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sys/vm/vm_fault.c
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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, bool obj_locked); 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, since the page is now dirty, we can possibly tell 240 * the pager to release any swap backing the page. Calling 241 * the pager requires a write lock on the object. 242 */ 243 if (need_dirty) 244 vm_page_dirty(m); 245 if (!set_wd) 246 vm_page_unlock(m); 247 else if (need_dirty) 248 vm_pager_page_unswapped(m); 249 } 250 251 static void 252 vm_fault_fill_hold(vm_page_t *m_hold, vm_page_t m) 253 { 254 255 if (m_hold != NULL) { 256 *m_hold = m; 257 vm_page_lock(m); 258 vm_page_hold(m); 259 vm_page_unlock(m); 260 } 261 } 262 263 /* 264 * Unlocks fs.first_object and fs.map on success. 265 */ 266 static int 267 vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot, 268 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold) 269 { 270 vm_page_t m, m_map; 271 #if defined(__amd64__) && VM_NRESERVLEVEL > 0 272 vm_page_t m_super; 273 int flags; 274 #endif 275 int psind, rv; 276 277 MPASS(fs->vp == NULL); 278 m = vm_page_lookup(fs->first_object, fs->first_pindex); 279 /* A busy page can be mapped for read|execute access. */ 280 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 281 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 282 return (KERN_FAILURE); 283 m_map = m; 284 psind = 0; 285 #if defined(__amd64__) && VM_NRESERVLEVEL > 0 286 if ((m->flags & PG_FICTITIOUS) == 0 && 287 (m_super = vm_reserv_to_superpage(m)) != NULL && 288 rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start && 289 roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end && 290 (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) & 291 (pagesizes[m_super->psind] - 1)) && 292 pmap_ps_enabled(fs->map->pmap)) { 293 flags = PS_ALL_VALID; 294 if ((prot & VM_PROT_WRITE) != 0) { 295 /* 296 * Create a superpage mapping allowing write access 297 * only if none of the constituent pages are busy and 298 * all of them are already dirty (except possibly for 299 * the page that was faulted on). 300 */ 301 flags |= PS_NONE_BUSY; 302 if ((fs->first_object->flags & OBJ_UNMANAGED) == 0) 303 flags |= PS_ALL_DIRTY; 304 } 305 if (vm_page_ps_test(m_super, flags, m)) { 306 m_map = m_super; 307 psind = m_super->psind; 308 vaddr = rounddown2(vaddr, pagesizes[psind]); 309 /* Preset the modified bit for dirty superpages. */ 310 if ((flags & PS_ALL_DIRTY) != 0) 311 fault_type |= VM_PROT_WRITE; 312 } 313 } 314 #endif 315 rv = pmap_enter(fs->map->pmap, vaddr, m_map, prot, fault_type | 316 PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), psind); 317 if (rv != KERN_SUCCESS) 318 return (rv); 319 vm_fault_fill_hold(m_hold, m); 320 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false); 321 if (psind == 0 && !wired) 322 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true); 323 VM_OBJECT_RUNLOCK(fs->first_object); 324 vm_map_lookup_done(fs->map, fs->entry); 325 curthread->td_ru.ru_minflt++; 326 return (KERN_SUCCESS); 327 } 328 329 static void 330 vm_fault_restore_map_lock(struct faultstate *fs) 331 { 332 333 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 334 MPASS(fs->first_object->paging_in_progress > 0); 335 336 if (!vm_map_trylock_read(fs->map)) { 337 VM_OBJECT_WUNLOCK(fs->first_object); 338 vm_map_lock_read(fs->map); 339 VM_OBJECT_WLOCK(fs->first_object); 340 } 341 fs->lookup_still_valid = true; 342 } 343 344 static void 345 vm_fault_populate_check_page(vm_page_t m) 346 { 347 348 /* 349 * Check each page to ensure that the pager is obeying the 350 * interface: the page must be installed in the object, fully 351 * valid, and exclusively busied. 352 */ 353 MPASS(m != NULL); 354 MPASS(m->valid == VM_PAGE_BITS_ALL); 355 MPASS(vm_page_xbusied(m)); 356 } 357 358 static void 359 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first, 360 vm_pindex_t last) 361 { 362 vm_page_t m; 363 vm_pindex_t pidx; 364 365 VM_OBJECT_ASSERT_WLOCKED(object); 366 MPASS(first <= last); 367 for (pidx = first, m = vm_page_lookup(object, pidx); 368 pidx <= last; pidx++, m = vm_page_next(m)) { 369 vm_fault_populate_check_page(m); 370 vm_page_lock(m); 371 vm_page_deactivate(m); 372 vm_page_unlock(m); 373 vm_page_xunbusy(m); 374 } 375 } 376 377 static int 378 vm_fault_populate(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot, 379 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold) 380 { 381 vm_page_t m; 382 vm_pindex_t map_first, map_last, pager_first, pager_last, pidx; 383 int rv; 384 385 MPASS(fs->object == fs->first_object); 386 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 387 MPASS(fs->first_object->paging_in_progress > 0); 388 MPASS(fs->first_object->backing_object == NULL); 389 MPASS(fs->lookup_still_valid); 390 391 pager_first = OFF_TO_IDX(fs->entry->offset); 392 pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1; 393 unlock_map(fs); 394 unlock_vp(fs); 395 396 /* 397 * Call the pager (driver) populate() method. 398 * 399 * There is no guarantee that the method will be called again 400 * if the current fault is for read, and a future fault is 401 * for write. Report the entry's maximum allowed protection 402 * to the driver. 403 */ 404 rv = vm_pager_populate(fs->first_object, fs->first_pindex, 405 fault_type, fs->entry->max_protection, &pager_first, &pager_last); 406 407 VM_OBJECT_ASSERT_WLOCKED(fs->first_object); 408 if (rv == VM_PAGER_BAD) { 409 /* 410 * VM_PAGER_BAD is the backdoor for a pager to request 411 * normal fault handling. 412 */ 413 vm_fault_restore_map_lock(fs); 414 if (fs->map->timestamp != fs->map_generation) 415 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */ 416 return (KERN_NOT_RECEIVER); 417 } 418 if (rv != VM_PAGER_OK) 419 return (KERN_FAILURE); /* AKA SIGSEGV */ 420 421 /* Ensure that the driver is obeying the interface. */ 422 MPASS(pager_first <= pager_last); 423 MPASS(fs->first_pindex <= pager_last); 424 MPASS(fs->first_pindex >= pager_first); 425 MPASS(pager_last < fs->first_object->size); 426 427 vm_fault_restore_map_lock(fs); 428 if (fs->map->timestamp != fs->map_generation) { 429 vm_fault_populate_cleanup(fs->first_object, pager_first, 430 pager_last); 431 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */ 432 } 433 434 /* 435 * The map is unchanged after our last unlock. Process the fault. 436 * 437 * The range [pager_first, pager_last] that is given to the 438 * pager is only a hint. The pager may populate any range 439 * within the object that includes the requested page index. 440 * In case the pager expanded the range, clip it to fit into 441 * the map entry. 442 */ 443 map_first = OFF_TO_IDX(fs->entry->offset); 444 if (map_first > pager_first) { 445 vm_fault_populate_cleanup(fs->first_object, pager_first, 446 map_first - 1); 447 pager_first = map_first; 448 } 449 map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1; 450 if (map_last < pager_last) { 451 vm_fault_populate_cleanup(fs->first_object, map_last + 1, 452 pager_last); 453 pager_last = map_last; 454 } 455 for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx); 456 pidx <= pager_last; pidx++, m = vm_page_next(m)) { 457 vm_fault_populate_check_page(m); 458 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, 459 true); 460 VM_OBJECT_WUNLOCK(fs->first_object); 461 pmap_enter(fs->map->pmap, fs->entry->start + IDX_TO_OFF(pidx) - 462 fs->entry->offset, m, prot, fault_type | (wired ? 463 PMAP_ENTER_WIRED : 0), 0); 464 VM_OBJECT_WLOCK(fs->first_object); 465 if (pidx == fs->first_pindex) 466 vm_fault_fill_hold(m_hold, m); 467 vm_page_lock(m); 468 if ((fault_flags & VM_FAULT_WIRE) != 0) { 469 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 470 vm_page_wire(m); 471 } else { 472 vm_page_activate(m); 473 } 474 vm_page_unlock(m); 475 vm_page_xunbusy(m); 476 } 477 curthread->td_ru.ru_majflt++; 478 return (KERN_SUCCESS); 479 } 480 481 /* 482 * vm_fault: 483 * 484 * Handle a page fault occurring at the given address, 485 * requiring the given permissions, in the map specified. 486 * If successful, the page is inserted into the 487 * associated physical map. 488 * 489 * NOTE: the given address should be truncated to the 490 * proper page address. 491 * 492 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 493 * a standard error specifying why the fault is fatal is returned. 494 * 495 * The map in question must be referenced, and remains so. 496 * Caller may hold no locks. 497 */ 498 int 499 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 500 int fault_flags) 501 { 502 struct thread *td; 503 int result; 504 505 td = curthread; 506 if ((td->td_pflags & TDP_NOFAULTING) != 0) 507 return (KERN_PROTECTION_FAILURE); 508 #ifdef KTRACE 509 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 510 ktrfault(vaddr, fault_type); 511 #endif 512 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 513 NULL); 514 #ifdef KTRACE 515 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 516 ktrfaultend(result); 517 #endif 518 return (result); 519 } 520 521 int 522 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 523 int fault_flags, vm_page_t *m_hold) 524 { 525 struct faultstate fs; 526 struct vnode *vp; 527 vm_object_t next_object, retry_object; 528 vm_offset_t e_end, e_start; 529 vm_pindex_t retry_pindex; 530 vm_prot_t prot, retry_prot; 531 int ahead, alloc_req, behind, cluster_offset, error, era, faultcount; 532 int locked, nera, result, rv; 533 u_char behavior; 534 boolean_t wired; /* Passed by reference. */ 535 bool dead, hardfault, is_first_object_locked; 536 537 PCPU_INC(cnt.v_vm_faults); 538 fs.vp = NULL; 539 faultcount = 0; 540 nera = -1; 541 hardfault = false; 542 543 RetryFault:; 544 545 /* 546 * Find the backing store object and offset into it to begin the 547 * search. 548 */ 549 fs.map = map; 550 result = vm_map_lookup(&fs.map, vaddr, fault_type | 551 VM_PROT_FAULT_LOOKUP, &fs.entry, &fs.first_object, 552 &fs.first_pindex, &prot, &wired); 553 if (result != KERN_SUCCESS) { 554 unlock_vp(&fs); 555 return (result); 556 } 557 558 fs.map_generation = fs.map->timestamp; 559 560 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 561 panic("vm_fault: fault on nofault entry, addr: %lx", 562 (u_long)vaddr); 563 } 564 565 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 566 fs.entry->wiring_thread != curthread) { 567 vm_map_unlock_read(fs.map); 568 vm_map_lock(fs.map); 569 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 570 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 571 unlock_vp(&fs); 572 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 573 vm_map_unlock_and_wait(fs.map, 0); 574 } else 575 vm_map_unlock(fs.map); 576 goto RetryFault; 577 } 578 579 MPASS((fs.entry->eflags & MAP_ENTRY_GUARD) == 0); 580 581 if (wired) 582 fault_type = prot | (fault_type & VM_PROT_COPY); 583 else 584 KASSERT((fault_flags & VM_FAULT_WIRE) == 0, 585 ("!wired && VM_FAULT_WIRE")); 586 587 /* 588 * Try to avoid lock contention on the top-level object through 589 * special-case handling of some types of page faults, specifically, 590 * those that are both (1) mapping an existing page from the top- 591 * level object and (2) not having to mark that object as containing 592 * dirty pages. Under these conditions, a read lock on the top-level 593 * object suffices, allowing multiple page faults of a similar type to 594 * run in parallel on the same top-level object. 595 */ 596 if (fs.vp == NULL /* avoid locked vnode leak */ && 597 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 && 598 /* avoid calling vm_object_set_writeable_dirty() */ 599 ((prot & VM_PROT_WRITE) == 0 || 600 (fs.first_object->type != OBJT_VNODE && 601 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 602 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 603 VM_OBJECT_RLOCK(fs.first_object); 604 if ((prot & VM_PROT_WRITE) == 0 || 605 (fs.first_object->type != OBJT_VNODE && 606 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 607 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0) { 608 rv = vm_fault_soft_fast(&fs, vaddr, prot, fault_type, 609 fault_flags, wired, m_hold); 610 if (rv == KERN_SUCCESS) 611 return (rv); 612 } 613 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 614 VM_OBJECT_RUNLOCK(fs.first_object); 615 VM_OBJECT_WLOCK(fs.first_object); 616 } 617 } else { 618 VM_OBJECT_WLOCK(fs.first_object); 619 } 620 621 /* 622 * Make a reference to this object to prevent its disposal while we 623 * are messing with it. Once we have the reference, the map is free 624 * to be diddled. Since objects reference their shadows (and copies), 625 * they will stay around as well. 626 * 627 * Bump the paging-in-progress count to prevent size changes (e.g. 628 * truncation operations) during I/O. 629 */ 630 vm_object_reference_locked(fs.first_object); 631 vm_object_pip_add(fs.first_object, 1); 632 633 fs.lookup_still_valid = true; 634 635 fs.first_m = NULL; 636 637 /* 638 * Search for the page at object/offset. 639 */ 640 fs.object = fs.first_object; 641 fs.pindex = fs.first_pindex; 642 while (TRUE) { 643 /* 644 * If the object is marked for imminent termination, 645 * we retry here, since the collapse pass has raced 646 * with us. Otherwise, if we see terminally dead 647 * object, return fail. 648 */ 649 if ((fs.object->flags & OBJ_DEAD) != 0) { 650 dead = fs.object->type == OBJT_DEAD; 651 unlock_and_deallocate(&fs); 652 if (dead) 653 return (KERN_PROTECTION_FAILURE); 654 pause("vmf_de", 1); 655 goto RetryFault; 656 } 657 658 /* 659 * See if page is resident 660 */ 661 fs.m = vm_page_lookup(fs.object, fs.pindex); 662 if (fs.m != NULL) { 663 /* 664 * Wait/Retry if the page is busy. We have to do this 665 * if the page is either exclusive or shared busy 666 * because the vm_pager may be using read busy for 667 * pageouts (and even pageins if it is the vnode 668 * pager), and we could end up trying to pagein and 669 * pageout the same page simultaneously. 670 * 671 * We can theoretically allow the busy case on a read 672 * fault if the page is marked valid, but since such 673 * pages are typically already pmap'd, putting that 674 * special case in might be more effort then it is 675 * worth. We cannot under any circumstances mess 676 * around with a shared busied page except, perhaps, 677 * to pmap it. 678 */ 679 if (vm_page_busied(fs.m)) { 680 /* 681 * Reference the page before unlocking and 682 * sleeping so that the page daemon is less 683 * likely to reclaim it. 684 */ 685 vm_page_aflag_set(fs.m, PGA_REFERENCED); 686 if (fs.object != fs.first_object) { 687 if (!VM_OBJECT_TRYWLOCK( 688 fs.first_object)) { 689 VM_OBJECT_WUNLOCK(fs.object); 690 VM_OBJECT_WLOCK(fs.first_object); 691 VM_OBJECT_WLOCK(fs.object); 692 } 693 vm_page_lock(fs.first_m); 694 vm_page_free(fs.first_m); 695 vm_page_unlock(fs.first_m); 696 vm_object_pip_wakeup(fs.first_object); 697 VM_OBJECT_WUNLOCK(fs.first_object); 698 fs.first_m = NULL; 699 } 700 unlock_map(&fs); 701 if (fs.m == vm_page_lookup(fs.object, 702 fs.pindex)) { 703 vm_page_sleep_if_busy(fs.m, "vmpfw"); 704 } 705 vm_object_pip_wakeup(fs.object); 706 VM_OBJECT_WUNLOCK(fs.object); 707 PCPU_INC(cnt.v_intrans); 708 vm_object_deallocate(fs.first_object); 709 goto RetryFault; 710 } 711 vm_page_lock(fs.m); 712 vm_page_remque(fs.m); 713 vm_page_unlock(fs.m); 714 715 /* 716 * Mark page busy for other processes, and the 717 * pagedaemon. If it still isn't completely valid 718 * (readable), jump to readrest, else break-out ( we 719 * found the page ). 720 */ 721 vm_page_xbusy(fs.m); 722 if (fs.m->valid != VM_PAGE_BITS_ALL) 723 goto readrest; 724 break; 725 } 726 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m)); 727 728 /* 729 * Page is not resident. If the pager might contain the page 730 * or this is the beginning of the search, allocate a new 731 * page. (Default objects are zero-fill, so there is no real 732 * pager for them.) 733 */ 734 if (fs.object->type != OBJT_DEFAULT || 735 fs.object == fs.first_object) { 736 if (fs.pindex >= fs.object->size) { 737 unlock_and_deallocate(&fs); 738 return (KERN_PROTECTION_FAILURE); 739 } 740 741 if (fs.object == fs.first_object && 742 (fs.first_object->flags & OBJ_POPULATE) != 0 && 743 fs.first_object->shadow_count == 0) { 744 rv = vm_fault_populate(&fs, vaddr, prot, 745 fault_type, fault_flags, wired, m_hold); 746 switch (rv) { 747 case KERN_SUCCESS: 748 case KERN_FAILURE: 749 unlock_and_deallocate(&fs); 750 return (rv); 751 case KERN_RESOURCE_SHORTAGE: 752 unlock_and_deallocate(&fs); 753 goto RetryFault; 754 case KERN_NOT_RECEIVER: 755 /* 756 * Pager's populate() method 757 * returned VM_PAGER_BAD. 758 */ 759 break; 760 default: 761 panic("inconsistent return codes"); 762 } 763 } 764 765 /* 766 * Allocate a new page for this object/offset pair. 767 * 768 * Unlocked read of the p_flag is harmless. At 769 * worst, the P_KILLED might be not observed 770 * there, and allocation can fail, causing 771 * restart and new reading of the p_flag. 772 */ 773 if (!vm_page_count_severe() || P_KILLED(curproc)) { 774 #if VM_NRESERVLEVEL > 0 775 vm_object_color(fs.object, atop(vaddr) - 776 fs.pindex); 777 #endif 778 alloc_req = P_KILLED(curproc) ? 779 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 780 if (fs.object->type != OBJT_VNODE && 781 fs.object->backing_object == NULL) 782 alloc_req |= VM_ALLOC_ZERO; 783 fs.m = vm_page_alloc(fs.object, fs.pindex, 784 alloc_req); 785 } 786 if (fs.m == NULL) { 787 unlock_and_deallocate(&fs); 788 VM_WAITPFAULT; 789 goto RetryFault; 790 } 791 } 792 793 readrest: 794 /* 795 * At this point, we have either allocated a new page or found 796 * an existing page that is only partially valid. 797 * 798 * We hold a reference on the current object and the page is 799 * exclusive busied. 800 */ 801 802 /* 803 * If the pager for the current object might have the page, 804 * then determine the number of additional pages to read and 805 * potentially reprioritize previously read pages for earlier 806 * reclamation. These operations should only be performed 807 * once per page fault. Even if the current pager doesn't 808 * have the page, the number of additional pages to read will 809 * apply to subsequent objects in the shadow chain. 810 */ 811 if (fs.object->type != OBJT_DEFAULT && nera == -1 && 812 !P_KILLED(curproc)) { 813 KASSERT(fs.lookup_still_valid, ("map unlocked")); 814 era = fs.entry->read_ahead; 815 behavior = vm_map_entry_behavior(fs.entry); 816 if (behavior == MAP_ENTRY_BEHAV_RANDOM) { 817 nera = 0; 818 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 819 nera = VM_FAULT_READ_AHEAD_MAX; 820 if (vaddr == fs.entry->next_read) 821 vm_fault_dontneed(&fs, vaddr, nera); 822 } else if (vaddr == fs.entry->next_read) { 823 /* 824 * This is a sequential fault. Arithmetically 825 * increase the requested number of pages in 826 * the read-ahead window. The requested 827 * number of pages is "# of sequential faults 828 * x (read ahead min + 1) + read ahead min" 829 */ 830 nera = VM_FAULT_READ_AHEAD_MIN; 831 if (era > 0) { 832 nera += era + 1; 833 if (nera > VM_FAULT_READ_AHEAD_MAX) 834 nera = VM_FAULT_READ_AHEAD_MAX; 835 } 836 if (era == VM_FAULT_READ_AHEAD_MAX) 837 vm_fault_dontneed(&fs, vaddr, nera); 838 } else { 839 /* 840 * This is a non-sequential fault. 841 */ 842 nera = 0; 843 } 844 if (era != nera) { 845 /* 846 * A read lock on the map suffices to update 847 * the read ahead count safely. 848 */ 849 fs.entry->read_ahead = nera; 850 } 851 852 /* 853 * Prepare for unlocking the map. Save the map 854 * entry's start and end addresses, which are used to 855 * optimize the size of the pager operation below. 856 * Even if the map entry's addresses change after 857 * unlocking the map, using the saved addresses is 858 * safe. 859 */ 860 e_start = fs.entry->start; 861 e_end = fs.entry->end; 862 } 863 864 /* 865 * Call the pager to retrieve the page if there is a chance 866 * that the pager has it, and potentially retrieve additional 867 * pages at the same time. 868 */ 869 if (fs.object->type != OBJT_DEFAULT) { 870 /* 871 * Release the map lock before locking the vnode or 872 * sleeping in the pager. (If the current object has 873 * a shadow, then an earlier iteration of this loop 874 * may have already unlocked the map.) 875 */ 876 unlock_map(&fs); 877 878 if (fs.object->type == OBJT_VNODE && 879 (vp = fs.object->handle) != fs.vp) { 880 /* 881 * Perform an unlock in case the desired vnode 882 * changed while the map was unlocked during a 883 * retry. 884 */ 885 unlock_vp(&fs); 886 887 locked = VOP_ISLOCKED(vp); 888 if (locked != LK_EXCLUSIVE) 889 locked = LK_SHARED; 890 891 /* 892 * We must not sleep acquiring the vnode lock 893 * while we have the page exclusive busied or 894 * the object's paging-in-progress count 895 * incremented. Otherwise, we could deadlock. 896 */ 897 error = vget(vp, locked | LK_CANRECURSE | 898 LK_NOWAIT, curthread); 899 if (error != 0) { 900 vhold(vp); 901 release_page(&fs); 902 unlock_and_deallocate(&fs); 903 error = vget(vp, locked | LK_RETRY | 904 LK_CANRECURSE, curthread); 905 vdrop(vp); 906 fs.vp = vp; 907 KASSERT(error == 0, 908 ("vm_fault: vget failed")); 909 goto RetryFault; 910 } 911 fs.vp = vp; 912 } 913 KASSERT(fs.vp == NULL || !fs.map->system_map, 914 ("vm_fault: vnode-backed object mapped by system map")); 915 916 /* 917 * Page in the requested page and hint the pager, 918 * that it may bring up surrounding pages. 919 */ 920 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM || 921 P_KILLED(curproc)) { 922 behind = 0; 923 ahead = 0; 924 } else { 925 /* Is this a sequential fault? */ 926 if (nera > 0) { 927 behind = 0; 928 ahead = nera; 929 } else { 930 /* 931 * Request a cluster of pages that is 932 * aligned to a VM_FAULT_READ_DEFAULT 933 * page offset boundary within the 934 * object. Alignment to a page offset 935 * boundary is more likely to coincide 936 * with the underlying file system 937 * block than alignment to a virtual 938 * address boundary. 939 */ 940 cluster_offset = fs.pindex % 941 VM_FAULT_READ_DEFAULT; 942 behind = ulmin(cluster_offset, 943 atop(vaddr - e_start)); 944 ahead = VM_FAULT_READ_DEFAULT - 1 - 945 cluster_offset; 946 } 947 ahead = ulmin(ahead, atop(e_end - vaddr) - 1); 948 } 949 rv = vm_pager_get_pages(fs.object, &fs.m, 1, 950 &behind, &ahead); 951 if (rv == VM_PAGER_OK) { 952 faultcount = behind + 1 + ahead; 953 hardfault = true; 954 break; /* break to PAGE HAS BEEN FOUND */ 955 } 956 if (rv == VM_PAGER_ERROR) 957 printf("vm_fault: pager read error, pid %d (%s)\n", 958 curproc->p_pid, curproc->p_comm); 959 960 /* 961 * If an I/O error occurred or the requested page was 962 * outside the range of the pager, clean up and return 963 * an error. 964 */ 965 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) { 966 vm_page_lock(fs.m); 967 if (fs.m->wire_count == 0) 968 vm_page_free(fs.m); 969 else 970 vm_page_xunbusy_maybelocked(fs.m); 971 vm_page_unlock(fs.m); 972 fs.m = NULL; 973 unlock_and_deallocate(&fs); 974 return (rv == VM_PAGER_ERROR ? KERN_FAILURE : 975 KERN_PROTECTION_FAILURE); 976 } 977 978 /* 979 * The requested page does not exist at this object/ 980 * offset. Remove the invalid page from the object, 981 * waking up anyone waiting for it, and continue on to 982 * the next object. However, if this is the top-level 983 * object, we must leave the busy page in place to 984 * prevent another process from rushing past us, and 985 * inserting the page in that object at the same time 986 * that we are. 987 */ 988 if (fs.object != fs.first_object) { 989 vm_page_lock(fs.m); 990 if (fs.m->wire_count == 0) 991 vm_page_free(fs.m); 992 else 993 vm_page_xunbusy_maybelocked(fs.m); 994 vm_page_unlock(fs.m); 995 fs.m = NULL; 996 } 997 } 998 999 /* 1000 * We get here if the object has default pager (or unwiring) 1001 * or the pager doesn't have the page. 1002 */ 1003 if (fs.object == fs.first_object) 1004 fs.first_m = fs.m; 1005 1006 /* 1007 * Move on to the next object. Lock the next object before 1008 * unlocking the current one. 1009 */ 1010 next_object = fs.object->backing_object; 1011 if (next_object == NULL) { 1012 /* 1013 * If there's no object left, fill the page in the top 1014 * object with zeros. 1015 */ 1016 if (fs.object != fs.first_object) { 1017 vm_object_pip_wakeup(fs.object); 1018 VM_OBJECT_WUNLOCK(fs.object); 1019 1020 fs.object = fs.first_object; 1021 fs.pindex = fs.first_pindex; 1022 fs.m = fs.first_m; 1023 VM_OBJECT_WLOCK(fs.object); 1024 } 1025 fs.first_m = NULL; 1026 1027 /* 1028 * Zero the page if necessary and mark it valid. 1029 */ 1030 if ((fs.m->flags & PG_ZERO) == 0) { 1031 pmap_zero_page(fs.m); 1032 } else { 1033 PCPU_INC(cnt.v_ozfod); 1034 } 1035 PCPU_INC(cnt.v_zfod); 1036 fs.m->valid = VM_PAGE_BITS_ALL; 1037 /* Don't try to prefault neighboring pages. */ 1038 faultcount = 1; 1039 break; /* break to PAGE HAS BEEN FOUND */ 1040 } else { 1041 KASSERT(fs.object != next_object, 1042 ("object loop %p", next_object)); 1043 VM_OBJECT_WLOCK(next_object); 1044 vm_object_pip_add(next_object, 1); 1045 if (fs.object != fs.first_object) 1046 vm_object_pip_wakeup(fs.object); 1047 fs.pindex += 1048 OFF_TO_IDX(fs.object->backing_object_offset); 1049 VM_OBJECT_WUNLOCK(fs.object); 1050 fs.object = next_object; 1051 } 1052 } 1053 1054 vm_page_assert_xbusied(fs.m); 1055 1056 /* 1057 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 1058 * is held.] 1059 */ 1060 1061 /* 1062 * If the page is being written, but isn't already owned by the 1063 * top-level object, we have to copy it into a new page owned by the 1064 * top-level object. 1065 */ 1066 if (fs.object != fs.first_object) { 1067 /* 1068 * We only really need to copy if we want to write it. 1069 */ 1070 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1071 /* 1072 * This allows pages to be virtually copied from a 1073 * backing_object into the first_object, where the 1074 * backing object has no other refs to it, and cannot 1075 * gain any more refs. Instead of a bcopy, we just 1076 * move the page from the backing object to the 1077 * first object. Note that we must mark the page 1078 * dirty in the first object so that it will go out 1079 * to swap when needed. 1080 */ 1081 is_first_object_locked = false; 1082 if ( 1083 /* 1084 * Only one shadow object 1085 */ 1086 (fs.object->shadow_count == 1) && 1087 /* 1088 * No COW refs, except us 1089 */ 1090 (fs.object->ref_count == 1) && 1091 /* 1092 * No one else can look this object up 1093 */ 1094 (fs.object->handle == NULL) && 1095 /* 1096 * No other ways to look the object up 1097 */ 1098 ((fs.object->type == OBJT_DEFAULT) || 1099 (fs.object->type == OBJT_SWAP)) && 1100 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 1101 /* 1102 * We don't chase down the shadow chain 1103 */ 1104 fs.object == fs.first_object->backing_object) { 1105 vm_page_lock(fs.m); 1106 vm_page_remove(fs.m); 1107 vm_page_unlock(fs.m); 1108 vm_page_lock(fs.first_m); 1109 vm_page_replace_checked(fs.m, fs.first_object, 1110 fs.first_pindex, fs.first_m); 1111 vm_page_free(fs.first_m); 1112 vm_page_unlock(fs.first_m); 1113 vm_page_dirty(fs.m); 1114 #if VM_NRESERVLEVEL > 0 1115 /* 1116 * Rename the reservation. 1117 */ 1118 vm_reserv_rename(fs.m, fs.first_object, 1119 fs.object, OFF_TO_IDX( 1120 fs.first_object->backing_object_offset)); 1121 #endif 1122 /* 1123 * Removing the page from the backing object 1124 * unbusied it. 1125 */ 1126 vm_page_xbusy(fs.m); 1127 fs.first_m = fs.m; 1128 fs.m = NULL; 1129 PCPU_INC(cnt.v_cow_optim); 1130 } else { 1131 /* 1132 * Oh, well, lets copy it. 1133 */ 1134 pmap_copy_page(fs.m, fs.first_m); 1135 fs.first_m->valid = VM_PAGE_BITS_ALL; 1136 if ((fault_flags & VM_FAULT_WIRE) == 0) { 1137 prot &= ~VM_PROT_WRITE; 1138 fault_type &= ~VM_PROT_WRITE; 1139 } 1140 if (wired && (fault_flags & 1141 VM_FAULT_WIRE) == 0) { 1142 vm_page_lock(fs.first_m); 1143 vm_page_wire(fs.first_m); 1144 vm_page_unlock(fs.first_m); 1145 1146 vm_page_lock(fs.m); 1147 vm_page_unwire(fs.m, PQ_INACTIVE); 1148 vm_page_unlock(fs.m); 1149 } 1150 1151 /* 1152 * Typically, the shadow object is either 1153 * private to this address space 1154 * (OBJ_ONEMAPPING) or its pages are read only. 1155 * In the highly unusual case where the pages of 1156 * a shadow object are read/write shared between 1157 * this and other address spaces, we need to 1158 * ensure that any pmap-level mappings to the 1159 * original, copy-on-write page from the backing 1160 * object are removed from those other address 1161 * spaces. 1162 * 1163 * The flag check is racy, but this is 1164 * tolerable: if OBJ_ONEMAPPING is cleared after 1165 * the check, the busy state ensures that new 1166 * mappings of fs.m can't be created. 1167 * pmap_enter() will replace an existing mapping 1168 * in the current address space. If 1169 * OBJ_ONEMAPPING is set after the check, 1170 * removing mappings will at worse trigger some 1171 * unnecessary page faults. 1172 */ 1173 vm_page_assert_xbusied(fs.m); 1174 if ((fs.first_object->flags & OBJ_ONEMAPPING) == 0) 1175 pmap_remove_all(fs.m); 1176 1177 /* 1178 * We no longer need the old page or object. 1179 */ 1180 release_page(&fs); 1181 } 1182 /* 1183 * fs.object != fs.first_object due to above 1184 * conditional 1185 */ 1186 vm_object_pip_wakeup(fs.object); 1187 VM_OBJECT_WUNLOCK(fs.object); 1188 /* 1189 * Only use the new page below... 1190 */ 1191 fs.object = fs.first_object; 1192 fs.pindex = fs.first_pindex; 1193 fs.m = fs.first_m; 1194 if (!is_first_object_locked) 1195 VM_OBJECT_WLOCK(fs.object); 1196 PCPU_INC(cnt.v_cow_faults); 1197 curthread->td_cow++; 1198 } else { 1199 prot &= ~VM_PROT_WRITE; 1200 } 1201 } 1202 1203 /* 1204 * We must verify that the maps have not changed since our last 1205 * lookup. 1206 */ 1207 if (!fs.lookup_still_valid) { 1208 if (!vm_map_trylock_read(fs.map)) { 1209 release_page(&fs); 1210 unlock_and_deallocate(&fs); 1211 goto RetryFault; 1212 } 1213 fs.lookup_still_valid = true; 1214 if (fs.map->timestamp != fs.map_generation) { 1215 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 1216 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 1217 1218 /* 1219 * If we don't need the page any longer, put it on the inactive 1220 * list (the easiest thing to do here). If no one needs it, 1221 * pageout will grab it eventually. 1222 */ 1223 if (result != KERN_SUCCESS) { 1224 release_page(&fs); 1225 unlock_and_deallocate(&fs); 1226 1227 /* 1228 * If retry of map lookup would have blocked then 1229 * retry fault from start. 1230 */ 1231 if (result == KERN_FAILURE) 1232 goto RetryFault; 1233 return (result); 1234 } 1235 if ((retry_object != fs.first_object) || 1236 (retry_pindex != fs.first_pindex)) { 1237 release_page(&fs); 1238 unlock_and_deallocate(&fs); 1239 goto RetryFault; 1240 } 1241 1242 /* 1243 * Check whether the protection has changed or the object has 1244 * been copied while we left the map unlocked. Changing from 1245 * read to write permission is OK - we leave the page 1246 * write-protected, and catch the write fault. Changing from 1247 * write to read permission means that we can't mark the page 1248 * write-enabled after all. 1249 */ 1250 prot &= retry_prot; 1251 fault_type &= retry_prot; 1252 if (prot == 0) { 1253 release_page(&fs); 1254 unlock_and_deallocate(&fs); 1255 goto RetryFault; 1256 } 1257 } 1258 } 1259 1260 /* 1261 * If the page was filled by a pager, save the virtual address that 1262 * should be faulted on next under a sequential access pattern to the 1263 * map entry. A read lock on the map suffices to update this address 1264 * safely. 1265 */ 1266 if (hardfault) 1267 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE; 1268 1269 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true); 1270 vm_page_assert_xbusied(fs.m); 1271 1272 /* 1273 * Page must be completely valid or it is not fit to 1274 * map into user space. vm_pager_get_pages() ensures this. 1275 */ 1276 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 1277 ("vm_fault: page %p partially invalid", fs.m)); 1278 VM_OBJECT_WUNLOCK(fs.object); 1279 1280 /* 1281 * Put this page into the physical map. We had to do the unlock above 1282 * because pmap_enter() may sleep. We don't put the page 1283 * back on the active queue until later so that the pageout daemon 1284 * won't find it (yet). 1285 */ 1286 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 1287 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 1288 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 1289 wired == 0) 1290 vm_fault_prefault(&fs, vaddr, 1291 faultcount > 0 ? behind : PFBAK, 1292 faultcount > 0 ? ahead : PFFOR, false); 1293 VM_OBJECT_WLOCK(fs.object); 1294 vm_page_lock(fs.m); 1295 1296 /* 1297 * If the page is not wired down, then put it where the pageout daemon 1298 * can find it. 1299 */ 1300 if ((fault_flags & VM_FAULT_WIRE) != 0) { 1301 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 1302 vm_page_wire(fs.m); 1303 } else 1304 vm_page_activate(fs.m); 1305 if (m_hold != NULL) { 1306 *m_hold = fs.m; 1307 vm_page_hold(fs.m); 1308 } 1309 vm_page_unlock(fs.m); 1310 vm_page_xunbusy(fs.m); 1311 1312 /* 1313 * Unlock everything, and return 1314 */ 1315 unlock_and_deallocate(&fs); 1316 if (hardfault) { 1317 PCPU_INC(cnt.v_io_faults); 1318 curthread->td_ru.ru_majflt++; 1319 #ifdef RACCT 1320 if (racct_enable && fs.object->type == OBJT_VNODE) { 1321 PROC_LOCK(curproc); 1322 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 1323 racct_add_force(curproc, RACCT_WRITEBPS, 1324 PAGE_SIZE + behind * PAGE_SIZE); 1325 racct_add_force(curproc, RACCT_WRITEIOPS, 1); 1326 } else { 1327 racct_add_force(curproc, RACCT_READBPS, 1328 PAGE_SIZE + ahead * PAGE_SIZE); 1329 racct_add_force(curproc, RACCT_READIOPS, 1); 1330 } 1331 PROC_UNLOCK(curproc); 1332 } 1333 #endif 1334 } else 1335 curthread->td_ru.ru_minflt++; 1336 1337 return (KERN_SUCCESS); 1338 } 1339 1340 /* 1341 * Speed up the reclamation of pages that precede the faulting pindex within 1342 * the first object of the shadow chain. Essentially, perform the equivalent 1343 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1344 * the faulting pindex by the cluster size when the pages read by vm_fault() 1345 * cross a cluster-size boundary. The cluster size is the greater of the 1346 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1347 * 1348 * When "fs->first_object" is a shadow object, the pages in the backing object 1349 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1350 * function must only be concerned with pages in the first object. 1351 */ 1352 static void 1353 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1354 { 1355 vm_map_entry_t entry; 1356 vm_object_t first_object, object; 1357 vm_offset_t end, start; 1358 vm_page_t m, m_next; 1359 vm_pindex_t pend, pstart; 1360 vm_size_t size; 1361 1362 object = fs->object; 1363 VM_OBJECT_ASSERT_WLOCKED(object); 1364 first_object = fs->first_object; 1365 if (first_object != object) { 1366 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1367 VM_OBJECT_WUNLOCK(object); 1368 VM_OBJECT_WLOCK(first_object); 1369 VM_OBJECT_WLOCK(object); 1370 } 1371 } 1372 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1373 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1374 size = VM_FAULT_DONTNEED_MIN; 1375 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1376 size = pagesizes[1]; 1377 end = rounddown2(vaddr, size); 1378 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1379 (entry = fs->entry)->start < end) { 1380 if (end - entry->start < size) 1381 start = entry->start; 1382 else 1383 start = end - size; 1384 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1385 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1386 entry->start); 1387 m_next = vm_page_find_least(first_object, pstart); 1388 pend = OFF_TO_IDX(entry->offset) + atop(end - 1389 entry->start); 1390 while ((m = m_next) != NULL && m->pindex < pend) { 1391 m_next = TAILQ_NEXT(m, listq); 1392 if (m->valid != VM_PAGE_BITS_ALL || 1393 vm_page_busied(m)) 1394 continue; 1395 1396 /* 1397 * Don't clear PGA_REFERENCED, since it would 1398 * likely represent a reference by a different 1399 * process. 1400 * 1401 * Typically, at this point, prefetched pages 1402 * are still in the inactive queue. Only 1403 * pages that triggered page faults are in the 1404 * active queue. 1405 */ 1406 vm_page_lock(m); 1407 vm_page_deactivate(m); 1408 vm_page_unlock(m); 1409 } 1410 } 1411 } 1412 if (first_object != object) 1413 VM_OBJECT_WUNLOCK(first_object); 1414 } 1415 1416 /* 1417 * vm_fault_prefault provides a quick way of clustering 1418 * pagefaults into a processes address space. It is a "cousin" 1419 * of vm_map_pmap_enter, except it runs at page fault time instead 1420 * of mmap time. 1421 */ 1422 static void 1423 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1424 int backward, int forward, bool obj_locked) 1425 { 1426 pmap_t pmap; 1427 vm_map_entry_t entry; 1428 vm_object_t backing_object, lobject; 1429 vm_offset_t addr, starta; 1430 vm_pindex_t pindex; 1431 vm_page_t m; 1432 int i; 1433 1434 pmap = fs->map->pmap; 1435 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1436 return; 1437 1438 entry = fs->entry; 1439 1440 if (addra < backward * PAGE_SIZE) { 1441 starta = entry->start; 1442 } else { 1443 starta = addra - backward * PAGE_SIZE; 1444 if (starta < entry->start) 1445 starta = entry->start; 1446 } 1447 1448 /* 1449 * Generate the sequence of virtual addresses that are candidates for 1450 * prefaulting in an outward spiral from the faulting virtual address, 1451 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1452 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1453 * If the candidate address doesn't have a backing physical page, then 1454 * the loop immediately terminates. 1455 */ 1456 for (i = 0; i < 2 * imax(backward, forward); i++) { 1457 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1458 PAGE_SIZE); 1459 if (addr > addra + forward * PAGE_SIZE) 1460 addr = 0; 1461 1462 if (addr < starta || addr >= entry->end) 1463 continue; 1464 1465 if (!pmap_is_prefaultable(pmap, addr)) 1466 continue; 1467 1468 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1469 lobject = entry->object.vm_object; 1470 if (!obj_locked) 1471 VM_OBJECT_RLOCK(lobject); 1472 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1473 lobject->type == OBJT_DEFAULT && 1474 (backing_object = lobject->backing_object) != NULL) { 1475 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1476 0, ("vm_fault_prefault: unaligned object offset")); 1477 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1478 VM_OBJECT_RLOCK(backing_object); 1479 if (!obj_locked || lobject != entry->object.vm_object) 1480 VM_OBJECT_RUNLOCK(lobject); 1481 lobject = backing_object; 1482 } 1483 if (m == NULL) { 1484 if (!obj_locked || lobject != entry->object.vm_object) 1485 VM_OBJECT_RUNLOCK(lobject); 1486 break; 1487 } 1488 if (m->valid == VM_PAGE_BITS_ALL && 1489 (m->flags & PG_FICTITIOUS) == 0) 1490 pmap_enter_quick(pmap, addr, m, entry->protection); 1491 if (!obj_locked || lobject != entry->object.vm_object) 1492 VM_OBJECT_RUNLOCK(lobject); 1493 } 1494 } 1495 1496 /* 1497 * Hold each of the physical pages that are mapped by the specified range of 1498 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1499 * and allow the specified types of access, "prot". If all of the implied 1500 * pages are successfully held, then the number of held pages is returned 1501 * together with pointers to those pages in the array "ma". However, if any 1502 * of the pages cannot be held, -1 is returned. 1503 */ 1504 int 1505 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1506 vm_prot_t prot, vm_page_t *ma, int max_count) 1507 { 1508 vm_offset_t end, va; 1509 vm_page_t *mp; 1510 int count; 1511 boolean_t pmap_failed; 1512 1513 if (len == 0) 1514 return (0); 1515 end = round_page(addr + len); 1516 addr = trunc_page(addr); 1517 1518 /* 1519 * Check for illegal addresses. 1520 */ 1521 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1522 return (-1); 1523 1524 if (atop(end - addr) > max_count) 1525 panic("vm_fault_quick_hold_pages: count > max_count"); 1526 count = atop(end - addr); 1527 1528 /* 1529 * Most likely, the physical pages are resident in the pmap, so it is 1530 * faster to try pmap_extract_and_hold() first. 1531 */ 1532 pmap_failed = FALSE; 1533 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1534 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1535 if (*mp == NULL) 1536 pmap_failed = TRUE; 1537 else if ((prot & VM_PROT_WRITE) != 0 && 1538 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1539 /* 1540 * Explicitly dirty the physical page. Otherwise, the 1541 * caller's changes may go unnoticed because they are 1542 * performed through an unmanaged mapping or by a DMA 1543 * operation. 1544 * 1545 * The object lock is not held here. 1546 * See vm_page_clear_dirty_mask(). 1547 */ 1548 vm_page_dirty(*mp); 1549 } 1550 } 1551 if (pmap_failed) { 1552 /* 1553 * One or more pages could not be held by the pmap. Either no 1554 * page was mapped at the specified virtual address or that 1555 * mapping had insufficient permissions. Attempt to fault in 1556 * and hold these pages. 1557 * 1558 * If vm_fault_disable_pagefaults() was called, 1559 * i.e., TDP_NOFAULTING is set, we must not sleep nor 1560 * acquire MD VM locks, which means we must not call 1561 * vm_fault_hold(). Some (out of tree) callers mark 1562 * too wide a code area with vm_fault_disable_pagefaults() 1563 * already, use the VM_PROT_QUICK_NOFAULT flag to request 1564 * the proper behaviour explicitly. 1565 */ 1566 if ((prot & VM_PROT_QUICK_NOFAULT) != 0 && 1567 (curthread->td_pflags & TDP_NOFAULTING) != 0) 1568 goto error; 1569 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1570 if (*mp == NULL && vm_fault_hold(map, va, prot, 1571 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1572 goto error; 1573 } 1574 return (count); 1575 error: 1576 for (mp = ma; mp < ma + count; mp++) 1577 if (*mp != NULL) { 1578 vm_page_lock(*mp); 1579 vm_page_unhold(*mp); 1580 vm_page_unlock(*mp); 1581 } 1582 return (-1); 1583 } 1584 1585 /* 1586 * Routine: 1587 * vm_fault_copy_entry 1588 * Function: 1589 * Create new shadow object backing dst_entry with private copy of 1590 * all underlying pages. When src_entry is equal to dst_entry, 1591 * function implements COW for wired-down map entry. Otherwise, 1592 * it forks wired entry into dst_map. 1593 * 1594 * In/out conditions: 1595 * The source and destination maps must be locked for write. 1596 * The source map entry must be wired down (or be a sharing map 1597 * entry corresponding to a main map entry that is wired down). 1598 */ 1599 void 1600 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1601 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1602 vm_ooffset_t *fork_charge) 1603 { 1604 vm_object_t backing_object, dst_object, object, src_object; 1605 vm_pindex_t dst_pindex, pindex, src_pindex; 1606 vm_prot_t access, prot; 1607 vm_offset_t vaddr; 1608 vm_page_t dst_m; 1609 vm_page_t src_m; 1610 boolean_t upgrade; 1611 1612 #ifdef lint 1613 src_map++; 1614 #endif /* lint */ 1615 1616 upgrade = src_entry == dst_entry; 1617 access = prot = dst_entry->protection; 1618 1619 src_object = src_entry->object.vm_object; 1620 src_pindex = OFF_TO_IDX(src_entry->offset); 1621 1622 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1623 dst_object = src_object; 1624 vm_object_reference(dst_object); 1625 } else { 1626 /* 1627 * Create the top-level object for the destination entry. (Doesn't 1628 * actually shadow anything - we copy the pages directly.) 1629 */ 1630 dst_object = vm_object_allocate(OBJT_DEFAULT, 1631 atop(dst_entry->end - dst_entry->start)); 1632 #if VM_NRESERVLEVEL > 0 1633 dst_object->flags |= OBJ_COLORED; 1634 dst_object->pg_color = atop(dst_entry->start); 1635 #endif 1636 dst_object->charge = dst_entry->end - dst_entry->start; 1637 } 1638 1639 VM_OBJECT_WLOCK(dst_object); 1640 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1641 ("vm_fault_copy_entry: vm_object not NULL")); 1642 if (src_object != dst_object) { 1643 dst_entry->object.vm_object = dst_object; 1644 dst_entry->offset = 0; 1645 } 1646 if (fork_charge != NULL) { 1647 KASSERT(dst_entry->cred == NULL, 1648 ("vm_fault_copy_entry: leaked swp charge")); 1649 dst_object->cred = curthread->td_ucred; 1650 crhold(dst_object->cred); 1651 *fork_charge += dst_object->charge; 1652 } else if ((dst_object->type == OBJT_DEFAULT || 1653 dst_object->type == OBJT_SWAP) && 1654 dst_object->cred == NULL) { 1655 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1656 dst_entry)); 1657 dst_object->cred = dst_entry->cred; 1658 dst_entry->cred = NULL; 1659 } 1660 1661 /* 1662 * If not an upgrade, then enter the mappings in the pmap as 1663 * read and/or execute accesses. Otherwise, enter them as 1664 * write accesses. 1665 * 1666 * A writeable large page mapping is only created if all of 1667 * the constituent small page mappings are modified. Marking 1668 * PTEs as modified on inception allows promotion to happen 1669 * without taking potentially large number of soft faults. 1670 */ 1671 if (!upgrade) 1672 access &= ~VM_PROT_WRITE; 1673 1674 /* 1675 * Loop through all of the virtual pages within the entry's 1676 * range, copying each page from the source object to the 1677 * destination object. Since the source is wired, those pages 1678 * must exist. In contrast, the destination is pageable. 1679 * Since the destination object doesn't share any backing storage 1680 * with the source object, all of its pages must be dirtied, 1681 * regardless of whether they can be written. 1682 */ 1683 for (vaddr = dst_entry->start, dst_pindex = 0; 1684 vaddr < dst_entry->end; 1685 vaddr += PAGE_SIZE, dst_pindex++) { 1686 again: 1687 /* 1688 * Find the page in the source object, and copy it in. 1689 * Because the source is wired down, the page will be 1690 * in memory. 1691 */ 1692 if (src_object != dst_object) 1693 VM_OBJECT_RLOCK(src_object); 1694 object = src_object; 1695 pindex = src_pindex + dst_pindex; 1696 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1697 (backing_object = object->backing_object) != NULL) { 1698 /* 1699 * Unless the source mapping is read-only or 1700 * it is presently being upgraded from 1701 * read-only, the first object in the shadow 1702 * chain should provide all of the pages. In 1703 * other words, this loop body should never be 1704 * executed when the source mapping is already 1705 * read/write. 1706 */ 1707 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1708 upgrade, 1709 ("vm_fault_copy_entry: main object missing page")); 1710 1711 VM_OBJECT_RLOCK(backing_object); 1712 pindex += OFF_TO_IDX(object->backing_object_offset); 1713 if (object != dst_object) 1714 VM_OBJECT_RUNLOCK(object); 1715 object = backing_object; 1716 } 1717 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1718 1719 if (object != dst_object) { 1720 /* 1721 * Allocate a page in the destination object. 1722 */ 1723 dst_m = vm_page_alloc(dst_object, (src_object == 1724 dst_object ? src_pindex : 0) + dst_pindex, 1725 VM_ALLOC_NORMAL); 1726 if (dst_m == NULL) { 1727 VM_OBJECT_WUNLOCK(dst_object); 1728 VM_OBJECT_RUNLOCK(object); 1729 VM_WAIT; 1730 VM_OBJECT_WLOCK(dst_object); 1731 goto again; 1732 } 1733 pmap_copy_page(src_m, dst_m); 1734 VM_OBJECT_RUNLOCK(object); 1735 dst_m->dirty = dst_m->valid = src_m->valid; 1736 } else { 1737 dst_m = src_m; 1738 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1739 goto again; 1740 if (dst_m->pindex >= dst_object->size) 1741 /* 1742 * We are upgrading. Index can occur 1743 * out of bounds if the object type is 1744 * vnode and the file was truncated. 1745 */ 1746 break; 1747 vm_page_xbusy(dst_m); 1748 } 1749 VM_OBJECT_WUNLOCK(dst_object); 1750 1751 /* 1752 * Enter it in the pmap. If a wired, copy-on-write 1753 * mapping is being replaced by a write-enabled 1754 * mapping, then wire that new mapping. 1755 * 1756 * The page can be invalid if the user called 1757 * msync(MS_INVALIDATE) or truncated the backing vnode 1758 * or shared memory object. In this case, do not 1759 * insert it into pmap, but still do the copy so that 1760 * all copies of the wired map entry have similar 1761 * backing pages. 1762 */ 1763 if (dst_m->valid == VM_PAGE_BITS_ALL) { 1764 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1765 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1766 } 1767 1768 /* 1769 * Mark it no longer busy, and put it on the active list. 1770 */ 1771 VM_OBJECT_WLOCK(dst_object); 1772 1773 if (upgrade) { 1774 if (src_m != dst_m) { 1775 vm_page_lock(src_m); 1776 vm_page_unwire(src_m, PQ_INACTIVE); 1777 vm_page_unlock(src_m); 1778 vm_page_lock(dst_m); 1779 vm_page_wire(dst_m); 1780 vm_page_unlock(dst_m); 1781 } else { 1782 KASSERT(dst_m->wire_count > 0, 1783 ("dst_m %p is not wired", dst_m)); 1784 } 1785 } else { 1786 vm_page_lock(dst_m); 1787 vm_page_activate(dst_m); 1788 vm_page_unlock(dst_m); 1789 } 1790 vm_page_xunbusy(dst_m); 1791 } 1792 VM_OBJECT_WUNLOCK(dst_object); 1793 if (upgrade) { 1794 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1795 vm_object_deallocate(src_object); 1796 } 1797 } 1798 1799 /* 1800 * Block entry into the machine-independent layer's page fault handler by 1801 * the calling thread. Subsequent calls to vm_fault() by that thread will 1802 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1803 * spurious page faults. 1804 */ 1805 int 1806 vm_fault_disable_pagefaults(void) 1807 { 1808 1809 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1810 } 1811 1812 void 1813 vm_fault_enable_pagefaults(int save) 1814 { 1815 1816 curthread_pflags_restore(save); 1817 }
Cache object: ea0af6436a008590e1f50b06aa754386
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