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