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 #include <sys/mount.h> /* XXX Temporary for VFS_LOCK_GIANT() */ 101 102 #define PFBAK 4 103 #define PFFOR 4 104 #define PAGEORDER_SIZE (PFBAK+PFFOR) 105 106 static int prefault_pageorder[] = { 107 -1 * PAGE_SIZE, 1 * PAGE_SIZE, 108 -2 * PAGE_SIZE, 2 * PAGE_SIZE, 109 -3 * PAGE_SIZE, 3 * PAGE_SIZE, 110 -4 * PAGE_SIZE, 4 * PAGE_SIZE 111 }; 112 113 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 114 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t); 115 116 #define VM_FAULT_READ_AHEAD 8 117 #define VM_FAULT_READ_BEHIND 7 118 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1) 119 120 struct faultstate { 121 vm_page_t m; 122 vm_object_t object; 123 vm_pindex_t pindex; 124 vm_page_t first_m; 125 vm_object_t first_object; 126 vm_pindex_t first_pindex; 127 vm_map_t map; 128 vm_map_entry_t entry; 129 int lookup_still_valid; 130 struct vnode *vp; 131 }; 132 133 static inline void 134 release_page(struct faultstate *fs) 135 { 136 vm_page_wakeup(fs->m); 137 vm_page_lock_queues(); 138 vm_page_deactivate(fs->m); 139 vm_page_unlock_queues(); 140 fs->m = NULL; 141 } 142 143 static inline void 144 unlock_map(struct faultstate *fs) 145 { 146 if (fs->lookup_still_valid) { 147 vm_map_lookup_done(fs->map, fs->entry); 148 fs->lookup_still_valid = FALSE; 149 } 150 } 151 152 static void 153 unlock_and_deallocate(struct faultstate *fs) 154 { 155 156 vm_object_pip_wakeup(fs->object); 157 VM_OBJECT_UNLOCK(fs->object); 158 if (fs->object != fs->first_object) { 159 VM_OBJECT_LOCK(fs->first_object); 160 vm_page_lock_queues(); 161 vm_page_free(fs->first_m); 162 vm_page_unlock_queues(); 163 vm_object_pip_wakeup(fs->first_object); 164 VM_OBJECT_UNLOCK(fs->first_object); 165 fs->first_m = NULL; 166 } 167 vm_object_deallocate(fs->first_object); 168 unlock_map(fs); 169 if (fs->vp != NULL) { 170 int vfslocked; 171 172 vfslocked = VFS_LOCK_GIANT(fs->vp->v_mount); 173 vput(fs->vp); 174 fs->vp = NULL; 175 VFS_UNLOCK_GIANT(vfslocked); 176 } 177 } 178 179 /* 180 * TRYPAGER - used by vm_fault to calculate whether the pager for the 181 * current object *might* contain the page. 182 * 183 * default objects are zero-fill, there is no real pager. 184 */ 185 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 186 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) 187 188 /* 189 * vm_fault: 190 * 191 * Handle a page fault occurring at the given address, 192 * requiring the given permissions, in the map specified. 193 * If successful, the page is inserted into the 194 * associated physical map. 195 * 196 * NOTE: the given address should be truncated to the 197 * proper page address. 198 * 199 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 200 * a standard error specifying why the fault is fatal is returned. 201 * 202 * 203 * The map in question must be referenced, and remains so. 204 * Caller may hold no locks. 205 */ 206 int 207 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 208 int fault_flags) 209 { 210 vm_prot_t prot; 211 int is_first_object_locked, result; 212 boolean_t growstack, wired; 213 int map_generation; 214 vm_object_t next_object; 215 vm_page_t marray[VM_FAULT_READ]; 216 int hardfault; 217 int faultcount; 218 struct faultstate fs; 219 220 hardfault = 0; 221 growstack = TRUE; 222 atomic_add_int(&cnt.v_vm_faults, 1); 223 224 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 return (KERN_FAILURE); 241 growstack = FALSE; 242 goto RetryFault; 243 } 244 return (result); 245 } 246 247 /* 248 * If we are user-wiring a r/w segment, and it is COW, then 249 * we need to do the COW operation. Note that we don't COW 250 * currently RO sections now, because it is NOT desirable 251 * to COW .text. We simply keep .text from ever being COW'ed 252 * and take the heat that one cannot debug wired .text sections. 253 */ 254 result = vm_map_lookup(&fs.map, vaddr, 255 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE, 256 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired); 257 if (result != KERN_SUCCESS) 258 return (result); 259 260 /* 261 * If we don't COW now, on a user wire, the user will never 262 * be able to write to the mapping. If we don't make this 263 * restriction, the bookkeeping would be nearly impossible. 264 * 265 * XXX The following assignment modifies the map without 266 * holding a write lock on it. 267 */ 268 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 269 fs.entry->max_protection &= ~VM_PROT_WRITE; 270 } 271 272 map_generation = fs.map->timestamp; 273 274 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 275 panic("vm_fault: fault on nofault entry, addr: %lx", 276 (u_long)vaddr); 277 } 278 279 /* 280 * Make a reference to this object to prevent its disposal while we 281 * are messing with it. Once we have the reference, the map is free 282 * to be diddled. Since objects reference their shadows (and copies), 283 * they will stay around as well. 284 * 285 * Bump the paging-in-progress count to prevent size changes (e.g. 286 * truncation operations) during I/O. This must be done after 287 * obtaining the vnode lock in order to avoid possible deadlocks. 288 * 289 * XXX vnode_pager_lock() can block without releasing the map lock. 290 */ 291 if (fs.first_object->flags & OBJ_NEEDGIANT) 292 mtx_lock(&Giant); 293 VM_OBJECT_LOCK(fs.first_object); 294 vm_object_reference_locked(fs.first_object); 295 fs.vp = vnode_pager_lock(fs.first_object); 296 KASSERT(fs.vp == NULL || !fs.map->system_map, 297 ("vm_fault: vnode-backed object mapped by system map")); 298 KASSERT((fs.first_object->flags & OBJ_NEEDGIANT) == 0 || 299 !fs.map->system_map, 300 ("vm_fault: Object requiring giant mapped by system map")); 301 if (fs.first_object->flags & OBJ_NEEDGIANT) 302 mtx_unlock(&Giant); 303 vm_object_pip_add(fs.first_object, 1); 304 305 fs.lookup_still_valid = TRUE; 306 307 if (wired) 308 fault_type = prot; 309 310 fs.first_m = NULL; 311 312 /* 313 * Search for the page at object/offset. 314 */ 315 fs.object = fs.first_object; 316 fs.pindex = fs.first_pindex; 317 while (TRUE) { 318 /* 319 * If the object is dead, we stop here 320 */ 321 if (fs.object->flags & OBJ_DEAD) { 322 unlock_and_deallocate(&fs); 323 return (KERN_PROTECTION_FAILURE); 324 } 325 326 /* 327 * See if page is resident 328 */ 329 fs.m = vm_page_lookup(fs.object, fs.pindex); 330 if (fs.m != NULL) { 331 int queue; 332 333 /* 334 * check for page-based copy on write. 335 * We check fs.object == fs.first_object so 336 * as to ensure the legacy COW mechanism is 337 * used when the page in question is part of 338 * a shadow object. Otherwise, vm_page_cowfault() 339 * removes the page from the backing object, 340 * which is not what we want. 341 */ 342 vm_page_lock_queues(); 343 if ((fs.m->cow) && 344 (fault_type & VM_PROT_WRITE) && 345 (fs.object == fs.first_object)) { 346 vm_page_cowfault(fs.m); 347 vm_page_unlock_queues(); 348 unlock_and_deallocate(&fs); 349 goto RetryFault; 350 } 351 352 /* 353 * Wait/Retry if the page is busy. We have to do this 354 * if the page is busy via either VPO_BUSY or 355 * vm_page_t->busy because the vm_pager may be using 356 * vm_page_t->busy for pageouts ( and even pageins if 357 * it is the vnode pager ), and we could end up trying 358 * to pagein and pageout the same page simultaneously. 359 * 360 * We can theoretically allow the busy case on a read 361 * fault if the page is marked valid, but since such 362 * pages are typically already pmap'd, putting that 363 * special case in might be more effort then it is 364 * worth. We cannot under any circumstances mess 365 * around with a vm_page_t->busy page except, perhaps, 366 * to pmap it. 367 */ 368 if ((fs.m->oflags & VPO_BUSY) || fs.m->busy) { 369 vm_page_unlock_queues(); 370 VM_OBJECT_UNLOCK(fs.object); 371 if (fs.object != fs.first_object) { 372 VM_OBJECT_LOCK(fs.first_object); 373 vm_page_lock_queues(); 374 vm_page_free(fs.first_m); 375 vm_page_unlock_queues(); 376 vm_object_pip_wakeup(fs.first_object); 377 VM_OBJECT_UNLOCK(fs.first_object); 378 fs.first_m = NULL; 379 } 380 unlock_map(&fs); 381 if (fs.vp != NULL) { 382 int vfslck; 383 384 vfslck = VFS_LOCK_GIANT(fs.vp->v_mount); 385 vput(fs.vp); 386 fs.vp = NULL; 387 VFS_UNLOCK_GIANT(vfslck); 388 } 389 VM_OBJECT_LOCK(fs.object); 390 if (fs.m == vm_page_lookup(fs.object, 391 fs.pindex)) { 392 vm_page_sleep_if_busy(fs.m, TRUE, 393 "vmpfw"); 394 } 395 vm_object_pip_wakeup(fs.object); 396 VM_OBJECT_UNLOCK(fs.object); 397 atomic_add_int(&cnt.v_intrans, 1); 398 vm_object_deallocate(fs.first_object); 399 goto RetryFault; 400 } 401 queue = fs.m->queue; 402 403 vm_pageq_remove_nowakeup(fs.m); 404 405 if (VM_PAGE_RESOLVEQUEUE(fs.m, queue) == PQ_CACHE && 406 vm_page_count_severe()) { 407 vm_page_activate(fs.m); 408 vm_page_unlock_queues(); 409 unlock_and_deallocate(&fs); 410 VM_WAITPFAULT; 411 goto RetryFault; 412 } 413 414 /* 415 * Mark page busy for other processes, and the 416 * pagedaemon. If it still isn't completely valid 417 * (readable), jump to readrest, else break-out ( we 418 * found the page ). 419 */ 420 vm_page_busy(fs.m); 421 vm_page_unlock_queues(); 422 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) && 423 fs.m->object != kernel_object && fs.m->object != kmem_object) { 424 goto readrest; 425 } 426 427 break; 428 } 429 430 /* 431 * Page is not resident, If this is the search termination 432 * or the pager might contain the page, allocate a new page. 433 */ 434 if (TRYPAGER || fs.object == fs.first_object) { 435 if (fs.pindex >= fs.object->size) { 436 unlock_and_deallocate(&fs); 437 return (KERN_PROTECTION_FAILURE); 438 } 439 440 /* 441 * Allocate a new page for this object/offset pair. 442 */ 443 fs.m = NULL; 444 if (!vm_page_count_severe()) { 445 fs.m = vm_page_alloc(fs.object, fs.pindex, 446 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO); 447 } 448 if (fs.m == NULL) { 449 unlock_and_deallocate(&fs); 450 VM_WAITPFAULT; 451 goto RetryFault; 452 } 453 } 454 455 readrest: 456 /* 457 * We have found a valid page or we have allocated a new page. 458 * The page thus may not be valid or may not be entirely 459 * valid. 460 * 461 * Attempt to fault-in the page if there is a chance that the 462 * pager has it, and potentially fault in additional pages 463 * at the same time. 464 */ 465 if (TRYPAGER) { 466 int rv; 467 int reqpage; 468 int ahead, behind; 469 u_char behavior = vm_map_entry_behavior(fs.entry); 470 471 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 472 ahead = 0; 473 behind = 0; 474 } else { 475 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT; 476 if (behind > VM_FAULT_READ_BEHIND) 477 behind = VM_FAULT_READ_BEHIND; 478 479 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1; 480 if (ahead > VM_FAULT_READ_AHEAD) 481 ahead = VM_FAULT_READ_AHEAD; 482 } 483 is_first_object_locked = FALSE; 484 if ((behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 485 (behavior != MAP_ENTRY_BEHAV_RANDOM && 486 fs.pindex >= fs.entry->lastr && 487 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) && 488 (fs.first_object == fs.object || 489 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object))) && 490 fs.first_object->type != OBJT_DEVICE) { 491 vm_pindex_t firstpindex, tmppindex; 492 493 if (fs.first_pindex < 2 * VM_FAULT_READ) 494 firstpindex = 0; 495 else 496 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ; 497 498 vm_page_lock_queues(); 499 /* 500 * note: partially valid pages cannot be 501 * included in the lookahead - NFS piecemeal 502 * writes will barf on it badly. 503 */ 504 for (tmppindex = fs.first_pindex - 1; 505 tmppindex >= firstpindex; 506 --tmppindex) { 507 vm_page_t mt; 508 509 mt = vm_page_lookup(fs.first_object, tmppindex); 510 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL)) 511 break; 512 if (mt->busy || 513 (mt->oflags & VPO_BUSY) || 514 (mt->flags & (PG_FICTITIOUS | PG_UNMANAGED)) || 515 mt->hold_count || 516 mt->wire_count) 517 continue; 518 pmap_remove_all(mt); 519 if (mt->dirty) { 520 vm_page_deactivate(mt); 521 } else { 522 vm_page_cache(mt); 523 } 524 } 525 vm_page_unlock_queues(); 526 ahead += behind; 527 behind = 0; 528 } 529 if (is_first_object_locked) 530 VM_OBJECT_UNLOCK(fs.first_object); 531 /* 532 * now we find out if any other pages should be paged 533 * in at this time this routine checks to see if the 534 * pages surrounding this fault reside in the same 535 * object as the page for this fault. If they do, 536 * then they are faulted in also into the object. The 537 * array "marray" returned contains an array of 538 * vm_page_t structs where one of them is the 539 * vm_page_t passed to the routine. The reqpage 540 * return value is the index into the marray for the 541 * vm_page_t passed to the routine. 542 * 543 * fs.m plus the additional pages are VPO_BUSY'd. 544 * 545 * XXX vm_fault_additional_pages() can block 546 * without releasing the map lock. 547 */ 548 faultcount = vm_fault_additional_pages( 549 fs.m, behind, ahead, marray, &reqpage); 550 551 /* 552 * update lastr imperfectly (we do not know how much 553 * getpages will actually read), but good enough. 554 * 555 * XXX The following assignment modifies the map 556 * without holding a write lock on it. 557 */ 558 fs.entry->lastr = fs.pindex + faultcount - behind; 559 560 /* 561 * Call the pager to retrieve the data, if any, after 562 * releasing the lock on the map. We hold a ref on 563 * fs.object and the pages are VPO_BUSY'd. 564 */ 565 unlock_map(&fs); 566 567 rv = faultcount ? 568 vm_pager_get_pages(fs.object, marray, faultcount, 569 reqpage) : VM_PAGER_FAIL; 570 571 if (rv == VM_PAGER_OK) { 572 /* 573 * Found the page. Leave it busy while we play 574 * with it. 575 */ 576 577 /* 578 * Relookup in case pager changed page. Pager 579 * is responsible for disposition of old page 580 * if moved. 581 */ 582 fs.m = vm_page_lookup(fs.object, fs.pindex); 583 if (!fs.m) { 584 unlock_and_deallocate(&fs); 585 goto RetryFault; 586 } 587 588 hardfault++; 589 break; /* break to PAGE HAS BEEN FOUND */ 590 } 591 /* 592 * Remove the bogus page (which does not exist at this 593 * object/offset); before doing so, we must get back 594 * our object lock to preserve our invariant. 595 * 596 * Also wake up any other process that may want to bring 597 * in this page. 598 * 599 * If this is the top-level object, we must leave the 600 * busy page to prevent another process from rushing 601 * past us, and inserting the page in that object at 602 * the same time that we are. 603 */ 604 if (rv == VM_PAGER_ERROR) 605 printf("vm_fault: pager read error, pid %d (%s)\n", 606 curproc->p_pid, curproc->p_comm); 607 /* 608 * Data outside the range of the pager or an I/O error 609 */ 610 /* 611 * XXX - the check for kernel_map is a kludge to work 612 * around having the machine panic on a kernel space 613 * fault w/ I/O error. 614 */ 615 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 616 (rv == VM_PAGER_BAD)) { 617 vm_page_lock_queues(); 618 vm_page_free(fs.m); 619 vm_page_unlock_queues(); 620 fs.m = NULL; 621 unlock_and_deallocate(&fs); 622 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 623 } 624 if (fs.object != fs.first_object) { 625 vm_page_lock_queues(); 626 vm_page_free(fs.m); 627 vm_page_unlock_queues(); 628 fs.m = NULL; 629 /* 630 * XXX - we cannot just fall out at this 631 * point, m has been freed and is invalid! 632 */ 633 } 634 } 635 636 /* 637 * We get here if the object has default pager (or unwiring) 638 * or the pager doesn't have the page. 639 */ 640 if (fs.object == fs.first_object) 641 fs.first_m = fs.m; 642 643 /* 644 * Move on to the next object. Lock the next object before 645 * unlocking the current one. 646 */ 647 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 648 next_object = fs.object->backing_object; 649 if (next_object == NULL) { 650 /* 651 * If there's no object left, fill the page in the top 652 * object with zeros. 653 */ 654 if (fs.object != fs.first_object) { 655 vm_object_pip_wakeup(fs.object); 656 VM_OBJECT_UNLOCK(fs.object); 657 658 fs.object = fs.first_object; 659 fs.pindex = fs.first_pindex; 660 fs.m = fs.first_m; 661 VM_OBJECT_LOCK(fs.object); 662 } 663 fs.first_m = NULL; 664 665 /* 666 * Zero the page if necessary and mark it valid. 667 */ 668 if ((fs.m->flags & PG_ZERO) == 0) { 669 pmap_zero_page(fs.m); 670 } else { 671 atomic_add_int(&cnt.v_ozfod, 1); 672 } 673 atomic_add_int(&cnt.v_zfod, 1); 674 fs.m->valid = VM_PAGE_BITS_ALL; 675 break; /* break to PAGE HAS BEEN FOUND */ 676 } else { 677 KASSERT(fs.object != next_object, 678 ("object loop %p", next_object)); 679 VM_OBJECT_LOCK(next_object); 680 vm_object_pip_add(next_object, 1); 681 if (fs.object != fs.first_object) 682 vm_object_pip_wakeup(fs.object); 683 VM_OBJECT_UNLOCK(fs.object); 684 fs.object = next_object; 685 } 686 } 687 688 KASSERT((fs.m->oflags & VPO_BUSY) != 0, 689 ("vm_fault: not busy after main loop")); 690 691 /* 692 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 693 * is held.] 694 */ 695 696 /* 697 * If the page is being written, but isn't already owned by the 698 * top-level object, we have to copy it into a new page owned by the 699 * top-level object. 700 */ 701 if (fs.object != fs.first_object) { 702 /* 703 * We only really need to copy if we want to write it. 704 */ 705 if (fault_type & VM_PROT_WRITE) { 706 /* 707 * This allows pages to be virtually copied from a 708 * backing_object into the first_object, where the 709 * backing object has no other refs to it, and cannot 710 * gain any more refs. Instead of a bcopy, we just 711 * move the page from the backing object to the 712 * first object. Note that we must mark the page 713 * dirty in the first object so that it will go out 714 * to swap when needed. 715 */ 716 is_first_object_locked = FALSE; 717 if ( 718 /* 719 * Only one shadow object 720 */ 721 (fs.object->shadow_count == 1) && 722 /* 723 * No COW refs, except us 724 */ 725 (fs.object->ref_count == 1) && 726 /* 727 * No one else can look this object up 728 */ 729 (fs.object->handle == NULL) && 730 /* 731 * No other ways to look the object up 732 */ 733 ((fs.object->type == OBJT_DEFAULT) || 734 (fs.object->type == OBJT_SWAP)) && 735 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) && 736 /* 737 * We don't chase down the shadow chain 738 */ 739 fs.object == fs.first_object->backing_object) { 740 vm_page_lock_queues(); 741 /* 742 * get rid of the unnecessary page 743 */ 744 vm_page_free(fs.first_m); 745 /* 746 * grab the page and put it into the 747 * process'es object. The page is 748 * automatically made dirty. 749 */ 750 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 751 vm_page_busy(fs.m); 752 vm_page_unlock_queues(); 753 fs.first_m = fs.m; 754 fs.m = NULL; 755 atomic_add_int(&cnt.v_cow_optim, 1); 756 } else { 757 /* 758 * Oh, well, lets copy it. 759 */ 760 pmap_copy_page(fs.m, fs.first_m); 761 fs.first_m->valid = VM_PAGE_BITS_ALL; 762 } 763 if (fs.m) { 764 /* 765 * We no longer need the old page or object. 766 */ 767 release_page(&fs); 768 } 769 /* 770 * fs.object != fs.first_object due to above 771 * conditional 772 */ 773 vm_object_pip_wakeup(fs.object); 774 VM_OBJECT_UNLOCK(fs.object); 775 /* 776 * Only use the new page below... 777 */ 778 fs.object = fs.first_object; 779 fs.pindex = fs.first_pindex; 780 fs.m = fs.first_m; 781 if (!is_first_object_locked) 782 VM_OBJECT_LOCK(fs.object); 783 atomic_add_int(&cnt.v_cow_faults, 1); 784 } else { 785 prot &= ~VM_PROT_WRITE; 786 } 787 } 788 789 /* 790 * We must verify that the maps have not changed since our last 791 * lookup. 792 */ 793 if (!fs.lookup_still_valid) { 794 vm_object_t retry_object; 795 vm_pindex_t retry_pindex; 796 vm_prot_t retry_prot; 797 798 if (!vm_map_trylock_read(fs.map)) { 799 release_page(&fs); 800 unlock_and_deallocate(&fs); 801 goto RetryFault; 802 } 803 fs.lookup_still_valid = TRUE; 804 if (fs.map->timestamp != map_generation) { 805 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 806 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 807 808 /* 809 * If we don't need the page any longer, put it on the inactive 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); 816 817 /* 818 * If retry of map lookup would have blocked then 819 * retry fault from start. 820 */ 821 if (result == KERN_FAILURE) 822 goto RetryFault; 823 return (result); 824 } 825 if ((retry_object != fs.first_object) || 826 (retry_pindex != fs.first_pindex)) { 827 release_page(&fs); 828 unlock_and_deallocate(&fs); 829 goto RetryFault; 830 } 831 832 /* 833 * Check whether the protection has changed or the object has 834 * been copied while we left the map unlocked. Changing from 835 * read to write permission is OK - we leave the page 836 * write-protected, and catch the write fault. Changing from 837 * write to read permission means that we can't mark the page 838 * write-enabled after all. 839 */ 840 prot &= retry_prot; 841 } 842 } 843 if (prot & VM_PROT_WRITE) { 844 vm_page_lock_queues(); 845 vm_page_flag_set(fs.m, PG_WRITEABLE); 846 vm_page_unlock_queues(); 847 vm_object_set_writeable_dirty(fs.object); 848 849 /* 850 * If the fault is a write, we know that this page is being 851 * written NOW so dirty it explicitly to save on 852 * pmap_is_modified() calls later. 853 * 854 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 855 * if the page is already dirty to prevent data written with 856 * the expectation of being synced from not being synced. 857 * Likewise if this entry does not request NOSYNC then make 858 * sure the page isn't marked NOSYNC. Applications sharing 859 * data should use the same flags to avoid ping ponging. 860 * 861 * Also tell the backing pager, if any, that it should remove 862 * any swap backing since the page is now dirty. 863 */ 864 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 865 if (fs.m->dirty == 0) 866 fs.m->oflags |= VPO_NOSYNC; 867 } else { 868 fs.m->oflags &= ~VPO_NOSYNC; 869 } 870 if (fault_flags & VM_FAULT_DIRTY) { 871 vm_page_dirty(fs.m); 872 vm_pager_page_unswapped(fs.m); 873 } 874 } 875 876 /* 877 * Page had better still be busy 878 */ 879 KASSERT(fs.m->oflags & VPO_BUSY, 880 ("vm_fault: page %p not busy!", fs.m)); 881 /* 882 * Sanity check: page must be completely valid or it is not fit to 883 * map into user space. vm_pager_get_pages() ensures this. 884 */ 885 if (fs.m->valid != VM_PAGE_BITS_ALL) { 886 vm_page_zero_invalid(fs.m, TRUE); 887 printf("Warning: page %p partially invalid on fault\n", fs.m); 888 } 889 VM_OBJECT_UNLOCK(fs.object); 890 891 /* 892 * Put this page into the physical map. We had to do the unlock above 893 * because pmap_enter() may sleep. We don't put the page 894 * back on the active queue until later so that the pageout daemon 895 * won't find it (yet). 896 */ 897 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired); 898 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 899 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry); 900 } 901 VM_OBJECT_LOCK(fs.object); 902 vm_page_lock_queues(); 903 vm_page_flag_set(fs.m, PG_REFERENCED); 904 905 /* 906 * If the page is not wired down, then put it where the pageout daemon 907 * can find it. 908 */ 909 if (fault_flags & VM_FAULT_WIRE_MASK) { 910 if (wired) 911 vm_page_wire(fs.m); 912 else 913 vm_page_unwire(fs.m, 1); 914 } else { 915 vm_page_activate(fs.m); 916 } 917 vm_page_unlock_queues(); 918 vm_page_wakeup(fs.m); 919 920 /* 921 * Unlock everything, and return 922 */ 923 unlock_and_deallocate(&fs); 924 PROC_LOCK(curproc); 925 if ((curproc->p_sflag & PS_INMEM) && curproc->p_stats) { 926 if (hardfault) { 927 curproc->p_stats->p_ru.ru_majflt++; 928 } else { 929 curproc->p_stats->p_ru.ru_minflt++; 930 } 931 } 932 PROC_UNLOCK(curproc); 933 934 return (KERN_SUCCESS); 935 } 936 937 /* 938 * vm_fault_prefault provides a quick way of clustering 939 * pagefaults into a processes address space. It is a "cousin" 940 * of vm_map_pmap_enter, except it runs at page fault time instead 941 * of mmap time. 942 */ 943 static void 944 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry) 945 { 946 int i; 947 vm_offset_t addr, starta; 948 vm_pindex_t pindex; 949 vm_page_t m; 950 vm_object_t object; 951 952 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 953 return; 954 955 object = entry->object.vm_object; 956 957 starta = addra - PFBAK * PAGE_SIZE; 958 if (starta < entry->start) { 959 starta = entry->start; 960 } else if (starta > addra) { 961 starta = 0; 962 } 963 964 for (i = 0; i < PAGEORDER_SIZE; i++) { 965 vm_object_t backing_object, lobject; 966 967 addr = addra + prefault_pageorder[i]; 968 if (addr > addra + (PFFOR * PAGE_SIZE)) 969 addr = 0; 970 971 if (addr < starta || addr >= entry->end) 972 continue; 973 974 if (!pmap_is_prefaultable(pmap, addr)) 975 continue; 976 977 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 978 lobject = object; 979 VM_OBJECT_LOCK(lobject); 980 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 981 lobject->type == OBJT_DEFAULT && 982 (backing_object = lobject->backing_object) != NULL) { 983 if (lobject->backing_object_offset & PAGE_MASK) 984 break; 985 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 986 VM_OBJECT_LOCK(backing_object); 987 VM_OBJECT_UNLOCK(lobject); 988 lobject = backing_object; 989 } 990 /* 991 * give-up when a page is not in memory 992 */ 993 if (m == NULL) { 994 VM_OBJECT_UNLOCK(lobject); 995 break; 996 } 997 if (((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) && 998 (m->busy == 0) && 999 (m->flags & PG_FICTITIOUS) == 0) { 1000 1001 vm_page_lock_queues(); 1002 if (VM_PAGE_INQUEUE1(m, PQ_CACHE)) 1003 vm_page_deactivate(m); 1004 pmap_enter_quick(pmap, addr, m, entry->protection); 1005 vm_page_unlock_queues(); 1006 } 1007 VM_OBJECT_UNLOCK(lobject); 1008 } 1009 } 1010 1011 /* 1012 * vm_fault_quick: 1013 * 1014 * Ensure that the requested virtual address, which may be in userland, 1015 * is valid. Fault-in the page if necessary. Return -1 on failure. 1016 */ 1017 int 1018 vm_fault_quick(caddr_t v, int prot) 1019 { 1020 int r; 1021 1022 if (prot & VM_PROT_WRITE) 1023 r = subyte(v, fubyte(v)); 1024 else 1025 r = fubyte(v); 1026 return(r); 1027 } 1028 1029 /* 1030 * vm_fault_wire: 1031 * 1032 * Wire down a range of virtual addresses in a map. 1033 */ 1034 int 1035 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1036 boolean_t user_wire, boolean_t fictitious) 1037 { 1038 vm_offset_t va; 1039 int rv; 1040 1041 /* 1042 * We simulate a fault to get the page and enter it in the physical 1043 * map. For user wiring, we only ask for read access on currently 1044 * read-only sections. 1045 */ 1046 for (va = start; va < end; va += PAGE_SIZE) { 1047 rv = vm_fault(map, va, 1048 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE, 1049 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING); 1050 if (rv) { 1051 if (va != start) 1052 vm_fault_unwire(map, start, va, fictitious); 1053 return (rv); 1054 } 1055 } 1056 return (KERN_SUCCESS); 1057 } 1058 1059 /* 1060 * vm_fault_unwire: 1061 * 1062 * Unwire a range of virtual addresses in a map. 1063 */ 1064 void 1065 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1066 boolean_t fictitious) 1067 { 1068 vm_paddr_t pa; 1069 vm_offset_t va; 1070 pmap_t pmap; 1071 1072 pmap = vm_map_pmap(map); 1073 1074 /* 1075 * Since the pages are wired down, we must be able to get their 1076 * mappings from the physical map system. 1077 */ 1078 for (va = start; va < end; va += PAGE_SIZE) { 1079 pa = pmap_extract(pmap, va); 1080 if (pa != 0) { 1081 pmap_change_wiring(pmap, va, FALSE); 1082 if (!fictitious) { 1083 vm_page_lock_queues(); 1084 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1085 vm_page_unlock_queues(); 1086 } 1087 } 1088 } 1089 } 1090 1091 /* 1092 * Routine: 1093 * vm_fault_copy_entry 1094 * Function: 1095 * Copy all of the pages from a wired-down map entry to another. 1096 * 1097 * In/out conditions: 1098 * The source and destination maps must be locked for write. 1099 * The source map entry must be wired down (or be a sharing map 1100 * entry corresponding to a main map entry that is wired down). 1101 */ 1102 void 1103 vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry) 1104 vm_map_t dst_map; 1105 vm_map_t src_map; 1106 vm_map_entry_t dst_entry; 1107 vm_map_entry_t src_entry; 1108 { 1109 vm_object_t backing_object, dst_object, object; 1110 vm_object_t src_object; 1111 vm_ooffset_t dst_offset; 1112 vm_ooffset_t src_offset; 1113 vm_pindex_t pindex; 1114 vm_prot_t prot; 1115 vm_offset_t vaddr; 1116 vm_page_t dst_m; 1117 vm_page_t src_m; 1118 1119 #ifdef lint 1120 src_map++; 1121 #endif /* lint */ 1122 1123 src_object = src_entry->object.vm_object; 1124 src_offset = src_entry->offset; 1125 1126 /* 1127 * Create the top-level object for the destination entry. (Doesn't 1128 * actually shadow anything - we copy the pages directly.) 1129 */ 1130 dst_object = vm_object_allocate(OBJT_DEFAULT, 1131 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1132 1133 VM_OBJECT_LOCK(dst_object); 1134 dst_entry->object.vm_object = dst_object; 1135 dst_entry->offset = 0; 1136 1137 prot = dst_entry->max_protection; 1138 1139 /* 1140 * Loop through all of the pages in the entry's range, copying each 1141 * one from the source object (it should be there) to the destination 1142 * object. 1143 */ 1144 for (vaddr = dst_entry->start, dst_offset = 0; 1145 vaddr < dst_entry->end; 1146 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { 1147 1148 /* 1149 * Allocate a page in the destination object 1150 */ 1151 do { 1152 dst_m = vm_page_alloc(dst_object, 1153 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); 1154 if (dst_m == NULL) { 1155 VM_OBJECT_UNLOCK(dst_object); 1156 VM_WAIT; 1157 VM_OBJECT_LOCK(dst_object); 1158 } 1159 } while (dst_m == NULL); 1160 1161 /* 1162 * Find the page in the source object, and copy it in. 1163 * (Because the source is wired down, the page will be in 1164 * memory.) 1165 */ 1166 VM_OBJECT_LOCK(src_object); 1167 object = src_object; 1168 pindex = 0; 1169 while ((src_m = vm_page_lookup(object, pindex + 1170 OFF_TO_IDX(dst_offset + src_offset))) == NULL && 1171 (src_entry->protection & VM_PROT_WRITE) == 0 && 1172 (backing_object = object->backing_object) != NULL) { 1173 /* 1174 * Allow fallback to backing objects if we are reading. 1175 */ 1176 VM_OBJECT_LOCK(backing_object); 1177 pindex += OFF_TO_IDX(object->backing_object_offset); 1178 VM_OBJECT_UNLOCK(object); 1179 object = backing_object; 1180 } 1181 if (src_m == NULL) 1182 panic("vm_fault_copy_wired: page missing"); 1183 pmap_copy_page(src_m, dst_m); 1184 VM_OBJECT_UNLOCK(object); 1185 dst_m->valid = VM_PAGE_BITS_ALL; 1186 VM_OBJECT_UNLOCK(dst_object); 1187 1188 /* 1189 * Enter it in the pmap... 1190 */ 1191 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE); 1192 VM_OBJECT_LOCK(dst_object); 1193 vm_page_lock_queues(); 1194 if ((prot & VM_PROT_WRITE) != 0) 1195 vm_page_flag_set(dst_m, PG_WRITEABLE); 1196 1197 /* 1198 * Mark it no longer busy, and put it on the active list. 1199 */ 1200 vm_page_activate(dst_m); 1201 vm_page_unlock_queues(); 1202 vm_page_wakeup(dst_m); 1203 } 1204 VM_OBJECT_UNLOCK(dst_object); 1205 } 1206 1207 1208 /* 1209 * This routine checks around the requested page for other pages that 1210 * might be able to be faulted in. This routine brackets the viable 1211 * pages for the pages to be paged in. 1212 * 1213 * Inputs: 1214 * m, rbehind, rahead 1215 * 1216 * Outputs: 1217 * marray (array of vm_page_t), reqpage (index of requested page) 1218 * 1219 * Return value: 1220 * number of pages in marray 1221 * 1222 * This routine can't block. 1223 */ 1224 static int 1225 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1226 vm_page_t m; 1227 int rbehind; 1228 int rahead; 1229 vm_page_t *marray; 1230 int *reqpage; 1231 { 1232 int i,j; 1233 vm_object_t object; 1234 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1235 vm_page_t rtm; 1236 int cbehind, cahead; 1237 1238 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED); 1239 1240 object = m->object; 1241 pindex = m->pindex; 1242 1243 /* 1244 * we don't fault-ahead for device pager 1245 */ 1246 if (object->type == OBJT_DEVICE) { 1247 *reqpage = 0; 1248 marray[0] = m; 1249 return 1; 1250 } 1251 1252 /* 1253 * if the requested page is not available, then give up now 1254 */ 1255 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1256 return 0; 1257 } 1258 1259 if ((cbehind == 0) && (cahead == 0)) { 1260 *reqpage = 0; 1261 marray[0] = m; 1262 return 1; 1263 } 1264 1265 if (rahead > cahead) { 1266 rahead = cahead; 1267 } 1268 1269 if (rbehind > cbehind) { 1270 rbehind = cbehind; 1271 } 1272 1273 /* 1274 * try to do any readahead that we might have free pages for. 1275 */ 1276 if ((rahead + rbehind) > 1277 ((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) { 1278 pagedaemon_wakeup(); 1279 marray[0] = m; 1280 *reqpage = 0; 1281 return 1; 1282 } 1283 1284 /* 1285 * scan backward for the read behind pages -- in memory 1286 */ 1287 if (pindex > 0) { 1288 if (rbehind > pindex) { 1289 rbehind = pindex; 1290 startpindex = 0; 1291 } else { 1292 startpindex = pindex - rbehind; 1293 } 1294 1295 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1296 rtm->pindex >= startpindex) 1297 startpindex = rtm->pindex + 1; 1298 1299 for (i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) { 1300 1301 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1302 if (rtm == NULL) { 1303 vm_page_lock_queues(); 1304 for (j = 0; j < i; j++) { 1305 vm_page_free(marray[j]); 1306 } 1307 vm_page_unlock_queues(); 1308 marray[0] = m; 1309 *reqpage = 0; 1310 return 1; 1311 } 1312 1313 marray[i] = rtm; 1314 } 1315 } else { 1316 startpindex = 0; 1317 i = 0; 1318 } 1319 1320 marray[i] = m; 1321 /* page offset of the required page */ 1322 *reqpage = i; 1323 1324 tpindex = pindex + 1; 1325 i++; 1326 1327 /* 1328 * scan forward for the read ahead pages 1329 */ 1330 endpindex = tpindex + rahead; 1331 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1332 endpindex = rtm->pindex; 1333 if (endpindex > object->size) 1334 endpindex = object->size; 1335 1336 for (; tpindex < endpindex; i++, tpindex++) { 1337 1338 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1339 if (rtm == NULL) { 1340 break; 1341 } 1342 1343 marray[i] = rtm; 1344 } 1345 1346 /* return number of bytes of pages */ 1347 return i; 1348 } 1349