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sys/vm/vm_fault.c
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1 /* 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 1994 John S. Dyson 5 * All rights reserved. 6 * Copyright (c) 1994 David Greenman 7 * All rights reserved. 8 * 9 * 10 * This code is derived from software contributed to Berkeley by 11 * The Mach Operating System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 42 * 43 * 44 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 45 * All rights reserved. 46 * 47 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 48 * 49 * Permission to use, copy, modify and distribute this software and 50 * its documentation is hereby granted, provided that both the copyright 51 * notice and this permission notice appear in all copies of the 52 * software, derivative works or modified versions, and any portions 53 * thereof, and that both notices appear in supporting documentation. 54 * 55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 58 * 59 * Carnegie Mellon requests users of this software to return to 60 * 61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 62 * School of Computer Science 63 * Carnegie Mellon University 64 * Pittsburgh PA 15213-3890 65 * 66 * any improvements or extensions that they make and grant Carnegie the 67 * rights to redistribute these changes. 68 */ 69 70 /* 71 * Page fault handling module. 72 */ 73 74 #include <sys/cdefs.h> 75 __FBSDID("$FreeBSD: releng/5.2/sys/vm/vm_fault.c 122383 2003-11-10 00:44:00Z mini $"); 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 vput(fs->vp); 171 fs->vp = NULL; 172 } 173 } 174 175 #define unlock_things(fs) _unlock_things(fs, 0) 176 #define unlock_and_deallocate(fs) _unlock_things(fs, 1) 177 178 /* 179 * TRYPAGER - used by vm_fault to calculate whether the pager for the 180 * current object *might* contain the page. 181 * 182 * default objects are zero-fill, there is no real pager. 183 */ 184 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 185 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) 186 187 /* 188 * vm_fault: 189 * 190 * Handle a page fault occurring at the given address, 191 * requiring the given permissions, in the map specified. 192 * If successful, the page is inserted into the 193 * associated physical map. 194 * 195 * NOTE: the given address should be truncated to the 196 * proper page address. 197 * 198 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 199 * a standard error specifying why the fault is fatal is returned. 200 * 201 * 202 * The map in question must be referenced, and remains so. 203 * Caller may hold no locks. 204 */ 205 int 206 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 207 int fault_flags) 208 { 209 vm_prot_t prot; 210 int is_first_object_locked, result; 211 boolean_t growstack, wired; 212 int map_generation; 213 vm_object_t next_object; 214 vm_page_t marray[VM_FAULT_READ]; 215 int hardfault; 216 int faultcount; 217 struct faultstate fs; 218 219 hardfault = 0; 220 growstack = TRUE; 221 atomic_add_int(&cnt.v_vm_faults, 1); 222 223 mtx_lock(&Giant); 224 RetryFault:; 225 226 /* 227 * Find the backing store object and offset into it to begin the 228 * search. 229 */ 230 fs.map = map; 231 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 232 &fs.first_object, &fs.first_pindex, &prot, &wired); 233 if (result != KERN_SUCCESS) { 234 if (result != KERN_PROTECTION_FAILURE || 235 (fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) { 236 if (growstack && result == KERN_INVALID_ADDRESS && 237 map != kernel_map && curproc != NULL) { 238 result = vm_map_growstack(curproc, vaddr); 239 if (result != KERN_SUCCESS) { 240 mtx_unlock(&Giant); 241 return (KERN_FAILURE); 242 } 243 growstack = FALSE; 244 goto RetryFault; 245 } 246 mtx_unlock(&Giant); 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 mtx_unlock(&Giant); 262 return (result); 263 } 264 265 /* 266 * If we don't COW now, on a user wire, the user will never 267 * be able to write to the mapping. If we don't make this 268 * restriction, the bookkeeping would be nearly impossible. 269 * 270 * XXX The following assignment modifies the map without 271 * holding a write lock on it. 272 */ 273 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 274 fs.entry->max_protection &= ~VM_PROT_WRITE; 275 } 276 277 map_generation = fs.map->timestamp; 278 279 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 280 panic("vm_fault: fault on nofault entry, addr: %lx", 281 (u_long)vaddr); 282 } 283 284 /* 285 * Make a reference to this object to prevent its disposal while we 286 * are messing with it. Once we have the reference, the map is free 287 * to be diddled. Since objects reference their shadows (and copies), 288 * they will stay around as well. 289 * 290 * Bump the paging-in-progress count to prevent size changes (e.g. 291 * truncation operations) during I/O. This must be done after 292 * obtaining the vnode lock in order to avoid possible deadlocks. 293 * 294 * XXX vnode_pager_lock() can block without releasing the map lock. 295 */ 296 vm_object_reference(fs.first_object); 297 VM_OBJECT_LOCK(fs.first_object); 298 fs.vp = vnode_pager_lock(fs.first_object); 299 vm_object_pip_add(fs.first_object, 1); 300 301 fs.lookup_still_valid = TRUE; 302 303 if (wired) 304 fault_type = prot; 305 306 fs.first_m = NULL; 307 308 /* 309 * Search for the page at object/offset. 310 */ 311 fs.object = fs.first_object; 312 fs.pindex = fs.first_pindex; 313 while (TRUE) { 314 /* 315 * If the object is dead, we stop here 316 */ 317 if (fs.object->flags & OBJ_DEAD) { 318 unlock_and_deallocate(&fs); 319 mtx_unlock(&Giant); 320 return (KERN_PROTECTION_FAILURE); 321 } 322 323 /* 324 * See if page is resident 325 */ 326 fs.m = vm_page_lookup(fs.object, fs.pindex); 327 if (fs.m != NULL) { 328 int queue, s; 329 330 /* 331 * check for page-based copy on write. 332 * We check fs.object == fs.first_object so 333 * as to ensure the legacy COW mechanism is 334 * used when the page in question is part of 335 * a shadow object. Otherwise, vm_page_cowfault() 336 * removes the page from the backing object, 337 * which is not what we want. 338 */ 339 vm_page_lock_queues(); 340 if ((fs.m->cow) && 341 (fault_type & VM_PROT_WRITE) && 342 (fs.object == fs.first_object)) { 343 s = splvm(); 344 vm_page_cowfault(fs.m); 345 splx(s); 346 vm_page_unlock_queues(); 347 unlock_and_deallocate(&fs); 348 goto RetryFault; 349 } 350 351 /* 352 * Wait/Retry if the page is busy. We have to do this 353 * if the page is busy via either PG_BUSY or 354 * vm_page_t->busy because the vm_pager may be using 355 * vm_page_t->busy for pageouts ( and even pageins if 356 * it is the vnode pager ), and we could end up trying 357 * to pagein and pageout the same page simultaneously. 358 * 359 * We can theoretically allow the busy case on a read 360 * fault if the page is marked valid, but since such 361 * pages are typically already pmap'd, putting that 362 * special case in might be more effort then it is 363 * worth. We cannot under any circumstances mess 364 * around with a vm_page_t->busy page except, perhaps, 365 * to pmap it. 366 */ 367 if ((fs.m->flags & PG_BUSY) || fs.m->busy) { 368 vm_page_unlock_queues(); 369 unlock_things(&fs); 370 vm_page_lock_queues(); 371 if (!vm_page_sleep_if_busy(fs.m, TRUE, "vmpfw")) 372 vm_page_unlock_queues(); 373 cnt.v_intrans++; 374 vm_object_deallocate(fs.first_object); 375 goto RetryFault; 376 } 377 queue = fs.m->queue; 378 379 s = splvm(); 380 vm_pageq_remove_nowakeup(fs.m); 381 splx(s); 382 383 if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) { 384 vm_page_activate(fs.m); 385 vm_page_unlock_queues(); 386 unlock_and_deallocate(&fs); 387 VM_WAITPFAULT; 388 goto RetryFault; 389 } 390 391 /* 392 * Mark page busy for other processes, and the 393 * pagedaemon. If it still isn't completely valid 394 * (readable), jump to readrest, else break-out ( we 395 * found the page ). 396 */ 397 vm_page_busy(fs.m); 398 vm_page_unlock_queues(); 399 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) && 400 fs.m->object != kernel_object && fs.m->object != kmem_object) { 401 goto readrest; 402 } 403 404 break; 405 } 406 407 /* 408 * Page is not resident, If this is the search termination 409 * or the pager might contain the page, allocate a new page. 410 */ 411 if (TRYPAGER || fs.object == fs.first_object) { 412 if (fs.pindex >= fs.object->size) { 413 unlock_and_deallocate(&fs); 414 mtx_unlock(&Giant); 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 if (mt->dirty == 0) 496 vm_page_test_dirty(mt); 497 if (mt->dirty) { 498 pmap_remove_all(mt); 499 vm_page_deactivate(mt); 500 } else { 501 vm_page_cache(mt); 502 } 503 } 504 vm_page_unlock_queues(); 505 ahead += behind; 506 behind = 0; 507 } 508 if (is_first_object_locked) 509 VM_OBJECT_UNLOCK(fs.first_object); 510 /* 511 * now we find out if any other pages should be paged 512 * in at this time this routine checks to see if the 513 * pages surrounding this fault reside in the same 514 * object as the page for this fault. If they do, 515 * then they are faulted in also into the object. The 516 * array "marray" returned contains an array of 517 * vm_page_t structs where one of them is the 518 * vm_page_t passed to the routine. The reqpage 519 * return value is the index into the marray for the 520 * vm_page_t passed to the routine. 521 * 522 * fs.m plus the additional pages are PG_BUSY'd. 523 * 524 * XXX vm_fault_additional_pages() can block 525 * without releasing the map lock. 526 */ 527 faultcount = vm_fault_additional_pages( 528 fs.m, behind, ahead, marray, &reqpage); 529 530 /* 531 * update lastr imperfectly (we do not know how much 532 * getpages will actually read), but good enough. 533 * 534 * XXX The following assignment modifies the map 535 * without holding a write lock on it. 536 */ 537 fs.entry->lastr = fs.pindex + faultcount - behind; 538 539 /* 540 * Call the pager to retrieve the data, if any, after 541 * releasing the lock on the map. We hold a ref on 542 * fs.object and the pages are PG_BUSY'd. 543 */ 544 unlock_map(&fs); 545 546 rv = faultcount ? 547 vm_pager_get_pages(fs.object, marray, faultcount, 548 reqpage) : VM_PAGER_FAIL; 549 550 if (rv == VM_PAGER_OK) { 551 /* 552 * Found the page. Leave it busy while we play 553 * with it. 554 */ 555 556 /* 557 * Relookup in case pager changed page. Pager 558 * is responsible for disposition of old page 559 * if moved. 560 */ 561 fs.m = vm_page_lookup(fs.object, fs.pindex); 562 if (!fs.m) { 563 unlock_and_deallocate(&fs); 564 goto RetryFault; 565 } 566 567 hardfault++; 568 break; /* break to PAGE HAS BEEN FOUND */ 569 } 570 /* 571 * Remove the bogus page (which does not exist at this 572 * object/offset); before doing so, we must get back 573 * our object lock to preserve our invariant. 574 * 575 * Also wake up any other process that may want to bring 576 * in this page. 577 * 578 * If this is the top-level object, we must leave the 579 * busy page to prevent another process from rushing 580 * past us, and inserting the page in that object at 581 * the same time that we are. 582 */ 583 if (rv == VM_PAGER_ERROR) 584 printf("vm_fault: pager read error, pid %d (%s)\n", 585 curproc->p_pid, curproc->p_comm); 586 /* 587 * Data outside the range of the pager or an I/O error 588 */ 589 /* 590 * XXX - the check for kernel_map is a kludge to work 591 * around having the machine panic on a kernel space 592 * fault w/ I/O error. 593 */ 594 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 595 (rv == VM_PAGER_BAD)) { 596 vm_page_lock_queues(); 597 vm_page_free(fs.m); 598 vm_page_unlock_queues(); 599 fs.m = NULL; 600 unlock_and_deallocate(&fs); 601 mtx_unlock(&Giant); 602 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 603 } 604 if (fs.object != fs.first_object) { 605 vm_page_lock_queues(); 606 vm_page_free(fs.m); 607 vm_page_unlock_queues(); 608 fs.m = NULL; 609 /* 610 * XXX - we cannot just fall out at this 611 * point, m has been freed and is invalid! 612 */ 613 } 614 } 615 616 /* 617 * We get here if the object has default pager (or unwiring) 618 * or the pager doesn't have the page. 619 */ 620 if (fs.object == fs.first_object) 621 fs.first_m = fs.m; 622 623 /* 624 * Move on to the next object. Lock the next object before 625 * unlocking the current one. 626 */ 627 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 628 next_object = fs.object->backing_object; 629 if (next_object == NULL) { 630 /* 631 * If there's no object left, fill the page in the top 632 * object with zeros. 633 */ 634 if (fs.object != fs.first_object) { 635 vm_object_pip_wakeup(fs.object); 636 VM_OBJECT_UNLOCK(fs.object); 637 638 fs.object = fs.first_object; 639 fs.pindex = fs.first_pindex; 640 fs.m = fs.first_m; 641 VM_OBJECT_LOCK(fs.object); 642 } 643 fs.first_m = NULL; 644 645 /* 646 * Zero the page if necessary and mark it valid. 647 */ 648 if ((fs.m->flags & PG_ZERO) == 0) { 649 pmap_zero_page(fs.m); 650 } else { 651 cnt.v_ozfod++; 652 } 653 cnt.v_zfod++; 654 fs.m->valid = VM_PAGE_BITS_ALL; 655 break; /* break to PAGE HAS BEEN FOUND */ 656 } else { 657 KASSERT(fs.object != next_object, 658 ("object loop %p", next_object)); 659 VM_OBJECT_LOCK(next_object); 660 vm_object_pip_add(next_object, 1); 661 if (fs.object != fs.first_object) 662 vm_object_pip_wakeup(fs.object); 663 VM_OBJECT_UNLOCK(fs.object); 664 fs.object = next_object; 665 } 666 } 667 668 KASSERT((fs.m->flags & PG_BUSY) != 0, 669 ("vm_fault: not busy after main loop")); 670 671 /* 672 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 673 * is held.] 674 */ 675 676 /* 677 * If the page is being written, but isn't already owned by the 678 * top-level object, we have to copy it into a new page owned by the 679 * top-level object. 680 */ 681 if (fs.object != fs.first_object) { 682 /* 683 * We only really need to copy if we want to write it. 684 */ 685 if (fault_type & VM_PROT_WRITE) { 686 /* 687 * This allows pages to be virtually copied from a 688 * backing_object into the first_object, where the 689 * backing object has no other refs to it, and cannot 690 * gain any more refs. Instead of a bcopy, we just 691 * move the page from the backing object to the 692 * first object. Note that we must mark the page 693 * dirty in the first object so that it will go out 694 * to swap when needed. 695 */ 696 is_first_object_locked = FALSE; 697 if ( 698 /* 699 * Only one shadow object 700 */ 701 (fs.object->shadow_count == 1) && 702 /* 703 * No COW refs, except us 704 */ 705 (fs.object->ref_count == 1) && 706 /* 707 * No one else can look this object up 708 */ 709 (fs.object->handle == NULL) && 710 /* 711 * No other ways to look the object up 712 */ 713 ((fs.object->type == OBJT_DEFAULT) || 714 (fs.object->type == OBJT_SWAP)) && 715 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) && 716 /* 717 * We don't chase down the shadow chain 718 */ 719 fs.object == fs.first_object->backing_object) { 720 vm_page_lock_queues(); 721 /* 722 * get rid of the unnecessary page 723 */ 724 pmap_remove_all(fs.first_m); 725 vm_page_free(fs.first_m); 726 /* 727 * grab the page and put it into the 728 * process'es object. The page is 729 * automatically made dirty. 730 */ 731 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 732 vm_page_busy(fs.m); 733 vm_page_unlock_queues(); 734 fs.first_m = fs.m; 735 fs.m = NULL; 736 cnt.v_cow_optim++; 737 } else { 738 /* 739 * Oh, well, lets copy it. 740 */ 741 pmap_copy_page(fs.m, fs.first_m); 742 fs.first_m->valid = VM_PAGE_BITS_ALL; 743 } 744 if (fs.m) { 745 /* 746 * We no longer need the old page or object. 747 */ 748 release_page(&fs); 749 } 750 /* 751 * fs.object != fs.first_object due to above 752 * conditional 753 */ 754 vm_object_pip_wakeup(fs.object); 755 VM_OBJECT_UNLOCK(fs.object); 756 /* 757 * Only use the new page below... 758 */ 759 fs.object = fs.first_object; 760 fs.pindex = fs.first_pindex; 761 fs.m = fs.first_m; 762 if (!is_first_object_locked) 763 VM_OBJECT_LOCK(fs.object); 764 cnt.v_cow_faults++; 765 } else { 766 prot &= ~VM_PROT_WRITE; 767 } 768 } 769 770 /* 771 * We must verify that the maps have not changed since our last 772 * lookup. 773 */ 774 if (!fs.lookup_still_valid && 775 (fs.map->timestamp != map_generation)) { 776 vm_object_t retry_object; 777 vm_pindex_t retry_pindex; 778 vm_prot_t retry_prot; 779 780 /* 781 * Since map entries may be pageable, make sure we can take a 782 * page fault on them. 783 */ 784 785 /* 786 * Unlock vnode before the lookup to avoid deadlock. E.G. 787 * avoid a deadlock between the inode and exec_map that can 788 * occur due to locks being obtained in different orders. 789 */ 790 if (fs.vp != NULL) { 791 vput(fs.vp); 792 fs.vp = NULL; 793 } 794 795 if (fs.map->infork) { 796 release_page(&fs); 797 unlock_and_deallocate(&fs); 798 goto RetryFault; 799 } 800 VM_OBJECT_UNLOCK(fs.object); 801 802 /* 803 * To avoid trying to write_lock the map while another process 804 * has it read_locked (in vm_map_wire), we do not try for 805 * write permission. If the page is still writable, we will 806 * get write permission. If it is not, or has been marked 807 * needs_copy, we enter the mapping without write permission, 808 * and will merely take another fault. 809 */ 810 result = vm_map_lookup(&fs.map, vaddr, fault_type & ~VM_PROT_WRITE, 811 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 812 map_generation = fs.map->timestamp; 813 814 VM_OBJECT_LOCK(fs.object); 815 /* 816 * If we don't need the page any longer, put it on the active 817 * list (the easiest thing to do here). If no one needs it, 818 * pageout will grab it eventually. 819 */ 820 if (result != KERN_SUCCESS) { 821 release_page(&fs); 822 unlock_and_deallocate(&fs); 823 mtx_unlock(&Giant); 824 return (result); 825 } 826 fs.lookup_still_valid = TRUE; 827 828 if ((retry_object != fs.first_object) || 829 (retry_pindex != fs.first_pindex)) { 830 release_page(&fs); 831 unlock_and_deallocate(&fs); 832 goto RetryFault; 833 } 834 /* 835 * Check whether the protection has changed or the object has 836 * been copied while we left the map unlocked. Changing from 837 * read to write permission is OK - we leave the page 838 * write-protected, and catch the write fault. Changing from 839 * write to read permission means that we can't mark the page 840 * write-enabled after all. 841 */ 842 prot &= retry_prot; 843 } 844 845 /* 846 * Put this page into the physical map. We had to do the unlock above 847 * because pmap_enter may cause other faults. We don't put the page 848 * back on the active queue until later so that the page-out daemon 849 * won't find us (yet). 850 */ 851 852 if (prot & VM_PROT_WRITE) { 853 vm_page_lock_queues(); 854 vm_page_flag_set(fs.m, PG_WRITEABLE); 855 vm_object_set_writeable_dirty(fs.m->object); 856 857 /* 858 * If the fault is a write, we know that this page is being 859 * written NOW so dirty it explicitly to save on 860 * pmap_is_modified() calls later. 861 * 862 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC 863 * if the page is already dirty to prevent data written with 864 * the expectation of being synced from not being synced. 865 * Likewise if this entry does not request NOSYNC then make 866 * sure the page isn't marked NOSYNC. Applications sharing 867 * data should use the same flags to avoid ping ponging. 868 * 869 * Also tell the backing pager, if any, that it should remove 870 * any swap backing since the page is now dirty. 871 */ 872 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 873 if (fs.m->dirty == 0) 874 vm_page_flag_set(fs.m, PG_NOSYNC); 875 } else { 876 vm_page_flag_clear(fs.m, PG_NOSYNC); 877 } 878 vm_page_unlock_queues(); 879 if (fault_flags & VM_FAULT_DIRTY) { 880 int s; 881 vm_page_dirty(fs.m); 882 s = splvm(); 883 vm_pager_page_unswapped(fs.m); 884 splx(s); 885 } 886 } 887 888 /* 889 * Page had better still be busy 890 */ 891 KASSERT(fs.m->flags & PG_BUSY, 892 ("vm_fault: page %p not busy!", fs.m)); 893 /* 894 * Sanity check: page must be completely valid or it is not fit to 895 * map into user space. vm_pager_get_pages() ensures this. 896 */ 897 if (fs.m->valid != VM_PAGE_BITS_ALL) { 898 vm_page_zero_invalid(fs.m, TRUE); 899 printf("Warning: page %p partially invalid on fault\n", fs.m); 900 } 901 unlock_things(&fs); 902 903 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired); 904 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 905 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry); 906 } 907 vm_page_lock_queues(); 908 vm_page_flag_clear(fs.m, PG_ZERO); 909 vm_page_flag_set(fs.m, PG_REFERENCED); 910 911 /* 912 * If the page is not wired down, then put it where the pageout daemon 913 * can find it. 914 */ 915 if (fault_flags & VM_FAULT_WIRE_MASK) { 916 if (wired) 917 vm_page_wire(fs.m); 918 else 919 vm_page_unwire(fs.m, 1); 920 } else { 921 vm_page_activate(fs.m); 922 } 923 vm_page_wakeup(fs.m); 924 vm_page_unlock_queues(); 925 926 PROC_LOCK(curproc); 927 if ((curproc->p_sflag & PS_INMEM) && curproc->p_stats) { 928 if (hardfault) { 929 curproc->p_stats->p_ru.ru_majflt++; 930 } else { 931 curproc->p_stats->p_ru.ru_minflt++; 932 } 933 } 934 PROC_UNLOCK(curproc); 935 936 /* 937 * Unlock everything, and return 938 */ 939 vm_object_deallocate(fs.first_object); 940 mtx_unlock(&Giant); 941 return (KERN_SUCCESS); 942 } 943 944 /* 945 * vm_fault_prefault provides a quick way of clustering 946 * pagefaults into a processes address space. It is a "cousin" 947 * of vm_map_pmap_enter, except it runs at page fault time instead 948 * of mmap time. 949 */ 950 static void 951 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry) 952 { 953 int i; 954 vm_offset_t addr, starta; 955 vm_pindex_t pindex; 956 vm_page_t m, mpte; 957 vm_object_t object; 958 959 if (!curthread || (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))) 960 return; 961 962 object = entry->object.vm_object; 963 964 starta = addra - PFBAK * PAGE_SIZE; 965 if (starta < entry->start) { 966 starta = entry->start; 967 } else if (starta > addra) { 968 starta = 0; 969 } 970 971 mpte = NULL; 972 for (i = 0; i < PAGEORDER_SIZE; i++) { 973 vm_object_t backing_object, lobject; 974 975 addr = addra + prefault_pageorder[i]; 976 if (addr > addra + (PFFOR * PAGE_SIZE)) 977 addr = 0; 978 979 if (addr < starta || addr >= entry->end) 980 continue; 981 982 if (!pmap_is_prefaultable(pmap, addr)) 983 continue; 984 985 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 986 lobject = object; 987 VM_OBJECT_LOCK(lobject); 988 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 989 lobject->type == OBJT_DEFAULT && 990 (backing_object = lobject->backing_object) != NULL) { 991 if (lobject->backing_object_offset & PAGE_MASK) 992 break; 993 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 994 VM_OBJECT_LOCK(backing_object); 995 VM_OBJECT_UNLOCK(lobject); 996 lobject = backing_object; 997 } 998 /* 999 * give-up when a page is not in memory 1000 */ 1001 if (m == NULL) { 1002 VM_OBJECT_UNLOCK(lobject); 1003 break; 1004 } 1005 vm_page_lock_queues(); 1006 if (((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) && 1007 (m->busy == 0) && 1008 (m->flags & (PG_BUSY | PG_FICTITIOUS)) == 0) { 1009 1010 if ((m->queue - m->pc) == PQ_CACHE) { 1011 vm_page_deactivate(m); 1012 } 1013 vm_page_busy(m); 1014 vm_page_unlock_queues(); 1015 VM_OBJECT_UNLOCK(lobject); 1016 mpte = pmap_enter_quick(pmap, addr, m, mpte); 1017 VM_OBJECT_LOCK(lobject); 1018 vm_page_lock_queues(); 1019 vm_page_wakeup(m); 1020 } 1021 vm_page_unlock_queues(); 1022 VM_OBJECT_UNLOCK(lobject); 1023 } 1024 } 1025 1026 /* 1027 * vm_fault_quick: 1028 * 1029 * Ensure that the requested virtual address, which may be in userland, 1030 * is valid. Fault-in the page if necessary. Return -1 on failure. 1031 */ 1032 int 1033 vm_fault_quick(caddr_t v, int prot) 1034 { 1035 int r; 1036 1037 if (prot & VM_PROT_WRITE) 1038 r = subyte(v, fubyte(v)); 1039 else 1040 r = fubyte(v); 1041 return(r); 1042 } 1043 1044 /* 1045 * vm_fault_wire: 1046 * 1047 * Wire down a range of virtual addresses in a map. 1048 */ 1049 int 1050 vm_fault_wire(map, start, end, user_wire) 1051 vm_map_t map; 1052 vm_offset_t start, end; 1053 boolean_t user_wire; 1054 { 1055 vm_offset_t va; 1056 int rv; 1057 1058 /* 1059 * We simulate a fault to get the page and enter it in the physical 1060 * map. For user wiring, we only ask for read access on currently 1061 * read-only sections. 1062 */ 1063 for (va = start; va < end; va += PAGE_SIZE) { 1064 rv = vm_fault(map, va, 1065 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE, 1066 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING); 1067 if (rv) { 1068 if (va != start) 1069 vm_fault_unwire(map, start, va); 1070 return (rv); 1071 } 1072 } 1073 return (KERN_SUCCESS); 1074 } 1075 1076 /* 1077 * vm_fault_unwire: 1078 * 1079 * Unwire a range of virtual addresses in a map. 1080 */ 1081 void 1082 vm_fault_unwire(map, start, end) 1083 vm_map_t map; 1084 vm_offset_t start, end; 1085 { 1086 vm_paddr_t pa; 1087 vm_offset_t va; 1088 pmap_t pmap; 1089 1090 pmap = vm_map_pmap(map); 1091 1092 mtx_lock(&Giant); 1093 /* 1094 * Since the pages are wired down, we must be able to get their 1095 * mappings from the physical map system. 1096 */ 1097 for (va = start; va < end; va += PAGE_SIZE) { 1098 pa = pmap_extract(pmap, va); 1099 if (pa != 0) { 1100 pmap_change_wiring(pmap, va, FALSE); 1101 vm_page_lock_queues(); 1102 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1103 vm_page_unlock_queues(); 1104 } 1105 } 1106 mtx_unlock(&Giant); 1107 } 1108 1109 /* 1110 * Routine: 1111 * vm_fault_copy_entry 1112 * Function: 1113 * Copy all of the pages from a wired-down map entry to another. 1114 * 1115 * In/out conditions: 1116 * The source and destination maps must be locked for write. 1117 * The source map entry must be wired down (or be a sharing map 1118 * entry corresponding to a main map entry that is wired down). 1119 */ 1120 void 1121 vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry) 1122 vm_map_t dst_map; 1123 vm_map_t src_map; 1124 vm_map_entry_t dst_entry; 1125 vm_map_entry_t src_entry; 1126 { 1127 vm_object_t backing_object, dst_object, object; 1128 vm_object_t src_object; 1129 vm_ooffset_t dst_offset; 1130 vm_ooffset_t src_offset; 1131 vm_pindex_t pindex; 1132 vm_prot_t prot; 1133 vm_offset_t vaddr; 1134 vm_page_t dst_m; 1135 vm_page_t src_m; 1136 1137 #ifdef lint 1138 src_map++; 1139 #endif /* lint */ 1140 1141 src_object = src_entry->object.vm_object; 1142 src_offset = src_entry->offset; 1143 1144 /* 1145 * Create the top-level object for the destination entry. (Doesn't 1146 * actually shadow anything - we copy the pages directly.) 1147 */ 1148 dst_object = vm_object_allocate(OBJT_DEFAULT, 1149 (vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1150 1151 VM_OBJECT_LOCK(dst_object); 1152 dst_entry->object.vm_object = dst_object; 1153 dst_entry->offset = 0; 1154 1155 prot = dst_entry->max_protection; 1156 1157 /* 1158 * Loop through all of the pages in the entry's range, copying each 1159 * one from the source object (it should be there) to the destination 1160 * object. 1161 */ 1162 for (vaddr = dst_entry->start, dst_offset = 0; 1163 vaddr < dst_entry->end; 1164 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { 1165 1166 /* 1167 * Allocate a page in the destination object 1168 */ 1169 do { 1170 dst_m = vm_page_alloc(dst_object, 1171 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); 1172 if (dst_m == NULL) { 1173 VM_OBJECT_UNLOCK(dst_object); 1174 VM_WAIT; 1175 VM_OBJECT_LOCK(dst_object); 1176 } 1177 } while (dst_m == NULL); 1178 1179 /* 1180 * Find the page in the source object, and copy it in. 1181 * (Because the source is wired down, the page will be in 1182 * memory.) 1183 */ 1184 VM_OBJECT_LOCK(src_object); 1185 object = src_object; 1186 pindex = 0; 1187 while ((src_m = vm_page_lookup(object, pindex + 1188 OFF_TO_IDX(dst_offset + src_offset))) == NULL && 1189 (src_entry->protection & VM_PROT_WRITE) == 0 && 1190 (backing_object = object->backing_object) != NULL) { 1191 /* 1192 * Allow fallback to backing objects if we are reading. 1193 */ 1194 VM_OBJECT_LOCK(backing_object); 1195 pindex += OFF_TO_IDX(object->backing_object_offset); 1196 VM_OBJECT_UNLOCK(object); 1197 object = backing_object; 1198 } 1199 if (src_m == NULL) 1200 panic("vm_fault_copy_wired: page missing"); 1201 pmap_copy_page(src_m, dst_m); 1202 VM_OBJECT_UNLOCK(object); 1203 dst_m->valid = VM_PAGE_BITS_ALL; 1204 VM_OBJECT_UNLOCK(dst_object); 1205 1206 /* 1207 * Enter it in the pmap... 1208 */ 1209 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE); 1210 VM_OBJECT_LOCK(dst_object); 1211 vm_page_lock_queues(); 1212 if ((prot & VM_PROT_WRITE) != 0) 1213 vm_page_flag_set(dst_m, PG_WRITEABLE); 1214 1215 /* 1216 * Mark it no longer busy, and put it on the active list. 1217 */ 1218 vm_page_activate(dst_m); 1219 vm_page_wakeup(dst_m); 1220 vm_page_unlock_queues(); 1221 } 1222 VM_OBJECT_UNLOCK(dst_object); 1223 } 1224 1225 1226 /* 1227 * This routine checks around the requested page for other pages that 1228 * might be able to be faulted in. This routine brackets the viable 1229 * pages for the pages to be paged in. 1230 * 1231 * Inputs: 1232 * m, rbehind, rahead 1233 * 1234 * Outputs: 1235 * marray (array of vm_page_t), reqpage (index of requested page) 1236 * 1237 * Return value: 1238 * number of pages in marray 1239 * 1240 * This routine can't block. 1241 */ 1242 static int 1243 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1244 vm_page_t m; 1245 int rbehind; 1246 int rahead; 1247 vm_page_t *marray; 1248 int *reqpage; 1249 { 1250 int i,j; 1251 vm_object_t object; 1252 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1253 vm_page_t rtm; 1254 int cbehind, cahead; 1255 1256 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED); 1257 1258 object = m->object; 1259 pindex = m->pindex; 1260 1261 /* 1262 * we don't fault-ahead for device pager 1263 */ 1264 if (object->type == OBJT_DEVICE) { 1265 *reqpage = 0; 1266 marray[0] = m; 1267 return 1; 1268 } 1269 1270 /* 1271 * if the requested page is not available, then give up now 1272 */ 1273 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1274 return 0; 1275 } 1276 1277 if ((cbehind == 0) && (cahead == 0)) { 1278 *reqpage = 0; 1279 marray[0] = m; 1280 return 1; 1281 } 1282 1283 if (rahead > cahead) { 1284 rahead = cahead; 1285 } 1286 1287 if (rbehind > cbehind) { 1288 rbehind = cbehind; 1289 } 1290 1291 /* 1292 * try to do any readahead that we might have free pages for. 1293 */ 1294 if ((rahead + rbehind) > 1295 ((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) { 1296 pagedaemon_wakeup(); 1297 marray[0] = m; 1298 *reqpage = 0; 1299 return 1; 1300 } 1301 1302 /* 1303 * scan backward for the read behind pages -- in memory 1304 */ 1305 if (pindex > 0) { 1306 if (rbehind > pindex) { 1307 rbehind = pindex; 1308 startpindex = 0; 1309 } else { 1310 startpindex = pindex - rbehind; 1311 } 1312 1313 for (tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) { 1314 if (vm_page_lookup(object, tpindex)) { 1315 startpindex = tpindex + 1; 1316 break; 1317 } 1318 if (tpindex == 0) 1319 break; 1320 } 1321 1322 for (i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) { 1323 1324 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1325 if (rtm == NULL) { 1326 vm_page_lock_queues(); 1327 for (j = 0; j < i; j++) { 1328 vm_page_free(marray[j]); 1329 } 1330 vm_page_unlock_queues(); 1331 marray[0] = m; 1332 *reqpage = 0; 1333 return 1; 1334 } 1335 1336 marray[i] = rtm; 1337 } 1338 } else { 1339 startpindex = 0; 1340 i = 0; 1341 } 1342 1343 marray[i] = m; 1344 /* page offset of the required page */ 1345 *reqpage = i; 1346 1347 tpindex = pindex + 1; 1348 i++; 1349 1350 /* 1351 * scan forward for the read ahead pages 1352 */ 1353 endpindex = tpindex + rahead; 1354 if (endpindex > object->size) 1355 endpindex = object->size; 1356 1357 for (; tpindex < endpindex; i++, tpindex++) { 1358 1359 if (vm_page_lookup(object, tpindex)) { 1360 break; 1361 } 1362 1363 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1364 if (rtm == NULL) { 1365 break; 1366 } 1367 1368 marray[i] = rtm; 1369 } 1370 1371 /* return number of bytes of pages */ 1372 return i; 1373 }
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