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/proc.h>
  85 #include <sys/resourcevar.h>
  86 #include <sys/rwlock.h>
  87 #include <sys/sysctl.h>
  88 #include <sys/vmmeter.h>
  89 #include <sys/vnode.h>
  90 #ifdef KTRACE
  91 #include <sys/ktrace.h>
  92 #endif
  93
  94 #include <vm/vm.h>
  95 #include <vm/vm_param.h>
  96 #include <vm/pmap.h>
  97 #include <vm/vm_map.h>
  98 #include <vm/vm_object.h>
  99 #include <vm/vm_page.h>
 100 #include <vm/vm_pageout.h>
 101 #include <vm/vm_kern.h>
 102 #include <vm/vm_pager.h>
 103 #include <vm/vm_extern.h>
 104 #include <vm/vm_reserv.h>
 105
 106 #define PFBAK 4
 107 #define PFFOR 4
 108
 109 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
 110
 111 #define VM_FAULT_READ_BEHIND    8
 112 #define VM_FAULT_READ_MAX       (1 + VM_FAULT_READ_AHEAD_MAX)
 113 #define VM_FAULT_NINCR          (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND)
 114 #define VM_FAULT_SUM            (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2)
 115 #define VM_FAULT_CACHE_BEHIND   (VM_FAULT_READ_BEHIND * VM_FAULT_SUM)
 116
 117 struct faultstate {
 118         vm_page_t m;
 119         vm_object_t object;
 120         vm_pindex_t pindex;
 121         vm_page_t first_m;
 122         vm_object_t     first_object;
 123         vm_pindex_t first_pindex;
 124         vm_map_t map;
 125         vm_map_entry_t entry;
 126         int lookup_still_valid;
 127         struct vnode *vp;
 128 };
 129
 130 static void vm_fault_cache_behind(const struct faultstate *fs, int distance);
 131 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
 132             int faultcount, int reqpage);
 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 /*
 250  *      vm_fault:
 251  *
 252  *      Handle a page fault occurring at the given address,
 253  *      requiring the given permissions, in the map specified.
 254  *      If successful, the page is inserted into the
 255  *      associated physical map.
 256  *
 257  *      NOTE: the given address should be truncated to the
 258  *      proper page address.
 259  *
 260  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 261  *      a standard error specifying why the fault is fatal is returned.
 262  *
 263  *      The map in question must be referenced, and remains so.
 264  *      Caller may hold no locks.
 265  */
 266 int
 267 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 268     int fault_flags)
 269 {
 270         struct thread *td;
 271         int result;
 272
 273         td = curthread;
 274         if ((td->td_pflags & TDP_NOFAULTING) != 0)
 275                 return (KERN_PROTECTION_FAILURE);
 276 #ifdef KTRACE
 277         if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
 278                 ktrfault(vaddr, fault_type);
 279 #endif
 280         result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
 281             NULL);
 282 #ifdef KTRACE
 283         if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
 284                 ktrfaultend(result);
 285 #endif
 286         return (result);
 287 }
 288
 289 int
 290 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 291     int fault_flags, vm_page_t *m_hold)
 292 {
 293         vm_prot_t prot;
 294         long ahead, behind;
 295         int alloc_req, era, faultcount, nera, reqpage, result;
 296         boolean_t dead, growstack, is_first_object_locked, wired;
 297         int map_generation;
 298         vm_object_t next_object;
 299         vm_page_t marray[VM_FAULT_READ_MAX];
 300         int hardfault;
 301         struct faultstate fs;
 302         struct vnode *vp;
 303         vm_page_t m;
 304         int locked, error;
 305
 306         hardfault = 0;
 307         growstack = TRUE;
 308         PCPU_INC(cnt.v_vm_faults);
 309         fs.vp = NULL;
 310         faultcount = reqpage = 0;
 311
 312 RetryFault:;
 313
 314         /*
 315          * Find the backing store object and offset into it to begin the
 316          * search.
 317          */
 318         fs.map = map;
 319         result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
 320             &fs.first_object, &fs.first_pindex, &prot, &wired);
 321         if (result != KERN_SUCCESS) {
 322                 if (growstack && result == KERN_INVALID_ADDRESS &&
 323                     map != kernel_map) {
 324                         result = vm_map_growstack(curproc, vaddr);
 325                         if (result != KERN_SUCCESS)
 326                                 return (KERN_FAILURE);
 327                         growstack = FALSE;
 328                         goto RetryFault;
 329                 }
 330                 unlock_vp(&fs);
 331                 return (result);
 332         }
 333
 334         map_generation = fs.map->timestamp;
 335
 336         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 337                 panic("vm_fault: fault on nofault entry, addr: %lx",
 338                     (u_long)vaddr);
 339         }
 340
 341         if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
 342             fs.entry->wiring_thread != curthread) {
 343                 vm_map_unlock_read(fs.map);
 344                 vm_map_lock(fs.map);
 345                 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
 346                     (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
 347                         unlock_vp(&fs);
 348                         fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
 349                         vm_map_unlock_and_wait(fs.map, 0);
 350                 } else
 351                         vm_map_unlock(fs.map);
 352                 goto RetryFault;
 353         }
 354
 355         if (wired)
 356                 fault_type = prot | (fault_type & VM_PROT_COPY);
 357         else
 358                 KASSERT((fault_flags & VM_FAULT_WIRE) == 0,
 359                     ("!wired && VM_FAULT_WIRE"));
 360
 361         /*
 362          * Try to avoid lock contention on the top-level object through
 363          * special-case handling of some types of page faults, specifically,
 364          * those that are both (1) mapping an existing page from the top-
 365          * level object and (2) not having to mark that object as containing
 366          * dirty pages.  Under these conditions, a read lock on the top-level
 367          * object suffices, allowing multiple page faults of a similar type to
 368          * run in parallel on the same top-level object.
 369          */
 370         if (fs.vp == NULL /* avoid locked vnode leak */ &&
 371             (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 &&
 372             /* avoid calling vm_object_set_writeable_dirty() */
 373             ((prot & VM_PROT_WRITE) == 0 ||
 374             (fs.first_object->type != OBJT_VNODE &&
 375             (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
 376             (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
 377                 VM_OBJECT_RLOCK(fs.first_object);
 378                 if ((prot & VM_PROT_WRITE) != 0 &&
 379                     (fs.first_object->type == OBJT_VNODE ||
 380                     (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) &&
 381                     (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0)
 382                         goto fast_failed;
 383                 m = vm_page_lookup(fs.first_object, fs.first_pindex);
 384                 /* A busy page can be mapped for read|execute access. */
 385                 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
 386                     vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
 387                         goto fast_failed;
 388                 result = pmap_enter(fs.map->pmap, vaddr, m, prot,
 389                    fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED :
 390                    0), 0);
 391                 if (result != KERN_SUCCESS)
 392                         goto fast_failed;
 393                 if (m_hold != NULL) {
 394                         *m_hold = m;
 395                         vm_page_lock(m);
 396                         vm_page_hold(m);
 397                         vm_page_unlock(m);
 398                 }
 399                 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags,
 400                     false);
 401                 VM_OBJECT_RUNLOCK(fs.first_object);
 402                 if (!wired)
 403                         vm_fault_prefault(&fs, vaddr, 0, 0);
 404                 vm_map_lookup_done(fs.map, fs.entry);
 405                 curthread->td_ru.ru_minflt++;
 406                 return (KERN_SUCCESS);
 407 fast_failed:
 408                 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
 409                         VM_OBJECT_RUNLOCK(fs.first_object);
 410                         VM_OBJECT_WLOCK(fs.first_object);
 411                 }
 412         } else {
 413                 VM_OBJECT_WLOCK(fs.first_object);
 414         }
 415
 416         /*
 417          * Make a reference to this object to prevent its disposal while we
 418          * are messing with it.  Once we have the reference, the map is free
 419          * to be diddled.  Since objects reference their shadows (and copies),
 420          * they will stay around as well.
 421          *
 422          * Bump the paging-in-progress count to prevent size changes (e.g.
 423          * truncation operations) during I/O.  This must be done after
 424          * obtaining the vnode lock in order to avoid possible deadlocks.
 425          */
 426         vm_object_reference_locked(fs.first_object);
 427         vm_object_pip_add(fs.first_object, 1);
 428
 429         fs.lookup_still_valid = TRUE;
 430
 431         fs.first_m = NULL;
 432
 433         /*
 434          * Search for the page at object/offset.
 435          */
 436         fs.object = fs.first_object;
 437         fs.pindex = fs.first_pindex;
 438         while (TRUE) {
 439                 /*
 440                  * If the object is marked for imminent termination,
 441                  * we retry here, since the collapse pass has raced
 442                  * with us.  Otherwise, if we see terminally dead
 443                  * object, return fail.
 444                  */
 445                 if ((fs.object->flags & OBJ_DEAD) != 0) {
 446                         dead = fs.object->type == OBJT_DEAD;
 447                         unlock_and_deallocate(&fs);
 448                         if (dead)
 449                                 return (KERN_PROTECTION_FAILURE);
 450                         pause("vmf_de", 1);
 451                         goto RetryFault;
 452                 }
 453
 454                 /*
 455                  * See if page is resident
 456                  */
 457                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 458                 if (fs.m != NULL) {
 459                         /*
 460                          * Wait/Retry if the page is busy.  We have to do this
 461                          * if the page is either exclusive or shared busy
 462                          * because the vm_pager may be using read busy for
 463                          * pageouts (and even pageins if it is the vnode
 464                          * pager), and we could end up trying to pagein and
 465                          * pageout the same page simultaneously.
 466                          *
 467                          * We can theoretically allow the busy case on a read
 468                          * fault if the page is marked valid, but since such
 469                          * pages are typically already pmap'd, putting that
 470                          * special case in might be more effort then it is
 471                          * worth.  We cannot under any circumstances mess
 472                          * around with a shared busied page except, perhaps,
 473                          * to pmap it.
 474                          */
 475                         if (vm_page_busied(fs.m)) {
 476                                 /*
 477                                  * Reference the page before unlocking and
 478                                  * sleeping so that the page daemon is less
 479                                  * likely to reclaim it.
 480                                  */
 481                                 vm_page_aflag_set(fs.m, PGA_REFERENCED);
 482                                 if (fs.object != fs.first_object) {
 483                                         if (!VM_OBJECT_TRYWLOCK(
 484                                             fs.first_object)) {
 485                                                 VM_OBJECT_WUNLOCK(fs.object);
 486                                                 VM_OBJECT_WLOCK(fs.first_object);
 487                                                 VM_OBJECT_WLOCK(fs.object);
 488                                         }
 489                                         vm_page_lock(fs.first_m);
 490                                         vm_page_free(fs.first_m);
 491                                         vm_page_unlock(fs.first_m);
 492                                         vm_object_pip_wakeup(fs.first_object);
 493                                         VM_OBJECT_WUNLOCK(fs.first_object);
 494                                         fs.first_m = NULL;
 495                                 }
 496                                 unlock_map(&fs);
 497                                 if (fs.m == vm_page_lookup(fs.object,
 498                                     fs.pindex)) {
 499                                         vm_page_sleep_if_busy(fs.m, "vmpfw");
 500                                 }
 501                                 vm_object_pip_wakeup(fs.object);
 502                                 VM_OBJECT_WUNLOCK(fs.object);
 503                                 PCPU_INC(cnt.v_intrans);
 504                                 vm_object_deallocate(fs.first_object);
 505                                 goto RetryFault;
 506                         }
 507                         vm_page_lock(fs.m);
 508                         vm_page_remque(fs.m);
 509                         vm_page_unlock(fs.m);
 510
 511                         /*
 512                          * Mark page busy for other processes, and the
 513                          * pagedaemon.  If it still isn't completely valid
 514                          * (readable), jump to readrest, else break-out ( we
 515                          * found the page ).
 516                          */
 517                         vm_page_xbusy(fs.m);
 518                         if (fs.m->valid != VM_PAGE_BITS_ALL)
 519                                 goto readrest;
 520                         break;
 521                 }
 522
 523                 /*
 524                  * Page is not resident.  If this is the search termination
 525                  * or the pager might contain the page, allocate a new page.
 526                  * Default objects are zero-fill, there is no real pager.
 527                  */
 528                 if (fs.object->type != OBJT_DEFAULT ||
 529                     fs.object == fs.first_object) {
 530                         if (fs.pindex >= fs.object->size) {
 531                                 unlock_and_deallocate(&fs);
 532                                 return (KERN_PROTECTION_FAILURE);
 533                         }
 534
 535                         /*
 536                          * Allocate a new page for this object/offset pair.
 537                          *
 538                          * Unlocked read of the p_flag is harmless. At
 539                          * worst, the P_KILLED might be not observed
 540                          * there, and allocation can fail, causing
 541                          * restart and new reading of the p_flag.
 542                          */
 543                         fs.m = NULL;
 544                         if (!vm_page_count_severe() || P_KILLED(curproc)) {
 545 #if VM_NRESERVLEVEL > 0
 546                                 if ((fs.object->flags & OBJ_COLORED) == 0) {
 547                                         fs.object->flags |= OBJ_COLORED;
 548                                         fs.object->pg_color = atop(vaddr) -
 549                                             fs.pindex;
 550                                 }
 551 #endif
 552                                 alloc_req = P_KILLED(curproc) ?
 553                                     VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
 554                                 if (fs.object->type != OBJT_VNODE &&
 555                                     fs.object->backing_object == NULL)
 556                                         alloc_req |= VM_ALLOC_ZERO;
 557                                 fs.m = vm_page_alloc(fs.object, fs.pindex,
 558                                     alloc_req);
 559                         }
 560                         if (fs.m == NULL) {
 561                                 unlock_and_deallocate(&fs);
 562                                 VM_WAITPFAULT;
 563                                 goto RetryFault;
 564                         } else if (fs.m->valid == VM_PAGE_BITS_ALL)
 565                                 break;
 566                 }
 567
 568 readrest:
 569                 /*
 570                  * We have found a valid page or we have allocated a new page.
 571                  * The page thus may not be valid or may not be entirely
 572                  * valid.
 573                  *
 574                  * Attempt to fault-in the page if there is a chance that the
 575                  * pager has it, and potentially fault in additional pages
 576                  * at the same time.  For default objects simply provide
 577                  * zero-filled pages.
 578                  */
 579                 if (fs.object->type != OBJT_DEFAULT) {
 580                         int rv;
 581                         u_char behavior = vm_map_entry_behavior(fs.entry);
 582
 583                         if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
 584                             P_KILLED(curproc)) {
 585                                 behind = 0;
 586                                 ahead = 0;
 587                         } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
 588                                 behind = 0;
 589                                 ahead = atop(fs.entry->end - vaddr) - 1;
 590                                 if (ahead > VM_FAULT_READ_AHEAD_MAX)
 591                                         ahead = VM_FAULT_READ_AHEAD_MAX;
 592                                 if (fs.pindex == fs.entry->next_read)
 593                                         vm_fault_cache_behind(&fs,
 594                                             VM_FAULT_READ_MAX);
 595                         } else {
 596                                 /*
 597                                  * If this is a sequential page fault, then
 598                                  * arithmetically increase the number of pages
 599                                  * in the read-ahead window.  Otherwise, reset
 600                                  * the read-ahead window to its smallest size.
 601                                  */
 602                                 behind = atop(vaddr - fs.entry->start);
 603                                 if (behind > VM_FAULT_READ_BEHIND)
 604                                         behind = VM_FAULT_READ_BEHIND;
 605                                 ahead = atop(fs.entry->end - vaddr) - 1;
 606                                 era = fs.entry->read_ahead;
 607                                 if (fs.pindex == fs.entry->next_read) {
 608                                         nera = era + behind;
 609                                         if (nera > VM_FAULT_READ_AHEAD_MAX)
 610                                                 nera = VM_FAULT_READ_AHEAD_MAX;
 611                                         behind = 0;
 612                                         if (ahead > nera)
 613                                                 ahead = nera;
 614                                         if (era == VM_FAULT_READ_AHEAD_MAX)
 615                                                 vm_fault_cache_behind(&fs,
 616                                                     VM_FAULT_CACHE_BEHIND);
 617                                 } else if (ahead > VM_FAULT_READ_AHEAD_MIN)
 618                                         ahead = VM_FAULT_READ_AHEAD_MIN;
 619                                 if (era != ahead)
 620                                         fs.entry->read_ahead = ahead;
 621                         }
 622
 623                         /*
 624                          * Call the pager to retrieve the data, if any, after
 625                          * releasing the lock on the map.  We hold a ref on
 626                          * fs.object and the pages are exclusive busied.
 627                          */
 628                         unlock_map(&fs);
 629
 630                         if (fs.object->type == OBJT_VNODE &&
 631                             (vp = fs.object->handle) != fs.vp) {
 632                                 unlock_vp(&fs);
 633                                 locked = VOP_ISLOCKED(vp);
 634
 635                                 if (locked != LK_EXCLUSIVE)
 636                                         locked = LK_SHARED;
 637                                 /* Do not sleep for vnode lock while fs.m is busy */
 638                                 error = vget(vp, locked | LK_CANRECURSE |
 639                                     LK_NOWAIT, curthread);
 640                                 if (error != 0) {
 641                                         vhold(vp);
 642                                         release_page(&fs);
 643                                         unlock_and_deallocate(&fs);
 644                                         error = vget(vp, locked | LK_RETRY |
 645                                             LK_CANRECURSE, curthread);
 646                                         vdrop(vp);
 647                                         fs.vp = vp;
 648                                         KASSERT(error == 0,
 649                                             ("vm_fault: vget failed"));
 650                                         goto RetryFault;
 651                                 }
 652                                 fs.vp = vp;
 653                         }
 654                         KASSERT(fs.vp == NULL || !fs.map->system_map,
 655                             ("vm_fault: vnode-backed object mapped by system map"));
 656
 657                         /*
 658                          * now we find out if any other pages should be paged
 659                          * in at this time this routine checks to see if the
 660                          * pages surrounding this fault reside in the same
 661                          * object as the page for this fault.  If they do,
 662                          * then they are faulted in also into the object.  The
 663                          * array "marray" returned contains an array of
 664                          * vm_page_t structs where one of them is the
 665                          * vm_page_t passed to the routine.  The reqpage
 666                          * return value is the index into the marray for the
 667                          * vm_page_t passed to the routine.
 668                          *
 669                          * fs.m plus the additional pages are exclusive busied.
 670                          */
 671                         faultcount = vm_fault_additional_pages(
 672                             fs.m, behind, ahead, marray, &reqpage);
 673
 674                         rv = faultcount ?
 675                             vm_pager_get_pages(fs.object, marray, faultcount,
 676                                 reqpage) : VM_PAGER_FAIL;
 677
 678                         if (rv == VM_PAGER_OK) {
 679                                 /*
 680                                  * Found the page. Leave it busy while we play
 681                                  * with it.
 682                                  */
 683
 684                                 /*
 685                                  * Relookup in case pager changed page. Pager
 686                                  * is responsible for disposition of old page
 687                                  * if moved.
 688                                  */
 689                                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 690                                 if (!fs.m) {
 691                                         unlock_and_deallocate(&fs);
 692                                         goto RetryFault;
 693                                 }
 694
 695                                 hardfault++;
 696                                 break; /* break to PAGE HAS BEEN FOUND */
 697                         }
 698                         /*
 699                          * Remove the bogus page (which does not exist at this
 700                          * object/offset); before doing so, we must get back
 701                          * our object lock to preserve our invariant.
 702                          *
 703                          * Also wake up any other process that may want to bring
 704                          * in this page.
 705                          *
 706                          * If this is the top-level object, we must leave the
 707                          * busy page to prevent another process from rushing
 708                          * past us, and inserting the page in that object at
 709                          * the same time that we are.
 710                          */
 711                         if (rv == VM_PAGER_ERROR)
 712                                 printf("vm_fault: pager read error, pid %d (%s)\n",
 713                                     curproc->p_pid, curproc->p_comm);
 714                         /*
 715                          * Data outside the range of the pager or an I/O error
 716                          */
 717                         /*
 718                          * XXX - the check for kernel_map is a kludge to work
 719                          * around having the machine panic on a kernel space
 720                          * fault w/ I/O error.
 721                          */
 722                         if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
 723                                 (rv == VM_PAGER_BAD)) {
 724                                 vm_page_lock(fs.m);
 725                                 vm_page_free(fs.m);
 726                                 vm_page_unlock(fs.m);
 727                                 fs.m = NULL;
 728                                 unlock_and_deallocate(&fs);
 729                                 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
 730                         }
 731                         if (fs.object != fs.first_object) {
 732                                 vm_page_lock(fs.m);
 733                                 vm_page_free(fs.m);
 734                                 vm_page_unlock(fs.m);
 735                                 fs.m = NULL;
 736                                 /*
 737                                  * XXX - we cannot just fall out at this
 738                                  * point, m has been freed and is invalid!
 739                                  */
 740                         }
 741                 }
 742
 743                 /*
 744                  * We get here if the object has default pager (or unwiring)
 745                  * or the pager doesn't have the page.
 746                  */
 747                 if (fs.object == fs.first_object)
 748                         fs.first_m = fs.m;
 749
 750                 /*
 751                  * Move on to the next object.  Lock the next object before
 752                  * unlocking the current one.
 753                  */
 754                 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
 755                 next_object = fs.object->backing_object;
 756                 if (next_object == NULL) {
 757                         /*
 758                          * If there's no object left, fill the page in the top
 759                          * object with zeros.
 760                          */
 761                         if (fs.object != fs.first_object) {
 762                                 vm_object_pip_wakeup(fs.object);
 763                                 VM_OBJECT_WUNLOCK(fs.object);
 764
 765                                 fs.object = fs.first_object;
 766                                 fs.pindex = fs.first_pindex;
 767                                 fs.m = fs.first_m;
 768                                 VM_OBJECT_WLOCK(fs.object);
 769                         }
 770                         fs.first_m = NULL;
 771
 772                         /*
 773                          * Zero the page if necessary and mark it valid.
 774                          */
 775                         if ((fs.m->flags & PG_ZERO) == 0) {
 776                                 pmap_zero_page(fs.m);
 777                         } else {
 778                                 PCPU_INC(cnt.v_ozfod);
 779                         }
 780                         PCPU_INC(cnt.v_zfod);
 781                         fs.m->valid = VM_PAGE_BITS_ALL;
 782                         /* Don't try to prefault neighboring pages. */
 783                         faultcount = 1;
 784                         break;  /* break to PAGE HAS BEEN FOUND */
 785                 } else {
 786                         KASSERT(fs.object != next_object,
 787                             ("object loop %p", next_object));
 788                         VM_OBJECT_WLOCK(next_object);
 789                         vm_object_pip_add(next_object, 1);
 790                         if (fs.object != fs.first_object)
 791                                 vm_object_pip_wakeup(fs.object);
 792                         VM_OBJECT_WUNLOCK(fs.object);
 793                         fs.object = next_object;
 794                 }
 795         }
 796
 797         vm_page_assert_xbusied(fs.m);
 798
 799         /*
 800          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
 801          * is held.]
 802          */
 803
 804         /*
 805          * If the page is being written, but isn't already owned by the
 806          * top-level object, we have to copy it into a new page owned by the
 807          * top-level object.
 808          */
 809         if (fs.object != fs.first_object) {
 810                 /*
 811                  * We only really need to copy if we want to write it.
 812                  */
 813                 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
 814                         /*
 815                          * This allows pages to be virtually copied from a
 816                          * backing_object into the first_object, where the
 817                          * backing object has no other refs to it, and cannot
 818                          * gain any more refs.  Instead of a bcopy, we just
 819                          * move the page from the backing object to the
 820                          * first object.  Note that we must mark the page
 821                          * dirty in the first object so that it will go out
 822                          * to swap when needed.
 823                          */
 824                         is_first_object_locked = FALSE;
 825                         if (
 826                                 /*
 827                                  * Only one shadow object
 828                                  */
 829                                 (fs.object->shadow_count == 1) &&
 830                                 /*
 831                                  * No COW refs, except us
 832                                  */
 833                                 (fs.object->ref_count == 1) &&
 834                                 /*
 835                                  * No one else can look this object up
 836                                  */
 837                                 (fs.object->handle == NULL) &&
 838                                 /*
 839                                  * No other ways to look the object up
 840                                  */
 841                                 ((fs.object->type == OBJT_DEFAULT) ||
 842                                  (fs.object->type == OBJT_SWAP)) &&
 843                             (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
 844                                 /*
 845                                  * We don't chase down the shadow chain
 846                                  */
 847                             fs.object == fs.first_object->backing_object) {
 848                                 /*
 849                                  * get rid of the unnecessary page
 850                                  */
 851                                 vm_page_lock(fs.first_m);
 852                                 vm_page_free(fs.first_m);
 853                                 vm_page_unlock(fs.first_m);
 854                                 /*
 855                                  * grab the page and put it into the
 856                                  * process'es object.  The page is
 857                                  * automatically made dirty.
 858                                  */
 859                                 if (vm_page_rename(fs.m, fs.first_object,
 860                                     fs.first_pindex)) {
 861                                         unlock_and_deallocate(&fs);
 862                                         goto RetryFault;
 863                                 }
 864 #if VM_NRESERVLEVEL > 0
 865                                 /*
 866                                  * Rename the reservation.
 867                                  */
 868                                 vm_reserv_rename(fs.m, fs.first_object,
 869                                     fs.object, OFF_TO_IDX(
 870                                     fs.first_object->backing_object_offset));
 871 #endif
 872                                 vm_page_xbusy(fs.m);
 873                                 fs.first_m = fs.m;
 874                                 fs.m = NULL;
 875                                 PCPU_INC(cnt.v_cow_optim);
 876                         } else {
 877                                 /*
 878                                  * Oh, well, lets copy it.
 879                                  */
 880                                 pmap_copy_page(fs.m, fs.first_m);
 881                                 fs.first_m->valid = VM_PAGE_BITS_ALL;
 882                                 if (wired && (fault_flags &
 883                                     VM_FAULT_WIRE) == 0) {
 884                                         vm_page_lock(fs.first_m);
 885                                         vm_page_wire(fs.first_m);
 886                                         vm_page_unlock(fs.first_m);
 887
 888                                         vm_page_lock(fs.m);
 889                                         vm_page_unwire(fs.m, FALSE);
 890                                         vm_page_unlock(fs.m);
 891                                 }
 892                                 /*
 893                                  * We no longer need the old page or object.
 894                                  */
 895                                 release_page(&fs);
 896                         }
 897                         /*
 898                          * fs.object != fs.first_object due to above
 899                          * conditional
 900                          */
 901                         vm_object_pip_wakeup(fs.object);
 902                         VM_OBJECT_WUNLOCK(fs.object);
 903                         /*
 904                          * Only use the new page below...
 905                          */
 906                         fs.object = fs.first_object;
 907                         fs.pindex = fs.first_pindex;
 908                         fs.m = fs.first_m;
 909                         if (!is_first_object_locked)
 910                                 VM_OBJECT_WLOCK(fs.object);
 911                         PCPU_INC(cnt.v_cow_faults);
 912                         curthread->td_cow++;
 913                 } else {
 914                         prot &= ~VM_PROT_WRITE;
 915                 }
 916         }
 917
 918         /*
 919          * We must verify that the maps have not changed since our last
 920          * lookup.
 921          */
 922         if (!fs.lookup_still_valid) {
 923                 vm_object_t retry_object;
 924                 vm_pindex_t retry_pindex;
 925                 vm_prot_t retry_prot;
 926
 927                 if (!vm_map_trylock_read(fs.map)) {
 928                         release_page(&fs);
 929                         unlock_and_deallocate(&fs);
 930                         goto RetryFault;
 931                 }
 932                 fs.lookup_still_valid = TRUE;
 933                 if (fs.map->timestamp != map_generation) {
 934                         result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
 935                             &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
 936
 937                         /*
 938                          * If we don't need the page any longer, put it on the inactive
 939                          * list (the easiest thing to do here).  If no one needs it,
 940                          * pageout will grab it eventually.
 941                          */
 942                         if (result != KERN_SUCCESS) {
 943                                 release_page(&fs);
 944                                 unlock_and_deallocate(&fs);
 945
 946                                 /*
 947                                  * If retry of map lookup would have blocked then
 948                                  * retry fault from start.
 949                                  */
 950                                 if (result == KERN_FAILURE)
 951                                         goto RetryFault;
 952                                 return (result);
 953                         }
 954                         if ((retry_object != fs.first_object) ||
 955                             (retry_pindex != fs.first_pindex)) {
 956                                 release_page(&fs);
 957                                 unlock_and_deallocate(&fs);
 958                                 goto RetryFault;
 959                         }
 960
 961                         /*
 962                          * Check whether the protection has changed or the object has
 963                          * been copied while we left the map unlocked. Changing from
 964                          * read to write permission is OK - we leave the page
 965                          * write-protected, and catch the write fault. Changing from
 966                          * write to read permission means that we can't mark the page
 967                          * write-enabled after all.
 968                          */
 969                         prot &= retry_prot;
 970                 }
 971         }
 972         /*
 973          * If the page was filled by a pager, update the map entry's
 974          * last read offset.  Since the pager does not return the
 975          * actual set of pages that it read, this update is based on
 976          * the requested set.  Typically, the requested and actual
 977          * sets are the same.
 978          *
 979          * XXX The following assignment modifies the map
 980          * without holding a write lock on it.
 981          */
 982         if (hardfault)
 983                 fs.entry->next_read = fs.pindex + faultcount - reqpage;
 984
 985         vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true);
 986         vm_page_assert_xbusied(fs.m);
 987
 988         /*
 989          * Page must be completely valid or it is not fit to
 990          * map into user space.  vm_pager_get_pages() ensures this.
 991          */
 992         KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
 993             ("vm_fault: page %p partially invalid", fs.m));
 994         VM_OBJECT_WUNLOCK(fs.object);
 995
 996         /*
 997          * Put this page into the physical map.  We had to do the unlock above
 998          * because pmap_enter() may sleep.  We don't put the page
 999          * back on the active queue until later so that the pageout daemon
1000          * won't find it (yet).
1001          */
1002         pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
1003             fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
1004         if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 &&
1005             wired == 0)
1006                 vm_fault_prefault(&fs, vaddr, faultcount, reqpage);
1007         VM_OBJECT_WLOCK(fs.object);
1008         vm_page_lock(fs.m);
1009
1010         /*
1011          * If the page is not wired down, then put it where the pageout daemon
1012          * can find it.
1013          */
1014         if ((fault_flags & VM_FAULT_WIRE) != 0) {
1015                 KASSERT(wired, ("VM_FAULT_WIRE && !wired"));
1016                 vm_page_wire(fs.m);
1017         } else
1018                 vm_page_activate(fs.m);
1019         if (m_hold != NULL) {
1020                 *m_hold = fs.m;
1021                 vm_page_hold(fs.m);
1022         }
1023         vm_page_unlock(fs.m);
1024         vm_page_xunbusy(fs.m);
1025
1026         /*
1027          * Unlock everything, and return
1028          */
1029         unlock_and_deallocate(&fs);
1030         if (hardfault) {
1031                 PCPU_INC(cnt.v_io_faults);
1032                 curthread->td_ru.ru_majflt++;
1033         } else
1034                 curthread->td_ru.ru_minflt++;
1035
1036         return (KERN_SUCCESS);
1037 }
1038
1039 /*
1040  * Speed up the reclamation of up to "distance" pages that precede the
1041  * faulting pindex within the first object of the shadow chain.
1042  */
1043 static void
1044 vm_fault_cache_behind(const struct faultstate *fs, int distance)
1045 {
1046         vm_object_t first_object, object;
1047         vm_page_t m, m_prev;
1048         vm_pindex_t pindex;
1049
1050         object = fs->object;
1051         VM_OBJECT_ASSERT_WLOCKED(object);
1052         first_object = fs->first_object;
1053         if (first_object != object) {
1054                 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1055                         VM_OBJECT_WUNLOCK(object);
1056                         VM_OBJECT_WLOCK(first_object);
1057                         VM_OBJECT_WLOCK(object);
1058                 }
1059         }
1060         /* Neither fictitious nor unmanaged pages can be cached. */
1061         if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1062                 if (fs->first_pindex < distance)
1063                         pindex = 0;
1064                 else
1065                         pindex = fs->first_pindex - distance;
1066                 if (pindex < OFF_TO_IDX(fs->entry->offset))
1067                         pindex = OFF_TO_IDX(fs->entry->offset);
1068                 m = first_object != object ? fs->first_m : fs->m;
1069                 vm_page_assert_xbusied(m);
1070                 m_prev = vm_page_prev(m);
1071                 while ((m = m_prev) != NULL && m->pindex >= pindex &&
1072                     m->valid == VM_PAGE_BITS_ALL) {
1073                         m_prev = vm_page_prev(m);
1074                         if (vm_page_busied(m))
1075                                 continue;
1076                         vm_page_lock(m);
1077                         if (m->hold_count == 0 && m->wire_count == 0) {
1078                                 pmap_remove_all(m);
1079                                 vm_page_aflag_clear(m, PGA_REFERENCED);
1080                                 if (m->dirty != 0)
1081                                         vm_page_deactivate(m);
1082                                 else
1083                                         vm_page_cache(m);
1084                         }
1085                         vm_page_unlock(m);
1086                 }
1087         }
1088         if (first_object != object)
1089                 VM_OBJECT_WUNLOCK(first_object);
1090 }
1091
1092 /*
1093  * vm_fault_prefault provides a quick way of clustering
1094  * pagefaults into a processes address space.  It is a "cousin"
1095  * of vm_map_pmap_enter, except it runs at page fault time instead
1096  * of mmap time.
1097  */
1098 static void
1099 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1100     int faultcount, int reqpage)
1101 {
1102         pmap_t pmap;
1103         vm_map_entry_t entry;
1104         vm_object_t backing_object, lobject;
1105         vm_offset_t addr, starta;
1106         vm_pindex_t pindex;
1107         vm_page_t m;
1108         int backward, forward, i;
1109
1110         pmap = fs->map->pmap;
1111         if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1112                 return;
1113
1114         if (faultcount > 0) {
1115                 backward = reqpage;
1116                 forward = faultcount - reqpage - 1;
1117         } else {
1118                 backward = PFBAK;
1119                 forward = PFFOR;
1120         }
1121         entry = fs->entry;
1122
1123         starta = addra - backward * PAGE_SIZE;
1124         if (starta < entry->start) {
1125                 starta = entry->start;
1126         } else if (starta > addra) {
1127                 starta = 0;
1128         }
1129
1130         /*
1131          * Generate the sequence of virtual addresses that are candidates for
1132          * prefaulting in an outward spiral from the faulting virtual address,
1133          * "addra".  Specifically, the sequence is "addra - PAGE_SIZE", "addra
1134          * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1135          * If the candidate address doesn't have a backing physical page, then
1136          * the loop immediately terminates.
1137          */
1138         for (i = 0; i < 2 * imax(backward, forward); i++) {
1139                 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1140                     PAGE_SIZE);
1141                 if (addr > addra + forward * PAGE_SIZE)
1142                         addr = 0;
1143
1144                 if (addr < starta || addr >= entry->end)
1145                         continue;
1146
1147                 if (!pmap_is_prefaultable(pmap, addr))
1148                         continue;
1149
1150                 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1151                 lobject = entry->object.vm_object;
1152                 VM_OBJECT_RLOCK(lobject);
1153                 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1154                     lobject->type == OBJT_DEFAULT &&
1155                     (backing_object = lobject->backing_object) != NULL) {
1156                         KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1157                             0, ("vm_fault_prefault: unaligned object offset"));
1158                         pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1159                         VM_OBJECT_RLOCK(backing_object);
1160                         VM_OBJECT_RUNLOCK(lobject);
1161                         lobject = backing_object;
1162                 }
1163                 if (m == NULL) {
1164                         VM_OBJECT_RUNLOCK(lobject);
1165                         break;
1166                 }
1167                 if (m->valid == VM_PAGE_BITS_ALL &&
1168                     (m->flags & PG_FICTITIOUS) == 0)
1169                         pmap_enter_quick(pmap, addr, m, entry->protection);
1170                 VM_OBJECT_RUNLOCK(lobject);
1171         }
1172 }
1173
1174 /*
1175  * Hold each of the physical pages that are mapped by the specified range of
1176  * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1177  * and allow the specified types of access, "prot".  If all of the implied
1178  * pages are successfully held, then the number of held pages is returned
1179  * together with pointers to those pages in the array "ma".  However, if any
1180  * of the pages cannot be held, -1 is returned.
1181  */
1182 int
1183 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1184     vm_prot_t prot, vm_page_t *ma, int max_count)
1185 {
1186         vm_offset_t end, va;
1187         vm_page_t *mp;
1188         int count;
1189         boolean_t pmap_failed;
1190
1191         if (len == 0)
1192                 return (0);
1193         end = round_page(addr + len);
1194         addr = trunc_page(addr);
1195
1196         /*
1197          * Check for illegal addresses.
1198          */
1199         if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1200                 return (-1);
1201
1202         if (atop(end - addr) > max_count)
1203                 panic("vm_fault_quick_hold_pages: count > max_count");
1204         count = atop(end - addr);
1205
1206         /*
1207          * Most likely, the physical pages are resident in the pmap, so it is
1208          * faster to try pmap_extract_and_hold() first.
1209          */
1210         pmap_failed = FALSE;
1211         for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1212                 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1213                 if (*mp == NULL)
1214                         pmap_failed = TRUE;
1215                 else if ((prot & VM_PROT_WRITE) != 0 &&
1216                     (*mp)->dirty != VM_PAGE_BITS_ALL) {
1217                         /*
1218                          * Explicitly dirty the physical page.  Otherwise, the
1219                          * caller's changes may go unnoticed because they are
1220                          * performed through an unmanaged mapping or by a DMA
1221                          * operation.
1222                          *
1223                          * The object lock is not held here.
1224                          * See vm_page_clear_dirty_mask().
1225                          */
1226                         vm_page_dirty(*mp);
1227                 }
1228         }
1229         if (pmap_failed) {
1230                 /*
1231                  * One or more pages could not be held by the pmap.  Either no
1232                  * page was mapped at the specified virtual address or that
1233                  * mapping had insufficient permissions.  Attempt to fault in
1234                  * and hold these pages.
1235                  */
1236                 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1237                         if (*mp == NULL && vm_fault_hold(map, va, prot,
1238                             VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1239                                 goto error;
1240         }
1241         return (count);
1242 error:
1243         for (mp = ma; mp < ma + count; mp++)
1244                 if (*mp != NULL) {
1245                         vm_page_lock(*mp);
1246                         vm_page_unhold(*mp);
1247                         vm_page_unlock(*mp);
1248                 }
1249         return (-1);
1250 }
1251
1252 /*
1253  *      Routine:
1254  *              vm_fault_copy_entry
1255  *      Function:
1256  *              Create new shadow object backing dst_entry with private copy of
1257  *              all underlying pages. When src_entry is equal to dst_entry,
1258  *              function implements COW for wired-down map entry. Otherwise,
1259  *              it forks wired entry into dst_map.
1260  *
1261  *      In/out conditions:
1262  *              The source and destination maps must be locked for write.
1263  *              The source map entry must be wired down (or be a sharing map
1264  *              entry corresponding to a main map entry that is wired down).
1265  */
1266 void
1267 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1268     vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1269     vm_ooffset_t *fork_charge)
1270 {
1271         vm_object_t backing_object, dst_object, object, src_object;
1272         vm_pindex_t dst_pindex, pindex, src_pindex;
1273         vm_prot_t access, prot;
1274         vm_offset_t vaddr;
1275         vm_page_t dst_m;
1276         vm_page_t src_m;
1277         boolean_t upgrade;
1278
1279 #ifdef  lint
1280         src_map++;
1281 #endif  /* lint */
1282
1283         upgrade = src_entry == dst_entry;
1284         access = prot = dst_entry->protection;
1285
1286         src_object = src_entry->object.vm_object;
1287         src_pindex = OFF_TO_IDX(src_entry->offset);
1288
1289         if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1290                 dst_object = src_object;
1291                 vm_object_reference(dst_object);
1292         } else {
1293                 /*
1294                  * Create the top-level object for the destination entry. (Doesn't
1295                  * actually shadow anything - we copy the pages directly.)
1296                  */
1297                 dst_object = vm_object_allocate(OBJT_DEFAULT,
1298                     OFF_TO_IDX(dst_entry->end - dst_entry->start));
1299 #if VM_NRESERVLEVEL > 0
1300                 dst_object->flags |= OBJ_COLORED;
1301                 dst_object->pg_color = atop(dst_entry->start);
1302 #endif
1303         }
1304
1305         VM_OBJECT_WLOCK(dst_object);
1306         KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1307             ("vm_fault_copy_entry: vm_object not NULL"));
1308         if (src_object != dst_object) {
1309                 dst_entry->object.vm_object = dst_object;
1310                 dst_entry->offset = 0;
1311                 dst_object->charge = dst_entry->end - dst_entry->start;
1312         }
1313         if (fork_charge != NULL) {
1314                 KASSERT(dst_entry->cred == NULL,
1315                     ("vm_fault_copy_entry: leaked swp charge"));
1316                 dst_object->cred = curthread->td_ucred;
1317                 crhold(dst_object->cred);
1318                 *fork_charge += dst_object->charge;
1319         } else if (dst_object->cred == NULL) {
1320                 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1321                     dst_entry));
1322                 dst_object->cred = dst_entry->cred;
1323                 dst_entry->cred = NULL;
1324         }
1325
1326         /*
1327          * If not an upgrade, then enter the mappings in the pmap as
1328          * read and/or execute accesses.  Otherwise, enter them as
1329          * write accesses.
1330          *
1331          * A writeable large page mapping is only created if all of
1332          * the constituent small page mappings are modified. Marking
1333          * PTEs as modified on inception allows promotion to happen
1334          * without taking potentially large number of soft faults.
1335          */
1336         if (!upgrade)
1337                 access &= ~VM_PROT_WRITE;
1338
1339         /*
1340          * Loop through all of the virtual pages within the entry's
1341          * range, copying each page from the source object to the
1342          * destination object.  Since the source is wired, those pages
1343          * must exist.  In contrast, the destination is pageable.
1344          * Since the destination object does share any backing storage
1345          * with the source object, all of its pages must be dirtied,
1346          * regardless of whether they can be written.
1347          */
1348         for (vaddr = dst_entry->start, dst_pindex = 0;
1349             vaddr < dst_entry->end;
1350             vaddr += PAGE_SIZE, dst_pindex++) {
1351 again:
1352                 /*
1353                  * Find the page in the source object, and copy it in.
1354                  * Because the source is wired down, the page will be
1355                  * in memory.
1356                  */
1357                 if (src_object != dst_object)
1358                         VM_OBJECT_RLOCK(src_object);
1359                 object = src_object;
1360                 pindex = src_pindex + dst_pindex;
1361                 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1362                     (backing_object = object->backing_object) != NULL) {
1363                         /*
1364                          * Unless the source mapping is read-only or
1365                          * it is presently being upgraded from
1366                          * read-only, the first object in the shadow
1367                          * chain should provide all of the pages.  In
1368                          * other words, this loop body should never be
1369                          * executed when the source mapping is already
1370                          * read/write.
1371                          */
1372                         KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1373                             upgrade,
1374                             ("vm_fault_copy_entry: main object missing page"));
1375
1376                         VM_OBJECT_RLOCK(backing_object);
1377                         pindex += OFF_TO_IDX(object->backing_object_offset);
1378                         if (object != dst_object)
1379                                 VM_OBJECT_RUNLOCK(object);
1380                         object = backing_object;
1381                 }
1382                 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1383
1384                 if (object != dst_object) {
1385                         /*
1386                          * Allocate a page in the destination object.
1387                          */
1388                         dst_m = vm_page_alloc(dst_object, (src_object ==
1389                             dst_object ? src_pindex : 0) + dst_pindex,
1390                             VM_ALLOC_NORMAL);
1391                         if (dst_m == NULL) {
1392                                 VM_OBJECT_WUNLOCK(dst_object);
1393                                 VM_OBJECT_RUNLOCK(object);
1394                                 VM_WAIT;
1395                                 VM_OBJECT_WLOCK(dst_object);
1396                                 goto again;
1397                         }
1398                         pmap_copy_page(src_m, dst_m);
1399                         VM_OBJECT_RUNLOCK(object);
1400                         dst_m->valid = VM_PAGE_BITS_ALL;
1401                         dst_m->dirty = VM_PAGE_BITS_ALL;
1402                 } else {
1403                         dst_m = src_m;
1404                         if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1405                                 goto again;
1406                         vm_page_xbusy(dst_m);
1407                         KASSERT(dst_m->valid == VM_PAGE_BITS_ALL,
1408                             ("invalid dst page %p", dst_m));
1409                 }
1410                 VM_OBJECT_WUNLOCK(dst_object);
1411
1412                 /*
1413                  * Enter it in the pmap. If a wired, copy-on-write
1414                  * mapping is being replaced by a write-enabled
1415                  * mapping, then wire that new mapping.
1416                  */
1417                 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1418                     access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1419
1420                 /*
1421                  * Mark it no longer busy, and put it on the active list.
1422                  */
1423                 VM_OBJECT_WLOCK(dst_object);
1424
1425                 if (upgrade) {
1426                         if (src_m != dst_m) {
1427                                 vm_page_lock(src_m);
1428                                 vm_page_unwire(src_m, 0);
1429                                 vm_page_unlock(src_m);
1430                                 vm_page_lock(dst_m);
1431                                 vm_page_wire(dst_m);
1432                                 vm_page_unlock(dst_m);
1433                         } else {
1434                                 KASSERT(dst_m->wire_count > 0,
1435                                     ("dst_m %p is not wired", dst_m));
1436                         }
1437                 } else {
1438                         vm_page_lock(dst_m);
1439                         vm_page_activate(dst_m);
1440                         vm_page_unlock(dst_m);
1441                 }
1442                 vm_page_xunbusy(dst_m);
1443         }
1444         VM_OBJECT_WUNLOCK(dst_object);
1445         if (upgrade) {
1446                 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1447                 vm_object_deallocate(src_object);
1448         }
1449 }
1450
1451
1452 /*
1453  * This routine checks around the requested page for other pages that
1454  * might be able to be faulted in.  This routine brackets the viable
1455  * pages for the pages to be paged in.
1456  *
1457  * Inputs:
1458  *      m, rbehind, rahead
1459  *
1460  * Outputs:
1461  *  marray (array of vm_page_t), reqpage (index of requested page)
1462  *
1463  * Return value:
1464  *  number of pages in marray
1465  */
1466 static int
1467 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1468         vm_page_t m;
1469         int rbehind;
1470         int rahead;
1471         vm_page_t *marray;
1472         int *reqpage;
1473 {
1474         int i,j;
1475         vm_object_t object;
1476         vm_pindex_t pindex, startpindex, endpindex, tpindex;
1477         vm_page_t rtm;
1478         int cbehind, cahead;
1479
1480         VM_OBJECT_ASSERT_WLOCKED(m->object);
1481
1482         object = m->object;
1483         pindex = m->pindex;
1484         cbehind = cahead = 0;
1485
1486         /*
1487          * if the requested page is not available, then give up now
1488          */
1489         if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1490                 return 0;
1491         }
1492
1493         if ((cbehind == 0) && (cahead == 0)) {
1494                 *reqpage = 0;
1495                 marray[0] = m;
1496                 return 1;
1497         }
1498
1499         if (rahead > cahead) {
1500                 rahead = cahead;
1501         }
1502
1503         if (rbehind > cbehind) {
1504                 rbehind = cbehind;
1505         }
1506
1507         /*
1508          * scan backward for the read behind pages -- in memory
1509          */
1510         if (pindex > 0) {
1511                 if (rbehind > pindex) {
1512                         rbehind = pindex;
1513                         startpindex = 0;
1514                 } else {
1515                         startpindex = pindex - rbehind;
1516                 }
1517
1518                 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL &&
1519                     rtm->pindex >= startpindex)
1520                         startpindex = rtm->pindex + 1;
1521
1522                 /* tpindex is unsigned; beware of numeric underflow. */
1523                 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex &&
1524                     tpindex < pindex; i++, tpindex--) {
1525
1526                         rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1527                             VM_ALLOC_IFNOTCACHED);
1528                         if (rtm == NULL) {
1529                                 /*
1530                                  * Shift the allocated pages to the
1531                                  * beginning of the array.
1532                                  */
1533                                 for (j = 0; j < i; j++) {
1534                                         marray[j] = marray[j + tpindex + 1 -
1535                                             startpindex];
1536                                 }
1537                                 break;
1538                         }
1539
1540                         marray[tpindex - startpindex] = rtm;
1541                 }
1542         } else {
1543                 startpindex = 0;
1544                 i = 0;
1545         }
1546
1547         marray[i] = m;
1548         /* page offset of the required page */
1549         *reqpage = i;
1550
1551         tpindex = pindex + 1;
1552         i++;
1553
1554         /*
1555          * scan forward for the read ahead pages
1556          */
1557         endpindex = tpindex + rahead;
1558         if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex)
1559                 endpindex = rtm->pindex;
1560         if (endpindex > object->size)
1561                 endpindex = object->size;
1562
1563         for (; tpindex < endpindex; i++, tpindex++) {
1564
1565                 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1566                     VM_ALLOC_IFNOTCACHED);
1567                 if (rtm == NULL) {
1568                         break;
1569                 }
1570
1571                 marray[i] = rtm;
1572         }
1573
1574         /* return number of pages */
1575         return i;
1576 }
1577
1578 /*
1579  * Block entry into the machine-independent layer's page fault handler by
1580  * the calling thread.  Subsequent calls to vm_fault() by that thread will
1581  * return KERN_PROTECTION_FAILURE.  Enable machine-dependent handling of
1582  * spurious page faults.
1583  */
1584 int
1585 vm_fault_disable_pagefaults(void)
1586 {
1587
1588         return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1589 }
1590
1591 void
1592 vm_fault_enable_pagefaults(int save)
1593 {
1594
1595         curthread_pflags_restore(save);
1596 }