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 static void 308 vm_fault_populate_check_page(vm_page_t m) 309 { 310 311 /* 312 * Check each page to ensure that the pager is obeying the 313 * interface: the page must be installed in the object, fully 314 * valid, and exclusively busied. 315 */ 316 MPASS(m != NULL); 317 MPASS(m->valid == VM_PAGE_BITS_ALL); 318 MPASS(vm_page_xbusied(m)); 319 } 320 321 static void 322 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first, 323 vm_pindex_t last) 324 { 325 vm_page_t m; 326 vm_pindex_t pidx; 327 328 VM_OBJECT_ASSERT_WLOCKED(object); 329 MPASS(first <= last); 330 for (pidx = first, m = vm_page_lookup(object, pidx); 331 pidx <= last; pidx++, m = vm_page_next(m)) { 332 vm_fault_populate_check_page(m); 333 vm_page_lock(m); 334 vm_page_deactivate(m); 335 vm_page_unlock(m); 336 vm_page_xunbusy(m); 337 } 338 } 339 340 static int 341 vm_fault_populate(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot, 342 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold) 343 { 344 vm_page_t m; 345 vm_pindex_t map_first, map_last, pager_first, pager_last, pidx; 346 int rv; 347 348 MPASS(fs->object == fs->first_object); 349 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 350 MPASS(fs->first_object->paging_in_progress > 0); 351 MPASS(fs->first_object->backing_object == NULL); 352 MPASS(fs->lookup_still_valid); 353 354 pager_first = OFF_TO_IDX(fs->entry->offset); 355 pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1; 356 unlock_map(fs); 357 unlock_vp(fs); 358 359 /* 360 * Call the pager (driver) populate() method. 361 * 362 * There is no guarantee that the method will be called again 363 * if the current fault is for read, and a future fault is 364 * for write. Report the entry's maximum allowed protection 365 * to the driver. 366 */ 367 rv = vm_pager_populate(fs->first_object, fs->first_pindex, 368 fault_type, fs->entry->max_protection, &pager_first, &pager_last); 369 370 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 371 if (rv == VM_PAGER_BAD) { 372 /* 373 * VM_PAGER_BAD is the backdoor for a pager to request 374 * normal fault handling. 375 */ 376 vm_fault_restore_map_lock(fs); 377 if (fs->map->timestamp != fs->map_generation) 378 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */ 379 return (KERN_NOT_RECEIVER); 380 } 381 if (rv != VM_PAGER_OK) 382 return (KERN_FAILURE); /* AKA SIGSEGV */ 383 384 /* Ensure that the driver is obeying the interface. */ 385 MPASS(pager_first <= pager_last); 386 MPASS(fs->first_pindex <= pager_last); 387 MPASS(fs->first_pindex >= pager_first); 388 MPASS(pager_last < fs->first_object->size); 389 390 vm_fault_restore_map_lock(fs); 391 if (fs->map->timestamp != fs->map_generation) { 392 vm_fault_populate_cleanup(fs->first_object, pager_first, 393 pager_last); 394 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */ 395 } 396 397 /* 398 * The map is unchanged after our last unlock. Process the fault. 399 * 400 * The range [pager_first, pager_last] that is given to the 401 * pager is only a hint. The pager may populate any range 402 * within the object that includes the requested page index. 403 * In case the pager expanded the range, clip it to fit into 404 * the map entry. 405 */ 406 map_first = OFF_TO_IDX(fs->entry->offset); 407 if (map_first > pager_first) { 408 vm_fault_populate_cleanup(fs->first_object, pager_first, 409 map_first - 1); 410 pager_first = map_first; 411 } 412 map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1; 413 if (map_last < pager_last) { 414 vm_fault_populate_cleanup(fs->first_object, map_last + 1, 415 pager_last); 416 pager_last = map_last; 417 } 418 for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx); 419 pidx <= pager_last; pidx++, m = vm_page_next(m)) { 420 vm_fault_populate_check_page(m); 421 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, 422 true); 423 VM_OBJECT_WUNLOCK(fs->first_object); 424 pmap_enter(fs->map->pmap, fs->entry->start + IDX_TO_OFF(pidx) - 425 fs->entry->offset, m, prot, fault_type | (wired ? 426 PMAP_ENTER_WIRED : 0), 0); 427 VM_OBJECT_WLOCK(fs->first_object); 428 if (pidx == fs->first_pindex) 429 vm_fault_fill_hold(m_hold, m); 430 vm_page_lock(m); 431 if ((fault_flags & VM_FAULT_WIRE) != 0) { 432 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 433 vm_page_wire(m); 434 } else { 435 vm_page_activate(m); 436 } 437 vm_page_unlock(m); 438 vm_page_xunbusy(m); 439 } 440 curthread->td_ru.ru_majflt++; 441 return (KERN_SUCCESS); 442 } 443 444 /* 445 * vm_fault: 446 * 447 * Handle a page fault occurring at the given address, 448 * requiring the given permissions, in the map specified. 449 * If successful, the page is inserted into the 450 * associated physical map. 451 * 452 * NOTE: the given address should be truncated to the 453 * proper page address. 454 * 455 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 456 * a standard error specifying why the fault is fatal is returned. 457 * 458 * The map in question must be referenced, and remains so. 459 * Caller may hold no locks. 460 */ 461 int 462 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 463 int fault_flags) 464 { 465 struct thread *td; 466 int result; 467 468 td = curthread; 469 if ((td->td_pflags & TDP_NOFAULTING) != 0) 470 return (KERN_PROTECTION_FAILURE); 471 #ifdef KTRACE 472 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 473 ktrfault(vaddr, fault_type); 474 #endif 475 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 476 NULL); 477 #ifdef KTRACE 478 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 479 ktrfaultend(result); 480 #endif 481 return (result); 482 } 483 484 int 485 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 486 int fault_flags, vm_page_t *m_hold) 487 { 488 struct faultstate fs; 489 struct vnode *vp; 490 vm_object_t next_object, retry_object; 491 vm_offset_t e_end, e_start; 492 vm_pindex_t retry_pindex; 493 vm_prot_t prot, retry_prot; 494 int ahead, alloc_req, behind, cluster_offset, error, era, faultcount; 495 int locked, nera, result, rv; 496 u_char behavior; 497 boolean_t wired; /* Passed by reference. */ 498 bool dead, growstack, hardfault, is_first_object_locked; 499 500 VM_CNT_INC(v_vm_faults); 501 fs.vp = NULL; 502 faultcount = 0; 503 nera = -1; 504 growstack = true; 505 hardfault = false; 506 507 RetryFault:; 508 509 /* 510 * Find the backing store object and offset into it to begin the 511 * search. 512 */ 513 fs.map = map; 514 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 515 &fs.first_object, &fs.first_pindex, &prot, &wired); 516 if (result != KERN_SUCCESS) { 517 if (growstack && result == KERN_INVALID_ADDRESS && 518 map != kernel_map) { 519 result = vm_map_growstack(curproc, vaddr); 520 if (result != KERN_SUCCESS) 521 return (KERN_FAILURE); 522 growstack = false; 523 goto RetryFault; 524 } 525 unlock_vp(&fs); 526 return (result); 527 } 528 529 fs.map_generation = fs.map->timestamp; 530 531 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 532 panic("%s: fault on nofault entry, addr: %#lx", 533 __func__, (u_long)vaddr); 534 } 535 536 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 537 fs.entry->wiring_thread != curthread) { 538 vm_map_unlock_read(fs.map); 539 vm_map_lock(fs.map); 540 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 541 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 542 unlock_vp(&fs); 543 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 544 vm_map_unlock_and_wait(fs.map, 0); 545 } else 546 vm_map_unlock(fs.map); 547 goto RetryFault; 548 } 549 550 if (wired) 551 fault_type = prot | (fault_type & VM_PROT_COPY); 552 else 553 KASSERT((fault_flags & VM_FAULT_WIRE) == 0, 554 ("!wired && VM_FAULT_WIRE")); 555 556 /* 557 * Try to avoid lock contention on the top-level object through 558 * special-case handling of some types of page faults, specifically, 559 * those that are both (1) mapping an existing page from the top- 560 * level object and (2) not having to mark that object as containing 561 * dirty pages. Under these conditions, a read lock on the top-level 562 * object suffices, allowing multiple page faults of a similar type to 563 * run in parallel on the same top-level object. 564 */ 565 if (fs.vp == NULL /* avoid locked vnode leak */ && 566 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 && 567 /* avoid calling vm_object_set_writeable_dirty() */ 568 ((prot & VM_PROT_WRITE) == 0 || 569 (fs.first_object->type != OBJT_VNODE && 570 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 571 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 572 VM_OBJECT_RLOCK(fs.first_object); 573 if ((prot & VM_PROT_WRITE) == 0 || 574 (fs.first_object->type != OBJT_VNODE && 575 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 576 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0) { 577 rv = vm_fault_soft_fast(&fs, vaddr, prot, fault_type, 578 fault_flags, wired, m_hold); 579 if (rv == KERN_SUCCESS) 580 return (rv); 581 } 582 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 583 VM_OBJECT_RUNLOCK(fs.first_object); 584 VM_OBJECT_WLOCK(fs.first_object); 585 } 586 } else { 587 VM_OBJECT_WLOCK(fs.first_object); 588 } 589 590 /* 591 * Make a reference to this object to prevent its disposal while we 592 * are messing with it. Once we have the reference, the map is free 593 * to be diddled. Since objects reference their shadows (and copies), 594 * they will stay around as well. 595 * 596 * Bump the paging-in-progress count to prevent size changes (e.g. 597 * truncation operations) during I/O. 598 */ 599 vm_object_reference_locked(fs.first_object); 600 vm_object_pip_add(fs.first_object, 1); 601 602 fs.lookup_still_valid = true; 603 604 fs.first_m = NULL; 605 606 /* 607 * Search for the page at object/offset. 608 */ 609 fs.object = fs.first_object; 610 fs.pindex = fs.first_pindex; 611 while (TRUE) { 612 /* 613 * If the object is marked for imminent termination, 614 * we retry here, since the collapse pass has raced 615 * with us. Otherwise, if we see terminally dead 616 * object, return fail. 617 */ 618 if ((fs.object->flags & OBJ_DEAD) != 0) { 619 dead = fs.object->type == OBJT_DEAD; 620 unlock_and_deallocate(&fs); 621 if (dead) 622 return (KERN_PROTECTION_FAILURE); 623 pause("vmf_de", 1); 624 goto RetryFault; 625 } 626 627 /* 628 * See if page is resident 629 */ 630 fs.m = vm_page_lookup(fs.object, fs.pindex); 631 if (fs.m != NULL) { 632 /* 633 * Wait/Retry if the page is busy. We have to do this 634 * if the page is either exclusive or shared busy 635 * because the vm_pager may be using read busy for 636 * pageouts (and even pageins if it is the vnode 637 * pager), and we could end up trying to pagein and 638 * pageout the same page simultaneously. 639 * 640 * We can theoretically allow the busy case on a read 641 * fault if the page is marked valid, but since such 642 * pages are typically already pmap'd, putting that 643 * special case in might be more effort then it is 644 * worth. We cannot under any circumstances mess 645 * around with a shared busied page except, perhaps, 646 * to pmap it. 647 */ 648 if (vm_page_busied(fs.m)) { 649 /* 650 * Reference the page before unlocking and 651 * sleeping so that the page daemon is less 652 * likely to reclaim it. 653 */ 654 vm_page_aflag_set(fs.m, PGA_REFERENCED); 655 if (fs.object != fs.first_object) { 656 if (!VM_OBJECT_TRYWLOCK( 657 fs.first_object)) { 658 VM_OBJECT_WUNLOCK(fs.object); 659 VM_OBJECT_WLOCK(fs.first_object); 660 VM_OBJECT_WLOCK(fs.object); 661 } 662 vm_page_lock(fs.first_m); 663 vm_page_free(fs.first_m); 664 vm_page_unlock(fs.first_m); 665 vm_object_pip_wakeup(fs.first_object); 666 VM_OBJECT_WUNLOCK(fs.first_object); 667 fs.first_m = NULL; 668 } 669 unlock_map(&fs); 670 if (fs.m == vm_page_lookup(fs.object, 671 fs.pindex)) { 672 vm_page_sleep_if_busy(fs.m, "vmpfw"); 673 } 674 vm_object_pip_wakeup(fs.object); 675 VM_OBJECT_WUNLOCK(fs.object); 676 VM_CNT_INC(v_intrans); 677 vm_object_deallocate(fs.first_object); 678 goto RetryFault; 679 } 680 vm_page_lock(fs.m); 681 vm_page_remque(fs.m); 682 vm_page_unlock(fs.m); 683 684 /* 685 * Mark page busy for other processes, and the 686 * pagedaemon. If it still isn't completely valid 687 * (readable), jump to readrest, else break-out ( we 688 * found the page ). 689 */ 690 vm_page_xbusy(fs.m); 691 if (fs.m->valid != VM_PAGE_BITS_ALL) 692 goto readrest; 693 break; 694 } 695 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m)); 696 697 /* 698 * Page is not resident. If the pager might contain the page 699 * or this is the beginning of the search, allocate a new 700 * page. (Default objects are zero-fill, so there is no real 701 * pager for them.) 702 */ 703 if (fs.object->type != OBJT_DEFAULT || 704 fs.object == fs.first_object) { 705 if (fs.pindex >= fs.object->size) { 706 unlock_and_deallocate(&fs); 707 return (KERN_PROTECTION_FAILURE); 708 } 709 710 if (fs.object == fs.first_object && 711 (fs.first_object->flags & OBJ_POPULATE) != 0 && 712 fs.first_object->shadow_count == 0) { 713 rv = vm_fault_populate(&fs, vaddr, prot, 714 fault_type, fault_flags, wired, m_hold); 715 switch (rv) { 716 case KERN_SUCCESS: 717 case KERN_FAILURE: 718 unlock_and_deallocate(&fs); 719 return (rv); 720 case KERN_RESOURCE_SHORTAGE: 721 unlock_and_deallocate(&fs); 722 goto RetryFault; 723 case KERN_NOT_RECEIVER: 724 /* 725 * Pager's populate() method 726 * returned VM_PAGER_BAD. 727 */ 728 break; 729 default: 730 panic("inconsistent return codes"); 731 } 732 } 733 734 /* 735 * Allocate a new page for this object/offset pair. 736 * 737 * Unlocked read of the p_flag is harmless. At 738 * worst, the P_KILLED might be not observed 739 * there, and allocation can fail, causing 740 * restart and new reading of the p_flag. 741 */ 742 if (!vm_page_count_severe() || P_KILLED(curproc)) { 743 #if VM_NRESERVLEVEL > 0 744 vm_object_color(fs.object, atop(vaddr) - 745 fs.pindex); 746 #endif 747 alloc_req = P_KILLED(curproc) ? 748 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 749 if (fs.object->type != OBJT_VNODE && 750 fs.object->backing_object == NULL) 751 alloc_req |= VM_ALLOC_ZERO; 752 fs.m = vm_page_alloc(fs.object, fs.pindex, 753 alloc_req); 754 } 755 if (fs.m == NULL) { 756 unlock_and_deallocate(&fs); 757 VM_WAITPFAULT; 758 goto RetryFault; 759 } 760 } 761 762 readrest: 763 /* 764 * At this point, we have either allocated a new page or found 765 * an existing page that is only partially valid. 766 * 767 * We hold a reference on the current object and the page is 768 * exclusive busied. 769 */ 770 771 /* 772 * If the pager for the current object might have the page, 773 * then determine the number of additional pages to read and 774 * potentially reprioritize previously read pages for earlier 775 * reclamation. These operations should only be performed 776 * once per page fault. Even if the current pager doesn't 777 * have the page, the number of additional pages to read will 778 * apply to subsequent objects in the shadow chain. 779 */ 780 if (fs.object->type != OBJT_DEFAULT && nera == -1 && 781 !P_KILLED(curproc)) { 782 KASSERT(fs.lookup_still_valid, ("map unlocked")); 783 era = fs.entry->read_ahead; 784 behavior = vm_map_entry_behavior(fs.entry); 785 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 786 nera = 0; 787 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 788 nera = VM_FAULT_READ_AHEAD_MAX; 789 if (vaddr == fs.entry->next_read) 790 vm_fault_dontneed(&fs, vaddr, nera); 791 } else if (vaddr == fs.entry->next_read) { 792 /* 793 * This is a sequential fault. Arithmetically 794 * increase the requested number of pages in 795 * the read-ahead window. The requested 796 * number of pages is "# of sequential faults 797 * x (read ahead min + 1) + read ahead min" 798 */ 799 nera = VM_FAULT_READ_AHEAD_MIN; 800 if (era > 0) { 801 nera += era + 1; 802 if (nera > VM_FAULT_READ_AHEAD_MAX) 803 nera = VM_FAULT_READ_AHEAD_MAX; 804 } 805 if (era == VM_FAULT_READ_AHEAD_MAX) 806 vm_fault_dontneed(&fs, vaddr, nera); 807 } else { 808 /* 809 * This is a non-sequential fault. 810 */ 811 nera = 0; 812 } 813 if (era != nera) { 814 /* 815 * A read lock on the map suffices to update 816 * the read ahead count safely. 817 */ 818 fs.entry->read_ahead = nera; 819 } 820 821 /* 822 * Prepare for unlocking the map. Save the map 823 * entry's start and end addresses, which are used to 824 * optimize the size of the pager operation below. 825 * Even if the map entry's addresses change after 826 * unlocking the map, using the saved addresses is 827 * safe. 828 */ 829 e_start = fs.entry->start; 830 e_end = fs.entry->end; 831 } 832 833 /* 834 * Call the pager to retrieve the page if there is a chance 835 * that the pager has it, and potentially retrieve additional 836 * pages at the same time. 837 */ 838 if (fs.object->type != OBJT_DEFAULT) { 839 /* 840 * Release the map lock before locking the vnode or 841 * sleeping in the pager. (If the current object has 842 * a shadow, then an earlier iteration of this loop 843 * may have already unlocked the map.) 844 */ 845 unlock_map(&fs); 846 847 if (fs.object->type == OBJT_VNODE && 848 (vp = fs.object->handle) != fs.vp) { 849 /* 850 * Perform an unlock in case the desired vnode 851 * changed while the map was unlocked during a 852 * retry. 853 */ 854 unlock_vp(&fs); 855 856 locked = VOP_ISLOCKED(vp); 857 if (locked != LK_EXCLUSIVE) 858 locked = LK_SHARED; 859 860 /* 861 * We must not sleep acquiring the vnode lock 862 * while we have the page exclusive busied or 863 * the object's paging-in-progress count 864 * incremented. Otherwise, we could deadlock. 865 */ 866 error = vget(vp, locked | LK_CANRECURSE | 867 LK_NOWAIT, curthread); 868 if (error != 0) { 869 vhold(vp); 870 release_page(&fs); 871 unlock_and_deallocate(&fs); 872 error = vget(vp, locked | LK_RETRY | 873 LK_CANRECURSE, curthread); 874 vdrop(vp); 875 fs.vp = vp; 876 KASSERT(error == 0, 877 ("vm_fault: vget failed")); 878 goto RetryFault; 879 } 880 fs.vp = vp; 881 } 882 KASSERT(fs.vp == NULL || !fs.map->system_map, 883 ("vm_fault: vnode-backed object mapped by system map")); 884 885 /* 886 * Page in the requested page and hint the pager, 887 * that it may bring up surrounding pages. 888 */ 889 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM || 890 P_KILLED(curproc)) { 891 behind = 0; 892 ahead = 0; 893 } else { 894 /* Is this a sequential fault? */ 895 if (nera > 0) { 896 behind = 0; 897 ahead = nera; 898 } else { 899 /* 900 * Request a cluster of pages that is 901 * aligned to a VM_FAULT_READ_DEFAULT 902 * page offset boundary within the 903 * object. Alignment to a page offset 904 * boundary is more likely to coincide 905 * with the underlying file system 906 * block than alignment to a virtual 907 * address boundary. 908 */ 909 cluster_offset = fs.pindex % 910 VM_FAULT_READ_DEFAULT; 911 behind = ulmin(cluster_offset, 912 atop(vaddr - e_start)); 913 ahead = VM_FAULT_READ_DEFAULT - 1 - 914 cluster_offset; 915 } 916 ahead = ulmin(ahead, atop(e_end - vaddr) - 1); 917 } 918 rv = vm_pager_get_pages(fs.object, &fs.m, 1, 919 &behind, &ahead); 920 if (rv == VM_PAGER_OK) { 921 faultcount = behind + 1 + ahead; 922 hardfault = true; 923 break; /* break to PAGE HAS BEEN FOUND */ 924 } 925 if (rv == VM_PAGER_ERROR) 926 printf("vm_fault: pager read error, pid %d (%s)\n", 927 curproc->p_pid, curproc->p_comm); 928 929 /* 930 * If an I/O error occurred or the requested page was 931 * outside the range of the pager, clean up and return 932 * an error. 933 */ 934 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) { 935 vm_page_lock(fs.m); 936 if (fs.m->wire_count == 0) 937 vm_page_free(fs.m); 938 else 939 vm_page_xunbusy_maybelocked(fs.m); 940 vm_page_unlock(fs.m); 941 fs.m = NULL; 942 unlock_and_deallocate(&fs); 943 return (rv == VM_PAGER_ERROR ? KERN_FAILURE : 944 KERN_PROTECTION_FAILURE); 945 } 946 947 /* 948 * The requested page does not exist at this object/ 949 * offset. Remove the invalid page from the object, 950 * waking up anyone waiting for it, and continue on to 951 * the next object. However, if this is the top-level 952 * object, we must leave the busy page in place to 953 * prevent another process from rushing past us, and 954 * inserting the page in that object at the same time 955 * that we are. 956 */ 957 if (fs.object != fs.first_object) { 958 vm_page_lock(fs.m); 959 if (fs.m->wire_count == 0) 960 vm_page_free(fs.m); 961 else 962 vm_page_xunbusy_maybelocked(fs.m); 963 vm_page_unlock(fs.m); 964 fs.m = NULL; 965 } 966 } 967 968 /* 969 * We get here if the object has default pager (or unwiring) 970 * or the pager doesn't have the page. 971 */ 972 if (fs.object == fs.first_object) 973 fs.first_m = fs.m; 974 975 /* 976 * Move on to the next object. Lock the next object before 977 * unlocking the current one. 978 */ 979 next_object = fs.object->backing_object; 980 if (next_object == NULL) { 981 /* 982 * If there's no object left, fill the page in the top 983 * object with zeros. 984 */ 985 if (fs.object != fs.first_object) { 986 vm_object_pip_wakeup(fs.object); 987 VM_OBJECT_WUNLOCK(fs.object); 988 989 fs.object = fs.first_object; 990 fs.pindex = fs.first_pindex; 991 fs.m = fs.first_m; 992 VM_OBJECT_WLOCK(fs.object); 993 } 994 fs.first_m = NULL; 995 996 /* 997 * Zero the page if necessary and mark it valid. 998 */ 999 if ((fs.m->flags & PG_ZERO) == 0) { 1000 pmap_zero_page(fs.m); 1001 } else { 1002 VM_CNT_INC(v_ozfod); 1003 } 1004 VM_CNT_INC(v_zfod); 1005 fs.m->valid = VM_PAGE_BITS_ALL; 1006 /* Don't try to prefault neighboring pages. */ 1007 faultcount = 1; 1008 break; /* break to PAGE HAS BEEN FOUND */ 1009 } else { 1010 KASSERT(fs.object != next_object, 1011 ("object loop %p", next_object)); 1012 VM_OBJECT_WLOCK(next_object); 1013 vm_object_pip_add(next_object, 1); 1014 if (fs.object != fs.first_object) 1015 vm_object_pip_wakeup(fs.object); 1016 fs.pindex += 1017 OFF_TO_IDX(fs.object->backing_object_offset); 1018 VM_OBJECT_WUNLOCK(fs.object); 1019 fs.object = next_object; 1020 } 1021 } 1022 1023 vm_page_assert_xbusied(fs.m); 1024 1025 /* 1026 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 1027 * is held.] 1028 */ 1029 1030 /* 1031 * If the page is being written, but isn't already owned by the 1032 * top-level object, we have to copy it into a new page owned by the 1033 * top-level object. 1034 */ 1035 if (fs.object != fs.first_object) { 1036 /* 1037 * We only really need to copy if we want to write it. 1038 */ 1039 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1040 /* 1041 * This allows pages to be virtually copied from a 1042 * backing_object into the first_object, where the 1043 * backing object has no other refs to it, and cannot 1044 * gain any more refs. Instead of a bcopy, we just 1045 * move the page from the backing object to the 1046 * first object. Note that we must mark the page 1047 * dirty in the first object so that it will go out 1048 * to swap when needed. 1049 */ 1050 is_first_object_locked = false; 1051 if ( 1052 /* 1053 * Only one shadow object 1054 */ 1055 (fs.object->shadow_count == 1) && 1056 /* 1057 * No COW refs, except us 1058 */ 1059 (fs.object->ref_count == 1) && 1060 /* 1061 * No one else can look this object up 1062 */ 1063 (fs.object->handle == NULL) && 1064 /* 1065 * No other ways to look the object up 1066 */ 1067 ((fs.object->type == OBJT_DEFAULT) || 1068 (fs.object->type == OBJT_SWAP)) && 1069 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 1070 /* 1071 * We don't chase down the shadow chain 1072 */ 1073 fs.object == fs.first_object->backing_object) { 1074 vm_page_lock(fs.m); 1075 vm_page_remove(fs.m); 1076 vm_page_unlock(fs.m); 1077 vm_page_lock(fs.first_m); 1078 vm_page_replace_checked(fs.m, fs.first_object, 1079 fs.first_pindex, fs.first_m); 1080 vm_page_free(fs.first_m); 1081 vm_page_unlock(fs.first_m); 1082 vm_page_dirty(fs.m); 1083 #if VM_NRESERVLEVEL > 0 1084 /* 1085 * Rename the reservation. 1086 */ 1087 vm_reserv_rename(fs.m, fs.first_object, 1088 fs.object, OFF_TO_IDX( 1089 fs.first_object->backing_object_offset)); 1090 #endif 1091 /* 1092 * Removing the page from the backing object 1093 * unbusied it. 1094 */ 1095 vm_page_xbusy(fs.m); 1096 fs.first_m = fs.m; 1097 fs.m = NULL; 1098 VM_CNT_INC(v_cow_optim); 1099 } else { 1100 /* 1101 * Oh, well, lets copy it. 1102 */ 1103 pmap_copy_page(fs.m, fs.first_m); 1104 fs.first_m->valid = VM_PAGE_BITS_ALL; 1105 if (wired && (fault_flags & 1106 VM_FAULT_WIRE) == 0) { 1107 vm_page_lock(fs.first_m); 1108 vm_page_wire(fs.first_m); 1109 vm_page_unlock(fs.first_m); 1110 1111 vm_page_lock(fs.m); 1112 vm_page_unwire(fs.m, PQ_INACTIVE); 1113 vm_page_unlock(fs.m); 1114 } 1115 /* 1116 * We no longer need the old page or object. 1117 */ 1118 release_page(&fs); 1119 } 1120 /* 1121 * fs.object != fs.first_object due to above 1122 * conditional 1123 */ 1124 vm_object_pip_wakeup(fs.object); 1125 VM_OBJECT_WUNLOCK(fs.object); 1126 /* 1127 * Only use the new page below... 1128 */ 1129 fs.object = fs.first_object; 1130 fs.pindex = fs.first_pindex; 1131 fs.m = fs.first_m; 1132 if (!is_first_object_locked) 1133 VM_OBJECT_WLOCK(fs.object); 1134 VM_CNT_INC(v_cow_faults); 1135 curthread->td_cow++; 1136 } else { 1137 prot &= ~VM_PROT_WRITE; 1138 } 1139 } 1140 1141 /* 1142 * We must verify that the maps have not changed since our last 1143 * lookup. 1144 */ 1145 if (!fs.lookup_still_valid) { 1146 if (!vm_map_trylock_read(fs.map)) { 1147 release_page(&fs); 1148 unlock_and_deallocate(&fs); 1149 goto RetryFault; 1150 } 1151 fs.lookup_still_valid = true; 1152 if (fs.map->timestamp != fs.map_generation) { 1153 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 1154 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 1155 1156 /* 1157 * If we don't need the page any longer, put it on the inactive 1158 * list (the easiest thing to do here). If no one needs it, 1159 * pageout will grab it eventually. 1160 */ 1161 if (result != KERN_SUCCESS) { 1162 release_page(&fs); 1163 unlock_and_deallocate(&fs); 1164 1165 /* 1166 * If retry of map lookup would have blocked then 1167 * retry fault from start. 1168 */ 1169 if (result == KERN_FAILURE) 1170 goto RetryFault; 1171 return (result); 1172 } 1173 if ((retry_object != fs.first_object) || 1174 (retry_pindex != fs.first_pindex)) { 1175 release_page(&fs); 1176 unlock_and_deallocate(&fs); 1177 goto RetryFault; 1178 } 1179 1180 /* 1181 * Check whether the protection has changed or the object has 1182 * been copied while we left the map unlocked. Changing from 1183 * read to write permission is OK - we leave the page 1184 * write-protected, and catch the write fault. Changing from 1185 * write to read permission means that we can't mark the page 1186 * write-enabled after all. 1187 */ 1188 prot &= retry_prot; 1189 } 1190 } 1191 1192 /* 1193 * If the page was filled by a pager, save the virtual address that 1194 * should be faulted on next under a sequential access pattern to the 1195 * map entry. A read lock on the map suffices to update this address 1196 * safely. 1197 */ 1198 if (hardfault) 1199 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE; 1200 1201 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true); 1202 vm_page_assert_xbusied(fs.m); 1203 1204 /* 1205 * Page must be completely valid or it is not fit to 1206 * map into user space. vm_pager_get_pages() ensures this. 1207 */ 1208 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 1209 ("vm_fault: page %p partially invalid", fs.m)); 1210 VM_OBJECT_WUNLOCK(fs.object); 1211 1212 /* 1213 * Put this page into the physical map. We had to do the unlock above 1214 * because pmap_enter() may sleep. We don't put the page 1215 * back on the active queue until later so that the pageout daemon 1216 * won't find it (yet). 1217 */ 1218 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 1219 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 1220 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 1221 wired == 0) 1222 vm_fault_prefault(&fs, vaddr, 1223 faultcount > 0 ? behind : PFBAK, 1224 faultcount > 0 ? ahead : PFFOR); 1225 VM_OBJECT_WLOCK(fs.object); 1226 vm_page_lock(fs.m); 1227 1228 /* 1229 * If the page is not wired down, then put it where the pageout daemon 1230 * can find it. 1231 */ 1232 if ((fault_flags & VM_FAULT_WIRE) != 0) { 1233 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 1234 vm_page_wire(fs.m); 1235 } else 1236 vm_page_activate(fs.m); 1237 if (m_hold != NULL) { 1238 *m_hold = fs.m; 1239 vm_page_hold(fs.m); 1240 } 1241 vm_page_unlock(fs.m); 1242 vm_page_xunbusy(fs.m); 1243 1244 /* 1245 * Unlock everything, and return 1246 */ 1247 unlock_and_deallocate(&fs); 1248 if (hardfault) { 1249 VM_CNT_INC(v_io_faults); 1250 curthread->td_ru.ru_majflt++; 1251 #ifdef RACCT 1252 if (racct_enable && fs.object->type == OBJT_VNODE) { 1253 PROC_LOCK(curproc); 1254 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1255 racct_add_force(curproc, RACCT_WRITEBPS, 1256 PAGE_SIZE + behind * PAGE_SIZE); 1257 racct_add_force(curproc, RACCT_WRITEIOPS, 1); 1258 } else { 1259 racct_add_force(curproc, RACCT_READBPS, 1260 PAGE_SIZE + ahead * PAGE_SIZE); 1261 racct_add_force(curproc, RACCT_READIOPS, 1); 1262 } 1263 PROC_UNLOCK(curproc); 1264 } 1265 #endif 1266 } else 1267 curthread->td_ru.ru_minflt++; 1268 1269 return (KERN_SUCCESS); 1270 } 1271 1272 /* 1273 * Speed up the reclamation of pages that precede the faulting pindex within 1274 * the first object of the shadow chain. Essentially, perform the equivalent 1275 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1276 * the faulting pindex by the cluster size when the pages read by vm_fault() 1277 * cross a cluster-size boundary. The cluster size is the greater of the 1278 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1279 * 1280 * When "fs->first_object" is a shadow object, the pages in the backing object 1281 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1282 * function must only be concerned with pages in the first object. 1283 */ 1284 static void 1285 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1286 { 1287 vm_map_entry_t entry; 1288 vm_object_t first_object, object; 1289 vm_offset_t end, start; 1290 vm_page_t m, m_next; 1291 vm_pindex_t pend, pstart; 1292 vm_size_t size; 1293 1294 object = fs->object; 1295 VM_OBJECT_ASSERT_WLOCKED(object); 1296 first_object = fs->first_object; 1297 if (first_object != object) { 1298 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1299 VM_OBJECT_WUNLOCK(object); 1300 VM_OBJECT_WLOCK(first_object); 1301 VM_OBJECT_WLOCK(object); 1302 } 1303 } 1304 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1305 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1306 size = VM_FAULT_DONTNEED_MIN; 1307 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1308 size = pagesizes[1]; 1309 end = rounddown2(vaddr, size); 1310 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1311 (entry = fs->entry)->start < end) { 1312 if (end - entry->start < size) 1313 start = entry->start; 1314 else 1315 start = end - size; 1316 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1317 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1318 entry->start); 1319 m_next = vm_page_find_least(first_object, pstart); 1320 pend = OFF_TO_IDX(entry->offset) + atop(end - 1321 entry->start); 1322 while ((m = m_next) != NULL && m->pindex < pend) { 1323 m_next = TAILQ_NEXT(m, listq); 1324 if (m->valid != VM_PAGE_BITS_ALL || 1325 vm_page_busied(m)) 1326 continue; 1327 1328 /* 1329 * Don't clear PGA_REFERENCED, since it would 1330 * likely represent a reference by a different 1331 * process. 1332 * 1333 * Typically, at this point, prefetched pages 1334 * are still in the inactive queue. Only 1335 * pages that triggered page faults are in the 1336 * active queue. 1337 */ 1338 vm_page_lock(m); 1339 vm_page_deactivate(m); 1340 vm_page_unlock(m); 1341 } 1342 } 1343 } 1344 if (first_object != object) 1345 VM_OBJECT_WUNLOCK(first_object); 1346 } 1347 1348 /* 1349 * vm_fault_prefault provides a quick way of clustering 1350 * pagefaults into a processes address space. It is a "cousin" 1351 * of vm_map_pmap_enter, except it runs at page fault time instead 1352 * of mmap time. 1353 */ 1354 static void 1355 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1356 int backward, int forward) 1357 { 1358 pmap_t pmap; 1359 vm_map_entry_t entry; 1360 vm_object_t backing_object, lobject; 1361 vm_offset_t addr, starta; 1362 vm_pindex_t pindex; 1363 vm_page_t m; 1364 int i; 1365 1366 pmap = fs->map->pmap; 1367 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1368 return; 1369 1370 entry = fs->entry; 1371 1372 if (addra < backward * PAGE_SIZE) { 1373 starta = entry->start; 1374 } else { 1375 starta = addra - backward * PAGE_SIZE; 1376 if (starta < entry->start) 1377 starta = entry->start; 1378 } 1379 1380 /* 1381 * Generate the sequence of virtual addresses that are candidates for 1382 * prefaulting in an outward spiral from the faulting virtual address, 1383 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1384 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1385 * If the candidate address doesn't have a backing physical page, then 1386 * the loop immediately terminates. 1387 */ 1388 for (i = 0; i < 2 * imax(backward, forward); i++) { 1389 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1390 PAGE_SIZE); 1391 if (addr > addra + forward * PAGE_SIZE) 1392 addr = 0; 1393 1394 if (addr < starta || addr >= entry->end) 1395 continue; 1396 1397 if (!pmap_is_prefaultable(pmap, addr)) 1398 continue; 1399 1400 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1401 lobject = entry->object.vm_object; 1402 VM_OBJECT_RLOCK(lobject); 1403 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1404 lobject->type == OBJT_DEFAULT && 1405 (backing_object = lobject->backing_object) != NULL) { 1406 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1407 0, ("vm_fault_prefault: unaligned object offset")); 1408 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1409 VM_OBJECT_RLOCK(backing_object); 1410 VM_OBJECT_RUNLOCK(lobject); 1411 lobject = backing_object; 1412 } 1413 if (m == NULL) { 1414 VM_OBJECT_RUNLOCK(lobject); 1415 break; 1416 } 1417 if (m->valid == VM_PAGE_BITS_ALL && 1418 (m->flags & PG_FICTITIOUS) == 0) 1419 pmap_enter_quick(pmap, addr, m, entry->protection); 1420 VM_OBJECT_RUNLOCK(lobject); 1421 } 1422 } 1423 1424 /* 1425 * Hold each of the physical pages that are mapped by the specified range of 1426 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1427 * and allow the specified types of access, "prot". If all of the implied 1428 * pages are successfully held, then the number of held pages is returned 1429 * together with pointers to those pages in the array "ma". However, if any 1430 * of the pages cannot be held, -1 is returned. 1431 */ 1432 int 1433 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1434 vm_prot_t prot, vm_page_t *ma, int max_count) 1435 { 1436 vm_offset_t end, va; 1437 vm_page_t *mp; 1438 int count; 1439 boolean_t pmap_failed; 1440 1441 if (len == 0) 1442 return (0); 1443 end = round_page(addr + len); 1444 addr = trunc_page(addr); 1445 1446 /* 1447 * Check for illegal addresses. 1448 */ 1449 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1450 return (-1); 1451 1452 if (atop(end - addr) > max_count) 1453 panic("vm_fault_quick_hold_pages: count > max_count"); 1454 count = atop(end - addr); 1455 1456 /* 1457 * Most likely, the physical pages are resident in the pmap, so it is 1458 * faster to try pmap_extract_and_hold() first. 1459 */ 1460 pmap_failed = FALSE; 1461 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1462 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1463 if (*mp == NULL) 1464 pmap_failed = TRUE; 1465 else if ((prot & VM_PROT_WRITE) != 0 && 1466 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1467 /* 1468 * Explicitly dirty the physical page. Otherwise, the 1469 * caller's changes may go unnoticed because they are 1470 * performed through an unmanaged mapping or by a DMA 1471 * operation. 1472 * 1473 * The object lock is not held here. 1474 * See vm_page_clear_dirty_mask(). 1475 */ 1476 vm_page_dirty(*mp); 1477 } 1478 } 1479 if (pmap_failed) { 1480 /* 1481 * One or more pages could not be held by the pmap. Either no 1482 * page was mapped at the specified virtual address or that 1483 * mapping had insufficient permissions. Attempt to fault in 1484 * and hold these pages. 1485 */ 1486 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1487 if (*mp == NULL && vm_fault_hold(map, va, prot, 1488 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1489 goto error; 1490 } 1491 return (count); 1492 error: 1493 for (mp = ma; mp < ma + count; mp++) 1494 if (*mp != NULL) { 1495 vm_page_lock(*mp); 1496 vm_page_unhold(*mp); 1497 vm_page_unlock(*mp); 1498 } 1499 return (-1); 1500 } 1501 1502 /* 1503 * Routine: 1504 * vm_fault_copy_entry 1505 * Function: 1506 * Create new shadow object backing dst_entry with private copy of 1507 * all underlying pages. When src_entry is equal to dst_entry, 1508 * function implements COW for wired-down map entry. Otherwise, 1509 * it forks wired entry into dst_map. 1510 * 1511 * In/out conditions: 1512 * The source and destination maps must be locked for write. 1513 * The source map entry must be wired down (or be a sharing map 1514 * entry corresponding to a main map entry that is wired down). 1515 */ 1516 void 1517 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1518 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1519 vm_ooffset_t *fork_charge) 1520 { 1521 vm_object_t backing_object, dst_object, object, src_object; 1522 vm_pindex_t dst_pindex, pindex, src_pindex; 1523 vm_prot_t access, prot; 1524 vm_offset_t vaddr; 1525 vm_page_t dst_m; 1526 vm_page_t src_m; 1527 boolean_t upgrade; 1528 1529 #ifdef lint 1530 src_map++; 1531 #endif /* lint */ 1532 1533 upgrade = src_entry == dst_entry; 1534 access = prot = dst_entry->protection; 1535 1536 src_object = src_entry->object.vm_object; 1537 src_pindex = OFF_TO_IDX(src_entry->offset); 1538 1539 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1540 dst_object = src_object; 1541 vm_object_reference(dst_object); 1542 } else { 1543 /* 1544 * Create the top-level object for the destination entry. (Doesn't 1545 * actually shadow anything - we copy the pages directly.) 1546 */ 1547 dst_object = vm_object_allocate(OBJT_DEFAULT, 1548 atop(dst_entry->end - dst_entry->start)); 1549 #if VM_NRESERVLEVEL > 0 1550 dst_object->flags |= OBJ_COLORED; 1551 dst_object->pg_color = atop(dst_entry->start); 1552 #endif 1553 } 1554 1555 VM_OBJECT_WLOCK(dst_object); 1556 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1557 ("vm_fault_copy_entry: vm_object not NULL")); 1558 if (src_object != dst_object) { 1559 dst_entry->object.vm_object = dst_object; 1560 dst_entry->offset = 0; 1561 dst_object->charge = dst_entry->end - dst_entry->start; 1562 } 1563 if (fork_charge != NULL) { 1564 KASSERT(dst_entry->cred == NULL, 1565 ("vm_fault_copy_entry: leaked swp charge")); 1566 dst_object->cred = curthread->td_ucred; 1567 crhold(dst_object->cred); 1568 *fork_charge += dst_object->charge; 1569 } else if (dst_object->cred == NULL) { 1570 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1571 dst_entry)); 1572 dst_object->cred = dst_entry->cred; 1573 dst_entry->cred = NULL; 1574 } 1575 1576 /* 1577 * If not an upgrade, then enter the mappings in the pmap as 1578 * read and/or execute accesses. Otherwise, enter them as 1579 * write accesses. 1580 * 1581 * A writeable large page mapping is only created if all of 1582 * the constituent small page mappings are modified. Marking 1583 * PTEs as modified on inception allows promotion to happen 1584 * without taking potentially large number of soft faults. 1585 */ 1586 if (!upgrade) 1587 access &= ~VM_PROT_WRITE; 1588 1589 /* 1590 * Loop through all of the virtual pages within the entry's 1591 * range, copying each page from the source object to the 1592 * destination object. Since the source is wired, those pages 1593 * must exist. In contrast, the destination is pageable. 1594 * Since the destination object does share any backing storage 1595 * with the source object, all of its pages must be dirtied, 1596 * regardless of whether they can be written. 1597 */ 1598 for (vaddr = dst_entry->start, dst_pindex = 0; 1599 vaddr < dst_entry->end; 1600 vaddr += PAGE_SIZE, dst_pindex++) { 1601 again: 1602 /* 1603 * Find the page in the source object, and copy it in. 1604 * Because the source is wired down, the page will be 1605 * in memory. 1606 */ 1607 if (src_object != dst_object) 1608 VM_OBJECT_RLOCK(src_object); 1609 object = src_object; 1610 pindex = src_pindex + dst_pindex; 1611 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1612 (backing_object = object->backing_object) != NULL) { 1613 /* 1614 * Unless the source mapping is read-only or 1615 * it is presently being upgraded from 1616 * read-only, the first object in the shadow 1617 * chain should provide all of the pages. In 1618 * other words, this loop body should never be 1619 * executed when the source mapping is already 1620 * read/write. 1621 */ 1622 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1623 upgrade, 1624 ("vm_fault_copy_entry: main object missing page")); 1625 1626 VM_OBJECT_RLOCK(backing_object); 1627 pindex += OFF_TO_IDX(object->backing_object_offset); 1628 if (object != dst_object) 1629 VM_OBJECT_RUNLOCK(object); 1630 object = backing_object; 1631 } 1632 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1633 1634 if (object != dst_object) { 1635 /* 1636 * Allocate a page in the destination object. 1637 */ 1638 dst_m = vm_page_alloc(dst_object, (src_object == 1639 dst_object ? src_pindex : 0) + dst_pindex, 1640 VM_ALLOC_NORMAL); 1641 if (dst_m == NULL) { 1642 VM_OBJECT_WUNLOCK(dst_object); 1643 VM_OBJECT_RUNLOCK(object); 1644 VM_WAIT; 1645 VM_OBJECT_WLOCK(dst_object); 1646 goto again; 1647 } 1648 pmap_copy_page(src_m, dst_m); 1649 VM_OBJECT_RUNLOCK(object); 1650 dst_m->valid = VM_PAGE_BITS_ALL; 1651 dst_m->dirty = VM_PAGE_BITS_ALL; 1652 } else { 1653 dst_m = src_m; 1654 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1655 goto again; 1656 vm_page_xbusy(dst_m); 1657 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1658 ("invalid dst page %p", dst_m)); 1659 } 1660 VM_OBJECT_WUNLOCK(dst_object); 1661 1662 /* 1663 * Enter it in the pmap. If a wired, copy-on-write 1664 * mapping is being replaced by a write-enabled 1665 * mapping, then wire that new mapping. 1666 */ 1667 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1668 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1669 1670 /* 1671 * Mark it no longer busy, and put it on the active list. 1672 */ 1673 VM_OBJECT_WLOCK(dst_object); 1674 1675 if (upgrade) { 1676 if (src_m != dst_m) { 1677 vm_page_lock(src_m); 1678 vm_page_unwire(src_m, PQ_INACTIVE); 1679 vm_page_unlock(src_m); 1680 vm_page_lock(dst_m); 1681 vm_page_wire(dst_m); 1682 vm_page_unlock(dst_m); 1683 } else { 1684 KASSERT(dst_m->wire_count > 0, 1685 ("dst_m %p is not wired", dst_m)); 1686 } 1687 } else { 1688 vm_page_lock(dst_m); 1689 vm_page_activate(dst_m); 1690 vm_page_unlock(dst_m); 1691 } 1692 vm_page_xunbusy(dst_m); 1693 } 1694 VM_OBJECT_WUNLOCK(dst_object); 1695 if (upgrade) { 1696 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1697 vm_object_deallocate(src_object); 1698 } 1699 } 1700 1701 /* 1702 * Block entry into the machine-independent layer's page fault handler by 1703 * the calling thread. Subsequent calls to vm_fault() by that thread will 1704 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1705 * spurious page faults. 1706 */ 1707 int 1708 vm_fault_disable_pagefaults(void) 1709 { 1710 1711 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1712 } 1713 1714 void 1715 vm_fault_enable_pagefaults(int save) 1716 { 1717 1718 curthread_pflags_restore(save); 1719 } 1720