sys/vm/vm_fault.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  * Copyright (c) 1994 John S. Dyson
   5  * All rights reserved.
   6  * Copyright (c) 1994 David Greenman
   7  * All rights reserved.
   8  *
   9  *
  10  * This code is derived from software contributed to Berkeley by
  11  * The Mach Operating System project at Carnegie-Mellon University.
  12  *
  13  * Redistribution and use in source and binary forms, with or without
  14  * modification, are permitted provided that the following conditions
  15  * are met:
  16  * 1. Redistributions of source code must retain the above copyright
  17  *    notice, this list of conditions and the following disclaimer.
  18  * 2. Redistributions in binary form must reproduce the above copyright
  19  *    notice, this list of conditions and the following disclaimer in the
  20  *    documentation and/or other materials provided with the distribution.
  21  * 3. All advertising materials mentioning features or use of this software
  22  *    must display the following acknowledgement:
  23  *      This product includes software developed by the University of
  24  *      California, Berkeley and its contributors.
  25  * 4. Neither the name of the University nor the names of its contributors
  26  *    may be used to endorse or promote products derived from this software
  27  *    without specific prior written permission.
  28  *
  29  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  30  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  31  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  32  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  33  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  34  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  35  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  36  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  37  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  38  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  39  * SUCH DAMAGE.
  40  *
  41  *      from: @(#)vm_fault.c    8.4 (Berkeley) 1/12/94
  42  *
  43  *
  44  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
  45  * All rights reserved.
  46  *
  47  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
  48  *
  49  * Permission to use, copy, modify and distribute this software and
  50  * its documentation is hereby granted, provided that both the copyright
  51  * notice and this permission notice appear in all copies of the
  52  * software, derivative works or modified versions, and any portions
  53  * thereof, and that both notices appear in supporting documentation.
  54  *
  55  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  56  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
  57  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  58  *
  59  * Carnegie Mellon requests users of this software to return to
  60  *
  61  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  62  *  School of Computer Science
  63  *  Carnegie Mellon University
  64  *  Pittsburgh PA 15213-3890
  65  *
  66  * any improvements or extensions that they make and grant Carnegie the
  67  * rights to redistribute these changes.
  68  */
  69
  70 /*
  71  *      Page fault handling module.
  72  */
  73
  74 #include <sys/cdefs.h>
  75 __FBSDID("$FreeBSD$");
  76
  77 #include "opt_ktrace.h"
  78 #include "opt_vm.h"
  79
  80 #include <sys/param.h>
  81 #include <sys/systm.h>
  82 #include <sys/kernel.h>
  83 #include <sys/lock.h>
  84 #include <sys/proc.h>
  85 #include <sys/resourcevar.h>
  86 #include <sys/rwlock.h>
  87 #include <sys/sysctl.h>
  88 #include <sys/vmmeter.h>
  89 #include <sys/vnode.h>
  90 #ifdef KTRACE
  91 #include <sys/ktrace.h>
  92 #endif
  93
  94 #include <vm/vm.h>
  95 #include <vm/vm_param.h>
  96 #include <vm/pmap.h>
  97 #include <vm/vm_map.h>
  98 #include <vm/vm_object.h>
  99 #include <vm/vm_page.h>
 100 #include <vm/vm_pageout.h>
 101 #include <vm/vm_kern.h>
 102 #include <vm/vm_pager.h>
 103 #include <vm/vm_extern.h>
 104 #include <vm/vm_reserv.h>
 105
 106 #define PFBAK 4
 107 #define PFFOR 4
 108
 109 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
 110
 111 #define VM_FAULT_READ_BEHIND    8
 112 #define VM_FAULT_READ_MAX       (1 + VM_FAULT_READ_AHEAD_MAX)
 113 #define VM_FAULT_NINCR          (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND)
 114 #define VM_FAULT_SUM            (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2)
 115 #define VM_FAULT_CACHE_BEHIND   (VM_FAULT_READ_BEHIND * VM_FAULT_SUM)
 116
 117 struct faultstate {
 118         vm_page_t m;
 119         vm_object_t object;
 120         vm_pindex_t pindex;
 121         vm_page_t first_m;
 122         vm_object_t     first_object;
 123         vm_pindex_t first_pindex;
 124         vm_map_t map;
 125         vm_map_entry_t entry;
 126         int lookup_still_valid;
 127         struct vnode *vp;
 128 };
 129
 130 static void vm_fault_cache_behind(const struct faultstate *fs, int distance);
 131 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
 132             int faultcount, int reqpage);
 133
 134 static inline void
 135 release_page(struct faultstate *fs)
 136 {
 137
 138         vm_page_xunbusy(fs->m);
 139         vm_page_lock(fs->m);
 140         vm_page_deactivate(fs->m);
 141         vm_page_unlock(fs->m);
 142         fs->m = NULL;
 143 }
 144
 145 static inline void
 146 unlock_map(struct faultstate *fs)
 147 {
 148
 149         if (fs->lookup_still_valid) {
 150                 vm_map_lookup_done(fs->map, fs->entry);
 151                 fs->lookup_still_valid = FALSE;
 152         }
 153 }
 154
 155 static void
 156 unlock_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_WIRE) == 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  *      vm_fault:
 244  *
 245  *      Handle a page fault occurring at the given address,
 246  *      requiring the given permissions, in the map specified.
 247  *      If successful, the page is inserted into the
 248  *      associated physical map.
 249  *
 250  *      NOTE: the given address should be truncated to the
 251  *      proper page address.
 252  *
 253  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 254  *      a standard error specifying why the fault is fatal is returned.
 255  *
 256  *      The map in question must be referenced, and remains so.
 257  *      Caller may hold no locks.
 258  */
 259 int
 260 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 261     int fault_flags)
 262 {
 263         struct thread *td;
 264         int result;
 265
 266         td = curthread;
 267         if ((td->td_pflags & TDP_NOFAULTING) != 0)
 268                 return (KERN_PROTECTION_FAILURE);
 269 #ifdef KTRACE
 270         if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
 271                 ktrfault(vaddr, fault_type);
 272 #endif
 273         result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
 274             NULL);
 275 #ifdef KTRACE
 276         if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
 277                 ktrfaultend(result);
 278 #endif
 279         return (result);
 280 }
 281
 282 int
 283 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 284     int fault_flags, vm_page_t *m_hold)
 285 {
 286         vm_prot_t prot;
 287         long ahead, behind;
 288         int alloc_req, era, faultcount, nera, reqpage, result;
 289         boolean_t growstack, is_first_object_locked, wired;
 290         int map_generation;
 291         vm_object_t next_object;
 292         vm_page_t marray[VM_FAULT_READ_MAX];
 293         int hardfault;
 294         struct faultstate fs;
 295         struct vnode *vp;
 296         vm_page_t m;
 297         int locked, error;
 298
 299         hardfault = 0;
 300         growstack = TRUE;
 301         PCPU_INC(cnt.v_vm_faults);
 302         fs.vp = NULL;
 303         faultcount = reqpage = 0;
 304
 305 RetryFault:;
 306
 307         /*
 308          * Find the backing store object and offset into it to begin the
 309          * search.
 310          */
 311         fs.map = map;
 312         result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
 313             &fs.first_object, &fs.first_pindex, &prot, &wired);
 314         if (result != KERN_SUCCESS) {
 315                 if (growstack && result == KERN_INVALID_ADDRESS &&
 316                     map != kernel_map) {
 317                         result = vm_map_growstack(curproc, vaddr);
 318                         if (result != KERN_SUCCESS)
 319                                 return (KERN_FAILURE);
 320                         growstack = FALSE;
 321                         goto RetryFault;
 322                 }
 323                 return (result);
 324         }
 325
 326         map_generation = fs.map->timestamp;
 327
 328         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 329                 panic("vm_fault: fault on nofault entry, addr: %lx",
 330                     (u_long)vaddr);
 331         }
 332
 333         if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
 334             fs.entry->wiring_thread != curthread) {
 335                 vm_map_unlock_read(fs.map);
 336                 vm_map_lock(fs.map);
 337                 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
 338                     (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
 339                         if (fs.vp != NULL) {
 340                                 vput(fs.vp);
 341                                 fs.vp = NULL;
 342                         }
 343                         fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
 344                         vm_map_unlock_and_wait(fs.map, 0);
 345                 } else
 346                         vm_map_unlock(fs.map);
 347                 goto RetryFault;
 348         }
 349
 350         if (wired)
 351                 fault_type = prot | (fault_type & VM_PROT_COPY);
 352         else
 353                 KASSERT((fault_flags & VM_FAULT_WIRE) == 0,
 354                     ("!wired && VM_FAULT_WIRE"));
 355
 356         if (fs.vp == NULL /* avoid locked vnode leak */ &&
 357             (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 &&
 358             /* avoid calling vm_object_set_writeable_dirty() */
 359             ((prot & VM_PROT_WRITE) == 0 ||
 360             (fs.first_object->type != OBJT_VNODE &&
 361             (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
 362             (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
 363                 VM_OBJECT_RLOCK(fs.first_object);
 364                 if ((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                         goto fast_failed;
 369                 m = vm_page_lookup(fs.first_object, fs.first_pindex);
 370                 /* A busy page can be mapped for read|execute access. */
 371                 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
 372                     vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
 373                         goto fast_failed;
 374                 result = pmap_enter(fs.map->pmap, vaddr, m, prot,
 375                    fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED :
 376                    0), 0);
 377                 if (result != KERN_SUCCESS)
 378                         goto fast_failed;
 379                 if (m_hold != NULL) {
 380                         *m_hold = m;
 381                         vm_page_lock(m);
 382                         vm_page_hold(m);
 383                         vm_page_unlock(m);
 384                 }
 385                 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags,
 386                     FALSE);
 387                 VM_OBJECT_RUNLOCK(fs.first_object);
 388                 if (!wired)
 389                         vm_fault_prefault(&fs, vaddr, 0, 0);
 390                 vm_map_lookup_done(fs.map, fs.entry);
 391                 curthread->td_ru.ru_minflt++;
 392                 return (KERN_SUCCESS);
 393 fast_failed:
 394                 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
 395                         VM_OBJECT_RUNLOCK(fs.first_object);
 396                         VM_OBJECT_WLOCK(fs.first_object);
 397                 }
 398         } else {
 399                 VM_OBJECT_WLOCK(fs.first_object);
 400         }
 401
 402         /*
 403          * Make a reference to this object to prevent its disposal while we
 404          * are messing with it.  Once we have the reference, the map is free
 405          * to be diddled.  Since objects reference their shadows (and copies),
 406          * they will stay around as well.
 407          *
 408          * Bump the paging-in-progress count to prevent size changes (e.g.
 409          * truncation operations) during I/O.  This must be done after
 410          * obtaining the vnode lock in order to avoid possible deadlocks.
 411          */
 412         vm_object_reference_locked(fs.first_object);
 413         vm_object_pip_add(fs.first_object, 1);
 414
 415         fs.lookup_still_valid = TRUE;
 416
 417         fs.first_m = NULL;
 418
 419         /*
 420          * Search for the page at object/offset.
 421          */
 422         fs.object = fs.first_object;
 423         fs.pindex = fs.first_pindex;
 424         while (TRUE) {
 425                 /*
 426                  * If the object is dead, we stop here
 427                  */
 428                 if (fs.object->flags & OBJ_DEAD) {
 429                         unlock_and_deallocate(&fs);
 430                         return (KERN_PROTECTION_FAILURE);
 431                 }
 432
 433                 /*
 434                  * See if page is resident
 435                  */
 436                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 437                 if (fs.m != NULL) {
 438                         /*
 439                          * Wait/Retry if the page is busy.  We have to do this
 440                          * if the page is either exclusive or shared busy
 441                          * because the vm_pager may be using read busy for
 442                          * pageouts (and even pageins if it is the vnode
 443                          * pager), and we could end up trying to pagein and
 444                          * pageout the same page simultaneously.
 445                          *
 446                          * We can theoretically allow the busy case on a read
 447                          * fault if the page is marked valid, but since such
 448                          * pages are typically already pmap'd, putting that
 449                          * special case in might be more effort then it is
 450                          * worth.  We cannot under any circumstances mess
 451                          * around with a shared busied page except, perhaps,
 452                          * to pmap it.
 453                          */
 454                         if (vm_page_busied(fs.m)) {
 455                                 /*
 456                                  * Reference the page before unlocking and
 457                                  * sleeping so that the page daemon is less
 458                                  * likely to reclaim it.
 459                                  */
 460                                 vm_page_aflag_set(fs.m, PGA_REFERENCED);
 461                                 if (fs.object != fs.first_object) {
 462                                         if (!VM_OBJECT_TRYWLOCK(
 463                                             fs.first_object)) {
 464                                                 VM_OBJECT_WUNLOCK(fs.object);
 465                                                 VM_OBJECT_WLOCK(fs.first_object);
 466                                                 VM_OBJECT_WLOCK(fs.object);
 467                                         }
 468                                         vm_page_lock(fs.first_m);
 469                                         vm_page_free(fs.first_m);
 470                                         vm_page_unlock(fs.first_m);
 471                                         vm_object_pip_wakeup(fs.first_object);
 472                                         VM_OBJECT_WUNLOCK(fs.first_object);
 473                                         fs.first_m = NULL;
 474                                 }
 475                                 unlock_map(&fs);
 476                                 if (fs.m == vm_page_lookup(fs.object,
 477                                     fs.pindex)) {
 478                                         vm_page_sleep_if_busy(fs.m, "vmpfw");
 479                                 }
 480                                 vm_object_pip_wakeup(fs.object);
 481                                 VM_OBJECT_WUNLOCK(fs.object);
 482                                 PCPU_INC(cnt.v_intrans);
 483                                 vm_object_deallocate(fs.first_object);
 484                                 goto RetryFault;
 485                         }
 486                         vm_page_lock(fs.m);
 487                         vm_page_remque(fs.m);
 488                         vm_page_unlock(fs.m);
 489
 490                         /*
 491                          * Mark page busy for other processes, and the
 492                          * pagedaemon.  If it still isn't completely valid
 493                          * (readable), jump to readrest, else break-out ( we
 494                          * found the page ).
 495                          */
 496                         vm_page_xbusy(fs.m);
 497                         if (fs.m->valid != VM_PAGE_BITS_ALL)
 498                                 goto readrest;
 499                         break;
 500                 }
 501
 502                 /*
 503                  * Page is not resident.  If this is the search termination
 504                  * or the pager might contain the page, allocate a new page.
 505                  * Default objects are zero-fill, there is no real pager.
 506                  */
 507                 if (fs.object->type != OBJT_DEFAULT ||
 508                     fs.object == fs.first_object) {
 509                         if (fs.pindex >= fs.object->size) {
 510                                 unlock_and_deallocate(&fs);
 511                                 return (KERN_PROTECTION_FAILURE);
 512                         }
 513
 514                         /*
 515                          * Allocate a new page for this object/offset pair.
 516                          *
 517                          * Unlocked read of the p_flag is harmless. At
 518                          * worst, the P_KILLED might be not observed
 519                          * there, and allocation can fail, causing
 520                          * restart and new reading of the p_flag.
 521                          */
 522                         fs.m = NULL;
 523                         if (!vm_page_count_severe() || P_KILLED(curproc)) {
 524 #if VM_NRESERVLEVEL > 0
 525                                 if ((fs.object->flags & OBJ_COLORED) == 0) {
 526                                         fs.object->flags |= OBJ_COLORED;
 527                                         fs.object->pg_color = atop(vaddr) -
 528                                             fs.pindex;
 529                                 }
 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.  For default objects simply provide
 556                  * zero-filled pages.
 557                  */
 558                 if (fs.object->type != OBJT_DEFAULT) {
 559                         int rv;
 560                         u_char behavior = vm_map_entry_behavior(fs.entry);
 561
 562                         if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
 563                             P_KILLED(curproc)) {
 564                                 behind = 0;
 565                                 ahead = 0;
 566                         } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
 567                                 behind = 0;
 568                                 ahead = atop(fs.entry->end - vaddr) - 1;
 569                                 if (ahead > VM_FAULT_READ_AHEAD_MAX)
 570                                         ahead = VM_FAULT_READ_AHEAD_MAX;
 571                                 if (fs.pindex == fs.entry->next_read)
 572                                         vm_fault_cache_behind(&fs,
 573                                             VM_FAULT_READ_MAX);
 574                         } else {
 575                                 /*
 576                                  * If this is a sequential page fault, then
 577                                  * arithmetically increase the number of pages
 578                                  * in the read-ahead window.  Otherwise, reset
 579                                  * the read-ahead window to its smallest size.
 580                                  */
 581                                 behind = atop(vaddr - fs.entry->start);
 582                                 if (behind > VM_FAULT_READ_BEHIND)
 583                                         behind = VM_FAULT_READ_BEHIND;
 584                                 ahead = atop(fs.entry->end - vaddr) - 1;
 585                                 era = fs.entry->read_ahead;
 586                                 if (fs.pindex == fs.entry->next_read) {
 587                                         nera = era + behind;
 588                                         if (nera > VM_FAULT_READ_AHEAD_MAX)
 589                                                 nera = VM_FAULT_READ_AHEAD_MAX;
 590                                         behind = 0;
 591                                         if (ahead > nera)
 592                                                 ahead = nera;
 593                                         if (era == VM_FAULT_READ_AHEAD_MAX)
 594                                                 vm_fault_cache_behind(&fs,
 595                                                     VM_FAULT_CACHE_BEHIND);
 596                                 } else if (ahead > VM_FAULT_READ_AHEAD_MIN)
 597                                         ahead = VM_FAULT_READ_AHEAD_MIN;
 598                                 if (era != ahead)
 599                                         fs.entry->read_ahead = ahead;
 600                         }
 601
 602                         /*
 603                          * Call the pager to retrieve the data, if any, after
 604                          * releasing the lock on the map.  We hold a ref on
 605                          * fs.object and the pages are exclusive busied.
 606                          */
 607                         unlock_map(&fs);
 608
 609                         if (fs.object->type == OBJT_VNODE) {
 610                                 vp = fs.object->handle;
 611                                 if (vp == fs.vp)
 612                                         goto vnode_locked;
 613                                 else if (fs.vp != NULL) {
 614                                         vput(fs.vp);
 615                                         fs.vp = NULL;
 616                                 }
 617                                 locked = VOP_ISLOCKED(vp);
 618
 619                                 if (locked != LK_EXCLUSIVE)
 620                                         locked = LK_SHARED;
 621                                 /* Do not sleep for vnode lock while fs.m is busy */
 622                                 error = vget(vp, locked | LK_CANRECURSE |
 623                                     LK_NOWAIT, curthread);
 624                                 if (error != 0) {
 625                                         vhold(vp);
 626                                         release_page(&fs);
 627                                         unlock_and_deallocate(&fs);
 628                                         error = vget(vp, locked | LK_RETRY |
 629                                             LK_CANRECURSE, curthread);
 630                                         vdrop(vp);
 631                                         fs.vp = vp;
 632                                         KASSERT(error == 0,
 633                                             ("vm_fault: vget failed"));
 634                                         goto RetryFault;
 635                                 }
 636                                 fs.vp = vp;
 637                         }
 638 vnode_locked:
 639                         KASSERT(fs.vp == NULL || !fs.map->system_map,
 640                             ("vm_fault: vnode-backed object mapped by system map"));
 641
 642                         /*
 643                          * now we find out if any other pages should be paged
 644                          * in at this time this routine checks to see if the
 645                          * pages surrounding this fault reside in the same
 646                          * object as the page for this fault.  If they do,
 647                          * then they are faulted in also into the object.  The
 648                          * array "marray" returned contains an array of
 649                          * vm_page_t structs where one of them is the
 650                          * vm_page_t passed to the routine.  The reqpage
 651                          * return value is the index into the marray for the
 652                          * vm_page_t passed to the routine.
 653                          *
 654                          * fs.m plus the additional pages are exclusive busied.
 655                          */
 656                         faultcount = vm_fault_additional_pages(
 657                             fs.m, behind, ahead, marray, &reqpage);
 658
 659                         rv = faultcount ?
 660                             vm_pager_get_pages(fs.object, marray, faultcount,
 661                                 reqpage) : VM_PAGER_FAIL;
 662
 663                         if (rv == VM_PAGER_OK) {
 664                                 /*
 665                                  * Found the page. Leave it busy while we play
 666                                  * with it.
 667                                  */
 668
 669                                 /*
 670                                  * Relookup in case pager changed page. Pager
 671                                  * is responsible for disposition of old page
 672                                  * if moved.
 673                                  */
 674                                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 675                                 if (!fs.m) {
 676                                         unlock_and_deallocate(&fs);
 677                                         goto RetryFault;
 678                                 }
 679
 680                                 hardfault++;
 681                                 break; /* break to PAGE HAS BEEN FOUND */
 682                         }
 683                         /*
 684                          * Remove the bogus page (which does not exist at this
 685                          * object/offset); before doing so, we must get back
 686                          * our object lock to preserve our invariant.
 687                          *
 688                          * Also wake up any other process that may want to bring
 689                          * in this page.
 690                          *
 691                          * If this is the top-level object, we must leave the
 692                          * busy page to prevent another process from rushing
 693                          * past us, and inserting the page in that object at
 694                          * the same time that we are.
 695                          */
 696                         if (rv == VM_PAGER_ERROR)
 697                                 printf("vm_fault: pager read error, pid %d (%s)\n",
 698                                     curproc->p_pid, curproc->p_comm);
 699                         /*
 700                          * Data outside the range of the pager or an I/O error
 701                          */
 702                         /*
 703                          * XXX - the check for kernel_map is a kludge to work
 704                          * around having the machine panic on a kernel space
 705                          * fault w/ I/O error.
 706                          */
 707                         if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
 708                                 (rv == VM_PAGER_BAD)) {
 709                                 vm_page_lock(fs.m);
 710                                 vm_page_free(fs.m);
 711                                 vm_page_unlock(fs.m);
 712                                 fs.m = NULL;
 713                                 unlock_and_deallocate(&fs);
 714                                 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
 715                         }
 716                         if (fs.object != fs.first_object) {
 717                                 vm_page_lock(fs.m);
 718                                 vm_page_free(fs.m);
 719                                 vm_page_unlock(fs.m);
 720                                 fs.m = NULL;
 721                                 /*
 722                                  * XXX - we cannot just fall out at this
 723                                  * point, m has been freed and is invalid!
 724                                  */
 725                         }
 726                 }
 727
 728                 /*
 729                  * We get here if the object has default pager (or unwiring)
 730                  * or the pager doesn't have the page.
 731                  */
 732                 if (fs.object == fs.first_object)
 733                         fs.first_m = fs.m;
 734
 735                 /*
 736                  * Move on to the next object.  Lock the next object before
 737                  * unlocking the current one.
 738                  */
 739                 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
 740                 next_object = fs.object->backing_object;
 741                 if (next_object == NULL) {
 742                         /*
 743                          * If there's no object left, fill the page in the top
 744                          * object with zeros.
 745                          */
 746                         if (fs.object != fs.first_object) {
 747                                 vm_object_pip_wakeup(fs.object);
 748                                 VM_OBJECT_WUNLOCK(fs.object);
 749
 750                                 fs.object = fs.first_object;
 751                                 fs.pindex = fs.first_pindex;
 752                                 fs.m = fs.first_m;
 753                                 VM_OBJECT_WLOCK(fs.object);
 754                         }
 755                         fs.first_m = NULL;
 756
 757                         /*
 758                          * Zero the page if necessary and mark it valid.
 759                          */
 760                         if ((fs.m->flags & PG_ZERO) == 0) {
 761                                 pmap_zero_page(fs.m);
 762                         } else {
 763                                 PCPU_INC(cnt.v_ozfod);
 764                         }
 765                         PCPU_INC(cnt.v_zfod);
 766                         fs.m->valid = VM_PAGE_BITS_ALL;
 767                         /* Don't try to prefault neighboring pages. */
 768                         faultcount = 1;
 769                         break;  /* break to PAGE HAS BEEN FOUND */
 770                 } else {
 771                         KASSERT(fs.object != next_object,
 772                             ("object loop %p", next_object));
 773                         VM_OBJECT_WLOCK(next_object);
 774                         vm_object_pip_add(next_object, 1);
 775                         if (fs.object != fs.first_object)
 776                                 vm_object_pip_wakeup(fs.object);
 777                         VM_OBJECT_WUNLOCK(fs.object);
 778                         fs.object = next_object;
 779                 }
 780         }
 781
 782         vm_page_assert_xbusied(fs.m);
 783
 784         /*
 785          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
 786          * is held.]
 787          */
 788
 789         /*
 790          * If the page is being written, but isn't already owned by the
 791          * top-level object, we have to copy it into a new page owned by the
 792          * top-level object.
 793          */
 794         if (fs.object != fs.first_object) {
 795                 /*
 796                  * We only really need to copy if we want to write it.
 797                  */
 798                 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
 799                         /*
 800                          * This allows pages to be virtually copied from a
 801                          * backing_object into the first_object, where the
 802                          * backing object has no other refs to it, and cannot
 803                          * gain any more refs.  Instead of a bcopy, we just
 804                          * move the page from the backing object to the
 805                          * first object.  Note that we must mark the page
 806                          * dirty in the first object so that it will go out
 807                          * to swap when needed.
 808                          */
 809                         is_first_object_locked = FALSE;
 810                         if (
 811                                 /*
 812                                  * Only one shadow object
 813                                  */
 814                                 (fs.object->shadow_count == 1) &&
 815                                 /*
 816                                  * No COW refs, except us
 817                                  */
 818                                 (fs.object->ref_count == 1) &&
 819                                 /*
 820                                  * No one else can look this object up
 821                                  */
 822                                 (fs.object->handle == NULL) &&
 823                                 /*
 824                                  * No other ways to look the object up
 825                                  */
 826                                 ((fs.object->type == OBJT_DEFAULT) ||
 827                                  (fs.object->type == OBJT_SWAP)) &&
 828                             (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
 829                                 /*
 830                                  * We don't chase down the shadow chain
 831                                  */
 832                             fs.object == fs.first_object->backing_object) {
 833                                 /*
 834                                  * get rid of the unnecessary page
 835                                  */
 836                                 vm_page_lock(fs.first_m);
 837                                 vm_page_free(fs.first_m);
 838                                 vm_page_unlock(fs.first_m);
 839                                 /*
 840                                  * grab the page and put it into the
 841                                  * process'es object.  The page is
 842                                  * automatically made dirty.
 843                                  */
 844                                 if (vm_page_rename(fs.m, fs.first_object,
 845                                     fs.first_pindex)) {
 846                                         unlock_and_deallocate(&fs);
 847                                         goto RetryFault;
 848                                 }
 849 #if VM_NRESERVLEVEL > 0
 850                                 /*
 851                                  * Rename the reservation.
 852                                  */
 853                                 vm_reserv_rename(fs.m, fs.first_object,
 854                                     fs.object, OFF_TO_IDX(
 855                                     fs.first_object->backing_object_offset));
 856 #endif
 857                                 vm_page_xbusy(fs.m);
 858                                 fs.first_m = fs.m;
 859                                 fs.m = NULL;
 860                                 PCPU_INC(cnt.v_cow_optim);
 861                         } else {
 862                                 /*
 863                                  * Oh, well, lets copy it.
 864                                  */
 865                                 pmap_copy_page(fs.m, fs.first_m);
 866                                 fs.first_m->valid = VM_PAGE_BITS_ALL;
 867                                 if (wired && (fault_flags &
 868                                     VM_FAULT_WIRE) == 0) {
 869                                         vm_page_lock(fs.first_m);
 870                                         vm_page_wire(fs.first_m);
 871                                         vm_page_unlock(fs.first_m);
 872
 873                                         vm_page_lock(fs.m);
 874                                         vm_page_unwire(fs.m, FALSE);
 875                                         vm_page_unlock(fs.m);
 876                                 }
 877                                 /*
 878                                  * We no longer need the old page or object.
 879                                  */
 880                                 release_page(&fs);
 881                         }
 882                         /*
 883                          * fs.object != fs.first_object due to above
 884                          * conditional
 885                          */
 886                         vm_object_pip_wakeup(fs.object);
 887                         VM_OBJECT_WUNLOCK(fs.object);
 888                         /*
 889                          * Only use the new page below...
 890                          */
 891                         fs.object = fs.first_object;
 892                         fs.pindex = fs.first_pindex;
 893                         fs.m = fs.first_m;
 894                         if (!is_first_object_locked)
 895                                 VM_OBJECT_WLOCK(fs.object);
 896                         PCPU_INC(cnt.v_cow_faults);
 897                         curthread->td_cow++;
 898                 } else {
 899                         prot &= ~VM_PROT_WRITE;
 900                 }
 901         }
 902
 903         /*
 904          * We must verify that the maps have not changed since our last
 905          * lookup.
 906          */
 907         if (!fs.lookup_still_valid) {
 908                 vm_object_t retry_object;
 909                 vm_pindex_t retry_pindex;
 910                 vm_prot_t retry_prot;
 911
 912                 if (!vm_map_trylock_read(fs.map)) {
 913                         release_page(&fs);
 914                         unlock_and_deallocate(&fs);
 915                         goto RetryFault;
 916                 }
 917                 fs.lookup_still_valid = TRUE;
 918                 if (fs.map->timestamp != map_generation) {
 919                         result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
 920                             &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
 921
 922                         /*
 923                          * If we don't need the page any longer, put it on the inactive
 924                          * list (the easiest thing to do here).  If no one needs it,
 925                          * pageout will grab it eventually.
 926                          */
 927                         if (result != KERN_SUCCESS) {
 928                                 release_page(&fs);
 929                                 unlock_and_deallocate(&fs);
 930
 931                                 /*
 932                                  * If retry of map lookup would have blocked then
 933                                  * retry fault from start.
 934                                  */
 935                                 if (result == KERN_FAILURE)
 936                                         goto RetryFault;
 937                                 return (result);
 938                         }
 939                         if ((retry_object != fs.first_object) ||
 940                             (retry_pindex != fs.first_pindex)) {
 941                                 release_page(&fs);
 942                                 unlock_and_deallocate(&fs);
 943                                 goto RetryFault;
 944                         }
 945
 946                         /*
 947                          * Check whether the protection has changed or the object has
 948                          * been copied while we left the map unlocked. Changing from
 949                          * read to write permission is OK - we leave the page
 950                          * write-protected, and catch the write fault. Changing from
 951                          * write to read permission means that we can't mark the page
 952                          * write-enabled after all.
 953                          */
 954                         prot &= retry_prot;
 955                 }
 956         }
 957         /*
 958          * If the page was filled by a pager, update the map entry's
 959          * last read offset.  Since the pager does not return the
 960          * actual set of pages that it read, this update is based on
 961          * the requested set.  Typically, the requested and actual
 962          * sets are the same.
 963          *
 964          * XXX The following assignment modifies the map
 965          * without holding a write lock on it.
 966          */
 967         if (hardfault)
 968                 fs.entry->next_read = fs.pindex + faultcount - reqpage;
 969
 970         vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE);
 971         vm_page_assert_xbusied(fs.m);
 972
 973         /*
 974          * Page must be completely valid or it is not fit to
 975          * map into user space.  vm_pager_get_pages() ensures this.
 976          */
 977         KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
 978             ("vm_fault: page %p partially invalid", fs.m));
 979         VM_OBJECT_WUNLOCK(fs.object);
 980
 981         /*
 982          * Put this page into the physical map.  We had to do the unlock above
 983          * because pmap_enter() may sleep.  We don't put the page
 984          * back on the active queue until later so that the pageout daemon
 985          * won't find it (yet).
 986          */
 987         pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
 988             fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
 989         if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 &&
 990             wired == 0)
 991                 vm_fault_prefault(&fs, vaddr, faultcount, reqpage);
 992         VM_OBJECT_WLOCK(fs.object);
 993         vm_page_lock(fs.m);
 994
 995         /*
 996          * If the page is not wired down, then put it where the pageout daemon
 997          * can find it.
 998          */
 999         if ((fault_flags & VM_FAULT_WIRE) != 0) {
1000                 KASSERT(wired, ("VM_FAULT_WIRE && !wired"));
1001                 vm_page_wire(fs.m);
1002         } else
1003                 vm_page_activate(fs.m);
1004         if (m_hold != NULL) {
1005                 *m_hold = fs.m;
1006                 vm_page_hold(fs.m);
1007         }
1008         vm_page_unlock(fs.m);
1009         vm_page_xunbusy(fs.m);
1010
1011         /*
1012          * Unlock everything, and return
1013          */
1014         unlock_and_deallocate(&fs);
1015         if (hardfault) {
1016                 PCPU_INC(cnt.v_io_faults);
1017                 curthread->td_ru.ru_majflt++;
1018         } else
1019                 curthread->td_ru.ru_minflt++;
1020
1021         return (KERN_SUCCESS);
1022 }
1023
1024 /*
1025  * Speed up the reclamation of up to "distance" pages that precede the
1026  * faulting pindex within the first object of the shadow chain.
1027  */
1028 static void
1029 vm_fault_cache_behind(const struct faultstate *fs, int distance)
1030 {
1031         vm_object_t first_object, object;
1032         vm_page_t m, m_prev;
1033         vm_pindex_t pindex;
1034
1035         object = fs->object;
1036         VM_OBJECT_ASSERT_WLOCKED(object);
1037         first_object = fs->first_object;
1038         if (first_object != object) {
1039                 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1040                         VM_OBJECT_WUNLOCK(object);
1041                         VM_OBJECT_WLOCK(first_object);
1042                         VM_OBJECT_WLOCK(object);
1043                 }
1044         }
1045         /* Neither fictitious nor unmanaged pages can be cached. */
1046         if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1047                 if (fs->first_pindex < distance)
1048                         pindex = 0;
1049                 else
1050                         pindex = fs->first_pindex - distance;
1051                 if (pindex < OFF_TO_IDX(fs->entry->offset))
1052                         pindex = OFF_TO_IDX(fs->entry->offset);
1053                 m = first_object != object ? fs->first_m : fs->m;
1054                 vm_page_assert_xbusied(m);
1055                 m_prev = vm_page_prev(m);
1056                 while ((m = m_prev) != NULL && m->pindex >= pindex &&
1057                     m->valid == VM_PAGE_BITS_ALL) {
1058                         m_prev = vm_page_prev(m);
1059                         if (vm_page_busied(m))
1060                                 continue;
1061                         vm_page_lock(m);
1062                         if (m->hold_count == 0 && m->wire_count == 0) {
1063                                 pmap_remove_all(m);
1064                                 vm_page_aflag_clear(m, PGA_REFERENCED);
1065                                 if (m->dirty != 0)
1066                                         vm_page_deactivate(m);
1067                                 else
1068                                         vm_page_cache(m);
1069                         }
1070                         vm_page_unlock(m);
1071                 }
1072         }
1073         if (first_object != object)
1074                 VM_OBJECT_WUNLOCK(first_object);
1075 }
1076
1077 /*
1078  * vm_fault_prefault provides a quick way of clustering
1079  * pagefaults into a processes address space.  It is a "cousin"
1080  * of vm_map_pmap_enter, except it runs at page fault time instead
1081  * of mmap time.
1082  */
1083 static void
1084 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1085     int faultcount, int reqpage)
1086 {
1087         pmap_t pmap;
1088         vm_map_entry_t entry;
1089         vm_object_t backing_object, lobject;
1090         vm_offset_t addr, starta;
1091         vm_pindex_t pindex;
1092         vm_page_t m;
1093         int backward, forward, i;
1094
1095         pmap = fs->map->pmap;
1096         if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1097                 return;
1098
1099         if (faultcount > 0) {
1100                 backward = reqpage;
1101                 forward = faultcount - reqpage - 1;
1102         } else {
1103                 backward = PFBAK;
1104                 forward = PFFOR;
1105         }
1106         entry = fs->entry;
1107
1108         starta = addra - backward * PAGE_SIZE;
1109         if (starta < entry->start) {
1110                 starta = entry->start;
1111         } else if (starta > addra) {
1112                 starta = 0;
1113         }
1114
1115         /*
1116          * Generate the sequence of virtual addresses that are candidates for
1117          * prefaulting in an outward spiral from the faulting virtual address,
1118          * "addra".  Specifically, the sequence is "addra - PAGE_SIZE", "addra
1119          * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1120          * If the candidate address doesn't have a backing physical page, then
1121          * the loop immediately terminates.
1122          */
1123         for (i = 0; i < 2 * imax(backward, forward); i++) {
1124                 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1125                     PAGE_SIZE);
1126                 if (addr > addra + forward * PAGE_SIZE)
1127                         addr = 0;
1128
1129                 if (addr < starta || addr >= entry->end)
1130                         continue;
1131
1132                 if (!pmap_is_prefaultable(pmap, addr))
1133                         continue;
1134
1135                 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1136                 lobject = entry->object.vm_object;
1137                 VM_OBJECT_RLOCK(lobject);
1138                 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1139                     lobject->type == OBJT_DEFAULT &&
1140                     (backing_object = lobject->backing_object) != NULL) {
1141                         KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1142                             0, ("vm_fault_prefault: unaligned object offset"));
1143                         pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1144                         VM_OBJECT_RLOCK(backing_object);
1145                         VM_OBJECT_RUNLOCK(lobject);
1146                         lobject = backing_object;
1147                 }
1148                 if (m == NULL) {
1149                         VM_OBJECT_RUNLOCK(lobject);
1150                         break;
1151                 }
1152                 if (m->valid == VM_PAGE_BITS_ALL &&
1153                     (m->flags & PG_FICTITIOUS) == 0)
1154                         pmap_enter_quick(pmap, addr, m, entry->protection);
1155                 VM_OBJECT_RUNLOCK(lobject);
1156         }
1157 }
1158
1159 /*
1160  * Hold each of the physical pages that are mapped by the specified range of
1161  * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1162  * and allow the specified types of access, "prot".  If all of the implied
1163  * pages are successfully held, then the number of held pages is returned
1164  * together with pointers to those pages in the array "ma".  However, if any
1165  * of the pages cannot be held, -1 is returned.
1166  */
1167 int
1168 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1169     vm_prot_t prot, vm_page_t *ma, int max_count)
1170 {
1171         vm_offset_t end, va;
1172         vm_page_t *mp;
1173         int count;
1174         boolean_t pmap_failed;
1175
1176         if (len == 0)
1177                 return (0);
1178         end = round_page(addr + len);
1179         addr = trunc_page(addr);
1180
1181         /*
1182          * Check for illegal addresses.
1183          */
1184         if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1185                 return (-1);
1186
1187         if (atop(end - addr) > max_count)
1188                 panic("vm_fault_quick_hold_pages: count > max_count");
1189         count = atop(end - addr);
1190
1191         /*
1192          * Most likely, the physical pages are resident in the pmap, so it is
1193          * faster to try pmap_extract_and_hold() first.
1194          */
1195         pmap_failed = FALSE;
1196         for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1197                 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1198                 if (*mp == NULL)
1199                         pmap_failed = TRUE;
1200                 else if ((prot & VM_PROT_WRITE) != 0 &&
1201                     (*mp)->dirty != VM_PAGE_BITS_ALL) {
1202                         /*
1203                          * Explicitly dirty the physical page.  Otherwise, the
1204                          * caller's changes may go unnoticed because they are
1205                          * performed through an unmanaged mapping or by a DMA
1206                          * operation.
1207                          *
1208                          * The object lock is not held here.
1209                          * See vm_page_clear_dirty_mask().
1210                          */
1211                         vm_page_dirty(*mp);
1212                 }
1213         }
1214         if (pmap_failed) {
1215                 /*
1216                  * One or more pages could not be held by the pmap.  Either no
1217                  * page was mapped at the specified virtual address or that
1218                  * mapping had insufficient permissions.  Attempt to fault in
1219                  * and hold these pages.
1220                  */
1221                 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1222                         if (*mp == NULL && vm_fault_hold(map, va, prot,
1223                             VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1224                                 goto error;
1225         }
1226         return (count);
1227 error:
1228         for (mp = ma; mp < ma + count; mp++)
1229                 if (*mp != NULL) {
1230                         vm_page_lock(*mp);
1231                         vm_page_unhold(*mp);
1232                         vm_page_unlock(*mp);
1233                 }
1234         return (-1);
1235 }
1236
1237 /*
1238  *      Routine:
1239  *              vm_fault_copy_entry
1240  *      Function:
1241  *              Create new shadow object backing dst_entry with private copy of
1242  *              all underlying pages. When src_entry is equal to dst_entry,
1243  *              function implements COW for wired-down map entry. Otherwise,
1244  *              it forks wired entry into dst_map.
1245  *
1246  *      In/out conditions:
1247  *              The source and destination maps must be locked for write.
1248  *              The source map entry must be wired down (or be a sharing map
1249  *              entry corresponding to a main map entry that is wired down).
1250  */
1251 void
1252 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1253     vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1254     vm_ooffset_t *fork_charge)
1255 {
1256         vm_object_t backing_object, dst_object, object, src_object;
1257         vm_pindex_t dst_pindex, pindex, src_pindex;
1258         vm_prot_t access, prot;
1259         vm_offset_t vaddr;
1260         vm_page_t dst_m;
1261         vm_page_t src_m;
1262         boolean_t upgrade;
1263
1264 #ifdef  lint
1265         src_map++;
1266 #endif  /* lint */
1267
1268         upgrade = src_entry == dst_entry;
1269         access = prot = dst_entry->protection;
1270
1271         src_object = src_entry->object.vm_object;
1272         src_pindex = OFF_TO_IDX(src_entry->offset);
1273
1274         if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1275                 dst_object = src_object;
1276                 vm_object_reference(dst_object);
1277         } else {
1278                 /*
1279                  * Create the top-level object for the destination entry. (Doesn't
1280                  * actually shadow anything - we copy the pages directly.)
1281                  */
1282                 dst_object = vm_object_allocate(OBJT_DEFAULT,
1283                     OFF_TO_IDX(dst_entry->end - dst_entry->start));
1284 #if VM_NRESERVLEVEL > 0
1285                 dst_object->flags |= OBJ_COLORED;
1286                 dst_object->pg_color = atop(dst_entry->start);
1287 #endif
1288         }
1289
1290         VM_OBJECT_WLOCK(dst_object);
1291         KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1292             ("vm_fault_copy_entry: vm_object not NULL"));
1293         if (src_object != dst_object) {
1294                 dst_entry->object.vm_object = dst_object;
1295                 dst_entry->offset = 0;
1296                 dst_object->charge = dst_entry->end - dst_entry->start;
1297         }
1298         if (fork_charge != NULL) {
1299                 KASSERT(dst_entry->cred == NULL,
1300                     ("vm_fault_copy_entry: leaked swp charge"));
1301                 dst_object->cred = curthread->td_ucred;
1302                 crhold(dst_object->cred);
1303                 *fork_charge += dst_object->charge;
1304         } else if (dst_object->cred == NULL) {
1305                 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1306                     dst_entry));
1307                 dst_object->cred = dst_entry->cred;
1308                 dst_entry->cred = NULL;
1309         }
1310
1311         /*
1312          * If not an upgrade, then enter the mappings in the pmap as
1313          * read and/or execute accesses.  Otherwise, enter them as
1314          * write accesses.
1315          *
1316          * A writeable large page mapping is only created if all of
1317          * the constituent small page mappings are modified. Marking
1318          * PTEs as modified on inception allows promotion to happen
1319          * without taking potentially large number of soft faults.
1320          */
1321         if (!upgrade)
1322                 access &= ~VM_PROT_WRITE;
1323
1324         /*
1325          * Loop through all of the virtual pages within the entry's
1326          * range, copying each page from the source object to the
1327          * destination object.  Since the source is wired, those pages
1328          * must exist.  In contrast, the destination is pageable.
1329          * Since the destination object does share any backing storage
1330          * with the source object, all of its pages must be dirtied,
1331          * regardless of whether they can be written.
1332          */
1333         for (vaddr = dst_entry->start, dst_pindex = 0;
1334             vaddr < dst_entry->end;
1335             vaddr += PAGE_SIZE, dst_pindex++) {
1336 again:
1337                 /*
1338                  * Find the page in the source object, and copy it in.
1339                  * Because the source is wired down, the page will be
1340                  * in memory.
1341                  */
1342                 if (src_object != dst_object)
1343                         VM_OBJECT_RLOCK(src_object);
1344                 object = src_object;
1345                 pindex = src_pindex + dst_pindex;
1346                 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1347                     (backing_object = object->backing_object) != NULL) {
1348                         /*
1349                          * Unless the source mapping is read-only or
1350                          * it is presently being upgraded from
1351                          * read-only, the first object in the shadow
1352                          * chain should provide all of the pages.  In
1353                          * other words, this loop body should never be
1354                          * executed when the source mapping is already
1355                          * read/write.
1356                          */
1357                         KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1358                             upgrade,
1359                             ("vm_fault_copy_entry: main object missing page"));
1360
1361                         VM_OBJECT_RLOCK(backing_object);
1362                         pindex += OFF_TO_IDX(object->backing_object_offset);
1363                         if (object != dst_object)
1364                                 VM_OBJECT_RUNLOCK(object);
1365                         object = backing_object;
1366                 }
1367                 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1368
1369                 if (object != dst_object) {
1370                         /*
1371                          * Allocate a page in the destination object.
1372                          */
1373                         dst_m = vm_page_alloc(dst_object, (src_object ==
1374                             dst_object ? src_pindex : 0) + dst_pindex,
1375                             VM_ALLOC_NORMAL);
1376                         if (dst_m == NULL) {
1377                                 VM_OBJECT_WUNLOCK(dst_object);
1378                                 VM_OBJECT_RUNLOCK(object);
1379                                 VM_WAIT;
1380                                 VM_OBJECT_WLOCK(dst_object);
1381                                 goto again;
1382                         }
1383                         pmap_copy_page(src_m, dst_m);
1384                         VM_OBJECT_RUNLOCK(object);
1385                         dst_m->valid = VM_PAGE_BITS_ALL;
1386                         dst_m->dirty = VM_PAGE_BITS_ALL;
1387                 } else {
1388                         dst_m = src_m;
1389                         if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1390                                 goto again;
1391                         vm_page_xbusy(dst_m);
1392                         KASSERT(dst_m->valid == VM_PAGE_BITS_ALL,
1393                             ("invalid dst page %p", dst_m));
1394                 }
1395                 VM_OBJECT_WUNLOCK(dst_object);
1396
1397                 /*
1398                  * Enter it in the pmap. If a wired, copy-on-write
1399                  * mapping is being replaced by a write-enabled
1400                  * mapping, then wire that new mapping.
1401                  */
1402                 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1403                     access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1404
1405                 /*
1406                  * Mark it no longer busy, and put it on the active list.
1407                  */
1408                 VM_OBJECT_WLOCK(dst_object);
1409
1410                 if (upgrade) {
1411                         if (src_m != dst_m) {
1412                                 vm_page_lock(src_m);
1413                                 vm_page_unwire(src_m, 0);
1414                                 vm_page_unlock(src_m);
1415                                 vm_page_lock(dst_m);
1416                                 vm_page_wire(dst_m);
1417                                 vm_page_unlock(dst_m);
1418                         } else {
1419                                 KASSERT(dst_m->wire_count > 0,
1420                                     ("dst_m %p is not wired", dst_m));
1421                         }
1422                 } else {
1423                         vm_page_lock(dst_m);
1424                         vm_page_activate(dst_m);
1425                         vm_page_unlock(dst_m);
1426                 }
1427                 vm_page_xunbusy(dst_m);
1428         }
1429         VM_OBJECT_WUNLOCK(dst_object);
1430         if (upgrade) {
1431                 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1432                 vm_object_deallocate(src_object);
1433         }
1434 }
1435
1436
1437 /*
1438  * This routine checks around the requested page for other pages that
1439  * might be able to be faulted in.  This routine brackets the viable
1440  * pages for the pages to be paged in.
1441  *
1442  * Inputs:
1443  *      m, rbehind, rahead
1444  *
1445  * Outputs:
1446  *  marray (array of vm_page_t), reqpage (index of requested page)
1447  *
1448  * Return value:
1449  *  number of pages in marray
1450  */
1451 static int
1452 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1453         vm_page_t m;
1454         int rbehind;
1455         int rahead;
1456         vm_page_t *marray;
1457         int *reqpage;
1458 {
1459         int i,j;
1460         vm_object_t object;
1461         vm_pindex_t pindex, startpindex, endpindex, tpindex;
1462         vm_page_t rtm;
1463         int cbehind, cahead;
1464
1465         VM_OBJECT_ASSERT_WLOCKED(m->object);
1466
1467         object = m->object;
1468         pindex = m->pindex;
1469         cbehind = cahead = 0;
1470
1471         /*
1472          * if the requested page is not available, then give up now
1473          */
1474         if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1475                 return 0;
1476         }
1477
1478         if ((cbehind == 0) && (cahead == 0)) {
1479                 *reqpage = 0;
1480                 marray[0] = m;
1481                 return 1;
1482         }
1483
1484         if (rahead > cahead) {
1485                 rahead = cahead;
1486         }
1487
1488         if (rbehind > cbehind) {
1489                 rbehind = cbehind;
1490         }
1491
1492         /*
1493          * scan backward for the read behind pages -- in memory
1494          */
1495         if (pindex > 0) {
1496                 if (rbehind > pindex) {
1497                         rbehind = pindex;
1498                         startpindex = 0;
1499                 } else {
1500                         startpindex = pindex - rbehind;
1501                 }
1502
1503                 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL &&
1504                     rtm->pindex >= startpindex)
1505                         startpindex = rtm->pindex + 1;
1506
1507                 /* tpindex is unsigned; beware of numeric underflow. */
1508                 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex &&
1509                     tpindex < pindex; i++, tpindex--) {
1510
1511                         rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1512                             VM_ALLOC_IFNOTCACHED);
1513                         if (rtm == NULL) {
1514                                 /*
1515                                  * Shift the allocated pages to the
1516                                  * beginning of the array.
1517                                  */
1518                                 for (j = 0; j < i; j++) {
1519                                         marray[j] = marray[j + tpindex + 1 -
1520                                             startpindex];
1521                                 }
1522                                 break;
1523                         }
1524
1525                         marray[tpindex - startpindex] = rtm;
1526                 }
1527         } else {
1528                 startpindex = 0;
1529                 i = 0;
1530         }
1531
1532         marray[i] = m;
1533         /* page offset of the required page */
1534         *reqpage = i;
1535
1536         tpindex = pindex + 1;
1537         i++;
1538
1539         /*
1540          * scan forward for the read ahead pages
1541          */
1542         endpindex = tpindex + rahead;
1543         if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex)
1544                 endpindex = rtm->pindex;
1545         if (endpindex > object->size)
1546                 endpindex = object->size;
1547
1548         for (; tpindex < endpindex; i++, tpindex++) {
1549
1550                 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1551                     VM_ALLOC_IFNOTCACHED);
1552                 if (rtm == NULL) {
1553                         break;
1554                 }
1555
1556                 marray[i] = rtm;
1557         }
1558
1559         /* return number of pages */
1560         return i;
1561 }
1562
1563 /*
1564  * Block entry into the machine-independent layer's page fault handler by
1565  * the calling thread.  Subsequent calls to vm_fault() by that thread will
1566  * return KERN_PROTECTION_FAILURE.  Enable machine-dependent handling of
1567  * spurious page faults.
1568  */
1569 int
1570 vm_fault_disable_pagefaults(void)
1571 {
1572
1573         return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1574 }
1575
1576 void
1577 vm_fault_enable_pagefaults(int save)
1578 {
1579
1580         curthread_pflags_restore(save);
1581 }