Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]
FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_fault.c
Version:
- FREEBSD - FREEBSD-13-STABLE - FREEBSD-13-0 - FREEBSD-12-STABLE - FREEBSD-12-0 - FREEBSD-11-STABLE - FREEBSD-11-0 - FREEBSD-10-STABLE - FREEBSD-10-0 - FREEBSD-9-STABLE - FREEBSD-9-0 - FREEBSD-8-STABLE - FREEBSD-8-0 - FREEBSD-7-STABLE - FREEBSD-7-0 - FREEBSD-6-STABLE - FREEBSD-6-0 - FREEBSD-5-STABLE - FREEBSD-5-0 - FREEBSD-4-STABLE - FREEBSD-3-STABLE - FREEBSD22 - l41 - OPENBSD - linux-2.6 - MK84 - PLAN9 - xnu-8792
SearchContext: - none - 3 - 10
SearchContext: - none - 3 - 10
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: releng/10.3/sys/vm/vm_fault.c 307929 2016-10-25 16:45:55Z glebius $"); 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 4 108 109 static 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) 116 117 struct faultstate { 118 vm_page_t m; 119 vm_object_t object; 120 vm_pindex_t pindex; 121 vm_page_t first_m; 122 vm_object_t first_object; 123 vm_pindex_t first_pindex; 124 vm_map_t map; 125 vm_map_entry_t entry; 126 int lookup_still_valid; 127 struct vnode *vp; 128 }; 129 130 static void vm_fault_cache_behind(const struct faultstate *fs, int distance); 131 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 132 int faultcount, int reqpage); 133 134 static inline void 135 release_page(struct faultstate *fs) 136 { 137 138 vm_page_xunbusy(fs->m); 139 vm_page_lock(fs->m); 140 vm_page_deactivate(fs->m); 141 vm_page_unlock(fs->m); 142 fs->m = NULL; 143 } 144 145 static inline void 146 unlock_map(struct faultstate *fs) 147 { 148 149 if (fs->lookup_still_valid) { 150 vm_map_lookup_done(fs->map, fs->entry); 151 fs->lookup_still_valid = FALSE; 152 } 153 } 154 155 static void 156 unlock_and_deallocate(struct faultstate *fs) 157 { 158 159 vm_object_pip_wakeup(fs->object); 160 VM_OBJECT_WUNLOCK(fs->object); 161 if (fs->object != fs->first_object) { 162 VM_OBJECT_WLOCK(fs->first_object); 163 vm_page_lock(fs->first_m); 164 vm_page_free(fs->first_m); 165 vm_page_unlock(fs->first_m); 166 vm_object_pip_wakeup(fs->first_object); 167 VM_OBJECT_WUNLOCK(fs->first_object); 168 fs->first_m = NULL; 169 } 170 vm_object_deallocate(fs->first_object); 171 unlock_map(fs); 172 if (fs->vp != NULL) { 173 vput(fs->vp); 174 fs->vp = NULL; 175 } 176 } 177 178 static void 179 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot, 180 vm_prot_t fault_type, int fault_flags, boolean_t set_wd) 181 { 182 boolean_t need_dirty; 183 184 if (((prot & VM_PROT_WRITE) == 0 && 185 (fault_flags & VM_FAULT_DIRTY) == 0) || 186 (m->oflags & VPO_UNMANAGED) != 0) 187 return; 188 189 VM_OBJECT_ASSERT_LOCKED(m->object); 190 191 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 && 192 (fault_flags & VM_FAULT_WIRE) == 0) || 193 (fault_flags & VM_FAULT_DIRTY) != 0; 194 195 if (set_wd) 196 vm_object_set_writeable_dirty(m->object); 197 else 198 /* 199 * If two callers of vm_fault_dirty() with set_wd == 200 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC 201 * flag set, other with flag clear, race, it is 202 * possible for the no-NOSYNC thread to see m->dirty 203 * != 0 and not clear VPO_NOSYNC. Take vm_page lock 204 * around manipulation of VPO_NOSYNC and 205 * vm_page_dirty() call, to avoid the race and keep 206 * m->oflags consistent. 207 */ 208 vm_page_lock(m); 209 210 /* 211 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 212 * if the page is already dirty to prevent data written with 213 * the expectation of being synced from not being synced. 214 * Likewise if this entry does not request NOSYNC then make 215 * sure the page isn't marked NOSYNC. Applications sharing 216 * data should use the same flags to avoid ping ponging. 217 */ 218 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) { 219 if (m->dirty == 0) { 220 m->oflags |= VPO_NOSYNC; 221 } 222 } else { 223 m->oflags &= ~VPO_NOSYNC; 224 } 225 226 /* 227 * If the fault is a write, we know that this page is being 228 * written NOW so dirty it explicitly to save on 229 * pmap_is_modified() calls later. 230 * 231 * Also tell the backing pager, if any, that it should remove 232 * any swap backing since the page is now dirty. 233 */ 234 if (need_dirty) 235 vm_page_dirty(m); 236 if (!set_wd) 237 vm_page_unlock(m); 238 if (need_dirty) 239 vm_pager_page_unswapped(m); 240 } 241 242 /* 243 * vm_fault: 244 * 245 * Handle a page fault occurring at the given address, 246 * requiring the given permissions, in the map specified. 247 * If successful, the page is inserted into the 248 * associated physical map. 249 * 250 * NOTE: the given address should be truncated to the 251 * proper page address. 252 * 253 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 254 * a standard error specifying why the fault is fatal is returned. 255 * 256 * The map in question must be referenced, and remains so. 257 * Caller may hold no locks. 258 */ 259 int 260 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 261 int fault_flags) 262 { 263 struct thread *td; 264 int result; 265 266 td = curthread; 267 if ((td->td_pflags & TDP_NOFAULTING) != 0) 268 return (KERN_PROTECTION_FAILURE); 269 #ifdef KTRACE 270 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 271 ktrfault(vaddr, fault_type); 272 #endif 273 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 274 NULL); 275 #ifdef KTRACE 276 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 277 ktrfaultend(result); 278 #endif 279 return (result); 280 } 281 282 int 283 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 284 int fault_flags, vm_page_t *m_hold) 285 { 286 vm_prot_t prot; 287 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; 304 305 RetryFault:; 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 if (fs.vp == NULL /* avoid locked vnode leak */ && 357 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 && 358 /* avoid calling vm_object_set_writeable_dirty() */ 359 ((prot & VM_PROT_WRITE) == 0 || 360 (fs.first_object->type != OBJT_VNODE && 361 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 362 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 363 VM_OBJECT_RLOCK(fs.first_object); 364 if ((prot & VM_PROT_WRITE) != 0 && 365 (fs.first_object->type == OBJT_VNODE || 366 (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) && 367 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0) 368 goto fast_failed; 369 m = vm_page_lookup(fs.first_object, fs.first_pindex); 370 /* A busy page can be mapped for read|execute access. */ 371 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 372 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 373 goto fast_failed; 374 result = pmap_enter(fs.map->pmap, vaddr, m, prot, 375 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 376 0), 0); 377 if (result != KERN_SUCCESS) 378 goto fast_failed; 379 if (m_hold != NULL) { 380 *m_hold = m; 381 vm_page_lock(m); 382 vm_page_hold(m); 383 vm_page_unlock(m); 384 } 385 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, 386 FALSE); 387 VM_OBJECT_RUNLOCK(fs.first_object); 388 if (!wired) 389 vm_fault_prefault(&fs, vaddr, 0, 0); 390 vm_map_lookup_done(fs.map, fs.entry); 391 curthread->td_ru.ru_minflt++; 392 return (KERN_SUCCESS); 393 fast_failed: 394 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 395 VM_OBJECT_RUNLOCK(fs.first_object); 396 VM_OBJECT_WLOCK(fs.first_object); 397 } 398 } else { 399 VM_OBJECT_WLOCK(fs.first_object); 400 } 401 402 /* 403 * Make a reference to this object to prevent its disposal while we 404 * are messing with it. Once we have the reference, the map is free 405 * to be diddled. Since objects reference their shadows (and copies), 406 * they will stay around as well. 407 * 408 * Bump the paging-in-progress count to prevent size changes (e.g. 409 * truncation operations) during I/O. This must be done after 410 * obtaining the vnode lock in order to avoid possible deadlocks. 411 */ 412 vm_object_reference_locked(fs.first_object); 413 vm_object_pip_add(fs.first_object, 1); 414 415 fs.lookup_still_valid = TRUE; 416 417 fs.first_m = NULL; 418 419 /* 420 * Search for the page at object/offset. 421 */ 422 fs.object = fs.first_object; 423 fs.pindex = fs.first_pindex; 424 while (TRUE) { 425 /* 426 * If the object is marked for imminent termination, 427 * we retry here, since the collapse pass has raced 428 * with us. Otherwise, if we see terminally dead 429 * object, return fail. 430 */ 431 if ((fs.object->flags & OBJ_DEAD) != 0) { 432 dead = fs.object->type == OBJT_DEAD; 433 unlock_and_deallocate(&fs); 434 if (dead) 435 return (KERN_PROTECTION_FAILURE); 436 pause("vmf_de", 1); 437 goto RetryFault; 438 } 439 440 /* 441 * See if page is resident 442 */ 443 fs.m = vm_page_lookup(fs.object, fs.pindex); 444 if (fs.m != NULL) { 445 /* 446 * Wait/Retry if the page is busy. We have to do this 447 * if the page is either exclusive or shared busy 448 * because the vm_pager may be using read busy for 449 * pageouts (and even pageins if it is the vnode 450 * pager), and we could end up trying to pagein and 451 * pageout the same page simultaneously. 452 * 453 * We can theoretically allow the busy case on a read 454 * fault if the page is marked valid, but since such 455 * pages are typically already pmap'd, putting that 456 * special case in might be more effort then it is 457 * worth. We cannot under any circumstances mess 458 * around with a shared busied page except, perhaps, 459 * to pmap it. 460 */ 461 if (vm_page_busied(fs.m)) { 462 /* 463 * Reference the page before unlocking and 464 * sleeping so that the page daemon is less 465 * likely to reclaim it. 466 */ 467 vm_page_aflag_set(fs.m, PGA_REFERENCED); 468 if (fs.object != fs.first_object) { 469 if (!VM_OBJECT_TRYWLOCK( 470 fs.first_object)) { 471 VM_OBJECT_WUNLOCK(fs.object); 472 VM_OBJECT_WLOCK(fs.first_object); 473 VM_OBJECT_WLOCK(fs.object); 474 } 475 vm_page_lock(fs.first_m); 476 vm_page_free(fs.first_m); 477 vm_page_unlock(fs.first_m); 478 vm_object_pip_wakeup(fs.first_object); 479 VM_OBJECT_WUNLOCK(fs.first_object); 480 fs.first_m = NULL; 481 } 482 unlock_map(&fs); 483 if (fs.m == vm_page_lookup(fs.object, 484 fs.pindex)) { 485 vm_page_sleep_if_busy(fs.m, "vmpfw"); 486 } 487 vm_object_pip_wakeup(fs.object); 488 VM_OBJECT_WUNLOCK(fs.object); 489 PCPU_INC(cnt.v_intrans); 490 vm_object_deallocate(fs.first_object); 491 goto RetryFault; 492 } 493 vm_page_lock(fs.m); 494 vm_page_remque(fs.m); 495 vm_page_unlock(fs.m); 496 497 /* 498 * Mark page busy for other processes, and the 499 * pagedaemon. If it still isn't completely valid 500 * (readable), jump to readrest, else break-out ( we 501 * found the page ). 502 */ 503 vm_page_xbusy(fs.m); 504 if (fs.m->valid != VM_PAGE_BITS_ALL) 505 goto readrest; 506 break; 507 } 508 509 /* 510 * Page is not resident. If this is the search termination 511 * or the pager might contain the page, allocate a new page. 512 * Default objects are zero-fill, there is no real pager. 513 */ 514 if (fs.object->type != OBJT_DEFAULT || 515 fs.object == fs.first_object) { 516 if (fs.pindex >= fs.object->size) { 517 unlock_and_deallocate(&fs); 518 return (KERN_PROTECTION_FAILURE); 519 } 520 521 /* 522 * Allocate a new page for this object/offset pair. 523 * 524 * Unlocked read of the p_flag is harmless. At 525 * worst, the P_KILLED might be not observed 526 * there, and allocation can fail, causing 527 * restart and new reading of the p_flag. 528 */ 529 fs.m = NULL; 530 if (!vm_page_count_severe() || P_KILLED(curproc)) { 531 #if VM_NRESERVLEVEL > 0 532 if ((fs.object->flags & OBJ_COLORED) == 0) { 533 fs.object->flags |= OBJ_COLORED; 534 fs.object->pg_color = atop(vaddr) - 535 fs.pindex; 536 } 537 #endif 538 alloc_req = P_KILLED(curproc) ? 539 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 540 if (fs.object->type != OBJT_VNODE && 541 fs.object->backing_object == NULL) 542 alloc_req |= VM_ALLOC_ZERO; 543 fs.m = vm_page_alloc(fs.object, fs.pindex, 544 alloc_req); 545 } 546 if (fs.m == NULL) { 547 unlock_and_deallocate(&fs); 548 VM_WAITPFAULT; 549 goto RetryFault; 550 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 551 break; 552 } 553 554 readrest: 555 /* 556 * We have found a valid page or we have allocated a new page. 557 * The page thus may not be valid or may not be entirely 558 * valid. 559 * 560 * Attempt to fault-in the page if there is a chance that the 561 * pager has it, and potentially fault in additional pages 562 * at the same time. For default objects simply provide 563 * zero-filled pages. 564 */ 565 if (fs.object->type != OBJT_DEFAULT) { 566 int rv; 567 u_char behavior = vm_map_entry_behavior(fs.entry); 568 569 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 570 P_KILLED(curproc)) { 571 behind = 0; 572 ahead = 0; 573 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 574 behind = 0; 575 ahead = atop(fs.entry->end - vaddr) - 1; 576 if (ahead > VM_FAULT_READ_AHEAD_MAX) 577 ahead = VM_FAULT_READ_AHEAD_MAX; 578 if (fs.pindex == fs.entry->next_read) 579 vm_fault_cache_behind(&fs, 580 VM_FAULT_READ_MAX); 581 } else { 582 /* 583 * If this is a sequential page fault, then 584 * arithmetically increase the number of pages 585 * in the read-ahead window. Otherwise, reset 586 * the read-ahead window to its smallest size. 587 */ 588 behind = atop(vaddr - fs.entry->start); 589 if (behind > VM_FAULT_READ_BEHIND) 590 behind = VM_FAULT_READ_BEHIND; 591 ahead = atop(fs.entry->end - vaddr) - 1; 592 era = fs.entry->read_ahead; 593 if (fs.pindex == fs.entry->next_read) { 594 nera = era + behind; 595 if (nera > VM_FAULT_READ_AHEAD_MAX) 596 nera = VM_FAULT_READ_AHEAD_MAX; 597 behind = 0; 598 if (ahead > nera) 599 ahead = nera; 600 if (era == VM_FAULT_READ_AHEAD_MAX) 601 vm_fault_cache_behind(&fs, 602 VM_FAULT_CACHE_BEHIND); 603 } else if (ahead > VM_FAULT_READ_AHEAD_MIN) 604 ahead = VM_FAULT_READ_AHEAD_MIN; 605 if (era != ahead) 606 fs.entry->read_ahead = ahead; 607 } 608 609 /* 610 * Call the pager to retrieve the data, if any, after 611 * releasing the lock on the map. We hold a ref on 612 * fs.object and the pages are exclusive busied. 613 */ 614 unlock_map(&fs); 615 616 if (fs.object->type == OBJT_VNODE) { 617 vp = fs.object->handle; 618 if (vp == fs.vp) 619 goto vnode_locked; 620 else if (fs.vp != NULL) { 621 vput(fs.vp); 622 fs.vp = NULL; 623 } 624 locked = VOP_ISLOCKED(vp); 625 626 if (locked != LK_EXCLUSIVE) 627 locked = LK_SHARED; 628 /* Do not sleep for vnode lock while fs.m is busy */ 629 error = vget(vp, locked | LK_CANRECURSE | 630 LK_NOWAIT, curthread); 631 if (error != 0) { 632 vhold(vp); 633 release_page(&fs); 634 unlock_and_deallocate(&fs); 635 error = vget(vp, locked | LK_RETRY | 636 LK_CANRECURSE, curthread); 637 vdrop(vp); 638 fs.vp = vp; 639 KASSERT(error == 0, 640 ("vm_fault: vget failed")); 641 goto RetryFault; 642 } 643 fs.vp = vp; 644 } 645 vnode_locked: 646 KASSERT(fs.vp == NULL || !fs.map->system_map, 647 ("vm_fault: vnode-backed object mapped by system map")); 648 649 /* 650 * now we find out if any other pages should be paged 651 * in at this time this routine checks to see if the 652 * pages surrounding this fault reside in the same 653 * object as the page for this fault. If they do, 654 * then they are faulted in also into the object. The 655 * array "marray" returned contains an array of 656 * vm_page_t structs where one of them is the 657 * vm_page_t passed to the routine. The reqpage 658 * return value is the index into the marray for the 659 * vm_page_t passed to the routine. 660 * 661 * fs.m plus the additional pages are exclusive busied. 662 */ 663 faultcount = vm_fault_additional_pages( 664 fs.m, behind, ahead, marray, &reqpage); 665 666 rv = faultcount ? 667 vm_pager_get_pages(fs.object, marray, faultcount, 668 reqpage) : VM_PAGER_FAIL; 669 670 if (rv == VM_PAGER_OK) { 671 /* 672 * Found the page. Leave it busy while we play 673 * with it. 674 */ 675 676 /* 677 * Relookup in case pager changed page. Pager 678 * is responsible for disposition of old page 679 * if moved. 680 */ 681 fs.m = vm_page_lookup(fs.object, fs.pindex); 682 if (!fs.m) { 683 unlock_and_deallocate(&fs); 684 goto RetryFault; 685 } 686 687 hardfault++; 688 break; /* break to PAGE HAS BEEN FOUND */ 689 } 690 /* 691 * Remove the bogus page (which does not exist at this 692 * object/offset); before doing so, we must get back 693 * our object lock to preserve our invariant. 694 * 695 * Also wake up any other process that may want to bring 696 * in this page. 697 * 698 * If this is the top-level object, we must leave the 699 * busy page to prevent another process from rushing 700 * past us, and inserting the page in that object at 701 * the same time that we are. 702 */ 703 if (rv == VM_PAGER_ERROR) 704 printf("vm_fault: pager read error, pid %d (%s)\n", 705 curproc->p_pid, curproc->p_comm); 706 /* 707 * Data outside the range of the pager or an I/O error 708 */ 709 /* 710 * XXX - the check for kernel_map is a kludge to work 711 * around having the machine panic on a kernel space 712 * fault w/ I/O error. 713 */ 714 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 715 (rv == VM_PAGER_BAD)) { 716 vm_page_lock(fs.m); 717 vm_page_free(fs.m); 718 vm_page_unlock(fs.m); 719 fs.m = NULL; 720 unlock_and_deallocate(&fs); 721 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 722 } 723 if (fs.object != fs.first_object) { 724 vm_page_lock(fs.m); 725 vm_page_free(fs.m); 726 vm_page_unlock(fs.m); 727 fs.m = NULL; 728 /* 729 * XXX - we cannot just fall out at this 730 * point, m has been freed and is invalid! 731 */ 732 } 733 } 734 735 /* 736 * We get here if the object has default pager (or unwiring) 737 * or the pager doesn't have the page. 738 */ 739 if (fs.object == fs.first_object) 740 fs.first_m = fs.m; 741 742 /* 743 * Move on to the next object. Lock the next object before 744 * unlocking the current one. 745 */ 746 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 747 next_object = fs.object->backing_object; 748 if (next_object == NULL) { 749 /* 750 * If there's no object left, fill the page in the top 751 * object with zeros. 752 */ 753 if (fs.object != fs.first_object) { 754 vm_object_pip_wakeup(fs.object); 755 VM_OBJECT_WUNLOCK(fs.object); 756 757 fs.object = fs.first_object; 758 fs.pindex = fs.first_pindex; 759 fs.m = fs.first_m; 760 VM_OBJECT_WLOCK(fs.object); 761 } 762 fs.first_m = NULL; 763 764 /* 765 * Zero the page if necessary and mark it valid. 766 */ 767 if ((fs.m->flags & PG_ZERO) == 0) { 768 pmap_zero_page(fs.m); 769 } else { 770 PCPU_INC(cnt.v_ozfod); 771 } 772 PCPU_INC(cnt.v_zfod); 773 fs.m->valid = VM_PAGE_BITS_ALL; 774 /* Don't try to prefault neighboring pages. */ 775 faultcount = 1; 776 break; /* break to PAGE HAS BEEN FOUND */ 777 } else { 778 KASSERT(fs.object != next_object, 779 ("object loop %p", next_object)); 780 VM_OBJECT_WLOCK(next_object); 781 vm_object_pip_add(next_object, 1); 782 if (fs.object != fs.first_object) 783 vm_object_pip_wakeup(fs.object); 784 VM_OBJECT_WUNLOCK(fs.object); 785 fs.object = next_object; 786 } 787 } 788 789 vm_page_assert_xbusied(fs.m); 790 791 /* 792 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 793 * is held.] 794 */ 795 796 /* 797 * If the page is being written, but isn't already owned by the 798 * top-level object, we have to copy it into a new page owned by the 799 * top-level object. 800 */ 801 if (fs.object != fs.first_object) { 802 /* 803 * We only really need to copy if we want to write it. 804 */ 805 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 806 /* 807 * This allows pages to be virtually copied from a 808 * backing_object into the first_object, where the 809 * backing object has no other refs to it, and cannot 810 * gain any more refs. Instead of a bcopy, we just 811 * move the page from the backing object to the 812 * first object. Note that we must mark the page 813 * dirty in the first object so that it will go out 814 * to swap when needed. 815 */ 816 is_first_object_locked = FALSE; 817 if ( 818 /* 819 * Only one shadow object 820 */ 821 (fs.object->shadow_count == 1) && 822 /* 823 * No COW refs, except us 824 */ 825 (fs.object->ref_count == 1) && 826 /* 827 * No one else can look this object up 828 */ 829 (fs.object->handle == NULL) && 830 /* 831 * No other ways to look the object up 832 */ 833 ((fs.object->type == OBJT_DEFAULT) || 834 (fs.object->type == OBJT_SWAP)) && 835 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 836 /* 837 * We don't chase down the shadow chain 838 */ 839 fs.object == fs.first_object->backing_object) { 840 /* 841 * get rid of the unnecessary page 842 */ 843 vm_page_lock(fs.first_m); 844 vm_page_free(fs.first_m); 845 vm_page_unlock(fs.first_m); 846 /* 847 * grab the page and put it into the 848 * process'es object. The page is 849 * automatically made dirty. 850 */ 851 if (vm_page_rename(fs.m, fs.first_object, 852 fs.first_pindex)) { 853 unlock_and_deallocate(&fs); 854 goto RetryFault; 855 } 856 #if VM_NRESERVLEVEL > 0 857 /* 858 * Rename the reservation. 859 */ 860 vm_reserv_rename(fs.m, fs.first_object, 861 fs.object, OFF_TO_IDX( 862 fs.first_object->backing_object_offset)); 863 #endif 864 vm_page_xbusy(fs.m); 865 fs.first_m = fs.m; 866 fs.m = NULL; 867 PCPU_INC(cnt.v_cow_optim); 868 } else { 869 /* 870 * Oh, well, lets copy it. 871 */ 872 pmap_copy_page(fs.m, fs.first_m); 873 fs.first_m->valid = VM_PAGE_BITS_ALL; 874 if (wired && (fault_flags & 875 VM_FAULT_WIRE) == 0) { 876 vm_page_lock(fs.first_m); 877 vm_page_wire(fs.first_m); 878 vm_page_unlock(fs.first_m); 879 880 vm_page_lock(fs.m); 881 vm_page_unwire(fs.m, FALSE); 882 vm_page_unlock(fs.m); 883 } 884 /* 885 * We no longer need the old page or object. 886 */ 887 release_page(&fs); 888 } 889 /* 890 * fs.object != fs.first_object due to above 891 * conditional 892 */ 893 vm_object_pip_wakeup(fs.object); 894 VM_OBJECT_WUNLOCK(fs.object); 895 /* 896 * Only use the new page below... 897 */ 898 fs.object = fs.first_object; 899 fs.pindex = fs.first_pindex; 900 fs.m = fs.first_m; 901 if (!is_first_object_locked) 902 VM_OBJECT_WLOCK(fs.object); 903 PCPU_INC(cnt.v_cow_faults); 904 curthread->td_cow++; 905 } else { 906 prot &= ~VM_PROT_WRITE; 907 } 908 } 909 910 /* 911 * We must verify that the maps have not changed since our last 912 * lookup. 913 */ 914 if (!fs.lookup_still_valid) { 915 vm_object_t retry_object; 916 vm_pindex_t retry_pindex; 917 vm_prot_t retry_prot; 918 919 if (!vm_map_trylock_read(fs.map)) { 920 release_page(&fs); 921 unlock_and_deallocate(&fs); 922 goto RetryFault; 923 } 924 fs.lookup_still_valid = TRUE; 925 if (fs.map->timestamp != map_generation) { 926 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 927 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 928 929 /* 930 * If we don't need the page any longer, put it on the inactive 931 * list (the easiest thing to do here). If no one needs it, 932 * pageout will grab it eventually. 933 */ 934 if (result != KERN_SUCCESS) { 935 release_page(&fs); 936 unlock_and_deallocate(&fs); 937 938 /* 939 * If retry of map lookup would have blocked then 940 * retry fault from start. 941 */ 942 if (result == KERN_FAILURE) 943 goto RetryFault; 944 return (result); 945 } 946 if ((retry_object != fs.first_object) || 947 (retry_pindex != fs.first_pindex)) { 948 release_page(&fs); 949 unlock_and_deallocate(&fs); 950 goto RetryFault; 951 } 952 953 /* 954 * Check whether the protection has changed or the object has 955 * been copied while we left the map unlocked. Changing from 956 * read to write permission is OK - we leave the page 957 * write-protected, and catch the write fault. Changing from 958 * write to read permission means that we can't mark the page 959 * write-enabled after all. 960 */ 961 prot &= retry_prot; 962 } 963 } 964 /* 965 * If the page was filled by a pager, update the map entry's 966 * last read offset. Since the pager does not return the 967 * actual set of pages that it read, this update is based on 968 * the requested set. Typically, the requested and actual 969 * sets are the same. 970 * 971 * XXX The following assignment modifies the map 972 * without holding a write lock on it. 973 */ 974 if (hardfault) 975 fs.entry->next_read = fs.pindex + faultcount - reqpage; 976 977 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); 978 vm_page_assert_xbusied(fs.m); 979 980 /* 981 * Page must be completely valid or it is not fit to 982 * map into user space. vm_pager_get_pages() ensures this. 983 */ 984 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 985 ("vm_fault: page %p partially invalid", fs.m)); 986 VM_OBJECT_WUNLOCK(fs.object); 987 988 /* 989 * Put this page into the physical map. We had to do the unlock above 990 * because pmap_enter() may sleep. We don't put the page 991 * back on the active queue until later so that the pageout daemon 992 * won't find it (yet). 993 */ 994 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 995 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 996 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 997 wired == 0) 998 vm_fault_prefault(&fs, vaddr, faultcount, reqpage); 999 VM_OBJECT_WLOCK(fs.object); 1000 vm_page_lock(fs.m); 1001 1002 /* 1003 * If the page is not wired down, then put it where the pageout daemon 1004 * can find it. 1005 */ 1006 if ((fault_flags & VM_FAULT_WIRE) != 0) { 1007 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 1008 vm_page_wire(fs.m); 1009 } else 1010 vm_page_activate(fs.m); 1011 if (m_hold != NULL) { 1012 *m_hold = fs.m; 1013 vm_page_hold(fs.m); 1014 } 1015 vm_page_unlock(fs.m); 1016 vm_page_xunbusy(fs.m); 1017 1018 /* 1019 * Unlock everything, and return 1020 */ 1021 unlock_and_deallocate(&fs); 1022 if (hardfault) { 1023 PCPU_INC(cnt.v_io_faults); 1024 curthread->td_ru.ru_majflt++; 1025 } else 1026 curthread->td_ru.ru_minflt++; 1027 1028 return (KERN_SUCCESS); 1029 } 1030 1031 /* 1032 * Speed up the reclamation of up to "distance" pages that precede the 1033 * faulting pindex within the first object of the shadow chain. 1034 */ 1035 static void 1036 vm_fault_cache_behind(const struct faultstate *fs, int distance) 1037 { 1038 vm_object_t first_object, object; 1039 vm_page_t m, m_prev; 1040 vm_pindex_t pindex; 1041 1042 object = fs->object; 1043 VM_OBJECT_ASSERT_WLOCKED(object); 1044 first_object = fs->first_object; 1045 if (first_object != object) { 1046 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1047 VM_OBJECT_WUNLOCK(object); 1048 VM_OBJECT_WLOCK(first_object); 1049 VM_OBJECT_WLOCK(object); 1050 } 1051 } 1052 /* Neither fictitious nor unmanaged pages can be cached. */ 1053 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1054 if (fs->first_pindex < distance) 1055 pindex = 0; 1056 else 1057 pindex = fs->first_pindex - distance; 1058 if (pindex < OFF_TO_IDX(fs->entry->offset)) 1059 pindex = OFF_TO_IDX(fs->entry->offset); 1060 m = first_object != object ? fs->first_m : fs->m; 1061 vm_page_assert_xbusied(m); 1062 m_prev = vm_page_prev(m); 1063 while ((m = m_prev) != NULL && m->pindex >= pindex && 1064 m->valid == VM_PAGE_BITS_ALL) { 1065 m_prev = vm_page_prev(m); 1066 if (vm_page_busied(m)) 1067 continue; 1068 vm_page_lock(m); 1069 if (m->hold_count == 0 && m->wire_count == 0) { 1070 pmap_remove_all(m); 1071 vm_page_aflag_clear(m, PGA_REFERENCED); 1072 if (m->dirty != 0) 1073 vm_page_deactivate(m); 1074 else 1075 vm_page_cache(m); 1076 } 1077 vm_page_unlock(m); 1078 } 1079 } 1080 if (first_object != object) 1081 VM_OBJECT_WUNLOCK(first_object); 1082 } 1083 1084 /* 1085 * vm_fault_prefault provides a quick way of clustering 1086 * pagefaults into a processes address space. It is a "cousin" 1087 * of vm_map_pmap_enter, except it runs at page fault time instead 1088 * of mmap time. 1089 */ 1090 static void 1091 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1092 int faultcount, int reqpage) 1093 { 1094 pmap_t pmap; 1095 vm_map_entry_t entry; 1096 vm_object_t backing_object, lobject; 1097 vm_offset_t addr, starta; 1098 vm_pindex_t pindex; 1099 vm_page_t m; 1100 int backward, forward, i; 1101 1102 pmap = fs->map->pmap; 1103 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1104 return; 1105 1106 if (faultcount > 0) { 1107 backward = reqpage; 1108 forward = faultcount - reqpage - 1; 1109 } else { 1110 backward = PFBAK; 1111 forward = PFFOR; 1112 } 1113 entry = fs->entry; 1114 1115 starta = addra - backward * PAGE_SIZE; 1116 if (starta < entry->start) { 1117 starta = entry->start; 1118 } else if (starta > addra) { 1119 starta = 0; 1120 } 1121 1122 /* 1123 * Generate the sequence of virtual addresses that are candidates for 1124 * prefaulting in an outward spiral from the faulting virtual address, 1125 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1126 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1127 * If the candidate address doesn't have a backing physical page, then 1128 * the loop immediately terminates. 1129 */ 1130 for (i = 0; i < 2 * imax(backward, forward); i++) { 1131 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1132 PAGE_SIZE); 1133 if (addr > addra + forward * PAGE_SIZE) 1134 addr = 0; 1135 1136 if (addr < starta || addr >= entry->end) 1137 continue; 1138 1139 if (!pmap_is_prefaultable(pmap, addr)) 1140 continue; 1141 1142 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1143 lobject = entry->object.vm_object; 1144 VM_OBJECT_RLOCK(lobject); 1145 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1146 lobject->type == OBJT_DEFAULT && 1147 (backing_object = lobject->backing_object) != NULL) { 1148 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1149 0, ("vm_fault_prefault: unaligned object offset")); 1150 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1151 VM_OBJECT_RLOCK(backing_object); 1152 VM_OBJECT_RUNLOCK(lobject); 1153 lobject = backing_object; 1154 } 1155 if (m == NULL) { 1156 VM_OBJECT_RUNLOCK(lobject); 1157 break; 1158 } 1159 if (m->valid == VM_PAGE_BITS_ALL && 1160 (m->flags & PG_FICTITIOUS) == 0) 1161 pmap_enter_quick(pmap, addr, m, entry->protection); 1162 VM_OBJECT_RUNLOCK(lobject); 1163 } 1164 } 1165 1166 /* 1167 * Hold each of the physical pages that are mapped by the specified range of 1168 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1169 * and allow the specified types of access, "prot". If all of the implied 1170 * pages are successfully held, then the number of held pages is returned 1171 * together with pointers to those pages in the array "ma". However, if any 1172 * of the pages cannot be held, -1 is returned. 1173 */ 1174 int 1175 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1176 vm_prot_t prot, vm_page_t *ma, int max_count) 1177 { 1178 vm_offset_t end, va; 1179 vm_page_t *mp; 1180 int count; 1181 boolean_t pmap_failed; 1182 1183 if (len == 0) 1184 return (0); 1185 end = round_page(addr + len); 1186 addr = trunc_page(addr); 1187 1188 /* 1189 * Check for illegal addresses. 1190 */ 1191 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1192 return (-1); 1193 1194 if (atop(end - addr) > max_count) 1195 panic("vm_fault_quick_hold_pages: count > max_count"); 1196 count = atop(end - addr); 1197 1198 /* 1199 * Most likely, the physical pages are resident in the pmap, so it is 1200 * faster to try pmap_extract_and_hold() first. 1201 */ 1202 pmap_failed = FALSE; 1203 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1204 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1205 if (*mp == NULL) 1206 pmap_failed = TRUE; 1207 else if ((prot & VM_PROT_WRITE) != 0 && 1208 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1209 /* 1210 * Explicitly dirty the physical page. Otherwise, the 1211 * caller's changes may go unnoticed because they are 1212 * performed through an unmanaged mapping or by a DMA 1213 * operation. 1214 * 1215 * The object lock is not held here. 1216 * See vm_page_clear_dirty_mask(). 1217 */ 1218 vm_page_dirty(*mp); 1219 } 1220 } 1221 if (pmap_failed) { 1222 /* 1223 * One or more pages could not be held by the pmap. Either no 1224 * page was mapped at the specified virtual address or that 1225 * mapping had insufficient permissions. Attempt to fault in 1226 * and hold these pages. 1227 */ 1228 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1229 if (*mp == NULL && vm_fault_hold(map, va, prot, 1230 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1231 goto error; 1232 } 1233 return (count); 1234 error: 1235 for (mp = ma; mp < ma + count; mp++) 1236 if (*mp != NULL) { 1237 vm_page_lock(*mp); 1238 vm_page_unhold(*mp); 1239 vm_page_unlock(*mp); 1240 } 1241 return (-1); 1242 } 1243 1244 /* 1245 * Routine: 1246 * vm_fault_copy_entry 1247 * Function: 1248 * Create new shadow object backing dst_entry with private copy of 1249 * all underlying pages. When src_entry is equal to dst_entry, 1250 * function implements COW for wired-down map entry. Otherwise, 1251 * it forks wired entry into dst_map. 1252 * 1253 * In/out conditions: 1254 * The source and destination maps must be locked for write. 1255 * The source map entry must be wired down (or be a sharing map 1256 * entry corresponding to a main map entry that is wired down). 1257 */ 1258 void 1259 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1260 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1261 vm_ooffset_t *fork_charge) 1262 { 1263 vm_object_t backing_object, dst_object, object, src_object; 1264 vm_pindex_t dst_pindex, pindex, src_pindex; 1265 vm_prot_t access, prot; 1266 vm_offset_t vaddr; 1267 vm_page_t dst_m; 1268 vm_page_t src_m; 1269 boolean_t upgrade; 1270 1271 #ifdef lint 1272 src_map++; 1273 #endif /* lint */ 1274 1275 upgrade = src_entry == dst_entry; 1276 access = prot = dst_entry->protection; 1277 1278 src_object = src_entry->object.vm_object; 1279 src_pindex = OFF_TO_IDX(src_entry->offset); 1280 1281 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1282 dst_object = src_object; 1283 vm_object_reference(dst_object); 1284 } else { 1285 /* 1286 * Create the top-level object for the destination entry. (Doesn't 1287 * actually shadow anything - we copy the pages directly.) 1288 */ 1289 dst_object = vm_object_allocate(OBJT_DEFAULT, 1290 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1291 #if VM_NRESERVLEVEL > 0 1292 dst_object->flags |= OBJ_COLORED; 1293 dst_object->pg_color = atop(dst_entry->start); 1294 #endif 1295 } 1296 1297 VM_OBJECT_WLOCK(dst_object); 1298 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1299 ("vm_fault_copy_entry: vm_object not NULL")); 1300 if (src_object != dst_object) { 1301 dst_entry->object.vm_object = dst_object; 1302 dst_entry->offset = 0; 1303 dst_object->charge = dst_entry->end - dst_entry->start; 1304 } 1305 if (fork_charge != NULL) { 1306 KASSERT(dst_entry->cred == NULL, 1307 ("vm_fault_copy_entry: leaked swp charge")); 1308 dst_object->cred = curthread->td_ucred; 1309 crhold(dst_object->cred); 1310 *fork_charge += dst_object->charge; 1311 } else if (dst_object->cred == NULL) { 1312 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1313 dst_entry)); 1314 dst_object->cred = dst_entry->cred; 1315 dst_entry->cred = NULL; 1316 } 1317 1318 /* 1319 * If not an upgrade, then enter the mappings in the pmap as 1320 * read and/or execute accesses. Otherwise, enter them as 1321 * write accesses. 1322 * 1323 * A writeable large page mapping is only created if all of 1324 * the constituent small page mappings are modified. Marking 1325 * PTEs as modified on inception allows promotion to happen 1326 * without taking potentially large number of soft faults. 1327 */ 1328 if (!upgrade) 1329 access &= ~VM_PROT_WRITE; 1330 1331 /* 1332 * Loop through all of the virtual pages within the entry's 1333 * range, copying each page from the source object to the 1334 * destination object. Since the source is wired, those pages 1335 * must exist. In contrast, the destination is pageable. 1336 * Since the destination object does share any backing storage 1337 * with the source object, all of its pages must be dirtied, 1338 * regardless of whether they can be written. 1339 */ 1340 for (vaddr = dst_entry->start, dst_pindex = 0; 1341 vaddr < dst_entry->end; 1342 vaddr += PAGE_SIZE, dst_pindex++) { 1343 again: 1344 /* 1345 * Find the page in the source object, and copy it in. 1346 * Because the source is wired down, the page will be 1347 * in memory. 1348 */ 1349 if (src_object != dst_object) 1350 VM_OBJECT_RLOCK(src_object); 1351 object = src_object; 1352 pindex = src_pindex + dst_pindex; 1353 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1354 (backing_object = object->backing_object) != NULL) { 1355 /* 1356 * Unless the source mapping is read-only or 1357 * it is presently being upgraded from 1358 * read-only, the first object in the shadow 1359 * chain should provide all of the pages. In 1360 * other words, this loop body should never be 1361 * executed when the source mapping is already 1362 * read/write. 1363 */ 1364 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1365 upgrade, 1366 ("vm_fault_copy_entry: main object missing page")); 1367 1368 VM_OBJECT_RLOCK(backing_object); 1369 pindex += OFF_TO_IDX(object->backing_object_offset); 1370 if (object != dst_object) 1371 VM_OBJECT_RUNLOCK(object); 1372 object = backing_object; 1373 } 1374 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1375 1376 if (object != dst_object) { 1377 /* 1378 * Allocate a page in the destination object. 1379 */ 1380 dst_m = vm_page_alloc(dst_object, (src_object == 1381 dst_object ? src_pindex : 0) + dst_pindex, 1382 VM_ALLOC_NORMAL); 1383 if (dst_m == NULL) { 1384 VM_OBJECT_WUNLOCK(dst_object); 1385 VM_OBJECT_RUNLOCK(object); 1386 VM_WAIT; 1387 VM_OBJECT_WLOCK(dst_object); 1388 goto again; 1389 } 1390 pmap_copy_page(src_m, dst_m); 1391 VM_OBJECT_RUNLOCK(object); 1392 dst_m->valid = VM_PAGE_BITS_ALL; 1393 dst_m->dirty = VM_PAGE_BITS_ALL; 1394 } else { 1395 dst_m = src_m; 1396 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1397 goto again; 1398 vm_page_xbusy(dst_m); 1399 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1400 ("invalid dst page %p", dst_m)); 1401 } 1402 VM_OBJECT_WUNLOCK(dst_object); 1403 1404 /* 1405 * Enter it in the pmap. If a wired, copy-on-write 1406 * mapping is being replaced by a write-enabled 1407 * mapping, then wire that new mapping. 1408 */ 1409 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1410 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1411 1412 /* 1413 * Mark it no longer busy, and put it on the active list. 1414 */ 1415 VM_OBJECT_WLOCK(dst_object); 1416 1417 if (upgrade) { 1418 if (src_m != dst_m) { 1419 vm_page_lock(src_m); 1420 vm_page_unwire(src_m, 0); 1421 vm_page_unlock(src_m); 1422 vm_page_lock(dst_m); 1423 vm_page_wire(dst_m); 1424 vm_page_unlock(dst_m); 1425 } else { 1426 KASSERT(dst_m->wire_count > 0, 1427 ("dst_m %p is not wired", dst_m)); 1428 } 1429 } else { 1430 vm_page_lock(dst_m); 1431 vm_page_activate(dst_m); 1432 vm_page_unlock(dst_m); 1433 } 1434 vm_page_xunbusy(dst_m); 1435 } 1436 VM_OBJECT_WUNLOCK(dst_object); 1437 if (upgrade) { 1438 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1439 vm_object_deallocate(src_object); 1440 } 1441 } 1442 1443 1444 /* 1445 * This routine checks around the requested page for other pages that 1446 * might be able to be faulted in. This routine brackets the viable 1447 * pages for the pages to be paged in. 1448 * 1449 * Inputs: 1450 * m, rbehind, rahead 1451 * 1452 * Outputs: 1453 * marray (array of vm_page_t), reqpage (index of requested page) 1454 * 1455 * Return value: 1456 * number of pages in marray 1457 */ 1458 static int 1459 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1460 vm_page_t m; 1461 int rbehind; 1462 int rahead; 1463 vm_page_t *marray; 1464 int *reqpage; 1465 { 1466 int i,j; 1467 vm_object_t object; 1468 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1469 vm_page_t rtm; 1470 int cbehind, cahead; 1471 1472 VM_OBJECT_ASSERT_WLOCKED(m->object); 1473 1474 object = m->object; 1475 pindex = m->pindex; 1476 cbehind = cahead = 0; 1477 1478 /* 1479 * if the requested page is not available, then give up now 1480 */ 1481 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1482 return 0; 1483 } 1484 1485 if ((cbehind == 0) && (cahead == 0)) { 1486 *reqpage = 0; 1487 marray[0] = m; 1488 return 1; 1489 } 1490 1491 if (rahead > cahead) { 1492 rahead = cahead; 1493 } 1494 1495 if (rbehind > cbehind) { 1496 rbehind = cbehind; 1497 } 1498 1499 /* 1500 * scan backward for the read behind pages -- in memory 1501 */ 1502 if (pindex > 0) { 1503 if (rbehind > pindex) { 1504 rbehind = pindex; 1505 startpindex = 0; 1506 } else { 1507 startpindex = pindex - rbehind; 1508 } 1509 1510 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1511 rtm->pindex >= startpindex) 1512 startpindex = rtm->pindex + 1; 1513 1514 /* tpindex is unsigned; beware of numeric underflow. */ 1515 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1516 tpindex < pindex; i++, tpindex--) { 1517 1518 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1519 VM_ALLOC_IFNOTCACHED); 1520 if (rtm == NULL) { 1521 /* 1522 * Shift the allocated pages to the 1523 * beginning of the array. 1524 */ 1525 for (j = 0; j < i; j++) { 1526 marray[j] = marray[j + tpindex + 1 - 1527 startpindex]; 1528 } 1529 break; 1530 } 1531 1532 marray[tpindex - startpindex] = rtm; 1533 } 1534 } else { 1535 startpindex = 0; 1536 i = 0; 1537 } 1538 1539 marray[i] = m; 1540 /* page offset of the required page */ 1541 *reqpage = i; 1542 1543 tpindex = pindex + 1; 1544 i++; 1545 1546 /* 1547 * scan forward for the read ahead pages 1548 */ 1549 endpindex = tpindex + rahead; 1550 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1551 endpindex = rtm->pindex; 1552 if (endpindex > object->size) 1553 endpindex = object->size; 1554 1555 for (; tpindex < endpindex; i++, tpindex++) { 1556 1557 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1558 VM_ALLOC_IFNOTCACHED); 1559 if (rtm == NULL) { 1560 break; 1561 } 1562 1563 marray[i] = rtm; 1564 } 1565 1566 /* return number of pages */ 1567 return i; 1568 } 1569 1570 /* 1571 * Block entry into the machine-independent layer's page fault handler by 1572 * the calling thread. Subsequent calls to vm_fault() by that thread will 1573 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1574 * spurious page faults. 1575 */ 1576 int 1577 vm_fault_disable_pagefaults(void) 1578 { 1579 1580 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1581 } 1582 1583 void 1584 vm_fault_enable_pagefaults(int save) 1585 { 1586 1587 curthread_pflags_restore(save); 1588 }
Cache object: 18a09a024dad2f67a8a01bd0b3b0c67e
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]