1 /* 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 1994 John S. Dyson 5 * All rights reserved. 6 * Copyright (c) 1994 David Greenman 7 * All rights reserved. 8 * 9 * 10 * This code is derived from software contributed to Berkeley by 11 * The Mach Operating System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 42 * 43 * 44 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 45 * All rights reserved. 46 * 47 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 48 * 49 * Permission to use, copy, modify and distribute this software and 50 * its documentation is hereby granted, provided that both the copyright 51 * notice and this permission notice appear in all copies of the 52 * software, derivative works or modified versions, and any portions 53 * thereof, and that both notices appear in supporting documentation. 54 * 55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 58 * 59 * Carnegie Mellon requests users of this software to return to 60 * 61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 62 * School of Computer Science 63 * Carnegie Mellon University 64 * Pittsburgh PA 15213-3890 65 * 66 * any improvements or extensions that they make and grant Carnegie the 67 * rights to redistribute these changes. 68 */ 69 70 /* 71 * Page fault handling module. 72 */ 73 74 #include <sys/cdefs.h> 75 __FBSDID("$FreeBSD$"); 76 77 #include <sys/param.h> 78 #include <sys/systm.h> 79 #include <sys/kernel.h> 80 #include <sys/lock.h> 81 #include <sys/mutex.h> 82 #include <sys/proc.h> 83 #include <sys/resourcevar.h> 84 #include <sys/sysctl.h> 85 #include <sys/vmmeter.h> 86 #include <sys/vnode.h> 87 88 #include <vm/vm.h> 89 #include <vm/vm_param.h> 90 #include <vm/pmap.h> 91 #include <vm/vm_map.h> 92 #include <vm/vm_object.h> 93 #include <vm/vm_page.h> 94 #include <vm/vm_pageout.h> 95 #include <vm/vm_kern.h> 96 #include <vm/vm_pager.h> 97 #include <vm/vnode_pager.h> 98 #include <vm/vm_extern.h> 99 100 #define PFBAK 4 101 #define PFFOR 4 102 #define PAGEORDER_SIZE (PFBAK+PFFOR) 103 104 static int prefault_pageorder[] = { 105 -1 * PAGE_SIZE, 1 * PAGE_SIZE, 106 -2 * PAGE_SIZE, 2 * PAGE_SIZE, 107 -3 * PAGE_SIZE, 3 * PAGE_SIZE, 108 -4 * PAGE_SIZE, 4 * PAGE_SIZE 109 }; 110 111 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 112 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t); 113 114 #define VM_FAULT_READ_AHEAD 8 115 #define VM_FAULT_READ_BEHIND 7 116 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1) 117 118 struct faultstate { 119 vm_page_t m; 120 vm_object_t object; 121 vm_pindex_t pindex; 122 vm_page_t first_m; 123 vm_object_t first_object; 124 vm_pindex_t first_pindex; 125 vm_map_t map; 126 vm_map_entry_t entry; 127 int lookup_still_valid; 128 struct vnode *vp; 129 }; 130 131 static __inline void 132 release_page(struct faultstate *fs) 133 { 134 vm_page_lock_queues(); 135 vm_page_wakeup(fs->m); 136 vm_page_deactivate(fs->m); 137 vm_page_unlock_queues(); 138 fs->m = NULL; 139 } 140 141 static __inline void 142 unlock_map(struct faultstate *fs) 143 { 144 if (fs->lookup_still_valid) { 145 vm_map_lookup_done(fs->map, fs->entry); 146 fs->lookup_still_valid = FALSE; 147 } 148 } 149 150 static void 151 _unlock_things(struct faultstate *fs, int dealloc) 152 { 153 154 vm_object_pip_wakeup(fs->object); 155 VM_OBJECT_UNLOCK(fs->object); 156 if (fs->object != fs->first_object) { 157 VM_OBJECT_LOCK(fs->first_object); 158 vm_page_lock_queues(); 159 vm_page_free(fs->first_m); 160 vm_page_unlock_queues(); 161 vm_object_pip_wakeup(fs->first_object); 162 VM_OBJECT_UNLOCK(fs->first_object); 163 fs->first_m = NULL; 164 } 165 if (dealloc) { 166 vm_object_deallocate(fs->first_object); 167 } 168 unlock_map(fs); 169 if (fs->vp != NULL) { 170 mtx_lock(&Giant); 171 vput(fs->vp); 172 mtx_unlock(&Giant); 173 fs->vp = NULL; 174 } 175 if (dealloc && !fs->map->system_map) 176 VM_UNLOCK_GIANT(); 177 } 178 179 #define unlock_things(fs) _unlock_things(fs, 0) 180 #define unlock_and_deallocate(fs) _unlock_things(fs, 1) 181 182 /* 183 * TRYPAGER - used by vm_fault to calculate whether the pager for the 184 * current object *might* contain the page. 185 * 186 * default objects are zero-fill, there is no real pager. 187 */ 188 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 189 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) 190 191 /* 192 * vm_fault: 193 * 194 * Handle a page fault occurring at the given address, 195 * requiring the given permissions, in the map specified. 196 * If successful, the page is inserted into the 197 * associated physical map. 198 * 199 * NOTE: the given address should be truncated to the 200 * proper page address. 201 * 202 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 203 * a standard error specifying why the fault is fatal is returned. 204 * 205 * 206 * The map in question must be referenced, and remains so. 207 * Caller may hold no locks. 208 */ 209 int 210 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 211 int fault_flags) 212 { 213 vm_prot_t prot; 214 int is_first_object_locked, result; 215 boolean_t growstack, wired; 216 int map_generation; 217 vm_object_t next_object; 218 vm_page_t marray[VM_FAULT_READ]; 219 int hardfault; 220 int faultcount; 221 struct faultstate fs; 222 223 hardfault = 0; 224 growstack = TRUE; 225 atomic_add_int(&cnt.v_vm_faults, 1); 226 227 RetryFault:; 228 229 /* 230 * Find the backing store object and offset into it to begin the 231 * search. 232 */ 233 fs.map = map; 234 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 235 &fs.first_object, &fs.first_pindex, &prot, &wired); 236 if (result != KERN_SUCCESS) { 237 if (result != KERN_PROTECTION_FAILURE || 238 (fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) { 239 if (growstack && result == KERN_INVALID_ADDRESS && 240 map != kernel_map && curproc != NULL) { 241 result = vm_map_growstack(curproc, vaddr); 242 if (result != KERN_SUCCESS) 243 return (KERN_FAILURE); 244 growstack = FALSE; 245 goto RetryFault; 246 } 247 return (result); 248 } 249 250 /* 251 * If we are user-wiring a r/w segment, and it is COW, then 252 * we need to do the COW operation. Note that we don't COW 253 * currently RO sections now, because it is NOT desirable 254 * to COW .text. We simply keep .text from ever being COW'ed 255 * and take the heat that one cannot debug wired .text sections. 256 */ 257 result = vm_map_lookup(&fs.map, vaddr, 258 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE, 259 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired); 260 if (result != KERN_SUCCESS) 261 return (result); 262 263 /* 264 * If we don't COW now, on a user wire, the user will never 265 * be able to write to the mapping. If we don't make this 266 * restriction, the bookkeeping would be nearly impossible. 267 * 268 * XXX The following assignment modifies the map without 269 * holding a write lock on it. 270 */ 271 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 272 fs.entry->max_protection &= ~VM_PROT_WRITE; 273 } 274 275 map_generation = fs.map->timestamp; 276 277 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 278 panic("vm_fault: fault on nofault entry, addr: %lx", 279 (u_long)vaddr); 280 } 281 282 /* 283 * Make a reference to this object to prevent its disposal while we 284 * are messing with it. Once we have the reference, the map is free 285 * to be diddled. Since objects reference their shadows (and copies), 286 * they will stay around as well. 287 * 288 * Bump the paging-in-progress count to prevent size changes (e.g. 289 * truncation operations) during I/O. This must be done after 290 * obtaining the vnode lock in order to avoid possible deadlocks. 291 * 292 * XXX vnode_pager_lock() can block without releasing the map lock. 293 */ 294 if (!fs.map->system_map) 295 mtx_lock(&Giant); 296 VM_OBJECT_LOCK(fs.first_object); 297 vm_object_reference_locked(fs.first_object); 298 fs.vp = vnode_pager_lock(fs.first_object); 299 KASSERT(fs.vp == NULL || !fs.map->system_map, 300 ("vm_fault: vnode-backed object mapped by system map")); 301 if (debug_mpsafevm && !fs.map->system_map) 302 mtx_unlock(&Giant); 303 vm_object_pip_add(fs.first_object, 1); 304 305 fs.lookup_still_valid = TRUE; 306 307 if (wired) 308 fault_type = prot; 309 310 fs.first_m = NULL; 311 312 /* 313 * Search for the page at object/offset. 314 */ 315 fs.object = fs.first_object; 316 fs.pindex = fs.first_pindex; 317 while (TRUE) { 318 /* 319 * If the object is dead, we stop here 320 */ 321 if (fs.object->flags & OBJ_DEAD) { 322 unlock_and_deallocate(&fs); 323 return (KERN_PROTECTION_FAILURE); 324 } 325 326 /* 327 * See if page is resident 328 */ 329 fs.m = vm_page_lookup(fs.object, fs.pindex); 330 if (fs.m != NULL) { 331 int queue; 332 333 /* 334 * check for page-based copy on write. 335 * We check fs.object == fs.first_object so 336 * as to ensure the legacy COW mechanism is 337 * used when the page in question is part of 338 * a shadow object. Otherwise, vm_page_cowfault() 339 * removes the page from the backing object, 340 * which is not what we want. 341 */ 342 vm_page_lock_queues(); 343 if ((fs.m->cow) && 344 (fault_type & VM_PROT_WRITE) && 345 (fs.object == fs.first_object)) { 346 vm_page_cowfault(fs.m); 347 vm_page_unlock_queues(); 348 unlock_and_deallocate(&fs); 349 goto RetryFault; 350 } 351 352 /* 353 * Wait/Retry if the page is busy. We have to do this 354 * if the page is busy via either PG_BUSY or 355 * vm_page_t->busy because the vm_pager may be using 356 * vm_page_t->busy for pageouts ( and even pageins if 357 * it is the vnode pager ), and we could end up trying 358 * to pagein and pageout the same page simultaneously. 359 * 360 * We can theoretically allow the busy case on a read 361 * fault if the page is marked valid, but since such 362 * pages are typically already pmap'd, putting that 363 * special case in might be more effort then it is 364 * worth. We cannot under any circumstances mess 365 * around with a vm_page_t->busy page except, perhaps, 366 * to pmap it. 367 */ 368 if ((fs.m->flags & PG_BUSY) || fs.m->busy) { 369 vm_page_unlock_queues(); 370 unlock_things(&fs); 371 vm_page_lock_queues(); 372 if (!vm_page_sleep_if_busy(fs.m, TRUE, "vmpfw")) 373 vm_page_unlock_queues(); 374 atomic_add_int(&cnt.v_intrans, 1); 375 if (!fs.map->system_map) 376 VM_UNLOCK_GIANT(); 377 vm_object_deallocate(fs.first_object); 378 goto RetryFault; 379 } 380 queue = fs.m->queue; 381 382 vm_pageq_remove_nowakeup(fs.m); 383 384 if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) { 385 vm_page_activate(fs.m); 386 vm_page_unlock_queues(); 387 unlock_and_deallocate(&fs); 388 VM_WAITPFAULT; 389 goto RetryFault; 390 } 391 392 /* 393 * Mark page busy for other processes, and the 394 * pagedaemon. If it still isn't completely valid 395 * (readable), jump to readrest, else break-out ( we 396 * found the page ). 397 */ 398 vm_page_busy(fs.m); 399 vm_page_unlock_queues(); 400 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) && 401 fs.m->object != kernel_object && fs.m->object != kmem_object) { 402 goto readrest; 403 } 404 405 break; 406 } 407 408 /* 409 * Page is not resident, If this is the search termination 410 * or the pager might contain the page, allocate a new page. 411 */ 412 if (TRYPAGER || fs.object == fs.first_object) { 413 if (fs.pindex >= fs.object->size) { 414 unlock_and_deallocate(&fs); 415 return (KERN_PROTECTION_FAILURE); 416 } 417 418 /* 419 * Allocate a new page for this object/offset pair. 420 */ 421 fs.m = NULL; 422 if (!vm_page_count_severe()) { 423 fs.m = vm_page_alloc(fs.object, fs.pindex, 424 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO); 425 } 426 if (fs.m == NULL) { 427 unlock_and_deallocate(&fs); 428 VM_WAITPFAULT; 429 goto RetryFault; 430 } 431 } 432 433 readrest: 434 /* 435 * We have found a valid page or we have allocated a new page. 436 * The page thus may not be valid or may not be entirely 437 * valid. 438 * 439 * Attempt to fault-in the page if there is a chance that the 440 * pager has it, and potentially fault in additional pages 441 * at the same time. 442 */ 443 if (TRYPAGER) { 444 int rv; 445 int reqpage; 446 int ahead, behind; 447 u_char behavior = vm_map_entry_behavior(fs.entry); 448 449 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 450 ahead = 0; 451 behind = 0; 452 } else { 453 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT; 454 if (behind > VM_FAULT_READ_BEHIND) 455 behind = VM_FAULT_READ_BEHIND; 456 457 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1; 458 if (ahead > VM_FAULT_READ_AHEAD) 459 ahead = VM_FAULT_READ_AHEAD; 460 } 461 is_first_object_locked = FALSE; 462 if ((behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 463 (behavior != MAP_ENTRY_BEHAV_RANDOM && 464 fs.pindex >= fs.entry->lastr && 465 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) && 466 (fs.first_object == fs.object || 467 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object))) && 468 fs.first_object->type != OBJT_DEVICE) { 469 vm_pindex_t firstpindex, tmppindex; 470 471 if (fs.first_pindex < 2 * VM_FAULT_READ) 472 firstpindex = 0; 473 else 474 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ; 475 476 vm_page_lock_queues(); 477 /* 478 * note: partially valid pages cannot be 479 * included in the lookahead - NFS piecemeal 480 * writes will barf on it badly. 481 */ 482 for (tmppindex = fs.first_pindex - 1; 483 tmppindex >= firstpindex; 484 --tmppindex) { 485 vm_page_t mt; 486 487 mt = vm_page_lookup(fs.first_object, tmppindex); 488 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL)) 489 break; 490 if (mt->busy || 491 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) || 492 mt->hold_count || 493 mt->wire_count) 494 continue; 495 pmap_remove_all(mt); 496 if (mt->dirty) { 497 vm_page_deactivate(mt); 498 } else { 499 vm_page_cache(mt); 500 } 501 } 502 vm_page_unlock_queues(); 503 ahead += behind; 504 behind = 0; 505 } 506 if (is_first_object_locked) 507 VM_OBJECT_UNLOCK(fs.first_object); 508 /* 509 * now we find out if any other pages should be paged 510 * in at this time this routine checks to see if the 511 * pages surrounding this fault reside in the same 512 * object as the page for this fault. If they do, 513 * then they are faulted in also into the object. The 514 * array "marray" returned contains an array of 515 * vm_page_t structs where one of them is the 516 * vm_page_t passed to the routine. The reqpage 517 * return value is the index into the marray for the 518 * vm_page_t passed to the routine. 519 * 520 * fs.m plus the additional pages are PG_BUSY'd. 521 * 522 * XXX vm_fault_additional_pages() can block 523 * without releasing the map lock. 524 */ 525 faultcount = vm_fault_additional_pages( 526 fs.m, behind, ahead, marray, &reqpage); 527 528 /* 529 * update lastr imperfectly (we do not know how much 530 * getpages will actually read), but good enough. 531 * 532 * XXX The following assignment modifies the map 533 * without holding a write lock on it. 534 */ 535 fs.entry->lastr = fs.pindex + faultcount - behind; 536 537 /* 538 * Call the pager to retrieve the data, if any, after 539 * releasing the lock on the map. We hold a ref on 540 * fs.object and the pages are PG_BUSY'd. 541 */ 542 unlock_map(&fs); 543 544 rv = faultcount ? 545 vm_pager_get_pages(fs.object, marray, faultcount, 546 reqpage) : VM_PAGER_FAIL; 547 548 if (rv == VM_PAGER_OK) { 549 /* 550 * Found the page. Leave it busy while we play 551 * with it. 552 */ 553 554 /* 555 * Relookup in case pager changed page. Pager 556 * is responsible for disposition of old page 557 * if moved. 558 */ 559 fs.m = vm_page_lookup(fs.object, fs.pindex); 560 if (!fs.m) { 561 unlock_and_deallocate(&fs); 562 goto RetryFault; 563 } 564 565 hardfault++; 566 break; /* break to PAGE HAS BEEN FOUND */ 567 } 568 /* 569 * Remove the bogus page (which does not exist at this 570 * object/offset); before doing so, we must get back 571 * our object lock to preserve our invariant. 572 * 573 * Also wake up any other process that may want to bring 574 * in this page. 575 * 576 * If this is the top-level object, we must leave the 577 * busy page to prevent another process from rushing 578 * past us, and inserting the page in that object at 579 * the same time that we are. 580 */ 581 if (rv == VM_PAGER_ERROR) 582 printf("vm_fault: pager read error, pid %d (%s)\n", 583 curproc->p_pid, curproc->p_comm); 584 /* 585 * Data outside the range of the pager or an I/O error 586 */ 587 /* 588 * XXX - the check for kernel_map is a kludge to work 589 * around having the machine panic on a kernel space 590 * fault w/ I/O error. 591 */ 592 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 593 (rv == VM_PAGER_BAD)) { 594 vm_page_lock_queues(); 595 vm_page_free(fs.m); 596 vm_page_unlock_queues(); 597 fs.m = NULL; 598 unlock_and_deallocate(&fs); 599 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 600 } 601 if (fs.object != fs.first_object) { 602 vm_page_lock_queues(); 603 vm_page_free(fs.m); 604 vm_page_unlock_queues(); 605 fs.m = NULL; 606 /* 607 * XXX - we cannot just fall out at this 608 * point, m has been freed and is invalid! 609 */ 610 } 611 } 612 613 /* 614 * We get here if the object has default pager (or unwiring) 615 * or the pager doesn't have the page. 616 */ 617 if (fs.object == fs.first_object) 618 fs.first_m = fs.m; 619 620 /* 621 * Move on to the next object. Lock the next object before 622 * unlocking the current one. 623 */ 624 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 625 next_object = fs.object->backing_object; 626 if (next_object == NULL) { 627 /* 628 * If there's no object left, fill the page in the top 629 * object with zeros. 630 */ 631 if (fs.object != fs.first_object) { 632 vm_object_pip_wakeup(fs.object); 633 VM_OBJECT_UNLOCK(fs.object); 634 635 fs.object = fs.first_object; 636 fs.pindex = fs.first_pindex; 637 fs.m = fs.first_m; 638 VM_OBJECT_LOCK(fs.object); 639 } 640 fs.first_m = NULL; 641 642 /* 643 * Zero the page if necessary and mark it valid. 644 */ 645 if ((fs.m->flags & PG_ZERO) == 0) { 646 pmap_zero_page(fs.m); 647 } else { 648 atomic_add_int(&cnt.v_ozfod, 1); 649 } 650 atomic_add_int(&cnt.v_zfod, 1); 651 fs.m->valid = VM_PAGE_BITS_ALL; 652 break; /* break to PAGE HAS BEEN FOUND */ 653 } else { 654 KASSERT(fs.object != next_object, 655 ("object loop %p", next_object)); 656 VM_OBJECT_LOCK(next_object); 657 vm_object_pip_add(next_object, 1); 658 if (fs.object != fs.first_object) 659 vm_object_pip_wakeup(fs.object); 660 VM_OBJECT_UNLOCK(fs.object); 661 fs.object = next_object; 662 } 663 } 664 665 KASSERT((fs.m->flags & PG_BUSY) != 0, 666 ("vm_fault: not busy after main loop")); 667 668 /* 669 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 670 * is held.] 671 */ 672 673 /* 674 * If the page is being written, but isn't already owned by the 675 * top-level object, we have to copy it into a new page owned by the 676 * top-level object. 677 */ 678 if (fs.object != fs.first_object) { 679 /* 680 * We only really need to copy if we want to write it. 681 */ 682 if (fault_type & VM_PROT_WRITE) { 683 /* 684 * This allows pages to be virtually copied from a 685 * backing_object into the first_object, where the 686 * backing object has no other refs to it, and cannot 687 * gain any more refs. Instead of a bcopy, we just 688 * move the page from the backing object to the 689 * first object. Note that we must mark the page 690 * dirty in the first object so that it will go out 691 * to swap when needed. 692 */ 693 is_first_object_locked = FALSE; 694 if ( 695 /* 696 * Only one shadow object 697 */ 698 (fs.object->shadow_count == 1) && 699 /* 700 * No COW refs, except us 701 */ 702 (fs.object->ref_count == 1) && 703 /* 704 * No one else can look this object up 705 */ 706 (fs.object->handle == NULL) && 707 /* 708 * No other ways to look the object up 709 */ 710 ((fs.object->type == OBJT_DEFAULT) || 711 (fs.object->type == OBJT_SWAP)) && 712 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) && 713 /* 714 * We don't chase down the shadow chain 715 */ 716 fs.object == fs.first_object->backing_object) { 717 vm_page_lock_queues(); 718 /* 719 * get rid of the unnecessary page 720 */ 721 pmap_remove_all(fs.first_m); 722 vm_page_free(fs.first_m); 723 /* 724 * grab the page and put it into the 725 * process'es object. The page is 726 * automatically made dirty. 727 */ 728 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 729 vm_page_busy(fs.m); 730 vm_page_unlock_queues(); 731 fs.first_m = fs.m; 732 fs.m = NULL; 733 atomic_add_int(&cnt.v_cow_optim, 1); 734 } else { 735 /* 736 * Oh, well, lets copy it. 737 */ 738 pmap_copy_page(fs.m, fs.first_m); 739 fs.first_m->valid = VM_PAGE_BITS_ALL; 740 } 741 if (fs.m) { 742 /* 743 * We no longer need the old page or object. 744 */ 745 release_page(&fs); 746 } 747 /* 748 * fs.object != fs.first_object due to above 749 * conditional 750 */ 751 vm_object_pip_wakeup(fs.object); 752 VM_OBJECT_UNLOCK(fs.object); 753 /* 754 * Only use the new page below... 755 */ 756 fs.object = fs.first_object; 757 fs.pindex = fs.first_pindex; 758 fs.m = fs.first_m; 759 if (!is_first_object_locked) 760 VM_OBJECT_LOCK(fs.object); 761 atomic_add_int(&cnt.v_cow_faults, 1); 762 } else { 763 prot &= ~VM_PROT_WRITE; 764 } 765 } 766 767 /* 768 * We must verify that the maps have not changed since our last 769 * lookup. 770 */ 771 if (!fs.lookup_still_valid) { 772 vm_object_t retry_object; 773 vm_pindex_t retry_pindex; 774 vm_prot_t retry_prot; 775 776 if (!vm_map_trylock_read(fs.map)) { 777 release_page(&fs); 778 unlock_and_deallocate(&fs); 779 goto RetryFault; 780 } 781 fs.lookup_still_valid = TRUE; 782 if (fs.map->timestamp != map_generation) { 783 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 784 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 785 786 /* 787 * If we don't need the page any longer, put it on the active 788 * list (the easiest thing to do here). If no one needs it, 789 * pageout will grab it eventually. 790 */ 791 if (result != KERN_SUCCESS) { 792 release_page(&fs); 793 unlock_and_deallocate(&fs); 794 795 /* 796 * If retry of map lookup would have blocked then 797 * retry fault from start. 798 */ 799 if (result == KERN_FAILURE) 800 goto RetryFault; 801 return (result); 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 /* 811 * Check whether the protection has changed or the object has 812 * been copied while we left the map unlocked. Changing from 813 * read to write permission is OK - we leave the page 814 * write-protected, and catch the write fault. Changing from 815 * write to read permission means that we can't mark the page 816 * write-enabled after all. 817 */ 818 prot &= retry_prot; 819 } 820 } 821 if (prot & VM_PROT_WRITE) { 822 vm_page_lock_queues(); 823 vm_page_flag_set(fs.m, PG_WRITEABLE); 824 vm_object_set_writeable_dirty(fs.m->object); 825 826 /* 827 * If the fault is a write, we know that this page is being 828 * written NOW so dirty it explicitly to save on 829 * pmap_is_modified() calls later. 830 * 831 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC 832 * if the page is already dirty to prevent data written with 833 * the expectation of being synced from not being synced. 834 * Likewise if this entry does not request NOSYNC then make 835 * sure the page isn't marked NOSYNC. Applications sharing 836 * data should use the same flags to avoid ping ponging. 837 * 838 * Also tell the backing pager, if any, that it should remove 839 * any swap backing since the page is now dirty. 840 */ 841 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 842 if (fs.m->dirty == 0) 843 vm_page_flag_set(fs.m, PG_NOSYNC); 844 } else { 845 vm_page_flag_clear(fs.m, PG_NOSYNC); 846 } 847 vm_page_unlock_queues(); 848 if (fault_flags & VM_FAULT_DIRTY) { 849 vm_page_dirty(fs.m); 850 vm_pager_page_unswapped(fs.m); 851 } 852 } 853 854 /* 855 * Page had better still be busy 856 */ 857 KASSERT(fs.m->flags & PG_BUSY, 858 ("vm_fault: page %p not busy!", fs.m)); 859 /* 860 * Sanity check: page must be completely valid or it is not fit to 861 * map into user space. vm_pager_get_pages() ensures this. 862 */ 863 if (fs.m->valid != VM_PAGE_BITS_ALL) { 864 vm_page_zero_invalid(fs.m, TRUE); 865 printf("Warning: page %p partially invalid on fault\n", fs.m); 866 } 867 VM_OBJECT_UNLOCK(fs.object); 868 869 /* 870 * Put this page into the physical map. We had to do the unlock above 871 * because pmap_enter() may sleep. We don't put the page 872 * back on the active queue until later so that the pageout daemon 873 * won't find it (yet). 874 */ 875 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired); 876 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 877 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry); 878 } 879 VM_OBJECT_LOCK(fs.object); 880 vm_page_lock_queues(); 881 vm_page_flag_set(fs.m, PG_REFERENCED); 882 883 /* 884 * If the page is not wired down, then put it where the pageout daemon 885 * can find it. 886 */ 887 if (fault_flags & VM_FAULT_WIRE_MASK) { 888 if (wired) 889 vm_page_wire(fs.m); 890 else 891 vm_page_unwire(fs.m, 1); 892 } else { 893 vm_page_activate(fs.m); 894 } 895 vm_page_wakeup(fs.m); 896 vm_page_unlock_queues(); 897 898 /* 899 * Unlock everything, and return 900 */ 901 unlock_and_deallocate(&fs); 902 PROC_LOCK(curproc); 903 if ((curproc->p_sflag & PS_INMEM) && curproc->p_stats) { 904 if (hardfault) { 905 curproc->p_stats->p_ru.ru_majflt++; 906 } else { 907 curproc->p_stats->p_ru.ru_minflt++; 908 } 909 } 910 PROC_UNLOCK(curproc); 911 912 return (KERN_SUCCESS); 913 } 914 915 /* 916 * vm_fault_prefault provides a quick way of clustering 917 * pagefaults into a processes address space. It is a "cousin" 918 * of vm_map_pmap_enter, except it runs at page fault time instead 919 * of mmap time. 920 */ 921 static void 922 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry) 923 { 924 int i; 925 vm_offset_t addr, starta; 926 vm_pindex_t pindex; 927 vm_page_t m, mpte; 928 vm_object_t object; 929 930 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 931 return; 932 933 object = entry->object.vm_object; 934 935 starta = addra - PFBAK * PAGE_SIZE; 936 if (starta < entry->start) { 937 starta = entry->start; 938 } else if (starta > addra) { 939 starta = 0; 940 } 941 942 mpte = NULL; 943 for (i = 0; i < PAGEORDER_SIZE; i++) { 944 vm_object_t backing_object, lobject; 945 946 addr = addra + prefault_pageorder[i]; 947 if (addr > addra + (PFFOR * PAGE_SIZE)) 948 addr = 0; 949 950 if (addr < starta || addr >= entry->end) 951 continue; 952 953 if (!pmap_is_prefaultable(pmap, addr)) 954 continue; 955 956 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 957 lobject = object; 958 VM_OBJECT_LOCK(lobject); 959 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 960 lobject->type == OBJT_DEFAULT && 961 (backing_object = lobject->backing_object) != NULL) { 962 if (lobject->backing_object_offset & PAGE_MASK) 963 break; 964 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 965 VM_OBJECT_LOCK(backing_object); 966 VM_OBJECT_UNLOCK(lobject); 967 lobject = backing_object; 968 } 969 /* 970 * give-up when a page is not in memory 971 */ 972 if (m == NULL) { 973 VM_OBJECT_UNLOCK(lobject); 974 break; 975 } 976 vm_page_lock_queues(); 977 if (((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) && 978 (m->busy == 0) && 979 (m->flags & (PG_BUSY | PG_FICTITIOUS)) == 0) { 980 981 if ((m->queue - m->pc) == PQ_CACHE) { 982 vm_page_deactivate(m); 983 } 984 vm_page_busy(m); 985 vm_page_unlock_queues(); 986 VM_OBJECT_UNLOCK(lobject); 987 mpte = pmap_enter_quick(pmap, addr, m, mpte); 988 VM_OBJECT_LOCK(lobject); 989 vm_page_lock_queues(); 990 vm_page_wakeup(m); 991 } 992 vm_page_unlock_queues(); 993 VM_OBJECT_UNLOCK(lobject); 994 } 995 } 996 997 /* 998 * vm_fault_quick: 999 * 1000 * Ensure that the requested virtual address, which may be in userland, 1001 * is valid. Fault-in the page if necessary. Return -1 on failure. 1002 */ 1003 int 1004 vm_fault_quick(caddr_t v, int prot) 1005 { 1006 int r; 1007 1008 if (prot & VM_PROT_WRITE) 1009 r = subyte(v, fubyte(v)); 1010 else 1011 r = fubyte(v); 1012 return(r); 1013 } 1014 1015 /* 1016 * vm_fault_wire: 1017 * 1018 * Wire down a range of virtual addresses in a map. 1019 */ 1020 int 1021 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1022 boolean_t user_wire, boolean_t fictitious) 1023 { 1024 vm_offset_t va; 1025 int rv; 1026 1027 /* 1028 * We simulate a fault to get the page and enter it in the physical 1029 * map. For user wiring, we only ask for read access on currently 1030 * read-only sections. 1031 */ 1032 for (va = start; va < end; va += PAGE_SIZE) { 1033 rv = vm_fault(map, va, 1034 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE, 1035 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING); 1036 if (rv) { 1037 if (va != start) 1038 vm_fault_unwire(map, start, va, fictitious); 1039 return (rv); 1040 } 1041 } 1042 return (KERN_SUCCESS); 1043 } 1044 1045 /* 1046 * vm_fault_unwire: 1047 * 1048 * Unwire a range of virtual addresses in a map. 1049 */ 1050 void 1051 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1052 boolean_t fictitious) 1053 { 1054 vm_paddr_t pa; 1055 vm_offset_t va; 1056 pmap_t pmap; 1057 1058 pmap = vm_map_pmap(map); 1059 1060 /* 1061 * Since the pages are wired down, we must be able to get their 1062 * mappings from the physical map system. 1063 */ 1064 for (va = start; va < end; va += PAGE_SIZE) { 1065 pa = pmap_extract(pmap, va); 1066 if (pa != 0) { 1067 pmap_change_wiring(pmap, va, FALSE); 1068 if (!fictitious) { 1069 vm_page_lock_queues(); 1070 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1071 vm_page_unlock_queues(); 1072 } 1073 } 1074 } 1075 } 1076 1077 /* 1078 * Routine: 1079 * vm_fault_copy_entry 1080 * Function: 1081 * Copy all of the pages from a wired-down map entry to another. 1082 * 1083 * In/out conditions: 1084 * The source and destination maps must be locked for write. 1085 * The source map entry must be wired down (or be a sharing map 1086 * entry corresponding to a main map entry that is wired down). 1087 */ 1088 void 1089 vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry) 1090 vm_map_t dst_map; 1091 vm_map_t src_map; 1092 vm_map_entry_t dst_entry; 1093 vm_map_entry_t src_entry; 1094 { 1095 vm_object_t backing_object, dst_object, object; 1096 vm_object_t src_object; 1097 vm_ooffset_t dst_offset; 1098 vm_ooffset_t src_offset; 1099 vm_pindex_t pindex; 1100 vm_prot_t prot; 1101 vm_offset_t vaddr; 1102 vm_page_t dst_m; 1103 vm_page_t src_m; 1104 1105 #ifdef lint 1106 src_map++; 1107 #endif /* lint */ 1108 1109 src_object = src_entry->object.vm_object; 1110 src_offset = src_entry->offset; 1111 1112 /* 1113 * Create the top-level object for the destination entry. (Doesn't 1114 * actually shadow anything - we copy the pages directly.) 1115 */ 1116 dst_object = vm_object_allocate(OBJT_DEFAULT, 1117 (vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1118 1119 VM_OBJECT_LOCK(dst_object); 1120 dst_entry->object.vm_object = dst_object; 1121 dst_entry->offset = 0; 1122 1123 prot = dst_entry->max_protection; 1124 1125 /* 1126 * Loop through all of the pages in the entry's range, copying each 1127 * one from the source object (it should be there) to the destination 1128 * object. 1129 */ 1130 for (vaddr = dst_entry->start, dst_offset = 0; 1131 vaddr < dst_entry->end; 1132 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { 1133 1134 /* 1135 * Allocate a page in the destination object 1136 */ 1137 do { 1138 dst_m = vm_page_alloc(dst_object, 1139 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); 1140 if (dst_m == NULL) { 1141 VM_OBJECT_UNLOCK(dst_object); 1142 VM_WAIT; 1143 VM_OBJECT_LOCK(dst_object); 1144 } 1145 } while (dst_m == NULL); 1146 1147 /* 1148 * Find the page in the source object, and copy it in. 1149 * (Because the source is wired down, the page will be in 1150 * memory.) 1151 */ 1152 VM_OBJECT_LOCK(src_object); 1153 object = src_object; 1154 pindex = 0; 1155 while ((src_m = vm_page_lookup(object, pindex + 1156 OFF_TO_IDX(dst_offset + src_offset))) == NULL && 1157 (src_entry->protection & VM_PROT_WRITE) == 0 && 1158 (backing_object = object->backing_object) != NULL) { 1159 /* 1160 * Allow fallback to backing objects if we are reading. 1161 */ 1162 VM_OBJECT_LOCK(backing_object); 1163 pindex += OFF_TO_IDX(object->backing_object_offset); 1164 VM_OBJECT_UNLOCK(object); 1165 object = backing_object; 1166 } 1167 if (src_m == NULL) 1168 panic("vm_fault_copy_wired: page missing"); 1169 pmap_copy_page(src_m, dst_m); 1170 VM_OBJECT_UNLOCK(object); 1171 dst_m->valid = VM_PAGE_BITS_ALL; 1172 VM_OBJECT_UNLOCK(dst_object); 1173 1174 /* 1175 * Enter it in the pmap... 1176 */ 1177 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE); 1178 VM_OBJECT_LOCK(dst_object); 1179 vm_page_lock_queues(); 1180 if ((prot & VM_PROT_WRITE) != 0) 1181 vm_page_flag_set(dst_m, PG_WRITEABLE); 1182 1183 /* 1184 * Mark it no longer busy, and put it on the active list. 1185 */ 1186 vm_page_activate(dst_m); 1187 vm_page_wakeup(dst_m); 1188 vm_page_unlock_queues(); 1189 } 1190 VM_OBJECT_UNLOCK(dst_object); 1191 } 1192 1193 1194 /* 1195 * This routine checks around the requested page for other pages that 1196 * might be able to be faulted in. This routine brackets the viable 1197 * pages for the pages to be paged in. 1198 * 1199 * Inputs: 1200 * m, rbehind, rahead 1201 * 1202 * Outputs: 1203 * marray (array of vm_page_t), reqpage (index of requested page) 1204 * 1205 * Return value: 1206 * number of pages in marray 1207 * 1208 * This routine can't block. 1209 */ 1210 static int 1211 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1212 vm_page_t m; 1213 int rbehind; 1214 int rahead; 1215 vm_page_t *marray; 1216 int *reqpage; 1217 { 1218 int i,j; 1219 vm_object_t object; 1220 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1221 vm_page_t rtm; 1222 int cbehind, cahead; 1223 1224 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED); 1225 1226 object = m->object; 1227 pindex = m->pindex; 1228 1229 /* 1230 * we don't fault-ahead for device pager 1231 */ 1232 if (object->type == OBJT_DEVICE) { 1233 *reqpage = 0; 1234 marray[0] = m; 1235 return 1; 1236 } 1237 1238 /* 1239 * if the requested page is not available, then give up now 1240 */ 1241 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1242 return 0; 1243 } 1244 1245 if ((cbehind == 0) && (cahead == 0)) { 1246 *reqpage = 0; 1247 marray[0] = m; 1248 return 1; 1249 } 1250 1251 if (rahead > cahead) { 1252 rahead = cahead; 1253 } 1254 1255 if (rbehind > cbehind) { 1256 rbehind = cbehind; 1257 } 1258 1259 /* 1260 * try to do any readahead that we might have free pages for. 1261 */ 1262 if ((rahead + rbehind) > 1263 ((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) { 1264 pagedaemon_wakeup(); 1265 marray[0] = m; 1266 *reqpage = 0; 1267 return 1; 1268 } 1269 1270 /* 1271 * scan backward for the read behind pages -- in memory 1272 */ 1273 if (pindex > 0) { 1274 if (rbehind > pindex) { 1275 rbehind = pindex; 1276 startpindex = 0; 1277 } else { 1278 startpindex = pindex - rbehind; 1279 } 1280 1281 for (tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) { 1282 if (vm_page_lookup(object, tpindex)) { 1283 startpindex = tpindex + 1; 1284 break; 1285 } 1286 if (tpindex == 0) 1287 break; 1288 } 1289 1290 for (i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) { 1291 1292 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1293 if (rtm == NULL) { 1294 vm_page_lock_queues(); 1295 for (j = 0; j < i; j++) { 1296 vm_page_free(marray[j]); 1297 } 1298 vm_page_unlock_queues(); 1299 marray[0] = m; 1300 *reqpage = 0; 1301 return 1; 1302 } 1303 1304 marray[i] = rtm; 1305 } 1306 } else { 1307 startpindex = 0; 1308 i = 0; 1309 } 1310 1311 marray[i] = m; 1312 /* page offset of the required page */ 1313 *reqpage = i; 1314 1315 tpindex = pindex + 1; 1316 i++; 1317 1318 /* 1319 * scan forward for the read ahead pages 1320 */ 1321 endpindex = tpindex + rahead; 1322 if (endpindex > object->size) 1323 endpindex = object->size; 1324 1325 for (; tpindex < endpindex; i++, tpindex++) { 1326 1327 if (vm_page_lookup(object, tpindex)) { 1328 break; 1329 } 1330 1331 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1332 if (rtm == NULL) { 1333 break; 1334 } 1335 1336 marray[i] = rtm; 1337 } 1338 1339 /* return number of bytes of pages */ 1340 return i; 1341 } 1342