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sys/vm/vm_fault.c
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1 /*- 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 1994 John S. Dyson 5 * All rights reserved. 6 * Copyright (c) 1994 David Greenman 7 * All rights reserved. 8 * 9 * 10 * This code is derived from software contributed to Berkeley by 11 * The Mach Operating System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 42 * 43 * 44 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 45 * All rights reserved. 46 * 47 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 48 * 49 * Permission to use, copy, modify and distribute this software and 50 * its documentation is hereby granted, provided that both the copyright 51 * notice and this permission notice appear in all copies of the 52 * software, derivative works or modified versions, and any portions 53 * thereof, and that both notices appear in supporting documentation. 54 * 55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 58 * 59 * Carnegie Mellon requests users of this software to return to 60 * 61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 62 * School of Computer Science 63 * Carnegie Mellon University 64 * Pittsburgh PA 15213-3890 65 * 66 * any improvements or extensions that they make and grant Carnegie the 67 * rights to redistribute these changes. 68 */ 69 70 /* 71 * Page fault handling module. 72 */ 73 74 #include <sys/cdefs.h> 75 __FBSDID("$FreeBSD: releng/7.4/sys/vm/vm_fault.c 215433 2010-11-17 18:21:29Z alc $"); 76 77 #include "opt_vm.h" 78 79 #include <sys/param.h> 80 #include <sys/systm.h> 81 #include <sys/kernel.h> 82 #include <sys/lock.h> 83 #include <sys/mutex.h> 84 #include <sys/proc.h> 85 #include <sys/resourcevar.h> 86 #include <sys/sysctl.h> 87 #include <sys/vmmeter.h> 88 #include <sys/vnode.h> 89 90 #include <vm/vm.h> 91 #include <vm/vm_param.h> 92 #include <vm/pmap.h> 93 #include <vm/vm_map.h> 94 #include <vm/vm_object.h> 95 #include <vm/vm_page.h> 96 #include <vm/vm_pageout.h> 97 #include <vm/vm_kern.h> 98 #include <vm/vm_pager.h> 99 #include <vm/vnode_pager.h> 100 #include <vm/vm_extern.h> 101 102 #include <sys/mount.h> /* XXX Temporary for VFS_LOCK_GIANT() */ 103 104 #define PFBAK 4 105 #define PFFOR 4 106 #define PAGEORDER_SIZE (PFBAK+PFFOR) 107 108 static int prefault_pageorder[] = { 109 -1 * PAGE_SIZE, 1 * PAGE_SIZE, 110 -2 * PAGE_SIZE, 2 * PAGE_SIZE, 111 -3 * PAGE_SIZE, 3 * PAGE_SIZE, 112 -4 * PAGE_SIZE, 4 * PAGE_SIZE 113 }; 114 115 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 116 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t); 117 118 #define VM_FAULT_READ_AHEAD 8 119 #define VM_FAULT_READ_BEHIND 7 120 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1) 121 122 struct faultstate { 123 vm_page_t m; 124 vm_object_t object; 125 vm_pindex_t pindex; 126 vm_page_t first_m; 127 vm_object_t first_object; 128 vm_pindex_t first_pindex; 129 vm_map_t map; 130 vm_map_entry_t entry; 131 int lookup_still_valid; 132 struct vnode *vp; 133 }; 134 135 static inline void 136 release_page(struct faultstate *fs) 137 { 138 vm_page_wakeup(fs->m); 139 vm_page_lock_queues(); 140 vm_page_deactivate(fs->m); 141 vm_page_unlock_queues(); 142 fs->m = NULL; 143 } 144 145 static inline void 146 unlock_map(struct faultstate *fs) 147 { 148 if (fs->lookup_still_valid) { 149 vm_map_lookup_done(fs->map, fs->entry); 150 fs->lookup_still_valid = FALSE; 151 } 152 } 153 154 static void 155 unlock_and_deallocate(struct faultstate *fs) 156 { 157 158 vm_object_pip_wakeup(fs->object); 159 VM_OBJECT_UNLOCK(fs->object); 160 if (fs->object != fs->first_object) { 161 VM_OBJECT_LOCK(fs->first_object); 162 vm_page_lock_queues(); 163 vm_page_free(fs->first_m); 164 vm_page_unlock_queues(); 165 vm_object_pip_wakeup(fs->first_object); 166 VM_OBJECT_UNLOCK(fs->first_object); 167 fs->first_m = NULL; 168 } 169 vm_object_deallocate(fs->first_object); 170 unlock_map(fs); 171 if (fs->vp != NULL) { 172 int vfslocked; 173 174 vfslocked = VFS_LOCK_GIANT(fs->vp->v_mount); 175 vput(fs->vp); 176 fs->vp = NULL; 177 VFS_UNLOCK_GIANT(vfslocked); 178 } 179 } 180 181 /* 182 * TRYPAGER - used by vm_fault to calculate whether the pager for the 183 * current object *might* contain the page. 184 * 185 * default objects are zero-fill, there is no real pager. 186 */ 187 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 188 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) 189 190 /* 191 * vm_fault: 192 * 193 * Handle a page fault occurring at the given address, 194 * requiring the given permissions, in the map specified. 195 * If successful, the page is inserted into the 196 * associated physical map. 197 * 198 * NOTE: the given address should be truncated to the 199 * proper page address. 200 * 201 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 202 * a standard error specifying why the fault is fatal is returned. 203 * 204 * 205 * The map in question must be referenced, and remains so. 206 * Caller may hold no locks. 207 */ 208 int 209 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 210 int fault_flags) 211 { 212 vm_prot_t prot; 213 int is_first_object_locked, result; 214 boolean_t growstack, wired; 215 int map_generation; 216 vm_object_t next_object; 217 vm_page_t marray[VM_FAULT_READ], mt, mt_prev; 218 int hardfault; 219 int faultcount; 220 struct faultstate fs; 221 222 hardfault = 0; 223 growstack = TRUE; 224 PCPU_INC(cnt.v_vm_faults); 225 226 RetryFault:; 227 228 /* 229 * Find the backing store object and offset into it to begin the 230 * search. 231 */ 232 fs.map = map; 233 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 234 &fs.first_object, &fs.first_pindex, &prot, &wired); 235 if (result != KERN_SUCCESS) { 236 if (result != KERN_PROTECTION_FAILURE || 237 (fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) { 238 if (growstack && result == KERN_INVALID_ADDRESS && 239 map != kernel_map && curproc != NULL) { 240 result = vm_map_growstack(curproc, vaddr); 241 if (result != KERN_SUCCESS) 242 return (KERN_FAILURE); 243 growstack = FALSE; 244 goto RetryFault; 245 } 246 return (result); 247 } 248 249 /* 250 * If we are user-wiring a r/w segment, and it is COW, then 251 * we need to do the COW operation. Note that we don't COW 252 * currently RO sections now, because it is NOT desirable 253 * to COW .text. We simply keep .text from ever being COW'ed 254 * and take the heat that one cannot debug wired .text sections. 255 */ 256 result = vm_map_lookup(&fs.map, vaddr, 257 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE, 258 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired); 259 if (result != KERN_SUCCESS) 260 return (result); 261 262 /* 263 * If we don't COW now, on a user wire, the user will never 264 * be able to write to the mapping. If we don't make this 265 * restriction, the bookkeeping would be nearly impossible. 266 * 267 * XXX The following assignment modifies the map without 268 * holding a write lock on it. 269 */ 270 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 271 fs.entry->max_protection &= ~VM_PROT_WRITE; 272 } 273 274 map_generation = fs.map->timestamp; 275 276 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 277 panic("vm_fault: fault on nofault entry, addr: %lx", 278 (u_long)vaddr); 279 } 280 281 /* 282 * Make a reference to this object to prevent its disposal while we 283 * are messing with it. Once we have the reference, the map is free 284 * to be diddled. Since objects reference their shadows (and copies), 285 * they will stay around as well. 286 * 287 * Bump the paging-in-progress count to prevent size changes (e.g. 288 * truncation operations) during I/O. This must be done after 289 * obtaining the vnode lock in order to avoid possible deadlocks. 290 * 291 * XXX vnode_pager_lock() can block without releasing the map lock. 292 */ 293 if (fs.first_object->flags & OBJ_NEEDGIANT) 294 mtx_lock(&Giant); 295 VM_OBJECT_LOCK(fs.first_object); 296 vm_object_reference_locked(fs.first_object); 297 fs.vp = vnode_pager_lock(fs.first_object); 298 KASSERT(fs.vp == NULL || !fs.map->system_map, 299 ("vm_fault: vnode-backed object mapped by system map")); 300 KASSERT((fs.first_object->flags & OBJ_NEEDGIANT) == 0 || 301 !fs.map->system_map, 302 ("vm_fault: Object requiring giant mapped by system map")); 303 if (fs.first_object->flags & OBJ_NEEDGIANT) 304 mtx_unlock(&Giant); 305 vm_object_pip_add(fs.first_object, 1); 306 307 fs.lookup_still_valid = TRUE; 308 309 if (wired) 310 fault_type = prot; 311 312 fs.first_m = NULL; 313 314 /* 315 * Search for the page at object/offset. 316 */ 317 fs.object = fs.first_object; 318 fs.pindex = fs.first_pindex; 319 while (TRUE) { 320 /* 321 * If the object is dead, we stop here 322 */ 323 if (fs.object->flags & OBJ_DEAD) { 324 unlock_and_deallocate(&fs); 325 return (KERN_PROTECTION_FAILURE); 326 } 327 328 /* 329 * See if page is resident 330 */ 331 fs.m = vm_page_lookup(fs.object, fs.pindex); 332 if (fs.m != NULL) { 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 PCPU_INC(cnt.v_intrans); 398 vm_object_deallocate(fs.first_object); 399 goto RetryFault; 400 } 401 vm_pageq_remove(fs.m); 402 vm_page_unlock_queues(); 403 404 /* 405 * Mark page busy for other processes, and the 406 * pagedaemon. If it still isn't completely valid 407 * (readable), jump to readrest, else break-out ( we 408 * found the page ). 409 */ 410 vm_page_busy(fs.m); 411 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) && 412 fs.m->object != kernel_object && fs.m->object != kmem_object) { 413 goto readrest; 414 } 415 416 break; 417 } 418 419 /* 420 * Page is not resident, If this is the search termination 421 * or the pager might contain the page, allocate a new page. 422 */ 423 if (TRYPAGER || fs.object == fs.first_object) { 424 if (fs.pindex >= fs.object->size) { 425 unlock_and_deallocate(&fs); 426 return (KERN_PROTECTION_FAILURE); 427 } 428 429 /* 430 * Allocate a new page for this object/offset pair. 431 */ 432 fs.m = NULL; 433 if (!vm_page_count_severe()) { 434 #if VM_NRESERVLEVEL > 0 435 if ((fs.object->flags & OBJ_COLORED) == 0) { 436 fs.object->flags |= OBJ_COLORED; 437 fs.object->pg_color = atop(vaddr) - 438 fs.pindex; 439 } 440 #endif 441 fs.m = vm_page_alloc(fs.object, fs.pindex, 442 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO); 443 } 444 if (fs.m == NULL) { 445 unlock_and_deallocate(&fs); 446 VM_WAITPFAULT; 447 goto RetryFault; 448 } else if ((fs.m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) 449 break; 450 } 451 452 readrest: 453 /* 454 * We have found a valid page or we have allocated a new page. 455 * The page thus may not be valid or may not be entirely 456 * valid. 457 * 458 * Attempt to fault-in the page if there is a chance that the 459 * pager has it, and potentially fault in additional pages 460 * at the same time. 461 */ 462 if (TRYPAGER) { 463 int rv; 464 int reqpage = 0; 465 int ahead, behind; 466 u_char behavior = vm_map_entry_behavior(fs.entry); 467 468 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 469 ahead = 0; 470 behind = 0; 471 } else { 472 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT; 473 if (behind > VM_FAULT_READ_BEHIND) 474 behind = VM_FAULT_READ_BEHIND; 475 476 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1; 477 if (ahead > VM_FAULT_READ_AHEAD) 478 ahead = VM_FAULT_READ_AHEAD; 479 } 480 is_first_object_locked = FALSE; 481 if ((behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 482 (behavior != MAP_ENTRY_BEHAV_RANDOM && 483 fs.pindex >= fs.entry->lastr && 484 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) && 485 (fs.first_object == fs.object || 486 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object))) && 487 fs.first_object->type != OBJT_DEVICE && 488 fs.first_object->type != OBJT_PHYS && 489 fs.first_object->type != OBJT_SG) { 490 vm_pindex_t firstpindex; 491 492 if (fs.first_pindex < 2 * VM_FAULT_READ) 493 firstpindex = 0; 494 else 495 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ; 496 mt = fs.first_object != fs.object ? 497 fs.first_m : fs.m; 498 KASSERT(mt != NULL, ("vm_fault: missing mt")); 499 KASSERT((mt->oflags & VPO_BUSY) != 0, 500 ("vm_fault: mt %p not busy", mt)); 501 mt_prev = vm_page_prev(mt); 502 503 vm_page_lock_queues(); 504 /* 505 * note: partially valid pages cannot be 506 * included in the lookahead - NFS piecemeal 507 * writes will barf on it badly. 508 */ 509 while ((mt = mt_prev) != NULL && 510 mt->pindex >= firstpindex && 511 mt->valid == VM_PAGE_BITS_ALL) { 512 mt_prev = vm_page_prev(mt); 513 if (mt->busy || 514 (mt->oflags & VPO_BUSY) || 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 PCPU_INC(cnt.v_ozfod); 672 } 673 PCPU_INC(cnt.v_zfod); 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_unlock_queues(); 752 vm_page_busy(fs.m); 753 fs.first_m = fs.m; 754 fs.m = NULL; 755 PCPU_INC(cnt.v_cow_optim); 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 PCPU_INC(cnt.v_cow_faults); 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, fault_type, 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 if (hardfault) 922 curthread->td_ru.ru_majflt++; 923 else 924 curthread->td_ru.ru_minflt++; 925 926 return (KERN_SUCCESS); 927 } 928 929 /* 930 * vm_fault_prefault provides a quick way of clustering 931 * pagefaults into a processes address space. It is a "cousin" 932 * of vm_map_pmap_enter, except it runs at page fault time instead 933 * of mmap time. 934 */ 935 static void 936 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry) 937 { 938 int i; 939 vm_offset_t addr, starta; 940 vm_pindex_t pindex; 941 vm_page_t m; 942 vm_object_t object; 943 944 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 945 return; 946 947 object = entry->object.vm_object; 948 949 starta = addra - PFBAK * PAGE_SIZE; 950 if (starta < entry->start) { 951 starta = entry->start; 952 } else if (starta > addra) { 953 starta = 0; 954 } 955 956 for (i = 0; i < PAGEORDER_SIZE; i++) { 957 vm_object_t backing_object, lobject; 958 959 addr = addra + prefault_pageorder[i]; 960 if (addr > addra + (PFFOR * PAGE_SIZE)) 961 addr = 0; 962 963 if (addr < starta || addr >= entry->end) 964 continue; 965 966 if (!pmap_is_prefaultable(pmap, addr)) 967 continue; 968 969 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 970 lobject = object; 971 VM_OBJECT_LOCK(lobject); 972 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 973 lobject->type == OBJT_DEFAULT && 974 (backing_object = lobject->backing_object) != NULL) { 975 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 976 0, ("vm_fault_prefault: unaligned object offset")); 977 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 978 VM_OBJECT_LOCK(backing_object); 979 VM_OBJECT_UNLOCK(lobject); 980 lobject = backing_object; 981 } 982 /* 983 * give-up when a page is not in memory 984 */ 985 if (m == NULL) { 986 VM_OBJECT_UNLOCK(lobject); 987 break; 988 } 989 if (((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) && 990 (m->busy == 0) && 991 (m->flags & PG_FICTITIOUS) == 0) { 992 993 vm_page_lock_queues(); 994 pmap_enter_quick(pmap, addr, m, entry->protection); 995 vm_page_unlock_queues(); 996 } 997 VM_OBJECT_UNLOCK(lobject); 998 } 999 } 1000 1001 /* 1002 * vm_fault_quick: 1003 * 1004 * Ensure that the requested virtual address, which may be in userland, 1005 * is valid. Fault-in the page if necessary. Return -1 on failure. 1006 */ 1007 int 1008 vm_fault_quick(caddr_t v, int prot) 1009 { 1010 int r; 1011 1012 if (prot & VM_PROT_WRITE) 1013 r = subyte(v, fubyte(v)); 1014 else 1015 r = fubyte(v); 1016 return(r); 1017 } 1018 1019 /* 1020 * vm_fault_wire: 1021 * 1022 * Wire down a range of virtual addresses in a map. 1023 */ 1024 int 1025 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1026 boolean_t user_wire, boolean_t fictitious) 1027 { 1028 vm_offset_t va; 1029 int rv; 1030 1031 /* 1032 * We simulate a fault to get the page and enter it in the physical 1033 * map. For user wiring, we only ask for read access on currently 1034 * read-only sections. 1035 */ 1036 for (va = start; va < end; va += PAGE_SIZE) { 1037 rv = vm_fault(map, va, 1038 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE, 1039 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING); 1040 if (rv) { 1041 if (va != start) 1042 vm_fault_unwire(map, start, va, fictitious); 1043 return (rv); 1044 } 1045 } 1046 return (KERN_SUCCESS); 1047 } 1048 1049 /* 1050 * vm_fault_unwire: 1051 * 1052 * Unwire a range of virtual addresses in a map. 1053 */ 1054 void 1055 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1056 boolean_t fictitious) 1057 { 1058 vm_paddr_t pa; 1059 vm_offset_t va; 1060 pmap_t pmap; 1061 1062 pmap = vm_map_pmap(map); 1063 1064 /* 1065 * Since the pages are wired down, we must be able to get their 1066 * mappings from the physical map system. 1067 */ 1068 for (va = start; va < end; va += PAGE_SIZE) { 1069 pa = pmap_extract(pmap, va); 1070 if (pa != 0) { 1071 pmap_change_wiring(pmap, va, FALSE); 1072 if (!fictitious) { 1073 vm_page_lock_queues(); 1074 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1075 vm_page_unlock_queues(); 1076 } 1077 } 1078 } 1079 } 1080 1081 /* 1082 * Routine: 1083 * vm_fault_copy_entry 1084 * Function: 1085 * Copy all of the pages from a wired-down map entry to another. 1086 * 1087 * In/out conditions: 1088 * The source and destination maps must be locked for write. 1089 * The source map entry must be wired down (or be a sharing map 1090 * entry corresponding to a main map entry that is wired down). 1091 */ 1092 void 1093 vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry) 1094 vm_map_t dst_map; 1095 vm_map_t src_map; 1096 vm_map_entry_t dst_entry; 1097 vm_map_entry_t src_entry; 1098 { 1099 vm_object_t backing_object, dst_object, object; 1100 vm_object_t src_object; 1101 vm_ooffset_t dst_offset; 1102 vm_ooffset_t src_offset; 1103 vm_pindex_t pindex; 1104 vm_prot_t prot; 1105 vm_offset_t vaddr; 1106 vm_page_t dst_m; 1107 vm_page_t src_m; 1108 1109 #ifdef lint 1110 src_map++; 1111 #endif /* lint */ 1112 1113 src_object = src_entry->object.vm_object; 1114 src_offset = src_entry->offset; 1115 1116 /* 1117 * Create the top-level object for the destination entry. (Doesn't 1118 * actually shadow anything - we copy the pages directly.) 1119 */ 1120 dst_object = vm_object_allocate(OBJT_DEFAULT, 1121 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1122 #if VM_NRESERVLEVEL > 0 1123 dst_object->flags |= OBJ_COLORED; 1124 dst_object->pg_color = atop(dst_entry->start); 1125 #endif 1126 1127 VM_OBJECT_LOCK(dst_object); 1128 dst_entry->object.vm_object = dst_object; 1129 dst_entry->offset = 0; 1130 1131 prot = dst_entry->max_protection; 1132 1133 /* 1134 * Loop through all of the pages in the entry's range, copying each 1135 * one from the source object (it should be there) to the destination 1136 * object. 1137 */ 1138 for (vaddr = dst_entry->start, dst_offset = 0; 1139 vaddr < dst_entry->end; 1140 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { 1141 1142 /* 1143 * Allocate a page in the destination object 1144 */ 1145 do { 1146 dst_m = vm_page_alloc(dst_object, 1147 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); 1148 if (dst_m == NULL) { 1149 VM_OBJECT_UNLOCK(dst_object); 1150 VM_WAIT; 1151 VM_OBJECT_LOCK(dst_object); 1152 } 1153 } while (dst_m == NULL); 1154 1155 /* 1156 * Find the page in the source object, and copy it in. 1157 * (Because the source is wired down, the page will be in 1158 * memory.) 1159 */ 1160 VM_OBJECT_LOCK(src_object); 1161 object = src_object; 1162 pindex = 0; 1163 while ((src_m = vm_page_lookup(object, pindex + 1164 OFF_TO_IDX(dst_offset + src_offset))) == NULL && 1165 (src_entry->protection & VM_PROT_WRITE) == 0 && 1166 (backing_object = object->backing_object) != NULL) { 1167 /* 1168 * Allow fallback to backing objects if we are reading. 1169 */ 1170 VM_OBJECT_LOCK(backing_object); 1171 pindex += OFF_TO_IDX(object->backing_object_offset); 1172 VM_OBJECT_UNLOCK(object); 1173 object = backing_object; 1174 } 1175 if (src_m == NULL) 1176 panic("vm_fault_copy_wired: page missing"); 1177 pmap_copy_page(src_m, dst_m); 1178 VM_OBJECT_UNLOCK(object); 1179 dst_m->valid = VM_PAGE_BITS_ALL; 1180 VM_OBJECT_UNLOCK(dst_object); 1181 1182 /* 1183 * Enter it in the pmap as a read and/or execute access. 1184 */ 1185 pmap_enter(dst_map->pmap, vaddr, prot & ~VM_PROT_WRITE, dst_m, 1186 prot, FALSE); 1187 1188 /* 1189 * Mark it no longer busy, and put it on the active list. 1190 */ 1191 VM_OBJECT_LOCK(dst_object); 1192 vm_page_lock_queues(); 1193 vm_page_activate(dst_m); 1194 vm_page_unlock_queues(); 1195 vm_page_wakeup(dst_m); 1196 } 1197 VM_OBJECT_UNLOCK(dst_object); 1198 } 1199 1200 1201 /* 1202 * This routine checks around the requested page for other pages that 1203 * might be able to be faulted in. This routine brackets the viable 1204 * pages for the pages to be paged in. 1205 * 1206 * Inputs: 1207 * m, rbehind, rahead 1208 * 1209 * Outputs: 1210 * marray (array of vm_page_t), reqpage (index of requested page) 1211 * 1212 * Return value: 1213 * number of pages in marray 1214 * 1215 * This routine can't block. 1216 */ 1217 static int 1218 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1219 vm_page_t m; 1220 int rbehind; 1221 int rahead; 1222 vm_page_t *marray; 1223 int *reqpage; 1224 { 1225 int i,j; 1226 vm_object_t object; 1227 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1228 vm_page_t rtm; 1229 int cbehind, cahead; 1230 1231 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED); 1232 1233 object = m->object; 1234 pindex = m->pindex; 1235 cbehind = cahead = 0; 1236 1237 /* 1238 * if the requested page is not available, then give up now 1239 */ 1240 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1241 return 0; 1242 } 1243 1244 if ((cbehind == 0) && (cahead == 0)) { 1245 *reqpage = 0; 1246 marray[0] = m; 1247 return 1; 1248 } 1249 1250 if (rahead > cahead) { 1251 rahead = cahead; 1252 } 1253 1254 if (rbehind > cbehind) { 1255 rbehind = cbehind; 1256 } 1257 1258 /* 1259 * scan backward for the read behind pages -- in memory 1260 */ 1261 if (pindex > 0) { 1262 if (rbehind > pindex) { 1263 rbehind = pindex; 1264 startpindex = 0; 1265 } else { 1266 startpindex = pindex - rbehind; 1267 } 1268 1269 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1270 rtm->pindex >= startpindex) 1271 startpindex = rtm->pindex + 1; 1272 1273 /* tpindex is unsigned; beware of numeric underflow. */ 1274 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1275 tpindex < pindex; i++, tpindex--) { 1276 1277 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1278 VM_ALLOC_IFNOTCACHED); 1279 if (rtm == NULL) { 1280 /* 1281 * Shift the allocated pages to the 1282 * beginning of the array. 1283 */ 1284 for (j = 0; j < i; j++) { 1285 marray[j] = marray[j + tpindex + 1 - 1286 startpindex]; 1287 } 1288 break; 1289 } 1290 1291 marray[tpindex - startpindex] = rtm; 1292 } 1293 } else { 1294 startpindex = 0; 1295 i = 0; 1296 } 1297 1298 marray[i] = m; 1299 /* page offset of the required page */ 1300 *reqpage = i; 1301 1302 tpindex = pindex + 1; 1303 i++; 1304 1305 /* 1306 * scan forward for the read ahead pages 1307 */ 1308 endpindex = tpindex + rahead; 1309 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1310 endpindex = rtm->pindex; 1311 if (endpindex > object->size) 1312 endpindex = object->size; 1313 1314 for (; tpindex < endpindex; i++, tpindex++) { 1315 1316 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1317 VM_ALLOC_IFNOTCACHED); 1318 if (rtm == NULL) { 1319 break; 1320 } 1321 1322 marray[i] = rtm; 1323 } 1324 1325 /* return number of pages */ 1326 return i; 1327 }
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