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/11.1/sys/vm/vm_fault.c 320763 2017-07-07 06:29:18Z kib $");
76
77 #include "opt_ktrace.h"
78 #include "opt_vm.h"
79
80 #include <sys/param.h>
81 #include <sys/systm.h>
82 #include <sys/kernel.h>
83 #include <sys/lock.h>
84 #include <sys/mman.h>
85 #include <sys/proc.h>
86 #include <sys/racct.h>
87 #include <sys/resourcevar.h>
88 #include <sys/rwlock.h>
89 #include <sys/sysctl.h>
90 #include <sys/vmmeter.h>
91 #include <sys/vnode.h>
92 #ifdef KTRACE
93 #include <sys/ktrace.h>
94 #endif
95
96 #include <vm/vm.h>
97 #include <vm/vm_param.h>
98 #include <vm/pmap.h>
99 #include <vm/vm_map.h>
100 #include <vm/vm_object.h>
101 #include <vm/vm_page.h>
102 #include <vm/vm_pageout.h>
103 #include <vm/vm_kern.h>
104 #include <vm/vm_pager.h>
105 #include <vm/vm_extern.h>
106 #include <vm/vm_reserv.h>
107
108 #define PFBAK 4
109 #define PFFOR 4
110
111 #define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT)
112 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX)
113
114 #define VM_FAULT_DONTNEED_MIN 1048576
115
116 struct faultstate {
117 vm_page_t m;
118 vm_object_t object;
119 vm_pindex_t pindex;
120 vm_page_t first_m;
121 vm_object_t first_object;
122 vm_pindex_t first_pindex;
123 vm_map_t map;
124 vm_map_entry_t entry;
125 int map_generation;
126 bool lookup_still_valid;
127 struct vnode *vp;
128 };
129
130 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr,
131 int ahead);
132 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
133 int backward, int forward);
134
135 static inline void
136 release_page(struct faultstate *fs)
137 {
138
139 vm_page_xunbusy(fs->m);
140 vm_page_lock(fs->m);
141 vm_page_deactivate(fs->m);
142 vm_page_unlock(fs->m);
143 fs->m = NULL;
144 }
145
146 static inline void
147 unlock_map(struct faultstate *fs)
148 {
149
150 if (fs->lookup_still_valid) {
151 vm_map_lookup_done(fs->map, fs->entry);
152 fs->lookup_still_valid = false;
153 }
154 }
155
156 static void
157 unlock_vp(struct faultstate *fs)
158 {
159
160 if (fs->vp != NULL) {
161 vput(fs->vp);
162 fs->vp = NULL;
163 }
164 }
165
166 static void
167 unlock_and_deallocate(struct faultstate *fs)
168 {
169
170 vm_object_pip_wakeup(fs->object);
171 VM_OBJECT_WUNLOCK(fs->object);
172 if (fs->object != fs->first_object) {
173 VM_OBJECT_WLOCK(fs->first_object);
174 vm_page_lock(fs->first_m);
175 vm_page_free(fs->first_m);
176 vm_page_unlock(fs->first_m);
177 vm_object_pip_wakeup(fs->first_object);
178 VM_OBJECT_WUNLOCK(fs->first_object);
179 fs->first_m = NULL;
180 }
181 vm_object_deallocate(fs->first_object);
182 unlock_map(fs);
183 unlock_vp(fs);
184 }
185
186 static void
187 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot,
188 vm_prot_t fault_type, int fault_flags, bool set_wd)
189 {
190 bool need_dirty;
191
192 if (((prot & VM_PROT_WRITE) == 0 &&
193 (fault_flags & VM_FAULT_DIRTY) == 0) ||
194 (m->oflags & VPO_UNMANAGED) != 0)
195 return;
196
197 VM_OBJECT_ASSERT_LOCKED(m->object);
198
199 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 &&
200 (fault_flags & VM_FAULT_WIRE) == 0) ||
201 (fault_flags & VM_FAULT_DIRTY) != 0;
202
203 if (set_wd)
204 vm_object_set_writeable_dirty(m->object);
205 else
206 /*
207 * If two callers of vm_fault_dirty() with set_wd ==
208 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC
209 * flag set, other with flag clear, race, it is
210 * possible for the no-NOSYNC thread to see m->dirty
211 * != 0 and not clear VPO_NOSYNC. Take vm_page lock
212 * around manipulation of VPO_NOSYNC and
213 * vm_page_dirty() call, to avoid the race and keep
214 * m->oflags consistent.
215 */
216 vm_page_lock(m);
217
218 /*
219 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
220 * if the page is already dirty to prevent data written with
221 * the expectation of being synced from not being synced.
222 * Likewise if this entry does not request NOSYNC then make
223 * sure the page isn't marked NOSYNC. Applications sharing
224 * data should use the same flags to avoid ping ponging.
225 */
226 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) {
227 if (m->dirty == 0) {
228 m->oflags |= VPO_NOSYNC;
229 }
230 } else {
231 m->oflags &= ~VPO_NOSYNC;
232 }
233
234 /*
235 * If the fault is a write, we know that this page is being
236 * written NOW so dirty it explicitly to save on
237 * pmap_is_modified() calls later.
238 *
239 * Also tell the backing pager, if any, that it should remove
240 * any swap backing since the page is now dirty.
241 */
242 if (need_dirty)
243 vm_page_dirty(m);
244 if (!set_wd)
245 vm_page_unlock(m);
246 if (need_dirty)
247 vm_pager_page_unswapped(m);
248 }
249
250 static void
251 vm_fault_fill_hold(vm_page_t *m_hold, vm_page_t m)
252 {
253
254 if (m_hold != NULL) {
255 *m_hold = m;
256 vm_page_lock(m);
257 vm_page_hold(m);
258 vm_page_unlock(m);
259 }
260 }
261
262 /*
263 * Unlocks fs.first_object and fs.map on success.
264 */
265 static int
266 vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot,
267 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold)
268 {
269 vm_page_t m;
270 int rv;
271
272 MPASS(fs->vp == NULL);
273 m = vm_page_lookup(fs->first_object, fs->first_pindex);
274 /* A busy page can be mapped for read|execute access. */
275 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
276 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
277 return (KERN_FAILURE);
278 rv = pmap_enter(fs->map->pmap, vaddr, m, prot, fault_type |
279 PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), 0);
280 if (rv != KERN_SUCCESS)
281 return (rv);
282 vm_fault_fill_hold(m_hold, m);
283 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false);
284 VM_OBJECT_RUNLOCK(fs->first_object);
285 if (!wired)
286 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR);
287 vm_map_lookup_done(fs->map, fs->entry);
288 curthread->td_ru.ru_minflt++;
289 return (KERN_SUCCESS);
290 }
291
292 static void
293 vm_fault_restore_map_lock(struct faultstate *fs)
294 {
295
296 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
297 MPASS(fs->first_object->paging_in_progress > 0);
298
299 if (!vm_map_trylock_read(fs->map)) {
300 VM_OBJECT_WUNLOCK(fs->first_object);
301 vm_map_lock_read(fs->map);
302 VM_OBJECT_WLOCK(fs->first_object);
303 }
304 fs->lookup_still_valid = true;
305 }
306
307 static void
308 vm_fault_populate_check_page(vm_page_t m)
309 {
310
311 /*
312 * Check each page to ensure that the pager is obeying the
313 * interface: the page must be installed in the object, fully
314 * valid, and exclusively busied.
315 */
316 MPASS(m != NULL);
317 MPASS(m->valid == VM_PAGE_BITS_ALL);
318 MPASS(vm_page_xbusied(m));
319 }
320
321 static void
322 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first,
323 vm_pindex_t last)
324 {
325 vm_page_t m;
326 vm_pindex_t pidx;
327
328 VM_OBJECT_ASSERT_WLOCKED(object);
329 MPASS(first <= last);
330 for (pidx = first, m = vm_page_lookup(object, pidx);
331 pidx <= last; pidx++, m = vm_page_next(m)) {
332 vm_fault_populate_check_page(m);
333 vm_page_lock(m);
334 vm_page_deactivate(m);
335 vm_page_unlock(m);
336 vm_page_xunbusy(m);
337 }
338 }
339
340 static int
341 vm_fault_populate(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot,
342 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold)
343 {
344 vm_page_t m;
345 vm_pindex_t map_first, map_last, pager_first, pager_last, pidx;
346 int rv;
347
348 MPASS(fs->object == fs->first_object);
349 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
350 MPASS(fs->first_object->paging_in_progress > 0);
351 MPASS(fs->first_object->backing_object == NULL);
352 MPASS(fs->lookup_still_valid);
353
354 pager_first = OFF_TO_IDX(fs->entry->offset);
355 pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1;
356 unlock_map(fs);
357 unlock_vp(fs);
358
359 /*
360 * Call the pager (driver) populate() method.
361 *
362 * There is no guarantee that the method will be called again
363 * if the current fault is for read, and a future fault is
364 * for write. Report the entry's maximum allowed protection
365 * to the driver.
366 */
367 rv = vm_pager_populate(fs->first_object, fs->first_pindex,
368 fault_type, fs->entry->max_protection, &pager_first, &pager_last);
369
370 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
371 if (rv == VM_PAGER_BAD) {
372 /*
373 * VM_PAGER_BAD is the backdoor for a pager to request
374 * normal fault handling.
375 */
376 vm_fault_restore_map_lock(fs);
377 if (fs->map->timestamp != fs->map_generation)
378 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */
379 return (KERN_NOT_RECEIVER);
380 }
381 if (rv != VM_PAGER_OK)
382 return (KERN_FAILURE); /* AKA SIGSEGV */
383
384 /* Ensure that the driver is obeying the interface. */
385 MPASS(pager_first <= pager_last);
386 MPASS(fs->first_pindex <= pager_last);
387 MPASS(fs->first_pindex >= pager_first);
388 MPASS(pager_last < fs->first_object->size);
389
390 vm_fault_restore_map_lock(fs);
391 if (fs->map->timestamp != fs->map_generation) {
392 vm_fault_populate_cleanup(fs->first_object, pager_first,
393 pager_last);
394 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */
395 }
396
397 /*
398 * The map is unchanged after our last unlock. Process the fault.
399 *
400 * The range [pager_first, pager_last] that is given to the
401 * pager is only a hint. The pager may populate any range
402 * within the object that includes the requested page index.
403 * In case the pager expanded the range, clip it to fit into
404 * the map entry.
405 */
406 map_first = OFF_TO_IDX(fs->entry->offset);
407 if (map_first > pager_first) {
408 vm_fault_populate_cleanup(fs->first_object, pager_first,
409 map_first - 1);
410 pager_first = map_first;
411 }
412 map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1;
413 if (map_last < pager_last) {
414 vm_fault_populate_cleanup(fs->first_object, map_last + 1,
415 pager_last);
416 pager_last = map_last;
417 }
418 for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx);
419 pidx <= pager_last; pidx++, m = vm_page_next(m)) {
420 vm_fault_populate_check_page(m);
421 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags,
422 true);
423 VM_OBJECT_WUNLOCK(fs->first_object);
424 pmap_enter(fs->map->pmap, fs->entry->start + IDX_TO_OFF(pidx) -
425 fs->entry->offset, m, prot, fault_type | (wired ?
426 PMAP_ENTER_WIRED : 0), 0);
427 VM_OBJECT_WLOCK(fs->first_object);
428 if (pidx == fs->first_pindex)
429 vm_fault_fill_hold(m_hold, m);
430 vm_page_lock(m);
431 if ((fault_flags & VM_FAULT_WIRE) != 0) {
432 KASSERT(wired, ("VM_FAULT_WIRE && !wired"));
433 vm_page_wire(m);
434 } else {
435 vm_page_activate(m);
436 }
437 vm_page_unlock(m);
438 vm_page_xunbusy(m);
439 }
440 curthread->td_ru.ru_majflt++;
441 return (KERN_SUCCESS);
442 }
443
444 /*
445 * vm_fault:
446 *
447 * Handle a page fault occurring at the given address,
448 * requiring the given permissions, in the map specified.
449 * If successful, the page is inserted into the
450 * associated physical map.
451 *
452 * NOTE: the given address should be truncated to the
453 * proper page address.
454 *
455 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
456 * a standard error specifying why the fault is fatal is returned.
457 *
458 * The map in question must be referenced, and remains so.
459 * Caller may hold no locks.
460 */
461 int
462 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
463 int fault_flags)
464 {
465 struct thread *td;
466 int result;
467
468 td = curthread;
469 if ((td->td_pflags & TDP_NOFAULTING) != 0)
470 return (KERN_PROTECTION_FAILURE);
471 #ifdef KTRACE
472 if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
473 ktrfault(vaddr, fault_type);
474 #endif
475 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
476 NULL);
477 #ifdef KTRACE
478 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
479 ktrfaultend(result);
480 #endif
481 return (result);
482 }
483
484 int
485 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
486 int fault_flags, vm_page_t *m_hold)
487 {
488 struct faultstate fs;
489 struct vnode *vp;
490 vm_object_t next_object, retry_object;
491 vm_offset_t e_end, e_start;
492 vm_pindex_t retry_pindex;
493 vm_prot_t prot, retry_prot;
494 int ahead, alloc_req, behind, cluster_offset, error, era, faultcount;
495 int locked, nera, result, rv;
496 u_char behavior;
497 boolean_t wired; /* Passed by reference. */
498 bool dead, hardfault, is_first_object_locked;
499
500 PCPU_INC(cnt.v_vm_faults);
501 fs.vp = NULL;
502 faultcount = 0;
503 nera = -1;
504 hardfault = false;
505
506 RetryFault:;
507
508 /*
509 * Find the backing store object and offset into it to begin the
510 * search.
511 */
512 fs.map = map;
513 result = vm_map_lookup(&fs.map, vaddr, fault_type |
514 VM_PROT_FAULT_LOOKUP, &fs.entry, &fs.first_object,
515 &fs.first_pindex, &prot, &wired);
516 if (result != KERN_SUCCESS) {
517 unlock_vp(&fs);
518 return (result);
519 }
520
521 fs.map_generation = fs.map->timestamp;
522
523 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
524 panic("vm_fault: fault on nofault entry, addr: %lx",
525 (u_long)vaddr);
526 }
527
528 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
529 fs.entry->wiring_thread != curthread) {
530 vm_map_unlock_read(fs.map);
531 vm_map_lock(fs.map);
532 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
533 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
534 unlock_vp(&fs);
535 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
536 vm_map_unlock_and_wait(fs.map, 0);
537 } else
538 vm_map_unlock(fs.map);
539 goto RetryFault;
540 }
541
542 MPASS((fs.entry->eflags & MAP_ENTRY_GUARD) == 0);
543
544 if (wired)
545 fault_type = prot | (fault_type & VM_PROT_COPY);
546 else
547 KASSERT((fault_flags & VM_FAULT_WIRE) == 0,
548 ("!wired && VM_FAULT_WIRE"));
549
550 /*
551 * Try to avoid lock contention on the top-level object through
552 * special-case handling of some types of page faults, specifically,
553 * those that are both (1) mapping an existing page from the top-
554 * level object and (2) not having to mark that object as containing
555 * dirty pages. Under these conditions, a read lock on the top-level
556 * object suffices, allowing multiple page faults of a similar type to
557 * run in parallel on the same top-level object.
558 */
559 if (fs.vp == NULL /* avoid locked vnode leak */ &&
560 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 &&
561 /* avoid calling vm_object_set_writeable_dirty() */
562 ((prot & VM_PROT_WRITE) == 0 ||
563 (fs.first_object->type != OBJT_VNODE &&
564 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
565 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
566 VM_OBJECT_RLOCK(fs.first_object);
567 if ((prot & VM_PROT_WRITE) == 0 ||
568 (fs.first_object->type != OBJT_VNODE &&
569 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
570 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0) {
571 rv = vm_fault_soft_fast(&fs, vaddr, prot, fault_type,
572 fault_flags, wired, m_hold);
573 if (rv == KERN_SUCCESS)
574 return (rv);
575 }
576 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
577 VM_OBJECT_RUNLOCK(fs.first_object);
578 VM_OBJECT_WLOCK(fs.first_object);
579 }
580 } else {
581 VM_OBJECT_WLOCK(fs.first_object);
582 }
583
584 /*
585 * Make a reference to this object to prevent its disposal while we
586 * are messing with it. Once we have the reference, the map is free
587 * to be diddled. Since objects reference their shadows (and copies),
588 * they will stay around as well.
589 *
590 * Bump the paging-in-progress count to prevent size changes (e.g.
591 * truncation operations) during I/O.
592 */
593 vm_object_reference_locked(fs.first_object);
594 vm_object_pip_add(fs.first_object, 1);
595
596 fs.lookup_still_valid = true;
597
598 fs.first_m = NULL;
599
600 /*
601 * Search for the page at object/offset.
602 */
603 fs.object = fs.first_object;
604 fs.pindex = fs.first_pindex;
605 while (TRUE) {
606 /*
607 * If the object is marked for imminent termination,
608 * we retry here, since the collapse pass has raced
609 * with us. Otherwise, if we see terminally dead
610 * object, return fail.
611 */
612 if ((fs.object->flags & OBJ_DEAD) != 0) {
613 dead = fs.object->type == OBJT_DEAD;
614 unlock_and_deallocate(&fs);
615 if (dead)
616 return (KERN_PROTECTION_FAILURE);
617 pause("vmf_de", 1);
618 goto RetryFault;
619 }
620
621 /*
622 * See if page is resident
623 */
624 fs.m = vm_page_lookup(fs.object, fs.pindex);
625 if (fs.m != NULL) {
626 /*
627 * Wait/Retry if the page is busy. We have to do this
628 * if the page is either exclusive or shared busy
629 * because the vm_pager may be using read busy for
630 * pageouts (and even pageins if it is the vnode
631 * pager), and we could end up trying to pagein and
632 * pageout the same page simultaneously.
633 *
634 * We can theoretically allow the busy case on a read
635 * fault if the page is marked valid, but since such
636 * pages are typically already pmap'd, putting that
637 * special case in might be more effort then it is
638 * worth. We cannot under any circumstances mess
639 * around with a shared busied page except, perhaps,
640 * to pmap it.
641 */
642 if (vm_page_busied(fs.m)) {
643 /*
644 * Reference the page before unlocking and
645 * sleeping so that the page daemon is less
646 * likely to reclaim it.
647 */
648 vm_page_aflag_set(fs.m, PGA_REFERENCED);
649 if (fs.object != fs.first_object) {
650 if (!VM_OBJECT_TRYWLOCK(
651 fs.first_object)) {
652 VM_OBJECT_WUNLOCK(fs.object);
653 VM_OBJECT_WLOCK(fs.first_object);
654 VM_OBJECT_WLOCK(fs.object);
655 }
656 vm_page_lock(fs.first_m);
657 vm_page_free(fs.first_m);
658 vm_page_unlock(fs.first_m);
659 vm_object_pip_wakeup(fs.first_object);
660 VM_OBJECT_WUNLOCK(fs.first_object);
661 fs.first_m = NULL;
662 }
663 unlock_map(&fs);
664 if (fs.m == vm_page_lookup(fs.object,
665 fs.pindex)) {
666 vm_page_sleep_if_busy(fs.m, "vmpfw");
667 }
668 vm_object_pip_wakeup(fs.object);
669 VM_OBJECT_WUNLOCK(fs.object);
670 PCPU_INC(cnt.v_intrans);
671 vm_object_deallocate(fs.first_object);
672 goto RetryFault;
673 }
674 vm_page_lock(fs.m);
675 vm_page_remque(fs.m);
676 vm_page_unlock(fs.m);
677
678 /*
679 * Mark page busy for other processes, and the
680 * pagedaemon. If it still isn't completely valid
681 * (readable), jump to readrest, else break-out ( we
682 * found the page ).
683 */
684 vm_page_xbusy(fs.m);
685 if (fs.m->valid != VM_PAGE_BITS_ALL)
686 goto readrest;
687 break;
688 }
689 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m));
690
691 /*
692 * Page is not resident. If the pager might contain the page
693 * or this is the beginning of the search, allocate a new
694 * page. (Default objects are zero-fill, so there is no real
695 * pager for them.)
696 */
697 if (fs.object->type != OBJT_DEFAULT ||
698 fs.object == fs.first_object) {
699 if (fs.pindex >= fs.object->size) {
700 unlock_and_deallocate(&fs);
701 return (KERN_PROTECTION_FAILURE);
702 }
703
704 if (fs.object == fs.first_object &&
705 (fs.first_object->flags & OBJ_POPULATE) != 0 &&
706 fs.first_object->shadow_count == 0) {
707 rv = vm_fault_populate(&fs, vaddr, prot,
708 fault_type, fault_flags, wired, m_hold);
709 switch (rv) {
710 case KERN_SUCCESS:
711 case KERN_FAILURE:
712 unlock_and_deallocate(&fs);
713 return (rv);
714 case KERN_RESOURCE_SHORTAGE:
715 unlock_and_deallocate(&fs);
716 goto RetryFault;
717 case KERN_NOT_RECEIVER:
718 /*
719 * Pager's populate() method
720 * returned VM_PAGER_BAD.
721 */
722 break;
723 default:
724 panic("inconsistent return codes");
725 }
726 }
727
728 /*
729 * Allocate a new page for this object/offset pair.
730 *
731 * Unlocked read of the p_flag is harmless. At
732 * worst, the P_KILLED might be not observed
733 * there, and allocation can fail, causing
734 * restart and new reading of the p_flag.
735 */
736 if (!vm_page_count_severe() || P_KILLED(curproc)) {
737 #if VM_NRESERVLEVEL > 0
738 vm_object_color(fs.object, atop(vaddr) -
739 fs.pindex);
740 #endif
741 alloc_req = P_KILLED(curproc) ?
742 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
743 if (fs.object->type != OBJT_VNODE &&
744 fs.object->backing_object == NULL)
745 alloc_req |= VM_ALLOC_ZERO;
746 fs.m = vm_page_alloc(fs.object, fs.pindex,
747 alloc_req);
748 }
749 if (fs.m == NULL) {
750 unlock_and_deallocate(&fs);
751 VM_WAITPFAULT;
752 goto RetryFault;
753 }
754 }
755
756 readrest:
757 /*
758 * At this point, we have either allocated a new page or found
759 * an existing page that is only partially valid.
760 *
761 * We hold a reference on the current object and the page is
762 * exclusive busied.
763 */
764
765 /*
766 * If the pager for the current object might have the page,
767 * then determine the number of additional pages to read and
768 * potentially reprioritize previously read pages for earlier
769 * reclamation. These operations should only be performed
770 * once per page fault. Even if the current pager doesn't
771 * have the page, the number of additional pages to read will
772 * apply to subsequent objects in the shadow chain.
773 */
774 if (fs.object->type != OBJT_DEFAULT && nera == -1 &&
775 !P_KILLED(curproc)) {
776 KASSERT(fs.lookup_still_valid, ("map unlocked"));
777 era = fs.entry->read_ahead;
778 behavior = vm_map_entry_behavior(fs.entry);
779 if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
780 nera = 0;
781 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
782 nera = VM_FAULT_READ_AHEAD_MAX;
783 if (vaddr == fs.entry->next_read)
784 vm_fault_dontneed(&fs, vaddr, nera);
785 } else if (vaddr == fs.entry->next_read) {
786 /*
787 * This is a sequential fault. Arithmetically
788 * increase the requested number of pages in
789 * the read-ahead window. The requested
790 * number of pages is "# of sequential faults
791 * x (read ahead min + 1) + read ahead min"
792 */
793 nera = VM_FAULT_READ_AHEAD_MIN;
794 if (era > 0) {
795 nera += era + 1;
796 if (nera > VM_FAULT_READ_AHEAD_MAX)
797 nera = VM_FAULT_READ_AHEAD_MAX;
798 }
799 if (era == VM_FAULT_READ_AHEAD_MAX)
800 vm_fault_dontneed(&fs, vaddr, nera);
801 } else {
802 /*
803 * This is a non-sequential fault.
804 */
805 nera = 0;
806 }
807 if (era != nera) {
808 /*
809 * A read lock on the map suffices to update
810 * the read ahead count safely.
811 */
812 fs.entry->read_ahead = nera;
813 }
814
815 /*
816 * Prepare for unlocking the map. Save the map
817 * entry's start and end addresses, which are used to
818 * optimize the size of the pager operation below.
819 * Even if the map entry's addresses change after
820 * unlocking the map, using the saved addresses is
821 * safe.
822 */
823 e_start = fs.entry->start;
824 e_end = fs.entry->end;
825 }
826
827 /*
828 * Call the pager to retrieve the page if there is a chance
829 * that the pager has it, and potentially retrieve additional
830 * pages at the same time.
831 */
832 if (fs.object->type != OBJT_DEFAULT) {
833 /*
834 * Release the map lock before locking the vnode or
835 * sleeping in the pager. (If the current object has
836 * a shadow, then an earlier iteration of this loop
837 * may have already unlocked the map.)
838 */
839 unlock_map(&fs);
840
841 if (fs.object->type == OBJT_VNODE &&
842 (vp = fs.object->handle) != fs.vp) {
843 /*
844 * Perform an unlock in case the desired vnode
845 * changed while the map was unlocked during a
846 * retry.
847 */
848 unlock_vp(&fs);
849
850 locked = VOP_ISLOCKED(vp);
851 if (locked != LK_EXCLUSIVE)
852 locked = LK_SHARED;
853
854 /*
855 * We must not sleep acquiring the vnode lock
856 * while we have the page exclusive busied or
857 * the object's paging-in-progress count
858 * incremented. Otherwise, we could deadlock.
859 */
860 error = vget(vp, locked | LK_CANRECURSE |
861 LK_NOWAIT, curthread);
862 if (error != 0) {
863 vhold(vp);
864 release_page(&fs);
865 unlock_and_deallocate(&fs);
866 error = vget(vp, locked | LK_RETRY |
867 LK_CANRECURSE, curthread);
868 vdrop(vp);
869 fs.vp = vp;
870 KASSERT(error == 0,
871 ("vm_fault: vget failed"));
872 goto RetryFault;
873 }
874 fs.vp = vp;
875 }
876 KASSERT(fs.vp == NULL || !fs.map->system_map,
877 ("vm_fault: vnode-backed object mapped by system map"));
878
879 /*
880 * Page in the requested page and hint the pager,
881 * that it may bring up surrounding pages.
882 */
883 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM ||
884 P_KILLED(curproc)) {
885 behind = 0;
886 ahead = 0;
887 } else {
888 /* Is this a sequential fault? */
889 if (nera > 0) {
890 behind = 0;
891 ahead = nera;
892 } else {
893 /*
894 * Request a cluster of pages that is
895 * aligned to a VM_FAULT_READ_DEFAULT
896 * page offset boundary within the
897 * object. Alignment to a page offset
898 * boundary is more likely to coincide
899 * with the underlying file system
900 * block than alignment to a virtual
901 * address boundary.
902 */
903 cluster_offset = fs.pindex %
904 VM_FAULT_READ_DEFAULT;
905 behind = ulmin(cluster_offset,
906 atop(vaddr - e_start));
907 ahead = VM_FAULT_READ_DEFAULT - 1 -
908 cluster_offset;
909 }
910 ahead = ulmin(ahead, atop(e_end - vaddr) - 1);
911 }
912 rv = vm_pager_get_pages(fs.object, &fs.m, 1,
913 &behind, &ahead);
914 if (rv == VM_PAGER_OK) {
915 faultcount = behind + 1 + ahead;
916 hardfault = true;
917 break; /* break to PAGE HAS BEEN FOUND */
918 }
919 if (rv == VM_PAGER_ERROR)
920 printf("vm_fault: pager read error, pid %d (%s)\n",
921 curproc->p_pid, curproc->p_comm);
922
923 /*
924 * If an I/O error occurred or the requested page was
925 * outside the range of the pager, clean up and return
926 * an error.
927 */
928 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) {
929 vm_page_lock(fs.m);
930 if (fs.m->wire_count == 0)
931 vm_page_free(fs.m);
932 else
933 vm_page_xunbusy_maybelocked(fs.m);
934 vm_page_unlock(fs.m);
935 fs.m = NULL;
936 unlock_and_deallocate(&fs);
937 return (rv == VM_PAGER_ERROR ? KERN_FAILURE :
938 KERN_PROTECTION_FAILURE);
939 }
940
941 /*
942 * The requested page does not exist at this object/
943 * offset. Remove the invalid page from the object,
944 * waking up anyone waiting for it, and continue on to
945 * the next object. However, if this is the top-level
946 * object, we must leave the busy page in place to
947 * prevent another process from rushing past us, and
948 * inserting the page in that object at the same time
949 * that we are.
950 */
951 if (fs.object != fs.first_object) {
952 vm_page_lock(fs.m);
953 if (fs.m->wire_count == 0)
954 vm_page_free(fs.m);
955 else
956 vm_page_xunbusy_maybelocked(fs.m);
957 vm_page_unlock(fs.m);
958 fs.m = NULL;
959 }
960 }
961
962 /*
963 * We get here if the object has default pager (or unwiring)
964 * or the pager doesn't have the page.
965 */
966 if (fs.object == fs.first_object)
967 fs.first_m = fs.m;
968
969 /*
970 * Move on to the next object. Lock the next object before
971 * unlocking the current one.
972 */
973 next_object = fs.object->backing_object;
974 if (next_object == NULL) {
975 /*
976 * If there's no object left, fill the page in the top
977 * object with zeros.
978 */
979 if (fs.object != fs.first_object) {
980 vm_object_pip_wakeup(fs.object);
981 VM_OBJECT_WUNLOCK(fs.object);
982
983 fs.object = fs.first_object;
984 fs.pindex = fs.first_pindex;
985 fs.m = fs.first_m;
986 VM_OBJECT_WLOCK(fs.object);
987 }
988 fs.first_m = NULL;
989
990 /*
991 * Zero the page if necessary and mark it valid.
992 */
993 if ((fs.m->flags & PG_ZERO) == 0) {
994 pmap_zero_page(fs.m);
995 } else {
996 PCPU_INC(cnt.v_ozfod);
997 }
998 PCPU_INC(cnt.v_zfod);
999 fs.m->valid = VM_PAGE_BITS_ALL;
1000 /* Don't try to prefault neighboring pages. */
1001 faultcount = 1;
1002 break; /* break to PAGE HAS BEEN FOUND */
1003 } else {
1004 KASSERT(fs.object != next_object,
1005 ("object loop %p", next_object));
1006 VM_OBJECT_WLOCK(next_object);
1007 vm_object_pip_add(next_object, 1);
1008 if (fs.object != fs.first_object)
1009 vm_object_pip_wakeup(fs.object);
1010 fs.pindex +=
1011 OFF_TO_IDX(fs.object->backing_object_offset);
1012 VM_OBJECT_WUNLOCK(fs.object);
1013 fs.object = next_object;
1014 }
1015 }
1016
1017 vm_page_assert_xbusied(fs.m);
1018
1019 /*
1020 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
1021 * is held.]
1022 */
1023
1024 /*
1025 * If the page is being written, but isn't already owned by the
1026 * top-level object, we have to copy it into a new page owned by the
1027 * top-level object.
1028 */
1029 if (fs.object != fs.first_object) {
1030 /*
1031 * We only really need to copy if we want to write it.
1032 */
1033 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1034 /*
1035 * This allows pages to be virtually copied from a
1036 * backing_object into the first_object, where the
1037 * backing object has no other refs to it, and cannot
1038 * gain any more refs. Instead of a bcopy, we just
1039 * move the page from the backing object to the
1040 * first object. Note that we must mark the page
1041 * dirty in the first object so that it will go out
1042 * to swap when needed.
1043 */
1044 is_first_object_locked = false;
1045 if (
1046 /*
1047 * Only one shadow object
1048 */
1049 (fs.object->shadow_count == 1) &&
1050 /*
1051 * No COW refs, except us
1052 */
1053 (fs.object->ref_count == 1) &&
1054 /*
1055 * No one else can look this object up
1056 */
1057 (fs.object->handle == NULL) &&
1058 /*
1059 * No other ways to look the object up
1060 */
1061 ((fs.object->type == OBJT_DEFAULT) ||
1062 (fs.object->type == OBJT_SWAP)) &&
1063 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
1064 /*
1065 * We don't chase down the shadow chain
1066 */
1067 fs.object == fs.first_object->backing_object) {
1068 vm_page_lock(fs.m);
1069 vm_page_remove(fs.m);
1070 vm_page_unlock(fs.m);
1071 vm_page_lock(fs.first_m);
1072 vm_page_replace_checked(fs.m, fs.first_object,
1073 fs.first_pindex, fs.first_m);
1074 vm_page_free(fs.first_m);
1075 vm_page_unlock(fs.first_m);
1076 vm_page_dirty(fs.m);
1077 #if VM_NRESERVLEVEL > 0
1078 /*
1079 * Rename the reservation.
1080 */
1081 vm_reserv_rename(fs.m, fs.first_object,
1082 fs.object, OFF_TO_IDX(
1083 fs.first_object->backing_object_offset));
1084 #endif
1085 /*
1086 * Removing the page from the backing object
1087 * unbusied it.
1088 */
1089 vm_page_xbusy(fs.m);
1090 fs.first_m = fs.m;
1091 fs.m = NULL;
1092 PCPU_INC(cnt.v_cow_optim);
1093 } else {
1094 /*
1095 * Oh, well, lets copy it.
1096 */
1097 pmap_copy_page(fs.m, fs.first_m);
1098 fs.first_m->valid = VM_PAGE_BITS_ALL;
1099 if (wired && (fault_flags &
1100 VM_FAULT_WIRE) == 0) {
1101 vm_page_lock(fs.first_m);
1102 vm_page_wire(fs.first_m);
1103 vm_page_unlock(fs.first_m);
1104
1105 vm_page_lock(fs.m);
1106 vm_page_unwire(fs.m, PQ_INACTIVE);
1107 vm_page_unlock(fs.m);
1108 }
1109 /*
1110 * We no longer need the old page or object.
1111 */
1112 release_page(&fs);
1113 }
1114 /*
1115 * fs.object != fs.first_object due to above
1116 * conditional
1117 */
1118 vm_object_pip_wakeup(fs.object);
1119 VM_OBJECT_WUNLOCK(fs.object);
1120 /*
1121 * Only use the new page below...
1122 */
1123 fs.object = fs.first_object;
1124 fs.pindex = fs.first_pindex;
1125 fs.m = fs.first_m;
1126 if (!is_first_object_locked)
1127 VM_OBJECT_WLOCK(fs.object);
1128 PCPU_INC(cnt.v_cow_faults);
1129 curthread->td_cow++;
1130 } else {
1131 prot &= ~VM_PROT_WRITE;
1132 }
1133 }
1134
1135 /*
1136 * We must verify that the maps have not changed since our last
1137 * lookup.
1138 */
1139 if (!fs.lookup_still_valid) {
1140 if (!vm_map_trylock_read(fs.map)) {
1141 release_page(&fs);
1142 unlock_and_deallocate(&fs);
1143 goto RetryFault;
1144 }
1145 fs.lookup_still_valid = true;
1146 if (fs.map->timestamp != fs.map_generation) {
1147 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
1148 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
1149
1150 /*
1151 * If we don't need the page any longer, put it on the inactive
1152 * list (the easiest thing to do here). If no one needs it,
1153 * pageout will grab it eventually.
1154 */
1155 if (result != KERN_SUCCESS) {
1156 release_page(&fs);
1157 unlock_and_deallocate(&fs);
1158
1159 /*
1160 * If retry of map lookup would have blocked then
1161 * retry fault from start.
1162 */
1163 if (result == KERN_FAILURE)
1164 goto RetryFault;
1165 return (result);
1166 }
1167 if ((retry_object != fs.first_object) ||
1168 (retry_pindex != fs.first_pindex)) {
1169 release_page(&fs);
1170 unlock_and_deallocate(&fs);
1171 goto RetryFault;
1172 }
1173
1174 /*
1175 * Check whether the protection has changed or the object has
1176 * been copied while we left the map unlocked. Changing from
1177 * read to write permission is OK - we leave the page
1178 * write-protected, and catch the write fault. Changing from
1179 * write to read permission means that we can't mark the page
1180 * write-enabled after all.
1181 */
1182 prot &= retry_prot;
1183 }
1184 }
1185
1186 /*
1187 * If the page was filled by a pager, save the virtual address that
1188 * should be faulted on next under a sequential access pattern to the
1189 * map entry. A read lock on the map suffices to update this address
1190 * safely.
1191 */
1192 if (hardfault)
1193 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE;
1194
1195 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true);
1196 vm_page_assert_xbusied(fs.m);
1197
1198 /*
1199 * Page must be completely valid or it is not fit to
1200 * map into user space. vm_pager_get_pages() ensures this.
1201 */
1202 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
1203 ("vm_fault: page %p partially invalid", fs.m));
1204 VM_OBJECT_WUNLOCK(fs.object);
1205
1206 /*
1207 * Put this page into the physical map. We had to do the unlock above
1208 * because pmap_enter() may sleep. We don't put the page
1209 * back on the active queue until later so that the pageout daemon
1210 * won't find it (yet).
1211 */
1212 pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
1213 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
1214 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 &&
1215 wired == 0)
1216 vm_fault_prefault(&fs, vaddr,
1217 faultcount > 0 ? behind : PFBAK,
1218 faultcount > 0 ? ahead : PFFOR);
1219 VM_OBJECT_WLOCK(fs.object);
1220 vm_page_lock(fs.m);
1221
1222 /*
1223 * If the page is not wired down, then put it where the pageout daemon
1224 * can find it.
1225 */
1226 if ((fault_flags & VM_FAULT_WIRE) != 0) {
1227 KASSERT(wired, ("VM_FAULT_WIRE && !wired"));
1228 vm_page_wire(fs.m);
1229 } else
1230 vm_page_activate(fs.m);
1231 if (m_hold != NULL) {
1232 *m_hold = fs.m;
1233 vm_page_hold(fs.m);
1234 }
1235 vm_page_unlock(fs.m);
1236 vm_page_xunbusy(fs.m);
1237
1238 /*
1239 * Unlock everything, and return
1240 */
1241 unlock_and_deallocate(&fs);
1242 if (hardfault) {
1243 PCPU_INC(cnt.v_io_faults);
1244 curthread->td_ru.ru_majflt++;
1245 #ifdef RACCT
1246 if (racct_enable && fs.object->type == OBJT_VNODE) {
1247 PROC_LOCK(curproc);
1248 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1249 racct_add_force(curproc, RACCT_WRITEBPS,
1250 PAGE_SIZE + behind * PAGE_SIZE);
1251 racct_add_force(curproc, RACCT_WRITEIOPS, 1);
1252 } else {
1253 racct_add_force(curproc, RACCT_READBPS,
1254 PAGE_SIZE + ahead * PAGE_SIZE);
1255 racct_add_force(curproc, RACCT_READIOPS, 1);
1256 }
1257 PROC_UNLOCK(curproc);
1258 }
1259 #endif
1260 } else
1261 curthread->td_ru.ru_minflt++;
1262
1263 return (KERN_SUCCESS);
1264 }
1265
1266 /*
1267 * Speed up the reclamation of pages that precede the faulting pindex within
1268 * the first object of the shadow chain. Essentially, perform the equivalent
1269 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes
1270 * the faulting pindex by the cluster size when the pages read by vm_fault()
1271 * cross a cluster-size boundary. The cluster size is the greater of the
1272 * smallest superpage size and VM_FAULT_DONTNEED_MIN.
1273 *
1274 * When "fs->first_object" is a shadow object, the pages in the backing object
1275 * that precede the faulting pindex are deactivated by vm_fault(). So, this
1276 * function must only be concerned with pages in the first object.
1277 */
1278 static void
1279 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
1280 {
1281 vm_map_entry_t entry;
1282 vm_object_t first_object, object;
1283 vm_offset_t end, start;
1284 vm_page_t m, m_next;
1285 vm_pindex_t pend, pstart;
1286 vm_size_t size;
1287
1288 object = fs->object;
1289 VM_OBJECT_ASSERT_WLOCKED(object);
1290 first_object = fs->first_object;
1291 if (first_object != object) {
1292 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1293 VM_OBJECT_WUNLOCK(object);
1294 VM_OBJECT_WLOCK(first_object);
1295 VM_OBJECT_WLOCK(object);
1296 }
1297 }
1298 /* Neither fictitious nor unmanaged pages can be reclaimed. */
1299 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1300 size = VM_FAULT_DONTNEED_MIN;
1301 if (MAXPAGESIZES > 1 && size < pagesizes[1])
1302 size = pagesizes[1];
1303 end = rounddown2(vaddr, size);
1304 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) &&
1305 (entry = fs->entry)->start < end) {
1306 if (end - entry->start < size)
1307 start = entry->start;
1308 else
1309 start = end - size;
1310 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED);
1311 pstart = OFF_TO_IDX(entry->offset) + atop(start -
1312 entry->start);
1313 m_next = vm_page_find_least(first_object, pstart);
1314 pend = OFF_TO_IDX(entry->offset) + atop(end -
1315 entry->start);
1316 while ((m = m_next) != NULL && m->pindex < pend) {
1317 m_next = TAILQ_NEXT(m, listq);
1318 if (m->valid != VM_PAGE_BITS_ALL ||
1319 vm_page_busied(m))
1320 continue;
1321
1322 /*
1323 * Don't clear PGA_REFERENCED, since it would
1324 * likely represent a reference by a different
1325 * process.
1326 *
1327 * Typically, at this point, prefetched pages
1328 * are still in the inactive queue. Only
1329 * pages that triggered page faults are in the
1330 * active queue.
1331 */
1332 vm_page_lock(m);
1333 vm_page_deactivate(m);
1334 vm_page_unlock(m);
1335 }
1336 }
1337 }
1338 if (first_object != object)
1339 VM_OBJECT_WUNLOCK(first_object);
1340 }
1341
1342 /*
1343 * vm_fault_prefault provides a quick way of clustering
1344 * pagefaults into a processes address space. It is a "cousin"
1345 * of vm_map_pmap_enter, except it runs at page fault time instead
1346 * of mmap time.
1347 */
1348 static void
1349 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1350 int backward, int forward)
1351 {
1352 pmap_t pmap;
1353 vm_map_entry_t entry;
1354 vm_object_t backing_object, lobject;
1355 vm_offset_t addr, starta;
1356 vm_pindex_t pindex;
1357 vm_page_t m;
1358 int i;
1359
1360 pmap = fs->map->pmap;
1361 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1362 return;
1363
1364 entry = fs->entry;
1365
1366 if (addra < backward * PAGE_SIZE) {
1367 starta = entry->start;
1368 } else {
1369 starta = addra - backward * PAGE_SIZE;
1370 if (starta < entry->start)
1371 starta = entry->start;
1372 }
1373
1374 /*
1375 * Generate the sequence of virtual addresses that are candidates for
1376 * prefaulting in an outward spiral from the faulting virtual address,
1377 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra
1378 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1379 * If the candidate address doesn't have a backing physical page, then
1380 * the loop immediately terminates.
1381 */
1382 for (i = 0; i < 2 * imax(backward, forward); i++) {
1383 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1384 PAGE_SIZE);
1385 if (addr > addra + forward * PAGE_SIZE)
1386 addr = 0;
1387
1388 if (addr < starta || addr >= entry->end)
1389 continue;
1390
1391 if (!pmap_is_prefaultable(pmap, addr))
1392 continue;
1393
1394 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1395 lobject = entry->object.vm_object;
1396 VM_OBJECT_RLOCK(lobject);
1397 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1398 lobject->type == OBJT_DEFAULT &&
1399 (backing_object = lobject->backing_object) != NULL) {
1400 KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1401 0, ("vm_fault_prefault: unaligned object offset"));
1402 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1403 VM_OBJECT_RLOCK(backing_object);
1404 VM_OBJECT_RUNLOCK(lobject);
1405 lobject = backing_object;
1406 }
1407 if (m == NULL) {
1408 VM_OBJECT_RUNLOCK(lobject);
1409 break;
1410 }
1411 if (m->valid == VM_PAGE_BITS_ALL &&
1412 (m->flags & PG_FICTITIOUS) == 0)
1413 pmap_enter_quick(pmap, addr, m, entry->protection);
1414 VM_OBJECT_RUNLOCK(lobject);
1415 }
1416 }
1417
1418 /*
1419 * Hold each of the physical pages that are mapped by the specified range of
1420 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1421 * and allow the specified types of access, "prot". If all of the implied
1422 * pages are successfully held, then the number of held pages is returned
1423 * together with pointers to those pages in the array "ma". However, if any
1424 * of the pages cannot be held, -1 is returned.
1425 */
1426 int
1427 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1428 vm_prot_t prot, vm_page_t *ma, int max_count)
1429 {
1430 vm_offset_t end, va;
1431 vm_page_t *mp;
1432 int count;
1433 boolean_t pmap_failed;
1434
1435 if (len == 0)
1436 return (0);
1437 end = round_page(addr + len);
1438 addr = trunc_page(addr);
1439
1440 /*
1441 * Check for illegal addresses.
1442 */
1443 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1444 return (-1);
1445
1446 if (atop(end - addr) > max_count)
1447 panic("vm_fault_quick_hold_pages: count > max_count");
1448 count = atop(end - addr);
1449
1450 /*
1451 * Most likely, the physical pages are resident in the pmap, so it is
1452 * faster to try pmap_extract_and_hold() first.
1453 */
1454 pmap_failed = FALSE;
1455 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1456 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1457 if (*mp == NULL)
1458 pmap_failed = TRUE;
1459 else if ((prot & VM_PROT_WRITE) != 0 &&
1460 (*mp)->dirty != VM_PAGE_BITS_ALL) {
1461 /*
1462 * Explicitly dirty the physical page. Otherwise, the
1463 * caller's changes may go unnoticed because they are
1464 * performed through an unmanaged mapping or by a DMA
1465 * operation.
1466 *
1467 * The object lock is not held here.
1468 * See vm_page_clear_dirty_mask().
1469 */
1470 vm_page_dirty(*mp);
1471 }
1472 }
1473 if (pmap_failed) {
1474 /*
1475 * One or more pages could not be held by the pmap. Either no
1476 * page was mapped at the specified virtual address or that
1477 * mapping had insufficient permissions. Attempt to fault in
1478 * and hold these pages.
1479 */
1480 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1481 if (*mp == NULL && vm_fault_hold(map, va, prot,
1482 VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1483 goto error;
1484 }
1485 return (count);
1486 error:
1487 for (mp = ma; mp < ma + count; mp++)
1488 if (*mp != NULL) {
1489 vm_page_lock(*mp);
1490 vm_page_unhold(*mp);
1491 vm_page_unlock(*mp);
1492 }
1493 return (-1);
1494 }
1495
1496 /*
1497 * Routine:
1498 * vm_fault_copy_entry
1499 * Function:
1500 * Create new shadow object backing dst_entry with private copy of
1501 * all underlying pages. When src_entry is equal to dst_entry,
1502 * function implements COW for wired-down map entry. Otherwise,
1503 * it forks wired entry into dst_map.
1504 *
1505 * In/out conditions:
1506 * The source and destination maps must be locked for write.
1507 * The source map entry must be wired down (or be a sharing map
1508 * entry corresponding to a main map entry that is wired down).
1509 */
1510 void
1511 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1512 vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1513 vm_ooffset_t *fork_charge)
1514 {
1515 vm_object_t backing_object, dst_object, object, src_object;
1516 vm_pindex_t dst_pindex, pindex, src_pindex;
1517 vm_prot_t access, prot;
1518 vm_offset_t vaddr;
1519 vm_page_t dst_m;
1520 vm_page_t src_m;
1521 boolean_t upgrade;
1522
1523 #ifdef lint
1524 src_map++;
1525 #endif /* lint */
1526
1527 upgrade = src_entry == dst_entry;
1528 access = prot = dst_entry->protection;
1529
1530 src_object = src_entry->object.vm_object;
1531 src_pindex = OFF_TO_IDX(src_entry->offset);
1532
1533 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1534 dst_object = src_object;
1535 vm_object_reference(dst_object);
1536 } else {
1537 /*
1538 * Create the top-level object for the destination entry. (Doesn't
1539 * actually shadow anything - we copy the pages directly.)
1540 */
1541 dst_object = vm_object_allocate(OBJT_DEFAULT,
1542 atop(dst_entry->end - dst_entry->start));
1543 #if VM_NRESERVLEVEL > 0
1544 dst_object->flags |= OBJ_COLORED;
1545 dst_object->pg_color = atop(dst_entry->start);
1546 #endif
1547 }
1548
1549 VM_OBJECT_WLOCK(dst_object);
1550 KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1551 ("vm_fault_copy_entry: vm_object not NULL"));
1552 if (src_object != dst_object) {
1553 dst_entry->object.vm_object = dst_object;
1554 dst_entry->offset = 0;
1555 dst_object->charge = dst_entry->end - dst_entry->start;
1556 }
1557 if (fork_charge != NULL) {
1558 KASSERT(dst_entry->cred == NULL,
1559 ("vm_fault_copy_entry: leaked swp charge"));
1560 dst_object->cred = curthread->td_ucred;
1561 crhold(dst_object->cred);
1562 *fork_charge += dst_object->charge;
1563 } else if (dst_object->cred == NULL) {
1564 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1565 dst_entry));
1566 dst_object->cred = dst_entry->cred;
1567 dst_entry->cred = NULL;
1568 }
1569
1570 /*
1571 * If not an upgrade, then enter the mappings in the pmap as
1572 * read and/or execute accesses. Otherwise, enter them as
1573 * write accesses.
1574 *
1575 * A writeable large page mapping is only created if all of
1576 * the constituent small page mappings are modified. Marking
1577 * PTEs as modified on inception allows promotion to happen
1578 * without taking potentially large number of soft faults.
1579 */
1580 if (!upgrade)
1581 access &= ~VM_PROT_WRITE;
1582
1583 /*
1584 * Loop through all of the virtual pages within the entry's
1585 * range, copying each page from the source object to the
1586 * destination object. Since the source is wired, those pages
1587 * must exist. In contrast, the destination is pageable.
1588 * Since the destination object does share any backing storage
1589 * with the source object, all of its pages must be dirtied,
1590 * regardless of whether they can be written.
1591 */
1592 for (vaddr = dst_entry->start, dst_pindex = 0;
1593 vaddr < dst_entry->end;
1594 vaddr += PAGE_SIZE, dst_pindex++) {
1595 again:
1596 /*
1597 * Find the page in the source object, and copy it in.
1598 * Because the source is wired down, the page will be
1599 * in memory.
1600 */
1601 if (src_object != dst_object)
1602 VM_OBJECT_RLOCK(src_object);
1603 object = src_object;
1604 pindex = src_pindex + dst_pindex;
1605 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1606 (backing_object = object->backing_object) != NULL) {
1607 /*
1608 * Unless the source mapping is read-only or
1609 * it is presently being upgraded from
1610 * read-only, the first object in the shadow
1611 * chain should provide all of the pages. In
1612 * other words, this loop body should never be
1613 * executed when the source mapping is already
1614 * read/write.
1615 */
1616 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1617 upgrade,
1618 ("vm_fault_copy_entry: main object missing page"));
1619
1620 VM_OBJECT_RLOCK(backing_object);
1621 pindex += OFF_TO_IDX(object->backing_object_offset);
1622 if (object != dst_object)
1623 VM_OBJECT_RUNLOCK(object);
1624 object = backing_object;
1625 }
1626 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1627
1628 if (object != dst_object) {
1629 /*
1630 * Allocate a page in the destination object.
1631 */
1632 dst_m = vm_page_alloc(dst_object, (src_object ==
1633 dst_object ? src_pindex : 0) + dst_pindex,
1634 VM_ALLOC_NORMAL);
1635 if (dst_m == NULL) {
1636 VM_OBJECT_WUNLOCK(dst_object);
1637 VM_OBJECT_RUNLOCK(object);
1638 VM_WAIT;
1639 VM_OBJECT_WLOCK(dst_object);
1640 goto again;
1641 }
1642 pmap_copy_page(src_m, dst_m);
1643 VM_OBJECT_RUNLOCK(object);
1644 dst_m->valid = VM_PAGE_BITS_ALL;
1645 dst_m->dirty = VM_PAGE_BITS_ALL;
1646 } else {
1647 dst_m = src_m;
1648 if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1649 goto again;
1650 vm_page_xbusy(dst_m);
1651 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL,
1652 ("invalid dst page %p", dst_m));
1653 }
1654 VM_OBJECT_WUNLOCK(dst_object);
1655
1656 /*
1657 * Enter it in the pmap. If a wired, copy-on-write
1658 * mapping is being replaced by a write-enabled
1659 * mapping, then wire that new mapping.
1660 */
1661 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1662 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1663
1664 /*
1665 * Mark it no longer busy, and put it on the active list.
1666 */
1667 VM_OBJECT_WLOCK(dst_object);
1668
1669 if (upgrade) {
1670 if (src_m != dst_m) {
1671 vm_page_lock(src_m);
1672 vm_page_unwire(src_m, PQ_INACTIVE);
1673 vm_page_unlock(src_m);
1674 vm_page_lock(dst_m);
1675 vm_page_wire(dst_m);
1676 vm_page_unlock(dst_m);
1677 } else {
1678 KASSERT(dst_m->wire_count > 0,
1679 ("dst_m %p is not wired", dst_m));
1680 }
1681 } else {
1682 vm_page_lock(dst_m);
1683 vm_page_activate(dst_m);
1684 vm_page_unlock(dst_m);
1685 }
1686 vm_page_xunbusy(dst_m);
1687 }
1688 VM_OBJECT_WUNLOCK(dst_object);
1689 if (upgrade) {
1690 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1691 vm_object_deallocate(src_object);
1692 }
1693 }
1694
1695 /*
1696 * Block entry into the machine-independent layer's page fault handler by
1697 * the calling thread. Subsequent calls to vm_fault() by that thread will
1698 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of
1699 * spurious page faults.
1700 */
1701 int
1702 vm_fault_disable_pagefaults(void)
1703 {
1704
1705 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1706 }
1707
1708 void
1709 vm_fault_enable_pagefaults(int save)
1710 {
1711
1712 curthread_pflags_restore(save);
1713 }
Cache object: bfa64dd0c5a35b6ab2fa62c269d67246
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