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: releng/6.2/sys/vm/vm_fault.c 159542 2006-06-12 15:06:22Z maxim $");
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 #include <sys/mount.h> /* XXX Temporary for VFS_LOCK_GIANT() */
101
102 #define PFBAK 4
103 #define PFFOR 4
104 #define PAGEORDER_SIZE (PFBAK+PFFOR)
105
106 static int prefault_pageorder[] = {
107 -1 * PAGE_SIZE, 1 * PAGE_SIZE,
108 -2 * PAGE_SIZE, 2 * PAGE_SIZE,
109 -3 * PAGE_SIZE, 3 * PAGE_SIZE,
110 -4 * PAGE_SIZE, 4 * PAGE_SIZE
111 };
112
113 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
114 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t);
115
116 #define VM_FAULT_READ_AHEAD 8
117 #define VM_FAULT_READ_BEHIND 7
118 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1)
119
120 struct faultstate {
121 vm_page_t m;
122 vm_object_t object;
123 vm_pindex_t pindex;
124 vm_page_t first_m;
125 vm_object_t first_object;
126 vm_pindex_t first_pindex;
127 vm_map_t map;
128 vm_map_entry_t entry;
129 int lookup_still_valid;
130 struct vnode *vp;
131 };
132
133 static __inline void
134 release_page(struct faultstate *fs)
135 {
136 vm_page_lock_queues();
137 vm_page_wakeup(fs->m);
138 vm_page_deactivate(fs->m);
139 vm_page_unlock_queues();
140 fs->m = NULL;
141 }
142
143 static __inline void
144 unlock_map(struct faultstate *fs)
145 {
146 if (fs->lookup_still_valid) {
147 vm_map_lookup_done(fs->map, fs->entry);
148 fs->lookup_still_valid = FALSE;
149 }
150 }
151
152 static void
153 unlock_and_deallocate(struct faultstate *fs)
154 {
155 boolean_t firstobjneedgiant;
156
157 vm_object_pip_wakeup(fs->object);
158 VM_OBJECT_UNLOCK(fs->object);
159 if (fs->object != fs->first_object) {
160 VM_OBJECT_LOCK(fs->first_object);
161 vm_page_lock_queues();
162 vm_page_free(fs->first_m);
163 vm_page_unlock_queues();
164 vm_object_pip_wakeup(fs->first_object);
165 VM_OBJECT_UNLOCK(fs->first_object);
166 fs->first_m = NULL;
167 }
168 firstobjneedgiant = (fs->first_object->flags & OBJ_NEEDGIANT) != 0;
169 vm_object_deallocate(fs->first_object);
170 unlock_map(fs);
171 if (fs->vp != NULL) {
172 int vfslocked;
173
174 vfslocked = VFS_LOCK_GIANT(fs->vp->v_mount);
175 vput(fs->vp);
176 fs->vp = NULL;
177 VFS_UNLOCK_GIANT(vfslocked);
178 }
179 if (firstobjneedgiant)
180 VM_UNLOCK_GIANT();
181 }
182
183 /*
184 * TRYPAGER - used by vm_fault to calculate whether the pager for the
185 * current object *might* contain the page.
186 *
187 * default objects are zero-fill, there is no real pager.
188 */
189 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \
190 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired))
191
192 /*
193 * vm_fault:
194 *
195 * Handle a page fault occurring at the given address,
196 * requiring the given permissions, in the map specified.
197 * If successful, the page is inserted into the
198 * associated physical map.
199 *
200 * NOTE: the given address should be truncated to the
201 * proper page address.
202 *
203 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
204 * a standard error specifying why the fault is fatal is returned.
205 *
206 *
207 * The map in question must be referenced, and remains so.
208 * Caller may hold no locks.
209 */
210 int
211 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
212 int fault_flags)
213 {
214 vm_prot_t prot;
215 int is_first_object_locked, result;
216 boolean_t growstack, wired;
217 int map_generation;
218 vm_object_t next_object;
219 vm_page_t marray[VM_FAULT_READ];
220 int hardfault;
221 int faultcount;
222 struct faultstate fs;
223
224 hardfault = 0;
225 growstack = TRUE;
226 atomic_add_int(&cnt.v_vm_faults, 1);
227
228 RetryFault:;
229
230 /*
231 * Find the backing store object and offset into it to begin the
232 * search.
233 */
234 fs.map = map;
235 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
236 &fs.first_object, &fs.first_pindex, &prot, &wired);
237 if (result != KERN_SUCCESS) {
238 if (result != KERN_PROTECTION_FAILURE ||
239 (fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) {
240 if (growstack && result == KERN_INVALID_ADDRESS &&
241 map != kernel_map && curproc != NULL) {
242 result = vm_map_growstack(curproc, vaddr);
243 if (result != KERN_SUCCESS)
244 return (KERN_FAILURE);
245 growstack = FALSE;
246 goto RetryFault;
247 }
248 return (result);
249 }
250
251 /*
252 * If we are user-wiring a r/w segment, and it is COW, then
253 * we need to do the COW operation. Note that we don't COW
254 * currently RO sections now, because it is NOT desirable
255 * to COW .text. We simply keep .text from ever being COW'ed
256 * and take the heat that one cannot debug wired .text sections.
257 */
258 result = vm_map_lookup(&fs.map, vaddr,
259 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE,
260 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired);
261 if (result != KERN_SUCCESS)
262 return (result);
263
264 /*
265 * If we don't COW now, on a user wire, the user will never
266 * be able to write to the mapping. If we don't make this
267 * restriction, the bookkeeping would be nearly impossible.
268 *
269 * XXX The following assignment modifies the map without
270 * holding a write lock on it.
271 */
272 if ((fs.entry->protection & VM_PROT_WRITE) == 0)
273 fs.entry->max_protection &= ~VM_PROT_WRITE;
274 }
275
276 map_generation = fs.map->timestamp;
277
278 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
279 panic("vm_fault: fault on nofault entry, addr: %lx",
280 (u_long)vaddr);
281 }
282
283 /*
284 * Make a reference to this object to prevent its disposal while we
285 * are messing with it. Once we have the reference, the map is free
286 * to be diddled. Since objects reference their shadows (and copies),
287 * they will stay around as well.
288 *
289 * Bump the paging-in-progress count to prevent size changes (e.g.
290 * truncation operations) during I/O. This must be done after
291 * obtaining the vnode lock in order to avoid possible deadlocks.
292 *
293 * XXX vnode_pager_lock() can block without releasing the map lock.
294 */
295 if (fs.first_object->flags & OBJ_NEEDGIANT)
296 mtx_lock(&Giant);
297 VM_OBJECT_LOCK(fs.first_object);
298 vm_object_reference_locked(fs.first_object);
299 fs.vp = vnode_pager_lock(fs.first_object);
300 KASSERT(fs.vp == NULL || !fs.map->system_map,
301 ("vm_fault: vnode-backed object mapped by system map"));
302 KASSERT((fs.first_object->flags & OBJ_NEEDGIANT) == 0 ||
303 !fs.map->system_map,
304 ("vm_fault: Object requiring giant mapped by system map"));
305 if (fs.first_object->flags & OBJ_NEEDGIANT && debug_mpsafevm)
306 mtx_unlock(&Giant);
307 vm_object_pip_add(fs.first_object, 1);
308
309 fs.lookup_still_valid = TRUE;
310
311 if (wired)
312 fault_type = prot;
313
314 fs.first_m = NULL;
315
316 /*
317 * Search for the page at object/offset.
318 */
319 fs.object = fs.first_object;
320 fs.pindex = fs.first_pindex;
321 while (TRUE) {
322 /*
323 * If the object is dead, we stop here
324 */
325 if (fs.object->flags & OBJ_DEAD) {
326 unlock_and_deallocate(&fs);
327 return (KERN_PROTECTION_FAILURE);
328 }
329
330 /*
331 * See if page is resident
332 */
333 fs.m = vm_page_lookup(fs.object, fs.pindex);
334 if (fs.m != NULL) {
335 int queue;
336
337 /*
338 * check for page-based copy on write.
339 * We check fs.object == fs.first_object so
340 * as to ensure the legacy COW mechanism is
341 * used when the page in question is part of
342 * a shadow object. Otherwise, vm_page_cowfault()
343 * removes the page from the backing object,
344 * which is not what we want.
345 */
346 vm_page_lock_queues();
347 if ((fs.m->cow) &&
348 (fault_type & VM_PROT_WRITE) &&
349 (fs.object == fs.first_object)) {
350 vm_page_cowfault(fs.m);
351 vm_page_unlock_queues();
352 unlock_and_deallocate(&fs);
353 goto RetryFault;
354 }
355
356 /*
357 * Wait/Retry if the page is busy. We have to do this
358 * if the page is busy via either PG_BUSY or
359 * vm_page_t->busy because the vm_pager may be using
360 * vm_page_t->busy for pageouts ( and even pageins if
361 * it is the vnode pager ), and we could end up trying
362 * to pagein and pageout the same page simultaneously.
363 *
364 * We can theoretically allow the busy case on a read
365 * fault if the page is marked valid, but since such
366 * pages are typically already pmap'd, putting that
367 * special case in might be more effort then it is
368 * worth. We cannot under any circumstances mess
369 * around with a vm_page_t->busy page except, perhaps,
370 * to pmap it.
371 */
372 if ((fs.m->flags & PG_BUSY) || fs.m->busy) {
373 vm_page_unlock_queues();
374 VM_OBJECT_UNLOCK(fs.object);
375 if (fs.object != fs.first_object) {
376 VM_OBJECT_LOCK(fs.first_object);
377 vm_page_lock_queues();
378 vm_page_free(fs.first_m);
379 vm_page_unlock_queues();
380 vm_object_pip_wakeup(fs.first_object);
381 VM_OBJECT_UNLOCK(fs.first_object);
382 fs.first_m = NULL;
383 }
384 unlock_map(&fs);
385 if (fs.vp != NULL) {
386 int vfslck;
387
388 vfslck = VFS_LOCK_GIANT(fs.vp->v_mount);
389 vput(fs.vp);
390 fs.vp = NULL;
391 VFS_UNLOCK_GIANT(vfslck);
392 }
393 VM_OBJECT_LOCK(fs.object);
394 if (fs.m == vm_page_lookup(fs.object,
395 fs.pindex)) {
396 vm_page_lock_queues();
397 if (!vm_page_sleep_if_busy(fs.m, TRUE,
398 "vmpfw"))
399 vm_page_unlock_queues();
400 }
401 vm_object_pip_wakeup(fs.object);
402 VM_OBJECT_UNLOCK(fs.object);
403 atomic_add_int(&cnt.v_intrans, 1);
404 if (fs.first_object->flags & OBJ_NEEDGIANT)
405 VM_UNLOCK_GIANT();
406 vm_object_deallocate(fs.first_object);
407 goto RetryFault;
408 }
409 queue = fs.m->queue;
410
411 vm_pageq_remove_nowakeup(fs.m);
412
413 if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) {
414 vm_page_activate(fs.m);
415 vm_page_unlock_queues();
416 unlock_and_deallocate(&fs);
417 VM_WAITPFAULT;
418 goto RetryFault;
419 }
420
421 /*
422 * Mark page busy for other processes, and the
423 * pagedaemon. If it still isn't completely valid
424 * (readable), jump to readrest, else break-out ( we
425 * found the page ).
426 */
427 vm_page_busy(fs.m);
428 vm_page_unlock_queues();
429 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) &&
430 fs.m->object != kernel_object && fs.m->object != kmem_object) {
431 goto readrest;
432 }
433
434 break;
435 }
436
437 /*
438 * Page is not resident, If this is the search termination
439 * or the pager might contain the page, allocate a new page.
440 */
441 if (TRYPAGER || fs.object == fs.first_object) {
442 if (fs.pindex >= fs.object->size) {
443 unlock_and_deallocate(&fs);
444 return (KERN_PROTECTION_FAILURE);
445 }
446
447 /*
448 * Allocate a new page for this object/offset pair.
449 */
450 fs.m = NULL;
451 if (!vm_page_count_severe()) {
452 fs.m = vm_page_alloc(fs.object, fs.pindex,
453 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO);
454 }
455 if (fs.m == NULL) {
456 unlock_and_deallocate(&fs);
457 VM_WAITPFAULT;
458 goto RetryFault;
459 }
460 }
461
462 readrest:
463 /*
464 * We have found a valid page or we have allocated a new page.
465 * The page thus may not be valid or may not be entirely
466 * valid.
467 *
468 * Attempt to fault-in the page if there is a chance that the
469 * pager has it, and potentially fault in additional pages
470 * at the same time.
471 */
472 if (TRYPAGER) {
473 int rv;
474 int reqpage;
475 int ahead, behind;
476 u_char behavior = vm_map_entry_behavior(fs.entry);
477
478 if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
479 ahead = 0;
480 behind = 0;
481 } else {
482 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT;
483 if (behind > VM_FAULT_READ_BEHIND)
484 behind = VM_FAULT_READ_BEHIND;
485
486 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1;
487 if (ahead > VM_FAULT_READ_AHEAD)
488 ahead = VM_FAULT_READ_AHEAD;
489 }
490 is_first_object_locked = FALSE;
491 if ((behavior == MAP_ENTRY_BEHAV_SEQUENTIAL ||
492 (behavior != MAP_ENTRY_BEHAV_RANDOM &&
493 fs.pindex >= fs.entry->lastr &&
494 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) &&
495 (fs.first_object == fs.object ||
496 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object))) &&
497 fs.first_object->type != OBJT_DEVICE) {
498 vm_pindex_t firstpindex, tmppindex;
499
500 if (fs.first_pindex < 2 * VM_FAULT_READ)
501 firstpindex = 0;
502 else
503 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ;
504
505 vm_page_lock_queues();
506 /*
507 * note: partially valid pages cannot be
508 * included in the lookahead - NFS piecemeal
509 * writes will barf on it badly.
510 */
511 for (tmppindex = fs.first_pindex - 1;
512 tmppindex >= firstpindex;
513 --tmppindex) {
514 vm_page_t mt;
515
516 mt = vm_page_lookup(fs.first_object, tmppindex);
517 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL))
518 break;
519 if (mt->busy ||
520 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) ||
521 mt->hold_count ||
522 mt->wire_count)
523 continue;
524 pmap_remove_all(mt);
525 if (mt->dirty) {
526 vm_page_deactivate(mt);
527 } else {
528 vm_page_cache(mt);
529 }
530 }
531 vm_page_unlock_queues();
532 ahead += behind;
533 behind = 0;
534 }
535 if (is_first_object_locked)
536 VM_OBJECT_UNLOCK(fs.first_object);
537 /*
538 * now we find out if any other pages should be paged
539 * in at this time this routine checks to see if the
540 * pages surrounding this fault reside in the same
541 * object as the page for this fault. If they do,
542 * then they are faulted in also into the object. The
543 * array "marray" returned contains an array of
544 * vm_page_t structs where one of them is the
545 * vm_page_t passed to the routine. The reqpage
546 * return value is the index into the marray for the
547 * vm_page_t passed to the routine.
548 *
549 * fs.m plus the additional pages are PG_BUSY'd.
550 *
551 * XXX vm_fault_additional_pages() can block
552 * without releasing the map lock.
553 */
554 faultcount = vm_fault_additional_pages(
555 fs.m, behind, ahead, marray, &reqpage);
556
557 /*
558 * update lastr imperfectly (we do not know how much
559 * getpages will actually read), but good enough.
560 *
561 * XXX The following assignment modifies the map
562 * without holding a write lock on it.
563 */
564 fs.entry->lastr = fs.pindex + faultcount - behind;
565
566 /*
567 * Call the pager to retrieve the data, if any, after
568 * releasing the lock on the map. We hold a ref on
569 * fs.object and the pages are PG_BUSY'd.
570 */
571 unlock_map(&fs);
572
573 rv = faultcount ?
574 vm_pager_get_pages(fs.object, marray, faultcount,
575 reqpage) : VM_PAGER_FAIL;
576
577 if (rv == VM_PAGER_OK) {
578 /*
579 * Found the page. Leave it busy while we play
580 * with it.
581 */
582
583 /*
584 * Relookup in case pager changed page. Pager
585 * is responsible for disposition of old page
586 * if moved.
587 */
588 fs.m = vm_page_lookup(fs.object, fs.pindex);
589 if (!fs.m) {
590 unlock_and_deallocate(&fs);
591 goto RetryFault;
592 }
593
594 hardfault++;
595 break; /* break to PAGE HAS BEEN FOUND */
596 }
597 /*
598 * Remove the bogus page (which does not exist at this
599 * object/offset); before doing so, we must get back
600 * our object lock to preserve our invariant.
601 *
602 * Also wake up any other process that may want to bring
603 * in this page.
604 *
605 * If this is the top-level object, we must leave the
606 * busy page to prevent another process from rushing
607 * past us, and inserting the page in that object at
608 * the same time that we are.
609 */
610 if (rv == VM_PAGER_ERROR)
611 printf("vm_fault: pager read error, pid %d (%s)\n",
612 curproc->p_pid, curproc->p_comm);
613 /*
614 * Data outside the range of the pager or an I/O error
615 */
616 /*
617 * XXX - the check for kernel_map is a kludge to work
618 * around having the machine panic on a kernel space
619 * fault w/ I/O error.
620 */
621 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
622 (rv == VM_PAGER_BAD)) {
623 vm_page_lock_queues();
624 vm_page_free(fs.m);
625 vm_page_unlock_queues();
626 fs.m = NULL;
627 unlock_and_deallocate(&fs);
628 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
629 }
630 if (fs.object != fs.first_object) {
631 vm_page_lock_queues();
632 vm_page_free(fs.m);
633 vm_page_unlock_queues();
634 fs.m = NULL;
635 /*
636 * XXX - we cannot just fall out at this
637 * point, m has been freed and is invalid!
638 */
639 }
640 }
641
642 /*
643 * We get here if the object has default pager (or unwiring)
644 * or the pager doesn't have the page.
645 */
646 if (fs.object == fs.first_object)
647 fs.first_m = fs.m;
648
649 /*
650 * Move on to the next object. Lock the next object before
651 * unlocking the current one.
652 */
653 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
654 next_object = fs.object->backing_object;
655 if (next_object == NULL) {
656 /*
657 * If there's no object left, fill the page in the top
658 * object with zeros.
659 */
660 if (fs.object != fs.first_object) {
661 vm_object_pip_wakeup(fs.object);
662 VM_OBJECT_UNLOCK(fs.object);
663
664 fs.object = fs.first_object;
665 fs.pindex = fs.first_pindex;
666 fs.m = fs.first_m;
667 VM_OBJECT_LOCK(fs.object);
668 }
669 fs.first_m = NULL;
670
671 /*
672 * Zero the page if necessary and mark it valid.
673 */
674 if ((fs.m->flags & PG_ZERO) == 0) {
675 pmap_zero_page(fs.m);
676 } else {
677 atomic_add_int(&cnt.v_ozfod, 1);
678 }
679 atomic_add_int(&cnt.v_zfod, 1);
680 fs.m->valid = VM_PAGE_BITS_ALL;
681 break; /* break to PAGE HAS BEEN FOUND */
682 } else {
683 KASSERT(fs.object != next_object,
684 ("object loop %p", next_object));
685 VM_OBJECT_LOCK(next_object);
686 vm_object_pip_add(next_object, 1);
687 if (fs.object != fs.first_object)
688 vm_object_pip_wakeup(fs.object);
689 VM_OBJECT_UNLOCK(fs.object);
690 fs.object = next_object;
691 }
692 }
693
694 KASSERT((fs.m->flags & PG_BUSY) != 0,
695 ("vm_fault: not busy after main loop"));
696
697 /*
698 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
699 * is held.]
700 */
701
702 /*
703 * If the page is being written, but isn't already owned by the
704 * top-level object, we have to copy it into a new page owned by the
705 * top-level object.
706 */
707 if (fs.object != fs.first_object) {
708 /*
709 * We only really need to copy if we want to write it.
710 */
711 if (fault_type & VM_PROT_WRITE) {
712 /*
713 * This allows pages to be virtually copied from a
714 * backing_object into the first_object, where the
715 * backing object has no other refs to it, and cannot
716 * gain any more refs. Instead of a bcopy, we just
717 * move the page from the backing object to the
718 * first object. Note that we must mark the page
719 * dirty in the first object so that it will go out
720 * to swap when needed.
721 */
722 is_first_object_locked = FALSE;
723 if (
724 /*
725 * Only one shadow object
726 */
727 (fs.object->shadow_count == 1) &&
728 /*
729 * No COW refs, except us
730 */
731 (fs.object->ref_count == 1) &&
732 /*
733 * No one else can look this object up
734 */
735 (fs.object->handle == NULL) &&
736 /*
737 * No other ways to look the object up
738 */
739 ((fs.object->type == OBJT_DEFAULT) ||
740 (fs.object->type == OBJT_SWAP)) &&
741 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) &&
742 /*
743 * We don't chase down the shadow chain
744 */
745 fs.object == fs.first_object->backing_object) {
746 vm_page_lock_queues();
747 /*
748 * get rid of the unnecessary page
749 */
750 pmap_remove_all(fs.first_m);
751 vm_page_free(fs.first_m);
752 /*
753 * grab the page and put it into the
754 * process'es object. The page is
755 * automatically made dirty.
756 */
757 vm_page_rename(fs.m, fs.first_object, fs.first_pindex);
758 vm_page_busy(fs.m);
759 vm_page_unlock_queues();
760 fs.first_m = fs.m;
761 fs.m = NULL;
762 atomic_add_int(&cnt.v_cow_optim, 1);
763 } else {
764 /*
765 * Oh, well, lets copy it.
766 */
767 pmap_copy_page(fs.m, fs.first_m);
768 fs.first_m->valid = VM_PAGE_BITS_ALL;
769 }
770 if (fs.m) {
771 /*
772 * We no longer need the old page or object.
773 */
774 release_page(&fs);
775 }
776 /*
777 * fs.object != fs.first_object due to above
778 * conditional
779 */
780 vm_object_pip_wakeup(fs.object);
781 VM_OBJECT_UNLOCK(fs.object);
782 /*
783 * Only use the new page below...
784 */
785 fs.object = fs.first_object;
786 fs.pindex = fs.first_pindex;
787 fs.m = fs.first_m;
788 if (!is_first_object_locked)
789 VM_OBJECT_LOCK(fs.object);
790 atomic_add_int(&cnt.v_cow_faults, 1);
791 } else {
792 prot &= ~VM_PROT_WRITE;
793 }
794 }
795
796 /*
797 * We must verify that the maps have not changed since our last
798 * lookup.
799 */
800 if (!fs.lookup_still_valid) {
801 vm_object_t retry_object;
802 vm_pindex_t retry_pindex;
803 vm_prot_t retry_prot;
804
805 if (!vm_map_trylock_read(fs.map)) {
806 release_page(&fs);
807 unlock_and_deallocate(&fs);
808 goto RetryFault;
809 }
810 fs.lookup_still_valid = TRUE;
811 if (fs.map->timestamp != map_generation) {
812 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
813 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
814
815 /*
816 * If we don't need the page any longer, put it on the inactive
817 * list (the easiest thing to do here). If no one needs it,
818 * pageout will grab it eventually.
819 */
820 if (result != KERN_SUCCESS) {
821 release_page(&fs);
822 unlock_and_deallocate(&fs);
823
824 /*
825 * If retry of map lookup would have blocked then
826 * retry fault from start.
827 */
828 if (result == KERN_FAILURE)
829 goto RetryFault;
830 return (result);
831 }
832 if ((retry_object != fs.first_object) ||
833 (retry_pindex != fs.first_pindex)) {
834 release_page(&fs);
835 unlock_and_deallocate(&fs);
836 goto RetryFault;
837 }
838
839 /*
840 * Check whether the protection has changed or the object has
841 * been copied while we left the map unlocked. Changing from
842 * read to write permission is OK - we leave the page
843 * write-protected, and catch the write fault. Changing from
844 * write to read permission means that we can't mark the page
845 * write-enabled after all.
846 */
847 prot &= retry_prot;
848 }
849 }
850 if (prot & VM_PROT_WRITE) {
851 vm_page_lock_queues();
852 vm_page_flag_set(fs.m, PG_WRITEABLE);
853 vm_object_set_writeable_dirty(fs.m->object);
854
855 /*
856 * If the fault is a write, we know that this page is being
857 * written NOW so dirty it explicitly to save on
858 * pmap_is_modified() calls later.
859 *
860 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC
861 * if the page is already dirty to prevent data written with
862 * the expectation of being synced from not being synced.
863 * Likewise if this entry does not request NOSYNC then make
864 * sure the page isn't marked NOSYNC. Applications sharing
865 * data should use the same flags to avoid ping ponging.
866 *
867 * Also tell the backing pager, if any, that it should remove
868 * any swap backing since the page is now dirty.
869 */
870 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) {
871 if (fs.m->dirty == 0)
872 vm_page_flag_set(fs.m, PG_NOSYNC);
873 } else {
874 vm_page_flag_clear(fs.m, PG_NOSYNC);
875 }
876 vm_page_unlock_queues();
877 if (fault_flags & VM_FAULT_DIRTY) {
878 vm_page_dirty(fs.m);
879 vm_pager_page_unswapped(fs.m);
880 }
881 }
882
883 /*
884 * Page had better still be busy
885 */
886 KASSERT(fs.m->flags & PG_BUSY,
887 ("vm_fault: page %p not busy!", fs.m));
888 /*
889 * Sanity check: page must be completely valid or it is not fit to
890 * map into user space. vm_pager_get_pages() ensures this.
891 */
892 if (fs.m->valid != VM_PAGE_BITS_ALL) {
893 vm_page_zero_invalid(fs.m, TRUE);
894 printf("Warning: page %p partially invalid on fault\n", fs.m);
895 }
896 VM_OBJECT_UNLOCK(fs.object);
897
898 /*
899 * Put this page into the physical map. We had to do the unlock above
900 * because pmap_enter() may sleep. We don't put the page
901 * back on the active queue until later so that the pageout daemon
902 * won't find it (yet).
903 */
904 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired);
905 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) {
906 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry);
907 }
908 VM_OBJECT_LOCK(fs.object);
909 vm_page_lock_queues();
910 vm_page_flag_set(fs.m, PG_REFERENCED);
911
912 /*
913 * If the page is not wired down, then put it where the pageout daemon
914 * can find it.
915 */
916 if (fault_flags & VM_FAULT_WIRE_MASK) {
917 if (wired)
918 vm_page_wire(fs.m);
919 else
920 vm_page_unwire(fs.m, 1);
921 } else {
922 vm_page_activate(fs.m);
923 }
924 vm_page_wakeup(fs.m);
925 vm_page_unlock_queues();
926
927 /*
928 * Unlock everything, and return
929 */
930 unlock_and_deallocate(&fs);
931 PROC_LOCK(curproc);
932 if ((curproc->p_sflag & PS_INMEM) && curproc->p_stats) {
933 if (hardfault) {
934 curproc->p_stats->p_ru.ru_majflt++;
935 } else {
936 curproc->p_stats->p_ru.ru_minflt++;
937 }
938 }
939 PROC_UNLOCK(curproc);
940
941 return (KERN_SUCCESS);
942 }
943
944 /*
945 * vm_fault_prefault provides a quick way of clustering
946 * pagefaults into a processes address space. It is a "cousin"
947 * of vm_map_pmap_enter, except it runs at page fault time instead
948 * of mmap time.
949 */
950 static void
951 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry)
952 {
953 int i;
954 vm_offset_t addr, starta;
955 vm_pindex_t pindex;
956 vm_page_t m, mpte;
957 vm_object_t object;
958
959 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
960 return;
961
962 object = entry->object.vm_object;
963
964 starta = addra - PFBAK * PAGE_SIZE;
965 if (starta < entry->start) {
966 starta = entry->start;
967 } else if (starta > addra) {
968 starta = 0;
969 }
970
971 mpte = NULL;
972 for (i = 0; i < PAGEORDER_SIZE; i++) {
973 vm_object_t backing_object, lobject;
974
975 addr = addra + prefault_pageorder[i];
976 if (addr > addra + (PFFOR * PAGE_SIZE))
977 addr = 0;
978
979 if (addr < starta || addr >= entry->end)
980 continue;
981
982 if (!pmap_is_prefaultable(pmap, addr))
983 continue;
984
985 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
986 lobject = object;
987 VM_OBJECT_LOCK(lobject);
988 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
989 lobject->type == OBJT_DEFAULT &&
990 (backing_object = lobject->backing_object) != NULL) {
991 if (lobject->backing_object_offset & PAGE_MASK)
992 break;
993 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
994 VM_OBJECT_LOCK(backing_object);
995 VM_OBJECT_UNLOCK(lobject);
996 lobject = backing_object;
997 }
998 /*
999 * give-up when a page is not in memory
1000 */
1001 if (m == NULL) {
1002 VM_OBJECT_UNLOCK(lobject);
1003 break;
1004 }
1005 if (((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) &&
1006 (m->busy == 0) &&
1007 (m->flags & (PG_BUSY | PG_FICTITIOUS)) == 0) {
1008
1009 vm_page_lock_queues();
1010 if ((m->queue - m->pc) == PQ_CACHE)
1011 vm_page_deactivate(m);
1012 mpte = pmap_enter_quick(pmap, addr, m,
1013 entry->protection, mpte);
1014 vm_page_unlock_queues();
1015 }
1016 VM_OBJECT_UNLOCK(lobject);
1017 }
1018 }
1019
1020 /*
1021 * vm_fault_quick:
1022 *
1023 * Ensure that the requested virtual address, which may be in userland,
1024 * is valid. Fault-in the page if necessary. Return -1 on failure.
1025 */
1026 int
1027 vm_fault_quick(caddr_t v, int prot)
1028 {
1029 int r;
1030
1031 if (prot & VM_PROT_WRITE)
1032 r = subyte(v, fubyte(v));
1033 else
1034 r = fubyte(v);
1035 return(r);
1036 }
1037
1038 /*
1039 * vm_fault_wire:
1040 *
1041 * Wire down a range of virtual addresses in a map.
1042 */
1043 int
1044 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1045 boolean_t user_wire, boolean_t fictitious)
1046 {
1047 vm_offset_t va;
1048 int rv;
1049
1050 /*
1051 * We simulate a fault to get the page and enter it in the physical
1052 * map. For user wiring, we only ask for read access on currently
1053 * read-only sections.
1054 */
1055 for (va = start; va < end; va += PAGE_SIZE) {
1056 rv = vm_fault(map, va,
1057 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE,
1058 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING);
1059 if (rv) {
1060 if (va != start)
1061 vm_fault_unwire(map, start, va, fictitious);
1062 return (rv);
1063 }
1064 }
1065 return (KERN_SUCCESS);
1066 }
1067
1068 /*
1069 * vm_fault_unwire:
1070 *
1071 * Unwire a range of virtual addresses in a map.
1072 */
1073 void
1074 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1075 boolean_t fictitious)
1076 {
1077 vm_paddr_t pa;
1078 vm_offset_t va;
1079 pmap_t pmap;
1080
1081 pmap = vm_map_pmap(map);
1082
1083 /*
1084 * Since the pages are wired down, we must be able to get their
1085 * mappings from the physical map system.
1086 */
1087 for (va = start; va < end; va += PAGE_SIZE) {
1088 pa = pmap_extract(pmap, va);
1089 if (pa != 0) {
1090 pmap_change_wiring(pmap, va, FALSE);
1091 if (!fictitious) {
1092 vm_page_lock_queues();
1093 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1);
1094 vm_page_unlock_queues();
1095 }
1096 }
1097 }
1098 }
1099
1100 /*
1101 * Routine:
1102 * vm_fault_copy_entry
1103 * Function:
1104 * Copy all of the pages from a wired-down map entry to another.
1105 *
1106 * In/out conditions:
1107 * The source and destination maps must be locked for write.
1108 * The source map entry must be wired down (or be a sharing map
1109 * entry corresponding to a main map entry that is wired down).
1110 */
1111 void
1112 vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry)
1113 vm_map_t dst_map;
1114 vm_map_t src_map;
1115 vm_map_entry_t dst_entry;
1116 vm_map_entry_t src_entry;
1117 {
1118 vm_object_t backing_object, dst_object, object;
1119 vm_object_t src_object;
1120 vm_ooffset_t dst_offset;
1121 vm_ooffset_t src_offset;
1122 vm_pindex_t pindex;
1123 vm_prot_t prot;
1124 vm_offset_t vaddr;
1125 vm_page_t dst_m;
1126 vm_page_t src_m;
1127
1128 #ifdef lint
1129 src_map++;
1130 #endif /* lint */
1131
1132 src_object = src_entry->object.vm_object;
1133 src_offset = src_entry->offset;
1134
1135 /*
1136 * Create the top-level object for the destination entry. (Doesn't
1137 * actually shadow anything - we copy the pages directly.)
1138 */
1139 dst_object = vm_object_allocate(OBJT_DEFAULT,
1140 OFF_TO_IDX(dst_entry->end - dst_entry->start));
1141
1142 VM_OBJECT_LOCK(dst_object);
1143 dst_entry->object.vm_object = dst_object;
1144 dst_entry->offset = 0;
1145
1146 prot = dst_entry->max_protection;
1147
1148 /*
1149 * Loop through all of the pages in the entry's range, copying each
1150 * one from the source object (it should be there) to the destination
1151 * object.
1152 */
1153 for (vaddr = dst_entry->start, dst_offset = 0;
1154 vaddr < dst_entry->end;
1155 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) {
1156
1157 /*
1158 * Allocate a page in the destination object
1159 */
1160 do {
1161 dst_m = vm_page_alloc(dst_object,
1162 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL);
1163 if (dst_m == NULL) {
1164 VM_OBJECT_UNLOCK(dst_object);
1165 VM_WAIT;
1166 VM_OBJECT_LOCK(dst_object);
1167 }
1168 } while (dst_m == NULL);
1169
1170 /*
1171 * Find the page in the source object, and copy it in.
1172 * (Because the source is wired down, the page will be in
1173 * memory.)
1174 */
1175 VM_OBJECT_LOCK(src_object);
1176 object = src_object;
1177 pindex = 0;
1178 while ((src_m = vm_page_lookup(object, pindex +
1179 OFF_TO_IDX(dst_offset + src_offset))) == NULL &&
1180 (src_entry->protection & VM_PROT_WRITE) == 0 &&
1181 (backing_object = object->backing_object) != NULL) {
1182 /*
1183 * Allow fallback to backing objects if we are reading.
1184 */
1185 VM_OBJECT_LOCK(backing_object);
1186 pindex += OFF_TO_IDX(object->backing_object_offset);
1187 VM_OBJECT_UNLOCK(object);
1188 object = backing_object;
1189 }
1190 if (src_m == NULL)
1191 panic("vm_fault_copy_wired: page missing");
1192 pmap_copy_page(src_m, dst_m);
1193 VM_OBJECT_UNLOCK(object);
1194 dst_m->valid = VM_PAGE_BITS_ALL;
1195 VM_OBJECT_UNLOCK(dst_object);
1196
1197 /*
1198 * Enter it in the pmap...
1199 */
1200 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE);
1201 VM_OBJECT_LOCK(dst_object);
1202 vm_page_lock_queues();
1203 if ((prot & VM_PROT_WRITE) != 0)
1204 vm_page_flag_set(dst_m, PG_WRITEABLE);
1205
1206 /*
1207 * Mark it no longer busy, and put it on the active list.
1208 */
1209 vm_page_activate(dst_m);
1210 vm_page_wakeup(dst_m);
1211 vm_page_unlock_queues();
1212 }
1213 VM_OBJECT_UNLOCK(dst_object);
1214 }
1215
1216
1217 /*
1218 * This routine checks around the requested page for other pages that
1219 * might be able to be faulted in. This routine brackets the viable
1220 * pages for the pages to be paged in.
1221 *
1222 * Inputs:
1223 * m, rbehind, rahead
1224 *
1225 * Outputs:
1226 * marray (array of vm_page_t), reqpage (index of requested page)
1227 *
1228 * Return value:
1229 * number of pages in marray
1230 *
1231 * This routine can't block.
1232 */
1233 static int
1234 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1235 vm_page_t m;
1236 int rbehind;
1237 int rahead;
1238 vm_page_t *marray;
1239 int *reqpage;
1240 {
1241 int i,j;
1242 vm_object_t object;
1243 vm_pindex_t pindex, startpindex, endpindex, tpindex;
1244 vm_page_t rtm;
1245 int cbehind, cahead;
1246
1247 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
1248
1249 object = m->object;
1250 pindex = m->pindex;
1251
1252 /*
1253 * we don't fault-ahead for device pager
1254 */
1255 if (object->type == OBJT_DEVICE) {
1256 *reqpage = 0;
1257 marray[0] = m;
1258 return 1;
1259 }
1260
1261 /*
1262 * if the requested page is not available, then give up now
1263 */
1264 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1265 return 0;
1266 }
1267
1268 if ((cbehind == 0) && (cahead == 0)) {
1269 *reqpage = 0;
1270 marray[0] = m;
1271 return 1;
1272 }
1273
1274 if (rahead > cahead) {
1275 rahead = cahead;
1276 }
1277
1278 if (rbehind > cbehind) {
1279 rbehind = cbehind;
1280 }
1281
1282 /*
1283 * try to do any readahead that we might have free pages for.
1284 */
1285 if ((rahead + rbehind) >
1286 ((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) {
1287 pagedaemon_wakeup();
1288 marray[0] = m;
1289 *reqpage = 0;
1290 return 1;
1291 }
1292
1293 /*
1294 * scan backward for the read behind pages -- in memory
1295 */
1296 if (pindex > 0) {
1297 if (rbehind > pindex) {
1298 rbehind = pindex;
1299 startpindex = 0;
1300 } else {
1301 startpindex = pindex - rbehind;
1302 }
1303
1304 for (tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) {
1305 if (vm_page_lookup(object, tpindex)) {
1306 startpindex = tpindex + 1;
1307 break;
1308 }
1309 if (tpindex == 0)
1310 break;
1311 }
1312
1313 for (i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) {
1314
1315 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
1316 if (rtm == NULL) {
1317 vm_page_lock_queues();
1318 for (j = 0; j < i; j++) {
1319 vm_page_free(marray[j]);
1320 }
1321 vm_page_unlock_queues();
1322 marray[0] = m;
1323 *reqpage = 0;
1324 return 1;
1325 }
1326
1327 marray[i] = rtm;
1328 }
1329 } else {
1330 startpindex = 0;
1331 i = 0;
1332 }
1333
1334 marray[i] = m;
1335 /* page offset of the required page */
1336 *reqpage = i;
1337
1338 tpindex = pindex + 1;
1339 i++;
1340
1341 /*
1342 * scan forward for the read ahead pages
1343 */
1344 endpindex = tpindex + rahead;
1345 if (endpindex > object->size)
1346 endpindex = object->size;
1347
1348 for (; tpindex < endpindex; i++, tpindex++) {
1349
1350 if (vm_page_lookup(object, tpindex)) {
1351 break;
1352 }
1353
1354 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
1355 if (rtm == NULL) {
1356 break;
1357 }
1358
1359 marray[i] = rtm;
1360 }
1361
1362 /* return number of bytes of pages */
1363 return i;
1364 }
Cache object: fa0640754aa7a0dc581126fee09cd6ee
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