2 * Copyright (c) 1991, 1993
3 * The Regents of the University of California. All rights reserved.
4 * Copyright (c) 1994 John S. Dyson
6 * Copyright (c) 1994 David Greenman
10 * This code is derived from software contributed to Berkeley by
11 * The Mach Operating System project at Carnegie-Mellon University.
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
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.
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
41 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94
44 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
45 * All rights reserved.
47 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
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.
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.
59 * Carnegie Mellon requests users of this software to return to
61 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
62 * School of Computer Science
63 * Carnegie Mellon University
64 * Pittsburgh PA 15213-3890
66 * any improvements or extensions that they make and grant Carnegie the
67 * rights to redistribute these changes.
71 * Page fault handling module.
74 #include <sys/cdefs.h>
75 __FBSDID("$FreeBSD$");
77 #include "opt_ktrace.h"
80 #include <sys/param.h>
81 #include <sys/systm.h>
82 #include <sys/kernel.h>
85 #include <sys/resourcevar.h>
86 #include <sys/rwlock.h>
87 #include <sys/sysctl.h>
88 #include <sys/vmmeter.h>
89 #include <sys/vnode.h>
91 #include <sys/ktrace.h>
95 #include <vm/vm_param.h>
97 #include <vm/vm_map.h>
98 #include <vm/vm_object.h>
99 #include <vm/vm_page.h>
100 #include <vm/vm_pageout.h>
101 #include <vm/vm_kern.h>
102 #include <vm/vm_pager.h>
103 #include <vm/vm_extern.h>
104 #include <vm/vm_reserv.h>
109 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
111 #define VM_FAULT_READ_BEHIND 8
112 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX)
113 #define VM_FAULT_NINCR (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND)
114 #define VM_FAULT_SUM (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2)
115 #define VM_FAULT_CACHE_BEHIND (VM_FAULT_READ_BEHIND * VM_FAULT_SUM)
122 vm_object_t first_object;
123 vm_pindex_t first_pindex;
125 vm_map_entry_t entry;
126 int lookup_still_valid;
131 static void vm_fault_cache_behind(const struct faultstate *fs, int distance);
132 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
133 int faultcount, int reqpage);
136 release_page(struct faultstate *fs)
139 vm_page_xunbusy(fs->m);
141 vm_page_deactivate(fs->m);
142 vm_page_unlock(fs->m);
147 unlock_map(struct faultstate *fs)
150 if (fs->lookup_still_valid) {
151 vm_map_lookup_done(fs->map, fs->entry);
152 fs->lookup_still_valid = FALSE;
157 unlock_vp(struct faultstate *fs)
160 if (fs->vp != NULL) {
167 unlock_and_deallocate(struct faultstate *fs)
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);
181 vm_object_deallocate(fs->first_object);
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)
192 if (((prot & VM_PROT_WRITE) == 0 &&
193 (fault_flags & VM_FAULT_DIRTY) == 0) ||
194 (m->oflags & VPO_UNMANAGED) != 0)
197 VM_OBJECT_ASSERT_LOCKED(m->object);
199 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 &&
200 (fault_flags & VM_FAULT_WIRE) == 0) ||
201 (fault_flags & VM_FAULT_DIRTY) != 0;
204 vm_object_set_writeable_dirty(m->object);
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.
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.
226 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) {
228 m->oflags |= VPO_NOSYNC;
231 m->oflags &= ~VPO_NOSYNC;
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.
239 * Also tell the backing pager, if any, that it should remove
240 * any swap backing since the page is now dirty.
247 vm_pager_page_unswapped(m);
251 vm_fault_fill_hold(vm_page_t *m_hold, vm_page_t m)
254 if (m_hold != NULL) {
263 * Unlocks fs.first_object and fs.map on success.
266 vm_fault_soft_fast(struct faultstate *fs, vm_offset_t vaddr, vm_prot_t prot,
267 int fault_type, int fault_flags, boolean_t wired, vm_page_t *m_hold)
272 MPASS(fs->vp == NULL);
273 m = vm_page_lookup(fs->first_object, fs->first_pindex);
274 /* A busy page can be mapped for read|execute access. */
275 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
276 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
277 return (KERN_FAILURE);
278 rv = pmap_enter(fs->map->pmap, vaddr, m, prot, fault_type |
279 PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED : 0), 0);
280 if (rv != KERN_SUCCESS)
282 vm_fault_fill_hold(m_hold, m);
283 vm_fault_dirty(fs->entry, m, prot, fault_type, fault_flags, false);
284 VM_OBJECT_RUNLOCK(fs->first_object);
286 vm_fault_prefault(fs, vaddr, 0, 0);
287 vm_map_lookup_done(fs->map, fs->entry);
288 curthread->td_ru.ru_minflt++;
289 return (KERN_SUCCESS);
295 * Handle a page fault occurring at the given address,
296 * requiring the given permissions, in the map specified.
297 * If successful, the page is inserted into the
298 * associated physical map.
300 * NOTE: the given address should be truncated to the
301 * proper page address.
303 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
304 * a standard error specifying why the fault is fatal is returned.
306 * The map in question must be referenced, and remains so.
307 * Caller may hold no locks.
310 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
317 if ((td->td_pflags & TDP_NOFAULTING) != 0)
318 return (KERN_PROTECTION_FAILURE);
320 if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
321 ktrfault(vaddr, fault_type);
323 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
326 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
333 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
334 int fault_flags, vm_page_t *m_hold)
338 int alloc_req, era, faultcount, nera, reqpage, result;
339 boolean_t dead, growstack, is_first_object_locked, wired;
340 vm_object_t next_object;
341 vm_page_t marray[VM_FAULT_READ_MAX];
343 struct faultstate fs;
349 PCPU_INC(cnt.v_vm_faults);
351 faultcount = reqpage = 0;
356 * Find the backing store object and offset into it to begin the
360 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
361 &fs.first_object, &fs.first_pindex, &prot, &wired);
362 if (result != KERN_SUCCESS) {
363 if (growstack && result == KERN_INVALID_ADDRESS &&
365 result = vm_map_growstack(curproc, vaddr);
366 if (result != KERN_SUCCESS)
367 return (KERN_FAILURE);
375 fs.map_generation = fs.map->timestamp;
377 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
378 panic("vm_fault: fault on nofault entry, addr: %lx",
382 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
383 fs.entry->wiring_thread != curthread) {
384 vm_map_unlock_read(fs.map);
386 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
387 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
389 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
390 vm_map_unlock_and_wait(fs.map, 0);
392 vm_map_unlock(fs.map);
397 fault_type = prot | (fault_type & VM_PROT_COPY);
399 KASSERT((fault_flags & VM_FAULT_WIRE) == 0,
400 ("!wired && VM_FAULT_WIRE"));
403 * Try to avoid lock contention on the top-level object through
404 * special-case handling of some types of page faults, specifically,
405 * those that are both (1) mapping an existing page from the top-
406 * level object and (2) not having to mark that object as containing
407 * dirty pages. Under these conditions, a read lock on the top-level
408 * object suffices, allowing multiple page faults of a similar type to
409 * run in parallel on the same top-level object.
411 if (fs.vp == NULL /* avoid locked vnode leak */ &&
412 (fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0 &&
413 /* avoid calling vm_object_set_writeable_dirty() */
414 ((prot & VM_PROT_WRITE) == 0 ||
415 (fs.first_object->type != OBJT_VNODE &&
416 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
417 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
418 VM_OBJECT_RLOCK(fs.first_object);
419 if ((prot & VM_PROT_WRITE) == 0 ||
420 (fs.first_object->type != OBJT_VNODE &&
421 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
422 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0) {
423 result = vm_fault_soft_fast(&fs, vaddr, prot,
424 fault_type, fault_flags, wired, m_hold);
425 if (result == KERN_SUCCESS)
428 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
429 VM_OBJECT_RUNLOCK(fs.first_object);
430 VM_OBJECT_WLOCK(fs.first_object);
433 VM_OBJECT_WLOCK(fs.first_object);
437 * Make a reference to this object to prevent its disposal while we
438 * are messing with it. Once we have the reference, the map is free
439 * to be diddled. Since objects reference their shadows (and copies),
440 * they will stay around as well.
442 * Bump the paging-in-progress count to prevent size changes (e.g.
443 * truncation operations) during I/O. This must be done after
444 * obtaining the vnode lock in order to avoid possible deadlocks.
446 vm_object_reference_locked(fs.first_object);
447 vm_object_pip_add(fs.first_object, 1);
449 fs.lookup_still_valid = TRUE;
454 * Search for the page at object/offset.
456 fs.object = fs.first_object;
457 fs.pindex = fs.first_pindex;
460 * If the object is marked for imminent termination,
461 * we retry here, since the collapse pass has raced
462 * with us. Otherwise, if we see terminally dead
463 * object, return fail.
465 if ((fs.object->flags & OBJ_DEAD) != 0) {
466 dead = fs.object->type == OBJT_DEAD;
467 unlock_and_deallocate(&fs);
469 return (KERN_PROTECTION_FAILURE);
475 * See if page is resident
477 fs.m = vm_page_lookup(fs.object, fs.pindex);
480 * Wait/Retry if the page is busy. We have to do this
481 * if the page is either exclusive or shared busy
482 * because the vm_pager may be using read busy for
483 * pageouts (and even pageins if it is the vnode
484 * pager), and we could end up trying to pagein and
485 * pageout the same page simultaneously.
487 * We can theoretically allow the busy case on a read
488 * fault if the page is marked valid, but since such
489 * pages are typically already pmap'd, putting that
490 * special case in might be more effort then it is
491 * worth. We cannot under any circumstances mess
492 * around with a shared busied page except, perhaps,
495 if (vm_page_busied(fs.m)) {
497 * Reference the page before unlocking and
498 * sleeping so that the page daemon is less
499 * likely to reclaim it.
501 vm_page_aflag_set(fs.m, PGA_REFERENCED);
502 if (fs.object != fs.first_object) {
503 if (!VM_OBJECT_TRYWLOCK(
505 VM_OBJECT_WUNLOCK(fs.object);
506 VM_OBJECT_WLOCK(fs.first_object);
507 VM_OBJECT_WLOCK(fs.object);
509 vm_page_lock(fs.first_m);
510 vm_page_free(fs.first_m);
511 vm_page_unlock(fs.first_m);
512 vm_object_pip_wakeup(fs.first_object);
513 VM_OBJECT_WUNLOCK(fs.first_object);
517 if (fs.m == vm_page_lookup(fs.object,
519 vm_page_sleep_if_busy(fs.m, "vmpfw");
521 vm_object_pip_wakeup(fs.object);
522 VM_OBJECT_WUNLOCK(fs.object);
523 PCPU_INC(cnt.v_intrans);
524 vm_object_deallocate(fs.first_object);
528 vm_page_remque(fs.m);
529 vm_page_unlock(fs.m);
532 * Mark page busy for other processes, and the
533 * pagedaemon. If it still isn't completely valid
534 * (readable), jump to readrest, else break-out ( we
538 if (fs.m->valid != VM_PAGE_BITS_ALL)
544 * Page is not resident. If this is the search termination
545 * or the pager might contain the page, allocate a new page.
546 * Default objects are zero-fill, there is no real pager.
548 if (fs.object->type != OBJT_DEFAULT ||
549 fs.object == fs.first_object) {
550 if (fs.pindex >= fs.object->size) {
551 unlock_and_deallocate(&fs);
552 return (KERN_PROTECTION_FAILURE);
556 * Allocate a new page for this object/offset pair.
558 * Unlocked read of the p_flag is harmless. At
559 * worst, the P_KILLED might be not observed
560 * there, and allocation can fail, causing
561 * restart and new reading of the p_flag.
564 if (!vm_page_count_severe() || P_KILLED(curproc)) {
565 #if VM_NRESERVLEVEL > 0
566 if ((fs.object->flags & OBJ_COLORED) == 0) {
567 fs.object->flags |= OBJ_COLORED;
568 fs.object->pg_color = atop(vaddr) -
572 alloc_req = P_KILLED(curproc) ?
573 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
574 if (fs.object->type != OBJT_VNODE &&
575 fs.object->backing_object == NULL)
576 alloc_req |= VM_ALLOC_ZERO;
577 fs.m = vm_page_alloc(fs.object, fs.pindex,
581 unlock_and_deallocate(&fs);
584 } else if (fs.m->valid == VM_PAGE_BITS_ALL)
590 * We have found a valid page or we have allocated a new page.
591 * The page thus may not be valid or may not be entirely
594 * Attempt to fault-in the page if there is a chance that the
595 * pager has it, and potentially fault in additional pages
596 * at the same time. For default objects simply provide
599 if (fs.object->type != OBJT_DEFAULT) {
601 u_char behavior = vm_map_entry_behavior(fs.entry);
603 if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
607 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
609 ahead = atop(fs.entry->end - vaddr) - 1;
610 if (ahead > VM_FAULT_READ_AHEAD_MAX)
611 ahead = VM_FAULT_READ_AHEAD_MAX;
612 if (fs.pindex == fs.entry->next_read)
613 vm_fault_cache_behind(&fs,
617 * If this is a sequential page fault, then
618 * arithmetically increase the number of pages
619 * in the read-ahead window. Otherwise, reset
620 * the read-ahead window to its smallest size.
622 behind = atop(vaddr - fs.entry->start);
623 if (behind > VM_FAULT_READ_BEHIND)
624 behind = VM_FAULT_READ_BEHIND;
625 ahead = atop(fs.entry->end - vaddr) - 1;
626 era = fs.entry->read_ahead;
627 if (fs.pindex == fs.entry->next_read) {
629 if (nera > VM_FAULT_READ_AHEAD_MAX)
630 nera = VM_FAULT_READ_AHEAD_MAX;
634 if (era == VM_FAULT_READ_AHEAD_MAX)
635 vm_fault_cache_behind(&fs,
636 VM_FAULT_CACHE_BEHIND);
637 } else if (ahead > VM_FAULT_READ_AHEAD_MIN)
638 ahead = VM_FAULT_READ_AHEAD_MIN;
640 fs.entry->read_ahead = ahead;
644 * Call the pager to retrieve the data, if any, after
645 * releasing the lock on the map. We hold a ref on
646 * fs.object and the pages are exclusive busied.
650 if (fs.object->type == OBJT_VNODE &&
651 (vp = fs.object->handle) != fs.vp) {
653 locked = VOP_ISLOCKED(vp);
655 if (locked != LK_EXCLUSIVE)
657 /* Do not sleep for vnode lock while fs.m is busy */
658 error = vget(vp, locked | LK_CANRECURSE |
659 LK_NOWAIT, curthread);
663 unlock_and_deallocate(&fs);
664 error = vget(vp, locked | LK_RETRY |
665 LK_CANRECURSE, curthread);
669 ("vm_fault: vget failed"));
674 KASSERT(fs.vp == NULL || !fs.map->system_map,
675 ("vm_fault: vnode-backed object mapped by system map"));
678 * now we find out if any other pages should be paged
679 * in at this time this routine checks to see if the
680 * pages surrounding this fault reside in the same
681 * object as the page for this fault. If they do,
682 * then they are faulted in also into the object. The
683 * array "marray" returned contains an array of
684 * vm_page_t structs where one of them is the
685 * vm_page_t passed to the routine. The reqpage
686 * return value is the index into the marray for the
687 * vm_page_t passed to the routine.
689 * fs.m plus the additional pages are exclusive busied.
691 faultcount = vm_fault_additional_pages(
692 fs.m, behind, ahead, marray, &reqpage);
695 vm_pager_get_pages(fs.object, marray, faultcount,
696 reqpage) : VM_PAGER_FAIL;
698 if (rv == VM_PAGER_OK) {
700 * Found the page. Leave it busy while we play
705 * Relookup in case pager changed page. Pager
706 * is responsible for disposition of old page
709 fs.m = vm_page_lookup(fs.object, fs.pindex);
711 unlock_and_deallocate(&fs);
716 break; /* break to PAGE HAS BEEN FOUND */
719 * Remove the bogus page (which does not exist at this
720 * object/offset); before doing so, we must get back
721 * our object lock to preserve our invariant.
723 * Also wake up any other process that may want to bring
726 * If this is the top-level object, we must leave the
727 * busy page to prevent another process from rushing
728 * past us, and inserting the page in that object at
729 * the same time that we are.
731 if (rv == VM_PAGER_ERROR)
732 printf("vm_fault: pager read error, pid %d (%s)\n",
733 curproc->p_pid, curproc->p_comm);
735 * Data outside the range of the pager or an I/O error
738 * XXX - the check for kernel_map is a kludge to work
739 * around having the machine panic on a kernel space
740 * fault w/ I/O error.
742 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
743 (rv == VM_PAGER_BAD)) {
746 vm_page_unlock(fs.m);
748 unlock_and_deallocate(&fs);
749 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
751 if (fs.object != fs.first_object) {
754 vm_page_unlock(fs.m);
757 * XXX - we cannot just fall out at this
758 * point, m has been freed and is invalid!
764 * We get here if the object has default pager (or unwiring)
765 * or the pager doesn't have the page.
767 if (fs.object == fs.first_object)
771 * Move on to the next object. Lock the next object before
772 * unlocking the current one.
774 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
775 next_object = fs.object->backing_object;
776 if (next_object == NULL) {
778 * If there's no object left, fill the page in the top
781 if (fs.object != fs.first_object) {
782 vm_object_pip_wakeup(fs.object);
783 VM_OBJECT_WUNLOCK(fs.object);
785 fs.object = fs.first_object;
786 fs.pindex = fs.first_pindex;
788 VM_OBJECT_WLOCK(fs.object);
793 * Zero the page if necessary and mark it valid.
795 if ((fs.m->flags & PG_ZERO) == 0) {
796 pmap_zero_page(fs.m);
798 PCPU_INC(cnt.v_ozfod);
800 PCPU_INC(cnt.v_zfod);
801 fs.m->valid = VM_PAGE_BITS_ALL;
802 /* Don't try to prefault neighboring pages. */
804 break; /* break to PAGE HAS BEEN FOUND */
806 KASSERT(fs.object != next_object,
807 ("object loop %p", next_object));
808 VM_OBJECT_WLOCK(next_object);
809 vm_object_pip_add(next_object, 1);
810 if (fs.object != fs.first_object)
811 vm_object_pip_wakeup(fs.object);
812 VM_OBJECT_WUNLOCK(fs.object);
813 fs.object = next_object;
817 vm_page_assert_xbusied(fs.m);
820 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
825 * If the page is being written, but isn't already owned by the
826 * top-level object, we have to copy it into a new page owned by the
829 if (fs.object != fs.first_object) {
831 * We only really need to copy if we want to write it.
833 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
835 * This allows pages to be virtually copied from a
836 * backing_object into the first_object, where the
837 * backing object has no other refs to it, and cannot
838 * gain any more refs. Instead of a bcopy, we just
839 * move the page from the backing object to the
840 * first object. Note that we must mark the page
841 * dirty in the first object so that it will go out
842 * to swap when needed.
844 is_first_object_locked = FALSE;
847 * Only one shadow object
849 (fs.object->shadow_count == 1) &&
851 * No COW refs, except us
853 (fs.object->ref_count == 1) &&
855 * No one else can look this object up
857 (fs.object->handle == NULL) &&
859 * No other ways to look the object up
861 ((fs.object->type == OBJT_DEFAULT) ||
862 (fs.object->type == OBJT_SWAP)) &&
863 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
865 * We don't chase down the shadow chain
867 fs.object == fs.first_object->backing_object) {
869 * get rid of the unnecessary page
871 vm_page_lock(fs.first_m);
872 vm_page_free(fs.first_m);
873 vm_page_unlock(fs.first_m);
875 * grab the page and put it into the
876 * process'es object. The page is
877 * automatically made dirty.
879 if (vm_page_rename(fs.m, fs.first_object,
881 unlock_and_deallocate(&fs);
884 #if VM_NRESERVLEVEL > 0
886 * Rename the reservation.
888 vm_reserv_rename(fs.m, fs.first_object,
889 fs.object, OFF_TO_IDX(
890 fs.first_object->backing_object_offset));
895 PCPU_INC(cnt.v_cow_optim);
898 * Oh, well, lets copy it.
900 pmap_copy_page(fs.m, fs.first_m);
901 fs.first_m->valid = VM_PAGE_BITS_ALL;
902 if (wired && (fault_flags &
903 VM_FAULT_WIRE) == 0) {
904 vm_page_lock(fs.first_m);
905 vm_page_wire(fs.first_m);
906 vm_page_unlock(fs.first_m);
909 vm_page_unwire(fs.m, FALSE);
910 vm_page_unlock(fs.m);
913 * We no longer need the old page or object.
918 * fs.object != fs.first_object due to above
921 vm_object_pip_wakeup(fs.object);
922 VM_OBJECT_WUNLOCK(fs.object);
924 * Only use the new page below...
926 fs.object = fs.first_object;
927 fs.pindex = fs.first_pindex;
929 if (!is_first_object_locked)
930 VM_OBJECT_WLOCK(fs.object);
931 PCPU_INC(cnt.v_cow_faults);
934 prot &= ~VM_PROT_WRITE;
939 * We must verify that the maps have not changed since our last
942 if (!fs.lookup_still_valid) {
943 vm_object_t retry_object;
944 vm_pindex_t retry_pindex;
945 vm_prot_t retry_prot;
947 if (!vm_map_trylock_read(fs.map)) {
949 unlock_and_deallocate(&fs);
952 fs.lookup_still_valid = TRUE;
953 if (fs.map->timestamp != fs.map_generation) {
954 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
955 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
958 * If we don't need the page any longer, put it on the inactive
959 * list (the easiest thing to do here). If no one needs it,
960 * pageout will grab it eventually.
962 if (result != KERN_SUCCESS) {
964 unlock_and_deallocate(&fs);
967 * If retry of map lookup would have blocked then
968 * retry fault from start.
970 if (result == KERN_FAILURE)
974 if ((retry_object != fs.first_object) ||
975 (retry_pindex != fs.first_pindex)) {
977 unlock_and_deallocate(&fs);
982 * Check whether the protection has changed or the object has
983 * been copied while we left the map unlocked. Changing from
984 * read to write permission is OK - we leave the page
985 * write-protected, and catch the write fault. Changing from
986 * write to read permission means that we can't mark the page
987 * write-enabled after all.
993 * If the page was filled by a pager, update the map entry's
994 * last read offset. Since the pager does not return the
995 * actual set of pages that it read, this update is based on
996 * the requested set. Typically, the requested and actual
999 * XXX The following assignment modifies the map
1000 * without holding a write lock on it.
1003 fs.entry->next_read = fs.pindex + faultcount - reqpage;
1005 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, true);
1006 vm_page_assert_xbusied(fs.m);
1009 * Page must be completely valid or it is not fit to
1010 * map into user space. vm_pager_get_pages() ensures this.
1012 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
1013 ("vm_fault: page %p partially invalid", fs.m));
1014 VM_OBJECT_WUNLOCK(fs.object);
1017 * Put this page into the physical map. We had to do the unlock above
1018 * because pmap_enter() may sleep. We don't put the page
1019 * back on the active queue until later so that the pageout daemon
1020 * won't find it (yet).
1022 pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
1023 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
1024 if (faultcount != 1 && (fault_flags & VM_FAULT_WIRE) == 0 &&
1026 vm_fault_prefault(&fs, vaddr, faultcount, reqpage);
1027 VM_OBJECT_WLOCK(fs.object);
1031 * If the page is not wired down, then put it where the pageout daemon
1034 if ((fault_flags & VM_FAULT_WIRE) != 0) {
1035 KASSERT(wired, ("VM_FAULT_WIRE && !wired"));
1038 vm_page_activate(fs.m);
1039 if (m_hold != NULL) {
1043 vm_page_unlock(fs.m);
1044 vm_page_xunbusy(fs.m);
1047 * Unlock everything, and return
1049 unlock_and_deallocate(&fs);
1051 PCPU_INC(cnt.v_io_faults);
1052 curthread->td_ru.ru_majflt++;
1054 curthread->td_ru.ru_minflt++;
1056 return (KERN_SUCCESS);
1060 * Speed up the reclamation of up to "distance" pages that precede the
1061 * faulting pindex within the first object of the shadow chain.
1064 vm_fault_cache_behind(const struct faultstate *fs, int distance)
1066 vm_object_t first_object, object;
1067 vm_page_t m, m_prev;
1070 object = fs->object;
1071 VM_OBJECT_ASSERT_WLOCKED(object);
1072 first_object = fs->first_object;
1073 if (first_object != object) {
1074 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1075 VM_OBJECT_WUNLOCK(object);
1076 VM_OBJECT_WLOCK(first_object);
1077 VM_OBJECT_WLOCK(object);
1080 /* Neither fictitious nor unmanaged pages can be cached. */
1081 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1082 if (fs->first_pindex < distance)
1085 pindex = fs->first_pindex - distance;
1086 if (pindex < OFF_TO_IDX(fs->entry->offset))
1087 pindex = OFF_TO_IDX(fs->entry->offset);
1088 m = first_object != object ? fs->first_m : fs->m;
1089 vm_page_assert_xbusied(m);
1090 m_prev = vm_page_prev(m);
1091 while ((m = m_prev) != NULL && m->pindex >= pindex &&
1092 m->valid == VM_PAGE_BITS_ALL) {
1093 m_prev = vm_page_prev(m);
1094 if (vm_page_busied(m))
1097 if (m->hold_count == 0 && m->wire_count == 0) {
1099 vm_page_aflag_clear(m, PGA_REFERENCED);
1101 vm_page_deactivate(m);
1108 if (first_object != object)
1109 VM_OBJECT_WUNLOCK(first_object);
1113 * vm_fault_prefault provides a quick way of clustering
1114 * pagefaults into a processes address space. It is a "cousin"
1115 * of vm_map_pmap_enter, except it runs at page fault time instead
1119 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1120 int faultcount, int reqpage)
1123 vm_map_entry_t entry;
1124 vm_object_t backing_object, lobject;
1125 vm_offset_t addr, starta;
1128 int backward, forward, i;
1130 pmap = fs->map->pmap;
1131 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1134 if (faultcount > 0) {
1136 forward = faultcount - reqpage - 1;
1143 if (addra < backward * PAGE_SIZE) {
1144 starta = entry->start;
1146 starta = addra - backward * PAGE_SIZE;
1147 if (starta < entry->start)
1148 starta = entry->start;
1152 * Generate the sequence of virtual addresses that are candidates for
1153 * prefaulting in an outward spiral from the faulting virtual address,
1154 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra
1155 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1156 * If the candidate address doesn't have a backing physical page, then
1157 * the loop immediately terminates.
1159 for (i = 0; i < 2 * imax(backward, forward); i++) {
1160 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1162 if (addr > addra + forward * PAGE_SIZE)
1165 if (addr < starta || addr >= entry->end)
1168 if (!pmap_is_prefaultable(pmap, addr))
1171 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1172 lobject = entry->object.vm_object;
1173 VM_OBJECT_RLOCK(lobject);
1174 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1175 lobject->type == OBJT_DEFAULT &&
1176 (backing_object = lobject->backing_object) != NULL) {
1177 KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1178 0, ("vm_fault_prefault: unaligned object offset"));
1179 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1180 VM_OBJECT_RLOCK(backing_object);
1181 VM_OBJECT_RUNLOCK(lobject);
1182 lobject = backing_object;
1185 VM_OBJECT_RUNLOCK(lobject);
1188 if (m->valid == VM_PAGE_BITS_ALL &&
1189 (m->flags & PG_FICTITIOUS) == 0)
1190 pmap_enter_quick(pmap, addr, m, entry->protection);
1191 VM_OBJECT_RUNLOCK(lobject);
1196 * Hold each of the physical pages that are mapped by the specified range of
1197 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1198 * and allow the specified types of access, "prot". If all of the implied
1199 * pages are successfully held, then the number of held pages is returned
1200 * together with pointers to those pages in the array "ma". However, if any
1201 * of the pages cannot be held, -1 is returned.
1204 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1205 vm_prot_t prot, vm_page_t *ma, int max_count)
1207 vm_offset_t end, va;
1210 boolean_t pmap_failed;
1214 end = round_page(addr + len);
1215 addr = trunc_page(addr);
1218 * Check for illegal addresses.
1220 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1223 if (atop(end - addr) > max_count)
1224 panic("vm_fault_quick_hold_pages: count > max_count");
1225 count = atop(end - addr);
1228 * Most likely, the physical pages are resident in the pmap, so it is
1229 * faster to try pmap_extract_and_hold() first.
1231 pmap_failed = FALSE;
1232 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1233 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1236 else if ((prot & VM_PROT_WRITE) != 0 &&
1237 (*mp)->dirty != VM_PAGE_BITS_ALL) {
1239 * Explicitly dirty the physical page. Otherwise, the
1240 * caller's changes may go unnoticed because they are
1241 * performed through an unmanaged mapping or by a DMA
1244 * The object lock is not held here.
1245 * See vm_page_clear_dirty_mask().
1252 * One or more pages could not be held by the pmap. Either no
1253 * page was mapped at the specified virtual address or that
1254 * mapping had insufficient permissions. Attempt to fault in
1255 * and hold these pages.
1257 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1258 if (*mp == NULL && vm_fault_hold(map, va, prot,
1259 VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1264 for (mp = ma; mp < ma + count; mp++)
1267 vm_page_unhold(*mp);
1268 vm_page_unlock(*mp);
1275 * vm_fault_copy_entry
1277 * Create new shadow object backing dst_entry with private copy of
1278 * all underlying pages. When src_entry is equal to dst_entry,
1279 * function implements COW for wired-down map entry. Otherwise,
1280 * it forks wired entry into dst_map.
1282 * In/out conditions:
1283 * The source and destination maps must be locked for write.
1284 * The source map entry must be wired down (or be a sharing map
1285 * entry corresponding to a main map entry that is wired down).
1288 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1289 vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1290 vm_ooffset_t *fork_charge)
1292 vm_object_t backing_object, dst_object, object, src_object;
1293 vm_pindex_t dst_pindex, pindex, src_pindex;
1294 vm_prot_t access, prot;
1304 upgrade = src_entry == dst_entry;
1305 access = prot = dst_entry->protection;
1307 src_object = src_entry->object.vm_object;
1308 src_pindex = OFF_TO_IDX(src_entry->offset);
1310 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1311 dst_object = src_object;
1312 vm_object_reference(dst_object);
1315 * Create the top-level object for the destination entry. (Doesn't
1316 * actually shadow anything - we copy the pages directly.)
1318 dst_object = vm_object_allocate(OBJT_DEFAULT,
1319 OFF_TO_IDX(dst_entry->end - dst_entry->start));
1320 #if VM_NRESERVLEVEL > 0
1321 dst_object->flags |= OBJ_COLORED;
1322 dst_object->pg_color = atop(dst_entry->start);
1326 VM_OBJECT_WLOCK(dst_object);
1327 KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1328 ("vm_fault_copy_entry: vm_object not NULL"));
1329 if (src_object != dst_object) {
1330 dst_entry->object.vm_object = dst_object;
1331 dst_entry->offset = 0;
1332 dst_object->charge = dst_entry->end - dst_entry->start;
1334 if (fork_charge != NULL) {
1335 KASSERT(dst_entry->cred == NULL,
1336 ("vm_fault_copy_entry: leaked swp charge"));
1337 dst_object->cred = curthread->td_ucred;
1338 crhold(dst_object->cred);
1339 *fork_charge += dst_object->charge;
1340 } else if (dst_object->cred == NULL) {
1341 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1343 dst_object->cred = dst_entry->cred;
1344 dst_entry->cred = NULL;
1348 * If not an upgrade, then enter the mappings in the pmap as
1349 * read and/or execute accesses. Otherwise, enter them as
1352 * A writeable large page mapping is only created if all of
1353 * the constituent small page mappings are modified. Marking
1354 * PTEs as modified on inception allows promotion to happen
1355 * without taking potentially large number of soft faults.
1358 access &= ~VM_PROT_WRITE;
1361 * Loop through all of the virtual pages within the entry's
1362 * range, copying each page from the source object to the
1363 * destination object. Since the source is wired, those pages
1364 * must exist. In contrast, the destination is pageable.
1365 * Since the destination object does share any backing storage
1366 * with the source object, all of its pages must be dirtied,
1367 * regardless of whether they can be written.
1369 for (vaddr = dst_entry->start, dst_pindex = 0;
1370 vaddr < dst_entry->end;
1371 vaddr += PAGE_SIZE, dst_pindex++) {
1374 * Find the page in the source object, and copy it in.
1375 * Because the source is wired down, the page will be
1378 if (src_object != dst_object)
1379 VM_OBJECT_RLOCK(src_object);
1380 object = src_object;
1381 pindex = src_pindex + dst_pindex;
1382 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1383 (backing_object = object->backing_object) != NULL) {
1385 * Unless the source mapping is read-only or
1386 * it is presently being upgraded from
1387 * read-only, the first object in the shadow
1388 * chain should provide all of the pages. In
1389 * other words, this loop body should never be
1390 * executed when the source mapping is already
1393 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1395 ("vm_fault_copy_entry: main object missing page"));
1397 VM_OBJECT_RLOCK(backing_object);
1398 pindex += OFF_TO_IDX(object->backing_object_offset);
1399 if (object != dst_object)
1400 VM_OBJECT_RUNLOCK(object);
1401 object = backing_object;
1403 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1405 if (object != dst_object) {
1407 * Allocate a page in the destination object.
1409 dst_m = vm_page_alloc(dst_object, (src_object ==
1410 dst_object ? src_pindex : 0) + dst_pindex,
1412 if (dst_m == NULL) {
1413 VM_OBJECT_WUNLOCK(dst_object);
1414 VM_OBJECT_RUNLOCK(object);
1416 VM_OBJECT_WLOCK(dst_object);
1419 pmap_copy_page(src_m, dst_m);
1420 VM_OBJECT_RUNLOCK(object);
1421 dst_m->valid = VM_PAGE_BITS_ALL;
1422 dst_m->dirty = VM_PAGE_BITS_ALL;
1425 if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1427 vm_page_xbusy(dst_m);
1428 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL,
1429 ("invalid dst page %p", dst_m));
1431 VM_OBJECT_WUNLOCK(dst_object);
1434 * Enter it in the pmap. If a wired, copy-on-write
1435 * mapping is being replaced by a write-enabled
1436 * mapping, then wire that new mapping.
1438 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1439 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1442 * Mark it no longer busy, and put it on the active list.
1444 VM_OBJECT_WLOCK(dst_object);
1447 if (src_m != dst_m) {
1448 vm_page_lock(src_m);
1449 vm_page_unwire(src_m, 0);
1450 vm_page_unlock(src_m);
1451 vm_page_lock(dst_m);
1452 vm_page_wire(dst_m);
1453 vm_page_unlock(dst_m);
1455 KASSERT(dst_m->wire_count > 0,
1456 ("dst_m %p is not wired", dst_m));
1459 vm_page_lock(dst_m);
1460 vm_page_activate(dst_m);
1461 vm_page_unlock(dst_m);
1463 vm_page_xunbusy(dst_m);
1465 VM_OBJECT_WUNLOCK(dst_object);
1467 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1468 vm_object_deallocate(src_object);
1474 * This routine checks around the requested page for other pages that
1475 * might be able to be faulted in. This routine brackets the viable
1476 * pages for the pages to be paged in.
1479 * m, rbehind, rahead
1482 * marray (array of vm_page_t), reqpage (index of requested page)
1485 * number of pages in marray
1488 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1497 vm_pindex_t pindex, startpindex, endpindex, tpindex;
1499 int cbehind, cahead;
1501 VM_OBJECT_ASSERT_WLOCKED(m->object);
1505 cbehind = cahead = 0;
1508 * if the requested page is not available, then give up now
1510 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1514 if ((cbehind == 0) && (cahead == 0)) {
1520 if (rahead > cahead) {
1524 if (rbehind > cbehind) {
1529 * scan backward for the read behind pages -- in memory
1532 if (rbehind > pindex) {
1536 startpindex = pindex - rbehind;
1539 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL &&
1540 rtm->pindex >= startpindex)
1541 startpindex = rtm->pindex + 1;
1543 /* tpindex is unsigned; beware of numeric underflow. */
1544 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex &&
1545 tpindex < pindex; i++, tpindex--) {
1547 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1548 VM_ALLOC_IFNOTCACHED);
1551 * Shift the allocated pages to the
1552 * beginning of the array.
1554 for (j = 0; j < i; j++) {
1555 marray[j] = marray[j + tpindex + 1 -
1561 marray[tpindex - startpindex] = rtm;
1569 /* page offset of the required page */
1572 tpindex = pindex + 1;
1576 * scan forward for the read ahead pages
1578 endpindex = tpindex + rahead;
1579 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex)
1580 endpindex = rtm->pindex;
1581 if (endpindex > object->size)
1582 endpindex = object->size;
1584 for (; tpindex < endpindex; i++, tpindex++) {
1586 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1587 VM_ALLOC_IFNOTCACHED);
1595 /* return number of pages */
1600 * Block entry into the machine-independent layer's page fault handler by
1601 * the calling thread. Subsequent calls to vm_fault() by that thread will
1602 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of
1603 * spurious page faults.
1606 vm_fault_disable_pagefaults(void)
1609 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1613 vm_fault_enable_pagefaults(int save)
1616 curthread_pflags_restore(save);