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