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: src/sys/vm/vm_fault.c,v 1.108.2.8 2002/02/26 05:49:27 silby Exp $ 70 * $DragonFly: src/sys/vm/vm_fault.c,v 1.17 2004/05/31 11:43:49 hmp Exp $ 71 */ 72 73 /* 74 * Page fault handling module. 75 */ 76 77 #include <sys/param.h> 78 #include <sys/systm.h> 79 #include <sys/proc.h> 80 #include <sys/vnode.h> 81 #include <sys/resourcevar.h> 82 #include <sys/vmmeter.h> 83 84 #include <vm/vm.h> 85 #include <vm/vm_param.h> 86 #include <sys/lock.h> 87 #include <vm/pmap.h> 88 #include <vm/vm_map.h> 89 #include <vm/vm_object.h> 90 #include <vm/vm_page.h> 91 #include <vm/vm_pageout.h> 92 #include <vm/vm_kern.h> 93 #include <vm/vm_pager.h> 94 #include <vm/vnode_pager.h> 95 #include <vm/vm_extern.h> 96 #include <vm/vm_page2.h> 97 98 static int vm_fault_additional_pages (vm_page_t, int, 99 int, vm_page_t *, int *); 100 101 #define VM_FAULT_READ_AHEAD 8 102 #define VM_FAULT_READ_BEHIND 7 103 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1) 104 105 struct faultstate { 106 vm_page_t m; 107 vm_object_t object; 108 vm_pindex_t pindex; 109 vm_page_t first_m; 110 vm_object_t first_object; 111 vm_pindex_t first_pindex; 112 vm_map_t map; 113 vm_map_entry_t entry; 114 int lookup_still_valid; 115 struct vnode *vp; 116 }; 117 118 static __inline void 119 release_page(struct faultstate *fs) 120 { 121 vm_page_wakeup(fs->m); 122 vm_page_deactivate(fs->m); 123 fs->m = NULL; 124 } 125 126 static __inline void 127 unlock_map(struct faultstate *fs) 128 { 129 if (fs->lookup_still_valid) { 130 vm_map_lookup_done(fs->map, fs->entry, 0); 131 fs->lookup_still_valid = FALSE; 132 } 133 } 134 135 static void 136 _unlock_things(struct faultstate *fs, int dealloc) 137 { 138 vm_object_pip_wakeup(fs->object); 139 if (fs->object != fs->first_object) { 140 vm_page_free(fs->first_m); 141 vm_object_pip_wakeup(fs->first_object); 142 fs->first_m = NULL; 143 } 144 if (dealloc) { 145 vm_object_deallocate(fs->first_object); 146 } 147 unlock_map(fs); 148 if (fs->vp != NULL) { 149 vput(fs->vp); 150 fs->vp = NULL; 151 } 152 } 153 154 #define unlock_things(fs) _unlock_things(fs, 0) 155 #define unlock_and_deallocate(fs) _unlock_things(fs, 1) 156 157 /* 158 * TRYPAGER - used by vm_fault to calculate whether the pager for the 159 * current object *might* contain the page. 160 * 161 * default objects are zero-fill, there is no real pager. 162 */ 163 164 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 165 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) 166 167 /* 168 * vm_fault: 169 * 170 * Handle a page fault occurring at the given address, 171 * requiring the given permissions, in the map specified. 172 * If successful, the page is inserted into the 173 * associated physical map. 174 * 175 * NOTE: the given address should be truncated to the 176 * proper page address. 177 * 178 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 179 * a standard error specifying why the fault is fatal is returned. 180 * 181 * 182 * The map in question must be referenced, and remains so. 183 * Caller may hold no locks. 184 */ 185 int 186 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, int fault_flags) 187 { 188 vm_prot_t prot; 189 int result; 190 boolean_t wired; 191 int map_generation; 192 vm_object_t next_object; 193 vm_page_t marray[VM_FAULT_READ]; 194 int hardfault; 195 int faultcount; 196 int s; 197 struct faultstate fs; 198 199 mycpu->gd_cnt.v_vm_faults++; 200 hardfault = 0; 201 202 RetryFault: 203 /* 204 * Find the backing store object and offset into it to begin the 205 * search. 206 */ 207 fs.map = map; 208 if ((result = vm_map_lookup(&fs.map, vaddr, 209 fault_type, &fs.entry, &fs.first_object, 210 &fs.first_pindex, &prot, &wired)) != KERN_SUCCESS) { 211 if ((result != KERN_PROTECTION_FAILURE) || 212 ((fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE)) { 213 return result; 214 } 215 216 /* 217 * If we are user-wiring a r/w segment, and it is COW, then 218 * we need to do the COW operation. Note that we don't COW 219 * currently RO sections now, because it is NOT desirable 220 * to COW .text. We simply keep .text from ever being COW'ed 221 * and take the heat that one cannot debug wired .text sections. 222 */ 223 result = vm_map_lookup(&fs.map, vaddr, 224 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE, 225 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired); 226 if (result != KERN_SUCCESS) { 227 return result; 228 } 229 230 /* 231 * If we don't COW now, on a user wire, the user will never 232 * be able to write to the mapping. If we don't make this 233 * restriction, the bookkeeping would be nearly impossible. 234 */ 235 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 236 fs.entry->max_protection &= ~VM_PROT_WRITE; 237 } 238 239 map_generation = fs.map->timestamp; 240 241 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 242 panic("vm_fault: fault on nofault entry, addr: %lx", 243 (u_long)vaddr); 244 } 245 246 /* 247 * Make a reference to this object to prevent its disposal while we 248 * are messing with it. Once we have the reference, the map is free 249 * to be diddled. Since objects reference their shadows (and copies), 250 * they will stay around as well. 251 * 252 * Bump the paging-in-progress count to prevent size changes (e.g. 253 * truncation operations) during I/O. This must be done after 254 * obtaining the vnode lock in order to avoid possible deadlocks. 255 */ 256 vm_object_reference(fs.first_object); 257 fs.vp = vnode_pager_lock(fs.first_object); 258 vm_object_pip_add(fs.first_object, 1); 259 260 if ((fault_type & VM_PROT_WRITE) && 261 (fs.first_object->type == OBJT_VNODE)) { 262 vm_freeze_copyopts(fs.first_object, 263 fs.first_pindex, fs.first_pindex + 1); 264 } 265 266 fs.lookup_still_valid = TRUE; 267 268 if (wired) 269 fault_type = prot; 270 271 fs.first_m = NULL; 272 273 /* 274 * Search for the page at object/offset. 275 */ 276 277 fs.object = fs.first_object; 278 fs.pindex = fs.first_pindex; 279 280 while (TRUE) { 281 /* 282 * If the object is dead, we stop here 283 */ 284 285 if (fs.object->flags & OBJ_DEAD) { 286 unlock_and_deallocate(&fs); 287 return (KERN_PROTECTION_FAILURE); 288 } 289 290 /* 291 * See if page is resident. spl protection is required 292 * to avoid an interrupt unbusy/free race against our 293 * lookup. We must hold the protection through a page 294 * allocation or busy. 295 */ 296 s = splvm(); 297 fs.m = vm_page_lookup(fs.object, fs.pindex); 298 if (fs.m != NULL) { 299 int queue; 300 /* 301 * Wait/Retry if the page is busy. We have to do this 302 * if the page is busy via either PG_BUSY or 303 * vm_page_t->busy because the vm_pager may be using 304 * vm_page_t->busy for pageouts ( and even pageins if 305 * it is the vnode pager ), and we could end up trying 306 * to pagein and pageout the same page simultaneously. 307 * 308 * We can theoretically allow the busy case on a read 309 * fault if the page is marked valid, but since such 310 * pages are typically already pmap'd, putting that 311 * special case in might be more effort then it is 312 * worth. We cannot under any circumstances mess 313 * around with a vm_page_t->busy page except, perhaps, 314 * to pmap it. 315 */ 316 if ((fs.m->flags & PG_BUSY) || fs.m->busy) { 317 unlock_things(&fs); 318 vm_page_sleep_busy(fs.m, TRUE, "vmpfw"); 319 mycpu->gd_cnt.v_intrans++; 320 vm_object_deallocate(fs.first_object); 321 splx(s); 322 goto RetryFault; 323 } 324 325 queue = fs.m->queue; 326 vm_page_unqueue_nowakeup(fs.m); 327 328 if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) { 329 vm_page_activate(fs.m); 330 unlock_and_deallocate(&fs); 331 vm_waitpfault(); 332 splx(s); 333 goto RetryFault; 334 } 335 336 /* 337 * Mark page busy for other processes, and the 338 * pagedaemon. If it still isn't completely valid 339 * (readable), jump to readrest, else break-out ( we 340 * found the page ). 341 * 342 * We can release the spl once we have marked the 343 * page busy. 344 */ 345 346 vm_page_busy(fs.m); 347 splx(s); 348 349 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) && 350 fs.m->object != kernel_object && fs.m->object != kmem_object) { 351 goto readrest; 352 } 353 354 break; 355 } 356 357 /* 358 * Page is not resident, If this is the search termination 359 * or the pager might contain the page, allocate a new page. 360 * 361 * note: we are still in splvm(). 362 */ 363 364 if (TRYPAGER || fs.object == fs.first_object) { 365 if (fs.pindex >= fs.object->size) { 366 splx(s); 367 unlock_and_deallocate(&fs); 368 return (KERN_PROTECTION_FAILURE); 369 } 370 371 /* 372 * Allocate a new page for this object/offset pair. 373 */ 374 fs.m = NULL; 375 if (!vm_page_count_severe()) { 376 fs.m = vm_page_alloc(fs.object, fs.pindex, 377 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_NORMAL | VM_ALLOC_ZERO); 378 } 379 if (fs.m == NULL) { 380 splx(s); 381 unlock_and_deallocate(&fs); 382 vm_waitpfault(); 383 goto RetryFault; 384 } 385 } 386 splx(s); 387 388 readrest: 389 /* 390 * We have found a valid page or we have allocated a new page. 391 * The page thus may not be valid or may not be entirely 392 * valid. 393 * 394 * Attempt to fault-in the page if there is a chance that the 395 * pager has it, and potentially fault in additional pages 396 * at the same time. 397 * 398 * We are NOT in splvm here and if TRYPAGER is true then 399 * fs.m will be non-NULL and will be PG_BUSY for us. 400 */ 401 402 if (TRYPAGER) { 403 int rv; 404 int reqpage; 405 int ahead, behind; 406 u_char behavior = vm_map_entry_behavior(fs.entry); 407 408 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 409 ahead = 0; 410 behind = 0; 411 } else { 412 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT; 413 if (behind > VM_FAULT_READ_BEHIND) 414 behind = VM_FAULT_READ_BEHIND; 415 416 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1; 417 if (ahead > VM_FAULT_READ_AHEAD) 418 ahead = VM_FAULT_READ_AHEAD; 419 } 420 421 if ((fs.first_object->type != OBJT_DEVICE) && 422 (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 423 (behavior != MAP_ENTRY_BEHAV_RANDOM && 424 fs.pindex >= fs.entry->lastr && 425 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) 426 ) { 427 vm_pindex_t firstpindex, tmppindex; 428 429 if (fs.first_pindex < 2 * VM_FAULT_READ) 430 firstpindex = 0; 431 else 432 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ; 433 434 /* 435 * note: partially valid pages cannot be 436 * included in the lookahead - NFS piecemeal 437 * writes will barf on it badly. 438 * 439 * spl protection is required to avoid races 440 * between the lookup and an interrupt 441 * unbusy/free sequence occuring prior to 442 * our busy check. 443 */ 444 s = splvm(); 445 for (tmppindex = fs.first_pindex - 1; 446 tmppindex >= firstpindex; 447 --tmppindex 448 ) { 449 vm_page_t mt; 450 mt = vm_page_lookup( fs.first_object, tmppindex); 451 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL)) 452 break; 453 if (mt->busy || 454 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) || 455 mt->hold_count || 456 mt->wire_count) 457 continue; 458 if (mt->dirty == 0) 459 vm_page_test_dirty(mt); 460 if (mt->dirty) { 461 vm_page_protect(mt, VM_PROT_NONE); 462 vm_page_deactivate(mt); 463 } else { 464 vm_page_cache(mt); 465 } 466 } 467 splx(s); 468 469 ahead += behind; 470 behind = 0; 471 } 472 473 /* 474 * now we find out if any other pages should be paged 475 * in at this time this routine checks to see if the 476 * pages surrounding this fault reside in the same 477 * object as the page for this fault. If they do, 478 * then they are faulted in also into the object. The 479 * array "marray" returned contains an array of 480 * vm_page_t structs where one of them is the 481 * vm_page_t passed to the routine. The reqpage 482 * return value is the index into the marray for the 483 * vm_page_t passed to the routine. 484 * 485 * fs.m plus the additional pages are PG_BUSY'd. 486 */ 487 faultcount = vm_fault_additional_pages( 488 fs.m, behind, ahead, marray, &reqpage); 489 490 /* 491 * update lastr imperfectly (we do not know how much 492 * getpages will actually read), but good enough. 493 */ 494 fs.entry->lastr = fs.pindex + faultcount - behind; 495 496 /* 497 * Call the pager to retrieve the data, if any, after 498 * releasing the lock on the map. We hold a ref on 499 * fs.object and the pages are PG_BUSY'd. 500 */ 501 unlock_map(&fs); 502 503 rv = faultcount ? 504 vm_pager_get_pages(fs.object, marray, faultcount, 505 reqpage) : VM_PAGER_FAIL; 506 507 if (rv == VM_PAGER_OK) { 508 /* 509 * Found the page. Leave it busy while we play 510 * with it. 511 */ 512 513 /* 514 * Relookup in case pager changed page. Pager 515 * is responsible for disposition of old page 516 * if moved. 517 * 518 * XXX other code segments do relookups too. 519 * It's a bad abstraction that needs to be 520 * fixed/removed. 521 */ 522 fs.m = vm_page_lookup(fs.object, fs.pindex); 523 if (fs.m == NULL) { 524 unlock_and_deallocate(&fs); 525 goto RetryFault; 526 } 527 528 hardfault++; 529 break; /* break to PAGE HAS BEEN FOUND */ 530 } 531 /* 532 * Remove the bogus page (which does not exist at this 533 * object/offset); before doing so, we must get back 534 * our object lock to preserve our invariant. 535 * 536 * Also wake up any other process that may want to bring 537 * in this page. 538 * 539 * If this is the top-level object, we must leave the 540 * busy page to prevent another process from rushing 541 * past us, and inserting the page in that object at 542 * the same time that we are. 543 */ 544 545 if (rv == VM_PAGER_ERROR) 546 printf("vm_fault: pager read error, pid %d (%s)\n", 547 curproc->p_pid, curproc->p_comm); 548 /* 549 * Data outside the range of the pager or an I/O error 550 */ 551 /* 552 * XXX - the check for kernel_map is a kludge to work 553 * around having the machine panic on a kernel space 554 * fault w/ I/O error. 555 */ 556 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 557 (rv == VM_PAGER_BAD)) { 558 vm_page_free(fs.m); 559 fs.m = NULL; 560 unlock_and_deallocate(&fs); 561 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 562 } 563 if (fs.object != fs.first_object) { 564 vm_page_free(fs.m); 565 fs.m = NULL; 566 /* 567 * XXX - we cannot just fall out at this 568 * point, m has been freed and is invalid! 569 */ 570 } 571 } 572 573 /* 574 * We get here if the object has default pager (or unwiring) 575 * or the pager doesn't have the page. 576 */ 577 if (fs.object == fs.first_object) 578 fs.first_m = fs.m; 579 580 /* 581 * Move on to the next object. Lock the next object before 582 * unlocking the current one. 583 */ 584 585 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 586 next_object = fs.object->backing_object; 587 if (next_object == NULL) { 588 /* 589 * If there's no object left, fill the page in the top 590 * object with zeros. 591 */ 592 if (fs.object != fs.first_object) { 593 vm_object_pip_wakeup(fs.object); 594 595 fs.object = fs.first_object; 596 fs.pindex = fs.first_pindex; 597 fs.m = fs.first_m; 598 } 599 fs.first_m = NULL; 600 601 /* 602 * Zero the page if necessary and mark it valid. 603 */ 604 if ((fs.m->flags & PG_ZERO) == 0) { 605 vm_page_zero_fill(fs.m); 606 } else { 607 mycpu->gd_cnt.v_ozfod++; 608 } 609 mycpu->gd_cnt.v_zfod++; 610 fs.m->valid = VM_PAGE_BITS_ALL; 611 break; /* break to PAGE HAS BEEN FOUND */ 612 } else { 613 if (fs.object != fs.first_object) { 614 vm_object_pip_wakeup(fs.object); 615 } 616 KASSERT(fs.object != next_object, ("object loop %p", next_object)); 617 fs.object = next_object; 618 vm_object_pip_add(fs.object, 1); 619 } 620 } 621 622 KASSERT((fs.m->flags & PG_BUSY) != 0, 623 ("vm_fault: not busy after main loop")); 624 625 /* 626 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 627 * is held.] 628 */ 629 630 /* 631 * If the page is being written, but isn't already owned by the 632 * top-level object, we have to copy it into a new page owned by the 633 * top-level object. 634 */ 635 636 if (fs.object != fs.first_object) { 637 /* 638 * We only really need to copy if we want to write it. 639 */ 640 641 if (fault_type & VM_PROT_WRITE) { 642 /* 643 * This allows pages to be virtually copied from a 644 * backing_object into the first_object, where the 645 * backing object has no other refs to it, and cannot 646 * gain any more refs. Instead of a bcopy, we just 647 * move the page from the backing object to the 648 * first object. Note that we must mark the page 649 * dirty in the first object so that it will go out 650 * to swap when needed. 651 */ 652 if (map_generation == fs.map->timestamp && 653 /* 654 * Only one shadow object 655 */ 656 (fs.object->shadow_count == 1) && 657 /* 658 * No COW refs, except us 659 */ 660 (fs.object->ref_count == 1) && 661 /* 662 * No one else can look this object up 663 */ 664 (fs.object->handle == NULL) && 665 /* 666 * No other ways to look the object up 667 */ 668 ((fs.object->type == OBJT_DEFAULT) || 669 (fs.object->type == OBJT_SWAP)) && 670 /* 671 * We don't chase down the shadow chain 672 */ 673 (fs.object == fs.first_object->backing_object) && 674 675 /* 676 * grab the lock if we need to 677 */ 678 (fs.lookup_still_valid || 679 lockmgr(&fs.map->lock, LK_EXCLUSIVE|LK_NOWAIT, NULL, curthread) == 0) 680 ) { 681 682 fs.lookup_still_valid = 1; 683 /* 684 * get rid of the unnecessary page 685 */ 686 vm_page_protect(fs.first_m, VM_PROT_NONE); 687 vm_page_free(fs.first_m); 688 fs.first_m = NULL; 689 690 /* 691 * grab the page and put it into the 692 * process'es object. The page is 693 * automatically made dirty. 694 */ 695 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 696 fs.first_m = fs.m; 697 vm_page_busy(fs.first_m); 698 fs.m = NULL; 699 mycpu->gd_cnt.v_cow_optim++; 700 } else { 701 /* 702 * Oh, well, lets copy it. 703 */ 704 vm_page_copy(fs.m, fs.first_m); 705 } 706 707 if (fs.m) { 708 /* 709 * We no longer need the old page or object. 710 */ 711 release_page(&fs); 712 } 713 714 /* 715 * fs.object != fs.first_object due to above 716 * conditional 717 */ 718 719 vm_object_pip_wakeup(fs.object); 720 721 /* 722 * Only use the new page below... 723 */ 724 725 mycpu->gd_cnt.v_cow_faults++; 726 fs.m = fs.first_m; 727 fs.object = fs.first_object; 728 fs.pindex = fs.first_pindex; 729 730 } else { 731 prot &= ~VM_PROT_WRITE; 732 } 733 } 734 735 /* 736 * We must verify that the maps have not changed since our last 737 * lookup. 738 */ 739 740 if (!fs.lookup_still_valid && 741 (fs.map->timestamp != map_generation)) { 742 vm_object_t retry_object; 743 vm_pindex_t retry_pindex; 744 vm_prot_t retry_prot; 745 746 /* 747 * Since map entries may be pageable, make sure we can take a 748 * page fault on them. 749 */ 750 751 /* 752 * Unlock vnode before the lookup to avoid deadlock. E.G. 753 * avoid a deadlock between the inode and exec_map that can 754 * occur due to locks being obtained in different orders. 755 */ 756 757 if (fs.vp != NULL) { 758 vput(fs.vp); 759 fs.vp = NULL; 760 } 761 762 if (fs.map->infork) { 763 release_page(&fs); 764 unlock_and_deallocate(&fs); 765 goto RetryFault; 766 } 767 768 /* 769 * To avoid trying to write_lock the map while another process 770 * has it read_locked (in vm_map_wire), we do not try for 771 * write permission. If the page is still writable, we will 772 * get write permission. If it is not, or has been marked 773 * needs_copy, we enter the mapping without write permission, 774 * and will merely take another fault. 775 */ 776 result = vm_map_lookup(&fs.map, vaddr, fault_type & ~VM_PROT_WRITE, 777 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 778 map_generation = fs.map->timestamp; 779 780 /* 781 * If we don't need the page any longer, put it on the active 782 * list (the easiest thing to do here). If no one needs it, 783 * pageout will grab it eventually. 784 */ 785 786 if (result != KERN_SUCCESS) { 787 release_page(&fs); 788 unlock_and_deallocate(&fs); 789 return (result); 790 } 791 fs.lookup_still_valid = TRUE; 792 793 if ((retry_object != fs.first_object) || 794 (retry_pindex != fs.first_pindex)) { 795 release_page(&fs); 796 unlock_and_deallocate(&fs); 797 goto RetryFault; 798 } 799 /* 800 * Check whether the protection has changed or the object has 801 * been copied while we left the map unlocked. Changing from 802 * read to write permission is OK - we leave the page 803 * write-protected, and catch the write fault. Changing from 804 * write to read permission means that we can't mark the page 805 * write-enabled after all. 806 */ 807 prot &= retry_prot; 808 } 809 810 /* 811 * Put this page into the physical map. We had to do the unlock above 812 * because pmap_enter may cause other faults. We don't put the page 813 * back on the active queue until later so that the page-out daemon 814 * won't find us (yet). 815 */ 816 817 if (prot & VM_PROT_WRITE) { 818 vm_page_flag_set(fs.m, PG_WRITEABLE); 819 vm_object_set_writeable_dirty(fs.m->object); 820 821 /* 822 * If the fault is a write, we know that this page is being 823 * written NOW so dirty it explicitly to save on 824 * pmap_is_modified() calls later. 825 * 826 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC 827 * if the page is already dirty to prevent data written with 828 * the expectation of being synced from not being synced. 829 * Likewise if this entry does not request NOSYNC then make 830 * sure the page isn't marked NOSYNC. Applications sharing 831 * data should use the same flags to avoid ping ponging. 832 * 833 * Also tell the backing pager, if any, that it should remove 834 * any swap backing since the page is now dirty. 835 */ 836 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 837 if (fs.m->dirty == 0) 838 vm_page_flag_set(fs.m, PG_NOSYNC); 839 } else { 840 vm_page_flag_clear(fs.m, PG_NOSYNC); 841 } 842 if (fault_flags & VM_FAULT_DIRTY) { 843 int s; 844 vm_page_dirty(fs.m); 845 s = splvm(); 846 vm_pager_page_unswapped(fs.m); 847 splx(s); 848 } 849 } 850 851 /* 852 * Page had better still be busy 853 */ 854 855 KASSERT(fs.m->flags & PG_BUSY, 856 ("vm_fault: page %p not busy!", fs.m)); 857 858 unlock_things(&fs); 859 860 /* 861 * Sanity check: page must be completely valid or it is not fit to 862 * map into user space. vm_pager_get_pages() ensures this. 863 */ 864 865 if (fs.m->valid != VM_PAGE_BITS_ALL) { 866 vm_page_zero_invalid(fs.m, TRUE); 867 printf("Warning: page %p partially invalid on fault\n", fs.m); 868 } 869 870 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired); 871 872 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 873 pmap_prefault(fs.map->pmap, vaddr, fs.entry); 874 } 875 876 vm_page_flag_clear(fs.m, PG_ZERO); 877 vm_page_flag_set(fs.m, PG_MAPPED|PG_REFERENCED); 878 if (fault_flags & VM_FAULT_HOLD) 879 vm_page_hold(fs.m); 880 881 /* 882 * If the page is not wired down, then put it where the pageout daemon 883 * can find it. 884 */ 885 886 if (fault_flags & VM_FAULT_WIRE_MASK) { 887 if (wired) 888 vm_page_wire(fs.m); 889 else 890 vm_page_unwire(fs.m, 1); 891 } else { 892 vm_page_activate(fs.m); 893 } 894 895 if (curproc && (curproc->p_flag & P_INMEM) && curproc->p_stats) { 896 if (hardfault) { 897 curproc->p_stats->p_ru.ru_majflt++; 898 } else { 899 curproc->p_stats->p_ru.ru_minflt++; 900 } 901 } 902 903 /* 904 * Unlock everything, and return 905 */ 906 907 vm_page_wakeup(fs.m); 908 vm_object_deallocate(fs.first_object); 909 910 return (KERN_SUCCESS); 911 912 } 913 914 /* 915 * quick version of vm_fault 916 */ 917 int 918 vm_fault_quick(caddr_t v, int prot) 919 { 920 int r; 921 922 if (prot & VM_PROT_WRITE) 923 r = subyte(v, fubyte(v)); 924 else 925 r = fubyte(v); 926 return(r); 927 } 928 929 /* 930 * Wire down a range of virtual addresses in a map. The entry in question 931 * should be marked in-transition and the map must be locked. We must 932 * release the map temporarily while faulting-in the page to avoid a 933 * deadlock. Note that the entry may be clipped while we are blocked but 934 * will never be freed. 935 */ 936 int 937 vm_fault_wire(vm_map_t map, vm_map_entry_t entry, boolean_t user_wire) 938 { 939 boolean_t fictitious; 940 vm_offset_t start; 941 vm_offset_t end; 942 vm_offset_t va; 943 vm_paddr_t pa; 944 pmap_t pmap; 945 int rv; 946 947 pmap = vm_map_pmap(map); 948 start = entry->start; 949 end = entry->end; 950 fictitious = entry->object.vm_object && 951 (entry->object.vm_object->type == OBJT_DEVICE); 952 953 vm_map_unlock(map); 954 map->timestamp++; 955 956 /* 957 * We simulate a fault to get the page and enter it in the physical 958 * map. 959 */ 960 for (va = start; va < end; va += PAGE_SIZE) { 961 if (user_wire) { 962 rv = vm_fault(map, va, VM_PROT_READ, 963 VM_FAULT_USER_WIRE); 964 } else { 965 rv = vm_fault(map, va, VM_PROT_READ|VM_PROT_WRITE, 966 VM_FAULT_CHANGE_WIRING); 967 } 968 if (rv) { 969 while (va > start) { 970 va -= PAGE_SIZE; 971 if ((pa = pmap_extract(pmap, va)) == 0) 972 continue; 973 pmap_change_wiring(pmap, va, FALSE); 974 if (!fictitious) 975 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 976 } 977 vm_map_lock(map); 978 return (rv); 979 } 980 } 981 vm_map_lock(map); 982 return (KERN_SUCCESS); 983 } 984 985 /* 986 * Unwire a range of virtual addresses in a map. The map should be 987 * locked. 988 */ 989 void 990 vm_fault_unwire(vm_map_t map, vm_map_entry_t entry) 991 { 992 boolean_t fictitious; 993 vm_offset_t start; 994 vm_offset_t end; 995 vm_offset_t va; 996 vm_paddr_t pa; 997 pmap_t pmap; 998 999 pmap = vm_map_pmap(map); 1000 start = entry->start; 1001 end = entry->end; 1002 fictitious = entry->object.vm_object && 1003 (entry->object.vm_object->type == OBJT_DEVICE); 1004 1005 /* 1006 * Since the pages are wired down, we must be able to get their 1007 * mappings from the physical map system. 1008 */ 1009 for (va = start; va < end; va += PAGE_SIZE) { 1010 pa = pmap_extract(pmap, va); 1011 if (pa != 0) { 1012 pmap_change_wiring(pmap, va, FALSE); 1013 if (!fictitious) 1014 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1015 } 1016 } 1017 } 1018 1019 /* 1020 * Routine: 1021 * vm_fault_copy_entry 1022 * Function: 1023 * Copy all of the pages from a wired-down map entry to another. 1024 * 1025 * In/out conditions: 1026 * The source and destination maps must be locked for write. 1027 * The source map entry must be wired down (or be a sharing map 1028 * entry corresponding to a main map entry that is wired down). 1029 */ 1030 1031 void 1032 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1033 vm_map_entry_t dst_entry, vm_map_entry_t src_entry) 1034 { 1035 vm_object_t dst_object; 1036 vm_object_t src_object; 1037 vm_ooffset_t dst_offset; 1038 vm_ooffset_t src_offset; 1039 vm_prot_t prot; 1040 vm_offset_t vaddr; 1041 vm_page_t dst_m; 1042 vm_page_t src_m; 1043 1044 #ifdef lint 1045 src_map++; 1046 #endif /* lint */ 1047 1048 src_object = src_entry->object.vm_object; 1049 src_offset = src_entry->offset; 1050 1051 /* 1052 * Create the top-level object for the destination entry. (Doesn't 1053 * actually shadow anything - we copy the pages directly.) 1054 */ 1055 dst_object = vm_object_allocate(OBJT_DEFAULT, 1056 (vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1057 1058 dst_entry->object.vm_object = dst_object; 1059 dst_entry->offset = 0; 1060 1061 prot = dst_entry->max_protection; 1062 1063 /* 1064 * Loop through all of the pages in the entry's range, copying each 1065 * one from the source object (it should be there) to the destination 1066 * object. 1067 */ 1068 for (vaddr = dst_entry->start, dst_offset = 0; 1069 vaddr < dst_entry->end; 1070 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { 1071 1072 /* 1073 * Allocate a page in the destination object 1074 */ 1075 do { 1076 dst_m = vm_page_alloc(dst_object, 1077 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); 1078 if (dst_m == NULL) { 1079 vm_wait(); 1080 } 1081 } while (dst_m == NULL); 1082 1083 /* 1084 * Find the page in the source object, and copy it in. 1085 * (Because the source is wired down, the page will be in 1086 * memory.) 1087 */ 1088 src_m = vm_page_lookup(src_object, 1089 OFF_TO_IDX(dst_offset + src_offset)); 1090 if (src_m == NULL) 1091 panic("vm_fault_copy_wired: page missing"); 1092 1093 vm_page_copy(src_m, dst_m); 1094 1095 /* 1096 * Enter it in the pmap... 1097 */ 1098 1099 vm_page_flag_clear(dst_m, PG_ZERO); 1100 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE); 1101 vm_page_flag_set(dst_m, PG_WRITEABLE|PG_MAPPED); 1102 1103 /* 1104 * Mark it no longer busy, and put it on the active list. 1105 */ 1106 vm_page_activate(dst_m); 1107 vm_page_wakeup(dst_m); 1108 } 1109 } 1110 1111 1112 /* 1113 * This routine checks around the requested page for other pages that 1114 * might be able to be faulted in. This routine brackets the viable 1115 * pages for the pages to be paged in. 1116 * 1117 * Inputs: 1118 * m, rbehind, rahead 1119 * 1120 * Outputs: 1121 * marray (array of vm_page_t), reqpage (index of requested page) 1122 * 1123 * Return value: 1124 * number of pages in marray 1125 */ 1126 static int 1127 vm_fault_additional_pages(vm_page_t m, int rbehind, int rahead, 1128 vm_page_t *marray, int *reqpage) 1129 { 1130 int i,j; 1131 vm_object_t object; 1132 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1133 vm_page_t rtm; 1134 int cbehind, cahead; 1135 1136 object = m->object; 1137 pindex = m->pindex; 1138 1139 /* 1140 * we don't fault-ahead for device pager 1141 */ 1142 if (object->type == OBJT_DEVICE) { 1143 *reqpage = 0; 1144 marray[0] = m; 1145 return 1; 1146 } 1147 1148 /* 1149 * if the requested page is not available, then give up now 1150 */ 1151 1152 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1153 return 0; 1154 } 1155 1156 if ((cbehind == 0) && (cahead == 0)) { 1157 *reqpage = 0; 1158 marray[0] = m; 1159 return 1; 1160 } 1161 1162 if (rahead > cahead) { 1163 rahead = cahead; 1164 } 1165 1166 if (rbehind > cbehind) { 1167 rbehind = cbehind; 1168 } 1169 1170 /* 1171 * try to do any readahead that we might have free pages for. 1172 */ 1173 if ((rahead + rbehind) > 1174 ((vmstats.v_free_count + vmstats.v_cache_count) - vmstats.v_free_reserved)) { 1175 pagedaemon_wakeup(); 1176 marray[0] = m; 1177 *reqpage = 0; 1178 return 1; 1179 } 1180 1181 /* 1182 * scan backward for the read behind pages -- in memory 1183 * 1184 * Assume that if the page is not found an interrupt will not 1185 * create it. Theoretically interrupts can only remove (busy) 1186 * pages, not create new associations. 1187 */ 1188 if (pindex > 0) { 1189 if (rbehind > pindex) { 1190 rbehind = pindex; 1191 startpindex = 0; 1192 } else { 1193 startpindex = pindex - rbehind; 1194 } 1195 1196 for ( tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) { 1197 if (vm_page_lookup( object, tpindex)) { 1198 startpindex = tpindex + 1; 1199 break; 1200 } 1201 if (tpindex == 0) 1202 break; 1203 } 1204 1205 for(i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) { 1206 1207 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1208 if (rtm == NULL) { 1209 for (j = 0; j < i; j++) { 1210 vm_page_free(marray[j]); 1211 } 1212 marray[0] = m; 1213 *reqpage = 0; 1214 return 1; 1215 } 1216 1217 marray[i] = rtm; 1218 } 1219 } else { 1220 startpindex = 0; 1221 i = 0; 1222 } 1223 1224 marray[i] = m; 1225 /* page offset of the required page */ 1226 *reqpage = i; 1227 1228 tpindex = pindex + 1; 1229 i++; 1230 1231 /* 1232 * scan forward for the read ahead pages 1233 */ 1234 endpindex = tpindex + rahead; 1235 if (endpindex > object->size) 1236 endpindex = object->size; 1237 1238 for( ; tpindex < endpindex; i++, tpindex++) { 1239 1240 if (vm_page_lookup(object, tpindex)) { 1241 break; 1242 } 1243 1244 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1245 if (rtm == NULL) { 1246 break; 1247 } 1248 1249 marray[i] = rtm; 1250 } 1251 1252 /* return number of bytes of pages */ 1253 return i; 1254 } 1255