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/resourcevar.h>
  87 #include <sys/rwlock.h>
  88 #include <sys/sysctl.h>
  89 #include <sys/vmmeter.h>
  90 #include <sys/vnode.h>
  91 #ifdef KTRACE
  92 #include <sys/ktrace.h>
  93 #endif
  94
  95 #include <vm/vm.h>
  96 #include <vm/vm_param.h>
  97 #include <vm/pmap.h>
  98 #include <vm/vm_map.h>
  99 #include <vm/vm_object.h>
 100 #include <vm/vm_page.h>
 101 #include <vm/vm_pageout.h>
 102 #include <vm/vm_kern.h>
 103 #include <vm/vm_pager.h>
 104 #include <vm/vm_extern.h>
 105 #include <vm/vm_reserv.h>
 106
 107 #define PFBAK 4
 108 #define PFFOR 4
 109
 110 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
 111
 112 #define VM_FAULT_READ_BEHIND    8
 113 #define VM_FAULT_READ_DEFAULT   (1 + VM_FAULT_READ_AHEAD_INIT)
 114 #define VM_FAULT_READ_MAX       (1 + VM_FAULT_READ_AHEAD_MAX)
 115 #define VM_FAULT_NINCR          (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND)
 116 #define VM_FAULT_SUM            (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2)
 117
 118 #define VM_FAULT_DONTNEED_MIN   1048576
 119
 120 struct faultstate {
 121         vm_page_t m;
 122         vm_object_t object;
 123         vm_pindex_t pindex;
 124         vm_page_t first_m;
 125         vm_object_t     first_object;
 126         vm_pindex_t first_pindex;
 127         vm_map_t map;
 128         vm_map_entry_t entry;
 129         int lookup_still_valid;
 130         struct vnode *vp;
 131 };
 132
 133 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr,
 134             int ahead);
 135 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
 136             int faultcount, int reqpage);
 137
 138 static inline void
 139 release_page(struct faultstate *fs)
 140 {
 141
 142         vm_page_xunbusy(fs->m);
 143         vm_page_lock(fs->m);
 144         vm_page_deactivate(fs->m);
 145         vm_page_unlock(fs->m);
 146         fs->m = NULL;
 147 }
 148
 149 static inline void
 150 unlock_map(struct faultstate *fs)
 151 {
 152
 153         if (fs->lookup_still_valid) {
 154                 vm_map_lookup_done(fs->map, fs->entry);
 155                 fs->lookup_still_valid = FALSE;
 156         }
 157 }
 158
 159 static void
 160 unlock_and_deallocate(struct faultstate *fs)
 161 {
 162
 163         vm_object_pip_wakeup(fs->object);
 164         VM_OBJECT_WUNLOCK(fs->object);
 165         if (fs->object != fs->first_object) {
 166                 VM_OBJECT_WLOCK(fs->first_object);
 167                 vm_page_lock(fs->first_m);
 168                 vm_page_free(fs->first_m);
 169                 vm_page_unlock(fs->first_m);
 170                 vm_object_pip_wakeup(fs->first_object);
 171                 VM_OBJECT_WUNLOCK(fs->first_object);
 172                 fs->first_m = NULL;
 173         }
 174         vm_object_deallocate(fs->first_object);
 175         unlock_map(fs);
 176         if (fs->vp != NULL) {
 177                 vput(fs->vp);
 178                 fs->vp = NULL;
 179         }
 180 }
 181
 182 static void
 183 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot,
 184     vm_prot_t fault_type, int fault_flags, boolean_t set_wd)
 185 {
 186         boolean_t need_dirty;
 187
 188         if (((prot & VM_PROT_WRITE) == 0 &&
 189             (fault_flags & VM_FAULT_DIRTY) == 0) ||
 190             (m->oflags & VPO_UNMANAGED) != 0)
 191                 return;
 192
 193         VM_OBJECT_ASSERT_LOCKED(m->object);
 194
 195         need_dirty = ((fault_type & VM_PROT_WRITE) != 0 &&
 196             (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) ||
 197             (fault_flags & VM_FAULT_DIRTY) != 0;
 198
 199         if (set_wd)
 200                 vm_object_set_writeable_dirty(m->object);
 201         else
 202                 /*
 203                  * If two callers of vm_fault_dirty() with set_wd ==
 204                  * FALSE, one for the map entry with MAP_ENTRY_NOSYNC
 205                  * flag set, other with flag clear, race, it is
 206                  * possible for the no-NOSYNC thread to see m->dirty
 207                  * != 0 and not clear VPO_NOSYNC.  Take vm_page lock
 208                  * around manipulation of VPO_NOSYNC and
 209                  * vm_page_dirty() call, to avoid the race and keep
 210                  * m->oflags consistent.
 211                  */
 212                 vm_page_lock(m);
 213
 214         /*
 215          * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
 216          * if the page is already dirty to prevent data written with
 217          * the expectation of being synced from not being synced.
 218          * Likewise if this entry does not request NOSYNC then make
 219          * sure the page isn't marked NOSYNC.  Applications sharing
 220          * data should use the same flags to avoid ping ponging.
 221          */
 222         if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) {
 223                 if (m->dirty == 0) {
 224                         m->oflags |= VPO_NOSYNC;
 225                 }
 226         } else {
 227                 m->oflags &= ~VPO_NOSYNC;
 228         }
 229
 230         /*
 231          * If the fault is a write, we know that this page is being
 232          * written NOW so dirty it explicitly to save on
 233          * pmap_is_modified() calls later.
 234          *
 235          * Also tell the backing pager, if any, that it should remove
 236          * any swap backing since the page is now dirty.
 237          */
 238         if (need_dirty)
 239                 vm_page_dirty(m);
 240         if (!set_wd)
 241                 vm_page_unlock(m);
 242         if (need_dirty)
 243                 vm_pager_page_unswapped(m);
 244 }
 245
 246 /*
 247  * TRYPAGER - used by vm_fault to calculate whether the pager for the
 248  *            current object *might* contain the page.
 249  *
 250  *            default objects are zero-fill, there is no real pager.
 251  */
 252 #define TRYPAGER        (fs.object->type != OBJT_DEFAULT && \
 253                         ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 || wired))
 254
 255 /*
 256  *      vm_fault:
 257  *
 258  *      Handle a page fault occurring at the given address,
 259  *      requiring the given permissions, in the map specified.
 260  *      If successful, the page is inserted into the
 261  *      associated physical map.
 262  *
 263  *      NOTE: the given address should be truncated to the
 264  *      proper page address.
 265  *
 266  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 267  *      a standard error specifying why the fault is fatal is returned.
 268  *
 269  *      The map in question must be referenced, and remains so.
 270  *      Caller may hold no locks.
 271  */
 272 int
 273 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 274     int fault_flags)
 275 {
 276         struct thread *td;
 277         int result;
 278
 279         td = curthread;
 280         if ((td->td_pflags & TDP_NOFAULTING) != 0)
 281                 return (KERN_PROTECTION_FAILURE);
 282 #ifdef KTRACE
 283         if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
 284                 ktrfault(vaddr, fault_type);
 285 #endif
 286         result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
 287             NULL);
 288 #ifdef KTRACE
 289         if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
 290                 ktrfaultend(result);
 291 #endif
 292         return (result);
 293 }
 294
 295 int
 296 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 297     int fault_flags, vm_page_t *m_hold)
 298 {
 299         vm_prot_t prot;
 300         int alloc_req, era, faultcount, nera, reqpage, result;
 301         boolean_t growstack, is_first_object_locked, wired;
 302         int map_generation;
 303         vm_object_t next_object;
 304         vm_page_t marray[VM_FAULT_READ_MAX];
 305         int hardfault;
 306         struct faultstate fs;
 307         struct vnode *vp;
 308         vm_page_t m;
 309         int ahead, behind, cluster_offset, error, locked;
 310
 311         hardfault = 0;
 312         growstack = TRUE;
 313         PCPU_INC(cnt.v_vm_faults);
 314         fs.vp = NULL;
 315         faultcount = reqpage = 0;
 316
 317 RetryFault:;
 318
 319         /*
 320          * Find the backing store object and offset into it to begin the
 321          * search.
 322          */
 323         fs.map = map;
 324         result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
 325             &fs.first_object, &fs.first_pindex, &prot, &wired);
 326         if (result != KERN_SUCCESS) {
 327                 if (growstack && result == KERN_INVALID_ADDRESS &&
 328                     map != kernel_map) {
 329                         result = vm_map_growstack(curproc, vaddr);
 330                         if (result != KERN_SUCCESS)
 331                                 return (KERN_FAILURE);
 332                         growstack = FALSE;
 333                         goto RetryFault;
 334                 }
 335                 return (result);
 336         }
 337
 338         map_generation = fs.map->timestamp;
 339
 340         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 341                 panic("vm_fault: fault on nofault entry, addr: %lx",
 342                     (u_long)vaddr);
 343         }
 344
 345         if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
 346             fs.entry->wiring_thread != curthread) {
 347                 vm_map_unlock_read(fs.map);
 348                 vm_map_lock(fs.map);
 349                 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
 350                     (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
 351                         fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
 352                         vm_map_unlock_and_wait(fs.map, 0);
 353                 } else
 354                         vm_map_unlock(fs.map);
 355                 goto RetryFault;
 356         }
 357
 358         if (wired)
 359                 fault_type = prot | (fault_type & VM_PROT_COPY);
 360
 361         if (fs.vp == NULL /* avoid locked vnode leak */ &&
 362             (fault_flags & (VM_FAULT_CHANGE_WIRING | VM_FAULT_DIRTY)) == 0 &&
 363             /* avoid calling vm_object_set_writeable_dirty() */
 364             ((prot & VM_PROT_WRITE) == 0 ||
 365             (fs.first_object->type != OBJT_VNODE &&
 366             (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
 367             (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
 368                 VM_OBJECT_RLOCK(fs.first_object);
 369                 if ((prot & VM_PROT_WRITE) != 0 &&
 370                     (fs.first_object->type == OBJT_VNODE ||
 371                     (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) &&
 372                     (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0)
 373                         goto fast_failed;
 374                 m = vm_page_lookup(fs.first_object, fs.first_pindex);
 375                 /* A busy page can be mapped for read|execute access. */
 376                 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
 377                     vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
 378                         goto fast_failed;
 379                 result = pmap_enter(fs.map->pmap, vaddr, m, prot,
 380                    fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED :
 381                    0), 0);
 382                 if (result != KERN_SUCCESS)
 383                         goto fast_failed;
 384                 if (m_hold != NULL) {
 385                         *m_hold = m;
 386                         vm_page_lock(m);
 387                         vm_page_hold(m);
 388                         vm_page_unlock(m);
 389                 }
 390                 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags,
 391                     FALSE);
 392                 VM_OBJECT_RUNLOCK(fs.first_object);
 393                 if (!wired)
 394                         vm_fault_prefault(&fs, vaddr, 0, 0);
 395                 vm_map_lookup_done(fs.map, fs.entry);
 396                 curthread->td_ru.ru_minflt++;
 397                 return (KERN_SUCCESS);
 398 fast_failed:
 399                 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
 400                         VM_OBJECT_RUNLOCK(fs.first_object);
 401                         VM_OBJECT_WLOCK(fs.first_object);
 402                 }
 403         } else {
 404                 VM_OBJECT_WLOCK(fs.first_object);
 405         }
 406
 407         /*
 408          * Make a reference to this object to prevent its disposal while we
 409          * are messing with it.  Once we have the reference, the map is free
 410          * to be diddled.  Since objects reference their shadows (and copies),
 411          * they will stay around as well.
 412          *
 413          * Bump the paging-in-progress count to prevent size changes (e.g.
 414          * truncation operations) during I/O.  This must be done after
 415          * obtaining the vnode lock in order to avoid possible deadlocks.
 416          */
 417         vm_object_reference_locked(fs.first_object);
 418         vm_object_pip_add(fs.first_object, 1);
 419
 420         fs.lookup_still_valid = TRUE;
 421
 422         fs.first_m = NULL;
 423
 424         /*
 425          * Search for the page at object/offset.
 426          */
 427         fs.object = fs.first_object;
 428         fs.pindex = fs.first_pindex;
 429         while (TRUE) {
 430                 /*
 431                  * If the object is dead, we stop here
 432                  */
 433                 if (fs.object->flags & OBJ_DEAD) {
 434                         unlock_and_deallocate(&fs);
 435                         return (KERN_PROTECTION_FAILURE);
 436                 }
 437
 438                 /*
 439                  * See if page is resident
 440                  */
 441                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 442                 if (fs.m != NULL) {
 443                         /*
 444                          * Wait/Retry if the page is busy.  We have to do this
 445                          * if the page is either exclusive or shared busy
 446                          * because the vm_pager may be using read busy for
 447                          * pageouts (and even pageins if it is the vnode
 448                          * pager), and we could end up trying to pagein and
 449                          * pageout the same page simultaneously.
 450                          *
 451                          * We can theoretically allow the busy case on a read
 452                          * fault if the page is marked valid, but since such
 453                          * pages are typically already pmap'd, putting that
 454                          * special case in might be more effort then it is
 455                          * worth.  We cannot under any circumstances mess
 456                          * around with a shared busied page except, perhaps,
 457                          * to pmap it.
 458                          */
 459                         if (vm_page_busied(fs.m)) {
 460                                 /*
 461                                  * Reference the page before unlocking and
 462                                  * sleeping so that the page daemon is less
 463                                  * likely to reclaim it.
 464                                  */
 465                                 vm_page_aflag_set(fs.m, PGA_REFERENCED);
 466                                 if (fs.object != fs.first_object) {
 467                                         if (!VM_OBJECT_TRYWLOCK(
 468                                             fs.first_object)) {
 469                                                 VM_OBJECT_WUNLOCK(fs.object);
 470                                                 VM_OBJECT_WLOCK(fs.first_object);
 471                                                 VM_OBJECT_WLOCK(fs.object);
 472                                         }
 473                                         vm_page_lock(fs.first_m);
 474                                         vm_page_free(fs.first_m);
 475                                         vm_page_unlock(fs.first_m);
 476                                         vm_object_pip_wakeup(fs.first_object);
 477                                         VM_OBJECT_WUNLOCK(fs.first_object);
 478                                         fs.first_m = NULL;
 479                                 }
 480                                 unlock_map(&fs);
 481                                 if (fs.m == vm_page_lookup(fs.object,
 482                                     fs.pindex)) {
 483                                         vm_page_sleep_if_busy(fs.m, "vmpfw");
 484                                 }
 485                                 vm_object_pip_wakeup(fs.object);
 486                                 VM_OBJECT_WUNLOCK(fs.object);
 487                                 PCPU_INC(cnt.v_intrans);
 488                                 vm_object_deallocate(fs.first_object);
 489                                 goto RetryFault;
 490                         }
 491                         vm_page_lock(fs.m);
 492                         vm_page_remque(fs.m);
 493                         vm_page_unlock(fs.m);
 494
 495                         /*
 496                          * Mark page busy for other processes, and the
 497                          * pagedaemon.  If it still isn't completely valid
 498                          * (readable), jump to readrest, else break-out ( we
 499                          * found the page ).
 500                          */
 501                         vm_page_xbusy(fs.m);
 502                         if (fs.m->valid != VM_PAGE_BITS_ALL)
 503                                 goto readrest;
 504                         break;
 505                 }
 506
 507                 /*
 508                  * Page is not resident, If this is the search termination
 509                  * or the pager might contain the page, allocate a new page.
 510                  */
 511                 if (TRYPAGER || fs.object == fs.first_object) {
 512                         if (fs.pindex >= fs.object->size) {
 513                                 unlock_and_deallocate(&fs);
 514                                 return (KERN_PROTECTION_FAILURE);
 515                         }
 516
 517                         /*
 518                          * Allocate a new page for this object/offset pair.
 519                          *
 520                          * Unlocked read of the p_flag is harmless. At
 521                          * worst, the P_KILLED might be not observed
 522                          * there, and allocation can fail, causing
 523                          * restart and new reading of the p_flag.
 524                          */
 525                         fs.m = NULL;
 526                         if (!vm_page_count_severe() || P_KILLED(curproc)) {
 527 #if VM_NRESERVLEVEL > 0
 528                                 vm_object_color(fs.object, atop(vaddr) -
 529                                     fs.pindex);
 530 #endif
 531                                 alloc_req = P_KILLED(curproc) ?
 532                                     VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
 533                                 if (fs.object->type != OBJT_VNODE &&
 534                                     fs.object->backing_object == NULL)
 535                                         alloc_req |= VM_ALLOC_ZERO;
 536                                 fs.m = vm_page_alloc(fs.object, fs.pindex,
 537                                     alloc_req);
 538                         }
 539                         if (fs.m == NULL) {
 540                                 unlock_and_deallocate(&fs);
 541                                 VM_WAITPFAULT;
 542                                 goto RetryFault;
 543                         } else if (fs.m->valid == VM_PAGE_BITS_ALL)
 544                                 break;
 545                 }
 546
 547 readrest:
 548                 /*
 549                  * We have found a valid page or we have allocated a new page.
 550                  * The page thus may not be valid or may not be entirely
 551                  * valid.
 552                  *
 553                  * Attempt to fault-in the page if there is a chance that the
 554                  * pager has it, and potentially fault in additional pages
 555                  * at the same time.
 556                  */
 557                 if (TRYPAGER) {
 558                         int rv;
 559                         u_char behavior = vm_map_entry_behavior(fs.entry);
 560
 561                         era = fs.entry->read_ahead;
 562                         if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
 563                             P_KILLED(curproc)) {
 564                                 behind = 0;
 565                                 nera = 0;
 566                                 ahead = 0;
 567                         } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
 568                                 behind = 0;
 569                                 nera = VM_FAULT_READ_AHEAD_MAX;
 570                                 ahead = nera;
 571                                 if (fs.pindex == fs.entry->next_read)
 572                                         vm_fault_dontneed(&fs, vaddr, ahead);
 573                         } else if (fs.pindex == fs.entry->next_read) {
 574                                 /*
 575                                  * This is a sequential fault.  Arithmetically
 576                                  * increase the requested number of pages in
 577                                  * the read-ahead window.  The requested
 578                                  * number of pages is "# of sequential faults
 579                                  * x (read ahead min + 1) + read ahead min"
 580                                  */
 581                                 behind = 0;
 582                                 nera = VM_FAULT_READ_AHEAD_MIN;
 583                                 if (era > 0) {
 584                                         nera += era + 1;
 585                                         if (nera > VM_FAULT_READ_AHEAD_MAX)
 586                                                 nera = VM_FAULT_READ_AHEAD_MAX;
 587                                 }
 588                                 ahead = nera;
 589                                 if (era == VM_FAULT_READ_AHEAD_MAX)
 590                                         vm_fault_dontneed(&fs, vaddr, ahead);
 591                         } else {
 592                                 /*
 593                                  * This is a non-sequential fault.  Request a
 594                                  * cluster of pages that is aligned to a
 595                                  * VM_FAULT_READ_DEFAULT page offset boundary
 596                                  * within the object.  Alignment to a page
 597                                  * offset boundary is more likely to coincide
 598                                  * with the underlying file system block than
 599                                  * alignment to a virtual address boundary.
 600                                  */
 601                                 cluster_offset = fs.pindex %
 602                                     VM_FAULT_READ_DEFAULT;
 603                                 behind = ulmin(cluster_offset,
 604                                     atop(vaddr - fs.entry->start));
 605                                 nera = 0;
 606                                 ahead = VM_FAULT_READ_DEFAULT - 1 -
 607                                     cluster_offset;
 608                         }
 609                         ahead = ulmin(ahead, atop(fs.entry->end - vaddr) - 1);
 610                         if (era != nera)
 611                                 fs.entry->read_ahead = nera;
 612
 613                         /*
 614                          * Call the pager to retrieve the data, if any, after
 615                          * releasing the lock on the map.  We hold a ref on
 616                          * fs.object and the pages are exclusive busied.
 617                          */
 618                         unlock_map(&fs);
 619
 620                         if (fs.object->type == OBJT_VNODE) {
 621                                 vp = fs.object->handle;
 622                                 if (vp == fs.vp)
 623                                         goto vnode_locked;
 624                                 else if (fs.vp != NULL) {
 625                                         vput(fs.vp);
 626                                         fs.vp = NULL;
 627                                 }
 628                                 locked = VOP_ISLOCKED(vp);
 629
 630                                 if (locked != LK_EXCLUSIVE)
 631                                         locked = LK_SHARED;
 632                                 /* Do not sleep for vnode lock while fs.m is busy */
 633                                 error = vget(vp, locked | LK_CANRECURSE |
 634                                     LK_NOWAIT, curthread);
 635                                 if (error != 0) {
 636                                         vhold(vp);
 637                                         release_page(&fs);
 638                                         unlock_and_deallocate(&fs);
 639                                         error = vget(vp, locked | LK_RETRY |
 640                                             LK_CANRECURSE, curthread);
 641                                         vdrop(vp);
 642                                         fs.vp = vp;
 643                                         KASSERT(error == 0,
 644                                             ("vm_fault: vget failed"));
 645                                         goto RetryFault;
 646                                 }
 647                                 fs.vp = vp;
 648                         }
 649 vnode_locked:
 650                         KASSERT(fs.vp == NULL || !fs.map->system_map,
 651                             ("vm_fault: vnode-backed object mapped by system map"));
 652
 653                         /*
 654                          * now we find out if any other pages should be paged
 655                          * in at this time this routine checks to see if the
 656                          * pages surrounding this fault reside in the same
 657                          * object as the page for this fault.  If they do,
 658                          * then they are faulted in also into the object.  The
 659                          * array "marray" returned contains an array of
 660                          * vm_page_t structs where one of them is the
 661                          * vm_page_t passed to the routine.  The reqpage
 662                          * return value is the index into the marray for the
 663                          * vm_page_t passed to the routine.
 664                          *
 665                          * fs.m plus the additional pages are exclusive busied.
 666                          */
 667                         faultcount = vm_fault_additional_pages(
 668                             fs.m, behind, ahead, marray, &reqpage);
 669
 670                         rv = faultcount ?
 671                             vm_pager_get_pages(fs.object, marray, faultcount,
 672                                 reqpage) : VM_PAGER_FAIL;
 673
 674                         if (rv == VM_PAGER_OK) {
 675                                 /*
 676                                  * Found the page. Leave it busy while we play
 677                                  * with it.
 678                                  */
 679
 680                                 /*
 681                                  * Relookup in case pager changed page. Pager
 682                                  * is responsible for disposition of old page
 683                                  * if moved.
 684                                  */
 685                                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 686                                 if (!fs.m) {
 687                                         unlock_and_deallocate(&fs);
 688                                         goto RetryFault;
 689                                 }
 690
 691                                 hardfault++;
 692                                 break; /* break to PAGE HAS BEEN FOUND */
 693                         }
 694                         /*
 695                          * Remove the bogus page (which does not exist at this
 696                          * object/offset); before doing so, we must get back
 697                          * our object lock to preserve our invariant.
 698                          *
 699                          * Also wake up any other process that may want to bring
 700                          * in this page.
 701                          *
 702                          * If this is the top-level object, we must leave the
 703                          * busy page to prevent another process from rushing
 704                          * past us, and inserting the page in that object at
 705                          * the same time that we are.
 706                          */
 707                         if (rv == VM_PAGER_ERROR)
 708                                 printf("vm_fault: pager read error, pid %d (%s)\n",
 709                                     curproc->p_pid, curproc->p_comm);
 710                         /*
 711                          * Data outside the range of the pager or an I/O error
 712                          */
 713                         /*
 714                          * XXX - the check for kernel_map is a kludge to work
 715                          * around having the machine panic on a kernel space
 716                          * fault w/ I/O error.
 717                          */
 718                         if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
 719                                 (rv == VM_PAGER_BAD)) {
 720                                 vm_page_lock(fs.m);
 721                                 vm_page_free(fs.m);
 722                                 vm_page_unlock(fs.m);
 723                                 fs.m = NULL;
 724                                 unlock_and_deallocate(&fs);
 725                                 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
 726                         }
 727                         if (fs.object != fs.first_object) {
 728                                 vm_page_lock(fs.m);
 729                                 vm_page_free(fs.m);
 730                                 vm_page_unlock(fs.m);
 731                                 fs.m = NULL;
 732                                 /*
 733                                  * XXX - we cannot just fall out at this
 734                                  * point, m has been freed and is invalid!
 735                                  */
 736                         }
 737                 }
 738
 739                 /*
 740                  * We get here if the object has default pager (or unwiring)
 741                  * or the pager doesn't have the page.
 742                  */
 743                 if (fs.object == fs.first_object)
 744                         fs.first_m = fs.m;
 745
 746                 /*
 747                  * Move on to the next object.  Lock the next object before
 748                  * unlocking the current one.
 749                  */
 750                 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
 751                 next_object = fs.object->backing_object;
 752                 if (next_object == NULL) {
 753                         /*
 754                          * If there's no object left, fill the page in the top
 755                          * object with zeros.
 756                          */
 757                         if (fs.object != fs.first_object) {
 758                                 vm_object_pip_wakeup(fs.object);
 759                                 VM_OBJECT_WUNLOCK(fs.object);
 760
 761                                 fs.object = fs.first_object;
 762                                 fs.pindex = fs.first_pindex;
 763                                 fs.m = fs.first_m;
 764                                 VM_OBJECT_WLOCK(fs.object);
 765                         }
 766                         fs.first_m = NULL;
 767
 768                         /*
 769                          * Zero the page if necessary and mark it valid.
 770                          */
 771                         if ((fs.m->flags & PG_ZERO) == 0) {
 772                                 pmap_zero_page(fs.m);
 773                         } else {
 774                                 PCPU_INC(cnt.v_ozfod);
 775                         }
 776                         PCPU_INC(cnt.v_zfod);
 777                         fs.m->valid = VM_PAGE_BITS_ALL;
 778                         /* Don't try to prefault neighboring pages. */
 779                         faultcount = 1;
 780                         break;  /* break to PAGE HAS BEEN FOUND */
 781                 } else {
 782                         KASSERT(fs.object != next_object,
 783                             ("object loop %p", next_object));
 784                         VM_OBJECT_WLOCK(next_object);
 785                         vm_object_pip_add(next_object, 1);
 786                         if (fs.object != fs.first_object)
 787                                 vm_object_pip_wakeup(fs.object);
 788                         VM_OBJECT_WUNLOCK(fs.object);
 789                         fs.object = next_object;
 790                 }
 791         }
 792
 793         vm_page_assert_xbusied(fs.m);
 794
 795         /*
 796          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
 797          * is held.]
 798          */
 799
 800         /*
 801          * If the page is being written, but isn't already owned by the
 802          * top-level object, we have to copy it into a new page owned by the
 803          * top-level object.
 804          */
 805         if (fs.object != fs.first_object) {
 806                 /*
 807                  * We only really need to copy if we want to write it.
 808                  */
 809                 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
 810                         /*
 811                          * This allows pages to be virtually copied from a
 812                          * backing_object into the first_object, where the
 813                          * backing object has no other refs to it, and cannot
 814                          * gain any more refs.  Instead of a bcopy, we just
 815                          * move the page from the backing object to the
 816                          * first object.  Note that we must mark the page
 817                          * dirty in the first object so that it will go out
 818                          * to swap when needed.
 819                          */
 820                         is_first_object_locked = FALSE;
 821                         if (
 822                                 /*
 823                                  * Only one shadow object
 824                                  */
 825                                 (fs.object->shadow_count == 1) &&
 826                                 /*
 827                                  * No COW refs, except us
 828                                  */
 829                                 (fs.object->ref_count == 1) &&
 830                                 /*
 831                                  * No one else can look this object up
 832                                  */
 833                                 (fs.object->handle == NULL) &&
 834                                 /*
 835                                  * No other ways to look the object up
 836                                  */
 837                                 ((fs.object->type == OBJT_DEFAULT) ||
 838                                  (fs.object->type == OBJT_SWAP)) &&
 839                             (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
 840                                 /*
 841                                  * We don't chase down the shadow chain
 842                                  */
 843                             fs.object == fs.first_object->backing_object) {
 844                                 /*
 845                                  * get rid of the unnecessary page
 846                                  */
 847                                 vm_page_lock(fs.first_m);
 848                                 vm_page_free(fs.first_m);
 849                                 vm_page_unlock(fs.first_m);
 850                                 /*
 851                                  * grab the page and put it into the
 852                                  * process'es object.  The page is
 853                                  * automatically made dirty.
 854                                  */
 855                                 if (vm_page_rename(fs.m, fs.first_object,
 856                                     fs.first_pindex)) {
 857                                         unlock_and_deallocate(&fs);
 858                                         goto RetryFault;
 859                                 }
 860 #if VM_NRESERVLEVEL > 0
 861                                 /*
 862                                  * Rename the reservation.
 863                                  */
 864                                 vm_reserv_rename(fs.m, fs.first_object,
 865                                     fs.object, OFF_TO_IDX(
 866                                     fs.first_object->backing_object_offset));
 867 #endif
 868                                 vm_page_xbusy(fs.m);
 869                                 fs.first_m = fs.m;
 870                                 fs.m = NULL;
 871                                 PCPU_INC(cnt.v_cow_optim);
 872                         } else {
 873                                 /*
 874                                  * Oh, well, lets copy it.
 875                                  */
 876                                 pmap_copy_page(fs.m, fs.first_m);
 877                                 fs.first_m->valid = VM_PAGE_BITS_ALL;
 878                                 if (wired && (fault_flags &
 879                                     VM_FAULT_CHANGE_WIRING) == 0) {
 880                                         vm_page_lock(fs.first_m);
 881                                         vm_page_wire(fs.first_m);
 882                                         vm_page_unlock(fs.first_m);
 883
 884                                         vm_page_lock(fs.m);
 885                                         vm_page_unwire(fs.m, PQ_INACTIVE);
 886                                         vm_page_unlock(fs.m);
 887                                 }
 888                                 /*
 889                                  * We no longer need the old page or object.
 890                                  */
 891                                 release_page(&fs);
 892                         }
 893                         /*
 894                          * fs.object != fs.first_object due to above
 895                          * conditional
 896                          */
 897                         vm_object_pip_wakeup(fs.object);
 898                         VM_OBJECT_WUNLOCK(fs.object);
 899                         /*
 900                          * Only use the new page below...
 901                          */
 902                         fs.object = fs.first_object;
 903                         fs.pindex = fs.first_pindex;
 904                         fs.m = fs.first_m;
 905                         if (!is_first_object_locked)
 906                                 VM_OBJECT_WLOCK(fs.object);
 907                         PCPU_INC(cnt.v_cow_faults);
 908                         curthread->td_cow++;
 909                 } else {
 910                         prot &= ~VM_PROT_WRITE;
 911                 }
 912         }
 913
 914         /*
 915          * We must verify that the maps have not changed since our last
 916          * lookup.
 917          */
 918         if (!fs.lookup_still_valid) {
 919                 vm_object_t retry_object;
 920                 vm_pindex_t retry_pindex;
 921                 vm_prot_t retry_prot;
 922
 923                 if (!vm_map_trylock_read(fs.map)) {
 924                         release_page(&fs);
 925                         unlock_and_deallocate(&fs);
 926                         goto RetryFault;
 927                 }
 928                 fs.lookup_still_valid = TRUE;
 929                 if (fs.map->timestamp != map_generation) {
 930                         result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
 931                             &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
 932
 933                         /*
 934                          * If we don't need the page any longer, put it on the inactive
 935                          * list (the easiest thing to do here).  If no one needs it,
 936                          * pageout will grab it eventually.
 937                          */
 938                         if (result != KERN_SUCCESS) {
 939                                 release_page(&fs);
 940                                 unlock_and_deallocate(&fs);
 941
 942                                 /*
 943                                  * If retry of map lookup would have blocked then
 944                                  * retry fault from start.
 945                                  */
 946                                 if (result == KERN_FAILURE)
 947                                         goto RetryFault;
 948                                 return (result);
 949                         }
 950                         if ((retry_object != fs.first_object) ||
 951                             (retry_pindex != fs.first_pindex)) {
 952                                 release_page(&fs);
 953                                 unlock_and_deallocate(&fs);
 954                                 goto RetryFault;
 955                         }
 956
 957                         /*
 958                          * Check whether the protection has changed or the object has
 959                          * been copied while we left the map unlocked. Changing from
 960                          * read to write permission is OK - we leave the page
 961                          * write-protected, and catch the write fault. Changing from
 962                          * write to read permission means that we can't mark the page
 963                          * write-enabled after all.
 964                          */
 965                         prot &= retry_prot;
 966                 }
 967         }
 968         /*
 969          * If the page was filled by a pager, update the map entry's
 970          * last read offset.  Since the pager does not return the
 971          * actual set of pages that it read, this update is based on
 972          * the requested set.  Typically, the requested and actual
 973          * sets are the same.
 974          *
 975          * XXX The following assignment modifies the map
 976          * without holding a write lock on it.
 977          */
 978         if (hardfault)
 979                 fs.entry->next_read = fs.pindex + faultcount - reqpage;
 980
 981         vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE);
 982         vm_page_assert_xbusied(fs.m);
 983
 984         /*
 985          * Page must be completely valid or it is not fit to
 986          * map into user space.  vm_pager_get_pages() ensures this.
 987          */
 988         KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
 989             ("vm_fault: page %p partially invalid", fs.m));
 990         VM_OBJECT_WUNLOCK(fs.object);
 991
 992         /*
 993          * Put this page into the physical map.  We had to do the unlock above
 994          * because pmap_enter() may sleep.  We don't put the page
 995          * back on the active queue until later so that the pageout daemon
 996          * won't find it (yet).
 997          */
 998         pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
 999             fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
1000         if (faultcount != 1 && (fault_flags & VM_FAULT_CHANGE_WIRING) == 0 &&
1001             wired == 0)
1002                 vm_fault_prefault(&fs, vaddr, faultcount, reqpage);
1003         VM_OBJECT_WLOCK(fs.object);
1004         vm_page_lock(fs.m);
1005
1006         /*
1007          * If the page is not wired down, then put it where the pageout daemon
1008          * can find it.
1009          */
1010         if (fault_flags & VM_FAULT_CHANGE_WIRING) {
1011                 if (wired)
1012                         vm_page_wire(fs.m);
1013                 else
1014                         vm_page_unwire(fs.m, PQ_ACTIVE);
1015         } else
1016                 vm_page_activate(fs.m);
1017         if (m_hold != NULL) {
1018                 *m_hold = fs.m;
1019                 vm_page_hold(fs.m);
1020         }
1021         vm_page_unlock(fs.m);
1022         vm_page_xunbusy(fs.m);
1023
1024         /*
1025          * Unlock everything, and return
1026          */
1027         unlock_and_deallocate(&fs);
1028         if (hardfault) {
1029                 PCPU_INC(cnt.v_io_faults);
1030                 curthread->td_ru.ru_majflt++;
1031         } else
1032                 curthread->td_ru.ru_minflt++;
1033
1034         return (KERN_SUCCESS);
1035 }
1036
1037 /*
1038  * Speed up the reclamation of pages that precede the faulting pindex within
1039  * the first object of the shadow chain.  Essentially, perform the equivalent
1040  * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes
1041  * the faulting pindex by the cluster size when the pages read by vm_fault()
1042  * cross a cluster-size boundary.  The cluster size is the greater of the
1043  * smallest superpage size and VM_FAULT_DONTNEED_MIN.
1044  *
1045  * When "fs->first_object" is a shadow object, the pages in the backing object
1046  * that precede the faulting pindex are deactivated by vm_fault().  So, this
1047  * function must only be concerned with pages in the first object.
1048  */
1049 static void
1050 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
1051 {
1052         vm_map_entry_t entry;
1053         vm_object_t first_object, object;
1054         vm_offset_t end, start;
1055         vm_page_t m, m_next;
1056         vm_pindex_t pend, pstart;
1057         vm_size_t size;
1058
1059         object = fs->object;
1060         VM_OBJECT_ASSERT_WLOCKED(object);
1061         first_object = fs->first_object;
1062         if (first_object != object) {
1063                 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1064                         VM_OBJECT_WUNLOCK(object);
1065                         VM_OBJECT_WLOCK(first_object);
1066                         VM_OBJECT_WLOCK(object);
1067                 }
1068         }
1069         /* Neither fictitious nor unmanaged pages can be reclaimed. */
1070         if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1071                 size = VM_FAULT_DONTNEED_MIN;
1072                 if (MAXPAGESIZES > 1 && size < pagesizes[1])
1073                         size = pagesizes[1];
1074                 end = rounddown2(vaddr, size);
1075                 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) &&
1076                     (entry = fs->entry)->start < end) {
1077                         if (end - entry->start < size)
1078                                 start = entry->start;
1079                         else
1080                                 start = end - size;
1081                         pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED);
1082                         pstart = OFF_TO_IDX(entry->offset) + atop(start -
1083                             entry->start);
1084                         m_next = vm_page_find_least(first_object, pstart);
1085                         pend = OFF_TO_IDX(entry->offset) + atop(end -
1086                             entry->start);
1087                         while ((m = m_next) != NULL && m->pindex < pend) {
1088                                 m_next = TAILQ_NEXT(m, listq);
1089                                 if (m->valid != VM_PAGE_BITS_ALL ||
1090                                     vm_page_busied(m))
1091                                         continue;
1092                                 vm_page_lock(m);
1093                                 if (m->hold_count == 0 && m->wire_count == 0)
1094                                         vm_page_advise(m, MADV_DONTNEED);
1095                                 vm_page_unlock(m);
1096                         }
1097                 }
1098         }
1099         if (first_object != object)
1100                 VM_OBJECT_WUNLOCK(first_object);
1101 }
1102
1103 /*
1104  * vm_fault_prefault provides a quick way of clustering
1105  * pagefaults into a processes address space.  It is a "cousin"
1106  * of vm_map_pmap_enter, except it runs at page fault time instead
1107  * of mmap time.
1108  */
1109 static void
1110 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1111     int faultcount, int reqpage)
1112 {
1113         pmap_t pmap;
1114         vm_map_entry_t entry;
1115         vm_object_t backing_object, lobject;
1116         vm_offset_t addr, starta;
1117         vm_pindex_t pindex;
1118         vm_page_t m;
1119         int backward, forward, i;
1120
1121         pmap = fs->map->pmap;
1122         if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1123                 return;
1124
1125         if (faultcount > 0) {
1126                 backward = reqpage;
1127                 forward = faultcount - reqpage - 1;
1128         } else {
1129                 backward = PFBAK;
1130                 forward = PFFOR;
1131         }
1132         entry = fs->entry;
1133
1134         starta = addra - backward * PAGE_SIZE;
1135         if (starta < entry->start) {
1136                 starta = entry->start;
1137         } else if (starta > addra) {
1138                 starta = 0;
1139         }
1140
1141         /*
1142          * Generate the sequence of virtual addresses that are candidates for
1143          * prefaulting in an outward spiral from the faulting virtual address,
1144          * "addra".  Specifically, the sequence is "addra - PAGE_SIZE", "addra
1145          * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1146          * If the candidate address doesn't have a backing physical page, then
1147          * the loop immediately terminates.
1148          */
1149         for (i = 0; i < 2 * imax(backward, forward); i++) {
1150                 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1151                     PAGE_SIZE);
1152                 if (addr > addra + forward * PAGE_SIZE)
1153                         addr = 0;
1154
1155                 if (addr < starta || addr >= entry->end)
1156                         continue;
1157
1158                 if (!pmap_is_prefaultable(pmap, addr))
1159                         continue;
1160
1161                 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1162                 lobject = entry->object.vm_object;
1163                 VM_OBJECT_RLOCK(lobject);
1164                 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1165                     lobject->type == OBJT_DEFAULT &&
1166                     (backing_object = lobject->backing_object) != NULL) {
1167                         KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1168                             0, ("vm_fault_prefault: unaligned object offset"));
1169                         pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1170                         VM_OBJECT_RLOCK(backing_object);
1171                         VM_OBJECT_RUNLOCK(lobject);
1172                         lobject = backing_object;
1173                 }
1174                 if (m == NULL) {
1175                         VM_OBJECT_RUNLOCK(lobject);
1176                         break;
1177                 }
1178                 if (m->valid == VM_PAGE_BITS_ALL &&
1179                     (m->flags & PG_FICTITIOUS) == 0)
1180                         pmap_enter_quick(pmap, addr, m, entry->protection);
1181                 VM_OBJECT_RUNLOCK(lobject);
1182         }
1183 }
1184
1185 /*
1186  * Hold each of the physical pages that are mapped by the specified range of
1187  * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1188  * and allow the specified types of access, "prot".  If all of the implied
1189  * pages are successfully held, then the number of held pages is returned
1190  * together with pointers to those pages in the array "ma".  However, if any
1191  * of the pages cannot be held, -1 is returned.
1192  */
1193 int
1194 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1195     vm_prot_t prot, vm_page_t *ma, int max_count)
1196 {
1197         vm_offset_t end, va;
1198         vm_page_t *mp;
1199         int count;
1200         boolean_t pmap_failed;
1201
1202         if (len == 0)
1203                 return (0);
1204         end = round_page(addr + len);
1205         addr = trunc_page(addr);
1206
1207         /*
1208          * Check for illegal addresses.
1209          */
1210         if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1211                 return (-1);
1212
1213         if (atop(end - addr) > max_count)
1214                 panic("vm_fault_quick_hold_pages: count > max_count");
1215         count = atop(end - addr);
1216
1217         /*
1218          * Most likely, the physical pages are resident in the pmap, so it is
1219          * faster to try pmap_extract_and_hold() first.
1220          */
1221         pmap_failed = FALSE;
1222         for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1223                 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1224                 if (*mp == NULL)
1225                         pmap_failed = TRUE;
1226                 else if ((prot & VM_PROT_WRITE) != 0 &&
1227                     (*mp)->dirty != VM_PAGE_BITS_ALL) {
1228                         /*
1229                          * Explicitly dirty the physical page.  Otherwise, the
1230                          * caller's changes may go unnoticed because they are
1231                          * performed through an unmanaged mapping or by a DMA
1232                          * operation.
1233                          *
1234                          * The object lock is not held here.
1235                          * See vm_page_clear_dirty_mask().
1236                          */
1237                         vm_page_dirty(*mp);
1238                 }
1239         }
1240         if (pmap_failed) {
1241                 /*
1242                  * One or more pages could not be held by the pmap.  Either no
1243                  * page was mapped at the specified virtual address or that
1244                  * mapping had insufficient permissions.  Attempt to fault in
1245                  * and hold these pages.
1246                  */
1247                 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1248                         if (*mp == NULL && vm_fault_hold(map, va, prot,
1249                             VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1250                                 goto error;
1251         }
1252         return (count);
1253 error:
1254         for (mp = ma; mp < ma + count; mp++)
1255                 if (*mp != NULL) {
1256                         vm_page_lock(*mp);
1257                         vm_page_unhold(*mp);
1258                         vm_page_unlock(*mp);
1259                 }
1260         return (-1);
1261 }
1262
1263 /*
1264  *      Routine:
1265  *              vm_fault_copy_entry
1266  *      Function:
1267  *              Create new shadow object backing dst_entry with private copy of
1268  *              all underlying pages. When src_entry is equal to dst_entry,
1269  *              function implements COW for wired-down map entry. Otherwise,
1270  *              it forks wired entry into dst_map.
1271  *
1272  *      In/out conditions:
1273  *              The source and destination maps must be locked for write.
1274  *              The source map entry must be wired down (or be a sharing map
1275  *              entry corresponding to a main map entry that is wired down).
1276  */
1277 void
1278 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1279     vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1280     vm_ooffset_t *fork_charge)
1281 {
1282         vm_object_t backing_object, dst_object, object, src_object;
1283         vm_pindex_t dst_pindex, pindex, src_pindex;
1284         vm_prot_t access, prot;
1285         vm_offset_t vaddr;
1286         vm_page_t dst_m;
1287         vm_page_t src_m;
1288         boolean_t upgrade;
1289
1290 #ifdef  lint
1291         src_map++;
1292 #endif  /* lint */
1293
1294         upgrade = src_entry == dst_entry;
1295         access = prot = dst_entry->protection;
1296
1297         src_object = src_entry->object.vm_object;
1298         src_pindex = OFF_TO_IDX(src_entry->offset);
1299
1300         if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1301                 dst_object = src_object;
1302                 vm_object_reference(dst_object);
1303         } else {
1304                 /*
1305                  * Create the top-level object for the destination entry. (Doesn't
1306                  * actually shadow anything - we copy the pages directly.)
1307                  */
1308                 dst_object = vm_object_allocate(OBJT_DEFAULT,
1309                     OFF_TO_IDX(dst_entry->end - dst_entry->start));
1310 #if VM_NRESERVLEVEL > 0
1311                 dst_object->flags |= OBJ_COLORED;
1312                 dst_object->pg_color = atop(dst_entry->start);
1313 #endif
1314         }
1315
1316         VM_OBJECT_WLOCK(dst_object);
1317         KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1318             ("vm_fault_copy_entry: vm_object not NULL"));
1319         if (src_object != dst_object) {
1320                 dst_entry->object.vm_object = dst_object;
1321                 dst_entry->offset = 0;
1322                 dst_object->charge = dst_entry->end - dst_entry->start;
1323         }
1324         if (fork_charge != NULL) {
1325                 KASSERT(dst_entry->cred == NULL,
1326                     ("vm_fault_copy_entry: leaked swp charge"));
1327                 dst_object->cred = curthread->td_ucred;
1328                 crhold(dst_object->cred);
1329                 *fork_charge += dst_object->charge;
1330         } else if (dst_object->cred == NULL) {
1331                 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1332                     dst_entry));
1333                 dst_object->cred = dst_entry->cred;
1334                 dst_entry->cred = NULL;
1335         }
1336
1337         /*
1338          * If not an upgrade, then enter the mappings in the pmap as
1339          * read and/or execute accesses.  Otherwise, enter them as
1340          * write accesses.
1341          *
1342          * A writeable large page mapping is only created if all of
1343          * the constituent small page mappings are modified. Marking
1344          * PTEs as modified on inception allows promotion to happen
1345          * without taking potentially large number of soft faults.
1346          */
1347         if (!upgrade)
1348                 access &= ~VM_PROT_WRITE;
1349
1350         /*
1351          * Loop through all of the virtual pages within the entry's
1352          * range, copying each page from the source object to the
1353          * destination object.  Since the source is wired, those pages
1354          * must exist.  In contrast, the destination is pageable.
1355          * Since the destination object does share any backing storage
1356          * with the source object, all of its pages must be dirtied,
1357          * regardless of whether they can be written.
1358          */
1359         for (vaddr = dst_entry->start, dst_pindex = 0;
1360             vaddr < dst_entry->end;
1361             vaddr += PAGE_SIZE, dst_pindex++) {
1362 again:
1363                 /*
1364                  * Find the page in the source object, and copy it in.
1365                  * Because the source is wired down, the page will be
1366                  * in memory.
1367                  */
1368                 if (src_object != dst_object)
1369                         VM_OBJECT_RLOCK(src_object);
1370                 object = src_object;
1371                 pindex = src_pindex + dst_pindex;
1372                 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1373                     (backing_object = object->backing_object) != NULL) {
1374                         /*
1375                          * Unless the source mapping is read-only or
1376                          * it is presently being upgraded from
1377                          * read-only, the first object in the shadow
1378                          * chain should provide all of the pages.  In
1379                          * other words, this loop body should never be
1380                          * executed when the source mapping is already
1381                          * read/write.
1382                          */
1383                         KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1384                             upgrade,
1385                             ("vm_fault_copy_entry: main object missing page"));
1386
1387                         VM_OBJECT_RLOCK(backing_object);
1388                         pindex += OFF_TO_IDX(object->backing_object_offset);
1389                         if (object != dst_object)
1390                                 VM_OBJECT_RUNLOCK(object);
1391                         object = backing_object;
1392                 }
1393                 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1394
1395                 if (object != dst_object) {
1396                         /*
1397                          * Allocate a page in the destination object.
1398                          */
1399                         dst_m = vm_page_alloc(dst_object, (src_object ==
1400                             dst_object ? src_pindex : 0) + dst_pindex,
1401                             VM_ALLOC_NORMAL);
1402                         if (dst_m == NULL) {
1403                                 VM_OBJECT_WUNLOCK(dst_object);
1404                                 VM_OBJECT_RUNLOCK(object);
1405                                 VM_WAIT;
1406                                 VM_OBJECT_WLOCK(dst_object);
1407                                 goto again;
1408                         }
1409                         pmap_copy_page(src_m, dst_m);
1410                         VM_OBJECT_RUNLOCK(object);
1411                         dst_m->valid = VM_PAGE_BITS_ALL;
1412                         dst_m->dirty = VM_PAGE_BITS_ALL;
1413                 } else {
1414                         dst_m = src_m;
1415                         if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1416                                 goto again;
1417                         vm_page_xbusy(dst_m);
1418                         KASSERT(dst_m->valid == VM_PAGE_BITS_ALL,
1419                             ("invalid dst page %p", dst_m));
1420                 }
1421                 VM_OBJECT_WUNLOCK(dst_object);
1422
1423                 /*
1424                  * Enter it in the pmap. If a wired, copy-on-write
1425                  * mapping is being replaced by a write-enabled
1426                  * mapping, then wire that new mapping.
1427                  */
1428                 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1429                     access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1430
1431                 /*
1432                  * Mark it no longer busy, and put it on the active list.
1433                  */
1434                 VM_OBJECT_WLOCK(dst_object);
1435
1436                 if (upgrade) {
1437                         if (src_m != dst_m) {
1438                                 vm_page_lock(src_m);
1439                                 vm_page_unwire(src_m, PQ_INACTIVE);
1440                                 vm_page_unlock(src_m);
1441                                 vm_page_lock(dst_m);
1442                                 vm_page_wire(dst_m);
1443                                 vm_page_unlock(dst_m);
1444                         } else {
1445                                 KASSERT(dst_m->wire_count > 0,
1446                                     ("dst_m %p is not wired", dst_m));
1447                         }
1448                 } else {
1449                         vm_page_lock(dst_m);
1450                         vm_page_activate(dst_m);
1451                         vm_page_unlock(dst_m);
1452                 }
1453                 vm_page_xunbusy(dst_m);
1454         }
1455         VM_OBJECT_WUNLOCK(dst_object);
1456         if (upgrade) {
1457                 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1458                 vm_object_deallocate(src_object);
1459         }
1460 }
1461
1462
1463 /*
1464  * This routine checks around the requested page for other pages that
1465  * might be able to be faulted in.  This routine brackets the viable
1466  * pages for the pages to be paged in.
1467  *
1468  * Inputs:
1469  *      m, rbehind, rahead
1470  *
1471  * Outputs:
1472  *  marray (array of vm_page_t), reqpage (index of requested page)
1473  *
1474  * Return value:
1475  *  number of pages in marray
1476  */
1477 static int
1478 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1479         vm_page_t m;
1480         int rbehind;
1481         int rahead;
1482         vm_page_t *marray;
1483         int *reqpage;
1484 {
1485         int i,j;
1486         vm_object_t object;
1487         vm_pindex_t pindex, startpindex, endpindex, tpindex;
1488         vm_page_t rtm;
1489         int cbehind, cahead;
1490
1491         VM_OBJECT_ASSERT_WLOCKED(m->object);
1492
1493         object = m->object;
1494         pindex = m->pindex;
1495         cbehind = cahead = 0;
1496
1497         /*
1498          * if the requested page is not available, then give up now
1499          */
1500         if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1501                 return 0;
1502         }
1503
1504         if ((cbehind == 0) && (cahead == 0)) {
1505                 *reqpage = 0;
1506                 marray[0] = m;
1507                 return 1;
1508         }
1509
1510         if (rahead > cahead) {
1511                 rahead = cahead;
1512         }
1513
1514         if (rbehind > cbehind) {
1515                 rbehind = cbehind;
1516         }
1517
1518         /*
1519          * scan backward for the read behind pages -- in memory
1520          */
1521         if (pindex > 0) {
1522                 if (rbehind > pindex) {
1523                         rbehind = pindex;
1524                         startpindex = 0;
1525                 } else {
1526                         startpindex = pindex - rbehind;
1527                 }
1528
1529                 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL &&
1530                     rtm->pindex >= startpindex)
1531                         startpindex = rtm->pindex + 1;
1532
1533                 /* tpindex is unsigned; beware of numeric underflow. */
1534                 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex &&
1535                     tpindex < pindex; i++, tpindex--) {
1536
1537                         rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1538                             VM_ALLOC_IFNOTCACHED);
1539                         if (rtm == NULL) {
1540                                 /*
1541                                  * Shift the allocated pages to the
1542                                  * beginning of the array.
1543                                  */
1544                                 for (j = 0; j < i; j++) {
1545                                         marray[j] = marray[j + tpindex + 1 -
1546                                             startpindex];
1547                                 }
1548                                 break;
1549                         }
1550
1551                         marray[tpindex - startpindex] = rtm;
1552                 }
1553         } else {
1554                 startpindex = 0;
1555                 i = 0;
1556         }
1557
1558         marray[i] = m;
1559         /* page offset of the required page */
1560         *reqpage = i;
1561
1562         tpindex = pindex + 1;
1563         i++;
1564
1565         /*
1566          * scan forward for the read ahead pages
1567          */
1568         endpindex = tpindex + rahead;
1569         if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex)
1570                 endpindex = rtm->pindex;
1571         if (endpindex > object->size)
1572                 endpindex = object->size;
1573
1574         for (; tpindex < endpindex; i++, tpindex++) {
1575
1576                 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1577                     VM_ALLOC_IFNOTCACHED);
1578                 if (rtm == NULL) {
1579                         break;
1580                 }
1581
1582                 marray[i] = rtm;
1583         }
1584
1585         /* return number of pages */
1586         return i;
1587 }
1588
1589 /*
1590  * Block entry into the machine-independent layer's page fault handler by
1591  * the calling thread.  Subsequent calls to vm_fault() by that thread will
1592  * return KERN_PROTECTION_FAILURE.  Enable machine-dependent handling of
1593  * spurious page faults.
1594  */
1595 int
1596 vm_fault_disable_pagefaults(void)
1597 {
1598
1599         return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1600 }
1601
1602 void
1603 vm_fault_enable_pagefaults(int save)
1604 {
1605
1606         curthread_pflags_restore(save);
1607 }