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 1.20 2005/11/14 18:50:15 dillon 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 97 #include <sys/thread2.h> 98 #include <vm/vm_page2.h> 99 100 static int vm_fault_additional_pages (vm_page_t, int, 101 int, vm_page_t *, int *); 102 103 #define VM_FAULT_READ_AHEAD 8 104 #define VM_FAULT_READ_BEHIND 7 105 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1) 106 107 struct faultstate { 108 vm_page_t m; 109 vm_object_t object; 110 vm_pindex_t pindex; 111 vm_page_t first_m; 112 vm_object_t first_object; 113 vm_pindex_t first_pindex; 114 vm_map_t map; 115 vm_map_entry_t entry; 116 int lookup_still_valid; 117 struct vnode *vp; 118 }; 119 120 static __inline void 121 release_page(struct faultstate *fs) 122 { 123 vm_page_wakeup(fs->m); 124 vm_page_deactivate(fs->m); 125 fs->m = NULL; 126 } 127 128 static __inline void 129 unlock_map(struct faultstate *fs) 130 { 131 if (fs->lookup_still_valid) { 132 vm_map_lookup_done(fs->map, fs->entry, 0); 133 fs->lookup_still_valid = FALSE; 134 } 135 } 136 137 static void 138 _unlock_things(struct faultstate *fs, int dealloc) 139 { 140 vm_object_pip_wakeup(fs->object); 141 if (fs->object != fs->first_object) { 142 vm_page_free(fs->first_m); 143 vm_object_pip_wakeup(fs->first_object); 144 fs->first_m = NULL; 145 } 146 if (dealloc) { 147 vm_object_deallocate(fs->first_object); 148 } 149 unlock_map(fs); 150 if (fs->vp != NULL) { 151 vput(fs->vp); 152 fs->vp = NULL; 153 } 154 } 155 156 #define unlock_things(fs) _unlock_things(fs, 0) 157 #define unlock_and_deallocate(fs) _unlock_things(fs, 1) 158 159 /* 160 * TRYPAGER - used by vm_fault to calculate whether the pager for the 161 * current object *might* contain the page. 162 * 163 * default objects are zero-fill, there is no real pager. 164 */ 165 166 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 167 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) 168 169 /* 170 * vm_fault: 171 * 172 * Handle a page fault occurring at the given address, 173 * requiring the given permissions, in the map specified. 174 * If successful, the page is inserted into the 175 * associated physical map. 176 * 177 * NOTE: the given address should be truncated to the 178 * proper page address. 179 * 180 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 181 * a standard error specifying why the fault is fatal is returned. 182 * 183 * 184 * The map in question must be referenced, and remains so. 185 * Caller may hold no locks. 186 */ 187 int 188 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, int fault_flags) 189 { 190 vm_prot_t prot; 191 int result; 192 boolean_t wired; 193 int map_generation; 194 vm_object_t next_object; 195 vm_page_t marray[VM_FAULT_READ]; 196 int hardfault; 197 int faultcount; 198 struct faultstate fs; 199 200 mycpu->gd_cnt.v_vm_faults++; 201 hardfault = 0; 202 203 RetryFault: 204 /* 205 * Find the backing store object and offset into it to begin the 206 * search. 207 */ 208 fs.map = map; 209 if ((result = vm_map_lookup(&fs.map, vaddr, 210 fault_type, &fs.entry, &fs.first_object, 211 &fs.first_pindex, &prot, &wired)) != KERN_SUCCESS) { 212 if ((result != KERN_PROTECTION_FAILURE) || 213 ((fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE)) { 214 return result; 215 } 216 217 /* 218 * If we are user-wiring a r/w segment, and it is COW, then 219 * we need to do the COW operation. Note that we don't COW 220 * currently RO sections now, because it is NOT desirable 221 * to COW .text. We simply keep .text from ever being COW'ed 222 * and take the heat that one cannot debug wired .text sections. 223 */ 224 result = vm_map_lookup(&fs.map, vaddr, 225 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE, 226 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired); 227 if (result != KERN_SUCCESS) { 228 return result; 229 } 230 231 /* 232 * If we don't COW now, on a user wire, the user will never 233 * be able to write to the mapping. If we don't make this 234 * restriction, the bookkeeping would be nearly impossible. 235 */ 236 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 237 fs.entry->max_protection &= ~VM_PROT_WRITE; 238 } 239 240 map_generation = fs.map->timestamp; 241 242 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 243 panic("vm_fault: fault on nofault entry, addr: %lx", 244 (u_long)vaddr); 245 } 246 247 /* 248 * A system map entry may return a NULL object. No object means 249 * no pager means an unrecoverable kernel fault. 250 */ 251 if (fs.first_object == NULL) { 252 panic("vm_fault: unrecoverable fault at %p in entry %p", 253 (void *)vaddr, fs.entry); 254 } 255 256 /* 257 * Make a reference to this object to prevent its disposal while we 258 * are messing with it. Once we have the reference, the map is free 259 * to be diddled. Since objects reference their shadows (and copies), 260 * they will stay around as well. 261 * 262 * Bump the paging-in-progress count to prevent size changes (e.g. 263 * truncation operations) during I/O. This must be done after 264 * obtaining the vnode lock in order to avoid possible deadlocks. 265 */ 266 vm_object_reference(fs.first_object); 267 fs.vp = vnode_pager_lock(fs.first_object); 268 vm_object_pip_add(fs.first_object, 1); 269 270 if ((fault_type & VM_PROT_WRITE) && 271 (fs.first_object->type == OBJT_VNODE)) { 272 vm_freeze_copyopts(fs.first_object, 273 fs.first_pindex, fs.first_pindex + 1); 274 } 275 276 fs.lookup_still_valid = TRUE; 277 278 if (wired) 279 fault_type = prot; 280 281 fs.first_m = NULL; 282 283 /* 284 * Search for the page at object/offset. 285 */ 286 287 fs.object = fs.first_object; 288 fs.pindex = fs.first_pindex; 289 290 while (TRUE) { 291 /* 292 * If the object is dead, we stop here 293 */ 294 295 if (fs.object->flags & OBJ_DEAD) { 296 unlock_and_deallocate(&fs); 297 return (KERN_PROTECTION_FAILURE); 298 } 299 300 /* 301 * See if page is resident. spl protection is required 302 * to avoid an interrupt unbusy/free race against our 303 * lookup. We must hold the protection through a page 304 * allocation or busy. 305 */ 306 crit_enter(); 307 fs.m = vm_page_lookup(fs.object, fs.pindex); 308 if (fs.m != NULL) { 309 int queue; 310 /* 311 * Wait/Retry if the page is busy. We have to do this 312 * if the page is busy via either PG_BUSY or 313 * vm_page_t->busy because the vm_pager may be using 314 * vm_page_t->busy for pageouts ( and even pageins if 315 * it is the vnode pager ), and we could end up trying 316 * to pagein and pageout the same page simultaneously. 317 * 318 * We can theoretically allow the busy case on a read 319 * fault if the page is marked valid, but since such 320 * pages are typically already pmap'd, putting that 321 * special case in might be more effort then it is 322 * worth. We cannot under any circumstances mess 323 * around with a vm_page_t->busy page except, perhaps, 324 * to pmap it. 325 */ 326 if ((fs.m->flags & PG_BUSY) || fs.m->busy) { 327 unlock_things(&fs); 328 vm_page_sleep_busy(fs.m, TRUE, "vmpfw"); 329 mycpu->gd_cnt.v_intrans++; 330 vm_object_deallocate(fs.first_object); 331 crit_exit(); 332 goto RetryFault; 333 } 334 335 queue = fs.m->queue; 336 vm_page_unqueue_nowakeup(fs.m); 337 338 if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) { 339 vm_page_activate(fs.m); 340 unlock_and_deallocate(&fs); 341 vm_waitpfault(); 342 crit_exit(); 343 goto RetryFault; 344 } 345 346 /* 347 * Mark page busy for other processes, and the 348 * pagedaemon. If it still isn't completely valid 349 * (readable), jump to readrest, else break-out ( we 350 * found the page ). 351 * 352 * We can release the spl once we have marked the 353 * page busy. 354 */ 355 356 vm_page_busy(fs.m); 357 crit_exit(); 358 359 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) && 360 fs.m->object != kernel_object && fs.m->object != kmem_object) { 361 goto readrest; 362 } 363 364 break; 365 } 366 367 /* 368 * Page is not resident, If this is the search termination 369 * or the pager might contain the page, allocate a new page. 370 * 371 * note: we are still in splvm(). 372 */ 373 374 if (TRYPAGER || fs.object == fs.first_object) { 375 if (fs.pindex >= fs.object->size) { 376 crit_exit(); 377 unlock_and_deallocate(&fs); 378 return (KERN_PROTECTION_FAILURE); 379 } 380 381 /* 382 * Allocate a new page for this object/offset pair. 383 */ 384 fs.m = NULL; 385 if (!vm_page_count_severe()) { 386 fs.m = vm_page_alloc(fs.object, fs.pindex, 387 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_NORMAL | VM_ALLOC_ZERO); 388 } 389 if (fs.m == NULL) { 390 crit_exit(); 391 unlock_and_deallocate(&fs); 392 vm_waitpfault(); 393 goto RetryFault; 394 } 395 } 396 crit_exit(); 397 398 readrest: 399 /* 400 * We have found a valid page or we have allocated a new page. 401 * The page thus may not be valid or may not be entirely 402 * valid. 403 * 404 * Attempt to fault-in the page if there is a chance that the 405 * pager has it, and potentially fault in additional pages 406 * at the same time. 407 * 408 * We are NOT in splvm here and if TRYPAGER is true then 409 * fs.m will be non-NULL and will be PG_BUSY for us. 410 */ 411 412 if (TRYPAGER) { 413 int rv; 414 int reqpage; 415 int ahead, behind; 416 u_char behavior = vm_map_entry_behavior(fs.entry); 417 418 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 419 ahead = 0; 420 behind = 0; 421 } else { 422 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT; 423 if (behind > VM_FAULT_READ_BEHIND) 424 behind = VM_FAULT_READ_BEHIND; 425 426 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1; 427 if (ahead > VM_FAULT_READ_AHEAD) 428 ahead = VM_FAULT_READ_AHEAD; 429 } 430 431 if ((fs.first_object->type != OBJT_DEVICE) && 432 (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 433 (behavior != MAP_ENTRY_BEHAV_RANDOM && 434 fs.pindex >= fs.entry->lastr && 435 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) 436 ) { 437 vm_pindex_t firstpindex, tmppindex; 438 439 if (fs.first_pindex < 2 * VM_FAULT_READ) 440 firstpindex = 0; 441 else 442 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ; 443 444 /* 445 * note: partially valid pages cannot be 446 * included in the lookahead - NFS piecemeal 447 * writes will barf on it badly. 448 * 449 * spl protection is required to avoid races 450 * between the lookup and an interrupt 451 * unbusy/free sequence occuring prior to 452 * our busy check. 453 */ 454 crit_enter(); 455 for (tmppindex = fs.first_pindex - 1; 456 tmppindex >= firstpindex; 457 --tmppindex 458 ) { 459 vm_page_t mt; 460 mt = vm_page_lookup( fs.first_object, tmppindex); 461 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL)) 462 break; 463 if (mt->busy || 464 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) || 465 mt->hold_count || 466 mt->wire_count) 467 continue; 468 if (mt->dirty == 0) 469 vm_page_test_dirty(mt); 470 if (mt->dirty) { 471 vm_page_protect(mt, VM_PROT_NONE); 472 vm_page_deactivate(mt); 473 } else { 474 vm_page_cache(mt); 475 } 476 } 477 crit_exit(); 478 479 ahead += behind; 480 behind = 0; 481 } 482 483 /* 484 * now we find out if any other pages should be paged 485 * in at this time this routine checks to see if the 486 * pages surrounding this fault reside in the same 487 * object as the page for this fault. If they do, 488 * then they are faulted in also into the object. The 489 * array "marray" returned contains an array of 490 * vm_page_t structs where one of them is the 491 * vm_page_t passed to the routine. The reqpage 492 * return value is the index into the marray for the 493 * vm_page_t passed to the routine. 494 * 495 * fs.m plus the additional pages are PG_BUSY'd. 496 */ 497 faultcount = vm_fault_additional_pages( 498 fs.m, behind, ahead, marray, &reqpage); 499 500 /* 501 * update lastr imperfectly (we do not know how much 502 * getpages will actually read), but good enough. 503 */ 504 fs.entry->lastr = fs.pindex + faultcount - behind; 505 506 /* 507 * Call the pager to retrieve the data, if any, after 508 * releasing the lock on the map. We hold a ref on 509 * fs.object and the pages are PG_BUSY'd. 510 */ 511 unlock_map(&fs); 512 513 rv = faultcount ? 514 vm_pager_get_pages(fs.object, marray, faultcount, 515 reqpage) : VM_PAGER_FAIL; 516 517 if (rv == VM_PAGER_OK) { 518 /* 519 * Found the page. Leave it busy while we play 520 * with it. 521 */ 522 523 /* 524 * Relookup in case pager changed page. Pager 525 * is responsible for disposition of old page 526 * if moved. 527 * 528 * XXX other code segments do relookups too. 529 * It's a bad abstraction that needs to be 530 * fixed/removed. 531 */ 532 fs.m = vm_page_lookup(fs.object, fs.pindex); 533 if (fs.m == NULL) { 534 unlock_and_deallocate(&fs); 535 goto RetryFault; 536 } 537 538 hardfault++; 539 break; /* break to PAGE HAS BEEN FOUND */ 540 } 541 /* 542 * Remove the bogus page (which does not exist at this 543 * object/offset); before doing so, we must get back 544 * our object lock to preserve our invariant. 545 * 546 * Also wake up any other process that may want to bring 547 * in this page. 548 * 549 * If this is the top-level object, we must leave the 550 * busy page to prevent another process from rushing 551 * past us, and inserting the page in that object at 552 * the same time that we are. 553 */ 554 555 if (rv == VM_PAGER_ERROR) 556 printf("vm_fault: pager read error, pid %d (%s)\n", 557 curproc->p_pid, curproc->p_comm); 558 /* 559 * Data outside the range of the pager or an I/O error 560 */ 561 /* 562 * XXX - the check for kernel_map is a kludge to work 563 * around having the machine panic on a kernel space 564 * fault w/ I/O error. 565 */ 566 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 567 (rv == VM_PAGER_BAD)) { 568 vm_page_free(fs.m); 569 fs.m = NULL; 570 unlock_and_deallocate(&fs); 571 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 572 } 573 if (fs.object != fs.first_object) { 574 vm_page_free(fs.m); 575 fs.m = NULL; 576 /* 577 * XXX - we cannot just fall out at this 578 * point, m has been freed and is invalid! 579 */ 580 } 581 } 582 583 /* 584 * We get here if the object has default pager (or unwiring) 585 * or the pager doesn't have the page. 586 */ 587 if (fs.object == fs.first_object) 588 fs.first_m = fs.m; 589 590 /* 591 * Move on to the next object. Lock the next object before 592 * unlocking the current one. 593 */ 594 595 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 596 next_object = fs.object->backing_object; 597 if (next_object == NULL) { 598 /* 599 * If there's no object left, fill the page in the top 600 * object with zeros. 601 */ 602 if (fs.object != fs.first_object) { 603 vm_object_pip_wakeup(fs.object); 604 605 fs.object = fs.first_object; 606 fs.pindex = fs.first_pindex; 607 fs.m = fs.first_m; 608 } 609 fs.first_m = NULL; 610 611 /* 612 * Zero the page if necessary and mark it valid. 613 */ 614 if ((fs.m->flags & PG_ZERO) == 0) { 615 vm_page_zero_fill(fs.m); 616 } else { 617 mycpu->gd_cnt.v_ozfod++; 618 } 619 mycpu->gd_cnt.v_zfod++; 620 fs.m->valid = VM_PAGE_BITS_ALL; 621 break; /* break to PAGE HAS BEEN FOUND */ 622 } else { 623 if (fs.object != fs.first_object) { 624 vm_object_pip_wakeup(fs.object); 625 } 626 KASSERT(fs.object != next_object, ("object loop %p", next_object)); 627 fs.object = next_object; 628 vm_object_pip_add(fs.object, 1); 629 } 630 } 631 632 KASSERT((fs.m->flags & PG_BUSY) != 0, 633 ("vm_fault: not busy after main loop")); 634 635 /* 636 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 637 * is held.] 638 */ 639 640 /* 641 * If the page is being written, but isn't already owned by the 642 * top-level object, we have to copy it into a new page owned by the 643 * top-level object. 644 */ 645 646 if (fs.object != fs.first_object) { 647 /* 648 * We only really need to copy if we want to write it. 649 */ 650 651 if (fault_type & VM_PROT_WRITE) { 652 /* 653 * This allows pages to be virtually copied from a 654 * backing_object into the first_object, where the 655 * backing object has no other refs to it, and cannot 656 * gain any more refs. Instead of a bcopy, we just 657 * move the page from the backing object to the 658 * first object. Note that we must mark the page 659 * dirty in the first object so that it will go out 660 * to swap when needed. 661 */ 662 if (map_generation == fs.map->timestamp && 663 /* 664 * Only one shadow object 665 */ 666 (fs.object->shadow_count == 1) && 667 /* 668 * No COW refs, except us 669 */ 670 (fs.object->ref_count == 1) && 671 /* 672 * No one else can look this object up 673 */ 674 (fs.object->handle == NULL) && 675 /* 676 * No other ways to look the object up 677 */ 678 ((fs.object->type == OBJT_DEFAULT) || 679 (fs.object->type == OBJT_SWAP)) && 680 /* 681 * We don't chase down the shadow chain 682 */ 683 (fs.object == fs.first_object->backing_object) && 684 685 /* 686 * grab the lock if we need to 687 */ 688 (fs.lookup_still_valid || 689 lockmgr(&fs.map->lock, LK_EXCLUSIVE|LK_NOWAIT, NULL, curthread) == 0) 690 ) { 691 692 fs.lookup_still_valid = 1; 693 /* 694 * get rid of the unnecessary page 695 */ 696 vm_page_protect(fs.first_m, VM_PROT_NONE); 697 vm_page_free(fs.first_m); 698 fs.first_m = NULL; 699 700 /* 701 * grab the page and put it into the 702 * process'es object. The page is 703 * automatically made dirty. 704 */ 705 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 706 fs.first_m = fs.m; 707 vm_page_busy(fs.first_m); 708 fs.m = NULL; 709 mycpu->gd_cnt.v_cow_optim++; 710 } else { 711 /* 712 * Oh, well, lets copy it. 713 */ 714 vm_page_copy(fs.m, fs.first_m); 715 } 716 717 if (fs.m) { 718 /* 719 * We no longer need the old page or object. 720 */ 721 release_page(&fs); 722 } 723 724 /* 725 * fs.object != fs.first_object due to above 726 * conditional 727 */ 728 729 vm_object_pip_wakeup(fs.object); 730 731 /* 732 * Only use the new page below... 733 */ 734 735 mycpu->gd_cnt.v_cow_faults++; 736 fs.m = fs.first_m; 737 fs.object = fs.first_object; 738 fs.pindex = fs.first_pindex; 739 740 } else { 741 prot &= ~VM_PROT_WRITE; 742 } 743 } 744 745 /* 746 * We must verify that the maps have not changed since our last 747 * lookup. 748 */ 749 750 if (!fs.lookup_still_valid && 751 (fs.map->timestamp != map_generation)) { 752 vm_object_t retry_object; 753 vm_pindex_t retry_pindex; 754 vm_prot_t retry_prot; 755 756 /* 757 * Since map entries may be pageable, make sure we can take a 758 * page fault on them. 759 */ 760 761 /* 762 * Unlock vnode before the lookup to avoid deadlock. E.G. 763 * avoid a deadlock between the inode and exec_map that can 764 * occur due to locks being obtained in different orders. 765 */ 766 767 if (fs.vp != NULL) { 768 vput(fs.vp); 769 fs.vp = NULL; 770 } 771 772 if (fs.map->infork) { 773 release_page(&fs); 774 unlock_and_deallocate(&fs); 775 goto RetryFault; 776 } 777 778 /* 779 * To avoid trying to write_lock the map while another process 780 * has it read_locked (in vm_map_wire), we do not try for 781 * write permission. If the page is still writable, we will 782 * get write permission. If it is not, or has been marked 783 * needs_copy, we enter the mapping without write permission, 784 * and will merely take another fault. 785 */ 786 result = vm_map_lookup(&fs.map, vaddr, fault_type & ~VM_PROT_WRITE, 787 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 788 map_generation = fs.map->timestamp; 789 790 /* 791 * If we don't need the page any longer, put it on the active 792 * list (the easiest thing to do here). If no one needs it, 793 * pageout will grab it eventually. 794 */ 795 796 if (result != KERN_SUCCESS) { 797 release_page(&fs); 798 unlock_and_deallocate(&fs); 799 return (result); 800 } 801 fs.lookup_still_valid = TRUE; 802 803 if ((retry_object != fs.first_object) || 804 (retry_pindex != fs.first_pindex)) { 805 release_page(&fs); 806 unlock_and_deallocate(&fs); 807 goto RetryFault; 808 } 809 /* 810 * Check whether the protection has changed or the object has 811 * been copied while we left the map unlocked. Changing from 812 * read to write permission is OK - we leave the page 813 * write-protected, and catch the write fault. Changing from 814 * write to read permission means that we can't mark the page 815 * write-enabled after all. 816 */ 817 prot &= retry_prot; 818 } 819 820 /* 821 * Put this page into the physical map. We had to do the unlock above 822 * because pmap_enter may cause other faults. We don't put the page 823 * back on the active queue until later so that the page-out daemon 824 * won't find us (yet). 825 */ 826 827 if (prot & VM_PROT_WRITE) { 828 vm_page_flag_set(fs.m, PG_WRITEABLE); 829 vm_object_set_writeable_dirty(fs.m->object); 830 831 /* 832 * If the fault is a write, we know that this page is being 833 * written NOW so dirty it explicitly to save on 834 * pmap_is_modified() calls later. 835 * 836 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC 837 * if the page is already dirty to prevent data written with 838 * the expectation of being synced from not being synced. 839 * Likewise if this entry does not request NOSYNC then make 840 * sure the page isn't marked NOSYNC. Applications sharing 841 * data should use the same flags to avoid ping ponging. 842 * 843 * Also tell the backing pager, if any, that it should remove 844 * any swap backing since the page is now dirty. 845 */ 846 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 847 if (fs.m->dirty == 0) 848 vm_page_flag_set(fs.m, PG_NOSYNC); 849 } else { 850 vm_page_flag_clear(fs.m, PG_NOSYNC); 851 } 852 if (fault_flags & VM_FAULT_DIRTY) { 853 crit_enter(); 854 vm_page_dirty(fs.m); 855 vm_pager_page_unswapped(fs.m); 856 crit_exit(); 857 } 858 } 859 860 /* 861 * Page had better still be busy 862 */ 863 864 KASSERT(fs.m->flags & PG_BUSY, 865 ("vm_fault: page %p not busy!", fs.m)); 866 867 unlock_things(&fs); 868 869 /* 870 * Sanity check: page must be completely valid or it is not fit to 871 * map into user space. vm_pager_get_pages() ensures this. 872 */ 873 874 if (fs.m->valid != VM_PAGE_BITS_ALL) { 875 vm_page_zero_invalid(fs.m, TRUE); 876 printf("Warning: page %p partially invalid on fault\n", fs.m); 877 } 878 879 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired); 880 881 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 882 pmap_prefault(fs.map->pmap, vaddr, fs.entry); 883 } 884 885 vm_page_flag_clear(fs.m, PG_ZERO); 886 vm_page_flag_set(fs.m, PG_MAPPED|PG_REFERENCED); 887 if (fault_flags & VM_FAULT_HOLD) 888 vm_page_hold(fs.m); 889 890 /* 891 * If the page is not wired down, then put it where the pageout daemon 892 * can find it. 893 */ 894 895 if (fault_flags & VM_FAULT_WIRE_MASK) { 896 if (wired) 897 vm_page_wire(fs.m); 898 else 899 vm_page_unwire(fs.m, 1); 900 } else { 901 vm_page_activate(fs.m); 902 } 903 904 if (curproc && (curproc->p_flag & P_SWAPPEDOUT) == 0 && 905 curproc->p_stats) { 906 if (hardfault) { 907 curproc->p_stats->p_ru.ru_majflt++; 908 } else { 909 curproc->p_stats->p_ru.ru_minflt++; 910 } 911 } 912 913 /* 914 * Unlock everything, and return 915 */ 916 917 vm_page_wakeup(fs.m); 918 vm_object_deallocate(fs.first_object); 919 920 return (KERN_SUCCESS); 921 922 } 923 924 /* 925 * quick version of vm_fault 926 */ 927 int 928 vm_fault_quick(caddr_t v, int prot) 929 { 930 int r; 931 932 if (prot & VM_PROT_WRITE) 933 r = subyte(v, fubyte(v)); 934 else 935 r = fubyte(v); 936 return(r); 937 } 938 939 /* 940 * Wire down a range of virtual addresses in a map. The entry in question 941 * should be marked in-transition and the map must be locked. We must 942 * release the map temporarily while faulting-in the page to avoid a 943 * deadlock. Note that the entry may be clipped while we are blocked but 944 * will never be freed. 945 */ 946 int 947 vm_fault_wire(vm_map_t map, vm_map_entry_t entry, boolean_t user_wire) 948 { 949 boolean_t fictitious; 950 vm_offset_t start; 951 vm_offset_t end; 952 vm_offset_t va; 953 vm_paddr_t pa; 954 pmap_t pmap; 955 int rv; 956 957 pmap = vm_map_pmap(map); 958 start = entry->start; 959 end = entry->end; 960 fictitious = entry->object.vm_object && 961 (entry->object.vm_object->type == OBJT_DEVICE); 962 963 vm_map_unlock(map); 964 map->timestamp++; 965 966 /* 967 * We simulate a fault to get the page and enter it in the physical 968 * map. 969 */ 970 for (va = start; va < end; va += PAGE_SIZE) { 971 if (user_wire) { 972 rv = vm_fault(map, va, VM_PROT_READ, 973 VM_FAULT_USER_WIRE); 974 } else { 975 rv = vm_fault(map, va, VM_PROT_READ|VM_PROT_WRITE, 976 VM_FAULT_CHANGE_WIRING); 977 } 978 if (rv) { 979 while (va > start) { 980 va -= PAGE_SIZE; 981 if ((pa = pmap_extract(pmap, va)) == 0) 982 continue; 983 pmap_change_wiring(pmap, va, FALSE); 984 if (!fictitious) 985 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 986 } 987 vm_map_lock(map); 988 return (rv); 989 } 990 } 991 vm_map_lock(map); 992 return (KERN_SUCCESS); 993 } 994 995 /* 996 * Unwire a range of virtual addresses in a map. The map should be 997 * locked. 998 */ 999 void 1000 vm_fault_unwire(vm_map_t map, vm_map_entry_t entry) 1001 { 1002 boolean_t fictitious; 1003 vm_offset_t start; 1004 vm_offset_t end; 1005 vm_offset_t va; 1006 vm_paddr_t pa; 1007 pmap_t pmap; 1008 1009 pmap = vm_map_pmap(map); 1010 start = entry->start; 1011 end = entry->end; 1012 fictitious = entry->object.vm_object && 1013 (entry->object.vm_object->type == OBJT_DEVICE); 1014 1015 /* 1016 * Since the pages are wired down, we must be able to get their 1017 * mappings from the physical map system. 1018 */ 1019 for (va = start; va < end; va += PAGE_SIZE) { 1020 pa = pmap_extract(pmap, va); 1021 if (pa != 0) { 1022 pmap_change_wiring(pmap, va, FALSE); 1023 if (!fictitious) 1024 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1025 } 1026 } 1027 } 1028 1029 /* 1030 * Routine: 1031 * vm_fault_copy_entry 1032 * Function: 1033 * Copy all of the pages from a wired-down map entry to another. 1034 * 1035 * In/out conditions: 1036 * The source and destination maps must be locked for write. 1037 * The source map entry must be wired down (or be a sharing map 1038 * entry corresponding to a main map entry that is wired down). 1039 */ 1040 1041 void 1042 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1043 vm_map_entry_t dst_entry, vm_map_entry_t src_entry) 1044 { 1045 vm_object_t dst_object; 1046 vm_object_t src_object; 1047 vm_ooffset_t dst_offset; 1048 vm_ooffset_t src_offset; 1049 vm_prot_t prot; 1050 vm_offset_t vaddr; 1051 vm_page_t dst_m; 1052 vm_page_t src_m; 1053 1054 #ifdef lint 1055 src_map++; 1056 #endif /* lint */ 1057 1058 src_object = src_entry->object.vm_object; 1059 src_offset = src_entry->offset; 1060 1061 /* 1062 * Create the top-level object for the destination entry. (Doesn't 1063 * actually shadow anything - we copy the pages directly.) 1064 */ 1065 dst_object = vm_object_allocate(OBJT_DEFAULT, 1066 (vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1067 1068 dst_entry->object.vm_object = dst_object; 1069 dst_entry->offset = 0; 1070 1071 prot = dst_entry->max_protection; 1072 1073 /* 1074 * Loop through all of the pages in the entry's range, copying each 1075 * one from the source object (it should be there) to the destination 1076 * object. 1077 */ 1078 for (vaddr = dst_entry->start, dst_offset = 0; 1079 vaddr < dst_entry->end; 1080 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { 1081 1082 /* 1083 * Allocate a page in the destination object 1084 */ 1085 do { 1086 dst_m = vm_page_alloc(dst_object, 1087 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); 1088 if (dst_m == NULL) { 1089 vm_wait(); 1090 } 1091 } while (dst_m == NULL); 1092 1093 /* 1094 * Find the page in the source object, and copy it in. 1095 * (Because the source is wired down, the page will be in 1096 * memory.) 1097 */ 1098 src_m = vm_page_lookup(src_object, 1099 OFF_TO_IDX(dst_offset + src_offset)); 1100 if (src_m == NULL) 1101 panic("vm_fault_copy_wired: page missing"); 1102 1103 vm_page_copy(src_m, dst_m); 1104 1105 /* 1106 * Enter it in the pmap... 1107 */ 1108 1109 vm_page_flag_clear(dst_m, PG_ZERO); 1110 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE); 1111 vm_page_flag_set(dst_m, PG_WRITEABLE|PG_MAPPED); 1112 1113 /* 1114 * Mark it no longer busy, and put it on the active list. 1115 */ 1116 vm_page_activate(dst_m); 1117 vm_page_wakeup(dst_m); 1118 } 1119 } 1120 1121 1122 /* 1123 * This routine checks around the requested page for other pages that 1124 * might be able to be faulted in. This routine brackets the viable 1125 * pages for the pages to be paged in. 1126 * 1127 * Inputs: 1128 * m, rbehind, rahead 1129 * 1130 * Outputs: 1131 * marray (array of vm_page_t), reqpage (index of requested page) 1132 * 1133 * Return value: 1134 * number of pages in marray 1135 */ 1136 static int 1137 vm_fault_additional_pages(vm_page_t m, int rbehind, int rahead, 1138 vm_page_t *marray, int *reqpage) 1139 { 1140 int i,j; 1141 vm_object_t object; 1142 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1143 vm_page_t rtm; 1144 int cbehind, cahead; 1145 1146 object = m->object; 1147 pindex = m->pindex; 1148 1149 /* 1150 * we don't fault-ahead for device pager 1151 */ 1152 if (object->type == OBJT_DEVICE) { 1153 *reqpage = 0; 1154 marray[0] = m; 1155 return 1; 1156 } 1157 1158 /* 1159 * if the requested page is not available, then give up now 1160 */ 1161 1162 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1163 return 0; 1164 } 1165 1166 if ((cbehind == 0) && (cahead == 0)) { 1167 *reqpage = 0; 1168 marray[0] = m; 1169 return 1; 1170 } 1171 1172 if (rahead > cahead) { 1173 rahead = cahead; 1174 } 1175 1176 if (rbehind > cbehind) { 1177 rbehind = cbehind; 1178 } 1179 1180 /* 1181 * try to do any readahead that we might have free pages for. 1182 */ 1183 if ((rahead + rbehind) > 1184 ((vmstats.v_free_count + vmstats.v_cache_count) - vmstats.v_free_reserved)) { 1185 pagedaemon_wakeup(); 1186 marray[0] = m; 1187 *reqpage = 0; 1188 return 1; 1189 } 1190 1191 /* 1192 * scan backward for the read behind pages -- in memory 1193 * 1194 * Assume that if the page is not found an interrupt will not 1195 * create it. Theoretically interrupts can only remove (busy) 1196 * pages, not create new associations. 1197 */ 1198 if (pindex > 0) { 1199 if (rbehind > pindex) { 1200 rbehind = pindex; 1201 startpindex = 0; 1202 } else { 1203 startpindex = pindex - rbehind; 1204 } 1205 1206 crit_enter(); 1207 for ( tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) { 1208 if (vm_page_lookup( object, tpindex)) { 1209 startpindex = tpindex + 1; 1210 break; 1211 } 1212 if (tpindex == 0) 1213 break; 1214 } 1215 1216 for(i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) { 1217 1218 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1219 if (rtm == NULL) { 1220 crit_exit(); 1221 for (j = 0; j < i; j++) { 1222 vm_page_free(marray[j]); 1223 } 1224 marray[0] = m; 1225 *reqpage = 0; 1226 return 1; 1227 } 1228 1229 marray[i] = rtm; 1230 } 1231 crit_exit(); 1232 } else { 1233 startpindex = 0; 1234 i = 0; 1235 } 1236 1237 marray[i] = m; 1238 /* page offset of the required page */ 1239 *reqpage = i; 1240 1241 tpindex = pindex + 1; 1242 i++; 1243 1244 /* 1245 * scan forward for the read ahead pages 1246 */ 1247 endpindex = tpindex + rahead; 1248 if (endpindex > object->size) 1249 endpindex = object->size; 1250 1251 crit_enter(); 1252 for( ; tpindex < endpindex; i++, tpindex++) { 1253 1254 if (vm_page_lookup(object, tpindex)) { 1255 break; 1256 } 1257 1258 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1259 if (rtm == NULL) { 1260 break; 1261 } 1262 1263 marray[i] = rtm; 1264 } 1265 crit_exit(); 1266 1267 /* return number of bytes of pages */ 1268 return i; 1269 } 1270