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/mutex.h>
  85 #include <sys/proc.h>
  86 #include <sys/resourcevar.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 #include <sys/mount.h>  /* XXX Temporary for VFS_LOCK_GIANT() */
 106
 107 #define PFBAK 4
 108 #define PFFOR 4
 109 #define PAGEORDER_SIZE (PFBAK+PFFOR)
 110
 111 static int prefault_pageorder[] = {
 112         -1 * PAGE_SIZE, 1 * PAGE_SIZE,
 113         -2 * PAGE_SIZE, 2 * PAGE_SIZE,
 114         -3 * PAGE_SIZE, 3 * PAGE_SIZE,
 115         -4 * PAGE_SIZE, 4 * PAGE_SIZE
 116 };
 117
 118 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
 119 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t);
 120
 121 #define VM_FAULT_READ_BEHIND    8
 122 #define VM_FAULT_READ_MAX       (1 + VM_FAULT_READ_AHEAD_MAX)
 123 #define VM_FAULT_NINCR          (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND)
 124 #define VM_FAULT_SUM            (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2)
 125 #define VM_FAULT_CACHE_BEHIND   (VM_FAULT_READ_BEHIND * VM_FAULT_SUM)
 126
 127 struct faultstate {
 128         vm_page_t m;
 129         vm_object_t object;
 130         vm_pindex_t pindex;
 131         vm_page_t first_m;
 132         vm_object_t     first_object;
 133         vm_pindex_t first_pindex;
 134         vm_map_t map;
 135         vm_map_entry_t entry;
 136         int lookup_still_valid;
 137         struct vnode *vp;
 138         int vfslocked;
 139 };
 140
 141 static void vm_fault_cache_behind(const struct faultstate *fs, int distance);
 142
 143 static inline void
 144 release_page(struct faultstate *fs)
 145 {
 146
 147         vm_page_wakeup(fs->m);
 148         vm_page_lock(fs->m);
 149         vm_page_deactivate(fs->m);
 150         vm_page_unlock(fs->m);
 151         fs->m = NULL;
 152 }
 153
 154 static inline void
 155 unlock_map(struct faultstate *fs)
 156 {
 157
 158         if (fs->lookup_still_valid) {
 159                 vm_map_lookup_done(fs->map, fs->entry);
 160                 fs->lookup_still_valid = FALSE;
 161         }
 162 }
 163
 164 static void
 165 unlock_and_deallocate(struct faultstate *fs)
 166 {
 167
 168         vm_object_pip_wakeup(fs->object);
 169         VM_OBJECT_UNLOCK(fs->object);
 170         if (fs->object != fs->first_object) {
 171                 VM_OBJECT_LOCK(fs->first_object);
 172                 vm_page_lock(fs->first_m);
 173                 vm_page_free(fs->first_m);
 174                 vm_page_unlock(fs->first_m);
 175                 vm_object_pip_wakeup(fs->first_object);
 176                 VM_OBJECT_UNLOCK(fs->first_object);
 177                 fs->first_m = NULL;
 178         }
 179         vm_object_deallocate(fs->first_object);
 180         unlock_map(fs);
 181         if (fs->vp != NULL) {
 182                 vput(fs->vp);
 183                 fs->vp = NULL;
 184         }
 185         VFS_UNLOCK_GIANT(fs->vfslocked);
 186         fs->vfslocked = 0;
 187 }
 188
 189 /*
 190  * TRYPAGER - used by vm_fault to calculate whether the pager for the
 191  *            current object *might* contain the page.
 192  *
 193  *            default objects are zero-fill, there is no real pager.
 194  */
 195 #define TRYPAGER        (fs.object->type != OBJT_DEFAULT && \
 196                         ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 || wired))
 197
 198 /*
 199  *      vm_fault:
 200  *
 201  *      Handle a page fault occurring at the given address,
 202  *      requiring the given permissions, in the map specified.
 203  *      If successful, the page is inserted into the
 204  *      associated physical map.
 205  *
 206  *      NOTE: the given address should be truncated to the
 207  *      proper page address.
 208  *
 209  *      KERN_SUCCESS is returned if the page fault is handled; otherwise,
 210  *      a standard error specifying why the fault is fatal is returned.
 211  *
 212  *      The map in question must be referenced, and remains so.
 213  *      Caller may hold no locks.
 214  */
 215 int
 216 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 217     int fault_flags)
 218 {
 219         struct thread *td;
 220         int result;
 221
 222         td = curthread;
 223         if ((td->td_pflags & TDP_NOFAULTING) != 0)
 224                 return (KERN_PROTECTION_FAILURE);
 225 #ifdef KTRACE
 226         if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
 227                 ktrfault(vaddr, fault_type);
 228 #endif
 229         result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
 230             NULL);
 231 #ifdef KTRACE
 232         if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
 233                 ktrfaultend(result);
 234 #endif
 235         return (result);
 236 }
 237
 238 int
 239 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
 240     int fault_flags, vm_page_t *m_hold)
 241 {
 242         vm_prot_t prot;
 243         long ahead, behind;
 244         int alloc_req, era, faultcount, nera, reqpage, result;
 245         boolean_t growstack, is_first_object_locked, wired;
 246         int map_generation;
 247         vm_object_t next_object;
 248         vm_page_t marray[VM_FAULT_READ_MAX];
 249         int hardfault;
 250         struct faultstate fs;
 251         struct vnode *vp;
 252         int locked, error;
 253
 254         hardfault = 0;
 255         growstack = TRUE;
 256         PCPU_INC(cnt.v_vm_faults);
 257         fs.vp = NULL;
 258         fs.vfslocked = 0;
 259         faultcount = reqpage = 0;
 260
 261 RetryFault:;
 262
 263         /*
 264          * Find the backing store object and offset into it to begin the
 265          * search.
 266          */
 267         fs.map = map;
 268         result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
 269             &fs.first_object, &fs.first_pindex, &prot, &wired);
 270         if (result != KERN_SUCCESS) {
 271                 if (growstack && result == KERN_INVALID_ADDRESS &&
 272                     map != kernel_map) {
 273                         result = vm_map_growstack(curproc, vaddr);
 274                         if (result != KERN_SUCCESS)
 275                                 return (KERN_FAILURE);
 276                         growstack = FALSE;
 277                         goto RetryFault;
 278                 }
 279                 return (result);
 280         }
 281
 282         map_generation = fs.map->timestamp;
 283
 284         if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
 285                 panic("vm_fault: fault on nofault entry, addr: %lx",
 286                     (u_long)vaddr);
 287         }
 288
 289         if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
 290             fs.entry->wiring_thread != curthread) {
 291                 vm_map_unlock_read(fs.map);
 292                 vm_map_lock(fs.map);
 293                 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
 294                     (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
 295                         fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
 296                         vm_map_unlock_and_wait(fs.map, 0);
 297                 } else
 298                         vm_map_unlock(fs.map);
 299                 goto RetryFault;
 300         }
 301
 302         /*
 303          * Make a reference to this object to prevent its disposal while we
 304          * are messing with it.  Once we have the reference, the map is free
 305          * to be diddled.  Since objects reference their shadows (and copies),
 306          * they will stay around as well.
 307          *
 308          * Bump the paging-in-progress count to prevent size changes (e.g.
 309          * truncation operations) during I/O.  This must be done after
 310          * obtaining the vnode lock in order to avoid possible deadlocks.
 311          */
 312         VM_OBJECT_LOCK(fs.first_object);
 313         vm_object_reference_locked(fs.first_object);
 314         vm_object_pip_add(fs.first_object, 1);
 315
 316         fs.lookup_still_valid = TRUE;
 317
 318         if (wired)
 319                 fault_type = prot | (fault_type & VM_PROT_COPY);
 320
 321         fs.first_m = NULL;
 322
 323         /*
 324          * Search for the page at object/offset.
 325          */
 326         fs.object = fs.first_object;
 327         fs.pindex = fs.first_pindex;
 328         while (TRUE) {
 329                 /*
 330                  * If the object is dead, we stop here
 331                  */
 332                 if (fs.object->flags & OBJ_DEAD) {
 333                         unlock_and_deallocate(&fs);
 334                         return (KERN_PROTECTION_FAILURE);
 335                 }
 336
 337                 /*
 338                  * See if page is resident
 339                  */
 340                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 341                 if (fs.m != NULL) {
 342                         /*
 343                          * check for page-based copy on write.
 344                          * We check fs.object == fs.first_object so
 345                          * as to ensure the legacy COW mechanism is
 346                          * used when the page in question is part of
 347                          * a shadow object.  Otherwise, vm_page_cowfault()
 348                          * removes the page from the backing object,
 349                          * which is not what we want.
 350                          */
 351                         vm_page_lock(fs.m);
 352                         if ((fs.m->cow) &&
 353                             (fault_type & VM_PROT_WRITE) &&
 354                             (fs.object == fs.first_object)) {
 355                                 vm_page_cowfault(fs.m);
 356                                 unlock_and_deallocate(&fs);
 357                                 goto RetryFault;
 358                         }
 359
 360                         /*
 361                          * Wait/Retry if the page is busy.  We have to do this
 362                          * if the page is busy via either VPO_BUSY or
 363                          * vm_page_t->busy because the vm_pager may be using
 364                          * vm_page_t->busy for pageouts ( and even pageins if
 365                          * it is the vnode pager ), and we could end up trying
 366                          * to pagein and pageout the same page simultaneously.
 367                          *
 368                          * We can theoretically allow the busy case on a read
 369                          * fault if the page is marked valid, but since such
 370                          * pages are typically already pmap'd, putting that
 371                          * special case in might be more effort then it is
 372                          * worth.  We cannot under any circumstances mess
 373                          * around with a vm_page_t->busy page except, perhaps,
 374                          * to pmap it.
 375                          */
 376                         if ((fs.m->oflags & VPO_BUSY) || fs.m->busy) {
 377                                 /*
 378                                  * Reference the page before unlocking and
 379                                  * sleeping so that the page daemon is less
 380                                  * likely to reclaim it.
 381                                  */
 382                                 vm_page_aflag_set(fs.m, PGA_REFERENCED);
 383                                 vm_page_unlock(fs.m);
 384                                 if (fs.object != fs.first_object) {
 385                                         if (!VM_OBJECT_TRYLOCK(
 386                                             fs.first_object)) {
 387                                                 VM_OBJECT_UNLOCK(fs.object);
 388                                                 VM_OBJECT_LOCK(fs.first_object);
 389                                                 VM_OBJECT_LOCK(fs.object);
 390                                         }
 391                                         vm_page_lock(fs.first_m);
 392                                         vm_page_free(fs.first_m);
 393                                         vm_page_unlock(fs.first_m);
 394                                         vm_object_pip_wakeup(fs.first_object);
 395                                         VM_OBJECT_UNLOCK(fs.first_object);
 396                                         fs.first_m = NULL;
 397                                 }
 398                                 unlock_map(&fs);
 399                                 if (fs.m == vm_page_lookup(fs.object,
 400                                     fs.pindex)) {
 401                                         vm_page_sleep_if_busy(fs.m, TRUE,
 402                                             "vmpfw");
 403                                 }
 404                                 vm_object_pip_wakeup(fs.object);
 405                                 VM_OBJECT_UNLOCK(fs.object);
 406                                 PCPU_INC(cnt.v_intrans);
 407                                 vm_object_deallocate(fs.first_object);
 408                                 goto RetryFault;
 409                         }
 410                         vm_pageq_remove(fs.m);
 411                         vm_page_unlock(fs.m);
 412
 413                         /*
 414                          * Mark page busy for other processes, and the
 415                          * pagedaemon.  If it still isn't completely valid
 416                          * (readable), jump to readrest, else break-out ( we
 417                          * found the page ).
 418                          */
 419                         vm_page_busy(fs.m);
 420                         if (fs.m->valid != VM_PAGE_BITS_ALL)
 421                                 goto readrest;
 422                         break;
 423                 }
 424
 425                 /*
 426                  * Page is not resident, If this is the search termination
 427                  * or the pager might contain the page, allocate a new page.
 428                  */
 429                 if (TRYPAGER || fs.object == fs.first_object) {
 430                         if (fs.pindex >= fs.object->size) {
 431                                 unlock_and_deallocate(&fs);
 432                                 return (KERN_PROTECTION_FAILURE);
 433                         }
 434
 435                         /*
 436                          * Allocate a new page for this object/offset pair.
 437                          *
 438                          * Unlocked read of the p_flag is harmless. At
 439                          * worst, the P_KILLED might be not observed
 440                          * there, and allocation can fail, causing
 441                          * restart and new reading of the p_flag.
 442                          */
 443                         fs.m = NULL;
 444                         if (!vm_page_count_severe() || P_KILLED(curproc)) {
 445 #if VM_NRESERVLEVEL > 0
 446                                 if ((fs.object->flags & OBJ_COLORED) == 0) {
 447                                         fs.object->flags |= OBJ_COLORED;
 448                                         fs.object->pg_color = atop(vaddr) -
 449                                             fs.pindex;
 450                                 }
 451 #endif
 452                                 alloc_req = P_KILLED(curproc) ?
 453                                     VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
 454                                 if (fs.object->type != OBJT_VNODE &&
 455                                     fs.object->backing_object == NULL)
 456                                         alloc_req |= VM_ALLOC_ZERO;
 457                                 fs.m = vm_page_alloc(fs.object, fs.pindex,
 458                                     alloc_req);
 459                         }
 460                         if (fs.m == NULL) {
 461                                 unlock_and_deallocate(&fs);
 462                                 VM_WAITPFAULT;
 463                                 goto RetryFault;
 464                         } else if (fs.m->valid == VM_PAGE_BITS_ALL)
 465                                 break;
 466                 }
 467
 468 readrest:
 469                 /*
 470                  * We have found a valid page or we have allocated a new page.
 471                  * The page thus may not be valid or may not be entirely
 472                  * valid.
 473                  *
 474                  * Attempt to fault-in the page if there is a chance that the
 475                  * pager has it, and potentially fault in additional pages
 476                  * at the same time.
 477                  */
 478                 if (TRYPAGER) {
 479                         int rv;
 480                         u_char behavior = vm_map_entry_behavior(fs.entry);
 481
 482                         if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
 483                             P_KILLED(curproc)) {
 484                                 behind = 0;
 485                                 ahead = 0;
 486                         } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
 487                                 behind = 0;
 488                                 ahead = atop(fs.entry->end - vaddr) - 1;
 489                                 if (ahead > VM_FAULT_READ_AHEAD_MAX)
 490                                         ahead = VM_FAULT_READ_AHEAD_MAX;
 491                                 if (fs.pindex == fs.entry->next_read)
 492                                         vm_fault_cache_behind(&fs,
 493                                             VM_FAULT_READ_MAX);
 494                         } else {
 495                                 /*
 496                                  * If this is a sequential page fault, then
 497                                  * arithmetically increase the number of pages
 498                                  * in the read-ahead window.  Otherwise, reset
 499                                  * the read-ahead window to its smallest size.
 500                                  */
 501                                 behind = atop(vaddr - fs.entry->start);
 502                                 if (behind > VM_FAULT_READ_BEHIND)
 503                                         behind = VM_FAULT_READ_BEHIND;
 504                                 ahead = atop(fs.entry->end - vaddr) - 1;
 505                                 era = fs.entry->read_ahead;
 506                                 if (fs.pindex == fs.entry->next_read) {
 507                                         nera = era + behind;
 508                                         if (nera > VM_FAULT_READ_AHEAD_MAX)
 509                                                 nera = VM_FAULT_READ_AHEAD_MAX;
 510                                         behind = 0;
 511                                         if (ahead > nera)
 512                                                 ahead = nera;
 513                                         if (era == VM_FAULT_READ_AHEAD_MAX)
 514                                                 vm_fault_cache_behind(&fs,
 515                                                     VM_FAULT_CACHE_BEHIND);
 516                                 } else if (ahead > VM_FAULT_READ_AHEAD_MIN)
 517                                         ahead = VM_FAULT_READ_AHEAD_MIN;
 518                                 if (era != ahead)
 519                                         fs.entry->read_ahead = ahead;
 520                         }
 521
 522                         /*
 523                          * Call the pager to retrieve the data, if any, after
 524                          * releasing the lock on the map.  We hold a ref on
 525                          * fs.object and the pages are VPO_BUSY'd.
 526                          */
 527                         unlock_map(&fs);
 528
 529 vnode_lock:
 530                         if (fs.object->type == OBJT_VNODE) {
 531                                 vp = fs.object->handle;
 532                                 if (vp == fs.vp)
 533                                         goto vnode_locked;
 534                                 else if (fs.vp != NULL) {
 535                                         vput(fs.vp);
 536                                         fs.vp = NULL;
 537                                 }
 538                                 locked = VOP_ISLOCKED(vp);
 539
 540                                 if (VFS_NEEDSGIANT(vp->v_mount) && !fs.vfslocked) {
 541                                         fs.vfslocked = 1;
 542                                         if (!mtx_trylock(&Giant)) {
 543                                                 VM_OBJECT_UNLOCK(fs.object);
 544                                                 mtx_lock(&Giant);
 545                                                 VM_OBJECT_LOCK(fs.object);
 546                                                 goto vnode_lock;
 547                                         }
 548                                 }
 549                                 if (locked != LK_EXCLUSIVE)
 550                                         locked = LK_SHARED;
 551                                 /* Do not sleep for vnode lock while fs.m is busy */
 552                                 error = vget(vp, locked | LK_CANRECURSE |
 553                                     LK_NOWAIT, curthread);
 554                                 if (error != 0) {
 555                                         int vfslocked;
 556
 557                                         vfslocked = fs.vfslocked;
 558                                         fs.vfslocked = 0; /* Keep Giant */
 559                                         vhold(vp);
 560                                         release_page(&fs);
 561                                         unlock_and_deallocate(&fs);
 562                                         error = vget(vp, locked | LK_RETRY |
 563                                             LK_CANRECURSE, curthread);
 564                                         vdrop(vp);
 565                                         fs.vp = vp;
 566                                         fs.vfslocked = vfslocked;
 567                                         KASSERT(error == 0,
 568                                             ("vm_fault: vget failed"));
 569                                         goto RetryFault;
 570                                 }
 571                                 fs.vp = vp;
 572                         }
 573 vnode_locked:
 574                         KASSERT(fs.vp == NULL || !fs.map->system_map,
 575                             ("vm_fault: vnode-backed object mapped by system map"));
 576
 577                         /*
 578                          * now we find out if any other pages should be paged
 579                          * in at this time this routine checks to see if the
 580                          * pages surrounding this fault reside in the same
 581                          * object as the page for this fault.  If they do,
 582                          * then they are faulted in also into the object.  The
 583                          * array "marray" returned contains an array of
 584                          * vm_page_t structs where one of them is the
 585                          * vm_page_t passed to the routine.  The reqpage
 586                          * return value is the index into the marray for the
 587                          * vm_page_t passed to the routine.
 588                          *
 589                          * fs.m plus the additional pages are VPO_BUSY'd.
 590                          */
 591                         faultcount = vm_fault_additional_pages(
 592                             fs.m, behind, ahead, marray, &reqpage);
 593
 594                         rv = faultcount ?
 595                             vm_pager_get_pages(fs.object, marray, faultcount,
 596                                 reqpage) : VM_PAGER_FAIL;
 597
 598                         if (rv == VM_PAGER_OK) {
 599                                 /*
 600                                  * Found the page. Leave it busy while we play
 601                                  * with it.
 602                                  */
 603
 604                                 /*
 605                                  * Relookup in case pager changed page. Pager
 606                                  * is responsible for disposition of old page
 607                                  * if moved.
 608                                  */
 609                                 fs.m = vm_page_lookup(fs.object, fs.pindex);
 610                                 if (!fs.m) {
 611                                         unlock_and_deallocate(&fs);
 612                                         goto RetryFault;
 613                                 }
 614
 615                                 hardfault++;
 616                                 break; /* break to PAGE HAS BEEN FOUND */
 617                         }
 618                         /*
 619                          * Remove the bogus page (which does not exist at this
 620                          * object/offset); before doing so, we must get back
 621                          * our object lock to preserve our invariant.
 622                          *
 623                          * Also wake up any other process that may want to bring
 624                          * in this page.
 625                          *
 626                          * If this is the top-level object, we must leave the
 627                          * busy page to prevent another process from rushing
 628                          * past us, and inserting the page in that object at
 629                          * the same time that we are.
 630                          */
 631                         if (rv == VM_PAGER_ERROR)
 632                                 printf("vm_fault: pager read error, pid %d (%s)\n",
 633                                     curproc->p_pid, curproc->p_comm);
 634                         /*
 635                          * Data outside the range of the pager or an I/O error
 636                          */
 637                         /*
 638                          * XXX - the check for kernel_map is a kludge to work
 639                          * around having the machine panic on a kernel space
 640                          * fault w/ I/O error.
 641                          */
 642                         if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
 643                                 (rv == VM_PAGER_BAD)) {
 644                                 vm_page_lock(fs.m);
 645                                 vm_page_free(fs.m);
 646                                 vm_page_unlock(fs.m);
 647                                 fs.m = NULL;
 648                                 unlock_and_deallocate(&fs);
 649                                 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
 650                         }
 651                         if (fs.object != fs.first_object) {
 652                                 vm_page_lock(fs.m);
 653                                 vm_page_free(fs.m);
 654                                 vm_page_unlock(fs.m);
 655                                 fs.m = NULL;
 656                                 /*
 657                                  * XXX - we cannot just fall out at this
 658                                  * point, m has been freed and is invalid!
 659                                  */
 660                         }
 661                 }
 662
 663                 /*
 664                  * We get here if the object has default pager (or unwiring)
 665                  * or the pager doesn't have the page.
 666                  */
 667                 if (fs.object == fs.first_object)
 668                         fs.first_m = fs.m;
 669
 670                 /*
 671                  * Move on to the next object.  Lock the next object before
 672                  * unlocking the current one.
 673                  */
 674                 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
 675                 next_object = fs.object->backing_object;
 676                 if (next_object == NULL) {
 677                         /*
 678                          * If there's no object left, fill the page in the top
 679                          * object with zeros.
 680                          */
 681                         if (fs.object != fs.first_object) {
 682                                 vm_object_pip_wakeup(fs.object);
 683                                 VM_OBJECT_UNLOCK(fs.object);
 684
 685                                 fs.object = fs.first_object;
 686                                 fs.pindex = fs.first_pindex;
 687                                 fs.m = fs.first_m;
 688                                 VM_OBJECT_LOCK(fs.object);
 689                         }
 690                         fs.first_m = NULL;
 691
 692                         /*
 693                          * Zero the page if necessary and mark it valid.
 694                          */
 695                         if ((fs.m->flags & PG_ZERO) == 0) {
 696                                 pmap_zero_page(fs.m);
 697                         } else {
 698                                 PCPU_INC(cnt.v_ozfod);
 699                         }
 700                         PCPU_INC(cnt.v_zfod);
 701                         fs.m->valid = VM_PAGE_BITS_ALL;
 702                         break;  /* break to PAGE HAS BEEN FOUND */
 703                 } else {
 704                         KASSERT(fs.object != next_object,
 705                             ("object loop %p", next_object));
 706                         VM_OBJECT_LOCK(next_object);
 707                         vm_object_pip_add(next_object, 1);
 708                         if (fs.object != fs.first_object)
 709                                 vm_object_pip_wakeup(fs.object);
 710                         VM_OBJECT_UNLOCK(fs.object);
 711                         fs.object = next_object;
 712                 }
 713         }
 714
 715         KASSERT((fs.m->oflags & VPO_BUSY) != 0,
 716             ("vm_fault: not busy after main loop"));
 717
 718         /*
 719          * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
 720          * is held.]
 721          */
 722
 723         /*
 724          * If the page is being written, but isn't already owned by the
 725          * top-level object, we have to copy it into a new page owned by the
 726          * top-level object.
 727          */
 728         if (fs.object != fs.first_object) {
 729                 /*
 730                  * We only really need to copy if we want to write it.
 731                  */
 732                 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
 733                         /*
 734                          * This allows pages to be virtually copied from a
 735                          * backing_object into the first_object, where the
 736                          * backing object has no other refs to it, and cannot
 737                          * gain any more refs.  Instead of a bcopy, we just
 738                          * move the page from the backing object to the
 739                          * first object.  Note that we must mark the page
 740                          * dirty in the first object so that it will go out
 741                          * to swap when needed.
 742                          */
 743                         is_first_object_locked = FALSE;
 744                         if (
 745                                 /*
 746                                  * Only one shadow object
 747                                  */
 748                                 (fs.object->shadow_count == 1) &&
 749                                 /*
 750                                  * No COW refs, except us
 751                                  */
 752                                 (fs.object->ref_count == 1) &&
 753                                 /*
 754                                  * No one else can look this object up
 755                                  */
 756                                 (fs.object->handle == NULL) &&
 757                                 /*
 758                                  * No other ways to look the object up
 759                                  */
 760                                 ((fs.object->type == OBJT_DEFAULT) ||
 761                                  (fs.object->type == OBJT_SWAP)) &&
 762                             (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) &&
 763                                 /*
 764                                  * We don't chase down the shadow chain
 765                                  */
 766                             fs.object == fs.first_object->backing_object) {
 767                                 /*
 768                                  * get rid of the unnecessary page
 769                                  */
 770                                 vm_page_lock(fs.first_m);
 771                                 vm_page_free(fs.first_m);
 772                                 vm_page_unlock(fs.first_m);
 773                                 /*
 774                                  * grab the page and put it into the
 775                                  * process'es object.  The page is
 776                                  * automatically made dirty.
 777                                  */
 778                                 vm_page_lock(fs.m);
 779                                 vm_page_rename(fs.m, fs.first_object, fs.first_pindex);
 780                                 vm_page_unlock(fs.m);
 781                                 vm_page_busy(fs.m);
 782                                 fs.first_m = fs.m;
 783                                 fs.m = NULL;
 784                                 PCPU_INC(cnt.v_cow_optim);
 785                         } else {
 786                                 /*
 787                                  * Oh, well, lets copy it.
 788                                  */
 789                                 pmap_copy_page(fs.m, fs.first_m);
 790                                 fs.first_m->valid = VM_PAGE_BITS_ALL;
 791                                 if (wired && (fault_flags &
 792                                     VM_FAULT_CHANGE_WIRING) == 0) {
 793                                         vm_page_lock(fs.first_m);
 794                                         vm_page_wire(fs.first_m);
 795                                         vm_page_unlock(fs.first_m);
 796
 797                                         vm_page_lock(fs.m);
 798                                         vm_page_unwire(fs.m, FALSE);
 799                                         vm_page_unlock(fs.m);
 800                                 }
 801                                 /*
 802                                  * We no longer need the old page or object.
 803                                  */
 804                                 release_page(&fs);
 805                         }
 806                         /*
 807                          * fs.object != fs.first_object due to above
 808                          * conditional
 809                          */
 810                         vm_object_pip_wakeup(fs.object);
 811                         VM_OBJECT_UNLOCK(fs.object);
 812                         /*
 813                          * Only use the new page below...
 814                          */
 815                         fs.object = fs.first_object;
 816                         fs.pindex = fs.first_pindex;
 817                         fs.m = fs.first_m;
 818                         if (!is_first_object_locked)
 819                                 VM_OBJECT_LOCK(fs.object);
 820                         PCPU_INC(cnt.v_cow_faults);
 821                         curthread->td_cow++;
 822                 } else {
 823                         prot &= ~VM_PROT_WRITE;
 824                 }
 825         }
 826
 827         /*
 828          * We must verify that the maps have not changed since our last
 829          * lookup.
 830          */
 831         if (!fs.lookup_still_valid) {
 832                 vm_object_t retry_object;
 833                 vm_pindex_t retry_pindex;
 834                 vm_prot_t retry_prot;
 835
 836                 if (!vm_map_trylock_read(fs.map)) {
 837                         release_page(&fs);
 838                         unlock_and_deallocate(&fs);
 839                         goto RetryFault;
 840                 }
 841                 fs.lookup_still_valid = TRUE;
 842                 if (fs.map->timestamp != map_generation) {
 843                         result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
 844                             &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
 845
 846                         /*
 847                          * If we don't need the page any longer, put it on the inactive
 848                          * list (the easiest thing to do here).  If no one needs it,
 849                          * pageout will grab it eventually.
 850                          */
 851                         if (result != KERN_SUCCESS) {
 852                                 release_page(&fs);
 853                                 unlock_and_deallocate(&fs);
 854
 855                                 /*
 856                                  * If retry of map lookup would have blocked then
 857                                  * retry fault from start.
 858                                  */
 859                                 if (result == KERN_FAILURE)
 860                                         goto RetryFault;
 861                                 return (result);
 862                         }
 863                         if ((retry_object != fs.first_object) ||
 864                             (retry_pindex != fs.first_pindex)) {
 865                                 release_page(&fs);
 866                                 unlock_and_deallocate(&fs);
 867                                 goto RetryFault;
 868                         }
 869
 870                         /*
 871                          * Check whether the protection has changed or the object has
 872                          * been copied while we left the map unlocked. Changing from
 873                          * read to write permission is OK - we leave the page
 874                          * write-protected, and catch the write fault. Changing from
 875                          * write to read permission means that we can't mark the page
 876                          * write-enabled after all.
 877                          */
 878                         prot &= retry_prot;
 879                 }
 880         }
 881         /*
 882          * If the page was filled by a pager, update the map entry's
 883          * last read offset.  Since the pager does not return the
 884          * actual set of pages that it read, this update is based on
 885          * the requested set.  Typically, the requested and actual
 886          * sets are the same.
 887          *
 888          * XXX The following assignment modifies the map
 889          * without holding a write lock on it.
 890          */
 891         if (hardfault)
 892                 fs.entry->next_read = fs.pindex + faultcount - reqpage;
 893
 894         if ((prot & VM_PROT_WRITE) != 0 ||
 895             (fault_flags & VM_FAULT_DIRTY) != 0) {
 896                 vm_object_set_writeable_dirty(fs.object);
 897
 898                 /*
 899                  * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
 900                  * if the page is already dirty to prevent data written with
 901                  * the expectation of being synced from not being synced.
 902                  * Likewise if this entry does not request NOSYNC then make
 903                  * sure the page isn't marked NOSYNC.  Applications sharing
 904                  * data should use the same flags to avoid ping ponging.
 905                  */
 906                 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) {
 907                         if (fs.m->dirty == 0)
 908                                 fs.m->oflags |= VPO_NOSYNC;
 909                 } else {
 910                         fs.m->oflags &= ~VPO_NOSYNC;
 911                 }
 912
 913                 /*
 914                  * If the fault is a write, we know that this page is being
 915                  * written NOW so dirty it explicitly to save on
 916                  * pmap_is_modified() calls later.
 917                  *
 918                  * Also tell the backing pager, if any, that it should remove
 919                  * any swap backing since the page is now dirty.
 920                  */
 921                 if (((fault_type & VM_PROT_WRITE) != 0 &&
 922                     (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) ||
 923                     (fault_flags & VM_FAULT_DIRTY) != 0) {
 924                         vm_page_dirty(fs.m);
 925                         vm_pager_page_unswapped(fs.m);
 926                 }
 927         }
 928
 929         /*
 930          * Page had better still be busy
 931          */
 932         KASSERT(fs.m->oflags & VPO_BUSY,
 933                 ("vm_fault: page %p not busy!", fs.m));
 934         /*
 935          * Page must be completely valid or it is not fit to
 936          * map into user space.  vm_pager_get_pages() ensures this.
 937          */
 938         KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
 939             ("vm_fault: page %p partially invalid", fs.m));
 940         VM_OBJECT_UNLOCK(fs.object);
 941
 942         /*
 943          * Put this page into the physical map.  We had to do the unlock above
 944          * because pmap_enter() may sleep.  We don't put the page
 945          * back on the active queue until later so that the pageout daemon
 946          * won't find it (yet).
 947          */
 948         pmap_enter(fs.map->pmap, vaddr, fault_type, fs.m, prot, wired);
 949         if ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 && wired == 0)
 950                 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry);
 951         VM_OBJECT_LOCK(fs.object);
 952         vm_page_lock(fs.m);
 953
 954         /*
 955          * If the page is not wired down, then put it where the pageout daemon
 956          * can find it.
 957          */
 958         if (fault_flags & VM_FAULT_CHANGE_WIRING) {
 959                 if (wired)
 960                         vm_page_wire(fs.m);
 961                 else
 962                         vm_page_unwire(fs.m, 1);
 963         } else
 964                 vm_page_activate(fs.m);
 965         if (m_hold != NULL) {
 966                 *m_hold = fs.m;
 967                 vm_page_hold(fs.m);
 968         }
 969         vm_page_unlock(fs.m);
 970         vm_page_wakeup(fs.m);
 971
 972         /*
 973          * Unlock everything, and return
 974          */
 975         unlock_and_deallocate(&fs);
 976         if (hardfault)
 977                 curthread->td_ru.ru_majflt++;
 978         else
 979                 curthread->td_ru.ru_minflt++;
 980
 981         return (KERN_SUCCESS);
 982 }
 983
 984 /*
 985  * Speed up the reclamation of up to "distance" pages that precede the
 986  * faulting pindex within the first object of the shadow chain.
 987  */
 988 static void
 989 vm_fault_cache_behind(const struct faultstate *fs, int distance)
 990 {
 991         vm_object_t first_object, object;
 992         vm_page_t m, m_prev;
 993         vm_pindex_t pindex;
 994
 995         object = fs->object;
 996         VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
 997         first_object = fs->first_object;
 998         if (first_object != object) {
 999                 if (!VM_OBJECT_TRYLOCK(first_object)) {
1000                         VM_OBJECT_UNLOCK(object);
1001                         VM_OBJECT_LOCK(first_object);
1002                         VM_OBJECT_LOCK(object);
1003                 }
1004         }
1005         if (first_object->type != OBJT_DEVICE &&
1006             first_object->type != OBJT_PHYS && first_object->type != OBJT_SG) {
1007                 if (fs->first_pindex < distance)
1008                         pindex = 0;
1009                 else
1010                         pindex = fs->first_pindex - distance;
1011                 if (pindex < OFF_TO_IDX(fs->entry->offset))
1012                         pindex = OFF_TO_IDX(fs->entry->offset);
1013                 m = first_object != object ? fs->first_m : fs->m;
1014                 KASSERT((m->oflags & VPO_BUSY) != 0,
1015                     ("vm_fault_cache_behind: page %p is not busy", m));
1016                 m_prev = vm_page_prev(m);
1017                 while ((m = m_prev) != NULL && m->pindex >= pindex &&
1018                     m->valid == VM_PAGE_BITS_ALL) {
1019                         m_prev = vm_page_prev(m);
1020                         if (m->busy != 0 || (m->oflags & VPO_BUSY) != 0)
1021                                 continue;
1022                         vm_page_lock(m);
1023                         if (m->hold_count == 0 && m->wire_count == 0) {
1024                                 pmap_remove_all(m);
1025                                 vm_page_aflag_clear(m, PGA_REFERENCED);
1026                                 if (m->dirty != 0)
1027                                         vm_page_deactivate(m);
1028                                 else
1029                                         vm_page_cache(m);
1030                         }
1031                         vm_page_unlock(m);
1032                 }
1033         }
1034         if (first_object != object)
1035                 VM_OBJECT_UNLOCK(first_object);
1036 }
1037
1038 /*
1039  * vm_fault_prefault provides a quick way of clustering
1040  * pagefaults into a processes address space.  It is a "cousin"
1041  * of vm_map_pmap_enter, except it runs at page fault time instead
1042  * of mmap time.
1043  */
1044 static void
1045 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry)
1046 {
1047         int i;
1048         vm_offset_t addr, starta;
1049         vm_pindex_t pindex;
1050         vm_page_t m;
1051         vm_object_t object;
1052
1053         if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1054                 return;
1055
1056         object = entry->object.vm_object;
1057
1058         starta = addra - PFBAK * PAGE_SIZE;
1059         if (starta < entry->start) {
1060                 starta = entry->start;
1061         } else if (starta > addra) {
1062                 starta = 0;
1063         }
1064
1065         for (i = 0; i < PAGEORDER_SIZE; i++) {
1066                 vm_object_t backing_object, lobject;
1067
1068                 addr = addra + prefault_pageorder[i];
1069                 if (addr > addra + (PFFOR * PAGE_SIZE))
1070                         addr = 0;
1071
1072                 if (addr < starta || addr >= entry->end)
1073                         continue;
1074
1075                 if (!pmap_is_prefaultable(pmap, addr))
1076                         continue;
1077
1078                 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1079                 lobject = object;
1080                 VM_OBJECT_LOCK(lobject);
1081                 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1082                     lobject->type == OBJT_DEFAULT &&
1083                     (backing_object = lobject->backing_object) != NULL) {
1084                         KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1085                             0, ("vm_fault_prefault: unaligned object offset"));
1086                         pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1087                         VM_OBJECT_LOCK(backing_object);
1088                         VM_OBJECT_UNLOCK(lobject);
1089                         lobject = backing_object;
1090                 }
1091                 /*
1092                  * give-up when a page is not in memory
1093                  */
1094                 if (m == NULL) {
1095                         VM_OBJECT_UNLOCK(lobject);
1096                         break;
1097                 }
1098                 if (m->valid == VM_PAGE_BITS_ALL &&
1099                     (m->flags & PG_FICTITIOUS) == 0)
1100                         pmap_enter_quick(pmap, addr, m, entry->protection);
1101                 VM_OBJECT_UNLOCK(lobject);
1102         }
1103 }
1104
1105 /*
1106  * Hold each of the physical pages that are mapped by the specified range of
1107  * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1108  * and allow the specified types of access, "prot".  If all of the implied
1109  * pages are successfully held, then the number of held pages is returned
1110  * together with pointers to those pages in the array "ma".  However, if any
1111  * of the pages cannot be held, -1 is returned.
1112  */
1113 int
1114 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1115     vm_prot_t prot, vm_page_t *ma, int max_count)
1116 {
1117         vm_offset_t end, va;
1118         vm_page_t *mp;
1119         int count;
1120         boolean_t pmap_failed;
1121
1122         if (len == 0)
1123                 return (0);
1124         end = round_page(addr + len);
1125         addr = trunc_page(addr);
1126
1127         /*
1128          * Check for illegal addresses.
1129          */
1130         if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1131                 return (-1);
1132
1133         count = howmany(end - addr, PAGE_SIZE);
1134         if (count > max_count)
1135                 panic("vm_fault_quick_hold_pages: count > max_count");
1136
1137         /*
1138          * Most likely, the physical pages are resident in the pmap, so it is
1139          * faster to try pmap_extract_and_hold() first.
1140          */
1141         pmap_failed = FALSE;
1142         for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1143                 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1144                 if (*mp == NULL)
1145                         pmap_failed = TRUE;
1146                 else if ((prot & VM_PROT_WRITE) != 0 &&
1147                     (*mp)->dirty != VM_PAGE_BITS_ALL) {
1148                         /*
1149                          * Explicitly dirty the physical page.  Otherwise, the
1150                          * caller's changes may go unnoticed because they are
1151                          * performed through an unmanaged mapping or by a DMA
1152                          * operation.
1153                          *
1154                          * The object lock is not held here.
1155                          * See vm_page_clear_dirty_mask().
1156                          */
1157                         vm_page_dirty(*mp);
1158                 }
1159         }
1160         if (pmap_failed) {
1161                 /*
1162                  * One or more pages could not be held by the pmap.  Either no
1163                  * page was mapped at the specified virtual address or that
1164                  * mapping had insufficient permissions.  Attempt to fault in
1165                  * and hold these pages.
1166                  */
1167                 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1168                         if (*mp == NULL && vm_fault_hold(map, va, prot,
1169                             VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1170                                 goto error;
1171         }
1172         return (count);
1173 error:
1174         for (mp = ma; mp < ma + count; mp++)
1175                 if (*mp != NULL) {
1176                         vm_page_lock(*mp);
1177                         vm_page_unhold(*mp);
1178                         vm_page_unlock(*mp);
1179                 }
1180         return (-1);
1181 }
1182
1183 /*
1184  *      vm_fault_wire:
1185  *
1186  *      Wire down a range of virtual addresses in a map.
1187  */
1188 int
1189 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1190     boolean_t fictitious)
1191 {
1192         vm_offset_t va;
1193         int rv;
1194
1195         /*
1196          * We simulate a fault to get the page and enter it in the physical
1197          * map.  For user wiring, we only ask for read access on currently
1198          * read-only sections.
1199          */
1200         for (va = start; va < end; va += PAGE_SIZE) {
1201                 rv = vm_fault(map, va, VM_PROT_NONE, VM_FAULT_CHANGE_WIRING);
1202                 if (rv) {
1203                         if (va != start)
1204                                 vm_fault_unwire(map, start, va, fictitious);
1205                         return (rv);
1206                 }
1207         }
1208         return (KERN_SUCCESS);
1209 }
1210
1211 /*
1212  *      vm_fault_unwire:
1213  *
1214  *      Unwire a range of virtual addresses in a map.
1215  */
1216 void
1217 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1218     boolean_t fictitious)
1219 {
1220         vm_paddr_t pa;
1221         vm_offset_t va;
1222         vm_page_t m;
1223         pmap_t pmap;
1224
1225         pmap = vm_map_pmap(map);
1226
1227         /*
1228          * Since the pages are wired down, we must be able to get their
1229          * mappings from the physical map system.
1230          */
1231         for (va = start; va < end; va += PAGE_SIZE) {
1232                 pa = pmap_extract(pmap, va);
1233                 if (pa != 0) {
1234                         pmap_change_wiring(pmap, va, FALSE);
1235                         if (!fictitious) {
1236                                 m = PHYS_TO_VM_PAGE(pa);
1237                                 vm_page_lock(m);
1238                                 vm_page_unwire(m, TRUE);
1239                                 vm_page_unlock(m);
1240                         }
1241                 }
1242         }
1243 }
1244
1245 /*
1246  *      Routine:
1247  *              vm_fault_copy_entry
1248  *      Function:
1249  *              Create new shadow object backing dst_entry with private copy of
1250  *              all underlying pages. When src_entry is equal to dst_entry,
1251  *              function implements COW for wired-down map entry. Otherwise,
1252  *              it forks wired entry into dst_map.
1253  *
1254  *      In/out conditions:
1255  *              The source and destination maps must be locked for write.
1256  *              The source map entry must be wired down (or be a sharing map
1257  *              entry corresponding to a main map entry that is wired down).
1258  */
1259 void
1260 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1261     vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1262     vm_ooffset_t *fork_charge)
1263 {
1264         vm_object_t backing_object, dst_object, object, src_object;
1265         vm_pindex_t dst_pindex, pindex, src_pindex;
1266         vm_prot_t access, prot;
1267         vm_offset_t vaddr;
1268         vm_page_t dst_m;
1269         vm_page_t src_m;
1270         boolean_t src_readonly, upgrade;
1271
1272 #ifdef  lint
1273         src_map++;
1274 #endif  /* lint */
1275
1276         upgrade = src_entry == dst_entry;
1277
1278         src_object = src_entry->object.vm_object;
1279         src_pindex = OFF_TO_IDX(src_entry->offset);
1280         src_readonly = (src_entry->protection & VM_PROT_WRITE) == 0;
1281
1282         /*
1283          * Create the top-level object for the destination entry. (Doesn't
1284          * actually shadow anything - we copy the pages directly.)
1285          */
1286         dst_object = vm_object_allocate(OBJT_DEFAULT,
1287             OFF_TO_IDX(dst_entry->end - dst_entry->start));
1288 #if VM_NRESERVLEVEL > 0
1289         dst_object->flags |= OBJ_COLORED;
1290         dst_object->pg_color = atop(dst_entry->start);
1291 #endif
1292
1293         VM_OBJECT_LOCK(dst_object);
1294         KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1295             ("vm_fault_copy_entry: vm_object not NULL"));
1296         dst_entry->object.vm_object = dst_object;
1297         dst_entry->offset = 0;
1298         dst_object->charge = dst_entry->end - dst_entry->start;
1299         if (fork_charge != NULL) {
1300                 KASSERT(dst_entry->cred == NULL,
1301                     ("vm_fault_copy_entry: leaked swp charge"));
1302                 dst_object->cred = curthread->td_ucred;
1303                 crhold(dst_object->cred);
1304                 *fork_charge += dst_object->charge;
1305         } else {
1306                 dst_object->cred = dst_entry->cred;
1307                 dst_entry->cred = NULL;
1308         }
1309         access = prot = dst_entry->protection;
1310         /*
1311          * If not an upgrade, then enter the mappings in the pmap as
1312          * read and/or execute accesses.  Otherwise, enter them as
1313          * write accesses.
1314          *
1315          * A writeable large page mapping is only created if all of
1316          * the constituent small page mappings are modified. Marking
1317          * PTEs as modified on inception allows promotion to happen
1318          * without taking potentially large number of soft faults.
1319          */
1320         if (!upgrade)
1321                 access &= ~VM_PROT_WRITE;
1322
1323         /*
1324          * Loop through all of the virtual pages within the entry's
1325          * range, copying each page from the source object to the
1326          * destination object.  Since the source is wired, those pages
1327          * must exist.  In contrast, the destination is pageable.
1328          * Since the destination object does share any backing storage
1329          * with the source object, all of its pages must be dirtied,
1330          * regardless of whether they can be written.
1331          */
1332         for (vaddr = dst_entry->start, dst_pindex = 0;
1333             vaddr < dst_entry->end;
1334             vaddr += PAGE_SIZE, dst_pindex++) {
1335
1336                 /*
1337                  * Allocate a page in the destination object.
1338                  */
1339                 do {
1340                         dst_m = vm_page_alloc(dst_object, dst_pindex,
1341                             VM_ALLOC_NORMAL);
1342                         if (dst_m == NULL) {
1343                                 VM_OBJECT_UNLOCK(dst_object);
1344                                 VM_WAIT;
1345                                 VM_OBJECT_LOCK(dst_object);
1346                         }
1347                 } while (dst_m == NULL);
1348
1349                 /*
1350                  * Find the page in the source object, and copy it in.
1351                  * (Because the source is wired down, the page will be in
1352                  * memory.)
1353                  */
1354                 VM_OBJECT_LOCK(src_object);
1355                 object = src_object;
1356                 pindex = src_pindex + dst_pindex;
1357                 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1358                     src_readonly &&
1359                     (backing_object = object->backing_object) != NULL) {
1360                         /*
1361                          * Allow fallback to backing objects if we are reading.
1362                          */
1363                         VM_OBJECT_LOCK(backing_object);
1364                         pindex += OFF_TO_IDX(object->backing_object_offset);
1365                         VM_OBJECT_UNLOCK(object);
1366                         object = backing_object;
1367                 }
1368                 if (src_m == NULL)
1369                         panic("vm_fault_copy_wired: page missing");
1370                 pmap_copy_page(src_m, dst_m);
1371                 VM_OBJECT_UNLOCK(object);
1372                 dst_m->valid = VM_PAGE_BITS_ALL;
1373                 dst_m->dirty = VM_PAGE_BITS_ALL;
1374                 VM_OBJECT_UNLOCK(dst_object);
1375
1376                 /*
1377                  * Enter it in the pmap. If a wired, copy-on-write
1378                  * mapping is being replaced by a write-enabled
1379                  * mapping, then wire that new mapping.
1380                  */
1381                 pmap_enter(dst_map->pmap, vaddr, access, dst_m, prot, upgrade);
1382
1383                 /*
1384                  * Mark it no longer busy, and put it on the active list.
1385                  */
1386                 VM_OBJECT_LOCK(dst_object);
1387
1388                 if (upgrade) {
1389                         vm_page_lock(src_m);
1390                         vm_page_unwire(src_m, 0);
1391                         vm_page_unlock(src_m);
1392
1393                         vm_page_lock(dst_m);
1394                         vm_page_wire(dst_m);
1395                         vm_page_unlock(dst_m);
1396                 } else {
1397                         vm_page_lock(dst_m);
1398                         vm_page_activate(dst_m);
1399                         vm_page_unlock(dst_m);
1400                 }
1401                 vm_page_wakeup(dst_m);
1402         }
1403         VM_OBJECT_UNLOCK(dst_object);
1404         if (upgrade) {
1405                 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1406                 vm_object_deallocate(src_object);
1407         }
1408 }
1409
1410
1411 /*
1412  * This routine checks around the requested page for other pages that
1413  * might be able to be faulted in.  This routine brackets the viable
1414  * pages for the pages to be paged in.
1415  *
1416  * Inputs:
1417  *      m, rbehind, rahead
1418  *
1419  * Outputs:
1420  *  marray (array of vm_page_t), reqpage (index of requested page)
1421  *
1422  * Return value:
1423  *  number of pages in marray
1424  */
1425 static int
1426 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1427         vm_page_t m;
1428         int rbehind;
1429         int rahead;
1430         vm_page_t *marray;
1431         int *reqpage;
1432 {
1433         int i,j;
1434         vm_object_t object;
1435         vm_pindex_t pindex, startpindex, endpindex, tpindex;
1436         vm_page_t rtm;
1437         int cbehind, cahead;
1438
1439         VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
1440
1441         object = m->object;
1442         pindex = m->pindex;
1443         cbehind = cahead = 0;
1444
1445         /*
1446          * if the requested page is not available, then give up now
1447          */
1448         if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1449                 return 0;
1450         }
1451
1452         if ((cbehind == 0) && (cahead == 0)) {
1453                 *reqpage = 0;
1454                 marray[0] = m;
1455                 return 1;
1456         }
1457
1458         if (rahead > cahead) {
1459                 rahead = cahead;
1460         }
1461
1462         if (rbehind > cbehind) {
1463                 rbehind = cbehind;
1464         }
1465
1466         /*
1467          * scan backward for the read behind pages -- in memory
1468          */
1469         if (pindex > 0) {
1470                 if (rbehind > pindex) {
1471                         rbehind = pindex;
1472                         startpindex = 0;
1473                 } else {
1474                         startpindex = pindex - rbehind;
1475                 }
1476
1477                 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL &&
1478                     rtm->pindex >= startpindex)
1479                         startpindex = rtm->pindex + 1;
1480
1481                 /* tpindex is unsigned; beware of numeric underflow. */
1482                 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex &&
1483                     tpindex < pindex; i++, tpindex--) {
1484
1485                         rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1486                             VM_ALLOC_IFNOTCACHED);
1487                         if (rtm == NULL) {
1488                                 /*
1489                                  * Shift the allocated pages to the
1490                                  * beginning of the array.
1491                                  */
1492                                 for (j = 0; j < i; j++) {
1493                                         marray[j] = marray[j + tpindex + 1 -
1494                                             startpindex];
1495                                 }
1496                                 break;
1497                         }
1498
1499                         marray[tpindex - startpindex] = rtm;
1500                 }
1501         } else {
1502                 startpindex = 0;
1503                 i = 0;
1504         }
1505
1506         marray[i] = m;
1507         /* page offset of the required page */
1508         *reqpage = i;
1509
1510         tpindex = pindex + 1;
1511         i++;
1512
1513         /*
1514          * scan forward for the read ahead pages
1515          */
1516         endpindex = tpindex + rahead;
1517         if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex)
1518                 endpindex = rtm->pindex;
1519         if (endpindex > object->size)
1520                 endpindex = object->size;
1521
1522         for (; tpindex < endpindex; i++, tpindex++) {
1523
1524                 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1525                     VM_ALLOC_IFNOTCACHED);
1526                 if (rtm == NULL) {
1527                         break;
1528                 }
1529
1530                 marray[i] = rtm;
1531         }
1532
1533         /* return number of pages */
1534         return i;
1535 }
1536
1537 /*
1538  * Block entry into the machine-independent layer's page fault handler by
1539  * the calling thread.  Subsequent calls to vm_fault() by that thread will
1540  * return KERN_PROTECTION_FAILURE.  Enable machine-dependent handling of
1541  * spurious page faults.
1542  */
1543 int
1544 vm_fault_disable_pagefaults(void)
1545 {
1546
1547         return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1548 }
1549
1550 void
1551 vm_fault_enable_pagefaults(int save)
1552 {
1553
1554         curthread_pflags_restore(save);
1555 }