vm_fault.c revision 308332
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 308332 2016-11-05 10:22:51Z kib $"); 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_vp(struct faultstate *fs) 157{ 158 159 if (fs->vp != NULL) { 160 vput(fs->vp); 161 fs->vp = NULL; 162 } 163} 164 165static void 166unlock_and_deallocate(struct faultstate *fs) 167{ 168 169 vm_object_pip_wakeup(fs->object); 170 VM_OBJECT_WUNLOCK(fs->object); 171 if (fs->object != fs->first_object) { 172 VM_OBJECT_WLOCK(fs->first_object); 173 vm_page_lock(fs->first_m); 174 vm_page_free(fs->first_m); 175 vm_page_unlock(fs->first_m); 176 vm_object_pip_wakeup(fs->first_object); 177 VM_OBJECT_WUNLOCK(fs->first_object); 178 fs->first_m = NULL; 179 } 180 vm_object_deallocate(fs->first_object); 181 unlock_map(fs); 182 unlock_vp(fs); 183} 184 185static void 186vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot, 187 vm_prot_t fault_type, int fault_flags, boolean_t set_wd) 188{ 189 boolean_t need_dirty; 190 191 if (((prot & VM_PROT_WRITE) == 0 && 192 (fault_flags & VM_FAULT_DIRTY) == 0) || 193 (m->oflags & VPO_UNMANAGED) != 0) 194 return; 195 196 VM_OBJECT_ASSERT_LOCKED(m->object); 197 198 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 && 199 (fault_flags & VM_FAULT_WIRE) == 0) || 200 (fault_flags & VM_FAULT_DIRTY) != 0; 201 202 if (set_wd) 203 vm_object_set_writeable_dirty(m->object); 204 else 205 /* 206 * If two callers of vm_fault_dirty() with set_wd == 207 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC 208 * flag set, other with flag clear, race, it is 209 * possible for the no-NOSYNC thread to see m->dirty 210 * != 0 and not clear VPO_NOSYNC. Take vm_page lock 211 * around manipulation of VPO_NOSYNC and 212 * vm_page_dirty() call, to avoid the race and keep 213 * m->oflags consistent. 214 */ 215 vm_page_lock(m); 216 217 /* 218 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 219 * if the page is already dirty to prevent data written with 220 * the expectation of being synced from not being synced. 221 * Likewise if this entry does not request NOSYNC then make 222 * sure the page isn't marked NOSYNC. Applications sharing 223 * data should use the same flags to avoid ping ponging. 224 */ 225 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) { 226 if (m->dirty == 0) { 227 m->oflags |= VPO_NOSYNC; 228 } 229 } else { 230 m->oflags &= ~VPO_NOSYNC; 231 } 232 233 /* 234 * If the fault is a write, we know that this page is being 235 * written NOW so dirty it explicitly to save on 236 * pmap_is_modified() calls later. 237 * 238 * Also tell the backing pager, if any, that it should remove 239 * any swap backing since the page is now dirty. 240 */ 241 if (need_dirty) 242 vm_page_dirty(m); 243 if (!set_wd) 244 vm_page_unlock(m); 245 if (need_dirty) 246 vm_pager_page_unswapped(m); 247} 248 249/* 250 * vm_fault: 251 * 252 * Handle a page fault occurring at the given address, 253 * requiring the given permissions, in the map specified. 254 * If successful, the page is inserted into the 255 * associated physical map. 256 * 257 * NOTE: the given address should be truncated to the 258 * proper page address. 259 * 260 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 261 * a standard error specifying why the fault is fatal is returned. 262 * 263 * The map in question must be referenced, and remains so. 264 * Caller may hold no locks. 265 */ 266int 267vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 268 int fault_flags) 269{ 270 struct thread *td; 271 int result; 272 273 td = curthread; 274 if ((td->td_pflags & TDP_NOFAULTING) != 0) 275 return (KERN_PROTECTION_FAILURE); 276#ifdef KTRACE 277 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 278 ktrfault(vaddr, fault_type); 279#endif 280 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 281 NULL); 282#ifdef KTRACE 283 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 284 ktrfaultend(result); 285#endif 286 return (result); 287} 288 289int 290vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 291 int fault_flags, vm_page_t *m_hold) 292{ 293 vm_prot_t prot; 294 long ahead, behind; 295 int alloc_req, era, faultcount, nera, reqpage, result; 296 boolean_t dead, growstack, is_first_object_locked, wired; 297 int map_generation; 298 vm_object_t next_object; 299 vm_page_t marray[VM_FAULT_READ_MAX]; 300 int hardfault; 301 struct faultstate fs; 302 struct vnode *vp; 303 vm_page_t m; 304 int locked, error; 305 306 hardfault = 0; 307 growstack = TRUE; 308 PCPU_INC(cnt.v_vm_faults); 309 fs.vp = NULL; 310 faultcount = reqpage = 0; 311 312RetryFault:; 313 314 /* 315 * Find the backing store object and offset into it to begin the 316 * search. 317 */ 318 fs.map = map; 319 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 320 &fs.first_object, &fs.first_pindex, &prot, &wired); 321 if (result != KERN_SUCCESS) { 322 if (growstack && result == KERN_INVALID_ADDRESS && 323 map != kernel_map) { 324 result = vm_map_growstack(curproc, vaddr); 325 if (result != KERN_SUCCESS) 326 return (KERN_FAILURE); 327 growstack = FALSE; 328 goto RetryFault; 329 } 330 unlock_vp(&fs); 331 return (result); 332 } 333 334 map_generation = fs.map->timestamp; 335 336 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 337 panic("vm_fault: fault on nofault entry, addr: %lx", 338 (u_long)vaddr); 339 } 340 341 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 342 fs.entry->wiring_thread != curthread) { 343 vm_map_unlock_read(fs.map); 344 vm_map_lock(fs.map); 345 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 346 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 347 unlock_vp(&fs); 348 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 349 vm_map_unlock_and_wait(fs.map, 0); 350 } else 351 vm_map_unlock(fs.map); 352 goto RetryFault; 353 } 354 355 if (wired) 356 fault_type = prot | (fault_type & VM_PROT_COPY); 357 else 358 KASSERT((fault_flags & VM_FAULT_WIRE) == 0, 359 ("!wired && VM_FAULT_WIRE")); 360 361 /* 362 * Try to avoid lock contention on the top-level object through 363 * special-case handling of some types of page faults, specifically, 364 * those that are both (1) mapping an existing page from the top- 365 * level object and (2) not having to mark that object as containing 366 * dirty pages. Under these conditions, a read lock on the top-level 367 * object suffices, allowing multiple page faults of a similar type to 368 * run in parallel on the same top-level object. 369 */ 370 if (fs.vp == NULL /* avoid locked vnode leak */ && 371 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 && 372 /* avoid calling vm_object_set_writeable_dirty() */ 373 ((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 VM_OBJECT_RLOCK(fs.first_object); 378 if ((prot & VM_PROT_WRITE) != 0 && 379 (fs.first_object->type == OBJT_VNODE || 380 (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) && 381 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0) 382 goto fast_failed; 383 m = vm_page_lookup(fs.first_object, fs.first_pindex); 384 /* A busy page can be mapped for read|execute access. */ 385 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 386 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 387 goto fast_failed; 388 result = pmap_enter(fs.map->pmap, vaddr, m, prot, 389 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 390 0), 0); 391 if (result != KERN_SUCCESS) 392 goto fast_failed; 393 if (m_hold != NULL) { 394 *m_hold = m; 395 vm_page_lock(m); 396 vm_page_hold(m); 397 vm_page_unlock(m); 398 } 399 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, 400 FALSE); 401 VM_OBJECT_RUNLOCK(fs.first_object); 402 if (!wired) 403 vm_fault_prefault(&fs, vaddr, 0, 0); 404 vm_map_lookup_done(fs.map, fs.entry); 405 curthread->td_ru.ru_minflt++; 406 return (KERN_SUCCESS); 407fast_failed: 408 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 409 VM_OBJECT_RUNLOCK(fs.first_object); 410 VM_OBJECT_WLOCK(fs.first_object); 411 } 412 } else { 413 VM_OBJECT_WLOCK(fs.first_object); 414 } 415 416 /* 417 * Make a reference to this object to prevent its disposal while we 418 * are messing with it. Once we have the reference, the map is free 419 * to be diddled. Since objects reference their shadows (and copies), 420 * they will stay around as well. 421 * 422 * Bump the paging-in-progress count to prevent size changes (e.g. 423 * truncation operations) during I/O. This must be done after 424 * obtaining the vnode lock in order to avoid possible deadlocks. 425 */ 426 vm_object_reference_locked(fs.first_object); 427 vm_object_pip_add(fs.first_object, 1); 428 429 fs.lookup_still_valid = TRUE; 430 431 fs.first_m = NULL; 432 433 /* 434 * Search for the page at object/offset. 435 */ 436 fs.object = fs.first_object; 437 fs.pindex = fs.first_pindex; 438 while (TRUE) { 439 /* 440 * If the object is marked for imminent termination, 441 * we retry here, since the collapse pass has raced 442 * with us. Otherwise, if we see terminally dead 443 * object, return fail. 444 */ 445 if ((fs.object->flags & OBJ_DEAD) != 0) { 446 dead = fs.object->type == OBJT_DEAD; 447 unlock_and_deallocate(&fs); 448 if (dead) 449 return (KERN_PROTECTION_FAILURE); 450 pause("vmf_de", 1); 451 goto RetryFault; 452 } 453 454 /* 455 * See if page is resident 456 */ 457 fs.m = vm_page_lookup(fs.object, fs.pindex); 458 if (fs.m != NULL) { 459 /* 460 * Wait/Retry if the page is busy. We have to do this 461 * if the page is either exclusive or shared busy 462 * because the vm_pager may be using read busy for 463 * pageouts (and even pageins if it is the vnode 464 * pager), and we could end up trying to pagein and 465 * pageout the same page simultaneously. 466 * 467 * We can theoretically allow the busy case on a read 468 * fault if the page is marked valid, but since such 469 * pages are typically already pmap'd, putting that 470 * special case in might be more effort then it is 471 * worth. We cannot under any circumstances mess 472 * around with a shared busied page except, perhaps, 473 * to pmap it. 474 */ 475 if (vm_page_busied(fs.m)) { 476 /* 477 * Reference the page before unlocking and 478 * sleeping so that the page daemon is less 479 * likely to reclaim it. 480 */ 481 vm_page_aflag_set(fs.m, PGA_REFERENCED); 482 if (fs.object != fs.first_object) { 483 if (!VM_OBJECT_TRYWLOCK( 484 fs.first_object)) { 485 VM_OBJECT_WUNLOCK(fs.object); 486 VM_OBJECT_WLOCK(fs.first_object); 487 VM_OBJECT_WLOCK(fs.object); 488 } 489 vm_page_lock(fs.first_m); 490 vm_page_free(fs.first_m); 491 vm_page_unlock(fs.first_m); 492 vm_object_pip_wakeup(fs.first_object); 493 VM_OBJECT_WUNLOCK(fs.first_object); 494 fs.first_m = NULL; 495 } 496 unlock_map(&fs); 497 if (fs.m == vm_page_lookup(fs.object, 498 fs.pindex)) { 499 vm_page_sleep_if_busy(fs.m, "vmpfw"); 500 } 501 vm_object_pip_wakeup(fs.object); 502 VM_OBJECT_WUNLOCK(fs.object); 503 PCPU_INC(cnt.v_intrans); 504 vm_object_deallocate(fs.first_object); 505 goto RetryFault; 506 } 507 vm_page_lock(fs.m); 508 vm_page_remque(fs.m); 509 vm_page_unlock(fs.m); 510 511 /* 512 * Mark page busy for other processes, and the 513 * pagedaemon. If it still isn't completely valid 514 * (readable), jump to readrest, else break-out ( we 515 * found the page ). 516 */ 517 vm_page_xbusy(fs.m); 518 if (fs.m->valid != VM_PAGE_BITS_ALL) 519 goto readrest; 520 break; 521 } 522 523 /* 524 * Page is not resident. If this is the search termination 525 * or the pager might contain the page, allocate a new page. 526 * Default objects are zero-fill, there is no real pager. 527 */ 528 if (fs.object->type != OBJT_DEFAULT || 529 fs.object == fs.first_object) { 530 if (fs.pindex >= fs.object->size) { 531 unlock_and_deallocate(&fs); 532 return (KERN_PROTECTION_FAILURE); 533 } 534 535 /* 536 * Allocate a new page for this object/offset pair. 537 * 538 * Unlocked read of the p_flag is harmless. At 539 * worst, the P_KILLED might be not observed 540 * there, and allocation can fail, causing 541 * restart and new reading of the p_flag. 542 */ 543 fs.m = NULL; 544 if (!vm_page_count_severe() || P_KILLED(curproc)) { 545#if VM_NRESERVLEVEL > 0 546 if ((fs.object->flags & OBJ_COLORED) == 0) { 547 fs.object->flags |= OBJ_COLORED; 548 fs.object->pg_color = atop(vaddr) - 549 fs.pindex; 550 } 551#endif 552 alloc_req = P_KILLED(curproc) ? 553 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 554 if (fs.object->type != OBJT_VNODE && 555 fs.object->backing_object == NULL) 556 alloc_req |= VM_ALLOC_ZERO; 557 fs.m = vm_page_alloc(fs.object, fs.pindex, 558 alloc_req); 559 } 560 if (fs.m == NULL) { 561 unlock_and_deallocate(&fs); 562 VM_WAITPFAULT; 563 goto RetryFault; 564 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 565 break; 566 } 567 568readrest: 569 /* 570 * We have found a valid page or we have allocated a new page. 571 * The page thus may not be valid or may not be entirely 572 * valid. 573 * 574 * Attempt to fault-in the page if there is a chance that the 575 * pager has it, and potentially fault in additional pages 576 * at the same time. For default objects simply provide 577 * zero-filled pages. 578 */ 579 if (fs.object->type != OBJT_DEFAULT) { 580 int rv; 581 u_char behavior = vm_map_entry_behavior(fs.entry); 582 583 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 584 P_KILLED(curproc)) { 585 behind = 0; 586 ahead = 0; 587 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 588 behind = 0; 589 ahead = atop(fs.entry->end - vaddr) - 1; 590 if (ahead > VM_FAULT_READ_AHEAD_MAX) 591 ahead = VM_FAULT_READ_AHEAD_MAX; 592 if (fs.pindex == fs.entry->next_read) 593 vm_fault_cache_behind(&fs, 594 VM_FAULT_READ_MAX); 595 } else { 596 /* 597 * If this is a sequential page fault, then 598 * arithmetically increase the number of pages 599 * in the read-ahead window. Otherwise, reset 600 * the read-ahead window to its smallest size. 601 */ 602 behind = atop(vaddr - fs.entry->start); 603 if (behind > VM_FAULT_READ_BEHIND) 604 behind = VM_FAULT_READ_BEHIND; 605 ahead = atop(fs.entry->end - vaddr) - 1; 606 era = fs.entry->read_ahead; 607 if (fs.pindex == fs.entry->next_read) { 608 nera = era + behind; 609 if (nera > VM_FAULT_READ_AHEAD_MAX) 610 nera = VM_FAULT_READ_AHEAD_MAX; 611 behind = 0; 612 if (ahead > nera) 613 ahead = nera; 614 if (era == VM_FAULT_READ_AHEAD_MAX) 615 vm_fault_cache_behind(&fs, 616 VM_FAULT_CACHE_BEHIND); 617 } else if (ahead > VM_FAULT_READ_AHEAD_MIN) 618 ahead = VM_FAULT_READ_AHEAD_MIN; 619 if (era != ahead) 620 fs.entry->read_ahead = ahead; 621 } 622 623 /* 624 * Call the pager to retrieve the data, if any, after 625 * releasing the lock on the map. We hold a ref on 626 * fs.object and the pages are exclusive busied. 627 */ 628 unlock_map(&fs); 629 630 if (fs.object->type == OBJT_VNODE) { 631 vp = fs.object->handle; 632 if (vp == fs.vp) 633 goto vnode_locked; 634 unlock_vp(&fs); 635 locked = VOP_ISLOCKED(vp); 636 637 if (locked != LK_EXCLUSIVE) 638 locked = LK_SHARED; 639 /* Do not sleep for vnode lock while fs.m is busy */ 640 error = vget(vp, locked | LK_CANRECURSE | 641 LK_NOWAIT, curthread); 642 if (error != 0) { 643 vhold(vp); 644 release_page(&fs); 645 unlock_and_deallocate(&fs); 646 error = vget(vp, locked | LK_RETRY | 647 LK_CANRECURSE, curthread); 648 vdrop(vp); 649 fs.vp = vp; 650 KASSERT(error == 0, 651 ("vm_fault: vget failed")); 652 goto RetryFault; 653 } 654 fs.vp = vp; 655 } 656vnode_locked: 657 KASSERT(fs.vp == NULL || !fs.map->system_map, 658 ("vm_fault: vnode-backed object mapped by system map")); 659 660 /* 661 * now we find out if any other pages should be paged 662 * in at this time this routine checks to see if the 663 * pages surrounding this fault reside in the same 664 * object as the page for this fault. If they do, 665 * then they are faulted in also into the object. The 666 * array "marray" returned contains an array of 667 * vm_page_t structs where one of them is the 668 * vm_page_t passed to the routine. The reqpage 669 * return value is the index into the marray for the 670 * vm_page_t passed to the routine. 671 * 672 * fs.m plus the additional pages are exclusive busied. 673 */ 674 faultcount = vm_fault_additional_pages( 675 fs.m, behind, ahead, marray, &reqpage); 676 677 rv = faultcount ? 678 vm_pager_get_pages(fs.object, marray, faultcount, 679 reqpage) : VM_PAGER_FAIL; 680 681 if (rv == VM_PAGER_OK) { 682 /* 683 * Found the page. Leave it busy while we play 684 * with it. 685 */ 686 687 /* 688 * Relookup in case pager changed page. Pager 689 * is responsible for disposition of old page 690 * if moved. 691 */ 692 fs.m = vm_page_lookup(fs.object, fs.pindex); 693 if (!fs.m) { 694 unlock_and_deallocate(&fs); 695 goto RetryFault; 696 } 697 698 hardfault++; 699 break; /* break to PAGE HAS BEEN FOUND */ 700 } 701 /* 702 * Remove the bogus page (which does not exist at this 703 * object/offset); before doing so, we must get back 704 * our object lock to preserve our invariant. 705 * 706 * Also wake up any other process that may want to bring 707 * in this page. 708 * 709 * If this is the top-level object, we must leave the 710 * busy page to prevent another process from rushing 711 * past us, and inserting the page in that object at 712 * the same time that we are. 713 */ 714 if (rv == VM_PAGER_ERROR) 715 printf("vm_fault: pager read error, pid %d (%s)\n", 716 curproc->p_pid, curproc->p_comm); 717 /* 718 * Data outside the range of the pager or an I/O error 719 */ 720 /* 721 * XXX - the check for kernel_map is a kludge to work 722 * around having the machine panic on a kernel space 723 * fault w/ I/O error. 724 */ 725 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 726 (rv == VM_PAGER_BAD)) { 727 vm_page_lock(fs.m); 728 vm_page_free(fs.m); 729 vm_page_unlock(fs.m); 730 fs.m = NULL; 731 unlock_and_deallocate(&fs); 732 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 733 } 734 if (fs.object != fs.first_object) { 735 vm_page_lock(fs.m); 736 vm_page_free(fs.m); 737 vm_page_unlock(fs.m); 738 fs.m = NULL; 739 /* 740 * XXX - we cannot just fall out at this 741 * point, m has been freed and is invalid! 742 */ 743 } 744 } 745 746 /* 747 * We get here if the object has default pager (or unwiring) 748 * or the pager doesn't have the page. 749 */ 750 if (fs.object == fs.first_object) 751 fs.first_m = fs.m; 752 753 /* 754 * Move on to the next object. Lock the next object before 755 * unlocking the current one. 756 */ 757 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 758 next_object = fs.object->backing_object; 759 if (next_object == NULL) { 760 /* 761 * If there's no object left, fill the page in the top 762 * object with zeros. 763 */ 764 if (fs.object != fs.first_object) { 765 vm_object_pip_wakeup(fs.object); 766 VM_OBJECT_WUNLOCK(fs.object); 767 768 fs.object = fs.first_object; 769 fs.pindex = fs.first_pindex; 770 fs.m = fs.first_m; 771 VM_OBJECT_WLOCK(fs.object); 772 } 773 fs.first_m = NULL; 774 775 /* 776 * Zero the page if necessary and mark it valid. 777 */ 778 if ((fs.m->flags & PG_ZERO) == 0) { 779 pmap_zero_page(fs.m); 780 } else { 781 PCPU_INC(cnt.v_ozfod); 782 } 783 PCPU_INC(cnt.v_zfod); 784 fs.m->valid = VM_PAGE_BITS_ALL; 785 /* Don't try to prefault neighboring pages. */ 786 faultcount = 1; 787 break; /* break to PAGE HAS BEEN FOUND */ 788 } else { 789 KASSERT(fs.object != next_object, 790 ("object loop %p", next_object)); 791 VM_OBJECT_WLOCK(next_object); 792 vm_object_pip_add(next_object, 1); 793 if (fs.object != fs.first_object) 794 vm_object_pip_wakeup(fs.object); 795 VM_OBJECT_WUNLOCK(fs.object); 796 fs.object = next_object; 797 } 798 } 799 800 vm_page_assert_xbusied(fs.m); 801 802 /* 803 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 804 * is held.] 805 */ 806 807 /* 808 * If the page is being written, but isn't already owned by the 809 * top-level object, we have to copy it into a new page owned by the 810 * top-level object. 811 */ 812 if (fs.object != fs.first_object) { 813 /* 814 * We only really need to copy if we want to write it. 815 */ 816 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 817 /* 818 * This allows pages to be virtually copied from a 819 * backing_object into the first_object, where the 820 * backing object has no other refs to it, and cannot 821 * gain any more refs. Instead of a bcopy, we just 822 * move the page from the backing object to the 823 * first object. Note that we must mark the page 824 * dirty in the first object so that it will go out 825 * to swap when needed. 826 */ 827 is_first_object_locked = FALSE; 828 if ( 829 /* 830 * Only one shadow object 831 */ 832 (fs.object->shadow_count == 1) && 833 /* 834 * No COW refs, except us 835 */ 836 (fs.object->ref_count == 1) && 837 /* 838 * No one else can look this object up 839 */ 840 (fs.object->handle == NULL) && 841 /* 842 * No other ways to look the object up 843 */ 844 ((fs.object->type == OBJT_DEFAULT) || 845 (fs.object->type == OBJT_SWAP)) && 846 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 847 /* 848 * We don't chase down the shadow chain 849 */ 850 fs.object == fs.first_object->backing_object) { 851 /* 852 * get rid of the unnecessary page 853 */ 854 vm_page_lock(fs.first_m); 855 vm_page_free(fs.first_m); 856 vm_page_unlock(fs.first_m); 857 /* 858 * grab the page and put it into the 859 * process'es object. The page is 860 * automatically made dirty. 861 */ 862 if (vm_page_rename(fs.m, fs.first_object, 863 fs.first_pindex)) { 864 unlock_and_deallocate(&fs); 865 goto RetryFault; 866 } 867#if VM_NRESERVLEVEL > 0 868 /* 869 * Rename the reservation. 870 */ 871 vm_reserv_rename(fs.m, fs.first_object, 872 fs.object, OFF_TO_IDX( 873 fs.first_object->backing_object_offset)); 874#endif 875 vm_page_xbusy(fs.m); 876 fs.first_m = fs.m; 877 fs.m = NULL; 878 PCPU_INC(cnt.v_cow_optim); 879 } else { 880 /* 881 * Oh, well, lets copy it. 882 */ 883 pmap_copy_page(fs.m, fs.first_m); 884 fs.first_m->valid = VM_PAGE_BITS_ALL; 885 if (wired && (fault_flags & 886 VM_FAULT_WIRE) == 0) { 887 vm_page_lock(fs.first_m); 888 vm_page_wire(fs.first_m); 889 vm_page_unlock(fs.first_m); 890 891 vm_page_lock(fs.m); 892 vm_page_unwire(fs.m, FALSE); 893 vm_page_unlock(fs.m); 894 } 895 /* 896 * We no longer need the old page or object. 897 */ 898 release_page(&fs); 899 } 900 /* 901 * fs.object != fs.first_object due to above 902 * conditional 903 */ 904 vm_object_pip_wakeup(fs.object); 905 VM_OBJECT_WUNLOCK(fs.object); 906 /* 907 * Only use the new page below... 908 */ 909 fs.object = fs.first_object; 910 fs.pindex = fs.first_pindex; 911 fs.m = fs.first_m; 912 if (!is_first_object_locked) 913 VM_OBJECT_WLOCK(fs.object); 914 PCPU_INC(cnt.v_cow_faults); 915 curthread->td_cow++; 916 } else { 917 prot &= ~VM_PROT_WRITE; 918 } 919 } 920 921 /* 922 * We must verify that the maps have not changed since our last 923 * lookup. 924 */ 925 if (!fs.lookup_still_valid) { 926 vm_object_t retry_object; 927 vm_pindex_t retry_pindex; 928 vm_prot_t retry_prot; 929 930 if (!vm_map_trylock_read(fs.map)) { 931 release_page(&fs); 932 unlock_and_deallocate(&fs); 933 goto RetryFault; 934 } 935 fs.lookup_still_valid = TRUE; 936 if (fs.map->timestamp != map_generation) { 937 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 938 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 939 940 /* 941 * If we don't need the page any longer, put it on the inactive 942 * list (the easiest thing to do here). If no one needs it, 943 * pageout will grab it eventually. 944 */ 945 if (result != KERN_SUCCESS) { 946 release_page(&fs); 947 unlock_and_deallocate(&fs); 948 949 /* 950 * If retry of map lookup would have blocked then 951 * retry fault from start. 952 */ 953 if (result == KERN_FAILURE) 954 goto RetryFault; 955 return (result); 956 } 957 if ((retry_object != fs.first_object) || 958 (retry_pindex != fs.first_pindex)) { 959 release_page(&fs); 960 unlock_and_deallocate(&fs); 961 goto RetryFault; 962 } 963 964 /* 965 * Check whether the protection has changed or the object has 966 * been copied while we left the map unlocked. Changing from 967 * read to write permission is OK - we leave the page 968 * write-protected, and catch the write fault. Changing from 969 * write to read permission means that we can't mark the page 970 * write-enabled after all. 971 */ 972 prot &= retry_prot; 973 } 974 } 975 /* 976 * If the page was filled by a pager, update the map entry's 977 * last read offset. Since the pager does not return the 978 * actual set of pages that it read, this update is based on 979 * the requested set. Typically, the requested and actual 980 * sets are the same. 981 * 982 * XXX The following assignment modifies the map 983 * without holding a write lock on it. 984 */ 985 if (hardfault) 986 fs.entry->next_read = fs.pindex + faultcount - reqpage; 987 988 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); 989 vm_page_assert_xbusied(fs.m); 990 991 /* 992 * Page must be completely valid or it is not fit to 993 * map into user space. vm_pager_get_pages() ensures this. 994 */ 995 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 996 ("vm_fault: page %p partially invalid", fs.m)); 997 VM_OBJECT_WUNLOCK(fs.object); 998 999 /* 1000 * Put this page into the physical map. We had to do the unlock above 1001 * because pmap_enter() may sleep. We don't put the page 1002 * back on the active queue until later so that the pageout daemon 1003 * won't find it (yet). 1004 */ 1005 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 1006 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 1007 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 1008 wired == 0) 1009 vm_fault_prefault(&fs, vaddr, faultcount, reqpage); 1010 VM_OBJECT_WLOCK(fs.object); 1011 vm_page_lock(fs.m); 1012 1013 /* 1014 * If the page is not wired down, then put it where the pageout daemon 1015 * can find it. 1016 */ 1017 if ((fault_flags & VM_FAULT_WIRE) != 0) { 1018 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 1019 vm_page_wire(fs.m); 1020 } else 1021 vm_page_activate(fs.m); 1022 if (m_hold != NULL) { 1023 *m_hold = fs.m; 1024 vm_page_hold(fs.m); 1025 } 1026 vm_page_unlock(fs.m); 1027 vm_page_xunbusy(fs.m); 1028 1029 /* 1030 * Unlock everything, and return 1031 */ 1032 unlock_and_deallocate(&fs); 1033 if (hardfault) { 1034 PCPU_INC(cnt.v_io_faults); 1035 curthread->td_ru.ru_majflt++; 1036 } else 1037 curthread->td_ru.ru_minflt++; 1038 1039 return (KERN_SUCCESS); 1040} 1041 1042/* 1043 * Speed up the reclamation of up to "distance" pages that precede the 1044 * faulting pindex within the first object of the shadow chain. 1045 */ 1046static void 1047vm_fault_cache_behind(const struct faultstate *fs, int distance) 1048{ 1049 vm_object_t first_object, object; 1050 vm_page_t m, m_prev; 1051 vm_pindex_t pindex; 1052 1053 object = fs->object; 1054 VM_OBJECT_ASSERT_WLOCKED(object); 1055 first_object = fs->first_object; 1056 if (first_object != object) { 1057 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1058 VM_OBJECT_WUNLOCK(object); 1059 VM_OBJECT_WLOCK(first_object); 1060 VM_OBJECT_WLOCK(object); 1061 } 1062 } 1063 /* Neither fictitious nor unmanaged pages can be cached. */ 1064 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1065 if (fs->first_pindex < distance) 1066 pindex = 0; 1067 else 1068 pindex = fs->first_pindex - distance; 1069 if (pindex < OFF_TO_IDX(fs->entry->offset)) 1070 pindex = OFF_TO_IDX(fs->entry->offset); 1071 m = first_object != object ? fs->first_m : fs->m; 1072 vm_page_assert_xbusied(m); 1073 m_prev = vm_page_prev(m); 1074 while ((m = m_prev) != NULL && m->pindex >= pindex && 1075 m->valid == VM_PAGE_BITS_ALL) { 1076 m_prev = vm_page_prev(m); 1077 if (vm_page_busied(m)) 1078 continue; 1079 vm_page_lock(m); 1080 if (m->hold_count == 0 && m->wire_count == 0) { 1081 pmap_remove_all(m); 1082 vm_page_aflag_clear(m, PGA_REFERENCED); 1083 if (m->dirty != 0) 1084 vm_page_deactivate(m); 1085 else 1086 vm_page_cache(m); 1087 } 1088 vm_page_unlock(m); 1089 } 1090 } 1091 if (first_object != object) 1092 VM_OBJECT_WUNLOCK(first_object); 1093} 1094 1095/* 1096 * vm_fault_prefault provides a quick way of clustering 1097 * pagefaults into a processes address space. It is a "cousin" 1098 * of vm_map_pmap_enter, except it runs at page fault time instead 1099 * of mmap time. 1100 */ 1101static void 1102vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1103 int faultcount, int reqpage) 1104{ 1105 pmap_t pmap; 1106 vm_map_entry_t entry; 1107 vm_object_t backing_object, lobject; 1108 vm_offset_t addr, starta; 1109 vm_pindex_t pindex; 1110 vm_page_t m; 1111 int backward, forward, i; 1112 1113 pmap = fs->map->pmap; 1114 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1115 return; 1116 1117 if (faultcount > 0) { 1118 backward = reqpage; 1119 forward = faultcount - reqpage - 1; 1120 } else { 1121 backward = PFBAK; 1122 forward = PFFOR; 1123 } 1124 entry = fs->entry; 1125 1126 starta = addra - backward * PAGE_SIZE; 1127 if (starta < entry->start) { 1128 starta = entry->start; 1129 } else if (starta > addra) { 1130 starta = 0; 1131 } 1132 1133 /* 1134 * Generate the sequence of virtual addresses that are candidates for 1135 * prefaulting in an outward spiral from the faulting virtual address, 1136 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1137 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1138 * If the candidate address doesn't have a backing physical page, then 1139 * the loop immediately terminates. 1140 */ 1141 for (i = 0; i < 2 * imax(backward, forward); i++) { 1142 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1143 PAGE_SIZE); 1144 if (addr > addra + forward * PAGE_SIZE) 1145 addr = 0; 1146 1147 if (addr < starta || addr >= entry->end) 1148 continue; 1149 1150 if (!pmap_is_prefaultable(pmap, addr)) 1151 continue; 1152 1153 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1154 lobject = entry->object.vm_object; 1155 VM_OBJECT_RLOCK(lobject); 1156 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1157 lobject->type == OBJT_DEFAULT && 1158 (backing_object = lobject->backing_object) != NULL) { 1159 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1160 0, ("vm_fault_prefault: unaligned object offset")); 1161 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1162 VM_OBJECT_RLOCK(backing_object); 1163 VM_OBJECT_RUNLOCK(lobject); 1164 lobject = backing_object; 1165 } 1166 if (m == NULL) { 1167 VM_OBJECT_RUNLOCK(lobject); 1168 break; 1169 } 1170 if (m->valid == VM_PAGE_BITS_ALL && 1171 (m->flags & PG_FICTITIOUS) == 0) 1172 pmap_enter_quick(pmap, addr, m, entry->protection); 1173 VM_OBJECT_RUNLOCK(lobject); 1174 } 1175} 1176 1177/* 1178 * Hold each of the physical pages that are mapped by the specified range of 1179 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1180 * and allow the specified types of access, "prot". If all of the implied 1181 * pages are successfully held, then the number of held pages is returned 1182 * together with pointers to those pages in the array "ma". However, if any 1183 * of the pages cannot be held, -1 is returned. 1184 */ 1185int 1186vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1187 vm_prot_t prot, vm_page_t *ma, int max_count) 1188{ 1189 vm_offset_t end, va; 1190 vm_page_t *mp; 1191 int count; 1192 boolean_t pmap_failed; 1193 1194 if (len == 0) 1195 return (0); 1196 end = round_page(addr + len); 1197 addr = trunc_page(addr); 1198 1199 /* 1200 * Check for illegal addresses. 1201 */ 1202 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1203 return (-1); 1204 1205 if (atop(end - addr) > max_count) 1206 panic("vm_fault_quick_hold_pages: count > max_count"); 1207 count = atop(end - addr); 1208 1209 /* 1210 * Most likely, the physical pages are resident in the pmap, so it is 1211 * faster to try pmap_extract_and_hold() first. 1212 */ 1213 pmap_failed = FALSE; 1214 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1215 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1216 if (*mp == NULL) 1217 pmap_failed = TRUE; 1218 else if ((prot & VM_PROT_WRITE) != 0 && 1219 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1220 /* 1221 * Explicitly dirty the physical page. Otherwise, the 1222 * caller's changes may go unnoticed because they are 1223 * performed through an unmanaged mapping or by a DMA 1224 * operation. 1225 * 1226 * The object lock is not held here. 1227 * See vm_page_clear_dirty_mask(). 1228 */ 1229 vm_page_dirty(*mp); 1230 } 1231 } 1232 if (pmap_failed) { 1233 /* 1234 * One or more pages could not be held by the pmap. Either no 1235 * page was mapped at the specified virtual address or that 1236 * mapping had insufficient permissions. Attempt to fault in 1237 * and hold these pages. 1238 */ 1239 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1240 if (*mp == NULL && vm_fault_hold(map, va, prot, 1241 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1242 goto error; 1243 } 1244 return (count); 1245error: 1246 for (mp = ma; mp < ma + count; mp++) 1247 if (*mp != NULL) { 1248 vm_page_lock(*mp); 1249 vm_page_unhold(*mp); 1250 vm_page_unlock(*mp); 1251 } 1252 return (-1); 1253} 1254 1255/* 1256 * Routine: 1257 * vm_fault_copy_entry 1258 * Function: 1259 * Create new shadow object backing dst_entry with private copy of 1260 * all underlying pages. When src_entry is equal to dst_entry, 1261 * function implements COW for wired-down map entry. Otherwise, 1262 * it forks wired entry into dst_map. 1263 * 1264 * In/out conditions: 1265 * The source and destination maps must be locked for write. 1266 * The source map entry must be wired down (or be a sharing map 1267 * entry corresponding to a main map entry that is wired down). 1268 */ 1269void 1270vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1271 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1272 vm_ooffset_t *fork_charge) 1273{ 1274 vm_object_t backing_object, dst_object, object, src_object; 1275 vm_pindex_t dst_pindex, pindex, src_pindex; 1276 vm_prot_t access, prot; 1277 vm_offset_t vaddr; 1278 vm_page_t dst_m; 1279 vm_page_t src_m; 1280 boolean_t upgrade; 1281 1282#ifdef lint 1283 src_map++; 1284#endif /* lint */ 1285 1286 upgrade = src_entry == dst_entry; 1287 access = prot = dst_entry->protection; 1288 1289 src_object = src_entry->object.vm_object; 1290 src_pindex = OFF_TO_IDX(src_entry->offset); 1291 1292 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1293 dst_object = src_object; 1294 vm_object_reference(dst_object); 1295 } else { 1296 /* 1297 * Create the top-level object for the destination entry. (Doesn't 1298 * actually shadow anything - we copy the pages directly.) 1299 */ 1300 dst_object = vm_object_allocate(OBJT_DEFAULT, 1301 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1302#if VM_NRESERVLEVEL > 0 1303 dst_object->flags |= OBJ_COLORED; 1304 dst_object->pg_color = atop(dst_entry->start); 1305#endif 1306 } 1307 1308 VM_OBJECT_WLOCK(dst_object); 1309 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1310 ("vm_fault_copy_entry: vm_object not NULL")); 1311 if (src_object != dst_object) { 1312 dst_entry->object.vm_object = dst_object; 1313 dst_entry->offset = 0; 1314 dst_object->charge = dst_entry->end - dst_entry->start; 1315 } 1316 if (fork_charge != NULL) { 1317 KASSERT(dst_entry->cred == NULL, 1318 ("vm_fault_copy_entry: leaked swp charge")); 1319 dst_object->cred = curthread->td_ucred; 1320 crhold(dst_object->cred); 1321 *fork_charge += dst_object->charge; 1322 } else if (dst_object->cred == NULL) { 1323 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1324 dst_entry)); 1325 dst_object->cred = dst_entry->cred; 1326 dst_entry->cred = NULL; 1327 } 1328 1329 /* 1330 * If not an upgrade, then enter the mappings in the pmap as 1331 * read and/or execute accesses. Otherwise, enter them as 1332 * write accesses. 1333 * 1334 * A writeable large page mapping is only created if all of 1335 * the constituent small page mappings are modified. Marking 1336 * PTEs as modified on inception allows promotion to happen 1337 * without taking potentially large number of soft faults. 1338 */ 1339 if (!upgrade) 1340 access &= ~VM_PROT_WRITE; 1341 1342 /* 1343 * Loop through all of the virtual pages within the entry's 1344 * range, copying each page from the source object to the 1345 * destination object. Since the source is wired, those pages 1346 * must exist. In contrast, the destination is pageable. 1347 * Since the destination object does share any backing storage 1348 * with the source object, all of its pages must be dirtied, 1349 * regardless of whether they can be written. 1350 */ 1351 for (vaddr = dst_entry->start, dst_pindex = 0; 1352 vaddr < dst_entry->end; 1353 vaddr += PAGE_SIZE, dst_pindex++) { 1354again: 1355 /* 1356 * Find the page in the source object, and copy it in. 1357 * Because the source is wired down, the page will be 1358 * in memory. 1359 */ 1360 if (src_object != dst_object) 1361 VM_OBJECT_RLOCK(src_object); 1362 object = src_object; 1363 pindex = src_pindex + dst_pindex; 1364 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1365 (backing_object = object->backing_object) != NULL) { 1366 /* 1367 * Unless the source mapping is read-only or 1368 * it is presently being upgraded from 1369 * read-only, the first object in the shadow 1370 * chain should provide all of the pages. In 1371 * other words, this loop body should never be 1372 * executed when the source mapping is already 1373 * read/write. 1374 */ 1375 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1376 upgrade, 1377 ("vm_fault_copy_entry: main object missing page")); 1378 1379 VM_OBJECT_RLOCK(backing_object); 1380 pindex += OFF_TO_IDX(object->backing_object_offset); 1381 if (object != dst_object) 1382 VM_OBJECT_RUNLOCK(object); 1383 object = backing_object; 1384 } 1385 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1386 1387 if (object != dst_object) { 1388 /* 1389 * Allocate a page in the destination object. 1390 */ 1391 dst_m = vm_page_alloc(dst_object, (src_object == 1392 dst_object ? src_pindex : 0) + dst_pindex, 1393 VM_ALLOC_NORMAL); 1394 if (dst_m == NULL) { 1395 VM_OBJECT_WUNLOCK(dst_object); 1396 VM_OBJECT_RUNLOCK(object); 1397 VM_WAIT; 1398 VM_OBJECT_WLOCK(dst_object); 1399 goto again; 1400 } 1401 pmap_copy_page(src_m, dst_m); 1402 VM_OBJECT_RUNLOCK(object); 1403 dst_m->valid = VM_PAGE_BITS_ALL; 1404 dst_m->dirty = VM_PAGE_BITS_ALL; 1405 } else { 1406 dst_m = src_m; 1407 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1408 goto again; 1409 vm_page_xbusy(dst_m); 1410 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1411 ("invalid dst page %p", dst_m)); 1412 } 1413 VM_OBJECT_WUNLOCK(dst_object); 1414 1415 /* 1416 * Enter it in the pmap. If a wired, copy-on-write 1417 * mapping is being replaced by a write-enabled 1418 * mapping, then wire that new mapping. 1419 */ 1420 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1421 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1422 1423 /* 1424 * Mark it no longer busy, and put it on the active list. 1425 */ 1426 VM_OBJECT_WLOCK(dst_object); 1427 1428 if (upgrade) { 1429 if (src_m != dst_m) { 1430 vm_page_lock(src_m); 1431 vm_page_unwire(src_m, 0); 1432 vm_page_unlock(src_m); 1433 vm_page_lock(dst_m); 1434 vm_page_wire(dst_m); 1435 vm_page_unlock(dst_m); 1436 } else { 1437 KASSERT(dst_m->wire_count > 0, 1438 ("dst_m %p is not wired", dst_m)); 1439 } 1440 } else { 1441 vm_page_lock(dst_m); 1442 vm_page_activate(dst_m); 1443 vm_page_unlock(dst_m); 1444 } 1445 vm_page_xunbusy(dst_m); 1446 } 1447 VM_OBJECT_WUNLOCK(dst_object); 1448 if (upgrade) { 1449 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1450 vm_object_deallocate(src_object); 1451 } 1452} 1453 1454 1455/* 1456 * This routine checks around the requested page for other pages that 1457 * might be able to be faulted in. This routine brackets the viable 1458 * pages for the pages to be paged in. 1459 * 1460 * Inputs: 1461 * m, rbehind, rahead 1462 * 1463 * Outputs: 1464 * marray (array of vm_page_t), reqpage (index of requested page) 1465 * 1466 * Return value: 1467 * number of pages in marray 1468 */ 1469static int 1470vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1471 vm_page_t m; 1472 int rbehind; 1473 int rahead; 1474 vm_page_t *marray; 1475 int *reqpage; 1476{ 1477 int i,j; 1478 vm_object_t object; 1479 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1480 vm_page_t rtm; 1481 int cbehind, cahead; 1482 1483 VM_OBJECT_ASSERT_WLOCKED(m->object); 1484 1485 object = m->object; 1486 pindex = m->pindex; 1487 cbehind = cahead = 0; 1488 1489 /* 1490 * if the requested page is not available, then give up now 1491 */ 1492 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1493 return 0; 1494 } 1495 1496 if ((cbehind == 0) && (cahead == 0)) { 1497 *reqpage = 0; 1498 marray[0] = m; 1499 return 1; 1500 } 1501 1502 if (rahead > cahead) { 1503 rahead = cahead; 1504 } 1505 1506 if (rbehind > cbehind) { 1507 rbehind = cbehind; 1508 } 1509 1510 /* 1511 * scan backward for the read behind pages -- in memory 1512 */ 1513 if (pindex > 0) { 1514 if (rbehind > pindex) { 1515 rbehind = pindex; 1516 startpindex = 0; 1517 } else { 1518 startpindex = pindex - rbehind; 1519 } 1520 1521 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1522 rtm->pindex >= startpindex) 1523 startpindex = rtm->pindex + 1; 1524 1525 /* tpindex is unsigned; beware of numeric underflow. */ 1526 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1527 tpindex < pindex; i++, tpindex--) { 1528 1529 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1530 VM_ALLOC_IFNOTCACHED); 1531 if (rtm == NULL) { 1532 /* 1533 * Shift the allocated pages to the 1534 * beginning of the array. 1535 */ 1536 for (j = 0; j < i; j++) { 1537 marray[j] = marray[j + tpindex + 1 - 1538 startpindex]; 1539 } 1540 break; 1541 } 1542 1543 marray[tpindex - startpindex] = rtm; 1544 } 1545 } else { 1546 startpindex = 0; 1547 i = 0; 1548 } 1549 1550 marray[i] = m; 1551 /* page offset of the required page */ 1552 *reqpage = i; 1553 1554 tpindex = pindex + 1; 1555 i++; 1556 1557 /* 1558 * scan forward for the read ahead pages 1559 */ 1560 endpindex = tpindex + rahead; 1561 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1562 endpindex = rtm->pindex; 1563 if (endpindex > object->size) 1564 endpindex = object->size; 1565 1566 for (; tpindex < endpindex; i++, tpindex++) { 1567 1568 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1569 VM_ALLOC_IFNOTCACHED); 1570 if (rtm == NULL) { 1571 break; 1572 } 1573 1574 marray[i] = rtm; 1575 } 1576 1577 /* return number of pages */ 1578 return i; 1579} 1580 1581/* 1582 * Block entry into the machine-independent layer's page fault handler by 1583 * the calling thread. Subsequent calls to vm_fault() by that thread will 1584 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1585 * spurious page faults. 1586 */ 1587int 1588vm_fault_disable_pagefaults(void) 1589{ 1590 1591 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1592} 1593 1594void 1595vm_fault_enable_pagefaults(int save) 1596{ 1597 1598 curthread_pflags_restore(save); 1599} 1600