vm_fault.c revision 303246
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: stable/10/sys/vm/vm_fault.c 303246 2016-07-23 21:15:40Z alc $"); 76 77#include "opt_ktrace.h" 78#include "opt_vm.h" 79 80#include <sys/param.h> 81#include <sys/systm.h> 82#include <sys/kernel.h> 83#include <sys/lock.h> 84#include <sys/proc.h> 85#include <sys/resourcevar.h> 86#include <sys/rwlock.h> 87#include <sys/sysctl.h> 88#include <sys/vmmeter.h> 89#include <sys/vnode.h> 90#ifdef KTRACE 91#include <sys/ktrace.h> 92#endif 93 94#include <vm/vm.h> 95#include <vm/vm_param.h> 96#include <vm/pmap.h> 97#include <vm/vm_map.h> 98#include <vm/vm_object.h> 99#include <vm/vm_page.h> 100#include <vm/vm_pageout.h> 101#include <vm/vm_kern.h> 102#include <vm/vm_pager.h> 103#include <vm/vm_extern.h> 104#include <vm/vm_reserv.h> 105 106#define PFBAK 4 107#define PFFOR 4 108 109static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 110 111#define VM_FAULT_READ_BEHIND 8 112#define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX) 113#define VM_FAULT_NINCR (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND) 114#define VM_FAULT_SUM (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2) 115#define VM_FAULT_CACHE_BEHIND (VM_FAULT_READ_BEHIND * VM_FAULT_SUM) 116 117struct faultstate { 118 vm_page_t m; 119 vm_object_t object; 120 vm_pindex_t pindex; 121 vm_page_t first_m; 122 vm_object_t first_object; 123 vm_pindex_t first_pindex; 124 vm_map_t map; 125 vm_map_entry_t entry; 126 int lookup_still_valid; 127 struct vnode *vp; 128}; 129 130static void vm_fault_cache_behind(const struct faultstate *fs, int distance); 131static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 132 int faultcount, int reqpage); 133 134static inline void 135release_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 145static inline void 146unlock_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 155static void 156unlock_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 178static void 179vm_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 */ 259int 260vm_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 282int 283vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 284 int fault_flags, vm_page_t *m_hold) 285{ 286 vm_prot_t prot; 287 long ahead, behind; 288 int alloc_req, era, faultcount, nera, reqpage, result; 289 boolean_t dead, growstack, is_first_object_locked, wired; 290 int map_generation; 291 vm_object_t next_object; 292 vm_page_t marray[VM_FAULT_READ_MAX]; 293 int hardfault; 294 struct faultstate fs; 295 struct vnode *vp; 296 vm_page_t m; 297 int locked, error; 298 299 hardfault = 0; 300 growstack = TRUE; 301 PCPU_INC(cnt.v_vm_faults); 302 fs.vp = NULL; 303 faultcount = reqpage = 0; 304 305RetryFault:; 306 307 /* 308 * Find the backing store object and offset into it to begin the 309 * search. 310 */ 311 fs.map = map; 312 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 313 &fs.first_object, &fs.first_pindex, &prot, &wired); 314 if (result != KERN_SUCCESS) { 315 if (growstack && result == KERN_INVALID_ADDRESS && 316 map != kernel_map) { 317 result = vm_map_growstack(curproc, vaddr); 318 if (result != KERN_SUCCESS) 319 return (KERN_FAILURE); 320 growstack = FALSE; 321 goto RetryFault; 322 } 323 return (result); 324 } 325 326 map_generation = fs.map->timestamp; 327 328 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 329 panic("vm_fault: fault on nofault entry, addr: %lx", 330 (u_long)vaddr); 331 } 332 333 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 334 fs.entry->wiring_thread != curthread) { 335 vm_map_unlock_read(fs.map); 336 vm_map_lock(fs.map); 337 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 338 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 339 if (fs.vp != NULL) { 340 vput(fs.vp); 341 fs.vp = NULL; 342 } 343 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 344 vm_map_unlock_and_wait(fs.map, 0); 345 } else 346 vm_map_unlock(fs.map); 347 goto RetryFault; 348 } 349 350 if (wired) 351 fault_type = prot | (fault_type & VM_PROT_COPY); 352 else 353 KASSERT((fault_flags & VM_FAULT_WIRE) == 0, 354 ("!wired && VM_FAULT_WIRE")); 355 356 /* 357 * Try to avoid lock contention on the top-level object through 358 * special-case handling of some types of page faults, specifically, 359 * those that are both (1) mapping an existing page from the top- 360 * level object and (2) not having to mark that object as containing 361 * dirty pages. Under these conditions, a read lock on the top-level 362 * object suffices, allowing multiple page faults of a similar type to 363 * run in parallel on the same top-level object. 364 */ 365 if (fs.vp == NULL /* avoid locked vnode leak */ && 366 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 && 367 /* avoid calling vm_object_set_writeable_dirty() */ 368 ((prot & VM_PROT_WRITE) == 0 || 369 (fs.first_object->type != OBJT_VNODE && 370 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 371 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 372 VM_OBJECT_RLOCK(fs.first_object); 373 if ((prot & VM_PROT_WRITE) != 0 && 374 (fs.first_object->type == OBJT_VNODE || 375 (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) && 376 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0) 377 goto fast_failed; 378 m = vm_page_lookup(fs.first_object, fs.first_pindex); 379 /* A busy page can be mapped for read|execute access. */ 380 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 381 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 382 goto fast_failed; 383 result = pmap_enter(fs.map->pmap, vaddr, m, prot, 384 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 385 0), 0); 386 if (result != KERN_SUCCESS) 387 goto fast_failed; 388 if (m_hold != NULL) { 389 *m_hold = m; 390 vm_page_lock(m); 391 vm_page_hold(m); 392 vm_page_unlock(m); 393 } 394 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, 395 FALSE); 396 VM_OBJECT_RUNLOCK(fs.first_object); 397 if (!wired) 398 vm_fault_prefault(&fs, vaddr, 0, 0); 399 vm_map_lookup_done(fs.map, fs.entry); 400 curthread->td_ru.ru_minflt++; 401 return (KERN_SUCCESS); 402fast_failed: 403 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 404 VM_OBJECT_RUNLOCK(fs.first_object); 405 VM_OBJECT_WLOCK(fs.first_object); 406 } 407 } else { 408 VM_OBJECT_WLOCK(fs.first_object); 409 } 410 411 /* 412 * Make a reference to this object to prevent its disposal while we 413 * are messing with it. Once we have the reference, the map is free 414 * to be diddled. Since objects reference their shadows (and copies), 415 * they will stay around as well. 416 * 417 * Bump the paging-in-progress count to prevent size changes (e.g. 418 * truncation operations) during I/O. This must be done after 419 * obtaining the vnode lock in order to avoid possible deadlocks. 420 */ 421 vm_object_reference_locked(fs.first_object); 422 vm_object_pip_add(fs.first_object, 1); 423 424 fs.lookup_still_valid = TRUE; 425 426 fs.first_m = NULL; 427 428 /* 429 * Search for the page at object/offset. 430 */ 431 fs.object = fs.first_object; 432 fs.pindex = fs.first_pindex; 433 while (TRUE) { 434 /* 435 * If the object is marked for imminent termination, 436 * we retry here, since the collapse pass has raced 437 * with us. Otherwise, if we see terminally dead 438 * object, return fail. 439 */ 440 if ((fs.object->flags & OBJ_DEAD) != 0) { 441 dead = fs.object->type == OBJT_DEAD; 442 unlock_and_deallocate(&fs); 443 if (dead) 444 return (KERN_PROTECTION_FAILURE); 445 pause("vmf_de", 1); 446 goto RetryFault; 447 } 448 449 /* 450 * See if page is resident 451 */ 452 fs.m = vm_page_lookup(fs.object, fs.pindex); 453 if (fs.m != NULL) { 454 /* 455 * Wait/Retry if the page is busy. We have to do this 456 * if the page is either exclusive or shared busy 457 * because the vm_pager may be using read busy for 458 * pageouts (and even pageins if it is the vnode 459 * pager), and we could end up trying to pagein and 460 * pageout the same page simultaneously. 461 * 462 * We can theoretically allow the busy case on a read 463 * fault if the page is marked valid, but since such 464 * pages are typically already pmap'd, putting that 465 * special case in might be more effort then it is 466 * worth. We cannot under any circumstances mess 467 * around with a shared busied page except, perhaps, 468 * to pmap it. 469 */ 470 if (vm_page_busied(fs.m)) { 471 /* 472 * Reference the page before unlocking and 473 * sleeping so that the page daemon is less 474 * likely to reclaim it. 475 */ 476 vm_page_aflag_set(fs.m, PGA_REFERENCED); 477 if (fs.object != fs.first_object) { 478 if (!VM_OBJECT_TRYWLOCK( 479 fs.first_object)) { 480 VM_OBJECT_WUNLOCK(fs.object); 481 VM_OBJECT_WLOCK(fs.first_object); 482 VM_OBJECT_WLOCK(fs.object); 483 } 484 vm_page_lock(fs.first_m); 485 vm_page_free(fs.first_m); 486 vm_page_unlock(fs.first_m); 487 vm_object_pip_wakeup(fs.first_object); 488 VM_OBJECT_WUNLOCK(fs.first_object); 489 fs.first_m = NULL; 490 } 491 unlock_map(&fs); 492 if (fs.m == vm_page_lookup(fs.object, 493 fs.pindex)) { 494 vm_page_sleep_if_busy(fs.m, "vmpfw"); 495 } 496 vm_object_pip_wakeup(fs.object); 497 VM_OBJECT_WUNLOCK(fs.object); 498 PCPU_INC(cnt.v_intrans); 499 vm_object_deallocate(fs.first_object); 500 goto RetryFault; 501 } 502 vm_page_lock(fs.m); 503 vm_page_remque(fs.m); 504 vm_page_unlock(fs.m); 505 506 /* 507 * Mark page busy for other processes, and the 508 * pagedaemon. If it still isn't completely valid 509 * (readable), jump to readrest, else break-out ( we 510 * found the page ). 511 */ 512 vm_page_xbusy(fs.m); 513 if (fs.m->valid != VM_PAGE_BITS_ALL) 514 goto readrest; 515 break; 516 } 517 518 /* 519 * Page is not resident. If this is the search termination 520 * or the pager might contain the page, allocate a new page. 521 * Default objects are zero-fill, there is no real pager. 522 */ 523 if (fs.object->type != OBJT_DEFAULT || 524 fs.object == fs.first_object) { 525 if (fs.pindex >= fs.object->size) { 526 unlock_and_deallocate(&fs); 527 return (KERN_PROTECTION_FAILURE); 528 } 529 530 /* 531 * Allocate a new page for this object/offset pair. 532 * 533 * Unlocked read of the p_flag is harmless. At 534 * worst, the P_KILLED might be not observed 535 * there, and allocation can fail, causing 536 * restart and new reading of the p_flag. 537 */ 538 fs.m = NULL; 539 if (!vm_page_count_severe() || P_KILLED(curproc)) { 540#if VM_NRESERVLEVEL > 0 541 if ((fs.object->flags & OBJ_COLORED) == 0) { 542 fs.object->flags |= OBJ_COLORED; 543 fs.object->pg_color = atop(vaddr) - 544 fs.pindex; 545 } 546#endif 547 alloc_req = P_KILLED(curproc) ? 548 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 549 if (fs.object->type != OBJT_VNODE && 550 fs.object->backing_object == NULL) 551 alloc_req |= VM_ALLOC_ZERO; 552 fs.m = vm_page_alloc(fs.object, fs.pindex, 553 alloc_req); 554 } 555 if (fs.m == NULL) { 556 unlock_and_deallocate(&fs); 557 VM_WAITPFAULT; 558 goto RetryFault; 559 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 560 break; 561 } 562 563readrest: 564 /* 565 * We have found a valid page or we have allocated a new page. 566 * The page thus may not be valid or may not be entirely 567 * valid. 568 * 569 * Attempt to fault-in the page if there is a chance that the 570 * pager has it, and potentially fault in additional pages 571 * at the same time. For default objects simply provide 572 * zero-filled pages. 573 */ 574 if (fs.object->type != OBJT_DEFAULT) { 575 int rv; 576 u_char behavior = vm_map_entry_behavior(fs.entry); 577 578 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 579 P_KILLED(curproc)) { 580 behind = 0; 581 ahead = 0; 582 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 583 behind = 0; 584 ahead = atop(fs.entry->end - vaddr) - 1; 585 if (ahead > VM_FAULT_READ_AHEAD_MAX) 586 ahead = VM_FAULT_READ_AHEAD_MAX; 587 if (fs.pindex == fs.entry->next_read) 588 vm_fault_cache_behind(&fs, 589 VM_FAULT_READ_MAX); 590 } else { 591 /* 592 * If this is a sequential page fault, then 593 * arithmetically increase the number of pages 594 * in the read-ahead window. Otherwise, reset 595 * the read-ahead window to its smallest size. 596 */ 597 behind = atop(vaddr - fs.entry->start); 598 if (behind > VM_FAULT_READ_BEHIND) 599 behind = VM_FAULT_READ_BEHIND; 600 ahead = atop(fs.entry->end - vaddr) - 1; 601 era = fs.entry->read_ahead; 602 if (fs.pindex == fs.entry->next_read) { 603 nera = era + behind; 604 if (nera > VM_FAULT_READ_AHEAD_MAX) 605 nera = VM_FAULT_READ_AHEAD_MAX; 606 behind = 0; 607 if (ahead > nera) 608 ahead = nera; 609 if (era == VM_FAULT_READ_AHEAD_MAX) 610 vm_fault_cache_behind(&fs, 611 VM_FAULT_CACHE_BEHIND); 612 } else if (ahead > VM_FAULT_READ_AHEAD_MIN) 613 ahead = VM_FAULT_READ_AHEAD_MIN; 614 if (era != ahead) 615 fs.entry->read_ahead = ahead; 616 } 617 618 /* 619 * Call the pager to retrieve the data, if any, after 620 * releasing the lock on the map. We hold a ref on 621 * fs.object and the pages are exclusive busied. 622 */ 623 unlock_map(&fs); 624 625 if (fs.object->type == OBJT_VNODE) { 626 vp = fs.object->handle; 627 if (vp == fs.vp) 628 goto vnode_locked; 629 else if (fs.vp != NULL) { 630 vput(fs.vp); 631 fs.vp = NULL; 632 } 633 locked = VOP_ISLOCKED(vp); 634 635 if (locked != LK_EXCLUSIVE) 636 locked = LK_SHARED; 637 /* Do not sleep for vnode lock while fs.m is busy */ 638 error = vget(vp, locked | LK_CANRECURSE | 639 LK_NOWAIT, curthread); 640 if (error != 0) { 641 vhold(vp); 642 release_page(&fs); 643 unlock_and_deallocate(&fs); 644 error = vget(vp, locked | LK_RETRY | 645 LK_CANRECURSE, curthread); 646 vdrop(vp); 647 fs.vp = vp; 648 KASSERT(error == 0, 649 ("vm_fault: vget failed")); 650 goto RetryFault; 651 } 652 fs.vp = vp; 653 } 654vnode_locked: 655 KASSERT(fs.vp == NULL || !fs.map->system_map, 656 ("vm_fault: vnode-backed object mapped by system map")); 657 658 /* 659 * now we find out if any other pages should be paged 660 * in at this time this routine checks to see if the 661 * pages surrounding this fault reside in the same 662 * object as the page for this fault. If they do, 663 * then they are faulted in also into the object. The 664 * array "marray" returned contains an array of 665 * vm_page_t structs where one of them is the 666 * vm_page_t passed to the routine. The reqpage 667 * return value is the index into the marray for the 668 * vm_page_t passed to the routine. 669 * 670 * fs.m plus the additional pages are exclusive busied. 671 */ 672 faultcount = vm_fault_additional_pages( 673 fs.m, behind, ahead, marray, &reqpage); 674 675 rv = faultcount ? 676 vm_pager_get_pages(fs.object, marray, faultcount, 677 reqpage) : VM_PAGER_FAIL; 678 679 if (rv == VM_PAGER_OK) { 680 /* 681 * Found the page. Leave it busy while we play 682 * with it. 683 */ 684 685 /* 686 * Relookup in case pager changed page. Pager 687 * is responsible for disposition of old page 688 * if moved. 689 */ 690 fs.m = vm_page_lookup(fs.object, fs.pindex); 691 if (!fs.m) { 692 unlock_and_deallocate(&fs); 693 goto RetryFault; 694 } 695 696 hardfault++; 697 break; /* break to PAGE HAS BEEN FOUND */ 698 } 699 /* 700 * Remove the bogus page (which does not exist at this 701 * object/offset); before doing so, we must get back 702 * our object lock to preserve our invariant. 703 * 704 * Also wake up any other process that may want to bring 705 * in this page. 706 * 707 * If this is the top-level object, we must leave the 708 * busy page to prevent another process from rushing 709 * past us, and inserting the page in that object at 710 * the same time that we are. 711 */ 712 if (rv == VM_PAGER_ERROR) 713 printf("vm_fault: pager read error, pid %d (%s)\n", 714 curproc->p_pid, curproc->p_comm); 715 /* 716 * Data outside the range of the pager or an I/O error 717 */ 718 /* 719 * XXX - the check for kernel_map is a kludge to work 720 * around having the machine panic on a kernel space 721 * fault w/ I/O error. 722 */ 723 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 724 (rv == VM_PAGER_BAD)) { 725 vm_page_lock(fs.m); 726 vm_page_free(fs.m); 727 vm_page_unlock(fs.m); 728 fs.m = NULL; 729 unlock_and_deallocate(&fs); 730 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 731 } 732 if (fs.object != fs.first_object) { 733 vm_page_lock(fs.m); 734 vm_page_free(fs.m); 735 vm_page_unlock(fs.m); 736 fs.m = NULL; 737 /* 738 * XXX - we cannot just fall out at this 739 * point, m has been freed and is invalid! 740 */ 741 } 742 } 743 744 /* 745 * We get here if the object has default pager (or unwiring) 746 * or the pager doesn't have the page. 747 */ 748 if (fs.object == fs.first_object) 749 fs.first_m = fs.m; 750 751 /* 752 * Move on to the next object. Lock the next object before 753 * unlocking the current one. 754 */ 755 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 756 next_object = fs.object->backing_object; 757 if (next_object == NULL) { 758 /* 759 * If there's no object left, fill the page in the top 760 * object with zeros. 761 */ 762 if (fs.object != fs.first_object) { 763 vm_object_pip_wakeup(fs.object); 764 VM_OBJECT_WUNLOCK(fs.object); 765 766 fs.object = fs.first_object; 767 fs.pindex = fs.first_pindex; 768 fs.m = fs.first_m; 769 VM_OBJECT_WLOCK(fs.object); 770 } 771 fs.first_m = NULL; 772 773 /* 774 * Zero the page if necessary and mark it valid. 775 */ 776 if ((fs.m->flags & PG_ZERO) == 0) { 777 pmap_zero_page(fs.m); 778 } else { 779 PCPU_INC(cnt.v_ozfod); 780 } 781 PCPU_INC(cnt.v_zfod); 782 fs.m->valid = VM_PAGE_BITS_ALL; 783 /* Don't try to prefault neighboring pages. */ 784 faultcount = 1; 785 break; /* break to PAGE HAS BEEN FOUND */ 786 } else { 787 KASSERT(fs.object != next_object, 788 ("object loop %p", next_object)); 789 VM_OBJECT_WLOCK(next_object); 790 vm_object_pip_add(next_object, 1); 791 if (fs.object != fs.first_object) 792 vm_object_pip_wakeup(fs.object); 793 VM_OBJECT_WUNLOCK(fs.object); 794 fs.object = next_object; 795 } 796 } 797 798 vm_page_assert_xbusied(fs.m); 799 800 /* 801 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 802 * is held.] 803 */ 804 805 /* 806 * If the page is being written, but isn't already owned by the 807 * top-level object, we have to copy it into a new page owned by the 808 * top-level object. 809 */ 810 if (fs.object != fs.first_object) { 811 /* 812 * We only really need to copy if we want to write it. 813 */ 814 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 815 /* 816 * This allows pages to be virtually copied from a 817 * backing_object into the first_object, where the 818 * backing object has no other refs to it, and cannot 819 * gain any more refs. Instead of a bcopy, we just 820 * move the page from the backing object to the 821 * first object. Note that we must mark the page 822 * dirty in the first object so that it will go out 823 * to swap when needed. 824 */ 825 is_first_object_locked = FALSE; 826 if ( 827 /* 828 * Only one shadow object 829 */ 830 (fs.object->shadow_count == 1) && 831 /* 832 * No COW refs, except us 833 */ 834 (fs.object->ref_count == 1) && 835 /* 836 * No one else can look this object up 837 */ 838 (fs.object->handle == NULL) && 839 /* 840 * No other ways to look the object up 841 */ 842 ((fs.object->type == OBJT_DEFAULT) || 843 (fs.object->type == OBJT_SWAP)) && 844 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 845 /* 846 * We don't chase down the shadow chain 847 */ 848 fs.object == fs.first_object->backing_object) { 849 /* 850 * get rid of the unnecessary page 851 */ 852 vm_page_lock(fs.first_m); 853 vm_page_free(fs.first_m); 854 vm_page_unlock(fs.first_m); 855 /* 856 * grab the page and put it into the 857 * process'es object. The page is 858 * automatically made dirty. 859 */ 860 if (vm_page_rename(fs.m, fs.first_object, 861 fs.first_pindex)) { 862 unlock_and_deallocate(&fs); 863 goto RetryFault; 864 } 865#if VM_NRESERVLEVEL > 0 866 /* 867 * Rename the reservation. 868 */ 869 vm_reserv_rename(fs.m, fs.first_object, 870 fs.object, OFF_TO_IDX( 871 fs.first_object->backing_object_offset)); 872#endif 873 vm_page_xbusy(fs.m); 874 fs.first_m = fs.m; 875 fs.m = NULL; 876 PCPU_INC(cnt.v_cow_optim); 877 } else { 878 /* 879 * Oh, well, lets copy it. 880 */ 881 pmap_copy_page(fs.m, fs.first_m); 882 fs.first_m->valid = VM_PAGE_BITS_ALL; 883 if (wired && (fault_flags & 884 VM_FAULT_WIRE) == 0) { 885 vm_page_lock(fs.first_m); 886 vm_page_wire(fs.first_m); 887 vm_page_unlock(fs.first_m); 888 889 vm_page_lock(fs.m); 890 vm_page_unwire(fs.m, FALSE); 891 vm_page_unlock(fs.m); 892 } 893 /* 894 * We no longer need the old page or object. 895 */ 896 release_page(&fs); 897 } 898 /* 899 * fs.object != fs.first_object due to above 900 * conditional 901 */ 902 vm_object_pip_wakeup(fs.object); 903 VM_OBJECT_WUNLOCK(fs.object); 904 /* 905 * Only use the new page below... 906 */ 907 fs.object = fs.first_object; 908 fs.pindex = fs.first_pindex; 909 fs.m = fs.first_m; 910 if (!is_first_object_locked) 911 VM_OBJECT_WLOCK(fs.object); 912 PCPU_INC(cnt.v_cow_faults); 913 curthread->td_cow++; 914 } else { 915 prot &= ~VM_PROT_WRITE; 916 } 917 } 918 919 /* 920 * We must verify that the maps have not changed since our last 921 * lookup. 922 */ 923 if (!fs.lookup_still_valid) { 924 vm_object_t retry_object; 925 vm_pindex_t retry_pindex; 926 vm_prot_t retry_prot; 927 928 if (!vm_map_trylock_read(fs.map)) { 929 release_page(&fs); 930 unlock_and_deallocate(&fs); 931 goto RetryFault; 932 } 933 fs.lookup_still_valid = TRUE; 934 if (fs.map->timestamp != map_generation) { 935 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 936 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 937 938 /* 939 * If we don't need the page any longer, put it on the inactive 940 * list (the easiest thing to do here). If no one needs it, 941 * pageout will grab it eventually. 942 */ 943 if (result != KERN_SUCCESS) { 944 release_page(&fs); 945 unlock_and_deallocate(&fs); 946 947 /* 948 * If retry of map lookup would have blocked then 949 * retry fault from start. 950 */ 951 if (result == KERN_FAILURE) 952 goto RetryFault; 953 return (result); 954 } 955 if ((retry_object != fs.first_object) || 956 (retry_pindex != fs.first_pindex)) { 957 release_page(&fs); 958 unlock_and_deallocate(&fs); 959 goto RetryFault; 960 } 961 962 /* 963 * Check whether the protection has changed or the object has 964 * been copied while we left the map unlocked. Changing from 965 * read to write permission is OK - we leave the page 966 * write-protected, and catch the write fault. Changing from 967 * write to read permission means that we can't mark the page 968 * write-enabled after all. 969 */ 970 prot &= retry_prot; 971 } 972 } 973 /* 974 * If the page was filled by a pager, update the map entry's 975 * last read offset. Since the pager does not return the 976 * actual set of pages that it read, this update is based on 977 * the requested set. Typically, the requested and actual 978 * sets are the same. 979 * 980 * XXX The following assignment modifies the map 981 * without holding a write lock on it. 982 */ 983 if (hardfault) 984 fs.entry->next_read = fs.pindex + faultcount - reqpage; 985 986 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); 987 vm_page_assert_xbusied(fs.m); 988 989 /* 990 * Page must be completely valid or it is not fit to 991 * map into user space. vm_pager_get_pages() ensures this. 992 */ 993 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 994 ("vm_fault: page %p partially invalid", fs.m)); 995 VM_OBJECT_WUNLOCK(fs.object); 996 997 /* 998 * Put this page into the physical map. We had to do the unlock above 999 * because pmap_enter() may sleep. We don't put the page 1000 * back on the active queue until later so that the pageout daemon 1001 * won't find it (yet). 1002 */ 1003 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 1004 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 1005 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 1006 wired == 0) 1007 vm_fault_prefault(&fs, vaddr, faultcount, reqpage); 1008 VM_OBJECT_WLOCK(fs.object); 1009 vm_page_lock(fs.m); 1010 1011 /* 1012 * If the page is not wired down, then put it where the pageout daemon 1013 * can find it. 1014 */ 1015 if ((fault_flags & VM_FAULT_WIRE) != 0) { 1016 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 1017 vm_page_wire(fs.m); 1018 } else 1019 vm_page_activate(fs.m); 1020 if (m_hold != NULL) { 1021 *m_hold = fs.m; 1022 vm_page_hold(fs.m); 1023 } 1024 vm_page_unlock(fs.m); 1025 vm_page_xunbusy(fs.m); 1026 1027 /* 1028 * Unlock everything, and return 1029 */ 1030 unlock_and_deallocate(&fs); 1031 if (hardfault) { 1032 PCPU_INC(cnt.v_io_faults); 1033 curthread->td_ru.ru_majflt++; 1034 } else 1035 curthread->td_ru.ru_minflt++; 1036 1037 return (KERN_SUCCESS); 1038} 1039 1040/* 1041 * Speed up the reclamation of up to "distance" pages that precede the 1042 * faulting pindex within the first object of the shadow chain. 1043 */ 1044static void 1045vm_fault_cache_behind(const struct faultstate *fs, int distance) 1046{ 1047 vm_object_t first_object, object; 1048 vm_page_t m, m_prev; 1049 vm_pindex_t pindex; 1050 1051 object = fs->object; 1052 VM_OBJECT_ASSERT_WLOCKED(object); 1053 first_object = fs->first_object; 1054 if (first_object != object) { 1055 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1056 VM_OBJECT_WUNLOCK(object); 1057 VM_OBJECT_WLOCK(first_object); 1058 VM_OBJECT_WLOCK(object); 1059 } 1060 } 1061 /* Neither fictitious nor unmanaged pages can be cached. */ 1062 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1063 if (fs->first_pindex < distance) 1064 pindex = 0; 1065 else 1066 pindex = fs->first_pindex - distance; 1067 if (pindex < OFF_TO_IDX(fs->entry->offset)) 1068 pindex = OFF_TO_IDX(fs->entry->offset); 1069 m = first_object != object ? fs->first_m : fs->m; 1070 vm_page_assert_xbusied(m); 1071 m_prev = vm_page_prev(m); 1072 while ((m = m_prev) != NULL && m->pindex >= pindex && 1073 m->valid == VM_PAGE_BITS_ALL) { 1074 m_prev = vm_page_prev(m); 1075 if (vm_page_busied(m)) 1076 continue; 1077 vm_page_lock(m); 1078 if (m->hold_count == 0 && m->wire_count == 0) { 1079 pmap_remove_all(m); 1080 vm_page_aflag_clear(m, PGA_REFERENCED); 1081 if (m->dirty != 0) 1082 vm_page_deactivate(m); 1083 else 1084 vm_page_cache(m); 1085 } 1086 vm_page_unlock(m); 1087 } 1088 } 1089 if (first_object != object) 1090 VM_OBJECT_WUNLOCK(first_object); 1091} 1092 1093/* 1094 * vm_fault_prefault provides a quick way of clustering 1095 * pagefaults into a processes address space. It is a "cousin" 1096 * of vm_map_pmap_enter, except it runs at page fault time instead 1097 * of mmap time. 1098 */ 1099static void 1100vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1101 int faultcount, int reqpage) 1102{ 1103 pmap_t pmap; 1104 vm_map_entry_t entry; 1105 vm_object_t backing_object, lobject; 1106 vm_offset_t addr, starta; 1107 vm_pindex_t pindex; 1108 vm_page_t m; 1109 int backward, forward, i; 1110 1111 pmap = fs->map->pmap; 1112 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1113 return; 1114 1115 if (faultcount > 0) { 1116 backward = reqpage; 1117 forward = faultcount - reqpage - 1; 1118 } else { 1119 backward = PFBAK; 1120 forward = PFFOR; 1121 } 1122 entry = fs->entry; 1123 1124 starta = addra - backward * PAGE_SIZE; 1125 if (starta < entry->start) { 1126 starta = entry->start; 1127 } else if (starta > addra) { 1128 starta = 0; 1129 } 1130 1131 /* 1132 * Generate the sequence of virtual addresses that are candidates for 1133 * prefaulting in an outward spiral from the faulting virtual address, 1134 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1135 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1136 * If the candidate address doesn't have a backing physical page, then 1137 * the loop immediately terminates. 1138 */ 1139 for (i = 0; i < 2 * imax(backward, forward); i++) { 1140 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1141 PAGE_SIZE); 1142 if (addr > addra + forward * PAGE_SIZE) 1143 addr = 0; 1144 1145 if (addr < starta || addr >= entry->end) 1146 continue; 1147 1148 if (!pmap_is_prefaultable(pmap, addr)) 1149 continue; 1150 1151 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1152 lobject = entry->object.vm_object; 1153 VM_OBJECT_RLOCK(lobject); 1154 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1155 lobject->type == OBJT_DEFAULT && 1156 (backing_object = lobject->backing_object) != NULL) { 1157 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1158 0, ("vm_fault_prefault: unaligned object offset")); 1159 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1160 VM_OBJECT_RLOCK(backing_object); 1161 VM_OBJECT_RUNLOCK(lobject); 1162 lobject = backing_object; 1163 } 1164 if (m == NULL) { 1165 VM_OBJECT_RUNLOCK(lobject); 1166 break; 1167 } 1168 if (m->valid == VM_PAGE_BITS_ALL && 1169 (m->flags & PG_FICTITIOUS) == 0) 1170 pmap_enter_quick(pmap, addr, m, entry->protection); 1171 VM_OBJECT_RUNLOCK(lobject); 1172 } 1173} 1174 1175/* 1176 * Hold each of the physical pages that are mapped by the specified range of 1177 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1178 * and allow the specified types of access, "prot". If all of the implied 1179 * pages are successfully held, then the number of held pages is returned 1180 * together with pointers to those pages in the array "ma". However, if any 1181 * of the pages cannot be held, -1 is returned. 1182 */ 1183int 1184vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1185 vm_prot_t prot, vm_page_t *ma, int max_count) 1186{ 1187 vm_offset_t end, va; 1188 vm_page_t *mp; 1189 int count; 1190 boolean_t pmap_failed; 1191 1192 if (len == 0) 1193 return (0); 1194 end = round_page(addr + len); 1195 addr = trunc_page(addr); 1196 1197 /* 1198 * Check for illegal addresses. 1199 */ 1200 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1201 return (-1); 1202 1203 if (atop(end - addr) > max_count) 1204 panic("vm_fault_quick_hold_pages: count > max_count"); 1205 count = atop(end - addr); 1206 1207 /* 1208 * Most likely, the physical pages are resident in the pmap, so it is 1209 * faster to try pmap_extract_and_hold() first. 1210 */ 1211 pmap_failed = FALSE; 1212 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1213 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1214 if (*mp == NULL) 1215 pmap_failed = TRUE; 1216 else if ((prot & VM_PROT_WRITE) != 0 && 1217 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1218 /* 1219 * Explicitly dirty the physical page. Otherwise, the 1220 * caller's changes may go unnoticed because they are 1221 * performed through an unmanaged mapping or by a DMA 1222 * operation. 1223 * 1224 * The object lock is not held here. 1225 * See vm_page_clear_dirty_mask(). 1226 */ 1227 vm_page_dirty(*mp); 1228 } 1229 } 1230 if (pmap_failed) { 1231 /* 1232 * One or more pages could not be held by the pmap. Either no 1233 * page was mapped at the specified virtual address or that 1234 * mapping had insufficient permissions. Attempt to fault in 1235 * and hold these pages. 1236 */ 1237 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1238 if (*mp == NULL && vm_fault_hold(map, va, prot, 1239 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1240 goto error; 1241 } 1242 return (count); 1243error: 1244 for (mp = ma; mp < ma + count; mp++) 1245 if (*mp != NULL) { 1246 vm_page_lock(*mp); 1247 vm_page_unhold(*mp); 1248 vm_page_unlock(*mp); 1249 } 1250 return (-1); 1251} 1252 1253/* 1254 * Routine: 1255 * vm_fault_copy_entry 1256 * Function: 1257 * Create new shadow object backing dst_entry with private copy of 1258 * all underlying pages. When src_entry is equal to dst_entry, 1259 * function implements COW for wired-down map entry. Otherwise, 1260 * it forks wired entry into dst_map. 1261 * 1262 * In/out conditions: 1263 * The source and destination maps must be locked for write. 1264 * The source map entry must be wired down (or be a sharing map 1265 * entry corresponding to a main map entry that is wired down). 1266 */ 1267void 1268vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1269 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1270 vm_ooffset_t *fork_charge) 1271{ 1272 vm_object_t backing_object, dst_object, object, src_object; 1273 vm_pindex_t dst_pindex, pindex, src_pindex; 1274 vm_prot_t access, prot; 1275 vm_offset_t vaddr; 1276 vm_page_t dst_m; 1277 vm_page_t src_m; 1278 boolean_t upgrade; 1279 1280#ifdef lint 1281 src_map++; 1282#endif /* lint */ 1283 1284 upgrade = src_entry == dst_entry; 1285 access = prot = dst_entry->protection; 1286 1287 src_object = src_entry->object.vm_object; 1288 src_pindex = OFF_TO_IDX(src_entry->offset); 1289 1290 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1291 dst_object = src_object; 1292 vm_object_reference(dst_object); 1293 } else { 1294 /* 1295 * Create the top-level object for the destination entry. (Doesn't 1296 * actually shadow anything - we copy the pages directly.) 1297 */ 1298 dst_object = vm_object_allocate(OBJT_DEFAULT, 1299 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1300#if VM_NRESERVLEVEL > 0 1301 dst_object->flags |= OBJ_COLORED; 1302 dst_object->pg_color = atop(dst_entry->start); 1303#endif 1304 } 1305 1306 VM_OBJECT_WLOCK(dst_object); 1307 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1308 ("vm_fault_copy_entry: vm_object not NULL")); 1309 if (src_object != dst_object) { 1310 dst_entry->object.vm_object = dst_object; 1311 dst_entry->offset = 0; 1312 dst_object->charge = dst_entry->end - dst_entry->start; 1313 } 1314 if (fork_charge != NULL) { 1315 KASSERT(dst_entry->cred == NULL, 1316 ("vm_fault_copy_entry: leaked swp charge")); 1317 dst_object->cred = curthread->td_ucred; 1318 crhold(dst_object->cred); 1319 *fork_charge += dst_object->charge; 1320 } else if (dst_object->cred == NULL) { 1321 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1322 dst_entry)); 1323 dst_object->cred = dst_entry->cred; 1324 dst_entry->cred = NULL; 1325 } 1326 1327 /* 1328 * If not an upgrade, then enter the mappings in the pmap as 1329 * read and/or execute accesses. Otherwise, enter them as 1330 * write accesses. 1331 * 1332 * A writeable large page mapping is only created if all of 1333 * the constituent small page mappings are modified. Marking 1334 * PTEs as modified on inception allows promotion to happen 1335 * without taking potentially large number of soft faults. 1336 */ 1337 if (!upgrade) 1338 access &= ~VM_PROT_WRITE; 1339 1340 /* 1341 * Loop through all of the virtual pages within the entry's 1342 * range, copying each page from the source object to the 1343 * destination object. Since the source is wired, those pages 1344 * must exist. In contrast, the destination is pageable. 1345 * Since the destination object does share any backing storage 1346 * with the source object, all of its pages must be dirtied, 1347 * regardless of whether they can be written. 1348 */ 1349 for (vaddr = dst_entry->start, dst_pindex = 0; 1350 vaddr < dst_entry->end; 1351 vaddr += PAGE_SIZE, dst_pindex++) { 1352again: 1353 /* 1354 * Find the page in the source object, and copy it in. 1355 * Because the source is wired down, the page will be 1356 * in memory. 1357 */ 1358 if (src_object != dst_object) 1359 VM_OBJECT_RLOCK(src_object); 1360 object = src_object; 1361 pindex = src_pindex + dst_pindex; 1362 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1363 (backing_object = object->backing_object) != NULL) { 1364 /* 1365 * Unless the source mapping is read-only or 1366 * it is presently being upgraded from 1367 * read-only, the first object in the shadow 1368 * chain should provide all of the pages. In 1369 * other words, this loop body should never be 1370 * executed when the source mapping is already 1371 * read/write. 1372 */ 1373 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1374 upgrade, 1375 ("vm_fault_copy_entry: main object missing page")); 1376 1377 VM_OBJECT_RLOCK(backing_object); 1378 pindex += OFF_TO_IDX(object->backing_object_offset); 1379 if (object != dst_object) 1380 VM_OBJECT_RUNLOCK(object); 1381 object = backing_object; 1382 } 1383 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1384 1385 if (object != dst_object) { 1386 /* 1387 * Allocate a page in the destination object. 1388 */ 1389 dst_m = vm_page_alloc(dst_object, (src_object == 1390 dst_object ? src_pindex : 0) + dst_pindex, 1391 VM_ALLOC_NORMAL); 1392 if (dst_m == NULL) { 1393 VM_OBJECT_WUNLOCK(dst_object); 1394 VM_OBJECT_RUNLOCK(object); 1395 VM_WAIT; 1396 VM_OBJECT_WLOCK(dst_object); 1397 goto again; 1398 } 1399 pmap_copy_page(src_m, dst_m); 1400 VM_OBJECT_RUNLOCK(object); 1401 dst_m->valid = VM_PAGE_BITS_ALL; 1402 dst_m->dirty = VM_PAGE_BITS_ALL; 1403 } else { 1404 dst_m = src_m; 1405 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1406 goto again; 1407 vm_page_xbusy(dst_m); 1408 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1409 ("invalid dst page %p", dst_m)); 1410 } 1411 VM_OBJECT_WUNLOCK(dst_object); 1412 1413 /* 1414 * Enter it in the pmap. If a wired, copy-on-write 1415 * mapping is being replaced by a write-enabled 1416 * mapping, then wire that new mapping. 1417 */ 1418 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1419 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1420 1421 /* 1422 * Mark it no longer busy, and put it on the active list. 1423 */ 1424 VM_OBJECT_WLOCK(dst_object); 1425 1426 if (upgrade) { 1427 if (src_m != dst_m) { 1428 vm_page_lock(src_m); 1429 vm_page_unwire(src_m, 0); 1430 vm_page_unlock(src_m); 1431 vm_page_lock(dst_m); 1432 vm_page_wire(dst_m); 1433 vm_page_unlock(dst_m); 1434 } else { 1435 KASSERT(dst_m->wire_count > 0, 1436 ("dst_m %p is not wired", dst_m)); 1437 } 1438 } else { 1439 vm_page_lock(dst_m); 1440 vm_page_activate(dst_m); 1441 vm_page_unlock(dst_m); 1442 } 1443 vm_page_xunbusy(dst_m); 1444 } 1445 VM_OBJECT_WUNLOCK(dst_object); 1446 if (upgrade) { 1447 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1448 vm_object_deallocate(src_object); 1449 } 1450} 1451 1452 1453/* 1454 * This routine checks around the requested page for other pages that 1455 * might be able to be faulted in. This routine brackets the viable 1456 * pages for the pages to be paged in. 1457 * 1458 * Inputs: 1459 * m, rbehind, rahead 1460 * 1461 * Outputs: 1462 * marray (array of vm_page_t), reqpage (index of requested page) 1463 * 1464 * Return value: 1465 * number of pages in marray 1466 */ 1467static int 1468vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1469 vm_page_t m; 1470 int rbehind; 1471 int rahead; 1472 vm_page_t *marray; 1473 int *reqpage; 1474{ 1475 int i,j; 1476 vm_object_t object; 1477 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1478 vm_page_t rtm; 1479 int cbehind, cahead; 1480 1481 VM_OBJECT_ASSERT_WLOCKED(m->object); 1482 1483 object = m->object; 1484 pindex = m->pindex; 1485 cbehind = cahead = 0; 1486 1487 /* 1488 * if the requested page is not available, then give up now 1489 */ 1490 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1491 return 0; 1492 } 1493 1494 if ((cbehind == 0) && (cahead == 0)) { 1495 *reqpage = 0; 1496 marray[0] = m; 1497 return 1; 1498 } 1499 1500 if (rahead > cahead) { 1501 rahead = cahead; 1502 } 1503 1504 if (rbehind > cbehind) { 1505 rbehind = cbehind; 1506 } 1507 1508 /* 1509 * scan backward for the read behind pages -- in memory 1510 */ 1511 if (pindex > 0) { 1512 if (rbehind > pindex) { 1513 rbehind = pindex; 1514 startpindex = 0; 1515 } else { 1516 startpindex = pindex - rbehind; 1517 } 1518 1519 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1520 rtm->pindex >= startpindex) 1521 startpindex = rtm->pindex + 1; 1522 1523 /* tpindex is unsigned; beware of numeric underflow. */ 1524 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1525 tpindex < pindex; i++, tpindex--) { 1526 1527 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1528 VM_ALLOC_IFNOTCACHED); 1529 if (rtm == NULL) { 1530 /* 1531 * Shift the allocated pages to the 1532 * beginning of the array. 1533 */ 1534 for (j = 0; j < i; j++) { 1535 marray[j] = marray[j + tpindex + 1 - 1536 startpindex]; 1537 } 1538 break; 1539 } 1540 1541 marray[tpindex - startpindex] = rtm; 1542 } 1543 } else { 1544 startpindex = 0; 1545 i = 0; 1546 } 1547 1548 marray[i] = m; 1549 /* page offset of the required page */ 1550 *reqpage = i; 1551 1552 tpindex = pindex + 1; 1553 i++; 1554 1555 /* 1556 * scan forward for the read ahead pages 1557 */ 1558 endpindex = tpindex + rahead; 1559 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1560 endpindex = rtm->pindex; 1561 if (endpindex > object->size) 1562 endpindex = object->size; 1563 1564 for (; tpindex < endpindex; i++, tpindex++) { 1565 1566 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1567 VM_ALLOC_IFNOTCACHED); 1568 if (rtm == NULL) { 1569 break; 1570 } 1571 1572 marray[i] = rtm; 1573 } 1574 1575 /* return number of pages */ 1576 return i; 1577} 1578 1579/* 1580 * Block entry into the machine-independent layer's page fault handler by 1581 * the calling thread. Subsequent calls to vm_fault() by that thread will 1582 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1583 * spurious page faults. 1584 */ 1585int 1586vm_fault_disable_pagefaults(void) 1587{ 1588 1589 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1590} 1591 1592void 1593vm_fault_enable_pagefaults(int save) 1594{ 1595 1596 curthread_pflags_restore(save); 1597} 1598