1 /* 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 1994 John S. Dyson 5 * All rights reserved. 6 * Copyright (c) 1994 David Greenman 7 * All rights reserved. 8 * 9 * 10 * This code is derived from software contributed to Berkeley by 11 * The Mach Operating System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 42 * 43 * 44 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 45 * All rights reserved. 46 * 47 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 48 * 49 * Permission to use, copy, modify and distribute this software and 50 * its documentation is hereby granted, provided that both the copyright 51 * notice and this permission notice appear in all copies of the 52 * software, derivative works or modified versions, and any portions 53 * thereof, and that both notices appear in supporting documentation. 54 * 55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 58 * 59 * Carnegie Mellon requests users of this software to return to 60 * 61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 62 * School of Computer Science 63 * Carnegie Mellon University 64 * Pittsburgh PA 15213-3890 65 * 66 * any improvements or extensions that they make and grant Carnegie the 67 * rights to redistribute these changes. 68 * 69 * $FreeBSD: src/sys/vm/vm_fault.c,v 1.108.2.8 2002/02/26 05:49:27 silby Exp $ 70 * $DragonFly: src/sys/vm/vm_fault.c,v 1.21 2006/03/15 07:58:37 dillon Exp $ 71 */ 72 73 /* 74 * Page fault handling module. 75 */ 76 77 #include <sys/param.h> 78 #include <sys/systm.h> 79 #include <sys/kernel.h> 80 #include <sys/proc.h> 81 #include <sys/vnode.h> 82 #include <sys/resourcevar.h> 83 #include <sys/vmmeter.h> 84 85 #include <vm/vm.h> 86 #include <vm/vm_param.h> 87 #include <sys/lock.h> 88 #include <vm/pmap.h> 89 #include <vm/vm_map.h> 90 #include <vm/vm_object.h> 91 #include <vm/vm_page.h> 92 #include <vm/vm_pageout.h> 93 #include <vm/vm_kern.h> 94 #include <vm/vm_pager.h> 95 #include <vm/vnode_pager.h> 96 #include <vm/vm_extern.h> 97 98 #include <sys/thread2.h> 99 #include <vm/vm_page2.h> 100 101 static int vm_fault_additional_pages (vm_page_t, int, 102 int, vm_page_t *, int *); 103 static int vm_fault_ratelimit(struct vmspace *vmspace); 104 105 #define VM_FAULT_READ_AHEAD 8 106 #define VM_FAULT_READ_BEHIND 7 107 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1) 108 109 struct faultstate { 110 vm_page_t m; 111 vm_object_t object; 112 vm_pindex_t pindex; 113 vm_page_t first_m; 114 vm_object_t first_object; 115 vm_pindex_t first_pindex; 116 vm_map_t map; 117 vm_map_entry_t entry; 118 int lookup_still_valid; 119 struct vnode *vp; 120 }; 121 122 static __inline void 123 release_page(struct faultstate *fs) 124 { 125 vm_page_wakeup(fs->m); 126 vm_page_deactivate(fs->m); 127 fs->m = NULL; 128 } 129 130 static __inline void 131 unlock_map(struct faultstate *fs) 132 { 133 if (fs->lookup_still_valid) { 134 vm_map_lookup_done(fs->map, fs->entry, 0); 135 fs->lookup_still_valid = FALSE; 136 } 137 } 138 139 static void 140 _unlock_things(struct faultstate *fs, int dealloc) 141 { 142 vm_object_pip_wakeup(fs->object); 143 if (fs->object != fs->first_object) { 144 vm_page_free(fs->first_m); 145 vm_object_pip_wakeup(fs->first_object); 146 fs->first_m = NULL; 147 } 148 if (dealloc) { 149 vm_object_deallocate(fs->first_object); 150 } 151 unlock_map(fs); 152 if (fs->vp != NULL) { 153 vput(fs->vp); 154 fs->vp = NULL; 155 } 156 } 157 158 #define unlock_things(fs) _unlock_things(fs, 0) 159 #define unlock_and_deallocate(fs) _unlock_things(fs, 1) 160 161 /* 162 * TRYPAGER - used by vm_fault to calculate whether the pager for the 163 * current object *might* contain the page. 164 * 165 * default objects are zero-fill, there is no real pager. 166 */ 167 168 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 169 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) 170 171 /* 172 * vm_fault: 173 * 174 * Handle a page fault occurring at the given address, 175 * requiring the given permissions, in the map specified. 176 * If successful, the page is inserted into the 177 * associated physical map. 178 * 179 * NOTE: the given address should be truncated to the 180 * proper page address. 181 * 182 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 183 * a standard error specifying why the fault is fatal is returned. 184 * 185 * 186 * The map in question must be referenced, and remains so. 187 * Caller may hold no locks. 188 */ 189 int 190 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, int fault_flags) 191 { 192 vm_prot_t prot; 193 int result; 194 boolean_t wired; 195 int map_generation; 196 vm_object_t next_object; 197 vm_page_t marray[VM_FAULT_READ]; 198 int hardfault; 199 int faultcount; 200 int limticks; 201 int didlimit = 0; 202 struct faultstate fs; 203 204 mycpu->gd_cnt.v_vm_faults++; 205 hardfault = 0; 206 207 RetryFault: 208 /* 209 * Find the backing store object and offset into it to begin the 210 * search. 211 */ 212 fs.map = map; 213 if ((result = vm_map_lookup(&fs.map, vaddr, 214 fault_type, &fs.entry, &fs.first_object, 215 &fs.first_pindex, &prot, &wired)) != KERN_SUCCESS) { 216 if ((result != KERN_PROTECTION_FAILURE) || 217 ((fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE)) { 218 return result; 219 } 220 221 /* 222 * If we are user-wiring a r/w segment, and it is COW, then 223 * we need to do the COW operation. Note that we don't COW 224 * currently RO sections now, because it is NOT desirable 225 * to COW .text. We simply keep .text from ever being COW'ed 226 * and take the heat that one cannot debug wired .text sections. 227 */ 228 result = vm_map_lookup(&fs.map, vaddr, 229 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE, 230 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired); 231 if (result != KERN_SUCCESS) { 232 return result; 233 } 234 235 /* 236 * If we don't COW now, on a user wire, the user will never 237 * be able to write to the mapping. If we don't make this 238 * restriction, the bookkeeping would be nearly impossible. 239 */ 240 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 241 fs.entry->max_protection &= ~VM_PROT_WRITE; 242 } 243 244 map_generation = fs.map->timestamp; 245 246 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 247 panic("vm_fault: fault on nofault entry, addr: %lx", 248 (u_long)vaddr); 249 } 250 251 /* 252 * A system map entry may return a NULL object. No object means 253 * no pager means an unrecoverable kernel fault. 254 */ 255 if (fs.first_object == NULL) { 256 panic("vm_fault: unrecoverable fault at %p in entry %p", 257 (void *)vaddr, fs.entry); 258 } 259 260 /* 261 * Make a reference to this object to prevent its disposal while we 262 * are messing with it. Once we have the reference, the map is free 263 * to be diddled. Since objects reference their shadows (and copies), 264 * they will stay around as well. 265 * 266 * Bump the paging-in-progress count to prevent size changes (e.g. 267 * truncation operations) during I/O. This must be done after 268 * obtaining the vnode lock in order to avoid possible deadlocks. 269 */ 270 vm_object_reference(fs.first_object); 271 fs.vp = vnode_pager_lock(fs.first_object); 272 vm_object_pip_add(fs.first_object, 1); 273 274 if ((fault_type & VM_PROT_WRITE) && 275 (fs.first_object->type == OBJT_VNODE)) { 276 vm_freeze_copyopts(fs.first_object, 277 fs.first_pindex, fs.first_pindex + 1); 278 } 279 280 fs.lookup_still_valid = TRUE; 281 282 if (wired) 283 fault_type = prot; 284 285 fs.first_m = NULL; 286 287 /* 288 * Search for the page at object/offset. 289 */ 290 291 fs.object = fs.first_object; 292 fs.pindex = fs.first_pindex; 293 294 while (TRUE) { 295 /* 296 * If the object is dead, we stop here 297 */ 298 299 if (fs.object->flags & OBJ_DEAD) { 300 unlock_and_deallocate(&fs); 301 return (KERN_PROTECTION_FAILURE); 302 } 303 304 /* 305 * See if page is resident. spl protection is required 306 * to avoid an interrupt unbusy/free race against our 307 * lookup. We must hold the protection through a page 308 * allocation or busy. 309 */ 310 crit_enter(); 311 fs.m = vm_page_lookup(fs.object, fs.pindex); 312 if (fs.m != NULL) { 313 int queue; 314 /* 315 * Wait/Retry if the page is busy. We have to do this 316 * if the page is busy via either PG_BUSY or 317 * vm_page_t->busy because the vm_pager may be using 318 * vm_page_t->busy for pageouts ( and even pageins if 319 * it is the vnode pager ), and we could end up trying 320 * to pagein and pageout the same page simultaneously. 321 * 322 * We can theoretically allow the busy case on a read 323 * fault if the page is marked valid, but since such 324 * pages are typically already pmap'd, putting that 325 * special case in might be more effort then it is 326 * worth. We cannot under any circumstances mess 327 * around with a vm_page_t->busy page except, perhaps, 328 * to pmap it. 329 */ 330 if ((fs.m->flags & PG_BUSY) || fs.m->busy) { 331 unlock_things(&fs); 332 vm_page_sleep_busy(fs.m, TRUE, "vmpfw"); 333 mycpu->gd_cnt.v_intrans++; 334 vm_object_deallocate(fs.first_object); 335 crit_exit(); 336 goto RetryFault; 337 } 338 339 queue = fs.m->queue; 340 vm_page_unqueue_nowakeup(fs.m); 341 342 if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) { 343 vm_page_activate(fs.m); 344 unlock_and_deallocate(&fs); 345 vm_waitpfault(); 346 crit_exit(); 347 goto RetryFault; 348 } 349 350 /* 351 * Mark page busy for other processes, and the 352 * pagedaemon. If it still isn't completely valid 353 * (readable), jump to readrest, else break-out ( we 354 * found the page ). 355 * 356 * We can release the spl once we have marked the 357 * page busy. 358 */ 359 360 vm_page_busy(fs.m); 361 crit_exit(); 362 363 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) && 364 fs.m->object != kernel_object && fs.m->object != kmem_object) { 365 goto readrest; 366 } 367 368 break; 369 } 370 371 /* 372 * Page is not resident, If this is the search termination 373 * or the pager might contain the page, allocate a new page. 374 * 375 * note: we are still in splvm(). 376 */ 377 378 if (TRYPAGER || fs.object == fs.first_object) { 379 if (fs.pindex >= fs.object->size) { 380 crit_exit(); 381 unlock_and_deallocate(&fs); 382 return (KERN_PROTECTION_FAILURE); 383 } 384 385 /* 386 * Ratelimit. 387 */ 388 if (didlimit == 0) { 389 limticks = 390 vm_fault_ratelimit(curproc->p_vmspace); 391 if (limticks) { 392 crit_exit(); 393 unlock_and_deallocate(&fs); 394 tsleep(curproc, 0, "vmrate", limticks); 395 didlimit = 1; 396 goto RetryFault; 397 } 398 } 399 400 /* 401 * Allocate a new page for this object/offset pair. 402 */ 403 fs.m = NULL; 404 if (!vm_page_count_severe()) { 405 fs.m = vm_page_alloc(fs.object, fs.pindex, 406 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_NORMAL | VM_ALLOC_ZERO); 407 } 408 if (fs.m == NULL) { 409 crit_exit(); 410 unlock_and_deallocate(&fs); 411 vm_waitpfault(); 412 goto RetryFault; 413 } 414 } 415 crit_exit(); 416 417 readrest: 418 /* 419 * We have found a valid page or we have allocated a new page. 420 * The page thus may not be valid or may not be entirely 421 * valid. 422 * 423 * Attempt to fault-in the page if there is a chance that the 424 * pager has it, and potentially fault in additional pages 425 * at the same time. 426 * 427 * We are NOT in splvm here and if TRYPAGER is true then 428 * fs.m will be non-NULL and will be PG_BUSY for us. 429 */ 430 431 if (TRYPAGER) { 432 int rv; 433 int reqpage; 434 int ahead, behind; 435 u_char behavior = vm_map_entry_behavior(fs.entry); 436 437 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 438 ahead = 0; 439 behind = 0; 440 } else { 441 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT; 442 if (behind > VM_FAULT_READ_BEHIND) 443 behind = VM_FAULT_READ_BEHIND; 444 445 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1; 446 if (ahead > VM_FAULT_READ_AHEAD) 447 ahead = VM_FAULT_READ_AHEAD; 448 } 449 450 if ((fs.first_object->type != OBJT_DEVICE) && 451 (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 452 (behavior != MAP_ENTRY_BEHAV_RANDOM && 453 fs.pindex >= fs.entry->lastr && 454 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) 455 ) { 456 vm_pindex_t firstpindex, tmppindex; 457 458 if (fs.first_pindex < 2 * VM_FAULT_READ) 459 firstpindex = 0; 460 else 461 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ; 462 463 /* 464 * note: partially valid pages cannot be 465 * included in the lookahead - NFS piecemeal 466 * writes will barf on it badly. 467 * 468 * spl protection is required to avoid races 469 * between the lookup and an interrupt 470 * unbusy/free sequence occuring prior to 471 * our busy check. 472 */ 473 crit_enter(); 474 for (tmppindex = fs.first_pindex - 1; 475 tmppindex >= firstpindex; 476 --tmppindex 477 ) { 478 vm_page_t mt; 479 mt = vm_page_lookup( fs.first_object, tmppindex); 480 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL)) 481 break; 482 if (mt->busy || 483 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) || 484 mt->hold_count || 485 mt->wire_count) 486 continue; 487 if (mt->dirty == 0) 488 vm_page_test_dirty(mt); 489 if (mt->dirty) { 490 vm_page_protect(mt, VM_PROT_NONE); 491 vm_page_deactivate(mt); 492 } else { 493 vm_page_cache(mt); 494 } 495 } 496 crit_exit(); 497 498 ahead += behind; 499 behind = 0; 500 } 501 502 /* 503 * now we find out if any other pages should be paged 504 * in at this time this routine checks to see if the 505 * pages surrounding this fault reside in the same 506 * object as the page for this fault. If they do, 507 * then they are faulted in also into the object. The 508 * array "marray" returned contains an array of 509 * vm_page_t structs where one of them is the 510 * vm_page_t passed to the routine. The reqpage 511 * return value is the index into the marray for the 512 * vm_page_t passed to the routine. 513 * 514 * fs.m plus the additional pages are PG_BUSY'd. 515 */ 516 faultcount = vm_fault_additional_pages( 517 fs.m, behind, ahead, marray, &reqpage); 518 519 /* 520 * update lastr imperfectly (we do not know how much 521 * getpages will actually read), but good enough. 522 */ 523 fs.entry->lastr = fs.pindex + faultcount - behind; 524 525 /* 526 * Call the pager to retrieve the data, if any, after 527 * releasing the lock on the map. We hold a ref on 528 * fs.object and the pages are PG_BUSY'd. 529 */ 530 unlock_map(&fs); 531 532 rv = faultcount ? 533 vm_pager_get_pages(fs.object, marray, faultcount, 534 reqpage) : VM_PAGER_FAIL; 535 536 if (rv == VM_PAGER_OK) { 537 /* 538 * Found the page. Leave it busy while we play 539 * with it. 540 */ 541 542 /* 543 * Relookup in case pager changed page. Pager 544 * is responsible for disposition of old page 545 * if moved. 546 * 547 * XXX other code segments do relookups too. 548 * It's a bad abstraction that needs to be 549 * fixed/removed. 550 */ 551 fs.m = vm_page_lookup(fs.object, fs.pindex); 552 if (fs.m == NULL) { 553 unlock_and_deallocate(&fs); 554 goto RetryFault; 555 } 556 557 hardfault++; 558 break; /* break to PAGE HAS BEEN FOUND */ 559 } 560 /* 561 * Remove the bogus page (which does not exist at this 562 * object/offset); before doing so, we must get back 563 * our object lock to preserve our invariant. 564 * 565 * Also wake up any other process that may want to bring 566 * in this page. 567 * 568 * If this is the top-level object, we must leave the 569 * busy page to prevent another process from rushing 570 * past us, and inserting the page in that object at 571 * the same time that we are. 572 */ 573 574 if (rv == VM_PAGER_ERROR) 575 printf("vm_fault: pager read error, pid %d (%s)\n", 576 curproc->p_pid, curproc->p_comm); 577 /* 578 * Data outside the range of the pager or an I/O error 579 */ 580 /* 581 * XXX - the check for kernel_map is a kludge to work 582 * around having the machine panic on a kernel space 583 * fault w/ I/O error. 584 */ 585 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 586 (rv == VM_PAGER_BAD)) { 587 vm_page_free(fs.m); 588 fs.m = NULL; 589 unlock_and_deallocate(&fs); 590 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 591 } 592 if (fs.object != fs.first_object) { 593 vm_page_free(fs.m); 594 fs.m = NULL; 595 /* 596 * XXX - we cannot just fall out at this 597 * point, m has been freed and is invalid! 598 */ 599 } 600 } 601 602 /* 603 * We get here if the object has default pager (or unwiring) 604 * or the pager doesn't have the page. 605 */ 606 if (fs.object == fs.first_object) 607 fs.first_m = fs.m; 608 609 /* 610 * Move on to the next object. Lock the next object before 611 * unlocking the current one. 612 */ 613 614 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 615 next_object = fs.object->backing_object; 616 if (next_object == NULL) { 617 /* 618 * If there's no object left, fill the page in the top 619 * object with zeros. 620 */ 621 if (fs.object != fs.first_object) { 622 vm_object_pip_wakeup(fs.object); 623 624 fs.object = fs.first_object; 625 fs.pindex = fs.first_pindex; 626 fs.m = fs.first_m; 627 } 628 fs.first_m = NULL; 629 630 /* 631 * Zero the page if necessary and mark it valid. 632 */ 633 if ((fs.m->flags & PG_ZERO) == 0) { 634 vm_page_zero_fill(fs.m); 635 } else { 636 mycpu->gd_cnt.v_ozfod++; 637 } 638 mycpu->gd_cnt.v_zfod++; 639 fs.m->valid = VM_PAGE_BITS_ALL; 640 break; /* break to PAGE HAS BEEN FOUND */ 641 } else { 642 if (fs.object != fs.first_object) { 643 vm_object_pip_wakeup(fs.object); 644 } 645 KASSERT(fs.object != next_object, ("object loop %p", next_object)); 646 fs.object = next_object; 647 vm_object_pip_add(fs.object, 1); 648 } 649 } 650 651 KASSERT((fs.m->flags & PG_BUSY) != 0, 652 ("vm_fault: not busy after main loop")); 653 654 /* 655 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 656 * is held.] 657 */ 658 659 /* 660 * If the page is being written, but isn't already owned by the 661 * top-level object, we have to copy it into a new page owned by the 662 * top-level object. 663 */ 664 665 if (fs.object != fs.first_object) { 666 /* 667 * We only really need to copy if we want to write it. 668 */ 669 670 if (fault_type & VM_PROT_WRITE) { 671 /* 672 * This allows pages to be virtually copied from a 673 * backing_object into the first_object, where the 674 * backing object has no other refs to it, and cannot 675 * gain any more refs. Instead of a bcopy, we just 676 * move the page from the backing object to the 677 * first object. Note that we must mark the page 678 * dirty in the first object so that it will go out 679 * to swap when needed. 680 */ 681 if (map_generation == fs.map->timestamp && 682 /* 683 * Only one shadow object 684 */ 685 (fs.object->shadow_count == 1) && 686 /* 687 * No COW refs, except us 688 */ 689 (fs.object->ref_count == 1) && 690 /* 691 * No one else can look this object up 692 */ 693 (fs.object->handle == NULL) && 694 /* 695 * No other ways to look the object up 696 */ 697 ((fs.object->type == OBJT_DEFAULT) || 698 (fs.object->type == OBJT_SWAP)) && 699 /* 700 * We don't chase down the shadow chain 701 */ 702 (fs.object == fs.first_object->backing_object) && 703 704 /* 705 * grab the lock if we need to 706 */ 707 (fs.lookup_still_valid || 708 lockmgr(&fs.map->lock, LK_EXCLUSIVE|LK_NOWAIT, NULL, curthread) == 0) 709 ) { 710 711 fs.lookup_still_valid = 1; 712 /* 713 * get rid of the unnecessary page 714 */ 715 vm_page_protect(fs.first_m, VM_PROT_NONE); 716 vm_page_free(fs.first_m); 717 fs.first_m = NULL; 718 719 /* 720 * grab the page and put it into the 721 * process'es object. The page is 722 * automatically made dirty. 723 */ 724 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 725 fs.first_m = fs.m; 726 vm_page_busy(fs.first_m); 727 fs.m = NULL; 728 mycpu->gd_cnt.v_cow_optim++; 729 } else { 730 /* 731 * Oh, well, lets copy it. 732 */ 733 vm_page_copy(fs.m, fs.first_m); 734 } 735 736 if (fs.m) { 737 /* 738 * We no longer need the old page or object. 739 */ 740 release_page(&fs); 741 } 742 743 /* 744 * fs.object != fs.first_object due to above 745 * conditional 746 */ 747 748 vm_object_pip_wakeup(fs.object); 749 750 /* 751 * Only use the new page below... 752 */ 753 754 mycpu->gd_cnt.v_cow_faults++; 755 fs.m = fs.first_m; 756 fs.object = fs.first_object; 757 fs.pindex = fs.first_pindex; 758 759 } else { 760 prot &= ~VM_PROT_WRITE; 761 } 762 } 763 764 /* 765 * We must verify that the maps have not changed since our last 766 * lookup. 767 */ 768 769 if (!fs.lookup_still_valid && 770 (fs.map->timestamp != map_generation)) { 771 vm_object_t retry_object; 772 vm_pindex_t retry_pindex; 773 vm_prot_t retry_prot; 774 775 /* 776 * Since map entries may be pageable, make sure we can take a 777 * page fault on them. 778 */ 779 780 /* 781 * Unlock vnode before the lookup to avoid deadlock. E.G. 782 * avoid a deadlock between the inode and exec_map that can 783 * occur due to locks being obtained in different orders. 784 */ 785 786 if (fs.vp != NULL) { 787 vput(fs.vp); 788 fs.vp = NULL; 789 } 790 791 if (fs.map->infork) { 792 release_page(&fs); 793 unlock_and_deallocate(&fs); 794 goto RetryFault; 795 } 796 797 /* 798 * To avoid trying to write_lock the map while another process 799 * has it read_locked (in vm_map_wire), we do not try for 800 * write permission. If the page is still writable, we will 801 * get write permission. If it is not, or has been marked 802 * needs_copy, we enter the mapping without write permission, 803 * and will merely take another fault. 804 */ 805 result = vm_map_lookup(&fs.map, vaddr, fault_type & ~VM_PROT_WRITE, 806 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 807 map_generation = fs.map->timestamp; 808 809 /* 810 * If we don't need the page any longer, put it on the active 811 * list (the easiest thing to do here). If no one needs it, 812 * pageout will grab it eventually. 813 */ 814 815 if (result != KERN_SUCCESS) { 816 release_page(&fs); 817 unlock_and_deallocate(&fs); 818 return (result); 819 } 820 fs.lookup_still_valid = TRUE; 821 822 if ((retry_object != fs.first_object) || 823 (retry_pindex != fs.first_pindex)) { 824 release_page(&fs); 825 unlock_and_deallocate(&fs); 826 goto RetryFault; 827 } 828 /* 829 * Check whether the protection has changed or the object has 830 * been copied while we left the map unlocked. Changing from 831 * read to write permission is OK - we leave the page 832 * write-protected, and catch the write fault. Changing from 833 * write to read permission means that we can't mark the page 834 * write-enabled after all. 835 */ 836 prot &= retry_prot; 837 } 838 839 /* 840 * Put this page into the physical map. We had to do the unlock above 841 * because pmap_enter may cause other faults. We don't put the page 842 * back on the active queue until later so that the page-out daemon 843 * won't find us (yet). 844 */ 845 846 if (prot & VM_PROT_WRITE) { 847 vm_page_flag_set(fs.m, PG_WRITEABLE); 848 vm_object_set_writeable_dirty(fs.m->object); 849 850 /* 851 * If the fault is a write, we know that this page is being 852 * written NOW so dirty it explicitly to save on 853 * pmap_is_modified() calls later. 854 * 855 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC 856 * if the page is already dirty to prevent data written with 857 * the expectation of being synced from not being synced. 858 * Likewise if this entry does not request NOSYNC then make 859 * sure the page isn't marked NOSYNC. Applications sharing 860 * data should use the same flags to avoid ping ponging. 861 * 862 * Also tell the backing pager, if any, that it should remove 863 * any swap backing since the page is now dirty. 864 */ 865 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 866 if (fs.m->dirty == 0) 867 vm_page_flag_set(fs.m, PG_NOSYNC); 868 } else { 869 vm_page_flag_clear(fs.m, PG_NOSYNC); 870 } 871 if (fault_flags & VM_FAULT_DIRTY) { 872 crit_enter(); 873 vm_page_dirty(fs.m); 874 vm_pager_page_unswapped(fs.m); 875 crit_exit(); 876 } 877 } 878 879 /* 880 * Page had better still be busy 881 */ 882 883 KASSERT(fs.m->flags & PG_BUSY, 884 ("vm_fault: page %p not busy!", fs.m)); 885 886 unlock_things(&fs); 887 888 /* 889 * Sanity check: page must be completely valid or it is not fit to 890 * map into user space. vm_pager_get_pages() ensures this. 891 */ 892 893 if (fs.m->valid != VM_PAGE_BITS_ALL) { 894 vm_page_zero_invalid(fs.m, TRUE); 895 printf("Warning: page %p partially invalid on fault\n", fs.m); 896 } 897 898 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired); 899 900 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 901 pmap_prefault(fs.map->pmap, vaddr, fs.entry); 902 } 903 904 vm_page_flag_clear(fs.m, PG_ZERO); 905 vm_page_flag_set(fs.m, PG_MAPPED|PG_REFERENCED); 906 if (fault_flags & VM_FAULT_HOLD) 907 vm_page_hold(fs.m); 908 909 /* 910 * If the page is not wired down, then put it where the pageout daemon 911 * can find it. 912 */ 913 914 if (fault_flags & VM_FAULT_WIRE_MASK) { 915 if (wired) 916 vm_page_wire(fs.m); 917 else 918 vm_page_unwire(fs.m, 1); 919 } else { 920 vm_page_activate(fs.m); 921 } 922 923 if (curproc && (curproc->p_flag & P_SWAPPEDOUT) == 0 && 924 curproc->p_stats) { 925 if (hardfault) { 926 curproc->p_stats->p_ru.ru_majflt++; 927 } else { 928 curproc->p_stats->p_ru.ru_minflt++; 929 } 930 } 931 932 /* 933 * Unlock everything, and return 934 */ 935 936 vm_page_wakeup(fs.m); 937 vm_object_deallocate(fs.first_object); 938 939 return (KERN_SUCCESS); 940 941 } 942 943 /* 944 * quick version of vm_fault 945 */ 946 int 947 vm_fault_quick(caddr_t v, int prot) 948 { 949 int r; 950 951 if (prot & VM_PROT_WRITE) 952 r = subyte(v, fubyte(v)); 953 else 954 r = fubyte(v); 955 return(r); 956 } 957 958 /* 959 * Wire down a range of virtual addresses in a map. The entry in question 960 * should be marked in-transition and the map must be locked. We must 961 * release the map temporarily while faulting-in the page to avoid a 962 * deadlock. Note that the entry may be clipped while we are blocked but 963 * will never be freed. 964 */ 965 int 966 vm_fault_wire(vm_map_t map, vm_map_entry_t entry, boolean_t user_wire) 967 { 968 boolean_t fictitious; 969 vm_offset_t start; 970 vm_offset_t end; 971 vm_offset_t va; 972 vm_paddr_t pa; 973 pmap_t pmap; 974 int rv; 975 976 pmap = vm_map_pmap(map); 977 start = entry->start; 978 end = entry->end; 979 fictitious = entry->object.vm_object && 980 (entry->object.vm_object->type == OBJT_DEVICE); 981 982 vm_map_unlock(map); 983 map->timestamp++; 984 985 /* 986 * We simulate a fault to get the page and enter it in the physical 987 * map. 988 */ 989 for (va = start; va < end; va += PAGE_SIZE) { 990 if (user_wire) { 991 rv = vm_fault(map, va, VM_PROT_READ, 992 VM_FAULT_USER_WIRE); 993 } else { 994 rv = vm_fault(map, va, VM_PROT_READ|VM_PROT_WRITE, 995 VM_FAULT_CHANGE_WIRING); 996 } 997 if (rv) { 998 while (va > start) { 999 va -= PAGE_SIZE; 1000 if ((pa = pmap_extract(pmap, va)) == 0) 1001 continue; 1002 pmap_change_wiring(pmap, va, FALSE); 1003 if (!fictitious) 1004 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1005 } 1006 vm_map_lock(map); 1007 return (rv); 1008 } 1009 } 1010 vm_map_lock(map); 1011 return (KERN_SUCCESS); 1012 } 1013 1014 /* 1015 * Unwire a range of virtual addresses in a map. The map should be 1016 * locked. 1017 */ 1018 void 1019 vm_fault_unwire(vm_map_t map, vm_map_entry_t entry) 1020 { 1021 boolean_t fictitious; 1022 vm_offset_t start; 1023 vm_offset_t end; 1024 vm_offset_t va; 1025 vm_paddr_t pa; 1026 pmap_t pmap; 1027 1028 pmap = vm_map_pmap(map); 1029 start = entry->start; 1030 end = entry->end; 1031 fictitious = entry->object.vm_object && 1032 (entry->object.vm_object->type == OBJT_DEVICE); 1033 1034 /* 1035 * Since the pages are wired down, we must be able to get their 1036 * mappings from the physical map system. 1037 */ 1038 for (va = start; va < end; va += PAGE_SIZE) { 1039 pa = pmap_extract(pmap, va); 1040 if (pa != 0) { 1041 pmap_change_wiring(pmap, va, FALSE); 1042 if (!fictitious) 1043 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1044 } 1045 } 1046 } 1047 1048 /* 1049 * Reduce the rate at which memory is allocated to a process based 1050 * on the perceived load on the VM system. As the load increases 1051 * the allocation burst rate goes down and the delay increases. 1052 * 1053 * Rate limiting does not apply when faulting active or inactive 1054 * pages. When faulting 'cache' pages, rate limiting only applies 1055 * if the system currently has a severe page deficit. 1056 * 1057 * XXX vm_pagesupply should be increased when a page is freed. 1058 * 1059 * We sleep up to 1/10 of a second. 1060 */ 1061 static int 1062 vm_fault_ratelimit(struct vmspace *vmspace) 1063 { 1064 if (vm_load_enable == 0) 1065 return(0); 1066 if (vmspace->vm_pagesupply > 0) { 1067 --vmspace->vm_pagesupply; 1068 return(0); 1069 } 1070 #ifdef INVARIANTS 1071 if (vm_load_debug) { 1072 printf("load %-4d give %d pgs, wait %d, pid %-5d (%s)\n", 1073 vm_load, 1074 (1000 - vm_load ) / 10, vm_load * hz / 10000, 1075 curproc->p_pid, curproc->p_comm); 1076 } 1077 #endif 1078 vmspace->vm_pagesupply = (1000 - vm_load) / 10; 1079 return(vm_load * hz / 10000); 1080 } 1081 1082 /* 1083 * Routine: 1084 * vm_fault_copy_entry 1085 * Function: 1086 * Copy all of the pages from a wired-down map entry to another. 1087 * 1088 * In/out conditions: 1089 * The source and destination maps must be locked for write. 1090 * The source map entry must be wired down (or be a sharing map 1091 * entry corresponding to a main map entry that is wired down). 1092 */ 1093 1094 void 1095 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1096 vm_map_entry_t dst_entry, vm_map_entry_t src_entry) 1097 { 1098 vm_object_t dst_object; 1099 vm_object_t src_object; 1100 vm_ooffset_t dst_offset; 1101 vm_ooffset_t src_offset; 1102 vm_prot_t prot; 1103 vm_offset_t vaddr; 1104 vm_page_t dst_m; 1105 vm_page_t src_m; 1106 1107 #ifdef lint 1108 src_map++; 1109 #endif /* lint */ 1110 1111 src_object = src_entry->object.vm_object; 1112 src_offset = src_entry->offset; 1113 1114 /* 1115 * Create the top-level object for the destination entry. (Doesn't 1116 * actually shadow anything - we copy the pages directly.) 1117 */ 1118 dst_object = vm_object_allocate(OBJT_DEFAULT, 1119 (vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1120 1121 dst_entry->object.vm_object = dst_object; 1122 dst_entry->offset = 0; 1123 1124 prot = dst_entry->max_protection; 1125 1126 /* 1127 * Loop through all of the pages in the entry's range, copying each 1128 * one from the source object (it should be there) to the destination 1129 * object. 1130 */ 1131 for (vaddr = dst_entry->start, dst_offset = 0; 1132 vaddr < dst_entry->end; 1133 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { 1134 1135 /* 1136 * Allocate a page in the destination object 1137 */ 1138 do { 1139 dst_m = vm_page_alloc(dst_object, 1140 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); 1141 if (dst_m == NULL) { 1142 vm_wait(); 1143 } 1144 } while (dst_m == NULL); 1145 1146 /* 1147 * Find the page in the source object, and copy it in. 1148 * (Because the source is wired down, the page will be in 1149 * memory.) 1150 */ 1151 src_m = vm_page_lookup(src_object, 1152 OFF_TO_IDX(dst_offset + src_offset)); 1153 if (src_m == NULL) 1154 panic("vm_fault_copy_wired: page missing"); 1155 1156 vm_page_copy(src_m, dst_m); 1157 1158 /* 1159 * Enter it in the pmap... 1160 */ 1161 1162 vm_page_flag_clear(dst_m, PG_ZERO); 1163 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE); 1164 vm_page_flag_set(dst_m, PG_WRITEABLE|PG_MAPPED); 1165 1166 /* 1167 * Mark it no longer busy, and put it on the active list. 1168 */ 1169 vm_page_activate(dst_m); 1170 vm_page_wakeup(dst_m); 1171 } 1172 } 1173 1174 1175 /* 1176 * This routine checks around the requested page for other pages that 1177 * might be able to be faulted in. This routine brackets the viable 1178 * pages for the pages to be paged in. 1179 * 1180 * Inputs: 1181 * m, rbehind, rahead 1182 * 1183 * Outputs: 1184 * marray (array of vm_page_t), reqpage (index of requested page) 1185 * 1186 * Return value: 1187 * number of pages in marray 1188 */ 1189 static int 1190 vm_fault_additional_pages(vm_page_t m, int rbehind, int rahead, 1191 vm_page_t *marray, int *reqpage) 1192 { 1193 int i,j; 1194 vm_object_t object; 1195 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1196 vm_page_t rtm; 1197 int cbehind, cahead; 1198 1199 object = m->object; 1200 pindex = m->pindex; 1201 1202 /* 1203 * we don't fault-ahead for device pager 1204 */ 1205 if (object->type == OBJT_DEVICE) { 1206 *reqpage = 0; 1207 marray[0] = m; 1208 return 1; 1209 } 1210 1211 /* 1212 * if the requested page is not available, then give up now 1213 */ 1214 1215 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1216 return 0; 1217 } 1218 1219 if ((cbehind == 0) && (cahead == 0)) { 1220 *reqpage = 0; 1221 marray[0] = m; 1222 return 1; 1223 } 1224 1225 if (rahead > cahead) { 1226 rahead = cahead; 1227 } 1228 1229 if (rbehind > cbehind) { 1230 rbehind = cbehind; 1231 } 1232 1233 /* 1234 * try to do any readahead that we might have free pages for. 1235 */ 1236 if ((rahead + rbehind) > 1237 ((vmstats.v_free_count + vmstats.v_cache_count) - vmstats.v_free_reserved)) { 1238 pagedaemon_wakeup(); 1239 marray[0] = m; 1240 *reqpage = 0; 1241 return 1; 1242 } 1243 1244 /* 1245 * scan backward for the read behind pages -- in memory 1246 * 1247 * Assume that if the page is not found an interrupt will not 1248 * create it. Theoretically interrupts can only remove (busy) 1249 * pages, not create new associations. 1250 */ 1251 if (pindex > 0) { 1252 if (rbehind > pindex) { 1253 rbehind = pindex; 1254 startpindex = 0; 1255 } else { 1256 startpindex = pindex - rbehind; 1257 } 1258 1259 crit_enter(); 1260 for ( tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) { 1261 if (vm_page_lookup( object, tpindex)) { 1262 startpindex = tpindex + 1; 1263 break; 1264 } 1265 if (tpindex == 0) 1266 break; 1267 } 1268 1269 for(i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) { 1270 1271 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1272 if (rtm == NULL) { 1273 crit_exit(); 1274 for (j = 0; j < i; j++) { 1275 vm_page_free(marray[j]); 1276 } 1277 marray[0] = m; 1278 *reqpage = 0; 1279 return 1; 1280 } 1281 1282 marray[i] = rtm; 1283 } 1284 crit_exit(); 1285 } else { 1286 startpindex = 0; 1287 i = 0; 1288 } 1289 1290 marray[i] = m; 1291 /* page offset of the required page */ 1292 *reqpage = i; 1293 1294 tpindex = pindex + 1; 1295 i++; 1296 1297 /* 1298 * scan forward for the read ahead pages 1299 */ 1300 endpindex = tpindex + rahead; 1301 if (endpindex > object->size) 1302 endpindex = object->size; 1303 1304 crit_enter(); 1305 for( ; tpindex < endpindex; i++, tpindex++) { 1306 1307 if (vm_page_lookup(object, tpindex)) { 1308 break; 1309 } 1310 1311 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL); 1312 if (rtm == NULL) { 1313 break; 1314 } 1315 1316 marray[i] = rtm; 1317 } 1318 crit_exit(); 1319 1320 /* return number of bytes of pages */ 1321 return i; 1322 } 1323