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