1 /*- 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 1994 John S. Dyson 5 * All rights reserved. 6 * Copyright (c) 1994 David Greenman 7 * All rights reserved. 8 * 9 * 10 * This code is derived from software contributed to Berkeley by 11 * The Mach Operating System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 42 * 43 * 44 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 45 * All rights reserved. 46 * 47 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 48 * 49 * Permission to use, copy, modify and distribute this software and 50 * its documentation is hereby granted, provided that both the copyright 51 * notice and this permission notice appear in all copies of the 52 * software, derivative works or modified versions, and any portions 53 * thereof, and that both notices appear in supporting documentation. 54 * 55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 58 * 59 * Carnegie Mellon requests users of this software to return to 60 * 61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 62 * School of Computer Science 63 * Carnegie Mellon University 64 * Pittsburgh PA 15213-3890 65 * 66 * any improvements or extensions that they make and grant Carnegie the 67 * rights to redistribute these changes. 68 */ 69 70 /* 71 * Page fault handling module. 72 */ 73 74 #include <sys/cdefs.h> 75 __FBSDID("$FreeBSD$"); 76 77 #include "opt_ktrace.h" 78 #include "opt_vm.h" 79 80 #include <sys/param.h> 81 #include <sys/systm.h> 82 #include <sys/kernel.h> 83 #include <sys/lock.h> 84 #include <sys/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> 104 105 #define PFBAK 4 106 #define PFFOR 4 107 108 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 109 static void vm_fault_unwire(vm_map_t, vm_offset_t, vm_offset_t, boolean_t); 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 /* 179 * TRYPAGER - used by vm_fault to calculate whether the pager for the 180 * current object *might* contain the page. 181 * 182 * default objects are zero-fill, there is no real pager. 183 */ 184 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 185 ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 || wired)) 186 187 /* 188 * vm_fault: 189 * 190 * Handle a page fault occurring at the given address, 191 * requiring the given permissions, in the map specified. 192 * If successful, the page is inserted into the 193 * associated physical map. 194 * 195 * NOTE: the given address should be truncated to the 196 * proper page address. 197 * 198 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 199 * a standard error specifying why the fault is fatal is returned. 200 * 201 * The map in question must be referenced, and remains so. 202 * Caller may hold no locks. 203 */ 204 int 205 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 206 int fault_flags) 207 { 208 struct thread *td; 209 int result; 210 211 td = curthread; 212 if ((td->td_pflags & TDP_NOFAULTING) != 0) 213 return (KERN_PROTECTION_FAILURE); 214 #ifdef KTRACE 215 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 216 ktrfault(vaddr, fault_type); 217 #endif 218 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 219 NULL); 220 #ifdef KTRACE 221 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 222 ktrfaultend(result); 223 #endif 224 return (result); 225 } 226 227 int 228 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 229 int fault_flags, vm_page_t *m_hold) 230 { 231 vm_prot_t prot; 232 long ahead, behind; 233 int alloc_req, era, faultcount, nera, reqpage, result; 234 boolean_t growstack, is_first_object_locked, wired; 235 int map_generation; 236 vm_object_t next_object; 237 vm_page_t marray[VM_FAULT_READ_MAX]; 238 int hardfault; 239 struct faultstate fs; 240 struct vnode *vp; 241 int locked, error; 242 243 hardfault = 0; 244 growstack = TRUE; 245 PCPU_INC(cnt.v_vm_faults); 246 fs.vp = NULL; 247 faultcount = reqpage = 0; 248 249 RetryFault:; 250 251 /* 252 * Find the backing store object and offset into it to begin the 253 * search. 254 */ 255 fs.map = map; 256 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 257 &fs.first_object, &fs.first_pindex, &prot, &wired); 258 if (result != KERN_SUCCESS) { 259 if (growstack && result == KERN_INVALID_ADDRESS && 260 map != kernel_map) { 261 result = vm_map_growstack(curproc, vaddr); 262 if (result != KERN_SUCCESS) 263 return (KERN_FAILURE); 264 growstack = FALSE; 265 goto RetryFault; 266 } 267 return (result); 268 } 269 270 map_generation = fs.map->timestamp; 271 272 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 273 if ((curthread->td_pflags & TDP_DEVMEMIO) != 0) { 274 vm_map_unlock_read(fs.map); 275 return (KERN_FAILURE); 276 } 277 panic("vm_fault: fault on nofault entry, addr: %lx", 278 (u_long)vaddr); 279 } 280 281 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 282 fs.entry->wiring_thread != curthread) { 283 vm_map_unlock_read(fs.map); 284 vm_map_lock(fs.map); 285 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 286 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 287 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 288 vm_map_unlock_and_wait(fs.map, 0); 289 } else 290 vm_map_unlock(fs.map); 291 goto RetryFault; 292 } 293 294 /* 295 * Make a reference to this object to prevent its disposal while we 296 * are messing with it. Once we have the reference, the map is free 297 * to be diddled. Since objects reference their shadows (and copies), 298 * they will stay around as well. 299 * 300 * Bump the paging-in-progress count to prevent size changes (e.g. 301 * truncation operations) during I/O. This must be done after 302 * obtaining the vnode lock in order to avoid possible deadlocks. 303 */ 304 VM_OBJECT_WLOCK(fs.first_object); 305 vm_object_reference_locked(fs.first_object); 306 vm_object_pip_add(fs.first_object, 1); 307 308 fs.lookup_still_valid = TRUE; 309 310 if (wired) 311 fault_type = prot | (fault_type & VM_PROT_COPY); 312 313 fs.first_m = NULL; 314 315 /* 316 * Search for the page at object/offset. 317 */ 318 fs.object = fs.first_object; 319 fs.pindex = fs.first_pindex; 320 while (TRUE) { 321 /* 322 * If the object is dead, we stop here 323 */ 324 if (fs.object->flags & OBJ_DEAD) { 325 unlock_and_deallocate(&fs); 326 return (KERN_PROTECTION_FAILURE); 327 } 328 329 /* 330 * See if page is resident 331 */ 332 fs.m = vm_page_lookup(fs.object, fs.pindex); 333 if (fs.m != NULL) { 334 /* 335 * Wait/Retry if the page is busy. We have to do this 336 * if the page is either exclusive or shared busy 337 * because the vm_pager may be using read busy for 338 * pageouts (and even pageins if it is the vnode 339 * pager), and we could end up trying to pagein and 340 * pageout the same page simultaneously. 341 * 342 * We can theoretically allow the busy case on a read 343 * fault if the page is marked valid, but since such 344 * pages are typically already pmap'd, putting that 345 * special case in might be more effort then it is 346 * worth. We cannot under any circumstances mess 347 * around with a shared busied page except, perhaps, 348 * to pmap it. 349 */ 350 if (vm_page_busied(fs.m)) { 351 /* 352 * Reference the page before unlocking and 353 * sleeping so that the page daemon is less 354 * likely to reclaim it. 355 */ 356 vm_page_aflag_set(fs.m, PGA_REFERENCED); 357 if (fs.object != fs.first_object) { 358 if (!VM_OBJECT_TRYWLOCK( 359 fs.first_object)) { 360 VM_OBJECT_WUNLOCK(fs.object); 361 VM_OBJECT_WLOCK(fs.first_object); 362 VM_OBJECT_WLOCK(fs.object); 363 } 364 vm_page_lock(fs.first_m); 365 vm_page_free(fs.first_m); 366 vm_page_unlock(fs.first_m); 367 vm_object_pip_wakeup(fs.first_object); 368 VM_OBJECT_WUNLOCK(fs.first_object); 369 fs.first_m = NULL; 370 } 371 unlock_map(&fs); 372 if (fs.m == vm_page_lookup(fs.object, 373 fs.pindex)) { 374 vm_page_sleep_if_busy(fs.m, "vmpfw"); 375 } 376 vm_object_pip_wakeup(fs.object); 377 VM_OBJECT_WUNLOCK(fs.object); 378 PCPU_INC(cnt.v_intrans); 379 vm_object_deallocate(fs.first_object); 380 goto RetryFault; 381 } 382 vm_page_lock(fs.m); 383 vm_page_remque(fs.m); 384 vm_page_unlock(fs.m); 385 386 /* 387 * Mark page busy for other processes, and the 388 * pagedaemon. If it still isn't completely valid 389 * (readable), jump to readrest, else break-out ( we 390 * found the page ). 391 */ 392 vm_page_xbusy(fs.m); 393 if (fs.m->valid != VM_PAGE_BITS_ALL) 394 goto readrest; 395 break; 396 } 397 398 /* 399 * Page is not resident, If this is the search termination 400 * or the pager might contain the page, allocate a new page. 401 */ 402 if (TRYPAGER || fs.object == fs.first_object) { 403 if (fs.pindex >= fs.object->size) { 404 unlock_and_deallocate(&fs); 405 return (KERN_PROTECTION_FAILURE); 406 } 407 408 /* 409 * Allocate a new page for this object/offset pair. 410 * 411 * Unlocked read of the p_flag is harmless. At 412 * worst, the P_KILLED might be not observed 413 * there, and allocation can fail, causing 414 * restart and new reading of the p_flag. 415 */ 416 fs.m = NULL; 417 if (!vm_page_count_severe() || P_KILLED(curproc)) { 418 #if VM_NRESERVLEVEL > 0 419 if ((fs.object->flags & OBJ_COLORED) == 0) { 420 fs.object->flags |= OBJ_COLORED; 421 fs.object->pg_color = atop(vaddr) - 422 fs.pindex; 423 } 424 #endif 425 alloc_req = P_KILLED(curproc) ? 426 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 427 if (fs.object->type != OBJT_VNODE && 428 fs.object->backing_object == NULL) 429 alloc_req |= VM_ALLOC_ZERO; 430 fs.m = vm_page_alloc(fs.object, fs.pindex, 431 alloc_req); 432 } 433 if (fs.m == NULL) { 434 unlock_and_deallocate(&fs); 435 VM_WAITPFAULT; 436 goto RetryFault; 437 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 438 break; 439 } 440 441 readrest: 442 /* 443 * We have found a valid page or we have allocated a new page. 444 * The page thus may not be valid or may not be entirely 445 * valid. 446 * 447 * Attempt to fault-in the page if there is a chance that the 448 * pager has it, and potentially fault in additional pages 449 * at the same time. 450 */ 451 if (TRYPAGER) { 452 int rv; 453 u_char behavior = vm_map_entry_behavior(fs.entry); 454 455 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 456 P_KILLED(curproc)) { 457 behind = 0; 458 ahead = 0; 459 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 460 behind = 0; 461 ahead = atop(fs.entry->end - vaddr) - 1; 462 if (ahead > VM_FAULT_READ_AHEAD_MAX) 463 ahead = VM_FAULT_READ_AHEAD_MAX; 464 if (fs.pindex == fs.entry->next_read) 465 vm_fault_cache_behind(&fs, 466 VM_FAULT_READ_MAX); 467 } else { 468 /* 469 * If this is a sequential page fault, then 470 * arithmetically increase the number of pages 471 * in the read-ahead window. Otherwise, reset 472 * the read-ahead window to its smallest size. 473 */ 474 behind = atop(vaddr - fs.entry->start); 475 if (behind > VM_FAULT_READ_BEHIND) 476 behind = VM_FAULT_READ_BEHIND; 477 ahead = atop(fs.entry->end - vaddr) - 1; 478 era = fs.entry->read_ahead; 479 if (fs.pindex == fs.entry->next_read) { 480 nera = era + behind; 481 if (nera > VM_FAULT_READ_AHEAD_MAX) 482 nera = VM_FAULT_READ_AHEAD_MAX; 483 behind = 0; 484 if (ahead > nera) 485 ahead = nera; 486 if (era == VM_FAULT_READ_AHEAD_MAX) 487 vm_fault_cache_behind(&fs, 488 VM_FAULT_CACHE_BEHIND); 489 } else if (ahead > VM_FAULT_READ_AHEAD_MIN) 490 ahead = VM_FAULT_READ_AHEAD_MIN; 491 if (era != ahead) 492 fs.entry->read_ahead = ahead; 493 } 494 495 /* 496 * Call the pager to retrieve the data, if any, after 497 * releasing the lock on the map. We hold a ref on 498 * fs.object and the pages are exclusive busied. 499 */ 500 unlock_map(&fs); 501 502 if (fs.object->type == OBJT_VNODE) { 503 vp = fs.object->handle; 504 if (vp == fs.vp) 505 goto vnode_locked; 506 else if (fs.vp != NULL) { 507 vput(fs.vp); 508 fs.vp = NULL; 509 } 510 locked = VOP_ISLOCKED(vp); 511 512 if (locked != LK_EXCLUSIVE) 513 locked = LK_SHARED; 514 /* Do not sleep for vnode lock while fs.m is busy */ 515 error = vget(vp, locked | LK_CANRECURSE | 516 LK_NOWAIT, curthread); 517 if (error != 0) { 518 vhold(vp); 519 release_page(&fs); 520 unlock_and_deallocate(&fs); 521 error = vget(vp, locked | LK_RETRY | 522 LK_CANRECURSE, curthread); 523 vdrop(vp); 524 fs.vp = vp; 525 KASSERT(error == 0, 526 ("vm_fault: vget failed")); 527 goto RetryFault; 528 } 529 fs.vp = vp; 530 } 531 vnode_locked: 532 KASSERT(fs.vp == NULL || !fs.map->system_map, 533 ("vm_fault: vnode-backed object mapped by system map")); 534 535 /* 536 * now we find out if any other pages should be paged 537 * in at this time this routine checks to see if the 538 * pages surrounding this fault reside in the same 539 * object as the page for this fault. If they do, 540 * then they are faulted in also into the object. The 541 * array "marray" returned contains an array of 542 * vm_page_t structs where one of them is the 543 * vm_page_t passed to the routine. The reqpage 544 * return value is the index into the marray for the 545 * vm_page_t passed to the routine. 546 * 547 * fs.m plus the additional pages are exclusive busied. 548 */ 549 faultcount = vm_fault_additional_pages( 550 fs.m, behind, ahead, marray, &reqpage); 551 552 rv = faultcount ? 553 vm_pager_get_pages(fs.object, marray, faultcount, 554 reqpage) : VM_PAGER_FAIL; 555 556 if (rv == VM_PAGER_OK) { 557 /* 558 * Found the page. Leave it busy while we play 559 * with it. 560 */ 561 562 /* 563 * Relookup in case pager changed page. Pager 564 * is responsible for disposition of old page 565 * if moved. 566 */ 567 fs.m = vm_page_lookup(fs.object, fs.pindex); 568 if (!fs.m) { 569 unlock_and_deallocate(&fs); 570 goto RetryFault; 571 } 572 573 hardfault++; 574 break; /* break to PAGE HAS BEEN FOUND */ 575 } 576 /* 577 * Remove the bogus page (which does not exist at this 578 * object/offset); before doing so, we must get back 579 * our object lock to preserve our invariant. 580 * 581 * Also wake up any other process that may want to bring 582 * in this page. 583 * 584 * If this is the top-level object, we must leave the 585 * busy page to prevent another process from rushing 586 * past us, and inserting the page in that object at 587 * the same time that we are. 588 */ 589 if (rv == VM_PAGER_ERROR) 590 printf("vm_fault: pager read error, pid %d (%s)\n", 591 curproc->p_pid, curproc->p_comm); 592 /* 593 * Data outside the range of the pager or an I/O error 594 */ 595 /* 596 * XXX - the check for kernel_map is a kludge to work 597 * around having the machine panic on a kernel space 598 * fault w/ I/O error. 599 */ 600 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 601 (rv == VM_PAGER_BAD)) { 602 vm_page_lock(fs.m); 603 vm_page_free(fs.m); 604 vm_page_unlock(fs.m); 605 fs.m = NULL; 606 unlock_and_deallocate(&fs); 607 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 608 } 609 if (fs.object != fs.first_object) { 610 vm_page_lock(fs.m); 611 vm_page_free(fs.m); 612 vm_page_unlock(fs.m); 613 fs.m = NULL; 614 /* 615 * XXX - we cannot just fall out at this 616 * point, m has been freed and is invalid! 617 */ 618 } 619 } 620 621 /* 622 * We get here if the object has default pager (or unwiring) 623 * or the pager doesn't have the page. 624 */ 625 if (fs.object == fs.first_object) 626 fs.first_m = fs.m; 627 628 /* 629 * Move on to the next object. Lock the next object before 630 * unlocking the current one. 631 */ 632 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 633 next_object = fs.object->backing_object; 634 if (next_object == NULL) { 635 /* 636 * If there's no object left, fill the page in the top 637 * object with zeros. 638 */ 639 if (fs.object != fs.first_object) { 640 vm_object_pip_wakeup(fs.object); 641 VM_OBJECT_WUNLOCK(fs.object); 642 643 fs.object = fs.first_object; 644 fs.pindex = fs.first_pindex; 645 fs.m = fs.first_m; 646 VM_OBJECT_WLOCK(fs.object); 647 } 648 fs.first_m = NULL; 649 650 /* 651 * Zero the page if necessary and mark it valid. 652 */ 653 if ((fs.m->flags & PG_ZERO) == 0) { 654 pmap_zero_page(fs.m); 655 } else { 656 PCPU_INC(cnt.v_ozfod); 657 } 658 PCPU_INC(cnt.v_zfod); 659 fs.m->valid = VM_PAGE_BITS_ALL; 660 /* Don't try to prefault neighboring pages. */ 661 faultcount = 1; 662 break; /* break to PAGE HAS BEEN FOUND */ 663 } else { 664 KASSERT(fs.object != next_object, 665 ("object loop %p", next_object)); 666 VM_OBJECT_WLOCK(next_object); 667 vm_object_pip_add(next_object, 1); 668 if (fs.object != fs.first_object) 669 vm_object_pip_wakeup(fs.object); 670 VM_OBJECT_WUNLOCK(fs.object); 671 fs.object = next_object; 672 } 673 } 674 675 vm_page_assert_xbusied(fs.m); 676 677 /* 678 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 679 * is held.] 680 */ 681 682 /* 683 * If the page is being written, but isn't already owned by the 684 * top-level object, we have to copy it into a new page owned by the 685 * top-level object. 686 */ 687 if (fs.object != fs.first_object) { 688 /* 689 * We only really need to copy if we want to write it. 690 */ 691 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 692 /* 693 * This allows pages to be virtually copied from a 694 * backing_object into the first_object, where the 695 * backing object has no other refs to it, and cannot 696 * gain any more refs. Instead of a bcopy, we just 697 * move the page from the backing object to the 698 * first object. Note that we must mark the page 699 * dirty in the first object so that it will go out 700 * to swap when needed. 701 */ 702 is_first_object_locked = FALSE; 703 if ( 704 /* 705 * Only one shadow object 706 */ 707 (fs.object->shadow_count == 1) && 708 /* 709 * No COW refs, except us 710 */ 711 (fs.object->ref_count == 1) && 712 /* 713 * No one else can look this object up 714 */ 715 (fs.object->handle == NULL) && 716 /* 717 * No other ways to look the object up 718 */ 719 ((fs.object->type == OBJT_DEFAULT) || 720 (fs.object->type == OBJT_SWAP)) && 721 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 722 /* 723 * We don't chase down the shadow chain 724 */ 725 fs.object == fs.first_object->backing_object) { 726 /* 727 * get rid of the unnecessary page 728 */ 729 vm_page_lock(fs.first_m); 730 vm_page_free(fs.first_m); 731 vm_page_unlock(fs.first_m); 732 /* 733 * grab the page and put it into the 734 * process'es object. The page is 735 * automatically made dirty. 736 */ 737 if (vm_page_rename(fs.m, fs.first_object, 738 fs.first_pindex)) { 739 unlock_and_deallocate(&fs); 740 goto RetryFault; 741 } 742 vm_page_xbusy(fs.m); 743 fs.first_m = fs.m; 744 fs.m = NULL; 745 PCPU_INC(cnt.v_cow_optim); 746 } else { 747 /* 748 * Oh, well, lets copy it. 749 */ 750 pmap_copy_page(fs.m, fs.first_m); 751 fs.first_m->valid = VM_PAGE_BITS_ALL; 752 if (wired && (fault_flags & 753 VM_FAULT_CHANGE_WIRING) == 0) { 754 vm_page_lock(fs.first_m); 755 vm_page_wire(fs.first_m); 756 vm_page_unlock(fs.first_m); 757 758 vm_page_lock(fs.m); 759 vm_page_unwire(fs.m, PQ_INACTIVE); 760 vm_page_unlock(fs.m); 761 } 762 /* 763 * We no longer need the old page or object. 764 */ 765 release_page(&fs); 766 } 767 /* 768 * fs.object != fs.first_object due to above 769 * conditional 770 */ 771 vm_object_pip_wakeup(fs.object); 772 VM_OBJECT_WUNLOCK(fs.object); 773 /* 774 * Only use the new page below... 775 */ 776 fs.object = fs.first_object; 777 fs.pindex = fs.first_pindex; 778 fs.m = fs.first_m; 779 if (!is_first_object_locked) 780 VM_OBJECT_WLOCK(fs.object); 781 PCPU_INC(cnt.v_cow_faults); 782 curthread->td_cow++; 783 } else { 784 prot &= ~VM_PROT_WRITE; 785 } 786 } 787 788 /* 789 * We must verify that the maps have not changed since our last 790 * lookup. 791 */ 792 if (!fs.lookup_still_valid) { 793 vm_object_t retry_object; 794 vm_pindex_t retry_pindex; 795 vm_prot_t retry_prot; 796 797 if (!vm_map_trylock_read(fs.map)) { 798 release_page(&fs); 799 unlock_and_deallocate(&fs); 800 goto RetryFault; 801 } 802 fs.lookup_still_valid = TRUE; 803 if (fs.map->timestamp != map_generation) { 804 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 805 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 806 807 /* 808 * If we don't need the page any longer, put it on the inactive 809 * list (the easiest thing to do here). If no one needs it, 810 * pageout will grab it eventually. 811 */ 812 if (result != KERN_SUCCESS) { 813 release_page(&fs); 814 unlock_and_deallocate(&fs); 815 816 /* 817 * If retry of map lookup would have blocked then 818 * retry fault from start. 819 */ 820 if (result == KERN_FAILURE) 821 goto RetryFault; 822 return (result); 823 } 824 if ((retry_object != fs.first_object) || 825 (retry_pindex != fs.first_pindex)) { 826 release_page(&fs); 827 unlock_and_deallocate(&fs); 828 goto RetryFault; 829 } 830 831 /* 832 * Check whether the protection has changed or the object has 833 * been copied while we left the map unlocked. Changing from 834 * read to write permission is OK - we leave the page 835 * write-protected, and catch the write fault. Changing from 836 * write to read permission means that we can't mark the page 837 * write-enabled after all. 838 */ 839 prot &= retry_prot; 840 } 841 } 842 /* 843 * If the page was filled by a pager, update the map entry's 844 * last read offset. Since the pager does not return the 845 * actual set of pages that it read, this update is based on 846 * the requested set. Typically, the requested and actual 847 * sets are the same. 848 * 849 * XXX The following assignment modifies the map 850 * without holding a write lock on it. 851 */ 852 if (hardfault) 853 fs.entry->next_read = fs.pindex + faultcount - reqpage; 854 855 if ((prot & VM_PROT_WRITE) != 0 || 856 (fault_flags & VM_FAULT_DIRTY) != 0) { 857 vm_object_set_writeable_dirty(fs.object); 858 859 /* 860 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 861 * if the page is already dirty to prevent data written with 862 * the expectation of being synced from not being synced. 863 * Likewise if this entry does not request NOSYNC then make 864 * sure the page isn't marked NOSYNC. Applications sharing 865 * data should use the same flags to avoid ping ponging. 866 */ 867 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 868 if (fs.m->dirty == 0) 869 fs.m->oflags |= VPO_NOSYNC; 870 } else { 871 fs.m->oflags &= ~VPO_NOSYNC; 872 } 873 874 /* 875 * If the fault is a write, we know that this page is being 876 * written NOW so dirty it explicitly to save on 877 * pmap_is_modified() calls later. 878 * 879 * Also tell the backing pager, if any, that it should remove 880 * any swap backing since the page is now dirty. 881 */ 882 if (((fault_type & VM_PROT_WRITE) != 0 && 883 (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) || 884 (fault_flags & VM_FAULT_DIRTY) != 0) { 885 vm_page_dirty(fs.m); 886 vm_pager_page_unswapped(fs.m); 887 } 888 } 889 890 vm_page_assert_xbusied(fs.m); 891 892 /* 893 * Page must be completely valid or it is not fit to 894 * map into user space. vm_pager_get_pages() ensures this. 895 */ 896 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 897 ("vm_fault: page %p partially invalid", fs.m)); 898 VM_OBJECT_WUNLOCK(fs.object); 899 900 /* 901 * Put this page into the physical map. We had to do the unlock above 902 * because pmap_enter() may sleep. We don't put the page 903 * back on the active queue until later so that the pageout daemon 904 * won't find it (yet). 905 */ 906 pmap_enter(fs.map->pmap, vaddr, fault_type, fs.m, prot, wired); 907 if (faultcount != 1 && (fault_flags & VM_FAULT_CHANGE_WIRING) == 0 && 908 wired == 0) 909 vm_fault_prefault(&fs, vaddr, faultcount, reqpage); 910 VM_OBJECT_WLOCK(fs.object); 911 vm_page_lock(fs.m); 912 913 /* 914 * If the page is not wired down, then put it where the pageout daemon 915 * can find it. 916 */ 917 if (fault_flags & VM_FAULT_CHANGE_WIRING) { 918 if (wired) 919 vm_page_wire(fs.m); 920 else 921 vm_page_unwire(fs.m, PQ_ACTIVE); 922 } else 923 vm_page_activate(fs.m); 924 if (m_hold != NULL) { 925 *m_hold = fs.m; 926 vm_page_hold(fs.m); 927 } 928 vm_page_unlock(fs.m); 929 vm_page_xunbusy(fs.m); 930 931 /* 932 * Unlock everything, and return 933 */ 934 unlock_and_deallocate(&fs); 935 if (hardfault) { 936 PCPU_INC(cnt.v_io_faults); 937 curthread->td_ru.ru_majflt++; 938 } else 939 curthread->td_ru.ru_minflt++; 940 941 return (KERN_SUCCESS); 942 } 943 944 /* 945 * Speed up the reclamation of up to "distance" pages that precede the 946 * faulting pindex within the first object of the shadow chain. 947 */ 948 static void 949 vm_fault_cache_behind(const struct faultstate *fs, int distance) 950 { 951 vm_object_t first_object, object; 952 vm_page_t m, m_prev; 953 vm_pindex_t pindex; 954 955 object = fs->object; 956 VM_OBJECT_ASSERT_WLOCKED(object); 957 first_object = fs->first_object; 958 if (first_object != object) { 959 if (!VM_OBJECT_TRYWLOCK(first_object)) { 960 VM_OBJECT_WUNLOCK(object); 961 VM_OBJECT_WLOCK(first_object); 962 VM_OBJECT_WLOCK(object); 963 } 964 } 965 /* Neither fictitious nor unmanaged pages can be cached. */ 966 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 967 if (fs->first_pindex < distance) 968 pindex = 0; 969 else 970 pindex = fs->first_pindex - distance; 971 if (pindex < OFF_TO_IDX(fs->entry->offset)) 972 pindex = OFF_TO_IDX(fs->entry->offset); 973 m = first_object != object ? fs->first_m : fs->m; 974 vm_page_assert_xbusied(m); 975 m_prev = vm_page_prev(m); 976 while ((m = m_prev) != NULL && m->pindex >= pindex && 977 m->valid == VM_PAGE_BITS_ALL) { 978 m_prev = vm_page_prev(m); 979 if (vm_page_busied(m)) 980 continue; 981 vm_page_lock(m); 982 if (m->hold_count == 0 && m->wire_count == 0) { 983 pmap_remove_all(m); 984 vm_page_aflag_clear(m, PGA_REFERENCED); 985 if (m->dirty != 0) 986 vm_page_deactivate(m); 987 else 988 vm_page_cache(m); 989 } 990 vm_page_unlock(m); 991 } 992 } 993 if (first_object != object) 994 VM_OBJECT_WUNLOCK(first_object); 995 } 996 997 /* 998 * vm_fault_prefault provides a quick way of clustering 999 * pagefaults into a processes address space. It is a "cousin" 1000 * of vm_map_pmap_enter, except it runs at page fault time instead 1001 * of mmap time. 1002 */ 1003 static void 1004 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1005 int faultcount, int reqpage) 1006 { 1007 pmap_t pmap; 1008 vm_map_entry_t entry; 1009 vm_object_t backing_object, lobject; 1010 vm_offset_t addr, starta; 1011 vm_pindex_t pindex; 1012 vm_page_t m; 1013 int backward, forward, i; 1014 1015 pmap = fs->map->pmap; 1016 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1017 return; 1018 1019 if (faultcount > 0) { 1020 backward = reqpage; 1021 forward = faultcount - reqpage - 1; 1022 } else { 1023 backward = PFBAK; 1024 forward = PFFOR; 1025 } 1026 entry = fs->entry; 1027 1028 starta = addra - backward * PAGE_SIZE; 1029 if (starta < entry->start) { 1030 starta = entry->start; 1031 } else if (starta > addra) { 1032 starta = 0; 1033 } 1034 1035 /* 1036 * Generate the sequence of virtual addresses that are candidates for 1037 * prefaulting in an outward spiral from the faulting virtual address, 1038 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1039 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1040 * If the candidate address doesn't have a backing physical page, then 1041 * the loop immediately terminates. 1042 */ 1043 for (i = 0; i < 2 * imax(backward, forward); i++) { 1044 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1045 PAGE_SIZE); 1046 if (addr > addra + forward * PAGE_SIZE) 1047 addr = 0; 1048 1049 if (addr < starta || addr >= entry->end) 1050 continue; 1051 1052 if (!pmap_is_prefaultable(pmap, addr)) 1053 continue; 1054 1055 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1056 lobject = entry->object.vm_object; 1057 VM_OBJECT_RLOCK(lobject); 1058 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1059 lobject->type == OBJT_DEFAULT && 1060 (backing_object = lobject->backing_object) != NULL) { 1061 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1062 0, ("vm_fault_prefault: unaligned object offset")); 1063 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1064 VM_OBJECT_RLOCK(backing_object); 1065 VM_OBJECT_RUNLOCK(lobject); 1066 lobject = backing_object; 1067 } 1068 if (m == NULL) { 1069 VM_OBJECT_RUNLOCK(lobject); 1070 break; 1071 } 1072 if (m->valid == VM_PAGE_BITS_ALL && 1073 (m->flags & PG_FICTITIOUS) == 0) 1074 pmap_enter_quick(pmap, addr, m, entry->protection); 1075 VM_OBJECT_RUNLOCK(lobject); 1076 } 1077 } 1078 1079 /* 1080 * Hold each of the physical pages that are mapped by the specified range of 1081 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1082 * and allow the specified types of access, "prot". If all of the implied 1083 * pages are successfully held, then the number of held pages is returned 1084 * together with pointers to those pages in the array "ma". However, if any 1085 * of the pages cannot be held, -1 is returned. 1086 */ 1087 int 1088 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1089 vm_prot_t prot, vm_page_t *ma, int max_count) 1090 { 1091 vm_offset_t end, va; 1092 vm_page_t *mp; 1093 int count; 1094 boolean_t pmap_failed; 1095 1096 if (len == 0) 1097 return (0); 1098 end = round_page(addr + len); 1099 addr = trunc_page(addr); 1100 1101 /* 1102 * Check for illegal addresses. 1103 */ 1104 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1105 return (-1); 1106 1107 if (atop(end - addr) > max_count) 1108 panic("vm_fault_quick_hold_pages: count > max_count"); 1109 count = atop(end - addr); 1110 1111 /* 1112 * Most likely, the physical pages are resident in the pmap, so it is 1113 * faster to try pmap_extract_and_hold() first. 1114 */ 1115 pmap_failed = FALSE; 1116 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1117 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1118 if (*mp == NULL) 1119 pmap_failed = TRUE; 1120 else if ((prot & VM_PROT_WRITE) != 0 && 1121 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1122 /* 1123 * Explicitly dirty the physical page. Otherwise, the 1124 * caller's changes may go unnoticed because they are 1125 * performed through an unmanaged mapping or by a DMA 1126 * operation. 1127 * 1128 * The object lock is not held here. 1129 * See vm_page_clear_dirty_mask(). 1130 */ 1131 vm_page_dirty(*mp); 1132 } 1133 } 1134 if (pmap_failed) { 1135 /* 1136 * One or more pages could not be held by the pmap. Either no 1137 * page was mapped at the specified virtual address or that 1138 * mapping had insufficient permissions. Attempt to fault in 1139 * and hold these pages. 1140 */ 1141 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1142 if (*mp == NULL && vm_fault_hold(map, va, prot, 1143 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1144 goto error; 1145 } 1146 return (count); 1147 error: 1148 for (mp = ma; mp < ma + count; mp++) 1149 if (*mp != NULL) { 1150 vm_page_lock(*mp); 1151 vm_page_unhold(*mp); 1152 vm_page_unlock(*mp); 1153 } 1154 return (-1); 1155 } 1156 1157 /* 1158 * vm_fault_wire: 1159 * 1160 * Wire down a range of virtual addresses in a map. 1161 */ 1162 int 1163 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1164 boolean_t fictitious) 1165 { 1166 vm_offset_t va; 1167 int rv; 1168 1169 /* 1170 * We simulate a fault to get the page and enter it in the physical 1171 * map. For user wiring, we only ask for read access on currently 1172 * read-only sections. 1173 */ 1174 for (va = start; va < end; va += PAGE_SIZE) { 1175 rv = vm_fault(map, va, VM_PROT_NONE, VM_FAULT_CHANGE_WIRING); 1176 if (rv) { 1177 if (va != start) 1178 vm_fault_unwire(map, start, va, fictitious); 1179 return (rv); 1180 } 1181 } 1182 return (KERN_SUCCESS); 1183 } 1184 1185 /* 1186 * vm_fault_unwire: 1187 * 1188 * Unwire a range of virtual addresses in a map. 1189 */ 1190 static void 1191 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1192 boolean_t fictitious) 1193 { 1194 vm_paddr_t pa; 1195 vm_offset_t va; 1196 vm_page_t m; 1197 pmap_t pmap; 1198 1199 pmap = vm_map_pmap(map); 1200 1201 /* 1202 * Since the pages are wired down, we must be able to get their 1203 * mappings from the physical map system. 1204 */ 1205 for (va = start; va < end; va += PAGE_SIZE) { 1206 pa = pmap_extract(pmap, va); 1207 if (pa != 0) { 1208 pmap_change_wiring(pmap, va, FALSE); 1209 if (!fictitious) { 1210 m = PHYS_TO_VM_PAGE(pa); 1211 vm_page_lock(m); 1212 vm_page_unwire(m, PQ_ACTIVE); 1213 vm_page_unlock(m); 1214 } 1215 } 1216 } 1217 } 1218 1219 /* 1220 * Routine: 1221 * vm_fault_copy_entry 1222 * Function: 1223 * Create new shadow object backing dst_entry with private copy of 1224 * all underlying pages. When src_entry is equal to dst_entry, 1225 * function implements COW for wired-down map entry. Otherwise, 1226 * it forks wired entry into dst_map. 1227 * 1228 * In/out conditions: 1229 * The source and destination maps must be locked for write. 1230 * The source map entry must be wired down (or be a sharing map 1231 * entry corresponding to a main map entry that is wired down). 1232 */ 1233 void 1234 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1235 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1236 vm_ooffset_t *fork_charge) 1237 { 1238 vm_object_t backing_object, dst_object, object, src_object; 1239 vm_pindex_t dst_pindex, pindex, src_pindex; 1240 vm_prot_t access, prot; 1241 vm_offset_t vaddr; 1242 vm_page_t dst_m; 1243 vm_page_t src_m; 1244 boolean_t upgrade; 1245 1246 #ifdef lint 1247 src_map++; 1248 #endif /* lint */ 1249 1250 upgrade = src_entry == dst_entry; 1251 access = prot = dst_entry->protection; 1252 1253 src_object = src_entry->object.vm_object; 1254 src_pindex = OFF_TO_IDX(src_entry->offset); 1255 1256 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1257 dst_object = src_object; 1258 vm_object_reference(dst_object); 1259 } else { 1260 /* 1261 * Create the top-level object for the destination entry. (Doesn't 1262 * actually shadow anything - we copy the pages directly.) 1263 */ 1264 dst_object = vm_object_allocate(OBJT_DEFAULT, 1265 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1266 #if VM_NRESERVLEVEL > 0 1267 dst_object->flags |= OBJ_COLORED; 1268 dst_object->pg_color = atop(dst_entry->start); 1269 #endif 1270 } 1271 1272 VM_OBJECT_WLOCK(dst_object); 1273 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1274 ("vm_fault_copy_entry: vm_object not NULL")); 1275 if (src_object != dst_object) { 1276 dst_entry->object.vm_object = dst_object; 1277 dst_entry->offset = 0; 1278 dst_object->charge = dst_entry->end - dst_entry->start; 1279 } 1280 if (fork_charge != NULL) { 1281 KASSERT(dst_entry->cred == NULL, 1282 ("vm_fault_copy_entry: leaked swp charge")); 1283 dst_object->cred = curthread->td_ucred; 1284 crhold(dst_object->cred); 1285 *fork_charge += dst_object->charge; 1286 } else if (dst_object->cred == NULL) { 1287 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1288 dst_entry)); 1289 dst_object->cred = dst_entry->cred; 1290 dst_entry->cred = NULL; 1291 } 1292 1293 /* 1294 * If not an upgrade, then enter the mappings in the pmap as 1295 * read and/or execute accesses. Otherwise, enter them as 1296 * write accesses. 1297 * 1298 * A writeable large page mapping is only created if all of 1299 * the constituent small page mappings are modified. Marking 1300 * PTEs as modified on inception allows promotion to happen 1301 * without taking potentially large number of soft faults. 1302 */ 1303 if (!upgrade) 1304 access &= ~VM_PROT_WRITE; 1305 1306 /* 1307 * Loop through all of the virtual pages within the entry's 1308 * range, copying each page from the source object to the 1309 * destination object. Since the source is wired, those pages 1310 * must exist. In contrast, the destination is pageable. 1311 * Since the destination object does share any backing storage 1312 * with the source object, all of its pages must be dirtied, 1313 * regardless of whether they can be written. 1314 */ 1315 for (vaddr = dst_entry->start, dst_pindex = 0; 1316 vaddr < dst_entry->end; 1317 vaddr += PAGE_SIZE, dst_pindex++) { 1318 again: 1319 /* 1320 * Find the page in the source object, and copy it in. 1321 * Because the source is wired down, the page will be 1322 * in memory. 1323 */ 1324 if (src_object != dst_object) 1325 VM_OBJECT_RLOCK(src_object); 1326 object = src_object; 1327 pindex = src_pindex + dst_pindex; 1328 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1329 (backing_object = object->backing_object) != NULL) { 1330 /* 1331 * Unless the source mapping is read-only or 1332 * it is presently being upgraded from 1333 * read-only, the first object in the shadow 1334 * chain should provide all of the pages. In 1335 * other words, this loop body should never be 1336 * executed when the source mapping is already 1337 * read/write. 1338 */ 1339 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1340 upgrade, 1341 ("vm_fault_copy_entry: main object missing page")); 1342 1343 VM_OBJECT_RLOCK(backing_object); 1344 pindex += OFF_TO_IDX(object->backing_object_offset); 1345 if (object != dst_object) 1346 VM_OBJECT_RUNLOCK(object); 1347 object = backing_object; 1348 } 1349 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1350 1351 if (object != dst_object) { 1352 /* 1353 * Allocate a page in the destination object. 1354 */ 1355 dst_m = vm_page_alloc(dst_object, (src_object == 1356 dst_object ? src_pindex : 0) + dst_pindex, 1357 VM_ALLOC_NORMAL); 1358 if (dst_m == NULL) { 1359 VM_OBJECT_WUNLOCK(dst_object); 1360 VM_OBJECT_RUNLOCK(object); 1361 VM_WAIT; 1362 VM_OBJECT_WLOCK(dst_object); 1363 goto again; 1364 } 1365 pmap_copy_page(src_m, dst_m); 1366 VM_OBJECT_RUNLOCK(object); 1367 dst_m->valid = VM_PAGE_BITS_ALL; 1368 dst_m->dirty = VM_PAGE_BITS_ALL; 1369 } else { 1370 dst_m = src_m; 1371 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1372 goto again; 1373 vm_page_xbusy(dst_m); 1374 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1375 ("invalid dst page %p", dst_m)); 1376 } 1377 VM_OBJECT_WUNLOCK(dst_object); 1378 1379 /* 1380 * Enter it in the pmap. If a wired, copy-on-write 1381 * mapping is being replaced by a write-enabled 1382 * mapping, then wire that new mapping. 1383 */ 1384 pmap_enter(dst_map->pmap, vaddr, access, dst_m, prot, upgrade); 1385 1386 /* 1387 * Mark it no longer busy, and put it on the active list. 1388 */ 1389 VM_OBJECT_WLOCK(dst_object); 1390 1391 if (upgrade) { 1392 if (src_m != dst_m) { 1393 vm_page_lock(src_m); 1394 vm_page_unwire(src_m, PQ_INACTIVE); 1395 vm_page_unlock(src_m); 1396 vm_page_lock(dst_m); 1397 vm_page_wire(dst_m); 1398 vm_page_unlock(dst_m); 1399 } else { 1400 KASSERT(dst_m->wire_count > 0, 1401 ("dst_m %p is not wired", dst_m)); 1402 } 1403 } else { 1404 vm_page_lock(dst_m); 1405 vm_page_activate(dst_m); 1406 vm_page_unlock(dst_m); 1407 } 1408 vm_page_xunbusy(dst_m); 1409 } 1410 VM_OBJECT_WUNLOCK(dst_object); 1411 if (upgrade) { 1412 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1413 vm_object_deallocate(src_object); 1414 } 1415 } 1416 1417 1418 /* 1419 * This routine checks around the requested page for other pages that 1420 * might be able to be faulted in. This routine brackets the viable 1421 * pages for the pages to be paged in. 1422 * 1423 * Inputs: 1424 * m, rbehind, rahead 1425 * 1426 * Outputs: 1427 * marray (array of vm_page_t), reqpage (index of requested page) 1428 * 1429 * Return value: 1430 * number of pages in marray 1431 */ 1432 static int 1433 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1434 vm_page_t m; 1435 int rbehind; 1436 int rahead; 1437 vm_page_t *marray; 1438 int *reqpage; 1439 { 1440 int i,j; 1441 vm_object_t object; 1442 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1443 vm_page_t rtm; 1444 int cbehind, cahead; 1445 1446 VM_OBJECT_ASSERT_WLOCKED(m->object); 1447 1448 object = m->object; 1449 pindex = m->pindex; 1450 cbehind = cahead = 0; 1451 1452 /* 1453 * if the requested page is not available, then give up now 1454 */ 1455 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1456 return 0; 1457 } 1458 1459 if ((cbehind == 0) && (cahead == 0)) { 1460 *reqpage = 0; 1461 marray[0] = m; 1462 return 1; 1463 } 1464 1465 if (rahead > cahead) { 1466 rahead = cahead; 1467 } 1468 1469 if (rbehind > cbehind) { 1470 rbehind = cbehind; 1471 } 1472 1473 /* 1474 * scan backward for the read behind pages -- in memory 1475 */ 1476 if (pindex > 0) { 1477 if (rbehind > pindex) { 1478 rbehind = pindex; 1479 startpindex = 0; 1480 } else { 1481 startpindex = pindex - rbehind; 1482 } 1483 1484 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1485 rtm->pindex >= startpindex) 1486 startpindex = rtm->pindex + 1; 1487 1488 /* tpindex is unsigned; beware of numeric underflow. */ 1489 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1490 tpindex < pindex; i++, tpindex--) { 1491 1492 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1493 VM_ALLOC_IFNOTCACHED); 1494 if (rtm == NULL) { 1495 /* 1496 * Shift the allocated pages to the 1497 * beginning of the array. 1498 */ 1499 for (j = 0; j < i; j++) { 1500 marray[j] = marray[j + tpindex + 1 - 1501 startpindex]; 1502 } 1503 break; 1504 } 1505 1506 marray[tpindex - startpindex] = rtm; 1507 } 1508 } else { 1509 startpindex = 0; 1510 i = 0; 1511 } 1512 1513 marray[i] = m; 1514 /* page offset of the required page */ 1515 *reqpage = i; 1516 1517 tpindex = pindex + 1; 1518 i++; 1519 1520 /* 1521 * scan forward for the read ahead pages 1522 */ 1523 endpindex = tpindex + rahead; 1524 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1525 endpindex = rtm->pindex; 1526 if (endpindex > object->size) 1527 endpindex = object->size; 1528 1529 for (; tpindex < endpindex; i++, tpindex++) { 1530 1531 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1532 VM_ALLOC_IFNOTCACHED); 1533 if (rtm == NULL) { 1534 break; 1535 } 1536 1537 marray[i] = rtm; 1538 } 1539 1540 /* return number of pages */ 1541 return i; 1542 } 1543 1544 /* 1545 * Block entry into the machine-independent layer's page fault handler by 1546 * the calling thread. Subsequent calls to vm_fault() by that thread will 1547 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1548 * spurious page faults. 1549 */ 1550 int 1551 vm_fault_disable_pagefaults(void) 1552 { 1553 1554 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1555 } 1556 1557 void 1558 vm_fault_enable_pagefaults(int save) 1559 { 1560 1561 curthread_pflags_restore(save); 1562 } 1563