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 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 352 vm_map_unlock_and_wait(fs.map, 0); 353 } else 354 vm_map_unlock(fs.map); 355 goto RetryFault; 356 } 357 358 if (wired) 359 fault_type = prot | (fault_type & VM_PROT_COPY); 360 361 if (fs.vp == NULL /* avoid locked vnode leak */ && 362 (fault_flags & (VM_FAULT_CHANGE_WIRING | VM_FAULT_DIRTY)) == 0 && 363 /* avoid calling vm_object_set_writeable_dirty() */ 364 ((prot & VM_PROT_WRITE) == 0 || 365 (fs.first_object->type != OBJT_VNODE && 366 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 367 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 368 VM_OBJECT_RLOCK(fs.first_object); 369 if ((prot & VM_PROT_WRITE) != 0 && 370 (fs.first_object->type == OBJT_VNODE || 371 (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) && 372 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0) 373 goto fast_failed; 374 m = vm_page_lookup(fs.first_object, fs.first_pindex); 375 /* A busy page can be mapped for read|execute access. */ 376 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 377 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 378 goto fast_failed; 379 result = pmap_enter(fs.map->pmap, vaddr, m, prot, 380 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 381 0), 0); 382 if (result != KERN_SUCCESS) 383 goto fast_failed; 384 if (m_hold != NULL) { 385 *m_hold = m; 386 vm_page_lock(m); 387 vm_page_hold(m); 388 vm_page_unlock(m); 389 } 390 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, 391 FALSE); 392 VM_OBJECT_RUNLOCK(fs.first_object); 393 if (!wired) 394 vm_fault_prefault(&fs, vaddr, 0, 0); 395 vm_map_lookup_done(fs.map, fs.entry); 396 curthread->td_ru.ru_minflt++; 397 return (KERN_SUCCESS); 398 fast_failed: 399 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 400 VM_OBJECT_RUNLOCK(fs.first_object); 401 VM_OBJECT_WLOCK(fs.first_object); 402 } 403 } else { 404 VM_OBJECT_WLOCK(fs.first_object); 405 } 406 407 /* 408 * Make a reference to this object to prevent its disposal while we 409 * are messing with it. Once we have the reference, the map is free 410 * to be diddled. Since objects reference their shadows (and copies), 411 * they will stay around as well. 412 * 413 * Bump the paging-in-progress count to prevent size changes (e.g. 414 * truncation operations) during I/O. This must be done after 415 * obtaining the vnode lock in order to avoid possible deadlocks. 416 */ 417 vm_object_reference_locked(fs.first_object); 418 vm_object_pip_add(fs.first_object, 1); 419 420 fs.lookup_still_valid = TRUE; 421 422 fs.first_m = NULL; 423 424 /* 425 * Search for the page at object/offset. 426 */ 427 fs.object = fs.first_object; 428 fs.pindex = fs.first_pindex; 429 while (TRUE) { 430 /* 431 * If the object is dead, we stop here 432 */ 433 if (fs.object->flags & OBJ_DEAD) { 434 unlock_and_deallocate(&fs); 435 return (KERN_PROTECTION_FAILURE); 436 } 437 438 /* 439 * See if page is resident 440 */ 441 fs.m = vm_page_lookup(fs.object, fs.pindex); 442 if (fs.m != NULL) { 443 /* 444 * Wait/Retry if the page is busy. We have to do this 445 * if the page is either exclusive or shared busy 446 * because the vm_pager may be using read busy for 447 * pageouts (and even pageins if it is the vnode 448 * pager), and we could end up trying to pagein and 449 * pageout the same page simultaneously. 450 * 451 * We can theoretically allow the busy case on a read 452 * fault if the page is marked valid, but since such 453 * pages are typically already pmap'd, putting that 454 * special case in might be more effort then it is 455 * worth. We cannot under any circumstances mess 456 * around with a shared busied page except, perhaps, 457 * to pmap it. 458 */ 459 if (vm_page_busied(fs.m)) { 460 /* 461 * Reference the page before unlocking and 462 * sleeping so that the page daemon is less 463 * likely to reclaim it. 464 */ 465 vm_page_aflag_set(fs.m, PGA_REFERENCED); 466 if (fs.object != fs.first_object) { 467 if (!VM_OBJECT_TRYWLOCK( 468 fs.first_object)) { 469 VM_OBJECT_WUNLOCK(fs.object); 470 VM_OBJECT_WLOCK(fs.first_object); 471 VM_OBJECT_WLOCK(fs.object); 472 } 473 vm_page_lock(fs.first_m); 474 vm_page_free(fs.first_m); 475 vm_page_unlock(fs.first_m); 476 vm_object_pip_wakeup(fs.first_object); 477 VM_OBJECT_WUNLOCK(fs.first_object); 478 fs.first_m = NULL; 479 } 480 unlock_map(&fs); 481 if (fs.m == vm_page_lookup(fs.object, 482 fs.pindex)) { 483 vm_page_sleep_if_busy(fs.m, "vmpfw"); 484 } 485 vm_object_pip_wakeup(fs.object); 486 VM_OBJECT_WUNLOCK(fs.object); 487 PCPU_INC(cnt.v_intrans); 488 vm_object_deallocate(fs.first_object); 489 goto RetryFault; 490 } 491 vm_page_lock(fs.m); 492 vm_page_remque(fs.m); 493 vm_page_unlock(fs.m); 494 495 /* 496 * Mark page busy for other processes, and the 497 * pagedaemon. If it still isn't completely valid 498 * (readable), jump to readrest, else break-out ( we 499 * found the page ). 500 */ 501 vm_page_xbusy(fs.m); 502 if (fs.m->valid != VM_PAGE_BITS_ALL) 503 goto readrest; 504 break; 505 } 506 507 /* 508 * Page is not resident, If this is the search termination 509 * or the pager might contain the page, allocate a new page. 510 */ 511 if (TRYPAGER || fs.object == fs.first_object) { 512 if (fs.pindex >= fs.object->size) { 513 unlock_and_deallocate(&fs); 514 return (KERN_PROTECTION_FAILURE); 515 } 516 517 /* 518 * Allocate a new page for this object/offset pair. 519 * 520 * Unlocked read of the p_flag is harmless. At 521 * worst, the P_KILLED might be not observed 522 * there, and allocation can fail, causing 523 * restart and new reading of the p_flag. 524 */ 525 fs.m = NULL; 526 if (!vm_page_count_severe() || P_KILLED(curproc)) { 527 #if VM_NRESERVLEVEL > 0 528 vm_object_color(fs.object, atop(vaddr) - 529 fs.pindex); 530 #endif 531 alloc_req = P_KILLED(curproc) ? 532 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 533 if (fs.object->type != OBJT_VNODE && 534 fs.object->backing_object == NULL) 535 alloc_req |= VM_ALLOC_ZERO; 536 fs.m = vm_page_alloc(fs.object, fs.pindex, 537 alloc_req); 538 } 539 if (fs.m == NULL) { 540 unlock_and_deallocate(&fs); 541 VM_WAITPFAULT; 542 goto RetryFault; 543 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 544 break; 545 } 546 547 readrest: 548 /* 549 * We have found a valid page or we have allocated a new page. 550 * The page thus may not be valid or may not be entirely 551 * valid. 552 * 553 * Attempt to fault-in the page if there is a chance that the 554 * pager has it, and potentially fault in additional pages 555 * at the same time. 556 */ 557 if (TRYPAGER) { 558 int rv; 559 u_char behavior = vm_map_entry_behavior(fs.entry); 560 561 era = fs.entry->read_ahead; 562 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 563 P_KILLED(curproc)) { 564 behind = 0; 565 nera = 0; 566 ahead = 0; 567 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 568 behind = 0; 569 nera = VM_FAULT_READ_AHEAD_MAX; 570 ahead = nera; 571 if (fs.pindex == fs.entry->next_read) 572 vm_fault_dontneed(&fs, vaddr, ahead); 573 } else if (fs.pindex == fs.entry->next_read) { 574 /* 575 * This is a sequential fault. Arithmetically 576 * increase the requested number of pages in 577 * the read-ahead window. The requested 578 * number of pages is "# of sequential faults 579 * x (read ahead min + 1) + read ahead min" 580 */ 581 behind = 0; 582 nera = VM_FAULT_READ_AHEAD_MIN; 583 if (era > 0) { 584 nera += era + 1; 585 if (nera > VM_FAULT_READ_AHEAD_MAX) 586 nera = VM_FAULT_READ_AHEAD_MAX; 587 } 588 ahead = nera; 589 if (era == VM_FAULT_READ_AHEAD_MAX) 590 vm_fault_dontneed(&fs, vaddr, ahead); 591 } else { 592 /* 593 * This is a non-sequential fault. Request a 594 * cluster of pages that is aligned to a 595 * VM_FAULT_READ_DEFAULT page offset boundary 596 * within the object. Alignment to a page 597 * offset boundary is more likely to coincide 598 * with the underlying file system block than 599 * alignment to a virtual address boundary. 600 */ 601 cluster_offset = fs.pindex % 602 VM_FAULT_READ_DEFAULT; 603 behind = ulmin(cluster_offset, 604 atop(vaddr - fs.entry->start)); 605 nera = 0; 606 ahead = VM_FAULT_READ_DEFAULT - 1 - 607 cluster_offset; 608 } 609 ahead = ulmin(ahead, atop(fs.entry->end - vaddr) - 1); 610 if (era != nera) 611 fs.entry->read_ahead = nera; 612 613 /* 614 * Call the pager to retrieve the data, if any, after 615 * releasing the lock on the map. We hold a ref on 616 * fs.object and the pages are exclusive busied. 617 */ 618 unlock_map(&fs); 619 620 if (fs.object->type == OBJT_VNODE) { 621 vp = fs.object->handle; 622 if (vp == fs.vp) 623 goto vnode_locked; 624 else if (fs.vp != NULL) { 625 vput(fs.vp); 626 fs.vp = NULL; 627 } 628 locked = VOP_ISLOCKED(vp); 629 630 if (locked != LK_EXCLUSIVE) 631 locked = LK_SHARED; 632 /* Do not sleep for vnode lock while fs.m is busy */ 633 error = vget(vp, locked | LK_CANRECURSE | 634 LK_NOWAIT, curthread); 635 if (error != 0) { 636 vhold(vp); 637 release_page(&fs); 638 unlock_and_deallocate(&fs); 639 error = vget(vp, locked | LK_RETRY | 640 LK_CANRECURSE, curthread); 641 vdrop(vp); 642 fs.vp = vp; 643 KASSERT(error == 0, 644 ("vm_fault: vget failed")); 645 goto RetryFault; 646 } 647 fs.vp = vp; 648 } 649 vnode_locked: 650 KASSERT(fs.vp == NULL || !fs.map->system_map, 651 ("vm_fault: vnode-backed object mapped by system map")); 652 653 /* 654 * now we find out if any other pages should be paged 655 * in at this time this routine checks to see if the 656 * pages surrounding this fault reside in the same 657 * object as the page for this fault. If they do, 658 * then they are faulted in also into the object. The 659 * array "marray" returned contains an array of 660 * vm_page_t structs where one of them is the 661 * vm_page_t passed to the routine. The reqpage 662 * return value is the index into the marray for the 663 * vm_page_t passed to the routine. 664 * 665 * fs.m plus the additional pages are exclusive busied. 666 */ 667 faultcount = vm_fault_additional_pages( 668 fs.m, behind, ahead, marray, &reqpage); 669 670 rv = faultcount ? 671 vm_pager_get_pages(fs.object, marray, faultcount, 672 reqpage) : VM_PAGER_FAIL; 673 674 if (rv == VM_PAGER_OK) { 675 /* 676 * Found the page. Leave it busy while we play 677 * with it. 678 */ 679 680 /* 681 * Relookup in case pager changed page. Pager 682 * is responsible for disposition of old page 683 * if moved. 684 */ 685 fs.m = vm_page_lookup(fs.object, fs.pindex); 686 if (!fs.m) { 687 unlock_and_deallocate(&fs); 688 goto RetryFault; 689 } 690 691 hardfault++; 692 break; /* break to PAGE HAS BEEN FOUND */ 693 } 694 /* 695 * Remove the bogus page (which does not exist at this 696 * object/offset); before doing so, we must get back 697 * our object lock to preserve our invariant. 698 * 699 * Also wake up any other process that may want to bring 700 * in this page. 701 * 702 * If this is the top-level object, we must leave the 703 * busy page to prevent another process from rushing 704 * past us, and inserting the page in that object at 705 * the same time that we are. 706 */ 707 if (rv == VM_PAGER_ERROR) 708 printf("vm_fault: pager read error, pid %d (%s)\n", 709 curproc->p_pid, curproc->p_comm); 710 /* 711 * Data outside the range of the pager or an I/O error 712 */ 713 /* 714 * XXX - the check for kernel_map is a kludge to work 715 * around having the machine panic on a kernel space 716 * fault w/ I/O error. 717 */ 718 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 719 (rv == VM_PAGER_BAD)) { 720 vm_page_lock(fs.m); 721 vm_page_free(fs.m); 722 vm_page_unlock(fs.m); 723 fs.m = NULL; 724 unlock_and_deallocate(&fs); 725 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 726 } 727 if (fs.object != fs.first_object) { 728 vm_page_lock(fs.m); 729 vm_page_free(fs.m); 730 vm_page_unlock(fs.m); 731 fs.m = NULL; 732 /* 733 * XXX - we cannot just fall out at this 734 * point, m has been freed and is invalid! 735 */ 736 } 737 } 738 739 /* 740 * We get here if the object has default pager (or unwiring) 741 * or the pager doesn't have the page. 742 */ 743 if (fs.object == fs.first_object) 744 fs.first_m = fs.m; 745 746 /* 747 * Move on to the next object. Lock the next object before 748 * unlocking the current one. 749 */ 750 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 751 next_object = fs.object->backing_object; 752 if (next_object == NULL) { 753 /* 754 * If there's no object left, fill the page in the top 755 * object with zeros. 756 */ 757 if (fs.object != fs.first_object) { 758 vm_object_pip_wakeup(fs.object); 759 VM_OBJECT_WUNLOCK(fs.object); 760 761 fs.object = fs.first_object; 762 fs.pindex = fs.first_pindex; 763 fs.m = fs.first_m; 764 VM_OBJECT_WLOCK(fs.object); 765 } 766 fs.first_m = NULL; 767 768 /* 769 * Zero the page if necessary and mark it valid. 770 */ 771 if ((fs.m->flags & PG_ZERO) == 0) { 772 pmap_zero_page(fs.m); 773 } else { 774 PCPU_INC(cnt.v_ozfod); 775 } 776 PCPU_INC(cnt.v_zfod); 777 fs.m->valid = VM_PAGE_BITS_ALL; 778 /* Don't try to prefault neighboring pages. */ 779 faultcount = 1; 780 break; /* break to PAGE HAS BEEN FOUND */ 781 } else { 782 KASSERT(fs.object != next_object, 783 ("object loop %p", next_object)); 784 VM_OBJECT_WLOCK(next_object); 785 vm_object_pip_add(next_object, 1); 786 if (fs.object != fs.first_object) 787 vm_object_pip_wakeup(fs.object); 788 VM_OBJECT_WUNLOCK(fs.object); 789 fs.object = next_object; 790 } 791 } 792 793 vm_page_assert_xbusied(fs.m); 794 795 /* 796 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 797 * is held.] 798 */ 799 800 /* 801 * If the page is being written, but isn't already owned by the 802 * top-level object, we have to copy it into a new page owned by the 803 * top-level object. 804 */ 805 if (fs.object != fs.first_object) { 806 /* 807 * We only really need to copy if we want to write it. 808 */ 809 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 810 /* 811 * This allows pages to be virtually copied from a 812 * backing_object into the first_object, where the 813 * backing object has no other refs to it, and cannot 814 * gain any more refs. Instead of a bcopy, we just 815 * move the page from the backing object to the 816 * first object. Note that we must mark the page 817 * dirty in the first object so that it will go out 818 * to swap when needed. 819 */ 820 is_first_object_locked = FALSE; 821 if ( 822 /* 823 * Only one shadow object 824 */ 825 (fs.object->shadow_count == 1) && 826 /* 827 * No COW refs, except us 828 */ 829 (fs.object->ref_count == 1) && 830 /* 831 * No one else can look this object up 832 */ 833 (fs.object->handle == NULL) && 834 /* 835 * No other ways to look the object up 836 */ 837 ((fs.object->type == OBJT_DEFAULT) || 838 (fs.object->type == OBJT_SWAP)) && 839 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 840 /* 841 * We don't chase down the shadow chain 842 */ 843 fs.object == fs.first_object->backing_object) { 844 /* 845 * get rid of the unnecessary page 846 */ 847 vm_page_lock(fs.first_m); 848 vm_page_free(fs.first_m); 849 vm_page_unlock(fs.first_m); 850 /* 851 * grab the page and put it into the 852 * process'es object. The page is 853 * automatically made dirty. 854 */ 855 if (vm_page_rename(fs.m, fs.first_object, 856 fs.first_pindex)) { 857 unlock_and_deallocate(&fs); 858 goto RetryFault; 859 } 860 #if VM_NRESERVLEVEL > 0 861 /* 862 * Rename the reservation. 863 */ 864 vm_reserv_rename(fs.m, fs.first_object, 865 fs.object, OFF_TO_IDX( 866 fs.first_object->backing_object_offset)); 867 #endif 868 vm_page_xbusy(fs.m); 869 fs.first_m = fs.m; 870 fs.m = NULL; 871 PCPU_INC(cnt.v_cow_optim); 872 } else { 873 /* 874 * Oh, well, lets copy it. 875 */ 876 pmap_copy_page(fs.m, fs.first_m); 877 fs.first_m->valid = VM_PAGE_BITS_ALL; 878 if (wired && (fault_flags & 879 VM_FAULT_CHANGE_WIRING) == 0) { 880 vm_page_lock(fs.first_m); 881 vm_page_wire(fs.first_m); 882 vm_page_unlock(fs.first_m); 883 884 vm_page_lock(fs.m); 885 vm_page_unwire(fs.m, PQ_INACTIVE); 886 vm_page_unlock(fs.m); 887 } 888 /* 889 * We no longer need the old page or object. 890 */ 891 release_page(&fs); 892 } 893 /* 894 * fs.object != fs.first_object due to above 895 * conditional 896 */ 897 vm_object_pip_wakeup(fs.object); 898 VM_OBJECT_WUNLOCK(fs.object); 899 /* 900 * Only use the new page below... 901 */ 902 fs.object = fs.first_object; 903 fs.pindex = fs.first_pindex; 904 fs.m = fs.first_m; 905 if (!is_first_object_locked) 906 VM_OBJECT_WLOCK(fs.object); 907 PCPU_INC(cnt.v_cow_faults); 908 curthread->td_cow++; 909 } else { 910 prot &= ~VM_PROT_WRITE; 911 } 912 } 913 914 /* 915 * We must verify that the maps have not changed since our last 916 * lookup. 917 */ 918 if (!fs.lookup_still_valid) { 919 vm_object_t retry_object; 920 vm_pindex_t retry_pindex; 921 vm_prot_t retry_prot; 922 923 if (!vm_map_trylock_read(fs.map)) { 924 release_page(&fs); 925 unlock_and_deallocate(&fs); 926 goto RetryFault; 927 } 928 fs.lookup_still_valid = TRUE; 929 if (fs.map->timestamp != map_generation) { 930 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 931 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 932 933 /* 934 * If we don't need the page any longer, put it on the inactive 935 * list (the easiest thing to do here). If no one needs it, 936 * pageout will grab it eventually. 937 */ 938 if (result != KERN_SUCCESS) { 939 release_page(&fs); 940 unlock_and_deallocate(&fs); 941 942 /* 943 * If retry of map lookup would have blocked then 944 * retry fault from start. 945 */ 946 if (result == KERN_FAILURE) 947 goto RetryFault; 948 return (result); 949 } 950 if ((retry_object != fs.first_object) || 951 (retry_pindex != fs.first_pindex)) { 952 release_page(&fs); 953 unlock_and_deallocate(&fs); 954 goto RetryFault; 955 } 956 957 /* 958 * Check whether the protection has changed or the object has 959 * been copied while we left the map unlocked. Changing from 960 * read to write permission is OK - we leave the page 961 * write-protected, and catch the write fault. Changing from 962 * write to read permission means that we can't mark the page 963 * write-enabled after all. 964 */ 965 prot &= retry_prot; 966 } 967 } 968 /* 969 * If the page was filled by a pager, update the map entry's 970 * last read offset. Since the pager does not return the 971 * actual set of pages that it read, this update is based on 972 * the requested set. Typically, the requested and actual 973 * sets are the same. 974 * 975 * XXX The following assignment modifies the map 976 * without holding a write lock on it. 977 */ 978 if (hardfault) 979 fs.entry->next_read = fs.pindex + faultcount - reqpage; 980 981 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); 982 vm_page_assert_xbusied(fs.m); 983 984 /* 985 * Page must be completely valid or it is not fit to 986 * map into user space. vm_pager_get_pages() ensures this. 987 */ 988 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 989 ("vm_fault: page %p partially invalid", fs.m)); 990 VM_OBJECT_WUNLOCK(fs.object); 991 992 /* 993 * Put this page into the physical map. We had to do the unlock above 994 * because pmap_enter() may sleep. We don't put the page 995 * back on the active queue until later so that the pageout daemon 996 * won't find it (yet). 997 */ 998 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 999 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 1000 if (faultcount != 1 && (fault_flags & VM_FAULT_CHANGE_WIRING) == 0 && 1001 wired == 0) 1002 vm_fault_prefault(&fs, vaddr, faultcount, reqpage); 1003 VM_OBJECT_WLOCK(fs.object); 1004 vm_page_lock(fs.m); 1005 1006 /* 1007 * If the page is not wired down, then put it where the pageout daemon 1008 * can find it. 1009 */ 1010 if (fault_flags & VM_FAULT_CHANGE_WIRING) { 1011 if (wired) 1012 vm_page_wire(fs.m); 1013 else 1014 vm_page_unwire(fs.m, PQ_ACTIVE); 1015 } else 1016 vm_page_activate(fs.m); 1017 if (m_hold != NULL) { 1018 *m_hold = fs.m; 1019 vm_page_hold(fs.m); 1020 } 1021 vm_page_unlock(fs.m); 1022 vm_page_xunbusy(fs.m); 1023 1024 /* 1025 * Unlock everything, and return 1026 */ 1027 unlock_and_deallocate(&fs); 1028 if (hardfault) { 1029 PCPU_INC(cnt.v_io_faults); 1030 curthread->td_ru.ru_majflt++; 1031 } else 1032 curthread->td_ru.ru_minflt++; 1033 1034 return (KERN_SUCCESS); 1035 } 1036 1037 /* 1038 * Speed up the reclamation of pages that precede the faulting pindex within 1039 * the first object of the shadow chain. Essentially, perform the equivalent 1040 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1041 * the faulting pindex by the cluster size when the pages read by vm_fault() 1042 * cross a cluster-size boundary. The cluster size is the greater of the 1043 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1044 * 1045 * When "fs->first_object" is a shadow object, the pages in the backing object 1046 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1047 * function must only be concerned with pages in the first object. 1048 */ 1049 static void 1050 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1051 { 1052 vm_map_entry_t entry; 1053 vm_object_t first_object, object; 1054 vm_offset_t end, start; 1055 vm_page_t m, m_next; 1056 vm_pindex_t pend, pstart; 1057 vm_size_t size; 1058 1059 object = fs->object; 1060 VM_OBJECT_ASSERT_WLOCKED(object); 1061 first_object = fs->first_object; 1062 if (first_object != object) { 1063 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1064 VM_OBJECT_WUNLOCK(object); 1065 VM_OBJECT_WLOCK(first_object); 1066 VM_OBJECT_WLOCK(object); 1067 } 1068 } 1069 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1070 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1071 size = VM_FAULT_DONTNEED_MIN; 1072 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1073 size = pagesizes[1]; 1074 end = rounddown2(vaddr, size); 1075 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1076 (entry = fs->entry)->start < end) { 1077 if (end - entry->start < size) 1078 start = entry->start; 1079 else 1080 start = end - size; 1081 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1082 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1083 entry->start); 1084 m_next = vm_page_find_least(first_object, pstart); 1085 pend = OFF_TO_IDX(entry->offset) + atop(end - 1086 entry->start); 1087 while ((m = m_next) != NULL && m->pindex < pend) { 1088 m_next = TAILQ_NEXT(m, listq); 1089 if (m->valid != VM_PAGE_BITS_ALL || 1090 vm_page_busied(m)) 1091 continue; 1092 vm_page_lock(m); 1093 if (m->hold_count == 0 && m->wire_count == 0) 1094 vm_page_advise(m, MADV_DONTNEED); 1095 vm_page_unlock(m); 1096 } 1097 } 1098 } 1099 if (first_object != object) 1100 VM_OBJECT_WUNLOCK(first_object); 1101 } 1102 1103 /* 1104 * vm_fault_prefault provides a quick way of clustering 1105 * pagefaults into a processes address space. It is a "cousin" 1106 * of vm_map_pmap_enter, except it runs at page fault time instead 1107 * of mmap time. 1108 */ 1109 static void 1110 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1111 int faultcount, int reqpage) 1112 { 1113 pmap_t pmap; 1114 vm_map_entry_t entry; 1115 vm_object_t backing_object, lobject; 1116 vm_offset_t addr, starta; 1117 vm_pindex_t pindex; 1118 vm_page_t m; 1119 int backward, forward, i; 1120 1121 pmap = fs->map->pmap; 1122 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1123 return; 1124 1125 if (faultcount > 0) { 1126 backward = reqpage; 1127 forward = faultcount - reqpage - 1; 1128 } else { 1129 backward = PFBAK; 1130 forward = PFFOR; 1131 } 1132 entry = fs->entry; 1133 1134 starta = addra - backward * PAGE_SIZE; 1135 if (starta < entry->start) { 1136 starta = entry->start; 1137 } else if (starta > addra) { 1138 starta = 0; 1139 } 1140 1141 /* 1142 * Generate the sequence of virtual addresses that are candidates for 1143 * prefaulting in an outward spiral from the faulting virtual address, 1144 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1145 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1146 * If the candidate address doesn't have a backing physical page, then 1147 * the loop immediately terminates. 1148 */ 1149 for (i = 0; i < 2 * imax(backward, forward); i++) { 1150 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1151 PAGE_SIZE); 1152 if (addr > addra + forward * PAGE_SIZE) 1153 addr = 0; 1154 1155 if (addr < starta || addr >= entry->end) 1156 continue; 1157 1158 if (!pmap_is_prefaultable(pmap, addr)) 1159 continue; 1160 1161 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1162 lobject = entry->object.vm_object; 1163 VM_OBJECT_RLOCK(lobject); 1164 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1165 lobject->type == OBJT_DEFAULT && 1166 (backing_object = lobject->backing_object) != NULL) { 1167 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1168 0, ("vm_fault_prefault: unaligned object offset")); 1169 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1170 VM_OBJECT_RLOCK(backing_object); 1171 VM_OBJECT_RUNLOCK(lobject); 1172 lobject = backing_object; 1173 } 1174 if (m == NULL) { 1175 VM_OBJECT_RUNLOCK(lobject); 1176 break; 1177 } 1178 if (m->valid == VM_PAGE_BITS_ALL && 1179 (m->flags & PG_FICTITIOUS) == 0) 1180 pmap_enter_quick(pmap, addr, m, entry->protection); 1181 VM_OBJECT_RUNLOCK(lobject); 1182 } 1183 } 1184 1185 /* 1186 * Hold each of the physical pages that are mapped by the specified range of 1187 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1188 * and allow the specified types of access, "prot". If all of the implied 1189 * pages are successfully held, then the number of held pages is returned 1190 * together with pointers to those pages in the array "ma". However, if any 1191 * of the pages cannot be held, -1 is returned. 1192 */ 1193 int 1194 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1195 vm_prot_t prot, vm_page_t *ma, int max_count) 1196 { 1197 vm_offset_t end, va; 1198 vm_page_t *mp; 1199 int count; 1200 boolean_t pmap_failed; 1201 1202 if (len == 0) 1203 return (0); 1204 end = round_page(addr + len); 1205 addr = trunc_page(addr); 1206 1207 /* 1208 * Check for illegal addresses. 1209 */ 1210 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1211 return (-1); 1212 1213 if (atop(end - addr) > max_count) 1214 panic("vm_fault_quick_hold_pages: count > max_count"); 1215 count = atop(end - addr); 1216 1217 /* 1218 * Most likely, the physical pages are resident in the pmap, so it is 1219 * faster to try pmap_extract_and_hold() first. 1220 */ 1221 pmap_failed = FALSE; 1222 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1223 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1224 if (*mp == NULL) 1225 pmap_failed = TRUE; 1226 else if ((prot & VM_PROT_WRITE) != 0 && 1227 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1228 /* 1229 * Explicitly dirty the physical page. Otherwise, the 1230 * caller's changes may go unnoticed because they are 1231 * performed through an unmanaged mapping or by a DMA 1232 * operation. 1233 * 1234 * The object lock is not held here. 1235 * See vm_page_clear_dirty_mask(). 1236 */ 1237 vm_page_dirty(*mp); 1238 } 1239 } 1240 if (pmap_failed) { 1241 /* 1242 * One or more pages could not be held by the pmap. Either no 1243 * page was mapped at the specified virtual address or that 1244 * mapping had insufficient permissions. Attempt to fault in 1245 * and hold these pages. 1246 */ 1247 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1248 if (*mp == NULL && vm_fault_hold(map, va, prot, 1249 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1250 goto error; 1251 } 1252 return (count); 1253 error: 1254 for (mp = ma; mp < ma + count; mp++) 1255 if (*mp != NULL) { 1256 vm_page_lock(*mp); 1257 vm_page_unhold(*mp); 1258 vm_page_unlock(*mp); 1259 } 1260 return (-1); 1261 } 1262 1263 /* 1264 * Routine: 1265 * vm_fault_copy_entry 1266 * Function: 1267 * Create new shadow object backing dst_entry with private copy of 1268 * all underlying pages. When src_entry is equal to dst_entry, 1269 * function implements COW for wired-down map entry. Otherwise, 1270 * it forks wired entry into dst_map. 1271 * 1272 * In/out conditions: 1273 * The source and destination maps must be locked for write. 1274 * The source map entry must be wired down (or be a sharing map 1275 * entry corresponding to a main map entry that is wired down). 1276 */ 1277 void 1278 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1279 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1280 vm_ooffset_t *fork_charge) 1281 { 1282 vm_object_t backing_object, dst_object, object, src_object; 1283 vm_pindex_t dst_pindex, pindex, src_pindex; 1284 vm_prot_t access, prot; 1285 vm_offset_t vaddr; 1286 vm_page_t dst_m; 1287 vm_page_t src_m; 1288 boolean_t upgrade; 1289 1290 #ifdef lint 1291 src_map++; 1292 #endif /* lint */ 1293 1294 upgrade = src_entry == dst_entry; 1295 access = prot = dst_entry->protection; 1296 1297 src_object = src_entry->object.vm_object; 1298 src_pindex = OFF_TO_IDX(src_entry->offset); 1299 1300 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1301 dst_object = src_object; 1302 vm_object_reference(dst_object); 1303 } else { 1304 /* 1305 * Create the top-level object for the destination entry. (Doesn't 1306 * actually shadow anything - we copy the pages directly.) 1307 */ 1308 dst_object = vm_object_allocate(OBJT_DEFAULT, 1309 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1310 #if VM_NRESERVLEVEL > 0 1311 dst_object->flags |= OBJ_COLORED; 1312 dst_object->pg_color = atop(dst_entry->start); 1313 #endif 1314 } 1315 1316 VM_OBJECT_WLOCK(dst_object); 1317 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1318 ("vm_fault_copy_entry: vm_object not NULL")); 1319 if (src_object != dst_object) { 1320 dst_entry->object.vm_object = dst_object; 1321 dst_entry->offset = 0; 1322 dst_object->charge = dst_entry->end - dst_entry->start; 1323 } 1324 if (fork_charge != NULL) { 1325 KASSERT(dst_entry->cred == NULL, 1326 ("vm_fault_copy_entry: leaked swp charge")); 1327 dst_object->cred = curthread->td_ucred; 1328 crhold(dst_object->cred); 1329 *fork_charge += dst_object->charge; 1330 } else if (dst_object->cred == NULL) { 1331 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1332 dst_entry)); 1333 dst_object->cred = dst_entry->cred; 1334 dst_entry->cred = NULL; 1335 } 1336 1337 /* 1338 * If not an upgrade, then enter the mappings in the pmap as 1339 * read and/or execute accesses. Otherwise, enter them as 1340 * write accesses. 1341 * 1342 * A writeable large page mapping is only created if all of 1343 * the constituent small page mappings are modified. Marking 1344 * PTEs as modified on inception allows promotion to happen 1345 * without taking potentially large number of soft faults. 1346 */ 1347 if (!upgrade) 1348 access &= ~VM_PROT_WRITE; 1349 1350 /* 1351 * Loop through all of the virtual pages within the entry's 1352 * range, copying each page from the source object to the 1353 * destination object. Since the source is wired, those pages 1354 * must exist. In contrast, the destination is pageable. 1355 * Since the destination object does share any backing storage 1356 * with the source object, all of its pages must be dirtied, 1357 * regardless of whether they can be written. 1358 */ 1359 for (vaddr = dst_entry->start, dst_pindex = 0; 1360 vaddr < dst_entry->end; 1361 vaddr += PAGE_SIZE, dst_pindex++) { 1362 again: 1363 /* 1364 * Find the page in the source object, and copy it in. 1365 * Because the source is wired down, the page will be 1366 * in memory. 1367 */ 1368 if (src_object != dst_object) 1369 VM_OBJECT_RLOCK(src_object); 1370 object = src_object; 1371 pindex = src_pindex + dst_pindex; 1372 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1373 (backing_object = object->backing_object) != NULL) { 1374 /* 1375 * Unless the source mapping is read-only or 1376 * it is presently being upgraded from 1377 * read-only, the first object in the shadow 1378 * chain should provide all of the pages. In 1379 * other words, this loop body should never be 1380 * executed when the source mapping is already 1381 * read/write. 1382 */ 1383 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1384 upgrade, 1385 ("vm_fault_copy_entry: main object missing page")); 1386 1387 VM_OBJECT_RLOCK(backing_object); 1388 pindex += OFF_TO_IDX(object->backing_object_offset); 1389 if (object != dst_object) 1390 VM_OBJECT_RUNLOCK(object); 1391 object = backing_object; 1392 } 1393 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1394 1395 if (object != dst_object) { 1396 /* 1397 * Allocate a page in the destination object. 1398 */ 1399 dst_m = vm_page_alloc(dst_object, (src_object == 1400 dst_object ? src_pindex : 0) + dst_pindex, 1401 VM_ALLOC_NORMAL); 1402 if (dst_m == NULL) { 1403 VM_OBJECT_WUNLOCK(dst_object); 1404 VM_OBJECT_RUNLOCK(object); 1405 VM_WAIT; 1406 VM_OBJECT_WLOCK(dst_object); 1407 goto again; 1408 } 1409 pmap_copy_page(src_m, dst_m); 1410 VM_OBJECT_RUNLOCK(object); 1411 dst_m->valid = VM_PAGE_BITS_ALL; 1412 dst_m->dirty = VM_PAGE_BITS_ALL; 1413 } else { 1414 dst_m = src_m; 1415 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1416 goto again; 1417 vm_page_xbusy(dst_m); 1418 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1419 ("invalid dst page %p", dst_m)); 1420 } 1421 VM_OBJECT_WUNLOCK(dst_object); 1422 1423 /* 1424 * Enter it in the pmap. If a wired, copy-on-write 1425 * mapping is being replaced by a write-enabled 1426 * mapping, then wire that new mapping. 1427 */ 1428 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1429 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1430 1431 /* 1432 * Mark it no longer busy, and put it on the active list. 1433 */ 1434 VM_OBJECT_WLOCK(dst_object); 1435 1436 if (upgrade) { 1437 if (src_m != dst_m) { 1438 vm_page_lock(src_m); 1439 vm_page_unwire(src_m, PQ_INACTIVE); 1440 vm_page_unlock(src_m); 1441 vm_page_lock(dst_m); 1442 vm_page_wire(dst_m); 1443 vm_page_unlock(dst_m); 1444 } else { 1445 KASSERT(dst_m->wire_count > 0, 1446 ("dst_m %p is not wired", dst_m)); 1447 } 1448 } else { 1449 vm_page_lock(dst_m); 1450 vm_page_activate(dst_m); 1451 vm_page_unlock(dst_m); 1452 } 1453 vm_page_xunbusy(dst_m); 1454 } 1455 VM_OBJECT_WUNLOCK(dst_object); 1456 if (upgrade) { 1457 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1458 vm_object_deallocate(src_object); 1459 } 1460 } 1461 1462 1463 /* 1464 * This routine checks around the requested page for other pages that 1465 * might be able to be faulted in. This routine brackets the viable 1466 * pages for the pages to be paged in. 1467 * 1468 * Inputs: 1469 * m, rbehind, rahead 1470 * 1471 * Outputs: 1472 * marray (array of vm_page_t), reqpage (index of requested page) 1473 * 1474 * Return value: 1475 * number of pages in marray 1476 */ 1477 static int 1478 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1479 vm_page_t m; 1480 int rbehind; 1481 int rahead; 1482 vm_page_t *marray; 1483 int *reqpage; 1484 { 1485 int i,j; 1486 vm_object_t object; 1487 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1488 vm_page_t rtm; 1489 int cbehind, cahead; 1490 1491 VM_OBJECT_ASSERT_WLOCKED(m->object); 1492 1493 object = m->object; 1494 pindex = m->pindex; 1495 cbehind = cahead = 0; 1496 1497 /* 1498 * if the requested page is not available, then give up now 1499 */ 1500 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1501 return 0; 1502 } 1503 1504 if ((cbehind == 0) && (cahead == 0)) { 1505 *reqpage = 0; 1506 marray[0] = m; 1507 return 1; 1508 } 1509 1510 if (rahead > cahead) { 1511 rahead = cahead; 1512 } 1513 1514 if (rbehind > cbehind) { 1515 rbehind = cbehind; 1516 } 1517 1518 /* 1519 * scan backward for the read behind pages -- in memory 1520 */ 1521 if (pindex > 0) { 1522 if (rbehind > pindex) { 1523 rbehind = pindex; 1524 startpindex = 0; 1525 } else { 1526 startpindex = pindex - rbehind; 1527 } 1528 1529 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1530 rtm->pindex >= startpindex) 1531 startpindex = rtm->pindex + 1; 1532 1533 /* tpindex is unsigned; beware of numeric underflow. */ 1534 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1535 tpindex < pindex; i++, tpindex--) { 1536 1537 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1538 VM_ALLOC_IFNOTCACHED); 1539 if (rtm == NULL) { 1540 /* 1541 * Shift the allocated pages to the 1542 * beginning of the array. 1543 */ 1544 for (j = 0; j < i; j++) { 1545 marray[j] = marray[j + tpindex + 1 - 1546 startpindex]; 1547 } 1548 break; 1549 } 1550 1551 marray[tpindex - startpindex] = rtm; 1552 } 1553 } else { 1554 startpindex = 0; 1555 i = 0; 1556 } 1557 1558 marray[i] = m; 1559 /* page offset of the required page */ 1560 *reqpage = i; 1561 1562 tpindex = pindex + 1; 1563 i++; 1564 1565 /* 1566 * scan forward for the read ahead pages 1567 */ 1568 endpindex = tpindex + rahead; 1569 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1570 endpindex = rtm->pindex; 1571 if (endpindex > object->size) 1572 endpindex = object->size; 1573 1574 for (; tpindex < endpindex; i++, tpindex++) { 1575 1576 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1577 VM_ALLOC_IFNOTCACHED); 1578 if (rtm == NULL) { 1579 break; 1580 } 1581 1582 marray[i] = rtm; 1583 } 1584 1585 /* return number of pages */ 1586 return i; 1587 } 1588 1589 /* 1590 * Block entry into the machine-independent layer's page fault handler by 1591 * the calling thread. Subsequent calls to vm_fault() by that thread will 1592 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1593 * spurious page faults. 1594 */ 1595 int 1596 vm_fault_disable_pagefaults(void) 1597 { 1598 1599 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1600 } 1601 1602 void 1603 vm_fault_enable_pagefaults(int save) 1604 { 1605 1606 curthread_pflags_restore(save); 1607 } 1608