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 map_generation; 126 bool lookup_still_valid; 127 struct vnode *vp; 128 }; 129 130 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, 131 int ahead); 132 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 133 int backward, int forward); 134 135 static inline void 136 release_page(struct faultstate *fs) 137 { 138 139 vm_page_xunbusy(fs->m); 140 vm_page_lock(fs->m); 141 vm_page_deactivate(fs->m); 142 vm_page_unlock(fs->m); 143 fs->m = NULL; 144 } 145 146 static inline void 147 unlock_map(struct faultstate *fs) 148 { 149 150 if (fs->lookup_still_valid) { 151 vm_map_lookup_done(fs->map, fs->entry); 152 fs->lookup_still_valid = false; 153 } 154 } 155 156 static void 157 unlock_vp(struct faultstate *fs) 158 { 159 160 if (fs->vp != NULL) { 161 vput(fs->vp); 162 fs->vp = NULL; 163 } 164 } 165 166 static void 167 unlock_and_deallocate(struct faultstate *fs) 168 { 169 170 vm_object_pip_wakeup(fs->object); 171 VM_OBJECT_WUNLOCK(fs->object); 172 if (fs->object != fs->first_object) { 173 VM_OBJECT_WLOCK(fs->first_object); 174 vm_page_lock(fs->first_m); 175 vm_page_free(fs->first_m); 176 vm_page_unlock(fs->first_m); 177 vm_object_pip_wakeup(fs->first_object); 178 VM_OBJECT_WUNLOCK(fs->first_object); 179 fs->first_m = NULL; 180 } 181 vm_object_deallocate(fs->first_object); 182 unlock_map(fs); 183 unlock_vp(fs); 184 } 185 186 static void 187 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot, 188 vm_prot_t fault_type, int fault_flags, bool set_wd) 189 { 190 bool need_dirty; 191 192 if (((prot & VM_PROT_WRITE) == 0 && 193 (fault_flags & VM_FAULT_DIRTY) == 0) || 194 (m->oflags & VPO_UNMANAGED) != 0) 195 return; 196 197 VM_OBJECT_ASSERT_LOCKED(m->object); 198 199 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 && 200 (fault_flags & VM_FAULT_WIRE) == 0) || 201 (fault_flags & VM_FAULT_DIRTY) != 0; 202 203 if (set_wd) 204 vm_object_set_writeable_dirty(m->object); 205 else 206 /* 207 * If two callers of vm_fault_dirty() with set_wd == 208 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC 209 * flag set, other with flag clear, race, it is 210 * possible for the no-NOSYNC thread to see m->dirty 211 * != 0 and not clear VPO_NOSYNC. Take vm_page lock 212 * around manipulation of VPO_NOSYNC and 213 * vm_page_dirty() call, to avoid the race and keep 214 * m->oflags consistent. 215 */ 216 vm_page_lock(m); 217 218 /* 219 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 220 * if the page is already dirty to prevent data written with 221 * the expectation of being synced from not being synced. 222 * Likewise if this entry does not request NOSYNC then make 223 * sure the page isn't marked NOSYNC. Applications sharing 224 * data should use the same flags to avoid ping ponging. 225 */ 226 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) { 227 if (m->dirty == 0) { 228 m->oflags |= VPO_NOSYNC; 229 } 230 } else { 231 m->oflags &= ~VPO_NOSYNC; 232 } 233 234 /* 235 * If the fault is a write, we know that this page is being 236 * written NOW so dirty it explicitly to save on 237 * pmap_is_modified() calls later. 238 * 239 * Also tell the backing pager, if any, that it should remove 240 * any swap backing since the page is now dirty. 241 */ 242 if (need_dirty) 243 vm_page_dirty(m); 244 if (!set_wd) 245 vm_page_unlock(m); 246 if (need_dirty) 247 vm_pager_page_unswapped(m); 248 } 249 250 static void 251 vm_fault_fill_hold(vm_page_t *m_hold, vm_page_t m) 252 { 253 254 if (m_hold != NULL) { 255 *m_hold = m; 256 vm_page_lock(m); 257 vm_page_hold(m); 258 vm_page_unlock(m); 259 } 260 } 261 262 /* 263 * Unlocks fs.first_object and fs.map on success. 264 */ 265 static int 266 vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot, 267 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold) 268 { 269 vm_page_t m; 270 int rv; 271 272 MPASS(fs->vp == NULL); 273 m = vm_page_lookup(fs->first_object, fs->first_pindex); 274 /* A busy page can be mapped for read|execute access. */ 275 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 276 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 277 return (KERN_FAILURE); 278 rv = pmap_enter(fs->map->pmap, vaddr, m, prot, fault_type | 279 PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), 0); 280 if (rv != KERN_SUCCESS) 281 return (rv); 282 vm_fault_fill_hold(m_hold, m); 283 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false); 284 VM_OBJECT_RUNLOCK(fs->first_object); 285 if (!wired) 286 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR); 287 vm_map_lookup_done(fs->map, fs->entry); 288 curthread->td_ru.ru_minflt++; 289 return (KERN_SUCCESS); 290 } 291 292 static void 293 vm_fault_restore_map_lock(struct faultstate *fs) 294 { 295 296 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 297 MPASS(fs->first_object->paging_in_progress > 0); 298 299 if (!vm_map_trylock_read(fs->map)) { 300 VM_OBJECT_WUNLOCK(fs->first_object); 301 vm_map_lock_read(fs->map); 302 VM_OBJECT_WLOCK(fs->first_object); 303 } 304 fs->lookup_still_valid = true; 305 } 306 307 308 static int 309 vm_fault_populate(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot, 310 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold) 311 { 312 vm_page_t m; 313 vm_pindex_t f_first, f_last, pidx; 314 int rv; 315 316 MPASS(fs->object == fs->first_object); 317 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 318 MPASS(fs->first_object->paging_in_progress > 0); 319 MPASS(fs->first_object->backing_object == NULL); 320 MPASS(fs->lookup_still_valid); 321 322 f_first = OFF_TO_IDX(fs->entry->offset); 323 f_last = OFF_TO_IDX(fs->entry->offset + fs->entry->end - 324 fs->entry->start) - 1; 325 unlock_map(fs); 326 unlock_vp(fs); 327 328 /* 329 * Call the pager (driver) populate() method. 330 * 331 * There is no guarantee that the method will be called again 332 * if the current fault is for read, and a future fault is 333 * for write. Report the entry's maximum allowed protection 334 * to the driver. 335 */ 336 rv = vm_pager_populate(fs->first_object, fs->first_pindex, 337 fault_type, fs->entry->max_protection, &f_first, &f_last); 338 339 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 340 if (rv == VM_PAGER_BAD) { 341 /* 342 * VM_PAGER_BAD is the backdoor for a pager to request 343 * normal fault handling. 344 */ 345 vm_fault_restore_map_lock(fs); 346 if (fs->map->timestamp != fs->map_generation) 347 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */ 348 return (KERN_NOT_RECEIVER); 349 } 350 if (rv != VM_PAGER_OK) 351 return (KERN_FAILURE); /* AKA SIGSEGV */ 352 353 /* Ensure that the driver is obeying the interface. */ 354 MPASS(f_first <= f_last); 355 MPASS(fs->first_pindex <= f_last); 356 MPASS(fs->first_pindex >= f_first); 357 MPASS(f_last < fs->first_object->size); 358 359 vm_fault_restore_map_lock(fs); 360 if (fs->map->timestamp != fs->map_generation) 361 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */ 362 363 /* Clip pager response to fit into the vm_map_entry. */ 364 f_first = MAX(OFF_TO_IDX(fs->entry->offset), f_first); 365 f_last = MIN(OFF_TO_IDX(fs->entry->end - fs->entry->start + 366 fs->entry->offset), f_last); 367 368 pidx = f_first; 369 for (m = vm_page_lookup(fs->first_object, pidx); pidx <= f_last; 370 pidx++, m = vm_page_next(m)) { 371 /* 372 * Check each page to ensure that the driver is 373 * obeying the interface: the page must be installed 374 * in the object, fully valid, and exclusively busied. 375 */ 376 MPASS(m != NULL); 377 MPASS(vm_page_xbusied(m)); 378 MPASS(m->valid == VM_PAGE_BITS_ALL); 379 MPASS(m->object == fs->first_object); 380 MPASS(m->pindex == pidx); 381 382 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, 383 true); 384 VM_OBJECT_WUNLOCK(fs->first_object); 385 pmap_enter(fs->map->pmap, fs->entry->start + IDX_TO_OFF(pidx) - 386 fs->entry->offset, m, prot, fault_type | (wired ? 387 PMAP_ENTER_WIRED : 0), 0); 388 VM_OBJECT_WLOCK(fs->first_object); 389 if (pidx == fs->first_pindex) 390 vm_fault_fill_hold(m_hold, m); 391 vm_page_lock(m); 392 if ((fault_flags & VM_FAULT_WIRE) != 0) { 393 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 394 vm_page_wire(m); 395 } else { 396 vm_page_activate(m); 397 } 398 vm_page_unlock(m); 399 vm_page_xunbusy(m); 400 } 401 curthread->td_ru.ru_majflt++; 402 return (KERN_SUCCESS); 403 } 404 405 /* 406 * vm_fault: 407 * 408 * Handle a page fault occurring at the given address, 409 * requiring the given permissions, in the map specified. 410 * If successful, the page is inserted into the 411 * associated physical map. 412 * 413 * NOTE: the given address should be truncated to the 414 * proper page address. 415 * 416 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 417 * a standard error specifying why the fault is fatal is returned. 418 * 419 * The map in question must be referenced, and remains so. 420 * Caller may hold no locks. 421 */ 422 int 423 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 424 int fault_flags) 425 { 426 struct thread *td; 427 int result; 428 429 td = curthread; 430 if ((td->td_pflags & TDP_NOFAULTING) != 0) 431 return (KERN_PROTECTION_FAILURE); 432 #ifdef KTRACE 433 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 434 ktrfault(vaddr, fault_type); 435 #endif 436 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 437 NULL); 438 #ifdef KTRACE 439 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 440 ktrfaultend(result); 441 #endif 442 return (result); 443 } 444 445 int 446 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 447 int fault_flags, vm_page_t *m_hold) 448 { 449 struct faultstate fs; 450 struct vnode *vp; 451 vm_object_t next_object, retry_object; 452 vm_offset_t e_end, e_start; 453 vm_pindex_t retry_pindex; 454 vm_prot_t prot, retry_prot; 455 int ahead, alloc_req, behind, cluster_offset, error, era, faultcount; 456 int locked, nera, result, rv; 457 u_char behavior; 458 boolean_t wired; /* Passed by reference. */ 459 bool dead, growstack, hardfault, is_first_object_locked; 460 461 PCPU_INC(cnt.v_vm_faults); 462 fs.vp = NULL; 463 faultcount = 0; 464 nera = -1; 465 growstack = true; 466 hardfault = false; 467 468 RetryFault:; 469 470 /* 471 * Find the backing store object and offset into it to begin the 472 * search. 473 */ 474 fs.map = map; 475 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 476 &fs.first_object, &fs.first_pindex, &prot, &wired); 477 if (result != KERN_SUCCESS) { 478 if (growstack && result == KERN_INVALID_ADDRESS && 479 map != kernel_map) { 480 result = vm_map_growstack(curproc, vaddr); 481 if (result != KERN_SUCCESS) 482 return (KERN_FAILURE); 483 growstack = false; 484 goto RetryFault; 485 } 486 unlock_vp(&fs); 487 return (result); 488 } 489 490 fs.map_generation = fs.map->timestamp; 491 492 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 493 panic("vm_fault: fault on nofault entry, addr: %lx", 494 (u_long)vaddr); 495 } 496 497 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 498 fs.entry->wiring_thread != curthread) { 499 vm_map_unlock_read(fs.map); 500 vm_map_lock(fs.map); 501 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 502 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 503 unlock_vp(&fs); 504 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 505 vm_map_unlock_and_wait(fs.map, 0); 506 } else 507 vm_map_unlock(fs.map); 508 goto RetryFault; 509 } 510 511 if (wired) 512 fault_type = prot | (fault_type & VM_PROT_COPY); 513 else 514 KASSERT((fault_flags & VM_FAULT_WIRE) == 0, 515 ("!wired && VM_FAULT_WIRE")); 516 517 /* 518 * Try to avoid lock contention on the top-level object through 519 * special-case handling of some types of page faults, specifically, 520 * those that are both (1) mapping an existing page from the top- 521 * level object and (2) not having to mark that object as containing 522 * dirty pages. Under these conditions, a read lock on the top-level 523 * object suffices, allowing multiple page faults of a similar type to 524 * run in parallel on the same top-level object. 525 */ 526 if (fs.vp == NULL /* avoid locked vnode leak */ && 527 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 && 528 /* avoid calling vm_object_set_writeable_dirty() */ 529 ((prot & VM_PROT_WRITE) == 0 || 530 (fs.first_object->type != OBJT_VNODE && 531 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 532 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 533 VM_OBJECT_RLOCK(fs.first_object); 534 if ((prot & VM_PROT_WRITE) == 0 || 535 (fs.first_object->type != OBJT_VNODE && 536 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 537 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0) { 538 rv = vm_fault_soft_fast(&fs, vaddr, prot, fault_type, 539 fault_flags, wired, m_hold); 540 if (rv == KERN_SUCCESS) 541 return (rv); 542 } 543 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 544 VM_OBJECT_RUNLOCK(fs.first_object); 545 VM_OBJECT_WLOCK(fs.first_object); 546 } 547 } else { 548 VM_OBJECT_WLOCK(fs.first_object); 549 } 550 551 /* 552 * Make a reference to this object to prevent its disposal while we 553 * are messing with it. Once we have the reference, the map is free 554 * to be diddled. Since objects reference their shadows (and copies), 555 * they will stay around as well. 556 * 557 * Bump the paging-in-progress count to prevent size changes (e.g. 558 * truncation operations) during I/O. 559 */ 560 vm_object_reference_locked(fs.first_object); 561 vm_object_pip_add(fs.first_object, 1); 562 563 fs.lookup_still_valid = true; 564 565 fs.first_m = NULL; 566 567 /* 568 * Search for the page at object/offset. 569 */ 570 fs.object = fs.first_object; 571 fs.pindex = fs.first_pindex; 572 while (TRUE) { 573 /* 574 * If the object is marked for imminent termination, 575 * we retry here, since the collapse pass has raced 576 * with us. Otherwise, if we see terminally dead 577 * object, return fail. 578 */ 579 if ((fs.object->flags & OBJ_DEAD) != 0) { 580 dead = fs.object->type == OBJT_DEAD; 581 unlock_and_deallocate(&fs); 582 if (dead) 583 return (KERN_PROTECTION_FAILURE); 584 pause("vmf_de", 1); 585 goto RetryFault; 586 } 587 588 /* 589 * See if page is resident 590 */ 591 fs.m = vm_page_lookup(fs.object, fs.pindex); 592 if (fs.m != NULL) { 593 /* 594 * Wait/Retry if the page is busy. We have to do this 595 * if the page is either exclusive or shared busy 596 * because the vm_pager may be using read busy for 597 * pageouts (and even pageins if it is the vnode 598 * pager), and we could end up trying to pagein and 599 * pageout the same page simultaneously. 600 * 601 * We can theoretically allow the busy case on a read 602 * fault if the page is marked valid, but since such 603 * pages are typically already pmap'd, putting that 604 * special case in might be more effort then it is 605 * worth. We cannot under any circumstances mess 606 * around with a shared busied page except, perhaps, 607 * to pmap it. 608 */ 609 if (vm_page_busied(fs.m)) { 610 /* 611 * Reference the page before unlocking and 612 * sleeping so that the page daemon is less 613 * likely to reclaim it. 614 */ 615 vm_page_aflag_set(fs.m, PGA_REFERENCED); 616 if (fs.object != fs.first_object) { 617 if (!VM_OBJECT_TRYWLOCK( 618 fs.first_object)) { 619 VM_OBJECT_WUNLOCK(fs.object); 620 VM_OBJECT_WLOCK(fs.first_object); 621 VM_OBJECT_WLOCK(fs.object); 622 } 623 vm_page_lock(fs.first_m); 624 vm_page_free(fs.first_m); 625 vm_page_unlock(fs.first_m); 626 vm_object_pip_wakeup(fs.first_object); 627 VM_OBJECT_WUNLOCK(fs.first_object); 628 fs.first_m = NULL; 629 } 630 unlock_map(&fs); 631 if (fs.m == vm_page_lookup(fs.object, 632 fs.pindex)) { 633 vm_page_sleep_if_busy(fs.m, "vmpfw"); 634 } 635 vm_object_pip_wakeup(fs.object); 636 VM_OBJECT_WUNLOCK(fs.object); 637 PCPU_INC(cnt.v_intrans); 638 vm_object_deallocate(fs.first_object); 639 goto RetryFault; 640 } 641 vm_page_lock(fs.m); 642 vm_page_remque(fs.m); 643 vm_page_unlock(fs.m); 644 645 /* 646 * Mark page busy for other processes, and the 647 * pagedaemon. If it still isn't completely valid 648 * (readable), jump to readrest, else break-out ( we 649 * found the page ). 650 */ 651 vm_page_xbusy(fs.m); 652 if (fs.m->valid != VM_PAGE_BITS_ALL) 653 goto readrest; 654 break; 655 } 656 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m)); 657 658 /* 659 * Page is not resident. If the pager might contain the page 660 * or this is the beginning of the search, allocate a new 661 * page. (Default objects are zero-fill, so there is no real 662 * pager for them.) 663 */ 664 if (fs.object->type != OBJT_DEFAULT || 665 fs.object == fs.first_object) { 666 if (fs.pindex >= fs.object->size) { 667 unlock_and_deallocate(&fs); 668 return (KERN_PROTECTION_FAILURE); 669 } 670 671 if (fs.object == fs.first_object && 672 (fs.first_object->flags & OBJ_POPULATE) != 0 && 673 fs.first_object->shadow_count == 0) { 674 rv = vm_fault_populate(&fs, vaddr, prot, 675 fault_type, fault_flags, wired, m_hold); 676 switch (rv) { 677 case KERN_SUCCESS: 678 case KERN_FAILURE: 679 unlock_and_deallocate(&fs); 680 return (rv); 681 case KERN_RESOURCE_SHORTAGE: 682 unlock_and_deallocate(&fs); 683 goto RetryFault; 684 case KERN_NOT_RECEIVER: 685 /* 686 * Pager's populate() method 687 * returned VM_PAGER_BAD. 688 */ 689 break; 690 default: 691 panic("inconsistent return codes"); 692 } 693 } 694 695 /* 696 * Allocate a new page for this object/offset pair. 697 * 698 * Unlocked read of the p_flag is harmless. At 699 * worst, the P_KILLED might be not observed 700 * there, and allocation can fail, causing 701 * restart and new reading of the p_flag. 702 */ 703 if (!vm_page_count_severe() || P_KILLED(curproc)) { 704 #if VM_NRESERVLEVEL > 0 705 vm_object_color(fs.object, atop(vaddr) - 706 fs.pindex); 707 #endif 708 alloc_req = P_KILLED(curproc) ? 709 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 710 if (fs.object->type != OBJT_VNODE && 711 fs.object->backing_object == NULL) 712 alloc_req |= VM_ALLOC_ZERO; 713 fs.m = vm_page_alloc(fs.object, fs.pindex, 714 alloc_req); 715 } 716 if (fs.m == NULL) { 717 unlock_and_deallocate(&fs); 718 VM_WAITPFAULT; 719 goto RetryFault; 720 } 721 } 722 723 readrest: 724 /* 725 * At this point, we have either allocated a new page or found 726 * an existing page that is only partially valid. 727 * 728 * We hold a reference on the current object and the page is 729 * exclusive busied. 730 */ 731 732 /* 733 * If the pager for the current object might have the page, 734 * then determine the number of additional pages to read and 735 * potentially reprioritize previously read pages for earlier 736 * reclamation. These operations should only be performed 737 * once per page fault. Even if the current pager doesn't 738 * have the page, the number of additional pages to read will 739 * apply to subsequent objects in the shadow chain. 740 */ 741 if (fs.object->type != OBJT_DEFAULT && nera == -1 && 742 !P_KILLED(curproc)) { 743 KASSERT(fs.lookup_still_valid, ("map unlocked")); 744 era = fs.entry->read_ahead; 745 behavior = vm_map_entry_behavior(fs.entry); 746 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 747 nera = 0; 748 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 749 nera = VM_FAULT_READ_AHEAD_MAX; 750 if (vaddr == fs.entry->next_read) 751 vm_fault_dontneed(&fs, vaddr, nera); 752 } else if (vaddr == fs.entry->next_read) { 753 /* 754 * This is a sequential fault. Arithmetically 755 * increase the requested number of pages in 756 * the read-ahead window. The requested 757 * number of pages is "# of sequential faults 758 * x (read ahead min + 1) + read ahead min" 759 */ 760 nera = VM_FAULT_READ_AHEAD_MIN; 761 if (era > 0) { 762 nera += era + 1; 763 if (nera > VM_FAULT_READ_AHEAD_MAX) 764 nera = VM_FAULT_READ_AHEAD_MAX; 765 } 766 if (era == VM_FAULT_READ_AHEAD_MAX) 767 vm_fault_dontneed(&fs, vaddr, nera); 768 } else { 769 /* 770 * This is a non-sequential fault. 771 */ 772 nera = 0; 773 } 774 if (era != nera) { 775 /* 776 * A read lock on the map suffices to update 777 * the read ahead count safely. 778 */ 779 fs.entry->read_ahead = nera; 780 } 781 782 /* 783 * Prepare for unlocking the map. Save the map 784 * entry's start and end addresses, which are used to 785 * optimize the size of the pager operation below. 786 * Even if the map entry's addresses change after 787 * unlocking the map, using the saved addresses is 788 * safe. 789 */ 790 e_start = fs.entry->start; 791 e_end = fs.entry->end; 792 } 793 794 /* 795 * Call the pager to retrieve the page if there is a chance 796 * that the pager has it, and potentially retrieve additional 797 * pages at the same time. 798 */ 799 if (fs.object->type != OBJT_DEFAULT) { 800 /* 801 * Release the map lock before locking the vnode or 802 * sleeping in the pager. (If the current object has 803 * a shadow, then an earlier iteration of this loop 804 * may have already unlocked the map.) 805 */ 806 unlock_map(&fs); 807 808 if (fs.object->type == OBJT_VNODE && 809 (vp = fs.object->handle) != fs.vp) { 810 /* 811 * Perform an unlock in case the desired vnode 812 * changed while the map was unlocked during a 813 * retry. 814 */ 815 unlock_vp(&fs); 816 817 locked = VOP_ISLOCKED(vp); 818 if (locked != LK_EXCLUSIVE) 819 locked = LK_SHARED; 820 821 /* 822 * We must not sleep acquiring the vnode lock 823 * while we have the page exclusive busied or 824 * the object's paging-in-progress count 825 * incremented. Otherwise, we could deadlock. 826 */ 827 error = vget(vp, locked | LK_CANRECURSE | 828 LK_NOWAIT, curthread); 829 if (error != 0) { 830 vhold(vp); 831 release_page(&fs); 832 unlock_and_deallocate(&fs); 833 error = vget(vp, locked | LK_RETRY | 834 LK_CANRECURSE, curthread); 835 vdrop(vp); 836 fs.vp = vp; 837 KASSERT(error == 0, 838 ("vm_fault: vget failed")); 839 goto RetryFault; 840 } 841 fs.vp = vp; 842 } 843 KASSERT(fs.vp == NULL || !fs.map->system_map, 844 ("vm_fault: vnode-backed object mapped by system map")); 845 846 /* 847 * Page in the requested page and hint the pager, 848 * that it may bring up surrounding pages. 849 */ 850 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM || 851 P_KILLED(curproc)) { 852 behind = 0; 853 ahead = 0; 854 } else { 855 /* Is this a sequential fault? */ 856 if (nera > 0) { 857 behind = 0; 858 ahead = nera; 859 } else { 860 /* 861 * Request a cluster of pages that is 862 * aligned to a VM_FAULT_READ_DEFAULT 863 * page offset boundary within the 864 * object. Alignment to a page offset 865 * boundary is more likely to coincide 866 * with the underlying file system 867 * block than alignment to a virtual 868 * address boundary. 869 */ 870 cluster_offset = fs.pindex % 871 VM_FAULT_READ_DEFAULT; 872 behind = ulmin(cluster_offset, 873 atop(vaddr - e_start)); 874 ahead = VM_FAULT_READ_DEFAULT - 1 - 875 cluster_offset; 876 } 877 ahead = ulmin(ahead, atop(e_end - vaddr) - 1); 878 } 879 rv = vm_pager_get_pages(fs.object, &fs.m, 1, 880 &behind, &ahead); 881 if (rv == VM_PAGER_OK) { 882 faultcount = behind + 1 + ahead; 883 hardfault = true; 884 break; /* break to PAGE HAS BEEN FOUND */ 885 } 886 if (rv == VM_PAGER_ERROR) 887 printf("vm_fault: pager read error, pid %d (%s)\n", 888 curproc->p_pid, curproc->p_comm); 889 890 /* 891 * If an I/O error occurred or the requested page was 892 * outside the range of the pager, clean up and return 893 * an error. 894 */ 895 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) { 896 vm_page_lock(fs.m); 897 if (fs.m->wire_count == 0) 898 vm_page_free(fs.m); 899 else 900 vm_page_xunbusy_maybelocked(fs.m); 901 vm_page_unlock(fs.m); 902 fs.m = NULL; 903 unlock_and_deallocate(&fs); 904 return (rv == VM_PAGER_ERROR ? KERN_FAILURE : 905 KERN_PROTECTION_FAILURE); 906 } 907 908 /* 909 * The requested page does not exist at this object/ 910 * offset. Remove the invalid page from the object, 911 * waking up anyone waiting for it, and continue on to 912 * the next object. However, if this is the top-level 913 * object, we must leave the busy page in place to 914 * prevent another process from rushing past us, and 915 * inserting the page in that object at the same time 916 * that we are. 917 */ 918 if (fs.object != fs.first_object) { 919 vm_page_lock(fs.m); 920 if (fs.m->wire_count == 0) 921 vm_page_free(fs.m); 922 else 923 vm_page_xunbusy_maybelocked(fs.m); 924 vm_page_unlock(fs.m); 925 fs.m = NULL; 926 } 927 } 928 929 /* 930 * We get here if the object has default pager (or unwiring) 931 * or the pager doesn't have the page. 932 */ 933 if (fs.object == fs.first_object) 934 fs.first_m = fs.m; 935 936 /* 937 * Move on to the next object. Lock the next object before 938 * unlocking the current one. 939 */ 940 next_object = fs.object->backing_object; 941 if (next_object == NULL) { 942 /* 943 * If there's no object left, fill the page in the top 944 * object with zeros. 945 */ 946 if (fs.object != fs.first_object) { 947 vm_object_pip_wakeup(fs.object); 948 VM_OBJECT_WUNLOCK(fs.object); 949 950 fs.object = fs.first_object; 951 fs.pindex = fs.first_pindex; 952 fs.m = fs.first_m; 953 VM_OBJECT_WLOCK(fs.object); 954 } 955 fs.first_m = NULL; 956 957 /* 958 * Zero the page if necessary and mark it valid. 959 */ 960 if ((fs.m->flags & PG_ZERO) == 0) { 961 pmap_zero_page(fs.m); 962 } else { 963 PCPU_INC(cnt.v_ozfod); 964 } 965 PCPU_INC(cnt.v_zfod); 966 fs.m->valid = VM_PAGE_BITS_ALL; 967 /* Don't try to prefault neighboring pages. */ 968 faultcount = 1; 969 break; /* break to PAGE HAS BEEN FOUND */ 970 } else { 971 KASSERT(fs.object != next_object, 972 ("object loop %p", next_object)); 973 VM_OBJECT_WLOCK(next_object); 974 vm_object_pip_add(next_object, 1); 975 if (fs.object != fs.first_object) 976 vm_object_pip_wakeup(fs.object); 977 fs.pindex += 978 OFF_TO_IDX(fs.object->backing_object_offset); 979 VM_OBJECT_WUNLOCK(fs.object); 980 fs.object = next_object; 981 } 982 } 983 984 vm_page_assert_xbusied(fs.m); 985 986 /* 987 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 988 * is held.] 989 */ 990 991 /* 992 * If the page is being written, but isn't already owned by the 993 * top-level object, we have to copy it into a new page owned by the 994 * top-level object. 995 */ 996 if (fs.object != fs.first_object) { 997 /* 998 * We only really need to copy if we want to write it. 999 */ 1000 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1001 /* 1002 * This allows pages to be virtually copied from a 1003 * backing_object into the first_object, where the 1004 * backing object has no other refs to it, and cannot 1005 * gain any more refs. Instead of a bcopy, we just 1006 * move the page from the backing object to the 1007 * first object. Note that we must mark the page 1008 * dirty in the first object so that it will go out 1009 * to swap when needed. 1010 */ 1011 is_first_object_locked = false; 1012 if ( 1013 /* 1014 * Only one shadow object 1015 */ 1016 (fs.object->shadow_count == 1) && 1017 /* 1018 * No COW refs, except us 1019 */ 1020 (fs.object->ref_count == 1) && 1021 /* 1022 * No one else can look this object up 1023 */ 1024 (fs.object->handle == NULL) && 1025 /* 1026 * No other ways to look the object up 1027 */ 1028 ((fs.object->type == OBJT_DEFAULT) || 1029 (fs.object->type == OBJT_SWAP)) && 1030 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 1031 /* 1032 * We don't chase down the shadow chain 1033 */ 1034 fs.object == fs.first_object->backing_object) { 1035 vm_page_lock(fs.m); 1036 vm_page_remove(fs.m); 1037 vm_page_unlock(fs.m); 1038 vm_page_lock(fs.first_m); 1039 vm_page_replace_checked(fs.m, fs.first_object, 1040 fs.first_pindex, fs.first_m); 1041 vm_page_free(fs.first_m); 1042 vm_page_unlock(fs.first_m); 1043 vm_page_dirty(fs.m); 1044 #if VM_NRESERVLEVEL > 0 1045 /* 1046 * Rename the reservation. 1047 */ 1048 vm_reserv_rename(fs.m, fs.first_object, 1049 fs.object, OFF_TO_IDX( 1050 fs.first_object->backing_object_offset)); 1051 #endif 1052 /* 1053 * Removing the page from the backing object 1054 * unbusied it. 1055 */ 1056 vm_page_xbusy(fs.m); 1057 fs.first_m = fs.m; 1058 fs.m = NULL; 1059 PCPU_INC(cnt.v_cow_optim); 1060 } else { 1061 /* 1062 * Oh, well, lets copy it. 1063 */ 1064 pmap_copy_page(fs.m, fs.first_m); 1065 fs.first_m->valid = VM_PAGE_BITS_ALL; 1066 if (wired && (fault_flags & 1067 VM_FAULT_WIRE) == 0) { 1068 vm_page_lock(fs.first_m); 1069 vm_page_wire(fs.first_m); 1070 vm_page_unlock(fs.first_m); 1071 1072 vm_page_lock(fs.m); 1073 vm_page_unwire(fs.m, PQ_INACTIVE); 1074 vm_page_unlock(fs.m); 1075 } 1076 /* 1077 * We no longer need the old page or object. 1078 */ 1079 release_page(&fs); 1080 } 1081 /* 1082 * fs.object != fs.first_object due to above 1083 * conditional 1084 */ 1085 vm_object_pip_wakeup(fs.object); 1086 VM_OBJECT_WUNLOCK(fs.object); 1087 /* 1088 * Only use the new page below... 1089 */ 1090 fs.object = fs.first_object; 1091 fs.pindex = fs.first_pindex; 1092 fs.m = fs.first_m; 1093 if (!is_first_object_locked) 1094 VM_OBJECT_WLOCK(fs.object); 1095 PCPU_INC(cnt.v_cow_faults); 1096 curthread->td_cow++; 1097 } else { 1098 prot &= ~VM_PROT_WRITE; 1099 } 1100 } 1101 1102 /* 1103 * We must verify that the maps have not changed since our last 1104 * lookup. 1105 */ 1106 if (!fs.lookup_still_valid) { 1107 if (!vm_map_trylock_read(fs.map)) { 1108 release_page(&fs); 1109 unlock_and_deallocate(&fs); 1110 goto RetryFault; 1111 } 1112 fs.lookup_still_valid = true; 1113 if (fs.map->timestamp != fs.map_generation) { 1114 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 1115 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 1116 1117 /* 1118 * If we don't need the page any longer, put it on the inactive 1119 * list (the easiest thing to do here). If no one needs it, 1120 * pageout will grab it eventually. 1121 */ 1122 if (result != KERN_SUCCESS) { 1123 release_page(&fs); 1124 unlock_and_deallocate(&fs); 1125 1126 /* 1127 * If retry of map lookup would have blocked then 1128 * retry fault from start. 1129 */ 1130 if (result == KERN_FAILURE) 1131 goto RetryFault; 1132 return (result); 1133 } 1134 if ((retry_object != fs.first_object) || 1135 (retry_pindex != fs.first_pindex)) { 1136 release_page(&fs); 1137 unlock_and_deallocate(&fs); 1138 goto RetryFault; 1139 } 1140 1141 /* 1142 * Check whether the protection has changed or the object has 1143 * been copied while we left the map unlocked. Changing from 1144 * read to write permission is OK - we leave the page 1145 * write-protected, and catch the write fault. Changing from 1146 * write to read permission means that we can't mark the page 1147 * write-enabled after all. 1148 */ 1149 prot &= retry_prot; 1150 } 1151 } 1152 1153 /* 1154 * If the page was filled by a pager, save the virtual address that 1155 * should be faulted on next under a sequential access pattern to the 1156 * map entry. A read lock on the map suffices to update this address 1157 * safely. 1158 */ 1159 if (hardfault) 1160 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE; 1161 1162 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true); 1163 vm_page_assert_xbusied(fs.m); 1164 1165 /* 1166 * Page must be completely valid or it is not fit to 1167 * map into user space. vm_pager_get_pages() ensures this. 1168 */ 1169 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 1170 ("vm_fault: page %p partially invalid", fs.m)); 1171 VM_OBJECT_WUNLOCK(fs.object); 1172 1173 /* 1174 * Put this page into the physical map. We had to do the unlock above 1175 * because pmap_enter() may sleep. We don't put the page 1176 * back on the active queue until later so that the pageout daemon 1177 * won't find it (yet). 1178 */ 1179 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 1180 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 1181 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 1182 wired == 0) 1183 vm_fault_prefault(&fs, vaddr, 1184 faultcount > 0 ? behind : PFBAK, 1185 faultcount > 0 ? ahead : PFFOR); 1186 VM_OBJECT_WLOCK(fs.object); 1187 vm_page_lock(fs.m); 1188 1189 /* 1190 * If the page is not wired down, then put it where the pageout daemon 1191 * can find it. 1192 */ 1193 if ((fault_flags & VM_FAULT_WIRE) != 0) { 1194 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 1195 vm_page_wire(fs.m); 1196 } else 1197 vm_page_activate(fs.m); 1198 if (m_hold != NULL) { 1199 *m_hold = fs.m; 1200 vm_page_hold(fs.m); 1201 } 1202 vm_page_unlock(fs.m); 1203 vm_page_xunbusy(fs.m); 1204 1205 /* 1206 * Unlock everything, and return 1207 */ 1208 unlock_and_deallocate(&fs); 1209 if (hardfault) { 1210 PCPU_INC(cnt.v_io_faults); 1211 curthread->td_ru.ru_majflt++; 1212 #ifdef RACCT 1213 if (racct_enable && fs.object->type == OBJT_VNODE) { 1214 PROC_LOCK(curproc); 1215 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1216 racct_add_force(curproc, RACCT_WRITEBPS, 1217 PAGE_SIZE + behind * PAGE_SIZE); 1218 racct_add_force(curproc, RACCT_WRITEIOPS, 1); 1219 } else { 1220 racct_add_force(curproc, RACCT_READBPS, 1221 PAGE_SIZE + ahead * PAGE_SIZE); 1222 racct_add_force(curproc, RACCT_READIOPS, 1); 1223 } 1224 PROC_UNLOCK(curproc); 1225 } 1226 #endif 1227 } else 1228 curthread->td_ru.ru_minflt++; 1229 1230 return (KERN_SUCCESS); 1231 } 1232 1233 /* 1234 * Speed up the reclamation of pages that precede the faulting pindex within 1235 * the first object of the shadow chain. Essentially, perform the equivalent 1236 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1237 * the faulting pindex by the cluster size when the pages read by vm_fault() 1238 * cross a cluster-size boundary. The cluster size is the greater of the 1239 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1240 * 1241 * When "fs->first_object" is a shadow object, the pages in the backing object 1242 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1243 * function must only be concerned with pages in the first object. 1244 */ 1245 static void 1246 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1247 { 1248 vm_map_entry_t entry; 1249 vm_object_t first_object, object; 1250 vm_offset_t end, start; 1251 vm_page_t m, m_next; 1252 vm_pindex_t pend, pstart; 1253 vm_size_t size; 1254 1255 object = fs->object; 1256 VM_OBJECT_ASSERT_WLOCKED(object); 1257 first_object = fs->first_object; 1258 if (first_object != object) { 1259 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1260 VM_OBJECT_WUNLOCK(object); 1261 VM_OBJECT_WLOCK(first_object); 1262 VM_OBJECT_WLOCK(object); 1263 } 1264 } 1265 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1266 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1267 size = VM_FAULT_DONTNEED_MIN; 1268 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1269 size = pagesizes[1]; 1270 end = rounddown2(vaddr, size); 1271 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1272 (entry = fs->entry)->start < end) { 1273 if (end - entry->start < size) 1274 start = entry->start; 1275 else 1276 start = end - size; 1277 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1278 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1279 entry->start); 1280 m_next = vm_page_find_least(first_object, pstart); 1281 pend = OFF_TO_IDX(entry->offset) + atop(end - 1282 entry->start); 1283 while ((m = m_next) != NULL && m->pindex < pend) { 1284 m_next = TAILQ_NEXT(m, listq); 1285 if (m->valid != VM_PAGE_BITS_ALL || 1286 vm_page_busied(m)) 1287 continue; 1288 1289 /* 1290 * Don't clear PGA_REFERENCED, since it would 1291 * likely represent a reference by a different 1292 * process. 1293 * 1294 * Typically, at this point, prefetched pages 1295 * are still in the inactive queue. Only 1296 * pages that triggered page faults are in the 1297 * active queue. 1298 */ 1299 vm_page_lock(m); 1300 vm_page_deactivate(m); 1301 vm_page_unlock(m); 1302 } 1303 } 1304 } 1305 if (first_object != object) 1306 VM_OBJECT_WUNLOCK(first_object); 1307 } 1308 1309 /* 1310 * vm_fault_prefault provides a quick way of clustering 1311 * pagefaults into a processes address space. It is a "cousin" 1312 * of vm_map_pmap_enter, except it runs at page fault time instead 1313 * of mmap time. 1314 */ 1315 static void 1316 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1317 int backward, int forward) 1318 { 1319 pmap_t pmap; 1320 vm_map_entry_t entry; 1321 vm_object_t backing_object, lobject; 1322 vm_offset_t addr, starta; 1323 vm_pindex_t pindex; 1324 vm_page_t m; 1325 int i; 1326 1327 pmap = fs->map->pmap; 1328 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1329 return; 1330 1331 entry = fs->entry; 1332 1333 starta = addra - backward * PAGE_SIZE; 1334 if (starta < entry->start) { 1335 starta = entry->start; 1336 } else if (starta > addra) { 1337 starta = 0; 1338 } 1339 1340 /* 1341 * Generate the sequence of virtual addresses that are candidates for 1342 * prefaulting in an outward spiral from the faulting virtual address, 1343 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1344 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1345 * If the candidate address doesn't have a backing physical page, then 1346 * the loop immediately terminates. 1347 */ 1348 for (i = 0; i < 2 * imax(backward, forward); i++) { 1349 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1350 PAGE_SIZE); 1351 if (addr > addra + forward * PAGE_SIZE) 1352 addr = 0; 1353 1354 if (addr < starta || addr >= entry->end) 1355 continue; 1356 1357 if (!pmap_is_prefaultable(pmap, addr)) 1358 continue; 1359 1360 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1361 lobject = entry->object.vm_object; 1362 VM_OBJECT_RLOCK(lobject); 1363 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1364 lobject->type == OBJT_DEFAULT && 1365 (backing_object = lobject->backing_object) != NULL) { 1366 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1367 0, ("vm_fault_prefault: unaligned object offset")); 1368 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1369 VM_OBJECT_RLOCK(backing_object); 1370 VM_OBJECT_RUNLOCK(lobject); 1371 lobject = backing_object; 1372 } 1373 if (m == NULL) { 1374 VM_OBJECT_RUNLOCK(lobject); 1375 break; 1376 } 1377 if (m->valid == VM_PAGE_BITS_ALL && 1378 (m->flags & PG_FICTITIOUS) == 0) 1379 pmap_enter_quick(pmap, addr, m, entry->protection); 1380 VM_OBJECT_RUNLOCK(lobject); 1381 } 1382 } 1383 1384 /* 1385 * Hold each of the physical pages that are mapped by the specified range of 1386 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1387 * and allow the specified types of access, "prot". If all of the implied 1388 * pages are successfully held, then the number of held pages is returned 1389 * together with pointers to those pages in the array "ma". However, if any 1390 * of the pages cannot be held, -1 is returned. 1391 */ 1392 int 1393 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1394 vm_prot_t prot, vm_page_t *ma, int max_count) 1395 { 1396 vm_offset_t end, va; 1397 vm_page_t *mp; 1398 int count; 1399 boolean_t pmap_failed; 1400 1401 if (len == 0) 1402 return (0); 1403 end = round_page(addr + len); 1404 addr = trunc_page(addr); 1405 1406 /* 1407 * Check for illegal addresses. 1408 */ 1409 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1410 return (-1); 1411 1412 if (atop(end - addr) > max_count) 1413 panic("vm_fault_quick_hold_pages: count > max_count"); 1414 count = atop(end - addr); 1415 1416 /* 1417 * Most likely, the physical pages are resident in the pmap, so it is 1418 * faster to try pmap_extract_and_hold() first. 1419 */ 1420 pmap_failed = FALSE; 1421 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1422 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1423 if (*mp == NULL) 1424 pmap_failed = TRUE; 1425 else if ((prot & VM_PROT_WRITE) != 0 && 1426 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1427 /* 1428 * Explicitly dirty the physical page. Otherwise, the 1429 * caller's changes may go unnoticed because they are 1430 * performed through an unmanaged mapping or by a DMA 1431 * operation. 1432 * 1433 * The object lock is not held here. 1434 * See vm_page_clear_dirty_mask(). 1435 */ 1436 vm_page_dirty(*mp); 1437 } 1438 } 1439 if (pmap_failed) { 1440 /* 1441 * One or more pages could not be held by the pmap. Either no 1442 * page was mapped at the specified virtual address or that 1443 * mapping had insufficient permissions. Attempt to fault in 1444 * and hold these pages. 1445 */ 1446 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1447 if (*mp == NULL && vm_fault_hold(map, va, prot, 1448 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1449 goto error; 1450 } 1451 return (count); 1452 error: 1453 for (mp = ma; mp < ma + count; mp++) 1454 if (*mp != NULL) { 1455 vm_page_lock(*mp); 1456 vm_page_unhold(*mp); 1457 vm_page_unlock(*mp); 1458 } 1459 return (-1); 1460 } 1461 1462 /* 1463 * Routine: 1464 * vm_fault_copy_entry 1465 * Function: 1466 * Create new shadow object backing dst_entry with private copy of 1467 * all underlying pages. When src_entry is equal to dst_entry, 1468 * function implements COW for wired-down map entry. Otherwise, 1469 * it forks wired entry into dst_map. 1470 * 1471 * In/out conditions: 1472 * The source and destination maps must be locked for write. 1473 * The source map entry must be wired down (or be a sharing map 1474 * entry corresponding to a main map entry that is wired down). 1475 */ 1476 void 1477 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1478 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1479 vm_ooffset_t *fork_charge) 1480 { 1481 vm_object_t backing_object, dst_object, object, src_object; 1482 vm_pindex_t dst_pindex, pindex, src_pindex; 1483 vm_prot_t access, prot; 1484 vm_offset_t vaddr; 1485 vm_page_t dst_m; 1486 vm_page_t src_m; 1487 boolean_t upgrade; 1488 1489 #ifdef lint 1490 src_map++; 1491 #endif /* lint */ 1492 1493 upgrade = src_entry == dst_entry; 1494 access = prot = dst_entry->protection; 1495 1496 src_object = src_entry->object.vm_object; 1497 src_pindex = OFF_TO_IDX(src_entry->offset); 1498 1499 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1500 dst_object = src_object; 1501 vm_object_reference(dst_object); 1502 } else { 1503 /* 1504 * Create the top-level object for the destination entry. (Doesn't 1505 * actually shadow anything - we copy the pages directly.) 1506 */ 1507 dst_object = vm_object_allocate(OBJT_DEFAULT, 1508 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1509 #if VM_NRESERVLEVEL > 0 1510 dst_object->flags |= OBJ_COLORED; 1511 dst_object->pg_color = atop(dst_entry->start); 1512 #endif 1513 } 1514 1515 VM_OBJECT_WLOCK(dst_object); 1516 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1517 ("vm_fault_copy_entry: vm_object not NULL")); 1518 if (src_object != dst_object) { 1519 dst_entry->object.vm_object = dst_object; 1520 dst_entry->offset = 0; 1521 dst_object->charge = dst_entry->end - dst_entry->start; 1522 } 1523 if (fork_charge != NULL) { 1524 KASSERT(dst_entry->cred == NULL, 1525 ("vm_fault_copy_entry: leaked swp charge")); 1526 dst_object->cred = curthread->td_ucred; 1527 crhold(dst_object->cred); 1528 *fork_charge += dst_object->charge; 1529 } else if (dst_object->cred == NULL) { 1530 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1531 dst_entry)); 1532 dst_object->cred = dst_entry->cred; 1533 dst_entry->cred = NULL; 1534 } 1535 1536 /* 1537 * If not an upgrade, then enter the mappings in the pmap as 1538 * read and/or execute accesses. Otherwise, enter them as 1539 * write accesses. 1540 * 1541 * A writeable large page mapping is only created if all of 1542 * the constituent small page mappings are modified. Marking 1543 * PTEs as modified on inception allows promotion to happen 1544 * without taking potentially large number of soft faults. 1545 */ 1546 if (!upgrade) 1547 access &= ~VM_PROT_WRITE; 1548 1549 /* 1550 * Loop through all of the virtual pages within the entry's 1551 * range, copying each page from the source object to the 1552 * destination object. Since the source is wired, those pages 1553 * must exist. In contrast, the destination is pageable. 1554 * Since the destination object does share any backing storage 1555 * with the source object, all of its pages must be dirtied, 1556 * regardless of whether they can be written. 1557 */ 1558 for (vaddr = dst_entry->start, dst_pindex = 0; 1559 vaddr < dst_entry->end; 1560 vaddr += PAGE_SIZE, dst_pindex++) { 1561 again: 1562 /* 1563 * Find the page in the source object, and copy it in. 1564 * Because the source is wired down, the page will be 1565 * in memory. 1566 */ 1567 if (src_object != dst_object) 1568 VM_OBJECT_RLOCK(src_object); 1569 object = src_object; 1570 pindex = src_pindex + dst_pindex; 1571 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1572 (backing_object = object->backing_object) != NULL) { 1573 /* 1574 * Unless the source mapping is read-only or 1575 * it is presently being upgraded from 1576 * read-only, the first object in the shadow 1577 * chain should provide all of the pages. In 1578 * other words, this loop body should never be 1579 * executed when the source mapping is already 1580 * read/write. 1581 */ 1582 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1583 upgrade, 1584 ("vm_fault_copy_entry: main object missing page")); 1585 1586 VM_OBJECT_RLOCK(backing_object); 1587 pindex += OFF_TO_IDX(object->backing_object_offset); 1588 if (object != dst_object) 1589 VM_OBJECT_RUNLOCK(object); 1590 object = backing_object; 1591 } 1592 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1593 1594 if (object != dst_object) { 1595 /* 1596 * Allocate a page in the destination object. 1597 */ 1598 dst_m = vm_page_alloc(dst_object, (src_object == 1599 dst_object ? src_pindex : 0) + dst_pindex, 1600 VM_ALLOC_NORMAL); 1601 if (dst_m == NULL) { 1602 VM_OBJECT_WUNLOCK(dst_object); 1603 VM_OBJECT_RUNLOCK(object); 1604 VM_WAIT; 1605 VM_OBJECT_WLOCK(dst_object); 1606 goto again; 1607 } 1608 pmap_copy_page(src_m, dst_m); 1609 VM_OBJECT_RUNLOCK(object); 1610 dst_m->valid = VM_PAGE_BITS_ALL; 1611 dst_m->dirty = VM_PAGE_BITS_ALL; 1612 } else { 1613 dst_m = src_m; 1614 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1615 goto again; 1616 vm_page_xbusy(dst_m); 1617 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1618 ("invalid dst page %p", dst_m)); 1619 } 1620 VM_OBJECT_WUNLOCK(dst_object); 1621 1622 /* 1623 * Enter it in the pmap. If a wired, copy-on-write 1624 * mapping is being replaced by a write-enabled 1625 * mapping, then wire that new mapping. 1626 */ 1627 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1628 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1629 1630 /* 1631 * Mark it no longer busy, and put it on the active list. 1632 */ 1633 VM_OBJECT_WLOCK(dst_object); 1634 1635 if (upgrade) { 1636 if (src_m != dst_m) { 1637 vm_page_lock(src_m); 1638 vm_page_unwire(src_m, PQ_INACTIVE); 1639 vm_page_unlock(src_m); 1640 vm_page_lock(dst_m); 1641 vm_page_wire(dst_m); 1642 vm_page_unlock(dst_m); 1643 } else { 1644 KASSERT(dst_m->wire_count > 0, 1645 ("dst_m %p is not wired", dst_m)); 1646 } 1647 } else { 1648 vm_page_lock(dst_m); 1649 vm_page_activate(dst_m); 1650 vm_page_unlock(dst_m); 1651 } 1652 vm_page_xunbusy(dst_m); 1653 } 1654 VM_OBJECT_WUNLOCK(dst_object); 1655 if (upgrade) { 1656 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1657 vm_object_deallocate(src_object); 1658 } 1659 } 1660 1661 /* 1662 * Block entry into the machine-independent layer's page fault handler by 1663 * the calling thread. Subsequent calls to vm_fault() by that thread will 1664 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1665 * spurious page faults. 1666 */ 1667 int 1668 vm_fault_disable_pagefaults(void) 1669 { 1670 1671 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1672 } 1673 1674 void 1675 vm_fault_enable_pagefaults(int save) 1676 { 1677 1678 curthread_pflags_restore(save); 1679 } 1680