1 /*- 2 * Copyright (c) 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 1994 John S. Dyson 5 * All rights reserved. 6 * Copyright (c) 1994 David Greenman 7 * All rights reserved. 8 * 9 * 10 * This code is derived from software contributed to Berkeley by 11 * The Mach Operating System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. All advertising materials mentioning features or use of this software 22 * must display the following acknowledgement: 23 * This product includes software developed by the University of 24 * California, Berkeley and its contributors. 25 * 4. Neither the name of the University nor the names of its contributors 26 * may be used to endorse or promote products derived from this software 27 * without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 30 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 31 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 33 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 35 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 36 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 38 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 39 * SUCH DAMAGE. 40 * 41 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 42 * 43 * 44 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 45 * All rights reserved. 46 * 47 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 48 * 49 * Permission to use, copy, modify and distribute this software and 50 * its documentation is hereby granted, provided that both the copyright 51 * notice and this permission notice appear in all copies of the 52 * software, derivative works or modified versions, and any portions 53 * thereof, and that both notices appear in supporting documentation. 54 * 55 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 56 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 57 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 58 * 59 * Carnegie Mellon requests users of this software to return to 60 * 61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 62 * School of Computer Science 63 * Carnegie Mellon University 64 * Pittsburgh PA 15213-3890 65 * 66 * any improvements or extensions that they make and grant Carnegie the 67 * rights to redistribute these changes. 68 */ 69 70 /* 71 * Page fault handling module. 72 */ 73 74 #include <sys/cdefs.h> 75 __FBSDID("$FreeBSD$"); 76 77 #include "opt_ktrace.h" 78 #include "opt_vm.h" 79 80 #include <sys/param.h> 81 #include <sys/systm.h> 82 #include <sys/kernel.h> 83 #include <sys/lock.h> 84 #include <sys/mman.h> 85 #include <sys/proc.h> 86 #include <sys/resourcevar.h> 87 #include <sys/rwlock.h> 88 #include <sys/sysctl.h> 89 #include <sys/vmmeter.h> 90 #include <sys/vnode.h> 91 #ifdef KTRACE 92 #include <sys/ktrace.h> 93 #endif 94 95 #include <vm/vm.h> 96 #include <vm/vm_param.h> 97 #include <vm/pmap.h> 98 #include <vm/vm_map.h> 99 #include <vm/vm_object.h> 100 #include <vm/vm_page.h> 101 #include <vm/vm_pageout.h> 102 #include <vm/vm_kern.h> 103 #include <vm/vm_pager.h> 104 #include <vm/vm_extern.h> 105 #include <vm/vm_reserv.h> 106 107 #define PFBAK 4 108 #define PFFOR 4 109 110 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 111 112 #define VM_FAULT_READ_BEHIND 8 113 #define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT) 114 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX) 115 #define VM_FAULT_NINCR (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND) 116 #define VM_FAULT_SUM (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2) 117 118 #define VM_FAULT_DONTNEED_MIN 1048576 119 120 struct faultstate { 121 vm_page_t m; 122 vm_object_t object; 123 vm_pindex_t pindex; 124 vm_page_t first_m; 125 vm_object_t first_object; 126 vm_pindex_t first_pindex; 127 vm_map_t map; 128 vm_map_entry_t entry; 129 int lookup_still_valid; 130 struct vnode *vp; 131 }; 132 133 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, 134 int ahead); 135 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 136 int faultcount, int reqpage); 137 138 static inline void 139 release_page(struct faultstate *fs) 140 { 141 142 vm_page_xunbusy(fs->m); 143 vm_page_lock(fs->m); 144 vm_page_deactivate(fs->m); 145 vm_page_unlock(fs->m); 146 fs->m = NULL; 147 } 148 149 static inline void 150 unlock_map(struct faultstate *fs) 151 { 152 153 if (fs->lookup_still_valid) { 154 vm_map_lookup_done(fs->map, fs->entry); 155 fs->lookup_still_valid = FALSE; 156 } 157 } 158 159 static void 160 unlock_and_deallocate(struct faultstate *fs) 161 { 162 163 vm_object_pip_wakeup(fs->object); 164 VM_OBJECT_WUNLOCK(fs->object); 165 if (fs->object != fs->first_object) { 166 VM_OBJECT_WLOCK(fs->first_object); 167 vm_page_lock(fs->first_m); 168 vm_page_free(fs->first_m); 169 vm_page_unlock(fs->first_m); 170 vm_object_pip_wakeup(fs->first_object); 171 VM_OBJECT_WUNLOCK(fs->first_object); 172 fs->first_m = NULL; 173 } 174 vm_object_deallocate(fs->first_object); 175 unlock_map(fs); 176 if (fs->vp != NULL) { 177 vput(fs->vp); 178 fs->vp = NULL; 179 } 180 } 181 182 static void 183 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot, 184 vm_prot_t fault_type, int fault_flags, boolean_t set_wd) 185 { 186 boolean_t need_dirty; 187 188 if (((prot & VM_PROT_WRITE) == 0 && 189 (fault_flags & VM_FAULT_DIRTY) == 0) || 190 (m->oflags & VPO_UNMANAGED) != 0) 191 return; 192 193 VM_OBJECT_ASSERT_LOCKED(m->object); 194 195 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 && 196 (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) || 197 (fault_flags & VM_FAULT_DIRTY) != 0; 198 199 if (set_wd) 200 vm_object_set_writeable_dirty(m->object); 201 else 202 /* 203 * If two callers of vm_fault_dirty() with set_wd == 204 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC 205 * flag set, other with flag clear, race, it is 206 * possible for the no-NOSYNC thread to see m->dirty 207 * != 0 and not clear VPO_NOSYNC. Take vm_page lock 208 * around manipulation of VPO_NOSYNC and 209 * vm_page_dirty() call, to avoid the race and keep 210 * m->oflags consistent. 211 */ 212 vm_page_lock(m); 213 214 /* 215 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 216 * if the page is already dirty to prevent data written with 217 * the expectation of being synced from not being synced. 218 * Likewise if this entry does not request NOSYNC then make 219 * sure the page isn't marked NOSYNC. Applications sharing 220 * data should use the same flags to avoid ping ponging. 221 */ 222 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) { 223 if (m->dirty == 0) { 224 m->oflags |= VPO_NOSYNC; 225 } 226 } else { 227 m->oflags &= ~VPO_NOSYNC; 228 } 229 230 /* 231 * If the fault is a write, we know that this page is being 232 * written NOW so dirty it explicitly to save on 233 * pmap_is_modified() calls later. 234 * 235 * Also tell the backing pager, if any, that it should remove 236 * any swap backing since the page is now dirty. 237 */ 238 if (need_dirty) 239 vm_page_dirty(m); 240 if (!set_wd) 241 vm_page_unlock(m); 242 if (need_dirty) 243 vm_pager_page_unswapped(m); 244 } 245 246 /* 247 * TRYPAGER - used by vm_fault to calculate whether the pager for the 248 * current object *might* contain the page. 249 * 250 * default objects are zero-fill, there is no real pager. 251 */ 252 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \ 253 ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 || wired)) 254 255 /* 256 * vm_fault: 257 * 258 * Handle a page fault occurring at the given address, 259 * requiring the given permissions, in the map specified. 260 * If successful, the page is inserted into the 261 * associated physical map. 262 * 263 * NOTE: the given address should be truncated to the 264 * proper page address. 265 * 266 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 267 * a standard error specifying why the fault is fatal is returned. 268 * 269 * The map in question must be referenced, and remains so. 270 * Caller may hold no locks. 271 */ 272 int 273 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 274 int fault_flags) 275 { 276 struct thread *td; 277 int result; 278 279 td = curthread; 280 if ((td->td_pflags & TDP_NOFAULTING) != 0) 281 return (KERN_PROTECTION_FAILURE); 282 #ifdef KTRACE 283 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 284 ktrfault(vaddr, fault_type); 285 #endif 286 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 287 NULL); 288 #ifdef KTRACE 289 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 290 ktrfaultend(result); 291 #endif 292 return (result); 293 } 294 295 int 296 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 297 int fault_flags, vm_page_t *m_hold) 298 { 299 vm_prot_t prot; 300 int alloc_req, era, faultcount, nera, reqpage, result; 301 boolean_t growstack, is_first_object_locked, wired; 302 int map_generation; 303 vm_object_t next_object; 304 vm_page_t marray[VM_FAULT_READ_MAX]; 305 int hardfault; 306 struct faultstate fs; 307 struct vnode *vp; 308 vm_page_t m; 309 int ahead, behind, cluster_offset, error, locked; 310 311 hardfault = 0; 312 growstack = TRUE; 313 PCPU_INC(cnt.v_vm_faults); 314 fs.vp = NULL; 315 faultcount = reqpage = 0; 316 317 RetryFault:; 318 319 /* 320 * Find the backing store object and offset into it to begin the 321 * search. 322 */ 323 fs.map = map; 324 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 325 &fs.first_object, &fs.first_pindex, &prot, &wired); 326 if (result != KERN_SUCCESS) { 327 if (growstack && result == KERN_INVALID_ADDRESS && 328 map != kernel_map) { 329 result = vm_map_growstack(curproc, vaddr); 330 if (result != KERN_SUCCESS) 331 return (KERN_FAILURE); 332 growstack = FALSE; 333 goto RetryFault; 334 } 335 return (result); 336 } 337 338 map_generation = fs.map->timestamp; 339 340 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 341 panic("vm_fault: fault on nofault entry, addr: %lx", 342 (u_long)vaddr); 343 } 344 345 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 346 fs.entry->wiring_thread != curthread) { 347 vm_map_unlock_read(fs.map); 348 vm_map_lock(fs.map); 349 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 350 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 351 if (fs.vp != NULL) { 352 vput(fs.vp); 353 fs.vp = NULL; 354 } 355 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 356 vm_map_unlock_and_wait(fs.map, 0); 357 } else 358 vm_map_unlock(fs.map); 359 goto RetryFault; 360 } 361 362 if (wired) 363 fault_type = prot | (fault_type & VM_PROT_COPY); 364 365 if (fs.vp == NULL /* avoid locked vnode leak */ && 366 (fault_flags & (VM_FAULT_CHANGE_WIRING | VM_FAULT_DIRTY)) == 0 && 367 /* avoid calling vm_object_set_writeable_dirty() */ 368 ((prot & VM_PROT_WRITE) == 0 || 369 (fs.first_object->type != OBJT_VNODE && 370 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 371 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 372 VM_OBJECT_RLOCK(fs.first_object); 373 if ((prot & VM_PROT_WRITE) != 0 && 374 (fs.first_object->type == OBJT_VNODE || 375 (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) && 376 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0) 377 goto fast_failed; 378 m = vm_page_lookup(fs.first_object, fs.first_pindex); 379 /* A busy page can be mapped for read|execute access. */ 380 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 381 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 382 goto fast_failed; 383 result = pmap_enter(fs.map->pmap, vaddr, m, prot, 384 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 385 0), 0); 386 if (result != KERN_SUCCESS) 387 goto fast_failed; 388 if (m_hold != NULL) { 389 *m_hold = m; 390 vm_page_lock(m); 391 vm_page_hold(m); 392 vm_page_unlock(m); 393 } 394 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, 395 FALSE); 396 VM_OBJECT_RUNLOCK(fs.first_object); 397 if (!wired) 398 vm_fault_prefault(&fs, vaddr, 0, 0); 399 vm_map_lookup_done(fs.map, fs.entry); 400 curthread->td_ru.ru_minflt++; 401 return (KERN_SUCCESS); 402 fast_failed: 403 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 404 VM_OBJECT_RUNLOCK(fs.first_object); 405 VM_OBJECT_WLOCK(fs.first_object); 406 } 407 } else { 408 VM_OBJECT_WLOCK(fs.first_object); 409 } 410 411 /* 412 * Make a reference to this object to prevent its disposal while we 413 * are messing with it. Once we have the reference, the map is free 414 * to be diddled. Since objects reference their shadows (and copies), 415 * they will stay around as well. 416 * 417 * Bump the paging-in-progress count to prevent size changes (e.g. 418 * truncation operations) during I/O. This must be done after 419 * obtaining the vnode lock in order to avoid possible deadlocks. 420 */ 421 vm_object_reference_locked(fs.first_object); 422 vm_object_pip_add(fs.first_object, 1); 423 424 fs.lookup_still_valid = TRUE; 425 426 fs.first_m = NULL; 427 428 /* 429 * Search for the page at object/offset. 430 */ 431 fs.object = fs.first_object; 432 fs.pindex = fs.first_pindex; 433 while (TRUE) { 434 /* 435 * If the object is dead, we stop here 436 */ 437 if (fs.object->flags & OBJ_DEAD) { 438 unlock_and_deallocate(&fs); 439 return (KERN_PROTECTION_FAILURE); 440 } 441 442 /* 443 * See if page is resident 444 */ 445 fs.m = vm_page_lookup(fs.object, fs.pindex); 446 if (fs.m != NULL) { 447 /* 448 * Wait/Retry if the page is busy. We have to do this 449 * if the page is either exclusive or shared busy 450 * because the vm_pager may be using read busy for 451 * pageouts (and even pageins if it is the vnode 452 * pager), and we could end up trying to pagein and 453 * pageout the same page simultaneously. 454 * 455 * We can theoretically allow the busy case on a read 456 * fault if the page is marked valid, but since such 457 * pages are typically already pmap'd, putting that 458 * special case in might be more effort then it is 459 * worth. We cannot under any circumstances mess 460 * around with a shared busied page except, perhaps, 461 * to pmap it. 462 */ 463 if (vm_page_busied(fs.m)) { 464 /* 465 * Reference the page before unlocking and 466 * sleeping so that the page daemon is less 467 * likely to reclaim it. 468 */ 469 vm_page_aflag_set(fs.m, PGA_REFERENCED); 470 if (fs.object != fs.first_object) { 471 if (!VM_OBJECT_TRYWLOCK( 472 fs.first_object)) { 473 VM_OBJECT_WUNLOCK(fs.object); 474 VM_OBJECT_WLOCK(fs.first_object); 475 VM_OBJECT_WLOCK(fs.object); 476 } 477 vm_page_lock(fs.first_m); 478 vm_page_free(fs.first_m); 479 vm_page_unlock(fs.first_m); 480 vm_object_pip_wakeup(fs.first_object); 481 VM_OBJECT_WUNLOCK(fs.first_object); 482 fs.first_m = NULL; 483 } 484 unlock_map(&fs); 485 if (fs.m == vm_page_lookup(fs.object, 486 fs.pindex)) { 487 vm_page_sleep_if_busy(fs.m, "vmpfw"); 488 } 489 vm_object_pip_wakeup(fs.object); 490 VM_OBJECT_WUNLOCK(fs.object); 491 PCPU_INC(cnt.v_intrans); 492 vm_object_deallocate(fs.first_object); 493 goto RetryFault; 494 } 495 vm_page_lock(fs.m); 496 vm_page_remque(fs.m); 497 vm_page_unlock(fs.m); 498 499 /* 500 * Mark page busy for other processes, and the 501 * pagedaemon. If it still isn't completely valid 502 * (readable), jump to readrest, else break-out ( we 503 * found the page ). 504 */ 505 vm_page_xbusy(fs.m); 506 if (fs.m->valid != VM_PAGE_BITS_ALL) 507 goto readrest; 508 break; 509 } 510 511 /* 512 * Page is not resident, If this is the search termination 513 * or the pager might contain the page, allocate a new page. 514 */ 515 if (TRYPAGER || fs.object == fs.first_object) { 516 if (fs.pindex >= fs.object->size) { 517 unlock_and_deallocate(&fs); 518 return (KERN_PROTECTION_FAILURE); 519 } 520 521 /* 522 * Allocate a new page for this object/offset pair. 523 * 524 * Unlocked read of the p_flag is harmless. At 525 * worst, the P_KILLED might be not observed 526 * there, and allocation can fail, causing 527 * restart and new reading of the p_flag. 528 */ 529 fs.m = NULL; 530 if (!vm_page_count_severe() || P_KILLED(curproc)) { 531 #if VM_NRESERVLEVEL > 0 532 vm_object_color(fs.object, atop(vaddr) - 533 fs.pindex); 534 #endif 535 alloc_req = P_KILLED(curproc) ? 536 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 537 if (fs.object->type != OBJT_VNODE && 538 fs.object->backing_object == NULL) 539 alloc_req |= VM_ALLOC_ZERO; 540 fs.m = vm_page_alloc(fs.object, fs.pindex, 541 alloc_req); 542 } 543 if (fs.m == NULL) { 544 unlock_and_deallocate(&fs); 545 VM_WAITPFAULT; 546 goto RetryFault; 547 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 548 break; 549 } 550 551 readrest: 552 /* 553 * We have found a valid page or we have allocated a new page. 554 * The page thus may not be valid or may not be entirely 555 * valid. 556 * 557 * Attempt to fault-in the page if there is a chance that the 558 * pager has it, and potentially fault in additional pages 559 * at the same time. 560 */ 561 if (TRYPAGER) { 562 int rv; 563 u_char behavior = vm_map_entry_behavior(fs.entry); 564 565 era = fs.entry->read_ahead; 566 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 567 P_KILLED(curproc)) { 568 behind = 0; 569 nera = 0; 570 ahead = 0; 571 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 572 behind = 0; 573 nera = VM_FAULT_READ_AHEAD_MAX; 574 ahead = nera; 575 if (fs.pindex == fs.entry->next_read) 576 vm_fault_dontneed(&fs, vaddr, ahead); 577 } else if (fs.pindex == fs.entry->next_read) { 578 /* 579 * This is a sequential fault. Arithmetically 580 * increase the requested number of pages in 581 * the read-ahead window. The requested 582 * number of pages is "# of sequential faults 583 * x (read ahead min + 1) + read ahead min" 584 */ 585 behind = 0; 586 nera = VM_FAULT_READ_AHEAD_MIN; 587 if (era > 0) { 588 nera += era + 1; 589 if (nera > VM_FAULT_READ_AHEAD_MAX) 590 nera = VM_FAULT_READ_AHEAD_MAX; 591 } 592 ahead = nera; 593 if (era == VM_FAULT_READ_AHEAD_MAX) 594 vm_fault_dontneed(&fs, vaddr, ahead); 595 } else { 596 /* 597 * This is a non-sequential fault. Request a 598 * cluster of pages that is aligned to a 599 * VM_FAULT_READ_DEFAULT page offset boundary 600 * within the object. Alignment to a page 601 * offset boundary is more likely to coincide 602 * with the underlying file system block than 603 * alignment to a virtual address boundary. 604 */ 605 cluster_offset = fs.pindex % 606 VM_FAULT_READ_DEFAULT; 607 behind = ulmin(cluster_offset, 608 atop(vaddr - fs.entry->start)); 609 nera = 0; 610 ahead = VM_FAULT_READ_DEFAULT - 1 - 611 cluster_offset; 612 } 613 ahead = ulmin(ahead, atop(fs.entry->end - vaddr) - 1); 614 if (era != nera) 615 fs.entry->read_ahead = nera; 616 617 /* 618 * Call the pager to retrieve the data, if any, after 619 * releasing the lock on the map. We hold a ref on 620 * fs.object and the pages are exclusive busied. 621 */ 622 unlock_map(&fs); 623 624 if (fs.object->type == OBJT_VNODE) { 625 vp = fs.object->handle; 626 if (vp == fs.vp) 627 goto vnode_locked; 628 else if (fs.vp != NULL) { 629 vput(fs.vp); 630 fs.vp = NULL; 631 } 632 locked = VOP_ISLOCKED(vp); 633 634 if (locked != LK_EXCLUSIVE) 635 locked = LK_SHARED; 636 /* Do not sleep for vnode lock while fs.m is busy */ 637 error = vget(vp, locked | LK_CANRECURSE | 638 LK_NOWAIT, curthread); 639 if (error != 0) { 640 vhold(vp); 641 release_page(&fs); 642 unlock_and_deallocate(&fs); 643 error = vget(vp, locked | LK_RETRY | 644 LK_CANRECURSE, curthread); 645 vdrop(vp); 646 fs.vp = vp; 647 KASSERT(error == 0, 648 ("vm_fault: vget failed")); 649 goto RetryFault; 650 } 651 fs.vp = vp; 652 } 653 vnode_locked: 654 KASSERT(fs.vp == NULL || !fs.map->system_map, 655 ("vm_fault: vnode-backed object mapped by system map")); 656 657 /* 658 * now we find out if any other pages should be paged 659 * in at this time this routine checks to see if the 660 * pages surrounding this fault reside in the same 661 * object as the page for this fault. If they do, 662 * then they are faulted in also into the object. The 663 * array "marray" returned contains an array of 664 * vm_page_t structs where one of them is the 665 * vm_page_t passed to the routine. The reqpage 666 * return value is the index into the marray for the 667 * vm_page_t passed to the routine. 668 * 669 * fs.m plus the additional pages are exclusive busied. 670 */ 671 faultcount = vm_fault_additional_pages( 672 fs.m, behind, ahead, marray, &reqpage); 673 674 rv = faultcount ? 675 vm_pager_get_pages(fs.object, marray, faultcount, 676 reqpage) : VM_PAGER_FAIL; 677 678 if (rv == VM_PAGER_OK) { 679 /* 680 * Found the page. Leave it busy while we play 681 * with it. 682 */ 683 684 /* 685 * Relookup in case pager changed page. Pager 686 * is responsible for disposition of old page 687 * if moved. 688 */ 689 fs.m = vm_page_lookup(fs.object, fs.pindex); 690 if (!fs.m) { 691 unlock_and_deallocate(&fs); 692 goto RetryFault; 693 } 694 695 hardfault++; 696 break; /* break to PAGE HAS BEEN FOUND */ 697 } 698 /* 699 * Remove the bogus page (which does not exist at this 700 * object/offset); before doing so, we must get back 701 * our object lock to preserve our invariant. 702 * 703 * Also wake up any other process that may want to bring 704 * in this page. 705 * 706 * If this is the top-level object, we must leave the 707 * busy page to prevent another process from rushing 708 * past us, and inserting the page in that object at 709 * the same time that we are. 710 */ 711 if (rv == VM_PAGER_ERROR) 712 printf("vm_fault: pager read error, pid %d (%s)\n", 713 curproc->p_pid, curproc->p_comm); 714 /* 715 * Data outside the range of the pager or an I/O error 716 */ 717 /* 718 * XXX - the check for kernel_map is a kludge to work 719 * around having the machine panic on a kernel space 720 * fault w/ I/O error. 721 */ 722 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 723 (rv == VM_PAGER_BAD)) { 724 vm_page_lock(fs.m); 725 vm_page_free(fs.m); 726 vm_page_unlock(fs.m); 727 fs.m = NULL; 728 unlock_and_deallocate(&fs); 729 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 730 } 731 if (fs.object != fs.first_object) { 732 vm_page_lock(fs.m); 733 vm_page_free(fs.m); 734 vm_page_unlock(fs.m); 735 fs.m = NULL; 736 /* 737 * XXX - we cannot just fall out at this 738 * point, m has been freed and is invalid! 739 */ 740 } 741 } 742 743 /* 744 * We get here if the object has default pager (or unwiring) 745 * or the pager doesn't have the page. 746 */ 747 if (fs.object == fs.first_object) 748 fs.first_m = fs.m; 749 750 /* 751 * Move on to the next object. Lock the next object before 752 * unlocking the current one. 753 */ 754 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 755 next_object = fs.object->backing_object; 756 if (next_object == NULL) { 757 /* 758 * If there's no object left, fill the page in the top 759 * object with zeros. 760 */ 761 if (fs.object != fs.first_object) { 762 vm_object_pip_wakeup(fs.object); 763 VM_OBJECT_WUNLOCK(fs.object); 764 765 fs.object = fs.first_object; 766 fs.pindex = fs.first_pindex; 767 fs.m = fs.first_m; 768 VM_OBJECT_WLOCK(fs.object); 769 } 770 fs.first_m = NULL; 771 772 /* 773 * Zero the page if necessary and mark it valid. 774 */ 775 if ((fs.m->flags & PG_ZERO) == 0) { 776 pmap_zero_page(fs.m); 777 } else { 778 PCPU_INC(cnt.v_ozfod); 779 } 780 PCPU_INC(cnt.v_zfod); 781 fs.m->valid = VM_PAGE_BITS_ALL; 782 /* Don't try to prefault neighboring pages. */ 783 faultcount = 1; 784 break; /* break to PAGE HAS BEEN FOUND */ 785 } else { 786 KASSERT(fs.object != next_object, 787 ("object loop %p", next_object)); 788 VM_OBJECT_WLOCK(next_object); 789 vm_object_pip_add(next_object, 1); 790 if (fs.object != fs.first_object) 791 vm_object_pip_wakeup(fs.object); 792 VM_OBJECT_WUNLOCK(fs.object); 793 fs.object = next_object; 794 } 795 } 796 797 vm_page_assert_xbusied(fs.m); 798 799 /* 800 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 801 * is held.] 802 */ 803 804 /* 805 * If the page is being written, but isn't already owned by the 806 * top-level object, we have to copy it into a new page owned by the 807 * top-level object. 808 */ 809 if (fs.object != fs.first_object) { 810 /* 811 * We only really need to copy if we want to write it. 812 */ 813 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 814 /* 815 * This allows pages to be virtually copied from a 816 * backing_object into the first_object, where the 817 * backing object has no other refs to it, and cannot 818 * gain any more refs. Instead of a bcopy, we just 819 * move the page from the backing object to the 820 * first object. Note that we must mark the page 821 * dirty in the first object so that it will go out 822 * to swap when needed. 823 */ 824 is_first_object_locked = FALSE; 825 if ( 826 /* 827 * Only one shadow object 828 */ 829 (fs.object->shadow_count == 1) && 830 /* 831 * No COW refs, except us 832 */ 833 (fs.object->ref_count == 1) && 834 /* 835 * No one else can look this object up 836 */ 837 (fs.object->handle == NULL) && 838 /* 839 * No other ways to look the object up 840 */ 841 ((fs.object->type == OBJT_DEFAULT) || 842 (fs.object->type == OBJT_SWAP)) && 843 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 844 /* 845 * We don't chase down the shadow chain 846 */ 847 fs.object == fs.first_object->backing_object) { 848 /* 849 * get rid of the unnecessary page 850 */ 851 vm_page_lock(fs.first_m); 852 vm_page_free(fs.first_m); 853 vm_page_unlock(fs.first_m); 854 /* 855 * grab the page and put it into the 856 * process'es object. The page is 857 * automatically made dirty. 858 */ 859 if (vm_page_rename(fs.m, fs.first_object, 860 fs.first_pindex)) { 861 unlock_and_deallocate(&fs); 862 goto RetryFault; 863 } 864 #if VM_NRESERVLEVEL > 0 865 /* 866 * Rename the reservation. 867 */ 868 vm_reserv_rename(fs.m, fs.first_object, 869 fs.object, OFF_TO_IDX( 870 fs.first_object->backing_object_offset)); 871 #endif 872 vm_page_xbusy(fs.m); 873 fs.first_m = fs.m; 874 fs.m = NULL; 875 PCPU_INC(cnt.v_cow_optim); 876 } else { 877 /* 878 * Oh, well, lets copy it. 879 */ 880 pmap_copy_page(fs.m, fs.first_m); 881 fs.first_m->valid = VM_PAGE_BITS_ALL; 882 if (wired && (fault_flags & 883 VM_FAULT_CHANGE_WIRING) == 0) { 884 vm_page_lock(fs.first_m); 885 vm_page_wire(fs.first_m); 886 vm_page_unlock(fs.first_m); 887 888 vm_page_lock(fs.m); 889 vm_page_unwire(fs.m, PQ_INACTIVE); 890 vm_page_unlock(fs.m); 891 } 892 /* 893 * We no longer need the old page or object. 894 */ 895 release_page(&fs); 896 } 897 /* 898 * fs.object != fs.first_object due to above 899 * conditional 900 */ 901 vm_object_pip_wakeup(fs.object); 902 VM_OBJECT_WUNLOCK(fs.object); 903 /* 904 * Only use the new page below... 905 */ 906 fs.object = fs.first_object; 907 fs.pindex = fs.first_pindex; 908 fs.m = fs.first_m; 909 if (!is_first_object_locked) 910 VM_OBJECT_WLOCK(fs.object); 911 PCPU_INC(cnt.v_cow_faults); 912 curthread->td_cow++; 913 } else { 914 prot &= ~VM_PROT_WRITE; 915 } 916 } 917 918 /* 919 * We must verify that the maps have not changed since our last 920 * lookup. 921 */ 922 if (!fs.lookup_still_valid) { 923 vm_object_t retry_object; 924 vm_pindex_t retry_pindex; 925 vm_prot_t retry_prot; 926 927 if (!vm_map_trylock_read(fs.map)) { 928 release_page(&fs); 929 unlock_and_deallocate(&fs); 930 goto RetryFault; 931 } 932 fs.lookup_still_valid = TRUE; 933 if (fs.map->timestamp != map_generation) { 934 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 935 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 936 937 /* 938 * If we don't need the page any longer, put it on the inactive 939 * list (the easiest thing to do here). If no one needs it, 940 * pageout will grab it eventually. 941 */ 942 if (result != KERN_SUCCESS) { 943 release_page(&fs); 944 unlock_and_deallocate(&fs); 945 946 /* 947 * If retry of map lookup would have blocked then 948 * retry fault from start. 949 */ 950 if (result == KERN_FAILURE) 951 goto RetryFault; 952 return (result); 953 } 954 if ((retry_object != fs.first_object) || 955 (retry_pindex != fs.first_pindex)) { 956 release_page(&fs); 957 unlock_and_deallocate(&fs); 958 goto RetryFault; 959 } 960 961 /* 962 * Check whether the protection has changed or the object has 963 * been copied while we left the map unlocked. Changing from 964 * read to write permission is OK - we leave the page 965 * write-protected, and catch the write fault. Changing from 966 * write to read permission means that we can't mark the page 967 * write-enabled after all. 968 */ 969 prot &= retry_prot; 970 } 971 } 972 /* 973 * If the page was filled by a pager, update the map entry's 974 * last read offset. Since the pager does not return the 975 * actual set of pages that it read, this update is based on 976 * the requested set. Typically, the requested and actual 977 * sets are the same. 978 * 979 * XXX The following assignment modifies the map 980 * without holding a write lock on it. 981 */ 982 if (hardfault) 983 fs.entry->next_read = fs.pindex + faultcount - reqpage; 984 985 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); 986 vm_page_assert_xbusied(fs.m); 987 988 /* 989 * Page must be completely valid or it is not fit to 990 * map into user space. vm_pager_get_pages() ensures this. 991 */ 992 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 993 ("vm_fault: page %p partially invalid", fs.m)); 994 VM_OBJECT_WUNLOCK(fs.object); 995 996 /* 997 * Put this page into the physical map. We had to do the unlock above 998 * because pmap_enter() may sleep. We don't put the page 999 * back on the active queue until later so that the pageout daemon 1000 * won't find it (yet). 1001 */ 1002 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 1003 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 1004 if (faultcount != 1 && (fault_flags & VM_FAULT_CHANGE_WIRING) == 0 && 1005 wired == 0) 1006 vm_fault_prefault(&fs, vaddr, faultcount, reqpage); 1007 VM_OBJECT_WLOCK(fs.object); 1008 vm_page_lock(fs.m); 1009 1010 /* 1011 * If the page is not wired down, then put it where the pageout daemon 1012 * can find it. 1013 */ 1014 if (fault_flags & VM_FAULT_CHANGE_WIRING) { 1015 if (wired) 1016 vm_page_wire(fs.m); 1017 else 1018 vm_page_unwire(fs.m, PQ_ACTIVE); 1019 } else 1020 vm_page_activate(fs.m); 1021 if (m_hold != NULL) { 1022 *m_hold = fs.m; 1023 vm_page_hold(fs.m); 1024 } 1025 vm_page_unlock(fs.m); 1026 vm_page_xunbusy(fs.m); 1027 1028 /* 1029 * Unlock everything, and return 1030 */ 1031 unlock_and_deallocate(&fs); 1032 if (hardfault) { 1033 PCPU_INC(cnt.v_io_faults); 1034 curthread->td_ru.ru_majflt++; 1035 } else 1036 curthread->td_ru.ru_minflt++; 1037 1038 return (KERN_SUCCESS); 1039 } 1040 1041 /* 1042 * Speed up the reclamation of pages that precede the faulting pindex within 1043 * the first object of the shadow chain. Essentially, perform the equivalent 1044 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1045 * the faulting pindex by the cluster size when the pages read by vm_fault() 1046 * cross a cluster-size boundary. The cluster size is the greater of the 1047 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1048 * 1049 * When "fs->first_object" is a shadow object, the pages in the backing object 1050 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1051 * function must only be concerned with pages in the first object. 1052 */ 1053 static void 1054 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1055 { 1056 vm_map_entry_t entry; 1057 vm_object_t first_object, object; 1058 vm_offset_t end, start; 1059 vm_page_t m, m_next; 1060 vm_pindex_t pend, pstart; 1061 vm_size_t size; 1062 1063 object = fs->object; 1064 VM_OBJECT_ASSERT_WLOCKED(object); 1065 first_object = fs->first_object; 1066 if (first_object != object) { 1067 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1068 VM_OBJECT_WUNLOCK(object); 1069 VM_OBJECT_WLOCK(first_object); 1070 VM_OBJECT_WLOCK(object); 1071 } 1072 } 1073 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1074 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1075 size = VM_FAULT_DONTNEED_MIN; 1076 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1077 size = pagesizes[1]; 1078 end = rounddown2(vaddr, size); 1079 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1080 (entry = fs->entry)->start < end) { 1081 if (end - entry->start < size) 1082 start = entry->start; 1083 else 1084 start = end - size; 1085 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1086 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1087 entry->start); 1088 m_next = vm_page_find_least(first_object, pstart); 1089 pend = OFF_TO_IDX(entry->offset) + atop(end - 1090 entry->start); 1091 while ((m = m_next) != NULL && m->pindex < pend) { 1092 m_next = TAILQ_NEXT(m, listq); 1093 if (m->valid != VM_PAGE_BITS_ALL || 1094 vm_page_busied(m)) 1095 continue; 1096 vm_page_lock(m); 1097 if (m->hold_count == 0 && m->wire_count == 0) 1098 vm_page_advise(m, MADV_DONTNEED); 1099 vm_page_unlock(m); 1100 } 1101 } 1102 } 1103 if (first_object != object) 1104 VM_OBJECT_WUNLOCK(first_object); 1105 } 1106 1107 /* 1108 * vm_fault_prefault provides a quick way of clustering 1109 * pagefaults into a processes address space. It is a "cousin" 1110 * of vm_map_pmap_enter, except it runs at page fault time instead 1111 * of mmap time. 1112 */ 1113 static void 1114 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1115 int faultcount, int reqpage) 1116 { 1117 pmap_t pmap; 1118 vm_map_entry_t entry; 1119 vm_object_t backing_object, lobject; 1120 vm_offset_t addr, starta; 1121 vm_pindex_t pindex; 1122 vm_page_t m; 1123 int backward, forward, i; 1124 1125 pmap = fs->map->pmap; 1126 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1127 return; 1128 1129 if (faultcount > 0) { 1130 backward = reqpage; 1131 forward = faultcount - reqpage - 1; 1132 } else { 1133 backward = PFBAK; 1134 forward = PFFOR; 1135 } 1136 entry = fs->entry; 1137 1138 starta = addra - backward * PAGE_SIZE; 1139 if (starta < entry->start) { 1140 starta = entry->start; 1141 } else if (starta > addra) { 1142 starta = 0; 1143 } 1144 1145 /* 1146 * Generate the sequence of virtual addresses that are candidates for 1147 * prefaulting in an outward spiral from the faulting virtual address, 1148 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1149 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1150 * If the candidate address doesn't have a backing physical page, then 1151 * the loop immediately terminates. 1152 */ 1153 for (i = 0; i < 2 * imax(backward, forward); i++) { 1154 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1155 PAGE_SIZE); 1156 if (addr > addra + forward * PAGE_SIZE) 1157 addr = 0; 1158 1159 if (addr < starta || addr >= entry->end) 1160 continue; 1161 1162 if (!pmap_is_prefaultable(pmap, addr)) 1163 continue; 1164 1165 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1166 lobject = entry->object.vm_object; 1167 VM_OBJECT_RLOCK(lobject); 1168 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1169 lobject->type == OBJT_DEFAULT && 1170 (backing_object = lobject->backing_object) != NULL) { 1171 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1172 0, ("vm_fault_prefault: unaligned object offset")); 1173 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1174 VM_OBJECT_RLOCK(backing_object); 1175 VM_OBJECT_RUNLOCK(lobject); 1176 lobject = backing_object; 1177 } 1178 if (m == NULL) { 1179 VM_OBJECT_RUNLOCK(lobject); 1180 break; 1181 } 1182 if (m->valid == VM_PAGE_BITS_ALL && 1183 (m->flags & PG_FICTITIOUS) == 0) 1184 pmap_enter_quick(pmap, addr, m, entry->protection); 1185 VM_OBJECT_RUNLOCK(lobject); 1186 } 1187 } 1188 1189 /* 1190 * Hold each of the physical pages that are mapped by the specified range of 1191 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1192 * and allow the specified types of access, "prot". If all of the implied 1193 * pages are successfully held, then the number of held pages is returned 1194 * together with pointers to those pages in the array "ma". However, if any 1195 * of the pages cannot be held, -1 is returned. 1196 */ 1197 int 1198 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1199 vm_prot_t prot, vm_page_t *ma, int max_count) 1200 { 1201 vm_offset_t end, va; 1202 vm_page_t *mp; 1203 int count; 1204 boolean_t pmap_failed; 1205 1206 if (len == 0) 1207 return (0); 1208 end = round_page(addr + len); 1209 addr = trunc_page(addr); 1210 1211 /* 1212 * Check for illegal addresses. 1213 */ 1214 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1215 return (-1); 1216 1217 if (atop(end - addr) > max_count) 1218 panic("vm_fault_quick_hold_pages: count > max_count"); 1219 count = atop(end - addr); 1220 1221 /* 1222 * Most likely, the physical pages are resident in the pmap, so it is 1223 * faster to try pmap_extract_and_hold() first. 1224 */ 1225 pmap_failed = FALSE; 1226 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1227 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1228 if (*mp == NULL) 1229 pmap_failed = TRUE; 1230 else if ((prot & VM_PROT_WRITE) != 0 && 1231 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1232 /* 1233 * Explicitly dirty the physical page. Otherwise, the 1234 * caller's changes may go unnoticed because they are 1235 * performed through an unmanaged mapping or by a DMA 1236 * operation. 1237 * 1238 * The object lock is not held here. 1239 * See vm_page_clear_dirty_mask(). 1240 */ 1241 vm_page_dirty(*mp); 1242 } 1243 } 1244 if (pmap_failed) { 1245 /* 1246 * One or more pages could not be held by the pmap. Either no 1247 * page was mapped at the specified virtual address or that 1248 * mapping had insufficient permissions. Attempt to fault in 1249 * and hold these pages. 1250 */ 1251 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1252 if (*mp == NULL && vm_fault_hold(map, va, prot, 1253 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1254 goto error; 1255 } 1256 return (count); 1257 error: 1258 for (mp = ma; mp < ma + count; mp++) 1259 if (*mp != NULL) { 1260 vm_page_lock(*mp); 1261 vm_page_unhold(*mp); 1262 vm_page_unlock(*mp); 1263 } 1264 return (-1); 1265 } 1266 1267 /* 1268 * Routine: 1269 * vm_fault_copy_entry 1270 * Function: 1271 * Create new shadow object backing dst_entry with private copy of 1272 * all underlying pages. When src_entry is equal to dst_entry, 1273 * function implements COW for wired-down map entry. Otherwise, 1274 * it forks wired entry into dst_map. 1275 * 1276 * In/out conditions: 1277 * The source and destination maps must be locked for write. 1278 * The source map entry must be wired down (or be a sharing map 1279 * entry corresponding to a main map entry that is wired down). 1280 */ 1281 void 1282 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1283 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1284 vm_ooffset_t *fork_charge) 1285 { 1286 vm_object_t backing_object, dst_object, object, src_object; 1287 vm_pindex_t dst_pindex, pindex, src_pindex; 1288 vm_prot_t access, prot; 1289 vm_offset_t vaddr; 1290 vm_page_t dst_m; 1291 vm_page_t src_m; 1292 boolean_t upgrade; 1293 1294 #ifdef lint 1295 src_map++; 1296 #endif /* lint */ 1297 1298 upgrade = src_entry == dst_entry; 1299 access = prot = dst_entry->protection; 1300 1301 src_object = src_entry->object.vm_object; 1302 src_pindex = OFF_TO_IDX(src_entry->offset); 1303 1304 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1305 dst_object = src_object; 1306 vm_object_reference(dst_object); 1307 } else { 1308 /* 1309 * Create the top-level object for the destination entry. (Doesn't 1310 * actually shadow anything - we copy the pages directly.) 1311 */ 1312 dst_object = vm_object_allocate(OBJT_DEFAULT, 1313 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1314 #if VM_NRESERVLEVEL > 0 1315 dst_object->flags |= OBJ_COLORED; 1316 dst_object->pg_color = atop(dst_entry->start); 1317 #endif 1318 } 1319 1320 VM_OBJECT_WLOCK(dst_object); 1321 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1322 ("vm_fault_copy_entry: vm_object not NULL")); 1323 if (src_object != dst_object) { 1324 dst_entry->object.vm_object = dst_object; 1325 dst_entry->offset = 0; 1326 dst_object->charge = dst_entry->end - dst_entry->start; 1327 } 1328 if (fork_charge != NULL) { 1329 KASSERT(dst_entry->cred == NULL, 1330 ("vm_fault_copy_entry: leaked swp charge")); 1331 dst_object->cred = curthread->td_ucred; 1332 crhold(dst_object->cred); 1333 *fork_charge += dst_object->charge; 1334 } else if (dst_object->cred == NULL) { 1335 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1336 dst_entry)); 1337 dst_object->cred = dst_entry->cred; 1338 dst_entry->cred = NULL; 1339 } 1340 1341 /* 1342 * If not an upgrade, then enter the mappings in the pmap as 1343 * read and/or execute accesses. Otherwise, enter them as 1344 * write accesses. 1345 * 1346 * A writeable large page mapping is only created if all of 1347 * the constituent small page mappings are modified. Marking 1348 * PTEs as modified on inception allows promotion to happen 1349 * without taking potentially large number of soft faults. 1350 */ 1351 if (!upgrade) 1352 access &= ~VM_PROT_WRITE; 1353 1354 /* 1355 * Loop through all of the virtual pages within the entry's 1356 * range, copying each page from the source object to the 1357 * destination object. Since the source is wired, those pages 1358 * must exist. In contrast, the destination is pageable. 1359 * Since the destination object does share any backing storage 1360 * with the source object, all of its pages must be dirtied, 1361 * regardless of whether they can be written. 1362 */ 1363 for (vaddr = dst_entry->start, dst_pindex = 0; 1364 vaddr < dst_entry->end; 1365 vaddr += PAGE_SIZE, dst_pindex++) { 1366 again: 1367 /* 1368 * Find the page in the source object, and copy it in. 1369 * Because the source is wired down, the page will be 1370 * in memory. 1371 */ 1372 if (src_object != dst_object) 1373 VM_OBJECT_RLOCK(src_object); 1374 object = src_object; 1375 pindex = src_pindex + dst_pindex; 1376 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1377 (backing_object = object->backing_object) != NULL) { 1378 /* 1379 * Unless the source mapping is read-only or 1380 * it is presently being upgraded from 1381 * read-only, the first object in the shadow 1382 * chain should provide all of the pages. In 1383 * other words, this loop body should never be 1384 * executed when the source mapping is already 1385 * read/write. 1386 */ 1387 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1388 upgrade, 1389 ("vm_fault_copy_entry: main object missing page")); 1390 1391 VM_OBJECT_RLOCK(backing_object); 1392 pindex += OFF_TO_IDX(object->backing_object_offset); 1393 if (object != dst_object) 1394 VM_OBJECT_RUNLOCK(object); 1395 object = backing_object; 1396 } 1397 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1398 1399 if (object != dst_object) { 1400 /* 1401 * Allocate a page in the destination object. 1402 */ 1403 dst_m = vm_page_alloc(dst_object, (src_object == 1404 dst_object ? src_pindex : 0) + dst_pindex, 1405 VM_ALLOC_NORMAL); 1406 if (dst_m == NULL) { 1407 VM_OBJECT_WUNLOCK(dst_object); 1408 VM_OBJECT_RUNLOCK(object); 1409 VM_WAIT; 1410 VM_OBJECT_WLOCK(dst_object); 1411 goto again; 1412 } 1413 pmap_copy_page(src_m, dst_m); 1414 VM_OBJECT_RUNLOCK(object); 1415 dst_m->valid = VM_PAGE_BITS_ALL; 1416 dst_m->dirty = VM_PAGE_BITS_ALL; 1417 } else { 1418 dst_m = src_m; 1419 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1420 goto again; 1421 vm_page_xbusy(dst_m); 1422 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1423 ("invalid dst page %p", dst_m)); 1424 } 1425 VM_OBJECT_WUNLOCK(dst_object); 1426 1427 /* 1428 * Enter it in the pmap. If a wired, copy-on-write 1429 * mapping is being replaced by a write-enabled 1430 * mapping, then wire that new mapping. 1431 */ 1432 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1433 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1434 1435 /* 1436 * Mark it no longer busy, and put it on the active list. 1437 */ 1438 VM_OBJECT_WLOCK(dst_object); 1439 1440 if (upgrade) { 1441 if (src_m != dst_m) { 1442 vm_page_lock(src_m); 1443 vm_page_unwire(src_m, PQ_INACTIVE); 1444 vm_page_unlock(src_m); 1445 vm_page_lock(dst_m); 1446 vm_page_wire(dst_m); 1447 vm_page_unlock(dst_m); 1448 } else { 1449 KASSERT(dst_m->wire_count > 0, 1450 ("dst_m %p is not wired", dst_m)); 1451 } 1452 } else { 1453 vm_page_lock(dst_m); 1454 vm_page_activate(dst_m); 1455 vm_page_unlock(dst_m); 1456 } 1457 vm_page_xunbusy(dst_m); 1458 } 1459 VM_OBJECT_WUNLOCK(dst_object); 1460 if (upgrade) { 1461 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1462 vm_object_deallocate(src_object); 1463 } 1464 } 1465 1466 1467 /* 1468 * This routine checks around the requested page for other pages that 1469 * might be able to be faulted in. This routine brackets the viable 1470 * pages for the pages to be paged in. 1471 * 1472 * Inputs: 1473 * m, rbehind, rahead 1474 * 1475 * Outputs: 1476 * marray (array of vm_page_t), reqpage (index of requested page) 1477 * 1478 * Return value: 1479 * number of pages in marray 1480 */ 1481 static int 1482 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1483 vm_page_t m; 1484 int rbehind; 1485 int rahead; 1486 vm_page_t *marray; 1487 int *reqpage; 1488 { 1489 int i,j; 1490 vm_object_t object; 1491 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1492 vm_page_t rtm; 1493 int cbehind, cahead; 1494 1495 VM_OBJECT_ASSERT_WLOCKED(m->object); 1496 1497 object = m->object; 1498 pindex = m->pindex; 1499 cbehind = cahead = 0; 1500 1501 /* 1502 * if the requested page is not available, then give up now 1503 */ 1504 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1505 return 0; 1506 } 1507 1508 if ((cbehind == 0) && (cahead == 0)) { 1509 *reqpage = 0; 1510 marray[0] = m; 1511 return 1; 1512 } 1513 1514 if (rahead > cahead) { 1515 rahead = cahead; 1516 } 1517 1518 if (rbehind > cbehind) { 1519 rbehind = cbehind; 1520 } 1521 1522 /* 1523 * scan backward for the read behind pages -- in memory 1524 */ 1525 if (pindex > 0) { 1526 if (rbehind > pindex) { 1527 rbehind = pindex; 1528 startpindex = 0; 1529 } else { 1530 startpindex = pindex - rbehind; 1531 } 1532 1533 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1534 rtm->pindex >= startpindex) 1535 startpindex = rtm->pindex + 1; 1536 1537 /* tpindex is unsigned; beware of numeric underflow. */ 1538 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1539 tpindex < pindex; i++, tpindex--) { 1540 1541 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1542 VM_ALLOC_IFNOTCACHED); 1543 if (rtm == NULL) { 1544 /* 1545 * Shift the allocated pages to the 1546 * beginning of the array. 1547 */ 1548 for (j = 0; j < i; j++) { 1549 marray[j] = marray[j + tpindex + 1 - 1550 startpindex]; 1551 } 1552 break; 1553 } 1554 1555 marray[tpindex - startpindex] = rtm; 1556 } 1557 } else { 1558 startpindex = 0; 1559 i = 0; 1560 } 1561 1562 marray[i] = m; 1563 /* page offset of the required page */ 1564 *reqpage = i; 1565 1566 tpindex = pindex + 1; 1567 i++; 1568 1569 /* 1570 * scan forward for the read ahead pages 1571 */ 1572 endpindex = tpindex + rahead; 1573 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1574 endpindex = rtm->pindex; 1575 if (endpindex > object->size) 1576 endpindex = object->size; 1577 1578 for (; tpindex < endpindex; i++, tpindex++) { 1579 1580 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1581 VM_ALLOC_IFNOTCACHED); 1582 if (rtm == NULL) { 1583 break; 1584 } 1585 1586 marray[i] = rtm; 1587 } 1588 1589 /* return number of pages */ 1590 return i; 1591 } 1592 1593 /* 1594 * Block entry into the machine-independent layer's page fault handler by 1595 * the calling thread. Subsequent calls to vm_fault() by that thread will 1596 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1597 * spurious page faults. 1598 */ 1599 int 1600 vm_fault_disable_pagefaults(void) 1601 { 1602 1603 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1604 } 1605 1606 void 1607 vm_fault_enable_pagefaults(int save) 1608 { 1609 1610 curthread_pflags_restore(save); 1611 } 1612