1 /*- 2 * SPDX-License-Identifier: (BSD-4-Clause AND MIT-CMU) 3 * 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * Copyright (c) 1994 John S. Dyson 7 * All rights reserved. 8 * Copyright (c) 1994 David Greenman 9 * All rights reserved. 10 * 11 * 12 * This code is derived from software contributed to Berkeley by 13 * The Mach Operating System project at Carnegie-Mellon University. 14 * 15 * Redistribution and use in source and binary forms, with or without 16 * modification, are permitted provided that the following conditions 17 * are met: 18 * 1. Redistributions of source code must retain the above copyright 19 * notice, this list of conditions and the following disclaimer. 20 * 2. Redistributions in binary form must reproduce the above copyright 21 * notice, this list of conditions and the following disclaimer in the 22 * documentation and/or other materials provided with the distribution. 23 * 3. All advertising materials mentioning features or use of this software 24 * must display the following acknowledgement: 25 * This product includes software developed by the University of 26 * California, Berkeley and its contributors. 27 * 4. Neither the name of the University nor the names of its contributors 28 * may be used to endorse or promote products derived from this software 29 * without specific prior written permission. 30 * 31 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 32 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 33 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 34 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 35 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 36 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 37 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 39 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 40 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 41 * SUCH DAMAGE. 42 * 43 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 44 * 45 * 46 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 47 * All rights reserved. 48 * 49 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 50 * 51 * Permission to use, copy, modify and distribute this software and 52 * its documentation is hereby granted, provided that both the copyright 53 * notice and this permission notice appear in all copies of the 54 * software, derivative works or modified versions, and any portions 55 * thereof, and that both notices appear in supporting documentation. 56 * 57 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 58 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 59 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 60 * 61 * Carnegie Mellon requests users of this software to return to 62 * 63 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 64 * School of Computer Science 65 * Carnegie Mellon University 66 * Pittsburgh PA 15213-3890 67 * 68 * any improvements or extensions that they make and grant Carnegie the 69 * rights to redistribute these changes. 70 */ 71 72 /* 73 * Page fault handling module. 74 */ 75 76 #include <sys/cdefs.h> 77 __FBSDID("$FreeBSD$"); 78 79 #include "opt_ktrace.h" 80 #include "opt_vm.h" 81 82 #include <sys/param.h> 83 #include <sys/systm.h> 84 #include <sys/kernel.h> 85 #include <sys/lock.h> 86 #include <sys/mman.h> 87 #include <sys/proc.h> 88 #include <sys/racct.h> 89 #include <sys/resourcevar.h> 90 #include <sys/rwlock.h> 91 #include <sys/sysctl.h> 92 #include <sys/vmmeter.h> 93 #include <sys/vnode.h> 94 #ifdef KTRACE 95 #include <sys/ktrace.h> 96 #endif 97 98 #include <vm/vm.h> 99 #include <vm/vm_param.h> 100 #include <vm/pmap.h> 101 #include <vm/vm_map.h> 102 #include <vm/vm_object.h> 103 #include <vm/vm_page.h> 104 #include <vm/vm_pageout.h> 105 #include <vm/vm_kern.h> 106 #include <vm/vm_pager.h> 107 #include <vm/vm_extern.h> 108 #include <vm/vm_reserv.h> 109 110 #define PFBAK 4 111 #define PFFOR 4 112 113 #define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT) 114 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX) 115 116 #define VM_FAULT_DONTNEED_MIN 1048576 117 118 struct faultstate { 119 vm_page_t m; 120 vm_object_t object; 121 vm_pindex_t pindex; 122 vm_page_t first_m; 123 vm_object_t first_object; 124 vm_pindex_t first_pindex; 125 vm_map_t map; 126 vm_map_entry_t entry; 127 int map_generation; 128 bool lookup_still_valid; 129 struct vnode *vp; 130 }; 131 132 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, 133 int ahead); 134 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 135 int backward, int forward); 136 137 static inline void 138 release_page(struct faultstate *fs) 139 { 140 141 vm_page_xunbusy(fs->m); 142 vm_page_lock(fs->m); 143 vm_page_deactivate(fs->m); 144 vm_page_unlock(fs->m); 145 fs->m = NULL; 146 } 147 148 static inline void 149 unlock_map(struct faultstate *fs) 150 { 151 152 if (fs->lookup_still_valid) { 153 vm_map_lookup_done(fs->map, fs->entry); 154 fs->lookup_still_valid = false; 155 } 156 } 157 158 static void 159 unlock_vp(struct faultstate *fs) 160 { 161 162 if (fs->vp != NULL) { 163 vput(fs->vp); 164 fs->vp = NULL; 165 } 166 } 167 168 static void 169 unlock_and_deallocate(struct faultstate *fs) 170 { 171 172 vm_object_pip_wakeup(fs->object); 173 VM_OBJECT_WUNLOCK(fs->object); 174 if (fs->object != fs->first_object) { 175 VM_OBJECT_WLOCK(fs->first_object); 176 vm_page_lock(fs->first_m); 177 vm_page_free(fs->first_m); 178 vm_page_unlock(fs->first_m); 179 vm_object_pip_wakeup(fs->first_object); 180 VM_OBJECT_WUNLOCK(fs->first_object); 181 fs->first_m = NULL; 182 } 183 vm_object_deallocate(fs->first_object); 184 unlock_map(fs); 185 unlock_vp(fs); 186 } 187 188 static void 189 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot, 190 vm_prot_t fault_type, int fault_flags, bool set_wd) 191 { 192 bool need_dirty; 193 194 if (((prot & VM_PROT_WRITE) == 0 && 195 (fault_flags & VM_FAULT_DIRTY) == 0) || 196 (m->oflags & VPO_UNMANAGED) != 0) 197 return; 198 199 VM_OBJECT_ASSERT_LOCKED(m->object); 200 201 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 && 202 (fault_flags & VM_FAULT_WIRE) == 0) || 203 (fault_flags & VM_FAULT_DIRTY) != 0; 204 205 if (set_wd) 206 vm_object_set_writeable_dirty(m->object); 207 else 208 /* 209 * If two callers of vm_fault_dirty() with set_wd == 210 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC 211 * flag set, other with flag clear, race, it is 212 * possible for the no-NOSYNC thread to see m->dirty 213 * != 0 and not clear VPO_NOSYNC. Take vm_page lock 214 * around manipulation of VPO_NOSYNC and 215 * vm_page_dirty() call, to avoid the race and keep 216 * m->oflags consistent. 217 */ 218 vm_page_lock(m); 219 220 /* 221 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 222 * if the page is already dirty to prevent data written with 223 * the expectation of being synced from not being synced. 224 * Likewise if this entry does not request NOSYNC then make 225 * sure the page isn't marked NOSYNC. Applications sharing 226 * data should use the same flags to avoid ping ponging. 227 */ 228 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) { 229 if (m->dirty == 0) { 230 m->oflags |= VPO_NOSYNC; 231 } 232 } else { 233 m->oflags &= ~VPO_NOSYNC; 234 } 235 236 /* 237 * If the fault is a write, we know that this page is being 238 * written NOW so dirty it explicitly to save on 239 * pmap_is_modified() calls later. 240 * 241 * Also, since the page is now dirty, we can possibly tell 242 * the pager to release any swap backing the page. Calling 243 * the pager requires a write lock on the object. 244 */ 245 if (need_dirty) 246 vm_page_dirty(m); 247 if (!set_wd) 248 vm_page_unlock(m); 249 else if (need_dirty) 250 vm_pager_page_unswapped(m); 251 } 252 253 static void 254 vm_fault_fill_hold(vm_page_t *m_hold, vm_page_t m) 255 { 256 257 if (m_hold != NULL) { 258 *m_hold = m; 259 vm_page_lock(m); 260 vm_page_hold(m); 261 vm_page_unlock(m); 262 } 263 } 264 265 /* 266 * Unlocks fs.first_object and fs.map on success. 267 */ 268 static int 269 vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot, 270 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold) 271 { 272 vm_page_t m, m_map; 273 #if defined(__amd64__) && VM_NRESERVLEVEL > 0 274 vm_page_t m_super; 275 int flags; 276 #endif 277 int psind, rv; 278 279 MPASS(fs->vp == NULL); 280 m = vm_page_lookup(fs->first_object, fs->first_pindex); 281 /* A busy page can be mapped for read|execute access. */ 282 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 283 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 284 return (KERN_FAILURE); 285 m_map = m; 286 psind = 0; 287 #if defined(__amd64__) && VM_NRESERVLEVEL > 0 288 if ((m->flags & PG_FICTITIOUS) == 0 && 289 (m_super = vm_reserv_to_superpage(m)) != NULL && 290 rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start && 291 roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end && 292 (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) & 293 (pagesizes[m_super->psind] - 1)) && 294 pmap_ps_enabled(fs->map->pmap)) { 295 flags = PS_ALL_VALID; 296 if ((prot & VM_PROT_WRITE) != 0) { 297 /* 298 * Create a superpage mapping allowing write access 299 * only if none of the constituent pages are busy and 300 * all of them are already dirty (except possibly for 301 * the page that was faulted on). 302 */ 303 flags |= PS_NONE_BUSY; 304 if ((fs->first_object->flags & OBJ_UNMANAGED) == 0) 305 flags |= PS_ALL_DIRTY; 306 } 307 if (vm_page_ps_test(m_super, flags, m)) { 308 m_map = m_super; 309 psind = m_super->psind; 310 vaddr = rounddown2(vaddr, pagesizes[psind]); 311 /* Preset the modified bit for dirty superpages. */ 312 if ((flags & PS_ALL_DIRTY) != 0) 313 fault_type |= VM_PROT_WRITE; 314 } 315 } 316 #endif 317 rv = pmap_enter(fs->map->pmap, vaddr, m_map, prot, fault_type | 318 PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), psind); 319 if (rv != KERN_SUCCESS) 320 return (rv); 321 vm_fault_fill_hold(m_hold, m); 322 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false); 323 VM_OBJECT_RUNLOCK(fs->first_object); 324 if (psind == 0 && !wired) 325 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR); 326 vm_map_lookup_done(fs->map, fs->entry); 327 curthread->td_ru.ru_minflt++; 328 return (KERN_SUCCESS); 329 } 330 331 static void 332 vm_fault_restore_map_lock(struct faultstate *fs) 333 { 334 335 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 336 MPASS(fs->first_object->paging_in_progress > 0); 337 338 if (!vm_map_trylock_read(fs->map)) { 339 VM_OBJECT_WUNLOCK(fs->first_object); 340 vm_map_lock_read(fs->map); 341 VM_OBJECT_WLOCK(fs->first_object); 342 } 343 fs->lookup_still_valid = true; 344 } 345 346 static void 347 vm_fault_populate_check_page(vm_page_t m) 348 { 349 350 /* 351 * Check each page to ensure that the pager is obeying the 352 * interface: the page must be installed in the object, fully 353 * valid, and exclusively busied. 354 */ 355 MPASS(m != NULL); 356 MPASS(m->valid == VM_PAGE_BITS_ALL); 357 MPASS(vm_page_xbusied(m)); 358 } 359 360 static void 361 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first, 362 vm_pindex_t last) 363 { 364 vm_page_t m; 365 vm_pindex_t pidx; 366 367 VM_OBJECT_ASSERT_WLOCKED(object); 368 MPASS(first <= last); 369 for (pidx = first, m = vm_page_lookup(object, pidx); 370 pidx <= last; pidx++, m = vm_page_next(m)) { 371 vm_fault_populate_check_page(m); 372 vm_page_lock(m); 373 vm_page_deactivate(m); 374 vm_page_unlock(m); 375 vm_page_xunbusy(m); 376 } 377 } 378 379 static int 380 vm_fault_populate(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot, 381 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold) 382 { 383 vm_page_t m; 384 vm_pindex_t map_first, map_last, pager_first, pager_last, pidx; 385 int rv; 386 387 MPASS(fs->object == fs->first_object); 388 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 389 MPASS(fs->first_object->paging_in_progress > 0); 390 MPASS(fs->first_object->backing_object == NULL); 391 MPASS(fs->lookup_still_valid); 392 393 pager_first = OFF_TO_IDX(fs->entry->offset); 394 pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1; 395 unlock_map(fs); 396 unlock_vp(fs); 397 398 /* 399 * Call the pager (driver) populate() method. 400 * 401 * There is no guarantee that the method will be called again 402 * if the current fault is for read, and a future fault is 403 * for write. Report the entry's maximum allowed protection 404 * to the driver. 405 */ 406 rv = vm_pager_populate(fs->first_object, fs->first_pindex, 407 fault_type, fs->entry->max_protection, &pager_first, &pager_last); 408 409 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 410 if (rv == VM_PAGER_BAD) { 411 /* 412 * VM_PAGER_BAD is the backdoor for a pager to request 413 * normal fault handling. 414 */ 415 vm_fault_restore_map_lock(fs); 416 if (fs->map->timestamp != fs->map_generation) 417 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */ 418 return (KERN_NOT_RECEIVER); 419 } 420 if (rv != VM_PAGER_OK) 421 return (KERN_FAILURE); /* AKA SIGSEGV */ 422 423 /* Ensure that the driver is obeying the interface. */ 424 MPASS(pager_first <= pager_last); 425 MPASS(fs->first_pindex <= pager_last); 426 MPASS(fs->first_pindex >= pager_first); 427 MPASS(pager_last < fs->first_object->size); 428 429 vm_fault_restore_map_lock(fs); 430 if (fs->map->timestamp != fs->map_generation) { 431 vm_fault_populate_cleanup(fs->first_object, pager_first, 432 pager_last); 433 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */ 434 } 435 436 /* 437 * The map is unchanged after our last unlock. Process the fault. 438 * 439 * The range [pager_first, pager_last] that is given to the 440 * pager is only a hint. The pager may populate any range 441 * within the object that includes the requested page index. 442 * In case the pager expanded the range, clip it to fit into 443 * the map entry. 444 */ 445 map_first = OFF_TO_IDX(fs->entry->offset); 446 if (map_first > pager_first) { 447 vm_fault_populate_cleanup(fs->first_object, pager_first, 448 map_first - 1); 449 pager_first = map_first; 450 } 451 map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1; 452 if (map_last < pager_last) { 453 vm_fault_populate_cleanup(fs->first_object, map_last + 1, 454 pager_last); 455 pager_last = map_last; 456 } 457 for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx); 458 pidx <= pager_last; pidx++, m = vm_page_next(m)) { 459 vm_fault_populate_check_page(m); 460 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, 461 true); 462 VM_OBJECT_WUNLOCK(fs->first_object); 463 pmap_enter(fs->map->pmap, fs->entry->start + IDX_TO_OFF(pidx) - 464 fs->entry->offset, m, prot, fault_type | (wired ? 465 PMAP_ENTER_WIRED : 0), 0); 466 VM_OBJECT_WLOCK(fs->first_object); 467 if (pidx == fs->first_pindex) 468 vm_fault_fill_hold(m_hold, m); 469 vm_page_lock(m); 470 if ((fault_flags & VM_FAULT_WIRE) != 0) { 471 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 472 vm_page_wire(m); 473 } else { 474 vm_page_activate(m); 475 } 476 vm_page_unlock(m); 477 vm_page_xunbusy(m); 478 } 479 curthread->td_ru.ru_majflt++; 480 return (KERN_SUCCESS); 481 } 482 483 /* 484 * vm_fault: 485 * 486 * Handle a page fault occurring at the given address, 487 * requiring the given permissions, in the map specified. 488 * If successful, the page is inserted into the 489 * associated physical map. 490 * 491 * NOTE: the given address should be truncated to the 492 * proper page address. 493 * 494 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 495 * a standard error specifying why the fault is fatal is returned. 496 * 497 * The map in question must be referenced, and remains so. 498 * Caller may hold no locks. 499 */ 500 int 501 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 502 int fault_flags) 503 { 504 struct thread *td; 505 int result; 506 507 td = curthread; 508 if ((td->td_pflags & TDP_NOFAULTING) != 0) 509 return (KERN_PROTECTION_FAILURE); 510 #ifdef KTRACE 511 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 512 ktrfault(vaddr, fault_type); 513 #endif 514 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 515 NULL); 516 #ifdef KTRACE 517 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 518 ktrfaultend(result); 519 #endif 520 return (result); 521 } 522 523 int 524 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 525 int fault_flags, vm_page_t *m_hold) 526 { 527 struct faultstate fs; 528 struct vnode *vp; 529 vm_object_t next_object, retry_object; 530 vm_offset_t e_end, e_start; 531 vm_pindex_t retry_pindex; 532 vm_prot_t prot, retry_prot; 533 int ahead, alloc_req, behind, cluster_offset, error, era, faultcount; 534 int locked, nera, result, rv; 535 u_char behavior; 536 boolean_t wired; /* Passed by reference. */ 537 bool dead, hardfault, is_first_object_locked; 538 539 VM_CNT_INC(v_vm_faults); 540 fs.vp = NULL; 541 faultcount = 0; 542 nera = -1; 543 hardfault = false; 544 545 RetryFault:; 546 547 /* 548 * Find the backing store object and offset into it to begin the 549 * search. 550 */ 551 fs.map = map; 552 result = vm_map_lookup(&fs.map, vaddr, fault_type | 553 VM_PROT_FAULT_LOOKUP, &fs.entry, &fs.first_object, 554 &fs.first_pindex, &prot, &wired); 555 if (result != KERN_SUCCESS) { 556 unlock_vp(&fs); 557 return (result); 558 } 559 560 fs.map_generation = fs.map->timestamp; 561 562 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 563 panic("%s: fault on nofault entry, addr: %#lx", 564 __func__, (u_long)vaddr); 565 } 566 567 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 568 fs.entry->wiring_thread != curthread) { 569 vm_map_unlock_read(fs.map); 570 vm_map_lock(fs.map); 571 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 572 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 573 unlock_vp(&fs); 574 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 575 vm_map_unlock_and_wait(fs.map, 0); 576 } else 577 vm_map_unlock(fs.map); 578 goto RetryFault; 579 } 580 581 MPASS((fs.entry->eflags & MAP_ENTRY_GUARD) == 0); 582 583 if (wired) 584 fault_type = prot | (fault_type & VM_PROT_COPY); 585 else 586 KASSERT((fault_flags & VM_FAULT_WIRE) == 0, 587 ("!wired && VM_FAULT_WIRE")); 588 589 /* 590 * Try to avoid lock contention on the top-level object through 591 * special-case handling of some types of page faults, specifically, 592 * those that are both (1) mapping an existing page from the top- 593 * level object and (2) not having to mark that object as containing 594 * dirty pages. Under these conditions, a read lock on the top-level 595 * object suffices, allowing multiple page faults of a similar type to 596 * run in parallel on the same top-level object. 597 */ 598 if (fs.vp == NULL /* avoid locked vnode leak */ && 599 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 && 600 /* avoid calling vm_object_set_writeable_dirty() */ 601 ((prot & VM_PROT_WRITE) == 0 || 602 (fs.first_object->type != OBJT_VNODE && 603 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 604 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 605 VM_OBJECT_RLOCK(fs.first_object); 606 if ((prot & VM_PROT_WRITE) == 0 || 607 (fs.first_object->type != OBJT_VNODE && 608 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 609 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0) { 610 rv = vm_fault_soft_fast(&fs, vaddr, prot, fault_type, 611 fault_flags, wired, m_hold); 612 if (rv == KERN_SUCCESS) 613 return (rv); 614 } 615 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 616 VM_OBJECT_RUNLOCK(fs.first_object); 617 VM_OBJECT_WLOCK(fs.first_object); 618 } 619 } else { 620 VM_OBJECT_WLOCK(fs.first_object); 621 } 622 623 /* 624 * Make a reference to this object to prevent its disposal while we 625 * are messing with it. Once we have the reference, the map is free 626 * to be diddled. Since objects reference their shadows (and copies), 627 * they will stay around as well. 628 * 629 * Bump the paging-in-progress count to prevent size changes (e.g. 630 * truncation operations) during I/O. 631 */ 632 vm_object_reference_locked(fs.first_object); 633 vm_object_pip_add(fs.first_object, 1); 634 635 fs.lookup_still_valid = true; 636 637 fs.first_m = NULL; 638 639 /* 640 * Search for the page at object/offset. 641 */ 642 fs.object = fs.first_object; 643 fs.pindex = fs.first_pindex; 644 while (TRUE) { 645 /* 646 * If the object is marked for imminent termination, 647 * we retry here, since the collapse pass has raced 648 * with us. Otherwise, if we see terminally dead 649 * object, return fail. 650 */ 651 if ((fs.object->flags & OBJ_DEAD) != 0) { 652 dead = fs.object->type == OBJT_DEAD; 653 unlock_and_deallocate(&fs); 654 if (dead) 655 return (KERN_PROTECTION_FAILURE); 656 pause("vmf_de", 1); 657 goto RetryFault; 658 } 659 660 /* 661 * See if page is resident 662 */ 663 fs.m = vm_page_lookup(fs.object, fs.pindex); 664 if (fs.m != NULL) { 665 /* 666 * Wait/Retry if the page is busy. We have to do this 667 * if the page is either exclusive or shared busy 668 * because the vm_pager may be using read busy for 669 * pageouts (and even pageins if it is the vnode 670 * pager), and we could end up trying to pagein and 671 * pageout the same page simultaneously. 672 * 673 * We can theoretically allow the busy case on a read 674 * fault if the page is marked valid, but since such 675 * pages are typically already pmap'd, putting that 676 * special case in might be more effort then it is 677 * worth. We cannot under any circumstances mess 678 * around with a shared busied page except, perhaps, 679 * to pmap it. 680 */ 681 if (vm_page_busied(fs.m)) { 682 /* 683 * Reference the page before unlocking and 684 * sleeping so that the page daemon is less 685 * likely to reclaim it. 686 */ 687 vm_page_aflag_set(fs.m, PGA_REFERENCED); 688 if (fs.object != fs.first_object) { 689 if (!VM_OBJECT_TRYWLOCK( 690 fs.first_object)) { 691 VM_OBJECT_WUNLOCK(fs.object); 692 VM_OBJECT_WLOCK(fs.first_object); 693 VM_OBJECT_WLOCK(fs.object); 694 } 695 vm_page_lock(fs.first_m); 696 vm_page_free(fs.first_m); 697 vm_page_unlock(fs.first_m); 698 vm_object_pip_wakeup(fs.first_object); 699 VM_OBJECT_WUNLOCK(fs.first_object); 700 fs.first_m = NULL; 701 } 702 unlock_map(&fs); 703 if (fs.m == vm_page_lookup(fs.object, 704 fs.pindex)) { 705 vm_page_sleep_if_busy(fs.m, "vmpfw"); 706 } 707 vm_object_pip_wakeup(fs.object); 708 VM_OBJECT_WUNLOCK(fs.object); 709 VM_CNT_INC(v_intrans); 710 vm_object_deallocate(fs.first_object); 711 goto RetryFault; 712 } 713 vm_page_lock(fs.m); 714 vm_page_remque(fs.m); 715 vm_page_unlock(fs.m); 716 717 /* 718 * Mark page busy for other processes, and the 719 * pagedaemon. If it still isn't completely valid 720 * (readable), jump to readrest, else break-out ( we 721 * found the page ). 722 */ 723 vm_page_xbusy(fs.m); 724 if (fs.m->valid != VM_PAGE_BITS_ALL) 725 goto readrest; 726 break; 727 } 728 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m)); 729 730 /* 731 * Page is not resident. If the pager might contain the page 732 * or this is the beginning of the search, allocate a new 733 * page. (Default objects are zero-fill, so there is no real 734 * pager for them.) 735 */ 736 if (fs.object->type != OBJT_DEFAULT || 737 fs.object == fs.first_object) { 738 if (fs.pindex >= fs.object->size) { 739 unlock_and_deallocate(&fs); 740 return (KERN_PROTECTION_FAILURE); 741 } 742 743 if (fs.object == fs.first_object && 744 (fs.first_object->flags & OBJ_POPULATE) != 0 && 745 fs.first_object->shadow_count == 0) { 746 rv = vm_fault_populate(&fs, vaddr, prot, 747 fault_type, fault_flags, wired, m_hold); 748 switch (rv) { 749 case KERN_SUCCESS: 750 case KERN_FAILURE: 751 unlock_and_deallocate(&fs); 752 return (rv); 753 case KERN_RESOURCE_SHORTAGE: 754 unlock_and_deallocate(&fs); 755 goto RetryFault; 756 case KERN_NOT_RECEIVER: 757 /* 758 * Pager's populate() method 759 * returned VM_PAGER_BAD. 760 */ 761 break; 762 default: 763 panic("inconsistent return codes"); 764 } 765 } 766 767 /* 768 * Allocate a new page for this object/offset pair. 769 * 770 * Unlocked read of the p_flag is harmless. At 771 * worst, the P_KILLED might be not observed 772 * there, and allocation can fail, causing 773 * restart and new reading of the p_flag. 774 */ 775 if (!vm_page_count_severe() || P_KILLED(curproc)) { 776 #if VM_NRESERVLEVEL > 0 777 vm_object_color(fs.object, atop(vaddr) - 778 fs.pindex); 779 #endif 780 alloc_req = P_KILLED(curproc) ? 781 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 782 if (fs.object->type != OBJT_VNODE && 783 fs.object->backing_object == NULL) 784 alloc_req |= VM_ALLOC_ZERO; 785 fs.m = vm_page_alloc(fs.object, fs.pindex, 786 alloc_req); 787 } 788 if (fs.m == NULL) { 789 unlock_and_deallocate(&fs); 790 VM_WAITPFAULT; 791 goto RetryFault; 792 } 793 } 794 795 readrest: 796 /* 797 * At this point, we have either allocated a new page or found 798 * an existing page that is only partially valid. 799 * 800 * We hold a reference on the current object and the page is 801 * exclusive busied. 802 */ 803 804 /* 805 * If the pager for the current object might have the page, 806 * then determine the number of additional pages to read and 807 * potentially reprioritize previously read pages for earlier 808 * reclamation. These operations should only be performed 809 * once per page fault. Even if the current pager doesn't 810 * have the page, the number of additional pages to read will 811 * apply to subsequent objects in the shadow chain. 812 */ 813 if (fs.object->type != OBJT_DEFAULT && nera == -1 && 814 !P_KILLED(curproc)) { 815 KASSERT(fs.lookup_still_valid, ("map unlocked")); 816 era = fs.entry->read_ahead; 817 behavior = vm_map_entry_behavior(fs.entry); 818 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 819 nera = 0; 820 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 821 nera = VM_FAULT_READ_AHEAD_MAX; 822 if (vaddr == fs.entry->next_read) 823 vm_fault_dontneed(&fs, vaddr, nera); 824 } else if (vaddr == fs.entry->next_read) { 825 /* 826 * This is a sequential fault. Arithmetically 827 * increase the requested number of pages in 828 * the read-ahead window. The requested 829 * number of pages is "# of sequential faults 830 * x (read ahead min + 1) + read ahead min" 831 */ 832 nera = VM_FAULT_READ_AHEAD_MIN; 833 if (era > 0) { 834 nera += era + 1; 835 if (nera > VM_FAULT_READ_AHEAD_MAX) 836 nera = VM_FAULT_READ_AHEAD_MAX; 837 } 838 if (era == VM_FAULT_READ_AHEAD_MAX) 839 vm_fault_dontneed(&fs, vaddr, nera); 840 } else { 841 /* 842 * This is a non-sequential fault. 843 */ 844 nera = 0; 845 } 846 if (era != nera) { 847 /* 848 * A read lock on the map suffices to update 849 * the read ahead count safely. 850 */ 851 fs.entry->read_ahead = nera; 852 } 853 854 /* 855 * Prepare for unlocking the map. Save the map 856 * entry's start and end addresses, which are used to 857 * optimize the size of the pager operation below. 858 * Even if the map entry's addresses change after 859 * unlocking the map, using the saved addresses is 860 * safe. 861 */ 862 e_start = fs.entry->start; 863 e_end = fs.entry->end; 864 } 865 866 /* 867 * Call the pager to retrieve the page if there is a chance 868 * that the pager has it, and potentially retrieve additional 869 * pages at the same time. 870 */ 871 if (fs.object->type != OBJT_DEFAULT) { 872 /* 873 * Release the map lock before locking the vnode or 874 * sleeping in the pager. (If the current object has 875 * a shadow, then an earlier iteration of this loop 876 * may have already unlocked the map.) 877 */ 878 unlock_map(&fs); 879 880 if (fs.object->type == OBJT_VNODE && 881 (vp = fs.object->handle) != fs.vp) { 882 /* 883 * Perform an unlock in case the desired vnode 884 * changed while the map was unlocked during a 885 * retry. 886 */ 887 unlock_vp(&fs); 888 889 locked = VOP_ISLOCKED(vp); 890 if (locked != LK_EXCLUSIVE) 891 locked = LK_SHARED; 892 893 /* 894 * We must not sleep acquiring the vnode lock 895 * while we have the page exclusive busied or 896 * the object's paging-in-progress count 897 * incremented. Otherwise, we could deadlock. 898 */ 899 error = vget(vp, locked | LK_CANRECURSE | 900 LK_NOWAIT, curthread); 901 if (error != 0) { 902 vhold(vp); 903 release_page(&fs); 904 unlock_and_deallocate(&fs); 905 error = vget(vp, locked | LK_RETRY | 906 LK_CANRECURSE, curthread); 907 vdrop(vp); 908 fs.vp = vp; 909 KASSERT(error == 0, 910 ("vm_fault: vget failed")); 911 goto RetryFault; 912 } 913 fs.vp = vp; 914 } 915 KASSERT(fs.vp == NULL || !fs.map->system_map, 916 ("vm_fault: vnode-backed object mapped by system map")); 917 918 /* 919 * Page in the requested page and hint the pager, 920 * that it may bring up surrounding pages. 921 */ 922 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM || 923 P_KILLED(curproc)) { 924 behind = 0; 925 ahead = 0; 926 } else { 927 /* Is this a sequential fault? */ 928 if (nera > 0) { 929 behind = 0; 930 ahead = nera; 931 } else { 932 /* 933 * Request a cluster of pages that is 934 * aligned to a VM_FAULT_READ_DEFAULT 935 * page offset boundary within the 936 * object. Alignment to a page offset 937 * boundary is more likely to coincide 938 * with the underlying file system 939 * block than alignment to a virtual 940 * address boundary. 941 */ 942 cluster_offset = fs.pindex % 943 VM_FAULT_READ_DEFAULT; 944 behind = ulmin(cluster_offset, 945 atop(vaddr - e_start)); 946 ahead = VM_FAULT_READ_DEFAULT - 1 - 947 cluster_offset; 948 } 949 ahead = ulmin(ahead, atop(e_end - vaddr) - 1); 950 } 951 rv = vm_pager_get_pages(fs.object, &fs.m, 1, 952 &behind, &ahead); 953 if (rv == VM_PAGER_OK) { 954 faultcount = behind + 1 + ahead; 955 hardfault = true; 956 break; /* break to PAGE HAS BEEN FOUND */ 957 } 958 if (rv == VM_PAGER_ERROR) 959 printf("vm_fault: pager read error, pid %d (%s)\n", 960 curproc->p_pid, curproc->p_comm); 961 962 /* 963 * If an I/O error occurred or the requested page was 964 * outside the range of the pager, clean up and return 965 * an error. 966 */ 967 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) { 968 vm_page_lock(fs.m); 969 if (fs.m->wire_count == 0) 970 vm_page_free(fs.m); 971 else 972 vm_page_xunbusy_maybelocked(fs.m); 973 vm_page_unlock(fs.m); 974 fs.m = NULL; 975 unlock_and_deallocate(&fs); 976 return (rv == VM_PAGER_ERROR ? KERN_FAILURE : 977 KERN_PROTECTION_FAILURE); 978 } 979 980 /* 981 * The requested page does not exist at this object/ 982 * offset. Remove the invalid page from the object, 983 * waking up anyone waiting for it, and continue on to 984 * the next object. However, if this is the top-level 985 * object, we must leave the busy page in place to 986 * prevent another process from rushing past us, and 987 * inserting the page in that object at the same time 988 * that we are. 989 */ 990 if (fs.object != fs.first_object) { 991 vm_page_lock(fs.m); 992 if (fs.m->wire_count == 0) 993 vm_page_free(fs.m); 994 else 995 vm_page_xunbusy_maybelocked(fs.m); 996 vm_page_unlock(fs.m); 997 fs.m = NULL; 998 } 999 } 1000 1001 /* 1002 * We get here if the object has default pager (or unwiring) 1003 * or the pager doesn't have the page. 1004 */ 1005 if (fs.object == fs.first_object) 1006 fs.first_m = fs.m; 1007 1008 /* 1009 * Move on to the next object. Lock the next object before 1010 * unlocking the current one. 1011 */ 1012 next_object = fs.object->backing_object; 1013 if (next_object == NULL) { 1014 /* 1015 * If there's no object left, fill the page in the top 1016 * object with zeros. 1017 */ 1018 if (fs.object != fs.first_object) { 1019 vm_object_pip_wakeup(fs.object); 1020 VM_OBJECT_WUNLOCK(fs.object); 1021 1022 fs.object = fs.first_object; 1023 fs.pindex = fs.first_pindex; 1024 fs.m = fs.first_m; 1025 VM_OBJECT_WLOCK(fs.object); 1026 } 1027 fs.first_m = NULL; 1028 1029 /* 1030 * Zero the page if necessary and mark it valid. 1031 */ 1032 if ((fs.m->flags & PG_ZERO) == 0) { 1033 pmap_zero_page(fs.m); 1034 } else { 1035 VM_CNT_INC(v_ozfod); 1036 } 1037 VM_CNT_INC(v_zfod); 1038 fs.m->valid = VM_PAGE_BITS_ALL; 1039 /* Don't try to prefault neighboring pages. */ 1040 faultcount = 1; 1041 break; /* break to PAGE HAS BEEN FOUND */ 1042 } else { 1043 KASSERT(fs.object != next_object, 1044 ("object loop %p", next_object)); 1045 VM_OBJECT_WLOCK(next_object); 1046 vm_object_pip_add(next_object, 1); 1047 if (fs.object != fs.first_object) 1048 vm_object_pip_wakeup(fs.object); 1049 fs.pindex += 1050 OFF_TO_IDX(fs.object->backing_object_offset); 1051 VM_OBJECT_WUNLOCK(fs.object); 1052 fs.object = next_object; 1053 } 1054 } 1055 1056 vm_page_assert_xbusied(fs.m); 1057 1058 /* 1059 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 1060 * is held.] 1061 */ 1062 1063 /* 1064 * If the page is being written, but isn't already owned by the 1065 * top-level object, we have to copy it into a new page owned by the 1066 * top-level object. 1067 */ 1068 if (fs.object != fs.first_object) { 1069 /* 1070 * We only really need to copy if we want to write it. 1071 */ 1072 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1073 /* 1074 * This allows pages to be virtually copied from a 1075 * backing_object into the first_object, where the 1076 * backing object has no other refs to it, and cannot 1077 * gain any more refs. Instead of a bcopy, we just 1078 * move the page from the backing object to the 1079 * first object. Note that we must mark the page 1080 * dirty in the first object so that it will go out 1081 * to swap when needed. 1082 */ 1083 is_first_object_locked = false; 1084 if ( 1085 /* 1086 * Only one shadow object 1087 */ 1088 (fs.object->shadow_count == 1) && 1089 /* 1090 * No COW refs, except us 1091 */ 1092 (fs.object->ref_count == 1) && 1093 /* 1094 * No one else can look this object up 1095 */ 1096 (fs.object->handle == NULL) && 1097 /* 1098 * No other ways to look the object up 1099 */ 1100 ((fs.object->type == OBJT_DEFAULT) || 1101 (fs.object->type == OBJT_SWAP)) && 1102 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 1103 /* 1104 * We don't chase down the shadow chain 1105 */ 1106 fs.object == fs.first_object->backing_object) { 1107 vm_page_lock(fs.m); 1108 vm_page_remove(fs.m); 1109 vm_page_unlock(fs.m); 1110 vm_page_lock(fs.first_m); 1111 vm_page_replace_checked(fs.m, fs.first_object, 1112 fs.first_pindex, fs.first_m); 1113 vm_page_free(fs.first_m); 1114 vm_page_unlock(fs.first_m); 1115 vm_page_dirty(fs.m); 1116 #if VM_NRESERVLEVEL > 0 1117 /* 1118 * Rename the reservation. 1119 */ 1120 vm_reserv_rename(fs.m, fs.first_object, 1121 fs.object, OFF_TO_IDX( 1122 fs.first_object->backing_object_offset)); 1123 #endif 1124 /* 1125 * Removing the page from the backing object 1126 * unbusied it. 1127 */ 1128 vm_page_xbusy(fs.m); 1129 fs.first_m = fs.m; 1130 fs.m = NULL; 1131 VM_CNT_INC(v_cow_optim); 1132 } else { 1133 /* 1134 * Oh, well, lets copy it. 1135 */ 1136 pmap_copy_page(fs.m, fs.first_m); 1137 fs.first_m->valid = VM_PAGE_BITS_ALL; 1138 if (wired && (fault_flags & 1139 VM_FAULT_WIRE) == 0) { 1140 vm_page_lock(fs.first_m); 1141 vm_page_wire(fs.first_m); 1142 vm_page_unlock(fs.first_m); 1143 1144 vm_page_lock(fs.m); 1145 vm_page_unwire(fs.m, PQ_INACTIVE); 1146 vm_page_unlock(fs.m); 1147 } 1148 /* 1149 * We no longer need the old page or object. 1150 */ 1151 release_page(&fs); 1152 } 1153 /* 1154 * fs.object != fs.first_object due to above 1155 * conditional 1156 */ 1157 vm_object_pip_wakeup(fs.object); 1158 VM_OBJECT_WUNLOCK(fs.object); 1159 /* 1160 * Only use the new page below... 1161 */ 1162 fs.object = fs.first_object; 1163 fs.pindex = fs.first_pindex; 1164 fs.m = fs.first_m; 1165 if (!is_first_object_locked) 1166 VM_OBJECT_WLOCK(fs.object); 1167 VM_CNT_INC(v_cow_faults); 1168 curthread->td_cow++; 1169 } else { 1170 prot &= ~VM_PROT_WRITE; 1171 } 1172 } 1173 1174 /* 1175 * We must verify that the maps have not changed since our last 1176 * lookup. 1177 */ 1178 if (!fs.lookup_still_valid) { 1179 if (!vm_map_trylock_read(fs.map)) { 1180 release_page(&fs); 1181 unlock_and_deallocate(&fs); 1182 goto RetryFault; 1183 } 1184 fs.lookup_still_valid = true; 1185 if (fs.map->timestamp != fs.map_generation) { 1186 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 1187 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 1188 1189 /* 1190 * If we don't need the page any longer, put it on the inactive 1191 * list (the easiest thing to do here). If no one needs it, 1192 * pageout will grab it eventually. 1193 */ 1194 if (result != KERN_SUCCESS) { 1195 release_page(&fs); 1196 unlock_and_deallocate(&fs); 1197 1198 /* 1199 * If retry of map lookup would have blocked then 1200 * retry fault from start. 1201 */ 1202 if (result == KERN_FAILURE) 1203 goto RetryFault; 1204 return (result); 1205 } 1206 if ((retry_object != fs.first_object) || 1207 (retry_pindex != fs.first_pindex)) { 1208 release_page(&fs); 1209 unlock_and_deallocate(&fs); 1210 goto RetryFault; 1211 } 1212 1213 /* 1214 * Check whether the protection has changed or the object has 1215 * been copied while we left the map unlocked. Changing from 1216 * read to write permission is OK - we leave the page 1217 * write-protected, and catch the write fault. Changing from 1218 * write to read permission means that we can't mark the page 1219 * write-enabled after all. 1220 */ 1221 prot &= retry_prot; 1222 } 1223 } 1224 1225 /* 1226 * If the page was filled by a pager, save the virtual address that 1227 * should be faulted on next under a sequential access pattern to the 1228 * map entry. A read lock on the map suffices to update this address 1229 * safely. 1230 */ 1231 if (hardfault) 1232 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE; 1233 1234 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true); 1235 vm_page_assert_xbusied(fs.m); 1236 1237 /* 1238 * Page must be completely valid or it is not fit to 1239 * map into user space. vm_pager_get_pages() ensures this. 1240 */ 1241 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 1242 ("vm_fault: page %p partially invalid", fs.m)); 1243 VM_OBJECT_WUNLOCK(fs.object); 1244 1245 /* 1246 * Put this page into the physical map. We had to do the unlock above 1247 * because pmap_enter() may sleep. We don't put the page 1248 * back on the active queue until later so that the pageout daemon 1249 * won't find it (yet). 1250 */ 1251 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 1252 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 1253 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 1254 wired == 0) 1255 vm_fault_prefault(&fs, vaddr, 1256 faultcount > 0 ? behind : PFBAK, 1257 faultcount > 0 ? ahead : PFFOR); 1258 VM_OBJECT_WLOCK(fs.object); 1259 vm_page_lock(fs.m); 1260 1261 /* 1262 * If the page is not wired down, then put it where the pageout daemon 1263 * can find it. 1264 */ 1265 if ((fault_flags & VM_FAULT_WIRE) != 0) { 1266 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 1267 vm_page_wire(fs.m); 1268 } else 1269 vm_page_activate(fs.m); 1270 if (m_hold != NULL) { 1271 *m_hold = fs.m; 1272 vm_page_hold(fs.m); 1273 } 1274 vm_page_unlock(fs.m); 1275 vm_page_xunbusy(fs.m); 1276 1277 /* 1278 * Unlock everything, and return 1279 */ 1280 unlock_and_deallocate(&fs); 1281 if (hardfault) { 1282 VM_CNT_INC(v_io_faults); 1283 curthread->td_ru.ru_majflt++; 1284 #ifdef RACCT 1285 if (racct_enable && fs.object->type == OBJT_VNODE) { 1286 PROC_LOCK(curproc); 1287 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1288 racct_add_force(curproc, RACCT_WRITEBPS, 1289 PAGE_SIZE + behind * PAGE_SIZE); 1290 racct_add_force(curproc, RACCT_WRITEIOPS, 1); 1291 } else { 1292 racct_add_force(curproc, RACCT_READBPS, 1293 PAGE_SIZE + ahead * PAGE_SIZE); 1294 racct_add_force(curproc, RACCT_READIOPS, 1); 1295 } 1296 PROC_UNLOCK(curproc); 1297 } 1298 #endif 1299 } else 1300 curthread->td_ru.ru_minflt++; 1301 1302 return (KERN_SUCCESS); 1303 } 1304 1305 /* 1306 * Speed up the reclamation of pages that precede the faulting pindex within 1307 * the first object of the shadow chain. Essentially, perform the equivalent 1308 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1309 * the faulting pindex by the cluster size when the pages read by vm_fault() 1310 * cross a cluster-size boundary. The cluster size is the greater of the 1311 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1312 * 1313 * When "fs->first_object" is a shadow object, the pages in the backing object 1314 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1315 * function must only be concerned with pages in the first object. 1316 */ 1317 static void 1318 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1319 { 1320 vm_map_entry_t entry; 1321 vm_object_t first_object, object; 1322 vm_offset_t end, start; 1323 vm_page_t m, m_next; 1324 vm_pindex_t pend, pstart; 1325 vm_size_t size; 1326 1327 object = fs->object; 1328 VM_OBJECT_ASSERT_WLOCKED(object); 1329 first_object = fs->first_object; 1330 if (first_object != object) { 1331 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1332 VM_OBJECT_WUNLOCK(object); 1333 VM_OBJECT_WLOCK(first_object); 1334 VM_OBJECT_WLOCK(object); 1335 } 1336 } 1337 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1338 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1339 size = VM_FAULT_DONTNEED_MIN; 1340 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1341 size = pagesizes[1]; 1342 end = rounddown2(vaddr, size); 1343 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1344 (entry = fs->entry)->start < end) { 1345 if (end - entry->start < size) 1346 start = entry->start; 1347 else 1348 start = end - size; 1349 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1350 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1351 entry->start); 1352 m_next = vm_page_find_least(first_object, pstart); 1353 pend = OFF_TO_IDX(entry->offset) + atop(end - 1354 entry->start); 1355 while ((m = m_next) != NULL && m->pindex < pend) { 1356 m_next = TAILQ_NEXT(m, listq); 1357 if (m->valid != VM_PAGE_BITS_ALL || 1358 vm_page_busied(m)) 1359 continue; 1360 1361 /* 1362 * Don't clear PGA_REFERENCED, since it would 1363 * likely represent a reference by a different 1364 * process. 1365 * 1366 * Typically, at this point, prefetched pages 1367 * are still in the inactive queue. Only 1368 * pages that triggered page faults are in the 1369 * active queue. 1370 */ 1371 vm_page_lock(m); 1372 vm_page_deactivate(m); 1373 vm_page_unlock(m); 1374 } 1375 } 1376 } 1377 if (first_object != object) 1378 VM_OBJECT_WUNLOCK(first_object); 1379 } 1380 1381 /* 1382 * vm_fault_prefault provides a quick way of clustering 1383 * pagefaults into a processes address space. It is a "cousin" 1384 * of vm_map_pmap_enter, except it runs at page fault time instead 1385 * of mmap time. 1386 */ 1387 static void 1388 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1389 int backward, int forward) 1390 { 1391 pmap_t pmap; 1392 vm_map_entry_t entry; 1393 vm_object_t backing_object, lobject; 1394 vm_offset_t addr, starta; 1395 vm_pindex_t pindex; 1396 vm_page_t m; 1397 int i; 1398 1399 pmap = fs->map->pmap; 1400 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1401 return; 1402 1403 entry = fs->entry; 1404 1405 if (addra < backward * PAGE_SIZE) { 1406 starta = entry->start; 1407 } else { 1408 starta = addra - backward * PAGE_SIZE; 1409 if (starta < entry->start) 1410 starta = entry->start; 1411 } 1412 1413 /* 1414 * Generate the sequence of virtual addresses that are candidates for 1415 * prefaulting in an outward spiral from the faulting virtual address, 1416 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1417 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1418 * If the candidate address doesn't have a backing physical page, then 1419 * the loop immediately terminates. 1420 */ 1421 for (i = 0; i < 2 * imax(backward, forward); i++) { 1422 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1423 PAGE_SIZE); 1424 if (addr > addra + forward * PAGE_SIZE) 1425 addr = 0; 1426 1427 if (addr < starta || addr >= entry->end) 1428 continue; 1429 1430 if (!pmap_is_prefaultable(pmap, addr)) 1431 continue; 1432 1433 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1434 lobject = entry->object.vm_object; 1435 VM_OBJECT_RLOCK(lobject); 1436 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1437 lobject->type == OBJT_DEFAULT && 1438 (backing_object = lobject->backing_object) != NULL) { 1439 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1440 0, ("vm_fault_prefault: unaligned object offset")); 1441 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1442 VM_OBJECT_RLOCK(backing_object); 1443 VM_OBJECT_RUNLOCK(lobject); 1444 lobject = backing_object; 1445 } 1446 if (m == NULL) { 1447 VM_OBJECT_RUNLOCK(lobject); 1448 break; 1449 } 1450 if (m->valid == VM_PAGE_BITS_ALL && 1451 (m->flags & PG_FICTITIOUS) == 0) 1452 pmap_enter_quick(pmap, addr, m, entry->protection); 1453 VM_OBJECT_RUNLOCK(lobject); 1454 } 1455 } 1456 1457 /* 1458 * Hold each of the physical pages that are mapped by the specified range of 1459 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1460 * and allow the specified types of access, "prot". If all of the implied 1461 * pages are successfully held, then the number of held pages is returned 1462 * together with pointers to those pages in the array "ma". However, if any 1463 * of the pages cannot be held, -1 is returned. 1464 */ 1465 int 1466 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1467 vm_prot_t prot, vm_page_t *ma, int max_count) 1468 { 1469 vm_offset_t end, va; 1470 vm_page_t *mp; 1471 int count; 1472 boolean_t pmap_failed; 1473 1474 if (len == 0) 1475 return (0); 1476 end = round_page(addr + len); 1477 addr = trunc_page(addr); 1478 1479 /* 1480 * Check for illegal addresses. 1481 */ 1482 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1483 return (-1); 1484 1485 if (atop(end - addr) > max_count) 1486 panic("vm_fault_quick_hold_pages: count > max_count"); 1487 count = atop(end - addr); 1488 1489 /* 1490 * Most likely, the physical pages are resident in the pmap, so it is 1491 * faster to try pmap_extract_and_hold() first. 1492 */ 1493 pmap_failed = FALSE; 1494 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1495 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1496 if (*mp == NULL) 1497 pmap_failed = TRUE; 1498 else if ((prot & VM_PROT_WRITE) != 0 && 1499 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1500 /* 1501 * Explicitly dirty the physical page. Otherwise, the 1502 * caller's changes may go unnoticed because they are 1503 * performed through an unmanaged mapping or by a DMA 1504 * operation. 1505 * 1506 * The object lock is not held here. 1507 * See vm_page_clear_dirty_mask(). 1508 */ 1509 vm_page_dirty(*mp); 1510 } 1511 } 1512 if (pmap_failed) { 1513 /* 1514 * One or more pages could not be held by the pmap. Either no 1515 * page was mapped at the specified virtual address or that 1516 * mapping had insufficient permissions. Attempt to fault in 1517 * and hold these pages. 1518 */ 1519 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1520 if (*mp == NULL && vm_fault_hold(map, va, prot, 1521 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1522 goto error; 1523 } 1524 return (count); 1525 error: 1526 for (mp = ma; mp < ma + count; mp++) 1527 if (*mp != NULL) { 1528 vm_page_lock(*mp); 1529 vm_page_unhold(*mp); 1530 vm_page_unlock(*mp); 1531 } 1532 return (-1); 1533 } 1534 1535 /* 1536 * Routine: 1537 * vm_fault_copy_entry 1538 * Function: 1539 * Create new shadow object backing dst_entry with private copy of 1540 * all underlying pages. When src_entry is equal to dst_entry, 1541 * function implements COW for wired-down map entry. Otherwise, 1542 * it forks wired entry into dst_map. 1543 * 1544 * In/out conditions: 1545 * The source and destination maps must be locked for write. 1546 * The source map entry must be wired down (or be a sharing map 1547 * entry corresponding to a main map entry that is wired down). 1548 */ 1549 void 1550 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1551 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1552 vm_ooffset_t *fork_charge) 1553 { 1554 vm_object_t backing_object, dst_object, object, src_object; 1555 vm_pindex_t dst_pindex, pindex, src_pindex; 1556 vm_prot_t access, prot; 1557 vm_offset_t vaddr; 1558 vm_page_t dst_m; 1559 vm_page_t src_m; 1560 boolean_t upgrade; 1561 1562 #ifdef lint 1563 src_map++; 1564 #endif /* lint */ 1565 1566 upgrade = src_entry == dst_entry; 1567 access = prot = dst_entry->protection; 1568 1569 src_object = src_entry->object.vm_object; 1570 src_pindex = OFF_TO_IDX(src_entry->offset); 1571 1572 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1573 dst_object = src_object; 1574 vm_object_reference(dst_object); 1575 } else { 1576 /* 1577 * Create the top-level object for the destination entry. (Doesn't 1578 * actually shadow anything - we copy the pages directly.) 1579 */ 1580 dst_object = vm_object_allocate(OBJT_DEFAULT, 1581 atop(dst_entry->end - dst_entry->start)); 1582 #if VM_NRESERVLEVEL > 0 1583 dst_object->flags |= OBJ_COLORED; 1584 dst_object->pg_color = atop(dst_entry->start); 1585 #endif 1586 } 1587 1588 VM_OBJECT_WLOCK(dst_object); 1589 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1590 ("vm_fault_copy_entry: vm_object not NULL")); 1591 if (src_object != dst_object) { 1592 dst_entry->object.vm_object = dst_object; 1593 dst_entry->offset = 0; 1594 dst_object->charge = dst_entry->end - dst_entry->start; 1595 } 1596 if (fork_charge != NULL) { 1597 KASSERT(dst_entry->cred == NULL, 1598 ("vm_fault_copy_entry: leaked swp charge")); 1599 dst_object->cred = curthread->td_ucred; 1600 crhold(dst_object->cred); 1601 *fork_charge += dst_object->charge; 1602 } else if (dst_object->cred == NULL) { 1603 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1604 dst_entry)); 1605 dst_object->cred = dst_entry->cred; 1606 dst_entry->cred = NULL; 1607 } 1608 1609 /* 1610 * If not an upgrade, then enter the mappings in the pmap as 1611 * read and/or execute accesses. Otherwise, enter them as 1612 * write accesses. 1613 * 1614 * A writeable large page mapping is only created if all of 1615 * the constituent small page mappings are modified. Marking 1616 * PTEs as modified on inception allows promotion to happen 1617 * without taking potentially large number of soft faults. 1618 */ 1619 if (!upgrade) 1620 access &= ~VM_PROT_WRITE; 1621 1622 /* 1623 * Loop through all of the virtual pages within the entry's 1624 * range, copying each page from the source object to the 1625 * destination object. Since the source is wired, those pages 1626 * must exist. In contrast, the destination is pageable. 1627 * Since the destination object does share any backing storage 1628 * with the source object, all of its pages must be dirtied, 1629 * regardless of whether they can be written. 1630 */ 1631 for (vaddr = dst_entry->start, dst_pindex = 0; 1632 vaddr < dst_entry->end; 1633 vaddr += PAGE_SIZE, dst_pindex++) { 1634 again: 1635 /* 1636 * Find the page in the source object, and copy it in. 1637 * Because the source is wired down, the page will be 1638 * in memory. 1639 */ 1640 if (src_object != dst_object) 1641 VM_OBJECT_RLOCK(src_object); 1642 object = src_object; 1643 pindex = src_pindex + dst_pindex; 1644 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1645 (backing_object = object->backing_object) != NULL) { 1646 /* 1647 * Unless the source mapping is read-only or 1648 * it is presently being upgraded from 1649 * read-only, the first object in the shadow 1650 * chain should provide all of the pages. In 1651 * other words, this loop body should never be 1652 * executed when the source mapping is already 1653 * read/write. 1654 */ 1655 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1656 upgrade, 1657 ("vm_fault_copy_entry: main object missing page")); 1658 1659 VM_OBJECT_RLOCK(backing_object); 1660 pindex += OFF_TO_IDX(object->backing_object_offset); 1661 if (object != dst_object) 1662 VM_OBJECT_RUNLOCK(object); 1663 object = backing_object; 1664 } 1665 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1666 1667 if (object != dst_object) { 1668 /* 1669 * Allocate a page in the destination object. 1670 */ 1671 dst_m = vm_page_alloc(dst_object, (src_object == 1672 dst_object ? src_pindex : 0) + dst_pindex, 1673 VM_ALLOC_NORMAL); 1674 if (dst_m == NULL) { 1675 VM_OBJECT_WUNLOCK(dst_object); 1676 VM_OBJECT_RUNLOCK(object); 1677 VM_WAIT; 1678 VM_OBJECT_WLOCK(dst_object); 1679 goto again; 1680 } 1681 pmap_copy_page(src_m, dst_m); 1682 VM_OBJECT_RUNLOCK(object); 1683 dst_m->valid = VM_PAGE_BITS_ALL; 1684 dst_m->dirty = VM_PAGE_BITS_ALL; 1685 } else { 1686 dst_m = src_m; 1687 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1688 goto again; 1689 vm_page_xbusy(dst_m); 1690 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1691 ("invalid dst page %p", dst_m)); 1692 } 1693 VM_OBJECT_WUNLOCK(dst_object); 1694 1695 /* 1696 * Enter it in the pmap. If a wired, copy-on-write 1697 * mapping is being replaced by a write-enabled 1698 * mapping, then wire that new mapping. 1699 */ 1700 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1701 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1702 1703 /* 1704 * Mark it no longer busy, and put it on the active list. 1705 */ 1706 VM_OBJECT_WLOCK(dst_object); 1707 1708 if (upgrade) { 1709 if (src_m != dst_m) { 1710 vm_page_lock(src_m); 1711 vm_page_unwire(src_m, PQ_INACTIVE); 1712 vm_page_unlock(src_m); 1713 vm_page_lock(dst_m); 1714 vm_page_wire(dst_m); 1715 vm_page_unlock(dst_m); 1716 } else { 1717 KASSERT(dst_m->wire_count > 0, 1718 ("dst_m %p is not wired", dst_m)); 1719 } 1720 } else { 1721 vm_page_lock(dst_m); 1722 vm_page_activate(dst_m); 1723 vm_page_unlock(dst_m); 1724 } 1725 vm_page_xunbusy(dst_m); 1726 } 1727 VM_OBJECT_WUNLOCK(dst_object); 1728 if (upgrade) { 1729 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1730 vm_object_deallocate(src_object); 1731 } 1732 } 1733 1734 /* 1735 * Block entry into the machine-independent layer's page fault handler by 1736 * the calling thread. Subsequent calls to vm_fault() by that thread will 1737 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1738 * spurious page faults. 1739 */ 1740 int 1741 vm_fault_disable_pagefaults(void) 1742 { 1743 1744 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1745 } 1746 1747 void 1748 vm_fault_enable_pagefaults(int save) 1749 { 1750 1751 curthread_pflags_restore(save); 1752 } 1753