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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/9.2/sys/vm/vm_fault.c 242397 2012-10-31 14:02:51Z kib $"); 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/vm_extern.h> 104 105 #include <sys/mount.h> /* XXX Temporary for VFS_LOCK_GIANT() */ 106 107 #define PFBAK 4 108 #define PFFOR 4 109 #define PAGEORDER_SIZE (PFBAK+PFFOR) 110 111 static int prefault_pageorder[] = { 112 -1 * PAGE_SIZE, 1 * PAGE_SIZE, 113 -2 * PAGE_SIZE, 2 * PAGE_SIZE, 114 -3 * PAGE_SIZE, 3 * PAGE_SIZE, 115 -4 * PAGE_SIZE, 4 * PAGE_SIZE 116 }; 117 118 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 119 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t); 120 121 #define VM_FAULT_READ_BEHIND 8 122 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX) 123 #define VM_FAULT_NINCR (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND) 124 #define VM_FAULT_SUM (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2) 125 #define VM_FAULT_CACHE_BEHIND (VM_FAULT_READ_BEHIND * VM_FAULT_SUM) 126 127 struct faultstate { 128 vm_page_t m; 129 vm_object_t object; 130 vm_pindex_t pindex; 131 vm_page_t first_m; 132 vm_object_t first_object; 133 vm_pindex_t first_pindex; 134 vm_map_t map; 135 vm_map_entry_t entry; 136 int lookup_still_valid; 137 struct vnode *vp; 138 int vfslocked; 139 }; 140 141 static void vm_fault_cache_behind(const struct faultstate *fs, int distance); 142 143 static inline void 144 release_page(struct faultstate *fs) 145 { 146 147 vm_page_wakeup(fs->m); 148 vm_page_lock(fs->m); 149 vm_page_deactivate(fs->m); 150 vm_page_unlock(fs->m); 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(fs->first_m); 173 vm_page_free(fs->first_m); 174 vm_page_unlock(fs->first_m); 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_CHANGE_WIRING) == 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 * The map in question must be referenced, and remains so. 213 * Caller may hold no locks. 214 */ 215 int 216 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 217 int fault_flags) 218 { 219 struct thread *td; 220 int result; 221 222 td = curthread; 223 if ((td->td_pflags & TDP_NOFAULTING) != 0) 224 return (KERN_PROTECTION_FAILURE); 225 #ifdef KTRACE 226 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 227 ktrfault(vaddr, fault_type); 228 #endif 229 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 230 NULL); 231 #ifdef KTRACE 232 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 233 ktrfaultend(result); 234 #endif 235 return (result); 236 } 237 238 int 239 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 240 int fault_flags, vm_page_t *m_hold) 241 { 242 vm_prot_t prot; 243 long ahead, behind; 244 int alloc_req, era, faultcount, nera, reqpage, result; 245 boolean_t growstack, is_first_object_locked, wired; 246 int map_generation; 247 vm_object_t next_object; 248 vm_page_t marray[VM_FAULT_READ_MAX]; 249 int hardfault; 250 struct faultstate fs; 251 struct vnode *vp; 252 int locked, error; 253 254 hardfault = 0; 255 growstack = TRUE; 256 PCPU_INC(cnt.v_vm_faults); 257 fs.vp = NULL; 258 fs.vfslocked = 0; 259 faultcount = reqpage = 0; 260 261 RetryFault:; 262 263 /* 264 * Find the backing store object and offset into it to begin the 265 * search. 266 */ 267 fs.map = map; 268 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 269 &fs.first_object, &fs.first_pindex, &prot, &wired); 270 if (result != KERN_SUCCESS) { 271 if (growstack && result == KERN_INVALID_ADDRESS && 272 map != kernel_map) { 273 result = vm_map_growstack(curproc, vaddr); 274 if (result != KERN_SUCCESS) 275 return (KERN_FAILURE); 276 growstack = FALSE; 277 goto RetryFault; 278 } 279 return (result); 280 } 281 282 map_generation = fs.map->timestamp; 283 284 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 285 panic("vm_fault: fault on nofault entry, addr: %lx", 286 (u_long)vaddr); 287 } 288 289 /* 290 * Make a reference to this object to prevent its disposal while we 291 * are messing with it. Once we have the reference, the map is free 292 * to be diddled. Since objects reference their shadows (and copies), 293 * they will stay around as well. 294 * 295 * Bump the paging-in-progress count to prevent size changes (e.g. 296 * truncation operations) during I/O. This must be done after 297 * obtaining the vnode lock in order to avoid possible deadlocks. 298 */ 299 VM_OBJECT_LOCK(fs.first_object); 300 vm_object_reference_locked(fs.first_object); 301 vm_object_pip_add(fs.first_object, 1); 302 303 fs.lookup_still_valid = TRUE; 304 305 if (wired) 306 fault_type = prot | (fault_type & VM_PROT_COPY); 307 308 fs.first_m = NULL; 309 310 /* 311 * Search for the page at object/offset. 312 */ 313 fs.object = fs.first_object; 314 fs.pindex = fs.first_pindex; 315 while (TRUE) { 316 /* 317 * If the object is dead, we stop here 318 */ 319 if (fs.object->flags & OBJ_DEAD) { 320 unlock_and_deallocate(&fs); 321 return (KERN_PROTECTION_FAILURE); 322 } 323 324 /* 325 * See if page is resident 326 */ 327 fs.m = vm_page_lookup(fs.object, fs.pindex); 328 if (fs.m != NULL) { 329 /* 330 * check for page-based copy on write. 331 * We check fs.object == fs.first_object so 332 * as to ensure the legacy COW mechanism is 333 * used when the page in question is part of 334 * a shadow object. Otherwise, vm_page_cowfault() 335 * removes the page from the backing object, 336 * which is not what we want. 337 */ 338 vm_page_lock(fs.m); 339 if ((fs.m->cow) && 340 (fault_type & VM_PROT_WRITE) && 341 (fs.object == fs.first_object)) { 342 vm_page_cowfault(fs.m); 343 unlock_and_deallocate(&fs); 344 goto RetryFault; 345 } 346 347 /* 348 * Wait/Retry if the page is busy. We have to do this 349 * if the page is busy via either VPO_BUSY or 350 * vm_page_t->busy because the vm_pager may be using 351 * vm_page_t->busy for pageouts ( and even pageins if 352 * it is the vnode pager ), and we could end up trying 353 * to pagein and pageout the same page simultaneously. 354 * 355 * We can theoretically allow the busy case on a read 356 * fault if the page is marked valid, but since such 357 * pages are typically already pmap'd, putting that 358 * special case in might be more effort then it is 359 * worth. We cannot under any circumstances mess 360 * around with a vm_page_t->busy page except, perhaps, 361 * to pmap it. 362 */ 363 if ((fs.m->oflags & VPO_BUSY) || fs.m->busy) { 364 /* 365 * Reference the page before unlocking and 366 * sleeping so that the page daemon is less 367 * likely to reclaim it. 368 */ 369 vm_page_aflag_set(fs.m, PGA_REFERENCED); 370 vm_page_unlock(fs.m); 371 if (fs.object != fs.first_object) { 372 if (!VM_OBJECT_TRYLOCK( 373 fs.first_object)) { 374 VM_OBJECT_UNLOCK(fs.object); 375 VM_OBJECT_LOCK(fs.first_object); 376 VM_OBJECT_LOCK(fs.object); 377 } 378 vm_page_lock(fs.first_m); 379 vm_page_free(fs.first_m); 380 vm_page_unlock(fs.first_m); 381 vm_object_pip_wakeup(fs.first_object); 382 VM_OBJECT_UNLOCK(fs.first_object); 383 fs.first_m = NULL; 384 } 385 unlock_map(&fs); 386 if (fs.m == vm_page_lookup(fs.object, 387 fs.pindex)) { 388 vm_page_sleep_if_busy(fs.m, TRUE, 389 "vmpfw"); 390 } 391 vm_object_pip_wakeup(fs.object); 392 VM_OBJECT_UNLOCK(fs.object); 393 PCPU_INC(cnt.v_intrans); 394 vm_object_deallocate(fs.first_object); 395 goto RetryFault; 396 } 397 vm_pageq_remove(fs.m); 398 vm_page_unlock(fs.m); 399 400 /* 401 * Mark page busy for other processes, and the 402 * pagedaemon. If it still isn't completely valid 403 * (readable), jump to readrest, else break-out ( we 404 * found the page ). 405 */ 406 vm_page_busy(fs.m); 407 if (fs.m->valid != VM_PAGE_BITS_ALL) 408 goto readrest; 409 break; 410 } 411 412 /* 413 * Page is not resident, If this is the search termination 414 * or the pager might contain the page, allocate a new page. 415 */ 416 if (TRYPAGER || fs.object == fs.first_object) { 417 if (fs.pindex >= fs.object->size) { 418 unlock_and_deallocate(&fs); 419 return (KERN_PROTECTION_FAILURE); 420 } 421 422 /* 423 * Allocate a new page for this object/offset pair. 424 * 425 * Unlocked read of the p_flag is harmless. At 426 * worst, the P_KILLED might be not observed 427 * there, and allocation can fail, causing 428 * restart and new reading of the p_flag. 429 */ 430 fs.m = NULL; 431 if (!vm_page_count_severe() || P_KILLED(curproc)) { 432 #if VM_NRESERVLEVEL > 0 433 if ((fs.object->flags & OBJ_COLORED) == 0) { 434 fs.object->flags |= OBJ_COLORED; 435 fs.object->pg_color = atop(vaddr) - 436 fs.pindex; 437 } 438 #endif 439 alloc_req = P_KILLED(curproc) ? 440 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 441 if (fs.object->type != OBJT_VNODE && 442 fs.object->backing_object == NULL) 443 alloc_req |= VM_ALLOC_ZERO; 444 fs.m = vm_page_alloc(fs.object, fs.pindex, 445 alloc_req); 446 } 447 if (fs.m == NULL) { 448 unlock_and_deallocate(&fs); 449 VM_WAITPFAULT; 450 goto RetryFault; 451 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 452 break; 453 } 454 455 readrest: 456 /* 457 * We have found a valid page or we have allocated a new page. 458 * The page thus may not be valid or may not be entirely 459 * valid. 460 * 461 * Attempt to fault-in the page if there is a chance that the 462 * pager has it, and potentially fault in additional pages 463 * at the same time. 464 */ 465 if (TRYPAGER) { 466 int rv; 467 u_char behavior = vm_map_entry_behavior(fs.entry); 468 469 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 470 P_KILLED(curproc)) { 471 behind = 0; 472 ahead = 0; 473 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 474 behind = 0; 475 ahead = atop(fs.entry->end - vaddr) - 1; 476 if (ahead > VM_FAULT_READ_AHEAD_MAX) 477 ahead = VM_FAULT_READ_AHEAD_MAX; 478 if (fs.pindex == fs.entry->next_read) 479 vm_fault_cache_behind(&fs, 480 VM_FAULT_READ_MAX); 481 } else { 482 /* 483 * If this is a sequential page fault, then 484 * arithmetically increase the number of pages 485 * in the read-ahead window. Otherwise, reset 486 * the read-ahead window to its smallest size. 487 */ 488 behind = atop(vaddr - fs.entry->start); 489 if (behind > VM_FAULT_READ_BEHIND) 490 behind = VM_FAULT_READ_BEHIND; 491 ahead = atop(fs.entry->end - vaddr) - 1; 492 era = fs.entry->read_ahead; 493 if (fs.pindex == fs.entry->next_read) { 494 nera = era + behind; 495 if (nera > VM_FAULT_READ_AHEAD_MAX) 496 nera = VM_FAULT_READ_AHEAD_MAX; 497 behind = 0; 498 if (ahead > nera) 499 ahead = nera; 500 if (era == VM_FAULT_READ_AHEAD_MAX) 501 vm_fault_cache_behind(&fs, 502 VM_FAULT_CACHE_BEHIND); 503 } else if (ahead > VM_FAULT_READ_AHEAD_MIN) 504 ahead = VM_FAULT_READ_AHEAD_MIN; 505 if (era != ahead) 506 fs.entry->read_ahead = ahead; 507 } 508 509 /* 510 * Call the pager to retrieve the data, if any, after 511 * releasing the lock on the map. We hold a ref on 512 * fs.object and the pages are VPO_BUSY'd. 513 */ 514 unlock_map(&fs); 515 516 vnode_lock: 517 if (fs.object->type == OBJT_VNODE) { 518 vp = fs.object->handle; 519 if (vp == fs.vp) 520 goto vnode_locked; 521 else if (fs.vp != NULL) { 522 vput(fs.vp); 523 fs.vp = NULL; 524 } 525 locked = VOP_ISLOCKED(vp); 526 527 if (VFS_NEEDSGIANT(vp->v_mount) && !fs.vfslocked) { 528 fs.vfslocked = 1; 529 if (!mtx_trylock(&Giant)) { 530 VM_OBJECT_UNLOCK(fs.object); 531 mtx_lock(&Giant); 532 VM_OBJECT_LOCK(fs.object); 533 goto vnode_lock; 534 } 535 } 536 if (locked != LK_EXCLUSIVE) 537 locked = LK_SHARED; 538 /* Do not sleep for vnode lock while fs.m is busy */ 539 error = vget(vp, locked | LK_CANRECURSE | 540 LK_NOWAIT, curthread); 541 if (error != 0) { 542 int vfslocked; 543 544 vfslocked = fs.vfslocked; 545 fs.vfslocked = 0; /* Keep Giant */ 546 vhold(vp); 547 release_page(&fs); 548 unlock_and_deallocate(&fs); 549 error = vget(vp, locked | LK_RETRY | 550 LK_CANRECURSE, curthread); 551 vdrop(vp); 552 fs.vp = vp; 553 fs.vfslocked = vfslocked; 554 KASSERT(error == 0, 555 ("vm_fault: vget failed")); 556 goto RetryFault; 557 } 558 fs.vp = vp; 559 } 560 vnode_locked: 561 KASSERT(fs.vp == NULL || !fs.map->system_map, 562 ("vm_fault: vnode-backed object mapped by system map")); 563 564 /* 565 * now we find out if any other pages should be paged 566 * in at this time this routine checks to see if the 567 * pages surrounding this fault reside in the same 568 * object as the page for this fault. If they do, 569 * then they are faulted in also into the object. The 570 * array "marray" returned contains an array of 571 * vm_page_t structs where one of them is the 572 * vm_page_t passed to the routine. The reqpage 573 * return value is the index into the marray for the 574 * vm_page_t passed to the routine. 575 * 576 * fs.m plus the additional pages are VPO_BUSY'd. 577 */ 578 faultcount = vm_fault_additional_pages( 579 fs.m, behind, ahead, marray, &reqpage); 580 581 rv = faultcount ? 582 vm_pager_get_pages(fs.object, marray, faultcount, 583 reqpage) : VM_PAGER_FAIL; 584 585 if (rv == VM_PAGER_OK) { 586 /* 587 * Found the page. Leave it busy while we play 588 * with it. 589 */ 590 591 /* 592 * Relookup in case pager changed page. Pager 593 * is responsible for disposition of old page 594 * if moved. 595 */ 596 fs.m = vm_page_lookup(fs.object, fs.pindex); 597 if (!fs.m) { 598 unlock_and_deallocate(&fs); 599 goto RetryFault; 600 } 601 602 hardfault++; 603 break; /* break to PAGE HAS BEEN FOUND */ 604 } 605 /* 606 * Remove the bogus page (which does not exist at this 607 * object/offset); before doing so, we must get back 608 * our object lock to preserve our invariant. 609 * 610 * Also wake up any other process that may want to bring 611 * in this page. 612 * 613 * If this is the top-level object, we must leave the 614 * busy page to prevent another process from rushing 615 * past us, and inserting the page in that object at 616 * the same time that we are. 617 */ 618 if (rv == VM_PAGER_ERROR) 619 printf("vm_fault: pager read error, pid %d (%s)\n", 620 curproc->p_pid, curproc->p_comm); 621 /* 622 * Data outside the range of the pager or an I/O error 623 */ 624 /* 625 * XXX - the check for kernel_map is a kludge to work 626 * around having the machine panic on a kernel space 627 * fault w/ I/O error. 628 */ 629 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 630 (rv == VM_PAGER_BAD)) { 631 vm_page_lock(fs.m); 632 vm_page_free(fs.m); 633 vm_page_unlock(fs.m); 634 fs.m = NULL; 635 unlock_and_deallocate(&fs); 636 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 637 } 638 if (fs.object != fs.first_object) { 639 vm_page_lock(fs.m); 640 vm_page_free(fs.m); 641 vm_page_unlock(fs.m); 642 fs.m = NULL; 643 /* 644 * XXX - we cannot just fall out at this 645 * point, m has been freed and is invalid! 646 */ 647 } 648 } 649 650 /* 651 * We get here if the object has default pager (or unwiring) 652 * or the pager doesn't have the page. 653 */ 654 if (fs.object == fs.first_object) 655 fs.first_m = fs.m; 656 657 /* 658 * Move on to the next object. Lock the next object before 659 * unlocking the current one. 660 */ 661 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 662 next_object = fs.object->backing_object; 663 if (next_object == NULL) { 664 /* 665 * If there's no object left, fill the page in the top 666 * object with zeros. 667 */ 668 if (fs.object != fs.first_object) { 669 vm_object_pip_wakeup(fs.object); 670 VM_OBJECT_UNLOCK(fs.object); 671 672 fs.object = fs.first_object; 673 fs.pindex = fs.first_pindex; 674 fs.m = fs.first_m; 675 VM_OBJECT_LOCK(fs.object); 676 } 677 fs.first_m = NULL; 678 679 /* 680 * Zero the page if necessary and mark it valid. 681 */ 682 if ((fs.m->flags & PG_ZERO) == 0) { 683 pmap_zero_page(fs.m); 684 } else { 685 PCPU_INC(cnt.v_ozfod); 686 } 687 PCPU_INC(cnt.v_zfod); 688 fs.m->valid = VM_PAGE_BITS_ALL; 689 break; /* break to PAGE HAS BEEN FOUND */ 690 } else { 691 KASSERT(fs.object != next_object, 692 ("object loop %p", next_object)); 693 VM_OBJECT_LOCK(next_object); 694 vm_object_pip_add(next_object, 1); 695 if (fs.object != fs.first_object) 696 vm_object_pip_wakeup(fs.object); 697 VM_OBJECT_UNLOCK(fs.object); 698 fs.object = next_object; 699 } 700 } 701 702 KASSERT((fs.m->oflags & VPO_BUSY) != 0, 703 ("vm_fault: not busy after main loop")); 704 705 /* 706 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 707 * is held.] 708 */ 709 710 /* 711 * If the page is being written, but isn't already owned by the 712 * top-level object, we have to copy it into a new page owned by the 713 * top-level object. 714 */ 715 if (fs.object != fs.first_object) { 716 /* 717 * We only really need to copy if we want to write it. 718 */ 719 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 720 /* 721 * This allows pages to be virtually copied from a 722 * backing_object into the first_object, where the 723 * backing object has no other refs to it, and cannot 724 * gain any more refs. Instead of a bcopy, we just 725 * move the page from the backing object to the 726 * first object. Note that we must mark the page 727 * dirty in the first object so that it will go out 728 * to swap when needed. 729 */ 730 is_first_object_locked = FALSE; 731 if ( 732 /* 733 * Only one shadow object 734 */ 735 (fs.object->shadow_count == 1) && 736 /* 737 * No COW refs, except us 738 */ 739 (fs.object->ref_count == 1) && 740 /* 741 * No one else can look this object up 742 */ 743 (fs.object->handle == NULL) && 744 /* 745 * No other ways to look the object up 746 */ 747 ((fs.object->type == OBJT_DEFAULT) || 748 (fs.object->type == OBJT_SWAP)) && 749 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) && 750 /* 751 * We don't chase down the shadow chain 752 */ 753 fs.object == fs.first_object->backing_object) { 754 /* 755 * get rid of the unnecessary page 756 */ 757 vm_page_lock(fs.first_m); 758 vm_page_free(fs.first_m); 759 vm_page_unlock(fs.first_m); 760 /* 761 * grab the page and put it into the 762 * process'es object. The page is 763 * automatically made dirty. 764 */ 765 vm_page_lock(fs.m); 766 vm_page_rename(fs.m, fs.first_object, fs.first_pindex); 767 vm_page_unlock(fs.m); 768 vm_page_busy(fs.m); 769 fs.first_m = fs.m; 770 fs.m = NULL; 771 PCPU_INC(cnt.v_cow_optim); 772 } else { 773 /* 774 * Oh, well, lets copy it. 775 */ 776 pmap_copy_page(fs.m, fs.first_m); 777 fs.first_m->valid = VM_PAGE_BITS_ALL; 778 if (wired && (fault_flags & 779 VM_FAULT_CHANGE_WIRING) == 0) { 780 vm_page_lock(fs.first_m); 781 vm_page_wire(fs.first_m); 782 vm_page_unlock(fs.first_m); 783 784 vm_page_lock(fs.m); 785 vm_page_unwire(fs.m, FALSE); 786 vm_page_unlock(fs.m); 787 } 788 /* 789 * We no longer need the old page or object. 790 */ 791 release_page(&fs); 792 } 793 /* 794 * fs.object != fs.first_object due to above 795 * conditional 796 */ 797 vm_object_pip_wakeup(fs.object); 798 VM_OBJECT_UNLOCK(fs.object); 799 /* 800 * Only use the new page below... 801 */ 802 fs.object = fs.first_object; 803 fs.pindex = fs.first_pindex; 804 fs.m = fs.first_m; 805 if (!is_first_object_locked) 806 VM_OBJECT_LOCK(fs.object); 807 PCPU_INC(cnt.v_cow_faults); 808 curthread->td_cow++; 809 } else { 810 prot &= ~VM_PROT_WRITE; 811 } 812 } 813 814 /* 815 * We must verify that the maps have not changed since our last 816 * lookup. 817 */ 818 if (!fs.lookup_still_valid) { 819 vm_object_t retry_object; 820 vm_pindex_t retry_pindex; 821 vm_prot_t retry_prot; 822 823 if (!vm_map_trylock_read(fs.map)) { 824 release_page(&fs); 825 unlock_and_deallocate(&fs); 826 goto RetryFault; 827 } 828 fs.lookup_still_valid = TRUE; 829 if (fs.map->timestamp != map_generation) { 830 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 831 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 832 833 /* 834 * If we don't need the page any longer, put it on the inactive 835 * list (the easiest thing to do here). If no one needs it, 836 * pageout will grab it eventually. 837 */ 838 if (result != KERN_SUCCESS) { 839 release_page(&fs); 840 unlock_and_deallocate(&fs); 841 842 /* 843 * If retry of map lookup would have blocked then 844 * retry fault from start. 845 */ 846 if (result == KERN_FAILURE) 847 goto RetryFault; 848 return (result); 849 } 850 if ((retry_object != fs.first_object) || 851 (retry_pindex != fs.first_pindex)) { 852 release_page(&fs); 853 unlock_and_deallocate(&fs); 854 goto RetryFault; 855 } 856 857 /* 858 * Check whether the protection has changed or the object has 859 * been copied while we left the map unlocked. Changing from 860 * read to write permission is OK - we leave the page 861 * write-protected, and catch the write fault. Changing from 862 * write to read permission means that we can't mark the page 863 * write-enabled after all. 864 */ 865 prot &= retry_prot; 866 } 867 } 868 /* 869 * If the page was filled by a pager, update the map entry's 870 * last read offset. Since the pager does not return the 871 * actual set of pages that it read, this update is based on 872 * the requested set. Typically, the requested and actual 873 * sets are the same. 874 * 875 * XXX The following assignment modifies the map 876 * without holding a write lock on it. 877 */ 878 if (hardfault) 879 fs.entry->next_read = fs.pindex + faultcount - reqpage; 880 881 if ((prot & VM_PROT_WRITE) != 0 || 882 (fault_flags & VM_FAULT_DIRTY) != 0) { 883 vm_object_set_writeable_dirty(fs.object); 884 885 /* 886 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 887 * if the page is already dirty to prevent data written with 888 * the expectation of being synced from not being synced. 889 * Likewise if this entry does not request NOSYNC then make 890 * sure the page isn't marked NOSYNC. Applications sharing 891 * data should use the same flags to avoid ping ponging. 892 */ 893 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) { 894 if (fs.m->dirty == 0) 895 fs.m->oflags |= VPO_NOSYNC; 896 } else { 897 fs.m->oflags &= ~VPO_NOSYNC; 898 } 899 900 /* 901 * If the fault is a write, we know that this page is being 902 * written NOW so dirty it explicitly to save on 903 * pmap_is_modified() calls later. 904 * 905 * Also tell the backing pager, if any, that it should remove 906 * any swap backing since the page is now dirty. 907 */ 908 if (((fault_type & VM_PROT_WRITE) != 0 && 909 (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) || 910 (fault_flags & VM_FAULT_DIRTY) != 0) { 911 vm_page_dirty(fs.m); 912 vm_pager_page_unswapped(fs.m); 913 } 914 } 915 916 /* 917 * Page had better still be busy 918 */ 919 KASSERT(fs.m->oflags & VPO_BUSY, 920 ("vm_fault: page %p not busy!", fs.m)); 921 /* 922 * Page must be completely valid or it is not fit to 923 * map into user space. vm_pager_get_pages() ensures this. 924 */ 925 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 926 ("vm_fault: page %p partially invalid", fs.m)); 927 VM_OBJECT_UNLOCK(fs.object); 928 929 /* 930 * Put this page into the physical map. We had to do the unlock above 931 * because pmap_enter() may sleep. We don't put the page 932 * back on the active queue until later so that the pageout daemon 933 * won't find it (yet). 934 */ 935 pmap_enter(fs.map->pmap, vaddr, fault_type, fs.m, prot, wired); 936 if ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 && wired == 0) 937 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry); 938 VM_OBJECT_LOCK(fs.object); 939 vm_page_lock(fs.m); 940 941 /* 942 * If the page is not wired down, then put it where the pageout daemon 943 * can find it. 944 */ 945 if (fault_flags & VM_FAULT_CHANGE_WIRING) { 946 if (wired) 947 vm_page_wire(fs.m); 948 else 949 vm_page_unwire(fs.m, 1); 950 } else 951 vm_page_activate(fs.m); 952 if (m_hold != NULL) { 953 *m_hold = fs.m; 954 vm_page_hold(fs.m); 955 } 956 vm_page_unlock(fs.m); 957 vm_page_wakeup(fs.m); 958 959 /* 960 * Unlock everything, and return 961 */ 962 unlock_and_deallocate(&fs); 963 if (hardfault) 964 curthread->td_ru.ru_majflt++; 965 else 966 curthread->td_ru.ru_minflt++; 967 968 return (KERN_SUCCESS); 969 } 970 971 /* 972 * Speed up the reclamation of up to "distance" pages that precede the 973 * faulting pindex within the first object of the shadow chain. 974 */ 975 static void 976 vm_fault_cache_behind(const struct faultstate *fs, int distance) 977 { 978 vm_object_t first_object, object; 979 vm_page_t m, m_prev; 980 vm_pindex_t pindex; 981 982 object = fs->object; 983 VM_OBJECT_LOCK_ASSERT(object, MA_OWNED); 984 first_object = fs->first_object; 985 if (first_object != object) { 986 if (!VM_OBJECT_TRYLOCK(first_object)) { 987 VM_OBJECT_UNLOCK(object); 988 VM_OBJECT_LOCK(first_object); 989 VM_OBJECT_LOCK(object); 990 } 991 } 992 if (first_object->type != OBJT_DEVICE && 993 first_object->type != OBJT_PHYS && first_object->type != OBJT_SG) { 994 if (fs->first_pindex < distance) 995 pindex = 0; 996 else 997 pindex = fs->first_pindex - distance; 998 if (pindex < OFF_TO_IDX(fs->entry->offset)) 999 pindex = OFF_TO_IDX(fs->entry->offset); 1000 m = first_object != object ? fs->first_m : fs->m; 1001 KASSERT((m->oflags & VPO_BUSY) != 0, 1002 ("vm_fault_cache_behind: page %p is not busy", m)); 1003 m_prev = vm_page_prev(m); 1004 while ((m = m_prev) != NULL && m->pindex >= pindex && 1005 m->valid == VM_PAGE_BITS_ALL) { 1006 m_prev = vm_page_prev(m); 1007 if (m->busy != 0 || (m->oflags & VPO_BUSY) != 0) 1008 continue; 1009 vm_page_lock(m); 1010 if (m->hold_count == 0 && m->wire_count == 0) { 1011 pmap_remove_all(m); 1012 vm_page_aflag_clear(m, PGA_REFERENCED); 1013 if (m->dirty != 0) 1014 vm_page_deactivate(m); 1015 else 1016 vm_page_cache(m); 1017 } 1018 vm_page_unlock(m); 1019 } 1020 } 1021 if (first_object != object) 1022 VM_OBJECT_UNLOCK(first_object); 1023 } 1024 1025 /* 1026 * vm_fault_prefault provides a quick way of clustering 1027 * pagefaults into a processes address space. It is a "cousin" 1028 * of vm_map_pmap_enter, except it runs at page fault time instead 1029 * of mmap time. 1030 */ 1031 static void 1032 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry) 1033 { 1034 int i; 1035 vm_offset_t addr, starta; 1036 vm_pindex_t pindex; 1037 vm_page_t m; 1038 vm_object_t object; 1039 1040 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1041 return; 1042 1043 object = entry->object.vm_object; 1044 1045 starta = addra - PFBAK * PAGE_SIZE; 1046 if (starta < entry->start) { 1047 starta = entry->start; 1048 } else if (starta > addra) { 1049 starta = 0; 1050 } 1051 1052 for (i = 0; i < PAGEORDER_SIZE; i++) { 1053 vm_object_t backing_object, lobject; 1054 1055 addr = addra + prefault_pageorder[i]; 1056 if (addr > addra + (PFFOR * PAGE_SIZE)) 1057 addr = 0; 1058 1059 if (addr < starta || addr >= entry->end) 1060 continue; 1061 1062 if (!pmap_is_prefaultable(pmap, addr)) 1063 continue; 1064 1065 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1066 lobject = object; 1067 VM_OBJECT_LOCK(lobject); 1068 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1069 lobject->type == OBJT_DEFAULT && 1070 (backing_object = lobject->backing_object) != NULL) { 1071 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1072 0, ("vm_fault_prefault: unaligned object offset")); 1073 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1074 VM_OBJECT_LOCK(backing_object); 1075 VM_OBJECT_UNLOCK(lobject); 1076 lobject = backing_object; 1077 } 1078 /* 1079 * give-up when a page is not in memory 1080 */ 1081 if (m == NULL) { 1082 VM_OBJECT_UNLOCK(lobject); 1083 break; 1084 } 1085 if (m->valid == VM_PAGE_BITS_ALL && 1086 (m->flags & PG_FICTITIOUS) == 0) 1087 pmap_enter_quick(pmap, addr, m, entry->protection); 1088 VM_OBJECT_UNLOCK(lobject); 1089 } 1090 } 1091 1092 /* 1093 * Hold each of the physical pages that are mapped by the specified range of 1094 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1095 * and allow the specified types of access, "prot". If all of the implied 1096 * pages are successfully held, then the number of held pages is returned 1097 * together with pointers to those pages in the array "ma". However, if any 1098 * of the pages cannot be held, -1 is returned. 1099 */ 1100 int 1101 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1102 vm_prot_t prot, vm_page_t *ma, int max_count) 1103 { 1104 vm_offset_t end, va; 1105 vm_page_t *mp; 1106 int count; 1107 boolean_t pmap_failed; 1108 1109 if (len == 0) 1110 return (0); 1111 end = round_page(addr + len); 1112 addr = trunc_page(addr); 1113 1114 /* 1115 * Check for illegal addresses. 1116 */ 1117 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1118 return (-1); 1119 1120 count = howmany(end - addr, PAGE_SIZE); 1121 if (count > max_count) 1122 panic("vm_fault_quick_hold_pages: count > max_count"); 1123 1124 /* 1125 * Most likely, the physical pages are resident in the pmap, so it is 1126 * faster to try pmap_extract_and_hold() first. 1127 */ 1128 pmap_failed = FALSE; 1129 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1130 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1131 if (*mp == NULL) 1132 pmap_failed = TRUE; 1133 else if ((prot & VM_PROT_WRITE) != 0 && 1134 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1135 /* 1136 * Explicitly dirty the physical page. Otherwise, the 1137 * caller's changes may go unnoticed because they are 1138 * performed through an unmanaged mapping or by a DMA 1139 * operation. 1140 * 1141 * The object lock is not held here. 1142 * See vm_page_clear_dirty_mask(). 1143 */ 1144 vm_page_dirty(*mp); 1145 } 1146 } 1147 if (pmap_failed) { 1148 /* 1149 * One or more pages could not be held by the pmap. Either no 1150 * page was mapped at the specified virtual address or that 1151 * mapping had insufficient permissions. Attempt to fault in 1152 * and hold these pages. 1153 */ 1154 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1155 if (*mp == NULL && vm_fault_hold(map, va, prot, 1156 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1157 goto error; 1158 } 1159 return (count); 1160 error: 1161 for (mp = ma; mp < ma + count; mp++) 1162 if (*mp != NULL) { 1163 vm_page_lock(*mp); 1164 vm_page_unhold(*mp); 1165 vm_page_unlock(*mp); 1166 } 1167 return (-1); 1168 } 1169 1170 /* 1171 * vm_fault_wire: 1172 * 1173 * Wire down a range of virtual addresses in a map. 1174 */ 1175 int 1176 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1177 boolean_t fictitious) 1178 { 1179 vm_offset_t va; 1180 int rv; 1181 1182 /* 1183 * We simulate a fault to get the page and enter it in the physical 1184 * map. For user wiring, we only ask for read access on currently 1185 * read-only sections. 1186 */ 1187 for (va = start; va < end; va += PAGE_SIZE) { 1188 rv = vm_fault(map, va, VM_PROT_NONE, VM_FAULT_CHANGE_WIRING); 1189 if (rv) { 1190 if (va != start) 1191 vm_fault_unwire(map, start, va, fictitious); 1192 return (rv); 1193 } 1194 } 1195 return (KERN_SUCCESS); 1196 } 1197 1198 /* 1199 * vm_fault_unwire: 1200 * 1201 * Unwire a range of virtual addresses in a map. 1202 */ 1203 void 1204 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end, 1205 boolean_t fictitious) 1206 { 1207 vm_paddr_t pa; 1208 vm_offset_t va; 1209 vm_page_t m; 1210 pmap_t pmap; 1211 1212 pmap = vm_map_pmap(map); 1213 1214 /* 1215 * Since the pages are wired down, we must be able to get their 1216 * mappings from the physical map system. 1217 */ 1218 for (va = start; va < end; va += PAGE_SIZE) { 1219 pa = pmap_extract(pmap, va); 1220 if (pa != 0) { 1221 pmap_change_wiring(pmap, va, FALSE); 1222 if (!fictitious) { 1223 m = PHYS_TO_VM_PAGE(pa); 1224 vm_page_lock(m); 1225 vm_page_unwire(m, TRUE); 1226 vm_page_unlock(m); 1227 } 1228 } 1229 } 1230 } 1231 1232 /* 1233 * Routine: 1234 * vm_fault_copy_entry 1235 * Function: 1236 * Create new shadow object backing dst_entry with private copy of 1237 * all underlying pages. When src_entry is equal to dst_entry, 1238 * function implements COW for wired-down map entry. Otherwise, 1239 * it forks wired entry into dst_map. 1240 * 1241 * In/out conditions: 1242 * The source and destination maps must be locked for write. 1243 * The source map entry must be wired down (or be a sharing map 1244 * entry corresponding to a main map entry that is wired down). 1245 */ 1246 void 1247 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1248 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1249 vm_ooffset_t *fork_charge) 1250 { 1251 vm_object_t backing_object, dst_object, object, src_object; 1252 vm_pindex_t dst_pindex, pindex, src_pindex; 1253 vm_prot_t access, prot; 1254 vm_offset_t vaddr; 1255 vm_page_t dst_m; 1256 vm_page_t src_m; 1257 boolean_t src_readonly, upgrade; 1258 1259 #ifdef lint 1260 src_map++; 1261 #endif /* lint */ 1262 1263 upgrade = src_entry == dst_entry; 1264 1265 src_object = src_entry->object.vm_object; 1266 src_pindex = OFF_TO_IDX(src_entry->offset); 1267 src_readonly = (src_entry->protection & VM_PROT_WRITE) == 0; 1268 1269 /* 1270 * Create the top-level object for the destination entry. (Doesn't 1271 * actually shadow anything - we copy the pages directly.) 1272 */ 1273 dst_object = vm_object_allocate(OBJT_DEFAULT, 1274 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1275 #if VM_NRESERVLEVEL > 0 1276 dst_object->flags |= OBJ_COLORED; 1277 dst_object->pg_color = atop(dst_entry->start); 1278 #endif 1279 1280 VM_OBJECT_LOCK(dst_object); 1281 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1282 ("vm_fault_copy_entry: vm_object not NULL")); 1283 dst_entry->object.vm_object = dst_object; 1284 dst_entry->offset = 0; 1285 dst_object->charge = dst_entry->end - dst_entry->start; 1286 if (fork_charge != NULL) { 1287 KASSERT(dst_entry->cred == NULL, 1288 ("vm_fault_copy_entry: leaked swp charge")); 1289 dst_object->cred = curthread->td_ucred; 1290 crhold(dst_object->cred); 1291 *fork_charge += dst_object->charge; 1292 } else { 1293 dst_object->cred = dst_entry->cred; 1294 dst_entry->cred = NULL; 1295 } 1296 access = prot = dst_entry->protection; 1297 /* 1298 * If not an upgrade, then enter the mappings in the pmap as 1299 * read and/or execute accesses. Otherwise, enter them as 1300 * write accesses. 1301 * 1302 * A writeable large page mapping is only created if all of 1303 * the constituent small page mappings are modified. Marking 1304 * PTEs as modified on inception allows promotion to happen 1305 * without taking potentially large number of soft faults. 1306 */ 1307 if (!upgrade) 1308 access &= ~VM_PROT_WRITE; 1309 1310 /* 1311 * Loop through all of the virtual pages within the entry's 1312 * range, copying each page from the source object to the 1313 * destination object. Since the source is wired, those pages 1314 * must exist. In contrast, the destination is pageable. 1315 * Since the destination object does share any backing storage 1316 * with the source object, all of its pages must be dirtied, 1317 * regardless of whether they can be written. 1318 */ 1319 for (vaddr = dst_entry->start, dst_pindex = 0; 1320 vaddr < dst_entry->end; 1321 vaddr += PAGE_SIZE, dst_pindex++) { 1322 1323 /* 1324 * Allocate a page in the destination object. 1325 */ 1326 do { 1327 dst_m = vm_page_alloc(dst_object, dst_pindex, 1328 VM_ALLOC_NORMAL); 1329 if (dst_m == NULL) { 1330 VM_OBJECT_UNLOCK(dst_object); 1331 VM_WAIT; 1332 VM_OBJECT_LOCK(dst_object); 1333 } 1334 } while (dst_m == NULL); 1335 1336 /* 1337 * Find the page in the source object, and copy it in. 1338 * (Because the source is wired down, the page will be in 1339 * memory.) 1340 */ 1341 VM_OBJECT_LOCK(src_object); 1342 object = src_object; 1343 pindex = src_pindex + dst_pindex; 1344 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1345 src_readonly && 1346 (backing_object = object->backing_object) != NULL) { 1347 /* 1348 * Allow fallback to backing objects if we are reading. 1349 */ 1350 VM_OBJECT_LOCK(backing_object); 1351 pindex += OFF_TO_IDX(object->backing_object_offset); 1352 VM_OBJECT_UNLOCK(object); 1353 object = backing_object; 1354 } 1355 if (src_m == NULL) 1356 panic("vm_fault_copy_wired: page missing"); 1357 pmap_copy_page(src_m, dst_m); 1358 VM_OBJECT_UNLOCK(object); 1359 dst_m->valid = VM_PAGE_BITS_ALL; 1360 dst_m->dirty = VM_PAGE_BITS_ALL; 1361 VM_OBJECT_UNLOCK(dst_object); 1362 1363 /* 1364 * Enter it in the pmap. If a wired, copy-on-write 1365 * mapping is being replaced by a write-enabled 1366 * mapping, then wire that new mapping. 1367 */ 1368 pmap_enter(dst_map->pmap, vaddr, access, dst_m, prot, upgrade); 1369 1370 /* 1371 * Mark it no longer busy, and put it on the active list. 1372 */ 1373 VM_OBJECT_LOCK(dst_object); 1374 1375 if (upgrade) { 1376 vm_page_lock(src_m); 1377 vm_page_unwire(src_m, 0); 1378 vm_page_unlock(src_m); 1379 1380 vm_page_lock(dst_m); 1381 vm_page_wire(dst_m); 1382 vm_page_unlock(dst_m); 1383 } else { 1384 vm_page_lock(dst_m); 1385 vm_page_activate(dst_m); 1386 vm_page_unlock(dst_m); 1387 } 1388 vm_page_wakeup(dst_m); 1389 } 1390 VM_OBJECT_UNLOCK(dst_object); 1391 if (upgrade) { 1392 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1393 vm_object_deallocate(src_object); 1394 } 1395 } 1396 1397 1398 /* 1399 * This routine checks around the requested page for other pages that 1400 * might be able to be faulted in. This routine brackets the viable 1401 * pages for the pages to be paged in. 1402 * 1403 * Inputs: 1404 * m, rbehind, rahead 1405 * 1406 * Outputs: 1407 * marray (array of vm_page_t), reqpage (index of requested page) 1408 * 1409 * Return value: 1410 * number of pages in marray 1411 */ 1412 static int 1413 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1414 vm_page_t m; 1415 int rbehind; 1416 int rahead; 1417 vm_page_t *marray; 1418 int *reqpage; 1419 { 1420 int i,j; 1421 vm_object_t object; 1422 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1423 vm_page_t rtm; 1424 int cbehind, cahead; 1425 1426 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED); 1427 1428 object = m->object; 1429 pindex = m->pindex; 1430 cbehind = cahead = 0; 1431 1432 /* 1433 * if the requested page is not available, then give up now 1434 */ 1435 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1436 return 0; 1437 } 1438 1439 if ((cbehind == 0) && (cahead == 0)) { 1440 *reqpage = 0; 1441 marray[0] = m; 1442 return 1; 1443 } 1444 1445 if (rahead > cahead) { 1446 rahead = cahead; 1447 } 1448 1449 if (rbehind > cbehind) { 1450 rbehind = cbehind; 1451 } 1452 1453 /* 1454 * scan backward for the read behind pages -- in memory 1455 */ 1456 if (pindex > 0) { 1457 if (rbehind > pindex) { 1458 rbehind = pindex; 1459 startpindex = 0; 1460 } else { 1461 startpindex = pindex - rbehind; 1462 } 1463 1464 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1465 rtm->pindex >= startpindex) 1466 startpindex = rtm->pindex + 1; 1467 1468 /* tpindex is unsigned; beware of numeric underflow. */ 1469 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1470 tpindex < pindex; i++, tpindex--) { 1471 1472 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1473 VM_ALLOC_IFNOTCACHED); 1474 if (rtm == NULL) { 1475 /* 1476 * Shift the allocated pages to the 1477 * beginning of the array. 1478 */ 1479 for (j = 0; j < i; j++) { 1480 marray[j] = marray[j + tpindex + 1 - 1481 startpindex]; 1482 } 1483 break; 1484 } 1485 1486 marray[tpindex - startpindex] = rtm; 1487 } 1488 } else { 1489 startpindex = 0; 1490 i = 0; 1491 } 1492 1493 marray[i] = m; 1494 /* page offset of the required page */ 1495 *reqpage = i; 1496 1497 tpindex = pindex + 1; 1498 i++; 1499 1500 /* 1501 * scan forward for the read ahead pages 1502 */ 1503 endpindex = tpindex + rahead; 1504 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1505 endpindex = rtm->pindex; 1506 if (endpindex > object->size) 1507 endpindex = object->size; 1508 1509 for (; tpindex < endpindex; i++, tpindex++) { 1510 1511 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1512 VM_ALLOC_IFNOTCACHED); 1513 if (rtm == NULL) { 1514 break; 1515 } 1516 1517 marray[i] = rtm; 1518 } 1519 1520 /* return number of pages */ 1521 return i; 1522 } 1523 1524 /* 1525 * Block entry into the machine-independent layer's page fault handler by 1526 * the calling thread. Subsequent calls to vm_fault() by that thread will 1527 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1528 * spurious page faults. 1529 */ 1530 int 1531 vm_fault_disable_pagefaults(void) 1532 { 1533 1534 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1535 } 1536 1537 void 1538 vm_fault_enable_pagefaults(int save) 1539 { 1540 1541 curthread_pflags_restore(save); 1542 }
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