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sys/vm/vm_fault.c
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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/10.2/sys/vm/vm_fault.c 282456 2015-05-05 08:12:24Z 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 4 108 109 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_CHANGE_WIRING) == 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 * TRYPAGER - used by vm_fault to calculate whether the pager for the 244 * current object *might* contain the page. 245 * 246 * default objects are zero-fill, there is no real pager. 247 */ 248 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 249 ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 || wired)) 250 251 /* 252 * vm_fault: 253 * 254 * Handle a page fault occurring at the given address, 255 * requiring the given permissions, in the map specified. 256 * If successful, the page is inserted into the 257 * associated physical map. 258 * 259 * NOTE: the given address should be truncated to the 260 * proper page address. 261 * 262 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 263 * a standard error specifying why the fault is fatal is returned. 264 * 265 * The map in question must be referenced, and remains so. 266 * Caller may hold no locks. 267 */ 268 int 269 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 270 int fault_flags) 271 { 272 struct thread *td; 273 int result; 274 275 td = curthread; 276 if ((td->td_pflags & TDP_NOFAULTING) != 0) 277 return (KERN_PROTECTION_FAILURE); 278 #ifdef KTRACE 279 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 280 ktrfault(vaddr, fault_type); 281 #endif 282 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 283 NULL); 284 #ifdef KTRACE 285 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 286 ktrfaultend(result); 287 #endif 288 return (result); 289 } 290 291 int 292 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 293 int fault_flags, vm_page_t *m_hold) 294 { 295 vm_prot_t prot; 296 long ahead, behind; 297 int alloc_req, era, faultcount, nera, reqpage, result; 298 boolean_t growstack, is_first_object_locked, wired; 299 int map_generation; 300 vm_object_t next_object; 301 vm_page_t marray[VM_FAULT_READ_MAX]; 302 int hardfault; 303 struct faultstate fs; 304 struct vnode *vp; 305 vm_page_t m; 306 int locked, error; 307 308 hardfault = 0; 309 growstack = TRUE; 310 PCPU_INC(cnt.v_vm_faults); 311 fs.vp = NULL; 312 faultcount = reqpage = 0; 313 314 RetryFault:; 315 316 /* 317 * Find the backing store object and offset into it to begin the 318 * search. 319 */ 320 fs.map = map; 321 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 322 &fs.first_object, &fs.first_pindex, &prot, &wired); 323 if (result != KERN_SUCCESS) { 324 if (growstack && result == KERN_INVALID_ADDRESS && 325 map != kernel_map) { 326 result = vm_map_growstack(curproc, vaddr); 327 if (result != KERN_SUCCESS) 328 return (KERN_FAILURE); 329 growstack = FALSE; 330 goto RetryFault; 331 } 332 return (result); 333 } 334 335 map_generation = fs.map->timestamp; 336 337 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 338 panic("vm_fault: fault on nofault entry, addr: %lx", 339 (u_long)vaddr); 340 } 341 342 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 343 fs.entry->wiring_thread != curthread) { 344 vm_map_unlock_read(fs.map); 345 vm_map_lock(fs.map); 346 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 347 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 348 if (fs.vp != NULL) { 349 vput(fs.vp); 350 fs.vp = NULL; 351 } 352 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 353 vm_map_unlock_and_wait(fs.map, 0); 354 } else 355 vm_map_unlock(fs.map); 356 goto RetryFault; 357 } 358 359 if (wired) 360 fault_type = prot | (fault_type & VM_PROT_COPY); 361 362 if (fs.vp == NULL /* avoid locked vnode leak */ && 363 (fault_flags & (VM_FAULT_CHANGE_WIRING | VM_FAULT_DIRTY)) == 0 && 364 /* avoid calling vm_object_set_writeable_dirty() */ 365 ((prot & VM_PROT_WRITE) == 0 || 366 (fs.first_object->type != OBJT_VNODE && 367 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 368 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 369 VM_OBJECT_RLOCK(fs.first_object); 370 if ((prot & VM_PROT_WRITE) != 0 && 371 (fs.first_object->type == OBJT_VNODE || 372 (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) && 373 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0) 374 goto fast_failed; 375 m = vm_page_lookup(fs.first_object, fs.first_pindex); 376 /* A busy page can be mapped for read|execute access. */ 377 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 378 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 379 goto fast_failed; 380 result = pmap_enter(fs.map->pmap, vaddr, m, prot, 381 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 382 0), 0); 383 if (result != KERN_SUCCESS) 384 goto fast_failed; 385 if (m_hold != NULL) { 386 *m_hold = m; 387 vm_page_lock(m); 388 vm_page_hold(m); 389 vm_page_unlock(m); 390 } 391 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, 392 FALSE); 393 VM_OBJECT_RUNLOCK(fs.first_object); 394 if (!wired) 395 vm_fault_prefault(&fs, vaddr, 0, 0); 396 vm_map_lookup_done(fs.map, fs.entry); 397 curthread->td_ru.ru_minflt++; 398 return (KERN_SUCCESS); 399 fast_failed: 400 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 401 VM_OBJECT_RUNLOCK(fs.first_object); 402 VM_OBJECT_WLOCK(fs.first_object); 403 } 404 } else { 405 VM_OBJECT_WLOCK(fs.first_object); 406 } 407 408 /* 409 * Make a reference to this object to prevent its disposal while we 410 * are messing with it. Once we have the reference, the map is free 411 * to be diddled. Since objects reference their shadows (and copies), 412 * they will stay around as well. 413 * 414 * Bump the paging-in-progress count to prevent size changes (e.g. 415 * truncation operations) during I/O. This must be done after 416 * obtaining the vnode lock in order to avoid possible deadlocks. 417 */ 418 vm_object_reference_locked(fs.first_object); 419 vm_object_pip_add(fs.first_object, 1); 420 421 fs.lookup_still_valid = TRUE; 422 423 fs.first_m = NULL; 424 425 /* 426 * Search for the page at object/offset. 427 */ 428 fs.object = fs.first_object; 429 fs.pindex = fs.first_pindex; 430 while (TRUE) { 431 /* 432 * If the object is dead, we stop here 433 */ 434 if (fs.object->flags & OBJ_DEAD) { 435 unlock_and_deallocate(&fs); 436 return (KERN_PROTECTION_FAILURE); 437 } 438 439 /* 440 * See if page is resident 441 */ 442 fs.m = vm_page_lookup(fs.object, fs.pindex); 443 if (fs.m != NULL) { 444 /* 445 * Wait/Retry if the page is busy. We have to do this 446 * if the page is either exclusive or shared busy 447 * because the vm_pager may be using read busy for 448 * pageouts (and even pageins if it is the vnode 449 * pager), and we could end up trying to pagein and 450 * pageout the same page simultaneously. 451 * 452 * We can theoretically allow the busy case on a read 453 * fault if the page is marked valid, but since such 454 * pages are typically already pmap'd, putting that 455 * special case in might be more effort then it is 456 * worth. We cannot under any circumstances mess 457 * around with a shared busied page except, perhaps, 458 * to pmap it. 459 */ 460 if (vm_page_busied(fs.m)) { 461 /* 462 * Reference the page before unlocking and 463 * sleeping so that the page daemon is less 464 * likely to reclaim it. 465 */ 466 vm_page_aflag_set(fs.m, PGA_REFERENCED); 467 if (fs.object != fs.first_object) { 468 if (!VM_OBJECT_TRYWLOCK( 469 fs.first_object)) { 470 VM_OBJECT_WUNLOCK(fs.object); 471 VM_OBJECT_WLOCK(fs.first_object); 472 VM_OBJECT_WLOCK(fs.object); 473 } 474 vm_page_lock(fs.first_m); 475 vm_page_free(fs.first_m); 476 vm_page_unlock(fs.first_m); 477 vm_object_pip_wakeup(fs.first_object); 478 VM_OBJECT_WUNLOCK(fs.first_object); 479 fs.first_m = NULL; 480 } 481 unlock_map(&fs); 482 if (fs.m == vm_page_lookup(fs.object, 483 fs.pindex)) { 484 vm_page_sleep_if_busy(fs.m, "vmpfw"); 485 } 486 vm_object_pip_wakeup(fs.object); 487 VM_OBJECT_WUNLOCK(fs.object); 488 PCPU_INC(cnt.v_intrans); 489 vm_object_deallocate(fs.first_object); 490 goto RetryFault; 491 } 492 vm_page_lock(fs.m); 493 vm_page_remque(fs.m); 494 vm_page_unlock(fs.m); 495 496 /* 497 * Mark page busy for other processes, and the 498 * pagedaemon. If it still isn't completely valid 499 * (readable), jump to readrest, else break-out ( we 500 * found the page ). 501 */ 502 vm_page_xbusy(fs.m); 503 if (fs.m->valid != VM_PAGE_BITS_ALL) 504 goto readrest; 505 break; 506 } 507 508 /* 509 * Page is not resident, If this is the search termination 510 * or the pager might contain the page, allocate a new page. 511 */ 512 if (TRYPAGER || fs.object == fs.first_object) { 513 if (fs.pindex >= fs.object->size) { 514 unlock_and_deallocate(&fs); 515 return (KERN_PROTECTION_FAILURE); 516 } 517 518 /* 519 * Allocate a new page for this object/offset pair. 520 * 521 * Unlocked read of the p_flag is harmless. At 522 * worst, the P_KILLED might be not observed 523 * there, and allocation can fail, causing 524 * restart and new reading of the p_flag. 525 */ 526 fs.m = NULL; 527 if (!vm_page_count_severe() || P_KILLED(curproc)) { 528 #if VM_NRESERVLEVEL > 0 529 if ((fs.object->flags & OBJ_COLORED) == 0) { 530 fs.object->flags |= OBJ_COLORED; 531 fs.object->pg_color = atop(vaddr) - 532 fs.pindex; 533 } 534 #endif 535 alloc_req = P_KILLED(curproc) ? 536 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 537 if (fs.object->type != OBJT_VNODE && 538 fs.object->backing_object == NULL) 539 alloc_req |= VM_ALLOC_ZERO; 540 fs.m = vm_page_alloc(fs.object, fs.pindex, 541 alloc_req); 542 } 543 if (fs.m == NULL) { 544 unlock_and_deallocate(&fs); 545 VM_WAITPFAULT; 546 goto RetryFault; 547 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 548 break; 549 } 550 551 readrest: 552 /* 553 * We have found a valid page or we have allocated a new page. 554 * The page thus may not be valid or may not be entirely 555 * valid. 556 * 557 * Attempt to fault-in the page if there is a chance that the 558 * pager has it, and potentially fault in additional pages 559 * at the same time. 560 */ 561 if (TRYPAGER) { 562 int rv; 563 u_char behavior = vm_map_entry_behavior(fs.entry); 564 565 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 566 P_KILLED(curproc)) { 567 behind = 0; 568 ahead = 0; 569 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 570 behind = 0; 571 ahead = atop(fs.entry->end - vaddr) - 1; 572 if (ahead > VM_FAULT_READ_AHEAD_MAX) 573 ahead = VM_FAULT_READ_AHEAD_MAX; 574 if (fs.pindex == fs.entry->next_read) 575 vm_fault_cache_behind(&fs, 576 VM_FAULT_READ_MAX); 577 } else { 578 /* 579 * If this is a sequential page fault, then 580 * arithmetically increase the number of pages 581 * in the read-ahead window. Otherwise, reset 582 * the read-ahead window to its smallest size. 583 */ 584 behind = atop(vaddr - fs.entry->start); 585 if (behind > VM_FAULT_READ_BEHIND) 586 behind = VM_FAULT_READ_BEHIND; 587 ahead = atop(fs.entry->end - vaddr) - 1; 588 era = fs.entry->read_ahead; 589 if (fs.pindex == fs.entry->next_read) { 590 nera = era + behind; 591 if (nera > VM_FAULT_READ_AHEAD_MAX) 592 nera = VM_FAULT_READ_AHEAD_MAX; 593 behind = 0; 594 if (ahead > nera) 595 ahead = nera; 596 if (era == VM_FAULT_READ_AHEAD_MAX) 597 vm_fault_cache_behind(&fs, 598 VM_FAULT_CACHE_BEHIND); 599 } else if (ahead > VM_FAULT_READ_AHEAD_MIN) 600 ahead = VM_FAULT_READ_AHEAD_MIN; 601 if (era != ahead) 602 fs.entry->read_ahead = ahead; 603 } 604 605 /* 606 * Call the pager to retrieve the data, if any, after 607 * releasing the lock on the map. We hold a ref on 608 * fs.object and the pages are exclusive busied. 609 */ 610 unlock_map(&fs); 611 612 if (fs.object->type == OBJT_VNODE) { 613 vp = fs.object->handle; 614 if (vp == fs.vp) 615 goto vnode_locked; 616 else if (fs.vp != NULL) { 617 vput(fs.vp); 618 fs.vp = NULL; 619 } 620 locked = VOP_ISLOCKED(vp); 621 622 if (locked != LK_EXCLUSIVE) 623 locked = LK_SHARED; 624 /* Do not sleep for vnode lock while fs.m is busy */ 625 error = vget(vp, locked | LK_CANRECURSE | 626 LK_NOWAIT, curthread); 627 if (error != 0) { 628 vhold(vp); 629 release_page(&fs); 630 unlock_and_deallocate(&fs); 631 error = vget(vp, locked | LK_RETRY | 632 LK_CANRECURSE, curthread); 633 vdrop(vp); 634 fs.vp = vp; 635 KASSERT(error == 0, 636 ("vm_fault: vget failed")); 637 goto RetryFault; 638 } 639 fs.vp = vp; 640 } 641 vnode_locked: 642 KASSERT(fs.vp == NULL || !fs.map->system_map, 643 ("vm_fault: vnode-backed object mapped by system map")); 644 645 /* 646 * now we find out if any other pages should be paged 647 * in at this time this routine checks to see if the 648 * pages surrounding this fault reside in the same 649 * object as the page for this fault. If they do, 650 * then they are faulted in also into the object. The 651 * array "marray" returned contains an array of 652 * vm_page_t structs where one of them is the 653 * vm_page_t passed to the routine. The reqpage 654 * return value is the index into the marray for the 655 * vm_page_t passed to the routine. 656 * 657 * fs.m plus the additional pages are exclusive busied. 658 */ 659 faultcount = vm_fault_additional_pages( 660 fs.m, behind, ahead, marray, &reqpage); 661 662 rv = faultcount ? 663 vm_pager_get_pages(fs.object, marray, faultcount, 664 reqpage) : VM_PAGER_FAIL; 665 666 if (rv == VM_PAGER_OK) { 667 /* 668 * Found the page. Leave it busy while we play 669 * with it. 670 */ 671 672 /* 673 * Relookup in case pager changed page. Pager 674 * is responsible for disposition of old page 675 * if moved. 676 */ 677 fs.m = vm_page_lookup(fs.object, fs.pindex); 678 if (!fs.m) { 679 unlock_and_deallocate(&fs); 680 goto RetryFault; 681 } 682 683 hardfault++; 684 break; /* break to PAGE HAS BEEN FOUND */ 685 } 686 /* 687 * Remove the bogus page (which does not exist at this 688 * object/offset); before doing so, we must get back 689 * our object lock to preserve our invariant. 690 * 691 * Also wake up any other process that may want to bring 692 * in this page. 693 * 694 * If this is the top-level object, we must leave the 695 * busy page to prevent another process from rushing 696 * past us, and inserting the page in that object at 697 * the same time that we are. 698 */ 699 if (rv == VM_PAGER_ERROR) 700 printf("vm_fault: pager read error, pid %d (%s)\n", 701 curproc->p_pid, curproc->p_comm); 702 /* 703 * Data outside the range of the pager or an I/O error 704 */ 705 /* 706 * XXX - the check for kernel_map is a kludge to work 707 * around having the machine panic on a kernel space 708 * fault w/ I/O error. 709 */ 710 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 711 (rv == VM_PAGER_BAD)) { 712 vm_page_lock(fs.m); 713 vm_page_free(fs.m); 714 vm_page_unlock(fs.m); 715 fs.m = NULL; 716 unlock_and_deallocate(&fs); 717 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 718 } 719 if (fs.object != fs.first_object) { 720 vm_page_lock(fs.m); 721 vm_page_free(fs.m); 722 vm_page_unlock(fs.m); 723 fs.m = NULL; 724 /* 725 * XXX - we cannot just fall out at this 726 * point, m has been freed and is invalid! 727 */ 728 } 729 } 730 731 /* 732 * We get here if the object has default pager (or unwiring) 733 * or the pager doesn't have the page. 734 */ 735 if (fs.object == fs.first_object) 736 fs.first_m = fs.m; 737 738 /* 739 * Move on to the next object. Lock the next object before 740 * unlocking the current one. 741 */ 742 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 743 next_object = fs.object->backing_object; 744 if (next_object == NULL) { 745 /* 746 * If there's no object left, fill the page in the top 747 * object with zeros. 748 */ 749 if (fs.object != fs.first_object) { 750 vm_object_pip_wakeup(fs.object); 751 VM_OBJECT_WUNLOCK(fs.object); 752 753 fs.object = fs.first_object; 754 fs.pindex = fs.first_pindex; 755 fs.m = fs.first_m; 756 VM_OBJECT_WLOCK(fs.object); 757 } 758 fs.first_m = NULL; 759 760 /* 761 * Zero the page if necessary and mark it valid. 762 */ 763 if ((fs.m->flags & PG_ZERO) == 0) { 764 pmap_zero_page(fs.m); 765 } else { 766 PCPU_INC(cnt.v_ozfod); 767 } 768 PCPU_INC(cnt.v_zfod); 769 fs.m->valid = VM_PAGE_BITS_ALL; 770 /* Don't try to prefault neighboring pages. */ 771 faultcount = 1; 772 break; /* break to PAGE HAS BEEN FOUND */ 773 } else { 774 KASSERT(fs.object != next_object, 775 ("object loop %p", next_object)); 776 VM_OBJECT_WLOCK(next_object); 777 vm_object_pip_add(next_object, 1); 778 if (fs.object != fs.first_object) 779 vm_object_pip_wakeup(fs.object); 780 VM_OBJECT_WUNLOCK(fs.object); 781 fs.object = next_object; 782 } 783 } 784 785 vm_page_assert_xbusied(fs.m); 786 787 /* 788 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 789 * is held.] 790 */ 791 792 /* 793 * If the page is being written, but isn't already owned by the 794 * top-level object, we have to copy it into a new page owned by the 795 * top-level object. 796 */ 797 if (fs.object != fs.first_object) { 798 /* 799 * We only really need to copy if we want to write it. 800 */ 801 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 802 /* 803 * This allows pages to be virtually copied from a 804 * backing_object into the first_object, where the 805 * backing object has no other refs to it, and cannot 806 * gain any more refs. Instead of a bcopy, we just 807 * move the page from the backing object to the 808 * first object. Note that we must mark the page 809 * dirty in the first object so that it will go out 810 * to swap when needed. 811 */ 812 is_first_object_locked = FALSE; 813 if ( 814 /* 815 * Only one shadow object 816 */ 817 (fs.object->shadow_count == 1) && 818 /* 819 * No COW refs, except us 820 */ 821 (fs.object->ref_count == 1) && 822 /* 823 * No one else can look this object up 824 */ 825 (fs.object->handle == NULL) && 826 /* 827 * No other ways to look the object up 828 */ 829 ((fs.object->type == OBJT_DEFAULT) || 830 (fs.object->type == OBJT_SWAP)) && 831 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 832 /* 833 * We don't chase down the shadow chain 834 */ 835 fs.object == fs.first_object->backing_object) { 836 /* 837 * get rid of the unnecessary page 838 */ 839 vm_page_lock(fs.first_m); 840 vm_page_free(fs.first_m); 841 vm_page_unlock(fs.first_m); 842 /* 843 * grab the page and put it into the 844 * process'es object. The page is 845 * automatically made dirty. 846 */ 847 if (vm_page_rename(fs.m, fs.first_object, 848 fs.first_pindex)) { 849 unlock_and_deallocate(&fs); 850 goto RetryFault; 851 } 852 #if VM_NRESERVLEVEL > 0 853 /* 854 * Rename the reservation. 855 */ 856 vm_reserv_rename(fs.m, fs.first_object, 857 fs.object, OFF_TO_IDX( 858 fs.first_object->backing_object_offset)); 859 #endif 860 vm_page_xbusy(fs.m); 861 fs.first_m = fs.m; 862 fs.m = NULL; 863 PCPU_INC(cnt.v_cow_optim); 864 } else { 865 /* 866 * Oh, well, lets copy it. 867 */ 868 pmap_copy_page(fs.m, fs.first_m); 869 fs.first_m->valid = VM_PAGE_BITS_ALL; 870 if (wired && (fault_flags & 871 VM_FAULT_CHANGE_WIRING) == 0) { 872 vm_page_lock(fs.first_m); 873 vm_page_wire(fs.first_m); 874 vm_page_unlock(fs.first_m); 875 876 vm_page_lock(fs.m); 877 vm_page_unwire(fs.m, FALSE); 878 vm_page_unlock(fs.m); 879 } 880 /* 881 * We no longer need the old page or object. 882 */ 883 release_page(&fs); 884 } 885 /* 886 * fs.object != fs.first_object due to above 887 * conditional 888 */ 889 vm_object_pip_wakeup(fs.object); 890 VM_OBJECT_WUNLOCK(fs.object); 891 /* 892 * Only use the new page below... 893 */ 894 fs.object = fs.first_object; 895 fs.pindex = fs.first_pindex; 896 fs.m = fs.first_m; 897 if (!is_first_object_locked) 898 VM_OBJECT_WLOCK(fs.object); 899 PCPU_INC(cnt.v_cow_faults); 900 curthread->td_cow++; 901 } else { 902 prot &= ~VM_PROT_WRITE; 903 } 904 } 905 906 /* 907 * We must verify that the maps have not changed since our last 908 * lookup. 909 */ 910 if (!fs.lookup_still_valid) { 911 vm_object_t retry_object; 912 vm_pindex_t retry_pindex; 913 vm_prot_t retry_prot; 914 915 if (!vm_map_trylock_read(fs.map)) { 916 release_page(&fs); 917 unlock_and_deallocate(&fs); 918 goto RetryFault; 919 } 920 fs.lookup_still_valid = TRUE; 921 if (fs.map->timestamp != map_generation) { 922 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 923 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 924 925 /* 926 * If we don't need the page any longer, put it on the inactive 927 * list (the easiest thing to do here). If no one needs it, 928 * pageout will grab it eventually. 929 */ 930 if (result != KERN_SUCCESS) { 931 release_page(&fs); 932 unlock_and_deallocate(&fs); 933 934 /* 935 * If retry of map lookup would have blocked then 936 * retry fault from start. 937 */ 938 if (result == KERN_FAILURE) 939 goto RetryFault; 940 return (result); 941 } 942 if ((retry_object != fs.first_object) || 943 (retry_pindex != fs.first_pindex)) { 944 release_page(&fs); 945 unlock_and_deallocate(&fs); 946 goto RetryFault; 947 } 948 949 /* 950 * Check whether the protection has changed or the object has 951 * been copied while we left the map unlocked. Changing from 952 * read to write permission is OK - we leave the page 953 * write-protected, and catch the write fault. Changing from 954 * write to read permission means that we can't mark the page 955 * write-enabled after all. 956 */ 957 prot &= retry_prot; 958 } 959 } 960 /* 961 * If the page was filled by a pager, update the map entry's 962 * last read offset. Since the pager does not return the 963 * actual set of pages that it read, this update is based on 964 * the requested set. Typically, the requested and actual 965 * sets are the same. 966 * 967 * XXX The following assignment modifies the map 968 * without holding a write lock on it. 969 */ 970 if (hardfault) 971 fs.entry->next_read = fs.pindex + faultcount - reqpage; 972 973 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); 974 vm_page_assert_xbusied(fs.m); 975 976 /* 977 * Page must be completely valid or it is not fit to 978 * map into user space. vm_pager_get_pages() ensures this. 979 */ 980 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 981 ("vm_fault: page %p partially invalid", fs.m)); 982 VM_OBJECT_WUNLOCK(fs.object); 983 984 /* 985 * Put this page into the physical map. We had to do the unlock above 986 * because pmap_enter() may sleep. We don't put the page 987 * back on the active queue until later so that the pageout daemon 988 * won't find it (yet). 989 */ 990 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 991 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 992 if (faultcount != 1 && (fault_flags & VM_FAULT_CHANGE_WIRING) == 0 && 993 wired == 0) 994 vm_fault_prefault(&fs, vaddr, faultcount, reqpage); 995 VM_OBJECT_WLOCK(fs.object); 996 vm_page_lock(fs.m); 997 998 /* 999 * If the page is not wired down, then put it where the pageout daemon 1000 * can find it. 1001 */ 1002 if (fault_flags & VM_FAULT_CHANGE_WIRING) { 1003 if (wired) 1004 vm_page_wire(fs.m); 1005 else 1006 vm_page_unwire(fs.m, 1); 1007 } else 1008 vm_page_activate(fs.m); 1009 if (m_hold != NULL) { 1010 *m_hold = fs.m; 1011 vm_page_hold(fs.m); 1012 } 1013 vm_page_unlock(fs.m); 1014 vm_page_xunbusy(fs.m); 1015 1016 /* 1017 * Unlock everything, and return 1018 */ 1019 unlock_and_deallocate(&fs); 1020 if (hardfault) { 1021 PCPU_INC(cnt.v_io_faults); 1022 curthread->td_ru.ru_majflt++; 1023 } else 1024 curthread->td_ru.ru_minflt++; 1025 1026 return (KERN_SUCCESS); 1027 } 1028 1029 /* 1030 * Speed up the reclamation of up to "distance" pages that precede the 1031 * faulting pindex within the first object of the shadow chain. 1032 */ 1033 static void 1034 vm_fault_cache_behind(const struct faultstate *fs, int distance) 1035 { 1036 vm_object_t first_object, object; 1037 vm_page_t m, m_prev; 1038 vm_pindex_t pindex; 1039 1040 object = fs->object; 1041 VM_OBJECT_ASSERT_WLOCKED(object); 1042 first_object = fs->first_object; 1043 if (first_object != object) { 1044 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1045 VM_OBJECT_WUNLOCK(object); 1046 VM_OBJECT_WLOCK(first_object); 1047 VM_OBJECT_WLOCK(object); 1048 } 1049 } 1050 /* Neither fictitious nor unmanaged pages can be cached. */ 1051 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1052 if (fs->first_pindex < distance) 1053 pindex = 0; 1054 else 1055 pindex = fs->first_pindex - distance; 1056 if (pindex < OFF_TO_IDX(fs->entry->offset)) 1057 pindex = OFF_TO_IDX(fs->entry->offset); 1058 m = first_object != object ? fs->first_m : fs->m; 1059 vm_page_assert_xbusied(m); 1060 m_prev = vm_page_prev(m); 1061 while ((m = m_prev) != NULL && m->pindex >= pindex && 1062 m->valid == VM_PAGE_BITS_ALL) { 1063 m_prev = vm_page_prev(m); 1064 if (vm_page_busied(m)) 1065 continue; 1066 vm_page_lock(m); 1067 if (m->hold_count == 0 && m->wire_count == 0) { 1068 pmap_remove_all(m); 1069 vm_page_aflag_clear(m, PGA_REFERENCED); 1070 if (m->dirty != 0) 1071 vm_page_deactivate(m); 1072 else 1073 vm_page_cache(m); 1074 } 1075 vm_page_unlock(m); 1076 } 1077 } 1078 if (first_object != object) 1079 VM_OBJECT_WUNLOCK(first_object); 1080 } 1081 1082 /* 1083 * vm_fault_prefault provides a quick way of clustering 1084 * pagefaults into a processes address space. It is a "cousin" 1085 * of vm_map_pmap_enter, except it runs at page fault time instead 1086 * of mmap time. 1087 */ 1088 static void 1089 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1090 int faultcount, int reqpage) 1091 { 1092 pmap_t pmap; 1093 vm_map_entry_t entry; 1094 vm_object_t backing_object, lobject; 1095 vm_offset_t addr, starta; 1096 vm_pindex_t pindex; 1097 vm_page_t m; 1098 int backward, forward, i; 1099 1100 pmap = fs->map->pmap; 1101 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1102 return; 1103 1104 if (faultcount > 0) { 1105 backward = reqpage; 1106 forward = faultcount - reqpage - 1; 1107 } else { 1108 backward = PFBAK; 1109 forward = PFFOR; 1110 } 1111 entry = fs->entry; 1112 1113 starta = addra - backward * PAGE_SIZE; 1114 if (starta < entry->start) { 1115 starta = entry->start; 1116 } else if (starta > addra) { 1117 starta = 0; 1118 } 1119 1120 /* 1121 * Generate the sequence of virtual addresses that are candidates for 1122 * prefaulting in an outward spiral from the faulting virtual address, 1123 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1124 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1125 * If the candidate address doesn't have a backing physical page, then 1126 * the loop immediately terminates. 1127 */ 1128 for (i = 0; i < 2 * imax(backward, forward); i++) { 1129 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1130 PAGE_SIZE); 1131 if (addr > addra + forward * PAGE_SIZE) 1132 addr = 0; 1133 1134 if (addr < starta || addr >= entry->end) 1135 continue; 1136 1137 if (!pmap_is_prefaultable(pmap, addr)) 1138 continue; 1139 1140 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1141 lobject = entry->object.vm_object; 1142 VM_OBJECT_RLOCK(lobject); 1143 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1144 lobject->type == OBJT_DEFAULT && 1145 (backing_object = lobject->backing_object) != NULL) { 1146 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1147 0, ("vm_fault_prefault: unaligned object offset")); 1148 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1149 VM_OBJECT_RLOCK(backing_object); 1150 VM_OBJECT_RUNLOCK(lobject); 1151 lobject = backing_object; 1152 } 1153 if (m == NULL) { 1154 VM_OBJECT_RUNLOCK(lobject); 1155 break; 1156 } 1157 if (m->valid == VM_PAGE_BITS_ALL && 1158 (m->flags & PG_FICTITIOUS) == 0) 1159 pmap_enter_quick(pmap, addr, m, entry->protection); 1160 VM_OBJECT_RUNLOCK(lobject); 1161 } 1162 } 1163 1164 /* 1165 * Hold each of the physical pages that are mapped by the specified range of 1166 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1167 * and allow the specified types of access, "prot". If all of the implied 1168 * pages are successfully held, then the number of held pages is returned 1169 * together with pointers to those pages in the array "ma". However, if any 1170 * of the pages cannot be held, -1 is returned. 1171 */ 1172 int 1173 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1174 vm_prot_t prot, vm_page_t *ma, int max_count) 1175 { 1176 vm_offset_t end, va; 1177 vm_page_t *mp; 1178 int count; 1179 boolean_t pmap_failed; 1180 1181 if (len == 0) 1182 return (0); 1183 end = round_page(addr + len); 1184 addr = trunc_page(addr); 1185 1186 /* 1187 * Check for illegal addresses. 1188 */ 1189 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1190 return (-1); 1191 1192 if (atop(end - addr) > max_count) 1193 panic("vm_fault_quick_hold_pages: count > max_count"); 1194 count = atop(end - addr); 1195 1196 /* 1197 * Most likely, the physical pages are resident in the pmap, so it is 1198 * faster to try pmap_extract_and_hold() first. 1199 */ 1200 pmap_failed = FALSE; 1201 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1202 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1203 if (*mp == NULL) 1204 pmap_failed = TRUE; 1205 else if ((prot & VM_PROT_WRITE) != 0 && 1206 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1207 /* 1208 * Explicitly dirty the physical page. Otherwise, the 1209 * caller's changes may go unnoticed because they are 1210 * performed through an unmanaged mapping or by a DMA 1211 * operation. 1212 * 1213 * The object lock is not held here. 1214 * See vm_page_clear_dirty_mask(). 1215 */ 1216 vm_page_dirty(*mp); 1217 } 1218 } 1219 if (pmap_failed) { 1220 /* 1221 * One or more pages could not be held by the pmap. Either no 1222 * page was mapped at the specified virtual address or that 1223 * mapping had insufficient permissions. Attempt to fault in 1224 * and hold these pages. 1225 */ 1226 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1227 if (*mp == NULL && vm_fault_hold(map, va, prot, 1228 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1229 goto error; 1230 } 1231 return (count); 1232 error: 1233 for (mp = ma; mp < ma + count; mp++) 1234 if (*mp != NULL) { 1235 vm_page_lock(*mp); 1236 vm_page_unhold(*mp); 1237 vm_page_unlock(*mp); 1238 } 1239 return (-1); 1240 } 1241 1242 /* 1243 * Routine: 1244 * vm_fault_copy_entry 1245 * Function: 1246 * Create new shadow object backing dst_entry with private copy of 1247 * all underlying pages. When src_entry is equal to dst_entry, 1248 * function implements COW for wired-down map entry. Otherwise, 1249 * it forks wired entry into dst_map. 1250 * 1251 * In/out conditions: 1252 * The source and destination maps must be locked for write. 1253 * The source map entry must be wired down (or be a sharing map 1254 * entry corresponding to a main map entry that is wired down). 1255 */ 1256 void 1257 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1258 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1259 vm_ooffset_t *fork_charge) 1260 { 1261 vm_object_t backing_object, dst_object, object, src_object; 1262 vm_pindex_t dst_pindex, pindex, src_pindex; 1263 vm_prot_t access, prot; 1264 vm_offset_t vaddr; 1265 vm_page_t dst_m; 1266 vm_page_t src_m; 1267 boolean_t upgrade; 1268 1269 #ifdef lint 1270 src_map++; 1271 #endif /* lint */ 1272 1273 upgrade = src_entry == dst_entry; 1274 access = prot = dst_entry->protection; 1275 1276 src_object = src_entry->object.vm_object; 1277 src_pindex = OFF_TO_IDX(src_entry->offset); 1278 1279 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1280 dst_object = src_object; 1281 vm_object_reference(dst_object); 1282 } else { 1283 /* 1284 * Create the top-level object for the destination entry. (Doesn't 1285 * actually shadow anything - we copy the pages directly.) 1286 */ 1287 dst_object = vm_object_allocate(OBJT_DEFAULT, 1288 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1289 #if VM_NRESERVLEVEL > 0 1290 dst_object->flags |= OBJ_COLORED; 1291 dst_object->pg_color = atop(dst_entry->start); 1292 #endif 1293 } 1294 1295 VM_OBJECT_WLOCK(dst_object); 1296 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1297 ("vm_fault_copy_entry: vm_object not NULL")); 1298 if (src_object != dst_object) { 1299 dst_entry->object.vm_object = dst_object; 1300 dst_entry->offset = 0; 1301 dst_object->charge = dst_entry->end - dst_entry->start; 1302 } 1303 if (fork_charge != NULL) { 1304 KASSERT(dst_entry->cred == NULL, 1305 ("vm_fault_copy_entry: leaked swp charge")); 1306 dst_object->cred = curthread->td_ucred; 1307 crhold(dst_object->cred); 1308 *fork_charge += dst_object->charge; 1309 } else if (dst_object->cred == NULL) { 1310 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1311 dst_entry)); 1312 dst_object->cred = dst_entry->cred; 1313 dst_entry->cred = NULL; 1314 } 1315 1316 /* 1317 * If not an upgrade, then enter the mappings in the pmap as 1318 * read and/or execute accesses. Otherwise, enter them as 1319 * write accesses. 1320 * 1321 * A writeable large page mapping is only created if all of 1322 * the constituent small page mappings are modified. Marking 1323 * PTEs as modified on inception allows promotion to happen 1324 * without taking potentially large number of soft faults. 1325 */ 1326 if (!upgrade) 1327 access &= ~VM_PROT_WRITE; 1328 1329 /* 1330 * Loop through all of the virtual pages within the entry's 1331 * range, copying each page from the source object to the 1332 * destination object. Since the source is wired, those pages 1333 * must exist. In contrast, the destination is pageable. 1334 * Since the destination object does share any backing storage 1335 * with the source object, all of its pages must be dirtied, 1336 * regardless of whether they can be written. 1337 */ 1338 for (vaddr = dst_entry->start, dst_pindex = 0; 1339 vaddr < dst_entry->end; 1340 vaddr += PAGE_SIZE, dst_pindex++) { 1341 again: 1342 /* 1343 * Find the page in the source object, and copy it in. 1344 * Because the source is wired down, the page will be 1345 * in memory. 1346 */ 1347 if (src_object != dst_object) 1348 VM_OBJECT_RLOCK(src_object); 1349 object = src_object; 1350 pindex = src_pindex + dst_pindex; 1351 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1352 (backing_object = object->backing_object) != NULL) { 1353 /* 1354 * Unless the source mapping is read-only or 1355 * it is presently being upgraded from 1356 * read-only, the first object in the shadow 1357 * chain should provide all of the pages. In 1358 * other words, this loop body should never be 1359 * executed when the source mapping is already 1360 * read/write. 1361 */ 1362 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1363 upgrade, 1364 ("vm_fault_copy_entry: main object missing page")); 1365 1366 VM_OBJECT_RLOCK(backing_object); 1367 pindex += OFF_TO_IDX(object->backing_object_offset); 1368 if (object != dst_object) 1369 VM_OBJECT_RUNLOCK(object); 1370 object = backing_object; 1371 } 1372 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1373 1374 if (object != dst_object) { 1375 /* 1376 * Allocate a page in the destination object. 1377 */ 1378 dst_m = vm_page_alloc(dst_object, (src_object == 1379 dst_object ? src_pindex : 0) + dst_pindex, 1380 VM_ALLOC_NORMAL); 1381 if (dst_m == NULL) { 1382 VM_OBJECT_WUNLOCK(dst_object); 1383 VM_OBJECT_RUNLOCK(object); 1384 VM_WAIT; 1385 VM_OBJECT_WLOCK(dst_object); 1386 goto again; 1387 } 1388 pmap_copy_page(src_m, dst_m); 1389 VM_OBJECT_RUNLOCK(object); 1390 dst_m->valid = VM_PAGE_BITS_ALL; 1391 dst_m->dirty = VM_PAGE_BITS_ALL; 1392 } else { 1393 dst_m = src_m; 1394 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1395 goto again; 1396 vm_page_xbusy(dst_m); 1397 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1398 ("invalid dst page %p", dst_m)); 1399 } 1400 VM_OBJECT_WUNLOCK(dst_object); 1401 1402 /* 1403 * Enter it in the pmap. If a wired, copy-on-write 1404 * mapping is being replaced by a write-enabled 1405 * mapping, then wire that new mapping. 1406 */ 1407 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1408 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1409 1410 /* 1411 * Mark it no longer busy, and put it on the active list. 1412 */ 1413 VM_OBJECT_WLOCK(dst_object); 1414 1415 if (upgrade) { 1416 if (src_m != dst_m) { 1417 vm_page_lock(src_m); 1418 vm_page_unwire(src_m, 0); 1419 vm_page_unlock(src_m); 1420 vm_page_lock(dst_m); 1421 vm_page_wire(dst_m); 1422 vm_page_unlock(dst_m); 1423 } else { 1424 KASSERT(dst_m->wire_count > 0, 1425 ("dst_m %p is not wired", dst_m)); 1426 } 1427 } else { 1428 vm_page_lock(dst_m); 1429 vm_page_activate(dst_m); 1430 vm_page_unlock(dst_m); 1431 } 1432 vm_page_xunbusy(dst_m); 1433 } 1434 VM_OBJECT_WUNLOCK(dst_object); 1435 if (upgrade) { 1436 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1437 vm_object_deallocate(src_object); 1438 } 1439 } 1440 1441 1442 /* 1443 * This routine checks around the requested page for other pages that 1444 * might be able to be faulted in. This routine brackets the viable 1445 * pages for the pages to be paged in. 1446 * 1447 * Inputs: 1448 * m, rbehind, rahead 1449 * 1450 * Outputs: 1451 * marray (array of vm_page_t), reqpage (index of requested page) 1452 * 1453 * Return value: 1454 * number of pages in marray 1455 */ 1456 static int 1457 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1458 vm_page_t m; 1459 int rbehind; 1460 int rahead; 1461 vm_page_t *marray; 1462 int *reqpage; 1463 { 1464 int i,j; 1465 vm_object_t object; 1466 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1467 vm_page_t rtm; 1468 int cbehind, cahead; 1469 1470 VM_OBJECT_ASSERT_WLOCKED(m->object); 1471 1472 object = m->object; 1473 pindex = m->pindex; 1474 cbehind = cahead = 0; 1475 1476 /* 1477 * if the requested page is not available, then give up now 1478 */ 1479 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1480 return 0; 1481 } 1482 1483 if ((cbehind == 0) && (cahead == 0)) { 1484 *reqpage = 0; 1485 marray[0] = m; 1486 return 1; 1487 } 1488 1489 if (rahead > cahead) { 1490 rahead = cahead; 1491 } 1492 1493 if (rbehind > cbehind) { 1494 rbehind = cbehind; 1495 } 1496 1497 /* 1498 * scan backward for the read behind pages -- in memory 1499 */ 1500 if (pindex > 0) { 1501 if (rbehind > pindex) { 1502 rbehind = pindex; 1503 startpindex = 0; 1504 } else { 1505 startpindex = pindex - rbehind; 1506 } 1507 1508 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1509 rtm->pindex >= startpindex) 1510 startpindex = rtm->pindex + 1; 1511 1512 /* tpindex is unsigned; beware of numeric underflow. */ 1513 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1514 tpindex < pindex; i++, tpindex--) { 1515 1516 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1517 VM_ALLOC_IFNOTCACHED); 1518 if (rtm == NULL) { 1519 /* 1520 * Shift the allocated pages to the 1521 * beginning of the array. 1522 */ 1523 for (j = 0; j < i; j++) { 1524 marray[j] = marray[j + tpindex + 1 - 1525 startpindex]; 1526 } 1527 break; 1528 } 1529 1530 marray[tpindex - startpindex] = rtm; 1531 } 1532 } else { 1533 startpindex = 0; 1534 i = 0; 1535 } 1536 1537 marray[i] = m; 1538 /* page offset of the required page */ 1539 *reqpage = i; 1540 1541 tpindex = pindex + 1; 1542 i++; 1543 1544 /* 1545 * scan forward for the read ahead pages 1546 */ 1547 endpindex = tpindex + rahead; 1548 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1549 endpindex = rtm->pindex; 1550 if (endpindex > object->size) 1551 endpindex = object->size; 1552 1553 for (; tpindex < endpindex; i++, tpindex++) { 1554 1555 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1556 VM_ALLOC_IFNOTCACHED); 1557 if (rtm == NULL) { 1558 break; 1559 } 1560 1561 marray[i] = rtm; 1562 } 1563 1564 /* return number of pages */ 1565 return i; 1566 } 1567 1568 /* 1569 * Block entry into the machine-independent layer's page fault handler by 1570 * the calling thread. Subsequent calls to vm_fault() by that thread will 1571 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1572 * spurious page faults. 1573 */ 1574 int 1575 vm_fault_disable_pagefaults(void) 1576 { 1577 1578 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1579 } 1580 1581 void 1582 vm_fault_enable_pagefaults(int save) 1583 { 1584 1585 curthread_pflags_restore(save); 1586 }
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