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