1 /* 2 * (MPSAFE) 3 * 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * Copyright (c) 1994 John S. Dyson 7 * All rights reserved. 8 * Copyright (c) 1994 David Greenman 9 * All rights reserved. 10 * 11 * 12 * This code is derived from software contributed to Berkeley by 13 * The Mach Operating System project at Carnegie-Mellon University. 14 * 15 * Redistribution and use in source and binary forms, with or without 16 * modification, are permitted provided that the following conditions 17 * are met: 18 * 1. Redistributions of source code must retain the above copyright 19 * notice, this list of conditions and the following disclaimer. 20 * 2. Redistributions in binary form must reproduce the above copyright 21 * notice, this list of conditions and the following disclaimer in the 22 * documentation and/or other materials provided with the distribution. 23 * 3. All advertising materials mentioning features or use of this software 24 * must display the following acknowledgement: 25 * This product includes software developed by the University of 26 * California, Berkeley and its contributors. 27 * 4. Neither the name of the University nor the names of its contributors 28 * may be used to endorse or promote products derived from this software 29 * without specific prior written permission. 30 * 31 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 32 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 33 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 34 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 35 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 36 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 37 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 39 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 40 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 41 * SUCH DAMAGE. 42 * 43 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94 44 * 45 * 46 * Copyright (c) 1987, 1990 Carnegie-Mellon University. 47 * All rights reserved. 48 * 49 * Authors: Avadis Tevanian, Jr., Michael Wayne Young 50 * 51 * Permission to use, copy, modify and distribute this software and 52 * its documentation is hereby granted, provided that both the copyright 53 * notice and this permission notice appear in all copies of the 54 * software, derivative works or modified versions, and any portions 55 * thereof, and that both notices appear in supporting documentation. 56 * 57 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 58 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 59 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 60 * 61 * Carnegie Mellon requests users of this software to return to 62 * 63 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU 64 * School of Computer Science 65 * Carnegie Mellon University 66 * Pittsburgh PA 15213-3890 67 * 68 * any improvements or extensions that they make and grant Carnegie the 69 * rights to redistribute these changes. 70 * 71 * $FreeBSD: src/sys/vm/vm_fault.c,v 1.108.2.8 2002/02/26 05:49:27 silby Exp $ 72 * $DragonFly: src/sys/vm/vm_fault.c,v 1.47 2008/07/01 02:02:56 dillon Exp $ 73 */ 74 75 /* 76 * Page fault handling module. 77 */ 78 79 #include <sys/param.h> 80 #include <sys/systm.h> 81 #include <sys/kernel.h> 82 #include <sys/proc.h> 83 #include <sys/vnode.h> 84 #include <sys/resourcevar.h> 85 #include <sys/vmmeter.h> 86 #include <sys/vkernel.h> 87 #include <sys/lock.h> 88 #include <sys/sysctl.h> 89 90 #include <cpu/lwbuf.h> 91 92 #include <vm/vm.h> 93 #include <vm/vm_param.h> 94 #include <vm/pmap.h> 95 #include <vm/vm_map.h> 96 #include <vm/vm_object.h> 97 #include <vm/vm_page.h> 98 #include <vm/vm_pageout.h> 99 #include <vm/vm_kern.h> 100 #include <vm/vm_pager.h> 101 #include <vm/vnode_pager.h> 102 #include <vm/vm_extern.h> 103 104 #include <sys/thread2.h> 105 #include <vm/vm_page2.h> 106 107 struct faultstate { 108 vm_page_t m; 109 vm_object_t object; 110 vm_pindex_t pindex; 111 vm_prot_t prot; 112 vm_page_t first_m; 113 vm_object_t first_object; 114 vm_prot_t first_prot; 115 vm_map_t map; 116 vm_map_entry_t entry; 117 int lookup_still_valid; 118 int didlimit; 119 int hardfault; 120 int fault_flags; 121 int map_generation; 122 boolean_t wired; 123 struct vnode *vp; 124 }; 125 126 static int vm_fast_fault = 1; 127 SYSCTL_INT(_vm, OID_AUTO, fast_fault, CTLFLAG_RW, &vm_fast_fault, 0, 128 "Burst fault zero-fill regions"); 129 static int debug_cluster = 0; 130 SYSCTL_INT(_vm, OID_AUTO, debug_cluster, CTLFLAG_RW, &debug_cluster, 0, ""); 131 132 static int vm_fault_object(struct faultstate *, vm_pindex_t, vm_prot_t); 133 static int vm_fault_vpagetable(struct faultstate *, vm_pindex_t *, vpte_t, int); 134 #if 0 135 static int vm_fault_additional_pages (vm_page_t, int, int, vm_page_t *, int *); 136 #endif 137 static int vm_fault_ratelimit(struct vmspace *); 138 static void vm_set_nosync(vm_page_t m, vm_map_entry_t entry); 139 static void vm_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry, 140 int prot); 141 142 /* 143 * The caller must hold vm_token. 144 */ 145 static __inline void 146 release_page(struct faultstate *fs) 147 { 148 vm_page_deactivate(fs->m); 149 vm_page_wakeup(fs->m); 150 fs->m = NULL; 151 } 152 153 /* 154 * The caller must hold vm_token. 155 * 156 * NOTE: Once unlocked any cached fs->entry becomes invalid, any reuse 157 * requires relocking and then checking the timestamp. 158 * 159 * NOTE: vm_map_lock_read() does not bump fs->map->timestamp so we do 160 * not have to update fs->map_generation here. 161 * 162 * NOTE: This function can fail due to a deadlock against the caller's 163 * holding of a vm_page BUSY. 164 */ 165 static __inline int 166 relock_map(struct faultstate *fs) 167 { 168 int error; 169 170 if (fs->lookup_still_valid == FALSE && fs->map) { 171 error = vm_map_lock_read_to(fs->map); 172 if (error == 0) 173 fs->lookup_still_valid = TRUE; 174 } else { 175 error = 0; 176 } 177 return error; 178 } 179 180 static __inline void 181 unlock_map(struct faultstate *fs) 182 { 183 if (fs->lookup_still_valid && fs->map) { 184 vm_map_lookup_done(fs->map, fs->entry, 0); 185 fs->lookup_still_valid = FALSE; 186 } 187 } 188 189 /* 190 * Clean up after a successful call to vm_fault_object() so another call 191 * to vm_fault_object() can be made. 192 * 193 * The caller must hold vm_token. 194 */ 195 static void 196 _cleanup_successful_fault(struct faultstate *fs, int relock) 197 { 198 if (fs->object != fs->first_object) { 199 vm_page_free(fs->first_m); 200 vm_object_pip_wakeup(fs->object); 201 fs->first_m = NULL; 202 } 203 fs->object = fs->first_object; 204 if (relock && fs->lookup_still_valid == FALSE) { 205 if (fs->map) 206 vm_map_lock_read(fs->map); 207 fs->lookup_still_valid = TRUE; 208 } 209 } 210 211 /* 212 * The caller must hold vm_token. 213 */ 214 static void 215 _unlock_things(struct faultstate *fs, int dealloc) 216 { 217 vm_object_pip_wakeup(fs->first_object); 218 _cleanup_successful_fault(fs, 0); 219 if (dealloc) { 220 vm_object_deallocate(fs->first_object); 221 fs->first_object = NULL; 222 } 223 unlock_map(fs); 224 if (fs->vp != NULL) { 225 vput(fs->vp); 226 fs->vp = NULL; 227 } 228 } 229 230 #define unlock_things(fs) _unlock_things(fs, 0) 231 #define unlock_and_deallocate(fs) _unlock_things(fs, 1) 232 #define cleanup_successful_fault(fs) _cleanup_successful_fault(fs, 1) 233 234 /* 235 * TRYPAGER 236 * 237 * Determine if the pager for the current object *might* contain the page. 238 * 239 * We only need to try the pager if this is not a default object (default 240 * objects are zero-fill and have no real pager), and if we are not taking 241 * a wiring fault or if the FS entry is wired. 242 */ 243 #define TRYPAGER(fs) \ 244 (fs->object->type != OBJT_DEFAULT && \ 245 (((fs->fault_flags & VM_FAULT_WIRE_MASK) == 0) || fs->wired)) 246 247 /* 248 * vm_fault: 249 * 250 * Handle a page fault occuring at the given address, requiring the given 251 * permissions, in the map specified. If successful, the page is inserted 252 * into the associated physical map. 253 * 254 * NOTE: The given address should be truncated to the proper page address. 255 * 256 * KERN_SUCCESS is returned if the page fault is handled; otherwise, 257 * a standard error specifying why the fault is fatal is returned. 258 * 259 * The map in question must be referenced, and remains so. 260 * The caller may hold no locks. 261 * No other requirements. 262 */ 263 int 264 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, int fault_flags) 265 { 266 int result; 267 vm_pindex_t first_pindex; 268 struct faultstate fs; 269 int growstack; 270 271 mycpu->gd_cnt.v_vm_faults++; 272 273 fs.didlimit = 0; 274 fs.hardfault = 0; 275 fs.fault_flags = fault_flags; 276 growstack = 1; 277 278 RetryFault: 279 /* 280 * Find the vm_map_entry representing the backing store and resolve 281 * the top level object and page index. This may have the side 282 * effect of executing a copy-on-write on the map entry and/or 283 * creating a shadow object, but will not COW any actual VM pages. 284 * 285 * On success fs.map is left read-locked and various other fields 286 * are initialized but not otherwise referenced or locked. 287 * 288 * NOTE! vm_map_lookup will try to upgrade the fault_type to 289 * VM_FAULT_WRITE if the map entry is a virtual page table and also 290 * writable, so we can set the 'A'accessed bit in the virtual page 291 * table entry. 292 */ 293 fs.map = map; 294 result = vm_map_lookup(&fs.map, vaddr, fault_type, 295 &fs.entry, &fs.first_object, 296 &first_pindex, &fs.first_prot, &fs.wired); 297 298 /* 299 * If the lookup failed or the map protections are incompatible, 300 * the fault generally fails. However, if the caller is trying 301 * to do a user wiring we have more work to do. 302 */ 303 if (result != KERN_SUCCESS) { 304 if (result != KERN_PROTECTION_FAILURE || 305 (fs.fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) 306 { 307 if (result == KERN_INVALID_ADDRESS && growstack && 308 map != &kernel_map && curproc != NULL) { 309 result = vm_map_growstack(curproc, vaddr); 310 if (result != KERN_SUCCESS) 311 return (KERN_FAILURE); 312 growstack = 0; 313 goto RetryFault; 314 } 315 return (result); 316 } 317 318 /* 319 * If we are user-wiring a r/w segment, and it is COW, then 320 * we need to do the COW operation. Note that we don't 321 * currently COW RO sections now, because it is NOT desirable 322 * to COW .text. We simply keep .text from ever being COW'ed 323 * and take the heat that one cannot debug wired .text sections. 324 */ 325 result = vm_map_lookup(&fs.map, vaddr, 326 VM_PROT_READ|VM_PROT_WRITE| 327 VM_PROT_OVERRIDE_WRITE, 328 &fs.entry, &fs.first_object, 329 &first_pindex, &fs.first_prot, 330 &fs.wired); 331 if (result != KERN_SUCCESS) 332 return result; 333 334 /* 335 * If we don't COW now, on a user wire, the user will never 336 * be able to write to the mapping. If we don't make this 337 * restriction, the bookkeeping would be nearly impossible. 338 */ 339 if ((fs.entry->protection & VM_PROT_WRITE) == 0) 340 fs.entry->max_protection &= ~VM_PROT_WRITE; 341 } 342 343 /* 344 * fs.map is read-locked 345 * 346 * Misc checks. Save the map generation number to detect races. 347 */ 348 fs.map_generation = fs.map->timestamp; 349 350 if (fs.entry->eflags & (MAP_ENTRY_NOFAULT | MAP_ENTRY_KSTACK)) { 351 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 352 panic("vm_fault: fault on nofault entry, addr: %p", 353 (void *)vaddr); 354 } 355 if ((fs.entry->eflags & MAP_ENTRY_KSTACK) && 356 vaddr >= fs.entry->start && 357 vaddr < fs.entry->start + PAGE_SIZE) { 358 panic("vm_fault: fault on stack guard, addr: %p", 359 (void *)vaddr); 360 } 361 } 362 363 /* 364 * A system map entry may return a NULL object. No object means 365 * no pager means an unrecoverable kernel fault. 366 */ 367 if (fs.first_object == NULL) { 368 panic("vm_fault: unrecoverable fault at %p in entry %p", 369 (void *)vaddr, fs.entry); 370 } 371 372 /* 373 * Make a reference to this object to prevent its disposal while we 374 * are messing with it. Once we have the reference, the map is free 375 * to be diddled. Since objects reference their shadows (and copies), 376 * they will stay around as well. 377 * 378 * Bump the paging-in-progress count to prevent size changes (e.g. 379 * truncation operations) during I/O. This must be done after 380 * obtaining the vnode lock in order to avoid possible deadlocks. 381 * 382 * The vm_object must be held before manipulation. 383 */ 384 lwkt_gettoken(&vm_token); 385 vm_object_hold(fs.first_object); 386 vm_object_reference(fs.first_object); 387 fs.vp = vnode_pager_lock(fs.first_object); 388 vm_object_pip_add(fs.first_object, 1); 389 vm_object_drop(fs.first_object); 390 lwkt_reltoken(&vm_token); 391 392 fs.lookup_still_valid = TRUE; 393 fs.first_m = NULL; 394 fs.object = fs.first_object; /* so unlock_and_deallocate works */ 395 396 /* 397 * If the entry is wired we cannot change the page protection. 398 */ 399 if (fs.wired) 400 fault_type = fs.first_prot; 401 402 /* 403 * The page we want is at (first_object, first_pindex), but if the 404 * vm_map_entry is VM_MAPTYPE_VPAGETABLE we have to traverse the 405 * page table to figure out the actual pindex. 406 * 407 * NOTE! DEVELOPMENT IN PROGRESS, THIS IS AN INITIAL IMPLEMENTATION 408 * ONLY 409 */ 410 if (fs.entry->maptype == VM_MAPTYPE_VPAGETABLE) { 411 result = vm_fault_vpagetable(&fs, &first_pindex, 412 fs.entry->aux.master_pde, 413 fault_type); 414 if (result == KERN_TRY_AGAIN) 415 goto RetryFault; 416 if (result != KERN_SUCCESS) 417 return (result); 418 } 419 420 /* 421 * Now we have the actual (object, pindex), fault in the page. If 422 * vm_fault_object() fails it will unlock and deallocate the FS 423 * data. If it succeeds everything remains locked and fs->object 424 * will have an additional PIP count if it is not equal to 425 * fs->first_object 426 * 427 * vm_fault_object will set fs->prot for the pmap operation. It is 428 * allowed to set VM_PROT_WRITE if fault_type == VM_PROT_READ if the 429 * page can be safely written. However, it will force a read-only 430 * mapping for a read fault if the memory is managed by a virtual 431 * page table. 432 */ 433 /* BEFORE */ 434 result = vm_fault_object(&fs, first_pindex, fault_type); 435 436 if (result == KERN_TRY_AGAIN) { 437 /*lwkt_reltoken(&vm_token);*/ 438 goto RetryFault; 439 } 440 if (result != KERN_SUCCESS) { 441 /*lwkt_reltoken(&vm_token);*/ 442 return (result); 443 } 444 445 /* 446 * On success vm_fault_object() does not unlock or deallocate, and fs.m 447 * will contain a busied page. 448 * 449 * Enter the page into the pmap and do pmap-related adjustments. 450 */ 451 vm_page_flag_set(fs.m, PG_REFERENCED); 452 pmap_enter(fs.map->pmap, vaddr, fs.m, fs.prot, fs.wired); 453 454 /* 455 * Burst in a few more pages if possible. The fs.map should still 456 * be locked. 457 */ 458 if (fault_flags & VM_FAULT_BURST) { 459 if ((fs.fault_flags & VM_FAULT_WIRE_MASK) == 0 && 460 fs.wired == 0) { 461 vm_prefault(fs.map->pmap, vaddr, fs.entry, fs.prot); 462 } 463 } 464 lwkt_gettoken(&vm_token); 465 unlock_things(&fs); 466 467 /*KKASSERT(fs.m->queue == PQ_NONE); page-in op may deactivate page */ 468 KKASSERT(fs.m->flags & PG_BUSY); 469 470 /* 471 * If the page is not wired down, then put it where the pageout daemon 472 * can find it. 473 * 474 * We do not really need to get vm_token here but since all the 475 * vm_*() calls have to doing it here improves efficiency. 476 */ 477 /*lwkt_gettoken(&vm_token);*/ 478 479 if (fs.fault_flags & VM_FAULT_WIRE_MASK) { 480 lwkt_reltoken(&vm_token); /* before wire activate does not */ 481 if (fs.wired) 482 vm_page_wire(fs.m); 483 else 484 vm_page_unwire(fs.m, 1); 485 } else { 486 vm_page_activate(fs.m); 487 lwkt_reltoken(&vm_token); /* before wire activate does not */ 488 } 489 /*lwkt_reltoken(&vm_token); after wire/activate works */ 490 491 if (curthread->td_lwp) { 492 if (fs.hardfault) { 493 curthread->td_lwp->lwp_ru.ru_majflt++; 494 } else { 495 curthread->td_lwp->lwp_ru.ru_minflt++; 496 } 497 } 498 499 /* 500 * Unlock everything, and return 501 */ 502 vm_page_wakeup(fs.m); 503 vm_object_deallocate(fs.first_object); 504 /*fs.m = NULL; */ 505 /*fs.first_object = NULL; */ 506 /*lwkt_reltoken(&vm_token);*/ 507 508 return (KERN_SUCCESS); 509 } 510 511 /* 512 * Fault in the specified virtual address in the current process map, 513 * returning a held VM page or NULL. See vm_fault_page() for more 514 * information. 515 * 516 * No requirements. 517 */ 518 vm_page_t 519 vm_fault_page_quick(vm_offset_t va, vm_prot_t fault_type, int *errorp) 520 { 521 struct lwp *lp = curthread->td_lwp; 522 vm_page_t m; 523 524 m = vm_fault_page(&lp->lwp_vmspace->vm_map, va, 525 fault_type, VM_FAULT_NORMAL, errorp); 526 return(m); 527 } 528 529 /* 530 * Fault in the specified virtual address in the specified map, doing all 531 * necessary manipulation of the object store and all necessary I/O. Return 532 * a held VM page or NULL, and set *errorp. The related pmap is not 533 * updated. 534 * 535 * The returned page will be properly dirtied if VM_PROT_WRITE was specified, 536 * and marked PG_REFERENCED as well. 537 * 538 * If the page cannot be faulted writable and VM_PROT_WRITE was specified, an 539 * error will be returned. 540 * 541 * No requirements. 542 */ 543 vm_page_t 544 vm_fault_page(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, 545 int fault_flags, int *errorp) 546 { 547 vm_pindex_t first_pindex; 548 struct faultstate fs; 549 int result; 550 vm_prot_t orig_fault_type = fault_type; 551 552 mycpu->gd_cnt.v_vm_faults++; 553 554 fs.didlimit = 0; 555 fs.hardfault = 0; 556 fs.fault_flags = fault_flags; 557 KKASSERT((fault_flags & VM_FAULT_WIRE_MASK) == 0); 558 559 RetryFault: 560 /* 561 * Find the vm_map_entry representing the backing store and resolve 562 * the top level object and page index. This may have the side 563 * effect of executing a copy-on-write on the map entry and/or 564 * creating a shadow object, but will not COW any actual VM pages. 565 * 566 * On success fs.map is left read-locked and various other fields 567 * are initialized but not otherwise referenced or locked. 568 * 569 * NOTE! vm_map_lookup will upgrade the fault_type to VM_FAULT_WRITE 570 * if the map entry is a virtual page table and also writable, 571 * so we can set the 'A'accessed bit in the virtual page table entry. 572 */ 573 fs.map = map; 574 result = vm_map_lookup(&fs.map, vaddr, fault_type, 575 &fs.entry, &fs.first_object, 576 &first_pindex, &fs.first_prot, &fs.wired); 577 578 if (result != KERN_SUCCESS) { 579 *errorp = result; 580 return (NULL); 581 } 582 583 /* 584 * fs.map is read-locked 585 * 586 * Misc checks. Save the map generation number to detect races. 587 */ 588 fs.map_generation = fs.map->timestamp; 589 590 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) { 591 panic("vm_fault: fault on nofault entry, addr: %lx", 592 (u_long)vaddr); 593 } 594 595 /* 596 * A system map entry may return a NULL object. No object means 597 * no pager means an unrecoverable kernel fault. 598 */ 599 if (fs.first_object == NULL) { 600 panic("vm_fault: unrecoverable fault at %p in entry %p", 601 (void *)vaddr, fs.entry); 602 } 603 604 /* 605 * Make a reference to this object to prevent its disposal while we 606 * are messing with it. Once we have the reference, the map is free 607 * to be diddled. Since objects reference their shadows (and copies), 608 * they will stay around as well. 609 * 610 * Bump the paging-in-progress count to prevent size changes (e.g. 611 * truncation operations) during I/O. This must be done after 612 * obtaining the vnode lock in order to avoid possible deadlocks. 613 * 614 * The vm_object must be held before manipulation. 615 */ 616 lwkt_gettoken(&vm_token); 617 vm_object_hold(fs.first_object); 618 vm_object_reference(fs.first_object); 619 fs.vp = vnode_pager_lock(fs.first_object); 620 vm_object_pip_add(fs.first_object, 1); 621 vm_object_drop(fs.first_object); 622 lwkt_reltoken(&vm_token); 623 624 fs.lookup_still_valid = TRUE; 625 fs.first_m = NULL; 626 fs.object = fs.first_object; /* so unlock_and_deallocate works */ 627 628 /* 629 * If the entry is wired we cannot change the page protection. 630 */ 631 if (fs.wired) 632 fault_type = fs.first_prot; 633 634 /* 635 * The page we want is at (first_object, first_pindex), but if the 636 * vm_map_entry is VM_MAPTYPE_VPAGETABLE we have to traverse the 637 * page table to figure out the actual pindex. 638 * 639 * NOTE! DEVELOPMENT IN PROGRESS, THIS IS AN INITIAL IMPLEMENTATION 640 * ONLY 641 */ 642 if (fs.entry->maptype == VM_MAPTYPE_VPAGETABLE) { 643 result = vm_fault_vpagetable(&fs, &first_pindex, 644 fs.entry->aux.master_pde, 645 fault_type); 646 if (result == KERN_TRY_AGAIN) 647 goto RetryFault; 648 if (result != KERN_SUCCESS) { 649 *errorp = result; 650 return (NULL); 651 } 652 } 653 654 /* 655 * Now we have the actual (object, pindex), fault in the page. If 656 * vm_fault_object() fails it will unlock and deallocate the FS 657 * data. If it succeeds everything remains locked and fs->object 658 * will have an additinal PIP count if it is not equal to 659 * fs->first_object 660 */ 661 result = vm_fault_object(&fs, first_pindex, fault_type); 662 663 if (result == KERN_TRY_AGAIN) 664 goto RetryFault; 665 if (result != KERN_SUCCESS) { 666 *errorp = result; 667 return(NULL); 668 } 669 670 if ((orig_fault_type & VM_PROT_WRITE) && 671 (fs.prot & VM_PROT_WRITE) == 0) { 672 *errorp = KERN_PROTECTION_FAILURE; 673 unlock_and_deallocate(&fs); 674 return(NULL); 675 } 676 677 /* 678 * On success vm_fault_object() does not unlock or deallocate, and fs.m 679 * will contain a busied page. 680 */ 681 unlock_things(&fs); 682 683 /* 684 * Return a held page. We are not doing any pmap manipulation so do 685 * not set PG_MAPPED. However, adjust the page flags according to 686 * the fault type because the caller may not use a managed pmapping 687 * (so we don't want to lose the fact that the page will be dirtied 688 * if a write fault was specified). 689 */ 690 lwkt_gettoken(&vm_token); 691 vm_page_hold(fs.m); 692 if (fault_type & VM_PROT_WRITE) 693 vm_page_dirty(fs.m); 694 695 /* 696 * Update the pmap. We really only have to do this if a COW 697 * occured to replace the read-only page with the new page. For 698 * now just do it unconditionally. XXX 699 */ 700 pmap_enter(fs.map->pmap, vaddr, fs.m, fs.prot, fs.wired); 701 vm_page_flag_set(fs.m, PG_REFERENCED); 702 703 /* 704 * Unbusy the page by activating it. It remains held and will not 705 * be reclaimed. 706 */ 707 vm_page_activate(fs.m); 708 709 if (curthread->td_lwp) { 710 if (fs.hardfault) { 711 curthread->td_lwp->lwp_ru.ru_majflt++; 712 } else { 713 curthread->td_lwp->lwp_ru.ru_minflt++; 714 } 715 } 716 717 /* 718 * Unlock everything, and return the held page. 719 */ 720 vm_page_wakeup(fs.m); 721 vm_object_deallocate(fs.first_object); 722 /*fs.first_object = NULL; */ 723 lwkt_reltoken(&vm_token); 724 725 *errorp = 0; 726 return(fs.m); 727 } 728 729 /* 730 * Fault in the specified (object,offset), dirty the returned page as 731 * needed. If the requested fault_type cannot be done NULL and an 732 * error is returned. 733 * 734 * A held (but not busied) page is returned. 735 * 736 * No requirements. 737 */ 738 vm_page_t 739 vm_fault_object_page(vm_object_t object, vm_ooffset_t offset, 740 vm_prot_t fault_type, int fault_flags, int *errorp) 741 { 742 int result; 743 vm_pindex_t first_pindex; 744 struct faultstate fs; 745 struct vm_map_entry entry; 746 747 bzero(&entry, sizeof(entry)); 748 entry.object.vm_object = object; 749 entry.maptype = VM_MAPTYPE_NORMAL; 750 entry.protection = entry.max_protection = fault_type; 751 752 fs.didlimit = 0; 753 fs.hardfault = 0; 754 fs.fault_flags = fault_flags; 755 fs.map = NULL; 756 KKASSERT((fault_flags & VM_FAULT_WIRE_MASK) == 0); 757 758 RetryFault: 759 760 fs.first_object = object; 761 first_pindex = OFF_TO_IDX(offset); 762 fs.entry = &entry; 763 fs.first_prot = fault_type; 764 fs.wired = 0; 765 /*fs.map_generation = 0; unused */ 766 767 /* 768 * Make a reference to this object to prevent its disposal while we 769 * are messing with it. Once we have the reference, the map is free 770 * to be diddled. Since objects reference their shadows (and copies), 771 * they will stay around as well. 772 * 773 * Bump the paging-in-progress count to prevent size changes (e.g. 774 * truncation operations) during I/O. This must be done after 775 * obtaining the vnode lock in order to avoid possible deadlocks. 776 */ 777 lwkt_gettoken(&vm_token); 778 vm_object_hold(fs.first_object); 779 vm_object_reference(fs.first_object); 780 fs.vp = vnode_pager_lock(fs.first_object); 781 vm_object_pip_add(fs.first_object, 1); 782 vm_object_drop(fs.first_object); 783 lwkt_reltoken(&vm_token); 784 785 fs.lookup_still_valid = TRUE; 786 fs.first_m = NULL; 787 fs.object = fs.first_object; /* so unlock_and_deallocate works */ 788 789 #if 0 790 /* XXX future - ability to operate on VM object using vpagetable */ 791 if (fs.entry->maptype == VM_MAPTYPE_VPAGETABLE) { 792 result = vm_fault_vpagetable(&fs, &first_pindex, 793 fs.entry->aux.master_pde, 794 fault_type); 795 if (result == KERN_TRY_AGAIN) 796 goto RetryFault; 797 if (result != KERN_SUCCESS) { 798 *errorp = result; 799 return (NULL); 800 } 801 } 802 #endif 803 804 /* 805 * Now we have the actual (object, pindex), fault in the page. If 806 * vm_fault_object() fails it will unlock and deallocate the FS 807 * data. If it succeeds everything remains locked and fs->object 808 * will have an additinal PIP count if it is not equal to 809 * fs->first_object 810 */ 811 result = vm_fault_object(&fs, first_pindex, fault_type); 812 813 if (result == KERN_TRY_AGAIN) 814 goto RetryFault; 815 if (result != KERN_SUCCESS) { 816 *errorp = result; 817 return(NULL); 818 } 819 820 if ((fault_type & VM_PROT_WRITE) && (fs.prot & VM_PROT_WRITE) == 0) { 821 *errorp = KERN_PROTECTION_FAILURE; 822 unlock_and_deallocate(&fs); 823 return(NULL); 824 } 825 826 /* 827 * On success vm_fault_object() does not unlock or deallocate, and fs.m 828 * will contain a busied page. 829 */ 830 unlock_things(&fs); 831 832 /* 833 * Return a held page. We are not doing any pmap manipulation so do 834 * not set PG_MAPPED. However, adjust the page flags according to 835 * the fault type because the caller may not use a managed pmapping 836 * (so we don't want to lose the fact that the page will be dirtied 837 * if a write fault was specified). 838 */ 839 lwkt_gettoken(&vm_token); 840 vm_page_hold(fs.m); 841 if (fault_type & VM_PROT_WRITE) 842 vm_page_dirty(fs.m); 843 844 if (fault_flags & VM_FAULT_DIRTY) 845 vm_page_dirty(fs.m); 846 if (fault_flags & VM_FAULT_UNSWAP) 847 swap_pager_unswapped(fs.m); 848 849 /* 850 * Indicate that the page was accessed. 851 */ 852 vm_page_flag_set(fs.m, PG_REFERENCED); 853 854 /* 855 * Unbusy the page by activating it. It remains held and will not 856 * be reclaimed. 857 */ 858 vm_page_activate(fs.m); 859 860 if (curthread->td_lwp) { 861 if (fs.hardfault) { 862 mycpu->gd_cnt.v_vm_faults++; 863 curthread->td_lwp->lwp_ru.ru_majflt++; 864 } else { 865 curthread->td_lwp->lwp_ru.ru_minflt++; 866 } 867 } 868 869 /* 870 * Unlock everything, and return the held page. 871 */ 872 vm_page_wakeup(fs.m); 873 vm_object_deallocate(fs.first_object); 874 /*fs.first_object = NULL; */ 875 lwkt_reltoken(&vm_token); 876 877 *errorp = 0; 878 return(fs.m); 879 } 880 881 /* 882 * Translate the virtual page number (first_pindex) that is relative 883 * to the address space into a logical page number that is relative to the 884 * backing object. Use the virtual page table pointed to by (vpte). 885 * 886 * This implements an N-level page table. Any level can terminate the 887 * scan by setting VPTE_PS. A linear mapping is accomplished by setting 888 * VPTE_PS in the master page directory entry set via mcontrol(MADV_SETMAP). 889 * 890 * No requirements (vm_token need not be held). 891 */ 892 static 893 int 894 vm_fault_vpagetable(struct faultstate *fs, vm_pindex_t *pindex, 895 vpte_t vpte, int fault_type) 896 { 897 struct lwbuf *lwb; 898 struct lwbuf lwb_cache; 899 int vshift = VPTE_FRAME_END - PAGE_SHIFT; /* index bits remaining */ 900 int result = KERN_SUCCESS; 901 vpte_t *ptep; 902 903 for (;;) { 904 /* 905 * We cannot proceed if the vpte is not valid, not readable 906 * for a read fault, or not writable for a write fault. 907 */ 908 if ((vpte & VPTE_V) == 0) { 909 unlock_and_deallocate(fs); 910 return (KERN_FAILURE); 911 } 912 if ((fault_type & VM_PROT_READ) && (vpte & VPTE_R) == 0) { 913 unlock_and_deallocate(fs); 914 return (KERN_FAILURE); 915 } 916 if ((fault_type & VM_PROT_WRITE) && (vpte & VPTE_W) == 0) { 917 unlock_and_deallocate(fs); 918 return (KERN_FAILURE); 919 } 920 if ((vpte & VPTE_PS) || vshift == 0) 921 break; 922 KKASSERT(vshift >= VPTE_PAGE_BITS); 923 924 /* 925 * Get the page table page. Nominally we only read the page 926 * table, but since we are actively setting VPTE_M and VPTE_A, 927 * tell vm_fault_object() that we are writing it. 928 * 929 * There is currently no real need to optimize this. 930 */ 931 result = vm_fault_object(fs, (vpte & VPTE_FRAME) >> PAGE_SHIFT, 932 VM_PROT_READ|VM_PROT_WRITE); 933 if (result != KERN_SUCCESS) 934 return (result); 935 936 /* 937 * Process the returned fs.m and look up the page table 938 * entry in the page table page. 939 */ 940 vshift -= VPTE_PAGE_BITS; 941 lwb = lwbuf_alloc(fs->m, &lwb_cache); 942 ptep = ((vpte_t *)lwbuf_kva(lwb) + 943 ((*pindex >> vshift) & VPTE_PAGE_MASK)); 944 vpte = *ptep; 945 946 /* 947 * Page table write-back. If the vpte is valid for the 948 * requested operation, do a write-back to the page table. 949 * 950 * XXX VPTE_M is not set properly for page directory pages. 951 * It doesn't get set in the page directory if the page table 952 * is modified during a read access. 953 */ 954 if ((fault_type & VM_PROT_WRITE) && (vpte & VPTE_V) && 955 (vpte & VPTE_W)) { 956 if ((vpte & (VPTE_M|VPTE_A)) != (VPTE_M|VPTE_A)) { 957 atomic_set_long(ptep, VPTE_M | VPTE_A); 958 vm_page_dirty(fs->m); 959 } 960 } 961 if ((fault_type & VM_PROT_READ) && (vpte & VPTE_V) && 962 (vpte & VPTE_R)) { 963 if ((vpte & VPTE_A) == 0) { 964 atomic_set_long(ptep, VPTE_A); 965 vm_page_dirty(fs->m); 966 } 967 } 968 lwbuf_free(lwb); 969 vm_page_flag_set(fs->m, PG_REFERENCED); 970 vm_page_activate(fs->m); 971 vm_page_wakeup(fs->m); 972 fs->m = NULL; 973 cleanup_successful_fault(fs); 974 } 975 /* 976 * Combine remaining address bits with the vpte. 977 */ 978 /* JG how many bits from each? */ 979 *pindex = ((vpte & VPTE_FRAME) >> PAGE_SHIFT) + 980 (*pindex & ((1L << vshift) - 1)); 981 return (KERN_SUCCESS); 982 } 983 984 985 /* 986 * This is the core of the vm_fault code. 987 * 988 * Do all operations required to fault-in (fs.first_object, pindex). Run 989 * through the shadow chain as necessary and do required COW or virtual 990 * copy operations. The caller has already fully resolved the vm_map_entry 991 * and, if appropriate, has created a copy-on-write layer. All we need to 992 * do is iterate the object chain. 993 * 994 * On failure (fs) is unlocked and deallocated and the caller may return or 995 * retry depending on the failure code. On success (fs) is NOT unlocked or 996 * deallocated, fs.m will contained a resolved, busied page, and fs.object 997 * will have an additional PIP count if it is not equal to fs.first_object. 998 * 999 * No requirements. 1000 */ 1001 static 1002 int 1003 vm_fault_object(struct faultstate *fs, 1004 vm_pindex_t first_pindex, vm_prot_t fault_type) 1005 { 1006 vm_object_t next_object; 1007 vm_pindex_t pindex; 1008 1009 fs->prot = fs->first_prot; 1010 fs->object = fs->first_object; 1011 pindex = first_pindex; 1012 1013 /* 1014 * If a read fault occurs we try to make the page writable if 1015 * possible. There are three cases where we cannot make the 1016 * page mapping writable: 1017 * 1018 * (1) The mapping is read-only or the VM object is read-only, 1019 * fs->prot above will simply not have VM_PROT_WRITE set. 1020 * 1021 * (2) If the mapping is a virtual page table we need to be able 1022 * to detect writes so we can set VPTE_M in the virtual page 1023 * table. 1024 * 1025 * (3) If the VM page is read-only or copy-on-write, upgrading would 1026 * just result in an unnecessary COW fault. 1027 * 1028 * VM_PROT_VPAGED is set if faulting via a virtual page table and 1029 * causes adjustments to the 'M'odify bit to also turn off write 1030 * access to force a re-fault. 1031 */ 1032 if (fs->entry->maptype == VM_MAPTYPE_VPAGETABLE) { 1033 if ((fault_type & VM_PROT_WRITE) == 0) 1034 fs->prot &= ~VM_PROT_WRITE; 1035 } 1036 1037 lwkt_gettoken(&vm_token); 1038 1039 for (;;) { 1040 /* 1041 * If the object is dead, we stop here 1042 */ 1043 if (fs->object->flags & OBJ_DEAD) { 1044 unlock_and_deallocate(fs); 1045 lwkt_reltoken(&vm_token); 1046 return (KERN_PROTECTION_FAILURE); 1047 } 1048 1049 /* 1050 * See if the page is resident. 1051 */ 1052 fs->m = vm_page_lookup(fs->object, pindex); 1053 if (fs->m != NULL) { 1054 int queue; 1055 /* 1056 * Wait/Retry if the page is busy. We have to do this 1057 * if the page is busy via either PG_BUSY or 1058 * vm_page_t->busy because the vm_pager may be using 1059 * vm_page_t->busy for pageouts ( and even pageins if 1060 * it is the vnode pager ), and we could end up trying 1061 * to pagein and pageout the same page simultaneously. 1062 * 1063 * We can theoretically allow the busy case on a read 1064 * fault if the page is marked valid, but since such 1065 * pages are typically already pmap'd, putting that 1066 * special case in might be more effort then it is 1067 * worth. We cannot under any circumstances mess 1068 * around with a vm_page_t->busy page except, perhaps, 1069 * to pmap it. 1070 */ 1071 if ((fs->m->flags & PG_BUSY) || fs->m->busy) { 1072 unlock_things(fs); 1073 vm_page_sleep_busy(fs->m, TRUE, "vmpfw"); 1074 mycpu->gd_cnt.v_intrans++; 1075 vm_object_deallocate(fs->first_object); 1076 fs->first_object = NULL; 1077 lwkt_reltoken(&vm_token); 1078 return (KERN_TRY_AGAIN); 1079 } 1080 1081 /* 1082 * If reactivating a page from PQ_CACHE we may have 1083 * to rate-limit. 1084 */ 1085 queue = fs->m->queue; 1086 vm_page_unqueue_nowakeup(fs->m); 1087 1088 if ((queue - fs->m->pc) == PQ_CACHE && 1089 vm_page_count_severe()) { 1090 vm_page_activate(fs->m); 1091 unlock_and_deallocate(fs); 1092 vm_waitpfault(); 1093 lwkt_reltoken(&vm_token); 1094 return (KERN_TRY_AGAIN); 1095 } 1096 1097 /* 1098 * Mark page busy for other processes, and the 1099 * pagedaemon. If it still isn't completely valid 1100 * (readable), or if a read-ahead-mark is set on 1101 * the VM page, jump to readrest, else we found the 1102 * page and can return. 1103 * 1104 * We can release the spl once we have marked the 1105 * page busy. 1106 */ 1107 vm_page_busy(fs->m); 1108 1109 if (fs->m->object != &kernel_object) { 1110 if ((fs->m->valid & VM_PAGE_BITS_ALL) != 1111 VM_PAGE_BITS_ALL) { 1112 goto readrest; 1113 } 1114 if (fs->m->flags & PG_RAM) { 1115 if (debug_cluster) 1116 kprintf("R"); 1117 vm_page_flag_clear(fs->m, PG_RAM); 1118 goto readrest; 1119 } 1120 } 1121 break; /* break to PAGE HAS BEEN FOUND */ 1122 } 1123 1124 /* 1125 * Page is not resident, If this is the search termination 1126 * or the pager might contain the page, allocate a new page. 1127 */ 1128 if (TRYPAGER(fs) || fs->object == fs->first_object) { 1129 /* 1130 * If the page is beyond the object size we fail 1131 */ 1132 if (pindex >= fs->object->size) { 1133 lwkt_reltoken(&vm_token); 1134 unlock_and_deallocate(fs); 1135 return (KERN_PROTECTION_FAILURE); 1136 } 1137 1138 /* 1139 * Ratelimit. 1140 */ 1141 if (fs->didlimit == 0 && curproc != NULL) { 1142 int limticks; 1143 1144 limticks = vm_fault_ratelimit(curproc->p_vmspace); 1145 if (limticks) { 1146 lwkt_reltoken(&vm_token); 1147 unlock_and_deallocate(fs); 1148 tsleep(curproc, 0, "vmrate", limticks); 1149 fs->didlimit = 1; 1150 return (KERN_TRY_AGAIN); 1151 } 1152 } 1153 1154 /* 1155 * Allocate a new page for this object/offset pair. 1156 */ 1157 fs->m = NULL; 1158 if (!vm_page_count_severe()) { 1159 fs->m = vm_page_alloc(fs->object, pindex, 1160 (fs->vp || fs->object->backing_object) ? VM_ALLOC_NORMAL : VM_ALLOC_NORMAL | VM_ALLOC_ZERO); 1161 } 1162 if (fs->m == NULL) { 1163 lwkt_reltoken(&vm_token); 1164 unlock_and_deallocate(fs); 1165 vm_waitpfault(); 1166 return (KERN_TRY_AGAIN); 1167 } 1168 } 1169 1170 readrest: 1171 /* 1172 * We have found an invalid or partially valid page, a 1173 * page with a read-ahead mark which might be partially or 1174 * fully valid (and maybe dirty too), or we have allocated 1175 * a new page. 1176 * 1177 * Attempt to fault-in the page if there is a chance that the 1178 * pager has it, and potentially fault in additional pages 1179 * at the same time. 1180 * 1181 * We are NOT in splvm here and if TRYPAGER is true then 1182 * fs.m will be non-NULL and will be PG_BUSY for us. 1183 */ 1184 if (TRYPAGER(fs)) { 1185 int rv; 1186 int seqaccess; 1187 u_char behavior = vm_map_entry_behavior(fs->entry); 1188 1189 if (behavior == MAP_ENTRY_BEHAV_RANDOM) 1190 seqaccess = 0; 1191 else 1192 seqaccess = -1; 1193 1194 /* 1195 * If sequential access is detected then attempt 1196 * to deactivate/cache pages behind the scan to 1197 * prevent resource hogging. 1198 * 1199 * Use of PG_RAM to detect sequential access 1200 * also simulates multi-zone sequential access 1201 * detection for free. 1202 * 1203 * NOTE: Partially valid dirty pages cannot be 1204 * deactivated without causing NFS picemeal 1205 * writes to barf. 1206 */ 1207 if ((fs->first_object->type != OBJT_DEVICE) && 1208 (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL || 1209 (behavior != MAP_ENTRY_BEHAV_RANDOM && 1210 (fs->m->flags & PG_RAM))) 1211 ) { 1212 vm_pindex_t scan_pindex; 1213 int scan_count = 16; 1214 1215 if (first_pindex < 16) { 1216 scan_pindex = 0; 1217 scan_count = 0; 1218 } else { 1219 scan_pindex = first_pindex - 16; 1220 if (scan_pindex < 16) 1221 scan_count = scan_pindex; 1222 else 1223 scan_count = 16; 1224 } 1225 1226 while (scan_count) { 1227 vm_page_t mt; 1228 1229 mt = vm_page_lookup(fs->first_object, 1230 scan_pindex); 1231 if (mt == NULL || 1232 (mt->valid != VM_PAGE_BITS_ALL)) { 1233 break; 1234 } 1235 if (mt->busy || 1236 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) || 1237 mt->hold_count || 1238 mt->wire_count) { 1239 goto skip; 1240 } 1241 vm_page_busy(mt); 1242 if (mt->dirty == 0) 1243 vm_page_test_dirty(mt); 1244 if (mt->dirty) { 1245 vm_page_protect(mt, 1246 VM_PROT_NONE); 1247 vm_page_deactivate(mt); 1248 vm_page_wakeup(mt); 1249 } else { 1250 vm_page_cache(mt); 1251 } 1252 skip: 1253 --scan_count; 1254 --scan_pindex; 1255 } 1256 1257 seqaccess = 1; 1258 } 1259 1260 /* 1261 * Avoid deadlocking against the map when doing I/O. 1262 * fs.object and the page is PG_BUSY'd. 1263 * 1264 * NOTE: Once unlocked, fs->entry can become stale 1265 * so this will NULL it out. 1266 * 1267 * NOTE: fs->entry is invalid until we relock the 1268 * map and verify that the timestamp has not 1269 * changed. 1270 */ 1271 unlock_map(fs); 1272 1273 /* 1274 * Acquire the page data. We still hold a ref on 1275 * fs.object and the page has been PG_BUSY's. 1276 * 1277 * The pager may replace the page (for example, in 1278 * order to enter a fictitious page into the 1279 * object). If it does so it is responsible for 1280 * cleaning up the passed page and properly setting 1281 * the new page PG_BUSY. 1282 * 1283 * If we got here through a PG_RAM read-ahead 1284 * mark the page may be partially dirty and thus 1285 * not freeable. Don't bother checking to see 1286 * if the pager has the page because we can't free 1287 * it anyway. We have to depend on the get_page 1288 * operation filling in any gaps whether there is 1289 * backing store or not. 1290 */ 1291 rv = vm_pager_get_page(fs->object, &fs->m, seqaccess); 1292 1293 if (rv == VM_PAGER_OK) { 1294 /* 1295 * Relookup in case pager changed page. Pager 1296 * is responsible for disposition of old page 1297 * if moved. 1298 * 1299 * XXX other code segments do relookups too. 1300 * It's a bad abstraction that needs to be 1301 * fixed/removed. 1302 */ 1303 fs->m = vm_page_lookup(fs->object, pindex); 1304 if (fs->m == NULL) { 1305 lwkt_reltoken(&vm_token); 1306 unlock_and_deallocate(fs); 1307 return (KERN_TRY_AGAIN); 1308 } 1309 1310 ++fs->hardfault; 1311 break; /* break to PAGE HAS BEEN FOUND */ 1312 } 1313 1314 /* 1315 * Remove the bogus page (which does not exist at this 1316 * object/offset); before doing so, we must get back 1317 * our object lock to preserve our invariant. 1318 * 1319 * Also wake up any other process that may want to bring 1320 * in this page. 1321 * 1322 * If this is the top-level object, we must leave the 1323 * busy page to prevent another process from rushing 1324 * past us, and inserting the page in that object at 1325 * the same time that we are. 1326 */ 1327 if (rv == VM_PAGER_ERROR) { 1328 if (curproc) 1329 kprintf("vm_fault: pager read error, pid %d (%s)\n", curproc->p_pid, curproc->p_comm); 1330 else 1331 kprintf("vm_fault: pager read error, thread %p (%s)\n", curthread, curproc->p_comm); 1332 } 1333 1334 /* 1335 * Data outside the range of the pager or an I/O error 1336 * 1337 * The page may have been wired during the pagein, 1338 * e.g. by the buffer cache, and cannot simply be 1339 * freed. Call vnode_pager_freepage() to deal with it. 1340 */ 1341 /* 1342 * XXX - the check for kernel_map is a kludge to work 1343 * around having the machine panic on a kernel space 1344 * fault w/ I/O error. 1345 */ 1346 if (((fs->map != &kernel_map) && 1347 (rv == VM_PAGER_ERROR)) || (rv == VM_PAGER_BAD)) { 1348 vnode_pager_freepage(fs->m); 1349 lwkt_reltoken(&vm_token); 1350 fs->m = NULL; 1351 unlock_and_deallocate(fs); 1352 if (rv == VM_PAGER_ERROR) 1353 return (KERN_FAILURE); 1354 else 1355 return (KERN_PROTECTION_FAILURE); 1356 /* NOT REACHED */ 1357 } 1358 if (fs->object != fs->first_object) { 1359 vnode_pager_freepage(fs->m); 1360 fs->m = NULL; 1361 /* 1362 * XXX - we cannot just fall out at this 1363 * point, m has been freed and is invalid! 1364 */ 1365 } 1366 } 1367 1368 /* 1369 * We get here if the object has a default pager (or unwiring) 1370 * or the pager doesn't have the page. 1371 */ 1372 if (fs->object == fs->first_object) 1373 fs->first_m = fs->m; 1374 1375 /* 1376 * Move on to the next object. Lock the next object before 1377 * unlocking the current one. 1378 */ 1379 pindex += OFF_TO_IDX(fs->object->backing_object_offset); 1380 next_object = fs->object->backing_object; 1381 if (next_object == NULL) { 1382 /* 1383 * If there's no object left, fill the page in the top 1384 * object with zeros. 1385 */ 1386 if (fs->object != fs->first_object) { 1387 vm_object_pip_wakeup(fs->object); 1388 1389 fs->object = fs->first_object; 1390 pindex = first_pindex; 1391 fs->m = fs->first_m; 1392 } 1393 fs->first_m = NULL; 1394 1395 /* 1396 * Zero the page if necessary and mark it valid. 1397 */ 1398 if ((fs->m->flags & PG_ZERO) == 0) { 1399 vm_page_zero_fill(fs->m); 1400 } else { 1401 #ifdef PMAP_DEBUG 1402 pmap_page_assertzero(VM_PAGE_TO_PHYS(fs->m)); 1403 #endif 1404 vm_page_flag_clear(fs->m, PG_ZERO); 1405 mycpu->gd_cnt.v_ozfod++; 1406 } 1407 mycpu->gd_cnt.v_zfod++; 1408 fs->m->valid = VM_PAGE_BITS_ALL; 1409 break; /* break to PAGE HAS BEEN FOUND */ 1410 } 1411 if (fs->object != fs->first_object) { 1412 vm_object_pip_wakeup(fs->object); 1413 } 1414 KASSERT(fs->object != next_object, 1415 ("object loop %p", next_object)); 1416 fs->object = next_object; 1417 vm_object_pip_add(fs->object, 1); 1418 } 1419 1420 /* 1421 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock 1422 * is held.] 1423 * 1424 * vm_token is still held 1425 * 1426 * If the page is being written, but isn't already owned by the 1427 * top-level object, we have to copy it into a new page owned by the 1428 * top-level object. 1429 */ 1430 KASSERT((fs->m->flags & PG_BUSY) != 0, 1431 ("vm_fault: not busy after main loop")); 1432 1433 if (fs->object != fs->first_object) { 1434 /* 1435 * We only really need to copy if we want to write it. 1436 */ 1437 if (fault_type & VM_PROT_WRITE) { 1438 /* 1439 * This allows pages to be virtually copied from a 1440 * backing_object into the first_object, where the 1441 * backing object has no other refs to it, and cannot 1442 * gain any more refs. Instead of a bcopy, we just 1443 * move the page from the backing object to the 1444 * first object. Note that we must mark the page 1445 * dirty in the first object so that it will go out 1446 * to swap when needed. 1447 */ 1448 if ( 1449 /* 1450 * Map, if present, has not changed 1451 */ 1452 (fs->map == NULL || 1453 fs->map_generation == fs->map->timestamp) && 1454 /* 1455 * Only one shadow object 1456 */ 1457 (fs->object->shadow_count == 1) && 1458 /* 1459 * No COW refs, except us 1460 */ 1461 (fs->object->ref_count == 1) && 1462 /* 1463 * No one else can look this object up 1464 */ 1465 (fs->object->handle == NULL) && 1466 /* 1467 * No other ways to look the object up 1468 */ 1469 ((fs->object->type == OBJT_DEFAULT) || 1470 (fs->object->type == OBJT_SWAP)) && 1471 /* 1472 * We don't chase down the shadow chain 1473 */ 1474 (fs->object == fs->first_object->backing_object) && 1475 1476 /* 1477 * grab the lock if we need to 1478 */ 1479 (fs->lookup_still_valid || 1480 fs->map == NULL || 1481 lockmgr(&fs->map->lock, LK_EXCLUSIVE|LK_NOWAIT) == 0) 1482 ) { 1483 1484 fs->lookup_still_valid = 1; 1485 /* 1486 * get rid of the unnecessary page 1487 */ 1488 vm_page_protect(fs->first_m, VM_PROT_NONE); 1489 vm_page_free(fs->first_m); 1490 fs->first_m = NULL; 1491 1492 /* 1493 * grab the page and put it into the 1494 * process'es object. The page is 1495 * automatically made dirty. 1496 */ 1497 vm_page_rename(fs->m, fs->first_object, first_pindex); 1498 fs->first_m = fs->m; 1499 vm_page_busy(fs->first_m); 1500 fs->m = NULL; 1501 mycpu->gd_cnt.v_cow_optim++; 1502 } else { 1503 /* 1504 * Oh, well, lets copy it. 1505 */ 1506 vm_page_copy(fs->m, fs->first_m); 1507 vm_page_event(fs->m, VMEVENT_COW); 1508 } 1509 1510 if (fs->m) { 1511 /* 1512 * We no longer need the old page or object. 1513 */ 1514 release_page(fs); 1515 } 1516 1517 /* 1518 * fs->object != fs->first_object due to above 1519 * conditional 1520 */ 1521 vm_object_pip_wakeup(fs->object); 1522 1523 /* 1524 * Only use the new page below... 1525 */ 1526 1527 mycpu->gd_cnt.v_cow_faults++; 1528 fs->m = fs->first_m; 1529 fs->object = fs->first_object; 1530 pindex = first_pindex; 1531 } else { 1532 /* 1533 * If it wasn't a write fault avoid having to copy 1534 * the page by mapping it read-only. 1535 */ 1536 fs->prot &= ~VM_PROT_WRITE; 1537 } 1538 } 1539 1540 /* 1541 * Relock the map if necessary, then check the generation count. 1542 * relock_map() will update fs->timestamp to account for the 1543 * relocking if necessary. 1544 * 1545 * If the count has changed after relocking then all sorts of 1546 * crap may have happened and we have to retry. 1547 * 1548 * NOTE: The relock_map() can fail due to a deadlock against 1549 * the vm_page we are holding BUSY. 1550 */ 1551 if (fs->lookup_still_valid == FALSE && fs->map) { 1552 if (relock_map(fs) || 1553 fs->map->timestamp != fs->map_generation) { 1554 release_page(fs); 1555 lwkt_reltoken(&vm_token); 1556 unlock_and_deallocate(fs); 1557 return (KERN_TRY_AGAIN); 1558 } 1559 } 1560 1561 /* 1562 * If the fault is a write, we know that this page is being 1563 * written NOW so dirty it explicitly to save on pmap_is_modified() 1564 * calls later. 1565 * 1566 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC 1567 * if the page is already dirty to prevent data written with 1568 * the expectation of being synced from not being synced. 1569 * Likewise if this entry does not request NOSYNC then make 1570 * sure the page isn't marked NOSYNC. Applications sharing 1571 * data should use the same flags to avoid ping ponging. 1572 * 1573 * Also tell the backing pager, if any, that it should remove 1574 * any swap backing since the page is now dirty. 1575 */ 1576 if (fs->prot & VM_PROT_WRITE) { 1577 vm_object_set_writeable_dirty(fs->m->object); 1578 vm_set_nosync(fs->m, fs->entry); 1579 if (fs->fault_flags & VM_FAULT_DIRTY) { 1580 vm_page_dirty(fs->m); 1581 swap_pager_unswapped(fs->m); 1582 } 1583 } 1584 1585 lwkt_reltoken(&vm_token); 1586 1587 /* 1588 * Page had better still be busy. We are still locked up and 1589 * fs->object will have another PIP reference if it is not equal 1590 * to fs->first_object. 1591 */ 1592 KASSERT(fs->m->flags & PG_BUSY, 1593 ("vm_fault: page %p not busy!", fs->m)); 1594 1595 /* 1596 * Sanity check: page must be completely valid or it is not fit to 1597 * map into user space. vm_pager_get_pages() ensures this. 1598 */ 1599 if (fs->m->valid != VM_PAGE_BITS_ALL) { 1600 vm_page_zero_invalid(fs->m, TRUE); 1601 kprintf("Warning: page %p partially invalid on fault\n", fs->m); 1602 } 1603 vm_page_flag_clear(fs->m, PG_ZERO); 1604 1605 return (KERN_SUCCESS); 1606 } 1607 1608 /* 1609 * Wire down a range of virtual addresses in a map. The entry in question 1610 * should be marked in-transition and the map must be locked. We must 1611 * release the map temporarily while faulting-in the page to avoid a 1612 * deadlock. Note that the entry may be clipped while we are blocked but 1613 * will never be freed. 1614 * 1615 * No requirements. 1616 */ 1617 int 1618 vm_fault_wire(vm_map_t map, vm_map_entry_t entry, boolean_t user_wire) 1619 { 1620 boolean_t fictitious; 1621 vm_offset_t start; 1622 vm_offset_t end; 1623 vm_offset_t va; 1624 vm_paddr_t pa; 1625 pmap_t pmap; 1626 int rv; 1627 1628 pmap = vm_map_pmap(map); 1629 start = entry->start; 1630 end = entry->end; 1631 fictitious = entry->object.vm_object && 1632 (entry->object.vm_object->type == OBJT_DEVICE); 1633 if (entry->eflags & MAP_ENTRY_KSTACK) 1634 start += PAGE_SIZE; 1635 lwkt_gettoken(&vm_token); 1636 map->timestamp++; 1637 vm_map_unlock(map); 1638 1639 /* 1640 * We simulate a fault to get the page and enter it in the physical 1641 * map. 1642 */ 1643 for (va = start; va < end; va += PAGE_SIZE) { 1644 if (user_wire) { 1645 rv = vm_fault(map, va, VM_PROT_READ, 1646 VM_FAULT_USER_WIRE); 1647 } else { 1648 rv = vm_fault(map, va, VM_PROT_READ|VM_PROT_WRITE, 1649 VM_FAULT_CHANGE_WIRING); 1650 } 1651 if (rv) { 1652 while (va > start) { 1653 va -= PAGE_SIZE; 1654 if ((pa = pmap_extract(pmap, va)) == 0) 1655 continue; 1656 pmap_change_wiring(pmap, va, FALSE); 1657 if (!fictitious) 1658 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1659 } 1660 vm_map_lock(map); 1661 lwkt_reltoken(&vm_token); 1662 return (rv); 1663 } 1664 } 1665 vm_map_lock(map); 1666 lwkt_reltoken(&vm_token); 1667 return (KERN_SUCCESS); 1668 } 1669 1670 /* 1671 * Unwire a range of virtual addresses in a map. The map should be 1672 * locked. 1673 */ 1674 void 1675 vm_fault_unwire(vm_map_t map, vm_map_entry_t entry) 1676 { 1677 boolean_t fictitious; 1678 vm_offset_t start; 1679 vm_offset_t end; 1680 vm_offset_t va; 1681 vm_paddr_t pa; 1682 pmap_t pmap; 1683 1684 pmap = vm_map_pmap(map); 1685 start = entry->start; 1686 end = entry->end; 1687 fictitious = entry->object.vm_object && 1688 (entry->object.vm_object->type == OBJT_DEVICE); 1689 if (entry->eflags & MAP_ENTRY_KSTACK) 1690 start += PAGE_SIZE; 1691 1692 /* 1693 * Since the pages are wired down, we must be able to get their 1694 * mappings from the physical map system. 1695 */ 1696 lwkt_gettoken(&vm_token); 1697 for (va = start; va < end; va += PAGE_SIZE) { 1698 pa = pmap_extract(pmap, va); 1699 if (pa != 0) { 1700 pmap_change_wiring(pmap, va, FALSE); 1701 if (!fictitious) 1702 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1); 1703 } 1704 } 1705 lwkt_reltoken(&vm_token); 1706 } 1707 1708 /* 1709 * Reduce the rate at which memory is allocated to a process based 1710 * on the perceived load on the VM system. As the load increases 1711 * the allocation burst rate goes down and the delay increases. 1712 * 1713 * Rate limiting does not apply when faulting active or inactive 1714 * pages. When faulting 'cache' pages, rate limiting only applies 1715 * if the system currently has a severe page deficit. 1716 * 1717 * XXX vm_pagesupply should be increased when a page is freed. 1718 * 1719 * We sleep up to 1/10 of a second. 1720 */ 1721 static int 1722 vm_fault_ratelimit(struct vmspace *vmspace) 1723 { 1724 if (vm_load_enable == 0) 1725 return(0); 1726 if (vmspace->vm_pagesupply > 0) { 1727 --vmspace->vm_pagesupply; /* SMP race ok */ 1728 return(0); 1729 } 1730 #ifdef INVARIANTS 1731 if (vm_load_debug) { 1732 kprintf("load %-4d give %d pgs, wait %d, pid %-5d (%s)\n", 1733 vm_load, 1734 (1000 - vm_load ) / 10, vm_load * hz / 10000, 1735 curproc->p_pid, curproc->p_comm); 1736 } 1737 #endif 1738 vmspace->vm_pagesupply = (1000 - vm_load) / 10; 1739 return(vm_load * hz / 10000); 1740 } 1741 1742 /* 1743 * Copy all of the pages from a wired-down map entry to another. 1744 * 1745 * The source and destination maps must be locked for write. 1746 * The source map entry must be wired down (or be a sharing map 1747 * entry corresponding to a main map entry that is wired down). 1748 * 1749 * No other requirements. 1750 */ 1751 void 1752 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map, 1753 vm_map_entry_t dst_entry, vm_map_entry_t src_entry) 1754 { 1755 vm_object_t dst_object; 1756 vm_object_t src_object; 1757 vm_ooffset_t dst_offset; 1758 vm_ooffset_t src_offset; 1759 vm_prot_t prot; 1760 vm_offset_t vaddr; 1761 vm_page_t dst_m; 1762 vm_page_t src_m; 1763 1764 #ifdef lint 1765 src_map++; 1766 #endif /* lint */ 1767 1768 src_object = src_entry->object.vm_object; 1769 src_offset = src_entry->offset; 1770 1771 /* 1772 * Create the top-level object for the destination entry. (Doesn't 1773 * actually shadow anything - we copy the pages directly.) 1774 */ 1775 vm_map_entry_allocate_object(dst_entry); 1776 dst_object = dst_entry->object.vm_object; 1777 1778 prot = dst_entry->max_protection; 1779 1780 /* 1781 * Loop through all of the pages in the entry's range, copying each 1782 * one from the source object (it should be there) to the destination 1783 * object. 1784 */ 1785 for (vaddr = dst_entry->start, dst_offset = 0; 1786 vaddr < dst_entry->end; 1787 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) { 1788 1789 /* 1790 * Allocate a page in the destination object 1791 */ 1792 do { 1793 dst_m = vm_page_alloc(dst_object, 1794 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL); 1795 if (dst_m == NULL) { 1796 vm_wait(0); 1797 } 1798 } while (dst_m == NULL); 1799 1800 /* 1801 * Find the page in the source object, and copy it in. 1802 * (Because the source is wired down, the page will be in 1803 * memory.) 1804 */ 1805 src_m = vm_page_lookup(src_object, 1806 OFF_TO_IDX(dst_offset + src_offset)); 1807 if (src_m == NULL) 1808 panic("vm_fault_copy_wired: page missing"); 1809 1810 vm_page_copy(src_m, dst_m); 1811 vm_page_event(src_m, VMEVENT_COW); 1812 1813 /* 1814 * Enter it in the pmap... 1815 */ 1816 1817 vm_page_flag_clear(dst_m, PG_ZERO); 1818 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE); 1819 1820 /* 1821 * Mark it no longer busy, and put it on the active list. 1822 */ 1823 vm_page_activate(dst_m); 1824 vm_page_wakeup(dst_m); 1825 } 1826 } 1827 1828 #if 0 1829 1830 /* 1831 * This routine checks around the requested page for other pages that 1832 * might be able to be faulted in. This routine brackets the viable 1833 * pages for the pages to be paged in. 1834 * 1835 * Inputs: 1836 * m, rbehind, rahead 1837 * 1838 * Outputs: 1839 * marray (array of vm_page_t), reqpage (index of requested page) 1840 * 1841 * Return value: 1842 * number of pages in marray 1843 */ 1844 static int 1845 vm_fault_additional_pages(vm_page_t m, int rbehind, int rahead, 1846 vm_page_t *marray, int *reqpage) 1847 { 1848 int i,j; 1849 vm_object_t object; 1850 vm_pindex_t pindex, startpindex, endpindex, tpindex; 1851 vm_page_t rtm; 1852 int cbehind, cahead; 1853 1854 object = m->object; 1855 pindex = m->pindex; 1856 1857 /* 1858 * we don't fault-ahead for device pager 1859 */ 1860 if (object->type == OBJT_DEVICE) { 1861 *reqpage = 0; 1862 marray[0] = m; 1863 return 1; 1864 } 1865 1866 /* 1867 * if the requested page is not available, then give up now 1868 */ 1869 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) { 1870 *reqpage = 0; /* not used by caller, fix compiler warn */ 1871 return 0; 1872 } 1873 1874 if ((cbehind == 0) && (cahead == 0)) { 1875 *reqpage = 0; 1876 marray[0] = m; 1877 return 1; 1878 } 1879 1880 if (rahead > cahead) { 1881 rahead = cahead; 1882 } 1883 1884 if (rbehind > cbehind) { 1885 rbehind = cbehind; 1886 } 1887 1888 /* 1889 * Do not do any readahead if we have insufficient free memory. 1890 * 1891 * XXX code was broken disabled before and has instability 1892 * with this conditonal fixed, so shortcut for now. 1893 */ 1894 if (burst_fault == 0 || vm_page_count_severe()) { 1895 marray[0] = m; 1896 *reqpage = 0; 1897 return 1; 1898 } 1899 1900 /* 1901 * scan backward for the read behind pages -- in memory 1902 * 1903 * Assume that if the page is not found an interrupt will not 1904 * create it. Theoretically interrupts can only remove (busy) 1905 * pages, not create new associations. 1906 */ 1907 if (pindex > 0) { 1908 if (rbehind > pindex) { 1909 rbehind = pindex; 1910 startpindex = 0; 1911 } else { 1912 startpindex = pindex - rbehind; 1913 } 1914 1915 lwkt_gettoken(&vm_token); 1916 for (tpindex = pindex; tpindex > startpindex; --tpindex) { 1917 if (vm_page_lookup(object, tpindex - 1)) 1918 break; 1919 } 1920 1921 i = 0; 1922 while (tpindex < pindex) { 1923 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_SYSTEM); 1924 if (rtm == NULL) { 1925 lwkt_reltoken(&vm_token); 1926 for (j = 0; j < i; j++) { 1927 vm_page_free(marray[j]); 1928 } 1929 marray[0] = m; 1930 *reqpage = 0; 1931 return 1; 1932 } 1933 marray[i] = rtm; 1934 ++i; 1935 ++tpindex; 1936 } 1937 lwkt_reltoken(&vm_token); 1938 } else { 1939 i = 0; 1940 } 1941 1942 /* 1943 * Assign requested page 1944 */ 1945 marray[i] = m; 1946 *reqpage = i; 1947 ++i; 1948 1949 /* 1950 * Scan forwards for read-ahead pages 1951 */ 1952 tpindex = pindex + 1; 1953 endpindex = tpindex + rahead; 1954 if (endpindex > object->size) 1955 endpindex = object->size; 1956 1957 lwkt_gettoken(&vm_token); 1958 while (tpindex < endpindex) { 1959 if (vm_page_lookup(object, tpindex)) 1960 break; 1961 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_SYSTEM); 1962 if (rtm == NULL) 1963 break; 1964 marray[i] = rtm; 1965 ++i; 1966 ++tpindex; 1967 } 1968 lwkt_reltoken(&vm_token); 1969 1970 return (i); 1971 } 1972 1973 #endif 1974 1975 /* 1976 * vm_prefault() provides a quick way of clustering pagefaults into a 1977 * processes address space. It is a "cousin" of pmap_object_init_pt, 1978 * except it runs at page fault time instead of mmap time. 1979 * 1980 * This code used to be per-platform pmap_prefault(). It is now 1981 * machine-independent and enhanced to also pre-fault zero-fill pages 1982 * (see vm.fast_fault) as well as make them writable, which greatly 1983 * reduces the number of page faults programs incur. 1984 * 1985 * Application performance when pre-faulting zero-fill pages is heavily 1986 * dependent on the application. Very tiny applications like /bin/echo 1987 * lose a little performance while applications of any appreciable size 1988 * gain performance. Prefaulting multiple pages also reduces SMP 1989 * congestion and can improve SMP performance significantly. 1990 * 1991 * NOTE! prot may allow writing but this only applies to the top level 1992 * object. If we wind up mapping a page extracted from a backing 1993 * object we have to make sure it is read-only. 1994 * 1995 * NOTE! The caller has already handled any COW operations on the 1996 * vm_map_entry via the normal fault code. Do NOT call this 1997 * shortcut unless the normal fault code has run on this entry. 1998 * 1999 * No other requirements. 2000 */ 2001 #define PFBAK 4 2002 #define PFFOR 4 2003 #define PAGEORDER_SIZE (PFBAK+PFFOR) 2004 2005 static int vm_prefault_pageorder[] = { 2006 -PAGE_SIZE, PAGE_SIZE, 2007 -2 * PAGE_SIZE, 2 * PAGE_SIZE, 2008 -3 * PAGE_SIZE, 3 * PAGE_SIZE, 2009 -4 * PAGE_SIZE, 4 * PAGE_SIZE 2010 }; 2011 2012 /* 2013 * Set PG_NOSYNC if the map entry indicates so, but only if the page 2014 * is not already dirty by other means. This will prevent passive 2015 * filesystem syncing as well as 'sync' from writing out the page. 2016 */ 2017 static void 2018 vm_set_nosync(vm_page_t m, vm_map_entry_t entry) 2019 { 2020 if (entry->eflags & MAP_ENTRY_NOSYNC) { 2021 if (m->dirty == 0) 2022 vm_page_flag_set(m, PG_NOSYNC); 2023 } else { 2024 vm_page_flag_clear(m, PG_NOSYNC); 2025 } 2026 } 2027 2028 static void 2029 vm_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry, int prot) 2030 { 2031 struct lwp *lp; 2032 vm_page_t m; 2033 vm_offset_t starta; 2034 vm_offset_t addr; 2035 vm_pindex_t index; 2036 vm_pindex_t pindex; 2037 vm_object_t object; 2038 int pprot; 2039 int i; 2040 2041 /* 2042 * We do not currently prefault mappings that use virtual page 2043 * tables. We do not prefault foreign pmaps. 2044 */ 2045 if (entry->maptype == VM_MAPTYPE_VPAGETABLE) 2046 return; 2047 lp = curthread->td_lwp; 2048 if (lp == NULL || (pmap != vmspace_pmap(lp->lwp_vmspace))) 2049 return; 2050 2051 lwkt_gettoken(&vm_token); 2052 2053 object = entry->object.vm_object; 2054 KKASSERT(object != NULL); 2055 vm_object_hold(object); 2056 2057 starta = addra - PFBAK * PAGE_SIZE; 2058 if (starta < entry->start) 2059 starta = entry->start; 2060 else if (starta > addra) 2061 starta = 0; 2062 2063 KKASSERT(object == entry->object.vm_object); 2064 for (i = 0; i < PAGEORDER_SIZE; i++) { 2065 vm_object_t lobject; 2066 vm_object_t nobject; 2067 int allocated = 0; 2068 2069 addr = addra + vm_prefault_pageorder[i]; 2070 if (addr > addra + (PFFOR * PAGE_SIZE)) 2071 addr = 0; 2072 2073 if (addr < starta || addr >= entry->end) 2074 continue; 2075 2076 if (pmap_prefault_ok(pmap, addr) == 0) 2077 continue; 2078 2079 /* 2080 * Follow the VM object chain to obtain the page to be mapped 2081 * into the pmap. 2082 * 2083 * If we reach the terminal object without finding a page 2084 * and we determine it would be advantageous, then allocate 2085 * a zero-fill page for the base object. The base object 2086 * is guaranteed to be OBJT_DEFAULT for this case. 2087 * 2088 * In order to not have to check the pager via *haspage*() 2089 * we stop if any non-default object is encountered. e.g. 2090 * a vnode or swap object would stop the loop. 2091 * 2092 * XXX It is unclear whether hold chaining is sufficient 2093 * to maintain the validity of the backing object chain. 2094 */ 2095 index = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT; 2096 lobject = object; 2097 pindex = index; 2098 pprot = prot; 2099 2100 KKASSERT(lobject == entry->object.vm_object); 2101 vm_object_hold(lobject); 2102 2103 while ((m = vm_page_lookup(lobject, pindex)) == NULL) { 2104 if (lobject->type != OBJT_DEFAULT) 2105 break; 2106 if (lobject->backing_object == NULL) { 2107 if (vm_fast_fault == 0) 2108 break; 2109 if (vm_prefault_pageorder[i] < 0 || 2110 (prot & VM_PROT_WRITE) == 0 || 2111 vm_page_count_min(0)) { 2112 break; 2113 } 2114 2115 /* NOTE: allocated from base object */ 2116 m = vm_page_alloc(object, index, 2117 VM_ALLOC_NORMAL | VM_ALLOC_ZERO); 2118 2119 if ((m->flags & PG_ZERO) == 0) { 2120 vm_page_zero_fill(m); 2121 } else { 2122 #ifdef PMAP_DEBUG 2123 pmap_page_assertzero( 2124 VM_PAGE_TO_PHYS(m)); 2125 #endif 2126 vm_page_flag_clear(m, PG_ZERO); 2127 mycpu->gd_cnt.v_ozfod++; 2128 } 2129 mycpu->gd_cnt.v_zfod++; 2130 m->valid = VM_PAGE_BITS_ALL; 2131 allocated = 1; 2132 pprot = prot; 2133 /* lobject = object .. not needed */ 2134 break; 2135 } 2136 if (lobject->backing_object_offset & PAGE_MASK) 2137 break; 2138 while ((nobject = lobject->backing_object) != NULL) { 2139 vm_object_hold(nobject); 2140 if (nobject == lobject->backing_object) { 2141 pindex += 2142 lobject->backing_object_offset >> 2143 PAGE_SHIFT; 2144 vm_object_lock_swap(); 2145 vm_object_drop(lobject); 2146 lobject = nobject; 2147 break; 2148 } 2149 vm_object_drop(nobject); 2150 } 2151 if (nobject == NULL) { 2152 kprintf("vm_prefault: Warning, backing object " 2153 "race averted lobject %p\n", 2154 lobject); 2155 continue; 2156 } 2157 pprot &= ~VM_PROT_WRITE; 2158 } 2159 vm_object_drop(lobject); 2160 2161 /* 2162 * NOTE: lobject now invalid (if we did a zero-fill we didn't 2163 * bother assigning lobject = object). 2164 * 2165 * Give-up if the page is not available. 2166 */ 2167 if (m == NULL) 2168 break; 2169 2170 /* 2171 * Do not conditionalize on PG_RAM. If pages are present in 2172 * the VM system we assume optimal caching. If caching is 2173 * not optimal the I/O gravy train will be restarted when we 2174 * hit an unavailable page. We do not want to try to restart 2175 * the gravy train now because we really don't know how much 2176 * of the object has been cached. The cost for restarting 2177 * the gravy train should be low (since accesses will likely 2178 * be I/O bound anyway). 2179 * 2180 * The object must be marked dirty if we are mapping a 2181 * writable page. 2182 */ 2183 if (pprot & VM_PROT_WRITE) 2184 vm_object_set_writeable_dirty(m->object); 2185 2186 /* 2187 * Enter the page into the pmap if appropriate. If we had 2188 * allocated the page we have to place it on a queue. If not 2189 * we just have to make sure it isn't on the cache queue 2190 * (pages on the cache queue are not allowed to be mapped). 2191 */ 2192 if (allocated) { 2193 if (pprot & VM_PROT_WRITE) 2194 vm_set_nosync(m, entry); 2195 pmap_enter(pmap, addr, m, pprot, 0); 2196 vm_page_deactivate(m); 2197 vm_page_wakeup(m); 2198 } else if ( 2199 ((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) && 2200 (m->busy == 0) && 2201 (m->flags & (PG_BUSY | PG_FICTITIOUS)) == 0) { 2202 /* 2203 * A fully valid page not undergoing soft I/O can 2204 * be immediately entered into the pmap. 2205 */ 2206 vm_page_busy(m); 2207 if ((m->queue - m->pc) == PQ_CACHE) { 2208 vm_page_deactivate(m); 2209 } 2210 if (pprot & VM_PROT_WRITE) 2211 vm_set_nosync(m, entry); 2212 pmap_enter(pmap, addr, m, pprot, 0); 2213 vm_page_wakeup(m); 2214 } 2215 } 2216 vm_object_drop(object); 2217 lwkt_reltoken(&vm_token); 2218 } 2219