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