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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/8.1/sys/vm/vm_fault.c 207596 2010-05-04 05:14:43Z kib $"); 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 int vfslocked; 134 }; 135 136 static inline void 137 release_page(struct faultstate *fs) 138 { 139 140 vm_page_wakeup(fs->m); 141 vm_page_lock_queues(); 142 vm_page_deactivate(fs->m); 143 vm_page_unlock_queues(); 144 fs->m = NULL; 145 } 146 147 static inline void 148 unlock_map(struct faultstate *fs) 149 { 150 151 if (fs->lookup_still_valid) { 152 vm_map_lookup_done(fs->map, fs->entry); 153 fs->lookup_still_valid = FALSE; 154 } 155 } 156 157 static void 158 unlock_and_deallocate(struct faultstate *fs) 159 { 160 161 vm_object_pip_wakeup(fs->object); 162 VM_OBJECT_UNLOCK(fs->object); 163 if (fs->object != fs->first_object) { 164 VM_OBJECT_LOCK(fs->first_object); 165 vm_page_lock_queues(); 166 vm_page_free(fs->first_m); 167 vm_page_unlock_queues(); 168 vm_object_pip_wakeup(fs->first_object); 169 VM_OBJECT_UNLOCK(fs->first_object); 170 fs->first_m = NULL; 171 } 172 vm_object_deallocate(fs->first_object); 173 unlock_map(fs); 174 if (fs->vp != NULL) { 175 vput(fs->vp); 176 fs->vp = NULL; 177 } 178 VFS_UNLOCK_GIANT(fs->vfslocked); 179 fs->vfslocked = 0; 180 } 181 182 /* 183 * TRYPAGER - used by vm_fault to calculate whether the pager for the 184 * current object *might* contain the page. 185 * 186 * default objects are zero-fill, there is no real pager. 187 */ 188 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 189 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired)) 190 191 /* 192 * vm_fault: 193 * 194 * Handle a page fault occurring at the given address, 195 * requiring the given permissions, in the map specified. 196 * If successful, the page is inserted into the 197 * associated physical map. 198 * 199 * NOTE: the given address should be truncated to the 200 * proper page address. 201 * 202 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 203 * a standard error specifying why the fault is fatal is returned. 204 * 205 * 206 * The map in question must be referenced, and remains so. 207 * Caller may hold no locks. 208 */ 209 int 210 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 211 int fault_flags) 212 { 213 vm_prot_t prot; 214 int is_first_object_locked, result; 215 boolean_t are_queues_locked, growstack, wired; 216 int map_generation; 217 vm_object_t next_object; 218 vm_page_t marray[VM_FAULT_READ]; 219 int hardfault; 220 int faultcount, ahead, behind, alloc_req; 221 struct faultstate fs; 222 struct vnode *vp; 223 int locked, error; 224 225 hardfault = 0; 226 growstack = TRUE; 227 PCPU_INC(cnt.v_vm_faults); 228 fs.vp = NULL; 229 fs.vfslocked = 0; 230 faultcount = behind = 0; 231 232 RetryFault:; 233 234 /* 235 * Find the backing store object and offset into it to begin the 236 * search. 237 */ 238 fs.map = map; 239 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 240 &fs.first_object, &fs.first_pindex, &prot, &wired); 241 if (result != KERN_SUCCESS) { 242 if (result != KERN_PROTECTION_FAILURE || 243 (fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) { 244 if (growstack && result == KERN_INVALID_ADDRESS && 245 map != kernel_map && curproc != NULL) { 246 result = vm_map_growstack(curproc, vaddr); 247 if (result != KERN_SUCCESS) 248 return (KERN_FAILURE); 249 growstack = FALSE; 250 goto RetryFault; 251 } 252 return (result); 253 } 254 255 /* 256 * If we are user-wiring a r/w segment, and it is COW, then 257 * we need to do the COW operation. Note that we don't COW 258 * currently RO sections now, because it is NOT desirable 259 * to COW .text. We simply keep .text from ever being COW'ed 260 * and take the heat that one cannot debug wired .text sections. 261 */ 262 result = vm_map_lookup(&fs.map, vaddr, 263 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE, 264 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired); 265 if (result != KERN_SUCCESS) 266 return (result); 267 268 /* 269 * If we don't COW now, on a user wire, the user will never 270 * be able to write to the mapping. If we don't make this 271 * restriction, the bookkeeping would be nearly impossible. 272 * 273 * XXX The following assignment modifies the map without 274 * holding a write lock on it. 275 */ 276 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 277 fs.entry->max_protection &= ~VM_PROT_WRITE; 278 } 279 280 map_generation = fs.map->timestamp; 281 282 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 283 panic("vm_fault: fault on nofault entry, addr: %lx", 284 (u_long)vaddr); 285 } 286 287 /* 288 * Make a reference to this object to prevent its disposal while we 289 * are messing with it. Once we have the reference, the map is free 290 * to be diddled. Since objects reference their shadows (and copies), 291 * they will stay around as well. 292 * 293 * Bump the paging-in-progress count to prevent size changes (e.g. 294 * truncation operations) during I/O. This must be done after 295 * obtaining the vnode lock in order to avoid possible deadlocks. 296 */ 297 VM_OBJECT_LOCK(fs.first_object); 298 vm_object_reference_locked(fs.first_object); 299 vm_object_pip_add(fs.first_object, 1); 300 301 fs.lookup_still_valid = TRUE; 302 303 if (wired) 304 fault_type = prot; 305 306 fs.first_m = NULL; 307 308 /* 309 * Search for the page at object/offset. 310 */ 311 fs.object = fs.first_object; 312 fs.pindex = fs.first_pindex; 313 while (TRUE) { 314 /* 315 * If the object is dead, we stop here 316 */ 317 if (fs.object->flags & OBJ_DEAD) { 318 unlock_and_deallocate(&fs); 319 return (KERN_PROTECTION_FAILURE); 320 } 321 322 /* 323 * See if page is resident 324 */ 325 fs.m = vm_page_lookup(fs.object, fs.pindex); 326 if (fs.m != NULL) { 327 /* 328 * check for page-based copy on write. 329 * We check fs.object == fs.first_object so 330 * as to ensure the legacy COW mechanism is 331 * used when the page in question is part of 332 * a shadow object. Otherwise, vm_page_cowfault() 333 * removes the page from the backing object, 334 * which is not what we want. 335 */ 336 vm_page_lock_queues(); 337 if ((fs.m->cow) && 338 (fault_type & VM_PROT_WRITE) && 339 (fs.object == fs.first_object)) { 340 vm_page_cowfault(fs.m); 341 vm_page_unlock_queues(); 342 unlock_and_deallocate(&fs); 343 goto RetryFault; 344 } 345 346 /* 347 * Wait/Retry if the page is busy. We have to do this 348 * if the page is busy via either VPO_BUSY or 349 * vm_page_t->busy because the vm_pager may be using 350 * vm_page_t->busy for pageouts ( and even pageins if 351 * it is the vnode pager ), and we could end up trying 352 * to pagein and pageout the same page simultaneously. 353 * 354 * We can theoretically allow the busy case on a read 355 * fault if the page is marked valid, but since such 356 * pages are typically already pmap'd, putting that 357 * special case in might be more effort then it is 358 * worth. We cannot under any circumstances mess 359 * around with a vm_page_t->busy page except, perhaps, 360 * to pmap it. 361 */ 362 if ((fs.m->oflags & VPO_BUSY) || fs.m->busy) { 363 vm_page_unlock_queues(); 364 VM_OBJECT_UNLOCK(fs.object); 365 if (fs.object != fs.first_object) { 366 VM_OBJECT_LOCK(fs.first_object); 367 vm_page_lock_queues(); 368 vm_page_free(fs.first_m); 369 vm_page_unlock_queues(); 370 vm_object_pip_wakeup(fs.first_object); 371 VM_OBJECT_UNLOCK(fs.first_object); 372 fs.first_m = NULL; 373 } 374 unlock_map(&fs); 375 VM_OBJECT_LOCK(fs.object); 376 if (fs.m == vm_page_lookup(fs.object, 377 fs.pindex)) { 378 vm_page_sleep_if_busy(fs.m, TRUE, 379 "vmpfw"); 380 } 381 vm_object_pip_wakeup(fs.object); 382 VM_OBJECT_UNLOCK(fs.object); 383 PCPU_INC(cnt.v_intrans); 384 vm_object_deallocate(fs.first_object); 385 goto RetryFault; 386 } 387 vm_pageq_remove(fs.m); 388 vm_page_unlock_queues(); 389 390 /* 391 * Mark page busy for other processes, and the 392 * pagedaemon. If it still isn't completely valid 393 * (readable), jump to readrest, else break-out ( we 394 * found the page ). 395 */ 396 vm_page_busy(fs.m); 397 if (fs.m->valid != VM_PAGE_BITS_ALL && 398 fs.m->object != kernel_object && fs.m->object != kmem_object) { 399 goto readrest; 400 } 401 402 break; 403 } 404 405 /* 406 * Page is not resident, If this is the search termination 407 * or the pager might contain the page, allocate a new page. 408 */ 409 if (TRYPAGER || fs.object == fs.first_object) { 410 if (fs.pindex >= fs.object->size) { 411 unlock_and_deallocate(&fs); 412 return (KERN_PROTECTION_FAILURE); 413 } 414 415 /* 416 * Allocate a new page for this object/offset pair. 417 * 418 * Unlocked read of the p_flag is harmless. At 419 * worst, the P_KILLED might be not observed 420 * there, and allocation can fail, causing 421 * restart and new reading of the p_flag. 422 */ 423 fs.m = NULL; 424 if (!vm_page_count_severe() || P_KILLED(curproc)) { 425 #if VM_NRESERVLEVEL > 0 426 if ((fs.object->flags & OBJ_COLORED) == 0) { 427 fs.object->flags |= OBJ_COLORED; 428 fs.object->pg_color = atop(vaddr) - 429 fs.pindex; 430 } 431 #endif 432 alloc_req = P_KILLED(curproc) ? 433 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 434 if (fs.object->type != OBJT_VNODE && 435 fs.object->backing_object == NULL) 436 alloc_req |= VM_ALLOC_ZERO; 437 fs.m = vm_page_alloc(fs.object, fs.pindex, 438 alloc_req); 439 } 440 if (fs.m == NULL) { 441 unlock_and_deallocate(&fs); 442 VM_WAITPFAULT; 443 goto RetryFault; 444 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 445 break; 446 } 447 448 readrest: 449 /* 450 * We have found a valid page or we have allocated a new page. 451 * The page thus may not be valid or may not be entirely 452 * valid. 453 * 454 * Attempt to fault-in the page if there is a chance that the 455 * pager has it, and potentially fault in additional pages 456 * at the same time. 457 */ 458 if (TRYPAGER) { 459 int rv; 460 int reqpage = 0; 461 u_char behavior = vm_map_entry_behavior(fs.entry); 462 463 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 464 P_KILLED(curproc)) { 465 ahead = 0; 466 behind = 0; 467 } else { 468 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT; 469 if (behind > VM_FAULT_READ_BEHIND) 470 behind = VM_FAULT_READ_BEHIND; 471 472 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1; 473 if (ahead > VM_FAULT_READ_AHEAD) 474 ahead = VM_FAULT_READ_AHEAD; 475 } 476 is_first_object_locked = FALSE; 477 if ((behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 478 (behavior != MAP_ENTRY_BEHAV_RANDOM && 479 fs.pindex >= fs.entry->lastr && 480 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) && 481 (fs.first_object == fs.object || 482 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object))) && 483 fs.first_object->type != OBJT_DEVICE && 484 fs.first_object->type != OBJT_PHYS && 485 fs.first_object->type != OBJT_SG) { 486 vm_pindex_t firstpindex, tmppindex; 487 488 if (fs.first_pindex < 2 * VM_FAULT_READ) 489 firstpindex = 0; 490 else 491 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ; 492 493 are_queues_locked = FALSE; 494 /* 495 * note: partially valid pages cannot be 496 * included in the lookahead - NFS piecemeal 497 * writes will barf on it badly. 498 */ 499 for (tmppindex = fs.first_pindex - 1; 500 tmppindex >= firstpindex; 501 --tmppindex) { 502 vm_page_t mt; 503 504 mt = vm_page_lookup(fs.first_object, tmppindex); 505 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL)) 506 break; 507 if (mt->busy || 508 (mt->oflags & VPO_BUSY)) 509 continue; 510 if (!are_queues_locked) { 511 are_queues_locked = TRUE; 512 vm_page_lock_queues(); 513 } 514 if (mt->hold_count || 515 mt->wire_count) 516 continue; 517 pmap_remove_all(mt); 518 if (mt->dirty) { 519 vm_page_deactivate(mt); 520 } else { 521 vm_page_cache(mt); 522 } 523 } 524 if (are_queues_locked) 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 /* 533 * Call the pager to retrieve the data, if any, after 534 * releasing the lock on the map. We hold a ref on 535 * fs.object and the pages are VPO_BUSY'd. 536 */ 537 unlock_map(&fs); 538 539 vnode_lock: 540 if (fs.object->type == OBJT_VNODE) { 541 vp = fs.object->handle; 542 if (vp == fs.vp) 543 goto vnode_locked; 544 else if (fs.vp != NULL) { 545 vput(fs.vp); 546 fs.vp = NULL; 547 } 548 locked = VOP_ISLOCKED(vp); 549 550 if (VFS_NEEDSGIANT(vp->v_mount) && !fs.vfslocked) { 551 fs.vfslocked = 1; 552 if (!mtx_trylock(&Giant)) { 553 VM_OBJECT_UNLOCK(fs.object); 554 mtx_lock(&Giant); 555 VM_OBJECT_LOCK(fs.object); 556 goto vnode_lock; 557 } 558 } 559 if (locked != LK_EXCLUSIVE) 560 locked = LK_SHARED; 561 /* Do not sleep for vnode lock while fs.m is busy */ 562 error = vget(vp, locked | LK_CANRECURSE | 563 LK_NOWAIT, curthread); 564 if (error != 0) { 565 int vfslocked; 566 567 vfslocked = fs.vfslocked; 568 fs.vfslocked = 0; /* Keep Giant */ 569 vhold(vp); 570 release_page(&fs); 571 unlock_and_deallocate(&fs); 572 error = vget(vp, locked | LK_RETRY | 573 LK_CANRECURSE, curthread); 574 vdrop(vp); 575 fs.vp = vp; 576 fs.vfslocked = vfslocked; 577 KASSERT(error == 0, 578 ("vm_fault: vget failed")); 579 goto RetryFault; 580 } 581 fs.vp = vp; 582 } 583 vnode_locked: 584 KASSERT(fs.vp == NULL || !fs.map->system_map, 585 ("vm_fault: vnode-backed object mapped by system map")); 586 587 /* 588 * now we find out if any other pages should be paged 589 * in at this time this routine checks to see if the 590 * pages surrounding this fault reside in the same 591 * object as the page for this fault. If they do, 592 * then they are faulted in also into the object. The 593 * array "marray" returned contains an array of 594 * vm_page_t structs where one of them is the 595 * vm_page_t passed to the routine. The reqpage 596 * return value is the index into the marray for the 597 * vm_page_t passed to the routine. 598 * 599 * fs.m plus the additional pages are VPO_BUSY'd. 600 */ 601 faultcount = vm_fault_additional_pages( 602 fs.m, behind, ahead, marray, &reqpage); 603 604 rv = faultcount ? 605 vm_pager_get_pages(fs.object, marray, faultcount, 606 reqpage) : VM_PAGER_FAIL; 607 608 if (rv == VM_PAGER_OK) { 609 /* 610 * Found the page. Leave it busy while we play 611 * with it. 612 */ 613 614 /* 615 * Relookup in case pager changed page. Pager 616 * is responsible for disposition of old page 617 * if moved. 618 */ 619 fs.m = vm_page_lookup(fs.object, fs.pindex); 620 if (!fs.m) { 621 unlock_and_deallocate(&fs); 622 goto RetryFault; 623 } 624 625 hardfault++; 626 break; /* break to PAGE HAS BEEN FOUND */ 627 } 628 /* 629 * Remove the bogus page (which does not exist at this 630 * object/offset); before doing so, we must get back 631 * our object lock to preserve our invariant. 632 * 633 * Also wake up any other process that may want to bring 634 * in this page. 635 * 636 * If this is the top-level object, we must leave the 637 * busy page to prevent another process from rushing 638 * past us, and inserting the page in that object at 639 * the same time that we are. 640 */ 641 if (rv == VM_PAGER_ERROR) 642 printf("vm_fault: pager read error, pid %d (%s)\n", 643 curproc->p_pid, curproc->p_comm); 644 /* 645 * Data outside the range of the pager or an I/O error 646 */ 647 /* 648 * XXX - the check for kernel_map is a kludge to work 649 * around having the machine panic on a kernel space 650 * fault w/ I/O error. 651 */ 652 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 653 (rv == VM_PAGER_BAD)) { 654 vm_page_lock_queues(); 655 vm_page_free(fs.m); 656 vm_page_unlock_queues(); 657 fs.m = NULL; 658 unlock_and_deallocate(&fs); 659 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 660 } 661 if (fs.object != fs.first_object) { 662 vm_page_lock_queues(); 663 vm_page_free(fs.m); 664 vm_page_unlock_queues(); 665 fs.m = NULL; 666 /* 667 * XXX - we cannot just fall out at this 668 * point, m has been freed and is invalid! 669 */ 670 } 671 } 672 673 /* 674 * We get here if the object has default pager (or unwiring) 675 * or the pager doesn't have the page. 676 */ 677 if (fs.object == fs.first_object) 678 fs.first_m = fs.m; 679 680 /* 681 * Move on to the next object. Lock the next object before 682 * unlocking the current one. 683 */ 684 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 685 next_object = fs.object->backing_object; 686 if (next_object == NULL) { 687 /* 688 * If there's no object left, fill the page in the top 689 * object with zeros. 690 */ 691 if (fs.object != fs.first_object) { 692 vm_object_pip_wakeup(fs.object); 693 VM_OBJECT_UNLOCK(fs.object); 694 695 fs.object = fs.first_object; 696 fs.pindex = fs.first_pindex; 697 fs.m = fs.first_m; 698 VM_OBJECT_LOCK(fs.object); 699 } 700 fs.first_m = NULL; 701 702 /* 703 * Zero the page if necessary and mark it valid. 704 */ 705 if ((fs.m->flags & PG_ZERO) == 0) { 706 pmap_zero_page(fs.m); 707 } else { 708 PCPU_INC(cnt.v_ozfod); 709 } 710 PCPU_INC(cnt.v_zfod); 711 fs.m->valid = VM_PAGE_BITS_ALL; 712 break; /* break to PAGE HAS BEEN FOUND */ 713 } else { 714 KASSERT(fs.object != next_object, 715 ("object loop %p", next_object)); 716 VM_OBJECT_LOCK(next_object); 717 vm_object_pip_add(next_object, 1); 718 if (fs.object != fs.first_object) 719 vm_object_pip_wakeup(fs.object); 720 VM_OBJECT_UNLOCK(fs.object); 721 fs.object = next_object; 722 } 723 } 724 725 KASSERT((fs.m->oflags & VPO_BUSY) != 0, 726 ("vm_fault: not busy after main loop")); 727 728 /* 729 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 730 * is held.] 731 */ 732 733 /* 734 * If the page is being written, but isn't already owned by the 735 * top-level object, we have to copy it into a new page owned by the 736 * top-level object. 737 */ 738 if (fs.object != fs.first_object) { 739 /* 740 * We only really need to copy if we want to write it. 741 */ 742 if (fault_type & VM_PROT_WRITE) { 743 /* 744 * This allows pages to be virtually copied from a 745 * backing_object into the first_object, where the 746 * backing object has no other refs to it, and cannot 747 * gain any more refs. Instead of a bcopy, we just 748 * move the page from the backing object to the 749 * first object. Note that we must mark the page 750 * dirty in the first object so that it will go out 751 * to swap when needed. 752 */ 753 is_first_object_locked = FALSE; 754 if ( 755 /* 756 * Only one shadow object 757 */ 758 (fs.object->shadow_count == 1) && 759 /* 760 * No COW refs, except us 761 */ 762 (fs.object->ref_count == 1) && 763 /* 764 * No one else can look this object up 765 */ 766 (fs.object->handle == NULL) && 767 /* 768 * No other ways to look the object up 769 */ 770 ((fs.object->type == OBJT_DEFAULT) || 771 (fs.object->type == OBJT_SWAP)) && 772 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) && 773 /* 774 * We don't chase down the shadow chain 775 */ 776 fs.object == fs.first_object->backing_object) { 777 vm_page_lock_queues(); 778 /* 779 * get rid of the unnecessary page 780 */ 781 vm_page_free(fs.first_m); 782 /* 783 * grab the page and put it into the 784 * process'es object. The page is 785 * automatically made dirty. 786 */ 787 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 788 vm_page_unlock_queues(); 789 vm_page_busy(fs.m); 790 fs.first_m = fs.m; 791 fs.m = NULL; 792 PCPU_INC(cnt.v_cow_optim); 793 } else { 794 /* 795 * Oh, well, lets copy it. 796 */ 797 pmap_copy_page(fs.m, fs.first_m); 798 fs.first_m->valid = VM_PAGE_BITS_ALL; 799 } 800 if (fs.m) { 801 /* 802 * We no longer need the old page or object. 803 */ 804 release_page(&fs); 805 } 806 /* 807 * fs.object != fs.first_object due to above 808 * conditional 809 */ 810 vm_object_pip_wakeup(fs.object); 811 VM_OBJECT_UNLOCK(fs.object); 812 /* 813 * Only use the new page below... 814 */ 815 fs.object = fs.first_object; 816 fs.pindex = fs.first_pindex; 817 fs.m = fs.first_m; 818 if (!is_first_object_locked) 819 VM_OBJECT_LOCK(fs.object); 820 PCPU_INC(cnt.v_cow_faults); 821 } else { 822 prot &= ~VM_PROT_WRITE; 823 } 824 } 825 826 /* 827 * We must verify that the maps have not changed since our last 828 * lookup. 829 */ 830 if (!fs.lookup_still_valid) { 831 vm_object_t retry_object; 832 vm_pindex_t retry_pindex; 833 vm_prot_t retry_prot; 834 835 if (!vm_map_trylock_read(fs.map)) { 836 release_page(&fs); 837 unlock_and_deallocate(&fs); 838 goto RetryFault; 839 } 840 fs.lookup_still_valid = TRUE; 841 if (fs.map->timestamp != map_generation) { 842 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 843 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 844 845 /* 846 * If we don't need the page any longer, put it on the inactive 847 * list (the easiest thing to do here). If no one needs it, 848 * pageout will grab it eventually. 849 */ 850 if (result != KERN_SUCCESS) { 851 release_page(&fs); 852 unlock_and_deallocate(&fs); 853 854 /* 855 * If retry of map lookup would have blocked then 856 * retry fault from start. 857 */ 858 if (result == KERN_FAILURE) 859 goto RetryFault; 860 return (result); 861 } 862 if ((retry_object != fs.first_object) || 863 (retry_pindex != fs.first_pindex)) { 864 release_page(&fs); 865 unlock_and_deallocate(&fs); 866 goto RetryFault; 867 } 868 869 /* 870 * Check whether the protection has changed or the object has 871 * been copied while we left the map unlocked. Changing from 872 * read to write permission is OK - we leave the page 873 * write-protected, and catch the write fault. Changing from 874 * write to read permission means that we can't mark the page 875 * write-enabled after all. 876 */ 877 prot &= retry_prot; 878 } 879 } 880 /* 881 * If the page was filled by a pager, update the map entry's 882 * last read offset. Since the pager does not return the 883 * actual set of pages that it read, this update is based on 884 * the requested set. Typically, the requested and actual 885 * sets are the same. 886 * 887 * XXX The following assignment modifies the map 888 * without holding a write lock on it. 889 */ 890 if (hardfault) 891 fs.entry->lastr = fs.pindex + faultcount - behind; 892 893 if (prot & VM_PROT_WRITE) { 894 vm_object_set_writeable_dirty(fs.object); 895 896 /* 897 * If the fault is a write, we know that this page is being 898 * written NOW so dirty it explicitly to save on 899 * pmap_is_modified() calls later. 900 * 901 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 902 * if the page is already dirty to prevent data written with 903 * the expectation of being synced from not being synced. 904 * Likewise if this entry does not request NOSYNC then make 905 * sure the page isn't marked NOSYNC. Applications sharing 906 * data should use the same flags to avoid ping ponging. 907 * 908 * Also tell the backing pager, if any, that it should remove 909 * any swap backing since the page is now dirty. 910 */ 911 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 912 if (fs.m->dirty == 0) 913 fs.m->oflags |= VPO_NOSYNC; 914 } else { 915 fs.m->oflags &= ~VPO_NOSYNC; 916 } 917 if (fault_flags & VM_FAULT_DIRTY) { 918 vm_page_dirty(fs.m); 919 vm_pager_page_unswapped(fs.m); 920 } 921 } 922 923 /* 924 * Page had better still be busy 925 */ 926 KASSERT(fs.m->oflags & VPO_BUSY, 927 ("vm_fault: page %p not busy!", fs.m)); 928 /* 929 * Page must be completely valid or it is not fit to 930 * map into user space. vm_pager_get_pages() ensures this. 931 */ 932 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 933 ("vm_fault: page %p partially invalid", fs.m)); 934 VM_OBJECT_UNLOCK(fs.object); 935 936 /* 937 * Put this page into the physical map. We had to do the unlock above 938 * because pmap_enter() may sleep. We don't put the page 939 * back on the active queue until later so that the pageout daemon 940 * won't find it (yet). 941 */ 942 pmap_enter(fs.map->pmap, vaddr, fault_type, fs.m, prot, wired); 943 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 944 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry); 945 } 946 VM_OBJECT_LOCK(fs.object); 947 vm_page_lock_queues(); 948 vm_page_flag_set(fs.m, PG_REFERENCED); 949 950 /* 951 * If the page is not wired down, then put it where the pageout daemon 952 * can find it. 953 */ 954 if (fault_flags & VM_FAULT_WIRE_MASK) { 955 if (wired) 956 vm_page_wire(fs.m); 957 else 958 vm_page_unwire(fs.m, 1); 959 } else { 960 vm_page_activate(fs.m); 961 } 962 vm_page_unlock_queues(); 963 vm_page_wakeup(fs.m); 964 965 /* 966 * Unlock everything, and return 967 */ 968 unlock_and_deallocate(&fs); 969 if (hardfault) 970 curthread->td_ru.ru_majflt++; 971 else 972 curthread->td_ru.ru_minflt++; 973 974 return (KERN_SUCCESS); 975 } 976 977 /* 978 * vm_fault_prefault provides a quick way of clustering 979 * pagefaults into a processes address space. It is a "cousin" 980 * of vm_map_pmap_enter, except it runs at page fault time instead 981 * of mmap time. 982 */ 983 static void 984 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry) 985 { 986 int i; 987 vm_offset_t addr, starta; 988 vm_pindex_t pindex; 989 vm_page_t m; 990 vm_object_t object; 991 992 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 993 return; 994 995 object = entry->object.vm_object; 996 997 starta = addra - PFBAK * PAGE_SIZE; 998 if (starta < entry->start) { 999 starta = entry->start; 1000 } else if (starta > addra) { 1001 starta = 0; 1002 } 1003 1004 for (i = 0; i < PAGEORDER_SIZE; i++) { 1005 vm_object_t backing_object, lobject; 1006 1007 addr = addra + prefault_pageorder[i]; 1008 if (addr > addra + (PFFOR * PAGE_SIZE)) 1009 addr = 0; 1010 1011 if (addr < starta || addr >= entry->end) 1012 continue; 1013 1014 if (!pmap_is_prefaultable(pmap, addr)) 1015 continue; 1016 1017 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1018 lobject = object; 1019 VM_OBJECT_LOCK(lobject); 1020 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1021 lobject->type == OBJT_DEFAULT && 1022 (backing_object = lobject->backing_object) != NULL) { 1023 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1024 0, ("vm_fault_prefault: unaligned object offset")); 1025 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1026 VM_OBJECT_LOCK(backing_object); 1027 VM_OBJECT_UNLOCK(lobject); 1028 lobject = backing_object; 1029 } 1030 /* 1031 * give-up when a page is not in memory 1032 */ 1033 if (m == NULL) { 1034 VM_OBJECT_UNLOCK(lobject); 1035 break; 1036 } 1037 if (m->valid == VM_PAGE_BITS_ALL && 1038 (m->flags & PG_FICTITIOUS) == 0) { 1039 vm_page_lock_queues(); 1040 pmap_enter_quick(pmap, addr, m, entry->protection); 1041 vm_page_unlock_queues(); 1042 } 1043 VM_OBJECT_UNLOCK(lobject); 1044 } 1045 } 1046 1047 /* 1048 * vm_fault_quick: 1049 * 1050 * Ensure that the requested virtual address, which may be in userland, 1051 * is valid. Fault-in the page if necessary. Return -1 on failure. 1052 */ 1053 int 1054 vm_fault_quick(caddr_t v, int prot) 1055 { 1056 int r; 1057 1058 if (prot & VM_PROT_WRITE) 1059 r = subyte(v, fubyte(v)); 1060 else 1061 r = fubyte(v); 1062 return(r); 1063 } 1064 1065 /* 1066 * vm_fault_wire: 1067 * 1068 * Wire down a range of virtual addresses in a map. 1069 */ 1070 int 1071 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1072 boolean_t user_wire, boolean_t fictitious) 1073 { 1074 vm_offset_t va; 1075 int rv; 1076 1077 /* 1078 * We simulate a fault to get the page and enter it in the physical 1079 * map. For user wiring, we only ask for read access on currently 1080 * read-only sections. 1081 */ 1082 for (va = start; va < end; va += PAGE_SIZE) { 1083 rv = vm_fault(map, va, 1084 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE, 1085 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING); 1086 if (rv) { 1087 if (va != start) 1088 vm_fault_unwire(map, start, va, fictitious); 1089 return (rv); 1090 } 1091 } 1092 return (KERN_SUCCESS); 1093 } 1094 1095 /* 1096 * vm_fault_unwire: 1097 * 1098 * Unwire a range of virtual addresses in a map. 1099 */ 1100 void 1101 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1102 boolean_t fictitious) 1103 { 1104 vm_paddr_t pa; 1105 vm_offset_t va; 1106 pmap_t pmap; 1107 1108 pmap = vm_map_pmap(map); 1109 1110 /* 1111 * Since the pages are wired down, we must be able to get their 1112 * mappings from the physical map system. 1113 */ 1114 for (va = start; va < end; va += PAGE_SIZE) { 1115 pa = pmap_extract(pmap, va); 1116 if (pa != 0) { 1117 pmap_change_wiring(pmap, va, FALSE); 1118 if (!fictitious) { 1119 vm_page_lock_queues(); 1120 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1121 vm_page_unlock_queues(); 1122 } 1123 } 1124 } 1125 } 1126 1127 /* 1128 * Routine: 1129 * vm_fault_copy_entry 1130 * Function: 1131 * Create new shadow object backing dst_entry with private copy of 1132 * all underlying pages. When src_entry is equal to dst_entry, 1133 * function implements COW for wired-down map entry. Otherwise, 1134 * it forks wired entry into dst_map. 1135 * 1136 * In/out conditions: 1137 * The source and destination maps must be locked for write. 1138 * The source map entry must be wired down (or be a sharing map 1139 * entry corresponding to a main map entry that is wired down). 1140 */ 1141 void 1142 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1143 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1144 vm_ooffset_t *fork_charge) 1145 { 1146 vm_object_t backing_object, dst_object, object, src_object; 1147 vm_pindex_t dst_pindex, pindex, src_pindex; 1148 vm_prot_t access, prot; 1149 vm_offset_t vaddr; 1150 vm_page_t dst_m; 1151 vm_page_t src_m; 1152 boolean_t src_readonly, upgrade; 1153 1154 #ifdef lint 1155 src_map++; 1156 #endif /* lint */ 1157 1158 upgrade = src_entry == dst_entry; 1159 1160 src_object = src_entry->object.vm_object; 1161 src_pindex = OFF_TO_IDX(src_entry->offset); 1162 src_readonly = (src_entry->protection & VM_PROT_WRITE) == 0; 1163 1164 /* 1165 * Create the top-level object for the destination entry. (Doesn't 1166 * actually shadow anything - we copy the pages directly.) 1167 */ 1168 dst_object = vm_object_allocate(OBJT_DEFAULT, 1169 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1170 #if VM_NRESERVLEVEL > 0 1171 dst_object->flags |= OBJ_COLORED; 1172 dst_object->pg_color = atop(dst_entry->start); 1173 #endif 1174 1175 VM_OBJECT_LOCK(dst_object); 1176 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1177 ("vm_fault_copy_entry: vm_object not NULL")); 1178 dst_entry->object.vm_object = dst_object; 1179 dst_entry->offset = 0; 1180 dst_object->charge = dst_entry->end - dst_entry->start; 1181 if (fork_charge != NULL) { 1182 KASSERT(dst_entry->uip == NULL, 1183 ("vm_fault_copy_entry: leaked swp charge")); 1184 dst_object->uip = curthread->td_ucred->cr_ruidinfo; 1185 uihold(dst_object->uip); 1186 *fork_charge += dst_object->charge; 1187 } else { 1188 dst_object->uip = dst_entry->uip; 1189 dst_entry->uip = NULL; 1190 } 1191 access = prot = dst_entry->max_protection; 1192 /* 1193 * If not an upgrade, then enter the mappings in the pmap as 1194 * read and/or execute accesses. Otherwise, enter them as 1195 * write accesses. 1196 * 1197 * A writeable large page mapping is only created if all of 1198 * the constituent small page mappings are modified. Marking 1199 * PTEs as modified on inception allows promotion to happen 1200 * without taking potentially large number of soft faults. 1201 */ 1202 if (!upgrade) 1203 access &= ~VM_PROT_WRITE; 1204 1205 /* 1206 * Loop through all of the pages in the entry's range, copying each 1207 * one from the source object (it should be there) to the destination 1208 * object. 1209 */ 1210 for (vaddr = dst_entry->start, dst_pindex = 0; 1211 vaddr < dst_entry->end; 1212 vaddr += PAGE_SIZE, dst_pindex++) { 1213 1214 /* 1215 * Allocate a page in the destination object. 1216 */ 1217 do { 1218 dst_m = vm_page_alloc(dst_object, dst_pindex, 1219 VM_ALLOC_NORMAL); 1220 if (dst_m == NULL) { 1221 VM_OBJECT_UNLOCK(dst_object); 1222 VM_WAIT; 1223 VM_OBJECT_LOCK(dst_object); 1224 } 1225 } while (dst_m == NULL); 1226 1227 /* 1228 * Find the page in the source object, and copy it in. 1229 * (Because the source is wired down, the page will be in 1230 * memory.) 1231 */ 1232 VM_OBJECT_LOCK(src_object); 1233 object = src_object; 1234 pindex = src_pindex + dst_pindex; 1235 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1236 src_readonly && 1237 (backing_object = object->backing_object) != NULL) { 1238 /* 1239 * Allow fallback to backing objects if we are reading. 1240 */ 1241 VM_OBJECT_LOCK(backing_object); 1242 pindex += OFF_TO_IDX(object->backing_object_offset); 1243 VM_OBJECT_UNLOCK(object); 1244 object = backing_object; 1245 } 1246 if (src_m == NULL) 1247 panic("vm_fault_copy_wired: page missing"); 1248 pmap_copy_page(src_m, dst_m); 1249 VM_OBJECT_UNLOCK(object); 1250 dst_m->valid = VM_PAGE_BITS_ALL; 1251 VM_OBJECT_UNLOCK(dst_object); 1252 1253 /* 1254 * Enter it in the pmap. If a wired, copy-on-write 1255 * mapping is being replaced by a write-enabled 1256 * mapping, then wire that new mapping. 1257 */ 1258 pmap_enter(dst_map->pmap, vaddr, access, dst_m, prot, upgrade); 1259 1260 /* 1261 * Mark it no longer busy, and put it on the active list. 1262 */ 1263 VM_OBJECT_LOCK(dst_object); 1264 vm_page_lock_queues(); 1265 if (upgrade) { 1266 vm_page_unwire(src_m, 0); 1267 vm_page_wire(dst_m); 1268 } else 1269 vm_page_activate(dst_m); 1270 vm_page_unlock_queues(); 1271 vm_page_wakeup(dst_m); 1272 } 1273 VM_OBJECT_UNLOCK(dst_object); 1274 if (upgrade) { 1275 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1276 vm_object_deallocate(src_object); 1277 } 1278 } 1279 1280 1281 /* 1282 * This routine checks around the requested page for other pages that 1283 * might be able to be faulted in. This routine brackets the viable 1284 * pages for the pages to be paged in. 1285 * 1286 * Inputs: 1287 * m, rbehind, rahead 1288 * 1289 * Outputs: 1290 * marray (array of vm_page_t), reqpage (index of requested page) 1291 * 1292 * Return value: 1293 * number of pages in marray 1294 */ 1295 static int 1296 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1297 vm_page_t m; 1298 int rbehind; 1299 int rahead; 1300 vm_page_t *marray; 1301 int *reqpage; 1302 { 1303 int i,j; 1304 vm_object_t object; 1305 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1306 vm_page_t rtm; 1307 int cbehind, cahead; 1308 1309 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED); 1310 1311 object = m->object; 1312 pindex = m->pindex; 1313 cbehind = cahead = 0; 1314 1315 /* 1316 * if the requested page is not available, then give up now 1317 */ 1318 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1319 return 0; 1320 } 1321 1322 if ((cbehind == 0) && (cahead == 0)) { 1323 *reqpage = 0; 1324 marray[0] = m; 1325 return 1; 1326 } 1327 1328 if (rahead > cahead) { 1329 rahead = cahead; 1330 } 1331 1332 if (rbehind > cbehind) { 1333 rbehind = cbehind; 1334 } 1335 1336 /* 1337 * scan backward for the read behind pages -- in memory 1338 */ 1339 if (pindex > 0) { 1340 if (rbehind > pindex) { 1341 rbehind = pindex; 1342 startpindex = 0; 1343 } else { 1344 startpindex = pindex - rbehind; 1345 } 1346 1347 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1348 rtm->pindex >= startpindex) 1349 startpindex = rtm->pindex + 1; 1350 1351 /* tpindex is unsigned; beware of numeric underflow. */ 1352 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1353 tpindex < pindex; i++, tpindex--) { 1354 1355 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1356 VM_ALLOC_IFNOTCACHED); 1357 if (rtm == NULL) { 1358 /* 1359 * Shift the allocated pages to the 1360 * beginning of the array. 1361 */ 1362 for (j = 0; j < i; j++) { 1363 marray[j] = marray[j + tpindex + 1 - 1364 startpindex]; 1365 } 1366 break; 1367 } 1368 1369 marray[tpindex - startpindex] = rtm; 1370 } 1371 } else { 1372 startpindex = 0; 1373 i = 0; 1374 } 1375 1376 marray[i] = m; 1377 /* page offset of the required page */ 1378 *reqpage = i; 1379 1380 tpindex = pindex + 1; 1381 i++; 1382 1383 /* 1384 * scan forward for the read ahead pages 1385 */ 1386 endpindex = tpindex + rahead; 1387 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1388 endpindex = rtm->pindex; 1389 if (endpindex > object->size) 1390 endpindex = object->size; 1391 1392 for (; tpindex < endpindex; i++, tpindex++) { 1393 1394 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1395 VM_ALLOC_IFNOTCACHED); 1396 if (rtm == NULL) { 1397 break; 1398 } 1399 1400 marray[i] = rtm; 1401 } 1402 1403 /* return number of pages */ 1404 return i; 1405 }
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