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/11.2/sys/vm/vm_fault.c 333360 2018-05-08 10:18:24Z 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, bool obj_locked);
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, since the page is now dirty, we can possibly tell
240 * the pager to release any swap backing the page. Calling
241 * the pager requires a write lock on the object.
242 */
243 if (need_dirty)
244 vm_page_dirty(m);
245 if (!set_wd)
246 vm_page_unlock(m);
247 else if (need_dirty)
248 vm_pager_page_unswapped(m);
249 }
250
251 static void
252 vm_fault_fill_hold(vm_page_t *m_hold, vm_page_t m)
253 {
254
255 if (m_hold != NULL) {
256 *m_hold = m;
257 vm_page_lock(m);
258 vm_page_hold(m);
259 vm_page_unlock(m);
260 }
261 }
262
263 /*
264 * Unlocks fs.first_object and fs.map on success.
265 */
266 static int
267 vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot,
268 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold)
269 {
270 vm_page_t m, m_map;
271 #if defined(__amd64__) && VM_NRESERVLEVEL > 0
272 vm_page_t m_super;
273 int flags;
274 #endif
275 int psind, rv;
276
277 MPASS(fs->vp == NULL);
278 m = vm_page_lookup(fs->first_object, fs->first_pindex);
279 /* A busy page can be mapped for read|execute access. */
280 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
281 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
282 return (KERN_FAILURE);
283 m_map = m;
284 psind = 0;
285 #if defined(__amd64__) && VM_NRESERVLEVEL > 0
286 if ((m->flags & PG_FICTITIOUS) == 0 &&
287 (m_super = vm_reserv_to_superpage(m)) != NULL &&
288 rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start &&
289 roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end &&
290 (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) &
291 (pagesizes[m_super->psind] - 1)) &&
292 pmap_ps_enabled(fs->map->pmap)) {
293 flags = PS_ALL_VALID;
294 if ((prot & VM_PROT_WRITE) != 0) {
295 /*
296 * Create a superpage mapping allowing write access
297 * only if none of the constituent pages are busy and
298 * all of them are already dirty (except possibly for
299 * the page that was faulted on).
300 */
301 flags |= PS_NONE_BUSY;
302 if ((fs->first_object->flags & OBJ_UNMANAGED) == 0)
303 flags |= PS_ALL_DIRTY;
304 }
305 if (vm_page_ps_test(m_super, flags, m)) {
306 m_map = m_super;
307 psind = m_super->psind;
308 vaddr = rounddown2(vaddr, pagesizes[psind]);
309 /* Preset the modified bit for dirty superpages. */
310 if ((flags & PS_ALL_DIRTY) != 0)
311 fault_type |= VM_PROT_WRITE;
312 }
313 }
314 #endif
315 rv = pmap_enter(fs->map->pmap, vaddr, m_map, prot, fault_type |
316 PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), psind);
317 if (rv != KERN_SUCCESS)
318 return (rv);
319 vm_fault_fill_hold(m_hold, m);
320 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false);
321 if (psind == 0 && !wired)
322 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true);
323 VM_OBJECT_RUNLOCK(fs->first_object);
324 vm_map_lookup_done(fs->map, fs->entry);
325 curthread->td_ru.ru_minflt++;
326 return (KERN_SUCCESS);
327 }
328
329 static void
330 vm_fault_restore_map_lock(struct faultstate *fs)
331 {
332
333 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
334 MPASS(fs->first_object->paging_in_progress > 0);
335
336 if (!vm_map_trylock_read(fs->map)) {
337 VM_OBJECT_WUNLOCK(fs->first_object);
338 vm_map_lock_read(fs->map);
339 VM_OBJECT_WLOCK(fs->first_object);
340 }
341 fs->lookup_still_valid = true;
342 }
343
344 static void
345 vm_fault_populate_check_page(vm_page_t m)
346 {
347
348 /*
349 * Check each page to ensure that the pager is obeying the
350 * interface: the page must be installed in the object, fully
351 * valid, and exclusively busied.
352 */
353 MPASS(m != NULL);
354 MPASS(m->valid == VM_PAGE_BITS_ALL);
355 MPASS(vm_page_xbusied(m));
356 }
357
358 static void
359 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first,
360 vm_pindex_t last)
361 {
362 vm_page_t m;
363 vm_pindex_t pidx;
364
365 VM_OBJECT_ASSERT_WLOCKED(object);
366 MPASS(first <= last);
367 for (pidx = first, m = vm_page_lookup(object, pidx);
368 pidx <= last; pidx++, m = vm_page_next(m)) {
369 vm_fault_populate_check_page(m);
370 vm_page_lock(m);
371 vm_page_deactivate(m);
372 vm_page_unlock(m);
373 vm_page_xunbusy(m);
374 }
375 }
376
377 static int
378 vm_fault_populate(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot,
379 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold)
380 {
381 vm_page_t m;
382 vm_pindex_t map_first, map_last, pager_first, pager_last, pidx;
383 int rv;
384
385 MPASS(fs->object == fs->first_object);
386 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
387 MPASS(fs->first_object->paging_in_progress > 0);
388 MPASS(fs->first_object->backing_object == NULL);
389 MPASS(fs->lookup_still_valid);
390
391 pager_first = OFF_TO_IDX(fs->entry->offset);
392 pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1;
393 unlock_map(fs);
394 unlock_vp(fs);
395
396 /*
397 * Call the pager (driver) populate() method.
398 *
399 * There is no guarantee that the method will be called again
400 * if the current fault is for read, and a future fault is
401 * for write. Report the entry's maximum allowed protection
402 * to the driver.
403 */
404 rv = vm_pager_populate(fs->first_object, fs->first_pindex,
405 fault_type, fs->entry->max_protection, &pager_first, &pager_last);
406
407 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
408 if (rv == VM_PAGER_BAD) {
409 /*
410 * VM_PAGER_BAD is the backdoor for a pager to request
411 * normal fault handling.
412 */
413 vm_fault_restore_map_lock(fs);
414 if (fs->map->timestamp != fs->map_generation)
415 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */
416 return (KERN_NOT_RECEIVER);
417 }
418 if (rv != VM_PAGER_OK)
419 return (KERN_FAILURE); /* AKA SIGSEGV */
420
421 /* Ensure that the driver is obeying the interface. */
422 MPASS(pager_first <= pager_last);
423 MPASS(fs->first_pindex <= pager_last);
424 MPASS(fs->first_pindex >= pager_first);
425 MPASS(pager_last < fs->first_object->size);
426
427 vm_fault_restore_map_lock(fs);
428 if (fs->map->timestamp != fs->map_generation) {
429 vm_fault_populate_cleanup(fs->first_object, pager_first,
430 pager_last);
431 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */
432 }
433
434 /*
435 * The map is unchanged after our last unlock. Process the fault.
436 *
437 * The range [pager_first, pager_last] that is given to the
438 * pager is only a hint. The pager may populate any range
439 * within the object that includes the requested page index.
440 * In case the pager expanded the range, clip it to fit into
441 * the map entry.
442 */
443 map_first = OFF_TO_IDX(fs->entry->offset);
444 if (map_first > pager_first) {
445 vm_fault_populate_cleanup(fs->first_object, pager_first,
446 map_first - 1);
447 pager_first = map_first;
448 }
449 map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1;
450 if (map_last < pager_last) {
451 vm_fault_populate_cleanup(fs->first_object, map_last + 1,
452 pager_last);
453 pager_last = map_last;
454 }
455 for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx);
456 pidx <= pager_last; pidx++, m = vm_page_next(m)) {
457 vm_fault_populate_check_page(m);
458 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags,
459 true);
460 VM_OBJECT_WUNLOCK(fs->first_object);
461 pmap_enter(fs->map->pmap, fs->entry->start + IDX_TO_OFF(pidx) -
462 fs->entry->offset, m, prot, fault_type | (wired ?
463 PMAP_ENTER_WIRED : 0), 0);
464 VM_OBJECT_WLOCK(fs->first_object);
465 if (pidx == fs->first_pindex)
466 vm_fault_fill_hold(m_hold, m);
467 vm_page_lock(m);
468 if ((fault_flags & VM_FAULT_WIRE) != 0) {
469 KASSERT(wired, ("VM_FAULT_WIRE && !wired"));
470 vm_page_wire(m);
471 } else {
472 vm_page_activate(m);
473 }
474 vm_page_unlock(m);
475 vm_page_xunbusy(m);
476 }
477 curthread->td_ru.ru_majflt++;
478 return (KERN_SUCCESS);
479 }
480
481 /*
482 * vm_fault:
483 *
484 * Handle a page fault occurring at the given address,
485 * requiring the given permissions, in the map specified.
486 * If successful, the page is inserted into the
487 * associated physical map.
488 *
489 * NOTE: the given address should be truncated to the
490 * proper page address.
491 *
492 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
493 * a standard error specifying why the fault is fatal is returned.
494 *
495 * The map in question must be referenced, and remains so.
496 * Caller may hold no locks.
497 */
498 int
499 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
500 int fault_flags)
501 {
502 struct thread *td;
503 int result;
504
505 td = curthread;
506 if ((td->td_pflags & TDP_NOFAULTING) != 0)
507 return (KERN_PROTECTION_FAILURE);
508 #ifdef KTRACE
509 if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
510 ktrfault(vaddr, fault_type);
511 #endif
512 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
513 NULL);
514 #ifdef KTRACE
515 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
516 ktrfaultend(result);
517 #endif
518 return (result);
519 }
520
521 int
522 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
523 int fault_flags, vm_page_t *m_hold)
524 {
525 struct faultstate fs;
526 struct vnode *vp;
527 vm_object_t next_object, retry_object;
528 vm_offset_t e_end, e_start;
529 vm_pindex_t retry_pindex;
530 vm_prot_t prot, retry_prot;
531 int ahead, alloc_req, behind, cluster_offset, error, era, faultcount;
532 int locked, nera, result, rv;
533 u_char behavior;
534 boolean_t wired; /* Passed by reference. */
535 bool dead, hardfault, is_first_object_locked;
536
537 PCPU_INC(cnt.v_vm_faults);
538 fs.vp = NULL;
539 faultcount = 0;
540 nera = -1;
541 hardfault = false;
542
543 RetryFault:;
544
545 /*
546 * Find the backing store object and offset into it to begin the
547 * search.
548 */
549 fs.map = map;
550 result = vm_map_lookup(&fs.map, vaddr, fault_type |
551 VM_PROT_FAULT_LOOKUP, &fs.entry, &fs.first_object,
552 &fs.first_pindex, &prot, &wired);
553 if (result != KERN_SUCCESS) {
554 unlock_vp(&fs);
555 return (result);
556 }
557
558 fs.map_generation = fs.map->timestamp;
559
560 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
561 panic("vm_fault: fault on nofault entry, addr: %lx",
562 (u_long)vaddr);
563 }
564
565 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
566 fs.entry->wiring_thread != curthread) {
567 vm_map_unlock_read(fs.map);
568 vm_map_lock(fs.map);
569 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
570 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
571 unlock_vp(&fs);
572 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
573 vm_map_unlock_and_wait(fs.map, 0);
574 } else
575 vm_map_unlock(fs.map);
576 goto RetryFault;
577 }
578
579 MPASS((fs.entry->eflags & MAP_ENTRY_GUARD) == 0);
580
581 if (wired)
582 fault_type = prot | (fault_type & VM_PROT_COPY);
583 else
584 KASSERT((fault_flags & VM_FAULT_WIRE) == 0,
585 ("!wired && VM_FAULT_WIRE"));
586
587 /*
588 * Try to avoid lock contention on the top-level object through
589 * special-case handling of some types of page faults, specifically,
590 * those that are both (1) mapping an existing page from the top-
591 * level object and (2) not having to mark that object as containing
592 * dirty pages. Under these conditions, a read lock on the top-level
593 * object suffices, allowing multiple page faults of a similar type to
594 * run in parallel on the same top-level object.
595 */
596 if (fs.vp == NULL /* avoid locked vnode leak */ &&
597 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 &&
598 /* avoid calling vm_object_set_writeable_dirty() */
599 ((prot & VM_PROT_WRITE) == 0 ||
600 (fs.first_object->type != OBJT_VNODE &&
601 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
602 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
603 VM_OBJECT_RLOCK(fs.first_object);
604 if ((prot & VM_PROT_WRITE) == 0 ||
605 (fs.first_object->type != OBJT_VNODE &&
606 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
607 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0) {
608 rv = vm_fault_soft_fast(&fs, vaddr, prot, fault_type,
609 fault_flags, wired, m_hold);
610 if (rv == KERN_SUCCESS)
611 return (rv);
612 }
613 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
614 VM_OBJECT_RUNLOCK(fs.first_object);
615 VM_OBJECT_WLOCK(fs.first_object);
616 }
617 } else {
618 VM_OBJECT_WLOCK(fs.first_object);
619 }
620
621 /*
622 * Make a reference to this object to prevent its disposal while we
623 * are messing with it. Once we have the reference, the map is free
624 * to be diddled. Since objects reference their shadows (and copies),
625 * they will stay around as well.
626 *
627 * Bump the paging-in-progress count to prevent size changes (e.g.
628 * truncation operations) during I/O.
629 */
630 vm_object_reference_locked(fs.first_object);
631 vm_object_pip_add(fs.first_object, 1);
632
633 fs.lookup_still_valid = true;
634
635 fs.first_m = NULL;
636
637 /*
638 * Search for the page at object/offset.
639 */
640 fs.object = fs.first_object;
641 fs.pindex = fs.first_pindex;
642 while (TRUE) {
643 /*
644 * If the object is marked for imminent termination,
645 * we retry here, since the collapse pass has raced
646 * with us. Otherwise, if we see terminally dead
647 * object, return fail.
648 */
649 if ((fs.object->flags & OBJ_DEAD) != 0) {
650 dead = fs.object->type == OBJT_DEAD;
651 unlock_and_deallocate(&fs);
652 if (dead)
653 return (KERN_PROTECTION_FAILURE);
654 pause("vmf_de", 1);
655 goto RetryFault;
656 }
657
658 /*
659 * See if page is resident
660 */
661 fs.m = vm_page_lookup(fs.object, fs.pindex);
662 if (fs.m != NULL) {
663 /*
664 * Wait/Retry if the page is busy. We have to do this
665 * if the page is either exclusive or shared busy
666 * because the vm_pager may be using read busy for
667 * pageouts (and even pageins if it is the vnode
668 * pager), and we could end up trying to pagein and
669 * pageout the same page simultaneously.
670 *
671 * We can theoretically allow the busy case on a read
672 * fault if the page is marked valid, but since such
673 * pages are typically already pmap'd, putting that
674 * special case in might be more effort then it is
675 * worth. We cannot under any circumstances mess
676 * around with a shared busied page except, perhaps,
677 * to pmap it.
678 */
679 if (vm_page_busied(fs.m)) {
680 /*
681 * Reference the page before unlocking and
682 * sleeping so that the page daemon is less
683 * likely to reclaim it.
684 */
685 vm_page_aflag_set(fs.m, PGA_REFERENCED);
686 if (fs.object != fs.first_object) {
687 if (!VM_OBJECT_TRYWLOCK(
688 fs.first_object)) {
689 VM_OBJECT_WUNLOCK(fs.object);
690 VM_OBJECT_WLOCK(fs.first_object);
691 VM_OBJECT_WLOCK(fs.object);
692 }
693 vm_page_lock(fs.first_m);
694 vm_page_free(fs.first_m);
695 vm_page_unlock(fs.first_m);
696 vm_object_pip_wakeup(fs.first_object);
697 VM_OBJECT_WUNLOCK(fs.first_object);
698 fs.first_m = NULL;
699 }
700 unlock_map(&fs);
701 if (fs.m == vm_page_lookup(fs.object,
702 fs.pindex)) {
703 vm_page_sleep_if_busy(fs.m, "vmpfw");
704 }
705 vm_object_pip_wakeup(fs.object);
706 VM_OBJECT_WUNLOCK(fs.object);
707 PCPU_INC(cnt.v_intrans);
708 vm_object_deallocate(fs.first_object);
709 goto RetryFault;
710 }
711 vm_page_lock(fs.m);
712 vm_page_remque(fs.m);
713 vm_page_unlock(fs.m);
714
715 /*
716 * Mark page busy for other processes, and the
717 * pagedaemon. If it still isn't completely valid
718 * (readable), jump to readrest, else break-out ( we
719 * found the page ).
720 */
721 vm_page_xbusy(fs.m);
722 if (fs.m->valid != VM_PAGE_BITS_ALL)
723 goto readrest;
724 break;
725 }
726 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m));
727
728 /*
729 * Page is not resident. If the pager might contain the page
730 * or this is the beginning of the search, allocate a new
731 * page. (Default objects are zero-fill, so there is no real
732 * pager for them.)
733 */
734 if (fs.object->type != OBJT_DEFAULT ||
735 fs.object == fs.first_object) {
736 if (fs.pindex >= fs.object->size) {
737 unlock_and_deallocate(&fs);
738 return (KERN_PROTECTION_FAILURE);
739 }
740
741 if (fs.object == fs.first_object &&
742 (fs.first_object->flags & OBJ_POPULATE) != 0 &&
743 fs.first_object->shadow_count == 0) {
744 rv = vm_fault_populate(&fs, vaddr, prot,
745 fault_type, fault_flags, wired, m_hold);
746 switch (rv) {
747 case KERN_SUCCESS:
748 case KERN_FAILURE:
749 unlock_and_deallocate(&fs);
750 return (rv);
751 case KERN_RESOURCE_SHORTAGE:
752 unlock_and_deallocate(&fs);
753 goto RetryFault;
754 case KERN_NOT_RECEIVER:
755 /*
756 * Pager's populate() method
757 * returned VM_PAGER_BAD.
758 */
759 break;
760 default:
761 panic("inconsistent return codes");
762 }
763 }
764
765 /*
766 * Allocate a new page for this object/offset pair.
767 *
768 * Unlocked read of the p_flag is harmless. At
769 * worst, the P_KILLED might be not observed
770 * there, and allocation can fail, causing
771 * restart and new reading of the p_flag.
772 */
773 if (!vm_page_count_severe() || P_KILLED(curproc)) {
774 #if VM_NRESERVLEVEL > 0
775 vm_object_color(fs.object, atop(vaddr) -
776 fs.pindex);
777 #endif
778 alloc_req = P_KILLED(curproc) ?
779 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
780 if (fs.object->type != OBJT_VNODE &&
781 fs.object->backing_object == NULL)
782 alloc_req |= VM_ALLOC_ZERO;
783 fs.m = vm_page_alloc(fs.object, fs.pindex,
784 alloc_req);
785 }
786 if (fs.m == NULL) {
787 unlock_and_deallocate(&fs);
788 VM_WAITPFAULT;
789 goto RetryFault;
790 }
791 }
792
793 readrest:
794 /*
795 * At this point, we have either allocated a new page or found
796 * an existing page that is only partially valid.
797 *
798 * We hold a reference on the current object and the page is
799 * exclusive busied.
800 */
801
802 /*
803 * If the pager for the current object might have the page,
804 * then determine the number of additional pages to read and
805 * potentially reprioritize previously read pages for earlier
806 * reclamation. These operations should only be performed
807 * once per page fault. Even if the current pager doesn't
808 * have the page, the number of additional pages to read will
809 * apply to subsequent objects in the shadow chain.
810 */
811 if (fs.object->type != OBJT_DEFAULT && nera == -1 &&
812 !P_KILLED(curproc)) {
813 KASSERT(fs.lookup_still_valid, ("map unlocked"));
814 era = fs.entry->read_ahead;
815 behavior = vm_map_entry_behavior(fs.entry);
816 if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
817 nera = 0;
818 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
819 nera = VM_FAULT_READ_AHEAD_MAX;
820 if (vaddr == fs.entry->next_read)
821 vm_fault_dontneed(&fs, vaddr, nera);
822 } else if (vaddr == fs.entry->next_read) {
823 /*
824 * This is a sequential fault. Arithmetically
825 * increase the requested number of pages in
826 * the read-ahead window. The requested
827 * number of pages is "# of sequential faults
828 * x (read ahead min + 1) + read ahead min"
829 */
830 nera = VM_FAULT_READ_AHEAD_MIN;
831 if (era > 0) {
832 nera += era + 1;
833 if (nera > VM_FAULT_READ_AHEAD_MAX)
834 nera = VM_FAULT_READ_AHEAD_MAX;
835 }
836 if (era == VM_FAULT_READ_AHEAD_MAX)
837 vm_fault_dontneed(&fs, vaddr, nera);
838 } else {
839 /*
840 * This is a non-sequential fault.
841 */
842 nera = 0;
843 }
844 if (era != nera) {
845 /*
846 * A read lock on the map suffices to update
847 * the read ahead count safely.
848 */
849 fs.entry->read_ahead = nera;
850 }
851
852 /*
853 * Prepare for unlocking the map. Save the map
854 * entry's start and end addresses, which are used to
855 * optimize the size of the pager operation below.
856 * Even if the map entry's addresses change after
857 * unlocking the map, using the saved addresses is
858 * safe.
859 */
860 e_start = fs.entry->start;
861 e_end = fs.entry->end;
862 }
863
864 /*
865 * Call the pager to retrieve the page if there is a chance
866 * that the pager has it, and potentially retrieve additional
867 * pages at the same time.
868 */
869 if (fs.object->type != OBJT_DEFAULT) {
870 /*
871 * Release the map lock before locking the vnode or
872 * sleeping in the pager. (If the current object has
873 * a shadow, then an earlier iteration of this loop
874 * may have already unlocked the map.)
875 */
876 unlock_map(&fs);
877
878 if (fs.object->type == OBJT_VNODE &&
879 (vp = fs.object->handle) != fs.vp) {
880 /*
881 * Perform an unlock in case the desired vnode
882 * changed while the map was unlocked during a
883 * retry.
884 */
885 unlock_vp(&fs);
886
887 locked = VOP_ISLOCKED(vp);
888 if (locked != LK_EXCLUSIVE)
889 locked = LK_SHARED;
890
891 /*
892 * We must not sleep acquiring the vnode lock
893 * while we have the page exclusive busied or
894 * the object's paging-in-progress count
895 * incremented. Otherwise, we could deadlock.
896 */
897 error = vget(vp, locked | LK_CANRECURSE |
898 LK_NOWAIT, curthread);
899 if (error != 0) {
900 vhold(vp);
901 release_page(&fs);
902 unlock_and_deallocate(&fs);
903 error = vget(vp, locked | LK_RETRY |
904 LK_CANRECURSE, curthread);
905 vdrop(vp);
906 fs.vp = vp;
907 KASSERT(error == 0,
908 ("vm_fault: vget failed"));
909 goto RetryFault;
910 }
911 fs.vp = vp;
912 }
913 KASSERT(fs.vp == NULL || !fs.map->system_map,
914 ("vm_fault: vnode-backed object mapped by system map"));
915
916 /*
917 * Page in the requested page and hint the pager,
918 * that it may bring up surrounding pages.
919 */
920 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM ||
921 P_KILLED(curproc)) {
922 behind = 0;
923 ahead = 0;
924 } else {
925 /* Is this a sequential fault? */
926 if (nera > 0) {
927 behind = 0;
928 ahead = nera;
929 } else {
930 /*
931 * Request a cluster of pages that is
932 * aligned to a VM_FAULT_READ_DEFAULT
933 * page offset boundary within the
934 * object. Alignment to a page offset
935 * boundary is more likely to coincide
936 * with the underlying file system
937 * block than alignment to a virtual
938 * address boundary.
939 */
940 cluster_offset = fs.pindex %
941 VM_FAULT_READ_DEFAULT;
942 behind = ulmin(cluster_offset,
943 atop(vaddr - e_start));
944 ahead = VM_FAULT_READ_DEFAULT - 1 -
945 cluster_offset;
946 }
947 ahead = ulmin(ahead, atop(e_end - vaddr) - 1);
948 }
949 rv = vm_pager_get_pages(fs.object, &fs.m, 1,
950 &behind, &ahead);
951 if (rv == VM_PAGER_OK) {
952 faultcount = behind + 1 + ahead;
953 hardfault = true;
954 break; /* break to PAGE HAS BEEN FOUND */
955 }
956 if (rv == VM_PAGER_ERROR)
957 printf("vm_fault: pager read error, pid %d (%s)\n",
958 curproc->p_pid, curproc->p_comm);
959
960 /*
961 * If an I/O error occurred or the requested page was
962 * outside the range of the pager, clean up and return
963 * an error.
964 */
965 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) {
966 vm_page_lock(fs.m);
967 if (fs.m->wire_count == 0)
968 vm_page_free(fs.m);
969 else
970 vm_page_xunbusy_maybelocked(fs.m);
971 vm_page_unlock(fs.m);
972 fs.m = NULL;
973 unlock_and_deallocate(&fs);
974 return (rv == VM_PAGER_ERROR ? KERN_FAILURE :
975 KERN_PROTECTION_FAILURE);
976 }
977
978 /*
979 * The requested page does not exist at this object/
980 * offset. Remove the invalid page from the object,
981 * waking up anyone waiting for it, and continue on to
982 * the next object. However, if this is the top-level
983 * object, we must leave the busy page in place to
984 * prevent another process from rushing past us, and
985 * inserting the page in that object at the same time
986 * that we are.
987 */
988 if (fs.object != fs.first_object) {
989 vm_page_lock(fs.m);
990 if (fs.m->wire_count == 0)
991 vm_page_free(fs.m);
992 else
993 vm_page_xunbusy_maybelocked(fs.m);
994 vm_page_unlock(fs.m);
995 fs.m = NULL;
996 }
997 }
998
999 /*
1000 * We get here if the object has default pager (or unwiring)
1001 * or the pager doesn't have the page.
1002 */
1003 if (fs.object == fs.first_object)
1004 fs.first_m = fs.m;
1005
1006 /*
1007 * Move on to the next object. Lock the next object before
1008 * unlocking the current one.
1009 */
1010 next_object = fs.object->backing_object;
1011 if (next_object == NULL) {
1012 /*
1013 * If there's no object left, fill the page in the top
1014 * object with zeros.
1015 */
1016 if (fs.object != fs.first_object) {
1017 vm_object_pip_wakeup(fs.object);
1018 VM_OBJECT_WUNLOCK(fs.object);
1019
1020 fs.object = fs.first_object;
1021 fs.pindex = fs.first_pindex;
1022 fs.m = fs.first_m;
1023 VM_OBJECT_WLOCK(fs.object);
1024 }
1025 fs.first_m = NULL;
1026
1027 /*
1028 * Zero the page if necessary and mark it valid.
1029 */
1030 if ((fs.m->flags & PG_ZERO) == 0) {
1031 pmap_zero_page(fs.m);
1032 } else {
1033 PCPU_INC(cnt.v_ozfod);
1034 }
1035 PCPU_INC(cnt.v_zfod);
1036 fs.m->valid = VM_PAGE_BITS_ALL;
1037 /* Don't try to prefault neighboring pages. */
1038 faultcount = 1;
1039 break; /* break to PAGE HAS BEEN FOUND */
1040 } else {
1041 KASSERT(fs.object != next_object,
1042 ("object loop %p", next_object));
1043 VM_OBJECT_WLOCK(next_object);
1044 vm_object_pip_add(next_object, 1);
1045 if (fs.object != fs.first_object)
1046 vm_object_pip_wakeup(fs.object);
1047 fs.pindex +=
1048 OFF_TO_IDX(fs.object->backing_object_offset);
1049 VM_OBJECT_WUNLOCK(fs.object);
1050 fs.object = next_object;
1051 }
1052 }
1053
1054 vm_page_assert_xbusied(fs.m);
1055
1056 /*
1057 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
1058 * is held.]
1059 */
1060
1061 /*
1062 * If the page is being written, but isn't already owned by the
1063 * top-level object, we have to copy it into a new page owned by the
1064 * top-level object.
1065 */
1066 if (fs.object != fs.first_object) {
1067 /*
1068 * We only really need to copy if we want to write it.
1069 */
1070 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1071 /*
1072 * This allows pages to be virtually copied from a
1073 * backing_object into the first_object, where the
1074 * backing object has no other refs to it, and cannot
1075 * gain any more refs. Instead of a bcopy, we just
1076 * move the page from the backing object to the
1077 * first object. Note that we must mark the page
1078 * dirty in the first object so that it will go out
1079 * to swap when needed.
1080 */
1081 is_first_object_locked = false;
1082 if (
1083 /*
1084 * Only one shadow object
1085 */
1086 (fs.object->shadow_count == 1) &&
1087 /*
1088 * No COW refs, except us
1089 */
1090 (fs.object->ref_count == 1) &&
1091 /*
1092 * No one else can look this object up
1093 */
1094 (fs.object->handle == NULL) &&
1095 /*
1096 * No other ways to look the object up
1097 */
1098 ((fs.object->type == OBJT_DEFAULT) ||
1099 (fs.object->type == OBJT_SWAP)) &&
1100 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
1101 /*
1102 * We don't chase down the shadow chain
1103 */
1104 fs.object == fs.first_object->backing_object) {
1105 vm_page_lock(fs.m);
1106 vm_page_remove(fs.m);
1107 vm_page_unlock(fs.m);
1108 vm_page_lock(fs.first_m);
1109 vm_page_replace_checked(fs.m, fs.first_object,
1110 fs.first_pindex, fs.first_m);
1111 vm_page_free(fs.first_m);
1112 vm_page_unlock(fs.first_m);
1113 vm_page_dirty(fs.m);
1114 #if VM_NRESERVLEVEL > 0
1115 /*
1116 * Rename the reservation.
1117 */
1118 vm_reserv_rename(fs.m, fs.first_object,
1119 fs.object, OFF_TO_IDX(
1120 fs.first_object->backing_object_offset));
1121 #endif
1122 /*
1123 * Removing the page from the backing object
1124 * unbusied it.
1125 */
1126 vm_page_xbusy(fs.m);
1127 fs.first_m = fs.m;
1128 fs.m = NULL;
1129 PCPU_INC(cnt.v_cow_optim);
1130 } else {
1131 /*
1132 * Oh, well, lets copy it.
1133 */
1134 pmap_copy_page(fs.m, fs.first_m);
1135 fs.first_m->valid = VM_PAGE_BITS_ALL;
1136 if ((fault_flags & VM_FAULT_WIRE) == 0) {
1137 prot &= ~VM_PROT_WRITE;
1138 fault_type &= ~VM_PROT_WRITE;
1139 }
1140 if (wired && (fault_flags &
1141 VM_FAULT_WIRE) == 0) {
1142 vm_page_lock(fs.first_m);
1143 vm_page_wire(fs.first_m);
1144 vm_page_unlock(fs.first_m);
1145
1146 vm_page_lock(fs.m);
1147 vm_page_unwire(fs.m, PQ_INACTIVE);
1148 vm_page_unlock(fs.m);
1149 }
1150 /*
1151 * We no longer need the old page or object.
1152 */
1153 release_page(&fs);
1154 }
1155 /*
1156 * fs.object != fs.first_object due to above
1157 * conditional
1158 */
1159 vm_object_pip_wakeup(fs.object);
1160 VM_OBJECT_WUNLOCK(fs.object);
1161 /*
1162 * Only use the new page below...
1163 */
1164 fs.object = fs.first_object;
1165 fs.pindex = fs.first_pindex;
1166 fs.m = fs.first_m;
1167 if (!is_first_object_locked)
1168 VM_OBJECT_WLOCK(fs.object);
1169 PCPU_INC(cnt.v_cow_faults);
1170 curthread->td_cow++;
1171 } else {
1172 prot &= ~VM_PROT_WRITE;
1173 }
1174 }
1175
1176 /*
1177 * We must verify that the maps have not changed since our last
1178 * lookup.
1179 */
1180 if (!fs.lookup_still_valid) {
1181 if (!vm_map_trylock_read(fs.map)) {
1182 release_page(&fs);
1183 unlock_and_deallocate(&fs);
1184 goto RetryFault;
1185 }
1186 fs.lookup_still_valid = true;
1187 if (fs.map->timestamp != fs.map_generation) {
1188 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
1189 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
1190
1191 /*
1192 * If we don't need the page any longer, put it on the inactive
1193 * list (the easiest thing to do here). If no one needs it,
1194 * pageout will grab it eventually.
1195 */
1196 if (result != KERN_SUCCESS) {
1197 release_page(&fs);
1198 unlock_and_deallocate(&fs);
1199
1200 /*
1201 * If retry of map lookup would have blocked then
1202 * retry fault from start.
1203 */
1204 if (result == KERN_FAILURE)
1205 goto RetryFault;
1206 return (result);
1207 }
1208 if ((retry_object != fs.first_object) ||
1209 (retry_pindex != fs.first_pindex)) {
1210 release_page(&fs);
1211 unlock_and_deallocate(&fs);
1212 goto RetryFault;
1213 }
1214
1215 /*
1216 * Check whether the protection has changed or the object has
1217 * been copied while we left the map unlocked. Changing from
1218 * read to write permission is OK - we leave the page
1219 * write-protected, and catch the write fault. Changing from
1220 * write to read permission means that we can't mark the page
1221 * write-enabled after all.
1222 */
1223 prot &= retry_prot;
1224 fault_type &= retry_prot;
1225 if (prot == 0) {
1226 release_page(&fs);
1227 unlock_and_deallocate(&fs);
1228 goto RetryFault;
1229 }
1230 }
1231 }
1232
1233 /*
1234 * If the page was filled by a pager, save the virtual address that
1235 * should be faulted on next under a sequential access pattern to the
1236 * map entry. A read lock on the map suffices to update this address
1237 * safely.
1238 */
1239 if (hardfault)
1240 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE;
1241
1242 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true);
1243 vm_page_assert_xbusied(fs.m);
1244
1245 /*
1246 * Page must be completely valid or it is not fit to
1247 * map into user space. vm_pager_get_pages() ensures this.
1248 */
1249 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
1250 ("vm_fault: page %p partially invalid", fs.m));
1251 VM_OBJECT_WUNLOCK(fs.object);
1252
1253 /*
1254 * Put this page into the physical map. We had to do the unlock above
1255 * because pmap_enter() may sleep. We don't put the page
1256 * back on the active queue until later so that the pageout daemon
1257 * won't find it (yet).
1258 */
1259 pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
1260 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
1261 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 &&
1262 wired == 0)
1263 vm_fault_prefault(&fs, vaddr,
1264 faultcount > 0 ? behind : PFBAK,
1265 faultcount > 0 ? ahead : PFFOR, false);
1266 VM_OBJECT_WLOCK(fs.object);
1267 vm_page_lock(fs.m);
1268
1269 /*
1270 * If the page is not wired down, then put it where the pageout daemon
1271 * can find it.
1272 */
1273 if ((fault_flags & VM_FAULT_WIRE) != 0) {
1274 KASSERT(wired, ("VM_FAULT_WIRE && !wired"));
1275 vm_page_wire(fs.m);
1276 } else
1277 vm_page_activate(fs.m);
1278 if (m_hold != NULL) {
1279 *m_hold = fs.m;
1280 vm_page_hold(fs.m);
1281 }
1282 vm_page_unlock(fs.m);
1283 vm_page_xunbusy(fs.m);
1284
1285 /*
1286 * Unlock everything, and return
1287 */
1288 unlock_and_deallocate(&fs);
1289 if (hardfault) {
1290 PCPU_INC(cnt.v_io_faults);
1291 curthread->td_ru.ru_majflt++;
1292 #ifdef RACCT
1293 if (racct_enable && fs.object->type == OBJT_VNODE) {
1294 PROC_LOCK(curproc);
1295 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1296 racct_add_force(curproc, RACCT_WRITEBPS,
1297 PAGE_SIZE + behind * PAGE_SIZE);
1298 racct_add_force(curproc, RACCT_WRITEIOPS, 1);
1299 } else {
1300 racct_add_force(curproc, RACCT_READBPS,
1301 PAGE_SIZE + ahead * PAGE_SIZE);
1302 racct_add_force(curproc, RACCT_READIOPS, 1);
1303 }
1304 PROC_UNLOCK(curproc);
1305 }
1306 #endif
1307 } else
1308 curthread->td_ru.ru_minflt++;
1309
1310 return (KERN_SUCCESS);
1311 }
1312
1313 /*
1314 * Speed up the reclamation of pages that precede the faulting pindex within
1315 * the first object of the shadow chain. Essentially, perform the equivalent
1316 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes
1317 * the faulting pindex by the cluster size when the pages read by vm_fault()
1318 * cross a cluster-size boundary. The cluster size is the greater of the
1319 * smallest superpage size and VM_FAULT_DONTNEED_MIN.
1320 *
1321 * When "fs->first_object" is a shadow object, the pages in the backing object
1322 * that precede the faulting pindex are deactivated by vm_fault(). So, this
1323 * function must only be concerned with pages in the first object.
1324 */
1325 static void
1326 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
1327 {
1328 vm_map_entry_t entry;
1329 vm_object_t first_object, object;
1330 vm_offset_t end, start;
1331 vm_page_t m, m_next;
1332 vm_pindex_t pend, pstart;
1333 vm_size_t size;
1334
1335 object = fs->object;
1336 VM_OBJECT_ASSERT_WLOCKED(object);
1337 first_object = fs->first_object;
1338 if (first_object != object) {
1339 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1340 VM_OBJECT_WUNLOCK(object);
1341 VM_OBJECT_WLOCK(first_object);
1342 VM_OBJECT_WLOCK(object);
1343 }
1344 }
1345 /* Neither fictitious nor unmanaged pages can be reclaimed. */
1346 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1347 size = VM_FAULT_DONTNEED_MIN;
1348 if (MAXPAGESIZES > 1 && size < pagesizes[1])
1349 size = pagesizes[1];
1350 end = rounddown2(vaddr, size);
1351 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) &&
1352 (entry = fs->entry)->start < end) {
1353 if (end - entry->start < size)
1354 start = entry->start;
1355 else
1356 start = end - size;
1357 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED);
1358 pstart = OFF_TO_IDX(entry->offset) + atop(start -
1359 entry->start);
1360 m_next = vm_page_find_least(first_object, pstart);
1361 pend = OFF_TO_IDX(entry->offset) + atop(end -
1362 entry->start);
1363 while ((m = m_next) != NULL && m->pindex < pend) {
1364 m_next = TAILQ_NEXT(m, listq);
1365 if (m->valid != VM_PAGE_BITS_ALL ||
1366 vm_page_busied(m))
1367 continue;
1368
1369 /*
1370 * Don't clear PGA_REFERENCED, since it would
1371 * likely represent a reference by a different
1372 * process.
1373 *
1374 * Typically, at this point, prefetched pages
1375 * are still in the inactive queue. Only
1376 * pages that triggered page faults are in the
1377 * active queue.
1378 */
1379 vm_page_lock(m);
1380 vm_page_deactivate(m);
1381 vm_page_unlock(m);
1382 }
1383 }
1384 }
1385 if (first_object != object)
1386 VM_OBJECT_WUNLOCK(first_object);
1387 }
1388
1389 /*
1390 * vm_fault_prefault provides a quick way of clustering
1391 * pagefaults into a processes address space. It is a "cousin"
1392 * of vm_map_pmap_enter, except it runs at page fault time instead
1393 * of mmap time.
1394 */
1395 static void
1396 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1397 int backward, int forward, bool obj_locked)
1398 {
1399 pmap_t pmap;
1400 vm_map_entry_t entry;
1401 vm_object_t backing_object, lobject;
1402 vm_offset_t addr, starta;
1403 vm_pindex_t pindex;
1404 vm_page_t m;
1405 int i;
1406
1407 pmap = fs->map->pmap;
1408 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1409 return;
1410
1411 entry = fs->entry;
1412
1413 if (addra < backward * PAGE_SIZE) {
1414 starta = entry->start;
1415 } else {
1416 starta = addra - backward * PAGE_SIZE;
1417 if (starta < entry->start)
1418 starta = entry->start;
1419 }
1420
1421 /*
1422 * Generate the sequence of virtual addresses that are candidates for
1423 * prefaulting in an outward spiral from the faulting virtual address,
1424 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra
1425 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1426 * If the candidate address doesn't have a backing physical page, then
1427 * the loop immediately terminates.
1428 */
1429 for (i = 0; i < 2 * imax(backward, forward); i++) {
1430 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1431 PAGE_SIZE);
1432 if (addr > addra + forward * PAGE_SIZE)
1433 addr = 0;
1434
1435 if (addr < starta || addr >= entry->end)
1436 continue;
1437
1438 if (!pmap_is_prefaultable(pmap, addr))
1439 continue;
1440
1441 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1442 lobject = entry->object.vm_object;
1443 if (!obj_locked)
1444 VM_OBJECT_RLOCK(lobject);
1445 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1446 lobject->type == OBJT_DEFAULT &&
1447 (backing_object = lobject->backing_object) != NULL) {
1448 KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1449 0, ("vm_fault_prefault: unaligned object offset"));
1450 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1451 VM_OBJECT_RLOCK(backing_object);
1452 if (!obj_locked || lobject != entry->object.vm_object)
1453 VM_OBJECT_RUNLOCK(lobject);
1454 lobject = backing_object;
1455 }
1456 if (m == NULL) {
1457 if (!obj_locked || lobject != entry->object.vm_object)
1458 VM_OBJECT_RUNLOCK(lobject);
1459 break;
1460 }
1461 if (m->valid == VM_PAGE_BITS_ALL &&
1462 (m->flags & PG_FICTITIOUS) == 0)
1463 pmap_enter_quick(pmap, addr, m, entry->protection);
1464 if (!obj_locked || lobject != entry->object.vm_object)
1465 VM_OBJECT_RUNLOCK(lobject);
1466 }
1467 }
1468
1469 /*
1470 * Hold each of the physical pages that are mapped by the specified range of
1471 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1472 * and allow the specified types of access, "prot". If all of the implied
1473 * pages are successfully held, then the number of held pages is returned
1474 * together with pointers to those pages in the array "ma". However, if any
1475 * of the pages cannot be held, -1 is returned.
1476 */
1477 int
1478 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1479 vm_prot_t prot, vm_page_t *ma, int max_count)
1480 {
1481 vm_offset_t end, va;
1482 vm_page_t *mp;
1483 int count;
1484 boolean_t pmap_failed;
1485
1486 if (len == 0)
1487 return (0);
1488 end = round_page(addr + len);
1489 addr = trunc_page(addr);
1490
1491 /*
1492 * Check for illegal addresses.
1493 */
1494 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1495 return (-1);
1496
1497 if (atop(end - addr) > max_count)
1498 panic("vm_fault_quick_hold_pages: count > max_count");
1499 count = atop(end - addr);
1500
1501 /*
1502 * Most likely, the physical pages are resident in the pmap, so it is
1503 * faster to try pmap_extract_and_hold() first.
1504 */
1505 pmap_failed = FALSE;
1506 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1507 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1508 if (*mp == NULL)
1509 pmap_failed = TRUE;
1510 else if ((prot & VM_PROT_WRITE) != 0 &&
1511 (*mp)->dirty != VM_PAGE_BITS_ALL) {
1512 /*
1513 * Explicitly dirty the physical page. Otherwise, the
1514 * caller's changes may go unnoticed because they are
1515 * performed through an unmanaged mapping or by a DMA
1516 * operation.
1517 *
1518 * The object lock is not held here.
1519 * See vm_page_clear_dirty_mask().
1520 */
1521 vm_page_dirty(*mp);
1522 }
1523 }
1524 if (pmap_failed) {
1525 /*
1526 * One or more pages could not be held by the pmap. Either no
1527 * page was mapped at the specified virtual address or that
1528 * mapping had insufficient permissions. Attempt to fault in
1529 * and hold these pages.
1530 *
1531 * If vm_fault_disable_pagefaults() was called,
1532 * i.e., TDP_NOFAULTING is set, we must not sleep nor
1533 * acquire MD VM locks, which means we must not call
1534 * vm_fault_hold(). Some (out of tree) callers mark
1535 * too wide a code area with vm_fault_disable_pagefaults()
1536 * already, use the VM_PROT_QUICK_NOFAULT flag to request
1537 * the proper behaviour explicitly.
1538 */
1539 if ((prot & VM_PROT_QUICK_NOFAULT) != 0 &&
1540 (curthread->td_pflags & TDP_NOFAULTING) != 0)
1541 goto error;
1542 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1543 if (*mp == NULL && vm_fault_hold(map, va, prot,
1544 VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1545 goto error;
1546 }
1547 return (count);
1548 error:
1549 for (mp = ma; mp < ma + count; mp++)
1550 if (*mp != NULL) {
1551 vm_page_lock(*mp);
1552 vm_page_unhold(*mp);
1553 vm_page_unlock(*mp);
1554 }
1555 return (-1);
1556 }
1557
1558 /*
1559 * Routine:
1560 * vm_fault_copy_entry
1561 * Function:
1562 * Create new shadow object backing dst_entry with private copy of
1563 * all underlying pages. When src_entry is equal to dst_entry,
1564 * function implements COW for wired-down map entry. Otherwise,
1565 * it forks wired entry into dst_map.
1566 *
1567 * In/out conditions:
1568 * The source and destination maps must be locked for write.
1569 * The source map entry must be wired down (or be a sharing map
1570 * entry corresponding to a main map entry that is wired down).
1571 */
1572 void
1573 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1574 vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1575 vm_ooffset_t *fork_charge)
1576 {
1577 vm_object_t backing_object, dst_object, object, src_object;
1578 vm_pindex_t dst_pindex, pindex, src_pindex;
1579 vm_prot_t access, prot;
1580 vm_offset_t vaddr;
1581 vm_page_t dst_m;
1582 vm_page_t src_m;
1583 boolean_t upgrade;
1584
1585 #ifdef lint
1586 src_map++;
1587 #endif /* lint */
1588
1589 upgrade = src_entry == dst_entry;
1590 access = prot = dst_entry->protection;
1591
1592 src_object = src_entry->object.vm_object;
1593 src_pindex = OFF_TO_IDX(src_entry->offset);
1594
1595 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1596 dst_object = src_object;
1597 vm_object_reference(dst_object);
1598 } else {
1599 /*
1600 * Create the top-level object for the destination entry. (Doesn't
1601 * actually shadow anything - we copy the pages directly.)
1602 */
1603 dst_object = vm_object_allocate(OBJT_DEFAULT,
1604 atop(dst_entry->end - dst_entry->start));
1605 #if VM_NRESERVLEVEL > 0
1606 dst_object->flags |= OBJ_COLORED;
1607 dst_object->pg_color = atop(dst_entry->start);
1608 #endif
1609 }
1610
1611 VM_OBJECT_WLOCK(dst_object);
1612 KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1613 ("vm_fault_copy_entry: vm_object not NULL"));
1614 if (src_object != dst_object) {
1615 dst_entry->object.vm_object = dst_object;
1616 dst_entry->offset = 0;
1617 dst_object->charge = dst_entry->end - dst_entry->start;
1618 }
1619 if (fork_charge != NULL) {
1620 KASSERT(dst_entry->cred == NULL,
1621 ("vm_fault_copy_entry: leaked swp charge"));
1622 dst_object->cred = curthread->td_ucred;
1623 crhold(dst_object->cred);
1624 *fork_charge += dst_object->charge;
1625 } else if (dst_object->cred == NULL) {
1626 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1627 dst_entry));
1628 dst_object->cred = dst_entry->cred;
1629 dst_entry->cred = NULL;
1630 }
1631
1632 /*
1633 * If not an upgrade, then enter the mappings in the pmap as
1634 * read and/or execute accesses. Otherwise, enter them as
1635 * write accesses.
1636 *
1637 * A writeable large page mapping is only created if all of
1638 * the constituent small page mappings are modified. Marking
1639 * PTEs as modified on inception allows promotion to happen
1640 * without taking potentially large number of soft faults.
1641 */
1642 if (!upgrade)
1643 access &= ~VM_PROT_WRITE;
1644
1645 /*
1646 * Loop through all of the virtual pages within the entry's
1647 * range, copying each page from the source object to the
1648 * destination object. Since the source is wired, those pages
1649 * must exist. In contrast, the destination is pageable.
1650 * Since the destination object does share any backing storage
1651 * with the source object, all of its pages must be dirtied,
1652 * regardless of whether they can be written.
1653 */
1654 for (vaddr = dst_entry->start, dst_pindex = 0;
1655 vaddr < dst_entry->end;
1656 vaddr += PAGE_SIZE, dst_pindex++) {
1657 again:
1658 /*
1659 * Find the page in the source object, and copy it in.
1660 * Because the source is wired down, the page will be
1661 * in memory.
1662 */
1663 if (src_object != dst_object)
1664 VM_OBJECT_RLOCK(src_object);
1665 object = src_object;
1666 pindex = src_pindex + dst_pindex;
1667 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1668 (backing_object = object->backing_object) != NULL) {
1669 /*
1670 * Unless the source mapping is read-only or
1671 * it is presently being upgraded from
1672 * read-only, the first object in the shadow
1673 * chain should provide all of the pages. In
1674 * other words, this loop body should never be
1675 * executed when the source mapping is already
1676 * read/write.
1677 */
1678 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1679 upgrade,
1680 ("vm_fault_copy_entry: main object missing page"));
1681
1682 VM_OBJECT_RLOCK(backing_object);
1683 pindex += OFF_TO_IDX(object->backing_object_offset);
1684 if (object != dst_object)
1685 VM_OBJECT_RUNLOCK(object);
1686 object = backing_object;
1687 }
1688 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1689
1690 if (object != dst_object) {
1691 /*
1692 * Allocate a page in the destination object.
1693 */
1694 dst_m = vm_page_alloc(dst_object, (src_object ==
1695 dst_object ? src_pindex : 0) + dst_pindex,
1696 VM_ALLOC_NORMAL);
1697 if (dst_m == NULL) {
1698 VM_OBJECT_WUNLOCK(dst_object);
1699 VM_OBJECT_RUNLOCK(object);
1700 VM_WAIT;
1701 VM_OBJECT_WLOCK(dst_object);
1702 goto again;
1703 }
1704 pmap_copy_page(src_m, dst_m);
1705 VM_OBJECT_RUNLOCK(object);
1706 dst_m->valid = VM_PAGE_BITS_ALL;
1707 dst_m->dirty = VM_PAGE_BITS_ALL;
1708 } else {
1709 dst_m = src_m;
1710 if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1711 goto again;
1712 vm_page_xbusy(dst_m);
1713 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL,
1714 ("invalid dst page %p", dst_m));
1715 }
1716 VM_OBJECT_WUNLOCK(dst_object);
1717
1718 /*
1719 * Enter it in the pmap. If a wired, copy-on-write
1720 * mapping is being replaced by a write-enabled
1721 * mapping, then wire that new mapping.
1722 */
1723 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1724 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1725
1726 /*
1727 * Mark it no longer busy, and put it on the active list.
1728 */
1729 VM_OBJECT_WLOCK(dst_object);
1730
1731 if (upgrade) {
1732 if (src_m != dst_m) {
1733 vm_page_lock(src_m);
1734 vm_page_unwire(src_m, PQ_INACTIVE);
1735 vm_page_unlock(src_m);
1736 vm_page_lock(dst_m);
1737 vm_page_wire(dst_m);
1738 vm_page_unlock(dst_m);
1739 } else {
1740 KASSERT(dst_m->wire_count > 0,
1741 ("dst_m %p is not wired", dst_m));
1742 }
1743 } else {
1744 vm_page_lock(dst_m);
1745 vm_page_activate(dst_m);
1746 vm_page_unlock(dst_m);
1747 }
1748 vm_page_xunbusy(dst_m);
1749 }
1750 VM_OBJECT_WUNLOCK(dst_object);
1751 if (upgrade) {
1752 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1753 vm_object_deallocate(src_object);
1754 }
1755 }
1756
1757 /*
1758 * Block entry into the machine-independent layer's page fault handler by
1759 * the calling thread. Subsequent calls to vm_fault() by that thread will
1760 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of
1761 * spurious page faults.
1762 */
1763 int
1764 vm_fault_disable_pagefaults(void)
1765 {
1766
1767 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1768 }
1769
1770 void
1771 vm_fault_enable_pagefaults(int save)
1772 {
1773
1774 curthread_pflags_restore(save);
1775 }
Cache object: d5522a1bd0bf65bcc864005f79773e42
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