sys/vm/vm_fault.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  * Copyright (c) 1994 John S. Dyson
   5  * All rights reserved.
   6  * Copyright (c) 1994 David Greenman
   7  * All rights reserved.
   8  *
   9  *
  10  * This code is derived from software contributed to Berkeley by
  11  * The Mach Operating System project at Carnegie-Mellon University.
  12  *
  13  * Redistribution and use in source and binary forms, with or without
  14  * modification, are permitted provided that the following conditions
  15  * are met:
  16  * 1. Redistributions of source code must retain the above copyright
  17  *    notice, this list of conditions and the following disclaimer.
  18  * 2. Redistributions in binary form must reproduce the above copyright
  19  *    notice, this list of conditions and the following disclaimer in the
  20  *    documentation and/or other materials provided with the distribution.
  21  * 3. All advertising materials mentioning features or use of this software
  22  *    must display the following acknowledgement:
  23  *      This product includes software developed by the University of
  24  *      California, Berkeley and its contributors.
  25  * 4. Neither the name of the University nor the names of its contributors
  26  *    may be used to endorse or promote products derived from this software
  27  *    without specific prior written permission.
  28  *
  29  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  30  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  31  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  32  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  33  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  34  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  35  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  36  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  37  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  38  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  39  * SUCH DAMAGE.
  40  *
  41  *      from: @(#)vm_fault.c    8.4 (Berkeley) 1/12/94
  42  *
  43  *
  44  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
  45  * All rights reserved.
  46  *
  47  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
  48  *
  49  * Permission to use, copy, modify and distribute this software and
  50  * its documentation is hereby granted, provided that both the copyright
  51  * notice and this permission notice appear in all copies of the
  52  * software, derivative works or modified versions, and any portions
  53  * thereof, and that both notices appear in supporting documentation.
  54  *
  55  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  56  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
  57  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  58  *
  59  * Carnegie Mellon requests users of this software to return to
  60  *
  61  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  62  *  School of Computer Science
  63  *  Carnegie Mellon University
  64  *  Pittsburgh PA 15213-3890
  65  *
  66  * any improvements or extensions that they make and grant Carnegie the
  67  * rights to redistribute these changes.
  68  */
  69
  70 /*
  71  *      Page fault handling module.
  72  */
  73
  74 #include <sys/cdefs.h>
  75 __FBSDID("$FreeBSD$");
  76
  77 #include "opt_ktrace.h"
  78 #include "opt_vm.h"
  79
  80 #include <sys/param.h>
  81 #include <sys/systm.h>
  82 #include <sys/kernel.h>
  83 #include <sys/lock.h>
  84 #include <sys/proc.h>
  85 #include <sys/resourcevar.h>
  86 #include <sys/rwlock.h>
  87 #include <sys/sysctl.h>
  88 #include <sys/vmmeter.h>
  89 #include <sys/vnode.h>
  90 #ifdef KTRACE
  91 #include <sys/ktrace.h>
  92 #endif
  93
  94 #include <vm/vm.h>
  95 #include <vm/vm_param.h>
  96 #include <vm/pmap.h>
  97 #include <vm/vm_map.h>
  98 #include <vm/vm_object.h>
  99 #include <vm/vm_page.h>
 100 #include <vm/vm_pageout.h>
 101 #include <vm/vm_kern.h>
 102 #include <vm/vm_pager.h>
 103 #include <vm/vm_extern.h>
 104
 105 #define PFBAK 4
 106 #define PFFOR 4
 107 #define PAGEORDER_SIZE (PFBAK+PFFOR)
 108
 109 static int prefault_pageorder[] = {
 110         -1 * PAGE_SIZE, 1 * PAGE_SIZE,
 111         -2 * PAGE_SIZE, 2 * PAGE_SIZE,
 112         -3 * PAGE_SIZE, 3 * PAGE_SIZE,
 113         -4 * PAGE_SIZE, 4 * PAGE_SIZE
 114 };
 115
 116 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
 117 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t);
 118
 119 #define VM_FAULT_READ_BEHIND    8
 120 #define VM_FAULT_READ_MAX       (1 + VM_FAULT_READ_AHEAD_MAX)
 121 #define VM_FAULT_NINCR          (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND)
 122 #define VM_FAULT_SUM            (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2)
 123 #define VM_FAULT_CACHE_BEHIND   (VM_FAULT_READ_BEHIND * VM_FAULT_SUM)
 124
 125 struct faultstate {
 126         vm_page_t m;
 127         vm_object_t object;
 128         vm_pindex_t pindex;
 129         vm_page_t first_m;
 130         vm_object_t     first_object;
 131         vm_pindex_t first_pindex;
 132         vm_map_t map;
 133         vm_map_entry_t entry;
 134         int lookup_still_valid;
 135         struct vnode *vp;
 136 };
 137
 138 static void vm_fault_cache_behind(const struct faultstate *fs, int distance);
 139
 140 static inline void
 141 release_page(struct faultstate *fs)
 142 {
 143
 144         vm_page_xunbusy(fs->m);
 145         vm_page_lock(fs->m);
 146         vm_page_deactivate(fs->m);
 147         vm_page_unlock(fs->m);
 148         fs->m = NULL;
 149 }
 150
 151 static inline void
 152 unlock_map(struct faultstate *fs)
 153 {
 154
 155         if (fs->lookup_still_valid) {
 156                 vm_map_lookup_done(fs->map, fs->entry);
 157                 fs->lookup_still_valid = FALSE;
 158         }
 159 }
 160
 161 static void
 162 unlock_and_deallocate(struct faultstate *fs)
 163 {
 164
 165         vm_object_pip_wakeup(fs->object);
 166         VM_OBJECT_WUNLOCK(fs->object);
 167         if (fs->object != fs->first_object) {
 168                 VM_OBJECT_WLOCK(fs->first_object);
 169                 vm_page_lock(fs->first_m);
 170                 vm_page_free(fs->first_m);
 171                 vm_page_unlock(fs->first_m);
 172                 vm_object_pip_wakeup(fs->first_object);
 173                 VM_OBJECT_WUNLOCK(fs->first_object);
 174                 fs->first_m = NULL;
 175         }
 176         vm_object_deallocate(fs->first_object);
 177         unlock_map(fs);
 178         if (fs->vp != NULL) {
 179                 vput(fs->vp);
 180                 fs->vp = NULL;
 181         }
 182 }
 183
 184 /*
 185  * TRYPAGER - used by vm_fault to calculate whether the pager for the
 186  *            current object *might* contain the page.
 187  *
 188  *            default objects are zero-fill, there is no real pager.
 189  */
 190 #define TRYPAGER        (fs.object->type != OBJT_DEFAULT && \
 191                         ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 || wired))
 192
 193 /*
 194  *      vm_fault:
 195  *
 196  *      Handle a page fault occurring at the given address,
 197  *      requiring the given permissions, in the map specified.
 198  *      If successful, the page is inserted into the
 199  *      associated physical map.
 200  *
 201  *      NOTE: the given address should be truncated to the
 202  *      proper page address.
 203  *
 204  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 205  *      a standard error specifying why the fault is fatal is returned.
 206  *
 207  *      The map in question must be referenced, and remains so.
 208  *      Caller may hold no locks.
 209  */
 210 int
 211 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 212     int fault_flags)
 213 {
 214         struct thread *td;
 215         int result;
 216
 217         td = curthread;
 218         if ((td->td_pflags & TDP_NOFAULTING) != 0)
 219                 return (KERN_PROTECTION_FAILURE);
 220 #ifdef KTRACE
 221         if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
 222                 ktrfault(vaddr, fault_type);
 223 #endif
 224         result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
 225             NULL);
 226 #ifdef KTRACE
 227         if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
 228                 ktrfaultend(result);
 229 #endif
 230         return (result);
 231 }
 232
 233 int
 234 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 235     int fault_flags, vm_page_t *m_hold)
 236 {
 237         vm_prot_t prot;
 238         long ahead, behind;
 239         int alloc_req, era, faultcount, nera, reqpage, result;
 240         boolean_t growstack, is_first_object_locked, wired;
 241         int map_generation;
 242         vm_object_t next_object;
 243         vm_page_t marray[VM_FAULT_READ_MAX];
 244         int hardfault;
 245         struct faultstate fs;
 246         struct vnode *vp;
 247         int locked, error;
 248
 249         hardfault = 0;
 250         growstack = TRUE;
 251         PCPU_INC(cnt.v_vm_faults);
 252         fs.vp = NULL;
 253         faultcount = reqpage = 0;
 254
 255 RetryFault:;
 256
 257         /*
 258          * Find the backing store object and offset into it to begin the
 259          * search.
 260          */
 261         fs.map = map;
 262         result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
 263             &fs.first_object, &fs.first_pindex, &prot, &wired);
 264         if (result != KERN_SUCCESS) {
 265                 if (growstack && result == KERN_INVALID_ADDRESS &&
 266                     map != kernel_map) {
 267                         result = vm_map_growstack(curproc, vaddr);
 268                         if (result != KERN_SUCCESS)
 269                                 return (KERN_FAILURE);
 270                         growstack = FALSE;
 271                         goto RetryFault;
 272                 }
 273                 return (result);
 274         }
 275
 276         map_generation = fs.map->timestamp;
 277
 278         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 279                 panic("vm_fault: fault on nofault entry, addr: %lx",
 280                     (u_long)vaddr);
 281         }
 282
 283         if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
 284             fs.entry->wiring_thread != curthread) {
 285                 vm_map_unlock_read(fs.map);
 286                 vm_map_lock(fs.map);
 287                 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
 288                     (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
 289                         fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
 290                         vm_map_unlock_and_wait(fs.map, 0);
 291                 } else
 292                         vm_map_unlock(fs.map);
 293                 goto RetryFault;
 294         }
 295
 296         /*
 297          * Make a reference to this object to prevent its disposal while we
 298          * are messing with it.  Once we have the reference, the map is free
 299          * to be diddled.  Since objects reference their shadows (and copies),
 300          * they will stay around as well.
 301          *
 302          * Bump the paging-in-progress count to prevent size changes (e.g.
 303          * truncation operations) during I/O.  This must be done after
 304          * obtaining the vnode lock in order to avoid possible deadlocks.
 305          */
 306         VM_OBJECT_WLOCK(fs.first_object);
 307         vm_object_reference_locked(fs.first_object);
 308         vm_object_pip_add(fs.first_object, 1);
 309
 310         fs.lookup_still_valid = TRUE;
 311
 312         if (wired)
 313                 fault_type = prot | (fault_type & VM_PROT_COPY);
 314
 315         fs.first_m = NULL;
 316
 317         /*
 318          * Search for the page at object/offset.
 319          */
 320         fs.object = fs.first_object;
 321         fs.pindex = fs.first_pindex;
 322         while (TRUE) {
 323                 /*
 324                  * If the object is dead, we stop here
 325                  */
 326                 if (fs.object->flags & OBJ_DEAD) {
 327                         unlock_and_deallocate(&fs);
 328                         return (KERN_PROTECTION_FAILURE);
 329                 }
 330
 331                 /*
 332                  * See if page is resident
 333                  */
 334                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 335                 if (fs.m != NULL) {
 336                         /*
 337                          * check for page-based copy on write.
 338                          * We check fs.object == fs.first_object so
 339                          * as to ensure the legacy COW mechanism is
 340                          * used when the page in question is part of
 341                          * a shadow object.  Otherwise, vm_page_cowfault()
 342                          * removes the page from the backing object,
 343                          * which is not what we want.
 344                          */
 345                         vm_page_lock(fs.m);
 346                         if ((fs.m->cow) &&
 347                             (fault_type & VM_PROT_WRITE) &&
 348                             (fs.object == fs.first_object)) {
 349                                 vm_page_cowfault(fs.m);
 350                                 unlock_and_deallocate(&fs);
 351                                 goto RetryFault;
 352                         }
 353
 354                         /*
 355                          * Wait/Retry if the page is busy.  We have to do this
 356                          * if the page is either exclusive or shared busy
 357                          * because the vm_pager may be using read busy for
 358                          * pageouts (and even pageins if it is the vnode
 359                          * pager), and we could end up trying to pagein and
 360                          * pageout the same page simultaneously.
 361                          *
 362                          * We can theoretically allow the busy case on a read
 363                          * fault if the page is marked valid, but since such
 364                          * pages are typically already pmap'd, putting that
 365                          * special case in might be more effort then it is
 366                          * worth.  We cannot under any circumstances mess
 367                          * around with a shared busied page except, perhaps,
 368                          * to pmap it.
 369                          */
 370                         if (vm_page_busied(fs.m)) {
 371                                 /*
 372                                  * Reference the page before unlocking and
 373                                  * sleeping so that the page daemon is less
 374                                  * likely to reclaim it.
 375                                  */
 376                                 vm_page_aflag_set(fs.m, PGA_REFERENCED);
 377                                 vm_page_unlock(fs.m);
 378                                 if (fs.object != fs.first_object) {
 379                                         if (!VM_OBJECT_TRYWLOCK(
 380                                             fs.first_object)) {
 381                                                 VM_OBJECT_WUNLOCK(fs.object);
 382                                                 VM_OBJECT_WLOCK(fs.first_object);
 383                                                 VM_OBJECT_WLOCK(fs.object);
 384                                         }
 385                                         vm_page_lock(fs.first_m);
 386                                         vm_page_free(fs.first_m);
 387                                         vm_page_unlock(fs.first_m);
 388                                         vm_object_pip_wakeup(fs.first_object);
 389                                         VM_OBJECT_WUNLOCK(fs.first_object);
 390                                         fs.first_m = NULL;
 391                                 }
 392                                 unlock_map(&fs);
 393                                 if (fs.m == vm_page_lookup(fs.object,
 394                                     fs.pindex)) {
 395                                         vm_page_sleep_if_busy(fs.m, "vmpfw");
 396                                 }
 397                                 vm_object_pip_wakeup(fs.object);
 398                                 VM_OBJECT_WUNLOCK(fs.object);
 399                                 PCPU_INC(cnt.v_intrans);
 400                                 vm_object_deallocate(fs.first_object);
 401                                 goto RetryFault;
 402                         }
 403                         vm_page_remque(fs.m);
 404                         vm_page_unlock(fs.m);
 405
 406                         /*
 407                          * Mark page busy for other processes, and the
 408                          * pagedaemon.  If it still isn't completely valid
 409                          * (readable), jump to readrest, else break-out ( we
 410                          * found the page ).
 411                          */
 412                         vm_page_xbusy(fs.m);
 413                         if (fs.m->valid != VM_PAGE_BITS_ALL)
 414                                 goto readrest;
 415                         break;
 416                 }
 417
 418                 /*
 419                  * Page is not resident, If this is the search termination
 420                  * or the pager might contain the page, allocate a new page.
 421                  */
 422                 if (TRYPAGER || fs.object == fs.first_object) {
 423                         if (fs.pindex >= fs.object->size) {
 424                                 unlock_and_deallocate(&fs);
 425                                 return (KERN_PROTECTION_FAILURE);
 426                         }
 427
 428                         /*
 429                          * Allocate a new page for this object/offset pair.
 430                          *
 431                          * Unlocked read of the p_flag is harmless. At
 432                          * worst, the P_KILLED might be not observed
 433                          * there, and allocation can fail, causing
 434                          * restart and new reading of the p_flag.
 435                          */
 436                         fs.m = NULL;
 437                         if (!vm_page_count_severe() || P_KILLED(curproc)) {
 438 #if VM_NRESERVLEVEL > 0
 439                                 if ((fs.object->flags & OBJ_COLORED) == 0) {
 440                                         fs.object->flags |= OBJ_COLORED;
 441                                         fs.object->pg_color = atop(vaddr) -
 442                                             fs.pindex;
 443                                 }
 444 #endif
 445                                 alloc_req = P_KILLED(curproc) ?
 446                                     VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
 447                                 if (fs.object->type != OBJT_VNODE &&
 448                                     fs.object->backing_object == NULL)
 449                                         alloc_req |= VM_ALLOC_ZERO;
 450                                 fs.m = vm_page_alloc(fs.object, fs.pindex,
 451                                     alloc_req);
 452                         }
 453                         if (fs.m == NULL) {
 454                                 unlock_and_deallocate(&fs);
 455                                 VM_WAITPFAULT;
 456                                 goto RetryFault;
 457                         } else if (fs.m->valid == VM_PAGE_BITS_ALL)
 458                                 break;
 459                 }
 460
 461 readrest:
 462                 /*
 463                  * We have found a valid page or we have allocated a new page.
 464                  * The page thus may not be valid or may not be entirely
 465                  * valid.
 466                  *
 467                  * Attempt to fault-in the page if there is a chance that the
 468                  * pager has it, and potentially fault in additional pages
 469                  * at the same time.
 470                  */
 471                 if (TRYPAGER) {
 472                         int rv;
 473                         u_char behavior = vm_map_entry_behavior(fs.entry);
 474
 475                         if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
 476                             P_KILLED(curproc)) {
 477                                 behind = 0;
 478                                 ahead = 0;
 479                         } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
 480                                 behind = 0;
 481                                 ahead = atop(fs.entry->end - vaddr) - 1;
 482                                 if (ahead > VM_FAULT_READ_AHEAD_MAX)
 483                                         ahead = VM_FAULT_READ_AHEAD_MAX;
 484                                 if (fs.pindex == fs.entry->next_read)
 485                                         vm_fault_cache_behind(&fs,
 486                                             VM_FAULT_READ_MAX);
 487                         } else {
 488                                 /*
 489                                  * If this is a sequential page fault, then
 490                                  * arithmetically increase the number of pages
 491                                  * in the read-ahead window.  Otherwise, reset
 492                                  * the read-ahead window to its smallest size.
 493                                  */
 494                                 behind = atop(vaddr - fs.entry->start);
 495                                 if (behind > VM_FAULT_READ_BEHIND)
 496                                         behind = VM_FAULT_READ_BEHIND;
 497                                 ahead = atop(fs.entry->end - vaddr) - 1;
 498                                 era = fs.entry->read_ahead;
 499                                 if (fs.pindex == fs.entry->next_read) {
 500                                         nera = era + behind;
 501                                         if (nera > VM_FAULT_READ_AHEAD_MAX)
 502                                                 nera = VM_FAULT_READ_AHEAD_MAX;
 503                                         behind = 0;
 504                                         if (ahead > nera)
 505                                                 ahead = nera;
 506                                         if (era == VM_FAULT_READ_AHEAD_MAX)
 507                                                 vm_fault_cache_behind(&fs,
 508                                                     VM_FAULT_CACHE_BEHIND);
 509                                 } else if (ahead > VM_FAULT_READ_AHEAD_MIN)
 510                                         ahead = VM_FAULT_READ_AHEAD_MIN;
 511                                 if (era != ahead)
 512                                         fs.entry->read_ahead = ahead;
 513                         }
 514
 515                         /*
 516                          * Call the pager to retrieve the data, if any, after
 517                          * releasing the lock on the map.  We hold a ref on
 518                          * fs.object and the pages are exclusive busied.
 519                          */
 520                         unlock_map(&fs);
 521
 522                         if (fs.object->type == OBJT_VNODE) {
 523                                 vp = fs.object->handle;
 524                                 if (vp == fs.vp)
 525                                         goto vnode_locked;
 526                                 else if (fs.vp != NULL) {
 527                                         vput(fs.vp);
 528                                         fs.vp = NULL;
 529                                 }
 530                                 locked = VOP_ISLOCKED(vp);
 531
 532                                 if (locked != LK_EXCLUSIVE)
 533                                         locked = LK_SHARED;
 534                                 /* Do not sleep for vnode lock while fs.m is busy */
 535                                 error = vget(vp, locked | LK_CANRECURSE |
 536                                     LK_NOWAIT, curthread);
 537                                 if (error != 0) {
 538                                         vhold(vp);
 539                                         release_page(&fs);
 540                                         unlock_and_deallocate(&fs);
 541                                         error = vget(vp, locked | LK_RETRY |
 542                                             LK_CANRECURSE, curthread);
 543                                         vdrop(vp);
 544                                         fs.vp = vp;
 545                                         KASSERT(error == 0,
 546                                             ("vm_fault: vget failed"));
 547                                         goto RetryFault;
 548                                 }
 549                                 fs.vp = vp;
 550                         }
 551 vnode_locked:
 552                         KASSERT(fs.vp == NULL || !fs.map->system_map,
 553                             ("vm_fault: vnode-backed object mapped by system map"));
 554
 555                         /*
 556                          * now we find out if any other pages should be paged
 557                          * in at this time this routine checks to see if the
 558                          * pages surrounding this fault reside in the same
 559                          * object as the page for this fault.  If they do,
 560                          * then they are faulted in also into the object.  The
 561                          * array "marray" returned contains an array of
 562                          * vm_page_t structs where one of them is the
 563                          * vm_page_t passed to the routine.  The reqpage
 564                          * return value is the index into the marray for the
 565                          * vm_page_t passed to the routine.
 566                          *
 567                          * fs.m plus the additional pages are exclusive busied.
 568                          */
 569                         faultcount = vm_fault_additional_pages(
 570                             fs.m, behind, ahead, marray, &reqpage);
 571
 572                         rv = faultcount ?
 573                             vm_pager_get_pages(fs.object, marray, faultcount,
 574                                 reqpage) : VM_PAGER_FAIL;
 575
 576                         if (rv == VM_PAGER_OK) {
 577                                 /*
 578                                  * Found the page. Leave it busy while we play
 579                                  * with it.
 580                                  */
 581
 582                                 /*
 583                                  * Relookup in case pager changed page. Pager
 584                                  * is responsible for disposition of old page
 585                                  * if moved.
 586                                  */
 587                                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 588                                 if (!fs.m) {
 589                                         unlock_and_deallocate(&fs);
 590                                         goto RetryFault;
 591                                 }
 592
 593                                 hardfault++;
 594                                 break; /* break to PAGE HAS BEEN FOUND */
 595                         }
 596                         /*
 597                          * Remove the bogus page (which does not exist at this
 598                          * object/offset); before doing so, we must get back
 599                          * our object lock to preserve our invariant.
 600                          *
 601                          * Also wake up any other process that may want to bring
 602                          * in this page.
 603                          *
 604                          * If this is the top-level object, we must leave the
 605                          * busy page to prevent another process from rushing
 606                          * past us, and inserting the page in that object at
 607                          * the same time that we are.
 608                          */
 609                         if (rv == VM_PAGER_ERROR)
 610                                 printf("vm_fault: pager read error, pid %d (%s)\n",
 611                                     curproc->p_pid, curproc->p_comm);
 612                         /*
 613                          * Data outside the range of the pager or an I/O error
 614                          */
 615                         /*
 616                          * XXX - the check for kernel_map is a kludge to work
 617                          * around having the machine panic on a kernel space
 618                          * fault w/ I/O error.
 619                          */
 620                         if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
 621                                 (rv == VM_PAGER_BAD)) {
 622                                 vm_page_lock(fs.m);
 623                                 vm_page_free(fs.m);
 624                                 vm_page_unlock(fs.m);
 625                                 fs.m = NULL;
 626                                 unlock_and_deallocate(&fs);
 627                                 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
 628                         }
 629                         if (fs.object != fs.first_object) {
 630                                 vm_page_lock(fs.m);
 631                                 vm_page_free(fs.m);
 632                                 vm_page_unlock(fs.m);
 633                                 fs.m = NULL;
 634                                 /*
 635                                  * XXX - we cannot just fall out at this
 636                                  * point, m has been freed and is invalid!
 637                                  */
 638                         }
 639                 }
 640
 641                 /*
 642                  * We get here if the object has default pager (or unwiring)
 643                  * or the pager doesn't have the page.
 644                  */
 645                 if (fs.object == fs.first_object)
 646                         fs.first_m = fs.m;
 647
 648                 /*
 649                  * Move on to the next object.  Lock the next object before
 650                  * unlocking the current one.
 651                  */
 652                 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
 653                 next_object = fs.object->backing_object;
 654                 if (next_object == NULL) {
 655                         /*
 656                          * If there's no object left, fill the page in the top
 657                          * object with zeros.
 658                          */
 659                         if (fs.object != fs.first_object) {
 660                                 vm_object_pip_wakeup(fs.object);
 661                                 VM_OBJECT_WUNLOCK(fs.object);
 662
 663                                 fs.object = fs.first_object;
 664                                 fs.pindex = fs.first_pindex;
 665                                 fs.m = fs.first_m;
 666                                 VM_OBJECT_WLOCK(fs.object);
 667                         }
 668                         fs.first_m = NULL;
 669
 670                         /*
 671                          * Zero the page if necessary and mark it valid.
 672                          */
 673                         if ((fs.m->flags & PG_ZERO) == 0) {
 674                                 pmap_zero_page(fs.m);
 675                         } else {
 676                                 PCPU_INC(cnt.v_ozfod);
 677                         }
 678                         PCPU_INC(cnt.v_zfod);
 679                         fs.m->valid = VM_PAGE_BITS_ALL;
 680                         break;  /* break to PAGE HAS BEEN FOUND */
 681                 } else {
 682                         KASSERT(fs.object != next_object,
 683                             ("object loop %p", next_object));
 684                         VM_OBJECT_WLOCK(next_object);
 685                         vm_object_pip_add(next_object, 1);
 686                         if (fs.object != fs.first_object)
 687                                 vm_object_pip_wakeup(fs.object);
 688                         VM_OBJECT_WUNLOCK(fs.object);
 689                         fs.object = next_object;
 690                 }
 691         }
 692
 693         vm_page_assert_xbusied(fs.m);
 694
 695         /*
 696          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
 697          * is held.]
 698          */
 699
 700         /*
 701          * If the page is being written, but isn't already owned by the
 702          * top-level object, we have to copy it into a new page owned by the
 703          * top-level object.
 704          */
 705         if (fs.object != fs.first_object) {
 706                 /*
 707                  * We only really need to copy if we want to write it.
 708                  */
 709                 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
 710                         /*
 711                          * This allows pages to be virtually copied from a
 712                          * backing_object into the first_object, where the
 713                          * backing object has no other refs to it, and cannot
 714                          * gain any more refs.  Instead of a bcopy, we just
 715                          * move the page from the backing object to the
 716                          * first object.  Note that we must mark the page
 717                          * dirty in the first object so that it will go out
 718                          * to swap when needed.
 719                          */
 720                         is_first_object_locked = FALSE;
 721                         if (
 722                                 /*
 723                                  * Only one shadow object
 724                                  */
 725                                 (fs.object->shadow_count == 1) &&
 726                                 /*
 727                                  * No COW refs, except us
 728                                  */
 729                                 (fs.object->ref_count == 1) &&
 730                                 /*
 731                                  * No one else can look this object up
 732                                  */
 733                                 (fs.object->handle == NULL) &&
 734                                 /*
 735                                  * No other ways to look the object up
 736                                  */
 737                                 ((fs.object->type == OBJT_DEFAULT) ||
 738                                  (fs.object->type == OBJT_SWAP)) &&
 739                             (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
 740                                 /*
 741                                  * We don't chase down the shadow chain
 742                                  */
 743                             fs.object == fs.first_object->backing_object) {
 744                                 /*
 745                                  * get rid of the unnecessary page
 746                                  */
 747                                 vm_page_lock(fs.first_m);
 748                                 vm_page_free(fs.first_m);
 749                                 vm_page_unlock(fs.first_m);
 750                                 /*
 751                                  * grab the page and put it into the
 752                                  * process'es object.  The page is
 753                                  * automatically made dirty.
 754                                  */
 755                                 if (vm_page_rename(fs.m, fs.first_object,
 756                                     fs.first_pindex)) {
 757                                         unlock_and_deallocate(&fs);
 758                                         goto RetryFault;
 759                                 }
 760                                 vm_page_xbusy(fs.m);
 761                                 fs.first_m = fs.m;
 762                                 fs.m = NULL;
 763                                 PCPU_INC(cnt.v_cow_optim);
 764                         } else {
 765                                 /*
 766                                  * Oh, well, lets copy it.
 767                                  */
 768                                 pmap_copy_page(fs.m, fs.first_m);
 769                                 fs.first_m->valid = VM_PAGE_BITS_ALL;
 770                                 if (wired && (fault_flags &
 771                                     VM_FAULT_CHANGE_WIRING) == 0) {
 772                                         vm_page_lock(fs.first_m);
 773                                         vm_page_wire(fs.first_m);
 774                                         vm_page_unlock(fs.first_m);
 775
 776                                         vm_page_lock(fs.m);
 777                                         vm_page_unwire(fs.m, FALSE);
 778                                         vm_page_unlock(fs.m);
 779                                 }
 780                                 /*
 781                                  * We no longer need the old page or object.
 782                                  */
 783                                 release_page(&fs);
 784                         }
 785                         /*
 786                          * fs.object != fs.first_object due to above
 787                          * conditional
 788                          */
 789                         vm_object_pip_wakeup(fs.object);
 790                         VM_OBJECT_WUNLOCK(fs.object);
 791                         /*
 792                          * Only use the new page below...
 793                          */
 794                         fs.object = fs.first_object;
 795                         fs.pindex = fs.first_pindex;
 796                         fs.m = fs.first_m;
 797                         if (!is_first_object_locked)
 798                                 VM_OBJECT_WLOCK(fs.object);
 799                         PCPU_INC(cnt.v_cow_faults);
 800                         curthread->td_cow++;
 801                 } else {
 802                         prot &= ~VM_PROT_WRITE;
 803                 }
 804         }
 805
 806         /*
 807          * We must verify that the maps have not changed since our last
 808          * lookup.
 809          */
 810         if (!fs.lookup_still_valid) {
 811                 vm_object_t retry_object;
 812                 vm_pindex_t retry_pindex;
 813                 vm_prot_t retry_prot;
 814
 815                 if (!vm_map_trylock_read(fs.map)) {
 816                         release_page(&fs);
 817                         unlock_and_deallocate(&fs);
 818                         goto RetryFault;
 819                 }
 820                 fs.lookup_still_valid = TRUE;
 821                 if (fs.map->timestamp != map_generation) {
 822                         result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
 823                             &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
 824
 825                         /*
 826                          * If we don't need the page any longer, put it on the inactive
 827                          * list (the easiest thing to do here).  If no one needs it,
 828                          * pageout will grab it eventually.
 829                          */
 830                         if (result != KERN_SUCCESS) {
 831                                 release_page(&fs);
 832                                 unlock_and_deallocate(&fs);
 833
 834                                 /*
 835                                  * If retry of map lookup would have blocked then
 836                                  * retry fault from start.
 837                                  */
 838                                 if (result == KERN_FAILURE)
 839                                         goto RetryFault;
 840                                 return (result);
 841                         }
 842                         if ((retry_object != fs.first_object) ||
 843                             (retry_pindex != fs.first_pindex)) {
 844                                 release_page(&fs);
 845                                 unlock_and_deallocate(&fs);
 846                                 goto RetryFault;
 847                         }
 848
 849                         /*
 850                          * Check whether the protection has changed or the object has
 851                          * been copied while we left the map unlocked. Changing from
 852                          * read to write permission is OK - we leave the page
 853                          * write-protected, and catch the write fault. Changing from
 854                          * write to read permission means that we can't mark the page
 855                          * write-enabled after all.
 856                          */
 857                         prot &= retry_prot;
 858                 }
 859         }
 860         /*
 861          * If the page was filled by a pager, update the map entry's
 862          * last read offset.  Since the pager does not return the
 863          * actual set of pages that it read, this update is based on
 864          * the requested set.  Typically, the requested and actual
 865          * sets are the same.
 866          *
 867          * XXX The following assignment modifies the map
 868          * without holding a write lock on it.
 869          */
 870         if (hardfault)
 871                 fs.entry->next_read = fs.pindex + faultcount - reqpage;
 872
 873         if ((prot & VM_PROT_WRITE) != 0 ||
 874             (fault_flags & VM_FAULT_DIRTY) != 0) {
 875                 vm_object_set_writeable_dirty(fs.object);
 876
 877                 /*
 878                  * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
 879                  * if the page is already dirty to prevent data written with
 880                  * the expectation of being synced from not being synced.
 881                  * Likewise if this entry does not request NOSYNC then make
 882                  * sure the page isn't marked NOSYNC.  Applications sharing
 883                  * data should use the same flags to avoid ping ponging.
 884                  */
 885                 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) {
 886                         if (fs.m->dirty == 0)
 887                                 fs.m->oflags |= VPO_NOSYNC;
 888                 } else {
 889                         fs.m->oflags &= ~VPO_NOSYNC;
 890                 }
 891
 892                 /*
 893                  * If the fault is a write, we know that this page is being
 894                  * written NOW so dirty it explicitly to save on
 895                  * pmap_is_modified() calls later.
 896                  *
 897                  * Also tell the backing pager, if any, that it should remove
 898                  * any swap backing since the page is now dirty.
 899                  */
 900                 if (((fault_type & VM_PROT_WRITE) != 0 &&
 901                     (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) ||
 902                     (fault_flags & VM_FAULT_DIRTY) != 0) {
 903                         vm_page_dirty(fs.m);
 904                         vm_pager_page_unswapped(fs.m);
 905                 }
 906         }
 907
 908         vm_page_assert_xbusied(fs.m);
 909
 910         /*
 911          * Page must be completely valid or it is not fit to
 912          * map into user space.  vm_pager_get_pages() ensures this.
 913          */
 914         KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
 915             ("vm_fault: page %p partially invalid", fs.m));
 916         VM_OBJECT_WUNLOCK(fs.object);
 917
 918         /*
 919          * Put this page into the physical map.  We had to do the unlock above
 920          * because pmap_enter() may sleep.  We don't put the page
 921          * back on the active queue until later so that the pageout daemon
 922          * won't find it (yet).
 923          */
 924         pmap_enter(fs.map->pmap, vaddr, fault_type, fs.m, prot, wired);
 925         if ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 && wired == 0)
 926                 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry);
 927         VM_OBJECT_WLOCK(fs.object);
 928         vm_page_lock(fs.m);
 929
 930         /*
 931          * If the page is not wired down, then put it where the pageout daemon
 932          * can find it.
 933          */
 934         if (fault_flags & VM_FAULT_CHANGE_WIRING) {
 935                 if (wired)
 936                         vm_page_wire(fs.m);
 937                 else
 938                         vm_page_unwire(fs.m, 1);
 939         } else
 940                 vm_page_activate(fs.m);
 941         if (m_hold != NULL) {
 942                 *m_hold = fs.m;
 943                 vm_page_hold(fs.m);
 944         }
 945         vm_page_unlock(fs.m);
 946         vm_page_xunbusy(fs.m);
 947
 948         /*
 949          * Unlock everything, and return
 950          */
 951         unlock_and_deallocate(&fs);
 952         if (hardfault) {
 953                 PCPU_INC(cnt.v_io_faults);
 954                 curthread->td_ru.ru_majflt++;
 955         } else
 956                 curthread->td_ru.ru_minflt++;
 957
 958         return (KERN_SUCCESS);
 959 }
 960
 961 /*
 962  * Speed up the reclamation of up to "distance" pages that precede the
 963  * faulting pindex within the first object of the shadow chain.
 964  */
 965 static void
 966 vm_fault_cache_behind(const struct faultstate *fs, int distance)
 967 {
 968         vm_object_t first_object, object;
 969         vm_page_t m, m_prev;
 970         vm_pindex_t pindex;
 971
 972         object = fs->object;
 973         VM_OBJECT_ASSERT_WLOCKED(object);
 974         first_object = fs->first_object;
 975         if (first_object != object) {
 976                 if (!VM_OBJECT_TRYWLOCK(first_object)) {
 977                         VM_OBJECT_WUNLOCK(object);
 978                         VM_OBJECT_WLOCK(first_object);
 979                         VM_OBJECT_WLOCK(object);
 980                 }
 981         }
 982         /* Neither fictitious nor unmanaged pages can be cached. */
 983         if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
 984                 if (fs->first_pindex < distance)
 985                         pindex = 0;
 986                 else
 987                         pindex = fs->first_pindex - distance;
 988                 if (pindex < OFF_TO_IDX(fs->entry->offset))
 989                         pindex = OFF_TO_IDX(fs->entry->offset);
 990                 m = first_object != object ? fs->first_m : fs->m;
 991                 vm_page_assert_xbusied(m);
 992                 m_prev = vm_page_prev(m);
 993                 while ((m = m_prev) != NULL && m->pindex >= pindex &&
 994                     m->valid == VM_PAGE_BITS_ALL) {
 995                         m_prev = vm_page_prev(m);
 996                         if (vm_page_busied(m))
 997                                 continue;
 998                         vm_page_lock(m);
 999                         if (m->hold_count == 0 && m->wire_count == 0) {
1000                                 pmap_remove_all(m);
1001                                 vm_page_aflag_clear(m, PGA_REFERENCED);
1002                                 if (m->dirty != 0)
1003                                         vm_page_deactivate(m);
1004                                 else
1005                                         vm_page_cache(m);
1006                         }
1007                         vm_page_unlock(m);
1008                 }
1009         }
1010         if (first_object != object)
1011                 VM_OBJECT_WUNLOCK(first_object);
1012 }
1013
1014 /*
1015  * vm_fault_prefault provides a quick way of clustering
1016  * pagefaults into a processes address space.  It is a "cousin"
1017  * of vm_map_pmap_enter, except it runs at page fault time instead
1018  * of mmap time.
1019  */
1020 static void
1021 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry)
1022 {
1023         int i;
1024         vm_offset_t addr, starta;
1025         vm_pindex_t pindex;
1026         vm_page_t m;
1027         vm_object_t object;
1028
1029         if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1030                 return;
1031
1032         object = entry->object.vm_object;
1033
1034         starta = addra - PFBAK * PAGE_SIZE;
1035         if (starta < entry->start) {
1036                 starta = entry->start;
1037         } else if (starta > addra) {
1038                 starta = 0;
1039         }
1040
1041         for (i = 0; i < PAGEORDER_SIZE; i++) {
1042                 vm_object_t backing_object, lobject;
1043
1044                 addr = addra + prefault_pageorder[i];
1045                 if (addr > addra + (PFFOR * PAGE_SIZE))
1046                         addr = 0;
1047
1048                 if (addr < starta || addr >= entry->end)
1049                         continue;
1050
1051                 if (!pmap_is_prefaultable(pmap, addr))
1052                         continue;
1053
1054                 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1055                 lobject = object;
1056                 VM_OBJECT_RLOCK(lobject);
1057                 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1058                     lobject->type == OBJT_DEFAULT &&
1059                     (backing_object = lobject->backing_object) != NULL) {
1060                         KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1061                             0, ("vm_fault_prefault: unaligned object offset"));
1062                         pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1063                         VM_OBJECT_RLOCK(backing_object);
1064                         VM_OBJECT_RUNLOCK(lobject);
1065                         lobject = backing_object;
1066                 }
1067                 /*
1068                  * give-up when a page is not in memory
1069                  */
1070                 if (m == NULL) {
1071                         VM_OBJECT_RUNLOCK(lobject);
1072                         break;
1073                 }
1074                 if (m->valid == VM_PAGE_BITS_ALL &&
1075                     (m->flags & PG_FICTITIOUS) == 0)
1076                         pmap_enter_quick(pmap, addr, m, entry->protection);
1077                 VM_OBJECT_RUNLOCK(lobject);
1078         }
1079 }
1080
1081 /*
1082  * Hold each of the physical pages that are mapped by the specified range of
1083  * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1084  * and allow the specified types of access, "prot".  If all of the implied
1085  * pages are successfully held, then the number of held pages is returned
1086  * together with pointers to those pages in the array "ma".  However, if any
1087  * of the pages cannot be held, -1 is returned.
1088  */
1089 int
1090 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1091     vm_prot_t prot, vm_page_t *ma, int max_count)
1092 {
1093         vm_offset_t end, va;
1094         vm_page_t *mp;
1095         int count;
1096         boolean_t pmap_failed;
1097
1098         if (len == 0)
1099                 return (0);
1100         end = round_page(addr + len);
1101         addr = trunc_page(addr);
1102
1103         /*
1104          * Check for illegal addresses.
1105          */
1106         if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1107                 return (-1);
1108
1109         count = howmany(end - addr, PAGE_SIZE);
1110         if (count > max_count)
1111                 panic("vm_fault_quick_hold_pages: count > max_count");
1112
1113         /*
1114          * Most likely, the physical pages are resident in the pmap, so it is
1115          * faster to try pmap_extract_and_hold() first.
1116          */
1117         pmap_failed = FALSE;
1118         for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1119                 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1120                 if (*mp == NULL)
1121                         pmap_failed = TRUE;
1122                 else if ((prot & VM_PROT_WRITE) != 0 &&
1123                     (*mp)->dirty != VM_PAGE_BITS_ALL) {
1124                         /*
1125                          * Explicitly dirty the physical page.  Otherwise, the
1126                          * caller's changes may go unnoticed because they are
1127                          * performed through an unmanaged mapping or by a DMA
1128                          * operation.
1129                          *
1130                          * The object lock is not held here.
1131                          * See vm_page_clear_dirty_mask().
1132                          */
1133                         vm_page_dirty(*mp);
1134                 }
1135         }
1136         if (pmap_failed) {
1137                 /*
1138                  * One or more pages could not be held by the pmap.  Either no
1139                  * page was mapped at the specified virtual address or that
1140                  * mapping had insufficient permissions.  Attempt to fault in
1141                  * and hold these pages.
1142                  */
1143                 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1144                         if (*mp == NULL && vm_fault_hold(map, va, prot,
1145                             VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1146                                 goto error;
1147         }
1148         return (count);
1149 error:
1150         for (mp = ma; mp < ma + count; mp++)
1151                 if (*mp != NULL) {
1152                         vm_page_lock(*mp);
1153                         vm_page_unhold(*mp);
1154                         vm_page_unlock(*mp);
1155                 }
1156         return (-1);
1157 }
1158
1159 /*
1160  *      vm_fault_wire:
1161  *
1162  *      Wire down a range of virtual addresses in a map.
1163  */
1164 int
1165 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1166     boolean_t fictitious)
1167 {
1168         vm_offset_t va;
1169         int rv;
1170
1171         /*
1172          * We simulate a fault to get the page and enter it in the physical
1173          * map.  For user wiring, we only ask for read access on currently
1174          * read-only sections.
1175          */
1176         for (va = start; va < end; va += PAGE_SIZE) {
1177                 rv = vm_fault(map, va, VM_PROT_NONE, VM_FAULT_CHANGE_WIRING);
1178                 if (rv) {
1179                         if (va != start)
1180                                 vm_fault_unwire(map, start, va, fictitious);
1181                         return (rv);
1182                 }
1183         }
1184         return (KERN_SUCCESS);
1185 }
1186
1187 /*
1188  *      vm_fault_unwire:
1189  *
1190  *      Unwire a range of virtual addresses in a map.
1191  */
1192 void
1193 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1194     boolean_t fictitious)
1195 {
1196         vm_paddr_t pa;
1197         vm_offset_t va;
1198         vm_page_t m;
1199         pmap_t pmap;
1200
1201         pmap = vm_map_pmap(map);
1202
1203         /*
1204          * Since the pages are wired down, we must be able to get their
1205          * mappings from the physical map system.
1206          */
1207         for (va = start; va < end; va += PAGE_SIZE) {
1208                 pa = pmap_extract(pmap, va);
1209                 if (pa != 0) {
1210                         pmap_change_wiring(pmap, va, FALSE);
1211                         if (!fictitious) {
1212                                 m = PHYS_TO_VM_PAGE(pa);
1213                                 vm_page_lock(m);
1214                                 vm_page_unwire(m, TRUE);
1215                                 vm_page_unlock(m);
1216                         }
1217                 }
1218         }
1219 }
1220
1221 /*
1222  *      Routine:
1223  *              vm_fault_copy_entry
1224  *      Function:
1225  *              Create new shadow object backing dst_entry with private copy of
1226  *              all underlying pages. When src_entry is equal to dst_entry,
1227  *              function implements COW for wired-down map entry. Otherwise,
1228  *              it forks wired entry into dst_map.
1229  *
1230  *      In/out conditions:
1231  *              The source and destination maps must be locked for write.
1232  *              The source map entry must be wired down (or be a sharing map
1233  *              entry corresponding to a main map entry that is wired down).
1234  */
1235 void
1236 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1237     vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1238     vm_ooffset_t *fork_charge)
1239 {
1240         vm_object_t backing_object, dst_object, object, src_object;
1241         vm_pindex_t dst_pindex, pindex, src_pindex;
1242         vm_prot_t access, prot;
1243         vm_offset_t vaddr;
1244         vm_page_t dst_m;
1245         vm_page_t src_m;
1246         boolean_t src_readonly, upgrade;
1247
1248 #ifdef  lint
1249         src_map++;
1250 #endif  /* lint */
1251
1252         upgrade = src_entry == dst_entry;
1253
1254         src_object = src_entry->object.vm_object;
1255         src_pindex = OFF_TO_IDX(src_entry->offset);
1256         src_readonly = (src_entry->protection & VM_PROT_WRITE) == 0;
1257
1258         /*
1259          * Create the top-level object for the destination entry. (Doesn't
1260          * actually shadow anything - we copy the pages directly.)
1261          */
1262         dst_object = vm_object_allocate(OBJT_DEFAULT,
1263             OFF_TO_IDX(dst_entry->end - dst_entry->start));
1264 #if VM_NRESERVLEVEL > 0
1265         dst_object->flags |= OBJ_COLORED;
1266         dst_object->pg_color = atop(dst_entry->start);
1267 #endif
1268
1269         VM_OBJECT_WLOCK(dst_object);
1270         KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1271             ("vm_fault_copy_entry: vm_object not NULL"));
1272         dst_entry->object.vm_object = dst_object;
1273         dst_entry->offset = 0;
1274         dst_object->charge = dst_entry->end - dst_entry->start;
1275         if (fork_charge != NULL) {
1276                 KASSERT(dst_entry->cred == NULL,
1277                     ("vm_fault_copy_entry: leaked swp charge"));
1278                 dst_object->cred = curthread->td_ucred;
1279                 crhold(dst_object->cred);
1280                 *fork_charge += dst_object->charge;
1281         } else {
1282                 dst_object->cred = dst_entry->cred;
1283                 dst_entry->cred = NULL;
1284         }
1285         access = prot = dst_entry->protection;
1286         /*
1287          * If not an upgrade, then enter the mappings in the pmap as
1288          * read and/or execute accesses.  Otherwise, enter them as
1289          * write accesses.
1290          *
1291          * A writeable large page mapping is only created if all of
1292          * the constituent small page mappings are modified. Marking
1293          * PTEs as modified on inception allows promotion to happen
1294          * without taking potentially large number of soft faults.
1295          */
1296         if (!upgrade)
1297                 access &= ~VM_PROT_WRITE;
1298
1299         /*
1300          * Loop through all of the virtual pages within the entry's
1301          * range, copying each page from the source object to the
1302          * destination object.  Since the source is wired, those pages
1303          * must exist.  In contrast, the destination is pageable.
1304          * Since the destination object does share any backing storage
1305          * with the source object, all of its pages must be dirtied,
1306          * regardless of whether they can be written.
1307          */
1308         for (vaddr = dst_entry->start, dst_pindex = 0;
1309             vaddr < dst_entry->end;
1310             vaddr += PAGE_SIZE, dst_pindex++) {
1311
1312                 /*
1313                  * Allocate a page in the destination object.
1314                  */
1315                 do {
1316                         dst_m = vm_page_alloc(dst_object, dst_pindex,
1317                             VM_ALLOC_NORMAL);
1318                         if (dst_m == NULL) {
1319                                 VM_OBJECT_WUNLOCK(dst_object);
1320                                 VM_WAIT;
1321                                 VM_OBJECT_WLOCK(dst_object);
1322                         }
1323                 } while (dst_m == NULL);
1324
1325                 /*
1326                  * Find the page in the source object, and copy it in.
1327                  * (Because the source is wired down, the page will be in
1328                  * memory.)
1329                  */
1330                 VM_OBJECT_RLOCK(src_object);
1331                 object = src_object;
1332                 pindex = src_pindex + dst_pindex;
1333                 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1334                     src_readonly &&
1335                     (backing_object = object->backing_object) != NULL) {
1336                         /*
1337                          * Allow fallback to backing objects if we are reading.
1338                          */
1339                         VM_OBJECT_RLOCK(backing_object);
1340                         pindex += OFF_TO_IDX(object->backing_object_offset);
1341                         VM_OBJECT_RUNLOCK(object);
1342                         object = backing_object;
1343                 }
1344                 if (src_m == NULL)
1345                         panic("vm_fault_copy_wired: page missing");
1346                 pmap_copy_page(src_m, dst_m);
1347                 VM_OBJECT_RUNLOCK(object);
1348                 dst_m->valid = VM_PAGE_BITS_ALL;
1349                 dst_m->dirty = VM_PAGE_BITS_ALL;
1350                 VM_OBJECT_WUNLOCK(dst_object);
1351
1352                 /*
1353                  * Enter it in the pmap. If a wired, copy-on-write
1354                  * mapping is being replaced by a write-enabled
1355                  * mapping, then wire that new mapping.
1356                  */
1357                 pmap_enter(dst_map->pmap, vaddr, access, dst_m, prot, upgrade);
1358
1359                 /*
1360                  * Mark it no longer busy, and put it on the active list.
1361                  */
1362                 VM_OBJECT_WLOCK(dst_object);
1363
1364                 if (upgrade) {
1365                         vm_page_lock(src_m);
1366                         vm_page_unwire(src_m, 0);
1367                         vm_page_unlock(src_m);
1368
1369                         vm_page_lock(dst_m);
1370                         vm_page_wire(dst_m);
1371                         vm_page_unlock(dst_m);
1372                 } else {
1373                         vm_page_lock(dst_m);
1374                         vm_page_activate(dst_m);
1375                         vm_page_unlock(dst_m);
1376                 }
1377                 vm_page_xunbusy(dst_m);
1378         }
1379         VM_OBJECT_WUNLOCK(dst_object);
1380         if (upgrade) {
1381                 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1382                 vm_object_deallocate(src_object);
1383         }
1384 }
1385
1386
1387 /*
1388  * This routine checks around the requested page for other pages that
1389  * might be able to be faulted in.  This routine brackets the viable
1390  * pages for the pages to be paged in.
1391  *
1392  * Inputs:
1393  *      m, rbehind, rahead
1394  *
1395  * Outputs:
1396  *  marray (array of vm_page_t), reqpage (index of requested page)
1397  *
1398  * Return value:
1399  *  number of pages in marray
1400  */
1401 static int
1402 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1403         vm_page_t m;
1404         int rbehind;
1405         int rahead;
1406         vm_page_t *marray;
1407         int *reqpage;
1408 {
1409         int i,j;
1410         vm_object_t object;
1411         vm_pindex_t pindex, startpindex, endpindex, tpindex;
1412         vm_page_t rtm;
1413         int cbehind, cahead;
1414
1415         VM_OBJECT_ASSERT_WLOCKED(m->object);
1416
1417         object = m->object;
1418         pindex = m->pindex;
1419         cbehind = cahead = 0;
1420
1421         /*
1422          * if the requested page is not available, then give up now
1423          */
1424         if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1425                 return 0;
1426         }
1427
1428         if ((cbehind == 0) && (cahead == 0)) {
1429                 *reqpage = 0;
1430                 marray[0] = m;
1431                 return 1;
1432         }
1433
1434         if (rahead > cahead) {
1435                 rahead = cahead;
1436         }
1437
1438         if (rbehind > cbehind) {
1439                 rbehind = cbehind;
1440         }
1441
1442         /*
1443          * scan backward for the read behind pages -- in memory
1444          */
1445         if (pindex > 0) {
1446                 if (rbehind > pindex) {
1447                         rbehind = pindex;
1448                         startpindex = 0;
1449                 } else {
1450                         startpindex = pindex - rbehind;
1451                 }
1452
1453                 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL &&
1454                     rtm->pindex >= startpindex)
1455                         startpindex = rtm->pindex + 1;
1456
1457                 /* tpindex is unsigned; beware of numeric underflow. */
1458                 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex &&
1459                     tpindex < pindex; i++, tpindex--) {
1460
1461                         rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1462                             VM_ALLOC_IFNOTCACHED);
1463                         if (rtm == NULL) {
1464                                 /*
1465                                  * Shift the allocated pages to the
1466                                  * beginning of the array.
1467                                  */
1468                                 for (j = 0; j < i; j++) {
1469                                         marray[j] = marray[j + tpindex + 1 -
1470                                             startpindex];
1471                                 }
1472                                 break;
1473                         }
1474
1475                         marray[tpindex - startpindex] = rtm;
1476                 }
1477         } else {
1478                 startpindex = 0;
1479                 i = 0;
1480         }
1481
1482         marray[i] = m;
1483         /* page offset of the required page */
1484         *reqpage = i;
1485
1486         tpindex = pindex + 1;
1487         i++;
1488
1489         /*
1490          * scan forward for the read ahead pages
1491          */
1492         endpindex = tpindex + rahead;
1493         if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex)
1494                 endpindex = rtm->pindex;
1495         if (endpindex > object->size)
1496                 endpindex = object->size;
1497
1498         for (; tpindex < endpindex; i++, tpindex++) {
1499
1500                 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1501                     VM_ALLOC_IFNOTCACHED);
1502                 if (rtm == NULL) {
1503                         break;
1504                 }
1505
1506                 marray[i] = rtm;
1507         }
1508
1509         /* return number of pages */
1510         return i;
1511 }
1512
1513 /*
1514  * Block entry into the machine-independent layer's page fault handler by
1515  * the calling thread.  Subsequent calls to vm_fault() by that thread will
1516  * return KERN_PROTECTION_FAILURE.  Enable machine-dependent handling of
1517  * spurious page faults.
1518  */
1519 int
1520 vm_fault_disable_pagefaults(void)
1521 {
1522
1523         return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1524 }
1525
1526 void
1527 vm_fault_enable_pagefaults(int save)
1528 {
1529
1530         curthread_pflags_restore(save);
1531 }