2 * SPDX-License-Identifier: BSD-4-Clause
4 * Copyright (c) 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 * Copyright (c) 1994 John S. Dyson
8 * Copyright (c) 1994 David Greenman
12 * This code is derived from software contributed to Berkeley by
13 * The Mach Operating System project at Carnegie-Mellon University.
15 * Redistribution and use in source and binary forms, with or without
16 * modification, are permitted provided that the following conditions
18 * 1. Redistributions of source code must retain the above copyright
19 * notice, this list of conditions and the following disclaimer.
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in the
22 * documentation and/or other materials provided with the distribution.
23 * 3. All advertising materials mentioning features or use of this software
24 * must display the following acknowledgement:
25 * This product includes software developed by the University of
26 * California, Berkeley and its contributors.
27 * 4. Neither the name of the University nor the names of its contributors
28 * may be used to endorse or promote products derived from this software
29 * without specific prior written permission.
31 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
32 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
33 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
34 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
35 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
36 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
37 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
39 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
40 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
43 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94
46 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
47 * All rights reserved.
49 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
51 * Permission to use, copy, modify and distribute this software and
52 * its documentation is hereby granted, provided that both the copyright
53 * notice and this permission notice appear in all copies of the
54 * software, derivative works or modified versions, and any portions
55 * thereof, and that both notices appear in supporting documentation.
57 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
58 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
59 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
61 * Carnegie Mellon requests users of this software to return to
63 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
64 * School of Computer Science
65 * Carnegie Mellon University
66 * Pittsburgh PA 15213-3890
68 * any improvements or extensions that they make and grant Carnegie the
69 * rights to redistribute these changes.
73 * Page fault handling module.
76 #include <sys/cdefs.h>
77 __FBSDID("$FreeBSD$");
79 #include "opt_ktrace.h"
82 #include <sys/param.h>
83 #include <sys/systm.h>
84 #include <sys/kernel.h>
88 #include <sys/racct.h>
89 #include <sys/resourcevar.h>
90 #include <sys/rwlock.h>
91 #include <sys/sysctl.h>
92 #include <sys/vmmeter.h>
93 #include <sys/vnode.h>
95 #include <sys/ktrace.h>
99 #include <vm/vm_param.h>
101 #include <vm/vm_map.h>
102 #include <vm/vm_object.h>
103 #include <vm/vm_page.h>
104 #include <vm/vm_pageout.h>
105 #include <vm/vm_kern.h>
106 #include <vm/vm_pager.h>
107 #include <vm/vm_extern.h>
108 #include <vm/vm_reserv.h>
113 #define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT)
114 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX)
116 #define VM_FAULT_DONTNEED_MIN 1048576
123 vm_object_t first_object;
124 vm_pindex_t first_pindex;
126 vm_map_entry_t entry;
128 bool lookup_still_valid;
132 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr,
134 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
135 int backward, int forward);
138 release_page(struct faultstate *fs)
141 vm_page_xunbusy(fs->m);
143 vm_page_deactivate(fs->m);
144 vm_page_unlock(fs->m);
149 unlock_map(struct faultstate *fs)
152 if (fs->lookup_still_valid) {
153 vm_map_lookup_done(fs->map, fs->entry);
154 fs->lookup_still_valid = false;
159 unlock_vp(struct faultstate *fs)
162 if (fs->vp != NULL) {
169 unlock_and_deallocate(struct faultstate *fs)
172 vm_object_pip_wakeup(fs->object);
173 VM_OBJECT_WUNLOCK(fs->object);
174 if (fs->object != fs->first_object) {
175 VM_OBJECT_WLOCK(fs->first_object);
176 vm_page_lock(fs->first_m);
177 vm_page_free(fs->first_m);
178 vm_page_unlock(fs->first_m);
179 vm_object_pip_wakeup(fs->first_object);
180 VM_OBJECT_WUNLOCK(fs->first_object);
183 vm_object_deallocate(fs->first_object);
189 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot,
190 vm_prot_t fault_type, int fault_flags, bool set_wd)
194 if (((prot & VM_PROT_WRITE) == 0 &&
195 (fault_flags & VM_FAULT_DIRTY) == 0) ||
196 (m->oflags & VPO_UNMANAGED) != 0)
199 VM_OBJECT_ASSERT_LOCKED(m->object);
201 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 &&
202 (fault_flags & VM_FAULT_WIRE) == 0) ||
203 (fault_flags & VM_FAULT_DIRTY) != 0;
206 vm_object_set_writeable_dirty(m->object);
209 * If two callers of vm_fault_dirty() with set_wd ==
210 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC
211 * flag set, other with flag clear, race, it is
212 * possible for the no-NOSYNC thread to see m->dirty
213 * != 0 and not clear VPO_NOSYNC. Take vm_page lock
214 * around manipulation of VPO_NOSYNC and
215 * vm_page_dirty() call, to avoid the race and keep
216 * m->oflags consistent.
221 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
222 * if the page is already dirty to prevent data written with
223 * the expectation of being synced from not being synced.
224 * Likewise if this entry does not request NOSYNC then make
225 * sure the page isn't marked NOSYNC. Applications sharing
226 * data should use the same flags to avoid ping ponging.
228 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) {
230 m->oflags |= VPO_NOSYNC;
233 m->oflags &= ~VPO_NOSYNC;
237 * If the fault is a write, we know that this page is being
238 * written NOW so dirty it explicitly to save on
239 * pmap_is_modified() calls later.
241 * Also, since the page is now dirty, we can possibly tell
242 * the pager to release any swap backing the page. Calling
243 * the pager requires a write lock on the object.
250 vm_pager_page_unswapped(m);
254 vm_fault_fill_hold(vm_page_t *m_hold, vm_page_t m)
257 if (m_hold != NULL) {
266 * Unlocks fs.first_object and fs.map on success.
269 vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot,
270 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold)
273 #if defined(__amd64__) && VM_NRESERVLEVEL > 0
279 MPASS(fs->vp == NULL);
280 m = vm_page_lookup(fs->first_object, fs->first_pindex);
281 /* A busy page can be mapped for read|execute access. */
282 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
283 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
284 return (KERN_FAILURE);
287 #if defined(__amd64__) && VM_NRESERVLEVEL > 0
288 if ((m->flags & PG_FICTITIOUS) == 0 &&
289 (m_super = vm_reserv_to_superpage(m)) != NULL &&
290 rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start &&
291 roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end &&
292 (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) &
293 (pagesizes[m_super->psind] - 1)) &&
294 pmap_ps_enabled(fs->map->pmap)) {
295 flags = PS_ALL_VALID;
296 if ((prot & VM_PROT_WRITE) != 0) {
298 * Create a superpage mapping allowing write access
299 * only if none of the constituent pages are busy and
300 * all of them are already dirty (except possibly for
301 * the page that was faulted on).
303 flags |= PS_NONE_BUSY;
304 if ((fs->first_object->flags & OBJ_UNMANAGED) == 0)
305 flags |= PS_ALL_DIRTY;
307 if (vm_page_ps_test(m_super, flags, m)) {
309 psind = m_super->psind;
310 vaddr = rounddown2(vaddr, pagesizes[psind]);
311 /* Preset the modified bit for dirty superpages. */
312 if ((flags & PS_ALL_DIRTY) != 0)
313 fault_type |= VM_PROT_WRITE;
317 rv = pmap_enter(fs->map->pmap, vaddr, m_map, prot, fault_type |
318 PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), psind);
319 if (rv != KERN_SUCCESS)
321 vm_fault_fill_hold(m_hold, m);
322 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false);
323 VM_OBJECT_RUNLOCK(fs->first_object);
324 if (psind == 0 && !wired)
325 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR);
326 vm_map_lookup_done(fs->map, fs->entry);
327 curthread->td_ru.ru_minflt++;
328 return (KERN_SUCCESS);
332 vm_fault_restore_map_lock(struct faultstate *fs)
335 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
336 MPASS(fs->first_object->paging_in_progress > 0);
338 if (!vm_map_trylock_read(fs->map)) {
339 VM_OBJECT_WUNLOCK(fs->first_object);
340 vm_map_lock_read(fs->map);
341 VM_OBJECT_WLOCK(fs->first_object);
343 fs->lookup_still_valid = true;
347 vm_fault_populate_check_page(vm_page_t m)
351 * Check each page to ensure that the pager is obeying the
352 * interface: the page must be installed in the object, fully
353 * valid, and exclusively busied.
356 MPASS(m->valid == VM_PAGE_BITS_ALL);
357 MPASS(vm_page_xbusied(m));
361 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first,
367 VM_OBJECT_ASSERT_WLOCKED(object);
368 MPASS(first <= last);
369 for (pidx = first, m = vm_page_lookup(object, pidx);
370 pidx <= last; pidx++, m = vm_page_next(m)) {
371 vm_fault_populate_check_page(m);
373 vm_page_deactivate(m);
380 vm_fault_populate(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot,
381 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold)
384 vm_pindex_t map_first, map_last, pager_first, pager_last, pidx;
387 MPASS(fs->object == fs->first_object);
388 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
389 MPASS(fs->first_object->paging_in_progress > 0);
390 MPASS(fs->first_object->backing_object == NULL);
391 MPASS(fs->lookup_still_valid);
393 pager_first = OFF_TO_IDX(fs->entry->offset);
394 pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1;
399 * Call the pager (driver) populate() method.
401 * There is no guarantee that the method will be called again
402 * if the current fault is for read, and a future fault is
403 * for write. Report the entry's maximum allowed protection
406 rv = vm_pager_populate(fs->first_object, fs->first_pindex,
407 fault_type, fs->entry->max_protection, &pager_first, &pager_last);
409 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
410 if (rv == VM_PAGER_BAD) {
412 * VM_PAGER_BAD is the backdoor for a pager to request
413 * normal fault handling.
415 vm_fault_restore_map_lock(fs);
416 if (fs->map->timestamp != fs->map_generation)
417 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */
418 return (KERN_NOT_RECEIVER);
420 if (rv != VM_PAGER_OK)
421 return (KERN_FAILURE); /* AKA SIGSEGV */
423 /* Ensure that the driver is obeying the interface. */
424 MPASS(pager_first <= pager_last);
425 MPASS(fs->first_pindex <= pager_last);
426 MPASS(fs->first_pindex >= pager_first);
427 MPASS(pager_last < fs->first_object->size);
429 vm_fault_restore_map_lock(fs);
430 if (fs->map->timestamp != fs->map_generation) {
431 vm_fault_populate_cleanup(fs->first_object, pager_first,
433 return (KERN_RESOURCE_SHORTAGE); /* RetryFault */
437 * The map is unchanged after our last unlock. Process the fault.
439 * The range [pager_first, pager_last] that is given to the
440 * pager is only a hint. The pager may populate any range
441 * within the object that includes the requested page index.
442 * In case the pager expanded the range, clip it to fit into
445 map_first = OFF_TO_IDX(fs->entry->offset);
446 if (map_first > pager_first) {
447 vm_fault_populate_cleanup(fs->first_object, pager_first,
449 pager_first = map_first;
451 map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1;
452 if (map_last < pager_last) {
453 vm_fault_populate_cleanup(fs->first_object, map_last + 1,
455 pager_last = map_last;
457 for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx);
458 pidx <= pager_last; pidx++, m = vm_page_next(m)) {
459 vm_fault_populate_check_page(m);
460 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags,
462 VM_OBJECT_WUNLOCK(fs->first_object);
463 pmap_enter(fs->map->pmap, fs->entry->start + IDX_TO_OFF(pidx) -
464 fs->entry->offset, m, prot, fault_type | (wired ?
465 PMAP_ENTER_WIRED : 0), 0);
466 VM_OBJECT_WLOCK(fs->first_object);
467 if (pidx == fs->first_pindex)
468 vm_fault_fill_hold(m_hold, m);
470 if ((fault_flags & VM_FAULT_WIRE) != 0) {
471 KASSERT(wired, ("VM_FAULT_WIRE && !wired"));
479 curthread->td_ru.ru_majflt++;
480 return (KERN_SUCCESS);
486 * Handle a page fault occurring at the given address,
487 * requiring the given permissions, in the map specified.
488 * If successful, the page is inserted into the
489 * associated physical map.
491 * NOTE: the given address should be truncated to the
492 * proper page address.
494 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
495 * a standard error specifying why the fault is fatal is returned.
497 * The map in question must be referenced, and remains so.
498 * Caller may hold no locks.
501 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
508 if ((td->td_pflags & TDP_NOFAULTING) != 0)
509 return (KERN_PROTECTION_FAILURE);
511 if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
512 ktrfault(vaddr, fault_type);
514 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
517 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
524 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
525 int fault_flags, vm_page_t *m_hold)
527 struct faultstate fs;
529 vm_object_t next_object, retry_object;
530 vm_offset_t e_end, e_start;
531 vm_pindex_t retry_pindex;
532 vm_prot_t prot, retry_prot;
533 int ahead, alloc_req, behind, cluster_offset, error, era, faultcount;
534 int locked, nera, result, rv;
536 boolean_t wired; /* Passed by reference. */
537 bool dead, hardfault, is_first_object_locked;
539 VM_CNT_INC(v_vm_faults);
548 * Find the backing store object and offset into it to begin the
552 result = vm_map_lookup(&fs.map, vaddr, fault_type |
553 VM_PROT_FAULT_LOOKUP, &fs.entry, &fs.first_object,
554 &fs.first_pindex, &prot, &wired);
555 if (result != KERN_SUCCESS) {
560 fs.map_generation = fs.map->timestamp;
562 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
563 panic("%s: fault on nofault entry, addr: %#lx",
564 __func__, (u_long)vaddr);
567 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
568 fs.entry->wiring_thread != curthread) {
569 vm_map_unlock_read(fs.map);
571 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
572 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
574 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
575 vm_map_unlock_and_wait(fs.map, 0);
577 vm_map_unlock(fs.map);
581 MPASS((fs.entry->eflags & MAP_ENTRY_GUARD) == 0);
584 fault_type = prot | (fault_type & VM_PROT_COPY);
586 KASSERT((fault_flags & VM_FAULT_WIRE) == 0,
587 ("!wired && VM_FAULT_WIRE"));
590 * Try to avoid lock contention on the top-level object through
591 * special-case handling of some types of page faults, specifically,
592 * those that are both (1) mapping an existing page from the top-
593 * level object and (2) not having to mark that object as containing
594 * dirty pages. Under these conditions, a read lock on the top-level
595 * object suffices, allowing multiple page faults of a similar type to
596 * run in parallel on the same top-level object.
598 if (fs.vp == NULL /* avoid locked vnode leak */ &&
599 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 &&
600 /* avoid calling vm_object_set_writeable_dirty() */
601 ((prot & VM_PROT_WRITE) == 0 ||
602 (fs.first_object->type != OBJT_VNODE &&
603 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
604 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
605 VM_OBJECT_RLOCK(fs.first_object);
606 if ((prot & VM_PROT_WRITE) == 0 ||
607 (fs.first_object->type != OBJT_VNODE &&
608 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
609 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0) {
610 rv = vm_fault_soft_fast(&fs, vaddr, prot, fault_type,
611 fault_flags, wired, m_hold);
612 if (rv == KERN_SUCCESS)
615 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
616 VM_OBJECT_RUNLOCK(fs.first_object);
617 VM_OBJECT_WLOCK(fs.first_object);
620 VM_OBJECT_WLOCK(fs.first_object);
624 * Make a reference to this object to prevent its disposal while we
625 * are messing with it. Once we have the reference, the map is free
626 * to be diddled. Since objects reference their shadows (and copies),
627 * they will stay around as well.
629 * Bump the paging-in-progress count to prevent size changes (e.g.
630 * truncation operations) during I/O.
632 vm_object_reference_locked(fs.first_object);
633 vm_object_pip_add(fs.first_object, 1);
635 fs.lookup_still_valid = true;
640 * Search for the page at object/offset.
642 fs.object = fs.first_object;
643 fs.pindex = fs.first_pindex;
646 * If the object is marked for imminent termination,
647 * we retry here, since the collapse pass has raced
648 * with us. Otherwise, if we see terminally dead
649 * object, return fail.
651 if ((fs.object->flags & OBJ_DEAD) != 0) {
652 dead = fs.object->type == OBJT_DEAD;
653 unlock_and_deallocate(&fs);
655 return (KERN_PROTECTION_FAILURE);
661 * See if page is resident
663 fs.m = vm_page_lookup(fs.object, fs.pindex);
666 * Wait/Retry if the page is busy. We have to do this
667 * if the page is either exclusive or shared busy
668 * because the vm_pager may be using read busy for
669 * pageouts (and even pageins if it is the vnode
670 * pager), and we could end up trying to pagein and
671 * pageout the same page simultaneously.
673 * We can theoretically allow the busy case on a read
674 * fault if the page is marked valid, but since such
675 * pages are typically already pmap'd, putting that
676 * special case in might be more effort then it is
677 * worth. We cannot under any circumstances mess
678 * around with a shared busied page except, perhaps,
681 if (vm_page_busied(fs.m)) {
683 * Reference the page before unlocking and
684 * sleeping so that the page daemon is less
685 * likely to reclaim it.
687 vm_page_aflag_set(fs.m, PGA_REFERENCED);
688 if (fs.object != fs.first_object) {
689 if (!VM_OBJECT_TRYWLOCK(
691 VM_OBJECT_WUNLOCK(fs.object);
692 VM_OBJECT_WLOCK(fs.first_object);
693 VM_OBJECT_WLOCK(fs.object);
695 vm_page_lock(fs.first_m);
696 vm_page_free(fs.first_m);
697 vm_page_unlock(fs.first_m);
698 vm_object_pip_wakeup(fs.first_object);
699 VM_OBJECT_WUNLOCK(fs.first_object);
703 if (fs.m == vm_page_lookup(fs.object,
705 vm_page_sleep_if_busy(fs.m, "vmpfw");
707 vm_object_pip_wakeup(fs.object);
708 VM_OBJECT_WUNLOCK(fs.object);
709 VM_CNT_INC(v_intrans);
710 vm_object_deallocate(fs.first_object);
714 vm_page_remque(fs.m);
715 vm_page_unlock(fs.m);
718 * Mark page busy for other processes, and the
719 * pagedaemon. If it still isn't completely valid
720 * (readable), jump to readrest, else break-out ( we
724 if (fs.m->valid != VM_PAGE_BITS_ALL)
728 KASSERT(fs.m == NULL, ("fs.m should be NULL, not %p", fs.m));
731 * Page is not resident. If the pager might contain the page
732 * or this is the beginning of the search, allocate a new
733 * page. (Default objects are zero-fill, so there is no real
736 if (fs.object->type != OBJT_DEFAULT ||
737 fs.object == fs.first_object) {
738 if (fs.pindex >= fs.object->size) {
739 unlock_and_deallocate(&fs);
740 return (KERN_PROTECTION_FAILURE);
743 if (fs.object == fs.first_object &&
744 (fs.first_object->flags & OBJ_POPULATE) != 0 &&
745 fs.first_object->shadow_count == 0) {
746 rv = vm_fault_populate(&fs, vaddr, prot,
747 fault_type, fault_flags, wired, m_hold);
751 unlock_and_deallocate(&fs);
753 case KERN_RESOURCE_SHORTAGE:
754 unlock_and_deallocate(&fs);
756 case KERN_NOT_RECEIVER:
758 * Pager's populate() method
759 * returned VM_PAGER_BAD.
763 panic("inconsistent return codes");
768 * Allocate a new page for this object/offset pair.
770 * Unlocked read of the p_flag is harmless. At
771 * worst, the P_KILLED might be not observed
772 * there, and allocation can fail, causing
773 * restart and new reading of the p_flag.
775 if (!vm_page_count_severe() || P_KILLED(curproc)) {
776 #if VM_NRESERVLEVEL > 0
777 vm_object_color(fs.object, atop(vaddr) -
780 alloc_req = P_KILLED(curproc) ?
781 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
782 if (fs.object->type != OBJT_VNODE &&
783 fs.object->backing_object == NULL)
784 alloc_req |= VM_ALLOC_ZERO;
785 fs.m = vm_page_alloc(fs.object, fs.pindex,
789 unlock_and_deallocate(&fs);
797 * At this point, we have either allocated a new page or found
798 * an existing page that is only partially valid.
800 * We hold a reference on the current object and the page is
805 * If the pager for the current object might have the page,
806 * then determine the number of additional pages to read and
807 * potentially reprioritize previously read pages for earlier
808 * reclamation. These operations should only be performed
809 * once per page fault. Even if the current pager doesn't
810 * have the page, the number of additional pages to read will
811 * apply to subsequent objects in the shadow chain.
813 if (fs.object->type != OBJT_DEFAULT && nera == -1 &&
814 !P_KILLED(curproc)) {
815 KASSERT(fs.lookup_still_valid, ("map unlocked"));
816 era = fs.entry->read_ahead;
817 behavior = vm_map_entry_behavior(fs.entry);
818 if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
820 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
821 nera = VM_FAULT_READ_AHEAD_MAX;
822 if (vaddr == fs.entry->next_read)
823 vm_fault_dontneed(&fs, vaddr, nera);
824 } else if (vaddr == fs.entry->next_read) {
826 * This is a sequential fault. Arithmetically
827 * increase the requested number of pages in
828 * the read-ahead window. The requested
829 * number of pages is "# of sequential faults
830 * x (read ahead min + 1) + read ahead min"
832 nera = VM_FAULT_READ_AHEAD_MIN;
835 if (nera > VM_FAULT_READ_AHEAD_MAX)
836 nera = VM_FAULT_READ_AHEAD_MAX;
838 if (era == VM_FAULT_READ_AHEAD_MAX)
839 vm_fault_dontneed(&fs, vaddr, nera);
842 * This is a non-sequential fault.
848 * A read lock on the map suffices to update
849 * the read ahead count safely.
851 fs.entry->read_ahead = nera;
855 * Prepare for unlocking the map. Save the map
856 * entry's start and end addresses, which are used to
857 * optimize the size of the pager operation below.
858 * Even if the map entry's addresses change after
859 * unlocking the map, using the saved addresses is
862 e_start = fs.entry->start;
863 e_end = fs.entry->end;
867 * Call the pager to retrieve the page if there is a chance
868 * that the pager has it, and potentially retrieve additional
869 * pages at the same time.
871 if (fs.object->type != OBJT_DEFAULT) {
873 * Release the map lock before locking the vnode or
874 * sleeping in the pager. (If the current object has
875 * a shadow, then an earlier iteration of this loop
876 * may have already unlocked the map.)
880 if (fs.object->type == OBJT_VNODE &&
881 (vp = fs.object->handle) != fs.vp) {
883 * Perform an unlock in case the desired vnode
884 * changed while the map was unlocked during a
889 locked = VOP_ISLOCKED(vp);
890 if (locked != LK_EXCLUSIVE)
894 * We must not sleep acquiring the vnode lock
895 * while we have the page exclusive busied or
896 * the object's paging-in-progress count
897 * incremented. Otherwise, we could deadlock.
899 error = vget(vp, locked | LK_CANRECURSE |
900 LK_NOWAIT, curthread);
904 unlock_and_deallocate(&fs);
905 error = vget(vp, locked | LK_RETRY |
906 LK_CANRECURSE, curthread);
910 ("vm_fault: vget failed"));
915 KASSERT(fs.vp == NULL || !fs.map->system_map,
916 ("vm_fault: vnode-backed object mapped by system map"));
919 * Page in the requested page and hint the pager,
920 * that it may bring up surrounding pages.
922 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM ||
927 /* Is this a sequential fault? */
933 * Request a cluster of pages that is
934 * aligned to a VM_FAULT_READ_DEFAULT
935 * page offset boundary within the
936 * object. Alignment to a page offset
937 * boundary is more likely to coincide
938 * with the underlying file system
939 * block than alignment to a virtual
942 cluster_offset = fs.pindex %
943 VM_FAULT_READ_DEFAULT;
944 behind = ulmin(cluster_offset,
945 atop(vaddr - e_start));
946 ahead = VM_FAULT_READ_DEFAULT - 1 -
949 ahead = ulmin(ahead, atop(e_end - vaddr) - 1);
951 rv = vm_pager_get_pages(fs.object, &fs.m, 1,
953 if (rv == VM_PAGER_OK) {
954 faultcount = behind + 1 + ahead;
956 break; /* break to PAGE HAS BEEN FOUND */
958 if (rv == VM_PAGER_ERROR)
959 printf("vm_fault: pager read error, pid %d (%s)\n",
960 curproc->p_pid, curproc->p_comm);
963 * If an I/O error occurred or the requested page was
964 * outside the range of the pager, clean up and return
967 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) {
969 if (fs.m->wire_count == 0)
972 vm_page_xunbusy_maybelocked(fs.m);
973 vm_page_unlock(fs.m);
975 unlock_and_deallocate(&fs);
976 return (rv == VM_PAGER_ERROR ? KERN_FAILURE :
977 KERN_PROTECTION_FAILURE);
981 * The requested page does not exist at this object/
982 * offset. Remove the invalid page from the object,
983 * waking up anyone waiting for it, and continue on to
984 * the next object. However, if this is the top-level
985 * object, we must leave the busy page in place to
986 * prevent another process from rushing past us, and
987 * inserting the page in that object at the same time
990 if (fs.object != fs.first_object) {
992 if (fs.m->wire_count == 0)
995 vm_page_xunbusy_maybelocked(fs.m);
996 vm_page_unlock(fs.m);
1002 * We get here if the object has default pager (or unwiring)
1003 * or the pager doesn't have the page.
1005 if (fs.object == fs.first_object)
1009 * Move on to the next object. Lock the next object before
1010 * unlocking the current one.
1012 next_object = fs.object->backing_object;
1013 if (next_object == NULL) {
1015 * If there's no object left, fill the page in the top
1016 * object with zeros.
1018 if (fs.object != fs.first_object) {
1019 vm_object_pip_wakeup(fs.object);
1020 VM_OBJECT_WUNLOCK(fs.object);
1022 fs.object = fs.first_object;
1023 fs.pindex = fs.first_pindex;
1025 VM_OBJECT_WLOCK(fs.object);
1030 * Zero the page if necessary and mark it valid.
1032 if ((fs.m->flags & PG_ZERO) == 0) {
1033 pmap_zero_page(fs.m);
1035 VM_CNT_INC(v_ozfod);
1038 fs.m->valid = VM_PAGE_BITS_ALL;
1039 /* Don't try to prefault neighboring pages. */
1041 break; /* break to PAGE HAS BEEN FOUND */
1043 KASSERT(fs.object != next_object,
1044 ("object loop %p", next_object));
1045 VM_OBJECT_WLOCK(next_object);
1046 vm_object_pip_add(next_object, 1);
1047 if (fs.object != fs.first_object)
1048 vm_object_pip_wakeup(fs.object);
1050 OFF_TO_IDX(fs.object->backing_object_offset);
1051 VM_OBJECT_WUNLOCK(fs.object);
1052 fs.object = next_object;
1056 vm_page_assert_xbusied(fs.m);
1059 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
1064 * If the page is being written, but isn't already owned by the
1065 * top-level object, we have to copy it into a new page owned by the
1068 if (fs.object != fs.first_object) {
1070 * We only really need to copy if we want to write it.
1072 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1074 * This allows pages to be virtually copied from a
1075 * backing_object into the first_object, where the
1076 * backing object has no other refs to it, and cannot
1077 * gain any more refs. Instead of a bcopy, we just
1078 * move the page from the backing object to the
1079 * first object. Note that we must mark the page
1080 * dirty in the first object so that it will go out
1081 * to swap when needed.
1083 is_first_object_locked = false;
1086 * Only one shadow object
1088 (fs.object->shadow_count == 1) &&
1090 * No COW refs, except us
1092 (fs.object->ref_count == 1) &&
1094 * No one else can look this object up
1096 (fs.object->handle == NULL) &&
1098 * No other ways to look the object up
1100 ((fs.object->type == OBJT_DEFAULT) ||
1101 (fs.object->type == OBJT_SWAP)) &&
1102 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
1104 * We don't chase down the shadow chain
1106 fs.object == fs.first_object->backing_object) {
1108 vm_page_remove(fs.m);
1109 vm_page_unlock(fs.m);
1110 vm_page_lock(fs.first_m);
1111 vm_page_replace_checked(fs.m, fs.first_object,
1112 fs.first_pindex, fs.first_m);
1113 vm_page_free(fs.first_m);
1114 vm_page_unlock(fs.first_m);
1115 vm_page_dirty(fs.m);
1116 #if VM_NRESERVLEVEL > 0
1118 * Rename the reservation.
1120 vm_reserv_rename(fs.m, fs.first_object,
1121 fs.object, OFF_TO_IDX(
1122 fs.first_object->backing_object_offset));
1125 * Removing the page from the backing object
1128 vm_page_xbusy(fs.m);
1131 VM_CNT_INC(v_cow_optim);
1134 * Oh, well, lets copy it.
1136 pmap_copy_page(fs.m, fs.first_m);
1137 fs.first_m->valid = VM_PAGE_BITS_ALL;
1138 if (wired && (fault_flags &
1139 VM_FAULT_WIRE) == 0) {
1140 vm_page_lock(fs.first_m);
1141 vm_page_wire(fs.first_m);
1142 vm_page_unlock(fs.first_m);
1145 vm_page_unwire(fs.m, PQ_INACTIVE);
1146 vm_page_unlock(fs.m);
1149 * We no longer need the old page or object.
1154 * fs.object != fs.first_object due to above
1157 vm_object_pip_wakeup(fs.object);
1158 VM_OBJECT_WUNLOCK(fs.object);
1160 * Only use the new page below...
1162 fs.object = fs.first_object;
1163 fs.pindex = fs.first_pindex;
1165 if (!is_first_object_locked)
1166 VM_OBJECT_WLOCK(fs.object);
1167 VM_CNT_INC(v_cow_faults);
1168 curthread->td_cow++;
1170 prot &= ~VM_PROT_WRITE;
1175 * We must verify that the maps have not changed since our last
1178 if (!fs.lookup_still_valid) {
1179 if (!vm_map_trylock_read(fs.map)) {
1181 unlock_and_deallocate(&fs);
1184 fs.lookup_still_valid = true;
1185 if (fs.map->timestamp != fs.map_generation) {
1186 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
1187 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
1190 * If we don't need the page any longer, put it on the inactive
1191 * list (the easiest thing to do here). If no one needs it,
1192 * pageout will grab it eventually.
1194 if (result != KERN_SUCCESS) {
1196 unlock_and_deallocate(&fs);
1199 * If retry of map lookup would have blocked then
1200 * retry fault from start.
1202 if (result == KERN_FAILURE)
1206 if ((retry_object != fs.first_object) ||
1207 (retry_pindex != fs.first_pindex)) {
1209 unlock_and_deallocate(&fs);
1214 * Check whether the protection has changed or the object has
1215 * been copied while we left the map unlocked. Changing from
1216 * read to write permission is OK - we leave the page
1217 * write-protected, and catch the write fault. Changing from
1218 * write to read permission means that we can't mark the page
1219 * write-enabled after all.
1226 * If the page was filled by a pager, save the virtual address that
1227 * should be faulted on next under a sequential access pattern to the
1228 * map entry. A read lock on the map suffices to update this address
1232 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE;
1234 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true);
1235 vm_page_assert_xbusied(fs.m);
1238 * Page must be completely valid or it is not fit to
1239 * map into user space. vm_pager_get_pages() ensures this.
1241 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
1242 ("vm_fault: page %p partially invalid", fs.m));
1243 VM_OBJECT_WUNLOCK(fs.object);
1246 * Put this page into the physical map. We had to do the unlock above
1247 * because pmap_enter() may sleep. We don't put the page
1248 * back on the active queue until later so that the pageout daemon
1249 * won't find it (yet).
1251 pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
1252 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
1253 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 &&
1255 vm_fault_prefault(&fs, vaddr,
1256 faultcount > 0 ? behind : PFBAK,
1257 faultcount > 0 ? ahead : PFFOR);
1258 VM_OBJECT_WLOCK(fs.object);
1262 * If the page is not wired down, then put it where the pageout daemon
1265 if ((fault_flags & VM_FAULT_WIRE) != 0) {
1266 KASSERT(wired, ("VM_FAULT_WIRE && !wired"));
1269 vm_page_activate(fs.m);
1270 if (m_hold != NULL) {
1274 vm_page_unlock(fs.m);
1275 vm_page_xunbusy(fs.m);
1278 * Unlock everything, and return
1280 unlock_and_deallocate(&fs);
1282 VM_CNT_INC(v_io_faults);
1283 curthread->td_ru.ru_majflt++;
1285 if (racct_enable && fs.object->type == OBJT_VNODE) {
1287 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1288 racct_add_force(curproc, RACCT_WRITEBPS,
1289 PAGE_SIZE + behind * PAGE_SIZE);
1290 racct_add_force(curproc, RACCT_WRITEIOPS, 1);
1292 racct_add_force(curproc, RACCT_READBPS,
1293 PAGE_SIZE + ahead * PAGE_SIZE);
1294 racct_add_force(curproc, RACCT_READIOPS, 1);
1296 PROC_UNLOCK(curproc);
1300 curthread->td_ru.ru_minflt++;
1302 return (KERN_SUCCESS);
1306 * Speed up the reclamation of pages that precede the faulting pindex within
1307 * the first object of the shadow chain. Essentially, perform the equivalent
1308 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes
1309 * the faulting pindex by the cluster size when the pages read by vm_fault()
1310 * cross a cluster-size boundary. The cluster size is the greater of the
1311 * smallest superpage size and VM_FAULT_DONTNEED_MIN.
1313 * When "fs->first_object" is a shadow object, the pages in the backing object
1314 * that precede the faulting pindex are deactivated by vm_fault(). So, this
1315 * function must only be concerned with pages in the first object.
1318 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
1320 vm_map_entry_t entry;
1321 vm_object_t first_object, object;
1322 vm_offset_t end, start;
1323 vm_page_t m, m_next;
1324 vm_pindex_t pend, pstart;
1327 object = fs->object;
1328 VM_OBJECT_ASSERT_WLOCKED(object);
1329 first_object = fs->first_object;
1330 if (first_object != object) {
1331 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1332 VM_OBJECT_WUNLOCK(object);
1333 VM_OBJECT_WLOCK(first_object);
1334 VM_OBJECT_WLOCK(object);
1337 /* Neither fictitious nor unmanaged pages can be reclaimed. */
1338 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1339 size = VM_FAULT_DONTNEED_MIN;
1340 if (MAXPAGESIZES > 1 && size < pagesizes[1])
1341 size = pagesizes[1];
1342 end = rounddown2(vaddr, size);
1343 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) &&
1344 (entry = fs->entry)->start < end) {
1345 if (end - entry->start < size)
1346 start = entry->start;
1349 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED);
1350 pstart = OFF_TO_IDX(entry->offset) + atop(start -
1352 m_next = vm_page_find_least(first_object, pstart);
1353 pend = OFF_TO_IDX(entry->offset) + atop(end -
1355 while ((m = m_next) != NULL && m->pindex < pend) {
1356 m_next = TAILQ_NEXT(m, listq);
1357 if (m->valid != VM_PAGE_BITS_ALL ||
1362 * Don't clear PGA_REFERENCED, since it would
1363 * likely represent a reference by a different
1366 * Typically, at this point, prefetched pages
1367 * are still in the inactive queue. Only
1368 * pages that triggered page faults are in the
1372 vm_page_deactivate(m);
1377 if (first_object != object)
1378 VM_OBJECT_WUNLOCK(first_object);
1382 * vm_fault_prefault provides a quick way of clustering
1383 * pagefaults into a processes address space. It is a "cousin"
1384 * of vm_map_pmap_enter, except it runs at page fault time instead
1388 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1389 int backward, int forward)
1392 vm_map_entry_t entry;
1393 vm_object_t backing_object, lobject;
1394 vm_offset_t addr, starta;
1399 pmap = fs->map->pmap;
1400 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1405 if (addra < backward * PAGE_SIZE) {
1406 starta = entry->start;
1408 starta = addra - backward * PAGE_SIZE;
1409 if (starta < entry->start)
1410 starta = entry->start;
1414 * Generate the sequence of virtual addresses that are candidates for
1415 * prefaulting in an outward spiral from the faulting virtual address,
1416 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra
1417 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1418 * If the candidate address doesn't have a backing physical page, then
1419 * the loop immediately terminates.
1421 for (i = 0; i < 2 * imax(backward, forward); i++) {
1422 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1424 if (addr > addra + forward * PAGE_SIZE)
1427 if (addr < starta || addr >= entry->end)
1430 if (!pmap_is_prefaultable(pmap, addr))
1433 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1434 lobject = entry->object.vm_object;
1435 VM_OBJECT_RLOCK(lobject);
1436 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1437 lobject->type == OBJT_DEFAULT &&
1438 (backing_object = lobject->backing_object) != NULL) {
1439 KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1440 0, ("vm_fault_prefault: unaligned object offset"));
1441 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1442 VM_OBJECT_RLOCK(backing_object);
1443 VM_OBJECT_RUNLOCK(lobject);
1444 lobject = backing_object;
1447 VM_OBJECT_RUNLOCK(lobject);
1450 if (m->valid == VM_PAGE_BITS_ALL &&
1451 (m->flags & PG_FICTITIOUS) == 0)
1452 pmap_enter_quick(pmap, addr, m, entry->protection);
1453 VM_OBJECT_RUNLOCK(lobject);
1458 * Hold each of the physical pages that are mapped by the specified range of
1459 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1460 * and allow the specified types of access, "prot". If all of the implied
1461 * pages are successfully held, then the number of held pages is returned
1462 * together with pointers to those pages in the array "ma". However, if any
1463 * of the pages cannot be held, -1 is returned.
1466 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1467 vm_prot_t prot, vm_page_t *ma, int max_count)
1469 vm_offset_t end, va;
1472 boolean_t pmap_failed;
1476 end = round_page(addr + len);
1477 addr = trunc_page(addr);
1480 * Check for illegal addresses.
1482 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1485 if (atop(end - addr) > max_count)
1486 panic("vm_fault_quick_hold_pages: count > max_count");
1487 count = atop(end - addr);
1490 * Most likely, the physical pages are resident in the pmap, so it is
1491 * faster to try pmap_extract_and_hold() first.
1493 pmap_failed = FALSE;
1494 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1495 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1498 else if ((prot & VM_PROT_WRITE) != 0 &&
1499 (*mp)->dirty != VM_PAGE_BITS_ALL) {
1501 * Explicitly dirty the physical page. Otherwise, the
1502 * caller's changes may go unnoticed because they are
1503 * performed through an unmanaged mapping or by a DMA
1506 * The object lock is not held here.
1507 * See vm_page_clear_dirty_mask().
1514 * One or more pages could not be held by the pmap. Either no
1515 * page was mapped at the specified virtual address or that
1516 * mapping had insufficient permissions. Attempt to fault in
1517 * and hold these pages.
1519 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1520 if (*mp == NULL && vm_fault_hold(map, va, prot,
1521 VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1526 for (mp = ma; mp < ma + count; mp++)
1529 vm_page_unhold(*mp);
1530 vm_page_unlock(*mp);
1537 * vm_fault_copy_entry
1539 * Create new shadow object backing dst_entry with private copy of
1540 * all underlying pages. When src_entry is equal to dst_entry,
1541 * function implements COW for wired-down map entry. Otherwise,
1542 * it forks wired entry into dst_map.
1544 * In/out conditions:
1545 * The source and destination maps must be locked for write.
1546 * The source map entry must be wired down (or be a sharing map
1547 * entry corresponding to a main map entry that is wired down).
1550 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1551 vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1552 vm_ooffset_t *fork_charge)
1554 vm_object_t backing_object, dst_object, object, src_object;
1555 vm_pindex_t dst_pindex, pindex, src_pindex;
1556 vm_prot_t access, prot;
1566 upgrade = src_entry == dst_entry;
1567 access = prot = dst_entry->protection;
1569 src_object = src_entry->object.vm_object;
1570 src_pindex = OFF_TO_IDX(src_entry->offset);
1572 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1573 dst_object = src_object;
1574 vm_object_reference(dst_object);
1577 * Create the top-level object for the destination entry. (Doesn't
1578 * actually shadow anything - we copy the pages directly.)
1580 dst_object = vm_object_allocate(OBJT_DEFAULT,
1581 atop(dst_entry->end - dst_entry->start));
1582 #if VM_NRESERVLEVEL > 0
1583 dst_object->flags |= OBJ_COLORED;
1584 dst_object->pg_color = atop(dst_entry->start);
1588 VM_OBJECT_WLOCK(dst_object);
1589 KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1590 ("vm_fault_copy_entry: vm_object not NULL"));
1591 if (src_object != dst_object) {
1592 dst_entry->object.vm_object = dst_object;
1593 dst_entry->offset = 0;
1594 dst_object->charge = dst_entry->end - dst_entry->start;
1596 if (fork_charge != NULL) {
1597 KASSERT(dst_entry->cred == NULL,
1598 ("vm_fault_copy_entry: leaked swp charge"));
1599 dst_object->cred = curthread->td_ucred;
1600 crhold(dst_object->cred);
1601 *fork_charge += dst_object->charge;
1602 } else if (dst_object->cred == NULL) {
1603 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1605 dst_object->cred = dst_entry->cred;
1606 dst_entry->cred = NULL;
1610 * If not an upgrade, then enter the mappings in the pmap as
1611 * read and/or execute accesses. Otherwise, enter them as
1614 * A writeable large page mapping is only created if all of
1615 * the constituent small page mappings are modified. Marking
1616 * PTEs as modified on inception allows promotion to happen
1617 * without taking potentially large number of soft faults.
1620 access &= ~VM_PROT_WRITE;
1623 * Loop through all of the virtual pages within the entry's
1624 * range, copying each page from the source object to the
1625 * destination object. Since the source is wired, those pages
1626 * must exist. In contrast, the destination is pageable.
1627 * Since the destination object does share any backing storage
1628 * with the source object, all of its pages must be dirtied,
1629 * regardless of whether they can be written.
1631 for (vaddr = dst_entry->start, dst_pindex = 0;
1632 vaddr < dst_entry->end;
1633 vaddr += PAGE_SIZE, dst_pindex++) {
1636 * Find the page in the source object, and copy it in.
1637 * Because the source is wired down, the page will be
1640 if (src_object != dst_object)
1641 VM_OBJECT_RLOCK(src_object);
1642 object = src_object;
1643 pindex = src_pindex + dst_pindex;
1644 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1645 (backing_object = object->backing_object) != NULL) {
1647 * Unless the source mapping is read-only or
1648 * it is presently being upgraded from
1649 * read-only, the first object in the shadow
1650 * chain should provide all of the pages. In
1651 * other words, this loop body should never be
1652 * executed when the source mapping is already
1655 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1657 ("vm_fault_copy_entry: main object missing page"));
1659 VM_OBJECT_RLOCK(backing_object);
1660 pindex += OFF_TO_IDX(object->backing_object_offset);
1661 if (object != dst_object)
1662 VM_OBJECT_RUNLOCK(object);
1663 object = backing_object;
1665 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1667 if (object != dst_object) {
1669 * Allocate a page in the destination object.
1671 dst_m = vm_page_alloc(dst_object, (src_object ==
1672 dst_object ? src_pindex : 0) + dst_pindex,
1674 if (dst_m == NULL) {
1675 VM_OBJECT_WUNLOCK(dst_object);
1676 VM_OBJECT_RUNLOCK(object);
1678 VM_OBJECT_WLOCK(dst_object);
1681 pmap_copy_page(src_m, dst_m);
1682 VM_OBJECT_RUNLOCK(object);
1683 dst_m->valid = VM_PAGE_BITS_ALL;
1684 dst_m->dirty = VM_PAGE_BITS_ALL;
1687 if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1689 vm_page_xbusy(dst_m);
1690 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL,
1691 ("invalid dst page %p", dst_m));
1693 VM_OBJECT_WUNLOCK(dst_object);
1696 * Enter it in the pmap. If a wired, copy-on-write
1697 * mapping is being replaced by a write-enabled
1698 * mapping, then wire that new mapping.
1700 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1701 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1704 * Mark it no longer busy, and put it on the active list.
1706 VM_OBJECT_WLOCK(dst_object);
1709 if (src_m != dst_m) {
1710 vm_page_lock(src_m);
1711 vm_page_unwire(src_m, PQ_INACTIVE);
1712 vm_page_unlock(src_m);
1713 vm_page_lock(dst_m);
1714 vm_page_wire(dst_m);
1715 vm_page_unlock(dst_m);
1717 KASSERT(dst_m->wire_count > 0,
1718 ("dst_m %p is not wired", dst_m));
1721 vm_page_lock(dst_m);
1722 vm_page_activate(dst_m);
1723 vm_page_unlock(dst_m);
1725 vm_page_xunbusy(dst_m);
1727 VM_OBJECT_WUNLOCK(dst_object);
1729 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1730 vm_object_deallocate(src_object);
1735 * Block entry into the machine-independent layer's page fault handler by
1736 * the calling thread. Subsequent calls to vm_fault() by that thread will
1737 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of
1738 * spurious page faults.
1741 vm_fault_disable_pagefaults(void)
1744 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1748 vm_fault_enable_pagefaults(int save)
1751 curthread_pflags_restore(save);