sys/vm/vm_fault.c

   1 /*-
   2  * Copyright (c) 1991, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  * Copyright (c) 1994 John S. Dyson
   5  * All rights reserved.
   6  * Copyright (c) 1994 David Greenman
   7  * All rights reserved.
   8  *
   9  *
  10  * This code is derived from software contributed to Berkeley by
  11  * The Mach Operating System project at Carnegie-Mellon University.
  12  *
  13  * Redistribution and use in source and binary forms, with or without
  14  * modification, are permitted provided that the following conditions
  15  * are met:
  16  * 1. Redistributions of source code must retain the above copyright
  17  *    notice, this list of conditions and the following disclaimer.
  18  * 2. Redistributions in binary form must reproduce the above copyright
  19  *    notice, this list of conditions and the following disclaimer in the
  20  *    documentation and/or other materials provided with the distribution.
  21  * 3. All advertising materials mentioning features or use of this software
  22  *    must display the following acknowledgement:
  23  *      This product includes software developed by the University of
  24  *      California, Berkeley and its contributors.
  25  * 4. Neither the name of the University nor the names of its contributors
  26  *    may be used to endorse or promote products derived from this software
  27  *    without specific prior written permission.
  28  *
  29  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  30  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  31  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  32  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  33  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  34  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  35  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  36  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  37  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  38  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  39  * SUCH DAMAGE.
  40  *
  41  *      from: @(#)vm_fault.c    8.4 (Berkeley) 1/12/94
  42  *
  43  *
  44  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
  45  * All rights reserved.
  46  *
  47  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
  48  *
  49  * Permission to use, copy, modify and distribute this software and
  50  * its documentation is hereby granted, provided that both the copyright
  51  * notice and this permission notice appear in all copies of the
  52  * software, derivative works or modified versions, and any portions
  53  * thereof, and that both notices appear in supporting documentation.
  54  *
  55  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  56  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
  57  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  58  *
  59  * Carnegie Mellon requests users of this software to return to
  60  *
  61  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  62  *  School of Computer Science
  63  *  Carnegie Mellon University
  64  *  Pittsburgh PA 15213-3890
  65  *
  66  * any improvements or extensions that they make and grant Carnegie the
  67  * rights to redistribute these changes.
  68  */
  69
  70 /*
  71  *      Page fault handling module.
  72  */
  73
  74 #include <sys/cdefs.h>
  75 __FBSDID("$FreeBSD$");
  76
  77 #include "opt_ktrace.h"
  78 #include "opt_vm.h"
  79
  80 #include <sys/param.h>
  81 #include <sys/systm.h>
  82 #include <sys/kernel.h>
  83 #include <sys/lock.h>
  84 #include <sys/proc.h>
  85 #include <sys/resourcevar.h>
  86 #include <sys/rwlock.h>
  87 #include <sys/sysctl.h>
  88 #include <sys/vmmeter.h>
  89 #include <sys/vnode.h>
  90 #ifdef KTRACE
  91 #include <sys/ktrace.h>
  92 #endif
  93
  94 #include <vm/vm.h>
  95 #include <vm/vm_param.h>
  96 #include <vm/pmap.h>
  97 #include <vm/vm_map.h>
  98 #include <vm/vm_object.h>
  99 #include <vm/vm_page.h>
 100 #include <vm/vm_pageout.h>
 101 #include <vm/vm_kern.h>
 102 #include <vm/vm_pager.h>
 103 #include <vm/vm_extern.h>
 104
 105 #define PFBAK 4
 106 #define PFFOR 4
 107
 108 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
 109 static void vm_fault_unwire(vm_map_t, vm_offset_t, vm_offset_t, boolean_t);
 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 /*
 179  * TRYPAGER - used by vm_fault to calculate whether the pager for the
 180  *            current object *might* contain the page.
 181  *
 182  *            default objects are zero-fill, there is no real pager.
 183  */
 184 #define TRYPAGER        (fs.object->type != OBJT_DEFAULT && \
 185                         ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 || wired))
 186
 187 /*
 188  *      vm_fault:
 189  *
 190  *      Handle a page fault occurring at the given address,
 191  *      requiring the given permissions, in the map specified.
 192  *      If successful, the page is inserted into the
 193  *      associated physical map.
 194  *
 195  *      NOTE: the given address should be truncated to the
 196  *      proper page address.
 197  *
 198  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 199  *      a standard error specifying why the fault is fatal is returned.
 200  *
 201  *      The map in question must be referenced, and remains so.
 202  *      Caller may hold no locks.
 203  */
 204 int
 205 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 206     int fault_flags)
 207 {
 208         struct thread *td;
 209         int result;
 210
 211         td = curthread;
 212         if ((td->td_pflags & TDP_NOFAULTING) != 0)
 213                 return (KERN_PROTECTION_FAILURE);
 214 #ifdef KTRACE
 215         if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
 216                 ktrfault(vaddr, fault_type);
 217 #endif
 218         result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
 219             NULL);
 220 #ifdef KTRACE
 221         if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
 222                 ktrfaultend(result);
 223 #endif
 224         return (result);
 225 }
 226
 227 int
 228 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 229     int fault_flags, vm_page_t *m_hold)
 230 {
 231         vm_prot_t prot;
 232         long ahead, behind;
 233         int alloc_req, era, faultcount, nera, reqpage, result;
 234         boolean_t growstack, is_first_object_locked, wired;
 235         int map_generation;
 236         vm_object_t next_object;
 237         vm_page_t marray[VM_FAULT_READ_MAX];
 238         int hardfault;
 239         struct faultstate fs;
 240         struct vnode *vp;
 241         int locked, error;
 242
 243         hardfault = 0;
 244         growstack = TRUE;
 245         PCPU_INC(cnt.v_vm_faults);
 246         fs.vp = NULL;
 247         faultcount = reqpage = 0;
 248
 249 RetryFault:;
 250
 251         /*
 252          * Find the backing store object and offset into it to begin the
 253          * search.
 254          */
 255         fs.map = map;
 256         result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
 257             &fs.first_object, &fs.first_pindex, &prot, &wired);
 258         if (result != KERN_SUCCESS) {
 259                 if (growstack && result == KERN_INVALID_ADDRESS &&
 260                     map != kernel_map) {
 261                         result = vm_map_growstack(curproc, vaddr);
 262                         if (result != KERN_SUCCESS)
 263                                 return (KERN_FAILURE);
 264                         growstack = FALSE;
 265                         goto RetryFault;
 266                 }
 267                 return (result);
 268         }
 269
 270         map_generation = fs.map->timestamp;
 271
 272         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 273                 if ((curthread->td_pflags & TDP_DEVMEMIO) != 0) {
 274                         vm_map_unlock_read(fs.map);
 275                         return (KERN_FAILURE);
 276                 }
 277                 panic("vm_fault: fault on nofault entry, addr: %lx",
 278                     (u_long)vaddr);
 279         }
 280
 281         if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
 282             fs.entry->wiring_thread != curthread) {
 283                 vm_map_unlock_read(fs.map);
 284                 vm_map_lock(fs.map);
 285                 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
 286                     (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
 287                         fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
 288                         vm_map_unlock_and_wait(fs.map, 0);
 289                 } else
 290                         vm_map_unlock(fs.map);
 291                 goto RetryFault;
 292         }
 293
 294         /*
 295          * Make a reference to this object to prevent its disposal while we
 296          * are messing with it.  Once we have the reference, the map is free
 297          * to be diddled.  Since objects reference their shadows (and copies),
 298          * they will stay around as well.
 299          *
 300          * Bump the paging-in-progress count to prevent size changes (e.g.
 301          * truncation operations) during I/O.  This must be done after
 302          * obtaining the vnode lock in order to avoid possible deadlocks.
 303          */
 304         VM_OBJECT_WLOCK(fs.first_object);
 305         vm_object_reference_locked(fs.first_object);
 306         vm_object_pip_add(fs.first_object, 1);
 307
 308         fs.lookup_still_valid = TRUE;
 309
 310         if (wired)
 311                 fault_type = prot | (fault_type & VM_PROT_COPY);
 312
 313         fs.first_m = NULL;
 314
 315         /*
 316          * Search for the page at object/offset.
 317          */
 318         fs.object = fs.first_object;
 319         fs.pindex = fs.first_pindex;
 320         while (TRUE) {
 321                 /*
 322                  * If the object is dead, we stop here
 323                  */
 324                 if (fs.object->flags & OBJ_DEAD) {
 325                         unlock_and_deallocate(&fs);
 326                         return (KERN_PROTECTION_FAILURE);
 327                 }
 328
 329                 /*
 330                  * See if page is resident
 331                  */
 332                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 333                 if (fs.m != NULL) {
 334                         /*
 335                          * Wait/Retry if the page is busy.  We have to do this
 336                          * if the page is either exclusive or shared busy
 337                          * because the vm_pager may be using read busy for
 338                          * pageouts (and even pageins if it is the vnode
 339                          * pager), and we could end up trying to pagein and
 340                          * pageout the same page simultaneously.
 341                          *
 342                          * We can theoretically allow the busy case on a read
 343                          * fault if the page is marked valid, but since such
 344                          * pages are typically already pmap'd, putting that
 345                          * special case in might be more effort then it is
 346                          * worth.  We cannot under any circumstances mess
 347                          * around with a shared busied page except, perhaps,
 348                          * to pmap it.
 349                          */
 350                         if (vm_page_busied(fs.m)) {
 351                                 /*
 352                                  * Reference the page before unlocking and
 353                                  * sleeping so that the page daemon is less
 354                                  * likely to reclaim it.
 355                                  */
 356                                 vm_page_aflag_set(fs.m, PGA_REFERENCED);
 357                                 if (fs.object != fs.first_object) {
 358                                         if (!VM_OBJECT_TRYWLOCK(
 359                                             fs.first_object)) {
 360                                                 VM_OBJECT_WUNLOCK(fs.object);
 361                                                 VM_OBJECT_WLOCK(fs.first_object);
 362                                                 VM_OBJECT_WLOCK(fs.object);
 363                                         }
 364                                         vm_page_lock(fs.first_m);
 365                                         vm_page_free(fs.first_m);
 366                                         vm_page_unlock(fs.first_m);
 367                                         vm_object_pip_wakeup(fs.first_object);
 368                                         VM_OBJECT_WUNLOCK(fs.first_object);
 369                                         fs.first_m = NULL;
 370                                 }
 371                                 unlock_map(&fs);
 372                                 if (fs.m == vm_page_lookup(fs.object,
 373                                     fs.pindex)) {
 374                                         vm_page_sleep_if_busy(fs.m, "vmpfw");
 375                                 }
 376                                 vm_object_pip_wakeup(fs.object);
 377                                 VM_OBJECT_WUNLOCK(fs.object);
 378                                 PCPU_INC(cnt.v_intrans);
 379                                 vm_object_deallocate(fs.first_object);
 380                                 goto RetryFault;
 381                         }
 382                         vm_page_lock(fs.m);
 383                         vm_page_remque(fs.m);
 384                         vm_page_unlock(fs.m);
 385
 386                         /*
 387                          * Mark page busy for other processes, and the
 388                          * pagedaemon.  If it still isn't completely valid
 389                          * (readable), jump to readrest, else break-out ( we
 390                          * found the page ).
 391                          */
 392                         vm_page_xbusy(fs.m);
 393                         if (fs.m->valid != VM_PAGE_BITS_ALL)
 394                                 goto readrest;
 395                         break;
 396                 }
 397
 398                 /*
 399                  * Page is not resident, If this is the search termination
 400                  * or the pager might contain the page, allocate a new page.
 401                  */
 402                 if (TRYPAGER || fs.object == fs.first_object) {
 403                         if (fs.pindex >= fs.object->size) {
 404                                 unlock_and_deallocate(&fs);
 405                                 return (KERN_PROTECTION_FAILURE);
 406                         }
 407
 408                         /*
 409                          * Allocate a new page for this object/offset pair.
 410                          *
 411                          * Unlocked read of the p_flag is harmless. At
 412                          * worst, the P_KILLED might be not observed
 413                          * there, and allocation can fail, causing
 414                          * restart and new reading of the p_flag.
 415                          */
 416                         fs.m = NULL;
 417                         if (!vm_page_count_severe() || P_KILLED(curproc)) {
 418 #if VM_NRESERVLEVEL > 0
 419                                 if ((fs.object->flags & OBJ_COLORED) == 0) {
 420                                         fs.object->flags |= OBJ_COLORED;
 421                                         fs.object->pg_color = atop(vaddr) -
 422                                             fs.pindex;
 423                                 }
 424 #endif
 425                                 alloc_req = P_KILLED(curproc) ?
 426                                     VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
 427                                 if (fs.object->type != OBJT_VNODE &&
 428                                     fs.object->backing_object == NULL)
 429                                         alloc_req |= VM_ALLOC_ZERO;
 430                                 fs.m = vm_page_alloc(fs.object, fs.pindex,
 431                                     alloc_req);
 432                         }
 433                         if (fs.m == NULL) {
 434                                 unlock_and_deallocate(&fs);
 435                                 VM_WAITPFAULT;
 436                                 goto RetryFault;
 437                         } else if (fs.m->valid == VM_PAGE_BITS_ALL)
 438                                 break;
 439                 }
 440
 441 readrest:
 442                 /*
 443                  * We have found a valid page or we have allocated a new page.
 444                  * The page thus may not be valid or may not be entirely
 445                  * valid.
 446                  *
 447                  * Attempt to fault-in the page if there is a chance that the
 448                  * pager has it, and potentially fault in additional pages
 449                  * at the same time.
 450                  */
 451                 if (TRYPAGER) {
 452                         int rv;
 453                         u_char behavior = vm_map_entry_behavior(fs.entry);
 454
 455                         if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
 456                             P_KILLED(curproc)) {
 457                                 behind = 0;
 458                                 ahead = 0;
 459                         } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
 460                                 behind = 0;
 461                                 ahead = atop(fs.entry->end - vaddr) - 1;
 462                                 if (ahead > VM_FAULT_READ_AHEAD_MAX)
 463                                         ahead = VM_FAULT_READ_AHEAD_MAX;
 464                                 if (fs.pindex == fs.entry->next_read)
 465                                         vm_fault_cache_behind(&fs,
 466                                             VM_FAULT_READ_MAX);
 467                         } else {
 468                                 /*
 469                                  * If this is a sequential page fault, then
 470                                  * arithmetically increase the number of pages
 471                                  * in the read-ahead window.  Otherwise, reset
 472                                  * the read-ahead window to its smallest size.
 473                                  */
 474                                 behind = atop(vaddr - fs.entry->start);
 475                                 if (behind > VM_FAULT_READ_BEHIND)
 476                                         behind = VM_FAULT_READ_BEHIND;
 477                                 ahead = atop(fs.entry->end - vaddr) - 1;
 478                                 era = fs.entry->read_ahead;
 479                                 if (fs.pindex == fs.entry->next_read) {
 480                                         nera = era + behind;
 481                                         if (nera > VM_FAULT_READ_AHEAD_MAX)
 482                                                 nera = VM_FAULT_READ_AHEAD_MAX;
 483                                         behind = 0;
 484                                         if (ahead > nera)
 485                                                 ahead = nera;
 486                                         if (era == VM_FAULT_READ_AHEAD_MAX)
 487                                                 vm_fault_cache_behind(&fs,
 488                                                     VM_FAULT_CACHE_BEHIND);
 489                                 } else if (ahead > VM_FAULT_READ_AHEAD_MIN)
 490                                         ahead = VM_FAULT_READ_AHEAD_MIN;
 491                                 if (era != ahead)
 492                                         fs.entry->read_ahead = ahead;
 493                         }
 494
 495                         /*
 496                          * Call the pager to retrieve the data, if any, after
 497                          * releasing the lock on the map.  We hold a ref on
 498                          * fs.object and the pages are exclusive busied.
 499                          */
 500                         unlock_map(&fs);
 501
 502                         if (fs.object->type == OBJT_VNODE) {
 503                                 vp = fs.object->handle;
 504                                 if (vp == fs.vp)
 505                                         goto vnode_locked;
 506                                 else if (fs.vp != NULL) {
 507                                         vput(fs.vp);
 508                                         fs.vp = NULL;
 509                                 }
 510                                 locked = VOP_ISLOCKED(vp);
 511
 512                                 if (locked != LK_EXCLUSIVE)
 513                                         locked = LK_SHARED;
 514                                 /* Do not sleep for vnode lock while fs.m is busy */
 515                                 error = vget(vp, locked | LK_CANRECURSE |
 516                                     LK_NOWAIT, curthread);
 517                                 if (error != 0) {
 518                                         vhold(vp);
 519                                         release_page(&fs);
 520                                         unlock_and_deallocate(&fs);
 521                                         error = vget(vp, locked | LK_RETRY |
 522                                             LK_CANRECURSE, curthread);
 523                                         vdrop(vp);
 524                                         fs.vp = vp;
 525                                         KASSERT(error == 0,
 526                                             ("vm_fault: vget failed"));
 527                                         goto RetryFault;
 528                                 }
 529                                 fs.vp = vp;
 530                         }
 531 vnode_locked:
 532                         KASSERT(fs.vp == NULL || !fs.map->system_map,
 533                             ("vm_fault: vnode-backed object mapped by system map"));
 534
 535                         /*
 536                          * now we find out if any other pages should be paged
 537                          * in at this time this routine checks to see if the
 538                          * pages surrounding this fault reside in the same
 539                          * object as the page for this fault.  If they do,
 540                          * then they are faulted in also into the object.  The
 541                          * array "marray" returned contains an array of
 542                          * vm_page_t structs where one of them is the
 543                          * vm_page_t passed to the routine.  The reqpage
 544                          * return value is the index into the marray for the
 545                          * vm_page_t passed to the routine.
 546                          *
 547                          * fs.m plus the additional pages are exclusive busied.
 548                          */
 549                         faultcount = vm_fault_additional_pages(
 550                             fs.m, behind, ahead, marray, &reqpage);
 551
 552                         rv = faultcount ?
 553                             vm_pager_get_pages(fs.object, marray, faultcount,
 554                                 reqpage) : VM_PAGER_FAIL;
 555
 556                         if (rv == VM_PAGER_OK) {
 557                                 /*
 558                                  * Found the page. Leave it busy while we play
 559                                  * with it.
 560                                  */
 561
 562                                 /*
 563                                  * Relookup in case pager changed page. Pager
 564                                  * is responsible for disposition of old page
 565                                  * if moved.
 566                                  */
 567                                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 568                                 if (!fs.m) {
 569                                         unlock_and_deallocate(&fs);
 570                                         goto RetryFault;
 571                                 }
 572
 573                                 hardfault++;
 574                                 break; /* break to PAGE HAS BEEN FOUND */
 575                         }
 576                         /*
 577                          * Remove the bogus page (which does not exist at this
 578                          * object/offset); before doing so, we must get back
 579                          * our object lock to preserve our invariant.
 580                          *
 581                          * Also wake up any other process that may want to bring
 582                          * in this page.
 583                          *
 584                          * If this is the top-level object, we must leave the
 585                          * busy page to prevent another process from rushing
 586                          * past us, and inserting the page in that object at
 587                          * the same time that we are.
 588                          */
 589                         if (rv == VM_PAGER_ERROR)
 590                                 printf("vm_fault: pager read error, pid %d (%s)\n",
 591                                     curproc->p_pid, curproc->p_comm);
 592                         /*
 593                          * Data outside the range of the pager or an I/O error
 594                          */
 595                         /*
 596                          * XXX - the check for kernel_map is a kludge to work
 597                          * around having the machine panic on a kernel space
 598                          * fault w/ I/O error.
 599                          */
 600                         if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
 601                                 (rv == VM_PAGER_BAD)) {
 602                                 vm_page_lock(fs.m);
 603                                 vm_page_free(fs.m);
 604                                 vm_page_unlock(fs.m);
 605                                 fs.m = NULL;
 606                                 unlock_and_deallocate(&fs);
 607                                 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
 608                         }
 609                         if (fs.object != fs.first_object) {
 610                                 vm_page_lock(fs.m);
 611                                 vm_page_free(fs.m);
 612                                 vm_page_unlock(fs.m);
 613                                 fs.m = NULL;
 614                                 /*
 615                                  * XXX - we cannot just fall out at this
 616                                  * point, m has been freed and is invalid!
 617                                  */
 618                         }
 619                 }
 620
 621                 /*
 622                  * We get here if the object has default pager (or unwiring)
 623                  * or the pager doesn't have the page.
 624                  */
 625                 if (fs.object == fs.first_object)
 626                         fs.first_m = fs.m;
 627
 628                 /*
 629                  * Move on to the next object.  Lock the next object before
 630                  * unlocking the current one.
 631                  */
 632                 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
 633                 next_object = fs.object->backing_object;
 634                 if (next_object == NULL) {
 635                         /*
 636                          * If there's no object left, fill the page in the top
 637                          * object with zeros.
 638                          */
 639                         if (fs.object != fs.first_object) {
 640                                 vm_object_pip_wakeup(fs.object);
 641                                 VM_OBJECT_WUNLOCK(fs.object);
 642
 643                                 fs.object = fs.first_object;
 644                                 fs.pindex = fs.first_pindex;
 645                                 fs.m = fs.first_m;
 646                                 VM_OBJECT_WLOCK(fs.object);
 647                         }
 648                         fs.first_m = NULL;
 649
 650                         /*
 651                          * Zero the page if necessary and mark it valid.
 652                          */
 653                         if ((fs.m->flags & PG_ZERO) == 0) {
 654                                 pmap_zero_page(fs.m);
 655                         } else {
 656                                 PCPU_INC(cnt.v_ozfod);
 657                         }
 658                         PCPU_INC(cnt.v_zfod);
 659                         fs.m->valid = VM_PAGE_BITS_ALL;
 660                         /* Don't try to prefault neighboring pages. */
 661                         faultcount = 1;
 662                         break;  /* break to PAGE HAS BEEN FOUND */
 663                 } else {
 664                         KASSERT(fs.object != next_object,
 665                             ("object loop %p", next_object));
 666                         VM_OBJECT_WLOCK(next_object);
 667                         vm_object_pip_add(next_object, 1);
 668                         if (fs.object != fs.first_object)
 669                                 vm_object_pip_wakeup(fs.object);
 670                         VM_OBJECT_WUNLOCK(fs.object);
 671                         fs.object = next_object;
 672                 }
 673         }
 674
 675         vm_page_assert_xbusied(fs.m);
 676
 677         /*
 678          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
 679          * is held.]
 680          */
 681
 682         /*
 683          * If the page is being written, but isn't already owned by the
 684          * top-level object, we have to copy it into a new page owned by the
 685          * top-level object.
 686          */
 687         if (fs.object != fs.first_object) {
 688                 /*
 689                  * We only really need to copy if we want to write it.
 690                  */
 691                 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
 692                         /*
 693                          * This allows pages to be virtually copied from a
 694                          * backing_object into the first_object, where the
 695                          * backing object has no other refs to it, and cannot
 696                          * gain any more refs.  Instead of a bcopy, we just
 697                          * move the page from the backing object to the
 698                          * first object.  Note that we must mark the page
 699                          * dirty in the first object so that it will go out
 700                          * to swap when needed.
 701                          */
 702                         is_first_object_locked = FALSE;
 703                         if (
 704                                 /*
 705                                  * Only one shadow object
 706                                  */
 707                                 (fs.object->shadow_count == 1) &&
 708                                 /*
 709                                  * No COW refs, except us
 710                                  */
 711                                 (fs.object->ref_count == 1) &&
 712                                 /*
 713                                  * No one else can look this object up
 714                                  */
 715                                 (fs.object->handle == NULL) &&
 716                                 /*
 717                                  * No other ways to look the object up
 718                                  */
 719                                 ((fs.object->type == OBJT_DEFAULT) ||
 720                                  (fs.object->type == OBJT_SWAP)) &&
 721                             (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
 722                                 /*
 723                                  * We don't chase down the shadow chain
 724                                  */
 725                             fs.object == fs.first_object->backing_object) {
 726                                 /*
 727                                  * get rid of the unnecessary page
 728                                  */
 729                                 vm_page_lock(fs.first_m);
 730                                 vm_page_free(fs.first_m);
 731                                 vm_page_unlock(fs.first_m);
 732                                 /*
 733                                  * grab the page and put it into the
 734                                  * process'es object.  The page is
 735                                  * automatically made dirty.
 736                                  */
 737                                 if (vm_page_rename(fs.m, fs.first_object,
 738                                     fs.first_pindex)) {
 739                                         unlock_and_deallocate(&fs);
 740                                         goto RetryFault;
 741                                 }
 742                                 vm_page_xbusy(fs.m);
 743                                 fs.first_m = fs.m;
 744                                 fs.m = NULL;
 745                                 PCPU_INC(cnt.v_cow_optim);
 746                         } else {
 747                                 /*
 748                                  * Oh, well, lets copy it.
 749                                  */
 750                                 pmap_copy_page(fs.m, fs.first_m);
 751                                 fs.first_m->valid = VM_PAGE_BITS_ALL;
 752                                 if (wired && (fault_flags &
 753                                     VM_FAULT_CHANGE_WIRING) == 0) {
 754                                         vm_page_lock(fs.first_m);
 755                                         vm_page_wire(fs.first_m);
 756                                         vm_page_unlock(fs.first_m);
 757
 758                                         vm_page_lock(fs.m);
 759                                         vm_page_unwire(fs.m, PQ_INACTIVE);
 760                                         vm_page_unlock(fs.m);
 761                                 }
 762                                 /*
 763                                  * We no longer need the old page or object.
 764                                  */
 765                                 release_page(&fs);
 766                         }
 767                         /*
 768                          * fs.object != fs.first_object due to above
 769                          * conditional
 770                          */
 771                         vm_object_pip_wakeup(fs.object);
 772                         VM_OBJECT_WUNLOCK(fs.object);
 773                         /*
 774                          * Only use the new page below...
 775                          */
 776                         fs.object = fs.first_object;
 777                         fs.pindex = fs.first_pindex;
 778                         fs.m = fs.first_m;
 779                         if (!is_first_object_locked)
 780                                 VM_OBJECT_WLOCK(fs.object);
 781                         PCPU_INC(cnt.v_cow_faults);
 782                         curthread->td_cow++;
 783                 } else {
 784                         prot &= ~VM_PROT_WRITE;
 785                 }
 786         }
 787
 788         /*
 789          * We must verify that the maps have not changed since our last
 790          * lookup.
 791          */
 792         if (!fs.lookup_still_valid) {
 793                 vm_object_t retry_object;
 794                 vm_pindex_t retry_pindex;
 795                 vm_prot_t retry_prot;
 796
 797                 if (!vm_map_trylock_read(fs.map)) {
 798                         release_page(&fs);
 799                         unlock_and_deallocate(&fs);
 800                         goto RetryFault;
 801                 }
 802                 fs.lookup_still_valid = TRUE;
 803                 if (fs.map->timestamp != map_generation) {
 804                         result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
 805                             &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
 806
 807                         /*
 808                          * If we don't need the page any longer, put it on the inactive
 809                          * list (the easiest thing to do here).  If no one needs it,
 810                          * pageout will grab it eventually.
 811                          */
 812                         if (result != KERN_SUCCESS) {
 813                                 release_page(&fs);
 814                                 unlock_and_deallocate(&fs);
 815
 816                                 /*
 817                                  * If retry of map lookup would have blocked then
 818                                  * retry fault from start.
 819                                  */
 820                                 if (result == KERN_FAILURE)
 821                                         goto RetryFault;
 822                                 return (result);
 823                         }
 824                         if ((retry_object != fs.first_object) ||
 825                             (retry_pindex != fs.first_pindex)) {
 826                                 release_page(&fs);
 827                                 unlock_and_deallocate(&fs);
 828                                 goto RetryFault;
 829                         }
 830
 831                         /*
 832                          * Check whether the protection has changed or the object has
 833                          * been copied while we left the map unlocked. Changing from
 834                          * read to write permission is OK - we leave the page
 835                          * write-protected, and catch the write fault. Changing from
 836                          * write to read permission means that we can't mark the page
 837                          * write-enabled after all.
 838                          */
 839                         prot &= retry_prot;
 840                 }
 841         }
 842         /*
 843          * If the page was filled by a pager, update the map entry's
 844          * last read offset.  Since the pager does not return the
 845          * actual set of pages that it read, this update is based on
 846          * the requested set.  Typically, the requested and actual
 847          * sets are the same.
 848          *
 849          * XXX The following assignment modifies the map
 850          * without holding a write lock on it.
 851          */
 852         if (hardfault)
 853                 fs.entry->next_read = fs.pindex + faultcount - reqpage;
 854
 855         if ((prot & VM_PROT_WRITE) != 0 ||
 856             (fault_flags & VM_FAULT_DIRTY) != 0) {
 857                 vm_object_set_writeable_dirty(fs.object);
 858
 859                 /*
 860                  * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
 861                  * if the page is already dirty to prevent data written with
 862                  * the expectation of being synced from not being synced.
 863                  * Likewise if this entry does not request NOSYNC then make
 864                  * sure the page isn't marked NOSYNC.  Applications sharing
 865                  * data should use the same flags to avoid ping ponging.
 866                  */
 867                 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) {
 868                         if (fs.m->dirty == 0)
 869                                 fs.m->oflags |= VPO_NOSYNC;
 870                 } else {
 871                         fs.m->oflags &= ~VPO_NOSYNC;
 872                 }
 873
 874                 /*
 875                  * If the fault is a write, we know that this page is being
 876                  * written NOW so dirty it explicitly to save on
 877                  * pmap_is_modified() calls later.
 878                  *
 879                  * Also tell the backing pager, if any, that it should remove
 880                  * any swap backing since the page is now dirty.
 881                  */
 882                 if (((fault_type & VM_PROT_WRITE) != 0 &&
 883                     (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) ||
 884                     (fault_flags & VM_FAULT_DIRTY) != 0) {
 885                         vm_page_dirty(fs.m);
 886                         vm_pager_page_unswapped(fs.m);
 887                 }
 888         }
 889
 890         vm_page_assert_xbusied(fs.m);
 891
 892         /*
 893          * Page must be completely valid or it is not fit to
 894          * map into user space.  vm_pager_get_pages() ensures this.
 895          */
 896         KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
 897             ("vm_fault: page %p partially invalid", fs.m));
 898         VM_OBJECT_WUNLOCK(fs.object);
 899
 900         /*
 901          * Put this page into the physical map.  We had to do the unlock above
 902          * because pmap_enter() may sleep.  We don't put the page
 903          * back on the active queue until later so that the pageout daemon
 904          * won't find it (yet).
 905          */
 906         pmap_enter(fs.map->pmap, vaddr, fault_type, fs.m, prot, wired);
 907         if (faultcount != 1 && (fault_flags & VM_FAULT_CHANGE_WIRING) == 0 &&
 908             wired == 0)
 909                 vm_fault_prefault(&fs, vaddr, faultcount, reqpage);
 910         VM_OBJECT_WLOCK(fs.object);
 911         vm_page_lock(fs.m);
 912
 913         /*
 914          * If the page is not wired down, then put it where the pageout daemon
 915          * can find it.
 916          */
 917         if (fault_flags & VM_FAULT_CHANGE_WIRING) {
 918                 if (wired)
 919                         vm_page_wire(fs.m);
 920                 else
 921                         vm_page_unwire(fs.m, PQ_ACTIVE);
 922         } else
 923                 vm_page_activate(fs.m);
 924         if (m_hold != NULL) {
 925                 *m_hold = fs.m;
 926                 vm_page_hold(fs.m);
 927         }
 928         vm_page_unlock(fs.m);
 929         vm_page_xunbusy(fs.m);
 930
 931         /*
 932          * Unlock everything, and return
 933          */
 934         unlock_and_deallocate(&fs);
 935         if (hardfault) {
 936                 PCPU_INC(cnt.v_io_faults);
 937                 curthread->td_ru.ru_majflt++;
 938         } else
 939                 curthread->td_ru.ru_minflt++;
 940
 941         return (KERN_SUCCESS);
 942 }
 943
 944 /*
 945  * Speed up the reclamation of up to "distance" pages that precede the
 946  * faulting pindex within the first object of the shadow chain.
 947  */
 948 static void
 949 vm_fault_cache_behind(const struct faultstate *fs, int distance)
 950 {
 951         vm_object_t first_object, object;
 952         vm_page_t m, m_prev;
 953         vm_pindex_t pindex;
 954
 955         object = fs->object;
 956         VM_OBJECT_ASSERT_WLOCKED(object);
 957         first_object = fs->first_object;
 958         if (first_object != object) {
 959                 if (!VM_OBJECT_TRYWLOCK(first_object)) {
 960                         VM_OBJECT_WUNLOCK(object);
 961                         VM_OBJECT_WLOCK(first_object);
 962                         VM_OBJECT_WLOCK(object);
 963                 }
 964         }
 965         /* Neither fictitious nor unmanaged pages can be cached. */
 966         if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
 967                 if (fs->first_pindex < distance)
 968                         pindex = 0;
 969                 else
 970                         pindex = fs->first_pindex - distance;
 971                 if (pindex < OFF_TO_IDX(fs->entry->offset))
 972                         pindex = OFF_TO_IDX(fs->entry->offset);
 973                 m = first_object != object ? fs->first_m : fs->m;
 974                 vm_page_assert_xbusied(m);
 975                 m_prev = vm_page_prev(m);
 976                 while ((m = m_prev) != NULL && m->pindex >= pindex &&
 977                     m->valid == VM_PAGE_BITS_ALL) {
 978                         m_prev = vm_page_prev(m);
 979                         if (vm_page_busied(m))
 980                                 continue;
 981                         vm_page_lock(m);
 982                         if (m->hold_count == 0 && m->wire_count == 0) {
 983                                 pmap_remove_all(m);
 984                                 vm_page_aflag_clear(m, PGA_REFERENCED);
 985                                 if (m->dirty != 0)
 986                                         vm_page_deactivate(m);
 987                                 else
 988                                         vm_page_cache(m);
 989                         }
 990                         vm_page_unlock(m);
 991                 }
 992         }
 993         if (first_object != object)
 994                 VM_OBJECT_WUNLOCK(first_object);
 995 }
 996
 997 /*
 998  * vm_fault_prefault provides a quick way of clustering
 999  * pagefaults into a processes address space.  It is a "cousin"
1000  * of vm_map_pmap_enter, except it runs at page fault time instead
1001  * of mmap time.
1002  */
1003 static void
1004 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1005     int faultcount, int reqpage)
1006 {
1007         pmap_t pmap;
1008         vm_map_entry_t entry;
1009         vm_object_t backing_object, lobject;
1010         vm_offset_t addr, starta;
1011         vm_pindex_t pindex;
1012         vm_page_t m;
1013         int backward, forward, i;
1014
1015         pmap = fs->map->pmap;
1016         if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1017                 return;
1018
1019         if (faultcount > 0) {
1020                 backward = reqpage;
1021                 forward = faultcount - reqpage - 1;
1022         } else {
1023                 backward = PFBAK;
1024                 forward = PFFOR;
1025         }
1026         entry = fs->entry;
1027
1028         starta = addra - backward * PAGE_SIZE;
1029         if (starta < entry->start) {
1030                 starta = entry->start;
1031         } else if (starta > addra) {
1032                 starta = 0;
1033         }
1034
1035         /*
1036          * Generate the sequence of virtual addresses that are candidates for
1037          * prefaulting in an outward spiral from the faulting virtual address,
1038          * "addra".  Specifically, the sequence is "addra - PAGE_SIZE", "addra
1039          * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1040          * If the candidate address doesn't have a backing physical page, then
1041          * the loop immediately terminates.
1042          */
1043         for (i = 0; i < 2 * imax(backward, forward); i++) {
1044                 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1045                     PAGE_SIZE);
1046                 if (addr > addra + forward * PAGE_SIZE)
1047                         addr = 0;
1048
1049                 if (addr < starta || addr >= entry->end)
1050                         continue;
1051
1052                 if (!pmap_is_prefaultable(pmap, addr))
1053                         continue;
1054
1055                 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1056                 lobject = entry->object.vm_object;
1057                 VM_OBJECT_RLOCK(lobject);
1058                 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1059                     lobject->type == OBJT_DEFAULT &&
1060                     (backing_object = lobject->backing_object) != NULL) {
1061                         KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1062                             0, ("vm_fault_prefault: unaligned object offset"));
1063                         pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1064                         VM_OBJECT_RLOCK(backing_object);
1065                         VM_OBJECT_RUNLOCK(lobject);
1066                         lobject = backing_object;
1067                 }
1068                 if (m == NULL) {
1069                         VM_OBJECT_RUNLOCK(lobject);
1070                         break;
1071                 }
1072                 if (m->valid == VM_PAGE_BITS_ALL &&
1073                     (m->flags & PG_FICTITIOUS) == 0)
1074                         pmap_enter_quick(pmap, addr, m, entry->protection);
1075                 VM_OBJECT_RUNLOCK(lobject);
1076         }
1077 }
1078
1079 /*
1080  * Hold each of the physical pages that are mapped by the specified range of
1081  * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1082  * and allow the specified types of access, "prot".  If all of the implied
1083  * pages are successfully held, then the number of held pages is returned
1084  * together with pointers to those pages in the array "ma".  However, if any
1085  * of the pages cannot be held, -1 is returned.
1086  */
1087 int
1088 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1089     vm_prot_t prot, vm_page_t *ma, int max_count)
1090 {
1091         vm_offset_t end, va;
1092         vm_page_t *mp;
1093         int count;
1094         boolean_t pmap_failed;
1095
1096         if (len == 0)
1097                 return (0);
1098         end = round_page(addr + len);
1099         addr = trunc_page(addr);
1100
1101         /*
1102          * Check for illegal addresses.
1103          */
1104         if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1105                 return (-1);
1106
1107         if (atop(end - addr) > max_count)
1108                 panic("vm_fault_quick_hold_pages: count > max_count");
1109         count = atop(end - addr);
1110
1111         /*
1112          * Most likely, the physical pages are resident in the pmap, so it is
1113          * faster to try pmap_extract_and_hold() first.
1114          */
1115         pmap_failed = FALSE;
1116         for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1117                 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1118                 if (*mp == NULL)
1119                         pmap_failed = TRUE;
1120                 else if ((prot & VM_PROT_WRITE) != 0 &&
1121                     (*mp)->dirty != VM_PAGE_BITS_ALL) {
1122                         /*
1123                          * Explicitly dirty the physical page.  Otherwise, the
1124                          * caller's changes may go unnoticed because they are
1125                          * performed through an unmanaged mapping or by a DMA
1126                          * operation.
1127                          *
1128                          * The object lock is not held here.
1129                          * See vm_page_clear_dirty_mask().
1130                          */
1131                         vm_page_dirty(*mp);
1132                 }
1133         }
1134         if (pmap_failed) {
1135                 /*
1136                  * One or more pages could not be held by the pmap.  Either no
1137                  * page was mapped at the specified virtual address or that
1138                  * mapping had insufficient permissions.  Attempt to fault in
1139                  * and hold these pages.
1140                  */
1141                 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1142                         if (*mp == NULL && vm_fault_hold(map, va, prot,
1143                             VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1144                                 goto error;
1145         }
1146         return (count);
1147 error:
1148         for (mp = ma; mp < ma + count; mp++)
1149                 if (*mp != NULL) {
1150                         vm_page_lock(*mp);
1151                         vm_page_unhold(*mp);
1152                         vm_page_unlock(*mp);
1153                 }
1154         return (-1);
1155 }
1156
1157 /*
1158  *      vm_fault_wire:
1159  *
1160  *      Wire down a range of virtual addresses in a map.
1161  */
1162 int
1163 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1164     boolean_t fictitious)
1165 {
1166         vm_offset_t va;
1167         int rv;
1168
1169         /*
1170          * We simulate a fault to get the page and enter it in the physical
1171          * map.  For user wiring, we only ask for read access on currently
1172          * read-only sections.
1173          */
1174         for (va = start; va < end; va += PAGE_SIZE) {
1175                 rv = vm_fault(map, va, VM_PROT_NONE, VM_FAULT_CHANGE_WIRING);
1176                 if (rv) {
1177                         if (va != start)
1178                                 vm_fault_unwire(map, start, va, fictitious);
1179                         return (rv);
1180                 }
1181         }
1182         return (KERN_SUCCESS);
1183 }
1184
1185 /*
1186  *      vm_fault_unwire:
1187  *
1188  *      Unwire a range of virtual addresses in a map.
1189  */
1190 static void
1191 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1192     boolean_t fictitious)
1193 {
1194         vm_paddr_t pa;
1195         vm_offset_t va;
1196         vm_page_t m;
1197         pmap_t pmap;
1198
1199         pmap = vm_map_pmap(map);
1200
1201         /*
1202          * Since the pages are wired down, we must be able to get their
1203          * mappings from the physical map system.
1204          */
1205         for (va = start; va < end; va += PAGE_SIZE) {
1206                 pa = pmap_extract(pmap, va);
1207                 if (pa != 0) {
1208                         pmap_change_wiring(pmap, va, FALSE);
1209                         if (!fictitious) {
1210                                 m = PHYS_TO_VM_PAGE(pa);
1211                                 vm_page_lock(m);
1212                                 vm_page_unwire(m, PQ_ACTIVE);
1213                                 vm_page_unlock(m);
1214                         }
1215                 }
1216         }
1217 }
1218
1219 /*
1220  *      Routine:
1221  *              vm_fault_copy_entry
1222  *      Function:
1223  *              Create new shadow object backing dst_entry with private copy of
1224  *              all underlying pages. When src_entry is equal to dst_entry,
1225  *              function implements COW for wired-down map entry. Otherwise,
1226  *              it forks wired entry into dst_map.
1227  *
1228  *      In/out conditions:
1229  *              The source and destination maps must be locked for write.
1230  *              The source map entry must be wired down (or be a sharing map
1231  *              entry corresponding to a main map entry that is wired down).
1232  */
1233 void
1234 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1235     vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1236     vm_ooffset_t *fork_charge)
1237 {
1238         vm_object_t backing_object, dst_object, object, src_object;
1239         vm_pindex_t dst_pindex, pindex, src_pindex;
1240         vm_prot_t access, prot;
1241         vm_offset_t vaddr;
1242         vm_page_t dst_m;
1243         vm_page_t src_m;
1244         boolean_t upgrade;
1245
1246 #ifdef  lint
1247         src_map++;
1248 #endif  /* lint */
1249
1250         upgrade = src_entry == dst_entry;
1251         access = prot = dst_entry->protection;
1252
1253         src_object = src_entry->object.vm_object;
1254         src_pindex = OFF_TO_IDX(src_entry->offset);
1255
1256         if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1257                 dst_object = src_object;
1258                 vm_object_reference(dst_object);
1259         } else {
1260                 /*
1261                  * Create the top-level object for the destination entry. (Doesn't
1262                  * actually shadow anything - we copy the pages directly.)
1263                  */
1264                 dst_object = vm_object_allocate(OBJT_DEFAULT,
1265                     OFF_TO_IDX(dst_entry->end - dst_entry->start));
1266 #if VM_NRESERVLEVEL > 0
1267                 dst_object->flags |= OBJ_COLORED;
1268                 dst_object->pg_color = atop(dst_entry->start);
1269 #endif
1270         }
1271
1272         VM_OBJECT_WLOCK(dst_object);
1273         KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1274             ("vm_fault_copy_entry: vm_object not NULL"));
1275         if (src_object != dst_object) {
1276                 dst_entry->object.vm_object = dst_object;
1277                 dst_entry->offset = 0;
1278                 dst_object->charge = dst_entry->end - dst_entry->start;
1279         }
1280         if (fork_charge != NULL) {
1281                 KASSERT(dst_entry->cred == NULL,
1282                     ("vm_fault_copy_entry: leaked swp charge"));
1283                 dst_object->cred = curthread->td_ucred;
1284                 crhold(dst_object->cred);
1285                 *fork_charge += dst_object->charge;
1286         } else if (dst_object->cred == NULL) {
1287                 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1288                     dst_entry));
1289                 dst_object->cred = dst_entry->cred;
1290                 dst_entry->cred = NULL;
1291         }
1292
1293         /*
1294          * If not an upgrade, then enter the mappings in the pmap as
1295          * read and/or execute accesses.  Otherwise, enter them as
1296          * write accesses.
1297          *
1298          * A writeable large page mapping is only created if all of
1299          * the constituent small page mappings are modified. Marking
1300          * PTEs as modified on inception allows promotion to happen
1301          * without taking potentially large number of soft faults.
1302          */
1303         if (!upgrade)
1304                 access &= ~VM_PROT_WRITE;
1305
1306         /*
1307          * Loop through all of the virtual pages within the entry's
1308          * range, copying each page from the source object to the
1309          * destination object.  Since the source is wired, those pages
1310          * must exist.  In contrast, the destination is pageable.
1311          * Since the destination object does share any backing storage
1312          * with the source object, all of its pages must be dirtied,
1313          * regardless of whether they can be written.
1314          */
1315         for (vaddr = dst_entry->start, dst_pindex = 0;
1316             vaddr < dst_entry->end;
1317             vaddr += PAGE_SIZE, dst_pindex++) {
1318 again:
1319                 /*
1320                  * Find the page in the source object, and copy it in.
1321                  * Because the source is wired down, the page will be
1322                  * in memory.
1323                  */
1324                 if (src_object != dst_object)
1325                         VM_OBJECT_RLOCK(src_object);
1326                 object = src_object;
1327                 pindex = src_pindex + dst_pindex;
1328                 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1329                     (backing_object = object->backing_object) != NULL) {
1330                         /*
1331                          * Unless the source mapping is read-only or
1332                          * it is presently being upgraded from
1333                          * read-only, the first object in the shadow
1334                          * chain should provide all of the pages.  In
1335                          * other words, this loop body should never be
1336                          * executed when the source mapping is already
1337                          * read/write.
1338                          */
1339                         KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1340                             upgrade,
1341                             ("vm_fault_copy_entry: main object missing page"));
1342
1343                         VM_OBJECT_RLOCK(backing_object);
1344                         pindex += OFF_TO_IDX(object->backing_object_offset);
1345                         if (object != dst_object)
1346                                 VM_OBJECT_RUNLOCK(object);
1347                         object = backing_object;
1348                 }
1349                 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1350
1351                 if (object != dst_object) {
1352                         /*
1353                          * Allocate a page in the destination object.
1354                          */
1355                         dst_m = vm_page_alloc(dst_object, (src_object ==
1356                             dst_object ? src_pindex : 0) + dst_pindex,
1357                             VM_ALLOC_NORMAL);
1358                         if (dst_m == NULL) {
1359                                 VM_OBJECT_WUNLOCK(dst_object);
1360                                 VM_OBJECT_RUNLOCK(object);
1361                                 VM_WAIT;
1362                                 VM_OBJECT_WLOCK(dst_object);
1363                                 goto again;
1364                         }
1365                         pmap_copy_page(src_m, dst_m);
1366                         VM_OBJECT_RUNLOCK(object);
1367                         dst_m->valid = VM_PAGE_BITS_ALL;
1368                         dst_m->dirty = VM_PAGE_BITS_ALL;
1369                 } else {
1370                         dst_m = src_m;
1371                         if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1372                                 goto again;
1373                         vm_page_xbusy(dst_m);
1374                         KASSERT(dst_m->valid == VM_PAGE_BITS_ALL,
1375                             ("invalid dst page %p", dst_m));
1376                 }
1377                 VM_OBJECT_WUNLOCK(dst_object);
1378
1379                 /*
1380                  * Enter it in the pmap. If a wired, copy-on-write
1381                  * mapping is being replaced by a write-enabled
1382                  * mapping, then wire that new mapping.
1383                  */
1384                 pmap_enter(dst_map->pmap, vaddr, access, dst_m, prot, upgrade);
1385
1386                 /*
1387                  * Mark it no longer busy, and put it on the active list.
1388                  */
1389                 VM_OBJECT_WLOCK(dst_object);
1390
1391                 if (upgrade) {
1392                         if (src_m != dst_m) {
1393                                 vm_page_lock(src_m);
1394                                 vm_page_unwire(src_m, PQ_INACTIVE);
1395                                 vm_page_unlock(src_m);
1396                                 vm_page_lock(dst_m);
1397                                 vm_page_wire(dst_m);
1398                                 vm_page_unlock(dst_m);
1399                         } else {
1400                                 KASSERT(dst_m->wire_count > 0,
1401                                     ("dst_m %p is not wired", dst_m));
1402                         }
1403                 } else {
1404                         vm_page_lock(dst_m);
1405                         vm_page_activate(dst_m);
1406                         vm_page_unlock(dst_m);
1407                 }
1408                 vm_page_xunbusy(dst_m);
1409         }
1410         VM_OBJECT_WUNLOCK(dst_object);
1411         if (upgrade) {
1412                 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1413                 vm_object_deallocate(src_object);
1414         }
1415 }
1416
1417
1418 /*
1419  * This routine checks around the requested page for other pages that
1420  * might be able to be faulted in.  This routine brackets the viable
1421  * pages for the pages to be paged in.
1422  *
1423  * Inputs:
1424  *      m, rbehind, rahead
1425  *
1426  * Outputs:
1427  *  marray (array of vm_page_t), reqpage (index of requested page)
1428  *
1429  * Return value:
1430  *  number of pages in marray
1431  */
1432 static int
1433 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1434         vm_page_t m;
1435         int rbehind;
1436         int rahead;
1437         vm_page_t *marray;
1438         int *reqpage;
1439 {
1440         int i,j;
1441         vm_object_t object;
1442         vm_pindex_t pindex, startpindex, endpindex, tpindex;
1443         vm_page_t rtm;
1444         int cbehind, cahead;
1445
1446         VM_OBJECT_ASSERT_WLOCKED(m->object);
1447
1448         object = m->object;
1449         pindex = m->pindex;
1450         cbehind = cahead = 0;
1451
1452         /*
1453          * if the requested page is not available, then give up now
1454          */
1455         if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1456                 return 0;
1457         }
1458
1459         if ((cbehind == 0) && (cahead == 0)) {
1460                 *reqpage = 0;
1461                 marray[0] = m;
1462                 return 1;
1463         }
1464
1465         if (rahead > cahead) {
1466                 rahead = cahead;
1467         }
1468
1469         if (rbehind > cbehind) {
1470                 rbehind = cbehind;
1471         }
1472
1473         /*
1474          * scan backward for the read behind pages -- in memory
1475          */
1476         if (pindex > 0) {
1477                 if (rbehind > pindex) {
1478                         rbehind = pindex;
1479                         startpindex = 0;
1480                 } else {
1481                         startpindex = pindex - rbehind;
1482                 }
1483
1484                 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL &&
1485                     rtm->pindex >= startpindex)
1486                         startpindex = rtm->pindex + 1;
1487
1488                 /* tpindex is unsigned; beware of numeric underflow. */
1489                 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex &&
1490                     tpindex < pindex; i++, tpindex--) {
1491
1492                         rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1493                             VM_ALLOC_IFNOTCACHED);
1494                         if (rtm == NULL) {
1495                                 /*
1496                                  * Shift the allocated pages to the
1497                                  * beginning of the array.
1498                                  */
1499                                 for (j = 0; j < i; j++) {
1500                                         marray[j] = marray[j + tpindex + 1 -
1501                                             startpindex];
1502                                 }
1503                                 break;
1504                         }
1505
1506                         marray[tpindex - startpindex] = rtm;
1507                 }
1508         } else {
1509                 startpindex = 0;
1510                 i = 0;
1511         }
1512
1513         marray[i] = m;
1514         /* page offset of the required page */
1515         *reqpage = i;
1516
1517         tpindex = pindex + 1;
1518         i++;
1519
1520         /*
1521          * scan forward for the read ahead pages
1522          */
1523         endpindex = tpindex + rahead;
1524         if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex)
1525                 endpindex = rtm->pindex;
1526         if (endpindex > object->size)
1527                 endpindex = object->size;
1528
1529         for (; tpindex < endpindex; i++, tpindex++) {
1530
1531                 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1532                     VM_ALLOC_IFNOTCACHED);
1533                 if (rtm == NULL) {
1534                         break;
1535                 }
1536
1537                 marray[i] = rtm;
1538         }
1539
1540         /* return number of pages */
1541         return i;
1542 }
1543
1544 /*
1545  * Block entry into the machine-independent layer's page fault handler by
1546  * the calling thread.  Subsequent calls to vm_fault() by that thread will
1547  * return KERN_PROTECTION_FAILURE.  Enable machine-dependent handling of
1548  * spurious page faults.
1549  */
1550 int
1551 vm_fault_disable_pagefaults(void)
1552 {
1553
1554         return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1555 }
1556
1557 void
1558 vm_fault_enable_pagefaults(int save)
1559 {
1560
1561         curthread_pflags_restore(save);
1562 }