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