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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 * $FreeBSD: releng/5.1/sys/vm/vm_fault.c 113868 2003-04-22 20:01:56Z jhb $ 70 */ 71 72 /* 73 * Page fault handling module. 74 */ 75 #include <sys/param.h> 76 #include <sys/systm.h> 77 #include <sys/kernel.h> 78 #include <sys/lock.h> 79 #include <sys/mutex.h> 80 #include <sys/proc.h> 81 #include <sys/resourcevar.h> 82 #include <sys/sysctl.h> 83 #include <sys/vmmeter.h> 84 #include <sys/vnode.h> 85 86 #include <vm/vm.h> 87 #include <vm/vm_param.h> 88 #include <vm/pmap.h> 89 #include <vm/vm_map.h> 90 #include <vm/vm_object.h> 91 #include <vm/vm_page.h> 92 #include <vm/vm_pageout.h> 93 #include <vm/vm_kern.h> 94 #include <vm/vm_pager.h> 95 #include <vm/vnode_pager.h> 96 #include <vm/vm_extern.h> 97 98 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 99 100 #define VM_FAULT_READ_AHEAD 8 101 #define VM_FAULT_READ_BEHIND 7 102 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1) 103 104 struct faultstate { 105 vm_page_t m; 106 vm_object_t object; 107 vm_pindex_t pindex; 108 vm_page_t first_m; 109 vm_object_t first_object; 110 vm_pindex_t first_pindex; 111 vm_map_t map; 112 vm_map_entry_t entry; 113 int lookup_still_valid; 114 struct vnode *vp; 115 }; 116 117 static __inline void 118 release_page(struct faultstate *fs) 119 { 120 vm_page_lock_queues(); 121 vm_page_wakeup(fs->m); 122 vm_page_deactivate(fs->m); 123 vm_page_unlock_queues(); 124 fs->m = NULL; 125 } 126 127 static __inline void 128 unlock_map(struct faultstate *fs) 129 { 130 if (fs->lookup_still_valid) { 131 vm_map_lookup_done(fs->map, fs->entry); 132 fs->lookup_still_valid = FALSE; 133 } 134 } 135 136 static void 137 _unlock_things(struct faultstate *fs, int dealloc) 138 { 139 GIANT_REQUIRED; 140 VM_OBJECT_LOCK(fs->object); 141 vm_object_pip_wakeup(fs->object); 142 VM_OBJECT_UNLOCK(fs->object); 143 if (fs->object != fs->first_object) { 144 VM_OBJECT_LOCK(fs->first_object); 145 vm_page_lock_queues(); 146 vm_page_free(fs->first_m); 147 vm_page_unlock_queues(); 148 vm_object_pip_wakeup(fs->first_object); 149 VM_OBJECT_UNLOCK(fs->first_object); 150 fs->first_m = NULL; 151 } 152 if (dealloc) { 153 vm_object_deallocate(fs->first_object); 154 } 155 unlock_map(fs); 156 if (fs->vp != NULL) { 157 vput(fs->vp); 158 fs->vp = NULL; 159 } 160 } 161 162 #define unlock_things(fs) _unlock_things(fs, 0) 163 #define unlock_and_deallocate(fs) _unlock_things(fs, 1) 164 165 /* 166 * TRYPAGER - used by vm_fault to calculate whether the pager for the 167 * current object *might* contain the page. 168 * 169 * default objects are zero-fill, there is no real pager. 170 */ 171 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 172 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) 173 174 /* 175 * vm_fault: 176 * 177 * Handle a page fault occurring at the given address, 178 * requiring the given permissions, in the map specified. 179 * If successful, the page is inserted into the 180 * associated physical map. 181 * 182 * NOTE: the given address should be truncated to the 183 * proper page address. 184 * 185 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 186 * a standard error specifying why the fault is fatal is returned. 187 * 188 * 189 * The map in question must be referenced, and remains so. 190 * Caller may hold no locks. 191 */ 192 int 193 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 194 int fault_flags) 195 { 196 vm_prot_t prot; 197 int result; 198 boolean_t growstack, wired; 199 int map_generation; 200 vm_object_t next_object; 201 vm_page_t marray[VM_FAULT_READ]; 202 int hardfault; 203 int faultcount; 204 struct faultstate fs; 205 206 hardfault = 0; 207 growstack = TRUE; 208 atomic_add_int(&cnt.v_vm_faults, 1); 209 210 mtx_lock(&Giant); 211 RetryFault:; 212 213 /* 214 * Find the backing store object and offset into it to begin the 215 * search. 216 */ 217 fs.map = map; 218 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 219 &fs.first_object, &fs.first_pindex, &prot, &wired); 220 if (result != KERN_SUCCESS) { 221 if (result != KERN_PROTECTION_FAILURE || 222 (fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) { 223 if (growstack && result == KERN_INVALID_ADDRESS && 224 map != kernel_map && curproc != NULL) { 225 result = vm_map_growstack(curproc, vaddr); 226 if (result != KERN_SUCCESS) { 227 mtx_unlock(&Giant); 228 return (KERN_FAILURE); 229 } 230 growstack = FALSE; 231 goto RetryFault; 232 } 233 mtx_unlock(&Giant); 234 return (result); 235 } 236 237 /* 238 * If we are user-wiring a r/w segment, and it is COW, then 239 * we need to do the COW operation. Note that we don't COW 240 * currently RO sections now, because it is NOT desirable 241 * to COW .text. We simply keep .text from ever being COW'ed 242 * and take the heat that one cannot debug wired .text sections. 243 */ 244 result = vm_map_lookup(&fs.map, vaddr, 245 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE, 246 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired); 247 if (result != KERN_SUCCESS) { 248 mtx_unlock(&Giant); 249 return (result); 250 } 251 252 /* 253 * If we don't COW now, on a user wire, the user will never 254 * be able to write to the mapping. If we don't make this 255 * restriction, the bookkeeping would be nearly impossible. 256 * 257 * XXX The following assignment modifies the map without 258 * holding a write lock on it. 259 */ 260 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 261 fs.entry->max_protection &= ~VM_PROT_WRITE; 262 } 263 264 map_generation = fs.map->timestamp; 265 266 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 267 panic("vm_fault: fault on nofault entry, addr: %lx", 268 (u_long)vaddr); 269 } 270 271 /* 272 * Make a reference to this object to prevent its disposal while we 273 * are messing with it. Once we have the reference, the map is free 274 * to be diddled. Since objects reference their shadows (and copies), 275 * they will stay around as well. 276 * 277 * Bump the paging-in-progress count to prevent size changes (e.g. 278 * truncation operations) during I/O. This must be done after 279 * obtaining the vnode lock in order to avoid possible deadlocks. 280 * 281 * XXX vnode_pager_lock() can block without releasing the map lock. 282 */ 283 vm_object_reference(fs.first_object); 284 fs.vp = vnode_pager_lock(fs.first_object); 285 VM_OBJECT_LOCK(fs.first_object); 286 vm_object_pip_add(fs.first_object, 1); 287 VM_OBJECT_UNLOCK(fs.first_object); 288 289 fs.lookup_still_valid = TRUE; 290 291 if (wired) 292 fault_type = prot; 293 294 fs.first_m = NULL; 295 296 /* 297 * Search for the page at object/offset. 298 */ 299 fs.object = fs.first_object; 300 fs.pindex = fs.first_pindex; 301 while (TRUE) { 302 /* 303 * If the object is dead, we stop here 304 */ 305 if (fs.object->flags & OBJ_DEAD) { 306 unlock_and_deallocate(&fs); 307 mtx_unlock(&Giant); 308 return (KERN_PROTECTION_FAILURE); 309 } 310 311 /* 312 * See if page is resident 313 */ 314 fs.m = vm_page_lookup(fs.object, fs.pindex); 315 if (fs.m != NULL) { 316 int queue, s; 317 318 /* 319 * check for page-based copy on write. 320 * We check fs.object == fs.first_object so 321 * as to ensure the legacy COW mechanism is 322 * used when the page in question is part of 323 * a shadow object. Otherwise, vm_page_cowfault() 324 * removes the page from the backing object, 325 * which is not what we want. 326 */ 327 vm_page_lock_queues(); 328 if ((fs.m->cow) && 329 (fault_type & VM_PROT_WRITE) && 330 (fs.object == fs.first_object)) { 331 s = splvm(); 332 vm_page_cowfault(fs.m); 333 splx(s); 334 vm_page_unlock_queues(); 335 unlock_things(&fs); 336 goto RetryFault; 337 } 338 339 /* 340 * Wait/Retry if the page is busy. We have to do this 341 * if the page is busy via either PG_BUSY or 342 * vm_page_t->busy because the vm_pager may be using 343 * vm_page_t->busy for pageouts ( and even pageins if 344 * it is the vnode pager ), and we could end up trying 345 * to pagein and pageout the same page simultaneously. 346 * 347 * We can theoretically allow the busy case on a read 348 * fault if the page is marked valid, but since such 349 * pages are typically already pmap'd, putting that 350 * special case in might be more effort then it is 351 * worth. We cannot under any circumstances mess 352 * around with a vm_page_t->busy page except, perhaps, 353 * to pmap it. 354 */ 355 if ((fs.m->flags & PG_BUSY) || fs.m->busy) { 356 vm_page_unlock_queues(); 357 unlock_things(&fs); 358 vm_page_lock_queues(); 359 if (!vm_page_sleep_if_busy(fs.m, TRUE, "vmpfw")) 360 vm_page_unlock_queues(); 361 cnt.v_intrans++; 362 vm_object_deallocate(fs.first_object); 363 goto RetryFault; 364 } 365 queue = fs.m->queue; 366 367 s = splvm(); 368 vm_pageq_remove_nowakeup(fs.m); 369 splx(s); 370 371 if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) { 372 vm_page_activate(fs.m); 373 vm_page_unlock_queues(); 374 unlock_and_deallocate(&fs); 375 VM_WAITPFAULT; 376 goto RetryFault; 377 } 378 379 /* 380 * Mark page busy for other processes, and the 381 * pagedaemon. If it still isn't completely valid 382 * (readable), jump to readrest, else break-out ( we 383 * found the page ). 384 */ 385 vm_page_busy(fs.m); 386 vm_page_unlock_queues(); 387 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) && 388 fs.m->object != kernel_object && fs.m->object != kmem_object) { 389 goto readrest; 390 } 391 392 break; 393 } 394 395 /* 396 * Page is not resident, If this is the search termination 397 * or the pager might contain the page, allocate a new page. 398 */ 399 if (TRYPAGER || fs.object == fs.first_object) { 400 if (fs.pindex >= fs.object->size) { 401 unlock_and_deallocate(&fs); 402 mtx_unlock(&Giant); 403 return (KERN_PROTECTION_FAILURE); 404 } 405 406 /* 407 * Allocate a new page for this object/offset pair. 408 */ 409 fs.m = NULL; 410 if (!vm_page_count_severe()) { 411 fs.m = vm_page_alloc(fs.object, fs.pindex, 412 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO); 413 } 414 if (fs.m == NULL) { 415 unlock_and_deallocate(&fs); 416 VM_WAITPFAULT; 417 goto RetryFault; 418 } 419 } 420 421 readrest: 422 /* 423 * We have found a valid page or we have allocated a new page. 424 * The page thus may not be valid or may not be entirely 425 * valid. 426 * 427 * Attempt to fault-in the page if there is a chance that the 428 * pager has it, and potentially fault in additional pages 429 * at the same time. 430 */ 431 if (TRYPAGER) { 432 int rv; 433 int reqpage; 434 int ahead, behind; 435 u_char behavior = vm_map_entry_behavior(fs.entry); 436 437 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 438 ahead = 0; 439 behind = 0; 440 } else { 441 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT; 442 if (behind > VM_FAULT_READ_BEHIND) 443 behind = VM_FAULT_READ_BEHIND; 444 445 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1; 446 if (ahead > VM_FAULT_READ_AHEAD) 447 ahead = VM_FAULT_READ_AHEAD; 448 } 449 450 if ((fs.first_object->type != OBJT_DEVICE) && 451 (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 452 (behavior != MAP_ENTRY_BEHAV_RANDOM && 453 fs.pindex >= fs.entry->lastr && 454 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) 455 ) { 456 vm_pindex_t firstpindex, tmppindex; 457 458 if (fs.first_pindex < 2 * VM_FAULT_READ) 459 firstpindex = 0; 460 else 461 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ; 462 463 vm_page_lock_queues(); 464 /* 465 * note: partially valid pages cannot be 466 * included in the lookahead - NFS piecemeal 467 * writes will barf on it badly. 468 */ 469 for (tmppindex = fs.first_pindex - 1; 470 tmppindex >= firstpindex; 471 --tmppindex) { 472 vm_page_t mt; 473 474 mt = vm_page_lookup(fs.first_object, tmppindex); 475 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL)) 476 break; 477 if (mt->busy || 478 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) || 479 mt->hold_count || 480 mt->wire_count) 481 continue; 482 if (mt->dirty == 0) 483 vm_page_test_dirty(mt); 484 if (mt->dirty) { 485 pmap_remove_all(mt); 486 vm_page_deactivate(mt); 487 } else { 488 vm_page_cache(mt); 489 } 490 } 491 vm_page_unlock_queues(); 492 ahead += behind; 493 behind = 0; 494 } 495 496 /* 497 * now we find out if any other pages should be paged 498 * in at this time this routine checks to see if the 499 * pages surrounding this fault reside in the same 500 * object as the page for this fault. If they do, 501 * then they are faulted in also into the object. The 502 * array "marray" returned contains an array of 503 * vm_page_t structs where one of them is the 504 * vm_page_t passed to the routine. The reqpage 505 * return value is the index into the marray for the 506 * vm_page_t passed to the routine. 507 * 508 * fs.m plus the additional pages are PG_BUSY'd. 509 * 510 * XXX vm_fault_additional_pages() can block 511 * without releasing the map lock. 512 */ 513 faultcount = vm_fault_additional_pages( 514 fs.m, behind, ahead, marray, &reqpage); 515 516 /* 517 * update lastr imperfectly (we do not know how much 518 * getpages will actually read), but good enough. 519 * 520 * XXX The following assignment modifies the map 521 * without holding a write lock on it. 522 */ 523 fs.entry->lastr = fs.pindex + faultcount - behind; 524 525 /* 526 * Call the pager to retrieve the data, if any, after 527 * releasing the lock on the map. We hold a ref on 528 * fs.object and the pages are PG_BUSY'd. 529 */ 530 unlock_map(&fs); 531 532 rv = faultcount ? 533 vm_pager_get_pages(fs.object, marray, faultcount, 534 reqpage) : VM_PAGER_FAIL; 535 536 if (rv == VM_PAGER_OK) { 537 /* 538 * Found the page. Leave it busy while we play 539 * with it. 540 */ 541 542 /* 543 * Relookup in case pager changed page. Pager 544 * is responsible for disposition of old page 545 * if moved. 546 */ 547 fs.m = vm_page_lookup(fs.object, fs.pindex); 548 if (!fs.m) { 549 unlock_and_deallocate(&fs); 550 goto RetryFault; 551 } 552 553 hardfault++; 554 break; /* break to PAGE HAS BEEN FOUND */ 555 } 556 /* 557 * Remove the bogus page (which does not exist at this 558 * object/offset); before doing so, we must get back 559 * our object lock to preserve our invariant. 560 * 561 * Also wake up any other process that may want to bring 562 * in this page. 563 * 564 * If this is the top-level object, we must leave the 565 * busy page to prevent another process from rushing 566 * past us, and inserting the page in that object at 567 * the same time that we are. 568 */ 569 if (rv == VM_PAGER_ERROR) 570 printf("vm_fault: pager read error, pid %d (%s)\n", 571 curproc->p_pid, curproc->p_comm); 572 /* 573 * Data outside the range of the pager or an I/O error 574 */ 575 /* 576 * XXX - the check for kernel_map is a kludge to work 577 * around having the machine panic on a kernel space 578 * fault w/ I/O error. 579 */ 580 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 581 (rv == VM_PAGER_BAD)) { 582 vm_page_lock_queues(); 583 vm_page_free(fs.m); 584 vm_page_unlock_queues(); 585 fs.m = NULL; 586 unlock_and_deallocate(&fs); 587 mtx_unlock(&Giant); 588 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 589 } 590 if (fs.object != fs.first_object) { 591 vm_page_lock_queues(); 592 vm_page_free(fs.m); 593 vm_page_unlock_queues(); 594 fs.m = NULL; 595 /* 596 * XXX - we cannot just fall out at this 597 * point, m has been freed and is invalid! 598 */ 599 } 600 } 601 602 /* 603 * We get here if the object has default pager (or unwiring) 604 * or the pager doesn't have the page. 605 */ 606 if (fs.object == fs.first_object) 607 fs.first_m = fs.m; 608 609 /* 610 * Move on to the next object. Lock the next object before 611 * unlocking the current one. 612 */ 613 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 614 next_object = fs.object->backing_object; 615 if (next_object == NULL) { 616 /* 617 * If there's no object left, fill the page in the top 618 * object with zeros. 619 */ 620 if (fs.object != fs.first_object) { 621 VM_OBJECT_LOCK(fs.object); 622 vm_object_pip_wakeup(fs.object); 623 VM_OBJECT_UNLOCK(fs.object); 624 625 fs.object = fs.first_object; 626 fs.pindex = fs.first_pindex; 627 fs.m = fs.first_m; 628 } 629 fs.first_m = NULL; 630 631 /* 632 * Zero the page if necessary and mark it valid. 633 */ 634 if ((fs.m->flags & PG_ZERO) == 0) { 635 pmap_zero_page(fs.m); 636 } else { 637 cnt.v_ozfod++; 638 } 639 cnt.v_zfod++; 640 fs.m->valid = VM_PAGE_BITS_ALL; 641 break; /* break to PAGE HAS BEEN FOUND */ 642 } else { 643 if (fs.object != fs.first_object) { 644 VM_OBJECT_LOCK(fs.object); 645 vm_object_pip_wakeup(fs.object); 646 VM_OBJECT_UNLOCK(fs.object); 647 } 648 KASSERT(fs.object != next_object, ("object loop %p", next_object)); 649 fs.object = next_object; 650 VM_OBJECT_LOCK(fs.object); 651 vm_object_pip_add(fs.object, 1); 652 VM_OBJECT_UNLOCK(fs.object); 653 } 654 } 655 656 KASSERT((fs.m->flags & PG_BUSY) != 0, 657 ("vm_fault: not busy after main loop")); 658 659 /* 660 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 661 * is held.] 662 */ 663 664 /* 665 * If the page is being written, but isn't already owned by the 666 * top-level object, we have to copy it into a new page owned by the 667 * top-level object. 668 */ 669 if (fs.object != fs.first_object) { 670 /* 671 * We only really need to copy if we want to write it. 672 */ 673 if (fault_type & VM_PROT_WRITE) { 674 /* 675 * This allows pages to be virtually copied from a 676 * backing_object into the first_object, where the 677 * backing object has no other refs to it, and cannot 678 * gain any more refs. Instead of a bcopy, we just 679 * move the page from the backing object to the 680 * first object. Note that we must mark the page 681 * dirty in the first object so that it will go out 682 * to swap when needed. 683 */ 684 if (map_generation == fs.map->timestamp && 685 /* 686 * Only one shadow object 687 */ 688 (fs.object->shadow_count == 1) && 689 /* 690 * No COW refs, except us 691 */ 692 (fs.object->ref_count == 1) && 693 /* 694 * No one else can look this object up 695 */ 696 (fs.object->handle == NULL) && 697 /* 698 * No other ways to look the object up 699 */ 700 ((fs.object->type == OBJT_DEFAULT) || 701 (fs.object->type == OBJT_SWAP)) && 702 /* 703 * We don't chase down the shadow chain 704 */ 705 (fs.object == fs.first_object->backing_object) && 706 707 /* 708 * grab the lock if we need to 709 */ 710 (fs.lookup_still_valid || vm_map_trylock(fs.map))) { 711 712 fs.lookup_still_valid = 1; 713 /* 714 * get rid of the unnecessary page 715 */ 716 vm_page_lock_queues(); 717 pmap_remove_all(fs.first_m); 718 vm_page_free(fs.first_m); 719 fs.first_m = NULL; 720 721 /* 722 * grab the page and put it into the 723 * process'es object. The page is 724 * automatically made dirty. 725 */ 726 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 727 fs.first_m = fs.m; 728 vm_page_busy(fs.first_m); 729 vm_page_unlock_queues(); 730 fs.m = NULL; 731 cnt.v_cow_optim++; 732 } else { 733 /* 734 * Oh, well, lets copy it. 735 */ 736 vm_page_copy(fs.m, fs.first_m); 737 } 738 739 if (fs.m) { 740 /* 741 * We no longer need the old page or object. 742 */ 743 release_page(&fs); 744 } 745 746 /* 747 * fs.object != fs.first_object due to above 748 * conditional 749 */ 750 VM_OBJECT_LOCK(fs.object); 751 vm_object_pip_wakeup(fs.object); 752 VM_OBJECT_UNLOCK(fs.object); 753 754 /* 755 * Only use the new page below... 756 */ 757 cnt.v_cow_faults++; 758 fs.m = fs.first_m; 759 fs.object = fs.first_object; 760 fs.pindex = fs.first_pindex; 761 762 } 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 (fs.map->timestamp != map_generation)) { 773 vm_object_t retry_object; 774 vm_pindex_t retry_pindex; 775 vm_prot_t retry_prot; 776 777 /* 778 * Since map entries may be pageable, make sure we can take a 779 * page fault on them. 780 */ 781 782 /* 783 * Unlock vnode before the lookup to avoid deadlock. E.G. 784 * avoid a deadlock between the inode and exec_map that can 785 * occur due to locks being obtained in different orders. 786 */ 787 if (fs.vp != NULL) { 788 vput(fs.vp); 789 fs.vp = NULL; 790 } 791 792 if (fs.map->infork) { 793 release_page(&fs); 794 unlock_and_deallocate(&fs); 795 goto RetryFault; 796 } 797 798 /* 799 * To avoid trying to write_lock the map while another process 800 * has it read_locked (in vm_map_pageable), we do not try for 801 * write permission. If the page is still writable, we will 802 * get write permission. If it is not, or has been marked 803 * needs_copy, we enter the mapping without write permission, 804 * and will merely take another fault. 805 */ 806 result = vm_map_lookup(&fs.map, vaddr, fault_type & ~VM_PROT_WRITE, 807 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 808 map_generation = fs.map->timestamp; 809 810 /* 811 * If we don't need the page any longer, put it on the active 812 * list (the easiest thing to do here). If no one needs it, 813 * pageout will grab it eventually. 814 */ 815 if (result != KERN_SUCCESS) { 816 release_page(&fs); 817 unlock_and_deallocate(&fs); 818 mtx_unlock(&Giant); 819 return (result); 820 } 821 fs.lookup_still_valid = TRUE; 822 823 if ((retry_object != fs.first_object) || 824 (retry_pindex != fs.first_pindex)) { 825 release_page(&fs); 826 unlock_and_deallocate(&fs); 827 goto RetryFault; 828 } 829 /* 830 * Check whether the protection has changed or the object has 831 * been copied while we left the map unlocked. Changing from 832 * read to write permission is OK - we leave the page 833 * write-protected, and catch the write fault. Changing from 834 * write to read permission means that we can't mark the page 835 * write-enabled after all. 836 */ 837 prot &= retry_prot; 838 } 839 840 /* 841 * Put this page into the physical map. We had to do the unlock above 842 * because pmap_enter may cause other faults. We don't put the page 843 * back on the active queue until later so that the page-out daemon 844 * won't find us (yet). 845 */ 846 847 if (prot & VM_PROT_WRITE) { 848 vm_page_lock_queues(); 849 vm_page_flag_set(fs.m, PG_WRITEABLE); 850 vm_object_set_writeable_dirty(fs.m->object); 851 852 /* 853 * If the fault is a write, we know that this page is being 854 * written NOW so dirty it explicitly to save on 855 * pmap_is_modified() calls later. 856 * 857 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC 858 * if the page is already dirty to prevent data written with 859 * the expectation of being synced from not being synced. 860 * Likewise if this entry does not request NOSYNC then make 861 * sure the page isn't marked NOSYNC. Applications sharing 862 * data should use the same flags to avoid ping ponging. 863 * 864 * Also tell the backing pager, if any, that it should remove 865 * any swap backing since the page is now dirty. 866 */ 867 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 868 if (fs.m->dirty == 0) 869 vm_page_flag_set(fs.m, PG_NOSYNC); 870 } else { 871 vm_page_flag_clear(fs.m, PG_NOSYNC); 872 } 873 vm_page_unlock_queues(); 874 if (fault_flags & VM_FAULT_DIRTY) { 875 int s; 876 vm_page_dirty(fs.m); 877 s = splvm(); 878 vm_pager_page_unswapped(fs.m); 879 splx(s); 880 } 881 } 882 883 /* 884 * Page had better still be busy 885 */ 886 KASSERT(fs.m->flags & PG_BUSY, 887 ("vm_fault: page %p not busy!", fs.m)); 888 unlock_things(&fs); 889 890 /* 891 * Sanity check: page must be completely valid or it is not fit to 892 * map into user space. vm_pager_get_pages() ensures this. 893 */ 894 if (fs.m->valid != VM_PAGE_BITS_ALL) { 895 vm_page_zero_invalid(fs.m, TRUE); 896 printf("Warning: page %p partially invalid on fault\n", fs.m); 897 } 898 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired); 899 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 900 pmap_prefault(fs.map->pmap, vaddr, fs.entry); 901 } 902 vm_page_lock_queues(); 903 vm_page_flag_clear(fs.m, PG_ZERO); 904 vm_page_flag_set(fs.m, PG_REFERENCED); 905 906 /* 907 * If the page is not wired down, then put it where the pageout daemon 908 * can find it. 909 */ 910 if (fault_flags & VM_FAULT_WIRE_MASK) { 911 if (wired) 912 vm_page_wire(fs.m); 913 else 914 vm_page_unwire(fs.m, 1); 915 } else { 916 vm_page_activate(fs.m); 917 } 918 vm_page_wakeup(fs.m); 919 vm_page_unlock_queues(); 920 921 PROC_LOCK(curproc); 922 if ((curproc->p_sflag & PS_INMEM) && curproc->p_stats) { 923 if (hardfault) { 924 curproc->p_stats->p_ru.ru_majflt++; 925 } else { 926 curproc->p_stats->p_ru.ru_minflt++; 927 } 928 } 929 PROC_UNLOCK(curproc); 930 931 /* 932 * Unlock everything, and return 933 */ 934 vm_object_deallocate(fs.first_object); 935 mtx_unlock(&Giant); 936 return (KERN_SUCCESS); 937 } 938 939 /* 940 * vm_fault_quick: 941 * 942 * Ensure that the requested virtual address, which may be in userland, 943 * is valid. Fault-in the page if necessary. Return -1 on failure. 944 */ 945 int 946 vm_fault_quick(caddr_t v, int prot) 947 { 948 int r; 949 950 if (prot & VM_PROT_WRITE) 951 r = subyte(v, fubyte(v)); 952 else 953 r = fubyte(v); 954 return(r); 955 } 956 957 /* 958 * vm_fault_wire: 959 * 960 * Wire down a range of virtual addresses in a map. 961 */ 962 int 963 vm_fault_wire(map, start, end, user_wire) 964 vm_map_t map; 965 vm_offset_t start, end; 966 boolean_t user_wire; 967 { 968 vm_offset_t va; 969 int rv; 970 971 /* 972 * We simulate a fault to get the page and enter it in the physical 973 * map. For user wiring, we only ask for read access on currently 974 * read-only sections. 975 */ 976 for (va = start; va < end; va += PAGE_SIZE) { 977 rv = vm_fault(map, va, 978 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE, 979 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING); 980 if (rv) { 981 if (va != start) 982 vm_fault_unwire(map, start, va); 983 return (rv); 984 } 985 } 986 return (KERN_SUCCESS); 987 } 988 989 /* 990 * vm_fault_unwire: 991 * 992 * Unwire a range of virtual addresses in a map. 993 */ 994 void 995 vm_fault_unwire(map, start, end) 996 vm_map_t map; 997 vm_offset_t start, end; 998 { 999 vm_paddr_t pa; 1000 vm_offset_t va; 1001 pmap_t pmap; 1002 1003 pmap = vm_map_pmap(map); 1004 1005 mtx_lock(&Giant); 1006 /* 1007 * Since the pages are wired down, we must be able to get their 1008 * mappings from the physical map system. 1009 */ 1010 for (va = start; va < end; va += PAGE_SIZE) { 1011 pa = pmap_extract(pmap, va); 1012 if (pa != 0) { 1013 pmap_change_wiring(pmap, va, FALSE); 1014 vm_page_lock_queues(); 1015 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1016 vm_page_unlock_queues(); 1017 } 1018 } 1019 mtx_unlock(&Giant); 1020 } 1021 1022 /* 1023 * Routine: 1024 * vm_fault_copy_entry 1025 * Function: 1026 * Copy all of the pages from a wired-down map entry to another. 1027 * 1028 * In/out conditions: 1029 * The source and destination maps must be locked for write. 1030 * The source map entry must be wired down (or be a sharing map 1031 * entry corresponding to a main map entry that is wired down). 1032 */ 1033 void 1034 vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry) 1035 vm_map_t dst_map; 1036 vm_map_t src_map; 1037 vm_map_entry_t dst_entry; 1038 vm_map_entry_t src_entry; 1039 { 1040 vm_object_t dst_object; 1041 vm_object_t src_object; 1042 vm_ooffset_t dst_offset; 1043 vm_ooffset_t src_offset; 1044 vm_prot_t prot; 1045 vm_offset_t vaddr; 1046 vm_page_t dst_m; 1047 vm_page_t src_m; 1048 1049 #ifdef lint 1050 src_map++; 1051 #endif /* lint */ 1052 1053 src_object = src_entry->object.vm_object; 1054 src_offset = src_entry->offset; 1055 1056 /* 1057 * Create the top-level object for the destination entry. (Doesn't 1058 * actually shadow anything - we copy the pages directly.) 1059 */ 1060 dst_object = vm_object_allocate(OBJT_DEFAULT, 1061 (vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1062 1063 dst_entry->object.vm_object = dst_object; 1064 dst_entry->offset = 0; 1065 1066 prot = dst_entry->max_protection; 1067 1068 /* 1069 * Loop through all of the pages in the entry's range, copying each 1070 * one from the source object (it should be there) to the destination 1071 * object. 1072 */ 1073 for (vaddr = dst_entry->start, dst_offset = 0; 1074 vaddr < dst_entry->end; 1075 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { 1076 1077 /* 1078 * Allocate a page in the destination object 1079 */ 1080 do { 1081 dst_m = vm_page_alloc(dst_object, 1082 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); 1083 if (dst_m == NULL) { 1084 VM_WAIT; 1085 } 1086 } while (dst_m == NULL); 1087 1088 /* 1089 * Find the page in the source object, and copy it in. 1090 * (Because the source is wired down, the page will be in 1091 * memory.) 1092 */ 1093 src_m = vm_page_lookup(src_object, 1094 OFF_TO_IDX(dst_offset + src_offset)); 1095 if (src_m == NULL) 1096 panic("vm_fault_copy_wired: page missing"); 1097 1098 vm_page_copy(src_m, dst_m); 1099 1100 /* 1101 * Enter it in the pmap... 1102 */ 1103 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE); 1104 vm_page_lock_queues(); 1105 vm_page_flag_set(dst_m, PG_WRITEABLE); 1106 1107 /* 1108 * Mark it no longer busy, and put it on the active list. 1109 */ 1110 vm_page_activate(dst_m); 1111 vm_page_wakeup(dst_m); 1112 vm_page_unlock_queues(); 1113 } 1114 } 1115 1116 1117 /* 1118 * This routine checks around the requested page for other pages that 1119 * might be able to be faulted in. This routine brackets the viable 1120 * pages for the pages to be paged in. 1121 * 1122 * Inputs: 1123 * m, rbehind, rahead 1124 * 1125 * Outputs: 1126 * marray (array of vm_page_t), reqpage (index of requested page) 1127 * 1128 * Return value: 1129 * number of pages in marray 1130 * 1131 * This routine can't block. 1132 */ 1133 static int 1134 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1135 vm_page_t m; 1136 int rbehind; 1137 int rahead; 1138 vm_page_t *marray; 1139 int *reqpage; 1140 { 1141 int i,j; 1142 vm_object_t object; 1143 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1144 vm_page_t rtm; 1145 int cbehind, cahead; 1146 1147 GIANT_REQUIRED; 1148 1149 object = m->object; 1150 pindex = m->pindex; 1151 1152 /* 1153 * we don't fault-ahead for device pager 1154 */ 1155 if (object->type == OBJT_DEVICE) { 1156 *reqpage = 0; 1157 marray[0] = m; 1158 return 1; 1159 } 1160 1161 /* 1162 * if the requested page is not available, then give up now 1163 */ 1164 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1165 return 0; 1166 } 1167 1168 if ((cbehind == 0) && (cahead == 0)) { 1169 *reqpage = 0; 1170 marray[0] = m; 1171 return 1; 1172 } 1173 1174 if (rahead > cahead) { 1175 rahead = cahead; 1176 } 1177 1178 if (rbehind > cbehind) { 1179 rbehind = cbehind; 1180 } 1181 1182 /* 1183 * try to do any readahead that we might have free pages for. 1184 */ 1185 if ((rahead + rbehind) > 1186 ((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) { 1187 pagedaemon_wakeup(); 1188 marray[0] = m; 1189 *reqpage = 0; 1190 return 1; 1191 } 1192 1193 /* 1194 * scan backward for the read behind pages -- in memory 1195 */ 1196 if (pindex > 0) { 1197 if (rbehind > pindex) { 1198 rbehind = pindex; 1199 startpindex = 0; 1200 } else { 1201 startpindex = pindex - rbehind; 1202 } 1203 1204 for (tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) { 1205 if (vm_page_lookup(object, tpindex)) { 1206 startpindex = tpindex + 1; 1207 break; 1208 } 1209 if (tpindex == 0) 1210 break; 1211 } 1212 1213 for (i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) { 1214 1215 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1216 if (rtm == NULL) { 1217 vm_page_lock_queues(); 1218 for (j = 0; j < i; j++) { 1219 vm_page_free(marray[j]); 1220 } 1221 vm_page_unlock_queues(); 1222 marray[0] = m; 1223 *reqpage = 0; 1224 return 1; 1225 } 1226 1227 marray[i] = rtm; 1228 } 1229 } else { 1230 startpindex = 0; 1231 i = 0; 1232 } 1233 1234 marray[i] = m; 1235 /* page offset of the required page */ 1236 *reqpage = i; 1237 1238 tpindex = pindex + 1; 1239 i++; 1240 1241 /* 1242 * scan forward for the read ahead pages 1243 */ 1244 endpindex = tpindex + rahead; 1245 if (endpindex > object->size) 1246 endpindex = object->size; 1247 1248 for (; tpindex < endpindex; i++, tpindex++) { 1249 1250 if (vm_page_lookup(object, tpindex)) { 1251 break; 1252 } 1253 1254 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1255 if (rtm == NULL) { 1256 break; 1257 } 1258 1259 marray[i] = rtm; 1260 } 1261 1262 /* return number of bytes of pages */ 1263 return i; 1264 }
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