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/resourcevar.h> 87 #include <sys/rwlock.h> 88 #include <sys/sysctl.h> 89 #include <sys/vmmeter.h> 90 #include <sys/vnode.h> 91 #ifdef KTRACE 92 #include <sys/ktrace.h> 93 #endif 94 95 #include <vm/vm.h> 96 #include <vm/vm_param.h> 97 #include <vm/pmap.h> 98 #include <vm/vm_map.h> 99 #include <vm/vm_object.h> 100 #include <vm/vm_page.h> 101 #include <vm/vm_pageout.h> 102 #include <vm/vm_kern.h> 103 #include <vm/vm_pager.h> 104 #include <vm/vm_extern.h> 105 #include <vm/vm_reserv.h> 106 107 #define PFBAK 4 108 #define PFFOR 4 109 110 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *); 111 112 #define VM_FAULT_READ_BEHIND 8 113 #define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT) 114 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX) 115 #define VM_FAULT_NINCR (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND) 116 #define VM_FAULT_SUM (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2) 117 118 #define VM_FAULT_DONTNEED_MIN 1048576 119 120 struct faultstate { 121 vm_page_t m; 122 vm_object_t object; 123 vm_pindex_t pindex; 124 vm_page_t first_m; 125 vm_object_t first_object; 126 vm_pindex_t first_pindex; 127 vm_map_t map; 128 vm_map_entry_t entry; 129 int lookup_still_valid; 130 struct vnode *vp; 131 }; 132 133 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, 134 int ahead); 135 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 136 int faultcount, int reqpage); 137 138 static inline void 139 release_page(struct faultstate *fs) 140 { 141 142 vm_page_xunbusy(fs->m); 143 vm_page_lock(fs->m); 144 vm_page_deactivate(fs->m); 145 vm_page_unlock(fs->m); 146 fs->m = NULL; 147 } 148 149 static inline void 150 unlock_map(struct faultstate *fs) 151 { 152 153 if (fs->lookup_still_valid) { 154 vm_map_lookup_done(fs->map, fs->entry); 155 fs->lookup_still_valid = FALSE; 156 } 157 } 158 159 static void 160 unlock_and_deallocate(struct faultstate *fs) 161 { 162 163 vm_object_pip_wakeup(fs->object); 164 VM_OBJECT_WUNLOCK(fs->object); 165 if (fs->object != fs->first_object) { 166 VM_OBJECT_WLOCK(fs->first_object); 167 vm_page_lock(fs->first_m); 168 vm_page_free(fs->first_m); 169 vm_page_unlock(fs->first_m); 170 vm_object_pip_wakeup(fs->first_object); 171 VM_OBJECT_WUNLOCK(fs->first_object); 172 fs->first_m = NULL; 173 } 174 vm_object_deallocate(fs->first_object); 175 unlock_map(fs); 176 if (fs->vp != NULL) { 177 vput(fs->vp); 178 fs->vp = NULL; 179 } 180 } 181 182 static void 183 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot, 184 vm_prot_t fault_type, int fault_flags, boolean_t set_wd) 185 { 186 boolean_t need_dirty; 187 188 if (((prot & VM_PROT_WRITE) == 0 && 189 (fault_flags & VM_FAULT_DIRTY) == 0) || 190 (m->oflags & VPO_UNMANAGED) != 0) 191 return; 192 193 VM_OBJECT_ASSERT_LOCKED(m->object); 194 195 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 && 196 (fault_flags & VM_FAULT_WIRE) == 0) || 197 (fault_flags & VM_FAULT_DIRTY) != 0; 198 199 if (set_wd) 200 vm_object_set_writeable_dirty(m->object); 201 else 202 /* 203 * If two callers of vm_fault_dirty() with set_wd == 204 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC 205 * flag set, other with flag clear, race, it is 206 * possible for the no-NOSYNC thread to see m->dirty 207 * != 0 and not clear VPO_NOSYNC. Take vm_page lock 208 * around manipulation of VPO_NOSYNC and 209 * vm_page_dirty() call, to avoid the race and keep 210 * m->oflags consistent. 211 */ 212 vm_page_lock(m); 213 214 /* 215 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC 216 * if the page is already dirty to prevent data written with 217 * the expectation of being synced from not being synced. 218 * Likewise if this entry does not request NOSYNC then make 219 * sure the page isn't marked NOSYNC. Applications sharing 220 * data should use the same flags to avoid ping ponging. 221 */ 222 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) { 223 if (m->dirty == 0) { 224 m->oflags |= VPO_NOSYNC; 225 } 226 } else { 227 m->oflags &= ~VPO_NOSYNC; 228 } 229 230 /* 231 * If the fault is a write, we know that this page is being 232 * written NOW so dirty it explicitly to save on 233 * pmap_is_modified() calls later. 234 * 235 * Also tell the backing pager, if any, that it should remove 236 * any swap backing since the page is now dirty. 237 */ 238 if (need_dirty) 239 vm_page_dirty(m); 240 if (!set_wd) 241 vm_page_unlock(m); 242 if (need_dirty) 243 vm_pager_page_unswapped(m); 244 } 245 246 /* 247 * vm_fault: 248 * 249 * Handle a page fault occurring at the given address, 250 * requiring the given permissions, in the map specified. 251 * If successful, the page is inserted into the 252 * associated physical map. 253 * 254 * NOTE: the given address should be truncated to the 255 * proper page address. 256 * 257 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 258 * a standard error specifying why the fault is fatal is returned. 259 * 260 * The map in question must be referenced, and remains so. 261 * Caller may hold no locks. 262 */ 263 int 264 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 265 int fault_flags) 266 { 267 struct thread *td; 268 int result; 269 270 td = curthread; 271 if ((td->td_pflags & TDP_NOFAULTING) != 0) 272 return (KERN_PROTECTION_FAILURE); 273 #ifdef KTRACE 274 if (map != kernel_map && KTRPOINT(td, KTR_FAULT)) 275 ktrfault(vaddr, fault_type); 276 #endif 277 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags, 278 NULL); 279 #ifdef KTRACE 280 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND)) 281 ktrfaultend(result); 282 #endif 283 return (result); 284 } 285 286 int 287 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 288 int fault_flags, vm_page_t *m_hold) 289 { 290 vm_prot_t prot; 291 int alloc_req, era, faultcount, nera, reqpage, result; 292 boolean_t growstack, is_first_object_locked, wired; 293 int map_generation; 294 vm_object_t next_object; 295 vm_page_t marray[VM_FAULT_READ_MAX]; 296 int hardfault; 297 struct faultstate fs; 298 struct vnode *vp; 299 vm_page_t m; 300 int ahead, behind, cluster_offset, error, locked; 301 302 hardfault = 0; 303 growstack = TRUE; 304 PCPU_INC(cnt.v_vm_faults); 305 fs.vp = NULL; 306 faultcount = reqpage = 0; 307 308 RetryFault:; 309 310 /* 311 * Find the backing store object and offset into it to begin the 312 * search. 313 */ 314 fs.map = map; 315 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry, 316 &fs.first_object, &fs.first_pindex, &prot, &wired); 317 if (result != KERN_SUCCESS) { 318 if (growstack && result == KERN_INVALID_ADDRESS && 319 map != kernel_map) { 320 result = vm_map_growstack(curproc, vaddr); 321 if (result != KERN_SUCCESS) 322 return (KERN_FAILURE); 323 growstack = FALSE; 324 goto RetryFault; 325 } 326 return (result); 327 } 328 329 map_generation = fs.map->timestamp; 330 331 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 332 panic("vm_fault: fault on nofault entry, addr: %lx", 333 (u_long)vaddr); 334 } 335 336 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION && 337 fs.entry->wiring_thread != curthread) { 338 vm_map_unlock_read(fs.map); 339 vm_map_lock(fs.map); 340 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) && 341 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) { 342 if (fs.vp != NULL) { 343 vput(fs.vp); 344 fs.vp = NULL; 345 } 346 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP; 347 vm_map_unlock_and_wait(fs.map, 0); 348 } else 349 vm_map_unlock(fs.map); 350 goto RetryFault; 351 } 352 353 if (wired) 354 fault_type = prot | (fault_type & VM_PROT_COPY); 355 else 356 KASSERT((fault_flags & VM_FAULT_WIRE) == 0, 357 ("!wired && VM_FAULT_WIRE")); 358 359 if (fs.vp == NULL /* avoid locked vnode leak */ && 360 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 && 361 /* avoid calling vm_object_set_writeable_dirty() */ 362 ((prot & VM_PROT_WRITE) == 0 || 363 (fs.first_object->type != OBJT_VNODE && 364 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) || 365 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) { 366 VM_OBJECT_RLOCK(fs.first_object); 367 if ((prot & VM_PROT_WRITE) != 0 && 368 (fs.first_object->type == OBJT_VNODE || 369 (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) && 370 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0) 371 goto fast_failed; 372 m = vm_page_lookup(fs.first_object, fs.first_pindex); 373 /* A busy page can be mapped for read|execute access. */ 374 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 && 375 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL) 376 goto fast_failed; 377 result = pmap_enter(fs.map->pmap, vaddr, m, prot, 378 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 379 0), 0); 380 if (result != KERN_SUCCESS) 381 goto fast_failed; 382 if (m_hold != NULL) { 383 *m_hold = m; 384 vm_page_lock(m); 385 vm_page_hold(m); 386 vm_page_unlock(m); 387 } 388 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags, 389 FALSE); 390 VM_OBJECT_RUNLOCK(fs.first_object); 391 if (!wired) 392 vm_fault_prefault(&fs, vaddr, 0, 0); 393 vm_map_lookup_done(fs.map, fs.entry); 394 curthread->td_ru.ru_minflt++; 395 return (KERN_SUCCESS); 396 fast_failed: 397 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) { 398 VM_OBJECT_RUNLOCK(fs.first_object); 399 VM_OBJECT_WLOCK(fs.first_object); 400 } 401 } else { 402 VM_OBJECT_WLOCK(fs.first_object); 403 } 404 405 /* 406 * Make a reference to this object to prevent its disposal while we 407 * are messing with it. Once we have the reference, the map is free 408 * to be diddled. Since objects reference their shadows (and copies), 409 * they will stay around as well. 410 * 411 * Bump the paging-in-progress count to prevent size changes (e.g. 412 * truncation operations) during I/O. This must be done after 413 * obtaining the vnode lock in order to avoid possible deadlocks. 414 */ 415 vm_object_reference_locked(fs.first_object); 416 vm_object_pip_add(fs.first_object, 1); 417 418 fs.lookup_still_valid = TRUE; 419 420 fs.first_m = NULL; 421 422 /* 423 * Search for the page at object/offset. 424 */ 425 fs.object = fs.first_object; 426 fs.pindex = fs.first_pindex; 427 while (TRUE) { 428 /* 429 * If the object is dead, we stop here 430 */ 431 if (fs.object->flags & OBJ_DEAD) { 432 unlock_and_deallocate(&fs); 433 return (KERN_PROTECTION_FAILURE); 434 } 435 436 /* 437 * See if page is resident 438 */ 439 fs.m = vm_page_lookup(fs.object, fs.pindex); 440 if (fs.m != NULL) { 441 /* 442 * Wait/Retry if the page is busy. We have to do this 443 * if the page is either exclusive or shared busy 444 * because the vm_pager may be using read busy for 445 * pageouts (and even pageins if it is the vnode 446 * pager), and we could end up trying to pagein and 447 * pageout the same page simultaneously. 448 * 449 * We can theoretically allow the busy case on a read 450 * fault if the page is marked valid, but since such 451 * pages are typically already pmap'd, putting that 452 * special case in might be more effort then it is 453 * worth. We cannot under any circumstances mess 454 * around with a shared busied page except, perhaps, 455 * to pmap it. 456 */ 457 if (vm_page_busied(fs.m)) { 458 /* 459 * Reference the page before unlocking and 460 * sleeping so that the page daemon is less 461 * likely to reclaim it. 462 */ 463 vm_page_aflag_set(fs.m, PGA_REFERENCED); 464 if (fs.object != fs.first_object) { 465 if (!VM_OBJECT_TRYWLOCK( 466 fs.first_object)) { 467 VM_OBJECT_WUNLOCK(fs.object); 468 VM_OBJECT_WLOCK(fs.first_object); 469 VM_OBJECT_WLOCK(fs.object); 470 } 471 vm_page_lock(fs.first_m); 472 vm_page_free(fs.first_m); 473 vm_page_unlock(fs.first_m); 474 vm_object_pip_wakeup(fs.first_object); 475 VM_OBJECT_WUNLOCK(fs.first_object); 476 fs.first_m = NULL; 477 } 478 unlock_map(&fs); 479 if (fs.m == vm_page_lookup(fs.object, 480 fs.pindex)) { 481 vm_page_sleep_if_busy(fs.m, "vmpfw"); 482 } 483 vm_object_pip_wakeup(fs.object); 484 VM_OBJECT_WUNLOCK(fs.object); 485 PCPU_INC(cnt.v_intrans); 486 vm_object_deallocate(fs.first_object); 487 goto RetryFault; 488 } 489 vm_page_lock(fs.m); 490 vm_page_remque(fs.m); 491 vm_page_unlock(fs.m); 492 493 /* 494 * Mark page busy for other processes, and the 495 * pagedaemon. If it still isn't completely valid 496 * (readable), jump to readrest, else break-out ( we 497 * found the page ). 498 */ 499 vm_page_xbusy(fs.m); 500 if (fs.m->valid != VM_PAGE_BITS_ALL) 501 goto readrest; 502 break; 503 } 504 505 /* 506 * Page is not resident. If this is the search termination 507 * or the pager might contain the page, allocate a new page. 508 * Default objects are zero-fill, there is no real pager. 509 */ 510 if (fs.object->type != OBJT_DEFAULT || 511 fs.object == fs.first_object) { 512 if (fs.pindex >= fs.object->size) { 513 unlock_and_deallocate(&fs); 514 return (KERN_PROTECTION_FAILURE); 515 } 516 517 /* 518 * Allocate a new page for this object/offset pair. 519 * 520 * Unlocked read of the p_flag is harmless. At 521 * worst, the P_KILLED might be not observed 522 * there, and allocation can fail, causing 523 * restart and new reading of the p_flag. 524 */ 525 fs.m = NULL; 526 if (!vm_page_count_severe() || P_KILLED(curproc)) { 527 #if VM_NRESERVLEVEL > 0 528 vm_object_color(fs.object, atop(vaddr) - 529 fs.pindex); 530 #endif 531 alloc_req = P_KILLED(curproc) ? 532 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL; 533 if (fs.object->type != OBJT_VNODE && 534 fs.object->backing_object == NULL) 535 alloc_req |= VM_ALLOC_ZERO; 536 fs.m = vm_page_alloc(fs.object, fs.pindex, 537 alloc_req); 538 } 539 if (fs.m == NULL) { 540 unlock_and_deallocate(&fs); 541 VM_WAITPFAULT; 542 goto RetryFault; 543 } else if (fs.m->valid == VM_PAGE_BITS_ALL) 544 break; 545 } 546 547 readrest: 548 /* 549 * We have found a valid page or we have allocated a new page. 550 * The page thus may not be valid or may not be entirely 551 * valid. 552 * 553 * Attempt to fault-in the page if there is a chance that the 554 * pager has it, and potentially fault in additional pages 555 * at the same time. For default objects simply provide 556 * zero-filled pages. 557 */ 558 if (fs.object->type != OBJT_DEFAULT) { 559 int rv; 560 u_char behavior = vm_map_entry_behavior(fs.entry); 561 562 era = fs.entry->read_ahead; 563 if (behavior == MAP_ENTRY_BEHAV_RANDOM || 564 P_KILLED(curproc)) { 565 behind = 0; 566 nera = 0; 567 ahead = 0; 568 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) { 569 behind = 0; 570 nera = VM_FAULT_READ_AHEAD_MAX; 571 ahead = nera; 572 if (fs.pindex == fs.entry->next_read) 573 vm_fault_dontneed(&fs, vaddr, ahead); 574 } else if (fs.pindex == fs.entry->next_read) { 575 /* 576 * This is a sequential fault. Arithmetically 577 * increase the requested number of pages in 578 * the read-ahead window. The requested 579 * number of pages is "# of sequential faults 580 * x (read ahead min + 1) + read ahead min" 581 */ 582 behind = 0; 583 nera = VM_FAULT_READ_AHEAD_MIN; 584 if (era > 0) { 585 nera += era + 1; 586 if (nera > VM_FAULT_READ_AHEAD_MAX) 587 nera = VM_FAULT_READ_AHEAD_MAX; 588 } 589 ahead = nera; 590 if (era == VM_FAULT_READ_AHEAD_MAX) 591 vm_fault_dontneed(&fs, vaddr, ahead); 592 } else { 593 /* 594 * This is a non-sequential fault. Request a 595 * cluster of pages that is aligned to a 596 * VM_FAULT_READ_DEFAULT page offset boundary 597 * within the object. Alignment to a page 598 * offset boundary is more likely to coincide 599 * with the underlying file system block than 600 * alignment to a virtual address boundary. 601 */ 602 cluster_offset = fs.pindex % 603 VM_FAULT_READ_DEFAULT; 604 behind = ulmin(cluster_offset, 605 atop(vaddr - fs.entry->start)); 606 nera = 0; 607 ahead = VM_FAULT_READ_DEFAULT - 1 - 608 cluster_offset; 609 } 610 ahead = ulmin(ahead, atop(fs.entry->end - vaddr) - 1); 611 if (era != nera) 612 fs.entry->read_ahead = nera; 613 614 /* 615 * Call the pager to retrieve the data, if any, after 616 * releasing the lock on the map. We hold a ref on 617 * fs.object and the pages are exclusive busied. 618 */ 619 unlock_map(&fs); 620 621 if (fs.object->type == OBJT_VNODE) { 622 vp = fs.object->handle; 623 if (vp == fs.vp) 624 goto vnode_locked; 625 else if (fs.vp != NULL) { 626 vput(fs.vp); 627 fs.vp = NULL; 628 } 629 locked = VOP_ISLOCKED(vp); 630 631 if (locked != LK_EXCLUSIVE) 632 locked = LK_SHARED; 633 /* Do not sleep for vnode lock while fs.m is busy */ 634 error = vget(vp, locked | LK_CANRECURSE | 635 LK_NOWAIT, curthread); 636 if (error != 0) { 637 vhold(vp); 638 release_page(&fs); 639 unlock_and_deallocate(&fs); 640 error = vget(vp, locked | LK_RETRY | 641 LK_CANRECURSE, curthread); 642 vdrop(vp); 643 fs.vp = vp; 644 KASSERT(error == 0, 645 ("vm_fault: vget failed")); 646 goto RetryFault; 647 } 648 fs.vp = vp; 649 } 650 vnode_locked: 651 KASSERT(fs.vp == NULL || !fs.map->system_map, 652 ("vm_fault: vnode-backed object mapped by system map")); 653 654 /* 655 * now we find out if any other pages should be paged 656 * in at this time this routine checks to see if the 657 * pages surrounding this fault reside in the same 658 * object as the page for this fault. If they do, 659 * then they are faulted in also into the object. The 660 * array "marray" returned contains an array of 661 * vm_page_t structs where one of them is the 662 * vm_page_t passed to the routine. The reqpage 663 * return value is the index into the marray for the 664 * vm_page_t passed to the routine. 665 * 666 * fs.m plus the additional pages are exclusive busied. 667 */ 668 faultcount = vm_fault_additional_pages( 669 fs.m, behind, ahead, marray, &reqpage); 670 671 rv = faultcount ? 672 vm_pager_get_pages(fs.object, marray, faultcount, 673 reqpage) : VM_PAGER_FAIL; 674 675 if (rv == VM_PAGER_OK) { 676 /* 677 * Found the page. Leave it busy while we play 678 * with it. 679 * 680 * Pager could have changed the page. Pager 681 * is responsible for disposition of old page 682 * if moved. 683 */ 684 fs.m = marray[reqpage]; 685 hardfault++; 686 break; /* break to PAGE HAS BEEN FOUND */ 687 } 688 /* 689 * Remove the bogus page (which does not exist at this 690 * object/offset); before doing so, we must get back 691 * our object lock to preserve our invariant. 692 * 693 * Also wake up any other process that may want to bring 694 * in this page. 695 * 696 * If this is the top-level object, we must leave the 697 * busy page to prevent another process from rushing 698 * past us, and inserting the page in that object at 699 * the same time that we are. 700 */ 701 if (rv == VM_PAGER_ERROR) 702 printf("vm_fault: pager read error, pid %d (%s)\n", 703 curproc->p_pid, curproc->p_comm); 704 /* 705 * Data outside the range of the pager or an I/O error 706 */ 707 /* 708 * XXX - the check for kernel_map is a kludge to work 709 * around having the machine panic on a kernel space 710 * fault w/ I/O error. 711 */ 712 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) || 713 (rv == VM_PAGER_BAD)) { 714 vm_page_lock(fs.m); 715 vm_page_free(fs.m); 716 vm_page_unlock(fs.m); 717 fs.m = NULL; 718 unlock_and_deallocate(&fs); 719 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE); 720 } 721 if (fs.object != fs.first_object) { 722 vm_page_lock(fs.m); 723 vm_page_free(fs.m); 724 vm_page_unlock(fs.m); 725 fs.m = NULL; 726 /* 727 * XXX - we cannot just fall out at this 728 * point, m has been freed and is invalid! 729 */ 730 } 731 } 732 733 /* 734 * We get here if the object has default pager (or unwiring) 735 * or the pager doesn't have the page. 736 */ 737 if (fs.object == fs.first_object) 738 fs.first_m = fs.m; 739 740 /* 741 * Move on to the next object. Lock the next object before 742 * unlocking the current one. 743 */ 744 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset); 745 next_object = fs.object->backing_object; 746 if (next_object == NULL) { 747 /* 748 * If there's no object left, fill the page in the top 749 * object with zeros. 750 */ 751 if (fs.object != fs.first_object) { 752 vm_object_pip_wakeup(fs.object); 753 VM_OBJECT_WUNLOCK(fs.object); 754 755 fs.object = fs.first_object; 756 fs.pindex = fs.first_pindex; 757 fs.m = fs.first_m; 758 VM_OBJECT_WLOCK(fs.object); 759 } 760 fs.first_m = NULL; 761 762 /* 763 * Zero the page if necessary and mark it valid. 764 */ 765 if ((fs.m->flags & PG_ZERO) == 0) { 766 pmap_zero_page(fs.m); 767 } else { 768 PCPU_INC(cnt.v_ozfod); 769 } 770 PCPU_INC(cnt.v_zfod); 771 fs.m->valid = VM_PAGE_BITS_ALL; 772 /* Don't try to prefault neighboring pages. */ 773 faultcount = 1; 774 break; /* break to PAGE HAS BEEN FOUND */ 775 } else { 776 KASSERT(fs.object != next_object, 777 ("object loop %p", next_object)); 778 VM_OBJECT_WLOCK(next_object); 779 vm_object_pip_add(next_object, 1); 780 if (fs.object != fs.first_object) 781 vm_object_pip_wakeup(fs.object); 782 VM_OBJECT_WUNLOCK(fs.object); 783 fs.object = next_object; 784 } 785 } 786 787 vm_page_assert_xbusied(fs.m); 788 789 /* 790 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 791 * is held.] 792 */ 793 794 /* 795 * If the page is being written, but isn't already owned by the 796 * top-level object, we have to copy it into a new page owned by the 797 * top-level object. 798 */ 799 if (fs.object != fs.first_object) { 800 /* 801 * We only really need to copy if we want to write it. 802 */ 803 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) { 804 /* 805 * This allows pages to be virtually copied from a 806 * backing_object into the first_object, where the 807 * backing object has no other refs to it, and cannot 808 * gain any more refs. Instead of a bcopy, we just 809 * move the page from the backing object to the 810 * first object. Note that we must mark the page 811 * dirty in the first object so that it will go out 812 * to swap when needed. 813 */ 814 is_first_object_locked = FALSE; 815 if ( 816 /* 817 * Only one shadow object 818 */ 819 (fs.object->shadow_count == 1) && 820 /* 821 * No COW refs, except us 822 */ 823 (fs.object->ref_count == 1) && 824 /* 825 * No one else can look this object up 826 */ 827 (fs.object->handle == NULL) && 828 /* 829 * No other ways to look the object up 830 */ 831 ((fs.object->type == OBJT_DEFAULT) || 832 (fs.object->type == OBJT_SWAP)) && 833 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) && 834 /* 835 * We don't chase down the shadow chain 836 */ 837 fs.object == fs.first_object->backing_object) { 838 /* 839 * get rid of the unnecessary page 840 */ 841 vm_page_lock(fs.first_m); 842 vm_page_free(fs.first_m); 843 vm_page_unlock(fs.first_m); 844 /* 845 * grab the page and put it into the 846 * process'es object. The page is 847 * automatically made dirty. 848 */ 849 if (vm_page_rename(fs.m, fs.first_object, 850 fs.first_pindex)) { 851 unlock_and_deallocate(&fs); 852 goto RetryFault; 853 } 854 #if VM_NRESERVLEVEL > 0 855 /* 856 * Rename the reservation. 857 */ 858 vm_reserv_rename(fs.m, fs.first_object, 859 fs.object, OFF_TO_IDX( 860 fs.first_object->backing_object_offset)); 861 #endif 862 vm_page_xbusy(fs.m); 863 fs.first_m = fs.m; 864 fs.m = NULL; 865 PCPU_INC(cnt.v_cow_optim); 866 } else { 867 /* 868 * Oh, well, lets copy it. 869 */ 870 pmap_copy_page(fs.m, fs.first_m); 871 fs.first_m->valid = VM_PAGE_BITS_ALL; 872 if (wired && (fault_flags & 873 VM_FAULT_WIRE) == 0) { 874 vm_page_lock(fs.first_m); 875 vm_page_wire(fs.first_m); 876 vm_page_unlock(fs.first_m); 877 878 vm_page_lock(fs.m); 879 vm_page_unwire(fs.m, PQ_INACTIVE); 880 vm_page_unlock(fs.m); 881 } 882 /* 883 * We no longer need the old page or object. 884 */ 885 release_page(&fs); 886 } 887 /* 888 * fs.object != fs.first_object due to above 889 * conditional 890 */ 891 vm_object_pip_wakeup(fs.object); 892 VM_OBJECT_WUNLOCK(fs.object); 893 /* 894 * Only use the new page below... 895 */ 896 fs.object = fs.first_object; 897 fs.pindex = fs.first_pindex; 898 fs.m = fs.first_m; 899 if (!is_first_object_locked) 900 VM_OBJECT_WLOCK(fs.object); 901 PCPU_INC(cnt.v_cow_faults); 902 curthread->td_cow++; 903 } else { 904 prot &= ~VM_PROT_WRITE; 905 } 906 } 907 908 /* 909 * We must verify that the maps have not changed since our last 910 * lookup. 911 */ 912 if (!fs.lookup_still_valid) { 913 vm_object_t retry_object; 914 vm_pindex_t retry_pindex; 915 vm_prot_t retry_prot; 916 917 if (!vm_map_trylock_read(fs.map)) { 918 release_page(&fs); 919 unlock_and_deallocate(&fs); 920 goto RetryFault; 921 } 922 fs.lookup_still_valid = TRUE; 923 if (fs.map->timestamp != map_generation) { 924 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type, 925 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired); 926 927 /* 928 * If we don't need the page any longer, put it on the inactive 929 * list (the easiest thing to do here). If no one needs it, 930 * pageout will grab it eventually. 931 */ 932 if (result != KERN_SUCCESS) { 933 release_page(&fs); 934 unlock_and_deallocate(&fs); 935 936 /* 937 * If retry of map lookup would have blocked then 938 * retry fault from start. 939 */ 940 if (result == KERN_FAILURE) 941 goto RetryFault; 942 return (result); 943 } 944 if ((retry_object != fs.first_object) || 945 (retry_pindex != fs.first_pindex)) { 946 release_page(&fs); 947 unlock_and_deallocate(&fs); 948 goto RetryFault; 949 } 950 951 /* 952 * Check whether the protection has changed or the object has 953 * been copied while we left the map unlocked. Changing from 954 * read to write permission is OK - we leave the page 955 * write-protected, and catch the write fault. Changing from 956 * write to read permission means that we can't mark the page 957 * write-enabled after all. 958 */ 959 prot &= retry_prot; 960 } 961 } 962 /* 963 * If the page was filled by a pager, update the map entry's 964 * last read offset. Since the pager does not return the 965 * actual set of pages that it read, this update is based on 966 * the requested set. Typically, the requested and actual 967 * sets are the same. 968 * 969 * XXX The following assignment modifies the map 970 * without holding a write lock on it. 971 */ 972 if (hardfault) 973 fs.entry->next_read = fs.pindex + faultcount - reqpage; 974 975 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE); 976 vm_page_assert_xbusied(fs.m); 977 978 /* 979 * Page must be completely valid or it is not fit to 980 * map into user space. vm_pager_get_pages() ensures this. 981 */ 982 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL, 983 ("vm_fault: page %p partially invalid", fs.m)); 984 VM_OBJECT_WUNLOCK(fs.object); 985 986 /* 987 * Put this page into the physical map. We had to do the unlock above 988 * because pmap_enter() may sleep. We don't put the page 989 * back on the active queue until later so that the pageout daemon 990 * won't find it (yet). 991 */ 992 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, 993 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0); 994 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 && 995 wired == 0) 996 vm_fault_prefault(&fs, vaddr, faultcount, reqpage); 997 VM_OBJECT_WLOCK(fs.object); 998 vm_page_lock(fs.m); 999 1000 /* 1001 * If the page is not wired down, then put it where the pageout daemon 1002 * can find it. 1003 */ 1004 if ((fault_flags & VM_FAULT_WIRE) != 0) { 1005 KASSERT(wired, ("VM_FAULT_WIRE && !wired")); 1006 vm_page_wire(fs.m); 1007 } else 1008 vm_page_activate(fs.m); 1009 if (m_hold != NULL) { 1010 *m_hold = fs.m; 1011 vm_page_hold(fs.m); 1012 } 1013 vm_page_unlock(fs.m); 1014 vm_page_xunbusy(fs.m); 1015 1016 /* 1017 * Unlock everything, and return 1018 */ 1019 unlock_and_deallocate(&fs); 1020 if (hardfault) { 1021 PCPU_INC(cnt.v_io_faults); 1022 curthread->td_ru.ru_majflt++; 1023 } else 1024 curthread->td_ru.ru_minflt++; 1025 1026 return (KERN_SUCCESS); 1027 } 1028 1029 /* 1030 * Speed up the reclamation of pages that precede the faulting pindex within 1031 * the first object of the shadow chain. Essentially, perform the equivalent 1032 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes 1033 * the faulting pindex by the cluster size when the pages read by vm_fault() 1034 * cross a cluster-size boundary. The cluster size is the greater of the 1035 * smallest superpage size and VM_FAULT_DONTNEED_MIN. 1036 * 1037 * When "fs->first_object" is a shadow object, the pages in the backing object 1038 * that precede the faulting pindex are deactivated by vm_fault(). So, this 1039 * function must only be concerned with pages in the first object. 1040 */ 1041 static void 1042 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead) 1043 { 1044 vm_map_entry_t entry; 1045 vm_object_t first_object, object; 1046 vm_offset_t end, start; 1047 vm_page_t m, m_next; 1048 vm_pindex_t pend, pstart; 1049 vm_size_t size; 1050 1051 object = fs->object; 1052 VM_OBJECT_ASSERT_WLOCKED(object); 1053 first_object = fs->first_object; 1054 if (first_object != object) { 1055 if (!VM_OBJECT_TRYWLOCK(first_object)) { 1056 VM_OBJECT_WUNLOCK(object); 1057 VM_OBJECT_WLOCK(first_object); 1058 VM_OBJECT_WLOCK(object); 1059 } 1060 } 1061 /* Neither fictitious nor unmanaged pages can be reclaimed. */ 1062 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) { 1063 size = VM_FAULT_DONTNEED_MIN; 1064 if (MAXPAGESIZES > 1 && size < pagesizes[1]) 1065 size = pagesizes[1]; 1066 end = rounddown2(vaddr, size); 1067 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) && 1068 (entry = fs->entry)->start < end) { 1069 if (end - entry->start < size) 1070 start = entry->start; 1071 else 1072 start = end - size; 1073 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED); 1074 pstart = OFF_TO_IDX(entry->offset) + atop(start - 1075 entry->start); 1076 m_next = vm_page_find_least(first_object, pstart); 1077 pend = OFF_TO_IDX(entry->offset) + atop(end - 1078 entry->start); 1079 while ((m = m_next) != NULL && m->pindex < pend) { 1080 m_next = TAILQ_NEXT(m, listq); 1081 if (m->valid != VM_PAGE_BITS_ALL || 1082 vm_page_busied(m)) 1083 continue; 1084 1085 /* 1086 * Don't clear PGA_REFERENCED, since it would 1087 * likely represent a reference by a different 1088 * process. 1089 * 1090 * Typically, at this point, prefetched pages 1091 * are still in the inactive queue. Only 1092 * pages that triggered page faults are in the 1093 * active queue. 1094 */ 1095 vm_page_lock(m); 1096 vm_page_deactivate(m); 1097 vm_page_unlock(m); 1098 } 1099 } 1100 } 1101 if (first_object != object) 1102 VM_OBJECT_WUNLOCK(first_object); 1103 } 1104 1105 /* 1106 * vm_fault_prefault provides a quick way of clustering 1107 * pagefaults into a processes address space. It is a "cousin" 1108 * of vm_map_pmap_enter, except it runs at page fault time instead 1109 * of mmap time. 1110 */ 1111 static void 1112 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra, 1113 int faultcount, int reqpage) 1114 { 1115 pmap_t pmap; 1116 vm_map_entry_t entry; 1117 vm_object_t backing_object, lobject; 1118 vm_offset_t addr, starta; 1119 vm_pindex_t pindex; 1120 vm_page_t m; 1121 int backward, forward, i; 1122 1123 pmap = fs->map->pmap; 1124 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace)) 1125 return; 1126 1127 if (faultcount > 0) { 1128 backward = reqpage; 1129 forward = faultcount - reqpage - 1; 1130 } else { 1131 backward = PFBAK; 1132 forward = PFFOR; 1133 } 1134 entry = fs->entry; 1135 1136 starta = addra - backward * PAGE_SIZE; 1137 if (starta < entry->start) { 1138 starta = entry->start; 1139 } else if (starta > addra) { 1140 starta = 0; 1141 } 1142 1143 /* 1144 * Generate the sequence of virtual addresses that are candidates for 1145 * prefaulting in an outward spiral from the faulting virtual address, 1146 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra 1147 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ... 1148 * If the candidate address doesn't have a backing physical page, then 1149 * the loop immediately terminates. 1150 */ 1151 for (i = 0; i < 2 * imax(backward, forward); i++) { 1152 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE : 1153 PAGE_SIZE); 1154 if (addr > addra + forward * PAGE_SIZE) 1155 addr = 0; 1156 1157 if (addr < starta || addr >= entry->end) 1158 continue; 1159 1160 if (!pmap_is_prefaultable(pmap, addr)) 1161 continue; 1162 1163 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 1164 lobject = entry->object.vm_object; 1165 VM_OBJECT_RLOCK(lobject); 1166 while ((m = vm_page_lookup(lobject, pindex)) == NULL && 1167 lobject->type == OBJT_DEFAULT && 1168 (backing_object = lobject->backing_object) != NULL) { 1169 KASSERT((lobject->backing_object_offset & PAGE_MASK) == 1170 0, ("vm_fault_prefault: unaligned object offset")); 1171 pindex += lobject->backing_object_offset >> PAGE_SHIFT; 1172 VM_OBJECT_RLOCK(backing_object); 1173 VM_OBJECT_RUNLOCK(lobject); 1174 lobject = backing_object; 1175 } 1176 if (m == NULL) { 1177 VM_OBJECT_RUNLOCK(lobject); 1178 break; 1179 } 1180 if (m->valid == VM_PAGE_BITS_ALL && 1181 (m->flags & PG_FICTITIOUS) == 0) 1182 pmap_enter_quick(pmap, addr, m, entry->protection); 1183 VM_OBJECT_RUNLOCK(lobject); 1184 } 1185 } 1186 1187 /* 1188 * Hold each of the physical pages that are mapped by the specified range of 1189 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid 1190 * and allow the specified types of access, "prot". If all of the implied 1191 * pages are successfully held, then the number of held pages is returned 1192 * together with pointers to those pages in the array "ma". However, if any 1193 * of the pages cannot be held, -1 is returned. 1194 */ 1195 int 1196 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len, 1197 vm_prot_t prot, vm_page_t *ma, int max_count) 1198 { 1199 vm_offset_t end, va; 1200 vm_page_t *mp; 1201 int count; 1202 boolean_t pmap_failed; 1203 1204 if (len == 0) 1205 return (0); 1206 end = round_page(addr + len); 1207 addr = trunc_page(addr); 1208 1209 /* 1210 * Check for illegal addresses. 1211 */ 1212 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map)) 1213 return (-1); 1214 1215 if (atop(end - addr) > max_count) 1216 panic("vm_fault_quick_hold_pages: count > max_count"); 1217 count = atop(end - addr); 1218 1219 /* 1220 * Most likely, the physical pages are resident in the pmap, so it is 1221 * faster to try pmap_extract_and_hold() first. 1222 */ 1223 pmap_failed = FALSE; 1224 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) { 1225 *mp = pmap_extract_and_hold(map->pmap, va, prot); 1226 if (*mp == NULL) 1227 pmap_failed = TRUE; 1228 else if ((prot & VM_PROT_WRITE) != 0 && 1229 (*mp)->dirty != VM_PAGE_BITS_ALL) { 1230 /* 1231 * Explicitly dirty the physical page. Otherwise, the 1232 * caller's changes may go unnoticed because they are 1233 * performed through an unmanaged mapping or by a DMA 1234 * operation. 1235 * 1236 * The object lock is not held here. 1237 * See vm_page_clear_dirty_mask(). 1238 */ 1239 vm_page_dirty(*mp); 1240 } 1241 } 1242 if (pmap_failed) { 1243 /* 1244 * One or more pages could not be held by the pmap. Either no 1245 * page was mapped at the specified virtual address or that 1246 * mapping had insufficient permissions. Attempt to fault in 1247 * and hold these pages. 1248 */ 1249 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) 1250 if (*mp == NULL && vm_fault_hold(map, va, prot, 1251 VM_FAULT_NORMAL, mp) != KERN_SUCCESS) 1252 goto error; 1253 } 1254 return (count); 1255 error: 1256 for (mp = ma; mp < ma + count; mp++) 1257 if (*mp != NULL) { 1258 vm_page_lock(*mp); 1259 vm_page_unhold(*mp); 1260 vm_page_unlock(*mp); 1261 } 1262 return (-1); 1263 } 1264 1265 /* 1266 * Routine: 1267 * vm_fault_copy_entry 1268 * Function: 1269 * Create new shadow object backing dst_entry with private copy of 1270 * all underlying pages. When src_entry is equal to dst_entry, 1271 * function implements COW for wired-down map entry. Otherwise, 1272 * it forks wired entry into dst_map. 1273 * 1274 * In/out conditions: 1275 * The source and destination maps must be locked for write. 1276 * The source map entry must be wired down (or be a sharing map 1277 * entry corresponding to a main map entry that is wired down). 1278 */ 1279 void 1280 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1281 vm_map_entry_t dst_entry, vm_map_entry_t src_entry, 1282 vm_ooffset_t *fork_charge) 1283 { 1284 vm_object_t backing_object, dst_object, object, src_object; 1285 vm_pindex_t dst_pindex, pindex, src_pindex; 1286 vm_prot_t access, prot; 1287 vm_offset_t vaddr; 1288 vm_page_t dst_m; 1289 vm_page_t src_m; 1290 boolean_t upgrade; 1291 1292 #ifdef lint 1293 src_map++; 1294 #endif /* lint */ 1295 1296 upgrade = src_entry == dst_entry; 1297 access = prot = dst_entry->protection; 1298 1299 src_object = src_entry->object.vm_object; 1300 src_pindex = OFF_TO_IDX(src_entry->offset); 1301 1302 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) { 1303 dst_object = src_object; 1304 vm_object_reference(dst_object); 1305 } else { 1306 /* 1307 * Create the top-level object for the destination entry. (Doesn't 1308 * actually shadow anything - we copy the pages directly.) 1309 */ 1310 dst_object = vm_object_allocate(OBJT_DEFAULT, 1311 OFF_TO_IDX(dst_entry->end - dst_entry->start)); 1312 #if VM_NRESERVLEVEL > 0 1313 dst_object->flags |= OBJ_COLORED; 1314 dst_object->pg_color = atop(dst_entry->start); 1315 #endif 1316 } 1317 1318 VM_OBJECT_WLOCK(dst_object); 1319 KASSERT(upgrade || dst_entry->object.vm_object == NULL, 1320 ("vm_fault_copy_entry: vm_object not NULL")); 1321 if (src_object != dst_object) { 1322 dst_entry->object.vm_object = dst_object; 1323 dst_entry->offset = 0; 1324 dst_object->charge = dst_entry->end - dst_entry->start; 1325 } 1326 if (fork_charge != NULL) { 1327 KASSERT(dst_entry->cred == NULL, 1328 ("vm_fault_copy_entry: leaked swp charge")); 1329 dst_object->cred = curthread->td_ucred; 1330 crhold(dst_object->cred); 1331 *fork_charge += dst_object->charge; 1332 } else if (dst_object->cred == NULL) { 1333 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p", 1334 dst_entry)); 1335 dst_object->cred = dst_entry->cred; 1336 dst_entry->cred = NULL; 1337 } 1338 1339 /* 1340 * If not an upgrade, then enter the mappings in the pmap as 1341 * read and/or execute accesses. Otherwise, enter them as 1342 * write accesses. 1343 * 1344 * A writeable large page mapping is only created if all of 1345 * the constituent small page mappings are modified. Marking 1346 * PTEs as modified on inception allows promotion to happen 1347 * without taking potentially large number of soft faults. 1348 */ 1349 if (!upgrade) 1350 access &= ~VM_PROT_WRITE; 1351 1352 /* 1353 * Loop through all of the virtual pages within the entry's 1354 * range, copying each page from the source object to the 1355 * destination object. Since the source is wired, those pages 1356 * must exist. In contrast, the destination is pageable. 1357 * Since the destination object does share any backing storage 1358 * with the source object, all of its pages must be dirtied, 1359 * regardless of whether they can be written. 1360 */ 1361 for (vaddr = dst_entry->start, dst_pindex = 0; 1362 vaddr < dst_entry->end; 1363 vaddr += PAGE_SIZE, dst_pindex++) { 1364 again: 1365 /* 1366 * Find the page in the source object, and copy it in. 1367 * Because the source is wired down, the page will be 1368 * in memory. 1369 */ 1370 if (src_object != dst_object) 1371 VM_OBJECT_RLOCK(src_object); 1372 object = src_object; 1373 pindex = src_pindex + dst_pindex; 1374 while ((src_m = vm_page_lookup(object, pindex)) == NULL && 1375 (backing_object = object->backing_object) != NULL) { 1376 /* 1377 * Unless the source mapping is read-only or 1378 * it is presently being upgraded from 1379 * read-only, the first object in the shadow 1380 * chain should provide all of the pages. In 1381 * other words, this loop body should never be 1382 * executed when the source mapping is already 1383 * read/write. 1384 */ 1385 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 || 1386 upgrade, 1387 ("vm_fault_copy_entry: main object missing page")); 1388 1389 VM_OBJECT_RLOCK(backing_object); 1390 pindex += OFF_TO_IDX(object->backing_object_offset); 1391 if (object != dst_object) 1392 VM_OBJECT_RUNLOCK(object); 1393 object = backing_object; 1394 } 1395 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing")); 1396 1397 if (object != dst_object) { 1398 /* 1399 * Allocate a page in the destination object. 1400 */ 1401 dst_m = vm_page_alloc(dst_object, (src_object == 1402 dst_object ? src_pindex : 0) + dst_pindex, 1403 VM_ALLOC_NORMAL); 1404 if (dst_m == NULL) { 1405 VM_OBJECT_WUNLOCK(dst_object); 1406 VM_OBJECT_RUNLOCK(object); 1407 VM_WAIT; 1408 VM_OBJECT_WLOCK(dst_object); 1409 goto again; 1410 } 1411 pmap_copy_page(src_m, dst_m); 1412 VM_OBJECT_RUNLOCK(object); 1413 dst_m->valid = VM_PAGE_BITS_ALL; 1414 dst_m->dirty = VM_PAGE_BITS_ALL; 1415 } else { 1416 dst_m = src_m; 1417 if (vm_page_sleep_if_busy(dst_m, "fltupg")) 1418 goto again; 1419 vm_page_xbusy(dst_m); 1420 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL, 1421 ("invalid dst page %p", dst_m)); 1422 } 1423 VM_OBJECT_WUNLOCK(dst_object); 1424 1425 /* 1426 * Enter it in the pmap. If a wired, copy-on-write 1427 * mapping is being replaced by a write-enabled 1428 * mapping, then wire that new mapping. 1429 */ 1430 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, 1431 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0); 1432 1433 /* 1434 * Mark it no longer busy, and put it on the active list. 1435 */ 1436 VM_OBJECT_WLOCK(dst_object); 1437 1438 if (upgrade) { 1439 if (src_m != dst_m) { 1440 vm_page_lock(src_m); 1441 vm_page_unwire(src_m, PQ_INACTIVE); 1442 vm_page_unlock(src_m); 1443 vm_page_lock(dst_m); 1444 vm_page_wire(dst_m); 1445 vm_page_unlock(dst_m); 1446 } else { 1447 KASSERT(dst_m->wire_count > 0, 1448 ("dst_m %p is not wired", dst_m)); 1449 } 1450 } else { 1451 vm_page_lock(dst_m); 1452 vm_page_activate(dst_m); 1453 vm_page_unlock(dst_m); 1454 } 1455 vm_page_xunbusy(dst_m); 1456 } 1457 VM_OBJECT_WUNLOCK(dst_object); 1458 if (upgrade) { 1459 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY); 1460 vm_object_deallocate(src_object); 1461 } 1462 } 1463 1464 1465 /* 1466 * This routine checks around the requested page for other pages that 1467 * might be able to be faulted in. This routine brackets the viable 1468 * pages for the pages to be paged in. 1469 * 1470 * Inputs: 1471 * m, rbehind, rahead 1472 * 1473 * Outputs: 1474 * marray (array of vm_page_t), reqpage (index of requested page) 1475 * 1476 * Return value: 1477 * number of pages in marray 1478 */ 1479 static int 1480 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage) 1481 vm_page_t m; 1482 int rbehind; 1483 int rahead; 1484 vm_page_t *marray; 1485 int *reqpage; 1486 { 1487 int i,j; 1488 vm_object_t object; 1489 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1490 vm_page_t rtm; 1491 int cbehind, cahead; 1492 1493 VM_OBJECT_ASSERT_WLOCKED(m->object); 1494 1495 object = m->object; 1496 pindex = m->pindex; 1497 cbehind = cahead = 0; 1498 1499 /* 1500 * if the requested page is not available, then give up now 1501 */ 1502 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1503 return 0; 1504 } 1505 1506 if ((cbehind == 0) && (cahead == 0)) { 1507 *reqpage = 0; 1508 marray[0] = m; 1509 return 1; 1510 } 1511 1512 if (rahead > cahead) { 1513 rahead = cahead; 1514 } 1515 1516 if (rbehind > cbehind) { 1517 rbehind = cbehind; 1518 } 1519 1520 /* 1521 * scan backward for the read behind pages -- in memory 1522 */ 1523 if (pindex > 0) { 1524 if (rbehind > pindex) { 1525 rbehind = pindex; 1526 startpindex = 0; 1527 } else { 1528 startpindex = pindex - rbehind; 1529 } 1530 1531 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL && 1532 rtm->pindex >= startpindex) 1533 startpindex = rtm->pindex + 1; 1534 1535 /* tpindex is unsigned; beware of numeric underflow. */ 1536 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex && 1537 tpindex < pindex; i++, tpindex--) { 1538 1539 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1540 VM_ALLOC_IFNOTCACHED); 1541 if (rtm == NULL) { 1542 /* 1543 * Shift the allocated pages to the 1544 * beginning of the array. 1545 */ 1546 for (j = 0; j < i; j++) { 1547 marray[j] = marray[j + tpindex + 1 - 1548 startpindex]; 1549 } 1550 break; 1551 } 1552 1553 marray[tpindex - startpindex] = rtm; 1554 } 1555 } else { 1556 startpindex = 0; 1557 i = 0; 1558 } 1559 1560 marray[i] = m; 1561 /* page offset of the required page */ 1562 *reqpage = i; 1563 1564 tpindex = pindex + 1; 1565 i++; 1566 1567 /* 1568 * scan forward for the read ahead pages 1569 */ 1570 endpindex = tpindex + rahead; 1571 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex) 1572 endpindex = rtm->pindex; 1573 if (endpindex > object->size) 1574 endpindex = object->size; 1575 1576 for (; tpindex < endpindex; i++, tpindex++) { 1577 1578 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL | 1579 VM_ALLOC_IFNOTCACHED); 1580 if (rtm == NULL) { 1581 break; 1582 } 1583 1584 marray[i] = rtm; 1585 } 1586 1587 /* return number of pages */ 1588 return i; 1589 } 1590 1591 /* 1592 * Block entry into the machine-independent layer's page fault handler by 1593 * the calling thread. Subsequent calls to vm_fault() by that thread will 1594 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of 1595 * spurious page faults. 1596 */ 1597 int 1598 vm_fault_disable_pagefaults(void) 1599 { 1600 1601 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR)); 1602 } 1603 1604 void 1605 vm_fault_enable_pagefaults(int save) 1606 { 1607 1608 curthread_pflags_restore(save); 1609 } 1610