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>
107 #define PAGEORDER_SIZE (PFBAK+PFFOR)
109 static int prefault_pageorder[] = {
110 -1 * PAGE_SIZE, 1 * PAGE_SIZE,
111 -2 * PAGE_SIZE, 2 * PAGE_SIZE,
112 -3 * PAGE_SIZE, 3 * PAGE_SIZE,
113 -4 * PAGE_SIZE, 4 * PAGE_SIZE
116 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
117 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t);
119 #define VM_FAULT_READ_BEHIND 8
120 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX)
121 #define VM_FAULT_NINCR (VM_FAULT_READ_MAX / VM_FAULT_READ_BEHIND)
122 #define VM_FAULT_SUM (VM_FAULT_NINCR * (VM_FAULT_NINCR + 1) / 2)
123 #define VM_FAULT_CACHE_BEHIND (VM_FAULT_READ_BEHIND * VM_FAULT_SUM)
130 vm_object_t first_object;
131 vm_pindex_t first_pindex;
133 vm_map_entry_t entry;
134 int lookup_still_valid;
138 static void vm_fault_cache_behind(const struct faultstate *fs, int distance);
141 release_page(struct faultstate *fs)
144 vm_page_wakeup(fs->m);
146 vm_page_deactivate(fs->m);
147 vm_page_unlock(fs->m);
152 unlock_map(struct faultstate *fs)
155 if (fs->lookup_still_valid) {
156 vm_map_lookup_done(fs->map, fs->entry);
157 fs->lookup_still_valid = FALSE;
162 unlock_and_deallocate(struct faultstate *fs)
165 vm_object_pip_wakeup(fs->object);
166 VM_OBJECT_WUNLOCK(fs->object);
167 if (fs->object != fs->first_object) {
168 VM_OBJECT_WLOCK(fs->first_object);
169 vm_page_lock(fs->first_m);
170 vm_page_free(fs->first_m);
171 vm_page_unlock(fs->first_m);
172 vm_object_pip_wakeup(fs->first_object);
173 VM_OBJECT_WUNLOCK(fs->first_object);
176 vm_object_deallocate(fs->first_object);
178 if (fs->vp != NULL) {
185 * TRYPAGER - used by vm_fault to calculate whether the pager for the
186 * current object *might* contain the page.
188 * default objects are zero-fill, there is no real pager.
190 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \
191 ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 || wired))
196 * Handle a page fault occurring at the given address,
197 * requiring the given permissions, in the map specified.
198 * If successful, the page is inserted into the
199 * associated physical map.
201 * NOTE: the given address should be truncated to the
202 * proper page address.
204 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
205 * a standard error specifying why the fault is fatal is returned.
207 * The map in question must be referenced, and remains so.
208 * Caller may hold no locks.
211 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
218 if ((td->td_pflags & TDP_NOFAULTING) != 0)
219 return (KERN_PROTECTION_FAILURE);
221 if (map != kernel_map && KTRPOINT(td, KTR_FAULT))
222 ktrfault(vaddr, fault_type);
224 result = vm_fault_hold(map, trunc_page(vaddr), fault_type, fault_flags,
227 if (map != kernel_map && KTRPOINT(td, KTR_FAULTEND))
234 vm_fault_hold(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
235 int fault_flags, vm_page_t *m_hold)
239 int alloc_req, era, faultcount, nera, reqpage, result;
240 boolean_t growstack, is_first_object_locked, wired;
242 vm_object_t next_object;
243 vm_page_t marray[VM_FAULT_READ_MAX];
245 struct faultstate fs;
251 PCPU_INC(cnt.v_vm_faults);
253 faultcount = reqpage = 0;
258 * Find the backing store object and offset into it to begin the
262 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
263 &fs.first_object, &fs.first_pindex, &prot, &wired);
264 if (result != KERN_SUCCESS) {
265 if (growstack && result == KERN_INVALID_ADDRESS &&
267 result = vm_map_growstack(curproc, vaddr);
268 if (result != KERN_SUCCESS)
269 return (KERN_FAILURE);
276 map_generation = fs.map->timestamp;
278 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
279 panic("vm_fault: fault on nofault entry, addr: %lx",
284 * Make a reference to this object to prevent its disposal while we
285 * are messing with it. Once we have the reference, the map is free
286 * to be diddled. Since objects reference their shadows (and copies),
287 * they will stay around as well.
289 * Bump the paging-in-progress count to prevent size changes (e.g.
290 * truncation operations) during I/O. This must be done after
291 * obtaining the vnode lock in order to avoid possible deadlocks.
293 VM_OBJECT_WLOCK(fs.first_object);
294 vm_object_reference_locked(fs.first_object);
295 vm_object_pip_add(fs.first_object, 1);
297 fs.lookup_still_valid = TRUE;
300 fault_type = prot | (fault_type & VM_PROT_COPY);
305 * Search for the page at object/offset.
307 fs.object = fs.first_object;
308 fs.pindex = fs.first_pindex;
311 * If the object is dead, we stop here
313 if (fs.object->flags & OBJ_DEAD) {
314 unlock_and_deallocate(&fs);
315 return (KERN_PROTECTION_FAILURE);
319 * See if page is resident
321 fs.m = vm_page_lookup(fs.object, fs.pindex);
324 * check for page-based copy on write.
325 * We check fs.object == fs.first_object so
326 * as to ensure the legacy COW mechanism is
327 * used when the page in question is part of
328 * a shadow object. Otherwise, vm_page_cowfault()
329 * removes the page from the backing object,
330 * which is not what we want.
334 (fault_type & VM_PROT_WRITE) &&
335 (fs.object == fs.first_object)) {
336 vm_page_cowfault(fs.m);
337 unlock_and_deallocate(&fs);
342 * Wait/Retry if the page is busy. We have to do this
343 * if the page is busy via either VPO_BUSY or
344 * vm_page_t->busy because the vm_pager may be using
345 * vm_page_t->busy for pageouts ( and even pageins if
346 * it is the vnode pager ), and we could end up trying
347 * to pagein and pageout the same page simultaneously.
349 * We can theoretically allow the busy case on a read
350 * fault if the page is marked valid, but since such
351 * pages are typically already pmap'd, putting that
352 * special case in might be more effort then it is
353 * worth. We cannot under any circumstances mess
354 * around with a vm_page_t->busy page except, perhaps,
357 if ((fs.m->oflags & VPO_BUSY) || fs.m->busy) {
359 * Reference the page before unlocking and
360 * sleeping so that the page daemon is less
361 * likely to reclaim it.
363 vm_page_aflag_set(fs.m, PGA_REFERENCED);
364 vm_page_unlock(fs.m);
365 if (fs.object != fs.first_object) {
366 if (!VM_OBJECT_TRYWLOCK(
368 VM_OBJECT_WUNLOCK(fs.object);
369 VM_OBJECT_WLOCK(fs.first_object);
370 VM_OBJECT_WLOCK(fs.object);
372 vm_page_lock(fs.first_m);
373 vm_page_free(fs.first_m);
374 vm_page_unlock(fs.first_m);
375 vm_object_pip_wakeup(fs.first_object);
376 VM_OBJECT_WUNLOCK(fs.first_object);
380 if (fs.m == vm_page_lookup(fs.object,
382 vm_page_sleep_if_busy(fs.m, TRUE,
385 vm_object_pip_wakeup(fs.object);
386 VM_OBJECT_WUNLOCK(fs.object);
387 PCPU_INC(cnt.v_intrans);
388 vm_object_deallocate(fs.first_object);
391 vm_page_remque(fs.m);
392 vm_page_unlock(fs.m);
395 * Mark page busy for other processes, and the
396 * pagedaemon. If it still isn't completely valid
397 * (readable), jump to readrest, else break-out ( we
401 if (fs.m->valid != VM_PAGE_BITS_ALL)
407 * Page is not resident, If this is the search termination
408 * or the pager might contain the page, allocate a new page.
410 if (TRYPAGER || fs.object == fs.first_object) {
411 if (fs.pindex >= fs.object->size) {
412 unlock_and_deallocate(&fs);
413 return (KERN_PROTECTION_FAILURE);
417 * Allocate a new page for this object/offset pair.
419 * Unlocked read of the p_flag is harmless. At
420 * worst, the P_KILLED might be not observed
421 * there, and allocation can fail, causing
422 * restart and new reading of the p_flag.
425 if (!vm_page_count_severe() || P_KILLED(curproc)) {
426 #if VM_NRESERVLEVEL > 0
427 if ((fs.object->flags & OBJ_COLORED) == 0) {
428 fs.object->flags |= OBJ_COLORED;
429 fs.object->pg_color = atop(vaddr) -
433 alloc_req = P_KILLED(curproc) ?
434 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
435 if (fs.object->type != OBJT_VNODE &&
436 fs.object->backing_object == NULL)
437 alloc_req |= VM_ALLOC_ZERO;
438 fs.m = vm_page_alloc(fs.object, fs.pindex,
442 unlock_and_deallocate(&fs);
445 } else if (fs.m->valid == VM_PAGE_BITS_ALL)
451 * We have found a valid page or we have allocated a new page.
452 * The page thus may not be valid or may not be entirely
455 * Attempt to fault-in the page if there is a chance that the
456 * pager has it, and potentially fault in additional pages
461 u_char behavior = vm_map_entry_behavior(fs.entry);
463 if (behavior == MAP_ENTRY_BEHAV_RANDOM ||
467 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
469 ahead = atop(fs.entry->end - vaddr) - 1;
470 if (ahead > VM_FAULT_READ_AHEAD_MAX)
471 ahead = VM_FAULT_READ_AHEAD_MAX;
472 if (fs.pindex == fs.entry->next_read)
473 vm_fault_cache_behind(&fs,
477 * If this is a sequential page fault, then
478 * arithmetically increase the number of pages
479 * in the read-ahead window. Otherwise, reset
480 * the read-ahead window to its smallest size.
482 behind = atop(vaddr - fs.entry->start);
483 if (behind > VM_FAULT_READ_BEHIND)
484 behind = VM_FAULT_READ_BEHIND;
485 ahead = atop(fs.entry->end - vaddr) - 1;
486 era = fs.entry->read_ahead;
487 if (fs.pindex == fs.entry->next_read) {
489 if (nera > VM_FAULT_READ_AHEAD_MAX)
490 nera = VM_FAULT_READ_AHEAD_MAX;
494 if (era == VM_FAULT_READ_AHEAD_MAX)
495 vm_fault_cache_behind(&fs,
496 VM_FAULT_CACHE_BEHIND);
497 } else if (ahead > VM_FAULT_READ_AHEAD_MIN)
498 ahead = VM_FAULT_READ_AHEAD_MIN;
500 fs.entry->read_ahead = ahead;
504 * Call the pager to retrieve the data, if any, after
505 * releasing the lock on the map. We hold a ref on
506 * fs.object and the pages are VPO_BUSY'd.
510 if (fs.object->type == OBJT_VNODE) {
511 vp = fs.object->handle;
514 else if (fs.vp != NULL) {
518 locked = VOP_ISLOCKED(vp);
520 if (locked != LK_EXCLUSIVE)
522 /* Do not sleep for vnode lock while fs.m is busy */
523 error = vget(vp, locked | LK_CANRECURSE |
524 LK_NOWAIT, curthread);
528 unlock_and_deallocate(&fs);
529 error = vget(vp, locked | LK_RETRY |
530 LK_CANRECURSE, curthread);
534 ("vm_fault: vget failed"));
540 KASSERT(fs.vp == NULL || !fs.map->system_map,
541 ("vm_fault: vnode-backed object mapped by system map"));
544 * now we find out if any other pages should be paged
545 * in at this time this routine checks to see if the
546 * pages surrounding this fault reside in the same
547 * object as the page for this fault. If they do,
548 * then they are faulted in also into the object. The
549 * array "marray" returned contains an array of
550 * vm_page_t structs where one of them is the
551 * vm_page_t passed to the routine. The reqpage
552 * return value is the index into the marray for the
553 * vm_page_t passed to the routine.
555 * fs.m plus the additional pages are VPO_BUSY'd.
557 faultcount = vm_fault_additional_pages(
558 fs.m, behind, ahead, marray, &reqpage);
561 vm_pager_get_pages(fs.object, marray, faultcount,
562 reqpage) : VM_PAGER_FAIL;
564 if (rv == VM_PAGER_OK) {
566 * Found the page. Leave it busy while we play
571 * Relookup in case pager changed page. Pager
572 * is responsible for disposition of old page
575 fs.m = vm_page_lookup(fs.object, fs.pindex);
577 unlock_and_deallocate(&fs);
582 break; /* break to PAGE HAS BEEN FOUND */
585 * Remove the bogus page (which does not exist at this
586 * object/offset); before doing so, we must get back
587 * our object lock to preserve our invariant.
589 * Also wake up any other process that may want to bring
592 * If this is the top-level object, we must leave the
593 * busy page to prevent another process from rushing
594 * past us, and inserting the page in that object at
595 * the same time that we are.
597 if (rv == VM_PAGER_ERROR)
598 printf("vm_fault: pager read error, pid %d (%s)\n",
599 curproc->p_pid, curproc->p_comm);
601 * Data outside the range of the pager or an I/O error
604 * XXX - the check for kernel_map is a kludge to work
605 * around having the machine panic on a kernel space
606 * fault w/ I/O error.
608 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
609 (rv == VM_PAGER_BAD)) {
612 vm_page_unlock(fs.m);
614 unlock_and_deallocate(&fs);
615 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
617 if (fs.object != fs.first_object) {
620 vm_page_unlock(fs.m);
623 * XXX - we cannot just fall out at this
624 * point, m has been freed and is invalid!
630 * We get here if the object has default pager (or unwiring)
631 * or the pager doesn't have the page.
633 if (fs.object == fs.first_object)
637 * Move on to the next object. Lock the next object before
638 * unlocking the current one.
640 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
641 next_object = fs.object->backing_object;
642 if (next_object == NULL) {
644 * If there's no object left, fill the page in the top
647 if (fs.object != fs.first_object) {
648 vm_object_pip_wakeup(fs.object);
649 VM_OBJECT_WUNLOCK(fs.object);
651 fs.object = fs.first_object;
652 fs.pindex = fs.first_pindex;
654 VM_OBJECT_WLOCK(fs.object);
659 * Zero the page if necessary and mark it valid.
661 if ((fs.m->flags & PG_ZERO) == 0) {
662 pmap_zero_page(fs.m);
664 PCPU_INC(cnt.v_ozfod);
666 PCPU_INC(cnt.v_zfod);
667 fs.m->valid = VM_PAGE_BITS_ALL;
668 break; /* break to PAGE HAS BEEN FOUND */
670 KASSERT(fs.object != next_object,
671 ("object loop %p", next_object));
672 VM_OBJECT_WLOCK(next_object);
673 vm_object_pip_add(next_object, 1);
674 if (fs.object != fs.first_object)
675 vm_object_pip_wakeup(fs.object);
676 VM_OBJECT_WUNLOCK(fs.object);
677 fs.object = next_object;
681 KASSERT((fs.m->oflags & VPO_BUSY) != 0,
682 ("vm_fault: not busy after main loop"));
685 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
690 * If the page is being written, but isn't already owned by the
691 * top-level object, we have to copy it into a new page owned by the
694 if (fs.object != fs.first_object) {
696 * We only really need to copy if we want to write it.
698 if ((fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
700 * This allows pages to be virtually copied from a
701 * backing_object into the first_object, where the
702 * backing object has no other refs to it, and cannot
703 * gain any more refs. Instead of a bcopy, we just
704 * move the page from the backing object to the
705 * first object. Note that we must mark the page
706 * dirty in the first object so that it will go out
707 * to swap when needed.
709 is_first_object_locked = FALSE;
712 * Only one shadow object
714 (fs.object->shadow_count == 1) &&
716 * No COW refs, except us
718 (fs.object->ref_count == 1) &&
720 * No one else can look this object up
722 (fs.object->handle == NULL) &&
724 * No other ways to look the object up
726 ((fs.object->type == OBJT_DEFAULT) ||
727 (fs.object->type == OBJT_SWAP)) &&
728 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs.first_object)) &&
730 * We don't chase down the shadow chain
732 fs.object == fs.first_object->backing_object) {
734 * get rid of the unnecessary page
736 vm_page_lock(fs.first_m);
737 vm_page_free(fs.first_m);
738 vm_page_unlock(fs.first_m);
740 * grab the page and put it into the
741 * process'es object. The page is
742 * automatically made dirty.
745 vm_page_rename(fs.m, fs.first_object, fs.first_pindex);
746 vm_page_unlock(fs.m);
750 PCPU_INC(cnt.v_cow_optim);
753 * Oh, well, lets copy it.
755 pmap_copy_page(fs.m, fs.first_m);
756 fs.first_m->valid = VM_PAGE_BITS_ALL;
757 if (wired && (fault_flags &
758 VM_FAULT_CHANGE_WIRING) == 0) {
759 vm_page_lock(fs.first_m);
760 vm_page_wire(fs.first_m);
761 vm_page_unlock(fs.first_m);
764 vm_page_unwire(fs.m, FALSE);
765 vm_page_unlock(fs.m);
768 * We no longer need the old page or object.
773 * fs.object != fs.first_object due to above
776 vm_object_pip_wakeup(fs.object);
777 VM_OBJECT_WUNLOCK(fs.object);
779 * Only use the new page below...
781 fs.object = fs.first_object;
782 fs.pindex = fs.first_pindex;
784 if (!is_first_object_locked)
785 VM_OBJECT_WLOCK(fs.object);
786 PCPU_INC(cnt.v_cow_faults);
789 prot &= ~VM_PROT_WRITE;
794 * We must verify that the maps have not changed since our last
797 if (!fs.lookup_still_valid) {
798 vm_object_t retry_object;
799 vm_pindex_t retry_pindex;
800 vm_prot_t retry_prot;
802 if (!vm_map_trylock_read(fs.map)) {
804 unlock_and_deallocate(&fs);
807 fs.lookup_still_valid = TRUE;
808 if (fs.map->timestamp != map_generation) {
809 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
810 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
813 * If we don't need the page any longer, put it on the inactive
814 * list (the easiest thing to do here). If no one needs it,
815 * pageout will grab it eventually.
817 if (result != KERN_SUCCESS) {
819 unlock_and_deallocate(&fs);
822 * If retry of map lookup would have blocked then
823 * retry fault from start.
825 if (result == KERN_FAILURE)
829 if ((retry_object != fs.first_object) ||
830 (retry_pindex != fs.first_pindex)) {
832 unlock_and_deallocate(&fs);
837 * Check whether the protection has changed or the object has
838 * been copied while we left the map unlocked. Changing from
839 * read to write permission is OK - we leave the page
840 * write-protected, and catch the write fault. Changing from
841 * write to read permission means that we can't mark the page
842 * write-enabled after all.
848 * If the page was filled by a pager, update the map entry's
849 * last read offset. Since the pager does not return the
850 * actual set of pages that it read, this update is based on
851 * the requested set. Typically, the requested and actual
854 * XXX The following assignment modifies the map
855 * without holding a write lock on it.
858 fs.entry->next_read = fs.pindex + faultcount - reqpage;
860 if ((prot & VM_PROT_WRITE) != 0 ||
861 (fault_flags & VM_FAULT_DIRTY) != 0) {
862 vm_object_set_writeable_dirty(fs.object);
865 * If this is a NOSYNC mmap we do not want to set VPO_NOSYNC
866 * if the page is already dirty to prevent data written with
867 * the expectation of being synced from not being synced.
868 * Likewise if this entry does not request NOSYNC then make
869 * sure the page isn't marked NOSYNC. Applications sharing
870 * data should use the same flags to avoid ping ponging.
872 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) {
873 if (fs.m->dirty == 0)
874 fs.m->oflags |= VPO_NOSYNC;
876 fs.m->oflags &= ~VPO_NOSYNC;
880 * If the fault is a write, we know that this page is being
881 * written NOW so dirty it explicitly to save on
882 * pmap_is_modified() calls later.
884 * Also tell the backing pager, if any, that it should remove
885 * any swap backing since the page is now dirty.
887 if (((fault_type & VM_PROT_WRITE) != 0 &&
888 (fault_flags & VM_FAULT_CHANGE_WIRING) == 0) ||
889 (fault_flags & VM_FAULT_DIRTY) != 0) {
891 vm_pager_page_unswapped(fs.m);
896 * Page had better still be busy
898 KASSERT(fs.m->oflags & VPO_BUSY,
899 ("vm_fault: page %p not busy!", fs.m));
901 * Page must be completely valid or it is not fit to
902 * map into user space. vm_pager_get_pages() ensures this.
904 KASSERT(fs.m->valid == VM_PAGE_BITS_ALL,
905 ("vm_fault: page %p partially invalid", fs.m));
906 VM_OBJECT_WUNLOCK(fs.object);
909 * Put this page into the physical map. We had to do the unlock above
910 * because pmap_enter() may sleep. We don't put the page
911 * back on the active queue until later so that the pageout daemon
912 * won't find it (yet).
914 pmap_enter(fs.map->pmap, vaddr, fault_type, fs.m, prot, wired);
915 if ((fault_flags & VM_FAULT_CHANGE_WIRING) == 0 && wired == 0)
916 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry);
917 VM_OBJECT_WLOCK(fs.object);
921 * If the page is not wired down, then put it where the pageout daemon
924 if (fault_flags & VM_FAULT_CHANGE_WIRING) {
928 vm_page_unwire(fs.m, 1);
930 vm_page_activate(fs.m);
931 if (m_hold != NULL) {
935 vm_page_unlock(fs.m);
936 vm_page_wakeup(fs.m);
939 * Unlock everything, and return
941 unlock_and_deallocate(&fs);
943 PCPU_INC(cnt.v_io_faults);
944 curthread->td_ru.ru_majflt++;
946 curthread->td_ru.ru_minflt++;
948 return (KERN_SUCCESS);
952 * Speed up the reclamation of up to "distance" pages that precede the
953 * faulting pindex within the first object of the shadow chain.
956 vm_fault_cache_behind(const struct faultstate *fs, int distance)
958 vm_object_t first_object, object;
963 VM_OBJECT_ASSERT_WLOCKED(object);
964 first_object = fs->first_object;
965 if (first_object != object) {
966 if (!VM_OBJECT_TRYWLOCK(first_object)) {
967 VM_OBJECT_WUNLOCK(object);
968 VM_OBJECT_WLOCK(first_object);
969 VM_OBJECT_WLOCK(object);
972 /* Neither fictitious nor unmanaged pages can be cached. */
973 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
974 if (fs->first_pindex < distance)
977 pindex = fs->first_pindex - distance;
978 if (pindex < OFF_TO_IDX(fs->entry->offset))
979 pindex = OFF_TO_IDX(fs->entry->offset);
980 m = first_object != object ? fs->first_m : fs->m;
981 KASSERT((m->oflags & VPO_BUSY) != 0,
982 ("vm_fault_cache_behind: page %p is not busy", m));
983 m_prev = vm_page_prev(m);
984 while ((m = m_prev) != NULL && m->pindex >= pindex &&
985 m->valid == VM_PAGE_BITS_ALL) {
986 m_prev = vm_page_prev(m);
987 if (m->busy != 0 || (m->oflags & VPO_BUSY) != 0)
990 if (m->hold_count == 0 && m->wire_count == 0) {
992 vm_page_aflag_clear(m, PGA_REFERENCED);
994 vm_page_deactivate(m);
1001 if (first_object != object)
1002 VM_OBJECT_WUNLOCK(first_object);
1006 * vm_fault_prefault provides a quick way of clustering
1007 * pagefaults into a processes address space. It is a "cousin"
1008 * of vm_map_pmap_enter, except it runs at page fault time instead
1012 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry)
1015 vm_offset_t addr, starta;
1020 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1023 object = entry->object.vm_object;
1025 starta = addra - PFBAK * PAGE_SIZE;
1026 if (starta < entry->start) {
1027 starta = entry->start;
1028 } else if (starta > addra) {
1032 for (i = 0; i < PAGEORDER_SIZE; i++) {
1033 vm_object_t backing_object, lobject;
1035 addr = addra + prefault_pageorder[i];
1036 if (addr > addra + (PFFOR * PAGE_SIZE))
1039 if (addr < starta || addr >= entry->end)
1042 if (!pmap_is_prefaultable(pmap, addr))
1045 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1047 VM_OBJECT_WLOCK(lobject);
1048 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1049 lobject->type == OBJT_DEFAULT &&
1050 (backing_object = lobject->backing_object) != NULL) {
1051 KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1052 0, ("vm_fault_prefault: unaligned object offset"));
1053 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1054 VM_OBJECT_WLOCK(backing_object);
1055 VM_OBJECT_WUNLOCK(lobject);
1056 lobject = backing_object;
1059 * give-up when a page is not in memory
1062 VM_OBJECT_WUNLOCK(lobject);
1065 if (m->valid == VM_PAGE_BITS_ALL &&
1066 (m->flags & PG_FICTITIOUS) == 0)
1067 pmap_enter_quick(pmap, addr, m, entry->protection);
1068 VM_OBJECT_WUNLOCK(lobject);
1073 * Hold each of the physical pages that are mapped by the specified range of
1074 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1075 * and allow the specified types of access, "prot". If all of the implied
1076 * pages are successfully held, then the number of held pages is returned
1077 * together with pointers to those pages in the array "ma". However, if any
1078 * of the pages cannot be held, -1 is returned.
1081 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1082 vm_prot_t prot, vm_page_t *ma, int max_count)
1084 vm_offset_t end, va;
1087 boolean_t pmap_failed;
1091 end = round_page(addr + len);
1092 addr = trunc_page(addr);
1095 * Check for illegal addresses.
1097 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1100 count = howmany(end - addr, PAGE_SIZE);
1101 if (count > max_count)
1102 panic("vm_fault_quick_hold_pages: count > max_count");
1105 * Most likely, the physical pages are resident in the pmap, so it is
1106 * faster to try pmap_extract_and_hold() first.
1108 pmap_failed = FALSE;
1109 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1110 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1113 else if ((prot & VM_PROT_WRITE) != 0 &&
1114 (*mp)->dirty != VM_PAGE_BITS_ALL) {
1116 * Explicitly dirty the physical page. Otherwise, the
1117 * caller's changes may go unnoticed because they are
1118 * performed through an unmanaged mapping or by a DMA
1121 * The object lock is not held here.
1122 * See vm_page_clear_dirty_mask().
1129 * One or more pages could not be held by the pmap. Either no
1130 * page was mapped at the specified virtual address or that
1131 * mapping had insufficient permissions. Attempt to fault in
1132 * and hold these pages.
1134 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1135 if (*mp == NULL && vm_fault_hold(map, va, prot,
1136 VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1141 for (mp = ma; mp < ma + count; mp++)
1144 vm_page_unhold(*mp);
1145 vm_page_unlock(*mp);
1153 * Wire down a range of virtual addresses in a map.
1156 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1157 boolean_t fictitious)
1163 * We simulate a fault to get the page and enter it in the physical
1164 * map. For user wiring, we only ask for read access on currently
1165 * read-only sections.
1167 for (va = start; va < end; va += PAGE_SIZE) {
1168 rv = vm_fault(map, va, VM_PROT_NONE, VM_FAULT_CHANGE_WIRING);
1171 vm_fault_unwire(map, start, va, fictitious);
1175 return (KERN_SUCCESS);
1181 * Unwire a range of virtual addresses in a map.
1184 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1185 boolean_t fictitious)
1192 pmap = vm_map_pmap(map);
1195 * Since the pages are wired down, we must be able to get their
1196 * mappings from the physical map system.
1198 for (va = start; va < end; va += PAGE_SIZE) {
1199 pa = pmap_extract(pmap, va);
1201 pmap_change_wiring(pmap, va, FALSE);
1203 m = PHYS_TO_VM_PAGE(pa);
1205 vm_page_unwire(m, TRUE);
1214 * vm_fault_copy_entry
1216 * Create new shadow object backing dst_entry with private copy of
1217 * all underlying pages. When src_entry is equal to dst_entry,
1218 * function implements COW for wired-down map entry. Otherwise,
1219 * it forks wired entry into dst_map.
1221 * In/out conditions:
1222 * The source and destination maps must be locked for write.
1223 * The source map entry must be wired down (or be a sharing map
1224 * entry corresponding to a main map entry that is wired down).
1227 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1228 vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1229 vm_ooffset_t *fork_charge)
1231 vm_object_t backing_object, dst_object, object, src_object;
1232 vm_pindex_t dst_pindex, pindex, src_pindex;
1233 vm_prot_t access, prot;
1237 boolean_t src_readonly, upgrade;
1243 upgrade = src_entry == dst_entry;
1245 src_object = src_entry->object.vm_object;
1246 src_pindex = OFF_TO_IDX(src_entry->offset);
1247 src_readonly = (src_entry->protection & VM_PROT_WRITE) == 0;
1250 * Create the top-level object for the destination entry. (Doesn't
1251 * actually shadow anything - we copy the pages directly.)
1253 dst_object = vm_object_allocate(OBJT_DEFAULT,
1254 OFF_TO_IDX(dst_entry->end - dst_entry->start));
1255 #if VM_NRESERVLEVEL > 0
1256 dst_object->flags |= OBJ_COLORED;
1257 dst_object->pg_color = atop(dst_entry->start);
1260 VM_OBJECT_WLOCK(dst_object);
1261 KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1262 ("vm_fault_copy_entry: vm_object not NULL"));
1263 dst_entry->object.vm_object = dst_object;
1264 dst_entry->offset = 0;
1265 dst_object->charge = dst_entry->end - dst_entry->start;
1266 if (fork_charge != NULL) {
1267 KASSERT(dst_entry->cred == NULL,
1268 ("vm_fault_copy_entry: leaked swp charge"));
1269 dst_object->cred = curthread->td_ucred;
1270 crhold(dst_object->cred);
1271 *fork_charge += dst_object->charge;
1273 dst_object->cred = dst_entry->cred;
1274 dst_entry->cred = NULL;
1276 access = prot = dst_entry->protection;
1278 * If not an upgrade, then enter the mappings in the pmap as
1279 * read and/or execute accesses. Otherwise, enter them as
1282 * A writeable large page mapping is only created if all of
1283 * the constituent small page mappings are modified. Marking
1284 * PTEs as modified on inception allows promotion to happen
1285 * without taking potentially large number of soft faults.
1288 access &= ~VM_PROT_WRITE;
1291 * Loop through all of the virtual pages within the entry's
1292 * range, copying each page from the source object to the
1293 * destination object. Since the source is wired, those pages
1294 * must exist. In contrast, the destination is pageable.
1295 * Since the destination object does share any backing storage
1296 * with the source object, all of its pages must be dirtied,
1297 * regardless of whether they can be written.
1299 for (vaddr = dst_entry->start, dst_pindex = 0;
1300 vaddr < dst_entry->end;
1301 vaddr += PAGE_SIZE, dst_pindex++) {
1304 * Allocate a page in the destination object.
1307 dst_m = vm_page_alloc(dst_object, dst_pindex,
1309 if (dst_m == NULL) {
1310 VM_OBJECT_WUNLOCK(dst_object);
1312 VM_OBJECT_WLOCK(dst_object);
1314 } while (dst_m == NULL);
1317 * Find the page in the source object, and copy it in.
1318 * (Because the source is wired down, the page will be in
1321 VM_OBJECT_WLOCK(src_object);
1322 object = src_object;
1323 pindex = src_pindex + dst_pindex;
1324 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1326 (backing_object = object->backing_object) != NULL) {
1328 * Allow fallback to backing objects if we are reading.
1330 VM_OBJECT_WLOCK(backing_object);
1331 pindex += OFF_TO_IDX(object->backing_object_offset);
1332 VM_OBJECT_WUNLOCK(object);
1333 object = backing_object;
1336 panic("vm_fault_copy_wired: page missing");
1337 pmap_copy_page(src_m, dst_m);
1338 VM_OBJECT_WUNLOCK(object);
1339 dst_m->valid = VM_PAGE_BITS_ALL;
1340 dst_m->dirty = VM_PAGE_BITS_ALL;
1341 VM_OBJECT_WUNLOCK(dst_object);
1344 * Enter it in the pmap. If a wired, copy-on-write
1345 * mapping is being replaced by a write-enabled
1346 * mapping, then wire that new mapping.
1348 pmap_enter(dst_map->pmap, vaddr, access, dst_m, prot, upgrade);
1351 * Mark it no longer busy, and put it on the active list.
1353 VM_OBJECT_WLOCK(dst_object);
1356 vm_page_lock(src_m);
1357 vm_page_unwire(src_m, 0);
1358 vm_page_unlock(src_m);
1360 vm_page_lock(dst_m);
1361 vm_page_wire(dst_m);
1362 vm_page_unlock(dst_m);
1364 vm_page_lock(dst_m);
1365 vm_page_activate(dst_m);
1366 vm_page_unlock(dst_m);
1368 vm_page_wakeup(dst_m);
1370 VM_OBJECT_WUNLOCK(dst_object);
1372 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1373 vm_object_deallocate(src_object);
1379 * This routine checks around the requested page for other pages that
1380 * might be able to be faulted in. This routine brackets the viable
1381 * pages for the pages to be paged in.
1384 * m, rbehind, rahead
1387 * marray (array of vm_page_t), reqpage (index of requested page)
1390 * number of pages in marray
1393 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1402 vm_pindex_t pindex, startpindex, endpindex, tpindex;
1404 int cbehind, cahead;
1406 VM_OBJECT_ASSERT_WLOCKED(m->object);
1410 cbehind = cahead = 0;
1413 * if the requested page is not available, then give up now
1415 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1419 if ((cbehind == 0) && (cahead == 0)) {
1425 if (rahead > cahead) {
1429 if (rbehind > cbehind) {
1434 * scan backward for the read behind pages -- in memory
1437 if (rbehind > pindex) {
1441 startpindex = pindex - rbehind;
1444 if ((rtm = TAILQ_PREV(m, pglist, listq)) != NULL &&
1445 rtm->pindex >= startpindex)
1446 startpindex = rtm->pindex + 1;
1448 /* tpindex is unsigned; beware of numeric underflow. */
1449 for (i = 0, tpindex = pindex - 1; tpindex >= startpindex &&
1450 tpindex < pindex; i++, tpindex--) {
1452 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1453 VM_ALLOC_IFNOTCACHED);
1456 * Shift the allocated pages to the
1457 * beginning of the array.
1459 for (j = 0; j < i; j++) {
1460 marray[j] = marray[j + tpindex + 1 -
1466 marray[tpindex - startpindex] = rtm;
1474 /* page offset of the required page */
1477 tpindex = pindex + 1;
1481 * scan forward for the read ahead pages
1483 endpindex = tpindex + rahead;
1484 if ((rtm = TAILQ_NEXT(m, listq)) != NULL && rtm->pindex < endpindex)
1485 endpindex = rtm->pindex;
1486 if (endpindex > object->size)
1487 endpindex = object->size;
1489 for (; tpindex < endpindex; i++, tpindex++) {
1491 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL |
1492 VM_ALLOC_IFNOTCACHED);
1500 /* return number of pages */
1505 * Block entry into the machine-independent layer's page fault handler by
1506 * the calling thread. Subsequent calls to vm_fault() by that thread will
1507 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of
1508 * spurious page faults.
1511 vm_fault_disable_pagefaults(void)
1514 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
1518 vm_fault_enable_pagefaults(int save)
1521 curthread_pflags_restore(save);