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;
130 static void vm_fault_cache_behind(const struct faultstate *fs, int distance);
131 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
132 int faultcount, int reqpage);
135 release_page(struct faultstate *fs)
138 vm_page_xunbusy(fs->m);
140 vm_page_deactivate(fs->m);
141 vm_page_unlock(fs->m);
146 unlock_map(struct faultstate *fs)
149 if (fs->lookup_still_valid) {
150 vm_map_lookup_done(fs->map, fs->entry);
151 fs->lookup_still_valid = FALSE;
156 unlock_and_deallocate(struct faultstate *fs)
159 vm_object_pip_wakeup(fs->object);
160 VM_OBJECT_WUNLOCK(fs->object);
161 if (fs->object != fs->first_object) {
162 VM_OBJECT_WLOCK(fs->first_object);
163 vm_page_lock(fs->first_m);
164 vm_page_free(fs->first_m);
165 vm_page_unlock(fs->first_m);
166 vm_object_pip_wakeup(fs->first_object);
167 VM_OBJECT_WUNLOCK(fs->first_object);
170 vm_object_deallocate(fs->first_object);
172 if (fs->vp != NULL) {
179 vm_fault_dirty(vm_map_entry_t entry, vm_page_t m, vm_prot_t prot,
180 vm_prot_t fault_type, int fault_flags, boolean_t set_wd)
182 boolean_t need_dirty;
184 if (((prot & VM_PROT_WRITE) == 0 &&
185 (fault_flags & VM_FAULT_DIRTY) == 0) ||
186 (m->oflags & VPO_UNMANAGED) != 0)
189 VM_OBJECT_ASSERT_LOCKED(m->object);
191 need_dirty = ((fault_type & VM_PROT_WRITE) != 0 &&
192 (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) ||
193 (fault_flags & VM_FAULT_DIRTY) != 0;
196 vm_object_set_writeable_dirty(m->object);
199 * If two callers of vm_fault_dirty() with set_wd ==
200 * FALSE, one for the map entry with MAP_ENTRY_NOSYNC
201 * flag set, other with flag clear, race, it is
202 * possible for the no-NOSYNC thread to see m->dirty
203 * != 0 and not clear VPO_NOSYNC. Take vm_page lock
204 * around manipulation of VPO_NOSYNC and
205 * vm_page_dirty() call, to avoid the race and keep
206 * m->oflags consistent.
211 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
212 * if the page is already dirty to prevent data written with
213 * the expectation of being synced from not being synced.
214 * Likewise if this entry does not request NOSYNC then make
215 * sure the page isn't marked NOSYNC. Applications sharing
216 * data should use the same flags to avoid ping ponging.
218 if ((entry->eflags & MAP_ENTRY_NOSYNC) != 0) {
220 m->oflags |= VPO_NOSYNC;
223 m->oflags &= ~VPO_NOSYNC;
227 * If the fault is a write, we know that this page is being
228 * written NOW so dirty it explicitly to save on
229 * pmap_is_modified() calls later.
231 * Also tell the backing pager, if any, that it should remove
232 * any swap backing since the page is now dirty.
239 vm_pager_page_unswapped(m);
243 * TRYPAGER - used by vm_fault to calculate whether the pager for the
244 * current object *might* contain the page.
246 * default objects are zero-fill, there is no real pager.
248 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \
249 ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 || wired))
254 * Handle a page fault occurring at the given address,
255 * requiring the given permissions, in the map specified.
256 * If successful, the page is inserted into the
257 * associated physical map.
259 * NOTE: the given address should be truncated to the
260 * proper page address.
262 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
263 * a standard error specifying why the fault is fatal is returned.
265 * The map in question must be referenced, and remains so.
266 * Caller may hold no locks.
269 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
276 if ((td->td_pflags & TDP_NOFAULTING) != 0)
277 return (KERN_PROTECTION_FAILURE);
279 if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
280 ktrfault(vaddr, fault_type);
282 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
285 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
292 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
293 int fault_flags, vm_page_t *m_hold)
297 int alloc_req, era, faultcount, nera, reqpage, result;
298 boolean_t growstack, is_first_object_locked, wired;
300 vm_object_t next_object;
301 vm_page_t marray[VM_FAULT_READ_MAX];
303 struct faultstate fs;
310 PCPU_INC(cnt.v_vm_faults);
312 faultcount = reqpage = 0;
317 * Find the backing store object and offset into it to begin the
321 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
322 &fs.first_object, &fs.first_pindex, &prot, &wired);
323 if (result != KERN_SUCCESS) {
324 if (growstack && result == KERN_INVALID_ADDRESS &&
326 result = vm_map_growstack(curproc, vaddr);
327 if (result != KERN_SUCCESS)
328 return (KERN_FAILURE);
335 map_generation = fs.map->timestamp;
337 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
338 panic("vm_fault: fault on nofault entry, addr: %lx",
342 if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
343 fs.entry->wiring_thread != curthread) {
344 vm_map_unlock_read(fs.map);
346 if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
347 (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
352 fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
353 vm_map_unlock_and_wait(fs.map, 0);
355 vm_map_unlock(fs.map);
360 fault_type = prot | (fault_type & VM_PROT_COPY);
362 if (fs.vp == NULL /* avoid locked vnode leak */ &&
363 (fault_flags & (VM_FAULT_CHANGE_WIRING | VM_FAULT_DIRTY)) == 0 &&
364 /* avoid calling vm_object_set_writeable_dirty() */
365 ((prot & VM_PROT_WRITE) == 0 ||
366 (fs.first_object->type != OBJT_VNODE &&
367 (fs.first_object->flags & OBJ_TMPFS_NODE) == 0) ||
368 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) != 0)) {
369 VM_OBJECT_RLOCK(fs.first_object);
370 if ((prot & VM_PROT_WRITE) != 0 &&
371 (fs.first_object->type == OBJT_VNODE ||
372 (fs.first_object->flags & OBJ_TMPFS_NODE) != 0) &&
373 (fs.first_object->flags & OBJ_MIGHTBEDIRTY) == 0)
375 m = vm_page_lookup(fs.first_object, fs.first_pindex);
376 /* A busy page can be mapped for read|execute access. */
377 if (m == NULL || ((prot & VM_PROT_WRITE) != 0 &&
378 vm_page_busied(m)) || m->valid != VM_PAGE_BITS_ALL)
380 result = pmap_enter(fs.map->pmap, vaddr, m, prot,
381 fault_type | PMAP_ENTER_NOSLEEP | (wired ? PMAP_ENTER_WIRED :
383 if (result != KERN_SUCCESS)
385 if (m_hold != NULL) {
391 vm_fault_dirty(fs.entry, m, prot, fault_type, fault_flags,
393 VM_OBJECT_RUNLOCK(fs.first_object);
395 vm_fault_prefault(&fs, vaddr, 0, 0);
396 vm_map_lookup_done(fs.map, fs.entry);
397 curthread->td_ru.ru_minflt++;
398 return (KERN_SUCCESS);
400 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
401 VM_OBJECT_RUNLOCK(fs.first_object);
402 VM_OBJECT_WLOCK(fs.first_object);
405 VM_OBJECT_WLOCK(fs.first_object);
409 * Make a reference to this object to prevent its disposal while we
410 * are messing with it. Once we have the reference, the map is free
411 * to be diddled. Since objects reference their shadows (and copies),
412 * they will stay around as well.
414 * Bump the paging-in-progress count to prevent size changes (e.g.
415 * truncation operations) during I/O. This must be done after
416 * obtaining the vnode lock in order to avoid possible deadlocks.
418 vm_object_reference_locked(fs.first_object);
419 vm_object_pip_add(fs.first_object, 1);
421 fs.lookup_still_valid = TRUE;
426 * Search for the page at object/offset.
428 fs.object = fs.first_object;
429 fs.pindex = fs.first_pindex;
432 * If the object is dead, we stop here
434 if (fs.object->flags & OBJ_DEAD) {
435 unlock_and_deallocate(&fs);
436 return (KERN_PROTECTION_FAILURE);
440 * See if page is resident
442 fs.m = vm_page_lookup(fs.object, fs.pindex);
445 * Wait/Retry if the page is busy. We have to do this
446 * if the page is either exclusive or shared busy
447 * because the vm_pager may be using read busy for
448 * pageouts (and even pageins if it is the vnode
449 * pager), and we could end up trying to pagein and
450 * pageout the same page simultaneously.
452 * We can theoretically allow the busy case on a read
453 * fault if the page is marked valid, but since such
454 * pages are typically already pmap'd, putting that
455 * special case in might be more effort then it is
456 * worth. We cannot under any circumstances mess
457 * around with a shared busied page except, perhaps,
460 if (vm_page_busied(fs.m)) {
462 * Reference the page before unlocking and
463 * sleeping so that the page daemon is less
464 * likely to reclaim it.
466 vm_page_aflag_set(fs.m, PGA_REFERENCED);
467 if (fs.object != fs.first_object) {
468 if (!VM_OBJECT_TRYWLOCK(
470 VM_OBJECT_WUNLOCK(fs.object);
471 VM_OBJECT_WLOCK(fs.first_object);
472 VM_OBJECT_WLOCK(fs.object);
474 vm_page_lock(fs.first_m);
475 vm_page_free(fs.first_m);
476 vm_page_unlock(fs.first_m);
477 vm_object_pip_wakeup(fs.first_object);
478 VM_OBJECT_WUNLOCK(fs.first_object);
482 if (fs.m == vm_page_lookup(fs.object,
484 vm_page_sleep_if_busy(fs.m, "vmpfw");
486 vm_object_pip_wakeup(fs.object);
487 VM_OBJECT_WUNLOCK(fs.object);
488 PCPU_INC(cnt.v_intrans);
489 vm_object_deallocate(fs.first_object);
493 vm_page_remque(fs.m);
494 vm_page_unlock(fs.m);
497 * Mark page busy for other processes, and the
498 * pagedaemon. If it still isn't completely valid
499 * (readable), jump to readrest, else break-out ( we
503 if (fs.m->valid != VM_PAGE_BITS_ALL)
509 * Page is not resident, If this is the search termination
510 * or the pager might contain the page, allocate a new page.
512 if (TRYPAGER || fs.object == fs.first_object) {
513 if (fs.pindex >= fs.object->size) {
514 unlock_and_deallocate(&fs);
515 return (KERN_PROTECTION_FAILURE);
519 * Allocate a new page for this object/offset pair.
521 * Unlocked read of the p_flag is harmless. At
522 * worst, the P_KILLED might be not observed
523 * there, and allocation can fail, causing
524 * restart and new reading of the p_flag.
527 if (!vm_page_count_severe() || P_KILLED(curproc)) {
528 #if VM_NRESERVLEVEL > 0
529 if ((fs.object->flags & OBJ_COLORED) == 0) {
530 fs.object->flags |= OBJ_COLORED;
531 fs.object->pg_color = atop(vaddr) -
535 alloc_req = P_KILLED(curproc) ?
536 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
537 if (fs.object->type != OBJT_VNODE &&
538 fs.object->backing_object == NULL)
539 alloc_req |= VM_ALLOC_ZERO;
540 fs.m = vm_page_alloc(fs.object, fs.pindex,
544 unlock_and_deallocate(&fs);
547 } else if (fs.m->valid == VM_PAGE_BITS_ALL)
553 * We have found a valid page or we have allocated a new page.
554 * The page thus may not be valid or may not be entirely
557 * Attempt to fault-in the page if there is a chance that the
558 * pager has it, and potentially fault in additional pages
563 u_char behavior = vm_map_entry_behavior(fs.entry);
565 if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
569 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
571 ahead = atop(fs.entry->end - vaddr) - 1;
572 if (ahead > VM_FAULT_READ_AHEAD_MAX)
573 ahead = VM_FAULT_READ_AHEAD_MAX;
574 if (fs.pindex == fs.entry->next_read)
575 vm_fault_cache_behind(&fs,
579 * If this is a sequential page fault, then
580 * arithmetically increase the number of pages
581 * in the read-ahead window. Otherwise, reset
582 * the read-ahead window to its smallest size.
584 behind = atop(vaddr - fs.entry->start);
585 if (behind > VM_FAULT_READ_BEHIND)
586 behind = VM_FAULT_READ_BEHIND;
587 ahead = atop(fs.entry->end - vaddr) - 1;
588 era = fs.entry->read_ahead;
589 if (fs.pindex == fs.entry->next_read) {
591 if (nera > VM_FAULT_READ_AHEAD_MAX)
592 nera = VM_FAULT_READ_AHEAD_MAX;
596 if (era == VM_FAULT_READ_AHEAD_MAX)
597 vm_fault_cache_behind(&fs,
598 VM_FAULT_CACHE_BEHIND);
599 } else if (ahead > VM_FAULT_READ_AHEAD_MIN)
600 ahead = VM_FAULT_READ_AHEAD_MIN;
602 fs.entry->read_ahead = ahead;
606 * Call the pager to retrieve the data, if any, after
607 * releasing the lock on the map. We hold a ref on
608 * fs.object and the pages are exclusive busied.
612 if (fs.object->type == OBJT_VNODE) {
613 vp = fs.object->handle;
616 else if (fs.vp != NULL) {
620 locked = VOP_ISLOCKED(vp);
622 if (locked != LK_EXCLUSIVE)
624 /* Do not sleep for vnode lock while fs.m is busy */
625 error = vget(vp, locked | LK_CANRECURSE |
626 LK_NOWAIT, curthread);
630 unlock_and_deallocate(&fs);
631 error = vget(vp, locked | LK_RETRY |
632 LK_CANRECURSE, curthread);
636 ("vm_fault: vget failed"));
642 KASSERT(fs.vp == NULL || !fs.map->system_map,
643 ("vm_fault: vnode-backed object mapped by system map"));
646 * now we find out if any other pages should be paged
647 * in at this time this routine checks to see if the
648 * pages surrounding this fault reside in the same
649 * object as the page for this fault. If they do,
650 * then they are faulted in also into the object. The
651 * array "marray" returned contains an array of
652 * vm_page_t structs where one of them is the
653 * vm_page_t passed to the routine. The reqpage
654 * return value is the index into the marray for the
655 * vm_page_t passed to the routine.
657 * fs.m plus the additional pages are exclusive busied.
659 faultcount = vm_fault_additional_pages(
660 fs.m, behind, ahead, marray, &reqpage);
663 vm_pager_get_pages(fs.object, marray, faultcount,
664 reqpage) : VM_PAGER_FAIL;
666 if (rv == VM_PAGER_OK) {
668 * Found the page. Leave it busy while we play
673 * Relookup in case pager changed page. Pager
674 * is responsible for disposition of old page
677 fs.m = vm_page_lookup(fs.object, fs.pindex);
679 unlock_and_deallocate(&fs);
684 break; /* break to PAGE HAS BEEN FOUND */
687 * Remove the bogus page (which does not exist at this
688 * object/offset); before doing so, we must get back
689 * our object lock to preserve our invariant.
691 * Also wake up any other process that may want to bring
694 * If this is the top-level object, we must leave the
695 * busy page to prevent another process from rushing
696 * past us, and inserting the page in that object at
697 * the same time that we are.
699 if (rv == VM_PAGER_ERROR)
700 printf("vm_fault: pager read error, pid %d (%s)\n",
701 curproc->p_pid, curproc->p_comm);
703 * Data outside the range of the pager or an I/O error
706 * XXX - the check for kernel_map is a kludge to work
707 * around having the machine panic on a kernel space
708 * fault w/ I/O error.
710 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
711 (rv == VM_PAGER_BAD)) {
714 vm_page_unlock(fs.m);
716 unlock_and_deallocate(&fs);
717 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
719 if (fs.object != fs.first_object) {
722 vm_page_unlock(fs.m);
725 * XXX - we cannot just fall out at this
726 * point, m has been freed and is invalid!
732 * We get here if the object has default pager (or unwiring)
733 * or the pager doesn't have the page.
735 if (fs.object == fs.first_object)
739 * Move on to the next object. Lock the next object before
740 * unlocking the current one.
742 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
743 next_object = fs.object->backing_object;
744 if (next_object == NULL) {
746 * If there's no object left, fill the page in the top
749 if (fs.object != fs.first_object) {
750 vm_object_pip_wakeup(fs.object);
751 VM_OBJECT_WUNLOCK(fs.object);
753 fs.object = fs.first_object;
754 fs.pindex = fs.first_pindex;
756 VM_OBJECT_WLOCK(fs.object);
761 * Zero the page if necessary and mark it valid.
763 if ((fs.m->flags & PG_ZERO) == 0) {
764 pmap_zero_page(fs.m);
766 PCPU_INC(cnt.v_ozfod);
768 PCPU_INC(cnt.v_zfod);
769 fs.m->valid = VM_PAGE_BITS_ALL;
770 /* Don't try to prefault neighboring pages. */
772 break; /* break to PAGE HAS BEEN FOUND */
774 KASSERT(fs.object != next_object,
775 ("object loop %p", next_object));
776 VM_OBJECT_WLOCK(next_object);
777 vm_object_pip_add(next_object, 1);
778 if (fs.object != fs.first_object)
779 vm_object_pip_wakeup(fs.object);
780 VM_OBJECT_WUNLOCK(fs.object);
781 fs.object = next_object;
785 vm_page_assert_xbusied(fs.m);
788 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
793 * If the page is being written, but isn't already owned by the
794 * top-level object, we have to copy it into a new page owned by the
797 if (fs.object != fs.first_object) {
799 * We only really need to copy if we want to write it.
801 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
803 * This allows pages to be virtually copied from a
804 * backing_object into the first_object, where the
805 * backing object has no other refs to it, and cannot
806 * gain any more refs. Instead of a bcopy, we just
807 * move the page from the backing object to the
808 * first object. Note that we must mark the page
809 * dirty in the first object so that it will go out
810 * to swap when needed.
812 is_first_object_locked = FALSE;
815 * Only one shadow object
817 (fs.object->shadow_count == 1) &&
819 * No COW refs, except us
821 (fs.object->ref_count == 1) &&
823 * No one else can look this object up
825 (fs.object->handle == NULL) &&
827 * No other ways to look the object up
829 ((fs.object->type == OBJT_DEFAULT) ||
830 (fs.object->type == OBJT_SWAP)) &&
831 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
833 * We don't chase down the shadow chain
835 fs.object == fs.first_object->backing_object) {
837 * get rid of the unnecessary page
839 vm_page_lock(fs.first_m);
840 vm_page_free(fs.first_m);
841 vm_page_unlock(fs.first_m);
843 * grab the page and put it into the
844 * process'es object. The page is
845 * automatically made dirty.
847 if (vm_page_rename(fs.m, fs.first_object,
849 unlock_and_deallocate(&fs);
852 #if VM_NRESERVLEVEL > 0
854 * Rename the reservation.
856 vm_reserv_rename(fs.m, fs.first_object,
857 fs.object, OFF_TO_IDX(
858 fs.first_object->backing_object_offset));
863 PCPU_INC(cnt.v_cow_optim);
866 * Oh, well, lets copy it.
868 pmap_copy_page(fs.m, fs.first_m);
869 fs.first_m->valid = VM_PAGE_BITS_ALL;
870 if (wired && (fault_flags &
871 VM_FAULT_CHANGE_WIRING) == 0) {
872 vm_page_lock(fs.first_m);
873 vm_page_wire(fs.first_m);
874 vm_page_unlock(fs.first_m);
877 vm_page_unwire(fs.m, FALSE);
878 vm_page_unlock(fs.m);
881 * We no longer need the old page or object.
886 * fs.object != fs.first_object due to above
889 vm_object_pip_wakeup(fs.object);
890 VM_OBJECT_WUNLOCK(fs.object);
892 * Only use the new page below...
894 fs.object = fs.first_object;
895 fs.pindex = fs.first_pindex;
897 if (!is_first_object_locked)
898 VM_OBJECT_WLOCK(fs.object);
899 PCPU_INC(cnt.v_cow_faults);
902 prot &= ~VM_PROT_WRITE;
907 * We must verify that the maps have not changed since our last
910 if (!fs.lookup_still_valid) {
911 vm_object_t retry_object;
912 vm_pindex_t retry_pindex;
913 vm_prot_t retry_prot;
915 if (!vm_map_trylock_read(fs.map)) {
917 unlock_and_deallocate(&fs);
920 fs.lookup_still_valid = TRUE;
921 if (fs.map->timestamp != map_generation) {
922 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
923 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
926 * If we don't need the page any longer, put it on the inactive
927 * list (the easiest thing to do here). If no one needs it,
928 * pageout will grab it eventually.
930 if (result != KERN_SUCCESS) {
932 unlock_and_deallocate(&fs);
935 * If retry of map lookup would have blocked then
936 * retry fault from start.
938 if (result == KERN_FAILURE)
942 if ((retry_object != fs.first_object) ||
943 (retry_pindex != fs.first_pindex)) {
945 unlock_and_deallocate(&fs);
950 * Check whether the protection has changed or the object has
951 * been copied while we left the map unlocked. Changing from
952 * read to write permission is OK - we leave the page
953 * write-protected, and catch the write fault. Changing from
954 * write to read permission means that we can't mark the page
955 * write-enabled after all.
961 * If the page was filled by a pager, update the map entry's
962 * last read offset. Since the pager does not return the
963 * actual set of pages that it read, this update is based on
964 * the requested set. Typically, the requested and actual
967 * XXX The following assignment modifies the map
968 * without holding a write lock on it.
971 fs.entry->next_read = fs.pindex + faultcount - reqpage;
973 vm_fault_dirty(fs.entry, fs.m, prot, fault_type, fault_flags, TRUE);
974 vm_page_assert_xbusied(fs.m);
977 * Page must be completely valid or it is not fit to
978 * map into user space. vm_pager_get_pages() ensures this.
980 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
981 ("vm_fault: page %p partially invalid", fs.m));
982 VM_OBJECT_WUNLOCK(fs.object);
985 * Put this page into the physical map. We had to do the unlock above
986 * because pmap_enter() may sleep. We don't put the page
987 * back on the active queue until later so that the pageout daemon
988 * won't find it (yet).
990 pmap_enter(fs.map->pmap, vaddr, fs.m, prot,
991 fault_type | (wired ? PMAP_ENTER_WIRED : 0), 0);
992 if (faultcount != 1 && (fault_flags & VM_FAULT_CHANGE_WIRING) == 0 &&
994 vm_fault_prefault(&fs, vaddr, faultcount, reqpage);
995 VM_OBJECT_WLOCK(fs.object);
999 * If the page is not wired down, then put it where the pageout daemon
1002 if (fault_flags & VM_FAULT_CHANGE_WIRING) {
1006 vm_page_unwire(fs.m, 1);
1008 vm_page_activate(fs.m);
1009 if (m_hold != NULL) {
1013 vm_page_unlock(fs.m);
1014 vm_page_xunbusy(fs.m);
1017 * Unlock everything, and return
1019 unlock_and_deallocate(&fs);
1021 PCPU_INC(cnt.v_io_faults);
1022 curthread->td_ru.ru_majflt++;
1024 curthread->td_ru.ru_minflt++;
1026 return (KERN_SUCCESS);
1030 * Speed up the reclamation of up to "distance" pages that precede the
1031 * faulting pindex within the first object of the shadow chain.
1034 vm_fault_cache_behind(const struct faultstate *fs, int distance)
1036 vm_object_t first_object, object;
1037 vm_page_t m, m_prev;
1040 object = fs->object;
1041 VM_OBJECT_ASSERT_WLOCKED(object);
1042 first_object = fs->first_object;
1043 if (first_object != object) {
1044 if (!VM_OBJECT_TRYWLOCK(first_object)) {
1045 VM_OBJECT_WUNLOCK(object);
1046 VM_OBJECT_WLOCK(first_object);
1047 VM_OBJECT_WLOCK(object);
1050 /* Neither fictitious nor unmanaged pages can be cached. */
1051 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1052 if (fs->first_pindex < distance)
1055 pindex = fs->first_pindex - distance;
1056 if (pindex < OFF_TO_IDX(fs->entry->offset))
1057 pindex = OFF_TO_IDX(fs->entry->offset);
1058 m = first_object != object ? fs->first_m : fs->m;
1059 vm_page_assert_xbusied(m);
1060 m_prev = vm_page_prev(m);
1061 while ((m = m_prev) != NULL && m->pindex >= pindex &&
1062 m->valid == VM_PAGE_BITS_ALL) {
1063 m_prev = vm_page_prev(m);
1064 if (vm_page_busied(m))
1067 if (m->hold_count == 0 && m->wire_count == 0) {
1069 vm_page_aflag_clear(m, PGA_REFERENCED);
1071 vm_page_deactivate(m);
1078 if (first_object != object)
1079 VM_OBJECT_WUNLOCK(first_object);
1083 * vm_fault_prefault provides a quick way of clustering
1084 * pagefaults into a processes address space. It is a "cousin"
1085 * of vm_map_pmap_enter, except it runs at page fault time instead
1089 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1090 int faultcount, int reqpage)
1093 vm_map_entry_t entry;
1094 vm_object_t backing_object, lobject;
1095 vm_offset_t addr, starta;
1098 int backward, forward, i;
1100 pmap = fs->map->pmap;
1101 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1104 if (faultcount > 0) {
1106 forward = faultcount - reqpage - 1;
1113 starta = addra - backward * PAGE_SIZE;
1114 if (starta < entry->start) {
1115 starta = entry->start;
1116 } else if (starta > addra) {
1121 * Generate the sequence of virtual addresses that are candidates for
1122 * prefaulting in an outward spiral from the faulting virtual address,
1123 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra
1124 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1125 * If the candidate address doesn't have a backing physical page, then
1126 * the loop immediately terminates.
1128 for (i = 0; i < 2 * imax(backward, forward); i++) {
1129 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1131 if (addr > addra + forward * PAGE_SIZE)
1134 if (addr < starta || addr >= entry->end)
1137 if (!pmap_is_prefaultable(pmap, addr))
1140 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1141 lobject = entry->object.vm_object;
1142 VM_OBJECT_RLOCK(lobject);
1143 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1144 lobject->type == OBJT_DEFAULT &&
1145 (backing_object = lobject->backing_object) != NULL) {
1146 KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1147 0, ("vm_fault_prefault: unaligned object offset"));
1148 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1149 VM_OBJECT_RLOCK(backing_object);
1150 VM_OBJECT_RUNLOCK(lobject);
1151 lobject = backing_object;
1154 VM_OBJECT_RUNLOCK(lobject);
1157 if (m->valid == VM_PAGE_BITS_ALL &&
1158 (m->flags & PG_FICTITIOUS) == 0)
1159 pmap_enter_quick(pmap, addr, m, entry->protection);
1160 VM_OBJECT_RUNLOCK(lobject);
1165 * Hold each of the physical pages that are mapped by the specified range of
1166 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1167 * and allow the specified types of access, "prot". If all of the implied
1168 * pages are successfully held, then the number of held pages is returned
1169 * together with pointers to those pages in the array "ma". However, if any
1170 * of the pages cannot be held, -1 is returned.
1173 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1174 vm_prot_t prot, vm_page_t *ma, int max_count)
1176 vm_offset_t end, va;
1179 boolean_t pmap_failed;
1183 end = round_page(addr + len);
1184 addr = trunc_page(addr);
1187 * Check for illegal addresses.
1189 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1192 if (atop(end - addr) > max_count)
1193 panic("vm_fault_quick_hold_pages: count > max_count");
1194 count = atop(end - addr);
1197 * Most likely, the physical pages are resident in the pmap, so it is
1198 * faster to try pmap_extract_and_hold() first.
1200 pmap_failed = FALSE;
1201 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1202 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1205 else if ((prot & VM_PROT_WRITE) != 0 &&
1206 (*mp)->dirty != VM_PAGE_BITS_ALL) {
1208 * Explicitly dirty the physical page. Otherwise, the
1209 * caller's changes may go unnoticed because they are
1210 * performed through an unmanaged mapping or by a DMA
1213 * The object lock is not held here.
1214 * See vm_page_clear_dirty_mask().
1221 * One or more pages could not be held by the pmap. Either no
1222 * page was mapped at the specified virtual address or that
1223 * mapping had insufficient permissions. Attempt to fault in
1224 * and hold these pages.
1226 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1227 if (*mp == NULL && vm_fault_hold(map, va, prot,
1228 VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1233 for (mp = ma; mp < ma + count; mp++)
1236 vm_page_unhold(*mp);
1237 vm_page_unlock(*mp);
1244 * vm_fault_copy_entry
1246 * Create new shadow object backing dst_entry with private copy of
1247 * all underlying pages. When src_entry is equal to dst_entry,
1248 * function implements COW for wired-down map entry. Otherwise,
1249 * it forks wired entry into dst_map.
1251 * In/out conditions:
1252 * The source and destination maps must be locked for write.
1253 * The source map entry must be wired down (or be a sharing map
1254 * entry corresponding to a main map entry that is wired down).
1257 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1258 vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1259 vm_ooffset_t *fork_charge)
1261 vm_object_t backing_object, dst_object, object, src_object;
1262 vm_pindex_t dst_pindex, pindex, src_pindex;
1263 vm_prot_t access, prot;
1273 upgrade = src_entry == dst_entry;
1274 access = prot = dst_entry->protection;
1276 src_object = src_entry->object.vm_object;
1277 src_pindex = OFF_TO_IDX(src_entry->offset);
1279 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1280 dst_object = src_object;
1281 vm_object_reference(dst_object);
1284 * Create the top-level object for the destination entry. (Doesn't
1285 * actually shadow anything - we copy the pages directly.)
1287 dst_object = vm_object_allocate(OBJT_DEFAULT,
1288 OFF_TO_IDX(dst_entry->end - dst_entry->start));
1289 #if VM_NRESERVLEVEL > 0
1290 dst_object->flags |= OBJ_COLORED;
1291 dst_object->pg_color = atop(dst_entry->start);
1295 VM_OBJECT_WLOCK(dst_object);
1296 KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1297 ("vm_fault_copy_entry: vm_object not NULL"));
1298 if (src_object != dst_object) {
1299 dst_entry->object.vm_object = dst_object;
1300 dst_entry->offset = 0;
1301 dst_object->charge = dst_entry->end - dst_entry->start;
1303 if (fork_charge != NULL) {
1304 KASSERT(dst_entry->cred == NULL,
1305 ("vm_fault_copy_entry: leaked swp charge"));
1306 dst_object->cred = curthread->td_ucred;
1307 crhold(dst_object->cred);
1308 *fork_charge += dst_object->charge;
1309 } else if (dst_object->cred == NULL) {
1310 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1312 dst_object->cred = dst_entry->cred;
1313 dst_entry->cred = NULL;
1317 * If not an upgrade, then enter the mappings in the pmap as
1318 * read and/or execute accesses. Otherwise, enter them as
1321 * A writeable large page mapping is only created if all of
1322 * the constituent small page mappings are modified. Marking
1323 * PTEs as modified on inception allows promotion to happen
1324 * without taking potentially large number of soft faults.
1327 access &= ~VM_PROT_WRITE;
1330 * Loop through all of the virtual pages within the entry's
1331 * range, copying each page from the source object to the
1332 * destination object. Since the source is wired, those pages
1333 * must exist. In contrast, the destination is pageable.
1334 * Since the destination object does share any backing storage
1335 * with the source object, all of its pages must be dirtied,
1336 * regardless of whether they can be written.
1338 for (vaddr = dst_entry->start, dst_pindex = 0;
1339 vaddr < dst_entry->end;
1340 vaddr += PAGE_SIZE, dst_pindex++) {
1343 * Find the page in the source object, and copy it in.
1344 * Because the source is wired down, the page will be
1347 if (src_object != dst_object)
1348 VM_OBJECT_RLOCK(src_object);
1349 object = src_object;
1350 pindex = src_pindex + dst_pindex;
1351 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1352 (backing_object = object->backing_object) != NULL) {
1354 * Unless the source mapping is read-only or
1355 * it is presently being upgraded from
1356 * read-only, the first object in the shadow
1357 * chain should provide all of the pages. In
1358 * other words, this loop body should never be
1359 * executed when the source mapping is already
1362 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1364 ("vm_fault_copy_entry: main object missing page"));
1366 VM_OBJECT_RLOCK(backing_object);
1367 pindex += OFF_TO_IDX(object->backing_object_offset);
1368 if (object != dst_object)
1369 VM_OBJECT_RUNLOCK(object);
1370 object = backing_object;
1372 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1374 if (object != dst_object) {
1376 * Allocate a page in the destination object.
1378 dst_m = vm_page_alloc(dst_object, (src_object ==
1379 dst_object ? src_pindex : 0) + dst_pindex,
1381 if (dst_m == NULL) {
1382 VM_OBJECT_WUNLOCK(dst_object);
1383 VM_OBJECT_RUNLOCK(object);
1385 VM_OBJECT_WLOCK(dst_object);
1388 pmap_copy_page(src_m, dst_m);
1389 VM_OBJECT_RUNLOCK(object);
1390 dst_m->valid = VM_PAGE_BITS_ALL;
1391 dst_m->dirty = VM_PAGE_BITS_ALL;
1394 if (vm_page_sleep_if_busy(dst_m, "fltupg"))
1396 vm_page_xbusy(dst_m);
1397 KASSERT(dst_m->valid == VM_PAGE_BITS_ALL,
1398 ("invalid dst page %p", dst_m));
1400 VM_OBJECT_WUNLOCK(dst_object);
1403 * Enter it in the pmap. If a wired, copy-on-write
1404 * mapping is being replaced by a write-enabled
1405 * mapping, then wire that new mapping.
1407 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1408 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1411 * Mark it no longer busy, and put it on the active list.
1413 VM_OBJECT_WLOCK(dst_object);
1416 if (src_m != dst_m) {
1417 vm_page_lock(src_m);
1418 vm_page_unwire(src_m, 0);
1419 vm_page_unlock(src_m);
1420 vm_page_lock(dst_m);
1421 vm_page_wire(dst_m);
1422 vm_page_unlock(dst_m);
1424 KASSERT(dst_m->wire_count > 0,
1425 ("dst_m %p is not wired", dst_m));
1428 vm_page_lock(dst_m);
1429 vm_page_activate(dst_m);
1430 vm_page_unlock(dst_m);
1432 vm_page_xunbusy(dst_m);
1434 VM_OBJECT_WUNLOCK(dst_object);
1436 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1437 vm_object_deallocate(src_object);
1443 * This routine checks around the requested page for other pages that
1444 * might be able to be faulted in. This routine brackets the viable
1445 * pages for the pages to be paged in.
1448 * m, rbehind, rahead
1451 * marray (array of vm_page_t), reqpage (index of requested page)
1454 * number of pages in marray
1457 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1466 vm_pindex_t pindex, startpindex, endpindex, tpindex;
1468 int cbehind, cahead;
1470 VM_OBJECT_ASSERT_WLOCKED(m->object);
1474 cbehind = cahead = 0;
1477 * if the requested page is not available, then give up now
1479 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1483 if ((cbehind == 0) && (cahead == 0)) {
1489 if (rahead > cahead) {
1493 if (rbehind > cbehind) {
1498 * scan backward for the read behind pages -- in memory
1501 if (rbehind > pindex) {
1505 startpindex = pindex - rbehind;
1508 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL &&
1509 rtm->pindex >= startpindex)
1510 startpindex = rtm->pindex + 1;
1512 /* tpindex is unsigned; beware of numeric underflow. */
1513 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex &&
1514 tpindex < pindex; i++, tpindex--) {
1516 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1517 VM_ALLOC_IFNOTCACHED);
1520 * Shift the allocated pages to the
1521 * beginning of the array.
1523 for (j = 0; j < i; j++) {
1524 marray[j] = marray[j + tpindex + 1 -
1530 marray[tpindex - startpindex] = rtm;
1538 /* page offset of the required page */
1541 tpindex = pindex + 1;
1545 * scan forward for the read ahead pages
1547 endpindex = tpindex + rahead;
1548 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex)
1549 endpindex = rtm->pindex;
1550 if (endpindex > object->size)
1551 endpindex = object->size;
1553 for (; tpindex < endpindex; i++, tpindex++) {
1555 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1556 VM_ALLOC_IFNOTCACHED);
1564 /* return number of pages */
1569 * Block entry into the machine-independent layer's page fault handler by
1570 * the calling thread. Subsequent calls to vm_fault() by that thread will
1571 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of
1572 * spurious page faults.
1575 vm_fault_disable_pagefaults(void)
1578 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1582 vm_fault_enable_pagefaults(int save)
1585 curthread_pflags_restore(save);