sys/vm/vm_fault.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  * Copyright (c) 1994 John S. Dyson
   5  * All rights reserved.
   6  * Copyright (c) 1994 David Greenman
   7  * All rights reserved.
   8  *
   9  *
  10  * This code is derived from software contributed to Berkeley by
  11  * The Mach Operating System project at Carnegie-Mellon University.
  12  *
  13  * Redistribution and use in source and binary forms, with or without
  14  * modification, are permitted provided that the following conditions
  15  * are met:
  16  * 1. Redistributions of source code must retain the above copyright
  17  *    notice, this list of conditions and the following disclaimer.
  18  * 2. Redistributions in binary form must reproduce the above copyright
  19  *    notice, this list of conditions and the following disclaimer in the
  20  *    documentation and/or other materials provided with the distribution.
  21  * 3. All advertising materials mentioning features or use of this software
  22  *    must display the following acknowledgement:
  23  *      This product includes software developed by the University of
  24  *      California, Berkeley and its contributors.
  25  * 4. Neither the name of the University nor the names of its contributors
  26  *    may be used to endorse or promote products derived from this software
  27  *    without specific prior written permission.
  28  *
  29  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  30  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  31  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  32  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  33  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  34  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  35  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  36  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  37  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  38  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  39  * SUCH DAMAGE.
  40  *
  41  *      from: @(#)vm_fault.c    8.4 (Berkeley) 1/12/94
  42  *
  43  *
  44  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
  45  * All rights reserved.
  46  *
  47  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
  48  *
  49  * Permission to use, copy, modify and distribute this software and
  50  * its documentation is hereby granted, provided that both the copyright
  51  * notice and this permission notice appear in all copies of the
  52  * software, derivative works or modified versions, and any portions
  53  * thereof, and that both notices appear in supporting documentation.
  54  *
  55  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  56  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
  57  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  58  *
  59  * Carnegie Mellon requests users of this software to return to
  60  *
  61  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  62  *  School of Computer Science
  63  *  Carnegie Mellon University
  64  *  Pittsburgh PA 15213-3890
  65  *
  66  * any improvements or extensions that they make and grant Carnegie the
  67  * rights to redistribute these changes.
  68  */
  69
  70 /*
  71  *      Page fault handling module.
  72  */
  73
  74 #include <sys/cdefs.h>
  75 __FBSDID("$FreeBSD$");
  76
  77 #include "opt_ktrace.h"
  78 #include "opt_vm.h"
  79
  80 #include <sys/param.h>
  81 #include <sys/systm.h>
  82 #include <sys/kernel.h>
  83 #include <sys/lock.h>
  84 #include <sys/mman.h>
  85 #include <sys/proc.h>
  86 #include <sys/resourcevar.h>
  87 #include <sys/rwlock.h>
  88 #include <sys/sysctl.h>
  89 #include <sys/vmmeter.h>
  90 #include <sys/vnode.h>
  91 #ifdef KTRACE
  92 #include <sys/ktrace.h>
  93 #endif
  94
  95 #include <vm/vm.h>
  96 #include <vm/vm_param.h>
  97 #include <vm/pmap.h>
  98 #include <vm/vm_map.h>
  99 #include <vm/vm_object.h>
 100 #include <vm/vm_page.h>
 101 #include <vm/vm_pageout.h>
 102 #include <vm/vm_kern.h>
 103 #include <vm/vm_pager.h>
 104 #include <vm/vm_extern.h>
 105 #include <vm/vm_reserv.h>
 106
 107 #define PFBAK 4
 108 #define PFFOR 4
 109
 110 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
 111
 112 #define VM_FAULT_READ_BEHIND    8
 113 #define VM_FAULT_READ_DEFAULT   (1 + VM_FAULT_READ_AHEAD_INIT)
 114 #define VM_FAULT_READ_MAX       (1 + VM_FAULT_READ_AHEAD_MAX)
 115 #define VM_FAULT_NINCR          (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND)
 116 #define VM_FAULT_SUM            (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2)
 117
 118 #define VM_FAULT_DONTNEED_MIN   1048576
 119
 120 struct faultstate {
 121         vm_page_t m;
 122         vm_object_t object;
 123         vm_pindex_t pindex;
 124         vm_page_t first_m;
 125         vm_object_t     first_object;
 126         vm_pindex_t first_pindex;
 127         vm_map_t map;
 128         vm_map_entry_t entry;
 129         int lookup_still_valid;
 130         struct vnode *vp;
 131 };
 132
 133 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr,
 134             int ahead);
 135 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
 136             int faultcount, int reqpage);
 137
 138 static inline void
 139 release_page(struct faultstate *fs)
 140 {
 141
 142         vm_page_xunbusy(fs->m);
 143         vm_page_lock(fs->m);
 144         vm_page_deactivate(fs->m);
 145         vm_page_unlock(fs->m);
 146         fs->m = NULL;
 147 }
 148
 149 static inline void
 150 unlock_map(struct faultstate *fs)
 151 {
 152
 153         if (fs->lookup_still_valid) {
 154                 vm_map_lookup_done(fs->map, fs->entry);
 155                 fs->lookup_still_valid = FALSE;
 156         }
 157 }
 158
 159 static void
 160 unlock_and_deallocate(struct faultstate *fs)
 161 {
 162
 163         vm_object_pip_wakeup(fs->object);
 164         VM_OBJECT_WUNLOCK(fs->object);
 165         if (fs->object != fs->first_object) {
 166                 VM_OBJECT_WLOCK(fs->first_object);
 167                 vm_page_lock(fs->first_m);
 168                 vm_page_free(fs->first_m);
 169                 vm_page_unlock(fs->first_m);
 170                 vm_object_pip_wakeup(fs->first_object);
 171                 VM_OBJECT_WUNLOCK(fs->first_object);
 172                 fs->first_m = NULL;
 173         }
 174         vm_object_deallocate(fs->first_object);
 175         unlock_map(fs);
 176         if (fs->vp != NULL) {
 177                 vput(fs->vp);
 178                 fs->vp = NULL;
 179         }
 180 }
 181
 182 static void
 183 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot,
 184     vm_prot_t fault_type, int fault_flags, boolean_t set_wd)
 185 {
 186         boolean_t need_dirty;
 187
 188         if (((prot & VM_PROT_WRITE) == 0 &&
 189             (fault_flags & VM_FAULT_DIRTY) == 0) ||
 190             (m->oflags & VPO_UNMANAGED) != 0)
 191                 return;
 192
 193         VM_OBJECT_ASSERT_LOCKED(m->object);
 194
 195         need_dirty = ((fault_type & VM_PROT_WRITE) != 0 &&
 196             (fault_flags & VM_FAULT_WIRE) == 0) ||
 197             (fault_flags & VM_FAULT_DIRTY) != 0;
 198
 199         if (set_wd)
 200                 vm_object_set_writeable_dirty(m->object);
 201         else
 202                 /*
 203                  * If two callers of vm_fault_dirty() with set_wd ==
 204                  * FALSE, one for the map entry with MAP_ENTRY_NOSYNC
 205                  * flag set, other with flag clear, race, it is
 206                  * possible for the no-NOSYNC thread to see m->dirty
 207                  * != 0 and not clear VPO_NOSYNC.  Take vm_page lock
 208                  * around manipulation of VPO_NOSYNC and
 209                  * vm_page_dirty() call, to avoid the race and keep
 210                  * m->oflags consistent.
 211                  */
 212                 vm_page_lock(m);
 213
 214         /*
 215          * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
 216          * if the page is already dirty to prevent data written with
 217          * the expectation of being synced from not being synced.
 218          * Likewise if this entry does not request NOSYNC then make
 219          * sure the page isn't marked NOSYNC.  Applications sharing
 220          * data should use the same flags to avoid ping ponging.
 221          */
 222         if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) {
 223                 if (m->dirty == 0) {
 224                         m->oflags |= VPO_NOSYNC;
 225                 }
 226         } else {
 227                 m->oflags &= ~VPO_NOSYNC;
 228         }
 229
 230         /*
 231          * If the fault is a write, we know that this page is being
 232          * written NOW so dirty it explicitly to save on
 233          * pmap_is_modified() calls later.
 234          *
 235          * Also tell the backing pager, if any, that it should remove
 236          * any swap backing since the page is now dirty.
 237          */
 238         if (need_dirty)
 239                 vm_page_dirty(m);
 240         if (!set_wd)
 241                 vm_page_unlock(m);
 242         if (need_dirty)
 243                 vm_pager_page_unswapped(m);
 244 }
 245
 246 /*
 247  *      vm_fault:
 248  *
 249  *      Handle a page fault occurring at the given address,
 250  *      requiring the given permissions, in the map specified.
 251  *      If successful, the page is inserted into the
 252  *      associated physical map.
 253  *
 254  *      NOTE: the given address should be truncated to the
 255  *      proper page address.
 256  *
 257  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 258  *      a standard error specifying why the fault is fatal is returned.
 259  *
 260  *      The map in question must be referenced, and remains so.
 261  *      Caller may hold no locks.
 262  */
 263 int
 264 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 265     int fault_flags)
 266 {
 267         struct thread *td;
 268         int result;
 269
 270         td = curthread;
 271         if ((td->td_pflags & TDP_NOFAULTING) != 0)
 272                 return (KERN_PROTECTION_FAILURE);
 273 #ifdef KTRACE
 274         if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
 275                 ktrfault(vaddr, fault_type);
 276 #endif
 277         result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
 278             NULL);
 279 #ifdef KTRACE
 280         if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
 281                 ktrfaultend(result);
 282 #endif
 283         return (result);
 284 }
 285
 286 int
 287 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 288     int fault_flags, vm_page_t *m_hold)
 289 {
 290         vm_prot_t prot;
 291         int alloc_req, era, faultcount, nera, reqpage, result;
 292         boolean_t growstack, is_first_object_locked, wired;
 293         int map_generation;
 294         vm_object_t next_object;
 295         vm_page_t marray[VM_FAULT_READ_MAX];
 296         int hardfault;
 297         struct faultstate fs;
 298         struct vnode *vp;
 299         vm_page_t m;
 300         int ahead, behind, cluster_offset, error, locked;
 301
 302         hardfault = 0;
 303         growstack = TRUE;
 304         PCPU_INC(cnt.v_vm_faults);
 305         fs.vp = NULL;
 306         faultcount = reqpage = 0;
 307
 308 RetryFault:;
 309
 310         /*
 311          * Find the backing store object and offset into it to begin the
 312          * search.
 313          */
 314         fs.map = map;
 315         result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
 316             &fs.first_object, &fs.first_pindex, &prot, &wired);
 317         if (result != KERN_SUCCESS) {
 318                 if (growstack && result == KERN_INVALID_ADDRESS &&
 319                     map != kernel_map) {
 320                         result = vm_map_growstack(curproc, vaddr);
 321                         if (result != KERN_SUCCESS)
 322                                 return (KERN_FAILURE);
 323                         growstack = FALSE;
 324                         goto RetryFault;
 325                 }
 326                 return (result);
 327         }
 328
 329         map_generation = fs.map->timestamp;
 330
 331         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 332                 panic("vm_fault: fault on nofault entry, addr: %lx",
 333                     (u_long)vaddr);
 334         }
 335
 336         if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
 337             fs.entry->wiring_thread != curthread) {
 338                 vm_map_unlock_read(fs.map);
 339                 vm_map_lock(fs.map);
 340                 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
 341                     (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
 342                         if (fs.vp != NULL) {
 343                                 vput(fs.vp);
 344                                 fs.vp = NULL;
 345                         }
 346                         fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
 347                         vm_map_unlock_and_wait(fs.map, 0);
 348                 } else
 349                         vm_map_unlock(fs.map);
 350                 goto RetryFault;
 351         }
 352
 353         if (wired)
 354                 fault_type = prot | (fault_type & VM_PROT_COPY);
 355         else
 356                 KASSERT((fault_flags & VM_FAULT_WIRE) == 0,
 357                     ("!wired && VM_FAULT_WIRE"));
 358
 359         if (fs.vp == NULL /* avoid locked vnode leak */ &&
 360             (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 &&
 361             /* avoid calling vm_object_set_writeable_dirty() */
 362             ((prot & VM_PROT_WRITE) == 0 ||
 363             (fs.first_object->type != OBJT_VNODE &&
 364             (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
 365             (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
 366                 VM_OBJECT_RLOCK(fs.first_object);
 367                 if ((prot & VM_PROT_WRITE) != 0 &&
 368                     (fs.first_object->type == OBJT_VNODE ||
 369                     (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) &&
 370                     (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0)
 371                         goto fast_failed;
 372                 m = vm_page_lookup(fs.first_object, fs.first_pindex);
 373                 /* A busy page can be mapped for read|execute access. */
 374                 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
 375                     vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
 376                         goto fast_failed;
 377                 result = pmap_enter(fs.map->pmap, vaddr, m, prot,
 378                    fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED :
 379                    0), 0);
 380                 if (result != KERN_SUCCESS)
 381                         goto fast_failed;
 382                 if (m_hold != NULL) {
 383                         *m_hold = m;
 384                         vm_page_lock(m);
 385                         vm_page_hold(m);
 386                         vm_page_unlock(m);
 387                 }
 388                 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags,
 389                     FALSE);
 390                 VM_OBJECT_RUNLOCK(fs.first_object);
 391                 if (!wired)
 392                         vm_fault_prefault(&fs, vaddr, 0, 0);
 393                 vm_map_lookup_done(fs.map, fs.entry);
 394                 curthread->td_ru.ru_minflt++;
 395                 return (KERN_SUCCESS);
 396 fast_failed:
 397                 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
 398                         VM_OBJECT_RUNLOCK(fs.first_object);
 399                         VM_OBJECT_WLOCK(fs.first_object);
 400                 }
 401         } else {
 402                 VM_OBJECT_WLOCK(fs.first_object);
 403         }
 404
 405         /*
 406          * Make a reference to this object to prevent its disposal while we
 407          * are messing with it.  Once we have the reference, the map is free
 408          * to be diddled.  Since objects reference their shadows (and copies),
 409          * they will stay around as well.
 410          *
 411          * Bump the paging-in-progress count to prevent size changes (e.g.
 412          * truncation operations) during I/O.  This must be done after
 413          * obtaining the vnode lock in order to avoid possible deadlocks.
 414          */
 415         vm_object_reference_locked(fs.first_object);
 416         vm_object_pip_add(fs.first_object, 1);
 417
 418         fs.lookup_still_valid = TRUE;
 419
 420         fs.first_m = NULL;
 421
 422         /*
 423          * Search for the page at object/offset.
 424          */
 425         fs.object = fs.first_object;
 426         fs.pindex = fs.first_pindex;
 427         while (TRUE) {
 428                 /*
 429                  * If the object is dead, we stop here
 430                  */
 431                 if (fs.object->flags & OBJ_DEAD) {
 432                         unlock_and_deallocate(&fs);
 433                         return (KERN_PROTECTION_FAILURE);
 434                 }
 435
 436                 /*
 437                  * See if page is resident
 438                  */
 439                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 440                 if (fs.m != NULL) {
 441                         /*
 442                          * Wait/Retry if the page is busy.  We have to do this
 443                          * if the page is either exclusive or shared busy
 444                          * because the vm_pager may be using read busy for
 445                          * pageouts (and even pageins if it is the vnode
 446                          * pager), and we could end up trying to pagein and
 447                          * pageout the same page simultaneously.
 448                          *
 449                          * We can theoretically allow the busy case on a read
 450                          * fault if the page is marked valid, but since such
 451                          * pages are typically already pmap'd, putting that
 452                          * special case in might be more effort then it is
 453                          * worth.  We cannot under any circumstances mess
 454                          * around with a shared busied page except, perhaps,
 455                          * to pmap it.
 456                          */
 457                         if (vm_page_busied(fs.m)) {
 458                                 /*
 459                                  * Reference the page before unlocking and
 460                                  * sleeping so that the page daemon is less
 461                                  * likely to reclaim it.
 462                                  */
 463                                 vm_page_aflag_set(fs.m, PGA_REFERENCED);
 464                                 if (fs.object != fs.first_object) {
 465                                         if (!VM_OBJECT_TRYWLOCK(
 466                                             fs.first_object)) {
 467                                                 VM_OBJECT_WUNLOCK(fs.object);
 468                                                 VM_OBJECT_WLOCK(fs.first_object);
 469                                                 VM_OBJECT_WLOCK(fs.object);
 470                                         }
 471                                         vm_page_lock(fs.first_m);
 472                                         vm_page_free(fs.first_m);
 473                                         vm_page_unlock(fs.first_m);
 474                                         vm_object_pip_wakeup(fs.first_object);
 475                                         VM_OBJECT_WUNLOCK(fs.first_object);
 476                                         fs.first_m = NULL;
 477                                 }
 478                                 unlock_map(&fs);
 479                                 if (fs.m == vm_page_lookup(fs.object,
 480                                     fs.pindex)) {
 481                                         vm_page_sleep_if_busy(fs.m, "vmpfw");
 482                                 }
 483                                 vm_object_pip_wakeup(fs.object);
 484                                 VM_OBJECT_WUNLOCK(fs.object);
 485                                 PCPU_INC(cnt.v_intrans);
 486                                 vm_object_deallocate(fs.first_object);
 487                                 goto RetryFault;
 488                         }
 489                         vm_page_lock(fs.m);
 490                         vm_page_remque(fs.m);
 491                         vm_page_unlock(fs.m);
 492
 493                         /*
 494                          * Mark page busy for other processes, and the
 495                          * pagedaemon.  If it still isn't completely valid
 496                          * (readable), jump to readrest, else break-out ( we
 497                          * found the page ).
 498                          */
 499                         vm_page_xbusy(fs.m);
 500                         if (fs.m->valid != VM_PAGE_BITS_ALL)
 501                                 goto readrest;
 502                         break;
 503                 }
 504
 505                 /*
 506                  * Page is not resident.  If this is the search termination
 507                  * or the pager might contain the page, allocate a new page.
 508                  * Default objects are zero-fill, there is no real pager.
 509                  */
 510                 if (fs.object->type != OBJT_DEFAULT ||
 511                     fs.object == fs.first_object) {
 512                         if (fs.pindex >= fs.object->size) {
 513                                 unlock_and_deallocate(&fs);
 514                                 return (KERN_PROTECTION_FAILURE);
 515                         }
 516
 517                         /*
 518                          * Allocate a new page for this object/offset pair.
 519                          *
 520                          * Unlocked read of the p_flag is harmless. At
 521                          * worst, the P_KILLED might be not observed
 522                          * there, and allocation can fail, causing
 523                          * restart and new reading of the p_flag.
 524                          */
 525                         fs.m = NULL;
 526                         if (!vm_page_count_severe() || P_KILLED(curproc)) {
 527 #if VM_NRESERVLEVEL > 0
 528                                 vm_object_color(fs.object, atop(vaddr) -
 529                                     fs.pindex);
 530 #endif
 531                                 alloc_req = P_KILLED(curproc) ?
 532                                     VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
 533                                 if (fs.object->type != OBJT_VNODE &&
 534                                     fs.object->backing_object == NULL)
 535                                         alloc_req |= VM_ALLOC_ZERO;
 536                                 fs.m = vm_page_alloc(fs.object, fs.pindex,
 537                                     alloc_req);
 538                         }
 539                         if (fs.m == NULL) {
 540                                 unlock_and_deallocate(&fs);
 541                                 VM_WAITPFAULT;
 542                                 goto RetryFault;
 543                         } else if (fs.m->valid == VM_PAGE_BITS_ALL)
 544                                 break;
 545                 }
 546
 547 readrest:
 548                 /*
 549                  * We have found a valid page or we have allocated a new page.
 550                  * The page thus may not be valid or may not be entirely
 551                  * valid.
 552                  *
 553                  * Attempt to fault-in the page if there is a chance that the
 554                  * pager has it, and potentially fault in additional pages
 555                  * at the same time.  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                         era = fs.entry->read_ahead;
 563                         if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
 564                             P_KILLED(curproc)) {
 565                                 behind = 0;
 566                                 nera = 0;
 567                                 ahead = 0;
 568                         } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
 569                                 behind = 0;
 570                                 nera = VM_FAULT_READ_AHEAD_MAX;
 571                                 ahead = nera;
 572                                 if (fs.pindex == fs.entry->next_read)
 573                                         vm_fault_dontneed(&fs, vaddr, ahead);
 574                         } else if (fs.pindex == fs.entry->next_read) {
 575                                 /*
 576                                  * This is a sequential fault.  Arithmetically
 577                                  * increase the requested number of pages in
 578                                  * the read-ahead window.  The requested
 579                                  * number of pages is "# of sequential faults
 580                                  * x (read ahead min + 1) + read ahead min"
 581                                  */
 582                                 behind = 0;
 583                                 nera = VM_FAULT_READ_AHEAD_MIN;
 584                                 if (era > 0) {
 585                                         nera += era + 1;
 586                                         if (nera > VM_FAULT_READ_AHEAD_MAX)
 587                                                 nera = VM_FAULT_READ_AHEAD_MAX;
 588                                 }
 589                                 ahead = nera;
 590                                 if (era == VM_FAULT_READ_AHEAD_MAX)
 591                                         vm_fault_dontneed(&fs, vaddr, ahead);
 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                                  * Pager could have changed the page.  Pager
 681                                  * is responsible for disposition of old page
 682                                  * if moved.
 683                                  */
 684                                 fs.m = marray[reqpage];
 685                                 hardfault++;
 686                                 break; /* break to PAGE HAS BEEN FOUND */
 687                         }
 688                         /*
 689                          * Remove the bogus page (which does not exist at this
 690                          * object/offset); before doing so, we must get back
 691                          * our object lock to preserve our invariant.
 692                          *
 693                          * Also wake up any other process that may want to bring
 694                          * in this page.
 695                          *
 696                          * If this is the top-level object, we must leave the
 697                          * busy page to prevent another process from rushing
 698                          * past us, and inserting the page in that object at
 699                          * the same time that we are.
 700                          */
 701                         if (rv == VM_PAGER_ERROR)
 702                                 printf("vm_fault: pager read error, pid %d (%s)\n",
 703                                     curproc->p_pid, curproc->p_comm);
 704                         /*
 705                          * Data outside the range of the pager or an I/O error
 706                          */
 707                         /*
 708                          * XXX - the check for kernel_map is a kludge to work
 709                          * around having the machine panic on a kernel space
 710                          * fault w/ I/O error.
 711                          */
 712                         if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
 713                                 (rv == VM_PAGER_BAD)) {
 714                                 vm_page_lock(fs.m);
 715                                 vm_page_free(fs.m);
 716                                 vm_page_unlock(fs.m);
 717                                 fs.m = NULL;
 718                                 unlock_and_deallocate(&fs);
 719                                 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
 720                         }
 721                         if (fs.object != fs.first_object) {
 722                                 vm_page_lock(fs.m);
 723                                 vm_page_free(fs.m);
 724                                 vm_page_unlock(fs.m);
 725                                 fs.m = NULL;
 726                                 /*
 727                                  * XXX - we cannot just fall out at this
 728                                  * point, m has been freed and is invalid!
 729                                  */
 730                         }
 731                 }
 732
 733                 /*
 734                  * We get here if the object has default pager (or unwiring)
 735                  * or the pager doesn't have the page.
 736                  */
 737                 if (fs.object == fs.first_object)
 738                         fs.first_m = fs.m;
 739
 740                 /*
 741                  * Move on to the next object.  Lock the next object before
 742                  * unlocking the current one.
 743                  */
 744                 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
 745                 next_object = fs.object->backing_object;
 746                 if (next_object == NULL) {
 747                         /*
 748                          * If there's no object left, fill the page in the top
 749                          * object with zeros.
 750                          */
 751                         if (fs.object != fs.first_object) {
 752                                 vm_object_pip_wakeup(fs.object);
 753                                 VM_OBJECT_WUNLOCK(fs.object);
 754
 755                                 fs.object = fs.first_object;
 756                                 fs.pindex = fs.first_pindex;
 757                                 fs.m = fs.first_m;
 758                                 VM_OBJECT_WLOCK(fs.object);
 759                         }
 760                         fs.first_m = NULL;
 761
 762                         /*
 763                          * Zero the page if necessary and mark it valid.
 764                          */
 765                         if ((fs.m->flags & PG_ZERO) == 0) {
 766                                 pmap_zero_page(fs.m);
 767                         } else {
 768                                 PCPU_INC(cnt.v_ozfod);
 769                         }
 770                         PCPU_INC(cnt.v_zfod);
 771                         fs.m->valid = VM_PAGE_BITS_ALL;
 772                         /* Don't try to prefault neighboring pages. */
 773                         faultcount = 1;
 774                         break;  /* break to PAGE HAS BEEN FOUND */
 775                 } else {
 776                         KASSERT(fs.object != next_object,
 777                             ("object loop %p", next_object));
 778                         VM_OBJECT_WLOCK(next_object);
 779                         vm_object_pip_add(next_object, 1);
 780                         if (fs.object != fs.first_object)
 781                                 vm_object_pip_wakeup(fs.object);
 782                         VM_OBJECT_WUNLOCK(fs.object);
 783                         fs.object = next_object;
 784                 }
 785         }
 786
 787         vm_page_assert_xbusied(fs.m);
 788
 789         /*
 790          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
 791          * is held.]
 792          */
 793
 794         /*
 795          * If the page is being written, but isn't already owned by the
 796          * top-level object, we have to copy it into a new page owned by the
 797          * top-level object.
 798          */
 799         if (fs.object != fs.first_object) {
 800                 /*
 801                  * We only really need to copy if we want to write it.
 802                  */
 803                 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
 804                         /*
 805                          * This allows pages to be virtually copied from a
 806                          * backing_object into the first_object, where the
 807                          * backing object has no other refs to it, and cannot
 808                          * gain any more refs.  Instead of a bcopy, we just
 809                          * move the page from the backing object to the
 810                          * first object.  Note that we must mark the page
 811                          * dirty in the first object so that it will go out
 812                          * to swap when needed.
 813                          */
 814                         is_first_object_locked = FALSE;
 815                         if (
 816                                 /*
 817                                  * Only one shadow object
 818                                  */
 819                                 (fs.object->shadow_count == 1) &&
 820                                 /*
 821                                  * No COW refs, except us
 822                                  */
 823                                 (fs.object->ref_count == 1) &&
 824                                 /*
 825                                  * No one else can look this object up
 826                                  */
 827                                 (fs.object->handle == NULL) &&
 828                                 /*
 829                                  * No other ways to look the object up
 830                                  */
 831                                 ((fs.object->type == OBJT_DEFAULT) ||
 832                                  (fs.object->type == OBJT_SWAP)) &&
 833                             (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
 834                                 /*
 835                                  * We don't chase down the shadow chain
 836                                  */
 837                             fs.object == fs.first_object->backing_object) {
 838                                 /*
 839                                  * get rid of the unnecessary page
 840                                  */
 841                                 vm_page_lock(fs.first_m);
 842                                 vm_page_free(fs.first_m);
 843                                 vm_page_unlock(fs.first_m);
 844                                 /*
 845                                  * grab the page and put it into the
 846                                  * process'es object.  The page is
 847                                  * automatically made dirty.
 848                                  */
 849                                 if (vm_page_rename(fs.m, fs.first_object,
 850                                     fs.first_pindex)) {
 851                                         unlock_and_deallocate(&fs);
 852                                         goto RetryFault;
 853                                 }
 854 #if VM_NRESERVLEVEL > 0
 855                                 /*
 856                                  * Rename the reservation.
 857                                  */
 858                                 vm_reserv_rename(fs.m, fs.first_object,
 859                                     fs.object, OFF_TO_IDX(
 860                                     fs.first_object->backing_object_offset));
 861 #endif
 862                                 vm_page_xbusy(fs.m);
 863                                 fs.first_m = fs.m;
 864                                 fs.m = NULL;
 865                                 PCPU_INC(cnt.v_cow_optim);
 866                         } else {
 867                                 /*
 868                                  * Oh, well, lets copy it.
 869                                  */
 870                                 pmap_copy_page(fs.m, fs.first_m);
 871                                 fs.first_m->valid = VM_PAGE_BITS_ALL;
 872                                 if (wired && (fault_flags &
 873                                     VM_FAULT_WIRE) == 0) {
 874                                         vm_page_lock(fs.first_m);
 875                                         vm_page_wire(fs.first_m);
 876                                         vm_page_unlock(fs.first_m);
 877
 878                                         vm_page_lock(fs.m);
 879                                         vm_page_unwire(fs.m, PQ_INACTIVE);
 880                                         vm_page_unlock(fs.m);
 881                                 }
 882                                 /*
 883                                  * We no longer need the old page or object.
 884                                  */
 885                                 release_page(&fs);
 886                         }
 887                         /*
 888                          * fs.object != fs.first_object due to above
 889                          * conditional
 890                          */
 891                         vm_object_pip_wakeup(fs.object);
 892                         VM_OBJECT_WUNLOCK(fs.object);
 893                         /*
 894                          * Only use the new page below...
 895                          */
 896                         fs.object = fs.first_object;
 897                         fs.pindex = fs.first_pindex;
 898                         fs.m = fs.first_m;
 899                         if (!is_first_object_locked)
 900                                 VM_OBJECT_WLOCK(fs.object);
 901                         PCPU_INC(cnt.v_cow_faults);
 902                         curthread->td_cow++;
 903                 } else {
 904                         prot &= ~VM_PROT_WRITE;
 905                 }
 906         }
 907
 908         /*
 909          * We must verify that the maps have not changed since our last
 910          * lookup.
 911          */
 912         if (!fs.lookup_still_valid) {
 913                 vm_object_t retry_object;
 914                 vm_pindex_t retry_pindex;
 915                 vm_prot_t retry_prot;
 916
 917                 if (!vm_map_trylock_read(fs.map)) {
 918                         release_page(&fs);
 919                         unlock_and_deallocate(&fs);
 920                         goto RetryFault;
 921                 }
 922                 fs.lookup_still_valid = TRUE;
 923                 if (fs.map->timestamp != map_generation) {
 924                         result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
 925                             &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
 926
 927                         /*
 928                          * If we don't need the page any longer, put it on the inactive
 929                          * list (the easiest thing to do here).  If no one needs it,
 930                          * pageout will grab it eventually.
 931                          */
 932                         if (result != KERN_SUCCESS) {
 933                                 release_page(&fs);
 934                                 unlock_and_deallocate(&fs);
 935
 936                                 /*
 937                                  * If retry of map lookup would have blocked then
 938                                  * retry fault from start.
 939                                  */
 940                                 if (result == KERN_FAILURE)
 941                                         goto RetryFault;
 942                                 return (result);
 943                         }
 944                         if ((retry_object != fs.first_object) ||
 945                             (retry_pindex != fs.first_pindex)) {
 946                                 release_page(&fs);
 947                                 unlock_and_deallocate(&fs);
 948                                 goto RetryFault;
 949                         }
 950
 951                         /*
 952                          * Check whether the protection has changed or the object has
 953                          * been copied while we left the map unlocked. Changing from
 954                          * read to write permission is OK - we leave the page
 955                          * write-protected, and catch the write fault. Changing from
 956                          * write to read permission means that we can't mark the page
 957                          * write-enabled after all.
 958                          */
 959                         prot &= retry_prot;
 960                 }
 961         }
 962         /*
 963          * If the page was filled by a pager, update the map entry's
 964          * last read offset.  Since the pager does not return the
 965          * actual set of pages that it read, this update is based on
 966          * the requested set.  Typically, the requested and actual
 967          * sets are the same.
 968          *
 969          * XXX The following assignment modifies the map
 970          * without holding a write lock on it.
 971          */
 972         if (hardfault)
 973                 fs.entry->next_read = fs.pindex + faultcount - reqpage;
 974
 975         vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE);
 976         vm_page_assert_xbusied(fs.m);
 977
 978         /*
 979          * Page must be completely valid or it is not fit to
 980          * map into user space.  vm_pager_get_pages() ensures this.
 981          */
 982         KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
 983             ("vm_fault: page %p partially invalid", fs.m));
 984         VM_OBJECT_WUNLOCK(fs.object);
 985
 986         /*
 987          * Put this page into the physical map.  We had to do the unlock above
 988          * because pmap_enter() may sleep.  We don't put the page
 989          * back on the active queue until later so that the pageout daemon
 990          * won't find it (yet).
 991          */
 992         pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
 993             fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
 994         if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 &&
 995             wired == 0)
 996                 vm_fault_prefault(&fs, vaddr, faultcount, reqpage);
 997         VM_OBJECT_WLOCK(fs.object);
 998         vm_page_lock(fs.m);
 999
1000         /*
1001          * If the page is not wired down, then put it where the pageout daemon
1002          * can find it.
1003          */
1004         if ((fault_flags & VM_FAULT_WIRE) != 0) {
1005                 KASSERT(wired, ("VM_FAULT_WIRE && !wired"));
1006                 vm_page_wire(fs.m);
1007         } else
1008                 vm_page_activate(fs.m);
1009         if (m_hold != NULL) {
1010                 *m_hold = fs.m;
1011                 vm_page_hold(fs.m);
1012         }
1013         vm_page_unlock(fs.m);
1014         vm_page_xunbusy(fs.m);
1015
1016         /*
1017          * Unlock everything, and return
1018          */
1019         unlock_and_deallocate(&fs);
1020         if (hardfault) {
1021                 PCPU_INC(cnt.v_io_faults);
1022                 curthread->td_ru.ru_majflt++;
1023         } else
1024                 curthread->td_ru.ru_minflt++;
1025
1026         return (KERN_SUCCESS);
1027 }
1028
1029 /*
1030  * Speed up the reclamation of pages that precede the faulting pindex within
1031  * the first object of the shadow chain.  Essentially, perform the equivalent
1032  * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes
1033  * the faulting pindex by the cluster size when the pages read by vm_fault()
1034  * cross a cluster-size boundary.  The cluster size is the greater of the
1035  * smallest superpage size and VM_FAULT_DONTNEED_MIN.
1036  *
1037  * When "fs->first_object" is a shadow object, the pages in the backing object
1038  * that precede the faulting pindex are deactivated by vm_fault().  So, this
1039  * function must only be concerned with pages in the first object.
1040  */
1041 static void
1042 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
1043 {
1044         vm_map_entry_t entry;
1045         vm_object_t first_object, object;
1046         vm_offset_t end, start;
1047         vm_page_t m, m_next;
1048         vm_pindex_t pend, pstart;
1049         vm_size_t size;
1050
1051         object = fs->object;
1052         VM_OBJECT_ASSERT_WLOCKED(object);
1053         first_object = fs->first_object;
1054         if (first_object != object) {
1055                 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1056                         VM_OBJECT_WUNLOCK(object);
1057                         VM_OBJECT_WLOCK(first_object);
1058                         VM_OBJECT_WLOCK(object);
1059                 }
1060         }
1061         /* Neither fictitious nor unmanaged pages can be reclaimed. */
1062         if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1063                 size = VM_FAULT_DONTNEED_MIN;
1064                 if (MAXPAGESIZES > 1 && size < pagesizes[1])
1065                         size = pagesizes[1];
1066                 end = rounddown2(vaddr, size);
1067                 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) &&
1068                     (entry = fs->entry)->start < end) {
1069                         if (end - entry->start < size)
1070                                 start = entry->start;
1071                         else
1072                                 start = end - size;
1073                         pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED);
1074                         pstart = OFF_TO_IDX(entry->offset) + atop(start -
1075                             entry->start);
1076                         m_next = vm_page_find_least(first_object, pstart);
1077                         pend = OFF_TO_IDX(entry->offset) + atop(end -
1078                             entry->start);
1079                         while ((m = m_next) != NULL && m->pindex < pend) {
1080                                 m_next = TAILQ_NEXT(m, listq);
1081                                 if (m->valid != VM_PAGE_BITS_ALL ||
1082                                     vm_page_busied(m))
1083                                         continue;
1084
1085                                 /*
1086                                  * Don't clear PGA_REFERENCED, since it would
1087                                  * likely represent a reference by a different
1088                                  * process.
1089                                  *
1090                                  * Typically, at this point, prefetched pages
1091                                  * are still in the inactive queue.  Only
1092                                  * pages that triggered page faults are in the
1093                                  * active queue.
1094                                  */
1095                                 vm_page_lock(m);
1096                                 vm_page_deactivate(m);
1097                                 vm_page_unlock(m);
1098                         }
1099                 }
1100         }
1101         if (first_object != object)
1102                 VM_OBJECT_WUNLOCK(first_object);
1103 }
1104
1105 /*
1106  * vm_fault_prefault provides a quick way of clustering
1107  * pagefaults into a processes address space.  It is a "cousin"
1108  * of vm_map_pmap_enter, except it runs at page fault time instead
1109  * of mmap time.
1110  */
1111 static void
1112 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1113     int faultcount, int reqpage)
1114 {
1115         pmap_t pmap;
1116         vm_map_entry_t entry;
1117         vm_object_t backing_object, lobject;
1118         vm_offset_t addr, starta;
1119         vm_pindex_t pindex;
1120         vm_page_t m;
1121         int backward, forward, i;
1122
1123         pmap = fs->map->pmap;
1124         if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1125                 return;
1126
1127         if (faultcount > 0) {
1128                 backward = reqpage;
1129                 forward = faultcount - reqpage - 1;
1130         } else {
1131                 backward = PFBAK;
1132                 forward = PFFOR;
1133         }
1134         entry = fs->entry;
1135
1136         starta = addra - backward * PAGE_SIZE;
1137         if (starta < entry->start) {
1138                 starta = entry->start;
1139         } else if (starta > addra) {
1140                 starta = 0;
1141         }
1142
1143         /*
1144          * Generate the sequence of virtual addresses that are candidates for
1145          * prefaulting in an outward spiral from the faulting virtual address,
1146          * "addra".  Specifically, the sequence is "addra - PAGE_SIZE", "addra
1147          * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1148          * If the candidate address doesn't have a backing physical page, then
1149          * the loop immediately terminates.
1150          */
1151         for (i = 0; i < 2 * imax(backward, forward); i++) {
1152                 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1153                     PAGE_SIZE);
1154                 if (addr > addra + forward * PAGE_SIZE)
1155                         addr = 0;
1156
1157                 if (addr < starta || addr >= entry->end)
1158                         continue;
1159
1160                 if (!pmap_is_prefaultable(pmap, addr))
1161                         continue;
1162
1163                 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1164                 lobject = entry->object.vm_object;
1165                 VM_OBJECT_RLOCK(lobject);
1166                 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1167                     lobject->type == OBJT_DEFAULT &&
1168                     (backing_object = lobject->backing_object) != NULL) {
1169                         KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1170                             0, ("vm_fault_prefault: unaligned object offset"));
1171                         pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1172                         VM_OBJECT_RLOCK(backing_object);
1173                         VM_OBJECT_RUNLOCK(lobject);
1174                         lobject = backing_object;
1175                 }
1176                 if (m == NULL) {
1177                         VM_OBJECT_RUNLOCK(lobject);
1178                         break;
1179                 }
1180                 if (m->valid == VM_PAGE_BITS_ALL &&
1181                     (m->flags & PG_FICTITIOUS) == 0)
1182                         pmap_enter_quick(pmap, addr, m, entry->protection);
1183                 VM_OBJECT_RUNLOCK(lobject);
1184         }
1185 }
1186
1187 /*
1188  * Hold each of the physical pages that are mapped by the specified range of
1189  * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1190  * and allow the specified types of access, "prot".  If all of the implied
1191  * pages are successfully held, then the number of held pages is returned
1192  * together with pointers to those pages in the array "ma".  However, if any
1193  * of the pages cannot be held, -1 is returned.
1194  */
1195 int
1196 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1197     vm_prot_t prot, vm_page_t *ma, int max_count)
1198 {
1199         vm_offset_t end, va;
1200         vm_page_t *mp;
1201         int count;
1202         boolean_t pmap_failed;
1203
1204         if (len == 0)
1205                 return (0);
1206         end = round_page(addr + len);
1207         addr = trunc_page(addr);
1208
1209         /*
1210          * Check for illegal addresses.
1211          */
1212         if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1213                 return (-1);
1214
1215         if (atop(end - addr) > max_count)
1216                 panic("vm_fault_quick_hold_pages: count > max_count");
1217         count = atop(end - addr);
1218
1219         /*
1220          * Most likely, the physical pages are resident in the pmap, so it is
1221          * faster to try pmap_extract_and_hold() first.
1222          */
1223         pmap_failed = FALSE;
1224         for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1225                 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1226                 if (*mp == NULL)
1227                         pmap_failed = TRUE;
1228                 else if ((prot & VM_PROT_WRITE) != 0 &&
1229                     (*mp)->dirty != VM_PAGE_BITS_ALL) {
1230                         /*
1231                          * Explicitly dirty the physical page.  Otherwise, the
1232                          * caller's changes may go unnoticed because they are
1233                          * performed through an unmanaged mapping or by a DMA
1234                          * operation.
1235                          *
1236                          * The object lock is not held here.
1237                          * See vm_page_clear_dirty_mask().
1238                          */
1239                         vm_page_dirty(*mp);
1240                 }
1241         }
1242         if (pmap_failed) {
1243                 /*
1244                  * One or more pages could not be held by the pmap.  Either no
1245                  * page was mapped at the specified virtual address or that
1246                  * mapping had insufficient permissions.  Attempt to fault in
1247                  * and hold these pages.
1248                  */
1249                 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1250                         if (*mp == NULL && vm_fault_hold(map, va, prot,
1251                             VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1252                                 goto error;
1253         }
1254         return (count);
1255 error:
1256         for (mp = ma; mp < ma + count; mp++)
1257                 if (*mp != NULL) {
1258                         vm_page_lock(*mp);
1259                         vm_page_unhold(*mp);
1260                         vm_page_unlock(*mp);
1261                 }
1262         return (-1);
1263 }
1264
1265 /*
1266  *      Routine:
1267  *              vm_fault_copy_entry
1268  *      Function:
1269  *              Create new shadow object backing dst_entry with private copy of
1270  *              all underlying pages. When src_entry is equal to dst_entry,
1271  *              function implements COW for wired-down map entry. Otherwise,
1272  *              it forks wired entry into dst_map.
1273  *
1274  *      In/out conditions:
1275  *              The source and destination maps must be locked for write.
1276  *              The source map entry must be wired down (or be a sharing map
1277  *              entry corresponding to a main map entry that is wired down).
1278  */
1279 void
1280 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1281     vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1282     vm_ooffset_t *fork_charge)
1283 {
1284         vm_object_t backing_object, dst_object, object, src_object;
1285         vm_pindex_t dst_pindex, pindex, src_pindex;
1286         vm_prot_t access, prot;
1287         vm_offset_t vaddr;
1288         vm_page_t dst_m;
1289         vm_page_t src_m;
1290         boolean_t upgrade;
1291
1292 #ifdef  lint
1293         src_map++;
1294 #endif  /* lint */
1295
1296         upgrade = src_entry == dst_entry;
1297         access = prot = dst_entry->protection;
1298
1299         src_object = src_entry->object.vm_object;
1300         src_pindex = OFF_TO_IDX(src_entry->offset);
1301
1302         if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1303                 dst_object = src_object;
1304                 vm_object_reference(dst_object);
1305         } else {
1306                 /*
1307                  * Create the top-level object for the destination entry. (Doesn't
1308                  * actually shadow anything - we copy the pages directly.)
1309                  */
1310                 dst_object = vm_object_allocate(OBJT_DEFAULT,
1311                     OFF_TO_IDX(dst_entry->end - dst_entry->start));
1312 #if VM_NRESERVLEVEL > 0
1313                 dst_object->flags |= OBJ_COLORED;
1314                 dst_object->pg_color = atop(dst_entry->start);
1315 #endif
1316         }
1317
1318         VM_OBJECT_WLOCK(dst_object);
1319         KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1320             ("vm_fault_copy_entry: vm_object not NULL"));
1321         if (src_object != dst_object) {
1322                 dst_entry->object.vm_object = dst_object;
1323                 dst_entry->offset = 0;
1324                 dst_object->charge = dst_entry->end - dst_entry->start;
1325         }
1326         if (fork_charge != NULL) {
1327                 KASSERT(dst_entry->cred == NULL,
1328                     ("vm_fault_copy_entry: leaked swp charge"));
1329                 dst_object->cred = curthread->td_ucred;
1330                 crhold(dst_object->cred);
1331                 *fork_charge += dst_object->charge;
1332         } else if (dst_object->cred == NULL) {
1333                 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1334                     dst_entry));
1335                 dst_object->cred = dst_entry->cred;
1336                 dst_entry->cred = NULL;
1337         }
1338
1339         /*
1340          * If not an upgrade, then enter the mappings in the pmap as
1341          * read and/or execute accesses.  Otherwise, enter them as
1342          * write accesses.
1343          *
1344          * A writeable large page mapping is only created if all of
1345          * the constituent small page mappings are modified. Marking
1346          * PTEs as modified on inception allows promotion to happen
1347          * without taking potentially large number of soft faults.
1348          */
1349         if (!upgrade)
1350                 access &= ~VM_PROT_WRITE;
1351
1352         /*
1353          * Loop through all of the virtual pages within the entry's
1354          * range, copying each page from the source object to the
1355          * destination object.  Since the source is wired, those pages
1356          * must exist.  In contrast, the destination is pageable.
1357          * Since the destination object does share any backing storage
1358          * with the source object, all of its pages must be dirtied,
1359          * regardless of whether they can be written.
1360          */
1361         for (vaddr = dst_entry->start, dst_pindex = 0;
1362             vaddr < dst_entry->end;
1363             vaddr += PAGE_SIZE, dst_pindex++) {
1364 again:
1365                 /*
1366                  * Find the page in the source object, and copy it in.
1367                  * Because the source is wired down, the page will be
1368                  * in memory.
1369                  */
1370                 if (src_object != dst_object)
1371                         VM_OBJECT_RLOCK(src_object);
1372                 object = src_object;
1373                 pindex = src_pindex + dst_pindex;
1374                 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1375                     (backing_object = object->backing_object) != NULL) {
1376                         /*
1377                          * Unless the source mapping is read-only or
1378                          * it is presently being upgraded from
1379                          * read-only, the first object in the shadow
1380                          * chain should provide all of the pages.  In
1381                          * other words, this loop body should never be
1382                          * executed when the source mapping is already
1383                          * read/write.
1384                          */
1385                         KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1386                             upgrade,
1387                             ("vm_fault_copy_entry: main object missing page"));
1388
1389                         VM_OBJECT_RLOCK(backing_object);
1390                         pindex += OFF_TO_IDX(object->backing_object_offset);
1391                         if (object != dst_object)
1392                                 VM_OBJECT_RUNLOCK(object);
1393                         object = backing_object;
1394                 }
1395                 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1396
1397                 if (object != dst_object) {
1398                         /*
1399                          * Allocate a page in the destination object.
1400                          */
1401                         dst_m = vm_page_alloc(dst_object, (src_object ==
1402                             dst_object ? src_pindex : 0) + dst_pindex,
1403                             VM_ALLOC_NORMAL);
1404                         if (dst_m == NULL) {
1405                                 VM_OBJECT_WUNLOCK(dst_object);
1406                                 VM_OBJECT_RUNLOCK(object);
1407                                 VM_WAIT;
1408                                 VM_OBJECT_WLOCK(dst_object);
1409                                 goto again;
1410                         }
1411                         pmap_copy_page(src_m, dst_m);
1412                         VM_OBJECT_RUNLOCK(object);
1413                         dst_m->valid = VM_PAGE_BITS_ALL;
1414                         dst_m->dirty = VM_PAGE_BITS_ALL;
1415                 } else {
1416                         dst_m = src_m;
1417                         if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1418                                 goto again;
1419                         vm_page_xbusy(dst_m);
1420                         KASSERT(dst_m->valid == VM_PAGE_BITS_ALL,
1421                             ("invalid dst page %p", dst_m));
1422                 }
1423                 VM_OBJECT_WUNLOCK(dst_object);
1424
1425                 /*
1426                  * Enter it in the pmap. If a wired, copy-on-write
1427                  * mapping is being replaced by a write-enabled
1428                  * mapping, then wire that new mapping.
1429                  */
1430                 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1431                     access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1432
1433                 /*
1434                  * Mark it no longer busy, and put it on the active list.
1435                  */
1436                 VM_OBJECT_WLOCK(dst_object);
1437
1438                 if (upgrade) {
1439                         if (src_m != dst_m) {
1440                                 vm_page_lock(src_m);
1441                                 vm_page_unwire(src_m, PQ_INACTIVE);
1442                                 vm_page_unlock(src_m);
1443                                 vm_page_lock(dst_m);
1444                                 vm_page_wire(dst_m);
1445                                 vm_page_unlock(dst_m);
1446                         } else {
1447                                 KASSERT(dst_m->wire_count > 0,
1448                                     ("dst_m %p is not wired", dst_m));
1449                         }
1450                 } else {
1451                         vm_page_lock(dst_m);
1452                         vm_page_activate(dst_m);
1453                         vm_page_unlock(dst_m);
1454                 }
1455                 vm_page_xunbusy(dst_m);
1456         }
1457         VM_OBJECT_WUNLOCK(dst_object);
1458         if (upgrade) {
1459                 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1460                 vm_object_deallocate(src_object);
1461         }
1462 }
1463
1464
1465 /*
1466  * This routine checks around the requested page for other pages that
1467  * might be able to be faulted in.  This routine brackets the viable
1468  * pages for the pages to be paged in.
1469  *
1470  * Inputs:
1471  *      m, rbehind, rahead
1472  *
1473  * Outputs:
1474  *  marray (array of vm_page_t), reqpage (index of requested page)
1475  *
1476  * Return value:
1477  *  number of pages in marray
1478  */
1479 static int
1480 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1481         vm_page_t m;
1482         int rbehind;
1483         int rahead;
1484         vm_page_t *marray;
1485         int *reqpage;
1486 {
1487         int i,j;
1488         vm_object_t object;
1489         vm_pindex_t pindex, startpindex, endpindex, tpindex;
1490         vm_page_t rtm;
1491         int cbehind, cahead;
1492
1493         VM_OBJECT_ASSERT_WLOCKED(m->object);
1494
1495         object = m->object;
1496         pindex = m->pindex;
1497         cbehind = cahead = 0;
1498
1499         /*
1500          * if the requested page is not available, then give up now
1501          */
1502         if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1503                 return 0;
1504         }
1505
1506         if ((cbehind == 0) && (cahead == 0)) {
1507                 *reqpage = 0;
1508                 marray[0] = m;
1509                 return 1;
1510         }
1511
1512         if (rahead > cahead) {
1513                 rahead = cahead;
1514         }
1515
1516         if (rbehind > cbehind) {
1517                 rbehind = cbehind;
1518         }
1519
1520         /*
1521          * scan backward for the read behind pages -- in memory
1522          */
1523         if (pindex > 0) {
1524                 if (rbehind > pindex) {
1525                         rbehind = pindex;
1526                         startpindex = 0;
1527                 } else {
1528                         startpindex = pindex - rbehind;
1529                 }
1530
1531                 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL &&
1532                     rtm->pindex >= startpindex)
1533                         startpindex = rtm->pindex + 1;
1534
1535                 /* tpindex is unsigned; beware of numeric underflow. */
1536                 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex &&
1537                     tpindex < pindex; i++, tpindex--) {
1538
1539                         rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1540                             VM_ALLOC_IFNOTCACHED);
1541                         if (rtm == NULL) {
1542                                 /*
1543                                  * Shift the allocated pages to the
1544                                  * beginning of the array.
1545                                  */
1546                                 for (j = 0; j < i; j++) {
1547                                         marray[j] = marray[j + tpindex + 1 -
1548                                             startpindex];
1549                                 }
1550                                 break;
1551                         }
1552
1553                         marray[tpindex - startpindex] = rtm;
1554                 }
1555         } else {
1556                 startpindex = 0;
1557                 i = 0;
1558         }
1559
1560         marray[i] = m;
1561         /* page offset of the required page */
1562         *reqpage = i;
1563
1564         tpindex = pindex + 1;
1565         i++;
1566
1567         /*
1568          * scan forward for the read ahead pages
1569          */
1570         endpindex = tpindex + rahead;
1571         if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex)
1572                 endpindex = rtm->pindex;
1573         if (endpindex > object->size)
1574                 endpindex = object->size;
1575
1576         for (; tpindex < endpindex; i++, tpindex++) {
1577
1578                 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1579                     VM_ALLOC_IFNOTCACHED);
1580                 if (rtm == NULL) {
1581                         break;
1582                 }
1583
1584                 marray[i] = rtm;
1585         }
1586
1587         /* return number of pages */
1588         return i;
1589 }
1590
1591 /*
1592  * Block entry into the machine-independent layer's page fault handler by
1593  * the calling thread.  Subsequent calls to vm_fault() by that thread will
1594  * return KERN_PROTECTION_FAILURE.  Enable machine-dependent handling of
1595  * spurious page faults.
1596  */
1597 int
1598 vm_fault_disable_pagefaults(void)
1599 {
1600
1601         return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1602 }
1603
1604 void
1605 vm_fault_enable_pagefaults(int save)
1606 {
1607
1608         curthread_pflags_restore(save);
1609 }