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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("$FreeBSD$"); 76 77 #include "opt_ktrace.h" 78 #include "opt_vm.h" 79 80 #include <sys/param.h> 81 #include <sys/systm.h> 82 #include <sys/kernel.h> 83 #include <sys/lock.h> 84 #include <sys/mutex.h> 85 #include <sys/proc.h> 86 #include <sys/resourcevar.h> 87 #include <sys/sysctl.h> 88 #include <sys/vmmeter.h> 89 #include <sys/vnode.h> 90 #ifdef KTRACE 91 #include <sys/ktrace.h> 92 #endif 93 94 #include <vm/vm.h> 95 #include <vm/vm_param.h> 96 #include <vm/pmap.h> 97 #include <vm/vm_map.h> 98 #include <vm/vm_object.h> 99 #include <vm/vm_page.h> 100 #include <vm/vm_pageout.h> 101 #include <vm/vm_kern.h> 102 #include <vm/vm_pager.h> 103 #include <vm/vnode_pager.h> 104 #include <vm/vm_extern.h> 105 106 #include <sys/mount.h> /* XXX Temporary for VFS_LOCK_GIANT() */ 107 108 #define PFBAK 4 109 #define PFFOR 4 110 #define PAGEORDER_SIZE (PFBAK+PFFOR) 111 112 static int prefault_pageorder[] = { 113 -1 * PAGE_SIZE, 1 * PAGE_SIZE, 114 -2 * PAGE_SIZE, 2 * PAGE_SIZE, 115 -3 * PAGE_SIZE, 3 * PAGE_SIZE, 116 -4 * PAGE_SIZE, 4 * PAGE_SIZE 117 }; 118 119 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 120 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t); 121 #ifdef KTRACE 122 static int vm_fault_traced(vm_map_t, vm_offset_t, vm_prot_t, int); 123 #endif 124 125 #define VM_FAULT_READ_AHEAD 8 126 #define VM_FAULT_READ_BEHIND 7 127 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1) 128 129 struct faultstate { 130 vm_page_t m; 131 vm_object_t object; 132 vm_pindex_t pindex; 133 vm_page_t first_m; 134 vm_object_t first_object; 135 vm_pindex_t first_pindex; 136 vm_map_t map; 137 vm_map_entry_t entry; 138 int lookup_still_valid; 139 struct vnode *vp; 140 int vfslocked; 141 }; 142 143 static inline void 144 release_page(struct faultstate *fs) 145 { 146 147 vm_page_wakeup(fs->m); 148 vm_page_lock_queues(); 149 vm_page_deactivate(fs->m); 150 vm_page_unlock_queues(); 151 fs->m = NULL; 152 } 153 154 static inline void 155 unlock_map(struct faultstate *fs) 156 { 157 158 if (fs->lookup_still_valid) { 159 vm_map_lookup_done(fs->map, fs->entry); 160 fs->lookup_still_valid = FALSE; 161 } 162 } 163 164 static void 165 unlock_and_deallocate(struct faultstate *fs) 166 { 167 168 vm_object_pip_wakeup(fs->object); 169 VM_OBJECT_UNLOCK(fs->object); 170 if (fs->object != fs->first_object) { 171 VM_OBJECT_LOCK(fs->first_object); 172 vm_page_lock_queues(); 173 vm_page_free(fs->first_m); 174 vm_page_unlock_queues(); 175 vm_object_pip_wakeup(fs->first_object); 176 VM_OBJECT_UNLOCK(fs->first_object); 177 fs->first_m = NULL; 178 } 179 vm_object_deallocate(fs->first_object); 180 unlock_map(fs); 181 if (fs->vp != NULL) { 182 vput(fs->vp); 183 fs->vp = NULL; 184 } 185 VFS_UNLOCK_GIANT(fs->vfslocked); 186 fs->vfslocked = 0; 187 } 188 189 /* 190 * TRYPAGER - used by vm_fault to calculate whether the pager for the 191 * current object *might* contain the page. 192 * 193 * default objects are zero-fill, there is no real pager. 194 */ 195 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 196 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) 197 198 /* 199 * vm_fault: 200 * 201 * Handle a page fault occurring at the given address, 202 * requiring the given permissions, in the map specified. 203 * If successful, the page is inserted into the 204 * associated physical map. 205 * 206 * NOTE: the given address should be truncated to the 207 * proper page address. 208 * 209 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 210 * a standard error specifying why the fault is fatal is returned. 211 * 212 * 213 * The map in question must be referenced, and remains so. 214 * Caller may hold no locks. 215 */ 216 int 217 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 218 int fault_flags) 219 #ifdef KTRACE 220 { 221 struct thread *td; 222 int result; 223 224 td = curthread; 225 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 226 ktrfault(vaddr, fault_type); 227 result = vm_fault_traced(map, vaddr, fault_type, fault_flags); 228 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 229 ktrfaultend(result); 230 return (result); 231 } 232 233 int 234 vm_fault_traced(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 235 int fault_flags) 236 #endif 237 { 238 vm_prot_t prot; 239 int is_first_object_locked, result; 240 boolean_t are_queues_locked, growstack, wired; 241 int map_generation; 242 vm_object_t next_object; 243 vm_page_t marray[VM_FAULT_READ], mt, mt_prev; 244 int hardfault; 245 int faultcount, ahead, behind, alloc_req; 246 struct faultstate fs; 247 struct vnode *vp; 248 int locked, error; 249 250 if ((curthread->td_pflags & TDP_NOFAULTING) != 0) 251 return (KERN_PROTECTION_FAILURE); 252 253 hardfault = 0; 254 growstack = TRUE; 255 PCPU_INC(cnt.v_vm_faults); 256 fs.vp = NULL; 257 fs.vfslocked = 0; 258 faultcount = behind = 0; 259 260 RetryFault:; 261 262 /* 263 * Find the backing store object and offset into it to begin the 264 * search. 265 */ 266 fs.map = map; 267 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 268 &fs.first_object, &fs.first_pindex, &prot, &wired); 269 if (result != KERN_SUCCESS) { 270 if (result != KERN_PROTECTION_FAILURE || 271 (fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) { 272 if (growstack && result == KERN_INVALID_ADDRESS && 273 map != kernel_map && curproc != NULL) { 274 result = vm_map_growstack(curproc, vaddr); 275 if (result != KERN_SUCCESS) 276 return (KERN_FAILURE); 277 growstack = FALSE; 278 goto RetryFault; 279 } 280 return (result); 281 } 282 283 /* 284 * If we are user-wiring a r/w segment, and it is COW, then 285 * we need to do the COW operation. Note that we don't COW 286 * currently RO sections now, because it is NOT desirable 287 * to COW .text. We simply keep .text from ever being COW'ed 288 * and take the heat that one cannot debug wired .text sections. 289 */ 290 result = vm_map_lookup(&fs.map, vaddr, 291 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE, 292 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired); 293 if (result != KERN_SUCCESS) 294 return (result); 295 296 /* 297 * If we don't COW now, on a user wire, the user will never 298 * be able to write to the mapping. If we don't make this 299 * restriction, the bookkeeping would be nearly impossible. 300 * 301 * XXX The following assignment modifies the map without 302 * holding a write lock on it. 303 */ 304 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 305 fs.entry->max_protection &= ~VM_PROT_WRITE; 306 } 307 308 map_generation = fs.map->timestamp; 309 310 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 311 panic("vm_fault: fault on nofault entry, addr: %lx", 312 (u_long)vaddr); 313 } 314 315 /* 316 * Make a reference to this object to prevent its disposal while we 317 * are messing with it. Once we have the reference, the map is free 318 * to be diddled. Since objects reference their shadows (and copies), 319 * they will stay around as well. 320 * 321 * Bump the paging-in-progress count to prevent size changes (e.g. 322 * truncation operations) during I/O. This must be done after 323 * obtaining the vnode lock in order to avoid possible deadlocks. 324 */ 325 VM_OBJECT_LOCK(fs.first_object); 326 vm_object_reference_locked(fs.first_object); 327 vm_object_pip_add(fs.first_object, 1); 328 329 fs.lookup_still_valid = TRUE; 330 331 if (wired) 332 fault_type = prot; 333 334 fs.first_m = NULL; 335 336 /* 337 * Search for the page at object/offset. 338 */ 339 fs.object = fs.first_object; 340 fs.pindex = fs.first_pindex; 341 while (TRUE) { 342 /* 343 * If the object is dead, we stop here 344 */ 345 if (fs.object->flags & OBJ_DEAD) { 346 unlock_and_deallocate(&fs); 347 return (KERN_PROTECTION_FAILURE); 348 } 349 350 /* 351 * See if page is resident 352 */ 353 fs.m = vm_page_lookup(fs.object, fs.pindex); 354 if (fs.m != NULL) { 355 /* 356 * check for page-based copy on write. 357 * We check fs.object == fs.first_object so 358 * as to ensure the legacy COW mechanism is 359 * used when the page in question is part of 360 * a shadow object. Otherwise, vm_page_cowfault() 361 * removes the page from the backing object, 362 * which is not what we want. 363 */ 364 vm_page_lock_queues(); 365 if ((fs.m->cow) && 366 (fault_type & VM_PROT_WRITE) && 367 (fs.object == fs.first_object)) { 368 vm_page_cowfault(fs.m); 369 vm_page_unlock_queues(); 370 unlock_and_deallocate(&fs); 371 goto RetryFault; 372 } 373 374 /* 375 * Wait/Retry if the page is busy. We have to do this 376 * if the page is busy via either VPO_BUSY or 377 * vm_page_t->busy because the vm_pager may be using 378 * vm_page_t->busy for pageouts ( and even pageins if 379 * it is the vnode pager ), and we could end up trying 380 * to pagein and pageout the same page simultaneously. 381 * 382 * We can theoretically allow the busy case on a read 383 * fault if the page is marked valid, but since such 384 * pages are typically already pmap'd, putting that 385 * special case in might be more effort then it is 386 * worth. We cannot under any circumstances mess 387 * around with a vm_page_t->busy page except, perhaps, 388 * to pmap it. 389 */ 390 if ((fs.m->oflags & VPO_BUSY) || fs.m->busy) { 391 vm_page_unlock_queues(); 392 if (fs.object != fs.first_object) { 393 if (!VM_OBJECT_TRYLOCK( 394 fs.first_object)) { 395 VM_OBJECT_UNLOCK(fs.object); 396 VM_OBJECT_LOCK(fs.first_object); 397 VM_OBJECT_LOCK(fs.object); 398 } 399 vm_page_lock_queues(); 400 vm_page_free(fs.first_m); 401 vm_page_unlock_queues(); 402 vm_object_pip_wakeup(fs.first_object); 403 VM_OBJECT_UNLOCK(fs.first_object); 404 fs.first_m = NULL; 405 } 406 unlock_map(&fs); 407 if (fs.m == vm_page_lookup(fs.object, 408 fs.pindex)) { 409 vm_page_sleep_if_busy(fs.m, TRUE, 410 "vmpfw"); 411 } 412 vm_object_pip_wakeup(fs.object); 413 VM_OBJECT_UNLOCK(fs.object); 414 PCPU_INC(cnt.v_intrans); 415 vm_object_deallocate(fs.first_object); 416 goto RetryFault; 417 } 418 vm_pageq_remove(fs.m); 419 vm_page_unlock_queues(); 420 421 /* 422 * Mark page busy for other processes, and the 423 * pagedaemon. If it still isn't completely valid 424 * (readable), jump to readrest, else break-out ( we 425 * found the page ). 426 */ 427 vm_page_busy(fs.m); 428 if (fs.m->valid != VM_PAGE_BITS_ALL) 429 goto readrest; 430 break; 431 } 432 433 /* 434 * Page is not resident, If this is the search termination 435 * or the pager might contain the page, allocate a new page. 436 */ 437 if (TRYPAGER || fs.object == fs.first_object) { 438 if (fs.pindex >= fs.object->size) { 439 unlock_and_deallocate(&fs); 440 return (KERN_PROTECTION_FAILURE); 441 } 442 443 /* 444 * Allocate a new page for this object/offset pair. 445 * 446 * Unlocked read of the p_flag is harmless. At 447 * worst, the P_KILLED might be not observed 448 * there, and allocation can fail, causing 449 * restart and new reading of the p_flag. 450 */ 451 fs.m = NULL; 452 if (!vm_page_count_severe() || P_KILLED(curproc)) { 453 #if VM_NRESERVLEVEL > 0 454 if ((fs.object->flags & OBJ_COLORED) == 0) { 455 fs.object->flags |= OBJ_COLORED; 456 fs.object->pg_color = atop(vaddr) - 457 fs.pindex; 458 } 459 #endif 460 alloc_req = P_KILLED(curproc) ? 461 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 462 if (fs.object->type != OBJT_VNODE && 463 fs.object->backing_object == NULL) 464 alloc_req |= VM_ALLOC_ZERO; 465 fs.m = vm_page_alloc(fs.object, fs.pindex, 466 alloc_req); 467 } 468 if (fs.m == NULL) { 469 unlock_and_deallocate(&fs); 470 VM_WAITPFAULT; 471 goto RetryFault; 472 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 473 break; 474 } 475 476 readrest: 477 /* 478 * We have found a valid page or we have allocated a new page. 479 * The page thus may not be valid or may not be entirely 480 * valid. 481 * 482 * Attempt to fault-in the page if there is a chance that the 483 * pager has it, and potentially fault in additional pages 484 * at the same time. 485 */ 486 if (TRYPAGER) { 487 int rv; 488 int reqpage = 0; 489 u_char behavior = vm_map_entry_behavior(fs.entry); 490 491 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 492 P_KILLED(curproc)) { 493 ahead = 0; 494 behind = 0; 495 } else { 496 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT; 497 if (behind > VM_FAULT_READ_BEHIND) 498 behind = VM_FAULT_READ_BEHIND; 499 500 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1; 501 if (ahead > VM_FAULT_READ_AHEAD) 502 ahead = VM_FAULT_READ_AHEAD; 503 } 504 is_first_object_locked = FALSE; 505 if ((behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 506 (behavior != MAP_ENTRY_BEHAV_RANDOM && 507 fs.pindex >= fs.entry->lastr && 508 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) && 509 (fs.first_object == fs.object || 510 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object))) && 511 fs.first_object->type != OBJT_DEVICE && 512 fs.first_object->type != OBJT_PHYS && 513 fs.first_object->type != OBJT_SG) { 514 vm_pindex_t firstpindex; 515 516 if (fs.first_pindex < 2 * VM_FAULT_READ) 517 firstpindex = 0; 518 else 519 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ; 520 mt = fs.first_object != fs.object ? 521 fs.first_m : fs.m; 522 KASSERT(mt != NULL, ("vm_fault: missing mt")); 523 KASSERT((mt->oflags & VPO_BUSY) != 0, 524 ("vm_fault: mt %p not busy", mt)); 525 mt_prev = vm_page_prev(mt); 526 527 are_queues_locked = FALSE; 528 /* 529 * note: partially valid pages cannot be 530 * included in the lookahead - NFS piecemeal 531 * writes will barf on it badly. 532 */ 533 while ((mt = mt_prev) != NULL && 534 mt->pindex >= firstpindex && 535 mt->valid == VM_PAGE_BITS_ALL) { 536 mt_prev = vm_page_prev(mt); 537 if (mt->busy || 538 (mt->oflags & VPO_BUSY)) 539 continue; 540 if (!are_queues_locked) { 541 are_queues_locked = TRUE; 542 vm_page_lock_queues(); 543 } 544 if (mt->hold_count || 545 mt->wire_count) 546 continue; 547 pmap_remove_all(mt); 548 if (mt->dirty) { 549 vm_page_deactivate(mt); 550 } else { 551 vm_page_cache(mt); 552 } 553 } 554 if (are_queues_locked) 555 vm_page_unlock_queues(); 556 ahead += behind; 557 behind = 0; 558 } 559 if (is_first_object_locked) 560 VM_OBJECT_UNLOCK(fs.first_object); 561 562 /* 563 * Call the pager to retrieve the data, if any, after 564 * releasing the lock on the map. We hold a ref on 565 * fs.object and the pages are VPO_BUSY'd. 566 */ 567 unlock_map(&fs); 568 569 vnode_lock: 570 if (fs.object->type == OBJT_VNODE) { 571 vp = fs.object->handle; 572 if (vp == fs.vp) 573 goto vnode_locked; 574 else if (fs.vp != NULL) { 575 vput(fs.vp); 576 fs.vp = NULL; 577 } 578 locked = VOP_ISLOCKED(vp); 579 580 if (VFS_NEEDSGIANT(vp->v_mount) && !fs.vfslocked) { 581 fs.vfslocked = 1; 582 if (!mtx_trylock(&Giant)) { 583 VM_OBJECT_UNLOCK(fs.object); 584 mtx_lock(&Giant); 585 VM_OBJECT_LOCK(fs.object); 586 goto vnode_lock; 587 } 588 } 589 if (locked != LK_EXCLUSIVE) 590 locked = LK_SHARED; 591 /* Do not sleep for vnode lock while fs.m is busy */ 592 error = vget(vp, locked | LK_CANRECURSE | 593 LK_NOWAIT, curthread); 594 if (error != 0) { 595 int vfslocked; 596 597 vfslocked = fs.vfslocked; 598 fs.vfslocked = 0; /* Keep Giant */ 599 vhold(vp); 600 release_page(&fs); 601 unlock_and_deallocate(&fs); 602 error = vget(vp, locked | LK_RETRY | 603 LK_CANRECURSE, curthread); 604 vdrop(vp); 605 fs.vp = vp; 606 fs.vfslocked = vfslocked; 607 KASSERT(error == 0, 608 ("vm_fault: vget failed")); 609 goto RetryFault; 610 } 611 fs.vp = vp; 612 } 613 vnode_locked: 614 KASSERT(fs.vp == NULL || !fs.map->system_map, 615 ("vm_fault: vnode-backed object mapped by system map")); 616 617 /* 618 * now we find out if any other pages should be paged 619 * in at this time this routine checks to see if the 620 * pages surrounding this fault reside in the same 621 * object as the page for this fault. If they do, 622 * then they are faulted in also into the object. The 623 * array "marray" returned contains an array of 624 * vm_page_t structs where one of them is the 625 * vm_page_t passed to the routine. The reqpage 626 * return value is the index into the marray for the 627 * vm_page_t passed to the routine. 628 * 629 * fs.m plus the additional pages are VPO_BUSY'd. 630 */ 631 faultcount = vm_fault_additional_pages( 632 fs.m, behind, ahead, marray, &reqpage); 633 634 rv = faultcount ? 635 vm_pager_get_pages(fs.object, marray, faultcount, 636 reqpage) : VM_PAGER_FAIL; 637 638 if (rv == VM_PAGER_OK) { 639 /* 640 * Found the page. Leave it busy while we play 641 * with it. 642 */ 643 644 /* 645 * Relookup in case pager changed page. Pager 646 * is responsible for disposition of old page 647 * if moved. 648 */ 649 fs.m = vm_page_lookup(fs.object, fs.pindex); 650 if (!fs.m) { 651 unlock_and_deallocate(&fs); 652 goto RetryFault; 653 } 654 655 hardfault++; 656 break; /* break to PAGE HAS BEEN FOUND */ 657 } 658 /* 659 * Remove the bogus page (which does not exist at this 660 * object/offset); before doing so, we must get back 661 * our object lock to preserve our invariant. 662 * 663 * Also wake up any other process that may want to bring 664 * in this page. 665 * 666 * If this is the top-level object, we must leave the 667 * busy page to prevent another process from rushing 668 * past us, and inserting the page in that object at 669 * the same time that we are. 670 */ 671 if (rv == VM_PAGER_ERROR) 672 printf("vm_fault: pager read error, pid %d (%s)\n", 673 curproc->p_pid, curproc->p_comm); 674 /* 675 * Data outside the range of the pager or an I/O error 676 */ 677 /* 678 * XXX - the check for kernel_map is a kludge to work 679 * around having the machine panic on a kernel space 680 * fault w/ I/O error. 681 */ 682 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 683 (rv == VM_PAGER_BAD)) { 684 vm_page_lock_queues(); 685 vm_page_free(fs.m); 686 vm_page_unlock_queues(); 687 fs.m = NULL; 688 unlock_and_deallocate(&fs); 689 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 690 } 691 if (fs.object != fs.first_object) { 692 vm_page_lock_queues(); 693 vm_page_free(fs.m); 694 vm_page_unlock_queues(); 695 fs.m = NULL; 696 /* 697 * XXX - we cannot just fall out at this 698 * point, m has been freed and is invalid! 699 */ 700 } 701 } 702 703 /* 704 * We get here if the object has default pager (or unwiring) 705 * or the pager doesn't have the page. 706 */ 707 if (fs.object == fs.first_object) 708 fs.first_m = fs.m; 709 710 /* 711 * Move on to the next object. Lock the next object before 712 * unlocking the current one. 713 */ 714 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 715 next_object = fs.object->backing_object; 716 if (next_object == NULL) { 717 /* 718 * If there's no object left, fill the page in the top 719 * object with zeros. 720 */ 721 if (fs.object != fs.first_object) { 722 vm_object_pip_wakeup(fs.object); 723 VM_OBJECT_UNLOCK(fs.object); 724 725 fs.object = fs.first_object; 726 fs.pindex = fs.first_pindex; 727 fs.m = fs.first_m; 728 VM_OBJECT_LOCK(fs.object); 729 } 730 fs.first_m = NULL; 731 732 /* 733 * Zero the page if necessary and mark it valid. 734 */ 735 if ((fs.m->flags & PG_ZERO) == 0) { 736 pmap_zero_page(fs.m); 737 } else { 738 PCPU_INC(cnt.v_ozfod); 739 } 740 PCPU_INC(cnt.v_zfod); 741 fs.m->valid = VM_PAGE_BITS_ALL; 742 break; /* break to PAGE HAS BEEN FOUND */ 743 } else { 744 KASSERT(fs.object != next_object, 745 ("object loop %p", next_object)); 746 VM_OBJECT_LOCK(next_object); 747 vm_object_pip_add(next_object, 1); 748 if (fs.object != fs.first_object) 749 vm_object_pip_wakeup(fs.object); 750 VM_OBJECT_UNLOCK(fs.object); 751 fs.object = next_object; 752 } 753 } 754 755 KASSERT((fs.m->oflags & VPO_BUSY) != 0, 756 ("vm_fault: not busy after main loop")); 757 758 /* 759 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 760 * is held.] 761 */ 762 763 /* 764 * If the page is being written, but isn't already owned by the 765 * top-level object, we have to copy it into a new page owned by the 766 * top-level object. 767 */ 768 if (fs.object != fs.first_object) { 769 /* 770 * We only really need to copy if we want to write it. 771 */ 772 if (fault_type & VM_PROT_WRITE) { 773 /* 774 * This allows pages to be virtually copied from a 775 * backing_object into the first_object, where the 776 * backing object has no other refs to it, and cannot 777 * gain any more refs. Instead of a bcopy, we just 778 * move the page from the backing object to the 779 * first object. Note that we must mark the page 780 * dirty in the first object so that it will go out 781 * to swap when needed. 782 */ 783 is_first_object_locked = FALSE; 784 if ( 785 /* 786 * Only one shadow object 787 */ 788 (fs.object->shadow_count == 1) && 789 /* 790 * No COW refs, except us 791 */ 792 (fs.object->ref_count == 1) && 793 /* 794 * No one else can look this object up 795 */ 796 (fs.object->handle == NULL) && 797 /* 798 * No other ways to look the object up 799 */ 800 ((fs.object->type == OBJT_DEFAULT) || 801 (fs.object->type == OBJT_SWAP)) && 802 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) && 803 /* 804 * We don't chase down the shadow chain 805 */ 806 fs.object == fs.first_object->backing_object) { 807 vm_page_lock_queues(); 808 /* 809 * get rid of the unnecessary page 810 */ 811 vm_page_free(fs.first_m); 812 /* 813 * grab the page and put it into the 814 * process'es object. The page is 815 * automatically made dirty. 816 */ 817 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 818 vm_page_unlock_queues(); 819 vm_page_busy(fs.m); 820 fs.first_m = fs.m; 821 fs.m = NULL; 822 PCPU_INC(cnt.v_cow_optim); 823 } else { 824 /* 825 * Oh, well, lets copy it. 826 */ 827 pmap_copy_page(fs.m, fs.first_m); 828 fs.first_m->valid = VM_PAGE_BITS_ALL; 829 } 830 if (fs.m) { 831 /* 832 * We no longer need the old page or object. 833 */ 834 release_page(&fs); 835 } 836 /* 837 * fs.object != fs.first_object due to above 838 * conditional 839 */ 840 vm_object_pip_wakeup(fs.object); 841 VM_OBJECT_UNLOCK(fs.object); 842 /* 843 * Only use the new page below... 844 */ 845 fs.object = fs.first_object; 846 fs.pindex = fs.first_pindex; 847 fs.m = fs.first_m; 848 if (!is_first_object_locked) 849 VM_OBJECT_LOCK(fs.object); 850 PCPU_INC(cnt.v_cow_faults); 851 curthread->td_cow++; 852 } else { 853 prot &= ~VM_PROT_WRITE; 854 } 855 } 856 857 /* 858 * We must verify that the maps have not changed since our last 859 * lookup. 860 */ 861 if (!fs.lookup_still_valid) { 862 vm_object_t retry_object; 863 vm_pindex_t retry_pindex; 864 vm_prot_t retry_prot; 865 866 if (!vm_map_trylock_read(fs.map)) { 867 release_page(&fs); 868 unlock_and_deallocate(&fs); 869 goto RetryFault; 870 } 871 fs.lookup_still_valid = TRUE; 872 if (fs.map->timestamp != map_generation) { 873 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 874 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 875 876 /* 877 * If we don't need the page any longer, put it on the inactive 878 * list (the easiest thing to do here). If no one needs it, 879 * pageout will grab it eventually. 880 */ 881 if (result != KERN_SUCCESS) { 882 release_page(&fs); 883 unlock_and_deallocate(&fs); 884 885 /* 886 * If retry of map lookup would have blocked then 887 * retry fault from start. 888 */ 889 if (result == KERN_FAILURE) 890 goto RetryFault; 891 return (result); 892 } 893 if ((retry_object != fs.first_object) || 894 (retry_pindex != fs.first_pindex)) { 895 release_page(&fs); 896 unlock_and_deallocate(&fs); 897 goto RetryFault; 898 } 899 900 /* 901 * Check whether the protection has changed or the object has 902 * been copied while we left the map unlocked. Changing from 903 * read to write permission is OK - we leave the page 904 * write-protected, and catch the write fault. Changing from 905 * write to read permission means that we can't mark the page 906 * write-enabled after all. 907 */ 908 prot &= retry_prot; 909 } 910 } 911 /* 912 * If the page was filled by a pager, update the map entry's 913 * last read offset. Since the pager does not return the 914 * actual set of pages that it read, this update is based on 915 * the requested set. Typically, the requested and actual 916 * sets are the same. 917 * 918 * XXX The following assignment modifies the map 919 * without holding a write lock on it. 920 */ 921 if (hardfault) 922 fs.entry->lastr = fs.pindex + faultcount - behind; 923 924 if (prot & VM_PROT_WRITE) { 925 vm_object_set_writeable_dirty(fs.object); 926 927 /* 928 * If the fault is a write, we know that this page is being 929 * written NOW so dirty it explicitly to save on 930 * pmap_is_modified() calls later. 931 * 932 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 933 * if the page is already dirty to prevent data written with 934 * the expectation of being synced from not being synced. 935 * Likewise if this entry does not request NOSYNC then make 936 * sure the page isn't marked NOSYNC. Applications sharing 937 * data should use the same flags to avoid ping ponging. 938 * 939 * Also tell the backing pager, if any, that it should remove 940 * any swap backing since the page is now dirty. 941 */ 942 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 943 if (fs.m->dirty == 0) 944 fs.m->oflags |= VPO_NOSYNC; 945 } else { 946 fs.m->oflags &= ~VPO_NOSYNC; 947 } 948 if (fault_flags & VM_FAULT_DIRTY) { 949 vm_page_dirty(fs.m); 950 vm_pager_page_unswapped(fs.m); 951 } 952 } 953 954 /* 955 * Page had better still be busy 956 */ 957 KASSERT(fs.m->oflags & VPO_BUSY, 958 ("vm_fault: page %p not busy!", fs.m)); 959 /* 960 * Page must be completely valid or it is not fit to 961 * map into user space. vm_pager_get_pages() ensures this. 962 */ 963 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 964 ("vm_fault: page %p partially invalid", fs.m)); 965 VM_OBJECT_UNLOCK(fs.object); 966 967 /* 968 * Put this page into the physical map. We had to do the unlock above 969 * because pmap_enter() may sleep. We don't put the page 970 * back on the active queue until later so that the pageout daemon 971 * won't find it (yet). 972 */ 973 pmap_enter(fs.map->pmap, vaddr, fault_type, fs.m, prot, wired); 974 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 975 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry); 976 } 977 VM_OBJECT_LOCK(fs.object); 978 vm_page_lock_queues(); 979 vm_page_flag_set(fs.m, PG_REFERENCED); 980 981 /* 982 * If the page is not wired down, then put it where the pageout daemon 983 * can find it. 984 */ 985 if (fault_flags & VM_FAULT_WIRE_MASK) { 986 if (wired) 987 vm_page_wire(fs.m); 988 else 989 vm_page_unwire(fs.m, 1); 990 } else { 991 vm_page_activate(fs.m); 992 } 993 vm_page_unlock_queues(); 994 vm_page_wakeup(fs.m); 995 996 /* 997 * Unlock everything, and return 998 */ 999 unlock_and_deallocate(&fs); 1000 if (hardfault) 1001 curthread->td_ru.ru_majflt++; 1002 else 1003 curthread->td_ru.ru_minflt++; 1004 1005 return (KERN_SUCCESS); 1006 } 1007 1008 /* 1009 * vm_fault_prefault provides a quick way of clustering 1010 * pagefaults into a processes address space. It is a "cousin" 1011 * of vm_map_pmap_enter, except it runs at page fault time instead 1012 * of mmap time. 1013 */ 1014 static void 1015 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry) 1016 { 1017 int i; 1018 vm_offset_t addr, starta; 1019 vm_pindex_t pindex; 1020 vm_page_t m; 1021 vm_object_t object; 1022 1023 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1024 return; 1025 1026 object = entry->object.vm_object; 1027 1028 starta = addra - PFBAK * PAGE_SIZE; 1029 if (starta < entry->start) { 1030 starta = entry->start; 1031 } else if (starta > addra) { 1032 starta = 0; 1033 } 1034 1035 for (i = 0; i < PAGEORDER_SIZE; i++) { 1036 vm_object_t backing_object, lobject; 1037 1038 addr = addra + prefault_pageorder[i]; 1039 if (addr > addra + (PFFOR * PAGE_SIZE)) 1040 addr = 0; 1041 1042 if (addr < starta || addr >= entry->end) 1043 continue; 1044 1045 if (!pmap_is_prefaultable(pmap, addr)) 1046 continue; 1047 1048 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1049 lobject = object; 1050 VM_OBJECT_LOCK(lobject); 1051 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1052 lobject->type == OBJT_DEFAULT && 1053 (backing_object = lobject->backing_object) != NULL) { 1054 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1055 0, ("vm_fault_prefault: unaligned object offset")); 1056 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1057 VM_OBJECT_LOCK(backing_object); 1058 VM_OBJECT_UNLOCK(lobject); 1059 lobject = backing_object; 1060 } 1061 /* 1062 * give-up when a page is not in memory 1063 */ 1064 if (m == NULL) { 1065 VM_OBJECT_UNLOCK(lobject); 1066 break; 1067 } 1068 if (m->valid == VM_PAGE_BITS_ALL && 1069 (m->flags & PG_FICTITIOUS) == 0) { 1070 vm_page_lock_queues(); 1071 pmap_enter_quick(pmap, addr, m, entry->protection); 1072 vm_page_unlock_queues(); 1073 } 1074 VM_OBJECT_UNLOCK(lobject); 1075 } 1076 } 1077 1078 /* 1079 * vm_fault_quick: 1080 * 1081 * Ensure that the requested virtual address, which may be in userland, 1082 * is valid. Fault-in the page if necessary. Return -1 on failure. 1083 */ 1084 int 1085 vm_fault_quick(caddr_t v, int prot) 1086 { 1087 int r; 1088 1089 if (prot & VM_PROT_WRITE) 1090 r = subyte(v, fubyte(v)); 1091 else 1092 r = fubyte(v); 1093 return(r); 1094 } 1095 1096 /* 1097 * vm_fault_wire: 1098 * 1099 * Wire down a range of virtual addresses in a map. 1100 */ 1101 int 1102 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1103 boolean_t user_wire, boolean_t fictitious) 1104 { 1105 vm_offset_t va; 1106 int rv; 1107 1108 /* 1109 * We simulate a fault to get the page and enter it in the physical 1110 * map. For user wiring, we only ask for read access on currently 1111 * read-only sections. 1112 */ 1113 for (va = start; va < end; va += PAGE_SIZE) { 1114 rv = vm_fault(map, va, 1115 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE, 1116 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING); 1117 if (rv) { 1118 if (va != start) 1119 vm_fault_unwire(map, start, va, fictitious); 1120 return (rv); 1121 } 1122 } 1123 return (KERN_SUCCESS); 1124 } 1125 1126 /* 1127 * vm_fault_unwire: 1128 * 1129 * Unwire a range of virtual addresses in a map. 1130 */ 1131 void 1132 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1133 boolean_t fictitious) 1134 { 1135 vm_paddr_t pa; 1136 vm_offset_t va; 1137 pmap_t pmap; 1138 1139 pmap = vm_map_pmap(map); 1140 1141 /* 1142 * Since the pages are wired down, we must be able to get their 1143 * mappings from the physical map system. 1144 */ 1145 for (va = start; va < end; va += PAGE_SIZE) { 1146 pa = pmap_extract(pmap, va); 1147 if (pa != 0) { 1148 pmap_change_wiring(pmap, va, FALSE); 1149 if (!fictitious) { 1150 vm_page_lock_queues(); 1151 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1152 vm_page_unlock_queues(); 1153 } 1154 } 1155 } 1156 } 1157 1158 /* 1159 * Routine: 1160 * vm_fault_copy_entry 1161 * Function: 1162 * Create new shadow object backing dst_entry with private copy of 1163 * all underlying pages. When src_entry is equal to dst_entry, 1164 * function implements COW for wired-down map entry. Otherwise, 1165 * it forks wired entry into dst_map. 1166 * 1167 * In/out conditions: 1168 * The source and destination maps must be locked for write. 1169 * The source map entry must be wired down (or be a sharing map 1170 * entry corresponding to a main map entry that is wired down). 1171 */ 1172 void 1173 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1174 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1175 vm_ooffset_t *fork_charge) 1176 { 1177 vm_object_t backing_object, dst_object, object, src_object; 1178 vm_pindex_t dst_pindex, pindex, src_pindex; 1179 vm_prot_t access, prot; 1180 vm_offset_t vaddr; 1181 vm_page_t dst_m; 1182 vm_page_t src_m; 1183 boolean_t src_readonly, upgrade; 1184 1185 #ifdef lint 1186 src_map++; 1187 #endif /* lint */ 1188 1189 upgrade = src_entry == dst_entry; 1190 1191 src_object = src_entry->object.vm_object; 1192 src_pindex = OFF_TO_IDX(src_entry->offset); 1193 src_readonly = (src_entry->protection & VM_PROT_WRITE) == 0; 1194 1195 /* 1196 * Create the top-level object for the destination entry. (Doesn't 1197 * actually shadow anything - we copy the pages directly.) 1198 */ 1199 dst_object = vm_object_allocate(OBJT_DEFAULT, 1200 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1201 #if VM_NRESERVLEVEL > 0 1202 dst_object->flags |= OBJ_COLORED; 1203 dst_object->pg_color = atop(dst_entry->start); 1204 #endif 1205 1206 VM_OBJECT_LOCK(dst_object); 1207 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1208 ("vm_fault_copy_entry: vm_object not NULL")); 1209 dst_entry->object.vm_object = dst_object; 1210 dst_entry->offset = 0; 1211 dst_object->charge = dst_entry->end - dst_entry->start; 1212 if (fork_charge != NULL) { 1213 KASSERT(dst_entry->uip == NULL, 1214 ("vm_fault_copy_entry: leaked swp charge")); 1215 dst_object->uip = curthread->td_ucred->cr_ruidinfo; 1216 uihold(dst_object->uip); 1217 *fork_charge += dst_object->charge; 1218 } else { 1219 dst_object->uip = dst_entry->uip; 1220 dst_entry->uip = NULL; 1221 } 1222 access = prot = dst_entry->max_protection; 1223 /* 1224 * If not an upgrade, then enter the mappings in the pmap as 1225 * read and/or execute accesses. Otherwise, enter them as 1226 * write accesses. 1227 * 1228 * A writeable large page mapping is only created if all of 1229 * the constituent small page mappings are modified. Marking 1230 * PTEs as modified on inception allows promotion to happen 1231 * without taking potentially large number of soft faults. 1232 */ 1233 if (!upgrade) 1234 access &= ~VM_PROT_WRITE; 1235 1236 /* 1237 * Loop through all of the pages in the entry's range, copying each 1238 * one from the source object (it should be there) to the destination 1239 * object. 1240 */ 1241 for (vaddr = dst_entry->start, dst_pindex = 0; 1242 vaddr < dst_entry->end; 1243 vaddr += PAGE_SIZE, dst_pindex++) { 1244 1245 /* 1246 * Allocate a page in the destination object. 1247 */ 1248 do { 1249 dst_m = vm_page_alloc(dst_object, dst_pindex, 1250 VM_ALLOC_NORMAL); 1251 if (dst_m == NULL) { 1252 VM_OBJECT_UNLOCK(dst_object); 1253 VM_WAIT; 1254 VM_OBJECT_LOCK(dst_object); 1255 } 1256 } while (dst_m == NULL); 1257 1258 /* 1259 * Find the page in the source object, and copy it in. 1260 * (Because the source is wired down, the page will be in 1261 * memory.) 1262 */ 1263 VM_OBJECT_LOCK(src_object); 1264 object = src_object; 1265 pindex = src_pindex + dst_pindex; 1266 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1267 src_readonly && 1268 (backing_object = object->backing_object) != NULL) { 1269 /* 1270 * Allow fallback to backing objects if we are reading. 1271 */ 1272 VM_OBJECT_LOCK(backing_object); 1273 pindex += OFF_TO_IDX(object->backing_object_offset); 1274 VM_OBJECT_UNLOCK(object); 1275 object = backing_object; 1276 } 1277 if (src_m == NULL) 1278 panic("vm_fault_copy_wired: page missing"); 1279 pmap_copy_page(src_m, dst_m); 1280 VM_OBJECT_UNLOCK(object); 1281 dst_m->valid = VM_PAGE_BITS_ALL; 1282 VM_OBJECT_UNLOCK(dst_object); 1283 1284 /* 1285 * Enter it in the pmap. If a wired, copy-on-write 1286 * mapping is being replaced by a write-enabled 1287 * mapping, then wire that new mapping. 1288 */ 1289 pmap_enter(dst_map->pmap, vaddr, access, dst_m, prot, upgrade); 1290 1291 /* 1292 * Mark it no longer busy, and put it on the active list. 1293 */ 1294 VM_OBJECT_LOCK(dst_object); 1295 vm_page_lock_queues(); 1296 if (upgrade) { 1297 vm_page_unwire(src_m, 0); 1298 vm_page_wire(dst_m); 1299 } else 1300 vm_page_activate(dst_m); 1301 vm_page_unlock_queues(); 1302 vm_page_wakeup(dst_m); 1303 } 1304 VM_OBJECT_UNLOCK(dst_object); 1305 if (upgrade) { 1306 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1307 vm_object_deallocate(src_object); 1308 } 1309 } 1310 1311 1312 /* 1313 * This routine checks around the requested page for other pages that 1314 * might be able to be faulted in. This routine brackets the viable 1315 * pages for the pages to be paged in. 1316 * 1317 * Inputs: 1318 * m, rbehind, rahead 1319 * 1320 * Outputs: 1321 * marray (array of vm_page_t), reqpage (index of requested page) 1322 * 1323 * Return value: 1324 * number of pages in marray 1325 */ 1326 static int 1327 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1328 vm_page_t m; 1329 int rbehind; 1330 int rahead; 1331 vm_page_t *marray; 1332 int *reqpage; 1333 { 1334 int i,j; 1335 vm_object_t object; 1336 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1337 vm_page_t rtm; 1338 int cbehind, cahead; 1339 1340 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED); 1341 1342 object = m->object; 1343 pindex = m->pindex; 1344 cbehind = cahead = 0; 1345 1346 /* 1347 * if the requested page is not available, then give up now 1348 */ 1349 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1350 return 0; 1351 } 1352 1353 if ((cbehind == 0) && (cahead == 0)) { 1354 *reqpage = 0; 1355 marray[0] = m; 1356 return 1; 1357 } 1358 1359 if (rahead > cahead) { 1360 rahead = cahead; 1361 } 1362 1363 if (rbehind > cbehind) { 1364 rbehind = cbehind; 1365 } 1366 1367 /* 1368 * scan backward for the read behind pages -- in memory 1369 */ 1370 if (pindex > 0) { 1371 if (rbehind > pindex) { 1372 rbehind = pindex; 1373 startpindex = 0; 1374 } else { 1375 startpindex = pindex - rbehind; 1376 } 1377 1378 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1379 rtm->pindex >= startpindex) 1380 startpindex = rtm->pindex + 1; 1381 1382 /* tpindex is unsigned; beware of numeric underflow. */ 1383 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1384 tpindex < pindex; i++, tpindex--) { 1385 1386 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1387 VM_ALLOC_IFNOTCACHED); 1388 if (rtm == NULL) { 1389 /* 1390 * Shift the allocated pages to the 1391 * beginning of the array. 1392 */ 1393 for (j = 0; j < i; j++) { 1394 marray[j] = marray[j + tpindex + 1 - 1395 startpindex]; 1396 } 1397 break; 1398 } 1399 1400 marray[tpindex - startpindex] = rtm; 1401 } 1402 } else { 1403 startpindex = 0; 1404 i = 0; 1405 } 1406 1407 marray[i] = m; 1408 /* page offset of the required page */ 1409 *reqpage = i; 1410 1411 tpindex = pindex + 1; 1412 i++; 1413 1414 /* 1415 * scan forward for the read ahead pages 1416 */ 1417 endpindex = tpindex + rahead; 1418 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1419 endpindex = rtm->pindex; 1420 if (endpindex > object->size) 1421 endpindex = object->size; 1422 1423 for (; tpindex < endpindex; i++, tpindex++) { 1424 1425 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1426 VM_ALLOC_IFNOTCACHED); 1427 if (rtm == NULL) { 1428 break; 1429 } 1430 1431 marray[i] = rtm; 1432 } 1433 1434 /* return number of pages */ 1435 return i; 1436 } 1437 1438 /* 1439 * Block entry into the machine-independent layer's page fault handler by 1440 * the calling thread. Subsequent calls to vm_fault() by that thread will 1441 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1442 * spurious page faults. 1443 */ 1444 int 1445 vm_fault_disable_pagefaults(void) 1446 { 1447 1448 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1449 } 1450 1451 void 1452 vm_fault_enable_pagefaults(int save) 1453 { 1454 1455 curthread_pflags_restore(save); 1456 }
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