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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 * $FreeBSD$ 70 */ 71 72 /* 73 * Page fault handling module. 74 */ 75 76 #include <sys/param.h> 77 #include <sys/systm.h> 78 #include <sys/proc.h> 79 #include <sys/vnode.h> 80 #include <sys/resourcevar.h> 81 #include <sys/vmmeter.h> 82 83 #include <vm/vm.h> 84 #include <vm/vm_param.h> 85 #include <sys/lock.h> 86 #include <vm/pmap.h> 87 #include <vm/vm_map.h> 88 #include <vm/vm_object.h> 89 #include <vm/vm_page.h> 90 #include <vm/vm_pageout.h> 91 #include <vm/vm_kern.h> 92 #include <vm/vm_pager.h> 93 #include <vm/vnode_pager.h> 94 #include <vm/vm_extern.h> 95 96 static int vm_fault_additional_pages __P((vm_page_t, int, 97 int, vm_page_t *, int *)); 98 99 #define VM_FAULT_READ_AHEAD 8 100 #define VM_FAULT_READ_BEHIND 7 101 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1) 102 103 struct faultstate { 104 vm_page_t m; 105 vm_object_t object; 106 vm_pindex_t pindex; 107 vm_page_t first_m; 108 vm_object_t first_object; 109 vm_pindex_t first_pindex; 110 vm_map_t map; 111 vm_map_entry_t entry; 112 int lookup_still_valid; 113 struct vnode *vp; 114 }; 115 116 static __inline void 117 release_page(struct faultstate *fs) 118 { 119 vm_page_wakeup(fs->m); 120 vm_page_deactivate(fs->m); 121 fs->m = NULL; 122 } 123 124 static __inline void 125 unlock_map(struct faultstate *fs) 126 { 127 if (fs->lookup_still_valid) { 128 vm_map_lookup_done(fs->map, fs->entry); 129 fs->lookup_still_valid = FALSE; 130 } 131 } 132 133 static void 134 _unlock_things(struct faultstate *fs, int dealloc) 135 { 136 vm_object_pip_wakeup(fs->object); 137 if (fs->object != fs->first_object) { 138 vm_page_free(fs->first_m); 139 vm_object_pip_wakeup(fs->first_object); 140 fs->first_m = NULL; 141 } 142 if (dealloc) { 143 vm_object_deallocate(fs->first_object); 144 } 145 unlock_map(fs); 146 if (fs->vp != NULL) { 147 vput(fs->vp); 148 fs->vp = NULL; 149 } 150 } 151 152 #define unlock_things(fs) _unlock_things(fs, 0) 153 #define unlock_and_deallocate(fs) _unlock_things(fs, 1) 154 155 /* 156 * TRYPAGER - used by vm_fault to calculate whether the pager for the 157 * current object *might* contain the page. 158 * 159 * default objects are zero-fill, there is no real pager. 160 */ 161 162 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 163 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) 164 165 /* 166 * vm_fault: 167 * 168 * Handle a page fault occurring at the given address, 169 * requiring the given permissions, in the map specified. 170 * If successful, the page is inserted into the 171 * associated physical map. 172 * 173 * NOTE: the given address should be truncated to the 174 * proper page address. 175 * 176 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 177 * a standard error specifying why the fault is fatal is returned. 178 * 179 * 180 * The map in question must be referenced, and remains so. 181 * Caller may hold no locks. 182 */ 183 int 184 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, int fault_flags) 185 { 186 vm_prot_t prot; 187 int result; 188 boolean_t wired; 189 int map_generation; 190 vm_object_t next_object; 191 vm_page_t marray[VM_FAULT_READ]; 192 int hardfault; 193 int faultcount; 194 struct faultstate fs; 195 196 cnt.v_vm_faults++; /* needs lock XXX */ 197 hardfault = 0; 198 199 RetryFault:; 200 201 /* 202 * Find the backing store object and offset into it to begin the 203 * search. 204 */ 205 fs.map = map; 206 if ((result = vm_map_lookup(&fs.map, vaddr, 207 fault_type, &fs.entry, &fs.first_object, 208 &fs.first_pindex, &prot, &wired)) != KERN_SUCCESS) { 209 if ((result != KERN_PROTECTION_FAILURE) || 210 ((fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE)) { 211 return result; 212 } 213 214 /* 215 * If we are user-wiring a r/w segment, and it is COW, then 216 * we need to do the COW operation. Note that we don't COW 217 * currently RO sections now, because it is NOT desirable 218 * to COW .text. We simply keep .text from ever being COW'ed 219 * and take the heat that one cannot debug wired .text sections. 220 */ 221 result = vm_map_lookup(&fs.map, vaddr, 222 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE, 223 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired); 224 if (result != KERN_SUCCESS) { 225 return result; 226 } 227 228 /* 229 * If we don't COW now, on a user wire, the user will never 230 * be able to write to the mapping. If we don't make this 231 * restriction, the bookkeeping would be nearly impossible. 232 */ 233 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 234 fs.entry->max_protection &= ~VM_PROT_WRITE; 235 } 236 237 map_generation = fs.map->timestamp; 238 239 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 240 panic("vm_fault: fault on nofault entry, addr: %lx", 241 (u_long)vaddr); 242 } 243 244 /* 245 * Make a reference to this object to prevent its disposal while we 246 * are messing with it. Once we have the reference, the map is free 247 * to be diddled. Since objects reference their shadows (and copies), 248 * they will stay around as well. 249 * 250 * Bump the paging-in-progress count to prevent size changes (e.g. 251 * truncation operations) during I/O. This must be done after 252 * obtaining the vnode lock in order to avoid possible deadlocks. 253 */ 254 vm_object_reference(fs.first_object); 255 fs.vp = vnode_pager_lock(fs.first_object); 256 vm_object_pip_add(fs.first_object, 1); 257 258 if ((fault_type & VM_PROT_WRITE) && 259 (fs.first_object->type == OBJT_VNODE)) { 260 vm_freeze_copyopts(fs.first_object, 261 fs.first_pindex, fs.first_pindex + 1); 262 } 263 264 fs.lookup_still_valid = TRUE; 265 266 if (wired) 267 fault_type = prot; 268 269 fs.first_m = NULL; 270 271 /* 272 * Search for the page at object/offset. 273 */ 274 275 fs.object = fs.first_object; 276 fs.pindex = fs.first_pindex; 277 278 while (TRUE) { 279 /* 280 * If the object is dead, we stop here 281 */ 282 283 if (fs.object->flags & OBJ_DEAD) { 284 unlock_and_deallocate(&fs); 285 return (KERN_PROTECTION_FAILURE); 286 } 287 288 /* 289 * See if page is resident 290 */ 291 292 fs.m = vm_page_lookup(fs.object, fs.pindex); 293 if (fs.m != NULL) { 294 int queue, s; 295 /* 296 * Wait/Retry if the page is busy. We have to do this 297 * if the page is busy via either PG_BUSY or 298 * vm_page_t->busy because the vm_pager may be using 299 * vm_page_t->busy for pageouts ( and even pageins if 300 * it is the vnode pager ), and we could end up trying 301 * to pagein and pageout the same page simultaneously. 302 * 303 * We can theoretically allow the busy case on a read 304 * fault if the page is marked valid, but since such 305 * pages are typically already pmap'd, putting that 306 * special case in might be more effort then it is 307 * worth. We cannot under any circumstances mess 308 * around with a vm_page_t->busy page except, perhaps, 309 * to pmap it. 310 */ 311 if ((fs.m->flags & PG_BUSY) || fs.m->busy) { 312 unlock_things(&fs); 313 (void)vm_page_sleep_busy(fs.m, TRUE, "vmpfw"); 314 cnt.v_intrans++; 315 vm_object_deallocate(fs.first_object); 316 goto RetryFault; 317 } 318 319 queue = fs.m->queue; 320 s = splvm(); 321 vm_page_unqueue_nowakeup(fs.m); 322 splx(s); 323 324 if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) { 325 vm_page_activate(fs.m); 326 unlock_and_deallocate(&fs); 327 VM_WAITPFAULT; 328 goto RetryFault; 329 } 330 331 /* 332 * Mark page busy for other processes, and the 333 * pagedaemon. If it still isn't completely valid 334 * (readable), jump to readrest, else break-out ( we 335 * found the page ). 336 */ 337 338 vm_page_busy(fs.m); 339 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) && 340 fs.m->object != kernel_object && fs.m->object != kmem_object) { 341 goto readrest; 342 } 343 344 break; 345 } 346 347 /* 348 * Page is not resident, If this is the search termination 349 * or the pager might contain the page, allocate a new page. 350 */ 351 352 if (TRYPAGER || fs.object == fs.first_object) { 353 if (fs.pindex >= fs.object->size) { 354 unlock_and_deallocate(&fs); 355 return (KERN_PROTECTION_FAILURE); 356 } 357 358 /* 359 * Allocate a new page for this object/offset pair. 360 */ 361 fs.m = NULL; 362 if (!vm_page_count_severe()) { 363 fs.m = vm_page_alloc(fs.object, fs.pindex, 364 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO); 365 } 366 if (fs.m == NULL) { 367 unlock_and_deallocate(&fs); 368 VM_WAITPFAULT; 369 goto RetryFault; 370 } 371 } 372 373 readrest: 374 /* 375 * We have found a valid page or we have allocated a new page. 376 * The page thus may not be valid or may not be entirely 377 * valid. 378 * 379 * Attempt to fault-in the page if there is a chance that the 380 * pager has it, and potentially fault in additional pages 381 * at the same time. 382 */ 383 384 if (TRYPAGER) { 385 int rv; 386 int reqpage; 387 int ahead, behind; 388 u_char behavior = vm_map_entry_behavior(fs.entry); 389 390 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 391 ahead = 0; 392 behind = 0; 393 } else { 394 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT; 395 if (behind > VM_FAULT_READ_BEHIND) 396 behind = VM_FAULT_READ_BEHIND; 397 398 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1; 399 if (ahead > VM_FAULT_READ_AHEAD) 400 ahead = VM_FAULT_READ_AHEAD; 401 } 402 403 if ((fs.first_object->type != OBJT_DEVICE) && 404 (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 405 (behavior != MAP_ENTRY_BEHAV_RANDOM && 406 fs.pindex >= fs.entry->lastr && 407 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) 408 ) { 409 vm_pindex_t firstpindex, tmppindex; 410 411 if (fs.first_pindex < 2 * VM_FAULT_READ) 412 firstpindex = 0; 413 else 414 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ; 415 416 /* 417 * note: partially valid pages cannot be 418 * included in the lookahead - NFS piecemeal 419 * writes will barf on it badly. 420 */ 421 422 for(tmppindex = fs.first_pindex - 1; 423 tmppindex >= firstpindex; 424 --tmppindex) { 425 vm_page_t mt; 426 mt = vm_page_lookup( fs.first_object, tmppindex); 427 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL)) 428 break; 429 if (mt->busy || 430 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) || 431 mt->hold_count || 432 mt->wire_count) 433 continue; 434 if (mt->dirty == 0) 435 vm_page_test_dirty(mt); 436 if (mt->dirty) { 437 vm_page_protect(mt, VM_PROT_NONE); 438 vm_page_deactivate(mt); 439 } else { 440 vm_page_cache(mt); 441 } 442 } 443 444 ahead += behind; 445 behind = 0; 446 } 447 448 /* 449 * now we find out if any other pages should be paged 450 * in at this time this routine checks to see if the 451 * pages surrounding this fault reside in the same 452 * object as the page for this fault. If they do, 453 * then they are faulted in also into the object. The 454 * array "marray" returned contains an array of 455 * vm_page_t structs where one of them is the 456 * vm_page_t passed to the routine. The reqpage 457 * return value is the index into the marray for the 458 * vm_page_t passed to the routine. 459 * 460 * fs.m plus the additional pages are PG_BUSY'd. 461 */ 462 faultcount = vm_fault_additional_pages( 463 fs.m, behind, ahead, marray, &reqpage); 464 465 /* 466 * update lastr imperfectly (we do not know how much 467 * getpages will actually read), but good enough. 468 */ 469 fs.entry->lastr = fs.pindex + faultcount - behind; 470 471 /* 472 * Call the pager to retrieve the data, if any, after 473 * releasing the lock on the map. We hold a ref on 474 * fs.object and the pages are PG_BUSY'd. 475 */ 476 unlock_map(&fs); 477 478 rv = faultcount ? 479 vm_pager_get_pages(fs.object, marray, faultcount, 480 reqpage) : VM_PAGER_FAIL; 481 482 if (rv == VM_PAGER_OK) { 483 /* 484 * Found the page. Leave it busy while we play 485 * with it. 486 */ 487 488 /* 489 * Relookup in case pager changed page. Pager 490 * is responsible for disposition of old page 491 * if moved. 492 */ 493 fs.m = vm_page_lookup(fs.object, fs.pindex); 494 if(!fs.m) { 495 unlock_and_deallocate(&fs); 496 goto RetryFault; 497 } 498 499 hardfault++; 500 break; /* break to PAGE HAS BEEN FOUND */ 501 } 502 /* 503 * Remove the bogus page (which does not exist at this 504 * object/offset); before doing so, we must get back 505 * our object lock to preserve our invariant. 506 * 507 * Also wake up any other process that may want to bring 508 * in this page. 509 * 510 * If this is the top-level object, we must leave the 511 * busy page to prevent another process from rushing 512 * past us, and inserting the page in that object at 513 * the same time that we are. 514 */ 515 516 if (rv == VM_PAGER_ERROR) 517 printf("vm_fault: pager read error, pid %d (%s)\n", 518 curproc->p_pid, curproc->p_comm); 519 /* 520 * Data outside the range of the pager or an I/O error 521 */ 522 /* 523 * XXX - the check for kernel_map is a kludge to work 524 * around having the machine panic on a kernel space 525 * fault w/ I/O error. 526 */ 527 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 528 (rv == VM_PAGER_BAD)) { 529 vm_page_free(fs.m); 530 fs.m = NULL; 531 unlock_and_deallocate(&fs); 532 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 533 } 534 if (fs.object != fs.first_object) { 535 vm_page_free(fs.m); 536 fs.m = NULL; 537 /* 538 * XXX - we cannot just fall out at this 539 * point, m has been freed and is invalid! 540 */ 541 } 542 } 543 544 /* 545 * We get here if the object has default pager (or unwiring) 546 * or the pager doesn't have the page. 547 */ 548 if (fs.object == fs.first_object) 549 fs.first_m = fs.m; 550 551 /* 552 * Move on to the next object. Lock the next object before 553 * unlocking the current one. 554 */ 555 556 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 557 next_object = fs.object->backing_object; 558 if (next_object == NULL) { 559 /* 560 * If there's no object left, fill the page in the top 561 * object with zeros. 562 */ 563 if (fs.object != fs.first_object) { 564 vm_object_pip_wakeup(fs.object); 565 566 fs.object = fs.first_object; 567 fs.pindex = fs.first_pindex; 568 fs.m = fs.first_m; 569 } 570 fs.first_m = NULL; 571 572 /* 573 * Zero the page if necessary and mark it valid. 574 */ 575 if ((fs.m->flags & PG_ZERO) == 0) { 576 vm_page_zero_fill(fs.m); 577 } else { 578 cnt.v_ozfod++; 579 } 580 cnt.v_zfod++; 581 fs.m->valid = VM_PAGE_BITS_ALL; 582 break; /* break to PAGE HAS BEEN FOUND */ 583 } else { 584 if (fs.object != fs.first_object) { 585 vm_object_pip_wakeup(fs.object); 586 } 587 KASSERT(fs.object != next_object, ("object loop %p", next_object)); 588 fs.object = next_object; 589 vm_object_pip_add(fs.object, 1); 590 } 591 } 592 593 KASSERT((fs.m->flags & PG_BUSY) != 0, 594 ("vm_fault: not busy after main loop")); 595 596 /* 597 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 598 * is held.] 599 */ 600 601 /* 602 * If the page is being written, but isn't already owned by the 603 * top-level object, we have to copy it into a new page owned by the 604 * top-level object. 605 */ 606 607 if (fs.object != fs.first_object) { 608 /* 609 * We only really need to copy if we want to write it. 610 */ 611 612 if (fault_type & VM_PROT_WRITE) { 613 /* 614 * This allows pages to be virtually copied from a 615 * backing_object into the first_object, where the 616 * backing object has no other refs to it, and cannot 617 * gain any more refs. Instead of a bcopy, we just 618 * move the page from the backing object to the 619 * first object. Note that we must mark the page 620 * dirty in the first object so that it will go out 621 * to swap when needed. 622 */ 623 if (map_generation == fs.map->timestamp && 624 /* 625 * Only one shadow object 626 */ 627 (fs.object->shadow_count == 1) && 628 /* 629 * No COW refs, except us 630 */ 631 (fs.object->ref_count == 1) && 632 /* 633 * No one else can look this object up 634 */ 635 (fs.object->handle == NULL) && 636 /* 637 * No other ways to look the object up 638 */ 639 ((fs.object->type == OBJT_DEFAULT) || 640 (fs.object->type == OBJT_SWAP)) && 641 /* 642 * We don't chase down the shadow chain 643 */ 644 (fs.object == fs.first_object->backing_object) && 645 646 /* 647 * grab the lock if we need to 648 */ 649 (fs.lookup_still_valid || 650 lockmgr(&fs.map->lock, LK_EXCLUSIVE|LK_NOWAIT, (void *)0, curproc) == 0) 651 ) { 652 653 fs.lookup_still_valid = 1; 654 /* 655 * get rid of the unnecessary page 656 */ 657 vm_page_protect(fs.first_m, VM_PROT_NONE); 658 vm_page_free(fs.first_m); 659 fs.first_m = NULL; 660 661 /* 662 * grab the page and put it into the 663 * process'es object. The page is 664 * automatically made dirty. 665 */ 666 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 667 fs.first_m = fs.m; 668 vm_page_busy(fs.first_m); 669 fs.m = NULL; 670 cnt.v_cow_optim++; 671 } else { 672 /* 673 * Oh, well, lets copy it. 674 */ 675 vm_page_copy(fs.m, fs.first_m); 676 } 677 678 if (fs.m) { 679 /* 680 * We no longer need the old page or object. 681 */ 682 release_page(&fs); 683 } 684 685 /* 686 * fs.object != fs.first_object due to above 687 * conditional 688 */ 689 690 vm_object_pip_wakeup(fs.object); 691 692 /* 693 * Only use the new page below... 694 */ 695 696 cnt.v_cow_faults++; 697 fs.m = fs.first_m; 698 fs.object = fs.first_object; 699 fs.pindex = fs.first_pindex; 700 701 } else { 702 prot &= ~VM_PROT_WRITE; 703 } 704 } 705 706 /* 707 * We must verify that the maps have not changed since our last 708 * lookup. 709 */ 710 711 if (!fs.lookup_still_valid && 712 (fs.map->timestamp != map_generation)) { 713 vm_object_t retry_object; 714 vm_pindex_t retry_pindex; 715 vm_prot_t retry_prot; 716 717 /* 718 * Since map entries may be pageable, make sure we can take a 719 * page fault on them. 720 */ 721 722 /* 723 * Unlock vnode before the lookup to avoid deadlock. E.G. 724 * avoid a deadlock between the inode and exec_map that can 725 * occur due to locks being obtained in different orders. 726 */ 727 728 if (fs.vp != NULL) { 729 vput(fs.vp); 730 fs.vp = NULL; 731 } 732 733 if (fs.map->infork) { 734 release_page(&fs); 735 unlock_and_deallocate(&fs); 736 goto RetryFault; 737 } 738 739 /* 740 * To avoid trying to write_lock the map while another process 741 * has it read_locked (in vm_map_pageable), we do not try for 742 * write permission. If the page is still writable, we will 743 * get write permission. If it is not, or has been marked 744 * needs_copy, we enter the mapping without write permission, 745 * and will merely take another fault. 746 */ 747 result = vm_map_lookup(&fs.map, vaddr, fault_type & ~VM_PROT_WRITE, 748 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 749 map_generation = fs.map->timestamp; 750 751 /* 752 * If we don't need the page any longer, put it on the active 753 * list (the easiest thing to do here). If no one needs it, 754 * pageout will grab it eventually. 755 */ 756 757 if (result != KERN_SUCCESS) { 758 release_page(&fs); 759 unlock_and_deallocate(&fs); 760 return (result); 761 } 762 fs.lookup_still_valid = TRUE; 763 764 if ((retry_object != fs.first_object) || 765 (retry_pindex != fs.first_pindex)) { 766 release_page(&fs); 767 unlock_and_deallocate(&fs); 768 goto RetryFault; 769 } 770 /* 771 * Check whether the protection has changed or the object has 772 * been copied while we left the map unlocked. Changing from 773 * read to write permission is OK - we leave the page 774 * write-protected, and catch the write fault. Changing from 775 * write to read permission means that we can't mark the page 776 * write-enabled after all. 777 */ 778 prot &= retry_prot; 779 } 780 781 /* 782 * Put this page into the physical map. We had to do the unlock above 783 * because pmap_enter may cause other faults. We don't put the page 784 * back on the active queue until later so that the page-out daemon 785 * won't find us (yet). 786 */ 787 788 if (prot & VM_PROT_WRITE) { 789 vm_page_flag_set(fs.m, PG_WRITEABLE); 790 vm_object_set_writeable_dirty(fs.m->object); 791 792 /* 793 * If the fault is a write, we know that this page is being 794 * written NOW so dirty it explicitly to save on 795 * pmap_is_modified() calls later. 796 * 797 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC 798 * if the page is already dirty to prevent data written with 799 * the expectation of being synced from not being synced. 800 * Likewise if this entry does not request NOSYNC then make 801 * sure the page isn't marked NOSYNC. Applications sharing 802 * data should use the same flags to avoid ping ponging. 803 * 804 * Also tell the backing pager, if any, that it should remove 805 * any swap backing since the page is now dirty. 806 */ 807 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 808 if (fs.m->dirty == 0) 809 vm_page_flag_set(fs.m, PG_NOSYNC); 810 } else { 811 vm_page_flag_clear(fs.m, PG_NOSYNC); 812 } 813 if (fault_flags & VM_FAULT_DIRTY) { 814 int s; 815 vm_page_dirty(fs.m); 816 s = splvm(); 817 vm_pager_page_unswapped(fs.m); 818 splx(s); 819 } 820 } 821 822 /* 823 * Page had better still be busy 824 */ 825 826 KASSERT(fs.m->flags & PG_BUSY, 827 ("vm_fault: page %p not busy!", fs.m)); 828 829 unlock_things(&fs); 830 831 /* 832 * Sanity check: page must be completely valid or it is not fit to 833 * map into user space. vm_pager_get_pages() ensures this. 834 */ 835 836 if (fs.m->valid != VM_PAGE_BITS_ALL) { 837 vm_page_zero_invalid(fs.m, TRUE); 838 printf("Warning: page %p partially invalid on fault\n", fs.m); 839 } 840 841 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired); 842 843 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 844 pmap_prefault(fs.map->pmap, vaddr, fs.entry); 845 } 846 847 vm_page_flag_clear(fs.m, PG_ZERO); 848 vm_page_flag_set(fs.m, PG_MAPPED|PG_REFERENCED); 849 if (fault_flags & VM_FAULT_HOLD) 850 vm_page_hold(fs.m); 851 852 /* 853 * If the page is not wired down, then put it where the pageout daemon 854 * can find it. 855 */ 856 857 if (fault_flags & VM_FAULT_WIRE_MASK) { 858 if (wired) 859 vm_page_wire(fs.m); 860 else 861 vm_page_unwire(fs.m, 1); 862 } else { 863 vm_page_activate(fs.m); 864 } 865 866 if (curproc && (curproc->p_flag & P_INMEM) && curproc->p_stats) { 867 if (hardfault) { 868 curproc->p_stats->p_ru.ru_majflt++; 869 } else { 870 curproc->p_stats->p_ru.ru_minflt++; 871 } 872 } 873 874 /* 875 * Unlock everything, and return 876 */ 877 878 vm_page_wakeup(fs.m); 879 vm_object_deallocate(fs.first_object); 880 881 return (KERN_SUCCESS); 882 883 } 884 885 /* 886 * vm_fault_wire: 887 * 888 * Wire down a range of virtual addresses in a map. 889 */ 890 int 891 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end, 892 boolean_t user_wire, boolean_t fictitious) 893 { 894 895 register vm_offset_t va; 896 register pmap_t pmap; 897 int rv; 898 899 pmap = vm_map_pmap(map); 900 901 /* 902 * Inform the physical mapping system that the range of addresses may 903 * not fault, so that page tables and such can be locked down as well. 904 */ 905 906 pmap_pageable(pmap, start, end, FALSE); 907 908 /* 909 * We simulate a fault to get the page and enter it in the physical 910 * map. 911 */ 912 913 for (va = start; va < end; va += PAGE_SIZE) { 914 rv = vm_fault(map, va, 915 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE, 916 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING); 917 if (rv) { 918 if (va != start) 919 vm_fault_unwire(map, start, va, fictitious); 920 return (rv); 921 } 922 } 923 return (KERN_SUCCESS); 924 } 925 926 /* 927 * vm_fault_unwire: 928 * 929 * Unwire a range of virtual addresses in a map. 930 */ 931 void 932 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end, 933 boolean_t fictitious) 934 { 935 936 vm_offset_t va; 937 vm_paddr_t pa; 938 pmap_t pmap; 939 940 pmap = vm_map_pmap(map); 941 942 /* 943 * Since the pages are wired down, we must be able to get their 944 * mappings from the physical map system. 945 */ 946 947 for (va = start; va < end; va += PAGE_SIZE) { 948 pa = pmap_extract(pmap, va); 949 if (pa != 0) { 950 pmap_change_wiring(pmap, va, FALSE); 951 if (!fictitious) 952 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 953 } 954 } 955 956 /* 957 * Inform the physical mapping system that the range of addresses may 958 * fault, so that page tables and such may be unwired themselves. 959 */ 960 961 pmap_pageable(pmap, start, end, TRUE); 962 963 } 964 965 /* 966 * Routine: 967 * vm_fault_copy_entry 968 * Function: 969 * Copy all of the pages from a wired-down map entry to another. 970 * 971 * In/out conditions: 972 * The source and destination maps must be locked for write. 973 * The source map entry must be wired down (or be a sharing map 974 * entry corresponding to a main map entry that is wired down). 975 */ 976 977 void 978 vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry) 979 vm_map_t dst_map; 980 vm_map_t src_map; 981 vm_map_entry_t dst_entry; 982 vm_map_entry_t src_entry; 983 { 984 vm_object_t dst_object; 985 vm_object_t src_object; 986 vm_ooffset_t dst_offset; 987 vm_ooffset_t src_offset; 988 vm_prot_t prot; 989 vm_offset_t vaddr; 990 vm_page_t dst_m; 991 vm_page_t src_m; 992 993 #ifdef lint 994 src_map++; 995 #endif /* lint */ 996 997 src_object = src_entry->object.vm_object; 998 src_offset = src_entry->offset; 999 1000 /* 1001 * Create the top-level object for the destination entry. (Doesn't 1002 * actually shadow anything - we copy the pages directly.) 1003 */ 1004 dst_object = vm_object_allocate(OBJT_DEFAULT, 1005 (vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1006 1007 dst_entry->object.vm_object = dst_object; 1008 dst_entry->offset = 0; 1009 1010 prot = dst_entry->max_protection; 1011 1012 /* 1013 * Loop through all of the pages in the entry's range, copying each 1014 * one from the source object (it should be there) to the destination 1015 * object. 1016 */ 1017 for (vaddr = dst_entry->start, dst_offset = 0; 1018 vaddr < dst_entry->end; 1019 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { 1020 1021 /* 1022 * Allocate a page in the destination object 1023 */ 1024 do { 1025 dst_m = vm_page_alloc(dst_object, 1026 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); 1027 if (dst_m == NULL) { 1028 VM_WAIT; 1029 } 1030 } while (dst_m == NULL); 1031 1032 /* 1033 * Find the page in the source object, and copy it in. 1034 * (Because the source is wired down, the page will be in 1035 * memory.) 1036 */ 1037 src_m = vm_page_lookup(src_object, 1038 OFF_TO_IDX(dst_offset + src_offset)); 1039 if (src_m == NULL) 1040 panic("vm_fault_copy_wired: page missing"); 1041 1042 vm_page_copy(src_m, dst_m); 1043 1044 /* 1045 * Enter it in the pmap... 1046 */ 1047 1048 vm_page_flag_clear(dst_m, PG_ZERO); 1049 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE); 1050 vm_page_flag_set(dst_m, PG_WRITEABLE|PG_MAPPED); 1051 1052 /* 1053 * Mark it no longer busy, and put it on the active list. 1054 */ 1055 vm_page_activate(dst_m); 1056 vm_page_wakeup(dst_m); 1057 } 1058 } 1059 1060 1061 /* 1062 * This routine checks around the requested page for other pages that 1063 * might be able to be faulted in. This routine brackets the viable 1064 * pages for the pages to be paged in. 1065 * 1066 * Inputs: 1067 * m, rbehind, rahead 1068 * 1069 * Outputs: 1070 * marray (array of vm_page_t), reqpage (index of requested page) 1071 * 1072 * Return value: 1073 * number of pages in marray 1074 */ 1075 static int 1076 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1077 vm_page_t m; 1078 int rbehind; 1079 int rahead; 1080 vm_page_t *marray; 1081 int *reqpage; 1082 { 1083 int i,j; 1084 vm_object_t object; 1085 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1086 vm_page_t rtm; 1087 int cbehind, cahead; 1088 1089 object = m->object; 1090 pindex = m->pindex; 1091 1092 /* 1093 * we don't fault-ahead for device pager 1094 */ 1095 if (object->type == OBJT_DEVICE) { 1096 *reqpage = 0; 1097 marray[0] = m; 1098 return 1; 1099 } 1100 1101 /* 1102 * if the requested page is not available, then give up now 1103 */ 1104 1105 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1106 return 0; 1107 } 1108 1109 if ((cbehind == 0) && (cahead == 0)) { 1110 *reqpage = 0; 1111 marray[0] = m; 1112 return 1; 1113 } 1114 1115 if (rahead > cahead) { 1116 rahead = cahead; 1117 } 1118 1119 if (rbehind > cbehind) { 1120 rbehind = cbehind; 1121 } 1122 1123 /* 1124 * try to do any readahead that we might have free pages for. 1125 */ 1126 if ((rahead + rbehind) > 1127 ((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) { 1128 pagedaemon_wakeup(); 1129 marray[0] = m; 1130 *reqpage = 0; 1131 return 1; 1132 } 1133 1134 /* 1135 * scan backward for the read behind pages -- in memory 1136 */ 1137 if (pindex > 0) { 1138 if (rbehind > pindex) { 1139 rbehind = pindex; 1140 startpindex = 0; 1141 } else { 1142 startpindex = pindex - rbehind; 1143 } 1144 1145 for ( tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) { 1146 if (vm_page_lookup( object, tpindex)) { 1147 startpindex = tpindex + 1; 1148 break; 1149 } 1150 if (tpindex == 0) 1151 break; 1152 } 1153 1154 for(i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) { 1155 1156 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1157 if (rtm == NULL) { 1158 for (j = 0; j < i; j++) { 1159 vm_page_free(marray[j]); 1160 } 1161 marray[0] = m; 1162 *reqpage = 0; 1163 return 1; 1164 } 1165 1166 marray[i] = rtm; 1167 } 1168 } else { 1169 startpindex = 0; 1170 i = 0; 1171 } 1172 1173 marray[i] = m; 1174 /* page offset of the required page */ 1175 *reqpage = i; 1176 1177 tpindex = pindex + 1; 1178 i++; 1179 1180 /* 1181 * scan forward for the read ahead pages 1182 */ 1183 endpindex = tpindex + rahead; 1184 if (endpindex > object->size) 1185 endpindex = object->size; 1186 1187 for( ; tpindex < endpindex; i++, tpindex++) { 1188 1189 if (vm_page_lookup(object, tpindex)) { 1190 break; 1191 } 1192 1193 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1194 if (rtm == NULL) { 1195 break; 1196 } 1197 1198 marray[i] = rtm; 1199 } 1200 1201 /* return number of bytes of pages */ 1202 return i; 1203 }
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