FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_fault.c
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 <sys/param.h>
78 #include <sys/systm.h>
79 #include <sys/kernel.h>
80 #include <sys/lock.h>
81 #include <sys/mutex.h>
82 #include <sys/proc.h>
83 #include <sys/resourcevar.h>
84 #include <sys/sysctl.h>
85 #include <sys/vmmeter.h>
86 #include <sys/vnode.h>
87
88 #include <vm/vm.h>
89 #include <vm/vm_param.h>
90 #include <vm/pmap.h>
91 #include <vm/vm_map.h>
92 #include <vm/vm_object.h>
93 #include <vm/vm_page.h>
94 #include <vm/vm_pageout.h>
95 #include <vm/vm_kern.h>
96 #include <vm/vm_pager.h>
97 #include <vm/vnode_pager.h>
98 #include <vm/vm_extern.h>
99
100 #define PFBAK 4
101 #define PFFOR 4
102 #define PAGEORDER_SIZE (PFBAK+PFFOR)
103
104 static int prefault_pageorder[] = {
105 -1 * PAGE_SIZE, 1 * PAGE_SIZE,
106 -2 * PAGE_SIZE, 2 * PAGE_SIZE,
107 -3 * PAGE_SIZE, 3 * PAGE_SIZE,
108 -4 * PAGE_SIZE, 4 * PAGE_SIZE
109 };
110
111 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
112 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t);
113
114 #define VM_FAULT_READ_AHEAD 8
115 #define VM_FAULT_READ_BEHIND 7
116 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1)
117
118 struct faultstate {
119 vm_page_t m;
120 vm_object_t object;
121 vm_pindex_t pindex;
122 vm_page_t first_m;
123 vm_object_t first_object;
124 vm_pindex_t first_pindex;
125 vm_map_t map;
126 vm_map_entry_t entry;
127 int lookup_still_valid;
128 struct vnode *vp;
129 };
130
131 static __inline void
132 release_page(struct faultstate *fs)
133 {
134 vm_page_lock_queues();
135 vm_page_wakeup(fs->m);
136 vm_page_deactivate(fs->m);
137 vm_page_unlock_queues();
138 fs->m = NULL;
139 }
140
141 static __inline void
142 unlock_map(struct faultstate *fs)
143 {
144 if (fs->lookup_still_valid) {
145 vm_map_lookup_done(fs->map, fs->entry);
146 fs->lookup_still_valid = FALSE;
147 }
148 }
149
150 static void
151 unlock_and_deallocate(struct faultstate *fs)
152 {
153
154 vm_object_pip_wakeup(fs->object);
155 VM_OBJECT_UNLOCK(fs->object);
156 if (fs->object != fs->first_object) {
157 VM_OBJECT_LOCK(fs->first_object);
158 vm_page_lock_queues();
159 vm_page_free(fs->first_m);
160 vm_page_unlock_queues();
161 vm_object_pip_wakeup(fs->first_object);
162 VM_OBJECT_UNLOCK(fs->first_object);
163 fs->first_m = NULL;
164 }
165 vm_object_deallocate(fs->first_object);
166 unlock_map(fs);
167 if (fs->vp != NULL) {
168 mtx_lock(&Giant);
169 vput(fs->vp);
170 mtx_unlock(&Giant);
171 fs->vp = NULL;
172 }
173 if (!fs->map->system_map)
174 VM_UNLOCK_GIANT();
175 }
176
177 /*
178 * TRYPAGER - used by vm_fault to calculate whether the pager for the
179 * current object *might* contain the page.
180 *
181 * default objects are zero-fill, there is no real pager.
182 */
183 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \
184 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired))
185
186 /*
187 * vm_fault:
188 *
189 * Handle a page fault occurring at the given address,
190 * requiring the given permissions, in the map specified.
191 * If successful, the page is inserted into the
192 * associated physical map.
193 *
194 * NOTE: the given address should be truncated to the
195 * proper page address.
196 *
197 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
198 * a standard error specifying why the fault is fatal is returned.
199 *
200 *
201 * The map in question must be referenced, and remains so.
202 * Caller may hold no locks.
203 */
204 int
205 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
206 int fault_flags)
207 {
208 vm_prot_t prot;
209 int is_first_object_locked, result;
210 boolean_t growstack, wired;
211 int map_generation;
212 vm_object_t next_object;
213 vm_page_t marray[VM_FAULT_READ];
214 int hardfault;
215 int faultcount;
216 struct faultstate fs;
217
218 hardfault = 0;
219 growstack = TRUE;
220 atomic_add_int(&cnt.v_vm_faults, 1);
221
222 RetryFault:;
223
224 /*
225 * Find the backing store object and offset into it to begin the
226 * search.
227 */
228 fs.map = map;
229 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
230 &fs.first_object, &fs.first_pindex, &prot, &wired);
231 if (result != KERN_SUCCESS) {
232 if (result != KERN_PROTECTION_FAILURE ||
233 (fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) {
234 if (growstack && result == KERN_INVALID_ADDRESS &&
235 map != kernel_map && curproc != NULL) {
236 result = vm_map_growstack(curproc, vaddr);
237 if (result != KERN_SUCCESS)
238 return (KERN_FAILURE);
239 growstack = FALSE;
240 goto RetryFault;
241 }
242 return (result);
243 }
244
245 /*
246 * If we are user-wiring a r/w segment, and it is COW, then
247 * we need to do the COW operation. Note that we don't COW
248 * currently RO sections now, because it is NOT desirable
249 * to COW .text. We simply keep .text from ever being COW'ed
250 * and take the heat that one cannot debug wired .text sections.
251 */
252 result = vm_map_lookup(&fs.map, vaddr,
253 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE,
254 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired);
255 if (result != KERN_SUCCESS)
256 return (result);
257
258 /*
259 * If we don't COW now, on a user wire, the user will never
260 * be able to write to the mapping. If we don't make this
261 * restriction, the bookkeeping would be nearly impossible.
262 *
263 * XXX The following assignment modifies the map without
264 * holding a write lock on it.
265 */
266 if ((fs.entry->protection & VM_PROT_WRITE) == 0)
267 fs.entry->max_protection &= ~VM_PROT_WRITE;
268 }
269
270 map_generation = fs.map->timestamp;
271
272 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
273 panic("vm_fault: fault on nofault entry, addr: %lx",
274 (u_long)vaddr);
275 }
276
277 /*
278 * Make a reference to this object to prevent its disposal while we
279 * are messing with it. Once we have the reference, the map is free
280 * to be diddled. Since objects reference their shadows (and copies),
281 * they will stay around as well.
282 *
283 * Bump the paging-in-progress count to prevent size changes (e.g.
284 * truncation operations) during I/O. This must be done after
285 * obtaining the vnode lock in order to avoid possible deadlocks.
286 *
287 * XXX vnode_pager_lock() can block without releasing the map lock.
288 */
289 if (!fs.map->system_map)
290 mtx_lock(&Giant);
291 VM_OBJECT_LOCK(fs.first_object);
292 vm_object_reference_locked(fs.first_object);
293 fs.vp = vnode_pager_lock(fs.first_object);
294 KASSERT(fs.vp == NULL || !fs.map->system_map,
295 ("vm_fault: vnode-backed object mapped by system map"));
296 if (debug_mpsafevm && !fs.map->system_map)
297 mtx_unlock(&Giant);
298 vm_object_pip_add(fs.first_object, 1);
299
300 fs.lookup_still_valid = TRUE;
301
302 if (wired)
303 fault_type = prot;
304
305 fs.first_m = NULL;
306
307 /*
308 * Search for the page at object/offset.
309 */
310 fs.object = fs.first_object;
311 fs.pindex = fs.first_pindex;
312 while (TRUE) {
313 /*
314 * If the object is dead, we stop here
315 */
316 if (fs.object->flags & OBJ_DEAD) {
317 unlock_and_deallocate(&fs);
318 return (KERN_PROTECTION_FAILURE);
319 }
320
321 /*
322 * See if page is resident
323 */
324 fs.m = vm_page_lookup(fs.object, fs.pindex);
325 if (fs.m != NULL) {
326 int queue;
327
328 /*
329 * check for page-based copy on write.
330 * We check fs.object == fs.first_object so
331 * as to ensure the legacy COW mechanism is
332 * used when the page in question is part of
333 * a shadow object. Otherwise, vm_page_cowfault()
334 * removes the page from the backing object,
335 * which is not what we want.
336 */
337 vm_page_lock_queues();
338 if ((fs.m->cow) &&
339 (fault_type & VM_PROT_WRITE) &&
340 (fs.object == fs.first_object)) {
341 vm_page_cowfault(fs.m);
342 vm_page_unlock_queues();
343 unlock_and_deallocate(&fs);
344 goto RetryFault;
345 }
346
347 /*
348 * Wait/Retry if the page is busy. We have to do this
349 * if the page is busy via either PG_BUSY or
350 * vm_page_t->busy because the vm_pager may be using
351 * vm_page_t->busy for pageouts ( and even pageins if
352 * it is the vnode pager ), and we could end up trying
353 * to pagein and pageout the same page simultaneously.
354 *
355 * We can theoretically allow the busy case on a read
356 * fault if the page is marked valid, but since such
357 * pages are typically already pmap'd, putting that
358 * special case in might be more effort then it is
359 * worth. We cannot under any circumstances mess
360 * around with a vm_page_t->busy page except, perhaps,
361 * to pmap it.
362 */
363 if ((fs.m->flags & PG_BUSY) || fs.m->busy) {
364 vm_page_unlock_queues();
365 VM_OBJECT_UNLOCK(fs.object);
366 if (fs.object != fs.first_object) {
367 VM_OBJECT_LOCK(fs.first_object);
368 vm_page_lock_queues();
369 vm_page_free(fs.first_m);
370 vm_page_unlock_queues();
371 vm_object_pip_wakeup(fs.first_object);
372 VM_OBJECT_UNLOCK(fs.first_object);
373 fs.first_m = NULL;
374 }
375 unlock_map(&fs);
376 if (fs.vp != NULL) {
377 mtx_lock(&Giant);
378 vput(fs.vp);
379 mtx_unlock(&Giant);
380 fs.vp = NULL;
381 }
382 VM_OBJECT_LOCK(fs.object);
383 if (fs.m == vm_page_lookup(fs.object,
384 fs.pindex)) {
385 vm_page_lock_queues();
386 if (!vm_page_sleep_if_busy(fs.m, TRUE,
387 "vmpfw"))
388 vm_page_unlock_queues();
389 }
390 vm_object_pip_wakeup(fs.object);
391 VM_OBJECT_UNLOCK(fs.object);
392 atomic_add_int(&cnt.v_intrans, 1);
393 if (!fs.map->system_map)
394 VM_UNLOCK_GIANT();
395 vm_object_deallocate(fs.first_object);
396 goto RetryFault;
397 }
398 queue = fs.m->queue;
399
400 vm_pageq_remove_nowakeup(fs.m);
401
402 if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) {
403 vm_page_activate(fs.m);
404 vm_page_unlock_queues();
405 unlock_and_deallocate(&fs);
406 VM_WAITPFAULT;
407 goto RetryFault;
408 }
409
410 /*
411 * Mark page busy for other processes, and the
412 * pagedaemon. If it still isn't completely valid
413 * (readable), jump to readrest, else break-out ( we
414 * found the page ).
415 */
416 vm_page_busy(fs.m);
417 vm_page_unlock_queues();
418 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) &&
419 fs.m->object != kernel_object && fs.m->object != kmem_object) {
420 goto readrest;
421 }
422
423 break;
424 }
425
426 /*
427 * Page is not resident, If this is the search termination
428 * or the pager might contain the page, allocate a new page.
429 */
430 if (TRYPAGER || fs.object == fs.first_object) {
431 if (fs.pindex >= fs.object->size) {
432 unlock_and_deallocate(&fs);
433 return (KERN_PROTECTION_FAILURE);
434 }
435
436 /*
437 * Allocate a new page for this object/offset pair.
438 */
439 fs.m = NULL;
440 if (!vm_page_count_severe()) {
441 fs.m = vm_page_alloc(fs.object, fs.pindex,
442 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO);
443 }
444 if (fs.m == NULL) {
445 unlock_and_deallocate(&fs);
446 VM_WAITPFAULT;
447 goto RetryFault;
448 }
449 }
450
451 readrest:
452 /*
453 * We have found a valid page or we have allocated a new page.
454 * The page thus may not be valid or may not be entirely
455 * valid.
456 *
457 * Attempt to fault-in the page if there is a chance that the
458 * pager has it, and potentially fault in additional pages
459 * at the same time.
460 */
461 if (TRYPAGER) {
462 int rv;
463 int reqpage;
464 int ahead, behind;
465 u_char behavior = vm_map_entry_behavior(fs.entry);
466
467 if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
468 ahead = 0;
469 behind = 0;
470 } else {
471 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT;
472 if (behind > VM_FAULT_READ_BEHIND)
473 behind = VM_FAULT_READ_BEHIND;
474
475 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1;
476 if (ahead > VM_FAULT_READ_AHEAD)
477 ahead = VM_FAULT_READ_AHEAD;
478 }
479 is_first_object_locked = FALSE;
480 if ((behavior == MAP_ENTRY_BEHAV_SEQUENTIAL ||
481 (behavior != MAP_ENTRY_BEHAV_RANDOM &&
482 fs.pindex >= fs.entry->lastr &&
483 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) &&
484 (fs.first_object == fs.object ||
485 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object))) &&
486 fs.first_object->type != OBJT_DEVICE) {
487 vm_pindex_t firstpindex, tmppindex;
488
489 if (fs.first_pindex < 2 * VM_FAULT_READ)
490 firstpindex = 0;
491 else
492 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ;
493
494 vm_page_lock_queues();
495 /*
496 * note: partially valid pages cannot be
497 * included in the lookahead - NFS piecemeal
498 * writes will barf on it badly.
499 */
500 for (tmppindex = fs.first_pindex - 1;
501 tmppindex >= firstpindex;
502 --tmppindex) {
503 vm_page_t mt;
504
505 mt = vm_page_lookup(fs.first_object, tmppindex);
506 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL))
507 break;
508 if (mt->busy ||
509 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) ||
510 mt->hold_count ||
511 mt->wire_count)
512 continue;
513 pmap_remove_all(mt);
514 if (mt->dirty) {
515 vm_page_deactivate(mt);
516 } else {
517 vm_page_cache(mt);
518 }
519 }
520 vm_page_unlock_queues();
521 ahead += behind;
522 behind = 0;
523 }
524 if (is_first_object_locked)
525 VM_OBJECT_UNLOCK(fs.first_object);
526 /*
527 * now we find out if any other pages should be paged
528 * in at this time this routine checks to see if the
529 * pages surrounding this fault reside in the same
530 * object as the page for this fault. If they do,
531 * then they are faulted in also into the object. The
532 * array "marray" returned contains an array of
533 * vm_page_t structs where one of them is the
534 * vm_page_t passed to the routine. The reqpage
535 * return value is the index into the marray for the
536 * vm_page_t passed to the routine.
537 *
538 * fs.m plus the additional pages are PG_BUSY'd.
539 *
540 * XXX vm_fault_additional_pages() can block
541 * without releasing the map lock.
542 */
543 faultcount = vm_fault_additional_pages(
544 fs.m, behind, ahead, marray, &reqpage);
545
546 /*
547 * update lastr imperfectly (we do not know how much
548 * getpages will actually read), but good enough.
549 *
550 * XXX The following assignment modifies the map
551 * without holding a write lock on it.
552 */
553 fs.entry->lastr = fs.pindex + faultcount - behind;
554
555 /*
556 * Call the pager to retrieve the data, if any, after
557 * releasing the lock on the map. We hold a ref on
558 * fs.object and the pages are PG_BUSY'd.
559 */
560 unlock_map(&fs);
561
562 rv = faultcount ?
563 vm_pager_get_pages(fs.object, marray, faultcount,
564 reqpage) : VM_PAGER_FAIL;
565
566 if (rv == VM_PAGER_OK) {
567 /*
568 * Found the page. Leave it busy while we play
569 * with it.
570 */
571
572 /*
573 * Relookup in case pager changed page. Pager
574 * is responsible for disposition of old page
575 * if moved.
576 */
577 fs.m = vm_page_lookup(fs.object, fs.pindex);
578 if (!fs.m) {
579 unlock_and_deallocate(&fs);
580 goto RetryFault;
581 }
582
583 hardfault++;
584 break; /* break to PAGE HAS BEEN FOUND */
585 }
586 /*
587 * Remove the bogus page (which does not exist at this
588 * object/offset); before doing so, we must get back
589 * our object lock to preserve our invariant.
590 *
591 * Also wake up any other process that may want to bring
592 * in this page.
593 *
594 * If this is the top-level object, we must leave the
595 * busy page to prevent another process from rushing
596 * past us, and inserting the page in that object at
597 * the same time that we are.
598 */
599 if (rv == VM_PAGER_ERROR)
600 printf("vm_fault: pager read error, pid %d (%s)\n",
601 curproc->p_pid, curproc->p_comm);
602 /*
603 * Data outside the range of the pager or an I/O error
604 */
605 /*
606 * XXX - the check for kernel_map is a kludge to work
607 * around having the machine panic on a kernel space
608 * fault w/ I/O error.
609 */
610 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
611 (rv == VM_PAGER_BAD)) {
612 vm_page_lock_queues();
613 vm_page_free(fs.m);
614 vm_page_unlock_queues();
615 fs.m = NULL;
616 unlock_and_deallocate(&fs);
617 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
618 }
619 if (fs.object != fs.first_object) {
620 vm_page_lock_queues();
621 vm_page_free(fs.m);
622 vm_page_unlock_queues();
623 fs.m = NULL;
624 /*
625 * XXX - we cannot just fall out at this
626 * point, m has been freed and is invalid!
627 */
628 }
629 }
630
631 /*
632 * We get here if the object has default pager (or unwiring)
633 * or the pager doesn't have the page.
634 */
635 if (fs.object == fs.first_object)
636 fs.first_m = fs.m;
637
638 /*
639 * Move on to the next object. Lock the next object before
640 * unlocking the current one.
641 */
642 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
643 next_object = fs.object->backing_object;
644 if (next_object == NULL) {
645 /*
646 * If there's no object left, fill the page in the top
647 * object with zeros.
648 */
649 if (fs.object != fs.first_object) {
650 vm_object_pip_wakeup(fs.object);
651 VM_OBJECT_UNLOCK(fs.object);
652
653 fs.object = fs.first_object;
654 fs.pindex = fs.first_pindex;
655 fs.m = fs.first_m;
656 VM_OBJECT_LOCK(fs.object);
657 }
658 fs.first_m = NULL;
659
660 /*
661 * Zero the page if necessary and mark it valid.
662 */
663 if ((fs.m->flags & PG_ZERO) == 0) {
664 pmap_zero_page(fs.m);
665 } else {
666 atomic_add_int(&cnt.v_ozfod, 1);
667 }
668 atomic_add_int(&cnt.v_zfod, 1);
669 fs.m->valid = VM_PAGE_BITS_ALL;
670 break; /* break to PAGE HAS BEEN FOUND */
671 } else {
672 KASSERT(fs.object != next_object,
673 ("object loop %p", next_object));
674 VM_OBJECT_LOCK(next_object);
675 vm_object_pip_add(next_object, 1);
676 if (fs.object != fs.first_object)
677 vm_object_pip_wakeup(fs.object);
678 VM_OBJECT_UNLOCK(fs.object);
679 fs.object = next_object;
680 }
681 }
682
683 KASSERT((fs.m->flags & PG_BUSY) != 0,
684 ("vm_fault: not busy after main loop"));
685
686 /*
687 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
688 * is held.]
689 */
690
691 /*
692 * If the page is being written, but isn't already owned by the
693 * top-level object, we have to copy it into a new page owned by the
694 * top-level object.
695 */
696 if (fs.object != fs.first_object) {
697 /*
698 * We only really need to copy if we want to write it.
699 */
700 if (fault_type & VM_PROT_WRITE) {
701 /*
702 * This allows pages to be virtually copied from a
703 * backing_object into the first_object, where the
704 * backing object has no other refs to it, and cannot
705 * gain any more refs. Instead of a bcopy, we just
706 * move the page from the backing object to the
707 * first object. Note that we must mark the page
708 * dirty in the first object so that it will go out
709 * to swap when needed.
710 */
711 is_first_object_locked = FALSE;
712 if (
713 /*
714 * Only one shadow object
715 */
716 (fs.object->shadow_count == 1) &&
717 /*
718 * No COW refs, except us
719 */
720 (fs.object->ref_count == 1) &&
721 /*
722 * No one else can look this object up
723 */
724 (fs.object->handle == NULL) &&
725 /*
726 * No other ways to look the object up
727 */
728 ((fs.object->type == OBJT_DEFAULT) ||
729 (fs.object->type == OBJT_SWAP)) &&
730 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) &&
731 /*
732 * We don't chase down the shadow chain
733 */
734 fs.object == fs.first_object->backing_object) {
735 vm_page_lock_queues();
736 /*
737 * get rid of the unnecessary page
738 */
739 pmap_remove_all(fs.first_m);
740 vm_page_free(fs.first_m);
741 /*
742 * grab the page and put it into the
743 * process'es object. The page is
744 * automatically made dirty.
745 */
746 vm_page_rename(fs.m, fs.first_object, fs.first_pindex);
747 vm_page_busy(fs.m);
748 vm_page_unlock_queues();
749 fs.first_m = fs.m;
750 fs.m = NULL;
751 atomic_add_int(&cnt.v_cow_optim, 1);
752 } else {
753 /*
754 * Oh, well, lets copy it.
755 */
756 pmap_copy_page(fs.m, fs.first_m);
757 fs.first_m->valid = VM_PAGE_BITS_ALL;
758 }
759 if (fs.m) {
760 /*
761 * We no longer need the old page or object.
762 */
763 release_page(&fs);
764 }
765 /*
766 * fs.object != fs.first_object due to above
767 * conditional
768 */
769 vm_object_pip_wakeup(fs.object);
770 VM_OBJECT_UNLOCK(fs.object);
771 /*
772 * Only use the new page below...
773 */
774 fs.object = fs.first_object;
775 fs.pindex = fs.first_pindex;
776 fs.m = fs.first_m;
777 if (!is_first_object_locked)
778 VM_OBJECT_LOCK(fs.object);
779 atomic_add_int(&cnt.v_cow_faults, 1);
780 } else {
781 prot &= ~VM_PROT_WRITE;
782 }
783 }
784
785 /*
786 * We must verify that the maps have not changed since our last
787 * lookup.
788 */
789 if (!fs.lookup_still_valid) {
790 vm_object_t retry_object;
791 vm_pindex_t retry_pindex;
792 vm_prot_t retry_prot;
793
794 if (!vm_map_trylock_read(fs.map)) {
795 release_page(&fs);
796 unlock_and_deallocate(&fs);
797 goto RetryFault;
798 }
799 fs.lookup_still_valid = TRUE;
800 if (fs.map->timestamp != map_generation) {
801 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
802 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
803
804 /*
805 * If we don't need the page any longer, put it on the active
806 * list (the easiest thing to do here). If no one needs it,
807 * pageout will grab it eventually.
808 */
809 if (result != KERN_SUCCESS) {
810 release_page(&fs);
811 unlock_and_deallocate(&fs);
812
813 /*
814 * If retry of map lookup would have blocked then
815 * retry fault from start.
816 */
817 if (result == KERN_FAILURE)
818 goto RetryFault;
819 return (result);
820 }
821 if ((retry_object != fs.first_object) ||
822 (retry_pindex != fs.first_pindex)) {
823 release_page(&fs);
824 unlock_and_deallocate(&fs);
825 goto RetryFault;
826 }
827
828 /*
829 * Check whether the protection has changed or the object has
830 * been copied while we left the map unlocked. Changing from
831 * read to write permission is OK - we leave the page
832 * write-protected, and catch the write fault. Changing from
833 * write to read permission means that we can't mark the page
834 * write-enabled after all.
835 */
836 prot &= retry_prot;
837 }
838 }
839 if (prot & VM_PROT_WRITE) {
840 vm_page_lock_queues();
841 vm_page_flag_set(fs.m, PG_WRITEABLE);
842 vm_object_set_writeable_dirty(fs.m->object);
843
844 /*
845 * If the fault is a write, we know that this page is being
846 * written NOW so dirty it explicitly to save on
847 * pmap_is_modified() calls later.
848 *
849 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC
850 * if the page is already dirty to prevent data written with
851 * the expectation of being synced from not being synced.
852 * Likewise if this entry does not request NOSYNC then make
853 * sure the page isn't marked NOSYNC. Applications sharing
854 * data should use the same flags to avoid ping ponging.
855 *
856 * Also tell the backing pager, if any, that it should remove
857 * any swap backing since the page is now dirty.
858 */
859 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) {
860 if (fs.m->dirty == 0)
861 vm_page_flag_set(fs.m, PG_NOSYNC);
862 } else {
863 vm_page_flag_clear(fs.m, PG_NOSYNC);
864 }
865 vm_page_unlock_queues();
866 if (fault_flags & VM_FAULT_DIRTY) {
867 vm_page_dirty(fs.m);
868 vm_pager_page_unswapped(fs.m);
869 }
870 }
871
872 /*
873 * Page had better still be busy
874 */
875 KASSERT(fs.m->flags & PG_BUSY,
876 ("vm_fault: page %p not busy!", fs.m));
877 /*
878 * Sanity check: page must be completely valid or it is not fit to
879 * map into user space. vm_pager_get_pages() ensures this.
880 */
881 if (fs.m->valid != VM_PAGE_BITS_ALL) {
882 vm_page_zero_invalid(fs.m, TRUE);
883 printf("Warning: page %p partially invalid on fault\n", fs.m);
884 }
885 VM_OBJECT_UNLOCK(fs.object);
886
887 /*
888 * Put this page into the physical map. We had to do the unlock above
889 * because pmap_enter() may sleep. We don't put the page
890 * back on the active queue until later so that the pageout daemon
891 * won't find it (yet).
892 */
893 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired);
894 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) {
895 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry);
896 }
897 VM_OBJECT_LOCK(fs.object);
898 vm_page_lock_queues();
899 vm_page_flag_set(fs.m, PG_REFERENCED);
900
901 /*
902 * If the page is not wired down, then put it where the pageout daemon
903 * can find it.
904 */
905 if (fault_flags & VM_FAULT_WIRE_MASK) {
906 if (wired)
907 vm_page_wire(fs.m);
908 else
909 vm_page_unwire(fs.m, 1);
910 } else {
911 vm_page_activate(fs.m);
912 }
913 vm_page_wakeup(fs.m);
914 vm_page_unlock_queues();
915
916 /*
917 * Unlock everything, and return
918 */
919 unlock_and_deallocate(&fs);
920 PROC_LOCK(curproc);
921 if ((curproc->p_sflag & PS_INMEM) && curproc->p_stats) {
922 if (hardfault) {
923 curproc->p_stats->p_ru.ru_majflt++;
924 } else {
925 curproc->p_stats->p_ru.ru_minflt++;
926 }
927 }
928 PROC_UNLOCK(curproc);
929
930 return (KERN_SUCCESS);
931 }
932
933 /*
934 * vm_fault_prefault provides a quick way of clustering
935 * pagefaults into a processes address space. It is a "cousin"
936 * of vm_map_pmap_enter, except it runs at page fault time instead
937 * of mmap time.
938 */
939 static void
940 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry)
941 {
942 int i;
943 vm_offset_t addr, starta;
944 vm_pindex_t pindex;
945 vm_page_t m, mpte;
946 vm_object_t object;
947
948 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
949 return;
950
951 object = entry->object.vm_object;
952
953 starta = addra - PFBAK * PAGE_SIZE;
954 if (starta < entry->start) {
955 starta = entry->start;
956 } else if (starta > addra) {
957 starta = 0;
958 }
959
960 mpte = NULL;
961 for (i = 0; i < PAGEORDER_SIZE; i++) {
962 vm_object_t backing_object, lobject;
963
964 addr = addra + prefault_pageorder[i];
965 if (addr > addra + (PFFOR * PAGE_SIZE))
966 addr = 0;
967
968 if (addr < starta || addr >= entry->end)
969 continue;
970
971 if (!pmap_is_prefaultable(pmap, addr))
972 continue;
973
974 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
975 lobject = object;
976 VM_OBJECT_LOCK(lobject);
977 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
978 lobject->type == OBJT_DEFAULT &&
979 (backing_object = lobject->backing_object) != NULL) {
980 if (lobject->backing_object_offset & PAGE_MASK)
981 break;
982 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
983 VM_OBJECT_LOCK(backing_object);
984 VM_OBJECT_UNLOCK(lobject);
985 lobject = backing_object;
986 }
987 /*
988 * give-up when a page is not in memory
989 */
990 if (m == NULL) {
991 VM_OBJECT_UNLOCK(lobject);
992 break;
993 }
994 vm_page_lock_queues();
995 if (((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) &&
996 (m->busy == 0) &&
997 (m->flags & (PG_BUSY | PG_FICTITIOUS)) == 0) {
998
999 if ((m->queue - m->pc) == PQ_CACHE) {
1000 vm_page_deactivate(m);
1001 }
1002 vm_page_busy(m);
1003 vm_page_unlock_queues();
1004 VM_OBJECT_UNLOCK(lobject);
1005 mpte = pmap_enter_quick(pmap, addr, m, mpte);
1006 VM_OBJECT_LOCK(lobject);
1007 vm_page_lock_queues();
1008 vm_page_wakeup(m);
1009 }
1010 vm_page_unlock_queues();
1011 VM_OBJECT_UNLOCK(lobject);
1012 }
1013 }
1014
1015 /*
1016 * vm_fault_quick:
1017 *
1018 * Ensure that the requested virtual address, which may be in userland,
1019 * is valid. Fault-in the page if necessary. Return -1 on failure.
1020 */
1021 int
1022 vm_fault_quick(caddr_t v, int prot)
1023 {
1024 int r;
1025
1026 if (prot & VM_PROT_WRITE)
1027 r = subyte(v, fubyte(v));
1028 else
1029 r = fubyte(v);
1030 return(r);
1031 }
1032
1033 /*
1034 * vm_fault_wire:
1035 *
1036 * Wire down a range of virtual addresses in a map.
1037 */
1038 int
1039 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1040 boolean_t user_wire, boolean_t fictitious)
1041 {
1042 vm_offset_t va;
1043 int rv;
1044
1045 /*
1046 * We simulate a fault to get the page and enter it in the physical
1047 * map. For user wiring, we only ask for read access on currently
1048 * read-only sections.
1049 */
1050 for (va = start; va < end; va += PAGE_SIZE) {
1051 rv = vm_fault(map, va,
1052 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE,
1053 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING);
1054 if (rv) {
1055 if (va != start)
1056 vm_fault_unwire(map, start, va, fictitious);
1057 return (rv);
1058 }
1059 }
1060 return (KERN_SUCCESS);
1061 }
1062
1063 /*
1064 * vm_fault_unwire:
1065 *
1066 * Unwire a range of virtual addresses in a map.
1067 */
1068 void
1069 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1070 boolean_t fictitious)
1071 {
1072 vm_paddr_t pa;
1073 vm_offset_t va;
1074 pmap_t pmap;
1075
1076 pmap = vm_map_pmap(map);
1077
1078 /*
1079 * Since the pages are wired down, we must be able to get their
1080 * mappings from the physical map system.
1081 */
1082 for (va = start; va < end; va += PAGE_SIZE) {
1083 pa = pmap_extract(pmap, va);
1084 if (pa != 0) {
1085 pmap_change_wiring(pmap, va, FALSE);
1086 if (!fictitious) {
1087 vm_page_lock_queues();
1088 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1);
1089 vm_page_unlock_queues();
1090 }
1091 }
1092 }
1093 }
1094
1095 /*
1096 * Routine:
1097 * vm_fault_copy_entry
1098 * Function:
1099 * Copy all of the pages from a wired-down map entry to another.
1100 *
1101 * In/out conditions:
1102 * The source and destination maps must be locked for write.
1103 * The source map entry must be wired down (or be a sharing map
1104 * entry corresponding to a main map entry that is wired down).
1105 */
1106 void
1107 vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry)
1108 vm_map_t dst_map;
1109 vm_map_t src_map;
1110 vm_map_entry_t dst_entry;
1111 vm_map_entry_t src_entry;
1112 {
1113 vm_object_t backing_object, dst_object, object;
1114 vm_object_t src_object;
1115 vm_ooffset_t dst_offset;
1116 vm_ooffset_t src_offset;
1117 vm_pindex_t pindex;
1118 vm_prot_t prot;
1119 vm_offset_t vaddr;
1120 vm_page_t dst_m;
1121 vm_page_t src_m;
1122
1123 #ifdef lint
1124 src_map++;
1125 #endif /* lint */
1126
1127 src_object = src_entry->object.vm_object;
1128 src_offset = src_entry->offset;
1129
1130 /*
1131 * Create the top-level object for the destination entry. (Doesn't
1132 * actually shadow anything - we copy the pages directly.)
1133 */
1134 dst_object = vm_object_allocate(OBJT_DEFAULT,
1135 (vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start));
1136
1137 VM_OBJECT_LOCK(dst_object);
1138 dst_entry->object.vm_object = dst_object;
1139 dst_entry->offset = 0;
1140
1141 prot = dst_entry->max_protection;
1142
1143 /*
1144 * Loop through all of the pages in the entry's range, copying each
1145 * one from the source object (it should be there) to the destination
1146 * object.
1147 */
1148 for (vaddr = dst_entry->start, dst_offset = 0;
1149 vaddr < dst_entry->end;
1150 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) {
1151
1152 /*
1153 * Allocate a page in the destination object
1154 */
1155 do {
1156 dst_m = vm_page_alloc(dst_object,
1157 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL);
1158 if (dst_m == NULL) {
1159 VM_OBJECT_UNLOCK(dst_object);
1160 VM_WAIT;
1161 VM_OBJECT_LOCK(dst_object);
1162 }
1163 } while (dst_m == NULL);
1164
1165 /*
1166 * Find the page in the source object, and copy it in.
1167 * (Because the source is wired down, the page will be in
1168 * memory.)
1169 */
1170 VM_OBJECT_LOCK(src_object);
1171 object = src_object;
1172 pindex = 0;
1173 while ((src_m = vm_page_lookup(object, pindex +
1174 OFF_TO_IDX(dst_offset + src_offset))) == NULL &&
1175 (src_entry->protection & VM_PROT_WRITE) == 0 &&
1176 (backing_object = object->backing_object) != NULL) {
1177 /*
1178 * Allow fallback to backing objects if we are reading.
1179 */
1180 VM_OBJECT_LOCK(backing_object);
1181 pindex += OFF_TO_IDX(object->backing_object_offset);
1182 VM_OBJECT_UNLOCK(object);
1183 object = backing_object;
1184 }
1185 if (src_m == NULL)
1186 panic("vm_fault_copy_wired: page missing");
1187 pmap_copy_page(src_m, dst_m);
1188 VM_OBJECT_UNLOCK(object);
1189 dst_m->valid = VM_PAGE_BITS_ALL;
1190 VM_OBJECT_UNLOCK(dst_object);
1191
1192 /*
1193 * Enter it in the pmap...
1194 */
1195 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE);
1196 VM_OBJECT_LOCK(dst_object);
1197 vm_page_lock_queues();
1198 if ((prot & VM_PROT_WRITE) != 0)
1199 vm_page_flag_set(dst_m, PG_WRITEABLE);
1200
1201 /*
1202 * Mark it no longer busy, and put it on the active list.
1203 */
1204 vm_page_activate(dst_m);
1205 vm_page_wakeup(dst_m);
1206 vm_page_unlock_queues();
1207 }
1208 VM_OBJECT_UNLOCK(dst_object);
1209 }
1210
1211
1212 /*
1213 * This routine checks around the requested page for other pages that
1214 * might be able to be faulted in. This routine brackets the viable
1215 * pages for the pages to be paged in.
1216 *
1217 * Inputs:
1218 * m, rbehind, rahead
1219 *
1220 * Outputs:
1221 * marray (array of vm_page_t), reqpage (index of requested page)
1222 *
1223 * Return value:
1224 * number of pages in marray
1225 *
1226 * This routine can't block.
1227 */
1228 static int
1229 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1230 vm_page_t m;
1231 int rbehind;
1232 int rahead;
1233 vm_page_t *marray;
1234 int *reqpage;
1235 {
1236 int i,j;
1237 vm_object_t object;
1238 vm_pindex_t pindex, startpindex, endpindex, tpindex;
1239 vm_page_t rtm;
1240 int cbehind, cahead;
1241
1242 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
1243
1244 object = m->object;
1245 pindex = m->pindex;
1246
1247 /*
1248 * we don't fault-ahead for device pager
1249 */
1250 if (object->type == OBJT_DEVICE) {
1251 *reqpage = 0;
1252 marray[0] = m;
1253 return 1;
1254 }
1255
1256 /*
1257 * if the requested page is not available, then give up now
1258 */
1259 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1260 return 0;
1261 }
1262
1263 if ((cbehind == 0) && (cahead == 0)) {
1264 *reqpage = 0;
1265 marray[0] = m;
1266 return 1;
1267 }
1268
1269 if (rahead > cahead) {
1270 rahead = cahead;
1271 }
1272
1273 if (rbehind > cbehind) {
1274 rbehind = cbehind;
1275 }
1276
1277 /*
1278 * try to do any readahead that we might have free pages for.
1279 */
1280 if ((rahead + rbehind) >
1281 ((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) {
1282 pagedaemon_wakeup();
1283 marray[0] = m;
1284 *reqpage = 0;
1285 return 1;
1286 }
1287
1288 /*
1289 * scan backward for the read behind pages -- in memory
1290 */
1291 if (pindex > 0) {
1292 if (rbehind > pindex) {
1293 rbehind = pindex;
1294 startpindex = 0;
1295 } else {
1296 startpindex = pindex - rbehind;
1297 }
1298
1299 for (tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) {
1300 if (vm_page_lookup(object, tpindex)) {
1301 startpindex = tpindex + 1;
1302 break;
1303 }
1304 if (tpindex == 0)
1305 break;
1306 }
1307
1308 for (i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) {
1309
1310 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
1311 if (rtm == NULL) {
1312 vm_page_lock_queues();
1313 for (j = 0; j < i; j++) {
1314 vm_page_free(marray[j]);
1315 }
1316 vm_page_unlock_queues();
1317 marray[0] = m;
1318 *reqpage = 0;
1319 return 1;
1320 }
1321
1322 marray[i] = rtm;
1323 }
1324 } else {
1325 startpindex = 0;
1326 i = 0;
1327 }
1328
1329 marray[i] = m;
1330 /* page offset of the required page */
1331 *reqpage = i;
1332
1333 tpindex = pindex + 1;
1334 i++;
1335
1336 /*
1337 * scan forward for the read ahead pages
1338 */
1339 endpindex = tpindex + rahead;
1340 if (endpindex > object->size)
1341 endpindex = object->size;
1342
1343 for (; tpindex < endpindex; i++, tpindex++) {
1344
1345 if (vm_page_lookup(object, tpindex)) {
1346 break;
1347 }
1348
1349 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
1350 if (rtm == NULL) {
1351 break;
1352 }
1353
1354 marray[i] = rtm;
1355 }
1356
1357 /* return number of bytes of pages */
1358 return i;
1359 }
Cache object: 53b932557e29bd065e097d313f7fdfab
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