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 if (fs.vp != NULL) 325 vput(fs.vp); 326 return (result); 327 } 328 329 map_generation = fs.map->timestamp; 330 331 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 332 panic("vm_fault: fault on nofault entry, addr: %lx", 333 (u_long)vaddr); 334 } 335 336 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 337 fs.entry->wiring_thread != curthread) { 338 vm_map_unlock_read(fs.map); 339 vm_map_lock(fs.map); 340 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 341 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 342 if (fs.vp != NULL) { 343 vput(fs.vp); 344 fs.vp = NULL; 345 } 346 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 347 vm_map_unlock_and_wait(fs.map, 0); 348 } else 349 vm_map_unlock(fs.map); 350 goto RetryFault; 351 } 352 353 if (wired) 354 fault_type = prot | (fault_type & VM_PROT_COPY); 355 else 356 KASSERT((fault_flags & VM_FAULT_WIRE) == 0, 357 ("!wired && VM_FAULT_WIRE")); 358 359 /* 360 * Try to avoid lock contention on the top-level object through 361 * special-case handling of some types of page faults, specifically, 362 * those that are both (1) mapping an existing page from the top- 363 * level object and (2) not having to mark that object as containing 364 * dirty pages. Under these conditions, a read lock on the top-level 365 * object suffices, allowing multiple page faults of a similar type to 366 * run in parallel on the same top-level object. 367 */ 368 if (fs.vp == NULL /* avoid locked vnode leak */ && 369 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 && 370 /* avoid calling vm_object_set_writeable_dirty() */ 371 ((prot & VM_PROT_WRITE) == 0 || 372 (fs.first_object->type != OBJT_VNODE && 373 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 374 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 375 VM_OBJECT_RLOCK(fs.first_object); 376 if ((prot & VM_PROT_WRITE) != 0 && 377 (fs.first_object->type == OBJT_VNODE || 378 (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) && 379 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0) 380 goto fast_failed; 381 m = vm_page_lookup(fs.first_object, fs.first_pindex); 382 /* A busy page can be mapped for read|execute access. */ 383 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 384 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 385 goto fast_failed; 386 result = pmap_enter(fs.map->pmap, vaddr, m, prot, 387 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 388 0), 0); 389 if (result != KERN_SUCCESS) 390 goto fast_failed; 391 if (m_hold != NULL) { 392 *m_hold = m; 393 vm_page_lock(m); 394 vm_page_hold(m); 395 vm_page_unlock(m); 396 } 397 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, 398 FALSE); 399 VM_OBJECT_RUNLOCK(fs.first_object); 400 if (!wired) 401 vm_fault_prefault(&fs, vaddr, PFBAK, PFFOR); 402 vm_map_lookup_done(fs.map, fs.entry); 403 curthread->td_ru.ru_minflt++; 404 return (KERN_SUCCESS); 405 fast_failed: 406 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 407 VM_OBJECT_RUNLOCK(fs.first_object); 408 VM_OBJECT_WLOCK(fs.first_object); 409 } 410 } else { 411 VM_OBJECT_WLOCK(fs.first_object); 412 } 413 414 /* 415 * Make a reference to this object to prevent its disposal while we 416 * are messing with it. Once we have the reference, the map is free 417 * to be diddled. Since objects reference their shadows (and copies), 418 * they will stay around as well. 419 * 420 * Bump the paging-in-progress count to prevent size changes (e.g. 421 * truncation operations) during I/O. This must be done after 422 * obtaining the vnode lock in order to avoid possible deadlocks. 423 */ 424 vm_object_reference_locked(fs.first_object); 425 vm_object_pip_add(fs.first_object, 1); 426 427 fs.lookup_still_valid = TRUE; 428 429 fs.first_m = NULL; 430 431 /* 432 * Search for the page at object/offset. 433 */ 434 fs.object = fs.first_object; 435 fs.pindex = fs.first_pindex; 436 while (TRUE) { 437 /* 438 * If the object is marked for imminent termination, 439 * we retry here, since the collapse pass has raced 440 * with us. Otherwise, if we see terminally dead 441 * object, return fail. 442 */ 443 if ((fs.object->flags & OBJ_DEAD) != 0) { 444 dead = fs.object->type == OBJT_DEAD; 445 unlock_and_deallocate(&fs); 446 if (dead) 447 return (KERN_PROTECTION_FAILURE); 448 pause("vmf_de", 1); 449 goto RetryFault; 450 } 451 452 /* 453 * See if page is resident 454 */ 455 fs.m = vm_page_lookup(fs.object, fs.pindex); 456 if (fs.m != NULL) { 457 /* 458 * Wait/Retry if the page is busy. We have to do this 459 * if the page is either exclusive or shared busy 460 * because the vm_pager may be using read busy for 461 * pageouts (and even pageins if it is the vnode 462 * pager), and we could end up trying to pagein and 463 * pageout the same page simultaneously. 464 * 465 * We can theoretically allow the busy case on a read 466 * fault if the page is marked valid, but since such 467 * pages are typically already pmap'd, putting that 468 * special case in might be more effort then it is 469 * worth. We cannot under any circumstances mess 470 * around with a shared busied page except, perhaps, 471 * to pmap it. 472 */ 473 if (vm_page_busied(fs.m)) { 474 /* 475 * Reference the page before unlocking and 476 * sleeping so that the page daemon is less 477 * likely to reclaim it. 478 */ 479 vm_page_aflag_set(fs.m, PGA_REFERENCED); 480 if (fs.object != fs.first_object) { 481 if (!VM_OBJECT_TRYWLOCK( 482 fs.first_object)) { 483 VM_OBJECT_WUNLOCK(fs.object); 484 VM_OBJECT_WLOCK(fs.first_object); 485 VM_OBJECT_WLOCK(fs.object); 486 } 487 vm_page_lock(fs.first_m); 488 vm_page_free(fs.first_m); 489 vm_page_unlock(fs.first_m); 490 vm_object_pip_wakeup(fs.first_object); 491 VM_OBJECT_WUNLOCK(fs.first_object); 492 fs.first_m = NULL; 493 } 494 unlock_map(&fs); 495 if (fs.m == vm_page_lookup(fs.object, 496 fs.pindex)) { 497 vm_page_sleep_if_busy(fs.m, "vmpfw"); 498 } 499 vm_object_pip_wakeup(fs.object); 500 VM_OBJECT_WUNLOCK(fs.object); 501 PCPU_INC(cnt.v_intrans); 502 vm_object_deallocate(fs.first_object); 503 goto RetryFault; 504 } 505 vm_page_lock(fs.m); 506 vm_page_remque(fs.m); 507 vm_page_unlock(fs.m); 508 509 /* 510 * Mark page busy for other processes, and the 511 * pagedaemon. If it still isn't completely valid 512 * (readable), jump to readrest, else break-out ( we 513 * found the page ). 514 */ 515 vm_page_xbusy(fs.m); 516 if (fs.m->valid != VM_PAGE_BITS_ALL) 517 goto readrest; 518 break; 519 } 520 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m)); 521 522 /* 523 * Page is not resident. If the pager might contain the page 524 * or this is the beginning of the search, allocate a new 525 * page. (Default objects are zero-fill, so there is no real 526 * pager for them.) 527 */ 528 if (fs.object->type != OBJT_DEFAULT || 529 fs.object == fs.first_object) { 530 if (fs.pindex >= fs.object->size) { 531 unlock_and_deallocate(&fs); 532 return (KERN_PROTECTION_FAILURE); 533 } 534 535 /* 536 * Allocate a new page for this object/offset pair. 537 * 538 * Unlocked read of the p_flag is harmless. At 539 * worst, the P_KILLED might be not observed 540 * there, and allocation can fail, causing 541 * restart and new reading of the p_flag. 542 */ 543 if (!vm_page_count_severe() || P_KILLED(curproc)) { 544 #if VM_NRESERVLEVEL > 0 545 vm_object_color(fs.object, atop(vaddr) - 546 fs.pindex); 547 #endif 548 alloc_req = P_KILLED(curproc) ? 549 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 550 if (fs.object->type != OBJT_VNODE && 551 fs.object->backing_object == NULL) 552 alloc_req |= VM_ALLOC_ZERO; 553 fs.m = vm_page_alloc(fs.object, fs.pindex, 554 alloc_req); 555 } 556 if (fs.m == NULL) { 557 unlock_and_deallocate(&fs); 558 VM_WAITPFAULT; 559 goto RetryFault; 560 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 561 break; 562 } 563 564 readrest: 565 /* 566 * If the pager for the current object might have the page, 567 * then determine the number of additional pages to read and 568 * potentially reprioritize previously read pages for earlier 569 * reclamation. These operations should only be performed 570 * once per page fault. Even if the current pager doesn't 571 * have the page, the number of additional pages to read will 572 * apply to subsequent objects in the shadow chain. 573 */ 574 if (fs.object->type != OBJT_DEFAULT && nera == -1 && 575 !P_KILLED(curproc)) { 576 KASSERT(fs.lookup_still_valid, ("map unlocked")); 577 era = fs.entry->read_ahead; 578 behavior = vm_map_entry_behavior(fs.entry); 579 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 580 nera = 0; 581 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 582 nera = VM_FAULT_READ_AHEAD_MAX; 583 if (vaddr == fs.entry->next_read) 584 vm_fault_dontneed(&fs, vaddr, nera); 585 } else if (vaddr == fs.entry->next_read) { 586 /* 587 * This is a sequential fault. Arithmetically 588 * increase the requested number of pages in 589 * the read-ahead window. The requested 590 * number of pages is "# of sequential faults 591 * x (read ahead min + 1) + read ahead min" 592 */ 593 nera = VM_FAULT_READ_AHEAD_MIN; 594 if (era > 0) { 595 nera += era + 1; 596 if (nera > VM_FAULT_READ_AHEAD_MAX) 597 nera = VM_FAULT_READ_AHEAD_MAX; 598 } 599 if (era == VM_FAULT_READ_AHEAD_MAX) 600 vm_fault_dontneed(&fs, vaddr, nera); 601 } else { 602 /* 603 * This is a non-sequential fault. 604 */ 605 nera = 0; 606 } 607 if (era != nera) { 608 /* 609 * A read lock on the map suffices to update 610 * the read ahead count safely. 611 */ 612 fs.entry->read_ahead = nera; 613 } 614 615 /* 616 * Prepare for unlocking the map. Save the map 617 * entry's start and end addresses, which are used to 618 * optimize the size of the pager operation below. 619 * Even if the map entry's addresses change after 620 * unlocking the map, using the saved addresses is 621 * safe. 622 */ 623 e_start = fs.entry->start; 624 e_end = fs.entry->end; 625 } 626 627 /* 628 * Call the pager to retrieve the page if there is a chance 629 * that the pager has it, and potentially retrieve additional 630 * pages at the same time. 631 */ 632 if (fs.object->type != OBJT_DEFAULT) { 633 /* 634 * We have either allocated a new page or found an 635 * existing page that is only partially valid. We 636 * hold a reference on fs.object and the page is 637 * exclusive busied. 638 */ 639 unlock_map(&fs); 640 641 if (fs.object->type == OBJT_VNODE) { 642 vp = fs.object->handle; 643 if (vp == fs.vp) 644 goto vnode_locked; 645 else if (fs.vp != NULL) { 646 vput(fs.vp); 647 fs.vp = NULL; 648 } 649 locked = VOP_ISLOCKED(vp); 650 651 if (locked != LK_EXCLUSIVE) 652 locked = LK_SHARED; 653 /* Do not sleep for vnode lock while fs.m is busy */ 654 error = vget(vp, locked | LK_CANRECURSE | 655 LK_NOWAIT, curthread); 656 if (error != 0) { 657 vhold(vp); 658 release_page(&fs); 659 unlock_and_deallocate(&fs); 660 error = vget(vp, locked | LK_RETRY | 661 LK_CANRECURSE, curthread); 662 vdrop(vp); 663 fs.vp = vp; 664 KASSERT(error == 0, 665 ("vm_fault: vget failed")); 666 goto RetryFault; 667 } 668 fs.vp = vp; 669 } 670 vnode_locked: 671 KASSERT(fs.vp == NULL || !fs.map->system_map, 672 ("vm_fault: vnode-backed object mapped by system map")); 673 674 /* 675 * Page in the requested page and hint the pager, 676 * that it may bring up surrounding pages. 677 */ 678 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM || 679 P_KILLED(curproc)) { 680 behind = 0; 681 ahead = 0; 682 } else { 683 /* Is this a sequential fault? */ 684 if (nera > 0) { 685 behind = 0; 686 ahead = nera; 687 } else { 688 /* 689 * Request a cluster of pages that is 690 * aligned to a VM_FAULT_READ_DEFAULT 691 * page offset boundary within the 692 * object. Alignment to a page offset 693 * boundary is more likely to coincide 694 * with the underlying file system 695 * block than alignment to a virtual 696 * address boundary. 697 */ 698 cluster_offset = fs.pindex % 699 VM_FAULT_READ_DEFAULT; 700 behind = ulmin(cluster_offset, 701 atop(vaddr - e_start)); 702 ahead = VM_FAULT_READ_DEFAULT - 1 - 703 cluster_offset; 704 } 705 ahead = ulmin(ahead, atop(e_end - vaddr) - 1); 706 } 707 rv = vm_pager_get_pages(fs.object, &fs.m, 1, 708 &behind, &ahead); 709 if (rv == VM_PAGER_OK) { 710 faultcount = behind + 1 + ahead; 711 hardfault++; 712 break; /* break to PAGE HAS BEEN FOUND */ 713 } 714 if (rv == VM_PAGER_ERROR) 715 printf("vm_fault: pager read error, pid %d (%s)\n", 716 curproc->p_pid, curproc->p_comm); 717 718 /* 719 * If an I/O error occurred or the requested page was 720 * outside the range of the pager, clean up and return 721 * an error. 722 */ 723 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) { 724 vm_page_lock(fs.m); 725 if (fs.m->wire_count == 0) 726 vm_page_free(fs.m); 727 else 728 vm_page_xunbusy_maybelocked(fs.m); 729 vm_page_unlock(fs.m); 730 fs.m = NULL; 731 unlock_and_deallocate(&fs); 732 return (rv == VM_PAGER_ERROR ? KERN_FAILURE : 733 KERN_PROTECTION_FAILURE); 734 } 735 736 /* 737 * The requested page does not exist at this object/ 738 * offset. Remove the invalid page from the object, 739 * waking up anyone waiting for it, and continue on to 740 * the next object. However, if this is the top-level 741 * object, we must leave the busy page in place to 742 * prevent another process from rushing past us, and 743 * inserting the page in that object at the same time 744 * that we are. 745 */ 746 if (fs.object != fs.first_object) { 747 vm_page_lock(fs.m); 748 if (fs.m->wire_count == 0) 749 vm_page_free(fs.m); 750 else 751 vm_page_xunbusy_maybelocked(fs.m); 752 vm_page_unlock(fs.m); 753 fs.m = NULL; 754 } 755 } 756 757 /* 758 * We get here if the object has default pager (or unwiring) 759 * or the pager doesn't have the page. 760 */ 761 if (fs.object == fs.first_object) 762 fs.first_m = fs.m; 763 764 /* 765 * Move on to the next object. Lock the next object before 766 * unlocking the current one. 767 */ 768 next_object = fs.object->backing_object; 769 if (next_object == NULL) { 770 /* 771 * If there's no object left, fill the page in the top 772 * object with zeros. 773 */ 774 if (fs.object != fs.first_object) { 775 vm_object_pip_wakeup(fs.object); 776 VM_OBJECT_WUNLOCK(fs.object); 777 778 fs.object = fs.first_object; 779 fs.pindex = fs.first_pindex; 780 fs.m = fs.first_m; 781 VM_OBJECT_WLOCK(fs.object); 782 } 783 fs.first_m = NULL; 784 785 /* 786 * Zero the page if necessary and mark it valid. 787 */ 788 if ((fs.m->flags & PG_ZERO) == 0) { 789 pmap_zero_page(fs.m); 790 } else { 791 PCPU_INC(cnt.v_ozfod); 792 } 793 PCPU_INC(cnt.v_zfod); 794 fs.m->valid = VM_PAGE_BITS_ALL; 795 /* Don't try to prefault neighboring pages. */ 796 faultcount = 1; 797 break; /* break to PAGE HAS BEEN FOUND */ 798 } else { 799 KASSERT(fs.object != next_object, 800 ("object loop %p", next_object)); 801 VM_OBJECT_WLOCK(next_object); 802 vm_object_pip_add(next_object, 1); 803 if (fs.object != fs.first_object) 804 vm_object_pip_wakeup(fs.object); 805 fs.pindex += 806 OFF_TO_IDX(fs.object->backing_object_offset); 807 VM_OBJECT_WUNLOCK(fs.object); 808 fs.object = next_object; 809 } 810 } 811 812 vm_page_assert_xbusied(fs.m); 813 814 /* 815 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 816 * is held.] 817 */ 818 819 /* 820 * If the page is being written, but isn't already owned by the 821 * top-level object, we have to copy it into a new page owned by the 822 * top-level object. 823 */ 824 if (fs.object != fs.first_object) { 825 /* 826 * We only really need to copy if we want to write it. 827 */ 828 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 829 /* 830 * This allows pages to be virtually copied from a 831 * backing_object into the first_object, where the 832 * backing object has no other refs to it, and cannot 833 * gain any more refs. Instead of a bcopy, we just 834 * move the page from the backing object to the 835 * first object. Note that we must mark the page 836 * dirty in the first object so that it will go out 837 * to swap when needed. 838 */ 839 is_first_object_locked = FALSE; 840 if ( 841 /* 842 * Only one shadow object 843 */ 844 (fs.object->shadow_count == 1) && 845 /* 846 * No COW refs, except us 847 */ 848 (fs.object->ref_count == 1) && 849 /* 850 * No one else can look this object up 851 */ 852 (fs.object->handle == NULL) && 853 /* 854 * No other ways to look the object up 855 */ 856 ((fs.object->type == OBJT_DEFAULT) || 857 (fs.object->type == OBJT_SWAP)) && 858 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 859 /* 860 * We don't chase down the shadow chain 861 */ 862 fs.object == fs.first_object->backing_object) { 863 vm_page_lock(fs.m); 864 vm_page_remove(fs.m); 865 vm_page_unlock(fs.m); 866 vm_page_lock(fs.first_m); 867 vm_page_replace_checked(fs.m, fs.first_object, 868 fs.first_pindex, fs.first_m); 869 vm_page_free(fs.first_m); 870 vm_page_unlock(fs.first_m); 871 vm_page_dirty(fs.m); 872 #if VM_NRESERVLEVEL > 0 873 /* 874 * Rename the reservation. 875 */ 876 vm_reserv_rename(fs.m, fs.first_object, 877 fs.object, OFF_TO_IDX( 878 fs.first_object->backing_object_offset)); 879 #endif 880 /* 881 * Removing the page from the backing object 882 * unbusied it. 883 */ 884 vm_page_xbusy(fs.m); 885 fs.first_m = fs.m; 886 fs.m = NULL; 887 PCPU_INC(cnt.v_cow_optim); 888 } else { 889 /* 890 * Oh, well, lets copy it. 891 */ 892 pmap_copy_page(fs.m, fs.first_m); 893 fs.first_m->valid = VM_PAGE_BITS_ALL; 894 if (wired && (fault_flags & 895 VM_FAULT_WIRE) == 0) { 896 vm_page_lock(fs.first_m); 897 vm_page_wire(fs.first_m); 898 vm_page_unlock(fs.first_m); 899 900 vm_page_lock(fs.m); 901 vm_page_unwire(fs.m, PQ_INACTIVE); 902 vm_page_unlock(fs.m); 903 } 904 /* 905 * We no longer need the old page or object. 906 */ 907 release_page(&fs); 908 } 909 /* 910 * fs.object != fs.first_object due to above 911 * conditional 912 */ 913 vm_object_pip_wakeup(fs.object); 914 VM_OBJECT_WUNLOCK(fs.object); 915 /* 916 * Only use the new page below... 917 */ 918 fs.object = fs.first_object; 919 fs.pindex = fs.first_pindex; 920 fs.m = fs.first_m; 921 if (!is_first_object_locked) 922 VM_OBJECT_WLOCK(fs.object); 923 PCPU_INC(cnt.v_cow_faults); 924 curthread->td_cow++; 925 } else { 926 prot &= ~VM_PROT_WRITE; 927 } 928 } 929 930 /* 931 * We must verify that the maps have not changed since our last 932 * lookup. 933 */ 934 if (!fs.lookup_still_valid) { 935 vm_object_t retry_object; 936 vm_pindex_t retry_pindex; 937 vm_prot_t retry_prot; 938 939 if (!vm_map_trylock_read(fs.map)) { 940 release_page(&fs); 941 unlock_and_deallocate(&fs); 942 goto RetryFault; 943 } 944 fs.lookup_still_valid = TRUE; 945 if (fs.map->timestamp != map_generation) { 946 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 947 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 948 949 /* 950 * If we don't need the page any longer, put it on the inactive 951 * list (the easiest thing to do here). If no one needs it, 952 * pageout will grab it eventually. 953 */ 954 if (result != KERN_SUCCESS) { 955 release_page(&fs); 956 unlock_and_deallocate(&fs); 957 958 /* 959 * If retry of map lookup would have blocked then 960 * retry fault from start. 961 */ 962 if (result == KERN_FAILURE) 963 goto RetryFault; 964 return (result); 965 } 966 if ((retry_object != fs.first_object) || 967 (retry_pindex != fs.first_pindex)) { 968 release_page(&fs); 969 unlock_and_deallocate(&fs); 970 goto RetryFault; 971 } 972 973 /* 974 * Check whether the protection has changed or the object has 975 * been copied while we left the map unlocked. Changing from 976 * read to write permission is OK - we leave the page 977 * write-protected, and catch the write fault. Changing from 978 * write to read permission means that we can't mark the page 979 * write-enabled after all. 980 */ 981 prot &= retry_prot; 982 } 983 } 984 985 /* 986 * If the page was filled by a pager, save the virtual address that 987 * should be faulted on next under a sequential access pattern to the 988 * map entry. A read lock on the map suffices to update this address 989 * safely. 990 */ 991 if (hardfault) 992 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE; 993 994 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); 995 vm_page_assert_xbusied(fs.m); 996 997 /* 998 * Page must be completely valid or it is not fit to 999 * map into user space. vm_pager_get_pages() ensures this. 1000 */ 1001 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 1002 ("vm_fault: page %p partially invalid", fs.m)); 1003 VM_OBJECT_WUNLOCK(fs.object); 1004 1005 /* 1006 * Put this page into the physical map. We had to do the unlock above 1007 * because pmap_enter() may sleep. We don't put the page 1008 * back on the active queue until later so that the pageout daemon 1009 * won't find it (yet). 1010 */ 1011 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 1012 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 1013 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 1014 wired == 0) 1015 vm_fault_prefault(&fs, vaddr, 1016 faultcount > 0 ? behind : PFBAK, 1017 faultcount > 0 ? ahead : PFFOR); 1018 VM_OBJECT_WLOCK(fs.object); 1019 vm_page_lock(fs.m); 1020 1021 /* 1022 * If the page is not wired down, then put it where the pageout daemon 1023 * can find it. 1024 */ 1025 if ((fault_flags & VM_FAULT_WIRE) != 0) { 1026 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 1027 vm_page_wire(fs.m); 1028 } else 1029 vm_page_activate(fs.m); 1030 if (m_hold != NULL) { 1031 *m_hold = fs.m; 1032 vm_page_hold(fs.m); 1033 } 1034 vm_page_unlock(fs.m); 1035 vm_page_xunbusy(fs.m); 1036 1037 /* 1038 * Unlock everything, and return 1039 */ 1040 unlock_and_deallocate(&fs); 1041 if (hardfault) { 1042 PCPU_INC(cnt.v_io_faults); 1043 curthread->td_ru.ru_majflt++; 1044 #ifdef RACCT 1045 if (racct_enable && fs.object->type == OBJT_VNODE) { 1046 PROC_LOCK(curproc); 1047 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1048 racct_add_force(curproc, RACCT_WRITEBPS, 1049 PAGE_SIZE + behind * PAGE_SIZE); 1050 racct_add_force(curproc, RACCT_WRITEIOPS, 1); 1051 } else { 1052 racct_add_force(curproc, RACCT_READBPS, 1053 PAGE_SIZE + ahead * PAGE_SIZE); 1054 racct_add_force(curproc, RACCT_READIOPS, 1); 1055 } 1056 PROC_UNLOCK(curproc); 1057 } 1058 #endif 1059 } else 1060 curthread->td_ru.ru_minflt++; 1061 1062 return (KERN_SUCCESS); 1063 } 1064 1065 /* 1066 * Speed up the reclamation of pages that precede the faulting pindex within 1067 * the first object of the shadow chain. Essentially, perform the equivalent 1068 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1069 * the faulting pindex by the cluster size when the pages read by vm_fault() 1070 * cross a cluster-size boundary. The cluster size is the greater of the 1071 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1072 * 1073 * When "fs->first_object" is a shadow object, the pages in the backing object 1074 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1075 * function must only be concerned with pages in the first object. 1076 */ 1077 static void 1078 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1079 { 1080 vm_map_entry_t entry; 1081 vm_object_t first_object, object; 1082 vm_offset_t end, start; 1083 vm_page_t m, m_next; 1084 vm_pindex_t pend, pstart; 1085 vm_size_t size; 1086 1087 object = fs->object; 1088 VM_OBJECT_ASSERT_WLOCKED(object); 1089 first_object = fs->first_object; 1090 if (first_object != object) { 1091 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1092 VM_OBJECT_WUNLOCK(object); 1093 VM_OBJECT_WLOCK(first_object); 1094 VM_OBJECT_WLOCK(object); 1095 } 1096 } 1097 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1098 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1099 size = VM_FAULT_DONTNEED_MIN; 1100 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1101 size = pagesizes[1]; 1102 end = rounddown2(vaddr, size); 1103 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1104 (entry = fs->entry)->start < end) { 1105 if (end - entry->start < size) 1106 start = entry->start; 1107 else 1108 start = end - size; 1109 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1110 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1111 entry->start); 1112 m_next = vm_page_find_least(first_object, pstart); 1113 pend = OFF_TO_IDX(entry->offset) + atop(end - 1114 entry->start); 1115 while ((m = m_next) != NULL && m->pindex < pend) { 1116 m_next = TAILQ_NEXT(m, listq); 1117 if (m->valid != VM_PAGE_BITS_ALL || 1118 vm_page_busied(m)) 1119 continue; 1120 1121 /* 1122 * Don't clear PGA_REFERENCED, since it would 1123 * likely represent a reference by a different 1124 * process. 1125 * 1126 * Typically, at this point, prefetched pages 1127 * are still in the inactive queue. Only 1128 * pages that triggered page faults are in the 1129 * active queue. 1130 */ 1131 vm_page_lock(m); 1132 vm_page_deactivate(m); 1133 vm_page_unlock(m); 1134 } 1135 } 1136 } 1137 if (first_object != object) 1138 VM_OBJECT_WUNLOCK(first_object); 1139 } 1140 1141 /* 1142 * vm_fault_prefault provides a quick way of clustering 1143 * pagefaults into a processes address space. It is a "cousin" 1144 * of vm_map_pmap_enter, except it runs at page fault time instead 1145 * of mmap time. 1146 */ 1147 static void 1148 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1149 int backward, int forward) 1150 { 1151 pmap_t pmap; 1152 vm_map_entry_t entry; 1153 vm_object_t backing_object, lobject; 1154 vm_offset_t addr, starta; 1155 vm_pindex_t pindex; 1156 vm_page_t m; 1157 int i; 1158 1159 pmap = fs->map->pmap; 1160 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1161 return; 1162 1163 entry = fs->entry; 1164 1165 starta = addra - backward * PAGE_SIZE; 1166 if (starta < entry->start) { 1167 starta = entry->start; 1168 } else if (starta > addra) { 1169 starta = 0; 1170 } 1171 1172 /* 1173 * Generate the sequence of virtual addresses that are candidates for 1174 * prefaulting in an outward spiral from the faulting virtual address, 1175 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1176 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1177 * If the candidate address doesn't have a backing physical page, then 1178 * the loop immediately terminates. 1179 */ 1180 for (i = 0; i < 2 * imax(backward, forward); i++) { 1181 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1182 PAGE_SIZE); 1183 if (addr > addra + forward * PAGE_SIZE) 1184 addr = 0; 1185 1186 if (addr < starta || addr >= entry->end) 1187 continue; 1188 1189 if (!pmap_is_prefaultable(pmap, addr)) 1190 continue; 1191 1192 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1193 lobject = entry->object.vm_object; 1194 VM_OBJECT_RLOCK(lobject); 1195 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1196 lobject->type == OBJT_DEFAULT && 1197 (backing_object = lobject->backing_object) != NULL) { 1198 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1199 0, ("vm_fault_prefault: unaligned object offset")); 1200 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1201 VM_OBJECT_RLOCK(backing_object); 1202 VM_OBJECT_RUNLOCK(lobject); 1203 lobject = backing_object; 1204 } 1205 if (m == NULL) { 1206 VM_OBJECT_RUNLOCK(lobject); 1207 break; 1208 } 1209 if (m->valid == VM_PAGE_BITS_ALL && 1210 (m->flags & PG_FICTITIOUS) == 0) 1211 pmap_enter_quick(pmap, addr, m, entry->protection); 1212 VM_OBJECT_RUNLOCK(lobject); 1213 } 1214 } 1215 1216 /* 1217 * Hold each of the physical pages that are mapped by the specified range of 1218 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1219 * and allow the specified types of access, "prot". If all of the implied 1220 * pages are successfully held, then the number of held pages is returned 1221 * together with pointers to those pages in the array "ma". However, if any 1222 * of the pages cannot be held, -1 is returned. 1223 */ 1224 int 1225 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1226 vm_prot_t prot, vm_page_t *ma, int max_count) 1227 { 1228 vm_offset_t end, va; 1229 vm_page_t *mp; 1230 int count; 1231 boolean_t pmap_failed; 1232 1233 if (len == 0) 1234 return (0); 1235 end = round_page(addr + len); 1236 addr = trunc_page(addr); 1237 1238 /* 1239 * Check for illegal addresses. 1240 */ 1241 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1242 return (-1); 1243 1244 if (atop(end - addr) > max_count) 1245 panic("vm_fault_quick_hold_pages: count > max_count"); 1246 count = atop(end - addr); 1247 1248 /* 1249 * Most likely, the physical pages are resident in the pmap, so it is 1250 * faster to try pmap_extract_and_hold() first. 1251 */ 1252 pmap_failed = FALSE; 1253 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1254 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1255 if (*mp == NULL) 1256 pmap_failed = TRUE; 1257 else if ((prot & VM_PROT_WRITE) != 0 && 1258 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1259 /* 1260 * Explicitly dirty the physical page. Otherwise, the 1261 * caller's changes may go unnoticed because they are 1262 * performed through an unmanaged mapping or by a DMA 1263 * operation. 1264 * 1265 * The object lock is not held here. 1266 * See vm_page_clear_dirty_mask(). 1267 */ 1268 vm_page_dirty(*mp); 1269 } 1270 } 1271 if (pmap_failed) { 1272 /* 1273 * One or more pages could not be held by the pmap. Either no 1274 * page was mapped at the specified virtual address or that 1275 * mapping had insufficient permissions. Attempt to fault in 1276 * and hold these pages. 1277 */ 1278 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1279 if (*mp == NULL && vm_fault_hold(map, va, prot, 1280 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1281 goto error; 1282 } 1283 return (count); 1284 error: 1285 for (mp = ma; mp < ma + count; mp++) 1286 if (*mp != NULL) { 1287 vm_page_lock(*mp); 1288 vm_page_unhold(*mp); 1289 vm_page_unlock(*mp); 1290 } 1291 return (-1); 1292 } 1293 1294 /* 1295 * Routine: 1296 * vm_fault_copy_entry 1297 * Function: 1298 * Create new shadow object backing dst_entry with private copy of 1299 * all underlying pages. When src_entry is equal to dst_entry, 1300 * function implements COW for wired-down map entry. Otherwise, 1301 * it forks wired entry into dst_map. 1302 * 1303 * In/out conditions: 1304 * The source and destination maps must be locked for write. 1305 * The source map entry must be wired down (or be a sharing map 1306 * entry corresponding to a main map entry that is wired down). 1307 */ 1308 void 1309 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1310 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1311 vm_ooffset_t *fork_charge) 1312 { 1313 vm_object_t backing_object, dst_object, object, src_object; 1314 vm_pindex_t dst_pindex, pindex, src_pindex; 1315 vm_prot_t access, prot; 1316 vm_offset_t vaddr; 1317 vm_page_t dst_m; 1318 vm_page_t src_m; 1319 boolean_t upgrade; 1320 1321 #ifdef lint 1322 src_map++; 1323 #endif /* lint */ 1324 1325 upgrade = src_entry == dst_entry; 1326 access = prot = dst_entry->protection; 1327 1328 src_object = src_entry->object.vm_object; 1329 src_pindex = OFF_TO_IDX(src_entry->offset); 1330 1331 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1332 dst_object = src_object; 1333 vm_object_reference(dst_object); 1334 } else { 1335 /* 1336 * Create the top-level object for the destination entry. (Doesn't 1337 * actually shadow anything - we copy the pages directly.) 1338 */ 1339 dst_object = vm_object_allocate(OBJT_DEFAULT, 1340 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1341 #if VM_NRESERVLEVEL > 0 1342 dst_object->flags |= OBJ_COLORED; 1343 dst_object->pg_color = atop(dst_entry->start); 1344 #endif 1345 } 1346 1347 VM_OBJECT_WLOCK(dst_object); 1348 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1349 ("vm_fault_copy_entry: vm_object not NULL")); 1350 if (src_object != dst_object) { 1351 dst_entry->object.vm_object = dst_object; 1352 dst_entry->offset = 0; 1353 dst_object->charge = dst_entry->end - dst_entry->start; 1354 } 1355 if (fork_charge != NULL) { 1356 KASSERT(dst_entry->cred == NULL, 1357 ("vm_fault_copy_entry: leaked swp charge")); 1358 dst_object->cred = curthread->td_ucred; 1359 crhold(dst_object->cred); 1360 *fork_charge += dst_object->charge; 1361 } else if (dst_object->cred == NULL) { 1362 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1363 dst_entry)); 1364 dst_object->cred = dst_entry->cred; 1365 dst_entry->cred = NULL; 1366 } 1367 1368 /* 1369 * If not an upgrade, then enter the mappings in the pmap as 1370 * read and/or execute accesses. Otherwise, enter them as 1371 * write accesses. 1372 * 1373 * A writeable large page mapping is only created if all of 1374 * the constituent small page mappings are modified. Marking 1375 * PTEs as modified on inception allows promotion to happen 1376 * without taking potentially large number of soft faults. 1377 */ 1378 if (!upgrade) 1379 access &= ~VM_PROT_WRITE; 1380 1381 /* 1382 * Loop through all of the virtual pages within the entry's 1383 * range, copying each page from the source object to the 1384 * destination object. Since the source is wired, those pages 1385 * must exist. In contrast, the destination is pageable. 1386 * Since the destination object does share any backing storage 1387 * with the source object, all of its pages must be dirtied, 1388 * regardless of whether they can be written. 1389 */ 1390 for (vaddr = dst_entry->start, dst_pindex = 0; 1391 vaddr < dst_entry->end; 1392 vaddr += PAGE_SIZE, dst_pindex++) { 1393 again: 1394 /* 1395 * Find the page in the source object, and copy it in. 1396 * Because the source is wired down, the page will be 1397 * in memory. 1398 */ 1399 if (src_object != dst_object) 1400 VM_OBJECT_RLOCK(src_object); 1401 object = src_object; 1402 pindex = src_pindex + dst_pindex; 1403 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1404 (backing_object = object->backing_object) != NULL) { 1405 /* 1406 * Unless the source mapping is read-only or 1407 * it is presently being upgraded from 1408 * read-only, the first object in the shadow 1409 * chain should provide all of the pages. In 1410 * other words, this loop body should never be 1411 * executed when the source mapping is already 1412 * read/write. 1413 */ 1414 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1415 upgrade, 1416 ("vm_fault_copy_entry: main object missing page")); 1417 1418 VM_OBJECT_RLOCK(backing_object); 1419 pindex += OFF_TO_IDX(object->backing_object_offset); 1420 if (object != dst_object) 1421 VM_OBJECT_RUNLOCK(object); 1422 object = backing_object; 1423 } 1424 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1425 1426 if (object != dst_object) { 1427 /* 1428 * Allocate a page in the destination object. 1429 */ 1430 dst_m = vm_page_alloc(dst_object, (src_object == 1431 dst_object ? src_pindex : 0) + dst_pindex, 1432 VM_ALLOC_NORMAL); 1433 if (dst_m == NULL) { 1434 VM_OBJECT_WUNLOCK(dst_object); 1435 VM_OBJECT_RUNLOCK(object); 1436 VM_WAIT; 1437 VM_OBJECT_WLOCK(dst_object); 1438 goto again; 1439 } 1440 pmap_copy_page(src_m, dst_m); 1441 VM_OBJECT_RUNLOCK(object); 1442 dst_m->valid = VM_PAGE_BITS_ALL; 1443 dst_m->dirty = VM_PAGE_BITS_ALL; 1444 } else { 1445 dst_m = src_m; 1446 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1447 goto again; 1448 vm_page_xbusy(dst_m); 1449 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1450 ("invalid dst page %p", dst_m)); 1451 } 1452 VM_OBJECT_WUNLOCK(dst_object); 1453 1454 /* 1455 * Enter it in the pmap. If a wired, copy-on-write 1456 * mapping is being replaced by a write-enabled 1457 * mapping, then wire that new mapping. 1458 */ 1459 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1460 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1461 1462 /* 1463 * Mark it no longer busy, and put it on the active list. 1464 */ 1465 VM_OBJECT_WLOCK(dst_object); 1466 1467 if (upgrade) { 1468 if (src_m != dst_m) { 1469 vm_page_lock(src_m); 1470 vm_page_unwire(src_m, PQ_INACTIVE); 1471 vm_page_unlock(src_m); 1472 vm_page_lock(dst_m); 1473 vm_page_wire(dst_m); 1474 vm_page_unlock(dst_m); 1475 } else { 1476 KASSERT(dst_m->wire_count > 0, 1477 ("dst_m %p is not wired", dst_m)); 1478 } 1479 } else { 1480 vm_page_lock(dst_m); 1481 vm_page_activate(dst_m); 1482 vm_page_unlock(dst_m); 1483 } 1484 vm_page_xunbusy(dst_m); 1485 } 1486 VM_OBJECT_WUNLOCK(dst_object); 1487 if (upgrade) { 1488 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1489 vm_object_deallocate(src_object); 1490 } 1491 } 1492 1493 /* 1494 * Block entry into the machine-independent layer's page fault handler by 1495 * the calling thread. Subsequent calls to vm_fault() by that thread will 1496 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1497 * spurious page faults. 1498 */ 1499 int 1500 vm_fault_disable_pagefaults(void) 1501 { 1502 1503 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1504 } 1505 1506 void 1507 vm_fault_enable_pagefaults(int save) 1508 { 1509 1510 curthread_pflags_restore(save); 1511 } 1512