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.
69 * $FreeBSD: src/sys/vm/vm_fault.c,v 1.108.2.8 2002/02/26 05:49:27 silby Exp $
70 * $DragonFly: src/sys/vm/vm_fault.c,v 1.21 2006/03/15 07:58:37 dillon Exp $
74 * Page fault handling module.
77 #include <sys/param.h>
78 #include <sys/systm.h>
79 #include <sys/kernel.h>
81 #include <sys/vnode.h>
82 #include <sys/resourcevar.h>
83 #include <sys/vmmeter.h>
86 #include <vm/vm_param.h>
89 #include <vm/vm_map.h>
90 #include <vm/vm_object.h>
91 #include <vm/vm_page.h>
92 #include <vm/vm_pageout.h>
93 #include <vm/vm_kern.h>
94 #include <vm/vm_pager.h>
95 #include <vm/vnode_pager.h>
96 #include <vm/vm_extern.h>
98 #include <sys/thread2.h>
99 #include <vm/vm_page2.h>
101 static int vm_fault_additional_pages (vm_page_t, int,
102 int, vm_page_t *, int *);
103 static int vm_fault_ratelimit(struct vmspace *vmspace);
105 #define VM_FAULT_READ_AHEAD 8
106 #define VM_FAULT_READ_BEHIND 7
107 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1)
114 vm_object_t first_object;
115 vm_pindex_t first_pindex;
117 vm_map_entry_t entry;
118 int lookup_still_valid;
123 release_page(struct faultstate *fs)
125 vm_page_wakeup(fs->m);
126 vm_page_deactivate(fs->m);
131 unlock_map(struct faultstate *fs)
133 if (fs->lookup_still_valid) {
134 vm_map_lookup_done(fs->map, fs->entry, 0);
135 fs->lookup_still_valid = FALSE;
140 _unlock_things(struct faultstate *fs, int dealloc)
142 vm_object_pip_wakeup(fs->object);
143 if (fs->object != fs->first_object) {
144 vm_page_free(fs->first_m);
145 vm_object_pip_wakeup(fs->first_object);
149 vm_object_deallocate(fs->first_object);
152 if (fs->vp != NULL) {
158 #define unlock_things(fs) _unlock_things(fs, 0)
159 #define unlock_and_deallocate(fs) _unlock_things(fs, 1)
162 * TRYPAGER - used by vm_fault to calculate whether the pager for the
163 * current object *might* contain the page.
165 * default objects are zero-fill, there is no real pager.
168 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \
169 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired))
174 * Handle a page fault occurring at the given address,
175 * requiring the given permissions, in the map specified.
176 * If successful, the page is inserted into the
177 * associated physical map.
179 * NOTE: the given address should be truncated to the
180 * proper page address.
182 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
183 * a standard error specifying why the fault is fatal is returned.
186 * The map in question must be referenced, and remains so.
187 * Caller may hold no locks.
190 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, int fault_flags)
196 vm_object_t next_object;
197 vm_page_t marray[VM_FAULT_READ];
202 struct faultstate fs;
204 mycpu->gd_cnt.v_vm_faults++;
209 * Find the backing store object and offset into it to begin the
213 if ((result = vm_map_lookup(&fs.map, vaddr,
214 fault_type, &fs.entry, &fs.first_object,
215 &fs.first_pindex, &prot, &wired)) != KERN_SUCCESS) {
216 if ((result != KERN_PROTECTION_FAILURE) ||
217 ((fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE)) {
222 * If we are user-wiring a r/w segment, and it is COW, then
223 * we need to do the COW operation. Note that we don't COW
224 * currently RO sections now, because it is NOT desirable
225 * to COW .text. We simply keep .text from ever being COW'ed
226 * and take the heat that one cannot debug wired .text sections.
228 result = vm_map_lookup(&fs.map, vaddr,
229 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE,
230 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired);
231 if (result != KERN_SUCCESS) {
236 * If we don't COW now, on a user wire, the user will never
237 * be able to write to the mapping. If we don't make this
238 * restriction, the bookkeeping would be nearly impossible.
240 if ((fs.entry->protection & VM_PROT_WRITE) == 0)
241 fs.entry->max_protection &= ~VM_PROT_WRITE;
244 map_generation = fs.map->timestamp;
246 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
247 panic("vm_fault: fault on nofault entry, addr: %lx",
252 * A system map entry may return a NULL object. No object means
253 * no pager means an unrecoverable kernel fault.
255 if (fs.first_object == NULL) {
256 panic("vm_fault: unrecoverable fault at %p in entry %p",
257 (void *)vaddr, fs.entry);
261 * Make a reference to this object to prevent its disposal while we
262 * are messing with it. Once we have the reference, the map is free
263 * to be diddled. Since objects reference their shadows (and copies),
264 * they will stay around as well.
266 * Bump the paging-in-progress count to prevent size changes (e.g.
267 * truncation operations) during I/O. This must be done after
268 * obtaining the vnode lock in order to avoid possible deadlocks.
270 vm_object_reference(fs.first_object);
271 fs.vp = vnode_pager_lock(fs.first_object);
272 vm_object_pip_add(fs.first_object, 1);
274 if ((fault_type & VM_PROT_WRITE) &&
275 (fs.first_object->type == OBJT_VNODE)) {
276 vm_freeze_copyopts(fs.first_object,
277 fs.first_pindex, fs.first_pindex + 1);
280 fs.lookup_still_valid = TRUE;
288 * Search for the page at object/offset.
291 fs.object = fs.first_object;
292 fs.pindex = fs.first_pindex;
296 * If the object is dead, we stop here
299 if (fs.object->flags & OBJ_DEAD) {
300 unlock_and_deallocate(&fs);
301 return (KERN_PROTECTION_FAILURE);
305 * See if page is resident. spl protection is required
306 * to avoid an interrupt unbusy/free race against our
307 * lookup. We must hold the protection through a page
308 * allocation or busy.
311 fs.m = vm_page_lookup(fs.object, fs.pindex);
315 * Wait/Retry if the page is busy. We have to do this
316 * if the page is busy via either PG_BUSY or
317 * vm_page_t->busy because the vm_pager may be using
318 * vm_page_t->busy for pageouts ( and even pageins if
319 * it is the vnode pager ), and we could end up trying
320 * to pagein and pageout the same page simultaneously.
322 * We can theoretically allow the busy case on a read
323 * fault if the page is marked valid, but since such
324 * pages are typically already pmap'd, putting that
325 * special case in might be more effort then it is
326 * worth. We cannot under any circumstances mess
327 * around with a vm_page_t->busy page except, perhaps,
330 if ((fs.m->flags & PG_BUSY) || fs.m->busy) {
332 vm_page_sleep_busy(fs.m, TRUE, "vmpfw");
333 mycpu->gd_cnt.v_intrans++;
334 vm_object_deallocate(fs.first_object);
340 vm_page_unqueue_nowakeup(fs.m);
342 if ((queue - fs.m->pc) == PQ_CACHE && vm_page_count_severe()) {
343 vm_page_activate(fs.m);
344 unlock_and_deallocate(&fs);
351 * Mark page busy for other processes, and the
352 * pagedaemon. If it still isn't completely valid
353 * (readable), jump to readrest, else break-out ( we
356 * We can release the spl once we have marked the
363 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) &&
364 fs.m->object != kernel_object && fs.m->object != kmem_object) {
372 * Page is not resident, If this is the search termination
373 * or the pager might contain the page, allocate a new page.
375 * note: we are still in splvm().
378 if (TRYPAGER || fs.object == fs.first_object) {
379 if (fs.pindex >= fs.object->size) {
381 unlock_and_deallocate(&fs);
382 return (KERN_PROTECTION_FAILURE);
390 vm_fault_ratelimit(curproc->p_vmspace);
393 unlock_and_deallocate(&fs);
394 tsleep(curproc, 0, "vmrate", limticks);
401 * Allocate a new page for this object/offset pair.
404 if (!vm_page_count_severe()) {
405 fs.m = vm_page_alloc(fs.object, fs.pindex,
406 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_NORMAL | VM_ALLOC_ZERO);
410 unlock_and_deallocate(&fs);
419 * We have found a valid page or we have allocated a new page.
420 * The page thus may not be valid or may not be entirely
423 * Attempt to fault-in the page if there is a chance that the
424 * pager has it, and potentially fault in additional pages
427 * We are NOT in splvm here and if TRYPAGER is true then
428 * fs.m will be non-NULL and will be PG_BUSY for us.
435 u_char behavior = vm_map_entry_behavior(fs.entry);
437 if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
441 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT;
442 if (behind > VM_FAULT_READ_BEHIND)
443 behind = VM_FAULT_READ_BEHIND;
445 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1;
446 if (ahead > VM_FAULT_READ_AHEAD)
447 ahead = VM_FAULT_READ_AHEAD;
450 if ((fs.first_object->type != OBJT_DEVICE) &&
451 (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL ||
452 (behavior != MAP_ENTRY_BEHAV_RANDOM &&
453 fs.pindex >= fs.entry->lastr &&
454 fs.pindex < fs.entry->lastr + VM_FAULT_READ))
456 vm_pindex_t firstpindex, tmppindex;
458 if (fs.first_pindex < 2 * VM_FAULT_READ)
461 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ;
464 * note: partially valid pages cannot be
465 * included in the lookahead - NFS piecemeal
466 * writes will barf on it badly.
468 * spl protection is required to avoid races
469 * between the lookup and an interrupt
470 * unbusy/free sequence occuring prior to
474 for (tmppindex = fs.first_pindex - 1;
475 tmppindex >= firstpindex;
479 mt = vm_page_lookup( fs.first_object, tmppindex);
480 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL))
483 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) ||
488 vm_page_test_dirty(mt);
490 vm_page_protect(mt, VM_PROT_NONE);
491 vm_page_deactivate(mt);
503 * now we find out if any other pages should be paged
504 * in at this time this routine checks to see if the
505 * pages surrounding this fault reside in the same
506 * object as the page for this fault. If they do,
507 * then they are faulted in also into the object. The
508 * array "marray" returned contains an array of
509 * vm_page_t structs where one of them is the
510 * vm_page_t passed to the routine. The reqpage
511 * return value is the index into the marray for the
512 * vm_page_t passed to the routine.
514 * fs.m plus the additional pages are PG_BUSY'd.
516 faultcount = vm_fault_additional_pages(
517 fs.m, behind, ahead, marray, &reqpage);
520 * update lastr imperfectly (we do not know how much
521 * getpages will actually read), but good enough.
523 fs.entry->lastr = fs.pindex + faultcount - behind;
526 * Call the pager to retrieve the data, if any, after
527 * releasing the lock on the map. We hold a ref on
528 * fs.object and the pages are PG_BUSY'd.
533 vm_pager_get_pages(fs.object, marray, faultcount,
534 reqpage) : VM_PAGER_FAIL;
536 if (rv == VM_PAGER_OK) {
538 * Found the page. Leave it busy while we play
543 * Relookup in case pager changed page. Pager
544 * is responsible for disposition of old page
547 * XXX other code segments do relookups too.
548 * It's a bad abstraction that needs to be
551 fs.m = vm_page_lookup(fs.object, fs.pindex);
553 unlock_and_deallocate(&fs);
558 break; /* break to PAGE HAS BEEN FOUND */
561 * Remove the bogus page (which does not exist at this
562 * object/offset); before doing so, we must get back
563 * our object lock to preserve our invariant.
565 * Also wake up any other process that may want to bring
568 * If this is the top-level object, we must leave the
569 * busy page to prevent another process from rushing
570 * past us, and inserting the page in that object at
571 * the same time that we are.
574 if (rv == VM_PAGER_ERROR)
575 printf("vm_fault: pager read error, pid %d (%s)\n",
576 curproc->p_pid, curproc->p_comm);
578 * Data outside the range of the pager or an I/O error
581 * XXX - the check for kernel_map is a kludge to work
582 * around having the machine panic on a kernel space
583 * fault w/ I/O error.
585 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
586 (rv == VM_PAGER_BAD)) {
589 unlock_and_deallocate(&fs);
590 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
592 if (fs.object != fs.first_object) {
596 * XXX - we cannot just fall out at this
597 * point, m has been freed and is invalid!
603 * We get here if the object has default pager (or unwiring)
604 * or the pager doesn't have the page.
606 if (fs.object == fs.first_object)
610 * Move on to the next object. Lock the next object before
611 * unlocking the current one.
614 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
615 next_object = fs.object->backing_object;
616 if (next_object == NULL) {
618 * If there's no object left, fill the page in the top
621 if (fs.object != fs.first_object) {
622 vm_object_pip_wakeup(fs.object);
624 fs.object = fs.first_object;
625 fs.pindex = fs.first_pindex;
631 * Zero the page if necessary and mark it valid.
633 if ((fs.m->flags & PG_ZERO) == 0) {
634 vm_page_zero_fill(fs.m);
636 mycpu->gd_cnt.v_ozfod++;
638 mycpu->gd_cnt.v_zfod++;
639 fs.m->valid = VM_PAGE_BITS_ALL;
640 break; /* break to PAGE HAS BEEN FOUND */
642 if (fs.object != fs.first_object) {
643 vm_object_pip_wakeup(fs.object);
645 KASSERT(fs.object != next_object, ("object loop %p", next_object));
646 fs.object = next_object;
647 vm_object_pip_add(fs.object, 1);
651 KASSERT((fs.m->flags & PG_BUSY) != 0,
652 ("vm_fault: not busy after main loop"));
655 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
660 * If the page is being written, but isn't already owned by the
661 * top-level object, we have to copy it into a new page owned by the
665 if (fs.object != fs.first_object) {
667 * We only really need to copy if we want to write it.
670 if (fault_type & VM_PROT_WRITE) {
672 * This allows pages to be virtually copied from a
673 * backing_object into the first_object, where the
674 * backing object has no other refs to it, and cannot
675 * gain any more refs. Instead of a bcopy, we just
676 * move the page from the backing object to the
677 * first object. Note that we must mark the page
678 * dirty in the first object so that it will go out
679 * to swap when needed.
681 if (map_generation == fs.map->timestamp &&
683 * Only one shadow object
685 (fs.object->shadow_count == 1) &&
687 * No COW refs, except us
689 (fs.object->ref_count == 1) &&
691 * No one else can look this object up
693 (fs.object->handle == NULL) &&
695 * No other ways to look the object up
697 ((fs.object->type == OBJT_DEFAULT) ||
698 (fs.object->type == OBJT_SWAP)) &&
700 * We don't chase down the shadow chain
702 (fs.object == fs.first_object->backing_object) &&
705 * grab the lock if we need to
707 (fs.lookup_still_valid ||
708 lockmgr(&fs.map->lock, LK_EXCLUSIVE|LK_NOWAIT, NULL, curthread) == 0)
711 fs.lookup_still_valid = 1;
713 * get rid of the unnecessary page
715 vm_page_protect(fs.first_m, VM_PROT_NONE);
716 vm_page_free(fs.first_m);
720 * grab the page and put it into the
721 * process'es object. The page is
722 * automatically made dirty.
724 vm_page_rename(fs.m, fs.first_object, fs.first_pindex);
726 vm_page_busy(fs.first_m);
728 mycpu->gd_cnt.v_cow_optim++;
731 * Oh, well, lets copy it.
733 vm_page_copy(fs.m, fs.first_m);
738 * We no longer need the old page or object.
744 * fs.object != fs.first_object due to above
748 vm_object_pip_wakeup(fs.object);
751 * Only use the new page below...
754 mycpu->gd_cnt.v_cow_faults++;
756 fs.object = fs.first_object;
757 fs.pindex = fs.first_pindex;
760 prot &= ~VM_PROT_WRITE;
765 * We must verify that the maps have not changed since our last
769 if (!fs.lookup_still_valid &&
770 (fs.map->timestamp != map_generation)) {
771 vm_object_t retry_object;
772 vm_pindex_t retry_pindex;
773 vm_prot_t retry_prot;
776 * Since map entries may be pageable, make sure we can take a
777 * page fault on them.
781 * Unlock vnode before the lookup to avoid deadlock. E.G.
782 * avoid a deadlock between the inode and exec_map that can
783 * occur due to locks being obtained in different orders.
791 if (fs.map->infork) {
793 unlock_and_deallocate(&fs);
798 * To avoid trying to write_lock the map while another process
799 * has it read_locked (in vm_map_wire), we do not try for
800 * write permission. If the page is still writable, we will
801 * get write permission. If it is not, or has been marked
802 * needs_copy, we enter the mapping without write permission,
803 * and will merely take another fault.
805 result = vm_map_lookup(&fs.map, vaddr, fault_type & ~VM_PROT_WRITE,
806 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
807 map_generation = fs.map->timestamp;
810 * If we don't need the page any longer, put it on the active
811 * list (the easiest thing to do here). If no one needs it,
812 * pageout will grab it eventually.
815 if (result != KERN_SUCCESS) {
817 unlock_and_deallocate(&fs);
820 fs.lookup_still_valid = TRUE;
822 if ((retry_object != fs.first_object) ||
823 (retry_pindex != fs.first_pindex)) {
825 unlock_and_deallocate(&fs);
829 * Check whether the protection has changed or the object has
830 * been copied while we left the map unlocked. Changing from
831 * read to write permission is OK - we leave the page
832 * write-protected, and catch the write fault. Changing from
833 * write to read permission means that we can't mark the page
834 * write-enabled after all.
840 * Put this page into the physical map. We had to do the unlock above
841 * because pmap_enter may cause other faults. We don't put the page
842 * back on the active queue until later so that the page-out daemon
843 * won't find us (yet).
846 if (prot & VM_PROT_WRITE) {
847 vm_page_flag_set(fs.m, PG_WRITEABLE);
848 vm_object_set_writeable_dirty(fs.m->object);
851 * If the fault is a write, we know that this page is being
852 * written NOW so dirty it explicitly to save on
853 * pmap_is_modified() calls later.
855 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC
856 * if the page is already dirty to prevent data written with
857 * the expectation of being synced from not being synced.
858 * Likewise if this entry does not request NOSYNC then make
859 * sure the page isn't marked NOSYNC. Applications sharing
860 * data should use the same flags to avoid ping ponging.
862 * Also tell the backing pager, if any, that it should remove
863 * any swap backing since the page is now dirty.
865 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) {
866 if (fs.m->dirty == 0)
867 vm_page_flag_set(fs.m, PG_NOSYNC);
869 vm_page_flag_clear(fs.m, PG_NOSYNC);
871 if (fault_flags & VM_FAULT_DIRTY) {
874 vm_pager_page_unswapped(fs.m);
880 * Page had better still be busy
883 KASSERT(fs.m->flags & PG_BUSY,
884 ("vm_fault: page %p not busy!", fs.m));
889 * Sanity check: page must be completely valid or it is not fit to
890 * map into user space. vm_pager_get_pages() ensures this.
893 if (fs.m->valid != VM_PAGE_BITS_ALL) {
894 vm_page_zero_invalid(fs.m, TRUE);
895 printf("Warning: page %p partially invalid on fault\n", fs.m);
898 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired);
900 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) {
901 pmap_prefault(fs.map->pmap, vaddr, fs.entry);
904 vm_page_flag_clear(fs.m, PG_ZERO);
905 vm_page_flag_set(fs.m, PG_MAPPED|PG_REFERENCED);
906 if (fault_flags & VM_FAULT_HOLD)
910 * If the page is not wired down, then put it where the pageout daemon
914 if (fault_flags & VM_FAULT_WIRE_MASK) {
918 vm_page_unwire(fs.m, 1);
920 vm_page_activate(fs.m);
923 if (curproc && (curproc->p_flag & P_SWAPPEDOUT) == 0 &&
926 curproc->p_stats->p_ru.ru_majflt++;
928 curproc->p_stats->p_ru.ru_minflt++;
933 * Unlock everything, and return
936 vm_page_wakeup(fs.m);
937 vm_object_deallocate(fs.first_object);
939 return (KERN_SUCCESS);
944 * quick version of vm_fault
947 vm_fault_quick(caddr_t v, int prot)
951 if (prot & VM_PROT_WRITE)
952 r = subyte(v, fubyte(v));
959 * Wire down a range of virtual addresses in a map. The entry in question
960 * should be marked in-transition and the map must be locked. We must
961 * release the map temporarily while faulting-in the page to avoid a
962 * deadlock. Note that the entry may be clipped while we are blocked but
963 * will never be freed.
966 vm_fault_wire(vm_map_t map, vm_map_entry_t entry, boolean_t user_wire)
968 boolean_t fictitious;
976 pmap = vm_map_pmap(map);
977 start = entry->start;
979 fictitious = entry->object.vm_object &&
980 (entry->object.vm_object->type == OBJT_DEVICE);
986 * We simulate a fault to get the page and enter it in the physical
989 for (va = start; va < end; va += PAGE_SIZE) {
991 rv = vm_fault(map, va, VM_PROT_READ,
994 rv = vm_fault(map, va, VM_PROT_READ|VM_PROT_WRITE,
995 VM_FAULT_CHANGE_WIRING);
1000 if ((pa = pmap_extract(pmap, va)) == 0)
1002 pmap_change_wiring(pmap, va, FALSE);
1004 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1);
1011 return (KERN_SUCCESS);
1015 * Unwire a range of virtual addresses in a map. The map should be
1019 vm_fault_unwire(vm_map_t map, vm_map_entry_t entry)
1021 boolean_t fictitious;
1028 pmap = vm_map_pmap(map);
1029 start = entry->start;
1031 fictitious = entry->object.vm_object &&
1032 (entry->object.vm_object->type == OBJT_DEVICE);
1035 * Since the pages are wired down, we must be able to get their
1036 * mappings from the physical map system.
1038 for (va = start; va < end; va += PAGE_SIZE) {
1039 pa = pmap_extract(pmap, va);
1041 pmap_change_wiring(pmap, va, FALSE);
1043 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1);
1049 * Reduce the rate at which memory is allocated to a process based
1050 * on the perceived load on the VM system. As the load increases
1051 * the allocation burst rate goes down and the delay increases.
1053 * Rate limiting does not apply when faulting active or inactive
1054 * pages. When faulting 'cache' pages, rate limiting only applies
1055 * if the system currently has a severe page deficit.
1057 * XXX vm_pagesupply should be increased when a page is freed.
1059 * We sleep up to 1/10 of a second.
1062 vm_fault_ratelimit(struct vmspace *vmspace)
1064 if (vm_load_enable == 0)
1066 if (vmspace->vm_pagesupply > 0) {
1067 --vmspace->vm_pagesupply;
1071 if (vm_load_debug) {
1072 printf("load %-4d give %d pgs, wait %d, pid %-5d (%s)\n",
1074 (1000 - vm_load ) / 10, vm_load * hz / 10000,
1075 curproc->p_pid, curproc->p_comm);
1078 vmspace->vm_pagesupply = (1000 - vm_load) / 10;
1079 return(vm_load * hz / 10000);
1084 * vm_fault_copy_entry
1086 * Copy all of the pages from a wired-down map entry to another.
1088 * In/out conditions:
1089 * The source and destination maps must be locked for write.
1090 * The source map entry must be wired down (or be a sharing map
1091 * entry corresponding to a main map entry that is wired down).
1095 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1096 vm_map_entry_t dst_entry, vm_map_entry_t src_entry)
1098 vm_object_t dst_object;
1099 vm_object_t src_object;
1100 vm_ooffset_t dst_offset;
1101 vm_ooffset_t src_offset;
1111 src_object = src_entry->object.vm_object;
1112 src_offset = src_entry->offset;
1115 * Create the top-level object for the destination entry. (Doesn't
1116 * actually shadow anything - we copy the pages directly.)
1118 dst_object = vm_object_allocate(OBJT_DEFAULT,
1119 (vm_size_t) OFF_TO_IDX(dst_entry->end - dst_entry->start));
1121 dst_entry->object.vm_object = dst_object;
1122 dst_entry->offset = 0;
1124 prot = dst_entry->max_protection;
1127 * Loop through all of the pages in the entry's range, copying each
1128 * one from the source object (it should be there) to the destination
1131 for (vaddr = dst_entry->start, dst_offset = 0;
1132 vaddr < dst_entry->end;
1133 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) {
1136 * Allocate a page in the destination object
1139 dst_m = vm_page_alloc(dst_object,
1140 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL);
1141 if (dst_m == NULL) {
1144 } while (dst_m == NULL);
1147 * Find the page in the source object, and copy it in.
1148 * (Because the source is wired down, the page will be in
1151 src_m = vm_page_lookup(src_object,
1152 OFF_TO_IDX(dst_offset + src_offset));
1154 panic("vm_fault_copy_wired: page missing");
1156 vm_page_copy(src_m, dst_m);
1159 * Enter it in the pmap...
1162 vm_page_flag_clear(dst_m, PG_ZERO);
1163 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE);
1164 vm_page_flag_set(dst_m, PG_WRITEABLE|PG_MAPPED);
1167 * Mark it no longer busy, and put it on the active list.
1169 vm_page_activate(dst_m);
1170 vm_page_wakeup(dst_m);
1176 * This routine checks around the requested page for other pages that
1177 * might be able to be faulted in. This routine brackets the viable
1178 * pages for the pages to be paged in.
1181 * m, rbehind, rahead
1184 * marray (array of vm_page_t), reqpage (index of requested page)
1187 * number of pages in marray
1190 vm_fault_additional_pages(vm_page_t m, int rbehind, int rahead,
1191 vm_page_t *marray, int *reqpage)
1195 vm_pindex_t pindex, startpindex, endpindex, tpindex;
1197 int cbehind, cahead;
1203 * we don't fault-ahead for device pager
1205 if (object->type == OBJT_DEVICE) {
1212 * if the requested page is not available, then give up now
1215 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1219 if ((cbehind == 0) && (cahead == 0)) {
1225 if (rahead > cahead) {
1229 if (rbehind > cbehind) {
1234 * try to do any readahead that we might have free pages for.
1236 if ((rahead + rbehind) >
1237 ((vmstats.v_free_count + vmstats.v_cache_count) - vmstats.v_free_reserved)) {
1238 pagedaemon_wakeup();
1245 * scan backward for the read behind pages -- in memory
1247 * Assume that if the page is not found an interrupt will not
1248 * create it. Theoretically interrupts can only remove (busy)
1249 * pages, not create new associations.
1252 if (rbehind > pindex) {
1256 startpindex = pindex - rbehind;
1260 for ( tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) {
1261 if (vm_page_lookup( object, tpindex)) {
1262 startpindex = tpindex + 1;
1269 for(i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) {
1271 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
1274 for (j = 0; j < i; j++) {
1275 vm_page_free(marray[j]);
1291 /* page offset of the required page */
1294 tpindex = pindex + 1;
1298 * scan forward for the read ahead pages
1300 endpindex = tpindex + rahead;
1301 if (endpindex > object->size)
1302 endpindex = object->size;
1305 for( ; tpindex < endpindex; i++, tpindex++) {
1307 if (vm_page_lookup(object, tpindex)) {
1311 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
1320 /* return number of bytes of pages */