sys/vm/vm_fault.c

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