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 int vm_pfault_oom_attempts = 3;
 138 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_attempts, CTLFLAG_RWTUN,
 139     &vm_pfault_oom_attempts, 0,
 140     "Number of page allocation attempts in page fault handler before it "
 141     "triggers OOM handling");
 142
 143 static int vm_pfault_oom_wait = 10;
 144 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_wait, CTLFLAG_RWTUN,
 145     &vm_pfault_oom_wait, 0,
 146     "Number of seconds to wait for free pages before retrying "
 147     "the page fault handler");
 148
 149 static inline void
 150 release_page(struct faultstate *fs)
 151 {
 152
 153         vm_page_xunbusy(fs->m);
 154         vm_page_lock(fs->m);
 155         vm_page_deactivate(fs->m);
 156         vm_page_unlock(fs->m);
 157         fs->m = NULL;
 158 }
 159
 160 static inline void
 161 unlock_map(struct faultstate *fs)
 162 {
 163
 164         if (fs->lookup_still_valid) {
 165                 vm_map_lookup_done(fs->map, fs->entry);
 166                 fs->lookup_still_valid = false;
 167         }
 168 }
 169
 170 static void
 171 unlock_vp(struct faultstate *fs)
 172 {
 173
 174         if (fs->vp != NULL) {
 175                 vput(fs->vp);
 176                 fs->vp = NULL;
 177         }
 178 }
 179
 180 static void
 181 unlock_and_deallocate(struct faultstate *fs)
 182 {
 183
 184         vm_object_pip_wakeup(fs->object);
 185         VM_OBJECT_WUNLOCK(fs->object);
 186         if (fs->object != fs->first_object) {
 187                 VM_OBJECT_WLOCK(fs->first_object);
 188                 vm_page_lock(fs->first_m);
 189                 vm_page_free(fs->first_m);
 190                 vm_page_unlock(fs->first_m);
 191                 vm_object_pip_wakeup(fs->first_object);
 192                 VM_OBJECT_WUNLOCK(fs->first_object);
 193                 fs->first_m = NULL;
 194         }
 195         vm_object_deallocate(fs->first_object);
 196         unlock_map(fs);
 197         unlock_vp(fs);
 198 }
 199
 200 static void
 201 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot,
 202     vm_prot_t fault_type, int fault_flags, bool set_wd)
 203 {
 204         bool need_dirty;
 205
 206         if (((prot & VM_PROT_WRITE) == 0 &&
 207             (fault_flags & VM_FAULT_DIRTY) == 0) ||
 208             (m->oflags & VPO_UNMANAGED) != 0)
 209                 return;
 210
 211         VM_OBJECT_ASSERT_LOCKED(m->object);
 212
 213         need_dirty = ((fault_type & VM_PROT_WRITE) != 0 &&
 214             (fault_flags & VM_FAULT_WIRE) == 0) ||
 215             (fault_flags & VM_FAULT_DIRTY) != 0;
 216
 217         if (set_wd)
 218                 vm_object_set_writeable_dirty(m->object);
 219         else
 220                 /*
 221                  * If two callers of vm_fault_dirty() with set_wd ==
 222                  * FALSE, one for the map entry with MAP_ENTRY_NOSYNC
 223                  * flag set, other with flag clear, race, it is
 224                  * possible for the no-NOSYNC thread to see m->dirty
 225                  * != 0 and not clear VPO_NOSYNC.  Take vm_page lock
 226                  * around manipulation of VPO_NOSYNC and
 227                  * vm_page_dirty() call, to avoid the race and keep
 228                  * m->oflags consistent.
 229                  */
 230                 vm_page_lock(m);
 231
 232         /*
 233          * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
 234          * if the page is already dirty to prevent data written with
 235          * the expectation of being synced from not being synced.
 236          * Likewise if this entry does not request NOSYNC then make
 237          * sure the page isn't marked NOSYNC.  Applications sharing
 238          * data should use the same flags to avoid ping ponging.
 239          */
 240         if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) {
 241                 if (m->dirty == 0) {
 242                         m->oflags |= VPO_NOSYNC;
 243                 }
 244         } else {
 245                 m->oflags &= ~VPO_NOSYNC;
 246         }
 247
 248         /*
 249          * If the fault is a write, we know that this page is being
 250          * written NOW so dirty it explicitly to save on
 251          * pmap_is_modified() calls later.
 252          *
 253          * Also, since the page is now dirty, we can possibly tell
 254          * the pager to release any swap backing the page.  Calling
 255          * the pager requires a write lock on the object.
 256          */
 257         if (need_dirty)
 258                 vm_page_dirty(m);
 259         if (!set_wd)
 260                 vm_page_unlock(m);
 261         else if (need_dirty)
 262                 vm_pager_page_unswapped(m);
 263 }
 264
 265 static void
 266 vm_fault_fill_hold(vm_page_t *m_hold, vm_page_t m)
 267 {
 268
 269         if (m_hold != NULL) {
 270                 *m_hold = m;
 271                 vm_page_lock(m);
 272                 vm_page_hold(m);
 273                 vm_page_unlock(m);
 274         }
 275 }
 276
 277 /*
 278  * Unlocks fs.first_object and fs.map on success.
 279  */
 280 static int
 281 vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot,
 282     int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold)
 283 {
 284         vm_page_t m, m_map;
 285 #if (defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \
 286     __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv)) && \
 287     VM_NRESERVLEVEL > 0
 288         vm_page_t m_super;
 289         int flags;
 290 #endif
 291         int psind, rv;
 292
 293         MPASS(fs->vp == NULL);
 294         m = vm_page_lookup(fs->first_object, fs->first_pindex);
 295         /* A busy page can be mapped for read|execute access. */
 296         if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
 297             vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
 298                 return (KERN_FAILURE);
 299         m_map = m;
 300         psind = 0;
 301 #if (defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \
 302     __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv)) && \
 303     VM_NRESERVLEVEL > 0
 304         if ((m->flags & PG_FICTITIOUS) == 0 &&
 305             (m_super = vm_reserv_to_superpage(m)) != NULL &&
 306             rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start &&
 307             roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end &&
 308             (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) &
 309             (pagesizes[m_super->psind] - 1)) &&
 310             pmap_ps_enabled(fs->map->pmap)) {
 311                 flags = PS_ALL_VALID;
 312                 if ((prot & VM_PROT_WRITE) != 0) {
 313                         /*
 314                          * Create a superpage mapping allowing write access
 315                          * only if none of the constituent pages are busy and
 316                          * all of them are already dirty (except possibly for
 317                          * the page that was faulted on).
 318                          */
 319                         flags |= PS_NONE_BUSY;
 320                         if ((fs->first_object->flags & OBJ_UNMANAGED) == 0)
 321                                 flags |= PS_ALL_DIRTY;
 322                 }
 323                 if (vm_page_ps_test(m_super, flags, m)) {
 324                         m_map = m_super;
 325                         psind = m_super->psind;
 326                         vaddr = rounddown2(vaddr, pagesizes[psind]);
 327                         /* Preset the modified bit for dirty superpages. */
 328                         if ((flags & PS_ALL_DIRTY) != 0)
 329                                 fault_type |= VM_PROT_WRITE;
 330                 }
 331         }
 332 #endif
 333         rv = pmap_enter(fs->map->pmap, vaddr, m_map, prot, fault_type |
 334             PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), psind);
 335         if (rv != KERN_SUCCESS)
 336                 return (rv);
 337         vm_fault_fill_hold(m_hold, m);
 338         vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false);
 339         if (psind == 0 && !wired)
 340                 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true);
 341         VM_OBJECT_RUNLOCK(fs->first_object);
 342         vm_map_lookup_done(fs->map, fs->entry);
 343         curthread->td_ru.ru_minflt++;
 344         return (KERN_SUCCESS);
 345 }
 346
 347 static void
 348 vm_fault_restore_map_lock(struct faultstate *fs)
 349 {
 350
 351         VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
 352         MPASS(fs->first_object->paging_in_progress > 0);
 353
 354         if (!vm_map_trylock_read(fs->map)) {
 355                 VM_OBJECT_WUNLOCK(fs->first_object);
 356                 vm_map_lock_read(fs->map);
 357                 VM_OBJECT_WLOCK(fs->first_object);
 358         }
 359         fs->lookup_still_valid = true;
 360 }
 361
 362 static void
 363 vm_fault_populate_check_page(vm_page_t m)
 364 {
 365
 366         /*
 367          * Check each page to ensure that the pager is obeying the
 368          * interface: the page must be installed in the object, fully
 369          * valid, and exclusively busied.
 370          */
 371         MPASS(m != NULL);
 372         MPASS(m->valid == VM_PAGE_BITS_ALL);
 373         MPASS(vm_page_xbusied(m));
 374 }
 375
 376 static void
 377 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first,
 378     vm_pindex_t last)
 379 {
 380         vm_page_t m;
 381         vm_pindex_t pidx;
 382
 383         VM_OBJECT_ASSERT_WLOCKED(object);
 384         MPASS(first <= last);
 385         for (pidx = first, m = vm_page_lookup(object, pidx);
 386             pidx <= last; pidx++, m = vm_page_next(m)) {
 387                 vm_fault_populate_check_page(m);
 388                 vm_page_lock(m);
 389                 vm_page_deactivate(m);
 390                 vm_page_unlock(m);
 391                 vm_page_xunbusy(m);
 392         }
 393 }
 394
 395 static int
 396 vm_fault_populate(struct faultstate *fs, vm_prot_t prot, int fault_type,
 397     int fault_flags, boolean_t wired, vm_page_t *m_hold)
 398 {
 399         struct mtx *m_mtx;
 400         vm_offset_t vaddr;
 401         vm_page_t m;
 402         vm_pindex_t map_first, map_last, pager_first, pager_last, pidx;
 403         int i, npages, psind, rv;
 404
 405         MPASS(fs->object == fs->first_object);
 406         VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
 407         MPASS(fs->first_object->paging_in_progress > 0);
 408         MPASS(fs->first_object->backing_object == NULL);
 409         MPASS(fs->lookup_still_valid);
 410
 411         pager_first = OFF_TO_IDX(fs->entry->offset);
 412         pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1;
 413         unlock_map(fs);
 414         unlock_vp(fs);
 415
 416         /*
 417          * Call the pager (driver) populate() method.
 418          *
 419          * There is no guarantee that the method will be called again
 420          * if the current fault is for read, and a future fault is
 421          * for write.  Report the entry's maximum allowed protection
 422          * to the driver.
 423          */
 424         rv = vm_pager_populate(fs->first_object, fs->first_pindex,
 425             fault_type, fs->entry->max_protection, &pager_first, &pager_last);
 426
 427         VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
 428         if (rv == VM_PAGER_BAD) {
 429                 /*
 430                  * VM_PAGER_BAD is the backdoor for a pager to request
 431                  * normal fault handling.
 432                  */
 433                 vm_fault_restore_map_lock(fs);
 434                 if (fs->map->timestamp != fs->map_generation)
 435                         return (KERN_RESOURCE_SHORTAGE); /* RetryFault */
 436                 return (KERN_NOT_RECEIVER);
 437         }
 438         if (rv != VM_PAGER_OK)
 439                 return (KERN_FAILURE); /* AKA SIGSEGV */
 440
 441         /* Ensure that the driver is obeying the interface. */
 442         MPASS(pager_first <= pager_last);
 443         MPASS(fs->first_pindex <= pager_last);
 444         MPASS(fs->first_pindex >= pager_first);
 445         MPASS(pager_last < fs->first_object->size);
 446
 447         vm_fault_restore_map_lock(fs);
 448         if (fs->map->timestamp != fs->map_generation) {
 449                 vm_fault_populate_cleanup(fs->first_object, pager_first,
 450                     pager_last);
 451                 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */
 452         }
 453
 454         /*
 455          * The map is unchanged after our last unlock.  Process the fault.
 456          *
 457          * The range [pager_first, pager_last] that is given to the
 458          * pager is only a hint.  The pager may populate any range
 459          * within the object that includes the requested page index.
 460          * In case the pager expanded the range, clip it to fit into
 461          * the map entry.
 462          */
 463         map_first = OFF_TO_IDX(fs->entry->offset);
 464         if (map_first > pager_first) {
 465                 vm_fault_populate_cleanup(fs->first_object, pager_first,
 466                     map_first - 1);
 467                 pager_first = map_first;
 468         }
 469         map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1;
 470         if (map_last < pager_last) {
 471                 vm_fault_populate_cleanup(fs->first_object, map_last + 1,
 472                     pager_last);
 473                 pager_last = map_last;
 474         }
 475         for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx);
 476             pidx <= pager_last;
 477             pidx += npages, m = vm_page_next(&m[npages - 1])) {
 478                 vaddr = fs->entry->start + IDX_TO_OFF(pidx) - fs->entry->offset;
 479 #if defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \
 480     __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv)
 481                 psind = m->psind;
 482                 if (psind > 0 && ((vaddr & (pagesizes[psind] - 1)) != 0 ||
 483                     pidx + OFF_TO_IDX(pagesizes[psind]) - 1 > pager_last ||
 484                     !pmap_ps_enabled(fs->map->pmap)))
 485                         psind = 0;
 486 #else
 487                 psind = 0;
 488 #endif
 489                 npages = atop(pagesizes[psind]);
 490                 for (i = 0; i < npages; i++) {
 491                         vm_fault_populate_check_page(&m[i]);
 492                         vm_fault_dirty(fs->entry, &m[i], prot, fault_type,
 493                             fault_flags, true);
 494                 }
 495                 VM_OBJECT_WUNLOCK(fs->first_object);
 496                 rv = pmap_enter(fs->map->pmap, vaddr, m, prot, fault_type |
 497                     (wired ? PMAP_ENTER_WIRED : 0), psind);
 498 #if defined(__amd64__)
 499                 if (psind > 0 && rv == KERN_FAILURE) {
 500                         for (i = 0; i < npages; i++) {
 501                                 rv = pmap_enter(fs->map->pmap, vaddr + ptoa(i),
 502                                     &m[i], prot, fault_type |
 503                                     (wired ? PMAP_ENTER_WIRED : 0), 0);
 504                                 MPASS(rv == KERN_SUCCESS);
 505                         }
 506                 }
 507 #else
 508                 MPASS(rv == KERN_SUCCESS);
 509 #endif
 510                 VM_OBJECT_WLOCK(fs->first_object);
 511                 m_mtx = NULL;
 512                 for (i = 0; i < npages; i++) {
 513                         vm_page_change_lock(&m[i], &m_mtx);
 514                         if ((fault_flags & VM_FAULT_WIRE) != 0)
 515                                 vm_page_wire(&m[i]);
 516                         else
 517                                 vm_page_activate(&m[i]);
 518                         if (m_hold != NULL && m[i].pindex == fs->first_pindex) {
 519                                 *m_hold = &m[i];
 520                                 vm_page_hold(&m[i]);
 521                         }
 522                         vm_page_xunbusy_maybelocked(&m[i]);
 523                 }
 524                 if (m_mtx != NULL)
 525                         mtx_unlock(m_mtx);
 526         }
 527         curthread->td_ru.ru_majflt++;
 528         return (KERN_SUCCESS);
 529 }
 530
 531 /*
 532  *      vm_fault:
 533  *
 534  *      Handle a page fault occurring at the given address,
 535  *      requiring the given permissions, in the map specified.
 536  *      If successful, the page is inserted into the
 537  *      associated physical map.
 538  *
 539  *      NOTE: the given address should be truncated to the
 540  *      proper page address.
 541  *
 542  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 543  *      a standard error specifying why the fault is fatal is returned.
 544  *
 545  *      The map in question must be referenced, and remains so.
 546  *      Caller may hold no locks.
 547  */
 548 int
 549 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 550     int fault_flags)
 551 {
 552         struct thread *td;
 553         int result;
 554
 555         td = curthread;
 556         if ((td->td_pflags & TDP_NOFAULTING) != 0)
 557                 return (KERN_PROTECTION_FAILURE);
 558 #ifdef KTRACE
 559         if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
 560                 ktrfault(vaddr, fault_type);
 561 #endif
 562         result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
 563             NULL);
 564 #ifdef KTRACE
 565         if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
 566                 ktrfaultend(result);
 567 #endif
 568         return (result);
 569 }
 570
 571 int
 572 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 573     int fault_flags, vm_page_t *m_hold)
 574 {
 575         struct faultstate fs;
 576         struct vnode *vp;
 577         struct domainset *dset;
 578         vm_object_t next_object, retry_object;
 579         vm_offset_t e_end, e_start;
 580         vm_pindex_t retry_pindex;
 581         vm_prot_t prot, retry_prot;
 582         int ahead, alloc_req, behind, cluster_offset, error, era, faultcount;
 583         int locked, nera, oom, result, rv;
 584         u_char behavior;
 585         boolean_t wired;        /* Passed by reference. */
 586         bool dead, hardfault, is_first_object_locked;
 587
 588         VM_CNT_INC(v_vm_faults);
 589         fs.vp = NULL;
 590         faultcount = 0;
 591         nera = -1;
 592         hardfault = false;
 593
 594 RetryFault:
 595         oom = 0;
 596 RetryFault_oom:
 597
 598         /*
 599          * Find the backing store object and offset into it to begin the
 600          * search.
 601          */
 602         fs.map = map;
 603         result = vm_map_lookup(&fs.map, vaddr, fault_type |
 604             VM_PROT_FAULT_LOOKUP, &fs.entry, &fs.first_object,
 605             &fs.first_pindex, &prot, &wired);
 606         if (result != KERN_SUCCESS) {
 607                 unlock_vp(&fs);
 608                 return (result);
 609         }
 610
 611         fs.map_generation = fs.map->timestamp;
 612
 613         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 614                 panic("%s: fault on nofault entry, addr: %#lx",
 615                     __func__, (u_long)vaddr);
 616         }
 617
 618         if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
 619             fs.entry->wiring_thread != curthread) {
 620                 vm_map_unlock_read(fs.map);
 621                 vm_map_lock(fs.map);
 622                 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
 623                     (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
 624                         unlock_vp(&fs);
 625                         fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
 626                         vm_map_unlock_and_wait(fs.map, 0);
 627                 } else
 628                         vm_map_unlock(fs.map);
 629                 goto RetryFault;
 630         }
 631
 632         MPASS((fs.entry->eflags & MAP_ENTRY_GUARD) == 0);
 633
 634         if (wired)
 635                 fault_type = prot | (fault_type & VM_PROT_COPY);
 636         else
 637                 KASSERT((fault_flags & VM_FAULT_WIRE) == 0,
 638                     ("!wired && VM_FAULT_WIRE"));
 639
 640         /*
 641          * Try to avoid lock contention on the top-level object through
 642          * special-case handling of some types of page faults, specifically,
 643          * those that are both (1) mapping an existing page from the top-
 644          * level object and (2) not having to mark that object as containing
 645          * dirty pages.  Under these conditions, a read lock on the top-level
 646          * object suffices, allowing multiple page faults of a similar type to
 647          * run in parallel on the same top-level object.
 648          */
 649         if (fs.vp == NULL /* avoid locked vnode leak */ &&
 650             (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 &&
 651             /* avoid calling vm_object_set_writeable_dirty() */
 652             ((prot & VM_PROT_WRITE) == 0 ||
 653             (fs.first_object->type != OBJT_VNODE &&
 654             (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
 655             (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
 656                 VM_OBJECT_RLOCK(fs.first_object);
 657                 if ((prot & VM_PROT_WRITE) == 0 ||
 658                     (fs.first_object->type != OBJT_VNODE &&
 659                     (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
 660                     (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0) {
 661                         rv = vm_fault_soft_fast(&fs, vaddr, prot, fault_type,
 662                             fault_flags, wired, m_hold);
 663                         if (rv == KERN_SUCCESS)
 664                                 return (rv);
 665                 }
 666                 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
 667                         VM_OBJECT_RUNLOCK(fs.first_object);
 668                         VM_OBJECT_WLOCK(fs.first_object);
 669                 }
 670         } else {
 671                 VM_OBJECT_WLOCK(fs.first_object);
 672         }
 673
 674         /*
 675          * Make a reference to this object to prevent its disposal while we
 676          * are messing with it.  Once we have the reference, the map is free
 677          * to be diddled.  Since objects reference their shadows (and copies),
 678          * they will stay around as well.
 679          *
 680          * Bump the paging-in-progress count to prevent size changes (e.g.
 681          * truncation operations) during I/O.
 682          */
 683         vm_object_reference_locked(fs.first_object);
 684         vm_object_pip_add(fs.first_object, 1);
 685
 686         fs.lookup_still_valid = true;
 687
 688         fs.first_m = NULL;
 689
 690         /*
 691          * Search for the page at object/offset.
 692          */
 693         fs.object = fs.first_object;
 694         fs.pindex = fs.first_pindex;
 695         while (TRUE) {
 696                 /*
 697                  * If the object is marked for imminent termination,
 698                  * we retry here, since the collapse pass has raced
 699                  * with us.  Otherwise, if we see terminally dead
 700                  * object, return fail.
 701                  */
 702                 if ((fs.object->flags & OBJ_DEAD) != 0) {
 703                         dead = fs.object->type == OBJT_DEAD;
 704                         unlock_and_deallocate(&fs);
 705                         if (dead)
 706                                 return (KERN_PROTECTION_FAILURE);
 707                         pause("vmf_de", 1);
 708                         goto RetryFault;
 709                 }
 710
 711                 /*
 712                  * See if page is resident
 713                  */
 714                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 715                 if (fs.m != NULL) {
 716                         /*
 717                          * Wait/Retry if the page is busy.  We have to do this
 718                          * if the page is either exclusive or shared busy
 719                          * because the vm_pager may be using read busy for
 720                          * pageouts (and even pageins if it is the vnode
 721                          * pager), and we could end up trying to pagein and
 722                          * pageout the same page simultaneously.
 723                          *
 724                          * We can theoretically allow the busy case on a read
 725                          * fault if the page is marked valid, but since such
 726                          * pages are typically already pmap'd, putting that
 727                          * special case in might be more effort then it is
 728                          * worth.  We cannot under any circumstances mess
 729                          * around with a shared busied page except, perhaps,
 730                          * to pmap it.
 731                          */
 732                         if (vm_page_busied(fs.m)) {
 733                                 /*
 734                                  * Reference the page before unlocking and
 735                                  * sleeping so that the page daemon is less
 736                                  * likely to reclaim it.
 737                                  */
 738                                 vm_page_aflag_set(fs.m, PGA_REFERENCED);
 739                                 if (fs.object != fs.first_object) {
 740                                         if (!VM_OBJECT_TRYWLOCK(
 741                                             fs.first_object)) {
 742                                                 VM_OBJECT_WUNLOCK(fs.object);
 743                                                 VM_OBJECT_WLOCK(fs.first_object);
 744                                                 VM_OBJECT_WLOCK(fs.object);
 745                                         }
 746                                         vm_page_lock(fs.first_m);
 747                                         vm_page_free(fs.first_m);
 748                                         vm_page_unlock(fs.first_m);
 749                                         vm_object_pip_wakeup(fs.first_object);
 750                                         VM_OBJECT_WUNLOCK(fs.first_object);
 751                                         fs.first_m = NULL;
 752                                 }
 753                                 unlock_map(&fs);
 754                                 if (fs.m == vm_page_lookup(fs.object,
 755                                     fs.pindex)) {
 756                                         vm_page_sleep_if_busy(fs.m, "vmpfw");
 757                                 }
 758                                 vm_object_pip_wakeup(fs.object);
 759                                 VM_OBJECT_WUNLOCK(fs.object);
 760                                 VM_CNT_INC(v_intrans);
 761                                 vm_object_deallocate(fs.first_object);
 762                                 goto RetryFault;
 763                         }
 764
 765                         /*
 766                          * Mark page busy for other processes, and the
 767                          * pagedaemon.  If it still isn't completely valid
 768                          * (readable), jump to readrest, else break-out ( we
 769                          * found the page ).
 770                          */
 771                         vm_page_xbusy(fs.m);
 772                         if (fs.m->valid != VM_PAGE_BITS_ALL)
 773                                 goto readrest;
 774                         break; /* break to PAGE HAS BEEN FOUND */
 775                 }
 776                 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m));
 777
 778                 /*
 779                  * Page is not resident.  If the pager might contain the page
 780                  * or this is the beginning of the search, allocate a new
 781                  * page.  (Default objects are zero-fill, so there is no real
 782                  * pager for them.)
 783                  */
 784                 if (fs.object->type != OBJT_DEFAULT ||
 785                     fs.object == fs.first_object) {
 786                         if (fs.pindex >= fs.object->size) {
 787                                 unlock_and_deallocate(&fs);
 788                                 return (KERN_PROTECTION_FAILURE);
 789                         }
 790
 791                         if (fs.object == fs.first_object &&
 792                             (fs.first_object->flags & OBJ_POPULATE) != 0 &&
 793                             fs.first_object->shadow_count == 0) {
 794                                 rv = vm_fault_populate(&fs, prot, fault_type,
 795                                     fault_flags, wired, m_hold);
 796                                 switch (rv) {
 797                                 case KERN_SUCCESS:
 798                                 case KERN_FAILURE:
 799                                         unlock_and_deallocate(&fs);
 800                                         return (rv);
 801                                 case KERN_RESOURCE_SHORTAGE:
 802                                         unlock_and_deallocate(&fs);
 803                                         goto RetryFault;
 804                                 case KERN_NOT_RECEIVER:
 805                                         /*
 806                                          * Pager's populate() method
 807                                          * returned VM_PAGER_BAD.
 808                                          */
 809                                         break;
 810                                 default:
 811                                         panic("inconsistent return codes");
 812                                 }
 813                         }
 814
 815                         /*
 816                          * Allocate a new page for this object/offset pair.
 817                          *
 818                          * Unlocked read of the p_flag is harmless. At
 819                          * worst, the P_KILLED might be not observed
 820                          * there, and allocation can fail, causing
 821                          * restart and new reading of the p_flag.
 822                          */
 823                         dset = fs.object->domain.dr_policy;
 824                         if (dset == NULL)
 825                                 dset = curthread->td_domain.dr_policy;
 826                         if (!vm_page_count_severe_set(&dset->ds_mask) ||
 827                             P_KILLED(curproc)) {
 828 #if VM_NRESERVLEVEL > 0
 829                                 vm_object_color(fs.object, atop(vaddr) -
 830                                     fs.pindex);
 831 #endif
 832                                 alloc_req = P_KILLED(curproc) ?
 833                                     VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
 834                                 if (fs.object->type != OBJT_VNODE &&
 835                                     fs.object->backing_object == NULL)
 836                                         alloc_req |= VM_ALLOC_ZERO;
 837                                 fs.m = vm_page_alloc(fs.object, fs.pindex,
 838                                     alloc_req);
 839                         }
 840                         if (fs.m == NULL) {
 841                                 unlock_and_deallocate(&fs);
 842                                 if (vm_pfault_oom_attempts < 0 ||
 843                                     oom < vm_pfault_oom_attempts) {
 844                                         oom++;
 845                                         vm_waitpfault(dset,
 846                                             vm_pfault_oom_wait * hz);
 847                                         goto RetryFault_oom;
 848                                 }
 849                                 if (bootverbose)
 850                                         printf(
 851         "proc %d (%s) failed to alloc page on fault, starting OOM\n",
 852                                             curproc->p_pid, curproc->p_comm);
 853                                 vm_pageout_oom(VM_OOM_MEM_PF);
 854                                 goto RetryFault;
 855                         }
 856                 }
 857
 858 readrest:
 859                 /*
 860                  * At this point, we have either allocated a new page or found
 861                  * an existing page that is only partially valid.
 862                  *
 863                  * We hold a reference on the current object and the page is
 864                  * exclusive busied.
 865                  */
 866
 867                 /*
 868                  * If the pager for the current object might have the page,
 869                  * then determine the number of additional pages to read and
 870                  * potentially reprioritize previously read pages for earlier
 871                  * reclamation.  These operations should only be performed
 872                  * once per page fault.  Even if the current pager doesn't
 873                  * have the page, the number of additional pages to read will
 874                  * apply to subsequent objects in the shadow chain.
 875                  */
 876                 if (fs.object->type != OBJT_DEFAULT && nera == -1 &&
 877                     !P_KILLED(curproc)) {
 878                         KASSERT(fs.lookup_still_valid, ("map unlocked"));
 879                         era = fs.entry->read_ahead;
 880                         behavior = vm_map_entry_behavior(fs.entry);
 881                         if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
 882                                 nera = 0;
 883                         } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
 884                                 nera = VM_FAULT_READ_AHEAD_MAX;
 885                                 if (vaddr == fs.entry->next_read)
 886                                         vm_fault_dontneed(&fs, vaddr, nera);
 887                         } else if (vaddr == fs.entry->next_read) {
 888                                 /*
 889                                  * This is a sequential fault.  Arithmetically
 890                                  * increase the requested number of pages in
 891                                  * the read-ahead window.  The requested
 892                                  * number of pages is "# of sequential faults
 893                                  * x (read ahead min + 1) + read ahead min"
 894                                  */
 895                                 nera = VM_FAULT_READ_AHEAD_MIN;
 896                                 if (era > 0) {
 897                                         nera += era + 1;
 898                                         if (nera > VM_FAULT_READ_AHEAD_MAX)
 899                                                 nera = VM_FAULT_READ_AHEAD_MAX;
 900                                 }
 901                                 if (era == VM_FAULT_READ_AHEAD_MAX)
 902                                         vm_fault_dontneed(&fs, vaddr, nera);
 903                         } else {
 904                                 /*
 905                                  * This is a non-sequential fault.
 906                                  */
 907                                 nera = 0;
 908                         }
 909                         if (era != nera) {
 910                                 /*
 911                                  * A read lock on the map suffices to update
 912                                  * the read ahead count safely.
 913                                  */
 914                                 fs.entry->read_ahead = nera;
 915                         }
 916
 917                         /*
 918                          * Prepare for unlocking the map.  Save the map
 919                          * entry's start and end addresses, which are used to
 920                          * optimize the size of the pager operation below.
 921                          * Even if the map entry's addresses change after
 922                          * unlocking the map, using the saved addresses is
 923                          * safe.
 924                          */
 925                         e_start = fs.entry->start;
 926                         e_end = fs.entry->end;
 927                 }
 928
 929                 /*
 930                  * Call the pager to retrieve the page if there is a chance
 931                  * that the pager has it, and potentially retrieve additional
 932                  * pages at the same time.
 933                  */
 934                 if (fs.object->type != OBJT_DEFAULT) {
 935                         /*
 936                          * Release the map lock before locking the vnode or
 937                          * sleeping in the pager.  (If the current object has
 938                          * a shadow, then an earlier iteration of this loop
 939                          * may have already unlocked the map.)
 940                          */
 941                         unlock_map(&fs);
 942
 943                         if (fs.object->type == OBJT_VNODE &&
 944                             (vp = fs.object->handle) != fs.vp) {
 945                                 /*
 946                                  * Perform an unlock in case the desired vnode
 947                                  * changed while the map was unlocked during a
 948                                  * retry.
 949                                  */
 950                                 unlock_vp(&fs);
 951
 952                                 locked = VOP_ISLOCKED(vp);
 953                                 if (locked != LK_EXCLUSIVE)
 954                                         locked = LK_SHARED;
 955
 956                                 /*
 957                                  * We must not sleep acquiring the vnode lock
 958                                  * while we have the page exclusive busied or
 959                                  * the object's paging-in-progress count
 960                                  * incremented.  Otherwise, we could deadlock.
 961                                  */
 962                                 error = vget(vp, locked | LK_CANRECURSE |
 963                                     LK_NOWAIT, curthread);
 964                                 if (error != 0) {
 965                                         vhold(vp);
 966                                         release_page(&fs);
 967                                         unlock_and_deallocate(&fs);
 968                                         error = vget(vp, locked | LK_RETRY |
 969                                             LK_CANRECURSE, curthread);
 970                                         vdrop(vp);
 971                                         fs.vp = vp;
 972                                         KASSERT(error == 0,
 973                                             ("vm_fault: vget failed"));
 974                                         goto RetryFault;
 975                                 }
 976                                 fs.vp = vp;
 977                         }
 978                         KASSERT(fs.vp == NULL || !fs.map->system_map,
 979                             ("vm_fault: vnode-backed object mapped by system map"));
 980
 981                         /*
 982                          * Page in the requested page and hint the pager,
 983                          * that it may bring up surrounding pages.
 984                          */
 985                         if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM ||
 986                             P_KILLED(curproc)) {
 987                                 behind = 0;
 988                                 ahead = 0;
 989                         } else {
 990                                 /* Is this a sequential fault? */
 991                                 if (nera > 0) {
 992                                         behind = 0;
 993                                         ahead = nera;
 994                                 } else {
 995                                         /*
 996                                          * Request a cluster of pages that is
 997                                          * aligned to a VM_FAULT_READ_DEFAULT
 998                                          * page offset boundary within the
 999                                          * object.  Alignment to a page offset
1000                                          * boundary is more likely to coincide
1001                                          * with the underlying file system
1002                                          * block than alignment to a virtual
1003                                          * address boundary.
1004                                          */
1005                                         cluster_offset = fs.pindex %
1006                                             VM_FAULT_READ_DEFAULT;
1007                                         behind = ulmin(cluster_offset,
1008                                             atop(vaddr - e_start));
1009                                         ahead = VM_FAULT_READ_DEFAULT - 1 -
1010                                             cluster_offset;
1011                                 }
1012                                 ahead = ulmin(ahead, atop(e_end - vaddr) - 1);
1013                         }
1014                         rv = vm_pager_get_pages(fs.object, &fs.m, 1,
1015                             &behind, &ahead);
1016                         if (rv == VM_PAGER_OK) {
1017                                 faultcount = behind + 1 + ahead;
1018                                 hardfault = true;
1019                                 break; /* break to PAGE HAS BEEN FOUND */
1020                         }
1021                         if (rv == VM_PAGER_ERROR)
1022                                 printf("vm_fault: pager read error, pid %d (%s)\n",
1023                                     curproc->p_pid, curproc->p_comm);
1024
1025                         /*
1026                          * If an I/O error occurred or the requested page was
1027                          * outside the range of the pager, clean up and return
1028                          * an error.
1029                          */
1030                         if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) {
1031                                 vm_page_lock(fs.m);
1032                                 if (!vm_page_wired(fs.m))
1033                                         vm_page_free(fs.m);
1034                                 else
1035                                         vm_page_xunbusy_maybelocked(fs.m);
1036                                 vm_page_unlock(fs.m);
1037                                 fs.m = NULL;
1038                                 unlock_and_deallocate(&fs);
1039                                 return (rv == VM_PAGER_ERROR ? KERN_FAILURE :
1040                                     KERN_PROTECTION_FAILURE);
1041                         }
1042
1043                         /*
1044                          * The requested page does not exist at this object/
1045                          * offset.  Remove the invalid page from the object,
1046                          * waking up anyone waiting for it, and continue on to
1047                          * the next object.  However, if this is the top-level
1048                          * object, we must leave the busy page in place to
1049                          * prevent another process from rushing past us, and
1050                          * inserting the page in that object at the same time
1051                          * that we are.
1052                          */
1053                         if (fs.object != fs.first_object) {
1054                                 vm_page_lock(fs.m);
1055                                 if (!vm_page_wired(fs.m))
1056                                         vm_page_free(fs.m);
1057                                 else
1058                                         vm_page_xunbusy_maybelocked(fs.m);
1059                                 vm_page_unlock(fs.m);
1060                                 fs.m = NULL;
1061                         }
1062                 }
1063
1064                 /*
1065                  * We get here if the object has default pager (or unwiring)
1066                  * or the pager doesn't have the page.
1067                  */
1068                 if (fs.object == fs.first_object)
1069                         fs.first_m = fs.m;
1070
1071                 /*
1072                  * Move on to the next object.  Lock the next object before
1073                  * unlocking the current one.
1074                  */
1075                 next_object = fs.object->backing_object;
1076                 if (next_object == NULL) {
1077                         /*
1078                          * If there's no object left, fill the page in the top
1079                          * object with zeros.
1080                          */
1081                         if (fs.object != fs.first_object) {
1082                                 vm_object_pip_wakeup(fs.object);
1083                                 VM_OBJECT_WUNLOCK(fs.object);
1084
1085                                 fs.object = fs.first_object;
1086                                 fs.pindex = fs.first_pindex;
1087                                 fs.m = fs.first_m;
1088                                 VM_OBJECT_WLOCK(fs.object);
1089                         }
1090                         fs.first_m = NULL;
1091
1092                         /*
1093                          * Zero the page if necessary and mark it valid.
1094                          */
1095                         if ((fs.m->flags & PG_ZERO) == 0) {
1096                                 pmap_zero_page(fs.m);
1097                         } else {
1098                                 VM_CNT_INC(v_ozfod);
1099                         }
1100                         VM_CNT_INC(v_zfod);
1101                         fs.m->valid = VM_PAGE_BITS_ALL;
1102                         /* Don't try to prefault neighboring pages. */
1103                         faultcount = 1;
1104                         break;  /* break to PAGE HAS BEEN FOUND */
1105                 } else {
1106                         KASSERT(fs.object != next_object,
1107                             ("object loop %p", next_object));
1108                         VM_OBJECT_WLOCK(next_object);
1109                         vm_object_pip_add(next_object, 1);
1110                         if (fs.object != fs.first_object)
1111                                 vm_object_pip_wakeup(fs.object);
1112                         fs.pindex +=
1113                             OFF_TO_IDX(fs.object->backing_object_offset);
1114                         VM_OBJECT_WUNLOCK(fs.object);
1115                         fs.object = next_object;
1116                 }
1117         }
1118
1119         vm_page_assert_xbusied(fs.m);
1120
1121         /*
1122          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
1123          * is held.]
1124          */
1125
1126         /*
1127          * If the page is being written, but isn't already owned by the
1128          * top-level object, we have to copy it into a new page owned by the
1129          * top-level object.
1130          */
1131         if (fs.object != fs.first_object) {
1132                 /*
1133                  * We only really need to copy if we want to write it.
1134                  */
1135                 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1136                         /*
1137                          * This allows pages to be virtually copied from a
1138                          * backing_object into the first_object, where the
1139                          * backing object has no other refs to it, and cannot
1140                          * gain any more refs.  Instead of a bcopy, we just
1141                          * move the page from the backing object to the
1142                          * first object.  Note that we must mark the page
1143                          * dirty in the first object so that it will go out
1144                          * to swap when needed.
1145                          */
1146                         is_first_object_locked = false;
1147                         if (
1148                                 /*
1149                                  * Only one shadow object
1150                                  */
1151                                 (fs.object->shadow_count == 1) &&
1152                                 /*
1153                                  * No COW refs, except us
1154                                  */
1155                                 (fs.object->ref_count == 1) &&
1156                                 /*
1157                                  * No one else can look this object up
1158                                  */
1159                                 (fs.object->handle == NULL) &&
1160                                 /*
1161                                  * No other ways to look the object up
1162                                  */
1163                                 ((fs.object->type == OBJT_DEFAULT) ||
1164                                  (fs.object->type == OBJT_SWAP)) &&
1165                             (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
1166                                 /*
1167                                  * We don't chase down the shadow chain
1168                                  */
1169                             fs.object == fs.first_object->backing_object) {
1170                                 vm_page_lock(fs.m);
1171                                 vm_page_dequeue(fs.m);
1172                                 (void)vm_page_remove(fs.m);
1173                                 vm_page_unlock(fs.m);
1174                                 vm_page_lock(fs.first_m);
1175                                 vm_page_replace_checked(fs.m, fs.first_object,
1176                                     fs.first_pindex, fs.first_m);
1177                                 vm_page_free(fs.first_m);
1178                                 vm_page_unlock(fs.first_m);
1179                                 vm_page_dirty(fs.m);
1180 #if VM_NRESERVLEVEL > 0
1181                                 /*
1182                                  * Rename the reservation.
1183                                  */
1184                                 vm_reserv_rename(fs.m, fs.first_object,
1185                                     fs.object, OFF_TO_IDX(
1186                                     fs.first_object->backing_object_offset));
1187 #endif
1188                                 /*
1189                                  * Removing the page from the backing object
1190                                  * unbusied it.
1191                                  */
1192                                 vm_page_xbusy(fs.m);
1193                                 fs.first_m = fs.m;
1194                                 fs.m = NULL;
1195                                 VM_CNT_INC(v_cow_optim);
1196                         } else {
1197                                 /*
1198                                  * Oh, well, lets copy it.
1199                                  */
1200                                 pmap_copy_page(fs.m, fs.first_m);
1201                                 fs.first_m->valid = VM_PAGE_BITS_ALL;
1202                                 if (wired && (fault_flags &
1203                                     VM_FAULT_WIRE) == 0) {
1204                                         vm_page_lock(fs.first_m);
1205                                         vm_page_wire(fs.first_m);
1206                                         vm_page_unlock(fs.first_m);
1207
1208                                         vm_page_lock(fs.m);
1209                                         vm_page_unwire(fs.m, PQ_INACTIVE);
1210                                         vm_page_unlock(fs.m);
1211                                 }
1212                                 /*
1213                                  * We no longer need the old page or object.
1214                                  */
1215                                 release_page(&fs);
1216                         }
1217                         /*
1218                          * fs.object != fs.first_object due to above
1219                          * conditional
1220                          */
1221                         vm_object_pip_wakeup(fs.object);
1222                         VM_OBJECT_WUNLOCK(fs.object);
1223                         /*
1224                          * Only use the new page below...
1225                          */
1226                         fs.object = fs.first_object;
1227                         fs.pindex = fs.first_pindex;
1228                         fs.m = fs.first_m;
1229                         if (!is_first_object_locked)
1230                                 VM_OBJECT_WLOCK(fs.object);
1231                         VM_CNT_INC(v_cow_faults);
1232                         curthread->td_cow++;
1233                 } else {
1234                         prot &= ~VM_PROT_WRITE;
1235                 }
1236         }
1237
1238         /*
1239          * We must verify that the maps have not changed since our last
1240          * lookup.
1241          */
1242         if (!fs.lookup_still_valid) {
1243                 if (!vm_map_trylock_read(fs.map)) {
1244                         release_page(&fs);
1245                         unlock_and_deallocate(&fs);
1246                         goto RetryFault;
1247                 }
1248                 fs.lookup_still_valid = true;
1249                 if (fs.map->timestamp != fs.map_generation) {
1250                         result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
1251                             &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
1252
1253                         /*
1254                          * If we don't need the page any longer, put it on the inactive
1255                          * list (the easiest thing to do here).  If no one needs it,
1256                          * pageout will grab it eventually.
1257                          */
1258                         if (result != KERN_SUCCESS) {
1259                                 release_page(&fs);
1260                                 unlock_and_deallocate(&fs);
1261
1262                                 /*
1263                                  * If retry of map lookup would have blocked then
1264                                  * retry fault from start.
1265                                  */
1266                                 if (result == KERN_FAILURE)
1267                                         goto RetryFault;
1268                                 return (result);
1269                         }
1270                         if ((retry_object != fs.first_object) ||
1271                             (retry_pindex != fs.first_pindex)) {
1272                                 release_page(&fs);
1273                                 unlock_and_deallocate(&fs);
1274                                 goto RetryFault;
1275                         }
1276
1277                         /*
1278                          * Check whether the protection has changed or the object has
1279                          * been copied while we left the map unlocked. Changing from
1280                          * read to write permission is OK - we leave the page
1281                          * write-protected, and catch the write fault. Changing from
1282                          * write to read permission means that we can't mark the page
1283                          * write-enabled after all.
1284                          */
1285                         prot &= retry_prot;
1286                         fault_type &= retry_prot;
1287                         if (prot == 0) {
1288                                 release_page(&fs);
1289                                 unlock_and_deallocate(&fs);
1290                                 goto RetryFault;
1291                         }
1292
1293                         /* Reassert because wired may have changed. */
1294                         KASSERT(wired || (fault_flags & VM_FAULT_WIRE) == 0,
1295                             ("!wired && VM_FAULT_WIRE"));
1296                 }
1297         }
1298
1299         /*
1300          * If the page was filled by a pager, save the virtual address that
1301          * should be faulted on next under a sequential access pattern to the
1302          * map entry.  A read lock on the map suffices to update this address
1303          * safely.
1304          */
1305         if (hardfault)
1306                 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE;
1307
1308         vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true);
1309         vm_page_assert_xbusied(fs.m);
1310
1311         /*
1312          * Page must be completely valid or it is not fit to
1313          * map into user space.  vm_pager_get_pages() ensures this.
1314          */
1315         KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
1316             ("vm_fault: page %p partially invalid", fs.m));
1317         VM_OBJECT_WUNLOCK(fs.object);
1318
1319         /*
1320          * Put this page into the physical map.  We had to do the unlock above
1321          * because pmap_enter() may sleep.  We don't put the page
1322          * back on the active queue until later so that the pageout daemon
1323          * won't find it (yet).
1324          */
1325         pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
1326             fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
1327         if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 &&
1328             wired == 0)
1329                 vm_fault_prefault(&fs, vaddr,
1330                     faultcount > 0 ? behind : PFBAK,
1331                     faultcount > 0 ? ahead : PFFOR, false);
1332         VM_OBJECT_WLOCK(fs.object);
1333         vm_page_lock(fs.m);
1334
1335         /*
1336          * If the page is not wired down, then put it where the pageout daemon
1337          * can find it.
1338          */
1339         if ((fault_flags & VM_FAULT_WIRE) != 0)
1340                 vm_page_wire(fs.m);
1341         else
1342                 vm_page_activate(fs.m);
1343         if (m_hold != NULL) {
1344                 *m_hold = fs.m;
1345                 vm_page_hold(fs.m);
1346         }
1347         vm_page_unlock(fs.m);
1348         vm_page_xunbusy(fs.m);
1349
1350         /*
1351          * Unlock everything, and return
1352          */
1353         unlock_and_deallocate(&fs);
1354         if (hardfault) {
1355                 VM_CNT_INC(v_io_faults);
1356                 curthread->td_ru.ru_majflt++;
1357 #ifdef RACCT
1358                 if (racct_enable && fs.object->type == OBJT_VNODE) {
1359                         PROC_LOCK(curproc);
1360                         if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1361                                 racct_add_force(curproc, RACCT_WRITEBPS,
1362                                     PAGE_SIZE + behind * PAGE_SIZE);
1363                                 racct_add_force(curproc, RACCT_WRITEIOPS, 1);
1364                         } else {
1365                                 racct_add_force(curproc, RACCT_READBPS,
1366                                     PAGE_SIZE + ahead * PAGE_SIZE);
1367                                 racct_add_force(curproc, RACCT_READIOPS, 1);
1368                         }
1369                         PROC_UNLOCK(curproc);
1370                 }
1371 #endif
1372         } else
1373                 curthread->td_ru.ru_minflt++;
1374
1375         return (KERN_SUCCESS);
1376 }
1377
1378 /*
1379  * Speed up the reclamation of pages that precede the faulting pindex within
1380  * the first object of the shadow chain.  Essentially, perform the equivalent
1381  * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes
1382  * the faulting pindex by the cluster size when the pages read by vm_fault()
1383  * cross a cluster-size boundary.  The cluster size is the greater of the
1384  * smallest superpage size and VM_FAULT_DONTNEED_MIN.
1385  *
1386  * When "fs->first_object" is a shadow object, the pages in the backing object
1387  * that precede the faulting pindex are deactivated by vm_fault().  So, this
1388  * function must only be concerned with pages in the first object.
1389  */
1390 static void
1391 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
1392 {
1393         vm_map_entry_t entry;
1394         vm_object_t first_object, object;
1395         vm_offset_t end, start;
1396         vm_page_t m, m_next;
1397         vm_pindex_t pend, pstart;
1398         vm_size_t size;
1399
1400         object = fs->object;
1401         VM_OBJECT_ASSERT_WLOCKED(object);
1402         first_object = fs->first_object;
1403         if (first_object != object) {
1404                 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1405                         VM_OBJECT_WUNLOCK(object);
1406                         VM_OBJECT_WLOCK(first_object);
1407                         VM_OBJECT_WLOCK(object);
1408                 }
1409         }
1410         /* Neither fictitious nor unmanaged pages can be reclaimed. */
1411         if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1412                 size = VM_FAULT_DONTNEED_MIN;
1413                 if (MAXPAGESIZES > 1 && size < pagesizes[1])
1414                         size = pagesizes[1];
1415                 end = rounddown2(vaddr, size);
1416                 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) &&
1417                     (entry = fs->entry)->start < end) {
1418                         if (end - entry->start < size)
1419                                 start = entry->start;
1420                         else
1421                                 start = end - size;
1422                         pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED);
1423                         pstart = OFF_TO_IDX(entry->offset) + atop(start -
1424                             entry->start);
1425                         m_next = vm_page_find_least(first_object, pstart);
1426                         pend = OFF_TO_IDX(entry->offset) + atop(end -
1427                             entry->start);
1428                         while ((m = m_next) != NULL && m->pindex < pend) {
1429                                 m_next = TAILQ_NEXT(m, listq);
1430                                 if (m->valid != VM_PAGE_BITS_ALL ||
1431                                     vm_page_busied(m))
1432                                         continue;
1433
1434                                 /*
1435                                  * Don't clear PGA_REFERENCED, since it would
1436                                  * likely represent a reference by a different
1437                                  * process.
1438                                  *
1439                                  * Typically, at this point, prefetched pages
1440                                  * are still in the inactive queue.  Only
1441                                  * pages that triggered page faults are in the
1442                                  * active queue.
1443                                  */
1444                                 vm_page_lock(m);
1445                                 if (!vm_page_inactive(m))
1446                                         vm_page_deactivate(m);
1447                                 vm_page_unlock(m);
1448                         }
1449                 }
1450         }
1451         if (first_object != object)
1452                 VM_OBJECT_WUNLOCK(first_object);
1453 }
1454
1455 /*
1456  * vm_fault_prefault provides a quick way of clustering
1457  * pagefaults into a processes address space.  It is a "cousin"
1458  * of vm_map_pmap_enter, except it runs at page fault time instead
1459  * of mmap time.
1460  */
1461 static void
1462 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1463     int backward, int forward, bool obj_locked)
1464 {
1465         pmap_t pmap;
1466         vm_map_entry_t entry;
1467         vm_object_t backing_object, lobject;
1468         vm_offset_t addr, starta;
1469         vm_pindex_t pindex;
1470         vm_page_t m;
1471         int i;
1472
1473         pmap = fs->map->pmap;
1474         if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1475                 return;
1476
1477         entry = fs->entry;
1478
1479         if (addra < backward * PAGE_SIZE) {
1480                 starta = entry->start;
1481         } else {
1482                 starta = addra - backward * PAGE_SIZE;
1483                 if (starta < entry->start)
1484                         starta = entry->start;
1485         }
1486
1487         /*
1488          * Generate the sequence of virtual addresses that are candidates for
1489          * prefaulting in an outward spiral from the faulting virtual address,
1490          * "addra".  Specifically, the sequence is "addra - PAGE_SIZE", "addra
1491          * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1492          * If the candidate address doesn't have a backing physical page, then
1493          * the loop immediately terminates.
1494          */
1495         for (i = 0; i < 2 * imax(backward, forward); i++) {
1496                 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1497                     PAGE_SIZE);
1498                 if (addr > addra + forward * PAGE_SIZE)
1499                         addr = 0;
1500
1501                 if (addr < starta || addr >= entry->end)
1502                         continue;
1503
1504                 if (!pmap_is_prefaultable(pmap, addr))
1505                         continue;
1506
1507                 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1508                 lobject = entry->object.vm_object;
1509                 if (!obj_locked)
1510                         VM_OBJECT_RLOCK(lobject);
1511                 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1512                     lobject->type == OBJT_DEFAULT &&
1513                     (backing_object = lobject->backing_object) != NULL) {
1514                         KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1515                             0, ("vm_fault_prefault: unaligned object offset"));
1516                         pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1517                         VM_OBJECT_RLOCK(backing_object);
1518                         if (!obj_locked || lobject != entry->object.vm_object)
1519                                 VM_OBJECT_RUNLOCK(lobject);
1520                         lobject = backing_object;
1521                 }
1522                 if (m == NULL) {
1523                         if (!obj_locked || lobject != entry->object.vm_object)
1524                                 VM_OBJECT_RUNLOCK(lobject);
1525                         break;
1526                 }
1527                 if (m->valid == VM_PAGE_BITS_ALL &&
1528                     (m->flags & PG_FICTITIOUS) == 0)
1529                         pmap_enter_quick(pmap, addr, m, entry->protection);
1530                 if (!obj_locked || lobject != entry->object.vm_object)
1531                         VM_OBJECT_RUNLOCK(lobject);
1532         }
1533 }
1534
1535 /*
1536  * Hold each of the physical pages that are mapped by the specified range of
1537  * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1538  * and allow the specified types of access, "prot".  If all of the implied
1539  * pages are successfully held, then the number of held pages is returned
1540  * together with pointers to those pages in the array "ma".  However, if any
1541  * of the pages cannot be held, -1 is returned.
1542  */
1543 int
1544 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1545     vm_prot_t prot, vm_page_t *ma, int max_count)
1546 {
1547         vm_offset_t end, va;
1548         vm_page_t *mp;
1549         int count;
1550         boolean_t pmap_failed;
1551
1552         if (len == 0)
1553                 return (0);
1554         end = round_page(addr + len);
1555         addr = trunc_page(addr);
1556
1557         /*
1558          * Check for illegal addresses.
1559          */
1560         if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1561                 return (-1);
1562
1563         if (atop(end - addr) > max_count)
1564                 panic("vm_fault_quick_hold_pages: count > max_count");
1565         count = atop(end - addr);
1566
1567         /*
1568          * Most likely, the physical pages are resident in the pmap, so it is
1569          * faster to try pmap_extract_and_hold() first.
1570          */
1571         pmap_failed = FALSE;
1572         for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1573                 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1574                 if (*mp == NULL)
1575                         pmap_failed = TRUE;
1576                 else if ((prot & VM_PROT_WRITE) != 0 &&
1577                     (*mp)->dirty != VM_PAGE_BITS_ALL) {
1578                         /*
1579                          * Explicitly dirty the physical page.  Otherwise, the
1580                          * caller's changes may go unnoticed because they are
1581                          * performed through an unmanaged mapping or by a DMA
1582                          * operation.
1583                          *
1584                          * The object lock is not held here.
1585                          * See vm_page_clear_dirty_mask().
1586                          */
1587                         vm_page_dirty(*mp);
1588                 }
1589         }
1590         if (pmap_failed) {
1591                 /*
1592                  * One or more pages could not be held by the pmap.  Either no
1593                  * page was mapped at the specified virtual address or that
1594                  * mapping had insufficient permissions.  Attempt to fault in
1595                  * and hold these pages.
1596                  *
1597                  * If vm_fault_disable_pagefaults() was called,
1598                  * i.e., TDP_NOFAULTING is set, we must not sleep nor
1599                  * acquire MD VM locks, which means we must not call
1600                  * vm_fault_hold().  Some (out of tree) callers mark
1601                  * too wide a code area with vm_fault_disable_pagefaults()
1602                  * already, use the VM_PROT_QUICK_NOFAULT flag to request
1603                  * the proper behaviour explicitly.
1604                  */
1605                 if ((prot & VM_PROT_QUICK_NOFAULT) != 0 &&
1606                     (curthread->td_pflags & TDP_NOFAULTING) != 0)
1607                         goto error;
1608                 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1609                         if (*mp == NULL && vm_fault_hold(map, va, prot,
1610                             VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1611                                 goto error;
1612         }
1613         return (count);
1614 error:
1615         for (mp = ma; mp < ma + count; mp++)
1616                 if (*mp != NULL) {
1617                         vm_page_lock(*mp);
1618                         vm_page_unhold(*mp);
1619                         vm_page_unlock(*mp);
1620                 }
1621         return (-1);
1622 }
1623
1624 /*
1625  *      Routine:
1626  *              vm_fault_copy_entry
1627  *      Function:
1628  *              Create new shadow object backing dst_entry with private copy of
1629  *              all underlying pages. When src_entry is equal to dst_entry,
1630  *              function implements COW for wired-down map entry. Otherwise,
1631  *              it forks wired entry into dst_map.
1632  *
1633  *      In/out conditions:
1634  *              The source and destination maps must be locked for write.
1635  *              The source map entry must be wired down (or be a sharing map
1636  *              entry corresponding to a main map entry that is wired down).
1637  */
1638 void
1639 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1640     vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1641     vm_ooffset_t *fork_charge)
1642 {
1643         vm_object_t backing_object, dst_object, object, src_object;
1644         vm_pindex_t dst_pindex, pindex, src_pindex;
1645         vm_prot_t access, prot;
1646         vm_offset_t vaddr;
1647         vm_page_t dst_m;
1648         vm_page_t src_m;
1649         boolean_t upgrade;
1650
1651 #ifdef  lint
1652         src_map++;
1653 #endif  /* lint */
1654
1655         upgrade = src_entry == dst_entry;
1656         access = prot = dst_entry->protection;
1657
1658         src_object = src_entry->object.vm_object;
1659         src_pindex = OFF_TO_IDX(src_entry->offset);
1660
1661         if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1662                 dst_object = src_object;
1663                 vm_object_reference(dst_object);
1664         } else {
1665                 /*
1666                  * Create the top-level object for the destination entry. (Doesn't
1667                  * actually shadow anything - we copy the pages directly.)
1668                  */
1669                 dst_object = vm_object_allocate(OBJT_DEFAULT,
1670                     atop(dst_entry->end - dst_entry->start));
1671 #if VM_NRESERVLEVEL > 0
1672                 dst_object->flags |= OBJ_COLORED;
1673                 dst_object->pg_color = atop(dst_entry->start);
1674 #endif
1675                 dst_object->domain = src_object->domain;
1676                 dst_object->charge = dst_entry->end - dst_entry->start;
1677         }
1678
1679         VM_OBJECT_WLOCK(dst_object);
1680         KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1681             ("vm_fault_copy_entry: vm_object not NULL"));
1682         if (src_object != dst_object) {
1683                 dst_entry->object.vm_object = dst_object;
1684                 dst_entry->offset = 0;
1685                 dst_entry->eflags &= ~MAP_ENTRY_VN_EXEC;
1686         }
1687         if (fork_charge != NULL) {
1688                 KASSERT(dst_entry->cred == NULL,
1689                     ("vm_fault_copy_entry: leaked swp charge"));
1690                 dst_object->cred = curthread->td_ucred;
1691                 crhold(dst_object->cred);
1692                 *fork_charge += dst_object->charge;
1693         } else if ((dst_object->type == OBJT_DEFAULT ||
1694             dst_object->type == OBJT_SWAP) &&
1695             dst_object->cred == NULL) {
1696                 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1697                     dst_entry));
1698                 dst_object->cred = dst_entry->cred;
1699                 dst_entry->cred = NULL;
1700         }
1701
1702         /*
1703          * If not an upgrade, then enter the mappings in the pmap as
1704          * read and/or execute accesses.  Otherwise, enter them as
1705          * write accesses.
1706          *
1707          * A writeable large page mapping is only created if all of
1708          * the constituent small page mappings are modified. Marking
1709          * PTEs as modified on inception allows promotion to happen
1710          * without taking potentially large number of soft faults.
1711          */
1712         if (!upgrade)
1713                 access &= ~VM_PROT_WRITE;
1714
1715         /*
1716          * Loop through all of the virtual pages within the entry's
1717          * range, copying each page from the source object to the
1718          * destination object.  Since the source is wired, those pages
1719          * must exist.  In contrast, the destination is pageable.
1720          * Since the destination object doesn't share any backing storage
1721          * with the source object, all of its pages must be dirtied,
1722          * regardless of whether they can be written.
1723          */
1724         for (vaddr = dst_entry->start, dst_pindex = 0;
1725             vaddr < dst_entry->end;
1726             vaddr += PAGE_SIZE, dst_pindex++) {
1727 again:
1728                 /*
1729                  * Find the page in the source object, and copy it in.
1730                  * Because the source is wired down, the page will be
1731                  * in memory.
1732                  */
1733                 if (src_object != dst_object)
1734                         VM_OBJECT_RLOCK(src_object);
1735                 object = src_object;
1736                 pindex = src_pindex + dst_pindex;
1737                 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1738                     (backing_object = object->backing_object) != NULL) {
1739                         /*
1740                          * Unless the source mapping is read-only or
1741                          * it is presently being upgraded from
1742                          * read-only, the first object in the shadow
1743                          * chain should provide all of the pages.  In
1744                          * other words, this loop body should never be
1745                          * executed when the source mapping is already
1746                          * read/write.
1747                          */
1748                         KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1749                             upgrade,
1750                             ("vm_fault_copy_entry: main object missing page"));
1751
1752                         VM_OBJECT_RLOCK(backing_object);
1753                         pindex += OFF_TO_IDX(object->backing_object_offset);
1754                         if (object != dst_object)
1755                                 VM_OBJECT_RUNLOCK(object);
1756                         object = backing_object;
1757                 }
1758                 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1759
1760                 if (object != dst_object) {
1761                         /*
1762                          * Allocate a page in the destination object.
1763                          */
1764                         dst_m = vm_page_alloc(dst_object, (src_object ==
1765                             dst_object ? src_pindex : 0) + dst_pindex,
1766                             VM_ALLOC_NORMAL);
1767                         if (dst_m == NULL) {
1768                                 VM_OBJECT_WUNLOCK(dst_object);
1769                                 VM_OBJECT_RUNLOCK(object);
1770                                 vm_wait(dst_object);
1771                                 VM_OBJECT_WLOCK(dst_object);
1772                                 goto again;
1773                         }
1774                         pmap_copy_page(src_m, dst_m);
1775                         VM_OBJECT_RUNLOCK(object);
1776                         dst_m->dirty = dst_m->valid = src_m->valid;
1777                 } else {
1778                         dst_m = src_m;
1779                         if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1780                                 goto again;
1781                         if (dst_m->pindex >= dst_object->size)
1782                                 /*
1783                                  * We are upgrading.  Index can occur
1784                                  * out of bounds if the object type is
1785                                  * vnode and the file was truncated.
1786                                  */
1787                                 break;
1788                         vm_page_xbusy(dst_m);
1789                 }
1790                 VM_OBJECT_WUNLOCK(dst_object);
1791
1792                 /*
1793                  * Enter it in the pmap. If a wired, copy-on-write
1794                  * mapping is being replaced by a write-enabled
1795                  * mapping, then wire that new mapping.
1796                  *
1797                  * The page can be invalid if the user called
1798                  * msync(MS_INVALIDATE) or truncated the backing vnode
1799                  * or shared memory object.  In this case, do not
1800                  * insert it into pmap, but still do the copy so that
1801                  * all copies of the wired map entry have similar
1802                  * backing pages.
1803                  */
1804                 if (dst_m->valid == VM_PAGE_BITS_ALL) {
1805                         pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1806                             access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1807                 }
1808
1809                 /*
1810                  * Mark it no longer busy, and put it on the active list.
1811                  */
1812                 VM_OBJECT_WLOCK(dst_object);
1813
1814                 if (upgrade) {
1815                         if (src_m != dst_m) {
1816                                 vm_page_lock(src_m);
1817                                 vm_page_unwire(src_m, PQ_INACTIVE);
1818                                 vm_page_unlock(src_m);
1819                                 vm_page_lock(dst_m);
1820                                 vm_page_wire(dst_m);
1821                                 vm_page_unlock(dst_m);
1822                         } else {
1823                                 KASSERT(vm_page_wired(dst_m),
1824                                     ("dst_m %p is not wired", dst_m));
1825                         }
1826                 } else {
1827                         vm_page_lock(dst_m);
1828                         vm_page_activate(dst_m);
1829                         vm_page_unlock(dst_m);
1830                 }
1831                 vm_page_xunbusy(dst_m);
1832         }
1833         VM_OBJECT_WUNLOCK(dst_object);
1834         if (upgrade) {
1835                 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1836                 vm_object_deallocate(src_object);
1837         }
1838 }
1839
1840 /*
1841  * Block entry into the machine-independent layer's page fault handler by
1842  * the calling thread.  Subsequent calls to vm_fault() by that thread will
1843  * return KERN_PROTECTION_FAILURE.  Enable machine-dependent handling of
1844  * spurious page faults.
1845  */
1846 int
1847 vm_fault_disable_pagefaults(void)
1848 {
1849
1850         return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1851 }
1852
1853 void
1854 vm_fault_enable_pagefaults(int save)
1855 {
1856
1857         curthread_pflags_restore(save);
1858 }