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_object_set_writeable_dirty(fs.object); 845 846 /* 847 * If the fault is a write, we know that this page is being 848 * written NOW so dirty it explicitly to save on 849 * pmap_is_modified() calls later. 850 * 851 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 852 * if the page is already dirty to prevent data written with 853 * the expectation of being synced from not being synced. 854 * Likewise if this entry does not request NOSYNC then make 855 * sure the page isn't marked NOSYNC. Applications sharing 856 * data should use the same flags to avoid ping ponging. 857 * 858 * Also tell the backing pager, if any, that it should remove 859 * any swap backing since the page is now dirty. 860 */ 861 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 862 if (fs.m->dirty == 0) 863 fs.m->oflags |= VPO_NOSYNC; 864 } else { 865 fs.m->oflags &= ~VPO_NOSYNC; 866 } 867 if (fault_flags & VM_FAULT_DIRTY) { 868 vm_page_dirty(fs.m); 869 vm_pager_page_unswapped(fs.m); 870 } 871 } 872 873 /* 874 * Page had better still be busy 875 */ 876 KASSERT(fs.m->oflags & VPO_BUSY, 877 ("vm_fault: page %p not busy!", fs.m)); 878 /* 879 * Sanity check: page must be completely valid or it is not fit to 880 * map into user space. vm_pager_get_pages() ensures this. 881 */ 882 if (fs.m->valid != VM_PAGE_BITS_ALL) { 883 vm_page_zero_invalid(fs.m, TRUE); 884 printf("Warning: page %p partially invalid on fault\n", fs.m); 885 } 886 VM_OBJECT_UNLOCK(fs.object); 887 888 /* 889 * Put this page into the physical map. We had to do the unlock above 890 * because pmap_enter() may sleep. We don't put the page 891 * back on the active queue until later so that the pageout daemon 892 * won't find it (yet). 893 */ 894 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired); 895 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 896 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry); 897 } 898 VM_OBJECT_LOCK(fs.object); 899 vm_page_lock_queues(); 900 vm_page_flag_set(fs.m, PG_REFERENCED); 901 902 /* 903 * If the page is not wired down, then put it where the pageout daemon 904 * can find it. 905 */ 906 if (fault_flags & VM_FAULT_WIRE_MASK) { 907 if (wired) 908 vm_page_wire(fs.m); 909 else 910 vm_page_unwire(fs.m, 1); 911 } else { 912 vm_page_activate(fs.m); 913 } 914 vm_page_unlock_queues(); 915 vm_page_wakeup(fs.m); 916 917 /* 918 * Unlock everything, and return 919 */ 920 unlock_and_deallocate(&fs); 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 return (KERN_SUCCESS); 932 } 933 934 /* 935 * vm_fault_prefault provides a quick way of clustering 936 * pagefaults into a processes address space. It is a "cousin" 937 * of vm_map_pmap_enter, except it runs at page fault time instead 938 * of mmap time. 939 */ 940 static void 941 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry) 942 { 943 int i; 944 vm_offset_t addr, starta; 945 vm_pindex_t pindex; 946 vm_page_t m; 947 vm_object_t object; 948 949 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 950 return; 951 952 object = entry->object.vm_object; 953 954 starta = addra - PFBAK * PAGE_SIZE; 955 if (starta < entry->start) { 956 starta = entry->start; 957 } else if (starta > addra) { 958 starta = 0; 959 } 960 961 for (i = 0; i < PAGEORDER_SIZE; i++) { 962 vm_object_t backing_object, lobject; 963 964 addr = addra + prefault_pageorder[i]; 965 if (addr > addra + (PFFOR * PAGE_SIZE)) 966 addr = 0; 967 968 if (addr < starta || addr >= entry->end) 969 continue; 970 971 if (!pmap_is_prefaultable(pmap, addr)) 972 continue; 973 974 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 975 lobject = object; 976 VM_OBJECT_LOCK(lobject); 977 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 978 lobject->type == OBJT_DEFAULT && 979 (backing_object = lobject->backing_object) != NULL) { 980 if (lobject->backing_object_offset & PAGE_MASK) 981 break; 982 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 983 VM_OBJECT_LOCK(backing_object); 984 VM_OBJECT_UNLOCK(lobject); 985 lobject = backing_object; 986 } 987 /* 988 * give-up when a page is not in memory 989 */ 990 if (m == NULL) { 991 VM_OBJECT_UNLOCK(lobject); 992 break; 993 } 994 if (((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) && 995 (m->busy == 0) && 996 (m->flags & PG_FICTITIOUS) == 0) { 997 998 vm_page_lock_queues(); 999 if (VM_PAGE_INQUEUE1(m, PQ_CACHE)) 1000 vm_page_deactivate(m); 1001 pmap_enter_quick(pmap, addr, m, entry->protection); 1002 vm_page_unlock_queues(); 1003 } 1004 VM_OBJECT_UNLOCK(lobject); 1005 } 1006 } 1007 1008 /* 1009 * vm_fault_quick: 1010 * 1011 * Ensure that the requested virtual address, which may be in userland, 1012 * is valid. Fault-in the page if necessary. Return -1 on failure. 1013 */ 1014 int 1015 vm_fault_quick(caddr_t v, int prot) 1016 { 1017 int r; 1018 1019 if (prot & VM_PROT_WRITE) 1020 r = subyte(v, fubyte(v)); 1021 else 1022 r = fubyte(v); 1023 return(r); 1024 } 1025 1026 /* 1027 * vm_fault_wire: 1028 * 1029 * Wire down a range of virtual addresses in a map. 1030 */ 1031 int 1032 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1033 boolean_t user_wire, boolean_t fictitious) 1034 { 1035 vm_offset_t va; 1036 int rv; 1037 1038 /* 1039 * We simulate a fault to get the page and enter it in the physical 1040 * map. For user wiring, we only ask for read access on currently 1041 * read-only sections. 1042 */ 1043 for (va = start; va < end; va += PAGE_SIZE) { 1044 rv = vm_fault(map, va, 1045 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE, 1046 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING); 1047 if (rv) { 1048 if (va != start) 1049 vm_fault_unwire(map, start, va, fictitious); 1050 return (rv); 1051 } 1052 } 1053 return (KERN_SUCCESS); 1054 } 1055 1056 /* 1057 * vm_fault_unwire: 1058 * 1059 * Unwire a range of virtual addresses in a map. 1060 */ 1061 void 1062 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1063 boolean_t fictitious) 1064 { 1065 vm_paddr_t pa; 1066 vm_offset_t va; 1067 pmap_t pmap; 1068 1069 pmap = vm_map_pmap(map); 1070 1071 /* 1072 * Since the pages are wired down, we must be able to get their 1073 * mappings from the physical map system. 1074 */ 1075 for (va = start; va < end; va += PAGE_SIZE) { 1076 pa = pmap_extract(pmap, va); 1077 if (pa != 0) { 1078 pmap_change_wiring(pmap, va, FALSE); 1079 if (!fictitious) { 1080 vm_page_lock_queues(); 1081 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1082 vm_page_unlock_queues(); 1083 } 1084 } 1085 } 1086 } 1087 1088 /* 1089 * Routine: 1090 * vm_fault_copy_entry 1091 * Function: 1092 * Copy all of the pages from a wired-down map entry to another. 1093 * 1094 * In/out conditions: 1095 * The source and destination maps must be locked for write. 1096 * The source map entry must be wired down (or be a sharing map 1097 * entry corresponding to a main map entry that is wired down). 1098 */ 1099 void 1100 vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry) 1101 vm_map_t dst_map; 1102 vm_map_t src_map; 1103 vm_map_entry_t dst_entry; 1104 vm_map_entry_t src_entry; 1105 { 1106 vm_object_t backing_object, dst_object, object; 1107 vm_object_t src_object; 1108 vm_ooffset_t dst_offset; 1109 vm_ooffset_t src_offset; 1110 vm_pindex_t pindex; 1111 vm_prot_t prot; 1112 vm_offset_t vaddr; 1113 vm_page_t dst_m; 1114 vm_page_t src_m; 1115 1116 #ifdef lint 1117 src_map++; 1118 #endif /* lint */ 1119 1120 src_object = src_entry->object.vm_object; 1121 src_offset = src_entry->offset; 1122 1123 /* 1124 * Create the top-level object for the destination entry. (Doesn't 1125 * actually shadow anything - we copy the pages directly.) 1126 */ 1127 dst_object = vm_object_allocate(OBJT_DEFAULT, 1128 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1129 1130 VM_OBJECT_LOCK(dst_object); 1131 dst_entry->object.vm_object = dst_object; 1132 dst_entry->offset = 0; 1133 1134 prot = dst_entry->max_protection; 1135 1136 /* 1137 * Loop through all of the pages in the entry's range, copying each 1138 * one from the source object (it should be there) to the destination 1139 * object. 1140 */ 1141 for (vaddr = dst_entry->start, dst_offset = 0; 1142 vaddr < dst_entry->end; 1143 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { 1144 1145 /* 1146 * Allocate a page in the destination object 1147 */ 1148 do { 1149 dst_m = vm_page_alloc(dst_object, 1150 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); 1151 if (dst_m == NULL) { 1152 VM_OBJECT_UNLOCK(dst_object); 1153 VM_WAIT; 1154 VM_OBJECT_LOCK(dst_object); 1155 } 1156 } while (dst_m == NULL); 1157 1158 /* 1159 * Find the page in the source object, and copy it in. 1160 * (Because the source is wired down, the page will be in 1161 * memory.) 1162 */ 1163 VM_OBJECT_LOCK(src_object); 1164 object = src_object; 1165 pindex = 0; 1166 while ((src_m = vm_page_lookup(object, pindex + 1167 OFF_TO_IDX(dst_offset + src_offset))) == NULL && 1168 (src_entry->protection & VM_PROT_WRITE) == 0 && 1169 (backing_object = object->backing_object) != NULL) { 1170 /* 1171 * Allow fallback to backing objects if we are reading. 1172 */ 1173 VM_OBJECT_LOCK(backing_object); 1174 pindex += OFF_TO_IDX(object->backing_object_offset); 1175 VM_OBJECT_UNLOCK(object); 1176 object = backing_object; 1177 } 1178 if (src_m == NULL) 1179 panic("vm_fault_copy_wired: page missing"); 1180 pmap_copy_page(src_m, dst_m); 1181 VM_OBJECT_UNLOCK(object); 1182 dst_m->valid = VM_PAGE_BITS_ALL; 1183 VM_OBJECT_UNLOCK(dst_object); 1184 1185 /* 1186 * Enter it in the pmap... 1187 */ 1188 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE); 1189 1190 /* 1191 * Mark it no longer busy, and put it on the active list. 1192 */ 1193 VM_OBJECT_LOCK(dst_object); 1194 vm_page_lock_queues(); 1195 vm_page_activate(dst_m); 1196 vm_page_unlock_queues(); 1197 vm_page_wakeup(dst_m); 1198 } 1199 VM_OBJECT_UNLOCK(dst_object); 1200 } 1201 1202 1203 /* 1204 * This routine checks around the requested page for other pages that 1205 * might be able to be faulted in. This routine brackets the viable 1206 * pages for the pages to be paged in. 1207 * 1208 * Inputs: 1209 * m, rbehind, rahead 1210 * 1211 * Outputs: 1212 * marray (array of vm_page_t), reqpage (index of requested page) 1213 * 1214 * Return value: 1215 * number of pages in marray 1216 * 1217 * This routine can't block. 1218 */ 1219 static int 1220 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1221 vm_page_t m; 1222 int rbehind; 1223 int rahead; 1224 vm_page_t *marray; 1225 int *reqpage; 1226 { 1227 int i,j; 1228 vm_object_t object; 1229 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1230 vm_page_t rtm; 1231 int cbehind, cahead; 1232 1233 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED); 1234 1235 object = m->object; 1236 pindex = m->pindex; 1237 1238 /* 1239 * we don't fault-ahead for device pager 1240 */ 1241 if (object->type == OBJT_DEVICE) { 1242 *reqpage = 0; 1243 marray[0] = m; 1244 return 1; 1245 } 1246 1247 /* 1248 * if the requested page is not available, then give up now 1249 */ 1250 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1251 return 0; 1252 } 1253 1254 if ((cbehind == 0) && (cahead == 0)) { 1255 *reqpage = 0; 1256 marray[0] = m; 1257 return 1; 1258 } 1259 1260 if (rahead > cahead) { 1261 rahead = cahead; 1262 } 1263 1264 if (rbehind > cbehind) { 1265 rbehind = cbehind; 1266 } 1267 1268 /* 1269 * try to do any readahead that we might have free pages for. 1270 */ 1271 if ((rahead + rbehind) > 1272 ((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) { 1273 pagedaemon_wakeup(); 1274 marray[0] = m; 1275 *reqpage = 0; 1276 return 1; 1277 } 1278 1279 /* 1280 * scan backward for the read behind pages -- in memory 1281 */ 1282 if (pindex > 0) { 1283 if (rbehind > pindex) { 1284 rbehind = pindex; 1285 startpindex = 0; 1286 } else { 1287 startpindex = pindex - rbehind; 1288 } 1289 1290 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1291 rtm->pindex >= startpindex) 1292 startpindex = rtm->pindex + 1; 1293 1294 for (i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) { 1295 1296 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1297 if (rtm == NULL) { 1298 vm_page_lock_queues(); 1299 for (j = 0; j < i; j++) { 1300 vm_page_free(marray[j]); 1301 } 1302 vm_page_unlock_queues(); 1303 marray[0] = m; 1304 *reqpage = 0; 1305 return 1; 1306 } 1307 1308 marray[i] = rtm; 1309 } 1310 } else { 1311 startpindex = 0; 1312 i = 0; 1313 } 1314 1315 marray[i] = m; 1316 /* page offset of the required page */ 1317 *reqpage = i; 1318 1319 tpindex = pindex + 1; 1320 i++; 1321 1322 /* 1323 * scan forward for the read ahead pages 1324 */ 1325 endpindex = tpindex + rahead; 1326 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1327 endpindex = rtm->pindex; 1328 if (endpindex > object->size) 1329 endpindex = object->size; 1330 1331 for (; tpindex < endpindex; i++, tpindex++) { 1332 1333 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1334 if (rtm == NULL) { 1335 break; 1336 } 1337 1338 marray[i] = rtm; 1339 } 1340 1341 /* return number of bytes of pages */ 1342 return i; 1343 } 1344