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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/8.2/sys/vm/vm_fault.c 215430 2010-11-17 17:29:22Z alc $"); 76 77 #include "opt_vm.h" 78 79 #include <sys/param.h> 80 #include <sys/systm.h> 81 #include <sys/kernel.h> 82 #include <sys/lock.h> 83 #include <sys/mutex.h> 84 #include <sys/proc.h> 85 #include <sys/resourcevar.h> 86 #include <sys/sysctl.h> 87 #include <sys/vmmeter.h> 88 #include <sys/vnode.h> 89 90 #include <vm/vm.h> 91 #include <vm/vm_param.h> 92 #include <vm/pmap.h> 93 #include <vm/vm_map.h> 94 #include <vm/vm_object.h> 95 #include <vm/vm_page.h> 96 #include <vm/vm_pageout.h> 97 #include <vm/vm_kern.h> 98 #include <vm/vm_pager.h> 99 #include <vm/vnode_pager.h> 100 #include <vm/vm_extern.h> 101 102 #include <sys/mount.h> /* XXX Temporary for VFS_LOCK_GIANT() */ 103 104 #define PFBAK 4 105 #define PFFOR 4 106 #define PAGEORDER_SIZE (PFBAK+PFFOR) 107 108 static int prefault_pageorder[] = { 109 -1 * PAGE_SIZE, 1 * PAGE_SIZE, 110 -2 * PAGE_SIZE, 2 * PAGE_SIZE, 111 -3 * PAGE_SIZE, 3 * PAGE_SIZE, 112 -4 * PAGE_SIZE, 4 * PAGE_SIZE 113 }; 114 115 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 116 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t); 117 118 #define VM_FAULT_READ_AHEAD 8 119 #define VM_FAULT_READ_BEHIND 7 120 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1) 121 122 struct faultstate { 123 vm_page_t m; 124 vm_object_t object; 125 vm_pindex_t pindex; 126 vm_page_t first_m; 127 vm_object_t first_object; 128 vm_pindex_t first_pindex; 129 vm_map_t map; 130 vm_map_entry_t entry; 131 int lookup_still_valid; 132 struct vnode *vp; 133 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], mt, mt_prev; 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 if (fs.object != fs.first_object) { 365 if (!VM_OBJECT_TRYLOCK( 366 fs.first_object)) { 367 VM_OBJECT_UNLOCK(fs.object); 368 VM_OBJECT_LOCK(fs.first_object); 369 VM_OBJECT_LOCK(fs.object); 370 } 371 vm_page_lock_queues(); 372 vm_page_free(fs.first_m); 373 vm_page_unlock_queues(); 374 vm_object_pip_wakeup(fs.first_object); 375 VM_OBJECT_UNLOCK(fs.first_object); 376 fs.first_m = NULL; 377 } 378 unlock_map(&fs); 379 if (fs.m == vm_page_lookup(fs.object, 380 fs.pindex)) { 381 vm_page_sleep_if_busy(fs.m, TRUE, 382 "vmpfw"); 383 } 384 vm_object_pip_wakeup(fs.object); 385 VM_OBJECT_UNLOCK(fs.object); 386 PCPU_INC(cnt.v_intrans); 387 vm_object_deallocate(fs.first_object); 388 goto RetryFault; 389 } 390 vm_pageq_remove(fs.m); 391 vm_page_unlock_queues(); 392 393 /* 394 * Mark page busy for other processes, and the 395 * pagedaemon. If it still isn't completely valid 396 * (readable), jump to readrest, else break-out ( we 397 * found the page ). 398 */ 399 vm_page_busy(fs.m); 400 if (fs.m->valid != VM_PAGE_BITS_ALL && 401 fs.m->object != kernel_object && fs.m->object != kmem_object) { 402 goto readrest; 403 } 404 405 break; 406 } 407 408 /* 409 * Page is not resident, If this is the search termination 410 * or the pager might contain the page, allocate a new page. 411 */ 412 if (TRYPAGER || fs.object == fs.first_object) { 413 if (fs.pindex >= fs.object->size) { 414 unlock_and_deallocate(&fs); 415 return (KERN_PROTECTION_FAILURE); 416 } 417 418 /* 419 * Allocate a new page for this object/offset pair. 420 * 421 * Unlocked read of the p_flag is harmless. At 422 * worst, the P_KILLED might be not observed 423 * there, and allocation can fail, causing 424 * restart and new reading of the p_flag. 425 */ 426 fs.m = NULL; 427 if (!vm_page_count_severe() || P_KILLED(curproc)) { 428 #if VM_NRESERVLEVEL > 0 429 if ((fs.object->flags & OBJ_COLORED) == 0) { 430 fs.object->flags |= OBJ_COLORED; 431 fs.object->pg_color = atop(vaddr) - 432 fs.pindex; 433 } 434 #endif 435 alloc_req = P_KILLED(curproc) ? 436 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 437 if (fs.object->type != OBJT_VNODE && 438 fs.object->backing_object == NULL) 439 alloc_req |= VM_ALLOC_ZERO; 440 fs.m = vm_page_alloc(fs.object, fs.pindex, 441 alloc_req); 442 } 443 if (fs.m == NULL) { 444 unlock_and_deallocate(&fs); 445 VM_WAITPFAULT; 446 goto RetryFault; 447 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 448 break; 449 } 450 451 readrest: 452 /* 453 * We have found a valid page or we have allocated a new page. 454 * The page thus may not be valid or may not be entirely 455 * valid. 456 * 457 * Attempt to fault-in the page if there is a chance that the 458 * pager has it, and potentially fault in additional pages 459 * at the same time. 460 */ 461 if (TRYPAGER) { 462 int rv; 463 int reqpage = 0; 464 u_char behavior = vm_map_entry_behavior(fs.entry); 465 466 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 467 P_KILLED(curproc)) { 468 ahead = 0; 469 behind = 0; 470 } else { 471 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT; 472 if (behind > VM_FAULT_READ_BEHIND) 473 behind = VM_FAULT_READ_BEHIND; 474 475 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1; 476 if (ahead > VM_FAULT_READ_AHEAD) 477 ahead = VM_FAULT_READ_AHEAD; 478 } 479 is_first_object_locked = FALSE; 480 if ((behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 481 (behavior != MAP_ENTRY_BEHAV_RANDOM && 482 fs.pindex >= fs.entry->lastr && 483 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) && 484 (fs.first_object == fs.object || 485 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object))) && 486 fs.first_object->type != OBJT_DEVICE && 487 fs.first_object->type != OBJT_PHYS && 488 fs.first_object->type != OBJT_SG) { 489 vm_pindex_t firstpindex; 490 491 if (fs.first_pindex < 2 * VM_FAULT_READ) 492 firstpindex = 0; 493 else 494 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ; 495 mt = fs.first_object != fs.object ? 496 fs.first_m : fs.m; 497 KASSERT(mt != NULL, ("vm_fault: missing mt")); 498 KASSERT((mt->oflags & VPO_BUSY) != 0, 499 ("vm_fault: mt %p not busy", mt)); 500 mt_prev = vm_page_prev(mt); 501 502 are_queues_locked = FALSE; 503 /* 504 * note: partially valid pages cannot be 505 * included in the lookahead - NFS piecemeal 506 * writes will barf on it badly. 507 */ 508 while ((mt = mt_prev) != NULL && 509 mt->pindex >= firstpindex && 510 mt->valid == VM_PAGE_BITS_ALL) { 511 mt_prev = vm_page_prev(mt); 512 if (mt->busy || 513 (mt->oflags & VPO_BUSY)) 514 continue; 515 if (!are_queues_locked) { 516 are_queues_locked = TRUE; 517 vm_page_lock_queues(); 518 } 519 if (mt->hold_count || 520 mt->wire_count) 521 continue; 522 pmap_remove_all(mt); 523 if (mt->dirty) { 524 vm_page_deactivate(mt); 525 } else { 526 vm_page_cache(mt); 527 } 528 } 529 if (are_queues_locked) 530 vm_page_unlock_queues(); 531 ahead += behind; 532 behind = 0; 533 } 534 if (is_first_object_locked) 535 VM_OBJECT_UNLOCK(fs.first_object); 536 537 /* 538 * Call the pager to retrieve the data, if any, after 539 * releasing the lock on the map. We hold a ref on 540 * fs.object and the pages are VPO_BUSY'd. 541 */ 542 unlock_map(&fs); 543 544 vnode_lock: 545 if (fs.object->type == OBJT_VNODE) { 546 vp = fs.object->handle; 547 if (vp == fs.vp) 548 goto vnode_locked; 549 else if (fs.vp != NULL) { 550 vput(fs.vp); 551 fs.vp = NULL; 552 } 553 locked = VOP_ISLOCKED(vp); 554 555 if (VFS_NEEDSGIANT(vp->v_mount) && !fs.vfslocked) { 556 fs.vfslocked = 1; 557 if (!mtx_trylock(&Giant)) { 558 VM_OBJECT_UNLOCK(fs.object); 559 mtx_lock(&Giant); 560 VM_OBJECT_LOCK(fs.object); 561 goto vnode_lock; 562 } 563 } 564 if (locked != LK_EXCLUSIVE) 565 locked = LK_SHARED; 566 /* Do not sleep for vnode lock while fs.m is busy */ 567 error = vget(vp, locked | LK_CANRECURSE | 568 LK_NOWAIT, curthread); 569 if (error != 0) { 570 int vfslocked; 571 572 vfslocked = fs.vfslocked; 573 fs.vfslocked = 0; /* Keep Giant */ 574 vhold(vp); 575 release_page(&fs); 576 unlock_and_deallocate(&fs); 577 error = vget(vp, locked | LK_RETRY | 578 LK_CANRECURSE, curthread); 579 vdrop(vp); 580 fs.vp = vp; 581 fs.vfslocked = vfslocked; 582 KASSERT(error == 0, 583 ("vm_fault: vget failed")); 584 goto RetryFault; 585 } 586 fs.vp = vp; 587 } 588 vnode_locked: 589 KASSERT(fs.vp == NULL || !fs.map->system_map, 590 ("vm_fault: vnode-backed object mapped by system map")); 591 592 /* 593 * now we find out if any other pages should be paged 594 * in at this time this routine checks to see if the 595 * pages surrounding this fault reside in the same 596 * object as the page for this fault. If they do, 597 * then they are faulted in also into the object. The 598 * array "marray" returned contains an array of 599 * vm_page_t structs where one of them is the 600 * vm_page_t passed to the routine. The reqpage 601 * return value is the index into the marray for the 602 * vm_page_t passed to the routine. 603 * 604 * fs.m plus the additional pages are VPO_BUSY'd. 605 */ 606 faultcount = vm_fault_additional_pages( 607 fs.m, behind, ahead, marray, &reqpage); 608 609 rv = faultcount ? 610 vm_pager_get_pages(fs.object, marray, faultcount, 611 reqpage) : VM_PAGER_FAIL; 612 613 if (rv == VM_PAGER_OK) { 614 /* 615 * Found the page. Leave it busy while we play 616 * with it. 617 */ 618 619 /* 620 * Relookup in case pager changed page. Pager 621 * is responsible for disposition of old page 622 * if moved. 623 */ 624 fs.m = vm_page_lookup(fs.object, fs.pindex); 625 if (!fs.m) { 626 unlock_and_deallocate(&fs); 627 goto RetryFault; 628 } 629 630 hardfault++; 631 break; /* break to PAGE HAS BEEN FOUND */ 632 } 633 /* 634 * Remove the bogus page (which does not exist at this 635 * object/offset); before doing so, we must get back 636 * our object lock to preserve our invariant. 637 * 638 * Also wake up any other process that may want to bring 639 * in this page. 640 * 641 * If this is the top-level object, we must leave the 642 * busy page to prevent another process from rushing 643 * past us, and inserting the page in that object at 644 * the same time that we are. 645 */ 646 if (rv == VM_PAGER_ERROR) 647 printf("vm_fault: pager read error, pid %d (%s)\n", 648 curproc->p_pid, curproc->p_comm); 649 /* 650 * Data outside the range of the pager or an I/O error 651 */ 652 /* 653 * XXX - the check for kernel_map is a kludge to work 654 * around having the machine panic on a kernel space 655 * fault w/ I/O error. 656 */ 657 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 658 (rv == VM_PAGER_BAD)) { 659 vm_page_lock_queues(); 660 vm_page_free(fs.m); 661 vm_page_unlock_queues(); 662 fs.m = NULL; 663 unlock_and_deallocate(&fs); 664 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 665 } 666 if (fs.object != fs.first_object) { 667 vm_page_lock_queues(); 668 vm_page_free(fs.m); 669 vm_page_unlock_queues(); 670 fs.m = NULL; 671 /* 672 * XXX - we cannot just fall out at this 673 * point, m has been freed and is invalid! 674 */ 675 } 676 } 677 678 /* 679 * We get here if the object has default pager (or unwiring) 680 * or the pager doesn't have the page. 681 */ 682 if (fs.object == fs.first_object) 683 fs.first_m = fs.m; 684 685 /* 686 * Move on to the next object. Lock the next object before 687 * unlocking the current one. 688 */ 689 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 690 next_object = fs.object->backing_object; 691 if (next_object == NULL) { 692 /* 693 * If there's no object left, fill the page in the top 694 * object with zeros. 695 */ 696 if (fs.object != fs.first_object) { 697 vm_object_pip_wakeup(fs.object); 698 VM_OBJECT_UNLOCK(fs.object); 699 700 fs.object = fs.first_object; 701 fs.pindex = fs.first_pindex; 702 fs.m = fs.first_m; 703 VM_OBJECT_LOCK(fs.object); 704 } 705 fs.first_m = NULL; 706 707 /* 708 * Zero the page if necessary and mark it valid. 709 */ 710 if ((fs.m->flags & PG_ZERO) == 0) { 711 pmap_zero_page(fs.m); 712 } else { 713 PCPU_INC(cnt.v_ozfod); 714 } 715 PCPU_INC(cnt.v_zfod); 716 fs.m->valid = VM_PAGE_BITS_ALL; 717 break; /* break to PAGE HAS BEEN FOUND */ 718 } else { 719 KASSERT(fs.object != next_object, 720 ("object loop %p", next_object)); 721 VM_OBJECT_LOCK(next_object); 722 vm_object_pip_add(next_object, 1); 723 if (fs.object != fs.first_object) 724 vm_object_pip_wakeup(fs.object); 725 VM_OBJECT_UNLOCK(fs.object); 726 fs.object = next_object; 727 } 728 } 729 730 KASSERT((fs.m->oflags & VPO_BUSY) != 0, 731 ("vm_fault: not busy after main loop")); 732 733 /* 734 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 735 * is held.] 736 */ 737 738 /* 739 * If the page is being written, but isn't already owned by the 740 * top-level object, we have to copy it into a new page owned by the 741 * top-level object. 742 */ 743 if (fs.object != fs.first_object) { 744 /* 745 * We only really need to copy if we want to write it. 746 */ 747 if (fault_type & VM_PROT_WRITE) { 748 /* 749 * This allows pages to be virtually copied from a 750 * backing_object into the first_object, where the 751 * backing object has no other refs to it, and cannot 752 * gain any more refs. Instead of a bcopy, we just 753 * move the page from the backing object to the 754 * first object. Note that we must mark the page 755 * dirty in the first object so that it will go out 756 * to swap when needed. 757 */ 758 is_first_object_locked = FALSE; 759 if ( 760 /* 761 * Only one shadow object 762 */ 763 (fs.object->shadow_count == 1) && 764 /* 765 * No COW refs, except us 766 */ 767 (fs.object->ref_count == 1) && 768 /* 769 * No one else can look this object up 770 */ 771 (fs.object->handle == NULL) && 772 /* 773 * No other ways to look the object up 774 */ 775 ((fs.object->type == OBJT_DEFAULT) || 776 (fs.object->type == OBJT_SWAP)) && 777 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) && 778 /* 779 * We don't chase down the shadow chain 780 */ 781 fs.object == fs.first_object->backing_object) { 782 vm_page_lock_queues(); 783 /* 784 * get rid of the unnecessary page 785 */ 786 vm_page_free(fs.first_m); 787 /* 788 * grab the page and put it into the 789 * process'es object. The page is 790 * automatically made dirty. 791 */ 792 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 793 vm_page_unlock_queues(); 794 vm_page_busy(fs.m); 795 fs.first_m = fs.m; 796 fs.m = NULL; 797 PCPU_INC(cnt.v_cow_optim); 798 } else { 799 /* 800 * Oh, well, lets copy it. 801 */ 802 pmap_copy_page(fs.m, fs.first_m); 803 fs.first_m->valid = VM_PAGE_BITS_ALL; 804 } 805 if (fs.m) { 806 /* 807 * We no longer need the old page or object. 808 */ 809 release_page(&fs); 810 } 811 /* 812 * fs.object != fs.first_object due to above 813 * conditional 814 */ 815 vm_object_pip_wakeup(fs.object); 816 VM_OBJECT_UNLOCK(fs.object); 817 /* 818 * Only use the new page below... 819 */ 820 fs.object = fs.first_object; 821 fs.pindex = fs.first_pindex; 822 fs.m = fs.first_m; 823 if (!is_first_object_locked) 824 VM_OBJECT_LOCK(fs.object); 825 PCPU_INC(cnt.v_cow_faults); 826 } else { 827 prot &= ~VM_PROT_WRITE; 828 } 829 } 830 831 /* 832 * We must verify that the maps have not changed since our last 833 * lookup. 834 */ 835 if (!fs.lookup_still_valid) { 836 vm_object_t retry_object; 837 vm_pindex_t retry_pindex; 838 vm_prot_t retry_prot; 839 840 if (!vm_map_trylock_read(fs.map)) { 841 release_page(&fs); 842 unlock_and_deallocate(&fs); 843 goto RetryFault; 844 } 845 fs.lookup_still_valid = TRUE; 846 if (fs.map->timestamp != map_generation) { 847 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 848 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 849 850 /* 851 * If we don't need the page any longer, put it on the inactive 852 * list (the easiest thing to do here). If no one needs it, 853 * pageout will grab it eventually. 854 */ 855 if (result != KERN_SUCCESS) { 856 release_page(&fs); 857 unlock_and_deallocate(&fs); 858 859 /* 860 * If retry of map lookup would have blocked then 861 * retry fault from start. 862 */ 863 if (result == KERN_FAILURE) 864 goto RetryFault; 865 return (result); 866 } 867 if ((retry_object != fs.first_object) || 868 (retry_pindex != fs.first_pindex)) { 869 release_page(&fs); 870 unlock_and_deallocate(&fs); 871 goto RetryFault; 872 } 873 874 /* 875 * Check whether the protection has changed or the object has 876 * been copied while we left the map unlocked. Changing from 877 * read to write permission is OK - we leave the page 878 * write-protected, and catch the write fault. Changing from 879 * write to read permission means that we can't mark the page 880 * write-enabled after all. 881 */ 882 prot &= retry_prot; 883 } 884 } 885 /* 886 * If the page was filled by a pager, update the map entry's 887 * last read offset. Since the pager does not return the 888 * actual set of pages that it read, this update is based on 889 * the requested set. Typically, the requested and actual 890 * sets are the same. 891 * 892 * XXX The following assignment modifies the map 893 * without holding a write lock on it. 894 */ 895 if (hardfault) 896 fs.entry->lastr = fs.pindex + faultcount - behind; 897 898 if (prot & VM_PROT_WRITE) { 899 vm_object_set_writeable_dirty(fs.object); 900 901 /* 902 * If the fault is a write, we know that this page is being 903 * written NOW so dirty it explicitly to save on 904 * pmap_is_modified() calls later. 905 * 906 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 907 * if the page is already dirty to prevent data written with 908 * the expectation of being synced from not being synced. 909 * Likewise if this entry does not request NOSYNC then make 910 * sure the page isn't marked NOSYNC. Applications sharing 911 * data should use the same flags to avoid ping ponging. 912 * 913 * Also tell the backing pager, if any, that it should remove 914 * any swap backing since the page is now dirty. 915 */ 916 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 917 if (fs.m->dirty == 0) 918 fs.m->oflags |= VPO_NOSYNC; 919 } else { 920 fs.m->oflags &= ~VPO_NOSYNC; 921 } 922 if (fault_flags & VM_FAULT_DIRTY) { 923 vm_page_dirty(fs.m); 924 vm_pager_page_unswapped(fs.m); 925 } 926 } 927 928 /* 929 * Page had better still be busy 930 */ 931 KASSERT(fs.m->oflags & VPO_BUSY, 932 ("vm_fault: page %p not busy!", fs.m)); 933 /* 934 * Page must be completely valid or it is not fit to 935 * map into user space. vm_pager_get_pages() ensures this. 936 */ 937 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 938 ("vm_fault: page %p partially invalid", fs.m)); 939 VM_OBJECT_UNLOCK(fs.object); 940 941 /* 942 * Put this page into the physical map. We had to do the unlock above 943 * because pmap_enter() may sleep. We don't put the page 944 * back on the active queue until later so that the pageout daemon 945 * won't find it (yet). 946 */ 947 pmap_enter(fs.map->pmap, vaddr, fault_type, fs.m, prot, wired); 948 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) { 949 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry); 950 } 951 VM_OBJECT_LOCK(fs.object); 952 vm_page_lock_queues(); 953 vm_page_flag_set(fs.m, PG_REFERENCED); 954 955 /* 956 * If the page is not wired down, then put it where the pageout daemon 957 * can find it. 958 */ 959 if (fault_flags & VM_FAULT_WIRE_MASK) { 960 if (wired) 961 vm_page_wire(fs.m); 962 else 963 vm_page_unwire(fs.m, 1); 964 } else { 965 vm_page_activate(fs.m); 966 } 967 vm_page_unlock_queues(); 968 vm_page_wakeup(fs.m); 969 970 /* 971 * Unlock everything, and return 972 */ 973 unlock_and_deallocate(&fs); 974 if (hardfault) 975 curthread->td_ru.ru_majflt++; 976 else 977 curthread->td_ru.ru_minflt++; 978 979 return (KERN_SUCCESS); 980 } 981 982 /* 983 * vm_fault_prefault provides a quick way of clustering 984 * pagefaults into a processes address space. It is a "cousin" 985 * of vm_map_pmap_enter, except it runs at page fault time instead 986 * of mmap time. 987 */ 988 static void 989 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry) 990 { 991 int i; 992 vm_offset_t addr, starta; 993 vm_pindex_t pindex; 994 vm_page_t m; 995 vm_object_t object; 996 997 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 998 return; 999 1000 object = entry->object.vm_object; 1001 1002 starta = addra - PFBAK * PAGE_SIZE; 1003 if (starta < entry->start) { 1004 starta = entry->start; 1005 } else if (starta > addra) { 1006 starta = 0; 1007 } 1008 1009 for (i = 0; i < PAGEORDER_SIZE; i++) { 1010 vm_object_t backing_object, lobject; 1011 1012 addr = addra + prefault_pageorder[i]; 1013 if (addr > addra + (PFFOR * PAGE_SIZE)) 1014 addr = 0; 1015 1016 if (addr < starta || addr >= entry->end) 1017 continue; 1018 1019 if (!pmap_is_prefaultable(pmap, addr)) 1020 continue; 1021 1022 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1023 lobject = object; 1024 VM_OBJECT_LOCK(lobject); 1025 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1026 lobject->type == OBJT_DEFAULT && 1027 (backing_object = lobject->backing_object) != NULL) { 1028 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1029 0, ("vm_fault_prefault: unaligned object offset")); 1030 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1031 VM_OBJECT_LOCK(backing_object); 1032 VM_OBJECT_UNLOCK(lobject); 1033 lobject = backing_object; 1034 } 1035 /* 1036 * give-up when a page is not in memory 1037 */ 1038 if (m == NULL) { 1039 VM_OBJECT_UNLOCK(lobject); 1040 break; 1041 } 1042 if (m->valid == VM_PAGE_BITS_ALL && 1043 (m->flags & PG_FICTITIOUS) == 0) { 1044 vm_page_lock_queues(); 1045 pmap_enter_quick(pmap, addr, m, entry->protection); 1046 vm_page_unlock_queues(); 1047 } 1048 VM_OBJECT_UNLOCK(lobject); 1049 } 1050 } 1051 1052 /* 1053 * vm_fault_quick: 1054 * 1055 * Ensure that the requested virtual address, which may be in userland, 1056 * is valid. Fault-in the page if necessary. Return -1 on failure. 1057 */ 1058 int 1059 vm_fault_quick(caddr_t v, int prot) 1060 { 1061 int r; 1062 1063 if (prot & VM_PROT_WRITE) 1064 r = subyte(v, fubyte(v)); 1065 else 1066 r = fubyte(v); 1067 return(r); 1068 } 1069 1070 /* 1071 * vm_fault_wire: 1072 * 1073 * Wire down a range of virtual addresses in a map. 1074 */ 1075 int 1076 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1077 boolean_t user_wire, boolean_t fictitious) 1078 { 1079 vm_offset_t va; 1080 int rv; 1081 1082 /* 1083 * We simulate a fault to get the page and enter it in the physical 1084 * map. For user wiring, we only ask for read access on currently 1085 * read-only sections. 1086 */ 1087 for (va = start; va < end; va += PAGE_SIZE) { 1088 rv = vm_fault(map, va, 1089 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE, 1090 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING); 1091 if (rv) { 1092 if (va != start) 1093 vm_fault_unwire(map, start, va, fictitious); 1094 return (rv); 1095 } 1096 } 1097 return (KERN_SUCCESS); 1098 } 1099 1100 /* 1101 * vm_fault_unwire: 1102 * 1103 * Unwire a range of virtual addresses in a map. 1104 */ 1105 void 1106 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1107 boolean_t fictitious) 1108 { 1109 vm_paddr_t pa; 1110 vm_offset_t va; 1111 pmap_t pmap; 1112 1113 pmap = vm_map_pmap(map); 1114 1115 /* 1116 * Since the pages are wired down, we must be able to get their 1117 * mappings from the physical map system. 1118 */ 1119 for (va = start; va < end; va += PAGE_SIZE) { 1120 pa = pmap_extract(pmap, va); 1121 if (pa != 0) { 1122 pmap_change_wiring(pmap, va, FALSE); 1123 if (!fictitious) { 1124 vm_page_lock_queues(); 1125 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1126 vm_page_unlock_queues(); 1127 } 1128 } 1129 } 1130 } 1131 1132 /* 1133 * Routine: 1134 * vm_fault_copy_entry 1135 * Function: 1136 * Create new shadow object backing dst_entry with private copy of 1137 * all underlying pages. When src_entry is equal to dst_entry, 1138 * function implements COW for wired-down map entry. Otherwise, 1139 * it forks wired entry into dst_map. 1140 * 1141 * In/out conditions: 1142 * The source and destination maps must be locked for write. 1143 * The source map entry must be wired down (or be a sharing map 1144 * entry corresponding to a main map entry that is wired down). 1145 */ 1146 void 1147 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1148 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1149 vm_ooffset_t *fork_charge) 1150 { 1151 vm_object_t backing_object, dst_object, object, src_object; 1152 vm_pindex_t dst_pindex, pindex, src_pindex; 1153 vm_prot_t access, prot; 1154 vm_offset_t vaddr; 1155 vm_page_t dst_m; 1156 vm_page_t src_m; 1157 boolean_t src_readonly, upgrade; 1158 1159 #ifdef lint 1160 src_map++; 1161 #endif /* lint */ 1162 1163 upgrade = src_entry == dst_entry; 1164 1165 src_object = src_entry->object.vm_object; 1166 src_pindex = OFF_TO_IDX(src_entry->offset); 1167 src_readonly = (src_entry->protection & VM_PROT_WRITE) == 0; 1168 1169 /* 1170 * Create the top-level object for the destination entry. (Doesn't 1171 * actually shadow anything - we copy the pages directly.) 1172 */ 1173 dst_object = vm_object_allocate(OBJT_DEFAULT, 1174 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1175 #if VM_NRESERVLEVEL > 0 1176 dst_object->flags |= OBJ_COLORED; 1177 dst_object->pg_color = atop(dst_entry->start); 1178 #endif 1179 1180 VM_OBJECT_LOCK(dst_object); 1181 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1182 ("vm_fault_copy_entry: vm_object not NULL")); 1183 dst_entry->object.vm_object = dst_object; 1184 dst_entry->offset = 0; 1185 dst_object->charge = dst_entry->end - dst_entry->start; 1186 if (fork_charge != NULL) { 1187 KASSERT(dst_entry->uip == NULL, 1188 ("vm_fault_copy_entry: leaked swp charge")); 1189 dst_object->uip = curthread->td_ucred->cr_ruidinfo; 1190 uihold(dst_object->uip); 1191 *fork_charge += dst_object->charge; 1192 } else { 1193 dst_object->uip = dst_entry->uip; 1194 dst_entry->uip = NULL; 1195 } 1196 access = prot = dst_entry->max_protection; 1197 /* 1198 * If not an upgrade, then enter the mappings in the pmap as 1199 * read and/or execute accesses. Otherwise, enter them as 1200 * write accesses. 1201 * 1202 * A writeable large page mapping is only created if all of 1203 * the constituent small page mappings are modified. Marking 1204 * PTEs as modified on inception allows promotion to happen 1205 * without taking potentially large number of soft faults. 1206 */ 1207 if (!upgrade) 1208 access &= ~VM_PROT_WRITE; 1209 1210 /* 1211 * Loop through all of the pages in the entry's range, copying each 1212 * one from the source object (it should be there) to the destination 1213 * object. 1214 */ 1215 for (vaddr = dst_entry->start, dst_pindex = 0; 1216 vaddr < dst_entry->end; 1217 vaddr += PAGE_SIZE, dst_pindex++) { 1218 1219 /* 1220 * Allocate a page in the destination object. 1221 */ 1222 do { 1223 dst_m = vm_page_alloc(dst_object, dst_pindex, 1224 VM_ALLOC_NORMAL); 1225 if (dst_m == NULL) { 1226 VM_OBJECT_UNLOCK(dst_object); 1227 VM_WAIT; 1228 VM_OBJECT_LOCK(dst_object); 1229 } 1230 } while (dst_m == NULL); 1231 1232 /* 1233 * Find the page in the source object, and copy it in. 1234 * (Because the source is wired down, the page will be in 1235 * memory.) 1236 */ 1237 VM_OBJECT_LOCK(src_object); 1238 object = src_object; 1239 pindex = src_pindex + dst_pindex; 1240 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1241 src_readonly && 1242 (backing_object = object->backing_object) != NULL) { 1243 /* 1244 * Allow fallback to backing objects if we are reading. 1245 */ 1246 VM_OBJECT_LOCK(backing_object); 1247 pindex += OFF_TO_IDX(object->backing_object_offset); 1248 VM_OBJECT_UNLOCK(object); 1249 object = backing_object; 1250 } 1251 if (src_m == NULL) 1252 panic("vm_fault_copy_wired: page missing"); 1253 pmap_copy_page(src_m, dst_m); 1254 VM_OBJECT_UNLOCK(object); 1255 dst_m->valid = VM_PAGE_BITS_ALL; 1256 VM_OBJECT_UNLOCK(dst_object); 1257 1258 /* 1259 * Enter it in the pmap. If a wired, copy-on-write 1260 * mapping is being replaced by a write-enabled 1261 * mapping, then wire that new mapping. 1262 */ 1263 pmap_enter(dst_map->pmap, vaddr, access, dst_m, prot, upgrade); 1264 1265 /* 1266 * Mark it no longer busy, and put it on the active list. 1267 */ 1268 VM_OBJECT_LOCK(dst_object); 1269 vm_page_lock_queues(); 1270 if (upgrade) { 1271 vm_page_unwire(src_m, 0); 1272 vm_page_wire(dst_m); 1273 } else 1274 vm_page_activate(dst_m); 1275 vm_page_unlock_queues(); 1276 vm_page_wakeup(dst_m); 1277 } 1278 VM_OBJECT_UNLOCK(dst_object); 1279 if (upgrade) { 1280 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1281 vm_object_deallocate(src_object); 1282 } 1283 } 1284 1285 1286 /* 1287 * This routine checks around the requested page for other pages that 1288 * might be able to be faulted in. This routine brackets the viable 1289 * pages for the pages to be paged in. 1290 * 1291 * Inputs: 1292 * m, rbehind, rahead 1293 * 1294 * Outputs: 1295 * marray (array of vm_page_t), reqpage (index of requested page) 1296 * 1297 * Return value: 1298 * number of pages in marray 1299 */ 1300 static int 1301 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1302 vm_page_t m; 1303 int rbehind; 1304 int rahead; 1305 vm_page_t *marray; 1306 int *reqpage; 1307 { 1308 int i,j; 1309 vm_object_t object; 1310 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1311 vm_page_t rtm; 1312 int cbehind, cahead; 1313 1314 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED); 1315 1316 object = m->object; 1317 pindex = m->pindex; 1318 cbehind = cahead = 0; 1319 1320 /* 1321 * if the requested page is not available, then give up now 1322 */ 1323 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1324 return 0; 1325 } 1326 1327 if ((cbehind == 0) && (cahead == 0)) { 1328 *reqpage = 0; 1329 marray[0] = m; 1330 return 1; 1331 } 1332 1333 if (rahead > cahead) { 1334 rahead = cahead; 1335 } 1336 1337 if (rbehind > cbehind) { 1338 rbehind = cbehind; 1339 } 1340 1341 /* 1342 * scan backward for the read behind pages -- in memory 1343 */ 1344 if (pindex > 0) { 1345 if (rbehind > pindex) { 1346 rbehind = pindex; 1347 startpindex = 0; 1348 } else { 1349 startpindex = pindex - rbehind; 1350 } 1351 1352 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1353 rtm->pindex >= startpindex) 1354 startpindex = rtm->pindex + 1; 1355 1356 /* tpindex is unsigned; beware of numeric underflow. */ 1357 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1358 tpindex < pindex; i++, tpindex--) { 1359 1360 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1361 VM_ALLOC_IFNOTCACHED); 1362 if (rtm == NULL) { 1363 /* 1364 * Shift the allocated pages to the 1365 * beginning of the array. 1366 */ 1367 for (j = 0; j < i; j++) { 1368 marray[j] = marray[j + tpindex + 1 - 1369 startpindex]; 1370 } 1371 break; 1372 } 1373 1374 marray[tpindex - startpindex] = rtm; 1375 } 1376 } else { 1377 startpindex = 0; 1378 i = 0; 1379 } 1380 1381 marray[i] = m; 1382 /* page offset of the required page */ 1383 *reqpage = i; 1384 1385 tpindex = pindex + 1; 1386 i++; 1387 1388 /* 1389 * scan forward for the read ahead pages 1390 */ 1391 endpindex = tpindex + rahead; 1392 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1393 endpindex = rtm->pindex; 1394 if (endpindex > object->size) 1395 endpindex = object->size; 1396 1397 for (; tpindex < endpindex; i++, tpindex++) { 1398 1399 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1400 VM_ALLOC_IFNOTCACHED); 1401 if (rtm == NULL) { 1402 break; 1403 } 1404 1405 marray[i] = rtm; 1406 } 1407 1408 /* return number of pages */ 1409 return i; 1410 }
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