1 /*- 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 1994 John S. Dyson 5 * All rights reserved. 6 * Copyright (c) 1994 David Greenman 7 * All rights reserved. 8 * 9 * 10 * This code is derived from software contributed to Berkeley by 11 * The Mach Operating System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 42 * 43 * 44 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 45 * All rights reserved. 46 * 47 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 48 * 49 * Permission to use, copy, modify and distribute this software and 50 * its documentation is hereby granted, provided that both the copyright 51 * notice and this permission notice appear in all copies of the 52 * software, derivative works or modified versions, and any portions 53 * thereof, and that both notices appear in supporting documentation. 54 * 55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 58 * 59 * Carnegie Mellon requests users of this software to return to 60 * 61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 62 * School of Computer Science 63 * Carnegie Mellon University 64 * Pittsburgh PA 15213-3890 65 * 66 * any improvements or extensions that they make and grant Carnegie the 67 * rights to redistribute these changes. 68 */ 69 70 /* 71 * Page fault handling module. 72 */ 73 74 #include <sys/cdefs.h> 75 __FBSDID("$FreeBSD$"); 76 77 #include "opt_ktrace.h" 78 #include "opt_vm.h" 79 80 #include <sys/param.h> 81 #include <sys/systm.h> 82 #include <sys/kernel.h> 83 #include <sys/lock.h> 84 #include <sys/mman.h> 85 #include <sys/proc.h> 86 #include <sys/racct.h> 87 #include <sys/resourcevar.h> 88 #include <sys/rwlock.h> 89 #include <sys/sysctl.h> 90 #include <sys/vmmeter.h> 91 #include <sys/vnode.h> 92 #ifdef KTRACE 93 #include <sys/ktrace.h> 94 #endif 95 96 #include <vm/vm.h> 97 #include <vm/vm_param.h> 98 #include <vm/pmap.h> 99 #include <vm/vm_map.h> 100 #include <vm/vm_object.h> 101 #include <vm/vm_page.h> 102 #include <vm/vm_pageout.h> 103 #include <vm/vm_kern.h> 104 #include <vm/vm_pager.h> 105 #include <vm/vm_extern.h> 106 #include <vm/vm_reserv.h> 107 108 #define PFBAK 4 109 #define PFFOR 4 110 111 #define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT) 112 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX) 113 114 #define VM_FAULT_DONTNEED_MIN 1048576 115 116 struct faultstate { 117 vm_page_t m; 118 vm_object_t object; 119 vm_pindex_t pindex; 120 vm_page_t first_m; 121 vm_object_t first_object; 122 vm_pindex_t first_pindex; 123 vm_map_t map; 124 vm_map_entry_t entry; 125 int lookup_still_valid; 126 struct vnode *vp; 127 }; 128 129 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, 130 int ahead); 131 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 132 int backward, int forward); 133 134 static inline void 135 release_page(struct faultstate *fs) 136 { 137 138 vm_page_xunbusy(fs->m); 139 vm_page_lock(fs->m); 140 vm_page_deactivate(fs->m); 141 vm_page_unlock(fs->m); 142 fs->m = NULL; 143 } 144 145 static inline void 146 unlock_map(struct faultstate *fs) 147 { 148 149 if (fs->lookup_still_valid) { 150 vm_map_lookup_done(fs->map, fs->entry); 151 fs->lookup_still_valid = FALSE; 152 } 153 } 154 155 static void 156 unlock_and_deallocate(struct faultstate *fs) 157 { 158 159 vm_object_pip_wakeup(fs->object); 160 VM_OBJECT_WUNLOCK(fs->object); 161 if (fs->object != fs->first_object) { 162 VM_OBJECT_WLOCK(fs->first_object); 163 vm_page_lock(fs->first_m); 164 vm_page_free(fs->first_m); 165 vm_page_unlock(fs->first_m); 166 vm_object_pip_wakeup(fs->first_object); 167 VM_OBJECT_WUNLOCK(fs->first_object); 168 fs->first_m = NULL; 169 } 170 vm_object_deallocate(fs->first_object); 171 unlock_map(fs); 172 if (fs->vp != NULL) { 173 vput(fs->vp); 174 fs->vp = NULL; 175 } 176 } 177 178 static void 179 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot, 180 vm_prot_t fault_type, int fault_flags, boolean_t set_wd) 181 { 182 boolean_t need_dirty; 183 184 if (((prot & VM_PROT_WRITE) == 0 && 185 (fault_flags & VM_FAULT_DIRTY) == 0) || 186 (m->oflags & VPO_UNMANAGED) != 0) 187 return; 188 189 VM_OBJECT_ASSERT_LOCKED(m->object); 190 191 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 && 192 (fault_flags & VM_FAULT_WIRE) == 0) || 193 (fault_flags & VM_FAULT_DIRTY) != 0; 194 195 if (set_wd) 196 vm_object_set_writeable_dirty(m->object); 197 else 198 /* 199 * If two callers of vm_fault_dirty() with set_wd == 200 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC 201 * flag set, other with flag clear, race, it is 202 * possible for the no-NOSYNC thread to see m->dirty 203 * != 0 and not clear VPO_NOSYNC. Take vm_page lock 204 * around manipulation of VPO_NOSYNC and 205 * vm_page_dirty() call, to avoid the race and keep 206 * m->oflags consistent. 207 */ 208 vm_page_lock(m); 209 210 /* 211 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 212 * if the page is already dirty to prevent data written with 213 * the expectation of being synced from not being synced. 214 * Likewise if this entry does not request NOSYNC then make 215 * sure the page isn't marked NOSYNC. Applications sharing 216 * data should use the same flags to avoid ping ponging. 217 */ 218 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) { 219 if (m->dirty == 0) { 220 m->oflags |= VPO_NOSYNC; 221 } 222 } else { 223 m->oflags &= ~VPO_NOSYNC; 224 } 225 226 /* 227 * If the fault is a write, we know that this page is being 228 * written NOW so dirty it explicitly to save on 229 * pmap_is_modified() calls later. 230 * 231 * Also tell the backing pager, if any, that it should remove 232 * any swap backing since the page is now dirty. 233 */ 234 if (need_dirty) 235 vm_page_dirty(m); 236 if (!set_wd) 237 vm_page_unlock(m); 238 if (need_dirty) 239 vm_pager_page_unswapped(m); 240 } 241 242 /* 243 * vm_fault: 244 * 245 * Handle a page fault occurring at the given address, 246 * requiring the given permissions, in the map specified. 247 * If successful, the page is inserted into the 248 * associated physical map. 249 * 250 * NOTE: the given address should be truncated to the 251 * proper page address. 252 * 253 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 254 * a standard error specifying why the fault is fatal is returned. 255 * 256 * The map in question must be referenced, and remains so. 257 * Caller may hold no locks. 258 */ 259 int 260 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 261 int fault_flags) 262 { 263 struct thread *td; 264 int result; 265 266 td = curthread; 267 if ((td->td_pflags & TDP_NOFAULTING) != 0) 268 return (KERN_PROTECTION_FAILURE); 269 #ifdef KTRACE 270 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 271 ktrfault(vaddr, fault_type); 272 #endif 273 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 274 NULL); 275 #ifdef KTRACE 276 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 277 ktrfaultend(result); 278 #endif 279 return (result); 280 } 281 282 int 283 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 284 int fault_flags, vm_page_t *m_hold) 285 { 286 vm_prot_t prot; 287 int alloc_req, era, faultcount, nera, result; 288 boolean_t growstack, is_first_object_locked, wired; 289 int map_generation; 290 vm_object_t next_object; 291 int hardfault; 292 struct faultstate fs; 293 struct vnode *vp; 294 vm_page_t m; 295 int ahead, behind, cluster_offset, error, locked; 296 297 hardfault = 0; 298 growstack = TRUE; 299 PCPU_INC(cnt.v_vm_faults); 300 fs.vp = NULL; 301 faultcount = 0; 302 303 RetryFault:; 304 305 /* 306 * Find the backing store object and offset into it to begin the 307 * search. 308 */ 309 fs.map = map; 310 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 311 &fs.first_object, &fs.first_pindex, &prot, &wired); 312 if (result != KERN_SUCCESS) { 313 if (growstack && result == KERN_INVALID_ADDRESS && 314 map != kernel_map) { 315 result = vm_map_growstack(curproc, vaddr); 316 if (result != KERN_SUCCESS) 317 return (KERN_FAILURE); 318 growstack = FALSE; 319 goto RetryFault; 320 } 321 return (result); 322 } 323 324 map_generation = fs.map->timestamp; 325 326 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 327 panic("vm_fault: fault on nofault entry, addr: %lx", 328 (u_long)vaddr); 329 } 330 331 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 332 fs.entry->wiring_thread != curthread) { 333 vm_map_unlock_read(fs.map); 334 vm_map_lock(fs.map); 335 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 336 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 337 if (fs.vp != NULL) { 338 vput(fs.vp); 339 fs.vp = NULL; 340 } 341 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 342 vm_map_unlock_and_wait(fs.map, 0); 343 } else 344 vm_map_unlock(fs.map); 345 goto RetryFault; 346 } 347 348 if (wired) 349 fault_type = prot | (fault_type & VM_PROT_COPY); 350 else 351 KASSERT((fault_flags & VM_FAULT_WIRE) == 0, 352 ("!wired && VM_FAULT_WIRE")); 353 354 if (fs.vp == NULL /* avoid locked vnode leak */ && 355 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 && 356 /* avoid calling vm_object_set_writeable_dirty() */ 357 ((prot & VM_PROT_WRITE) == 0 || 358 (fs.first_object->type != OBJT_VNODE && 359 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 360 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 361 VM_OBJECT_RLOCK(fs.first_object); 362 if ((prot & VM_PROT_WRITE) != 0 && 363 (fs.first_object->type == OBJT_VNODE || 364 (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) && 365 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0) 366 goto fast_failed; 367 m = vm_page_lookup(fs.first_object, fs.first_pindex); 368 /* A busy page can be mapped for read|execute access. */ 369 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 370 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 371 goto fast_failed; 372 result = pmap_enter(fs.map->pmap, vaddr, m, prot, 373 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 374 0), 0); 375 if (result != KERN_SUCCESS) 376 goto fast_failed; 377 if (m_hold != NULL) { 378 *m_hold = m; 379 vm_page_lock(m); 380 vm_page_hold(m); 381 vm_page_unlock(m); 382 } 383 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, 384 FALSE); 385 VM_OBJECT_RUNLOCK(fs.first_object); 386 if (!wired) 387 vm_fault_prefault(&fs, vaddr, PFBAK, PFFOR); 388 vm_map_lookup_done(fs.map, fs.entry); 389 curthread->td_ru.ru_minflt++; 390 return (KERN_SUCCESS); 391 fast_failed: 392 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 393 VM_OBJECT_RUNLOCK(fs.first_object); 394 VM_OBJECT_WLOCK(fs.first_object); 395 } 396 } else { 397 VM_OBJECT_WLOCK(fs.first_object); 398 } 399 400 /* 401 * Make a reference to this object to prevent its disposal while we 402 * are messing with it. Once we have the reference, the map is free 403 * to be diddled. Since objects reference their shadows (and copies), 404 * they will stay around as well. 405 * 406 * Bump the paging-in-progress count to prevent size changes (e.g. 407 * truncation operations) during I/O. This must be done after 408 * obtaining the vnode lock in order to avoid possible deadlocks. 409 */ 410 vm_object_reference_locked(fs.first_object); 411 vm_object_pip_add(fs.first_object, 1); 412 413 fs.lookup_still_valid = TRUE; 414 415 fs.first_m = NULL; 416 417 /* 418 * Search for the page at object/offset. 419 */ 420 fs.object = fs.first_object; 421 fs.pindex = fs.first_pindex; 422 while (TRUE) { 423 /* 424 * If the object is dead, we stop here 425 */ 426 if (fs.object->flags & OBJ_DEAD) { 427 unlock_and_deallocate(&fs); 428 return (KERN_PROTECTION_FAILURE); 429 } 430 431 /* 432 * See if page is resident 433 */ 434 fs.m = vm_page_lookup(fs.object, fs.pindex); 435 if (fs.m != NULL) { 436 /* 437 * Wait/Retry if the page is busy. We have to do this 438 * if the page is either exclusive or shared busy 439 * because the vm_pager may be using read busy for 440 * pageouts (and even pageins if it is the vnode 441 * pager), and we could end up trying to pagein and 442 * pageout the same page simultaneously. 443 * 444 * We can theoretically allow the busy case on a read 445 * fault if the page is marked valid, but since such 446 * pages are typically already pmap'd, putting that 447 * special case in might be more effort then it is 448 * worth. We cannot under any circumstances mess 449 * around with a shared busied page except, perhaps, 450 * to pmap it. 451 */ 452 if (vm_page_busied(fs.m)) { 453 /* 454 * Reference the page before unlocking and 455 * sleeping so that the page daemon is less 456 * likely to reclaim it. 457 */ 458 vm_page_aflag_set(fs.m, PGA_REFERENCED); 459 if (fs.object != fs.first_object) { 460 if (!VM_OBJECT_TRYWLOCK( 461 fs.first_object)) { 462 VM_OBJECT_WUNLOCK(fs.object); 463 VM_OBJECT_WLOCK(fs.first_object); 464 VM_OBJECT_WLOCK(fs.object); 465 } 466 vm_page_lock(fs.first_m); 467 vm_page_free(fs.first_m); 468 vm_page_unlock(fs.first_m); 469 vm_object_pip_wakeup(fs.first_object); 470 VM_OBJECT_WUNLOCK(fs.first_object); 471 fs.first_m = NULL; 472 } 473 unlock_map(&fs); 474 if (fs.m == vm_page_lookup(fs.object, 475 fs.pindex)) { 476 vm_page_sleep_if_busy(fs.m, "vmpfw"); 477 } 478 vm_object_pip_wakeup(fs.object); 479 VM_OBJECT_WUNLOCK(fs.object); 480 PCPU_INC(cnt.v_intrans); 481 vm_object_deallocate(fs.first_object); 482 goto RetryFault; 483 } 484 vm_page_lock(fs.m); 485 vm_page_remque(fs.m); 486 vm_page_unlock(fs.m); 487 488 /* 489 * Mark page busy for other processes, and the 490 * pagedaemon. If it still isn't completely valid 491 * (readable), jump to readrest, else break-out ( we 492 * found the page ). 493 */ 494 vm_page_xbusy(fs.m); 495 if (fs.m->valid != VM_PAGE_BITS_ALL) 496 goto readrest; 497 break; 498 } 499 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m)); 500 501 /* 502 * Page is not resident. If the pager might contain the page 503 * or this is the beginning of the search, allocate a new 504 * page. (Default objects are zero-fill, so there is no real 505 * pager for them.) 506 */ 507 if (fs.object->type != OBJT_DEFAULT || 508 fs.object == fs.first_object) { 509 if (fs.pindex >= fs.object->size) { 510 unlock_and_deallocate(&fs); 511 return (KERN_PROTECTION_FAILURE); 512 } 513 514 /* 515 * Allocate a new page for this object/offset pair. 516 * 517 * Unlocked read of the p_flag is harmless. At 518 * worst, the P_KILLED might be not observed 519 * there, and allocation can fail, causing 520 * restart and new reading of the p_flag. 521 */ 522 if (!vm_page_count_severe() || P_KILLED(curproc)) { 523 #if VM_NRESERVLEVEL > 0 524 vm_object_color(fs.object, atop(vaddr) - 525 fs.pindex); 526 #endif 527 alloc_req = P_KILLED(curproc) ? 528 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 529 if (fs.object->type != OBJT_VNODE && 530 fs.object->backing_object == NULL) 531 alloc_req |= VM_ALLOC_ZERO; 532 fs.m = vm_page_alloc(fs.object, fs.pindex, 533 alloc_req); 534 } 535 if (fs.m == NULL) { 536 unlock_and_deallocate(&fs); 537 VM_WAITPFAULT; 538 goto RetryFault; 539 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 540 break; 541 } 542 543 readrest: 544 /* 545 * We have either allocated a new page or found an existing 546 * page that is only partially valid. 547 * 548 * Attempt to fault-in the page if there is a chance that the 549 * pager has it, and potentially fault in additional pages 550 * at the same time. 551 */ 552 if (fs.object->type != OBJT_DEFAULT) { 553 int rv; 554 u_char behavior = vm_map_entry_behavior(fs.entry); 555 556 era = fs.entry->read_ahead; 557 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 558 P_KILLED(curproc)) { 559 behind = 0; 560 nera = 0; 561 ahead = 0; 562 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 563 behind = 0; 564 nera = VM_FAULT_READ_AHEAD_MAX; 565 ahead = nera; 566 if (fs.pindex == fs.entry->next_read) 567 vm_fault_dontneed(&fs, vaddr, ahead); 568 } else if (fs.pindex == fs.entry->next_read) { 569 /* 570 * This is a sequential fault. Arithmetically 571 * increase the requested number of pages in 572 * the read-ahead window. The requested 573 * number of pages is "# of sequential faults 574 * x (read ahead min + 1) + read ahead min" 575 */ 576 behind = 0; 577 nera = VM_FAULT_READ_AHEAD_MIN; 578 if (era > 0) { 579 nera += era + 1; 580 if (nera > VM_FAULT_READ_AHEAD_MAX) 581 nera = VM_FAULT_READ_AHEAD_MAX; 582 } 583 ahead = nera; 584 if (era == VM_FAULT_READ_AHEAD_MAX) 585 vm_fault_dontneed(&fs, vaddr, ahead); 586 } else { 587 /* 588 * This is a non-sequential fault. Request a 589 * cluster of pages that is aligned to a 590 * VM_FAULT_READ_DEFAULT page offset boundary 591 * within the object. Alignment to a page 592 * offset boundary is more likely to coincide 593 * with the underlying file system block than 594 * alignment to a virtual address boundary. 595 */ 596 cluster_offset = fs.pindex % 597 VM_FAULT_READ_DEFAULT; 598 behind = ulmin(cluster_offset, 599 atop(vaddr - fs.entry->start)); 600 nera = 0; 601 ahead = VM_FAULT_READ_DEFAULT - 1 - 602 cluster_offset; 603 } 604 ahead = ulmin(ahead, atop(fs.entry->end - vaddr) - 1); 605 if (era != nera) 606 fs.entry->read_ahead = nera; 607 608 /* 609 * Call the pager to retrieve the data, if any, after 610 * releasing the lock on the map. We hold a ref on 611 * fs.object and the pages are exclusive busied. 612 */ 613 unlock_map(&fs); 614 615 if (fs.object->type == OBJT_VNODE) { 616 vp = fs.object->handle; 617 if (vp == fs.vp) 618 goto vnode_locked; 619 else if (fs.vp != NULL) { 620 vput(fs.vp); 621 fs.vp = NULL; 622 } 623 locked = VOP_ISLOCKED(vp); 624 625 if (locked != LK_EXCLUSIVE) 626 locked = LK_SHARED; 627 /* Do not sleep for vnode lock while fs.m is busy */ 628 error = vget(vp, locked | LK_CANRECURSE | 629 LK_NOWAIT, curthread); 630 if (error != 0) { 631 vhold(vp); 632 release_page(&fs); 633 unlock_and_deallocate(&fs); 634 error = vget(vp, locked | LK_RETRY | 635 LK_CANRECURSE, curthread); 636 vdrop(vp); 637 fs.vp = vp; 638 KASSERT(error == 0, 639 ("vm_fault: vget failed")); 640 goto RetryFault; 641 } 642 fs.vp = vp; 643 } 644 vnode_locked: 645 KASSERT(fs.vp == NULL || !fs.map->system_map, 646 ("vm_fault: vnode-backed object mapped by system map")); 647 648 /* 649 * Page in the requested page and hint the pager, 650 * that it may bring up surrounding pages. 651 */ 652 rv = vm_pager_get_pages(fs.object, &fs.m, 1, 653 &behind, &ahead); 654 if (rv == VM_PAGER_OK) { 655 faultcount = behind + 1 + ahead; 656 hardfault++; 657 break; /* break to PAGE HAS BEEN FOUND */ 658 } 659 if (rv == VM_PAGER_ERROR) 660 printf("vm_fault: pager read error, pid %d (%s)\n", 661 curproc->p_pid, curproc->p_comm); 662 663 /* 664 * If an I/O error occurred or the requested page was 665 * outside the range of the pager, clean up and return 666 * an error. 667 */ 668 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) { 669 vm_page_lock(fs.m); 670 vm_page_free(fs.m); 671 vm_page_unlock(fs.m); 672 fs.m = NULL; 673 unlock_and_deallocate(&fs); 674 return (rv == VM_PAGER_ERROR ? KERN_FAILURE : 675 KERN_PROTECTION_FAILURE); 676 } 677 678 /* 679 * The requested page does not exist at this object/ 680 * offset. Remove the invalid page from the object, 681 * waking up anyone waiting for it, and continue on to 682 * the next object. However, if this is the top-level 683 * object, we must leave the busy page in place to 684 * prevent another process from rushing past us, and 685 * inserting the page in that object at the same time 686 * that we are. 687 */ 688 if (fs.object != fs.first_object) { 689 vm_page_lock(fs.m); 690 vm_page_free(fs.m); 691 vm_page_unlock(fs.m); 692 fs.m = NULL; 693 } 694 } 695 696 /* 697 * We get here if the object has default pager (or unwiring) 698 * or the pager doesn't have the page. 699 */ 700 if (fs.object == fs.first_object) 701 fs.first_m = fs.m; 702 703 /* 704 * Move on to the next object. Lock the next object before 705 * unlocking the current one. 706 */ 707 next_object = fs.object->backing_object; 708 if (next_object == NULL) { 709 /* 710 * If there's no object left, fill the page in the top 711 * object with zeros. 712 */ 713 if (fs.object != fs.first_object) { 714 vm_object_pip_wakeup(fs.object); 715 VM_OBJECT_WUNLOCK(fs.object); 716 717 fs.object = fs.first_object; 718 fs.pindex = fs.first_pindex; 719 fs.m = fs.first_m; 720 VM_OBJECT_WLOCK(fs.object); 721 } 722 fs.first_m = NULL; 723 724 /* 725 * Zero the page if necessary and mark it valid. 726 */ 727 if ((fs.m->flags & PG_ZERO) == 0) { 728 pmap_zero_page(fs.m); 729 } else { 730 PCPU_INC(cnt.v_ozfod); 731 } 732 PCPU_INC(cnt.v_zfod); 733 fs.m->valid = VM_PAGE_BITS_ALL; 734 /* Don't try to prefault neighboring pages. */ 735 faultcount = 1; 736 break; /* break to PAGE HAS BEEN FOUND */ 737 } else { 738 KASSERT(fs.object != next_object, 739 ("object loop %p", next_object)); 740 VM_OBJECT_WLOCK(next_object); 741 vm_object_pip_add(next_object, 1); 742 if (fs.object != fs.first_object) 743 vm_object_pip_wakeup(fs.object); 744 fs.pindex += 745 OFF_TO_IDX(fs.object->backing_object_offset); 746 VM_OBJECT_WUNLOCK(fs.object); 747 fs.object = next_object; 748 } 749 } 750 751 vm_page_assert_xbusied(fs.m); 752 753 /* 754 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 755 * is held.] 756 */ 757 758 /* 759 * If the page is being written, but isn't already owned by the 760 * top-level object, we have to copy it into a new page owned by the 761 * top-level object. 762 */ 763 if (fs.object != fs.first_object) { 764 /* 765 * We only really need to copy if we want to write it. 766 */ 767 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 768 /* 769 * This allows pages to be virtually copied from a 770 * backing_object into the first_object, where the 771 * backing object has no other refs to it, and cannot 772 * gain any more refs. Instead of a bcopy, we just 773 * move the page from the backing object to the 774 * first object. Note that we must mark the page 775 * dirty in the first object so that it will go out 776 * to swap when needed. 777 */ 778 is_first_object_locked = FALSE; 779 if ( 780 /* 781 * Only one shadow object 782 */ 783 (fs.object->shadow_count == 1) && 784 /* 785 * No COW refs, except us 786 */ 787 (fs.object->ref_count == 1) && 788 /* 789 * No one else can look this object up 790 */ 791 (fs.object->handle == NULL) && 792 /* 793 * No other ways to look the object up 794 */ 795 ((fs.object->type == OBJT_DEFAULT) || 796 (fs.object->type == OBJT_SWAP)) && 797 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 798 /* 799 * We don't chase down the shadow chain 800 */ 801 fs.object == fs.first_object->backing_object) { 802 vm_page_lock(fs.m); 803 vm_page_remove(fs.m); 804 vm_page_unlock(fs.m); 805 vm_page_lock(fs.first_m); 806 vm_page_replace_checked(fs.m, fs.first_object, 807 fs.first_pindex, fs.first_m); 808 vm_page_free(fs.first_m); 809 vm_page_unlock(fs.first_m); 810 vm_page_dirty(fs.m); 811 #if VM_NRESERVLEVEL > 0 812 /* 813 * Rename the reservation. 814 */ 815 vm_reserv_rename(fs.m, fs.first_object, 816 fs.object, OFF_TO_IDX( 817 fs.first_object->backing_object_offset)); 818 #endif 819 /* 820 * Removing the page from the backing object 821 * unbusied it. 822 */ 823 vm_page_xbusy(fs.m); 824 fs.first_m = fs.m; 825 fs.m = NULL; 826 PCPU_INC(cnt.v_cow_optim); 827 } else { 828 /* 829 * Oh, well, lets copy it. 830 */ 831 pmap_copy_page(fs.m, fs.first_m); 832 fs.first_m->valid = VM_PAGE_BITS_ALL; 833 if (wired && (fault_flags & 834 VM_FAULT_WIRE) == 0) { 835 vm_page_lock(fs.first_m); 836 vm_page_wire(fs.first_m); 837 vm_page_unlock(fs.first_m); 838 839 vm_page_lock(fs.m); 840 vm_page_unwire(fs.m, PQ_INACTIVE); 841 vm_page_unlock(fs.m); 842 } 843 /* 844 * We no longer need the old page or object. 845 */ 846 release_page(&fs); 847 } 848 /* 849 * fs.object != fs.first_object due to above 850 * conditional 851 */ 852 vm_object_pip_wakeup(fs.object); 853 VM_OBJECT_WUNLOCK(fs.object); 854 /* 855 * Only use the new page below... 856 */ 857 fs.object = fs.first_object; 858 fs.pindex = fs.first_pindex; 859 fs.m = fs.first_m; 860 if (!is_first_object_locked) 861 VM_OBJECT_WLOCK(fs.object); 862 PCPU_INC(cnt.v_cow_faults); 863 curthread->td_cow++; 864 } else { 865 prot &= ~VM_PROT_WRITE; 866 } 867 } 868 869 /* 870 * We must verify that the maps have not changed since our last 871 * lookup. 872 */ 873 if (!fs.lookup_still_valid) { 874 vm_object_t retry_object; 875 vm_pindex_t retry_pindex; 876 vm_prot_t retry_prot; 877 878 if (!vm_map_trylock_read(fs.map)) { 879 release_page(&fs); 880 unlock_and_deallocate(&fs); 881 goto RetryFault; 882 } 883 fs.lookup_still_valid = TRUE; 884 if (fs.map->timestamp != map_generation) { 885 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 886 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 887 888 /* 889 * If we don't need the page any longer, put it on the inactive 890 * list (the easiest thing to do here). If no one needs it, 891 * pageout will grab it eventually. 892 */ 893 if (result != KERN_SUCCESS) { 894 release_page(&fs); 895 unlock_and_deallocate(&fs); 896 897 /* 898 * If retry of map lookup would have blocked then 899 * retry fault from start. 900 */ 901 if (result == KERN_FAILURE) 902 goto RetryFault; 903 return (result); 904 } 905 if ((retry_object != fs.first_object) || 906 (retry_pindex != fs.first_pindex)) { 907 release_page(&fs); 908 unlock_and_deallocate(&fs); 909 goto RetryFault; 910 } 911 912 /* 913 * Check whether the protection has changed or the object has 914 * been copied while we left the map unlocked. Changing from 915 * read to write permission is OK - we leave the page 916 * write-protected, and catch the write fault. Changing from 917 * write to read permission means that we can't mark the page 918 * write-enabled after all. 919 */ 920 prot &= retry_prot; 921 } 922 } 923 /* 924 * If the page was filled by a pager, update the map entry's 925 * last read offset. 926 * 927 * XXX The following assignment modifies the map 928 * without holding a write lock on it. 929 */ 930 if (hardfault) 931 fs.entry->next_read = fs.pindex + ahead + 1; 932 933 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); 934 vm_page_assert_xbusied(fs.m); 935 936 /* 937 * Page must be completely valid or it is not fit to 938 * map into user space. vm_pager_get_pages() ensures this. 939 */ 940 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 941 ("vm_fault: page %p partially invalid", fs.m)); 942 VM_OBJECT_WUNLOCK(fs.object); 943 944 /* 945 * Put this page into the physical map. We had to do the unlock above 946 * because pmap_enter() may sleep. We don't put the page 947 * back on the active queue until later so that the pageout daemon 948 * won't find it (yet). 949 */ 950 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 951 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 952 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 953 wired == 0) 954 vm_fault_prefault(&fs, vaddr, 955 faultcount > 0 ? behind : PFBAK, 956 faultcount > 0 ? ahead : PFFOR); 957 VM_OBJECT_WLOCK(fs.object); 958 vm_page_lock(fs.m); 959 960 /* 961 * If the page is not wired down, then put it where the pageout daemon 962 * can find it. 963 */ 964 if ((fault_flags & VM_FAULT_WIRE) != 0) { 965 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 966 vm_page_wire(fs.m); 967 } else 968 vm_page_activate(fs.m); 969 if (m_hold != NULL) { 970 *m_hold = fs.m; 971 vm_page_hold(fs.m); 972 } 973 vm_page_unlock(fs.m); 974 vm_page_xunbusy(fs.m); 975 976 /* 977 * Unlock everything, and return 978 */ 979 unlock_and_deallocate(&fs); 980 if (hardfault) { 981 PCPU_INC(cnt.v_io_faults); 982 curthread->td_ru.ru_majflt++; 983 #ifdef RACCT 984 if (racct_enable && fs.object->type == OBJT_VNODE) { 985 PROC_LOCK(curproc); 986 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 987 racct_add_force(curproc, RACCT_WRITEBPS, 988 PAGE_SIZE + behind * PAGE_SIZE); 989 racct_add_force(curproc, RACCT_WRITEIOPS, 1); 990 } else { 991 racct_add_force(curproc, RACCT_READBPS, 992 PAGE_SIZE + ahead * PAGE_SIZE); 993 racct_add_force(curproc, RACCT_READIOPS, 1); 994 } 995 PROC_UNLOCK(curproc); 996 } 997 #endif 998 } else 999 curthread->td_ru.ru_minflt++; 1000 1001 return (KERN_SUCCESS); 1002 } 1003 1004 /* 1005 * Speed up the reclamation of pages that precede the faulting pindex within 1006 * the first object of the shadow chain. Essentially, perform the equivalent 1007 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1008 * the faulting pindex by the cluster size when the pages read by vm_fault() 1009 * cross a cluster-size boundary. The cluster size is the greater of the 1010 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1011 * 1012 * When "fs->first_object" is a shadow object, the pages in the backing object 1013 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1014 * function must only be concerned with pages in the first object. 1015 */ 1016 static void 1017 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1018 { 1019 vm_map_entry_t entry; 1020 vm_object_t first_object, object; 1021 vm_offset_t end, start; 1022 vm_page_t m, m_next; 1023 vm_pindex_t pend, pstart; 1024 vm_size_t size; 1025 1026 object = fs->object; 1027 VM_OBJECT_ASSERT_WLOCKED(object); 1028 first_object = fs->first_object; 1029 if (first_object != object) { 1030 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1031 VM_OBJECT_WUNLOCK(object); 1032 VM_OBJECT_WLOCK(first_object); 1033 VM_OBJECT_WLOCK(object); 1034 } 1035 } 1036 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1037 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1038 size = VM_FAULT_DONTNEED_MIN; 1039 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1040 size = pagesizes[1]; 1041 end = rounddown2(vaddr, size); 1042 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1043 (entry = fs->entry)->start < end) { 1044 if (end - entry->start < size) 1045 start = entry->start; 1046 else 1047 start = end - size; 1048 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1049 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1050 entry->start); 1051 m_next = vm_page_find_least(first_object, pstart); 1052 pend = OFF_TO_IDX(entry->offset) + atop(end - 1053 entry->start); 1054 while ((m = m_next) != NULL && m->pindex < pend) { 1055 m_next = TAILQ_NEXT(m, listq); 1056 if (m->valid != VM_PAGE_BITS_ALL || 1057 vm_page_busied(m)) 1058 continue; 1059 1060 /* 1061 * Don't clear PGA_REFERENCED, since it would 1062 * likely represent a reference by a different 1063 * process. 1064 * 1065 * Typically, at this point, prefetched pages 1066 * are still in the inactive queue. Only 1067 * pages that triggered page faults are in the 1068 * active queue. 1069 */ 1070 vm_page_lock(m); 1071 vm_page_deactivate(m); 1072 vm_page_unlock(m); 1073 } 1074 } 1075 } 1076 if (first_object != object) 1077 VM_OBJECT_WUNLOCK(first_object); 1078 } 1079 1080 /* 1081 * vm_fault_prefault provides a quick way of clustering 1082 * pagefaults into a processes address space. It is a "cousin" 1083 * of vm_map_pmap_enter, except it runs at page fault time instead 1084 * of mmap time. 1085 */ 1086 static void 1087 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1088 int backward, int forward) 1089 { 1090 pmap_t pmap; 1091 vm_map_entry_t entry; 1092 vm_object_t backing_object, lobject; 1093 vm_offset_t addr, starta; 1094 vm_pindex_t pindex; 1095 vm_page_t m; 1096 int i; 1097 1098 pmap = fs->map->pmap; 1099 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1100 return; 1101 1102 entry = fs->entry; 1103 1104 starta = addra - backward * PAGE_SIZE; 1105 if (starta < entry->start) { 1106 starta = entry->start; 1107 } else if (starta > addra) { 1108 starta = 0; 1109 } 1110 1111 /* 1112 * Generate the sequence of virtual addresses that are candidates for 1113 * prefaulting in an outward spiral from the faulting virtual address, 1114 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1115 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1116 * If the candidate address doesn't have a backing physical page, then 1117 * the loop immediately terminates. 1118 */ 1119 for (i = 0; i < 2 * imax(backward, forward); i++) { 1120 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1121 PAGE_SIZE); 1122 if (addr > addra + forward * PAGE_SIZE) 1123 addr = 0; 1124 1125 if (addr < starta || addr >= entry->end) 1126 continue; 1127 1128 if (!pmap_is_prefaultable(pmap, addr)) 1129 continue; 1130 1131 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1132 lobject = entry->object.vm_object; 1133 VM_OBJECT_RLOCK(lobject); 1134 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1135 lobject->type == OBJT_DEFAULT && 1136 (backing_object = lobject->backing_object) != NULL) { 1137 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1138 0, ("vm_fault_prefault: unaligned object offset")); 1139 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1140 VM_OBJECT_RLOCK(backing_object); 1141 VM_OBJECT_RUNLOCK(lobject); 1142 lobject = backing_object; 1143 } 1144 if (m == NULL) { 1145 VM_OBJECT_RUNLOCK(lobject); 1146 break; 1147 } 1148 if (m->valid == VM_PAGE_BITS_ALL && 1149 (m->flags & PG_FICTITIOUS) == 0) 1150 pmap_enter_quick(pmap, addr, m, entry->protection); 1151 VM_OBJECT_RUNLOCK(lobject); 1152 } 1153 } 1154 1155 /* 1156 * Hold each of the physical pages that are mapped by the specified range of 1157 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1158 * and allow the specified types of access, "prot". If all of the implied 1159 * pages are successfully held, then the number of held pages is returned 1160 * together with pointers to those pages in the array "ma". However, if any 1161 * of the pages cannot be held, -1 is returned. 1162 */ 1163 int 1164 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1165 vm_prot_t prot, vm_page_t *ma, int max_count) 1166 { 1167 vm_offset_t end, va; 1168 vm_page_t *mp; 1169 int count; 1170 boolean_t pmap_failed; 1171 1172 if (len == 0) 1173 return (0); 1174 end = round_page(addr + len); 1175 addr = trunc_page(addr); 1176 1177 /* 1178 * Check for illegal addresses. 1179 */ 1180 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1181 return (-1); 1182 1183 if (atop(end - addr) > max_count) 1184 panic("vm_fault_quick_hold_pages: count > max_count"); 1185 count = atop(end - addr); 1186 1187 /* 1188 * Most likely, the physical pages are resident in the pmap, so it is 1189 * faster to try pmap_extract_and_hold() first. 1190 */ 1191 pmap_failed = FALSE; 1192 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1193 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1194 if (*mp == NULL) 1195 pmap_failed = TRUE; 1196 else if ((prot & VM_PROT_WRITE) != 0 && 1197 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1198 /* 1199 * Explicitly dirty the physical page. Otherwise, the 1200 * caller's changes may go unnoticed because they are 1201 * performed through an unmanaged mapping or by a DMA 1202 * operation. 1203 * 1204 * The object lock is not held here. 1205 * See vm_page_clear_dirty_mask(). 1206 */ 1207 vm_page_dirty(*mp); 1208 } 1209 } 1210 if (pmap_failed) { 1211 /* 1212 * One or more pages could not be held by the pmap. Either no 1213 * page was mapped at the specified virtual address or that 1214 * mapping had insufficient permissions. Attempt to fault in 1215 * and hold these pages. 1216 */ 1217 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1218 if (*mp == NULL && vm_fault_hold(map, va, prot, 1219 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1220 goto error; 1221 } 1222 return (count); 1223 error: 1224 for (mp = ma; mp < ma + count; mp++) 1225 if (*mp != NULL) { 1226 vm_page_lock(*mp); 1227 vm_page_unhold(*mp); 1228 vm_page_unlock(*mp); 1229 } 1230 return (-1); 1231 } 1232 1233 /* 1234 * Routine: 1235 * vm_fault_copy_entry 1236 * Function: 1237 * Create new shadow object backing dst_entry with private copy of 1238 * all underlying pages. When src_entry is equal to dst_entry, 1239 * function implements COW for wired-down map entry. Otherwise, 1240 * it forks wired entry into dst_map. 1241 * 1242 * In/out conditions: 1243 * The source and destination maps must be locked for write. 1244 * The source map entry must be wired down (or be a sharing map 1245 * entry corresponding to a main map entry that is wired down). 1246 */ 1247 void 1248 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1249 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1250 vm_ooffset_t *fork_charge) 1251 { 1252 vm_object_t backing_object, dst_object, object, src_object; 1253 vm_pindex_t dst_pindex, pindex, src_pindex; 1254 vm_prot_t access, prot; 1255 vm_offset_t vaddr; 1256 vm_page_t dst_m; 1257 vm_page_t src_m; 1258 boolean_t upgrade; 1259 1260 #ifdef lint 1261 src_map++; 1262 #endif /* lint */ 1263 1264 upgrade = src_entry == dst_entry; 1265 access = prot = dst_entry->protection; 1266 1267 src_object = src_entry->object.vm_object; 1268 src_pindex = OFF_TO_IDX(src_entry->offset); 1269 1270 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1271 dst_object = src_object; 1272 vm_object_reference(dst_object); 1273 } else { 1274 /* 1275 * Create the top-level object for the destination entry. (Doesn't 1276 * actually shadow anything - we copy the pages directly.) 1277 */ 1278 dst_object = vm_object_allocate(OBJT_DEFAULT, 1279 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1280 #if VM_NRESERVLEVEL > 0 1281 dst_object->flags |= OBJ_COLORED; 1282 dst_object->pg_color = atop(dst_entry->start); 1283 #endif 1284 } 1285 1286 VM_OBJECT_WLOCK(dst_object); 1287 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1288 ("vm_fault_copy_entry: vm_object not NULL")); 1289 if (src_object != dst_object) { 1290 dst_entry->object.vm_object = dst_object; 1291 dst_entry->offset = 0; 1292 dst_object->charge = dst_entry->end - dst_entry->start; 1293 } 1294 if (fork_charge != NULL) { 1295 KASSERT(dst_entry->cred == NULL, 1296 ("vm_fault_copy_entry: leaked swp charge")); 1297 dst_object->cred = curthread->td_ucred; 1298 crhold(dst_object->cred); 1299 *fork_charge += dst_object->charge; 1300 } else if (dst_object->cred == NULL) { 1301 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1302 dst_entry)); 1303 dst_object->cred = dst_entry->cred; 1304 dst_entry->cred = NULL; 1305 } 1306 1307 /* 1308 * If not an upgrade, then enter the mappings in the pmap as 1309 * read and/or execute accesses. Otherwise, enter them as 1310 * write accesses. 1311 * 1312 * A writeable large page mapping is only created if all of 1313 * the constituent small page mappings are modified. Marking 1314 * PTEs as modified on inception allows promotion to happen 1315 * without taking potentially large number of soft faults. 1316 */ 1317 if (!upgrade) 1318 access &= ~VM_PROT_WRITE; 1319 1320 /* 1321 * Loop through all of the virtual pages within the entry's 1322 * range, copying each page from the source object to the 1323 * destination object. Since the source is wired, those pages 1324 * must exist. In contrast, the destination is pageable. 1325 * Since the destination object does share any backing storage 1326 * with the source object, all of its pages must be dirtied, 1327 * regardless of whether they can be written. 1328 */ 1329 for (vaddr = dst_entry->start, dst_pindex = 0; 1330 vaddr < dst_entry->end; 1331 vaddr += PAGE_SIZE, dst_pindex++) { 1332 again: 1333 /* 1334 * Find the page in the source object, and copy it in. 1335 * Because the source is wired down, the page will be 1336 * in memory. 1337 */ 1338 if (src_object != dst_object) 1339 VM_OBJECT_RLOCK(src_object); 1340 object = src_object; 1341 pindex = src_pindex + dst_pindex; 1342 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1343 (backing_object = object->backing_object) != NULL) { 1344 /* 1345 * Unless the source mapping is read-only or 1346 * it is presently being upgraded from 1347 * read-only, the first object in the shadow 1348 * chain should provide all of the pages. In 1349 * other words, this loop body should never be 1350 * executed when the source mapping is already 1351 * read/write. 1352 */ 1353 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1354 upgrade, 1355 ("vm_fault_copy_entry: main object missing page")); 1356 1357 VM_OBJECT_RLOCK(backing_object); 1358 pindex += OFF_TO_IDX(object->backing_object_offset); 1359 if (object != dst_object) 1360 VM_OBJECT_RUNLOCK(object); 1361 object = backing_object; 1362 } 1363 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1364 1365 if (object != dst_object) { 1366 /* 1367 * Allocate a page in the destination object. 1368 */ 1369 dst_m = vm_page_alloc(dst_object, (src_object == 1370 dst_object ? src_pindex : 0) + dst_pindex, 1371 VM_ALLOC_NORMAL); 1372 if (dst_m == NULL) { 1373 VM_OBJECT_WUNLOCK(dst_object); 1374 VM_OBJECT_RUNLOCK(object); 1375 VM_WAIT; 1376 VM_OBJECT_WLOCK(dst_object); 1377 goto again; 1378 } 1379 pmap_copy_page(src_m, dst_m); 1380 VM_OBJECT_RUNLOCK(object); 1381 dst_m->valid = VM_PAGE_BITS_ALL; 1382 dst_m->dirty = VM_PAGE_BITS_ALL; 1383 } else { 1384 dst_m = src_m; 1385 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1386 goto again; 1387 vm_page_xbusy(dst_m); 1388 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1389 ("invalid dst page %p", dst_m)); 1390 } 1391 VM_OBJECT_WUNLOCK(dst_object); 1392 1393 /* 1394 * Enter it in the pmap. If a wired, copy-on-write 1395 * mapping is being replaced by a write-enabled 1396 * mapping, then wire that new mapping. 1397 */ 1398 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1399 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1400 1401 /* 1402 * Mark it no longer busy, and put it on the active list. 1403 */ 1404 VM_OBJECT_WLOCK(dst_object); 1405 1406 if (upgrade) { 1407 if (src_m != dst_m) { 1408 vm_page_lock(src_m); 1409 vm_page_unwire(src_m, PQ_INACTIVE); 1410 vm_page_unlock(src_m); 1411 vm_page_lock(dst_m); 1412 vm_page_wire(dst_m); 1413 vm_page_unlock(dst_m); 1414 } else { 1415 KASSERT(dst_m->wire_count > 0, 1416 ("dst_m %p is not wired", dst_m)); 1417 } 1418 } else { 1419 vm_page_lock(dst_m); 1420 vm_page_activate(dst_m); 1421 vm_page_unlock(dst_m); 1422 } 1423 vm_page_xunbusy(dst_m); 1424 } 1425 VM_OBJECT_WUNLOCK(dst_object); 1426 if (upgrade) { 1427 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1428 vm_object_deallocate(src_object); 1429 } 1430 } 1431 1432 /* 1433 * Block entry into the machine-independent layer's page fault handler by 1434 * the calling thread. Subsequent calls to vm_fault() by that thread will 1435 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1436 * spurious page faults. 1437 */ 1438 int 1439 vm_fault_disable_pagefaults(void) 1440 { 1441 1442 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1443 } 1444 1445 void 1446 vm_fault_enable_pagefaults(int save) 1447 { 1448 1449 curthread_pflags_restore(save); 1450 } 1451