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/mutex.h>
  88 #include <sys/proc.h>
  89 #include <sys/racct.h>
  90 #include <sys/resourcevar.h>
  91 #include <sys/rwlock.h>
  92 #include <sys/sysctl.h>
  93 #include <sys/vmmeter.h>
  94 #include <sys/vnode.h>
  95 #ifdef KTRACE
  96 #include <sys/ktrace.h>
  97 #endif
  98
  99 #include <vm/vm.h>
 100 #include <vm/vm_param.h>
 101 #include <vm/pmap.h>
 102 #include <vm/vm_map.h>
 103 #include <vm/vm_object.h>
 104 #include <vm/vm_page.h>
 105 #include <vm/vm_pageout.h>
 106 #include <vm/vm_kern.h>
 107 #include <vm/vm_pager.h>
 108 #include <vm/vm_extern.h>
 109 #include <vm/vm_reserv.h>
 110
 111 #define PFBAK 4
 112 #define PFFOR 4
 113
 114 #define VM_FAULT_READ_DEFAULT   (1 + VM_FAULT_READ_AHEAD_INIT)
 115 #define VM_FAULT_READ_MAX       (1 + VM_FAULT_READ_AHEAD_MAX)
 116
 117 #define VM_FAULT_DONTNEED_MIN   1048576
 118
 119 struct faultstate {
 120         vm_page_t m;
 121         vm_object_t object;
 122         vm_pindex_t pindex;
 123         vm_page_t first_m;
 124         vm_object_t     first_object;
 125         vm_pindex_t first_pindex;
 126         vm_map_t map;
 127         vm_map_entry_t entry;
 128         int map_generation;
 129         bool lookup_still_valid;
 130         struct vnode *vp;
 131 };
 132
 133 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr,
 134             int ahead);
 135 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
 136             int backward, int forward, bool obj_locked);
 137
 138 static int vm_pfault_oom_attempts = 3;
 139 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_attempts, CTLFLAG_RWTUN,
 140     &vm_pfault_oom_attempts, 0,
 141     "Number of page allocation attempts in page fault handler before it "
 142     "triggers OOM handling");
 143
 144 static int vm_pfault_oom_wait = 10;
 145 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_wait, CTLFLAG_RWTUN,
 146     &vm_pfault_oom_wait, 0,
 147     "Number of seconds to wait for free pages before retrying "
 148     "the page fault handler");
 149
 150 static inline void
 151 release_page(struct faultstate *fs)
 152 {
 153
 154         vm_page_xunbusy(fs->m);
 155         vm_page_lock(fs->m);
 156         vm_page_deactivate(fs->m);
 157         vm_page_unlock(fs->m);
 158         fs->m = NULL;
 159 }
 160
 161 static inline void
 162 unlock_map(struct faultstate *fs)
 163 {
 164
 165         if (fs->lookup_still_valid) {
 166                 vm_map_lookup_done(fs->map, fs->entry);
 167                 fs->lookup_still_valid = false;
 168         }
 169 }
 170
 171 static void
 172 unlock_vp(struct faultstate *fs)
 173 {
 174
 175         if (fs->vp != NULL) {
 176                 vput(fs->vp);
 177                 fs->vp = NULL;
 178         }
 179 }
 180
 181 static void
 182 unlock_and_deallocate(struct faultstate *fs)
 183 {
 184
 185         vm_object_pip_wakeup(fs->object);
 186         VM_OBJECT_WUNLOCK(fs->object);
 187         if (fs->object != fs->first_object) {
 188                 VM_OBJECT_WLOCK(fs->first_object);
 189                 vm_page_free(fs->first_m);
 190                 vm_object_pip_wakeup(fs->first_object);
 191                 VM_OBJECT_WUNLOCK(fs->first_object);
 192                 fs->first_m = NULL;
 193         }
 194         vm_object_deallocate(fs->first_object);
 195         unlock_map(fs);
 196         unlock_vp(fs);
 197 }
 198
 199 static void
 200 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot,
 201     vm_prot_t fault_type, int fault_flags, bool set_wd)
 202 {
 203         bool need_dirty;
 204
 205         if (((prot & VM_PROT_WRITE) == 0 &&
 206             (fault_flags & VM_FAULT_DIRTY) == 0) ||
 207             (m->oflags & VPO_UNMANAGED) != 0)
 208                 return;
 209
 210         VM_OBJECT_ASSERT_LOCKED(m->object);
 211
 212         need_dirty = ((fault_type & VM_PROT_WRITE) != 0 &&
 213             (fault_flags & VM_FAULT_WIRE) == 0) ||
 214             (fault_flags & VM_FAULT_DIRTY) != 0;
 215
 216         if (set_wd)
 217                 vm_object_set_writeable_dirty(m->object);
 218         else
 219                 /*
 220                  * If two callers of vm_fault_dirty() with set_wd ==
 221                  * FALSE, one for the map entry with MAP_ENTRY_NOSYNC
 222                  * flag set, other with flag clear, race, it is
 223                  * possible for the no-NOSYNC thread to see m->dirty
 224                  * != 0 and not clear VPO_NOSYNC.  Take vm_page lock
 225                  * around manipulation of VPO_NOSYNC and
 226                  * vm_page_dirty() call, to avoid the race and keep
 227                  * m->oflags consistent.
 228                  */
 229                 vm_page_lock(m);
 230
 231         /*
 232          * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
 233          * if the page is already dirty to prevent data written with
 234          * the expectation of being synced from not being synced.
 235          * Likewise if this entry does not request NOSYNC then make
 236          * sure the page isn't marked NOSYNC.  Applications sharing
 237          * data should use the same flags to avoid ping ponging.
 238          */
 239         if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) {
 240                 if (m->dirty == 0) {
 241                         m->oflags |= VPO_NOSYNC;
 242                 }
 243         } else {
 244                 m->oflags &= ~VPO_NOSYNC;
 245         }
 246
 247         /*
 248          * If the fault is a write, we know that this page is being
 249          * written NOW so dirty it explicitly to save on
 250          * pmap_is_modified() calls later.
 251          *
 252          * Also, since the page is now dirty, we can possibly tell
 253          * the pager to release any swap backing the page.  Calling
 254          * the pager requires a write lock on the object.
 255          */
 256         if (need_dirty)
 257                 vm_page_dirty(m);
 258         if (!set_wd)
 259                 vm_page_unlock(m);
 260         else if (need_dirty)
 261                 vm_pager_page_unswapped(m);
 262 }
 263
 264 /*
 265  * Unlocks fs.first_object and fs.map on success.
 266  */
 267 static int
 268 vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot,
 269     int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold)
 270 {
 271         vm_page_t m, m_map;
 272 #if (defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \
 273     __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv)) && \
 274     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__) || defined(__riscv)) && \
 290     VM_NRESERVLEVEL > 0
 291         if ((m->flags & PG_FICTITIOUS) == 0 &&
 292             (m_super = vm_reserv_to_superpage(m)) != NULL &&
 293             rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start &&
 294             roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end &&
 295             (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) &
 296             (pagesizes[m_super->psind] - 1)) && !wired &&
 297             pmap_ps_enabled(fs->map->pmap)) {
 298                 flags = PS_ALL_VALID;
 299                 if ((prot & VM_PROT_WRITE) != 0) {
 300                         /*
 301                          * Create a superpage mapping allowing write access
 302                          * only if none of the constituent pages are busy and
 303                          * all of them are already dirty (except possibly for
 304                          * the page that was faulted on).
 305                          */
 306                         flags |= PS_NONE_BUSY;
 307                         if ((fs->first_object->flags & OBJ_UNMANAGED) == 0)
 308                                 flags |= PS_ALL_DIRTY;
 309                 }
 310                 if (vm_page_ps_test(m_super, flags, m)) {
 311                         m_map = m_super;
 312                         psind = m_super->psind;
 313                         vaddr = rounddown2(vaddr, pagesizes[psind]);
 314                         /* Preset the modified bit for dirty superpages. */
 315                         if ((flags & PS_ALL_DIRTY) != 0)
 316                                 fault_type |= VM_PROT_WRITE;
 317                 }
 318         }
 319 #endif
 320         rv = pmap_enter(fs->map->pmap, vaddr, m_map, prot, fault_type |
 321             PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), psind);
 322         if (rv != KERN_SUCCESS)
 323                 return (rv);
 324         if (m_hold != NULL) {
 325                 *m_hold = m;
 326                 vm_page_wire(m);
 327         }
 328         vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false);
 329         if (psind == 0 && !wired)
 330                 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true);
 331         VM_OBJECT_RUNLOCK(fs->first_object);
 332         vm_map_lookup_done(fs->map, fs->entry);
 333         curthread->td_ru.ru_minflt++;
 334         return (KERN_SUCCESS);
 335 }
 336
 337 static void
 338 vm_fault_restore_map_lock(struct faultstate *fs)
 339 {
 340
 341         VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
 342         MPASS(fs->first_object->paging_in_progress > 0);
 343
 344         if (!vm_map_trylock_read(fs->map)) {
 345                 VM_OBJECT_WUNLOCK(fs->first_object);
 346                 vm_map_lock_read(fs->map);
 347                 VM_OBJECT_WLOCK(fs->first_object);
 348         }
 349         fs->lookup_still_valid = true;
 350 }
 351
 352 static void
 353 vm_fault_populate_check_page(vm_page_t m)
 354 {
 355
 356         /*
 357          * Check each page to ensure that the pager is obeying the
 358          * interface: the page must be installed in the object, fully
 359          * valid, and exclusively busied.
 360          */
 361         MPASS(m != NULL);
 362         MPASS(m->valid == VM_PAGE_BITS_ALL);
 363         MPASS(vm_page_xbusied(m));
 364 }
 365
 366 static void
 367 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first,
 368     vm_pindex_t last)
 369 {
 370         vm_page_t m;
 371         vm_pindex_t pidx;
 372
 373         VM_OBJECT_ASSERT_WLOCKED(object);
 374         MPASS(first <= last);
 375         for (pidx = first, m = vm_page_lookup(object, pidx);
 376             pidx <= last; pidx++, m = vm_page_next(m)) {
 377                 vm_fault_populate_check_page(m);
 378                 vm_page_lock(m);
 379                 vm_page_deactivate(m);
 380                 vm_page_unlock(m);
 381                 vm_page_xunbusy(m);
 382         }
 383 }
 384
 385 static int
 386 vm_fault_populate(struct faultstate *fs, vm_prot_t prot, int fault_type,
 387     int fault_flags, boolean_t wired, vm_page_t *m_hold)
 388 {
 389         struct mtx *m_mtx;
 390         vm_offset_t vaddr;
 391         vm_page_t m;
 392         vm_pindex_t map_first, map_last, pager_first, pager_last, pidx;
 393         int i, npages, psind, rv;
 394
 395         MPASS(fs->object == fs->first_object);
 396         VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
 397         MPASS(fs->first_object->paging_in_progress > 0);
 398         MPASS(fs->first_object->backing_object == NULL);
 399         MPASS(fs->lookup_still_valid);
 400
 401         pager_first = OFF_TO_IDX(fs->entry->offset);
 402         pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1;
 403         unlock_map(fs);
 404         unlock_vp(fs);
 405
 406         /*
 407          * Call the pager (driver) populate() method.
 408          *
 409          * There is no guarantee that the method will be called again
 410          * if the current fault is for read, and a future fault is
 411          * for write.  Report the entry's maximum allowed protection
 412          * to the driver.
 413          */
 414         rv = vm_pager_populate(fs->first_object, fs->first_pindex,
 415             fault_type, fs->entry->max_protection, &pager_first, &pager_last);
 416
 417         VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
 418         if (rv == VM_PAGER_BAD) {
 419                 /*
 420                  * VM_PAGER_BAD is the backdoor for a pager to request
 421                  * normal fault handling.
 422                  */
 423                 vm_fault_restore_map_lock(fs);
 424                 if (fs->map->timestamp != fs->map_generation)
 425                         return (KERN_RESOURCE_SHORTAGE); /* RetryFault */
 426                 return (KERN_NOT_RECEIVER);
 427         }
 428         if (rv != VM_PAGER_OK)
 429                 return (KERN_FAILURE); /* AKA SIGSEGV */
 430
 431         /* Ensure that the driver is obeying the interface. */
 432         MPASS(pager_first <= pager_last);
 433         MPASS(fs->first_pindex <= pager_last);
 434         MPASS(fs->first_pindex >= pager_first);
 435         MPASS(pager_last < fs->first_object->size);
 436
 437         vm_fault_restore_map_lock(fs);
 438         if (fs->map->timestamp != fs->map_generation) {
 439                 vm_fault_populate_cleanup(fs->first_object, pager_first,
 440                     pager_last);
 441                 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */
 442         }
 443
 444         /*
 445          * The map is unchanged after our last unlock.  Process the fault.
 446          *
 447          * The range [pager_first, pager_last] that is given to the
 448          * pager is only a hint.  The pager may populate any range
 449          * within the object that includes the requested page index.
 450          * In case the pager expanded the range, clip it to fit into
 451          * the map entry.
 452          */
 453         map_first = OFF_TO_IDX(fs->entry->offset);
 454         if (map_first > pager_first) {
 455                 vm_fault_populate_cleanup(fs->first_object, pager_first,
 456                     map_first - 1);
 457                 pager_first = map_first;
 458         }
 459         map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1;
 460         if (map_last < pager_last) {
 461                 vm_fault_populate_cleanup(fs->first_object, map_last + 1,
 462                     pager_last);
 463                 pager_last = map_last;
 464         }
 465         for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx);
 466             pidx <= pager_last;
 467             pidx += npages, m = vm_page_next(&m[npages - 1])) {
 468                 vaddr = fs->entry->start + IDX_TO_OFF(pidx) - fs->entry->offset;
 469 #if defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \
 470     __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv)
 471                 psind = m->psind;
 472                 if (psind > 0 && ((vaddr & (pagesizes[psind] - 1)) != 0 ||
 473                     pidx + OFF_TO_IDX(pagesizes[psind]) - 1 > pager_last ||
 474                     !pmap_ps_enabled(fs->map->pmap) || wired))
 475                         psind = 0;
 476 #else
 477                 psind = 0;
 478 #endif
 479                 npages = atop(pagesizes[psind]);
 480                 for (i = 0; i < npages; i++) {
 481                         vm_fault_populate_check_page(&m[i]);
 482                         vm_fault_dirty(fs->entry, &m[i], prot, fault_type,
 483                             fault_flags, true);
 484                 }
 485                 VM_OBJECT_WUNLOCK(fs->first_object);
 486                 rv = pmap_enter(fs->map->pmap, vaddr, m, prot, fault_type |
 487                     (wired ? PMAP_ENTER_WIRED : 0), psind);
 488 #if defined(__amd64__)
 489                 if (psind > 0 && rv == KERN_FAILURE) {
 490                         for (i = 0; i < npages; i++) {
 491                                 rv = pmap_enter(fs->map->pmap, vaddr + ptoa(i),
 492                                     &m[i], prot, fault_type |
 493                                     (wired ? PMAP_ENTER_WIRED : 0), 0);
 494                                 MPASS(rv == KERN_SUCCESS);
 495                         }
 496                 }
 497 #else
 498                 MPASS(rv == KERN_SUCCESS);
 499 #endif
 500                 VM_OBJECT_WLOCK(fs->first_object);
 501                 m_mtx = NULL;
 502                 for (i = 0; i < npages; i++) {
 503                         if ((fault_flags & VM_FAULT_WIRE) != 0) {
 504                                 vm_page_wire(&m[i]);
 505                         } else {
 506                                 vm_page_change_lock(&m[i], &m_mtx);
 507                                 vm_page_activate(&m[i]);
 508                         }
 509                         if (m_hold != NULL && m[i].pindex == fs->first_pindex) {
 510                                 *m_hold = &m[i];
 511                                 vm_page_wire(&m[i]);
 512                         }
 513                         vm_page_xunbusy(&m[i]);
 514                 }
 515                 if (m_mtx != NULL)
 516                         mtx_unlock(m_mtx);
 517         }
 518         curthread->td_ru.ru_majflt++;
 519         return (KERN_SUCCESS);
 520 }
 521
 522 /*
 523  *      vm_fault:
 524  *
 525  *      Handle a page fault occurring at the given address,
 526  *      requiring the given permissions, in the map specified.
 527  *      If successful, the page is inserted into the
 528  *      associated physical map.
 529  *
 530  *      NOTE: the given address should be truncated to the
 531  *      proper page address.
 532  *
 533  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 534  *      a standard error specifying why the fault is fatal is returned.
 535  *
 536  *      The map in question must be referenced, and remains so.
 537  *      Caller may hold no locks.
 538  */
 539 int
 540 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 541     int fault_flags)
 542 {
 543         struct thread *td;
 544         int result;
 545
 546         td = curthread;
 547         if ((td->td_pflags & TDP_NOFAULTING) != 0)
 548                 return (KERN_PROTECTION_FAILURE);
 549 #ifdef KTRACE
 550         if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
 551                 ktrfault(vaddr, fault_type);
 552 #endif
 553         result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
 554             NULL);
 555 #ifdef KTRACE
 556         if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
 557                 ktrfaultend(result);
 558 #endif
 559         return (result);
 560 }
 561
 562 int
 563 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 564     int fault_flags, vm_page_t *m_hold)
 565 {
 566         struct faultstate fs;
 567         struct vnode *vp;
 568         struct domainset *dset;
 569         vm_object_t next_object, retry_object;
 570         vm_offset_t e_end, e_start;
 571         vm_pindex_t retry_pindex;
 572         vm_prot_t prot, retry_prot;
 573         int ahead, alloc_req, behind, cluster_offset, error, era, faultcount;
 574         int locked, nera, oom, result, rv;
 575         u_char behavior;
 576         boolean_t wired;        /* Passed by reference. */
 577         bool dead, hardfault, is_first_object_locked;
 578
 579         VM_CNT_INC(v_vm_faults);
 580         fs.vp = NULL;
 581         faultcount = 0;
 582         nera = -1;
 583         hardfault = false;
 584
 585 RetryFault:
 586         oom = 0;
 587 RetryFault_oom:
 588
 589         /*
 590          * Find the backing store object and offset into it to begin the
 591          * search.
 592          */
 593         fs.map = map;
 594         result = vm_map_lookup(&fs.map, vaddr, fault_type |
 595             VM_PROT_FAULT_LOOKUP, &fs.entry, &fs.first_object,
 596             &fs.first_pindex, &prot, &wired);
 597         if (result != KERN_SUCCESS) {
 598                 unlock_vp(&fs);
 599                 return (result);
 600         }
 601
 602         fs.map_generation = fs.map->timestamp;
 603
 604         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 605                 panic("%s: fault on nofault entry, addr: %#lx",
 606                     __func__, (u_long)vaddr);
 607         }
 608
 609         if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
 610             fs.entry->wiring_thread != curthread) {
 611                 vm_map_unlock_read(fs.map);
 612                 vm_map_lock(fs.map);
 613                 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
 614                     (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
 615                         unlock_vp(&fs);
 616                         fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
 617                         vm_map_unlock_and_wait(fs.map, 0);
 618                 } else
 619                         vm_map_unlock(fs.map);
 620                 goto RetryFault;
 621         }
 622
 623         MPASS((fs.entry->eflags & MAP_ENTRY_GUARD) == 0);
 624
 625         if (wired)
 626                 fault_type = prot | (fault_type & VM_PROT_COPY);
 627         else
 628                 KASSERT((fault_flags & VM_FAULT_WIRE) == 0,
 629                     ("!wired && VM_FAULT_WIRE"));
 630
 631         /*
 632          * Try to avoid lock contention on the top-level object through
 633          * special-case handling of some types of page faults, specifically,
 634          * those that are both (1) mapping an existing page from the top-
 635          * level object and (2) not having to mark that object as containing
 636          * dirty pages.  Under these conditions, a read lock on the top-level
 637          * object suffices, allowing multiple page faults of a similar type to
 638          * run in parallel on the same top-level object.
 639          */
 640         if (fs.vp == NULL /* avoid locked vnode leak */ &&
 641             (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 &&
 642             /* avoid calling vm_object_set_writeable_dirty() */
 643             ((prot & VM_PROT_WRITE) == 0 ||
 644             (fs.first_object->type != OBJT_VNODE &&
 645             (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
 646             (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
 647                 VM_OBJECT_RLOCK(fs.first_object);
 648                 if ((prot & VM_PROT_WRITE) == 0 ||
 649                     (fs.first_object->type != OBJT_VNODE &&
 650                     (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
 651                     (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0) {
 652                         rv = vm_fault_soft_fast(&fs, vaddr, prot, fault_type,
 653                             fault_flags, wired, m_hold);
 654                         if (rv == KERN_SUCCESS)
 655                                 return (rv);
 656                 }
 657                 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
 658                         VM_OBJECT_RUNLOCK(fs.first_object);
 659                         VM_OBJECT_WLOCK(fs.first_object);
 660                 }
 661         } else {
 662                 VM_OBJECT_WLOCK(fs.first_object);
 663         }
 664
 665         /*
 666          * Make a reference to this object to prevent its disposal while we
 667          * are messing with it.  Once we have the reference, the map is free
 668          * to be diddled.  Since objects reference their shadows (and copies),
 669          * they will stay around as well.
 670          *
 671          * Bump the paging-in-progress count to prevent size changes (e.g.
 672          * truncation operations) during I/O.
 673          */
 674         vm_object_reference_locked(fs.first_object);
 675         vm_object_pip_add(fs.first_object, 1);
 676
 677         fs.lookup_still_valid = true;
 678
 679         fs.first_m = NULL;
 680
 681         /*
 682          * Search for the page at object/offset.
 683          */
 684         fs.object = fs.first_object;
 685         fs.pindex = fs.first_pindex;
 686         while (TRUE) {
 687                 /*
 688                  * If the object is marked for imminent termination,
 689                  * we retry here, since the collapse pass has raced
 690                  * with us.  Otherwise, if we see terminally dead
 691                  * object, return fail.
 692                  */
 693                 if ((fs.object->flags & OBJ_DEAD) != 0) {
 694                         dead = fs.object->type == OBJT_DEAD;
 695                         unlock_and_deallocate(&fs);
 696                         if (dead)
 697                                 return (KERN_PROTECTION_FAILURE);
 698                         pause("vmf_de", 1);
 699                         goto RetryFault;
 700                 }
 701
 702                 /*
 703                  * See if page is resident
 704                  */
 705                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 706                 if (fs.m != NULL) {
 707                         /*
 708                          * Wait/Retry if the page is busy.  We have to do this
 709                          * if the page is either exclusive or shared busy
 710                          * because the vm_pager may be using read busy for
 711                          * pageouts (and even pageins if it is the vnode
 712                          * pager), and we could end up trying to pagein and
 713                          * pageout the same page simultaneously.
 714                          *
 715                          * We can theoretically allow the busy case on a read
 716                          * fault if the page is marked valid, but since such
 717                          * pages are typically already pmap'd, putting that
 718                          * special case in might be more effort then it is
 719                          * worth.  We cannot under any circumstances mess
 720                          * around with a shared busied page except, perhaps,
 721                          * to pmap it.
 722                          */
 723                         if (vm_page_busied(fs.m)) {
 724                                 /*
 725                                  * Reference the page before unlocking and
 726                                  * sleeping so that the page daemon is less
 727                                  * likely to reclaim it.
 728                                  */
 729                                 vm_page_aflag_set(fs.m, PGA_REFERENCED);
 730                                 if (fs.object != fs.first_object) {
 731                                         if (!VM_OBJECT_TRYWLOCK(
 732                                             fs.first_object)) {
 733                                                 VM_OBJECT_WUNLOCK(fs.object);
 734                                                 VM_OBJECT_WLOCK(fs.first_object);
 735                                                 VM_OBJECT_WLOCK(fs.object);
 736                                         }
 737                                         vm_page_free(fs.first_m);
 738                                         vm_object_pip_wakeup(fs.first_object);
 739                                         VM_OBJECT_WUNLOCK(fs.first_object);
 740                                         fs.first_m = NULL;
 741                                 }
 742                                 unlock_map(&fs);
 743                                 if (fs.m == vm_page_lookup(fs.object,
 744                                     fs.pindex)) {
 745                                         vm_page_sleep_if_busy(fs.m, "vmpfw");
 746                                 }
 747                                 vm_object_pip_wakeup(fs.object);
 748                                 VM_OBJECT_WUNLOCK(fs.object);
 749                                 VM_CNT_INC(v_intrans);
 750                                 vm_object_deallocate(fs.first_object);
 751                                 goto RetryFault;
 752                         }
 753
 754                         /*
 755                          * Mark page busy for other processes, and the
 756                          * pagedaemon.  If it still isn't completely valid
 757                          * (readable), jump to readrest, else break-out ( we
 758                          * found the page ).
 759                          */
 760                         vm_page_xbusy(fs.m);
 761                         if (fs.m->valid != VM_PAGE_BITS_ALL)
 762                                 goto readrest;
 763                         break; /* break to PAGE HAS BEEN FOUND */
 764                 }
 765                 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m));
 766
 767                 /*
 768                  * Page is not resident.  If the pager might contain the page
 769                  * or this is the beginning of the search, allocate a new
 770                  * page.  (Default objects are zero-fill, so there is no real
 771                  * pager for them.)
 772                  */
 773                 if (fs.object->type != OBJT_DEFAULT ||
 774                     fs.object == fs.first_object) {
 775                         if (fs.pindex >= fs.object->size) {
 776                                 unlock_and_deallocate(&fs);
 777                                 return (KERN_PROTECTION_FAILURE);
 778                         }
 779
 780                         if (fs.object == fs.first_object &&
 781                             (fs.first_object->flags & OBJ_POPULATE) != 0 &&
 782                             fs.first_object->shadow_count == 0) {
 783                                 rv = vm_fault_populate(&fs, prot, fault_type,
 784                                     fault_flags, wired, m_hold);
 785                                 switch (rv) {
 786                                 case KERN_SUCCESS:
 787                                 case KERN_FAILURE:
 788                                         unlock_and_deallocate(&fs);
 789                                         return (rv);
 790                                 case KERN_RESOURCE_SHORTAGE:
 791                                         unlock_and_deallocate(&fs);
 792                                         goto RetryFault;
 793                                 case KERN_NOT_RECEIVER:
 794                                         /*
 795                                          * Pager's populate() method
 796                                          * returned VM_PAGER_BAD.
 797                                          */
 798                                         break;
 799                                 default:
 800                                         panic("inconsistent return codes");
 801                                 }
 802                         }
 803
 804                         /*
 805                          * Allocate a new page for this object/offset pair.
 806                          *
 807                          * Unlocked read of the p_flag is harmless. At
 808                          * worst, the P_KILLED might be not observed
 809                          * there, and allocation can fail, causing
 810                          * restart and new reading of the p_flag.
 811                          */
 812                         dset = fs.object->domain.dr_policy;
 813                         if (dset == NULL)
 814                                 dset = curthread->td_domain.dr_policy;
 815                         if (!vm_page_count_severe_set(&dset->ds_mask) ||
 816                             P_KILLED(curproc)) {
 817 #if VM_NRESERVLEVEL > 0
 818                                 vm_object_color(fs.object, atop(vaddr) -
 819                                     fs.pindex);
 820 #endif
 821                                 alloc_req = P_KILLED(curproc) ?
 822                                     VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
 823                                 if (fs.object->type != OBJT_VNODE &&
 824                                     fs.object->backing_object == NULL)
 825                                         alloc_req |= VM_ALLOC_ZERO;
 826                                 fs.m = vm_page_alloc(fs.object, fs.pindex,
 827                                     alloc_req);
 828                         }
 829                         if (fs.m == NULL) {
 830                                 unlock_and_deallocate(&fs);
 831                                 if (vm_pfault_oom_attempts < 0 ||
 832                                     oom < vm_pfault_oom_attempts) {
 833                                         oom++;
 834                                         vm_waitpfault(dset,
 835                                             vm_pfault_oom_wait * hz);
 836                                         goto RetryFault_oom;
 837                                 }
 838                                 if (bootverbose)
 839                                         printf(
 840         "proc %d (%s) failed to alloc page on fault, starting OOM\n",
 841                                             curproc->p_pid, curproc->p_comm);
 842                                 vm_pageout_oom(VM_OOM_MEM_PF);
 843                                 goto RetryFault;
 844                         }
 845                 }
 846
 847 readrest:
 848                 /*
 849                  * At this point, we have either allocated a new page or found
 850                  * an existing page that is only partially valid.
 851                  *
 852                  * We hold a reference on the current object and the page is
 853                  * exclusive busied.
 854                  */
 855
 856                 /*
 857                  * If the pager for the current object might have the page,
 858                  * then determine the number of additional pages to read and
 859                  * potentially reprioritize previously read pages for earlier
 860                  * reclamation.  These operations should only be performed
 861                  * once per page fault.  Even if the current pager doesn't
 862                  * have the page, the number of additional pages to read will
 863                  * apply to subsequent objects in the shadow chain.
 864                  */
 865                 if (fs.object->type != OBJT_DEFAULT && nera == -1 &&
 866                     !P_KILLED(curproc)) {
 867                         KASSERT(fs.lookup_still_valid, ("map unlocked"));
 868                         era = fs.entry->read_ahead;
 869                         behavior = vm_map_entry_behavior(fs.entry);
 870                         if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
 871                                 nera = 0;
 872                         } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
 873                                 nera = VM_FAULT_READ_AHEAD_MAX;
 874                                 if (vaddr == fs.entry->next_read)
 875                                         vm_fault_dontneed(&fs, vaddr, nera);
 876                         } else if (vaddr == fs.entry->next_read) {
 877                                 /*
 878                                  * This is a sequential fault.  Arithmetically
 879                                  * increase the requested number of pages in
 880                                  * the read-ahead window.  The requested
 881                                  * number of pages is "# of sequential faults
 882                                  * x (read ahead min + 1) + read ahead min"
 883                                  */
 884                                 nera = VM_FAULT_READ_AHEAD_MIN;
 885                                 if (era > 0) {
 886                                         nera += era + 1;
 887                                         if (nera > VM_FAULT_READ_AHEAD_MAX)
 888                                                 nera = VM_FAULT_READ_AHEAD_MAX;
 889                                 }
 890                                 if (era == VM_FAULT_READ_AHEAD_MAX)
 891                                         vm_fault_dontneed(&fs, vaddr, nera);
 892                         } else {
 893                                 /*
 894                                  * This is a non-sequential fault.
 895                                  */
 896                                 nera = 0;
 897                         }
 898                         if (era != nera) {
 899                                 /*
 900                                  * A read lock on the map suffices to update
 901                                  * the read ahead count safely.
 902                                  */
 903                                 fs.entry->read_ahead = nera;
 904                         }
 905
 906                         /*
 907                          * Prepare for unlocking the map.  Save the map
 908                          * entry's start and end addresses, which are used to
 909                          * optimize the size of the pager operation below.
 910                          * Even if the map entry's addresses change after
 911                          * unlocking the map, using the saved addresses is
 912                          * safe.
 913                          */
 914                         e_start = fs.entry->start;
 915                         e_end = fs.entry->end;
 916                 }
 917
 918                 /*
 919                  * Call the pager to retrieve the page if there is a chance
 920                  * that the pager has it, and potentially retrieve additional
 921                  * pages at the same time.
 922                  */
 923                 if (fs.object->type != OBJT_DEFAULT) {
 924                         /*
 925                          * Release the map lock before locking the vnode or
 926                          * sleeping in the pager.  (If the current object has
 927                          * a shadow, then an earlier iteration of this loop
 928                          * may have already unlocked the map.)
 929                          */
 930                         unlock_map(&fs);
 931
 932                         if (fs.object->type == OBJT_VNODE &&
 933                             (vp = fs.object->handle) != fs.vp) {
 934                                 /*
 935                                  * Perform an unlock in case the desired vnode
 936                                  * changed while the map was unlocked during a
 937                                  * retry.
 938                                  */
 939                                 unlock_vp(&fs);
 940
 941                                 locked = VOP_ISLOCKED(vp);
 942                                 if (locked != LK_EXCLUSIVE)
 943                                         locked = LK_SHARED;
 944
 945                                 /*
 946                                  * We must not sleep acquiring the vnode lock
 947                                  * while we have the page exclusive busied or
 948                                  * the object's paging-in-progress count
 949                                  * incremented.  Otherwise, we could deadlock.
 950                                  */
 951                                 error = vget(vp, locked | LK_CANRECURSE |
 952                                     LK_NOWAIT, curthread);
 953                                 if (error != 0) {
 954                                         vhold(vp);
 955                                         release_page(&fs);
 956                                         unlock_and_deallocate(&fs);
 957                                         error = vget(vp, locked | LK_RETRY |
 958                                             LK_CANRECURSE, curthread);
 959                                         vdrop(vp);
 960                                         fs.vp = vp;
 961                                         KASSERT(error == 0,
 962                                             ("vm_fault: vget failed"));
 963                                         goto RetryFault;
 964                                 }
 965                                 fs.vp = vp;
 966                         }
 967                         KASSERT(fs.vp == NULL || !fs.map->system_map,
 968                             ("vm_fault: vnode-backed object mapped by system map"));
 969
 970                         /*
 971                          * Page in the requested page and hint the pager,
 972                          * that it may bring up surrounding pages.
 973                          */
 974                         if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM ||
 975                             P_KILLED(curproc)) {
 976                                 behind = 0;
 977                                 ahead = 0;
 978                         } else {
 979                                 /* Is this a sequential fault? */
 980                                 if (nera > 0) {
 981                                         behind = 0;
 982                                         ahead = nera;
 983                                 } else {
 984                                         /*
 985                                          * Request a cluster of pages that is
 986                                          * aligned to a VM_FAULT_READ_DEFAULT
 987                                          * page offset boundary within the
 988                                          * object.  Alignment to a page offset
 989                                          * boundary is more likely to coincide
 990                                          * with the underlying file system
 991                                          * block than alignment to a virtual
 992                                          * address boundary.
 993                                          */
 994                                         cluster_offset = fs.pindex %
 995                                             VM_FAULT_READ_DEFAULT;
 996                                         behind = ulmin(cluster_offset,
 997                                             atop(vaddr - e_start));
 998                                         ahead = VM_FAULT_READ_DEFAULT - 1 -
 999                                             cluster_offset;
1000                                 }
1001                                 ahead = ulmin(ahead, atop(e_end - vaddr) - 1);
1002                         }
1003                         rv = vm_pager_get_pages(fs.object, &fs.m, 1,
1004                             &behind, &ahead);
1005                         if (rv == VM_PAGER_OK) {
1006                                 faultcount = behind + 1 + ahead;
1007                                 hardfault = true;
1008                                 break; /* break to PAGE HAS BEEN FOUND */
1009                         }
1010                         if (rv == VM_PAGER_ERROR)
1011                                 printf("vm_fault: pager read error, pid %d (%s)\n",
1012                                     curproc->p_pid, curproc->p_comm);
1013
1014                         /*
1015                          * If an I/O error occurred or the requested page was
1016                          * outside the range of the pager, clean up and return
1017                          * an error.
1018                          */
1019                         if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) {
1020                                 if (!vm_page_wired(fs.m))
1021                                         vm_page_free(fs.m);
1022                                 else
1023                                         vm_page_xunbusy(fs.m);
1024                                 fs.m = NULL;
1025                                 unlock_and_deallocate(&fs);
1026                                 return (rv == VM_PAGER_ERROR ? KERN_FAILURE :
1027                                     KERN_PROTECTION_FAILURE);
1028                         }
1029
1030                         /*
1031                          * The requested page does not exist at this object/
1032                          * offset.  Remove the invalid page from the object,
1033                          * waking up anyone waiting for it, and continue on to
1034                          * the next object.  However, if this is the top-level
1035                          * object, we must leave the busy page in place to
1036                          * prevent another process from rushing past us, and
1037                          * inserting the page in that object at the same time
1038                          * that we are.
1039                          */
1040                         if (fs.object != fs.first_object) {
1041                                 if (!vm_page_wired(fs.m))
1042                                         vm_page_free(fs.m);
1043                                 else
1044                                         vm_page_xunbusy(fs.m);
1045                                 fs.m = NULL;
1046                         }
1047                 }
1048
1049                 /*
1050                  * We get here if the object has default pager (or unwiring)
1051                  * or the pager doesn't have the page.
1052                  */
1053                 if (fs.object == fs.first_object)
1054                         fs.first_m = fs.m;
1055
1056                 /*
1057                  * Move on to the next object.  Lock the next object before
1058                  * unlocking the current one.
1059                  */
1060                 next_object = fs.object->backing_object;
1061                 if (next_object == NULL) {
1062                         /*
1063                          * If there's no object left, fill the page in the top
1064                          * object with zeros.
1065                          */
1066                         if (fs.object != fs.first_object) {
1067                                 vm_object_pip_wakeup(fs.object);
1068                                 VM_OBJECT_WUNLOCK(fs.object);
1069
1070                                 fs.object = fs.first_object;
1071                                 fs.pindex = fs.first_pindex;
1072                                 fs.m = fs.first_m;
1073                                 VM_OBJECT_WLOCK(fs.object);
1074                         }
1075                         fs.first_m = NULL;
1076
1077                         /*
1078                          * Zero the page if necessary and mark it valid.
1079                          */
1080                         if ((fs.m->flags & PG_ZERO) == 0) {
1081                                 pmap_zero_page(fs.m);
1082                         } else {
1083                                 VM_CNT_INC(v_ozfod);
1084                         }
1085                         VM_CNT_INC(v_zfod);
1086                         fs.m->valid = VM_PAGE_BITS_ALL;
1087                         /* Don't try to prefault neighboring pages. */
1088                         faultcount = 1;
1089                         break;  /* break to PAGE HAS BEEN FOUND */
1090                 } else {
1091                         KASSERT(fs.object != next_object,
1092                             ("object loop %p", next_object));
1093                         VM_OBJECT_WLOCK(next_object);
1094                         vm_object_pip_add(next_object, 1);
1095                         if (fs.object != fs.first_object)
1096                                 vm_object_pip_wakeup(fs.object);
1097                         fs.pindex +=
1098                             OFF_TO_IDX(fs.object->backing_object_offset);
1099                         VM_OBJECT_WUNLOCK(fs.object);
1100                         fs.object = next_object;
1101                 }
1102         }
1103
1104         vm_page_assert_xbusied(fs.m);
1105
1106         /*
1107          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
1108          * is held.]
1109          */
1110
1111         /*
1112          * If the page is being written, but isn't already owned by the
1113          * top-level object, we have to copy it into a new page owned by the
1114          * top-level object.
1115          */
1116         if (fs.object != fs.first_object) {
1117                 /*
1118                  * We only really need to copy if we want to write it.
1119                  */
1120                 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1121                         /*
1122                          * This allows pages to be virtually copied from a
1123                          * backing_object into the first_object, where the
1124                          * backing object has no other refs to it, and cannot
1125                          * gain any more refs.  Instead of a bcopy, we just
1126                          * move the page from the backing object to the
1127                          * first object.  Note that we must mark the page
1128                          * dirty in the first object so that it will go out
1129                          * to swap when needed.
1130                          */
1131                         is_first_object_locked = false;
1132                         if (
1133                                 /*
1134                                  * Only one shadow object
1135                                  */
1136                                 (fs.object->shadow_count == 1) &&
1137                                 /*
1138                                  * No COW refs, except us
1139                                  */
1140                                 (fs.object->ref_count == 1) &&
1141                                 /*
1142                                  * No one else can look this object up
1143                                  */
1144                                 (fs.object->handle == NULL) &&
1145                                 /*
1146                                  * No other ways to look the object up
1147                                  */
1148                                 ((fs.object->type == OBJT_DEFAULT) ||
1149                                  (fs.object->type == OBJT_SWAP)) &&
1150                             (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
1151                                 /*
1152                                  * We don't chase down the shadow chain
1153                                  */
1154                             fs.object == fs.first_object->backing_object) {
1155
1156                                 (void)vm_page_remove(fs.m);
1157                                 vm_page_replace_checked(fs.m, fs.first_object,
1158                                     fs.first_pindex, fs.first_m);
1159                                 vm_page_free(fs.first_m);
1160                                 vm_page_dirty(fs.m);
1161 #if VM_NRESERVLEVEL > 0
1162                                 /*
1163                                  * Rename the reservation.
1164                                  */
1165                                 vm_reserv_rename(fs.m, fs.first_object,
1166                                     fs.object, OFF_TO_IDX(
1167                                     fs.first_object->backing_object_offset));
1168 #endif
1169                                 /*
1170                                  * Removing the page from the backing object
1171                                  * unbusied it.
1172                                  */
1173                                 vm_page_xbusy(fs.m);
1174                                 fs.first_m = fs.m;
1175                                 fs.m = NULL;
1176                                 VM_CNT_INC(v_cow_optim);
1177                         } else {
1178                                 /*
1179                                  * Oh, well, lets copy it.
1180                                  */
1181                                 pmap_copy_page(fs.m, fs.first_m);
1182                                 fs.first_m->valid = VM_PAGE_BITS_ALL;
1183                                 if (wired && (fault_flags &
1184                                     VM_FAULT_WIRE) == 0) {
1185                                         vm_page_wire(fs.first_m);
1186                                         vm_page_unwire(fs.m, PQ_INACTIVE);
1187                                 }
1188                                 /*
1189                                  * We no longer need the old page or object.
1190                                  */
1191                                 release_page(&fs);
1192                         }
1193                         /*
1194                          * fs.object != fs.first_object due to above
1195                          * conditional
1196                          */
1197                         vm_object_pip_wakeup(fs.object);
1198                         VM_OBJECT_WUNLOCK(fs.object);
1199
1200                         /*
1201                          * We only try to prefault read-only mappings to the
1202                          * neighboring pages when this copy-on-write fault is
1203                          * a hard fault.  In other cases, trying to prefault
1204                          * is typically wasted effort.
1205                          */
1206                         if (faultcount == 0)
1207                                 faultcount = 1;
1208
1209                         /*
1210                          * Only use the new page below...
1211                          */
1212                         fs.object = fs.first_object;
1213                         fs.pindex = fs.first_pindex;
1214                         fs.m = fs.first_m;
1215                         if (!is_first_object_locked)
1216                                 VM_OBJECT_WLOCK(fs.object);
1217                         VM_CNT_INC(v_cow_faults);
1218                         curthread->td_cow++;
1219                 } else {
1220                         prot &= ~VM_PROT_WRITE;
1221                 }
1222         }
1223
1224         /*
1225          * We must verify that the maps have not changed since our last
1226          * lookup.
1227          */
1228         if (!fs.lookup_still_valid) {
1229                 if (!vm_map_trylock_read(fs.map)) {
1230                         release_page(&fs);
1231                         unlock_and_deallocate(&fs);
1232                         goto RetryFault;
1233                 }
1234                 fs.lookup_still_valid = true;
1235                 if (fs.map->timestamp != fs.map_generation) {
1236                         result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
1237                             &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
1238
1239                         /*
1240                          * If we don't need the page any longer, put it on the inactive
1241                          * list (the easiest thing to do here).  If no one needs it,
1242                          * pageout will grab it eventually.
1243                          */
1244                         if (result != KERN_SUCCESS) {
1245                                 release_page(&fs);
1246                                 unlock_and_deallocate(&fs);
1247
1248                                 /*
1249                                  * If retry of map lookup would have blocked then
1250                                  * retry fault from start.
1251                                  */
1252                                 if (result == KERN_FAILURE)
1253                                         goto RetryFault;
1254                                 return (result);
1255                         }
1256                         if ((retry_object != fs.first_object) ||
1257                             (retry_pindex != fs.first_pindex)) {
1258                                 release_page(&fs);
1259                                 unlock_and_deallocate(&fs);
1260                                 goto RetryFault;
1261                         }
1262
1263                         /*
1264                          * Check whether the protection has changed or the object has
1265                          * been copied while we left the map unlocked. Changing from
1266                          * read to write permission is OK - we leave the page
1267                          * write-protected, and catch the write fault. Changing from
1268                          * write to read permission means that we can't mark the page
1269                          * write-enabled after all.
1270                          */
1271                         prot &= retry_prot;
1272                         fault_type &= retry_prot;
1273                         if (prot == 0) {
1274                                 release_page(&fs);
1275                                 unlock_and_deallocate(&fs);
1276                                 goto RetryFault;
1277                         }
1278
1279                         /* Reassert because wired may have changed. */
1280                         KASSERT(wired || (fault_flags & VM_FAULT_WIRE) == 0,
1281                             ("!wired && VM_FAULT_WIRE"));
1282                 }
1283         }
1284
1285         /*
1286          * If the page was filled by a pager, save the virtual address that
1287          * should be faulted on next under a sequential access pattern to the
1288          * map entry.  A read lock on the map suffices to update this address
1289          * safely.
1290          */
1291         if (hardfault)
1292                 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE;
1293
1294         vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true);
1295         vm_page_assert_xbusied(fs.m);
1296
1297         /*
1298          * Page must be completely valid or it is not fit to
1299          * map into user space.  vm_pager_get_pages() ensures this.
1300          */
1301         KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
1302             ("vm_fault: page %p partially invalid", fs.m));
1303         VM_OBJECT_WUNLOCK(fs.object);
1304
1305         /*
1306          * Put this page into the physical map.  We had to do the unlock above
1307          * because pmap_enter() may sleep.  We don't put the page
1308          * back on the active queue until later so that the pageout daemon
1309          * won't find it (yet).
1310          */
1311         pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
1312             fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
1313         if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 &&
1314             wired == 0)
1315                 vm_fault_prefault(&fs, vaddr,
1316                     faultcount > 0 ? behind : PFBAK,
1317                     faultcount > 0 ? ahead : PFFOR, false);
1318         VM_OBJECT_WLOCK(fs.object);
1319
1320         /*
1321          * If the page is not wired down, then put it where the pageout daemon
1322          * can find it.
1323          */
1324         if ((fault_flags & VM_FAULT_WIRE) != 0) {
1325                 vm_page_wire(fs.m);
1326         } else {
1327                 vm_page_lock(fs.m);
1328                 vm_page_activate(fs.m);
1329                 vm_page_unlock(fs.m);
1330         }
1331         if (m_hold != NULL) {
1332                 *m_hold = fs.m;
1333                 vm_page_wire(fs.m);
1334         }
1335         vm_page_xunbusy(fs.m);
1336
1337         /*
1338          * Unlock everything, and return
1339          */
1340         unlock_and_deallocate(&fs);
1341         if (hardfault) {
1342                 VM_CNT_INC(v_io_faults);
1343                 curthread->td_ru.ru_majflt++;
1344 #ifdef RACCT
1345                 if (racct_enable && fs.object->type == OBJT_VNODE) {
1346                         PROC_LOCK(curproc);
1347                         if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1348                                 racct_add_force(curproc, RACCT_WRITEBPS,
1349                                     PAGE_SIZE + behind * PAGE_SIZE);
1350                                 racct_add_force(curproc, RACCT_WRITEIOPS, 1);
1351                         } else {
1352                                 racct_add_force(curproc, RACCT_READBPS,
1353                                     PAGE_SIZE + ahead * PAGE_SIZE);
1354                                 racct_add_force(curproc, RACCT_READIOPS, 1);
1355                         }
1356                         PROC_UNLOCK(curproc);
1357                 }
1358 #endif
1359         } else
1360                 curthread->td_ru.ru_minflt++;
1361
1362         return (KERN_SUCCESS);
1363 }
1364
1365 /*
1366  * Speed up the reclamation of pages that precede the faulting pindex within
1367  * the first object of the shadow chain.  Essentially, perform the equivalent
1368  * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes
1369  * the faulting pindex by the cluster size when the pages read by vm_fault()
1370  * cross a cluster-size boundary.  The cluster size is the greater of the
1371  * smallest superpage size and VM_FAULT_DONTNEED_MIN.
1372  *
1373  * When "fs->first_object" is a shadow object, the pages in the backing object
1374  * that precede the faulting pindex are deactivated by vm_fault().  So, this
1375  * function must only be concerned with pages in the first object.
1376  */
1377 static void
1378 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
1379 {
1380         vm_map_entry_t entry;
1381         vm_object_t first_object, object;
1382         vm_offset_t end, start;
1383         vm_page_t m, m_next;
1384         vm_pindex_t pend, pstart;
1385         vm_size_t size;
1386
1387         object = fs->object;
1388         VM_OBJECT_ASSERT_WLOCKED(object);
1389         first_object = fs->first_object;
1390         if (first_object != object) {
1391                 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1392                         VM_OBJECT_WUNLOCK(object);
1393                         VM_OBJECT_WLOCK(first_object);
1394                         VM_OBJECT_WLOCK(object);
1395                 }
1396         }
1397         /* Neither fictitious nor unmanaged pages can be reclaimed. */
1398         if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1399                 size = VM_FAULT_DONTNEED_MIN;
1400                 if (MAXPAGESIZES > 1 && size < pagesizes[1])
1401                         size = pagesizes[1];
1402                 end = rounddown2(vaddr, size);
1403                 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) &&
1404                     (entry = fs->entry)->start < end) {
1405                         if (end - entry->start < size)
1406                                 start = entry->start;
1407                         else
1408                                 start = end - size;
1409                         pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED);
1410                         pstart = OFF_TO_IDX(entry->offset) + atop(start -
1411                             entry->start);
1412                         m_next = vm_page_find_least(first_object, pstart);
1413                         pend = OFF_TO_IDX(entry->offset) + atop(end -
1414                             entry->start);
1415                         while ((m = m_next) != NULL && m->pindex < pend) {
1416                                 m_next = TAILQ_NEXT(m, listq);
1417                                 if (m->valid != VM_PAGE_BITS_ALL ||
1418                                     vm_page_busied(m))
1419                                         continue;
1420
1421                                 /*
1422                                  * Don't clear PGA_REFERENCED, since it would
1423                                  * likely represent a reference by a different
1424                                  * process.
1425                                  *
1426                                  * Typically, at this point, prefetched pages
1427                                  * are still in the inactive queue.  Only
1428                                  * pages that triggered page faults are in the
1429                                  * active queue.
1430                                  */
1431                                 vm_page_lock(m);
1432                                 if (!vm_page_inactive(m))
1433                                         vm_page_deactivate(m);
1434                                 vm_page_unlock(m);
1435                         }
1436                 }
1437         }
1438         if (first_object != object)
1439                 VM_OBJECT_WUNLOCK(first_object);
1440 }
1441
1442 /*
1443  * vm_fault_prefault provides a quick way of clustering
1444  * pagefaults into a processes address space.  It is a "cousin"
1445  * of vm_map_pmap_enter, except it runs at page fault time instead
1446  * of mmap time.
1447  */
1448 static void
1449 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1450     int backward, int forward, bool obj_locked)
1451 {
1452         pmap_t pmap;
1453         vm_map_entry_t entry;
1454         vm_object_t backing_object, lobject;
1455         vm_offset_t addr, starta;
1456         vm_pindex_t pindex;
1457         vm_page_t m;
1458         int i;
1459
1460         pmap = fs->map->pmap;
1461         if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1462                 return;
1463
1464         entry = fs->entry;
1465
1466         if (addra < backward * PAGE_SIZE) {
1467                 starta = entry->start;
1468         } else {
1469                 starta = addra - backward * PAGE_SIZE;
1470                 if (starta < entry->start)
1471                         starta = entry->start;
1472         }
1473
1474         /*
1475          * Generate the sequence of virtual addresses that are candidates for
1476          * prefaulting in an outward spiral from the faulting virtual address,
1477          * "addra".  Specifically, the sequence is "addra - PAGE_SIZE", "addra
1478          * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1479          * If the candidate address doesn't have a backing physical page, then
1480          * the loop immediately terminates.
1481          */
1482         for (i = 0; i < 2 * imax(backward, forward); i++) {
1483                 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1484                     PAGE_SIZE);
1485                 if (addr > addra + forward * PAGE_SIZE)
1486                         addr = 0;
1487
1488                 if (addr < starta || addr >= entry->end)
1489                         continue;
1490
1491                 if (!pmap_is_prefaultable(pmap, addr))
1492                         continue;
1493
1494                 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1495                 lobject = entry->object.vm_object;
1496                 if (!obj_locked)
1497                         VM_OBJECT_RLOCK(lobject);
1498                 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1499                     lobject->type == OBJT_DEFAULT &&
1500                     (backing_object = lobject->backing_object) != NULL) {
1501                         KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1502                             0, ("vm_fault_prefault: unaligned object offset"));
1503                         pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1504                         VM_OBJECT_RLOCK(backing_object);
1505                         if (!obj_locked || lobject != entry->object.vm_object)
1506                                 VM_OBJECT_RUNLOCK(lobject);
1507                         lobject = backing_object;
1508                 }
1509                 if (m == NULL) {
1510                         if (!obj_locked || lobject != entry->object.vm_object)
1511                                 VM_OBJECT_RUNLOCK(lobject);
1512                         break;
1513                 }
1514                 if (m->valid == VM_PAGE_BITS_ALL &&
1515                     (m->flags & PG_FICTITIOUS) == 0)
1516                         pmap_enter_quick(pmap, addr, m, entry->protection);
1517                 if (!obj_locked || lobject != entry->object.vm_object)
1518                         VM_OBJECT_RUNLOCK(lobject);
1519         }
1520 }
1521
1522 /*
1523  * Hold each of the physical pages that are mapped by the specified range of
1524  * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1525  * and allow the specified types of access, "prot".  If all of the implied
1526  * pages are successfully held, then the number of held pages is returned
1527  * together with pointers to those pages in the array "ma".  However, if any
1528  * of the pages cannot be held, -1 is returned.
1529  */
1530 int
1531 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1532     vm_prot_t prot, vm_page_t *ma, int max_count)
1533 {
1534         vm_offset_t end, va;
1535         vm_page_t *mp;
1536         int count;
1537         boolean_t pmap_failed;
1538
1539         if (len == 0)
1540                 return (0);
1541         end = round_page(addr + len);
1542         addr = trunc_page(addr);
1543
1544         /*
1545          * Check for illegal addresses.
1546          */
1547         if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1548                 return (-1);
1549
1550         if (atop(end - addr) > max_count)
1551                 panic("vm_fault_quick_hold_pages: count > max_count");
1552         count = atop(end - addr);
1553
1554         /*
1555          * Most likely, the physical pages are resident in the pmap, so it is
1556          * faster to try pmap_extract_and_hold() first.
1557          */
1558         pmap_failed = FALSE;
1559         for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1560                 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1561                 if (*mp == NULL)
1562                         pmap_failed = TRUE;
1563                 else if ((prot & VM_PROT_WRITE) != 0 &&
1564                     (*mp)->dirty != VM_PAGE_BITS_ALL) {
1565                         /*
1566                          * Explicitly dirty the physical page.  Otherwise, the
1567                          * caller's changes may go unnoticed because they are
1568                          * performed through an unmanaged mapping or by a DMA
1569                          * operation.
1570                          *
1571                          * The object lock is not held here.
1572                          * See vm_page_clear_dirty_mask().
1573                          */
1574                         vm_page_dirty(*mp);
1575                 }
1576         }
1577         if (pmap_failed) {
1578                 /*
1579                  * One or more pages could not be held by the pmap.  Either no
1580                  * page was mapped at the specified virtual address or that
1581                  * mapping had insufficient permissions.  Attempt to fault in
1582                  * and hold these pages.
1583                  *
1584                  * If vm_fault_disable_pagefaults() was called,
1585                  * i.e., TDP_NOFAULTING is set, we must not sleep nor
1586                  * acquire MD VM locks, which means we must not call
1587                  * vm_fault_hold().  Some (out of tree) callers mark
1588                  * too wide a code area with vm_fault_disable_pagefaults()
1589                  * already, use the VM_PROT_QUICK_NOFAULT flag to request
1590                  * the proper behaviour explicitly.
1591                  */
1592                 if ((prot & VM_PROT_QUICK_NOFAULT) != 0 &&
1593                     (curthread->td_pflags & TDP_NOFAULTING) != 0)
1594                         goto error;
1595                 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1596                         if (*mp == NULL && vm_fault_hold(map, va, prot,
1597                             VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1598                                 goto error;
1599         }
1600         return (count);
1601 error:
1602         for (mp = ma; mp < ma + count; mp++)
1603                 if (*mp != NULL)
1604                         vm_page_unwire(*mp, PQ_INACTIVE);
1605         return (-1);
1606 }
1607
1608 /*
1609  *      Routine:
1610  *              vm_fault_copy_entry
1611  *      Function:
1612  *              Create new shadow object backing dst_entry with private copy of
1613  *              all underlying pages. When src_entry is equal to dst_entry,
1614  *              function implements COW for wired-down map entry. Otherwise,
1615  *              it forks wired entry into dst_map.
1616  *
1617  *      In/out conditions:
1618  *              The source and destination maps must be locked for write.
1619  *              The source map entry must be wired down (or be a sharing map
1620  *              entry corresponding to a main map entry that is wired down).
1621  */
1622 void
1623 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1624     vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1625     vm_ooffset_t *fork_charge)
1626 {
1627         vm_object_t backing_object, dst_object, object, src_object;
1628         vm_pindex_t dst_pindex, pindex, src_pindex;
1629         vm_prot_t access, prot;
1630         vm_offset_t vaddr;
1631         vm_page_t dst_m;
1632         vm_page_t src_m;
1633         boolean_t upgrade;
1634
1635 #ifdef  lint
1636         src_map++;
1637 #endif  /* lint */
1638
1639         upgrade = src_entry == dst_entry;
1640         access = prot = dst_entry->protection;
1641
1642         src_object = src_entry->object.vm_object;
1643         src_pindex = OFF_TO_IDX(src_entry->offset);
1644
1645         if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1646                 dst_object = src_object;
1647                 vm_object_reference(dst_object);
1648         } else {
1649                 /*
1650                  * Create the top-level object for the destination entry. (Doesn't
1651                  * actually shadow anything - we copy the pages directly.)
1652                  */
1653                 dst_object = vm_object_allocate(OBJT_DEFAULT,
1654                     atop(dst_entry->end - dst_entry->start));
1655 #if VM_NRESERVLEVEL > 0
1656                 dst_object->flags |= OBJ_COLORED;
1657                 dst_object->pg_color = atop(dst_entry->start);
1658 #endif
1659                 dst_object->domain = src_object->domain;
1660                 dst_object->charge = dst_entry->end - dst_entry->start;
1661         }
1662
1663         VM_OBJECT_WLOCK(dst_object);
1664         KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1665             ("vm_fault_copy_entry: vm_object not NULL"));
1666         if (src_object != dst_object) {
1667                 dst_entry->object.vm_object = dst_object;
1668                 dst_entry->offset = 0;
1669                 dst_entry->eflags &= ~MAP_ENTRY_VN_EXEC;
1670         }
1671         if (fork_charge != NULL) {
1672                 KASSERT(dst_entry->cred == NULL,
1673                     ("vm_fault_copy_entry: leaked swp charge"));
1674                 dst_object->cred = curthread->td_ucred;
1675                 crhold(dst_object->cred);
1676                 *fork_charge += dst_object->charge;
1677         } else if ((dst_object->type == OBJT_DEFAULT ||
1678             dst_object->type == OBJT_SWAP) &&
1679             dst_object->cred == NULL) {
1680                 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1681                     dst_entry));
1682                 dst_object->cred = dst_entry->cred;
1683                 dst_entry->cred = NULL;
1684         }
1685
1686         /*
1687          * If not an upgrade, then enter the mappings in the pmap as
1688          * read and/or execute accesses.  Otherwise, enter them as
1689          * write accesses.
1690          *
1691          * A writeable large page mapping is only created if all of
1692          * the constituent small page mappings are modified. Marking
1693          * PTEs as modified on inception allows promotion to happen
1694          * without taking potentially large number of soft faults.
1695          */
1696         if (!upgrade)
1697                 access &= ~VM_PROT_WRITE;
1698
1699         /*
1700          * Loop through all of the virtual pages within the entry's
1701          * range, copying each page from the source object to the
1702          * destination object.  Since the source is wired, those pages
1703          * must exist.  In contrast, the destination is pageable.
1704          * Since the destination object doesn't share any backing storage
1705          * with the source object, all of its pages must be dirtied,
1706          * regardless of whether they can be written.
1707          */
1708         for (vaddr = dst_entry->start, dst_pindex = 0;
1709             vaddr < dst_entry->end;
1710             vaddr += PAGE_SIZE, dst_pindex++) {
1711 again:
1712                 /*
1713                  * Find the page in the source object, and copy it in.
1714                  * Because the source is wired down, the page will be
1715                  * in memory.
1716                  */
1717                 if (src_object != dst_object)
1718                         VM_OBJECT_RLOCK(src_object);
1719                 object = src_object;
1720                 pindex = src_pindex + dst_pindex;
1721                 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1722                     (backing_object = object->backing_object) != NULL) {
1723                         /*
1724                          * Unless the source mapping is read-only or
1725                          * it is presently being upgraded from
1726                          * read-only, the first object in the shadow
1727                          * chain should provide all of the pages.  In
1728                          * other words, this loop body should never be
1729                          * executed when the source mapping is already
1730                          * read/write.
1731                          */
1732                         KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1733                             upgrade,
1734                             ("vm_fault_copy_entry: main object missing page"));
1735
1736                         VM_OBJECT_RLOCK(backing_object);
1737                         pindex += OFF_TO_IDX(object->backing_object_offset);
1738                         if (object != dst_object)
1739                                 VM_OBJECT_RUNLOCK(object);
1740                         object = backing_object;
1741                 }
1742                 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1743
1744                 if (object != dst_object) {
1745                         /*
1746                          * Allocate a page in the destination object.
1747                          */
1748                         dst_m = vm_page_alloc(dst_object, (src_object ==
1749                             dst_object ? src_pindex : 0) + dst_pindex,
1750                             VM_ALLOC_NORMAL);
1751                         if (dst_m == NULL) {
1752                                 VM_OBJECT_WUNLOCK(dst_object);
1753                                 VM_OBJECT_RUNLOCK(object);
1754                                 vm_wait(dst_object);
1755                                 VM_OBJECT_WLOCK(dst_object);
1756                                 goto again;
1757                         }
1758                         pmap_copy_page(src_m, dst_m);
1759                         VM_OBJECT_RUNLOCK(object);
1760                         dst_m->dirty = dst_m->valid = src_m->valid;
1761                 } else {
1762                         dst_m = src_m;
1763                         if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1764                                 goto again;
1765                         if (dst_m->pindex >= dst_object->size)
1766                                 /*
1767                                  * We are upgrading.  Index can occur
1768                                  * out of bounds if the object type is
1769                                  * vnode and the file was truncated.
1770                                  */
1771                                 break;
1772                         vm_page_xbusy(dst_m);
1773                 }
1774                 VM_OBJECT_WUNLOCK(dst_object);
1775
1776                 /*
1777                  * Enter it in the pmap. If a wired, copy-on-write
1778                  * mapping is being replaced by a write-enabled
1779                  * mapping, then wire that new mapping.
1780                  *
1781                  * The page can be invalid if the user called
1782                  * msync(MS_INVALIDATE) or truncated the backing vnode
1783                  * or shared memory object.  In this case, do not
1784                  * insert it into pmap, but still do the copy so that
1785                  * all copies of the wired map entry have similar
1786                  * backing pages.
1787                  */
1788                 if (dst_m->valid == VM_PAGE_BITS_ALL) {
1789                         pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1790                             access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1791                 }
1792
1793                 /*
1794                  * Mark it no longer busy, and put it on the active list.
1795                  */
1796                 VM_OBJECT_WLOCK(dst_object);
1797
1798                 if (upgrade) {
1799                         if (src_m != dst_m) {
1800                                 vm_page_unwire(src_m, PQ_INACTIVE);
1801                                 vm_page_wire(dst_m);
1802                         } else {
1803                                 KASSERT(vm_page_wired(dst_m),
1804                                     ("dst_m %p is not wired", dst_m));
1805                         }
1806                 } else {
1807                         vm_page_lock(dst_m);
1808                         vm_page_activate(dst_m);
1809                         vm_page_unlock(dst_m);
1810                 }
1811                 vm_page_xunbusy(dst_m);
1812         }
1813         VM_OBJECT_WUNLOCK(dst_object);
1814         if (upgrade) {
1815                 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1816                 vm_object_deallocate(src_object);
1817         }
1818 }
1819
1820 /*
1821  * Block entry into the machine-independent layer's page fault handler by
1822  * the calling thread.  Subsequent calls to vm_fault() by that thread will
1823  * return KERN_PROTECTION_FAILURE.  Enable machine-dependent handling of
1824  * spurious page faults.
1825  */
1826 int
1827 vm_fault_disable_pagefaults(void)
1828 {
1829
1830         return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1831 }
1832
1833 void
1834 vm_fault_enable_pagefaults(int save)
1835 {
1836
1837         curthread_pflags_restore(save);
1838 }