (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL ||
 402                                 (behavior != MAP_ENTRY_BEHAV_RANDOM &&
 403                                 fs.pindex >= fs.entry->lastr &&
 404                                 fs.pindex < fs.entry->lastr + VM_FAULT_READ))
 405                         ) {
 406                                 vm_pindex_t firstpindex, tmppindex;
 407
 408                                 if (fs.first_pindex < 2 * VM_FAULT_READ)
 409                                         firstpindex = 0;
 410                                 else
 411                                         firstpindex = fs.first_pindex - 2 * VM_FAULT_READ;
 412
 413                                 /*
 414                                  * note: partially valid pages cannot be
 415                                  * included in the lookahead - NFS piecemeal
 416                                  * writes will barf on it badly.
 417                                  */
 418
 419                                 for(tmppindex = fs.first_pindex - 1;
 420                                         tmppindex >= firstpindex;
 421                                         --tmppindex) {
 422                                         vm_page_t mt;
 423                                         mt = vm_page_lookup( fs.first_object, tmppindex);
 424                                         if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL))
 425                                                 break;
 426                                         if (mt->busy ||
 427                                                 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) ||
 428                                                 mt->hold_count ||
 429                                                 mt->wire_count)
 430                                                 continue;
 431                                         if (mt->dirty == 0)
 432                                                 vm_page_test_dirty(mt);
 433                                         if (mt->dirty) {
 434                                                 vm_page_protect(mt, VM_PROT_NONE);
 435                                                 vm_page_deactivate(mt);
 436                                         } else {
 437                                                 vm_page_cache(mt);
 438                                         }
 439                                 }
 440
 441                                 ahead += behind;
 442                                 behind = 0;
 443                         }
 444
 445                         /*
 446                          * now we find out if any other pages should be paged
 447                          * in at this time this routine checks to see if the
 448                          * pages surrounding this fault reside in the same
 449                          * object as the page for this fault.  If they do,
 450                          * then they are faulted in also into the object.  The
 451                          * array "marray" returned contains an array of
 452                          * vm_page_t structs where one of them is the
 453                          * vm_page_t passed to the routine.  The reqpage
 454                          * return value is the index into the marray for the
 455                          * vm_page_t passed to the routine.
 456                          *
 457                          * fs.m plus the additional pages are PG_BUSY'd.
 458                          */
 459                         faultcount = vm_fault_additional_pages(
 460                             fs.m, behind, ahead, marray, &reqpage);
 461
 462                         /*
 463                          * update lastr imperfectly (we do not know how much
 464                          * getpages will actually read), but good enough.
 465                          */
 466                         fs.entry->lastr = fs.pindex + faultcount - behind;
 467
 468                         /*
 469                          * Call the pager to retrieve the data, if any, after
 470                          * releasing the lock on the map.  We hold a ref on
 471                          * fs.object and the pages are PG_BUSY'd.
 472                          */
 473                         unlock_map(&fs);
 474
 475                         rv = faultcount ?
 476                             vm_pager_get_pages(fs.object, marray, faultcount,
 477                                 reqpage) : VM_PAGER_FAIL;
 478
 479                         if (rv == VM_PAGER_OK) {
 480                                 /*
 481                                  * Found the page. Leave it busy while we play
 482                                  * with it.
 483                                  */
 484
 485                                 /*
 486                                  * Relookup in case pager changed page. Pager
 487                                  * is responsible for disposition of old page
 488                                  * if moved.
 489                                  */
 490                                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 491                                 if(!fs.m) {
 492                                         unlock_and_deallocate(&fs);
 493                                         goto RetryFault;
 494                                 }
 495
 496                                 hardfault++;
 497                                 break; /* break to PAGE HAS BEEN FOUND */
 498                         }
 499                         /*
 500                          * Remove the bogus page (which does not exist at this
 501                          * object/offset); before doing so, we must get back
 502                          * our object lock to preserve our invariant.
 503                          *
 504                          * Also wake up any other process that may want to bring
 505                          * in this page.
 506                          *
 507                          * If this is the top-level object, we must leave the
 508                          * busy page to prevent another process from rushing
 509                          * past us, and inserting the page in that object at
 510                          * the same time that we are.
 511                          */
 512
 513                         if (rv == VM_PAGER_ERROR)
 514                                 printf("vm_fault: pager read error, pid %d (%s)\n",
 515                                     curproc->p_pid, curproc->p_comm);
 516                         /*
 517                          * Data outside the range of the pager or an I/O error
 518                          */
 519                         /*
 520                          * XXX - the check for kernel_map is a kludge to work
 521                          * around having the machine panic on a kernel space
 522                          * fault w/ I/O error.
 523                          */
 524                         if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
 525                                 (rv == VM_PAGER_BAD)) {
 526                                 vm_page_free(fs.m);
 527                                 fs.m = NULL;
 528                                 unlock_and_deallocate(&fs);
 529                                 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
 530                         }
 531                         if (fs.object != fs.first_object) {
 532                                 vm_page_free(fs.m);
 533                                 fs.m = NULL;
 534                                 /*
 535                                  * XXX - we cannot just fall out at this
 536                                  * point, m has been freed and is invalid!
 537                                  */
 538                         }
 539                 }
 540
 541                 /*
 542                  * We get here if the object has default pager (or unwiring)
 543                  * or the pager doesn't have the page.
 544                  */
 545                 if (fs.object == fs.first_object)
 546                         fs.first_m = fs.m;
 547
 548                 /*
 549                  * Move on to the next object.  Lock the next object before
 550                  * unlocking the current one.
 551                  */
 552
 553                 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
 554                 next_object = fs.object->backing_object;
 555                 if (next_object == NULL) {
 556                         /*
 557                          * If there's no object left, fill the page in the top
 558                          * object with zeros.
 559                          */
 560                         if (fs.object != fs.first_object) {
 561                                 vm_object_pip_wakeup(fs.object);
 562
 563                                 fs.object = fs.first_object;
 564                                 fs.pindex = fs.first_pindex;
 565                                 fs.m = fs.first_m;
 566                         }
 567                         fs.first_m = NULL;
 568
 569                         /*
 570                          * Zero the page if necessary and mark it valid.
 571                          */
 572                         if ((fs.m->flags & PG_ZERO) == 0) {
 573                                 vm_page_zero_fill(fs.m);
 574                         } else {
 575                                 cnt.v_ozfod++;
 576                         }
 577                         cnt.v_zfod++;
 578                         fs.m->valid = VM_PAGE_BITS_ALL;
 579                         break;  /* break to PAGE HAS BEEN FOUND */
 580                 } else {
 581                         if (fs.object != fs.first_object) {
 582                                 vm_object_pip_wakeup(fs.object);
 583                         }
 584                         KASSERT(fs.object != next_object, ("object loop %p", next_object));
 585                         fs.object = next_object;
 586                         vm_object_pip_add(fs.object, 1);
 587                 }
 588         }
 589
 590         KASSERT((fs.m->flags & PG_BUSY) != 0,
 591             ("vm_fault: not busy after main loop"));
 592
 593         /*
 594          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
 595          * is held.]
 596          */
 597
 598         /*
 599          * If the page is being written, but isn't already owned by the
 600          * top-level object, we have to copy it into a new page owned by the
 601          * top-level object.
 602          */
 603
 604         if (fs.object != fs.first_object) {
 605                 /*
 606                  * We only really need to copy if we want to write it.
 607                  */
 608
 609                 if (fault_type & VM_PROT_WRITE) {
 610                         /*
 611                          * This allows pages to be virtually copied from a
 612                          * backing_object into the first_object, where the
 613                          * backing object has no other refs to it, and cannot
 614                          * gain any more refs.  Instead of a bcopy, we just
 615                          * move the page from the backing object to the
 616                          * first object.  Note that we must mark the page
 617                          * dirty in the first object so that it will go out
 618                          * to swap when needed.
 619                          */
 620                         if (map_generation == fs.map->timestamp &&
 621                                 /*
 622                                  * Only one shadow object
 623                                  */
 624                                 (fs.object->shadow_count == 1) &&
 625                                 /*
 626                                  * No COW refs, except us
 627                                  */
 628                                 (fs.object->ref_count == 1) &&
 629                                 /*
 630                                  * No one else can look this object up
 631                                  */
 632                                 (fs.object->handle == NULL) &&
 633                                 /*
 634                                  * No other ways to look the object up
 635                                  */
 636                                 ((fs.object->type == OBJT_DEFAULT) ||
 637                                  (fs.object->type == OBJT_SWAP)) &&
 638                                 /*
 639                                  * We don't chase down the shadow chain
 640                                  */
 641                                 (fs.object == fs.first_object->backing_object) &&
 642
 643                                 /*
 644                                  * grab the lock if we need to
 645                                  */
 646                                 (fs.lookup_still_valid ||
 647                                  lockmgr(&fs.map->lock, LK_EXCLUSIVE|LK_NOWAIT, (void *)0, curproc) == 0)
 648                             ) {
 649
 650                                 fs.lookup_still_valid = 1;
 651                                 /*
 652                                  * get rid of the unnecessary page
 653                                  */
 654                                 vm_page_protect(fs.first_m, VM_PROT_NONE);
 655                                 vm_page_free(fs.first_m);
 656                                 fs.first_m = NULL;
 657
 658                                 /*
 659                                  * grab the page and put it into the
 660                                  * process'es object.  The page is
 661                                  * automatically made dirty.
 662                                  */
 663                                 vm_page_rename(fs.m, fs.first_object, fs.first_pindex);
 664                                 fs.first_m = fs.m;
 665                                 vm_page_busy(fs.first_m);
 666                                 fs.m = NULL;
 667                                 cnt.v_cow_optim++;
 668                         } else {
 669                                 /*
 670                                  * Oh, well, lets copy it.
 671                                  */
 672                                 vm_page_copy(fs.m, fs.first_m);
 673                         }
 674
 675                         if (fs.m) {
 676                                 /*
 677                                  * We no longer need the old page or object.
 678                                  */
 679                                 release_page(&fs);
 680                         }
 681
 682                         /*
 683                          * fs.object != fs.first_object due to above
 684                          * conditional
 685                          */
 686
 687                         vm_object_pip_wakeup(fs.object);
 688
 689                         /*
 690                          * Only use the new page below...
 691                          */
 692
 693                         cnt.v_cow_faults++;
 694                         fs.m = fs.first_m;
 695                         fs.object = fs.first_object;
 696                         fs.pindex = fs.first_pindex;
 697
 698                 } else {
 699                         prot &= ~VM_PROT_WRITE;
 700                 }
 701         }
 702
 703         /*
 704          * We must verify that the maps have not changed since our last
 705          * lookup.
 706          */
 707
 708         if (!fs.lookup_still_valid &&
 709                 (fs.map->timestamp != map_generation)) {
 710                 vm_object_t retry_object;
 711                 vm_pindex_t retry_pindex;
 712                 vm_prot_t retry_prot;
 713
 714                 /*
 715                  * Since map entries may be pageable, make sure we can take a
 716                  * page fault on them.
 717                  */
 718
 719                 /*
 720                  * Unlock vnode before the lookup to avoid deadlock.   E.G.
 721                  * avoid a deadlock between the inode and exec_map that can
 722                  * occur due to locks being obtained in different orders.
 723                  */
 724
 725                 if (fs.vp != NULL) {
 726                         vput(fs.vp);
 727                         fs.vp = NULL;
 728                 }
 729
 730                 if (fs.map->infork) {
 731                         release_page(&fs);
 732                         unlock_and_deallocate(&fs);
 733                         goto RetryFault;
 734                 }
 735
 736                 /*
 737                  * To avoid trying to write_lock the map while another process
 738                  * has it read_locked (in vm_map_pageable), we do not try for
 739                  * write permission.  If the page is still writable, we will
 740                  * get write permission.  If it is not, or has been marked
 741                  * needs_copy, we enter the mapping without write permission,
 742                  * and will merely take another fault.
 743                  */
 744                 result = vm_map_lookup(&fs.map, vaddr, fault_type & ~VM_PROT_WRITE,
 745                     &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
 746                 map_generation = fs.map->timestamp;
 747
 748                 /*
 749                  * If we don't need the page any longer, put it on the active
 750                  * list (the easiest thing to do here).  If no one needs it,
 751                  * pageout will grab it eventually.
 752                  */
 753
 754                 if (result != KERN_SUCCESS) {
 755                         release_page(&fs);
 756                         unlock_and_deallocate(&fs);
 757                         return (result);
 758                 }
 759                 fs.lookup_still_valid = TRUE;
 760
 761                 if ((retry_object != fs.first_object) ||
 762                     (retry_pindex != fs.first_pindex)) {
 763                         release_page(&fs);
 764                         unlock_and_deallocate(&fs);
 765                         goto RetryFault;
 766                 }
 767                 /*
 768                  * Check whether the protection has changed or the object has
 769                  * been copied while we left the map unlocked. Changing from
 770                  * read to write permission is OK - we leave the page
 771                  * write-protected, and catch the write fault. Changing from
 772                  * write to read permission means that we can't mark the page
 773                  * write-enabled after all.
 774                  */
 775                 prot &= retry_prot;
 776         }
 777
 778         /*
 779          * Put this page into the physical map. We had to do the unlock above
 780          * because pmap_enter may cause other faults.   We don't put the page
 781          * back on the active queue until later so that the page-out daemon
 782          * won't find us (yet).
 783          */
 784
 785         if (prot & VM_PROT_WRITE) {
 786                 vm_page_flag_set(fs.m, PG_WRITEABLE);
 787                 vm_object_set_flag(fs.m->object,
 788                                    OBJ_WRITEABLE|OBJ_MIGHTBEDIRTY);
 789
 790                 /*
 791                  * If the fault is a write, we know that this page is being
 792                  * written NOW so dirty it explicitly to save on
 793                  * pmap_is_modified() calls later.
 794                  *
 795                  * If this is a NOSYNC mmap we do not want to set PG_NOSYNC
 796                  * if the page is already dirty to prevent data written with
 797                  * the expectation of being synced from not being synced.
 798                  * Likewise if this entry does not request NOSYNC then make
 799                  * sure the page isn't marked NOSYNC.  Applications sharing
 800                  * data should use the same flags to avoid ping ponging.
 801                  *
 802                  * Also tell the backing pager, if any, that it should remove
 803                  * any swap backing since the page is now dirty.
 804                  */
 805                 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) {
 806                         if (fs.m->dirty == 0)
 807                                 vm_page_flag_set(fs.m, PG_NOSYNC);
 808                 } else {
 809                         vm_page_flag_clear(fs.m, PG_NOSYNC);
 810                 }
 811                 if (fault_flags & VM_FAULT_DIRTY) {
 812                         int s;
 813                         vm_page_dirty(fs.m);
 814                         s = splvm();
 815                         vm_pager_page_unswapped(fs.m);
 816                         splx(s);
 817                 }
 818         }
 819
 820         /*
 821          * Page had better still be busy
 822          */
 823
 824         KASSERT(fs.m->flags & PG_BUSY,
 825                 ("vm_fault: page %p not busy!", fs.m));
 826
 827         unlock_things(&fs);
 828
 829         /*
 830          * Sanity check: page must be completely valid or it is not fit to
 831          * map into user space.  vm_pager_get_pages() ensures this.
 832          */
 833
 834         if (fs.m->valid != VM_PAGE_BITS_ALL) {
 835                 vm_page_zero_invalid(fs.m, TRUE);
 836                 printf("Warning: page %p partially invalid on fault\n", fs.m);
 837         }
 838
 839         pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired);
 840
 841         if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) {
 842                 pmap_prefault(fs.map->pmap, vaddr, fs.entry);
 843         }
 844
 845         vm_page_flag_clear(fs.m, PG_ZERO);
 846         vm_page_flag_set(fs.m, PG_MAPPED|PG_REFERENCED);
 847         if (fault_flags & VM_FAULT_HOLD)
 848                 vm_page_hold(fs.m);
 849
 850         /*
 851          * If the page is not wired down, then put it where the pageout daemon
 852          * can find it.
 853          */
 854
 855         if (fault_flags & VM_FAULT_WIRE_MASK) {
 856                 if (wired)
 857                         vm_page_wire(fs.m);
 858                 else
 859                         vm_page_unwire(fs.m, 1);
 860         } else {
 861                 vm_page_activate(fs.m);
 862         }
 863
 864         mtx_lock_spin(&sched_lock);
 865         if (curproc && (curproc->p_sflag & PS_INMEM) && curproc->p_stats) {
 866                 if (hardfault) {
 867                         curproc->p_stats->p_ru.ru_majflt++;
 868                 } else {
 869                         curproc->p_stats->p_ru.ru_minflt++;
 870                 }
 871         }
 872         mtx_unlock_spin(&sched_lock);
 873
 874         /*
 875          * Unlock everything, and return
 876          */
 877
 878         vm_page_wakeup(fs.m);
 879         vm_object_deallocate(fs.first_object);
 880
 881         return (KERN_SUCCESS);
 882
 883 }
 884
 885 /*
 886  *      vm_fault_wire:
 887  *
 888  *      Wire down a range of virtual addresses in a map.
 889  */
 890 int
 891 vm_fault_wire(map, start, end)
 892         vm_map_t map;
 893         vm_offset_t start, end;
 894 {
 895
 896         register vm_offset_t va;
 897         register pmap_t pmap;
 898         int rv;
 899
 900         pmap = vm_map_pmap(map);
 901
 902         /*
 903          * Inform the physical mapping system that the range of addresses may
 904          * not fault, so that page tables and such can be locked down as well.
 905          */
 906
 907         pmap_pageable(pmap, start, end, FALSE);
 908
 909         /*
 910          * We simulate a fault to get the page and enter it in the physical
 911          * map.
 912          */
 913
 914         for (va = start; va < end; va += PAGE_SIZE) {
 915                 rv = vm_fault(map, va, VM_PROT_READ|VM_PROT_WRITE,
 916                         VM_FAULT_CHANGE_WIRING);
 917                 if (rv) {
 918                         if (va != start)
 919                                 vm_fault_unwire(map, start, va);
 920                         return (rv);
 921                 }
 922         }
 923         return (KERN_SUCCESS);
 924 }
 925
 926 /*
 927  *      vm_fault_user_wire:
 928  *
 929  *      Wire down a range of virtual addresses in a map.  This
 930  *      is for user mode though, so we only ask for read access
 931  *      on currently read only sections.
 932  */
 933 int
 934 vm_fault_user_wire(map, start, end)
 935         vm_map_t map;
 936         vm_offset_t start, end;
 937 {
 938
 939         register vm_offset_t va;
 940         register pmap_t pmap;
 941         int rv;
 942
 943         pmap = vm_map_pmap(map);
 944
 945         /*
 946          * Inform the physical mapping system that the range of addresses may
 947          * not fault, so that page tables and such can be locked down as well.
 948          */
 949
 950         pmap_pageable(pmap, start, end, FALSE);
 951
 952         /*
 953          * We simulate a fault to get the page and enter it in the physical
 954          * map.
 955          */
 956         for (va = start; va < end; va += PAGE_SIZE) {
 957                 rv = vm_fault(map, va, VM_PROT_READ, VM_FAULT_USER_WIRE);
 958                 if (rv) {
 959                         if (va != start)
 960                                 vm_fault_unwire(map, start, va);
 961                         return (rv);
 962                 }
 963         }
 964         return (KERN_SUCCESS);
 965 }
 966
 967
 968 /*
 969  *      vm_fault_unwire:
 970  *
 971  *      Unwire a range of virtual addresses in a map.
 972  */
 973 void
 974 vm_fault_unwire(map, start, end)
 975         vm_map_t map;
 976         vm_offset_t start, end;
 977 {
 978
 979         register vm_offset_t va, pa;
 980         register pmap_t pmap;
 981
 982         pmap = vm_map_pmap(map);
 983
 984         /*
 985          * Since the pages are wired down, we must be able to get their
 986          * mappings from the physical map system.
 987          */
 988
 989         for (va = start; va < end; va += PAGE_SIZE) {
 990                 pa = pmap_extract(pmap, va);
 991                 if (pa != (vm_offset_t) 0) {
 992                         pmap_change_wiring(pmap, va, FALSE);
 993                         vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1);
 994                 }
 995         }
 996
 997         /*
 998          * Inform the physical mapping system that the range of addresses may
 999          * fault, so that page tables and such may be unwired themselves.
1000          */
1001
1002         pmap_pageable(pmap, start, end, TRUE);
1003
1004 }
1005
1006 /*
1007  *      Routine:
1008  *              vm_fault_copy_entry
1009  *      Function:
1010  *              Copy all of the pages from a wired-down map entry to another.
1011  *
1012  *      In/out conditions:
1013  *              The source and destination maps must be locked for write.
1014  *              The source map entry must be wired down (or be a sharing map
1015  *              entry corresponding to a main map entry that is wired down).
1016  */
1017
1018 void
1019 vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry)
1020         vm_map_t dst_map;
1021         vm_map_t src_map;
1022         vm_map_entry_t dst_entry;
1023         vm_map_entry_t src_entry;
1024 {
1025         vm_object_t dst_object;
1026         vm_object_t src_object;
1027         vm_ooffset_t dst_offset;
1028         vm_ooffset_t src_offset;
1029         vm_prot_t prot;
1030         vm_offset_t vaddr;
1031         vm_page_t dst_m;
1032         vm_page_t src_m;
1033
1034 #ifdef  lint
1035         src_map++;
1036 #endif  /* lint */
1037
1038         src_object = src_entry->object.vm_object;
1039         src_offset = src_entry->offset;
1040
1041         /*
1042          * Create the top-level object for the destination entry. (Doesn't
1043          * actually shadow anything - we copy the pages directly.)
1044          */
1045         dst_object = vm_object_allocate(OBJT_DEFAULT,
1046             (vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start));
1047
1048         dst_entry->object.vm_object = dst_object;
1049         dst_entry->offset = 0;
1050
1051         prot = dst_entry->max_protection;
1052
1053         /*
1054          * Loop through all of the pages in the entry's range, copying each
1055          * one from the source object (it should be there) to the destination
1056          * object.
1057          */
1058         for (vaddr = dst_entry->start, dst_offset = 0;
1059             vaddr < dst_entry->end;
1060             vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) {
1061
1062                 /*
1063                  * Allocate a page in the destination object
1064                  */
1065                 do {
1066                         dst_m = vm_page_alloc(dst_object,
1067                                 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL);
1068                         if (dst_m == NULL) {
1069                                 VM_WAIT;
1070                         }
1071                 } while (dst_m == NULL);
1072
1073                 /*
1074                  * Find the page in the source object, and copy it in.
1075                  * (Because the source is wired down, the page will be in
1076                  * memory.)
1077                  */
1078                 src_m = vm_page_lookup(src_object,
1079                         OFF_TO_IDX(dst_offset + src_offset));
1080                 if (src_m == NULL)
1081                         panic("vm_fault_copy_wired: page missing");
1082
1083                 vm_page_copy(src_m, dst_m);
1084
1085                 /*
1086                  * Enter it in the pmap...
1087                  */
1088
1089                 vm_page_flag_clear(dst_m, PG_ZERO);
1090                 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE);
1091                 vm_page_flag_set(dst_m, PG_WRITEABLE|PG_MAPPED);
1092
1093                 /*
1094                  * Mark it no longer busy, and put it on the active list.
1095                  */
1096                 vm_page_activate(dst_m);
1097                 vm_page_wakeup(dst_m);
1098         }
1099 }
1100
1101
1102 /*
1103  * This routine checks around the requested page for other pages that
1104  * might be able to be faulted in.  This routine brackets the viable
1105  * pages for the pages to be paged in.
1106  *
1107  * Inputs:
1108  *      m, rbehind, rahead
1109  *
1110  * Outputs:
1111  *  marray (array of vm_page_t), reqpage (index of requested page)
1112  *
1113  * Return value:
1114  *  number of pages in marray
1115  */
1116 static int
1117 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1118         vm_page_t m;
1119         int rbehind;
1120         int rahead;
1121         vm_page_t *marray;
1122         int *reqpage;
1123 {
1124         int i,j;
1125         vm_object_t object;
1126         vm_pindex_t pindex, startpindex, endpindex, tpindex;
1127         vm_page_t rtm;
1128         int cbehind, cahead;
1129
1130         object = m->object;
1131         pindex = m->pindex;
1132
1133         /*
1134          * we don't fault-ahead for device pager
1135          */
1136         if (object->type == OBJT_DEVICE) {
1137                 *reqpage = 0;
1138                 marray[0] = m;
1139                 return 1;
1140         }
1141
1142         /*
1143          * if the requested page is not available, then give up now
1144          */
1145
1146         if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1147                 return 0;
1148         }
1149
1150         if ((cbehind == 0) && (cahead == 0)) {
1151                 *reqpage = 0;
1152                 marray[0] = m;
1153                 return 1;
1154         }
1155
1156         if (rahead > cahead) {
1157                 rahead = cahead;
1158         }
1159
1160         if (rbehind > cbehind) {
1161                 rbehind = cbehind;
1162         }
1163
1164         /*
1165          * try to do any readahead that we might have free pages for.
1166          */
1167         if ((rahead + rbehind) >
1168                 ((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) {
1169                 pagedaemon_wakeup();
1170                 marray[0] = m;
1171                 *reqpage = 0;
1172                 return 1;
1173         }
1174
1175         /*
1176          * scan backward for the read behind pages -- in memory
1177          */
1178         if (pindex > 0) {
1179                 if (rbehind > pindex) {
1180                         rbehind = pindex;
1181                         startpindex = 0;
1182                 } else {
1183                         startpindex = pindex - rbehind;
1184                 }
1185
1186                 for ( tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) {
1187                         if (vm_page_lookup( object, tpindex)) {
1188                                 startpindex = tpindex + 1;
1189                                 break;
1190                         }
1191                         if (tpindex == 0)
1192                                 break;
1193                 }
1194
1195                 for(i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) {
1196
1197                         rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
1198                         if (rtm == NULL) {
1199                                 for (j = 0; j < i; j++) {
1200                                         vm_page_free(marray[j]);
1201                                 }
1202                                 marray[0] = m;
1203                                 *reqpage = 0;
1204                                 return 1;
1205                         }
1206
1207                         marray[i] = rtm;
1208                 }
1209         } else {
1210                 startpindex = 0;
1211                 i = 0;
1212         }
1213
1214         marray[i] = m;
1215         /* page offset of the required page */
1216         *reqpage = i;
1217
1218         tpindex = pindex + 1;
1219         i++;
1220
1221         /*
1222          * scan forward for the read ahead pages
1223          */
1224         endpindex = tpindex + rahead;
1225         if (endpindex > object->size)
1226                 endpindex = object->size;
1227
1228         for( ; tpindex < endpindex; i++, tpindex++) {
1229
1230                 if (vm_page_lookup(object, tpindex)) {
1231                         break;
1232                 }
1233
1234                 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
1235                 if (rtm == NULL) {
1236                         break;
1237                 }
1238
1239                 marray[i] = rtm;
1240         }
1241
1242         /* return number of bytes of pages */
1243         return i;
1244 }