sys/vm/vm_fault.c

   1 /*-
   2  * SPDX-License-Identifier: (BSD-4-Clause AND MIT-CMU)
   3  *
   4  * Copyright (c) 1991, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  * Copyright (c) 1994 John S. Dyson
   7  * All rights reserved.
   8  * Copyright (c) 1994 David Greenman
   9  * All rights reserved.
  10  *
  11  *
  12  * This code is derived from software contributed to Berkeley by
  13  * The Mach Operating System project at Carnegie-Mellon University.
  14  *
  15  * Redistribution and use in source and binary forms, with or without
  16  * modification, are permitted provided that the following conditions
  17  * are met:
  18  * 1. Redistributions of source code must retain the above copyright
  19  *    notice, this list of conditions and the following disclaimer.
  20  * 2. Redistributions in binary form must reproduce the above copyright
  21  *    notice, this list of conditions and the following disclaimer in the
  22  *    documentation and/or other materials provided with the distribution.
  23  * 3. All advertising materials mentioning features or use of this software
  24  *    must display the following acknowledgement:
  25  *      This product includes software developed by the University of
  26  *      California, Berkeley and its contributors.
  27  * 4. Neither the name of the University nor the names of its contributors
  28  *    may be used to endorse or promote products derived from this software
  29  *    without specific prior written permission.
  30  *
  31  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  32  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  33  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  34  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  35  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  36  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  37  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  38  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  39  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  40  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  41  * SUCH DAMAGE.
  42  *
  43  *      from: @(#)vm_fault.c    8.4 (Berkeley) 1/12/94
  44  *
  45  *
  46  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
  47  * All rights reserved.
  48  *
  49  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
  50  *
  51  * Permission to use, copy, modify and distribute this software and
  52  * its documentation is hereby granted, provided that both the copyright
  53  * notice and this permission notice appear in all copies of the
  54  * software, derivative works or modified versions, and any portions
  55  * thereof, and that both notices appear in supporting documentation.
  56  *
  57  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  58  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
  59  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  60  *
  61  * Carnegie Mellon requests users of this software to return to
  62  *
  63  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  64  *  School of Computer Science
  65  *  Carnegie Mellon University
  66  *  Pittsburgh PA 15213-3890
  67  *
  68  * any improvements or extensions that they make and grant Carnegie the
  69  * rights to redistribute these changes.
  70  */
  71
  72 /*
  73  *      Page fault handling module.
  74  */
  75
  76 #include <sys/cdefs.h>
  77 __FBSDID("$FreeBSD$");
  78
  79 #include "opt_ktrace.h"
  80 #include "opt_vm.h"
  81
  82 #include <sys/param.h>
  83 #include <sys/systm.h>
  84 #include <sys/kernel.h>
  85 #include <sys/lock.h>
  86 #include <sys/mman.h>
  87 #include <sys/proc.h>
  88 #include <sys/racct.h>
  89 #include <sys/resourcevar.h>
  90 #include <sys/rwlock.h>
  91 #include <sys/sysctl.h>
  92 #include <sys/vmmeter.h>
  93 #include <sys/vnode.h>
  94 #ifdef KTRACE
  95 #include <sys/ktrace.h>
  96 #endif
  97
  98 #include <vm/vm.h>
  99 #include <vm/vm_param.h>
 100 #include <vm/pmap.h>
 101 #include <vm/vm_map.h>
 102 #include <vm/vm_object.h>
 103 #include <vm/vm_page.h>
 104 #include <vm/vm_pageout.h>
 105 #include <vm/vm_kern.h>
 106 #include <vm/vm_pager.h>
 107 #include <vm/vm_extern.h>
 108 #include <vm/vm_reserv.h>
 109
 110 #define PFBAK 4
 111 #define PFFOR 4
 112
 113 #define VM_FAULT_READ_DEFAULT   (1 + VM_FAULT_READ_AHEAD_INIT)
 114 #define VM_FAULT_READ_MAX       (1 + VM_FAULT_READ_AHEAD_MAX)
 115
 116 #define VM_FAULT_DONTNEED_MIN   1048576
 117
 118 struct faultstate {
 119         vm_page_t m;
 120         vm_object_t object;
 121         vm_pindex_t pindex;
 122         vm_page_t first_m;
 123         vm_object_t     first_object;
 124         vm_pindex_t first_pindex;
 125         vm_map_t map;
 126         vm_map_entry_t entry;
 127         int map_generation;
 128         bool lookup_still_valid;
 129         struct vnode *vp;
 130 };
 131
 132 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr,
 133             int ahead);
 134 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
 135             int backward, int forward, bool obj_locked);
 136
 137 static inline void
 138 release_page(struct faultstate *fs)
 139 {
 140
 141         vm_page_xunbusy(fs->m);
 142         vm_page_lock(fs->m);
 143         vm_page_deactivate(fs->m);
 144         vm_page_unlock(fs->m);
 145         fs->m = NULL;
 146 }
 147
 148 static inline void
 149 unlock_map(struct faultstate *fs)
 150 {
 151
 152         if (fs->lookup_still_valid) {
 153                 vm_map_lookup_done(fs->map, fs->entry);
 154                 fs->lookup_still_valid = false;
 155         }
 156 }
 157
 158 static void
 159 unlock_vp(struct faultstate *fs)
 160 {
 161
 162         if (fs->vp != NULL) {
 163                 vput(fs->vp);
 164                 fs->vp = NULL;
 165         }
 166 }
 167
 168 static void
 169 unlock_and_deallocate(struct faultstate *fs)
 170 {
 171
 172         vm_object_pip_wakeup(fs->object);
 173         VM_OBJECT_WUNLOCK(fs->object);
 174         if (fs->object != fs->first_object) {
 175                 VM_OBJECT_WLOCK(fs->first_object);
 176                 vm_page_lock(fs->first_m);
 177                 vm_page_free(fs->first_m);
 178                 vm_page_unlock(fs->first_m);
 179                 vm_object_pip_wakeup(fs->first_object);
 180                 VM_OBJECT_WUNLOCK(fs->first_object);
 181                 fs->first_m = NULL;
 182         }
 183         vm_object_deallocate(fs->first_object);
 184         unlock_map(fs);
 185         unlock_vp(fs);
 186 }
 187
 188 static void
 189 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot,
 190     vm_prot_t fault_type, int fault_flags, bool set_wd)
 191 {
 192         bool need_dirty;
 193
 194         if (((prot & VM_PROT_WRITE) == 0 &&
 195             (fault_flags & VM_FAULT_DIRTY) == 0) ||
 196             (m->oflags & VPO_UNMANAGED) != 0)
 197                 return;
 198
 199         VM_OBJECT_ASSERT_LOCKED(m->object);
 200
 201         need_dirty = ((fault_type & VM_PROT_WRITE) != 0 &&
 202             (fault_flags & VM_FAULT_WIRE) == 0) ||
 203             (fault_flags & VM_FAULT_DIRTY) != 0;
 204
 205         if (set_wd)
 206                 vm_object_set_writeable_dirty(m->object);
 207         else
 208                 /*
 209                  * If two callers of vm_fault_dirty() with set_wd ==
 210                  * FALSE, one for the map entry with MAP_ENTRY_NOSYNC
 211                  * flag set, other with flag clear, race, it is
 212                  * possible for the no-NOSYNC thread to see m->dirty
 213                  * != 0 and not clear VPO_NOSYNC.  Take vm_page lock
 214                  * around manipulation of VPO_NOSYNC and
 215                  * vm_page_dirty() call, to avoid the race and keep
 216                  * m->oflags consistent.
 217                  */
 218                 vm_page_lock(m);
 219
 220         /*
 221          * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
 222          * if the page is already dirty to prevent data written with
 223          * the expectation of being synced from not being synced.
 224          * Likewise if this entry does not request NOSYNC then make
 225          * sure the page isn't marked NOSYNC.  Applications sharing
 226          * data should use the same flags to avoid ping ponging.
 227          */
 228         if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) {
 229                 if (m->dirty == 0) {
 230                         m->oflags |= VPO_NOSYNC;
 231                 }
 232         } else {
 233                 m->oflags &= ~VPO_NOSYNC;
 234         }
 235
 236         /*
 237          * If the fault is a write, we know that this page is being
 238          * written NOW so dirty it explicitly to save on
 239          * pmap_is_modified() calls later.
 240          *
 241          * Also, since the page is now dirty, we can possibly tell
 242          * the pager to release any swap backing the page.  Calling
 243          * the pager requires a write lock on the object.
 244          */
 245         if (need_dirty)
 246                 vm_page_dirty(m);
 247         if (!set_wd)
 248                 vm_page_unlock(m);
 249         else if (need_dirty)
 250                 vm_pager_page_unswapped(m);
 251 }
 252
 253 static void
 254 vm_fault_fill_hold(vm_page_t *m_hold, vm_page_t m)
 255 {
 256
 257         if (m_hold != NULL) {
 258                 *m_hold = m;
 259                 vm_page_lock(m);
 260                 vm_page_hold(m);
 261                 vm_page_unlock(m);
 262         }
 263 }
 264
 265 /*
 266  * Unlocks fs.first_object and fs.map on success.
 267  */
 268 static int
 269 vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot,
 270     int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold)
 271 {
 272         vm_page_t m, m_map;
 273 #if (defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \
 274     __ARM_ARCH >= 6) || defined(__i386__)) && VM_NRESERVLEVEL > 0
 275         vm_page_t m_super;
 276         int flags;
 277 #endif
 278         int psind, rv;
 279
 280         MPASS(fs->vp == NULL);
 281         m = vm_page_lookup(fs->first_object, fs->first_pindex);
 282         /* A busy page can be mapped for read|execute access. */
 283         if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
 284             vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
 285                 return (KERN_FAILURE);
 286         m_map = m;
 287         psind = 0;
 288 #if (defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \
 289     __ARM_ARCH >= 6) || defined(__i386__)) && VM_NRESERVLEVEL > 0
 290         if ((m->flags & PG_FICTITIOUS) == 0 &&
 291             (m_super = vm_reserv_to_superpage(m)) != NULL &&
 292             rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start &&
 293             roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end &&
 294             (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) &
 295             (pagesizes[m_super->psind] - 1)) &&
 296             pmap_ps_enabled(fs->map->pmap)) {
 297                 flags = PS_ALL_VALID;
 298                 if ((prot & VM_PROT_WRITE) != 0) {
 299                         /*
 300                          * Create a superpage mapping allowing write access
 301                          * only if none of the constituent pages are busy and
 302                          * all of them are already dirty (except possibly for
 303                          * the page that was faulted on).
 304                          */
 305                         flags |= PS_NONE_BUSY;
 306                         if ((fs->first_object->flags & OBJ_UNMANAGED) == 0)
 307                                 flags |= PS_ALL_DIRTY;
 308                 }
 309                 if (vm_page_ps_test(m_super, flags, m)) {
 310                         m_map = m_super;
 311                         psind = m_super->psind;
 312                         vaddr = rounddown2(vaddr, pagesizes[psind]);
 313                         /* Preset the modified bit for dirty superpages. */
 314                         if ((flags & PS_ALL_DIRTY) != 0)
 315                                 fault_type |= VM_PROT_WRITE;
 316                 }
 317         }
 318 #endif
 319         rv = pmap_enter(fs->map->pmap, vaddr, m_map, prot, fault_type |
 320             PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), psind);
 321         if (rv != KERN_SUCCESS)
 322                 return (rv);
 323         vm_fault_fill_hold(m_hold, m);
 324         vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false);
 325         if (psind == 0 && !wired)
 326                 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true);
 327         VM_OBJECT_RUNLOCK(fs->first_object);
 328         vm_map_lookup_done(fs->map, fs->entry);
 329         curthread->td_ru.ru_minflt++;
 330         return (KERN_SUCCESS);
 331 }
 332
 333 static void
 334 vm_fault_restore_map_lock(struct faultstate *fs)
 335 {
 336
 337         VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
 338         MPASS(fs->first_object->paging_in_progress > 0);
 339
 340         if (!vm_map_trylock_read(fs->map)) {
 341                 VM_OBJECT_WUNLOCK(fs->first_object);
 342                 vm_map_lock_read(fs->map);
 343                 VM_OBJECT_WLOCK(fs->first_object);
 344         }
 345         fs->lookup_still_valid = true;
 346 }
 347
 348 static void
 349 vm_fault_populate_check_page(vm_page_t m)
 350 {
 351
 352         /*
 353          * Check each page to ensure that the pager is obeying the
 354          * interface: the page must be installed in the object, fully
 355          * valid, and exclusively busied.
 356          */
 357         MPASS(m != NULL);
 358         MPASS(m->valid == VM_PAGE_BITS_ALL);
 359         MPASS(vm_page_xbusied(m));
 360 }
 361
 362 static void
 363 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first,
 364     vm_pindex_t last)
 365 {
 366         vm_page_t m;
 367         vm_pindex_t pidx;
 368
 369         VM_OBJECT_ASSERT_WLOCKED(object);
 370         MPASS(first <= last);
 371         for (pidx = first, m = vm_page_lookup(object, pidx);
 372             pidx <= last; pidx++, m = vm_page_next(m)) {
 373                 vm_fault_populate_check_page(m);
 374                 vm_page_lock(m);
 375                 vm_page_deactivate(m);
 376                 vm_page_unlock(m);
 377                 vm_page_xunbusy(m);
 378         }
 379 }
 380
 381 static int
 382 vm_fault_populate(struct faultstate *fs, vm_prot_t prot, int fault_type,
 383     int fault_flags, boolean_t wired, vm_page_t *m_hold)
 384 {
 385         struct mtx *m_mtx;
 386         vm_offset_t vaddr;
 387         vm_page_t m;
 388         vm_pindex_t map_first, map_last, pager_first, pager_last, pidx;
 389         int i, npages, psind, rv;
 390
 391         MPASS(fs->object == fs->first_object);
 392         VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
 393         MPASS(fs->first_object->paging_in_progress > 0);
 394         MPASS(fs->first_object->backing_object == NULL);
 395         MPASS(fs->lookup_still_valid);
 396
 397         pager_first = OFF_TO_IDX(fs->entry->offset);
 398         pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1;
 399         unlock_map(fs);
 400         unlock_vp(fs);
 401
 402         /*
 403          * Call the pager (driver) populate() method.
 404          *
 405          * There is no guarantee that the method will be called again
 406          * if the current fault is for read, and a future fault is
 407          * for write.  Report the entry's maximum allowed protection
 408          * to the driver.
 409          */
 410         rv = vm_pager_populate(fs->first_object, fs->first_pindex,
 411             fault_type, fs->entry->max_protection, &pager_first, &pager_last);
 412
 413         VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
 414         if (rv == VM_PAGER_BAD) {
 415                 /*
 416                  * VM_PAGER_BAD is the backdoor for a pager to request
 417                  * normal fault handling.
 418                  */
 419                 vm_fault_restore_map_lock(fs);
 420                 if (fs->map->timestamp != fs->map_generation)
 421                         return (KERN_RESOURCE_SHORTAGE); /* RetryFault */
 422                 return (KERN_NOT_RECEIVER);
 423         }
 424         if (rv != VM_PAGER_OK)
 425                 return (KERN_FAILURE); /* AKA SIGSEGV */
 426
 427         /* Ensure that the driver is obeying the interface. */
 428         MPASS(pager_first <= pager_last);
 429         MPASS(fs->first_pindex <= pager_last);
 430         MPASS(fs->first_pindex >= pager_first);
 431         MPASS(pager_last < fs->first_object->size);
 432
 433         vm_fault_restore_map_lock(fs);
 434         if (fs->map->timestamp != fs->map_generation) {
 435                 vm_fault_populate_cleanup(fs->first_object, pager_first,
 436                     pager_last);
 437                 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */
 438         }
 439
 440         /*
 441          * The map is unchanged after our last unlock.  Process the fault.
 442          *
 443          * The range [pager_first, pager_last] that is given to the
 444          * pager is only a hint.  The pager may populate any range
 445          * within the object that includes the requested page index.
 446          * In case the pager expanded the range, clip it to fit into
 447          * the map entry.
 448          */
 449         map_first = OFF_TO_IDX(fs->entry->offset);
 450         if (map_first > pager_first) {
 451                 vm_fault_populate_cleanup(fs->first_object, pager_first,
 452                     map_first - 1);
 453                 pager_first = map_first;
 454         }
 455         map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1;
 456         if (map_last < pager_last) {
 457                 vm_fault_populate_cleanup(fs->first_object, map_last + 1,
 458                     pager_last);
 459                 pager_last = map_last;
 460         }
 461         for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx);
 462             pidx <= pager_last;
 463             pidx += npages, m = vm_page_next(&m[npages - 1])) {
 464                 vaddr = fs->entry->start + IDX_TO_OFF(pidx) - fs->entry->offset;
 465 #if defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \
 466     __ARM_ARCH >= 6) || defined(__i386__)
 467                 psind = m->psind;
 468                 if (psind > 0 && ((vaddr & (pagesizes[psind] - 1)) != 0 ||
 469                     pidx + OFF_TO_IDX(pagesizes[psind]) - 1 > pager_last ||
 470                     !pmap_ps_enabled(fs->map->pmap)))
 471                         psind = 0;
 472 #else
 473                 psind = 0;
 474 #endif
 475                 npages = atop(pagesizes[psind]);
 476                 for (i = 0; i < npages; i++) {
 477                         vm_fault_populate_check_page(&m[i]);
 478                         vm_fault_dirty(fs->entry, &m[i], prot, fault_type,
 479                             fault_flags, true);
 480                 }
 481                 VM_OBJECT_WUNLOCK(fs->first_object);
 482                 pmap_enter(fs->map->pmap, vaddr, m, prot, fault_type | (wired ?
 483                     PMAP_ENTER_WIRED : 0), psind);
 484                 VM_OBJECT_WLOCK(fs->first_object);
 485                 m_mtx = NULL;
 486                 for (i = 0; i < npages; i++) {
 487                         vm_page_change_lock(&m[i], &m_mtx);
 488                         if ((fault_flags & VM_FAULT_WIRE) != 0)
 489                                 vm_page_wire(&m[i]);
 490                         else
 491                                 vm_page_activate(&m[i]);
 492                         if (m_hold != NULL && m[i].pindex == fs->first_pindex) {
 493                                 *m_hold = &m[i];
 494                                 vm_page_hold(&m[i]);
 495                         }
 496                         vm_page_xunbusy_maybelocked(&m[i]);
 497                 }
 498                 if (m_mtx != NULL)
 499                         mtx_unlock(m_mtx);
 500         }
 501         curthread->td_ru.ru_majflt++;
 502         return (KERN_SUCCESS);
 503 }
 504
 505 /*
 506  *      vm_fault:
 507  *
 508  *      Handle a page fault occurring at the given address,
 509  *      requiring the given permissions, in the map specified.
 510  *      If successful, the page is inserted into the
 511  *      associated physical map.
 512  *
 513  *      NOTE: the given address should be truncated to the
 514  *      proper page address.
 515  *
 516  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 517  *      a standard error specifying why the fault is fatal is returned.
 518  *
 519  *      The map in question must be referenced, and remains so.
 520  *      Caller may hold no locks.
 521  */
 522 int
 523 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 524     int fault_flags)
 525 {
 526         struct thread *td;
 527         int result;
 528
 529         td = curthread;
 530         if ((td->td_pflags & TDP_NOFAULTING) != 0)
 531                 return (KERN_PROTECTION_FAILURE);
 532 #ifdef KTRACE
 533         if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
 534                 ktrfault(vaddr, fault_type);
 535 #endif
 536         result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
 537             NULL);
 538 #ifdef KTRACE
 539         if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
 540                 ktrfaultend(result);
 541 #endif
 542         return (result);
 543 }
 544
 545 int
 546 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 547     int fault_flags, vm_page_t *m_hold)
 548 {
 549         struct faultstate fs;
 550         struct vnode *vp;
 551         vm_object_t next_object, retry_object;
 552         vm_offset_t e_end, e_start;
 553         vm_pindex_t retry_pindex;
 554         vm_prot_t prot, retry_prot;
 555         int ahead, alloc_req, behind, cluster_offset, error, era, faultcount;
 556         int locked, nera, result, rv;
 557         u_char behavior;
 558         boolean_t wired;        /* Passed by reference. */
 559         bool dead, hardfault, is_first_object_locked;
 560
 561         VM_CNT_INC(v_vm_faults);
 562         fs.vp = NULL;
 563         faultcount = 0;
 564         nera = -1;
 565         hardfault = false;
 566
 567 RetryFault:;
 568
 569         /*
 570          * Find the backing store object and offset into it to begin the
 571          * search.
 572          */
 573         fs.map = map;
 574         result = vm_map_lookup(&fs.map, vaddr, fault_type |
 575             VM_PROT_FAULT_LOOKUP, &fs.entry, &fs.first_object,
 576             &fs.first_pindex, &prot, &wired);
 577         if (result != KERN_SUCCESS) {
 578                 unlock_vp(&fs);
 579                 return (result);
 580         }
 581
 582         fs.map_generation = fs.map->timestamp;
 583
 584         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 585                 panic("%s: fault on nofault entry, addr: %#lx",
 586                     __func__, (u_long)vaddr);
 587         }
 588
 589         if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
 590             fs.entry->wiring_thread != curthread) {
 591                 vm_map_unlock_read(fs.map);
 592                 vm_map_lock(fs.map);
 593                 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
 594                     (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
 595                         unlock_vp(&fs);
 596                         fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
 597                         vm_map_unlock_and_wait(fs.map, 0);
 598                 } else
 599                         vm_map_unlock(fs.map);
 600                 goto RetryFault;
 601         }
 602
 603         MPASS((fs.entry->eflags & MAP_ENTRY_GUARD) == 0);
 604
 605         if (wired)
 606                 fault_type = prot | (fault_type & VM_PROT_COPY);
 607         else
 608                 KASSERT((fault_flags & VM_FAULT_WIRE) == 0,
 609                     ("!wired && VM_FAULT_WIRE"));
 610
 611         /*
 612          * Try to avoid lock contention on the top-level object through
 613          * special-case handling of some types of page faults, specifically,
 614          * those that are both (1) mapping an existing page from the top-
 615          * level object and (2) not having to mark that object as containing
 616          * dirty pages.  Under these conditions, a read lock on the top-level
 617          * object suffices, allowing multiple page faults of a similar type to
 618          * run in parallel on the same top-level object.
 619          */
 620         if (fs.vp == NULL /* avoid locked vnode leak */ &&
 621             (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 &&
 622             /* avoid calling vm_object_set_writeable_dirty() */
 623             ((prot & VM_PROT_WRITE) == 0 ||
 624             (fs.first_object->type != OBJT_VNODE &&
 625             (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
 626             (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
 627                 VM_OBJECT_RLOCK(fs.first_object);
 628                 if ((prot & VM_PROT_WRITE) == 0 ||
 629                     (fs.first_object->type != OBJT_VNODE &&
 630                     (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
 631                     (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0) {
 632                         rv = vm_fault_soft_fast(&fs, vaddr, prot, fault_type,
 633                             fault_flags, wired, m_hold);
 634                         if (rv == KERN_SUCCESS)
 635                                 return (rv);
 636                 }
 637                 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
 638                         VM_OBJECT_RUNLOCK(fs.first_object);
 639                         VM_OBJECT_WLOCK(fs.first_object);
 640                 }
 641         } else {
 642                 VM_OBJECT_WLOCK(fs.first_object);
 643         }
 644
 645         /*
 646          * Make a reference to this object to prevent its disposal while we
 647          * are messing with it.  Once we have the reference, the map is free
 648          * to be diddled.  Since objects reference their shadows (and copies),
 649          * they will stay around as well.
 650          *
 651          * Bump the paging-in-progress count to prevent size changes (e.g.
 652          * truncation operations) during I/O.
 653          */
 654         vm_object_reference_locked(fs.first_object);
 655         vm_object_pip_add(fs.first_object, 1);
 656
 657         fs.lookup_still_valid = true;
 658
 659         fs.first_m = NULL;
 660
 661         /*
 662          * Search for the page at object/offset.
 663          */
 664         fs.object = fs.first_object;
 665         fs.pindex = fs.first_pindex;
 666         while (TRUE) {
 667                 /*
 668                  * If the object is marked for imminent termination,
 669                  * we retry here, since the collapse pass has raced
 670                  * with us.  Otherwise, if we see terminally dead
 671                  * object, return fail.
 672                  */
 673                 if ((fs.object->flags & OBJ_DEAD) != 0) {
 674                         dead = fs.object->type == OBJT_DEAD;
 675                         unlock_and_deallocate(&fs);
 676                         if (dead)
 677                                 return (KERN_PROTECTION_FAILURE);
 678                         pause("vmf_de", 1);
 679                         goto RetryFault;
 680                 }
 681
 682                 /*
 683                  * See if page is resident
 684                  */
 685                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 686                 if (fs.m != NULL) {
 687                         /*
 688                          * Wait/Retry if the page is busy.  We have to do this
 689                          * if the page is either exclusive or shared busy
 690                          * because the vm_pager may be using read busy for
 691                          * pageouts (and even pageins if it is the vnode
 692                          * pager), and we could end up trying to pagein and
 693                          * pageout the same page simultaneously.
 694                          *
 695                          * We can theoretically allow the busy case on a read
 696                          * fault if the page is marked valid, but since such
 697                          * pages are typically already pmap'd, putting that
 698                          * special case in might be more effort then it is
 699                          * worth.  We cannot under any circumstances mess
 700                          * around with a shared busied page except, perhaps,
 701                          * to pmap it.
 702                          */
 703                         if (vm_page_busied(fs.m)) {
 704                                 /*
 705                                  * Reference the page before unlocking and
 706                                  * sleeping so that the page daemon is less
 707                                  * likely to reclaim it.
 708                                  */
 709                                 vm_page_aflag_set(fs.m, PGA_REFERENCED);
 710                                 if (fs.object != fs.first_object) {
 711                                         if (!VM_OBJECT_TRYWLOCK(
 712                                             fs.first_object)) {
 713                                                 VM_OBJECT_WUNLOCK(fs.object);
 714                                                 VM_OBJECT_WLOCK(fs.first_object);
 715                                                 VM_OBJECT_WLOCK(fs.object);
 716                                         }
 717                                         vm_page_lock(fs.first_m);
 718                                         vm_page_free(fs.first_m);
 719                                         vm_page_unlock(fs.first_m);
 720                                         vm_object_pip_wakeup(fs.first_object);
 721                                         VM_OBJECT_WUNLOCK(fs.first_object);
 722                                         fs.first_m = NULL;
 723                                 }
 724                                 unlock_map(&fs);
 725                                 if (fs.m == vm_page_lookup(fs.object,
 726                                     fs.pindex)) {
 727                                         vm_page_sleep_if_busy(fs.m, "vmpfw");
 728                                 }
 729                                 vm_object_pip_wakeup(fs.object);
 730                                 VM_OBJECT_WUNLOCK(fs.object);
 731                                 VM_CNT_INC(v_intrans);
 732                                 vm_object_deallocate(fs.first_object);
 733                                 goto RetryFault;
 734                         }
 735
 736                         /*
 737                          * Mark page busy for other processes, and the
 738                          * pagedaemon.  If it still isn't completely valid
 739                          * (readable), jump to readrest, else break-out ( we
 740                          * found the page ).
 741                          */
 742                         vm_page_xbusy(fs.m);
 743                         if (fs.m->valid != VM_PAGE_BITS_ALL)
 744                                 goto readrest;
 745                         break; /* break to PAGE HAS BEEN FOUND */
 746                 }
 747                 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m));
 748
 749                 /*
 750                  * Page is not resident.  If the pager might contain the page
 751                  * or this is the beginning of the search, allocate a new
 752                  * page.  (Default objects are zero-fill, so there is no real
 753                  * pager for them.)
 754                  */
 755                 if (fs.object->type != OBJT_DEFAULT ||
 756                     fs.object == fs.first_object) {
 757                         if (fs.pindex >= fs.object->size) {
 758                                 unlock_and_deallocate(&fs);
 759                                 return (KERN_PROTECTION_FAILURE);
 760                         }
 761
 762                         if (fs.object == fs.first_object &&
 763                             (fs.first_object->flags & OBJ_POPULATE) != 0 &&
 764                             fs.first_object->shadow_count == 0) {
 765                                 rv = vm_fault_populate(&fs, prot, fault_type,
 766                                     fault_flags, wired, m_hold);
 767                                 switch (rv) {
 768                                 case KERN_SUCCESS:
 769                                 case KERN_FAILURE:
 770                                         unlock_and_deallocate(&fs);
 771                                         return (rv);
 772                                 case KERN_RESOURCE_SHORTAGE:
 773                                         unlock_and_deallocate(&fs);
 774                                         goto RetryFault;
 775                                 case KERN_NOT_RECEIVER:
 776                                         /*
 777                                          * Pager's populate() method
 778                                          * returned VM_PAGER_BAD.
 779                                          */
 780                                         break;
 781                                 default:
 782                                         panic("inconsistent return codes");
 783                                 }
 784                         }
 785
 786                         /*
 787                          * Allocate a new page for this object/offset pair.
 788                          *
 789                          * Unlocked read of the p_flag is harmless. At
 790                          * worst, the P_KILLED might be not observed
 791                          * there, and allocation can fail, causing
 792                          * restart and new reading of the p_flag.
 793                          */
 794                         if (!vm_page_count_severe() || P_KILLED(curproc)) {
 795 #if VM_NRESERVLEVEL > 0
 796                                 vm_object_color(fs.object, atop(vaddr) -
 797                                     fs.pindex);
 798 #endif
 799                                 alloc_req = P_KILLED(curproc) ?
 800                                     VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
 801                                 if (fs.object->type != OBJT_VNODE &&
 802                                     fs.object->backing_object == NULL)
 803                                         alloc_req |= VM_ALLOC_ZERO;
 804                                 fs.m = vm_page_alloc(fs.object, fs.pindex,
 805                                     alloc_req);
 806                         }
 807                         if (fs.m == NULL) {
 808                                 unlock_and_deallocate(&fs);
 809                                 vm_waitpfault();
 810                                 goto RetryFault;
 811                         }
 812                 }
 813
 814 readrest:
 815                 /*
 816                  * At this point, we have either allocated a new page or found
 817                  * an existing page that is only partially valid.
 818                  *
 819                  * We hold a reference on the current object and the page is
 820                  * exclusive busied.
 821                  */
 822
 823                 /*
 824                  * If the pager for the current object might have the page,
 825                  * then determine the number of additional pages to read and
 826                  * potentially reprioritize previously read pages for earlier
 827                  * reclamation.  These operations should only be performed
 828                  * once per page fault.  Even if the current pager doesn't
 829                  * have the page, the number of additional pages to read will
 830                  * apply to subsequent objects in the shadow chain.
 831                  */
 832                 if (fs.object->type != OBJT_DEFAULT && nera == -1 &&
 833                     !P_KILLED(curproc)) {
 834                         KASSERT(fs.lookup_still_valid, ("map unlocked"));
 835                         era = fs.entry->read_ahead;
 836                         behavior = vm_map_entry_behavior(fs.entry);
 837                         if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
 838                                 nera = 0;
 839                         } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
 840                                 nera = VM_FAULT_READ_AHEAD_MAX;
 841                                 if (vaddr == fs.entry->next_read)
 842                                         vm_fault_dontneed(&fs, vaddr, nera);
 843                         } else if (vaddr == fs.entry->next_read) {
 844                                 /*
 845                                  * This is a sequential fault.  Arithmetically
 846                                  * increase the requested number of pages in
 847                                  * the read-ahead window.  The requested
 848                                  * number of pages is "# of sequential faults
 849                                  * x (read ahead min + 1) + read ahead min"
 850                                  */
 851                                 nera = VM_FAULT_READ_AHEAD_MIN;
 852                                 if (era > 0) {
 853                                         nera += era + 1;
 854                                         if (nera > VM_FAULT_READ_AHEAD_MAX)
 855                                                 nera = VM_FAULT_READ_AHEAD_MAX;
 856                                 }
 857                                 if (era == VM_FAULT_READ_AHEAD_MAX)
 858                                         vm_fault_dontneed(&fs, vaddr, nera);
 859                         } else {
 860                                 /*
 861                                  * This is a non-sequential fault.
 862                                  */
 863                                 nera = 0;
 864                         }
 865                         if (era != nera) {
 866                                 /*
 867                                  * A read lock on the map suffices to update
 868                                  * the read ahead count safely.
 869                                  */
 870                                 fs.entry->read_ahead = nera;
 871                         }
 872
 873                         /*
 874                          * Prepare for unlocking the map.  Save the map
 875                          * entry's start and end addresses, which are used to
 876                          * optimize the size of the pager operation below.
 877                          * Even if the map entry's addresses change after
 878                          * unlocking the map, using the saved addresses is
 879                          * safe.
 880                          */
 881                         e_start = fs.entry->start;
 882                         e_end = fs.entry->end;
 883                 }
 884
 885                 /*
 886                  * Call the pager to retrieve the page if there is a chance
 887                  * that the pager has it, and potentially retrieve additional
 888                  * pages at the same time.
 889                  */
 890                 if (fs.object->type != OBJT_DEFAULT) {
 891                         /*
 892                          * Release the map lock before locking the vnode or
 893                          * sleeping in the pager.  (If the current object has
 894                          * a shadow, then an earlier iteration of this loop
 895                          * may have already unlocked the map.)
 896                          */
 897                         unlock_map(&fs);
 898
 899                         if (fs.object->type == OBJT_VNODE &&
 900                             (vp = fs.object->handle) != fs.vp) {
 901                                 /*
 902                                  * Perform an unlock in case the desired vnode
 903                                  * changed while the map was unlocked during a
 904                                  * retry.
 905                                  */
 906                                 unlock_vp(&fs);
 907
 908                                 locked = VOP_ISLOCKED(vp);
 909                                 if (locked != LK_EXCLUSIVE)
 910                                         locked = LK_SHARED;
 911
 912                                 /*
 913                                  * We must not sleep acquiring the vnode lock
 914                                  * while we have the page exclusive busied or
 915                                  * the object's paging-in-progress count
 916                                  * incremented.  Otherwise, we could deadlock.
 917                                  */
 918                                 error = vget(vp, locked | LK_CANRECURSE |
 919                                     LK_NOWAIT, curthread);
 920                                 if (error != 0) {
 921                                         vhold(vp);
 922                                         release_page(&fs);
 923                                         unlock_and_deallocate(&fs);
 924                                         error = vget(vp, locked | LK_RETRY |
 925                                             LK_CANRECURSE, curthread);
 926                                         vdrop(vp);
 927                                         fs.vp = vp;
 928                                         KASSERT(error == 0,
 929                                             ("vm_fault: vget failed"));
 930                                         goto RetryFault;
 931                                 }
 932                                 fs.vp = vp;
 933                         }
 934                         KASSERT(fs.vp == NULL || !fs.map->system_map,
 935                             ("vm_fault: vnode-backed object mapped by system map"));
 936
 937                         /*
 938                          * Page in the requested page and hint the pager,
 939                          * that it may bring up surrounding pages.
 940                          */
 941                         if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM ||
 942                             P_KILLED(curproc)) {
 943                                 behind = 0;
 944                                 ahead = 0;
 945                         } else {
 946                                 /* Is this a sequential fault? */
 947                                 if (nera > 0) {
 948                                         behind = 0;
 949                                         ahead = nera;
 950                                 } else {
 951                                         /*
 952                                          * Request a cluster of pages that is
 953                                          * aligned to a VM_FAULT_READ_DEFAULT
 954                                          * page offset boundary within the
 955                                          * object.  Alignment to a page offset
 956                                          * boundary is more likely to coincide
 957                                          * with the underlying file system
 958                                          * block than alignment to a virtual
 959                                          * address boundary.
 960                                          */
 961                                         cluster_offset = fs.pindex %
 962                                             VM_FAULT_READ_DEFAULT;
 963                                         behind = ulmin(cluster_offset,
 964                                             atop(vaddr - e_start));
 965                                         ahead = VM_FAULT_READ_DEFAULT - 1 -
 966                                             cluster_offset;
 967                                 }
 968                                 ahead = ulmin(ahead, atop(e_end - vaddr) - 1);
 969                         }
 970                         rv = vm_pager_get_pages(fs.object, &fs.m, 1,
 971                             &behind, &ahead);
 972                         if (rv == VM_PAGER_OK) {
 973                                 faultcount = behind + 1 + ahead;
 974                                 hardfault = true;
 975                                 break; /* break to PAGE HAS BEEN FOUND */
 976                         }
 977                         if (rv == VM_PAGER_ERROR)
 978                                 printf("vm_fault: pager read error, pid %d (%s)\n",
 979                                     curproc->p_pid, curproc->p_comm);
 980
 981                         /*
 982                          * If an I/O error occurred or the requested page was
 983                          * outside the range of the pager, clean up and return
 984                          * an error.
 985                          */
 986                         if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) {
 987                                 vm_page_lock(fs.m);
 988                                 if (fs.m->wire_count == 0)
 989                                         vm_page_free(fs.m);
 990                                 else
 991                                         vm_page_xunbusy_maybelocked(fs.m);
 992                                 vm_page_unlock(fs.m);
 993                                 fs.m = NULL;
 994                                 unlock_and_deallocate(&fs);
 995                                 return (rv == VM_PAGER_ERROR ? KERN_FAILURE :
 996                                     KERN_PROTECTION_FAILURE);
 997                         }
 998
 999                         /*
1000                          * The requested page does not exist at this object/
1001                          * offset.  Remove the invalid page from the object,
1002                          * waking up anyone waiting for it, and continue on to
1003                          * the next object.  However, if this is the top-level
1004                          * object, we must leave the busy page in place to
1005                          * prevent another process from rushing past us, and
1006                          * inserting the page in that object at the same time
1007                          * that we are.
1008                          */
1009                         if (fs.object != fs.first_object) {
1010                                 vm_page_lock(fs.m);
1011                                 if (fs.m->wire_count == 0)
1012                                         vm_page_free(fs.m);
1013                                 else
1014                                         vm_page_xunbusy_maybelocked(fs.m);
1015                                 vm_page_unlock(fs.m);
1016                                 fs.m = NULL;
1017                         }
1018                 }
1019
1020                 /*
1021                  * We get here if the object has default pager (or unwiring)
1022                  * or the pager doesn't have the page.
1023                  */
1024                 if (fs.object == fs.first_object)
1025                         fs.first_m = fs.m;
1026
1027                 /*
1028                  * Move on to the next object.  Lock the next object before
1029                  * unlocking the current one.
1030                  */
1031                 next_object = fs.object->backing_object;
1032                 if (next_object == NULL) {
1033                         /*
1034                          * If there's no object left, fill the page in the top
1035                          * object with zeros.
1036                          */
1037                         if (fs.object != fs.first_object) {
1038                                 vm_object_pip_wakeup(fs.object);
1039                                 VM_OBJECT_WUNLOCK(fs.object);
1040
1041                                 fs.object = fs.first_object;
1042                                 fs.pindex = fs.first_pindex;
1043                                 fs.m = fs.first_m;
1044                                 VM_OBJECT_WLOCK(fs.object);
1045                         }
1046                         fs.first_m = NULL;
1047
1048                         /*
1049                          * Zero the page if necessary and mark it valid.
1050                          */
1051                         if ((fs.m->flags & PG_ZERO) == 0) {
1052                                 pmap_zero_page(fs.m);
1053                         } else {
1054                                 VM_CNT_INC(v_ozfod);
1055                         }
1056                         VM_CNT_INC(v_zfod);
1057                         fs.m->valid = VM_PAGE_BITS_ALL;
1058                         /* Don't try to prefault neighboring pages. */
1059                         faultcount = 1;
1060                         break;  /* break to PAGE HAS BEEN FOUND */
1061                 } else {
1062                         KASSERT(fs.object != next_object,
1063                             ("object loop %p", next_object));
1064                         VM_OBJECT_WLOCK(next_object);
1065                         vm_object_pip_add(next_object, 1);
1066                         if (fs.object != fs.first_object)
1067                                 vm_object_pip_wakeup(fs.object);
1068                         fs.pindex +=
1069                             OFF_TO_IDX(fs.object->backing_object_offset);
1070                         VM_OBJECT_WUNLOCK(fs.object);
1071                         fs.object = next_object;
1072                 }
1073         }
1074
1075         vm_page_assert_xbusied(fs.m);
1076
1077         /*
1078          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
1079          * is held.]
1080          */
1081
1082         /*
1083          * If the page is being written, but isn't already owned by the
1084          * top-level object, we have to copy it into a new page owned by the
1085          * top-level object.
1086          */
1087         if (fs.object != fs.first_object) {
1088                 /*
1089                  * We only really need to copy if we want to write it.
1090                  */
1091                 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1092                         /*
1093                          * This allows pages to be virtually copied from a
1094                          * backing_object into the first_object, where the
1095                          * backing object has no other refs to it, and cannot
1096                          * gain any more refs.  Instead of a bcopy, we just
1097                          * move the page from the backing object to the
1098                          * first object.  Note that we must mark the page
1099                          * dirty in the first object so that it will go out
1100                          * to swap when needed.
1101                          */
1102                         is_first_object_locked = false;
1103                         if (
1104                                 /*
1105                                  * Only one shadow object
1106                                  */
1107                                 (fs.object->shadow_count == 1) &&
1108                                 /*
1109                                  * No COW refs, except us
1110                                  */
1111                                 (fs.object->ref_count == 1) &&
1112                                 /*
1113                                  * No one else can look this object up
1114                                  */
1115                                 (fs.object->handle == NULL) &&
1116                                 /*
1117                                  * No other ways to look the object up
1118                                  */
1119                                 ((fs.object->type == OBJT_DEFAULT) ||
1120                                  (fs.object->type == OBJT_SWAP)) &&
1121                             (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
1122                                 /*
1123                                  * We don't chase down the shadow chain
1124                                  */
1125                             fs.object == fs.first_object->backing_object) {
1126                                 vm_page_lock(fs.m);
1127                                 vm_page_remque(fs.m);
1128                                 vm_page_remove(fs.m);
1129                                 vm_page_unlock(fs.m);
1130                                 vm_page_lock(fs.first_m);
1131                                 vm_page_replace_checked(fs.m, fs.first_object,
1132                                     fs.first_pindex, fs.first_m);
1133                                 vm_page_free(fs.first_m);
1134                                 vm_page_unlock(fs.first_m);
1135                                 vm_page_dirty(fs.m);
1136 #if VM_NRESERVLEVEL > 0
1137                                 /*
1138                                  * Rename the reservation.
1139                                  */
1140                                 vm_reserv_rename(fs.m, fs.first_object,
1141                                     fs.object, OFF_TO_IDX(
1142                                     fs.first_object->backing_object_offset));
1143 #endif
1144                                 /*
1145                                  * Removing the page from the backing object
1146                                  * unbusied it.
1147                                  */
1148                                 vm_page_xbusy(fs.m);
1149                                 fs.first_m = fs.m;
1150                                 fs.m = NULL;
1151                                 VM_CNT_INC(v_cow_optim);
1152                         } else {
1153                                 /*
1154                                  * Oh, well, lets copy it.
1155                                  */
1156                                 pmap_copy_page(fs.m, fs.first_m);
1157                                 fs.first_m->valid = VM_PAGE_BITS_ALL;
1158                                 if (wired && (fault_flags &
1159                                     VM_FAULT_WIRE) == 0) {
1160                                         vm_page_lock(fs.first_m);
1161                                         vm_page_wire(fs.first_m);
1162                                         vm_page_unlock(fs.first_m);
1163
1164                                         vm_page_lock(fs.m);
1165                                         vm_page_unwire(fs.m, PQ_INACTIVE);
1166                                         vm_page_unlock(fs.m);
1167                                 }
1168                                 /*
1169                                  * We no longer need the old page or object.
1170                                  */
1171                                 release_page(&fs);
1172                         }
1173                         /*
1174                          * fs.object != fs.first_object due to above
1175                          * conditional
1176                          */
1177                         vm_object_pip_wakeup(fs.object);
1178                         VM_OBJECT_WUNLOCK(fs.object);
1179                         /*
1180                          * Only use the new page below...
1181                          */
1182                         fs.object = fs.first_object;
1183                         fs.pindex = fs.first_pindex;
1184                         fs.m = fs.first_m;
1185                         if (!is_first_object_locked)
1186                                 VM_OBJECT_WLOCK(fs.object);
1187                         VM_CNT_INC(v_cow_faults);
1188                         curthread->td_cow++;
1189                 } else {
1190                         prot &= ~VM_PROT_WRITE;
1191                 }
1192         }
1193
1194         /*
1195          * We must verify that the maps have not changed since our last
1196          * lookup.
1197          */
1198         if (!fs.lookup_still_valid) {
1199                 if (!vm_map_trylock_read(fs.map)) {
1200                         release_page(&fs);
1201                         unlock_and_deallocate(&fs);
1202                         goto RetryFault;
1203                 }
1204                 fs.lookup_still_valid = true;
1205                 if (fs.map->timestamp != fs.map_generation) {
1206                         result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
1207                             &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
1208
1209                         /*
1210                          * If we don't need the page any longer, put it on the inactive
1211                          * list (the easiest thing to do here).  If no one needs it,
1212                          * pageout will grab it eventually.
1213                          */
1214                         if (result != KERN_SUCCESS) {
1215                                 release_page(&fs);
1216                                 unlock_and_deallocate(&fs);
1217
1218                                 /*
1219                                  * If retry of map lookup would have blocked then
1220                                  * retry fault from start.
1221                                  */
1222                                 if (result == KERN_FAILURE)
1223                                         goto RetryFault;
1224                                 return (result);
1225                         }
1226                         if ((retry_object != fs.first_object) ||
1227                             (retry_pindex != fs.first_pindex)) {
1228                                 release_page(&fs);
1229                                 unlock_and_deallocate(&fs);
1230                                 goto RetryFault;
1231                         }
1232
1233                         /*
1234                          * Check whether the protection has changed or the object has
1235                          * been copied while we left the map unlocked. Changing from
1236                          * read to write permission is OK - we leave the page
1237                          * write-protected, and catch the write fault. Changing from
1238                          * write to read permission means that we can't mark the page
1239                          * write-enabled after all.
1240                          */
1241                         prot &= retry_prot;
1242                         fault_type &= retry_prot;
1243                         if (prot == 0) {
1244                                 release_page(&fs);
1245                                 unlock_and_deallocate(&fs);
1246                                 goto RetryFault;
1247                         }
1248
1249                         /* Reassert because wired may have changed. */
1250                         KASSERT(wired || (fault_flags & VM_FAULT_WIRE) == 0,
1251                             ("!wired && VM_FAULT_WIRE"));
1252                 }
1253         }
1254
1255         /*
1256          * If the page was filled by a pager, save the virtual address that
1257          * should be faulted on next under a sequential access pattern to the
1258          * map entry.  A read lock on the map suffices to update this address
1259          * safely.
1260          */
1261         if (hardfault)
1262                 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE;
1263
1264         vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true);
1265         vm_page_assert_xbusied(fs.m);
1266
1267         /*
1268          * Page must be completely valid or it is not fit to
1269          * map into user space.  vm_pager_get_pages() ensures this.
1270          */
1271         KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
1272             ("vm_fault: page %p partially invalid", fs.m));
1273         VM_OBJECT_WUNLOCK(fs.object);
1274
1275         /*
1276          * Put this page into the physical map.  We had to do the unlock above
1277          * because pmap_enter() may sleep.  We don't put the page
1278          * back on the active queue until later so that the pageout daemon
1279          * won't find it (yet).
1280          */
1281         pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
1282             fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
1283         if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 &&
1284             wired == 0)
1285                 vm_fault_prefault(&fs, vaddr,
1286                     faultcount > 0 ? behind : PFBAK,
1287                     faultcount > 0 ? ahead : PFFOR, false);
1288         VM_OBJECT_WLOCK(fs.object);
1289         vm_page_lock(fs.m);
1290
1291         /*
1292          * If the page is not wired down, then put it where the pageout daemon
1293          * can find it.
1294          */
1295         if ((fault_flags & VM_FAULT_WIRE) != 0)
1296                 vm_page_wire(fs.m);
1297         else
1298                 vm_page_activate(fs.m);
1299         if (m_hold != NULL) {
1300                 *m_hold = fs.m;
1301                 vm_page_hold(fs.m);
1302         }
1303         vm_page_unlock(fs.m);
1304         vm_page_xunbusy(fs.m);
1305
1306         /*
1307          * Unlock everything, and return
1308          */
1309         unlock_and_deallocate(&fs);
1310         if (hardfault) {
1311                 VM_CNT_INC(v_io_faults);
1312                 curthread->td_ru.ru_majflt++;
1313 #ifdef RACCT
1314                 if (racct_enable && fs.object->type == OBJT_VNODE) {
1315                         PROC_LOCK(curproc);
1316                         if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1317                                 racct_add_force(curproc, RACCT_WRITEBPS,
1318                                     PAGE_SIZE + behind * PAGE_SIZE);
1319                                 racct_add_force(curproc, RACCT_WRITEIOPS, 1);
1320                         } else {
1321                                 racct_add_force(curproc, RACCT_READBPS,
1322                                     PAGE_SIZE + ahead * PAGE_SIZE);
1323                                 racct_add_force(curproc, RACCT_READIOPS, 1);
1324                         }
1325                         PROC_UNLOCK(curproc);
1326                 }
1327 #endif
1328         } else
1329                 curthread->td_ru.ru_minflt++;
1330
1331         return (KERN_SUCCESS);
1332 }
1333
1334 /*
1335  * Speed up the reclamation of pages that precede the faulting pindex within
1336  * the first object of the shadow chain.  Essentially, perform the equivalent
1337  * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes
1338  * the faulting pindex by the cluster size when the pages read by vm_fault()
1339  * cross a cluster-size boundary.  The cluster size is the greater of the
1340  * smallest superpage size and VM_FAULT_DONTNEED_MIN.
1341  *
1342  * When "fs->first_object" is a shadow object, the pages in the backing object
1343  * that precede the faulting pindex are deactivated by vm_fault().  So, this
1344  * function must only be concerned with pages in the first object.
1345  */
1346 static void
1347 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
1348 {
1349         vm_map_entry_t entry;
1350         vm_object_t first_object, object;
1351         vm_offset_t end, start;
1352         vm_page_t m, m_next;
1353         vm_pindex_t pend, pstart;
1354         vm_size_t size;
1355
1356         object = fs->object;
1357         VM_OBJECT_ASSERT_WLOCKED(object);
1358         first_object = fs->first_object;
1359         if (first_object != object) {
1360                 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1361                         VM_OBJECT_WUNLOCK(object);
1362                         VM_OBJECT_WLOCK(first_object);
1363                         VM_OBJECT_WLOCK(object);
1364                 }
1365         }
1366         /* Neither fictitious nor unmanaged pages can be reclaimed. */
1367         if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1368                 size = VM_FAULT_DONTNEED_MIN;
1369                 if (MAXPAGESIZES > 1 && size < pagesizes[1])
1370                         size = pagesizes[1];
1371                 end = rounddown2(vaddr, size);
1372                 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) &&
1373                     (entry = fs->entry)->start < end) {
1374                         if (end - entry->start < size)
1375                                 start = entry->start;
1376                         else
1377                                 start = end - size;
1378                         pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED);
1379                         pstart = OFF_TO_IDX(entry->offset) + atop(start -
1380                             entry->start);
1381                         m_next = vm_page_find_least(first_object, pstart);
1382                         pend = OFF_TO_IDX(entry->offset) + atop(end -
1383                             entry->start);
1384                         while ((m = m_next) != NULL && m->pindex < pend) {
1385                                 m_next = TAILQ_NEXT(m, listq);
1386                                 if (m->valid != VM_PAGE_BITS_ALL ||
1387                                     vm_page_busied(m))
1388                                         continue;
1389
1390                                 /*
1391                                  * Don't clear PGA_REFERENCED, since it would
1392                                  * likely represent a reference by a different
1393                                  * process.
1394                                  *
1395                                  * Typically, at this point, prefetched pages
1396                                  * are still in the inactive queue.  Only
1397                                  * pages that triggered page faults are in the
1398                                  * active queue.
1399                                  */
1400                                 vm_page_lock(m);
1401                                 if (!vm_page_inactive(m))
1402                                         vm_page_deactivate(m);
1403                                 vm_page_unlock(m);
1404                         }
1405                 }
1406         }
1407         if (first_object != object)
1408                 VM_OBJECT_WUNLOCK(first_object);
1409 }
1410
1411 /*
1412  * vm_fault_prefault provides a quick way of clustering
1413  * pagefaults into a processes address space.  It is a "cousin"
1414  * of vm_map_pmap_enter, except it runs at page fault time instead
1415  * of mmap time.
1416  */
1417 static void
1418 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1419     int backward, int forward, bool obj_locked)
1420 {
1421         pmap_t pmap;
1422         vm_map_entry_t entry;
1423         vm_object_t backing_object, lobject;
1424         vm_offset_t addr, starta;
1425         vm_pindex_t pindex;
1426         vm_page_t m;
1427         int i;
1428
1429         pmap = fs->map->pmap;
1430         if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1431                 return;
1432
1433         entry = fs->entry;
1434
1435         if (addra < backward * PAGE_SIZE) {
1436                 starta = entry->start;
1437         } else {
1438                 starta = addra - backward * PAGE_SIZE;
1439                 if (starta < entry->start)
1440                         starta = entry->start;
1441         }
1442
1443         /*
1444          * Generate the sequence of virtual addresses that are candidates for
1445          * prefaulting in an outward spiral from the faulting virtual address,
1446          * "addra".  Specifically, the sequence is "addra - PAGE_SIZE", "addra
1447          * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1448          * If the candidate address doesn't have a backing physical page, then
1449          * the loop immediately terminates.
1450          */
1451         for (i = 0; i < 2 * imax(backward, forward); i++) {
1452                 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1453                     PAGE_SIZE);
1454                 if (addr > addra + forward * PAGE_SIZE)
1455                         addr = 0;
1456
1457                 if (addr < starta || addr >= entry->end)
1458                         continue;
1459
1460                 if (!pmap_is_prefaultable(pmap, addr))
1461                         continue;
1462
1463                 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1464                 lobject = entry->object.vm_object;
1465                 if (!obj_locked)
1466                         VM_OBJECT_RLOCK(lobject);
1467                 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1468                     lobject->type == OBJT_DEFAULT &&
1469                     (backing_object = lobject->backing_object) != NULL) {
1470                         KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1471                             0, ("vm_fault_prefault: unaligned object offset"));
1472                         pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1473                         VM_OBJECT_RLOCK(backing_object);
1474                         if (!obj_locked || lobject != entry->object.vm_object)
1475                                 VM_OBJECT_RUNLOCK(lobject);
1476                         lobject = backing_object;
1477                 }
1478                 if (m == NULL) {
1479                         if (!obj_locked || lobject != entry->object.vm_object)
1480                                 VM_OBJECT_RUNLOCK(lobject);
1481                         break;
1482                 }
1483                 if (m->valid == VM_PAGE_BITS_ALL &&
1484                     (m->flags & PG_FICTITIOUS) == 0)
1485                         pmap_enter_quick(pmap, addr, m, entry->protection);
1486                 if (!obj_locked || lobject != entry->object.vm_object)
1487                         VM_OBJECT_RUNLOCK(lobject);
1488         }
1489 }
1490
1491 /*
1492  * Hold each of the physical pages that are mapped by the specified range of
1493  * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1494  * and allow the specified types of access, "prot".  If all of the implied
1495  * pages are successfully held, then the number of held pages is returned
1496  * together with pointers to those pages in the array "ma".  However, if any
1497  * of the pages cannot be held, -1 is returned.
1498  */
1499 int
1500 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1501     vm_prot_t prot, vm_page_t *ma, int max_count)
1502 {
1503         vm_offset_t end, va;
1504         vm_page_t *mp;
1505         int count;
1506         boolean_t pmap_failed;
1507
1508         if (len == 0)
1509                 return (0);
1510         end = round_page(addr + len);
1511         addr = trunc_page(addr);
1512
1513         /*
1514          * Check for illegal addresses.
1515          */
1516         if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1517                 return (-1);
1518
1519         if (atop(end - addr) > max_count)
1520                 panic("vm_fault_quick_hold_pages: count > max_count");
1521         count = atop(end - addr);
1522
1523         /*
1524          * Most likely, the physical pages are resident in the pmap, so it is
1525          * faster to try pmap_extract_and_hold() first.
1526          */
1527         pmap_failed = FALSE;
1528         for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1529                 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1530                 if (*mp == NULL)
1531                         pmap_failed = TRUE;
1532                 else if ((prot & VM_PROT_WRITE) != 0 &&
1533                     (*mp)->dirty != VM_PAGE_BITS_ALL) {
1534                         /*
1535                          * Explicitly dirty the physical page.  Otherwise, the
1536                          * caller's changes may go unnoticed because they are
1537                          * performed through an unmanaged mapping or by a DMA
1538                          * operation.
1539                          *
1540                          * The object lock is not held here.
1541                          * See vm_page_clear_dirty_mask().
1542                          */
1543                         vm_page_dirty(*mp);
1544                 }
1545         }
1546         if (pmap_failed) {
1547                 /*
1548                  * One or more pages could not be held by the pmap.  Either no
1549                  * page was mapped at the specified virtual address or that
1550                  * mapping had insufficient permissions.  Attempt to fault in
1551                  * and hold these pages.
1552                  *
1553                  * If vm_fault_disable_pagefaults() was called,
1554                  * i.e., TDP_NOFAULTING is set, we must not sleep nor
1555                  * acquire MD VM locks, which means we must not call
1556                  * vm_fault_hold().  Some (out of tree) callers mark
1557                  * too wide a code area with vm_fault_disable_pagefaults()
1558                  * already, use the VM_PROT_QUICK_NOFAULT flag to request
1559                  * the proper behaviour explicitly.
1560                  */
1561                 if ((prot & VM_PROT_QUICK_NOFAULT) != 0 &&
1562                     (curthread->td_pflags & TDP_NOFAULTING) != 0)
1563                         goto error;
1564                 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1565                         if (*mp == NULL && vm_fault_hold(map, va, prot,
1566                             VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1567                                 goto error;
1568         }
1569         return (count);
1570 error:
1571         for (mp = ma; mp < ma + count; mp++)
1572                 if (*mp != NULL) {
1573                         vm_page_lock(*mp);
1574                         vm_page_unhold(*mp);
1575                         vm_page_unlock(*mp);
1576                 }
1577         return (-1);
1578 }
1579
1580 /*
1581  *      Routine:
1582  *              vm_fault_copy_entry
1583  *      Function:
1584  *              Create new shadow object backing dst_entry with private copy of
1585  *              all underlying pages. When src_entry is equal to dst_entry,
1586  *              function implements COW for wired-down map entry. Otherwise,
1587  *              it forks wired entry into dst_map.
1588  *
1589  *      In/out conditions:
1590  *              The source and destination maps must be locked for write.
1591  *              The source map entry must be wired down (or be a sharing map
1592  *              entry corresponding to a main map entry that is wired down).
1593  */
1594 void
1595 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1596     vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1597     vm_ooffset_t *fork_charge)
1598 {
1599         vm_object_t backing_object, dst_object, object, src_object;
1600         vm_pindex_t dst_pindex, pindex, src_pindex;
1601         vm_prot_t access, prot;
1602         vm_offset_t vaddr;
1603         vm_page_t dst_m;
1604         vm_page_t src_m;
1605         boolean_t upgrade;
1606
1607 #ifdef  lint
1608         src_map++;
1609 #endif  /* lint */
1610
1611         upgrade = src_entry == dst_entry;
1612         access = prot = dst_entry->protection;
1613
1614         src_object = src_entry->object.vm_object;
1615         src_pindex = OFF_TO_IDX(src_entry->offset);
1616
1617         if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1618                 dst_object = src_object;
1619                 vm_object_reference(dst_object);
1620         } else {
1621                 /*
1622                  * Create the top-level object for the destination entry. (Doesn't
1623                  * actually shadow anything - we copy the pages directly.)
1624                  */
1625                 dst_object = vm_object_allocate(OBJT_DEFAULT,
1626                     atop(dst_entry->end - dst_entry->start));
1627 #if VM_NRESERVLEVEL > 0
1628                 dst_object->flags |= OBJ_COLORED;
1629                 dst_object->pg_color = atop(dst_entry->start);
1630 #endif
1631         }
1632
1633         VM_OBJECT_WLOCK(dst_object);
1634         KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1635             ("vm_fault_copy_entry: vm_object not NULL"));
1636         if (src_object != dst_object) {
1637                 dst_object->domain = src_object->domain;
1638                 dst_entry->object.vm_object = dst_object;
1639                 dst_entry->offset = 0;
1640                 dst_object->charge = dst_entry->end - dst_entry->start;
1641         }
1642         if (fork_charge != NULL) {
1643                 KASSERT(dst_entry->cred == NULL,
1644                     ("vm_fault_copy_entry: leaked swp charge"));
1645                 dst_object->cred = curthread->td_ucred;
1646                 crhold(dst_object->cred);
1647                 *fork_charge += dst_object->charge;
1648         } else if (dst_object->cred == NULL) {
1649                 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1650                     dst_entry));
1651                 dst_object->cred = dst_entry->cred;
1652                 dst_entry->cred = NULL;
1653         }
1654
1655         /*
1656          * If not an upgrade, then enter the mappings in the pmap as
1657          * read and/or execute accesses.  Otherwise, enter them as
1658          * write accesses.
1659          *
1660          * A writeable large page mapping is only created if all of
1661          * the constituent small page mappings are modified. Marking
1662          * PTEs as modified on inception allows promotion to happen
1663          * without taking potentially large number of soft faults.
1664          */
1665         if (!upgrade)
1666                 access &= ~VM_PROT_WRITE;
1667
1668         /*
1669          * Loop through all of the virtual pages within the entry's
1670          * range, copying each page from the source object to the
1671          * destination object.  Since the source is wired, those pages
1672          * must exist.  In contrast, the destination is pageable.
1673          * Since the destination object doesn't share any backing storage
1674          * with the source object, all of its pages must be dirtied,
1675          * regardless of whether they can be written.
1676          */
1677         for (vaddr = dst_entry->start, dst_pindex = 0;
1678             vaddr < dst_entry->end;
1679             vaddr += PAGE_SIZE, dst_pindex++) {
1680 again:
1681                 /*
1682                  * Find the page in the source object, and copy it in.
1683                  * Because the source is wired down, the page will be
1684                  * in memory.
1685                  */
1686                 if (src_object != dst_object)
1687                         VM_OBJECT_RLOCK(src_object);
1688                 object = src_object;
1689                 pindex = src_pindex + dst_pindex;
1690                 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1691                     (backing_object = object->backing_object) != NULL) {
1692                         /*
1693                          * Unless the source mapping is read-only or
1694                          * it is presently being upgraded from
1695                          * read-only, the first object in the shadow
1696                          * chain should provide all of the pages.  In
1697                          * other words, this loop body should never be
1698                          * executed when the source mapping is already
1699                          * read/write.
1700                          */
1701                         KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1702                             upgrade,
1703                             ("vm_fault_copy_entry: main object missing page"));
1704
1705                         VM_OBJECT_RLOCK(backing_object);
1706                         pindex += OFF_TO_IDX(object->backing_object_offset);
1707                         if (object != dst_object)
1708                                 VM_OBJECT_RUNLOCK(object);
1709                         object = backing_object;
1710                 }
1711                 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1712
1713                 if (object != dst_object) {
1714                         /*
1715                          * Allocate a page in the destination object.
1716                          */
1717                         dst_m = vm_page_alloc(dst_object, (src_object ==
1718                             dst_object ? src_pindex : 0) + dst_pindex,
1719                             VM_ALLOC_NORMAL);
1720                         if (dst_m == NULL) {
1721                                 VM_OBJECT_WUNLOCK(dst_object);
1722                                 VM_OBJECT_RUNLOCK(object);
1723                                 vm_wait(dst_object);
1724                                 VM_OBJECT_WLOCK(dst_object);
1725                                 goto again;
1726                         }
1727                         pmap_copy_page(src_m, dst_m);
1728                         VM_OBJECT_RUNLOCK(object);
1729                         dst_m->valid = VM_PAGE_BITS_ALL;
1730                         dst_m->dirty = VM_PAGE_BITS_ALL;
1731                 } else {
1732                         dst_m = src_m;
1733                         if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1734                                 goto again;
1735                         vm_page_xbusy(dst_m);
1736                         KASSERT(dst_m->valid == VM_PAGE_BITS_ALL,
1737                             ("invalid dst page %p", dst_m));
1738                 }
1739                 VM_OBJECT_WUNLOCK(dst_object);
1740
1741                 /*
1742                  * Enter it in the pmap. If a wired, copy-on-write
1743                  * mapping is being replaced by a write-enabled
1744                  * mapping, then wire that new mapping.
1745                  */
1746                 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1747                     access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1748
1749                 /*
1750                  * Mark it no longer busy, and put it on the active list.
1751                  */
1752                 VM_OBJECT_WLOCK(dst_object);
1753
1754                 if (upgrade) {
1755                         if (src_m != dst_m) {
1756                                 vm_page_lock(src_m);
1757                                 vm_page_unwire(src_m, PQ_INACTIVE);
1758                                 vm_page_unlock(src_m);
1759                                 vm_page_lock(dst_m);
1760                                 vm_page_wire(dst_m);
1761                                 vm_page_unlock(dst_m);
1762                         } else {
1763                                 KASSERT(dst_m->wire_count > 0,
1764                                     ("dst_m %p is not wired", dst_m));
1765                         }
1766                 } else {
1767                         vm_page_lock(dst_m);
1768                         vm_page_activate(dst_m);
1769                         vm_page_unlock(dst_m);
1770                 }
1771                 vm_page_xunbusy(dst_m);
1772         }
1773         VM_OBJECT_WUNLOCK(dst_object);
1774         if (upgrade) {
1775                 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1776                 vm_object_deallocate(src_object);
1777         }
1778 }
1779
1780 /*
1781  * Block entry into the machine-independent layer's page fault handler by
1782  * the calling thread.  Subsequent calls to vm_fault() by that thread will
1783  * return KERN_PROTECTION_FAILURE.  Enable machine-dependent handling of
1784  * spurious page faults.
1785  */
1786 int
1787 vm_fault_disable_pagefaults(void)
1788 {
1789
1790         return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1791 }
1792
1793 void
1794 vm_fault_enable_pagefaults(int save)
1795 {
1796
1797         curthread_pflags_restore(save);
1798 }