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 <sys/param.h>
78 #include <sys/systm.h>
79 #include <sys/kernel.h>
81 #include <sys/mutex.h>
83 #include <sys/resourcevar.h>
84 #include <sys/sysctl.h>
85 #include <sys/vmmeter.h>
86 #include <sys/vnode.h>
89 #include <vm/vm_param.h>
91 #include <vm/vm_map.h>
92 #include <vm/vm_object.h>
93 #include <vm/vm_page.h>
94 #include <vm/vm_pageout.h>
95 #include <vm/vm_kern.h>
96 #include <vm/vm_pager.h>
97 #include <vm/vnode_pager.h>
98 #include <vm/vm_extern.h>
100 #include <sys/mount.h> /* XXX Temporary for VFS_LOCK_GIANT() */
104 #define PAGEORDER_SIZE (PFBAK+PFFOR)
106 static int prefault_pageorder[] = {
107 -1 * PAGE_SIZE, 1 * PAGE_SIZE,
108 -2 * PAGE_SIZE, 2 * PAGE_SIZE,
109 -3 * PAGE_SIZE, 3 * PAGE_SIZE,
110 -4 * PAGE_SIZE, 4 * PAGE_SIZE
113 static int vm_fault_additional_pages(vm_page_t, int, int, vm_page_t *, int *);
114 static void vm_fault_prefault(pmap_t, vm_offset_t, vm_map_entry_t);
116 #define VM_FAULT_READ_AHEAD 8
117 #define VM_FAULT_READ_BEHIND 7
118 #define VM_FAULT_READ (VM_FAULT_READ_AHEAD+VM_FAULT_READ_BEHIND+1)
125 vm_object_t first_object;
126 vm_pindex_t first_pindex;
128 vm_map_entry_t entry;
129 int lookup_still_valid;
134 release_page(struct faultstate *fs)
136 vm_page_lock_queues();
137 vm_page_wakeup(fs->m);
138 vm_page_deactivate(fs->m);
139 vm_page_unlock_queues();
144 unlock_map(struct faultstate *fs)
146 if (fs->lookup_still_valid) {
147 vm_map_lookup_done(fs->map, fs->entry);
148 fs->lookup_still_valid = FALSE;
153 unlock_and_deallocate(struct faultstate *fs)
155 boolean_t firstobjneedgiant;
157 vm_object_pip_wakeup(fs->object);
158 VM_OBJECT_UNLOCK(fs->object);
159 if (fs->object != fs->first_object) {
160 VM_OBJECT_LOCK(fs->first_object);
161 vm_page_lock_queues();
162 vm_page_free(fs->first_m);
163 vm_page_unlock_queues();
164 vm_object_pip_wakeup(fs->first_object);
165 VM_OBJECT_UNLOCK(fs->first_object);
168 firstobjneedgiant = (fs->first_object->flags & OBJ_NEEDGIANT) != 0;
169 vm_object_deallocate(fs->first_object);
171 if (fs->vp != NULL) {
174 vfslocked = VFS_LOCK_GIANT(fs->vp->v_mount);
177 VFS_UNLOCK_GIANT(vfslocked);
179 if (firstobjneedgiant)
184 * TRYPAGER - used by vm_fault to calculate whether the pager for the
185 * current object *might* contain the page.
187 * default objects are zero-fill, there is no real pager.
189 #define TRYPAGER (fs.object->type != OBJT_DEFAULT && \
190 (((fault_flags & VM_FAULT_WIRE_MASK) == 0) || wired))
195 * Handle a page fault occurring at the given address,
196 * requiring the given permissions, in the map specified.
197 * If successful, the page is inserted into the
198 * associated physical map.
200 * NOTE: the given address should be truncated to the
201 * proper page address.
203 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
204 * 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,
215 int is_first_object_locked, result;
216 boolean_t growstack, wired;
218 vm_object_t next_object;
219 vm_page_t marray[VM_FAULT_READ];
222 struct faultstate fs;
226 atomic_add_int(&cnt.v_vm_faults, 1);
231 * Find the backing store object and offset into it to begin the
235 result = vm_map_lookup(&fs.map, vaddr, fault_type, &fs.entry,
236 &fs.first_object, &fs.first_pindex, &prot, &wired);
237 if (result != KERN_SUCCESS) {
238 if (result != KERN_PROTECTION_FAILURE ||
239 (fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE) {
240 if (growstack && result == KERN_INVALID_ADDRESS &&
241 map != kernel_map && curproc != NULL) {
242 result = vm_map_growstack(curproc, vaddr);
243 if (result != KERN_SUCCESS)
244 return (KERN_FAILURE);
252 * If we are user-wiring a r/w segment, and it is COW, then
253 * we need to do the COW operation. Note that we don't COW
254 * currently RO sections now, because it is NOT desirable
255 * to COW .text. We simply keep .text from ever being COW'ed
256 * and take the heat that one cannot debug wired .text sections.
258 result = vm_map_lookup(&fs.map, vaddr,
259 VM_PROT_READ|VM_PROT_WRITE|VM_PROT_OVERRIDE_WRITE,
260 &fs.entry, &fs.first_object, &fs.first_pindex, &prot, &wired);
261 if (result != KERN_SUCCESS)
265 * If we don't COW now, on a user wire, the user will never
266 * be able to write to the mapping. If we don't make this
267 * restriction, the bookkeeping would be nearly impossible.
269 * XXX The following assignment modifies the map without
270 * holding a write lock on it.
272 if ((fs.entry->protection & VM_PROT_WRITE) == 0)
273 fs.entry->max_protection &= ~VM_PROT_WRITE;
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 * XXX vnode_pager_lock() can block without releasing the map lock.
295 if (fs.first_object->flags & OBJ_NEEDGIANT)
297 VM_OBJECT_LOCK(fs.first_object);
298 vm_object_reference_locked(fs.first_object);
299 fs.vp = vnode_pager_lock(fs.first_object);
300 KASSERT(fs.vp == NULL || !fs.map->system_map,
301 ("vm_fault: vnode-backed object mapped by system map"));
302 KASSERT((fs.first_object->flags & OBJ_NEEDGIANT) == 0 ||
304 ("vm_fault: Object requiring giant mapped by system map"));
305 if (fs.first_object->flags & OBJ_NEEDGIANT && debug_mpsafevm)
307 vm_object_pip_add(fs.first_object, 1);
309 fs.lookup_still_valid = TRUE;
317 * Search for the page at object/offset.
319 fs.object = fs.first_object;
320 fs.pindex = fs.first_pindex;
323 * If the object is dead, we stop here
325 if (fs.object->flags & OBJ_DEAD) {
326 unlock_and_deallocate(&fs);
327 return (KERN_PROTECTION_FAILURE);
331 * See if page is resident
333 fs.m = vm_page_lookup(fs.object, fs.pindex);
338 * check for page-based copy on write.
339 * We check fs.object == fs.first_object so
340 * as to ensure the legacy COW mechanism is
341 * used when the page in question is part of
342 * a shadow object. Otherwise, vm_page_cowfault()
343 * removes the page from the backing object,
344 * which is not what we want.
346 vm_page_lock_queues();
348 (fault_type & VM_PROT_WRITE) &&
349 (fs.object == fs.first_object)) {
350 vm_page_cowfault(fs.m);
351 vm_page_unlock_queues();
352 unlock_and_deallocate(&fs);
357 * Wait/Retry if the page is busy. We have to do this
358 * if the page is busy via either PG_BUSY or
359 * vm_page_t->busy because the vm_pager may be using
360 * vm_page_t->busy for pageouts ( and even pageins if
361 * it is the vnode pager ), and we could end up trying
362 * to pagein and pageout the same page simultaneously.
364 * We can theoretically allow the busy case on a read
365 * fault if the page is marked valid, but since such
366 * pages are typically already pmap'd, putting that
367 * special case in might be more effort then it is
368 * worth. We cannot under any circumstances mess
369 * around with a vm_page_t->busy page except, perhaps,
372 if ((fs.m->flags & PG_BUSY) || fs.m->busy) {
373 vm_page_unlock_queues();
374 VM_OBJECT_UNLOCK(fs.object);
375 if (fs.object != fs.first_object) {
376 VM_OBJECT_LOCK(fs.first_object);
377 vm_page_lock_queues();
378 vm_page_free(fs.first_m);
379 vm_page_unlock_queues();
380 vm_object_pip_wakeup(fs.first_object);
381 VM_OBJECT_UNLOCK(fs.first_object);
388 vfslck = VFS_LOCK_GIANT(fs.vp->v_mount);
391 VFS_UNLOCK_GIANT(vfslck);
393 VM_OBJECT_LOCK(fs.object);
394 if (fs.m == vm_page_lookup(fs.object,
396 vm_page_lock_queues();
397 if (!vm_page_sleep_if_busy(fs.m, TRUE,
399 vm_page_unlock_queues();
401 vm_object_pip_wakeup(fs.object);
402 VM_OBJECT_UNLOCK(fs.object);
403 atomic_add_int(&cnt.v_intrans, 1);
404 if (fs.first_object->flags & OBJ_NEEDGIANT)
406 vm_object_deallocate(fs.first_object);
411 vm_pageq_remove_nowakeup(fs.m);
413 if (VM_PAGE_RESOLVEQUEUE(fs.m, queue) == PQ_CACHE &&
414 vm_page_count_severe()) {
415 vm_page_activate(fs.m);
416 vm_page_unlock_queues();
417 unlock_and_deallocate(&fs);
423 * Mark page busy for other processes, and the
424 * pagedaemon. If it still isn't completely valid
425 * (readable), jump to readrest, else break-out ( we
429 vm_page_unlock_queues();
430 if (((fs.m->valid & VM_PAGE_BITS_ALL) != VM_PAGE_BITS_ALL) &&
431 fs.m->object != kernel_object && fs.m->object != kmem_object) {
439 * Page is not resident, If this is the search termination
440 * or the pager might contain the page, allocate a new page.
442 if (TRYPAGER || fs.object == fs.first_object) {
443 if (fs.pindex >= fs.object->size) {
444 unlock_and_deallocate(&fs);
445 return (KERN_PROTECTION_FAILURE);
449 * Allocate a new page for this object/offset pair.
452 if (!vm_page_count_severe()) {
453 fs.m = vm_page_alloc(fs.object, fs.pindex,
454 (fs.vp || fs.object->backing_object)? VM_ALLOC_NORMAL: VM_ALLOC_ZERO);
457 unlock_and_deallocate(&fs);
465 * We have found a valid page or we have allocated a new page.
466 * The page thus may not be valid or may not be entirely
469 * Attempt to fault-in the page if there is a chance that the
470 * pager has it, and potentially fault in additional pages
477 u_char behavior = vm_map_entry_behavior(fs.entry);
479 if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
483 behind = (vaddr - fs.entry->start) >> PAGE_SHIFT;
484 if (behind > VM_FAULT_READ_BEHIND)
485 behind = VM_FAULT_READ_BEHIND;
487 ahead = ((fs.entry->end - vaddr) >> PAGE_SHIFT) - 1;
488 if (ahead > VM_FAULT_READ_AHEAD)
489 ahead = VM_FAULT_READ_AHEAD;
491 is_first_object_locked = FALSE;
492 if ((behavior == MAP_ENTRY_BEHAV_SEQUENTIAL ||
493 (behavior != MAP_ENTRY_BEHAV_RANDOM &&
494 fs.pindex >= fs.entry->lastr &&
495 fs.pindex < fs.entry->lastr + VM_FAULT_READ)) &&
496 (fs.first_object == fs.object ||
497 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object))) &&
498 fs.first_object->type != OBJT_DEVICE) {
499 vm_pindex_t firstpindex, tmppindex;
501 if (fs.first_pindex < 2 * VM_FAULT_READ)
504 firstpindex = fs.first_pindex - 2 * VM_FAULT_READ;
506 vm_page_lock_queues();
508 * note: partially valid pages cannot be
509 * included in the lookahead - NFS piecemeal
510 * writes will barf on it badly.
512 for (tmppindex = fs.first_pindex - 1;
513 tmppindex >= firstpindex;
517 mt = vm_page_lookup(fs.first_object, tmppindex);
518 if (mt == NULL || (mt->valid != VM_PAGE_BITS_ALL))
521 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) ||
527 vm_page_deactivate(mt);
532 vm_page_unlock_queues();
536 if (is_first_object_locked)
537 VM_OBJECT_UNLOCK(fs.first_object);
539 * now we find out if any other pages should be paged
540 * in at this time this routine checks to see if the
541 * pages surrounding this fault reside in the same
542 * object as the page for this fault. If they do,
543 * then they are faulted in also into the object. The
544 * array "marray" returned contains an array of
545 * vm_page_t structs where one of them is the
546 * vm_page_t passed to the routine. The reqpage
547 * return value is the index into the marray for the
548 * vm_page_t passed to the routine.
550 * fs.m plus the additional pages are PG_BUSY'd.
552 * XXX vm_fault_additional_pages() can block
553 * without releasing the map lock.
555 faultcount = vm_fault_additional_pages(
556 fs.m, behind, ahead, marray, &reqpage);
559 * update lastr imperfectly (we do not know how much
560 * getpages will actually read), but good enough.
562 * XXX The following assignment modifies the map
563 * without holding a write lock on it.
565 fs.entry->lastr = fs.pindex + faultcount - behind;
568 * Call the pager to retrieve the data, if any, after
569 * releasing the lock on the map. We hold a ref on
570 * fs.object and the pages are PG_BUSY'd.
575 vm_pager_get_pages(fs.object, marray, faultcount,
576 reqpage) : VM_PAGER_FAIL;
578 if (rv == VM_PAGER_OK) {
580 * Found the page. Leave it busy while we play
585 * Relookup in case pager changed page. Pager
586 * is responsible for disposition of old page
589 fs.m = vm_page_lookup(fs.object, fs.pindex);
591 unlock_and_deallocate(&fs);
596 break; /* break to PAGE HAS BEEN FOUND */
599 * Remove the bogus page (which does not exist at this
600 * object/offset); before doing so, we must get back
601 * our object lock to preserve our invariant.
603 * Also wake up any other process that may want to bring
606 * If this is the top-level object, we must leave the
607 * busy page to prevent another process from rushing
608 * past us, and inserting the page in that object at
609 * the same time that we are.
611 if (rv == VM_PAGER_ERROR)
612 printf("vm_fault: pager read error, pid %d (%s)\n",
613 curproc->p_pid, curproc->p_comm);
615 * Data outside the range of the pager or an I/O error
618 * XXX - the check for kernel_map is a kludge to work
619 * around having the machine panic on a kernel space
620 * fault w/ I/O error.
622 if (((fs.map != kernel_map) && (rv == VM_PAGER_ERROR)) ||
623 (rv == VM_PAGER_BAD)) {
624 vm_page_lock_queues();
626 vm_page_unlock_queues();
628 unlock_and_deallocate(&fs);
629 return ((rv == VM_PAGER_ERROR) ? KERN_FAILURE : KERN_PROTECTION_FAILURE);
631 if (fs.object != fs.first_object) {
632 vm_page_lock_queues();
634 vm_page_unlock_queues();
637 * XXX - we cannot just fall out at this
638 * point, m has been freed and is invalid!
644 * We get here if the object has default pager (or unwiring)
645 * or the pager doesn't have the page.
647 if (fs.object == fs.first_object)
651 * Move on to the next object. Lock the next object before
652 * unlocking the current one.
654 fs.pindex += OFF_TO_IDX(fs.object->backing_object_offset);
655 next_object = fs.object->backing_object;
656 if (next_object == NULL) {
658 * If there's no object left, fill the page in the top
661 if (fs.object != fs.first_object) {
662 vm_object_pip_wakeup(fs.object);
663 VM_OBJECT_UNLOCK(fs.object);
665 fs.object = fs.first_object;
666 fs.pindex = fs.first_pindex;
668 VM_OBJECT_LOCK(fs.object);
673 * Zero the page if necessary and mark it valid.
675 if ((fs.m->flags & PG_ZERO) == 0) {
676 pmap_zero_page(fs.m);
678 atomic_add_int(&cnt.v_ozfod, 1);
680 atomic_add_int(&cnt.v_zfod, 1);
681 fs.m->valid = VM_PAGE_BITS_ALL;
682 break; /* break to PAGE HAS BEEN FOUND */
684 KASSERT(fs.object != next_object,
685 ("object loop %p", next_object));
686 VM_OBJECT_LOCK(next_object);
687 vm_object_pip_add(next_object, 1);
688 if (fs.object != fs.first_object)
689 vm_object_pip_wakeup(fs.object);
690 VM_OBJECT_UNLOCK(fs.object);
691 fs.object = next_object;
695 KASSERT((fs.m->flags & PG_BUSY) != 0,
696 ("vm_fault: not busy after main loop"));
699 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
704 * If the page is being written, but isn't already owned by the
705 * top-level object, we have to copy it into a new page owned by the
708 if (fs.object != fs.first_object) {
710 * We only really need to copy if we want to write it.
712 if (fault_type & VM_PROT_WRITE) {
714 * This allows pages to be virtually copied from a
715 * backing_object into the first_object, where the
716 * backing object has no other refs to it, and cannot
717 * gain any more refs. Instead of a bcopy, we just
718 * move the page from the backing object to the
719 * first object. Note that we must mark the page
720 * dirty in the first object so that it will go out
721 * to swap when needed.
723 is_first_object_locked = FALSE;
726 * Only one shadow object
728 (fs.object->shadow_count == 1) &&
730 * No COW refs, except us
732 (fs.object->ref_count == 1) &&
734 * No one else can look this object up
736 (fs.object->handle == NULL) &&
738 * No other ways to look the object up
740 ((fs.object->type == OBJT_DEFAULT) ||
741 (fs.object->type == OBJT_SWAP)) &&
742 (is_first_object_locked = VM_OBJECT_TRYLOCK(fs.first_object)) &&
744 * We don't chase down the shadow chain
746 fs.object == fs.first_object->backing_object) {
747 vm_page_lock_queues();
749 * get rid of the unnecessary page
751 vm_page_free(fs.first_m);
753 * grab the page and put it into the
754 * process'es object. The page is
755 * automatically made dirty.
757 vm_page_rename(fs.m, fs.first_object, fs.first_pindex);
759 vm_page_unlock_queues();
762 atomic_add_int(&cnt.v_cow_optim, 1);
765 * Oh, well, lets copy it.
767 pmap_copy_page(fs.m, fs.first_m);
768 fs.first_m->valid = VM_PAGE_BITS_ALL;
772 * We no longer need the old page or object.
777 * fs.object != fs.first_object due to above
780 vm_object_pip_wakeup(fs.object);
781 VM_OBJECT_UNLOCK(fs.object);
783 * Only use the new page below...
785 fs.object = fs.first_object;
786 fs.pindex = fs.first_pindex;
788 if (!is_first_object_locked)
789 VM_OBJECT_LOCK(fs.object);
790 atomic_add_int(&cnt.v_cow_faults, 1);
792 prot &= ~VM_PROT_WRITE;
797 * We must verify that the maps have not changed since our last
800 if (!fs.lookup_still_valid) {
801 vm_object_t retry_object;
802 vm_pindex_t retry_pindex;
803 vm_prot_t retry_prot;
805 if (!vm_map_trylock_read(fs.map)) {
807 unlock_and_deallocate(&fs);
810 fs.lookup_still_valid = TRUE;
811 if (fs.map->timestamp != map_generation) {
812 result = vm_map_lookup_locked(&fs.map, vaddr, fault_type,
813 &fs.entry, &retry_object, &retry_pindex, &retry_prot, &wired);
816 * If we don't need the page any longer, put it on the inactive
817 * list (the easiest thing to do here). If no one needs it,
818 * pageout will grab it eventually.
820 if (result != KERN_SUCCESS) {
822 unlock_and_deallocate(&fs);
825 * If retry of map lookup would have blocked then
826 * retry fault from start.
828 if (result == KERN_FAILURE)
832 if ((retry_object != fs.first_object) ||
833 (retry_pindex != fs.first_pindex)) {
835 unlock_and_deallocate(&fs);
840 * Check whether the protection has changed or the object has
841 * been copied while we left the map unlocked. Changing from
842 * read to write permission is OK - we leave the page
843 * write-protected, and catch the write fault. Changing from
844 * write to read permission means that we can't mark the page
845 * write-enabled after all.
850 if (prot & VM_PROT_WRITE) {
851 vm_page_lock_queues();
852 vm_page_flag_set(fs.m, PG_WRITEABLE);
853 vm_object_set_writeable_dirty(fs.m->object);
856 * If the fault is a write, we know that this page is being
857 * written NOW so dirty it explicitly to save on
858 * pmap_is_modified() calls later.
860 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC
861 * if the page is already dirty to prevent data written with
862 * the expectation of being synced from not being synced.
863 * Likewise if this entry does not request NOSYNC then make
864 * sure the page isn't marked NOSYNC. Applications sharing
865 * data should use the same flags to avoid ping ponging.
867 * Also tell the backing pager, if any, that it should remove
868 * any swap backing since the page is now dirty.
870 if (fs.entry->eflags & MAP_ENTRY_NOSYNC) {
871 if (fs.m->dirty == 0)
872 vm_page_flag_set(fs.m, PG_NOSYNC);
874 vm_page_flag_clear(fs.m, PG_NOSYNC);
876 vm_page_unlock_queues();
877 if (fault_flags & VM_FAULT_DIRTY) {
879 vm_pager_page_unswapped(fs.m);
884 * Page had better still be busy
886 KASSERT(fs.m->flags & PG_BUSY,
887 ("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.
892 if (fs.m->valid != VM_PAGE_BITS_ALL) {
893 vm_page_zero_invalid(fs.m, TRUE);
894 printf("Warning: page %p partially invalid on fault\n", fs.m);
896 VM_OBJECT_UNLOCK(fs.object);
899 * Put this page into the physical map. We had to do the unlock above
900 * because pmap_enter() may sleep. We don't put the page
901 * back on the active queue until later so that the pageout daemon
902 * won't find it (yet).
904 pmap_enter(fs.map->pmap, vaddr, fs.m, prot, wired);
905 if (((fault_flags & VM_FAULT_WIRE_MASK) == 0) && (wired == 0)) {
906 vm_fault_prefault(fs.map->pmap, vaddr, fs.entry);
908 VM_OBJECT_LOCK(fs.object);
909 vm_page_lock_queues();
910 vm_page_flag_set(fs.m, PG_REFERENCED);
913 * If the page is not wired down, then put it where the pageout daemon
916 if (fault_flags & VM_FAULT_WIRE_MASK) {
920 vm_page_unwire(fs.m, 1);
922 vm_page_activate(fs.m);
924 vm_page_wakeup(fs.m);
925 vm_page_unlock_queues();
928 * Unlock everything, and return
930 unlock_and_deallocate(&fs);
932 if ((curproc->p_sflag & PS_INMEM) && curproc->p_stats) {
934 curproc->p_stats->p_ru.ru_majflt++;
936 curproc->p_stats->p_ru.ru_minflt++;
939 PROC_UNLOCK(curproc);
941 return (KERN_SUCCESS);
945 * vm_fault_prefault provides a quick way of clustering
946 * pagefaults into a processes address space. It is a "cousin"
947 * of vm_map_pmap_enter, except it runs at page fault time instead
951 vm_fault_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry)
954 vm_offset_t addr, starta;
959 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
962 object = entry->object.vm_object;
964 starta = addra - PFBAK * PAGE_SIZE;
965 if (starta < entry->start) {
966 starta = entry->start;
967 } else if (starta > addra) {
972 for (i = 0; i < PAGEORDER_SIZE; i++) {
973 vm_object_t backing_object, lobject;
975 addr = addra + prefault_pageorder[i];
976 if (addr > addra + (PFFOR * PAGE_SIZE))
979 if (addr < starta || addr >= entry->end)
982 if (!pmap_is_prefaultable(pmap, addr))
985 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
987 VM_OBJECT_LOCK(lobject);
988 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
989 lobject->type == OBJT_DEFAULT &&
990 (backing_object = lobject->backing_object) != NULL) {
991 if (lobject->backing_object_offset & PAGE_MASK)
993 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
994 VM_OBJECT_LOCK(backing_object);
995 VM_OBJECT_UNLOCK(lobject);
996 lobject = backing_object;
999 * give-up when a page is not in memory
1002 VM_OBJECT_UNLOCK(lobject);
1005 if (((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) &&
1007 (m->flags & (PG_BUSY | PG_FICTITIOUS)) == 0) {
1009 vm_page_lock_queues();
1010 if (VM_PAGE_INQUEUE1(m, PQ_CACHE))
1011 vm_page_deactivate(m);
1012 mpte = pmap_enter_quick(pmap, addr, m,
1013 entry->protection, mpte);
1014 vm_page_unlock_queues();
1016 VM_OBJECT_UNLOCK(lobject);
1023 * Ensure that the requested virtual address, which may be in userland,
1024 * is valid. Fault-in the page if necessary. Return -1 on failure.
1027 vm_fault_quick(caddr_t v, int prot)
1031 if (prot & VM_PROT_WRITE)
1032 r = subyte(v, fubyte(v));
1041 * Wire down a range of virtual addresses in a map.
1044 vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1045 boolean_t user_wire, boolean_t fictitious)
1051 * We simulate a fault to get the page and enter it in the physical
1052 * map. For user wiring, we only ask for read access on currently
1053 * read-only sections.
1055 for (va = start; va < end; va += PAGE_SIZE) {
1056 rv = vm_fault(map, va,
1057 user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE,
1058 user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING);
1061 vm_fault_unwire(map, start, va, fictitious);
1065 return (KERN_SUCCESS);
1071 * Unwire a range of virtual addresses in a map.
1074 vm_fault_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
1075 boolean_t fictitious)
1081 pmap = vm_map_pmap(map);
1084 * Since the pages are wired down, we must be able to get their
1085 * mappings from the physical map system.
1087 for (va = start; va < end; va += PAGE_SIZE) {
1088 pa = pmap_extract(pmap, va);
1090 pmap_change_wiring(pmap, va, FALSE);
1092 vm_page_lock_queues();
1093 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1);
1094 vm_page_unlock_queues();
1102 * vm_fault_copy_entry
1104 * Copy all of the pages from a wired-down map entry to another.
1106 * In/out conditions:
1107 * The source and destination maps must be locked for write.
1108 * The source map entry must be wired down (or be a sharing map
1109 * entry corresponding to a main map entry that is wired down).
1112 vm_fault_copy_entry(dst_map, src_map, dst_entry, src_entry)
1115 vm_map_entry_t dst_entry;
1116 vm_map_entry_t src_entry;
1118 vm_object_t backing_object, dst_object, object;
1119 vm_object_t src_object;
1120 vm_ooffset_t dst_offset;
1121 vm_ooffset_t src_offset;
1132 src_object = src_entry->object.vm_object;
1133 src_offset = src_entry->offset;
1136 * Create the top-level object for the destination entry. (Doesn't
1137 * actually shadow anything - we copy the pages directly.)
1139 dst_object = vm_object_allocate(OBJT_DEFAULT,
1140 OFF_TO_IDX(dst_entry->end - dst_entry->start));
1142 VM_OBJECT_LOCK(dst_object);
1143 dst_entry->object.vm_object = dst_object;
1144 dst_entry->offset = 0;
1146 prot = dst_entry->max_protection;
1149 * Loop through all of the pages in the entry's range, copying each
1150 * one from the source object (it should be there) to the destination
1153 for (vaddr = dst_entry->start, dst_offset = 0;
1154 vaddr < dst_entry->end;
1155 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) {
1158 * Allocate a page in the destination object
1161 dst_m = vm_page_alloc(dst_object,
1162 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL);
1163 if (dst_m == NULL) {
1164 VM_OBJECT_UNLOCK(dst_object);
1166 VM_OBJECT_LOCK(dst_object);
1168 } while (dst_m == NULL);
1171 * Find the page in the source object, and copy it in.
1172 * (Because the source is wired down, the page will be in
1175 VM_OBJECT_LOCK(src_object);
1176 object = src_object;
1178 while ((src_m = vm_page_lookup(object, pindex +
1179 OFF_TO_IDX(dst_offset + src_offset))) == NULL &&
1180 (src_entry->protection & VM_PROT_WRITE) == 0 &&
1181 (backing_object = object->backing_object) != NULL) {
1183 * Allow fallback to backing objects if we are reading.
1185 VM_OBJECT_LOCK(backing_object);
1186 pindex += OFF_TO_IDX(object->backing_object_offset);
1187 VM_OBJECT_UNLOCK(object);
1188 object = backing_object;
1191 panic("vm_fault_copy_wired: page missing");
1192 pmap_copy_page(src_m, dst_m);
1193 VM_OBJECT_UNLOCK(object);
1194 dst_m->valid = VM_PAGE_BITS_ALL;
1195 VM_OBJECT_UNLOCK(dst_object);
1198 * Enter it in the pmap...
1200 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE);
1201 VM_OBJECT_LOCK(dst_object);
1202 vm_page_lock_queues();
1203 if ((prot & VM_PROT_WRITE) != 0)
1204 vm_page_flag_set(dst_m, PG_WRITEABLE);
1207 * Mark it no longer busy, and put it on the active list.
1209 vm_page_activate(dst_m);
1210 vm_page_wakeup(dst_m);
1211 vm_page_unlock_queues();
1213 VM_OBJECT_UNLOCK(dst_object);
1218 * This routine checks around the requested page for other pages that
1219 * might be able to be faulted in. This routine brackets the viable
1220 * pages for the pages to be paged in.
1223 * m, rbehind, rahead
1226 * marray (array of vm_page_t), reqpage (index of requested page)
1229 * number of pages in marray
1231 * This routine can't block.
1234 vm_fault_additional_pages(m, rbehind, rahead, marray, reqpage)
1243 vm_pindex_t pindex, startpindex, endpindex, tpindex;
1245 int cbehind, cahead;
1247 VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
1253 * we don't fault-ahead for device pager
1255 if (object->type == OBJT_DEVICE) {
1262 * if the requested page is not available, then give up now
1264 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1268 if ((cbehind == 0) && (cahead == 0)) {
1274 if (rahead > cahead) {
1278 if (rbehind > cbehind) {
1283 * try to do any readahead that we might have free pages for.
1285 if ((rahead + rbehind) >
1286 ((cnt.v_free_count + cnt.v_cache_count) - cnt.v_free_reserved)) {
1287 pagedaemon_wakeup();
1294 * scan backward for the read behind pages -- in memory
1297 if (rbehind > pindex) {
1301 startpindex = pindex - rbehind;
1304 for (tpindex = pindex - 1; tpindex >= startpindex; tpindex -= 1) {
1305 if (vm_page_lookup(object, tpindex)) {
1306 startpindex = tpindex + 1;
1313 for (i = 0, tpindex = startpindex; tpindex < pindex; i++, tpindex++) {
1315 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
1317 vm_page_lock_queues();
1318 for (j = 0; j < i; j++) {
1319 vm_page_free(marray[j]);
1321 vm_page_unlock_queues();
1335 /* page offset of the required page */
1338 tpindex = pindex + 1;
1342 * scan forward for the read ahead pages
1344 endpindex = tpindex + rahead;
1345 if (endpindex > object->size)
1346 endpindex = object->size;
1348 for (; tpindex < endpindex; i++, tpindex++) {
1350 if (vm_page_lookup(object, tpindex)) {
1354 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_NORMAL);
1362 /* return number of bytes of pages */