4 * Copyright (c) 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 * Copyright (c) 1994 John S. Dyson
8 * Copyright (c) 1994 David Greenman
12 * This code is derived from software contributed to Berkeley by
13 * The Mach Operating System project at Carnegie-Mellon University.
15 * Redistribution and use in source and binary forms, with or without
16 * modification, are permitted provided that the following conditions
18 * 1. Redistributions of source code must retain the above copyright
19 * notice, this list of conditions and the following disclaimer.
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in the
22 * documentation and/or other materials provided with the distribution.
23 * 3. All advertising materials mentioning features or use of this software
24 * must display the following acknowledgement:
25 * This product includes software developed by the University of
26 * California, Berkeley and its contributors.
27 * 4. Neither the name of the University nor the names of its contributors
28 * may be used to endorse or promote products derived from this software
29 * without specific prior written permission.
31 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
32 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
33 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
34 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
35 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
36 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
37 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
39 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
40 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
43 * from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94
46 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
47 * All rights reserved.
49 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
51 * Permission to use, copy, modify and distribute this software and
52 * its documentation is hereby granted, provided that both the copyright
53 * notice and this permission notice appear in all copies of the
54 * software, derivative works or modified versions, and any portions
55 * thereof, and that both notices appear in supporting documentation.
57 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
58 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
59 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
61 * Carnegie Mellon requests users of this software to return to
63 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
64 * School of Computer Science
65 * Carnegie Mellon University
66 * Pittsburgh PA 15213-3890
68 * any improvements or extensions that they make and grant Carnegie the
69 * rights to redistribute these changes.
71 * $FreeBSD: src/sys/vm/vm_fault.c,v 1.108.2.8 2002/02/26 05:49:27 silby Exp $
72 * $DragonFly: src/sys/vm/vm_fault.c,v 1.47 2008/07/01 02:02:56 dillon Exp $
76 * Page fault handling module.
79 #include <sys/param.h>
80 #include <sys/systm.h>
81 #include <sys/kernel.h>
83 #include <sys/vnode.h>
84 #include <sys/resourcevar.h>
85 #include <sys/vmmeter.h>
86 #include <sys/vkernel.h>
88 #include <sys/sysctl.h>
90 #include <cpu/lwbuf.h>
93 #include <vm/vm_param.h>
95 #include <vm/vm_map.h>
96 #include <vm/vm_object.h>
97 #include <vm/vm_page.h>
98 #include <vm/vm_pageout.h>
99 #include <vm/vm_kern.h>
100 #include <vm/vm_pager.h>
101 #include <vm/vnode_pager.h>
102 #include <vm/vm_extern.h>
104 #include <sys/thread2.h>
105 #include <vm/vm_page2.h>
113 vm_object_t first_object;
114 vm_prot_t first_prot;
116 vm_map_entry_t entry;
117 int lookup_still_valid;
126 static int vm_fast_fault = 1;
127 SYSCTL_INT(_vm, OID_AUTO, fast_fault, CTLFLAG_RW, &vm_fast_fault, 0,
128 "Burst fault zero-fill regions");
129 static int debug_cluster = 0;
130 SYSCTL_INT(_vm, OID_AUTO, debug_cluster, CTLFLAG_RW, &debug_cluster, 0, "");
132 static int vm_fault_object(struct faultstate *, vm_pindex_t, vm_prot_t);
133 static int vm_fault_vpagetable(struct faultstate *, vm_pindex_t *, vpte_t, int);
135 static int vm_fault_additional_pages (vm_page_t, int, int, vm_page_t *, int *);
137 static int vm_fault_ratelimit(struct vmspace *);
138 static void vm_set_nosync(vm_page_t m, vm_map_entry_t entry);
139 static void vm_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry,
143 * The caller must hold vm_token.
146 release_page(struct faultstate *fs)
148 vm_page_deactivate(fs->m);
149 vm_page_wakeup(fs->m);
154 * The caller must hold vm_token.
157 unlock_map(struct faultstate *fs)
159 if (fs->lookup_still_valid && fs->map) {
160 vm_map_lookup_done(fs->map, fs->entry, 0);
161 fs->lookup_still_valid = FALSE;
166 * Clean up after a successful call to vm_fault_object() so another call
167 * to vm_fault_object() can be made.
169 * The caller must hold vm_token.
172 _cleanup_successful_fault(struct faultstate *fs, int relock)
174 if (fs->object != fs->first_object) {
175 vm_page_free(fs->first_m);
176 vm_object_pip_wakeup(fs->object);
179 fs->object = fs->first_object;
180 if (relock && fs->lookup_still_valid == FALSE) {
182 vm_map_lock_read(fs->map);
183 fs->lookup_still_valid = TRUE;
188 * The caller must hold vm_token.
191 _unlock_things(struct faultstate *fs, int dealloc)
193 vm_object_pip_wakeup(fs->first_object);
194 _cleanup_successful_fault(fs, 0);
196 vm_object_deallocate(fs->first_object);
197 fs->first_object = NULL;
200 if (fs->vp != NULL) {
206 #define unlock_things(fs) _unlock_things(fs, 0)
207 #define unlock_and_deallocate(fs) _unlock_things(fs, 1)
208 #define cleanup_successful_fault(fs) _cleanup_successful_fault(fs, 1)
213 * Determine if the pager for the current object *might* contain the page.
215 * We only need to try the pager if this is not a default object (default
216 * objects are zero-fill and have no real pager), and if we are not taking
217 * a wiring fault or if the FS entry is wired.
219 #define TRYPAGER(fs) \
220 (fs->object->type != OBJT_DEFAULT && \
221 (((fs->fault_flags & VM_FAULT_WIRE_MASK) == 0) || fs->wired))
226 * Handle a page fault occuring at the given address, requiring the given
227 * permissions, in the map specified. If successful, the page is inserted
228 * into the associated physical map.
230 * NOTE: The given address should be truncated to the proper page address.
232 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
233 * a standard error specifying why the fault is fatal is returned.
235 * The map in question must be referenced, and remains so.
236 * The caller may hold no locks.
237 * No other requirements.
240 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type, int fault_flags)
243 vm_pindex_t first_pindex;
244 struct faultstate fs;
247 mycpu->gd_cnt.v_vm_faults++;
251 fs.fault_flags = fault_flags;
256 * Find the vm_map_entry representing the backing store and resolve
257 * the top level object and page index. This may have the side
258 * effect of executing a copy-on-write on the map entry and/or
259 * creating a shadow object, but will not COW any actual VM pages.
261 * On success fs.map is left read-locked and various other fields
262 * are initialized but not otherwise referenced or locked.
264 * NOTE! vm_map_lookup will try to upgrade the fault_type to
265 * VM_FAULT_WRITE if the map entry is a virtual page table and also
266 * writable, so we can set the 'A'accessed bit in the virtual page
270 result = vm_map_lookup(&fs.map, vaddr, fault_type,
271 &fs.entry, &fs.first_object,
272 &first_pindex, &fs.first_prot, &fs.wired);
275 * If the lookup failed or the map protections are incompatible,
276 * the fault generally fails. However, if the caller is trying
277 * to do a user wiring we have more work to do.
279 if (result != KERN_SUCCESS) {
280 if (result != KERN_PROTECTION_FAILURE ||
281 (fs.fault_flags & VM_FAULT_WIRE_MASK) != VM_FAULT_USER_WIRE)
283 if (result == KERN_INVALID_ADDRESS && growstack &&
284 map != &kernel_map && curproc != NULL) {
285 result = vm_map_growstack(curproc, vaddr);
286 if (result != KERN_SUCCESS)
287 return (KERN_FAILURE);
295 * If we are user-wiring a r/w segment, and it is COW, then
296 * we need to do the COW operation. Note that we don't
297 * currently COW RO sections now, because it is NOT desirable
298 * to COW .text. We simply keep .text from ever being COW'ed
299 * and take the heat that one cannot debug wired .text sections.
301 result = vm_map_lookup(&fs.map, vaddr,
302 VM_PROT_READ|VM_PROT_WRITE|
303 VM_PROT_OVERRIDE_WRITE,
304 &fs.entry, &fs.first_object,
305 &first_pindex, &fs.first_prot,
307 if (result != KERN_SUCCESS)
311 * If we don't COW now, on a user wire, the user will never
312 * be able to write to the mapping. If we don't make this
313 * restriction, the bookkeeping would be nearly impossible.
315 if ((fs.entry->protection & VM_PROT_WRITE) == 0)
316 fs.entry->max_protection &= ~VM_PROT_WRITE;
320 * fs.map is read-locked
322 * Misc checks. Save the map generation number to detect races.
324 fs.map_generation = fs.map->timestamp;
326 if (fs.entry->eflags & (MAP_ENTRY_NOFAULT | MAP_ENTRY_KSTACK)) {
327 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
328 panic("vm_fault: fault on nofault entry, addr: %p",
331 if ((fs.entry->eflags & MAP_ENTRY_KSTACK) &&
332 vaddr >= fs.entry->start &&
333 vaddr < fs.entry->start + PAGE_SIZE) {
334 panic("vm_fault: fault on stack guard, addr: %p",
340 * A system map entry may return a NULL object. No object means
341 * no pager means an unrecoverable kernel fault.
343 if (fs.first_object == NULL) {
344 panic("vm_fault: unrecoverable fault at %p in entry %p",
345 (void *)vaddr, fs.entry);
349 * Make a reference to this object to prevent its disposal while we
350 * are messing with it. Once we have the reference, the map is free
351 * to be diddled. Since objects reference their shadows (and copies),
352 * they will stay around as well.
354 * Bump the paging-in-progress count to prevent size changes (e.g.
355 * truncation operations) during I/O. This must be done after
356 * obtaining the vnode lock in order to avoid possible deadlocks.
358 * The vm_token is needed to manipulate the vm_object
360 lwkt_gettoken(&vm_token);
361 vm_object_reference(fs.first_object);
362 fs.vp = vnode_pager_lock(fs.first_object);
363 vm_object_pip_add(fs.first_object, 1);
364 lwkt_reltoken(&vm_token);
366 fs.lookup_still_valid = TRUE;
368 fs.object = fs.first_object; /* so unlock_and_deallocate works */
371 * If the entry is wired we cannot change the page protection.
374 fault_type = fs.first_prot;
377 * The page we want is at (first_object, first_pindex), but if the
378 * vm_map_entry is VM_MAPTYPE_VPAGETABLE we have to traverse the
379 * page table to figure out the actual pindex.
381 * NOTE! DEVELOPMENT IN PROGRESS, THIS IS AN INITIAL IMPLEMENTATION
384 if (fs.entry->maptype == VM_MAPTYPE_VPAGETABLE) {
385 result = vm_fault_vpagetable(&fs, &first_pindex,
386 fs.entry->aux.master_pde,
388 if (result == KERN_TRY_AGAIN)
390 if (result != KERN_SUCCESS)
395 * Now we have the actual (object, pindex), fault in the page. If
396 * vm_fault_object() fails it will unlock and deallocate the FS
397 * data. If it succeeds everything remains locked and fs->object
398 * will have an additional PIP count if it is not equal to
401 * vm_fault_object will set fs->prot for the pmap operation. It is
402 * allowed to set VM_PROT_WRITE if fault_type == VM_PROT_READ if the
403 * page can be safely written. However, it will force a read-only
404 * mapping for a read fault if the memory is managed by a virtual
407 result = vm_fault_object(&fs, first_pindex, fault_type);
409 if (result == KERN_TRY_AGAIN)
411 if (result != KERN_SUCCESS)
415 * On success vm_fault_object() does not unlock or deallocate, and fs.m
416 * will contain a busied page.
418 * Enter the page into the pmap and do pmap-related adjustments.
420 pmap_enter(fs.map->pmap, vaddr, fs.m, fs.prot, fs.wired);
423 * Burst in a few more pages if possible. The fs.map should still
426 if (fault_flags & VM_FAULT_BURST) {
427 if ((fs.fault_flags & VM_FAULT_WIRE_MASK) == 0 &&
429 vm_prefault(fs.map->pmap, vaddr, fs.entry, fs.prot);
434 vm_page_flag_clear(fs.m, PG_ZERO);
435 vm_page_flag_set(fs.m, PG_REFERENCED);
438 * If the page is not wired down, then put it where the pageout daemon
441 * We do not really need to get vm_token here but since all the
442 * vm_*() calls have to doing it here improves efficiency.
444 lwkt_gettoken(&vm_token);
445 if (fs.fault_flags & VM_FAULT_WIRE_MASK) {
449 vm_page_unwire(fs.m, 1);
451 vm_page_activate(fs.m);
454 if (curthread->td_lwp) {
456 curthread->td_lwp->lwp_ru.ru_majflt++;
458 curthread->td_lwp->lwp_ru.ru_minflt++;
463 * Unlock everything, and return
465 vm_page_wakeup(fs.m);
466 vm_object_deallocate(fs.first_object);
467 lwkt_reltoken(&vm_token);
469 return (KERN_SUCCESS);
473 * Fault in the specified virtual address in the current process map,
474 * returning a held VM page or NULL. See vm_fault_page() for more
480 vm_fault_page_quick(vm_offset_t va, vm_prot_t fault_type, int *errorp)
482 struct lwp *lp = curthread->td_lwp;
485 m = vm_fault_page(&lp->lwp_vmspace->vm_map, va,
486 fault_type, VM_FAULT_NORMAL, errorp);
491 * Fault in the specified virtual address in the specified map, doing all
492 * necessary manipulation of the object store and all necessary I/O. Return
493 * a held VM page or NULL, and set *errorp. The related pmap is not
496 * The returned page will be properly dirtied if VM_PROT_WRITE was specified,
497 * and marked PG_REFERENCED as well.
499 * If the page cannot be faulted writable and VM_PROT_WRITE was specified, an
500 * error will be returned.
505 vm_fault_page(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
506 int fault_flags, int *errorp)
508 vm_pindex_t first_pindex;
509 struct faultstate fs;
511 vm_prot_t orig_fault_type = fault_type;
513 mycpu->gd_cnt.v_vm_faults++;
517 fs.fault_flags = fault_flags;
518 KKASSERT((fault_flags & VM_FAULT_WIRE_MASK) == 0);
522 * Find the vm_map_entry representing the backing store and resolve
523 * the top level object and page index. This may have the side
524 * effect of executing a copy-on-write on the map entry and/or
525 * creating a shadow object, but will not COW any actual VM pages.
527 * On success fs.map is left read-locked and various other fields
528 * are initialized but not otherwise referenced or locked.
530 * NOTE! vm_map_lookup will upgrade the fault_type to VM_FAULT_WRITE
531 * if the map entry is a virtual page table and also writable,
532 * so we can set the 'A'accessed bit in the virtual page table entry.
535 result = vm_map_lookup(&fs.map, vaddr, fault_type,
536 &fs.entry, &fs.first_object,
537 &first_pindex, &fs.first_prot, &fs.wired);
539 if (result != KERN_SUCCESS) {
545 * fs.map is read-locked
547 * Misc checks. Save the map generation number to detect races.
549 fs.map_generation = fs.map->timestamp;
551 if (fs.entry->eflags & MAP_ENTRY_NOFAULT) {
552 panic("vm_fault: fault on nofault entry, addr: %lx",
557 * A system map entry may return a NULL object. No object means
558 * no pager means an unrecoverable kernel fault.
560 if (fs.first_object == NULL) {
561 panic("vm_fault: unrecoverable fault at %p in entry %p",
562 (void *)vaddr, fs.entry);
566 * Make a reference to this object to prevent its disposal while we
567 * are messing with it. Once we have the reference, the map is free
568 * to be diddled. Since objects reference their shadows (and copies),
569 * they will stay around as well.
571 * Bump the paging-in-progress count to prevent size changes (e.g.
572 * truncation operations) during I/O. This must be done after
573 * obtaining the vnode lock in order to avoid possible deadlocks.
575 * The vm_token is needed to manipulate the vm_object
577 lwkt_gettoken(&vm_token);
578 vm_object_reference(fs.first_object);
579 fs.vp = vnode_pager_lock(fs.first_object);
580 vm_object_pip_add(fs.first_object, 1);
581 lwkt_reltoken(&vm_token);
583 fs.lookup_still_valid = TRUE;
585 fs.object = fs.first_object; /* so unlock_and_deallocate works */
588 * If the entry is wired we cannot change the page protection.
591 fault_type = fs.first_prot;
594 * The page we want is at (first_object, first_pindex), but if the
595 * vm_map_entry is VM_MAPTYPE_VPAGETABLE we have to traverse the
596 * page table to figure out the actual pindex.
598 * NOTE! DEVELOPMENT IN PROGRESS, THIS IS AN INITIAL IMPLEMENTATION
601 if (fs.entry->maptype == VM_MAPTYPE_VPAGETABLE) {
602 result = vm_fault_vpagetable(&fs, &first_pindex,
603 fs.entry->aux.master_pde,
605 if (result == KERN_TRY_AGAIN)
607 if (result != KERN_SUCCESS) {
614 * Now we have the actual (object, pindex), fault in the page. If
615 * vm_fault_object() fails it will unlock and deallocate the FS
616 * data. If it succeeds everything remains locked and fs->object
617 * will have an additinal PIP count if it is not equal to
620 result = vm_fault_object(&fs, first_pindex, fault_type);
622 if (result == KERN_TRY_AGAIN)
624 if (result != KERN_SUCCESS) {
629 if ((orig_fault_type & VM_PROT_WRITE) &&
630 (fs.prot & VM_PROT_WRITE) == 0) {
631 *errorp = KERN_PROTECTION_FAILURE;
632 unlock_and_deallocate(&fs);
637 * On success vm_fault_object() does not unlock or deallocate, and fs.m
638 * will contain a busied page.
643 * Return a held page. We are not doing any pmap manipulation so do
644 * not set PG_MAPPED. However, adjust the page flags according to
645 * the fault type because the caller may not use a managed pmapping
646 * (so we don't want to lose the fact that the page will be dirtied
647 * if a write fault was specified).
649 lwkt_gettoken(&vm_token);
651 vm_page_flag_clear(fs.m, PG_ZERO);
652 if (fault_type & VM_PROT_WRITE)
656 * Update the pmap. We really only have to do this if a COW
657 * occured to replace the read-only page with the new page. For
658 * now just do it unconditionally. XXX
660 pmap_enter(fs.map->pmap, vaddr, fs.m, fs.prot, fs.wired);
661 vm_page_flag_set(fs.m, PG_REFERENCED);
664 * Unbusy the page by activating it. It remains held and will not
667 vm_page_activate(fs.m);
669 if (curthread->td_lwp) {
671 curthread->td_lwp->lwp_ru.ru_majflt++;
673 curthread->td_lwp->lwp_ru.ru_minflt++;
678 * Unlock everything, and return the held page.
680 vm_page_wakeup(fs.m);
681 vm_object_deallocate(fs.first_object);
682 lwkt_reltoken(&vm_token);
689 * Fault in the specified (object,offset), dirty the returned page as
690 * needed. If the requested fault_type cannot be done NULL and an
693 * A held (but not busied) page is returned.
698 vm_fault_object_page(vm_object_t object, vm_ooffset_t offset,
699 vm_prot_t fault_type, int fault_flags, int *errorp)
702 vm_pindex_t first_pindex;
703 struct faultstate fs;
704 struct vm_map_entry entry;
706 bzero(&entry, sizeof(entry));
707 entry.object.vm_object = object;
708 entry.maptype = VM_MAPTYPE_NORMAL;
709 entry.protection = entry.max_protection = fault_type;
713 fs.fault_flags = fault_flags;
715 KKASSERT((fault_flags & VM_FAULT_WIRE_MASK) == 0);
719 fs.first_object = object;
720 first_pindex = OFF_TO_IDX(offset);
722 fs.first_prot = fault_type;
724 /*fs.map_generation = 0; unused */
727 * Make a reference to this object to prevent its disposal while we
728 * are messing with it. Once we have the reference, the map is free
729 * to be diddled. Since objects reference their shadows (and copies),
730 * they will stay around as well.
732 * Bump the paging-in-progress count to prevent size changes (e.g.
733 * truncation operations) during I/O. This must be done after
734 * obtaining the vnode lock in order to avoid possible deadlocks.
736 lwkt_gettoken(&vm_token);
737 vm_object_reference(fs.first_object);
738 fs.vp = vnode_pager_lock(fs.first_object);
739 vm_object_pip_add(fs.first_object, 1);
740 lwkt_reltoken(&vm_token);
742 fs.lookup_still_valid = TRUE;
744 fs.object = fs.first_object; /* so unlock_and_deallocate works */
747 /* XXX future - ability to operate on VM object using vpagetable */
748 if (fs.entry->maptype == VM_MAPTYPE_VPAGETABLE) {
749 result = vm_fault_vpagetable(&fs, &first_pindex,
750 fs.entry->aux.master_pde,
752 if (result == KERN_TRY_AGAIN)
754 if (result != KERN_SUCCESS) {
762 * Now we have the actual (object, pindex), fault in the page. If
763 * vm_fault_object() fails it will unlock and deallocate the FS
764 * data. If it succeeds everything remains locked and fs->object
765 * will have an additinal PIP count if it is not equal to
768 result = vm_fault_object(&fs, first_pindex, fault_type);
770 if (result == KERN_TRY_AGAIN)
772 if (result != KERN_SUCCESS) {
777 if ((fault_type & VM_PROT_WRITE) && (fs.prot & VM_PROT_WRITE) == 0) {
778 *errorp = KERN_PROTECTION_FAILURE;
779 unlock_and_deallocate(&fs);
784 * On success vm_fault_object() does not unlock or deallocate, and fs.m
785 * will contain a busied page.
790 * Return a held page. We are not doing any pmap manipulation so do
791 * not set PG_MAPPED. However, adjust the page flags according to
792 * the fault type because the caller may not use a managed pmapping
793 * (so we don't want to lose the fact that the page will be dirtied
794 * if a write fault was specified).
796 lwkt_gettoken(&vm_token);
798 vm_page_flag_clear(fs.m, PG_ZERO);
799 if (fault_type & VM_PROT_WRITE)
802 if (fault_flags & VM_FAULT_DIRTY)
804 if (fault_flags & VM_FAULT_UNSWAP)
805 swap_pager_unswapped(fs.m);
808 * Indicate that the page was accessed.
810 vm_page_flag_set(fs.m, PG_REFERENCED);
813 * Unbusy the page by activating it. It remains held and will not
816 vm_page_activate(fs.m);
818 if (curthread->td_lwp) {
820 mycpu->gd_cnt.v_vm_faults++;
821 curthread->td_lwp->lwp_ru.ru_majflt++;
823 curthread->td_lwp->lwp_ru.ru_minflt++;
828 * Unlock everything, and return the held page.
830 vm_page_wakeup(fs.m);
831 vm_object_deallocate(fs.first_object);
832 lwkt_reltoken(&vm_token);
839 * Translate the virtual page number (first_pindex) that is relative
840 * to the address space into a logical page number that is relative to the
841 * backing object. Use the virtual page table pointed to by (vpte).
843 * This implements an N-level page table. Any level can terminate the
844 * scan by setting VPTE_PS. A linear mapping is accomplished by setting
845 * VPTE_PS in the master page directory entry set via mcontrol(MADV_SETMAP).
847 * No requirements (vm_token need not be held).
851 vm_fault_vpagetable(struct faultstate *fs, vm_pindex_t *pindex,
852 vpte_t vpte, int fault_type)
855 int vshift = VPTE_FRAME_END - PAGE_SHIFT; /* index bits remaining */
856 int result = KERN_SUCCESS;
861 * We cannot proceed if the vpte is not valid, not readable
862 * for a read fault, or not writable for a write fault.
864 if ((vpte & VPTE_V) == 0) {
865 unlock_and_deallocate(fs);
866 return (KERN_FAILURE);
868 if ((fault_type & VM_PROT_READ) && (vpte & VPTE_R) == 0) {
869 unlock_and_deallocate(fs);
870 return (KERN_FAILURE);
872 if ((fault_type & VM_PROT_WRITE) && (vpte & VPTE_W) == 0) {
873 unlock_and_deallocate(fs);
874 return (KERN_FAILURE);
876 if ((vpte & VPTE_PS) || vshift == 0)
878 KKASSERT(vshift >= VPTE_PAGE_BITS);
881 * Get the page table page. Nominally we only read the page
882 * table, but since we are actively setting VPTE_M and VPTE_A,
883 * tell vm_fault_object() that we are writing it.
885 * There is currently no real need to optimize this.
887 result = vm_fault_object(fs, (vpte & VPTE_FRAME) >> PAGE_SHIFT,
888 VM_PROT_READ|VM_PROT_WRITE);
889 if (result != KERN_SUCCESS)
893 * Process the returned fs.m and look up the page table
894 * entry in the page table page.
896 vshift -= VPTE_PAGE_BITS;
897 lwb = lwbuf_alloc(fs->m);
898 ptep = ((vpte_t *)lwbuf_kva(lwb) +
899 ((*pindex >> vshift) & VPTE_PAGE_MASK));
903 * Page table write-back. If the vpte is valid for the
904 * requested operation, do a write-back to the page table.
906 * XXX VPTE_M is not set properly for page directory pages.
907 * It doesn't get set in the page directory if the page table
908 * is modified during a read access.
910 if ((fault_type & VM_PROT_WRITE) && (vpte & VPTE_V) &&
912 if ((vpte & (VPTE_M|VPTE_A)) != (VPTE_M|VPTE_A)) {
913 atomic_set_long(ptep, VPTE_M | VPTE_A);
914 vm_page_dirty(fs->m);
917 if ((fault_type & VM_PROT_READ) && (vpte & VPTE_V) &&
919 if ((vpte & VPTE_A) == 0) {
920 atomic_set_long(ptep, VPTE_A);
921 vm_page_dirty(fs->m);
925 vm_page_flag_set(fs->m, PG_REFERENCED);
926 vm_page_activate(fs->m);
927 vm_page_wakeup(fs->m);
928 cleanup_successful_fault(fs);
931 * Combine remaining address bits with the vpte.
933 /* JG how many bits from each? */
934 *pindex = ((vpte & VPTE_FRAME) >> PAGE_SHIFT) +
935 (*pindex & ((1L << vshift) - 1));
936 return (KERN_SUCCESS);
941 * This is the core of the vm_fault code.
943 * Do all operations required to fault-in (fs.first_object, pindex). Run
944 * through the shadow chain as necessary and do required COW or virtual
945 * copy operations. The caller has already fully resolved the vm_map_entry
946 * and, if appropriate, has created a copy-on-write layer. All we need to
947 * do is iterate the object chain.
949 * On failure (fs) is unlocked and deallocated and the caller may return or
950 * retry depending on the failure code. On success (fs) is NOT unlocked or
951 * deallocated, fs.m will contained a resolved, busied page, and fs.object
952 * will have an additional PIP count if it is not equal to fs.first_object.
958 vm_fault_object(struct faultstate *fs,
959 vm_pindex_t first_pindex, vm_prot_t fault_type)
961 vm_object_t next_object;
964 fs->prot = fs->first_prot;
965 fs->object = fs->first_object;
966 pindex = first_pindex;
969 * If a read fault occurs we try to make the page writable if
970 * possible. There are three cases where we cannot make the
971 * page mapping writable:
973 * (1) The mapping is read-only or the VM object is read-only,
974 * fs->prot above will simply not have VM_PROT_WRITE set.
976 * (2) If the mapping is a virtual page table we need to be able
977 * to detect writes so we can set VPTE_M in the virtual page
980 * (3) If the VM page is read-only or copy-on-write, upgrading would
981 * just result in an unnecessary COW fault.
983 * VM_PROT_VPAGED is set if faulting via a virtual page table and
984 * causes adjustments to the 'M'odify bit to also turn off write
985 * access to force a re-fault.
987 if (fs->entry->maptype == VM_MAPTYPE_VPAGETABLE) {
988 if ((fault_type & VM_PROT_WRITE) == 0)
989 fs->prot &= ~VM_PROT_WRITE;
992 lwkt_gettoken(&vm_token);
996 * If the object is dead, we stop here
998 if (fs->object->flags & OBJ_DEAD) {
999 unlock_and_deallocate(fs);
1000 lwkt_reltoken(&vm_token);
1001 return (KERN_PROTECTION_FAILURE);
1005 * See if the page is resident.
1007 fs->m = vm_page_lookup(fs->object, pindex);
1008 if (fs->m != NULL) {
1011 * Wait/Retry if the page is busy. We have to do this
1012 * if the page is busy via either PG_BUSY or
1013 * vm_page_t->busy because the vm_pager may be using
1014 * vm_page_t->busy for pageouts ( and even pageins if
1015 * it is the vnode pager ), and we could end up trying
1016 * to pagein and pageout the same page simultaneously.
1018 * We can theoretically allow the busy case on a read
1019 * fault if the page is marked valid, but since such
1020 * pages are typically already pmap'd, putting that
1021 * special case in might be more effort then it is
1022 * worth. We cannot under any circumstances mess
1023 * around with a vm_page_t->busy page except, perhaps,
1026 if ((fs->m->flags & PG_BUSY) || fs->m->busy) {
1028 vm_page_sleep_busy(fs->m, TRUE, "vmpfw");
1029 mycpu->gd_cnt.v_intrans++;
1030 vm_object_deallocate(fs->first_object);
1031 fs->first_object = NULL;
1032 lwkt_reltoken(&vm_token);
1033 return (KERN_TRY_AGAIN);
1037 * If reactivating a page from PQ_CACHE we may have
1040 queue = fs->m->queue;
1041 vm_page_unqueue_nowakeup(fs->m);
1043 if ((queue - fs->m->pc) == PQ_CACHE &&
1044 vm_page_count_severe()) {
1045 vm_page_activate(fs->m);
1046 unlock_and_deallocate(fs);
1048 lwkt_reltoken(&vm_token);
1049 return (KERN_TRY_AGAIN);
1053 * Mark page busy for other processes, and the
1054 * pagedaemon. If it still isn't completely valid
1055 * (readable), or if a read-ahead-mark is set on
1056 * the VM page, jump to readrest, else we found the
1057 * page and can return.
1059 * We can release the spl once we have marked the
1062 vm_page_busy(fs->m);
1064 if (fs->m->object != &kernel_object) {
1065 if ((fs->m->valid & VM_PAGE_BITS_ALL) !=
1069 if (fs->m->flags & PG_RAM) {
1072 vm_page_flag_clear(fs->m, PG_RAM);
1076 break; /* break to PAGE HAS BEEN FOUND */
1080 * Page is not resident, If this is the search termination
1081 * or the pager might contain the page, allocate a new page.
1083 if (TRYPAGER(fs) || fs->object == fs->first_object) {
1085 * If the page is beyond the object size we fail
1087 if (pindex >= fs->object->size) {
1088 lwkt_reltoken(&vm_token);
1089 unlock_and_deallocate(fs);
1090 return (KERN_PROTECTION_FAILURE);
1096 if (fs->didlimit == 0 && curproc != NULL) {
1099 limticks = vm_fault_ratelimit(curproc->p_vmspace);
1101 lwkt_reltoken(&vm_token);
1102 unlock_and_deallocate(fs);
1103 tsleep(curproc, 0, "vmrate", limticks);
1105 return (KERN_TRY_AGAIN);
1110 * Allocate a new page for this object/offset pair.
1113 if (!vm_page_count_severe()) {
1114 fs->m = vm_page_alloc(fs->object, pindex,
1115 (fs->vp || fs->object->backing_object) ? VM_ALLOC_NORMAL : VM_ALLOC_NORMAL | VM_ALLOC_ZERO);
1117 if (fs->m == NULL) {
1118 lwkt_reltoken(&vm_token);
1119 unlock_and_deallocate(fs);
1121 return (KERN_TRY_AGAIN);
1127 * We have found an invalid or partially valid page, a
1128 * page with a read-ahead mark which might be partially or
1129 * fully valid (and maybe dirty too), or we have allocated
1132 * Attempt to fault-in the page if there is a chance that the
1133 * pager has it, and potentially fault in additional pages
1136 * We are NOT in splvm here and if TRYPAGER is true then
1137 * fs.m will be non-NULL and will be PG_BUSY for us.
1142 u_char behavior = vm_map_entry_behavior(fs->entry);
1144 if (behavior == MAP_ENTRY_BEHAV_RANDOM)
1150 * If sequential access is detected then attempt
1151 * to deactivate/cache pages behind the scan to
1152 * prevent resource hogging.
1154 * Use of PG_RAM to detect sequential access
1155 * also simulates multi-zone sequential access
1156 * detection for free.
1158 * NOTE: Partially valid dirty pages cannot be
1159 * deactivated without causing NFS picemeal
1162 if ((fs->first_object->type != OBJT_DEVICE) &&
1163 (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL ||
1164 (behavior != MAP_ENTRY_BEHAV_RANDOM &&
1165 (fs->m->flags & PG_RAM)))
1167 vm_pindex_t scan_pindex;
1168 int scan_count = 16;
1170 if (first_pindex < 16) {
1174 scan_pindex = first_pindex - 16;
1175 if (scan_pindex < 16)
1176 scan_count = scan_pindex;
1181 while (scan_count) {
1184 mt = vm_page_lookup(fs->first_object,
1187 (mt->valid != VM_PAGE_BITS_ALL)) {
1191 (mt->flags & (PG_BUSY | PG_FICTITIOUS | PG_UNMANAGED)) ||
1197 vm_page_test_dirty(mt);
1202 vm_page_deactivate(mt);
1216 * Avoid deadlocking against the map when doing I/O.
1217 * fs.object and the page is PG_BUSY'd.
1222 * Acquire the page data. We still hold a ref on
1223 * fs.object and the page has been PG_BUSY's.
1225 * The pager may replace the page (for example, in
1226 * order to enter a fictitious page into the
1227 * object). If it does so it is responsible for
1228 * cleaning up the passed page and properly setting
1229 * the new page PG_BUSY.
1231 * If we got here through a PG_RAM read-ahead
1232 * mark the page may be partially dirty and thus
1233 * not freeable. Don't bother checking to see
1234 * if the pager has the page because we can't free
1235 * it anyway. We have to depend on the get_page
1236 * operation filling in any gaps whether there is
1237 * backing store or not.
1239 rv = vm_pager_get_page(fs->object, &fs->m, seqaccess);
1241 if (rv == VM_PAGER_OK) {
1243 * Relookup in case pager changed page. Pager
1244 * is responsible for disposition of old page
1247 * XXX other code segments do relookups too.
1248 * It's a bad abstraction that needs to be
1251 fs->m = vm_page_lookup(fs->object, pindex);
1252 if (fs->m == NULL) {
1253 lwkt_reltoken(&vm_token);
1254 unlock_and_deallocate(fs);
1255 return (KERN_TRY_AGAIN);
1259 break; /* break to PAGE HAS BEEN FOUND */
1263 * Remove the bogus page (which does not exist at this
1264 * object/offset); before doing so, we must get back
1265 * our object lock to preserve our invariant.
1267 * Also wake up any other process that may want to bring
1270 * If this is the top-level object, we must leave the
1271 * busy page to prevent another process from rushing
1272 * past us, and inserting the page in that object at
1273 * the same time that we are.
1275 if (rv == VM_PAGER_ERROR) {
1277 kprintf("vm_fault: pager read error, pid %d (%s)\n", curproc->p_pid, curproc->p_comm);
1279 kprintf("vm_fault: pager read error, thread %p (%s)\n", curthread, curproc->p_comm);
1283 * Data outside the range of the pager or an I/O error
1285 * The page may have been wired during the pagein,
1286 * e.g. by the buffer cache, and cannot simply be
1287 * freed. Call vnode_pager_freepage() to deal with it.
1290 * XXX - the check for kernel_map is a kludge to work
1291 * around having the machine panic on a kernel space
1292 * fault w/ I/O error.
1294 if (((fs->map != &kernel_map) &&
1295 (rv == VM_PAGER_ERROR)) || (rv == VM_PAGER_BAD)) {
1296 vnode_pager_freepage(fs->m);
1297 lwkt_reltoken(&vm_token);
1299 unlock_and_deallocate(fs);
1300 if (rv == VM_PAGER_ERROR)
1301 return (KERN_FAILURE);
1303 return (KERN_PROTECTION_FAILURE);
1306 if (fs->object != fs->first_object) {
1307 vnode_pager_freepage(fs->m);
1310 * XXX - we cannot just fall out at this
1311 * point, m has been freed and is invalid!
1317 * We get here if the object has a default pager (or unwiring)
1318 * or the pager doesn't have the page.
1320 if (fs->object == fs->first_object)
1321 fs->first_m = fs->m;
1324 * Move on to the next object. Lock the next object before
1325 * unlocking the current one.
1327 pindex += OFF_TO_IDX(fs->object->backing_object_offset);
1328 next_object = fs->object->backing_object;
1329 if (next_object == NULL) {
1331 * If there's no object left, fill the page in the top
1332 * object with zeros.
1334 if (fs->object != fs->first_object) {
1335 vm_object_pip_wakeup(fs->object);
1337 fs->object = fs->first_object;
1338 pindex = first_pindex;
1339 fs->m = fs->first_m;
1344 * Zero the page if necessary and mark it valid.
1346 if ((fs->m->flags & PG_ZERO) == 0) {
1347 vm_page_zero_fill(fs->m);
1350 pmap_page_assertzero(VM_PAGE_TO_PHYS(fs->m));
1352 vm_page_flag_clear(fs->m, PG_ZERO);
1353 mycpu->gd_cnt.v_ozfod++;
1355 mycpu->gd_cnt.v_zfod++;
1356 fs->m->valid = VM_PAGE_BITS_ALL;
1357 break; /* break to PAGE HAS BEEN FOUND */
1359 if (fs->object != fs->first_object) {
1360 vm_object_pip_wakeup(fs->object);
1362 KASSERT(fs->object != next_object,
1363 ("object loop %p", next_object));
1364 fs->object = next_object;
1365 vm_object_pip_add(fs->object, 1);
1369 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
1372 * vm_token is still held
1374 * If the page is being written, but isn't already owned by the
1375 * top-level object, we have to copy it into a new page owned by the
1378 KASSERT((fs->m->flags & PG_BUSY) != 0,
1379 ("vm_fault: not busy after main loop"));
1381 if (fs->object != fs->first_object) {
1383 * We only really need to copy if we want to write it.
1385 if (fault_type & VM_PROT_WRITE) {
1387 * This allows pages to be virtually copied from a
1388 * backing_object into the first_object, where the
1389 * backing object has no other refs to it, and cannot
1390 * gain any more refs. Instead of a bcopy, we just
1391 * move the page from the backing object to the
1392 * first object. Note that we must mark the page
1393 * dirty in the first object so that it will go out
1394 * to swap when needed.
1398 * Map, if present, has not changed
1401 fs->map_generation == fs->map->timestamp) &&
1403 * Only one shadow object
1405 (fs->object->shadow_count == 1) &&
1407 * No COW refs, except us
1409 (fs->object->ref_count == 1) &&
1411 * No one else can look this object up
1413 (fs->object->handle == NULL) &&
1415 * No other ways to look the object up
1417 ((fs->object->type == OBJT_DEFAULT) ||
1418 (fs->object->type == OBJT_SWAP)) &&
1420 * We don't chase down the shadow chain
1422 (fs->object == fs->first_object->backing_object) &&
1425 * grab the lock if we need to
1427 (fs->lookup_still_valid ||
1429 lockmgr(&fs->map->lock, LK_EXCLUSIVE|LK_NOWAIT) == 0)
1432 fs->lookup_still_valid = 1;
1434 * get rid of the unnecessary page
1436 vm_page_protect(fs->first_m, VM_PROT_NONE);
1437 vm_page_free(fs->first_m);
1441 * grab the page and put it into the
1442 * process'es object. The page is
1443 * automatically made dirty.
1445 vm_page_rename(fs->m, fs->first_object, first_pindex);
1446 fs->first_m = fs->m;
1447 vm_page_busy(fs->first_m);
1449 mycpu->gd_cnt.v_cow_optim++;
1452 * Oh, well, lets copy it.
1454 vm_page_copy(fs->m, fs->first_m);
1455 vm_page_event(fs->m, VMEVENT_COW);
1460 * We no longer need the old page or object.
1466 * fs->object != fs->first_object due to above
1469 vm_object_pip_wakeup(fs->object);
1472 * Only use the new page below...
1475 mycpu->gd_cnt.v_cow_faults++;
1476 fs->m = fs->first_m;
1477 fs->object = fs->first_object;
1478 pindex = first_pindex;
1481 * If it wasn't a write fault avoid having to copy
1482 * the page by mapping it read-only.
1484 fs->prot &= ~VM_PROT_WRITE;
1489 * We may have had to unlock a map to do I/O. If we did then
1490 * lookup_still_valid will be FALSE. If the map generation count
1491 * also changed then all sorts of things could have happened while
1492 * we were doing the I/O and we need to retry.
1495 if (!fs->lookup_still_valid &&
1497 (fs->map->timestamp != fs->map_generation)) {
1499 lwkt_reltoken(&vm_token);
1500 unlock_and_deallocate(fs);
1501 return (KERN_TRY_AGAIN);
1505 * If the fault is a write, we know that this page is being
1506 * written NOW so dirty it explicitly to save on pmap_is_modified()
1509 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC
1510 * if the page is already dirty to prevent data written with
1511 * the expectation of being synced from not being synced.
1512 * Likewise if this entry does not request NOSYNC then make
1513 * sure the page isn't marked NOSYNC. Applications sharing
1514 * data should use the same flags to avoid ping ponging.
1516 * Also tell the backing pager, if any, that it should remove
1517 * any swap backing since the page is now dirty.
1519 if (fs->prot & VM_PROT_WRITE) {
1520 vm_object_set_writeable_dirty(fs->m->object);
1521 vm_set_nosync(fs->m, fs->entry);
1522 if (fs->fault_flags & VM_FAULT_DIRTY) {
1523 vm_page_dirty(fs->m);
1524 swap_pager_unswapped(fs->m);
1528 lwkt_reltoken(&vm_token);
1531 * Page had better still be busy. We are still locked up and
1532 * fs->object will have another PIP reference if it is not equal
1533 * to fs->first_object.
1535 KASSERT(fs->m->flags & PG_BUSY,
1536 ("vm_fault: page %p not busy!", fs->m));
1539 * Sanity check: page must be completely valid or it is not fit to
1540 * map into user space. vm_pager_get_pages() ensures this.
1542 if (fs->m->valid != VM_PAGE_BITS_ALL) {
1543 vm_page_zero_invalid(fs->m, TRUE);
1544 kprintf("Warning: page %p partially invalid on fault\n", fs->m);
1547 return (KERN_SUCCESS);
1551 * Wire down a range of virtual addresses in a map. The entry in question
1552 * should be marked in-transition and the map must be locked. We must
1553 * release the map temporarily while faulting-in the page to avoid a
1554 * deadlock. Note that the entry may be clipped while we are blocked but
1555 * will never be freed.
1560 vm_fault_wire(vm_map_t map, vm_map_entry_t entry, boolean_t user_wire)
1562 boolean_t fictitious;
1570 pmap = vm_map_pmap(map);
1571 start = entry->start;
1573 fictitious = entry->object.vm_object &&
1574 (entry->object.vm_object->type == OBJT_DEVICE);
1575 if (entry->eflags & MAP_ENTRY_KSTACK)
1577 lwkt_gettoken(&vm_token);
1582 * We simulate a fault to get the page and enter it in the physical
1585 for (va = start; va < end; va += PAGE_SIZE) {
1587 rv = vm_fault(map, va, VM_PROT_READ,
1588 VM_FAULT_USER_WIRE);
1590 rv = vm_fault(map, va, VM_PROT_READ|VM_PROT_WRITE,
1591 VM_FAULT_CHANGE_WIRING);
1594 while (va > start) {
1596 if ((pa = pmap_extract(pmap, va)) == 0)
1598 pmap_change_wiring(pmap, va, FALSE);
1600 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1);
1603 lwkt_reltoken(&vm_token);
1608 lwkt_reltoken(&vm_token);
1609 return (KERN_SUCCESS);
1613 * Unwire a range of virtual addresses in a map. The map should be
1617 vm_fault_unwire(vm_map_t map, vm_map_entry_t entry)
1619 boolean_t fictitious;
1626 pmap = vm_map_pmap(map);
1627 start = entry->start;
1629 fictitious = entry->object.vm_object &&
1630 (entry->object.vm_object->type == OBJT_DEVICE);
1631 if (entry->eflags & MAP_ENTRY_KSTACK)
1635 * Since the pages are wired down, we must be able to get their
1636 * mappings from the physical map system.
1638 lwkt_gettoken(&vm_token);
1639 for (va = start; va < end; va += PAGE_SIZE) {
1640 pa = pmap_extract(pmap, va);
1642 pmap_change_wiring(pmap, va, FALSE);
1644 vm_page_unwire(PHYS_TO_VM_PAGE(pa), 1);
1647 lwkt_reltoken(&vm_token);
1651 * Reduce the rate at which memory is allocated to a process based
1652 * on the perceived load on the VM system. As the load increases
1653 * the allocation burst rate goes down and the delay increases.
1655 * Rate limiting does not apply when faulting active or inactive
1656 * pages. When faulting 'cache' pages, rate limiting only applies
1657 * if the system currently has a severe page deficit.
1659 * XXX vm_pagesupply should be increased when a page is freed.
1661 * We sleep up to 1/10 of a second.
1664 vm_fault_ratelimit(struct vmspace *vmspace)
1666 if (vm_load_enable == 0)
1668 if (vmspace->vm_pagesupply > 0) {
1669 --vmspace->vm_pagesupply; /* SMP race ok */
1673 if (vm_load_debug) {
1674 kprintf("load %-4d give %d pgs, wait %d, pid %-5d (%s)\n",
1676 (1000 - vm_load ) / 10, vm_load * hz / 10000,
1677 curproc->p_pid, curproc->p_comm);
1680 vmspace->vm_pagesupply = (1000 - vm_load) / 10;
1681 return(vm_load * hz / 10000);
1685 * Copy all of the pages from a wired-down map entry to another.
1687 * The source and destination maps must be locked for write.
1688 * The source map entry must be wired down (or be a sharing map
1689 * entry corresponding to a main map entry that is wired down).
1691 * No other requirements.
1694 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1695 vm_map_entry_t dst_entry, vm_map_entry_t src_entry)
1697 vm_object_t dst_object;
1698 vm_object_t src_object;
1699 vm_ooffset_t dst_offset;
1700 vm_ooffset_t src_offset;
1710 src_object = src_entry->object.vm_object;
1711 src_offset = src_entry->offset;
1714 * Create the top-level object for the destination entry. (Doesn't
1715 * actually shadow anything - we copy the pages directly.)
1717 vm_map_entry_allocate_object(dst_entry);
1718 dst_object = dst_entry->object.vm_object;
1720 prot = dst_entry->max_protection;
1723 * Loop through all of the pages in the entry's range, copying each
1724 * one from the source object (it should be there) to the destination
1727 for (vaddr = dst_entry->start, dst_offset = 0;
1728 vaddr < dst_entry->end;
1729 vaddr += PAGE_SIZE, dst_offset += PAGE_SIZE) {
1732 * Allocate a page in the destination object
1735 dst_m = vm_page_alloc(dst_object,
1736 OFF_TO_IDX(dst_offset), VM_ALLOC_NORMAL);
1737 if (dst_m == NULL) {
1740 } while (dst_m == NULL);
1743 * Find the page in the source object, and copy it in.
1744 * (Because the source is wired down, the page will be in
1747 src_m = vm_page_lookup(src_object,
1748 OFF_TO_IDX(dst_offset + src_offset));
1750 panic("vm_fault_copy_wired: page missing");
1752 vm_page_copy(src_m, dst_m);
1753 vm_page_event(src_m, VMEVENT_COW);
1756 * Enter it in the pmap...
1759 vm_page_flag_clear(dst_m, PG_ZERO);
1760 pmap_enter(dst_map->pmap, vaddr, dst_m, prot, FALSE);
1763 * Mark it no longer busy, and put it on the active list.
1765 vm_page_activate(dst_m);
1766 vm_page_wakeup(dst_m);
1773 * This routine checks around the requested page for other pages that
1774 * might be able to be faulted in. This routine brackets the viable
1775 * pages for the pages to be paged in.
1778 * m, rbehind, rahead
1781 * marray (array of vm_page_t), reqpage (index of requested page)
1784 * number of pages in marray
1787 vm_fault_additional_pages(vm_page_t m, int rbehind, int rahead,
1788 vm_page_t *marray, int *reqpage)
1792 vm_pindex_t pindex, startpindex, endpindex, tpindex;
1794 int cbehind, cahead;
1800 * we don't fault-ahead for device pager
1802 if (object->type == OBJT_DEVICE) {
1809 * if the requested page is not available, then give up now
1811 if (!vm_pager_has_page(object, pindex, &cbehind, &cahead)) {
1812 *reqpage = 0; /* not used by caller, fix compiler warn */
1816 if ((cbehind == 0) && (cahead == 0)) {
1822 if (rahead > cahead) {
1826 if (rbehind > cbehind) {
1831 * Do not do any readahead if we have insufficient free memory.
1833 * XXX code was broken disabled before and has instability
1834 * with this conditonal fixed, so shortcut for now.
1836 if (burst_fault == 0 || vm_page_count_severe()) {
1843 * scan backward for the read behind pages -- in memory
1845 * Assume that if the page is not found an interrupt will not
1846 * create it. Theoretically interrupts can only remove (busy)
1847 * pages, not create new associations.
1850 if (rbehind > pindex) {
1854 startpindex = pindex - rbehind;
1857 lwkt_gettoken(&vm_token);
1858 for (tpindex = pindex; tpindex > startpindex; --tpindex) {
1859 if (vm_page_lookup(object, tpindex - 1))
1864 while (tpindex < pindex) {
1865 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_SYSTEM);
1867 lwkt_reltoken(&vm_token);
1868 for (j = 0; j < i; j++) {
1869 vm_page_free(marray[j]);
1879 lwkt_reltoken(&vm_token);
1885 * Assign requested page
1892 * Scan forwards for read-ahead pages
1894 tpindex = pindex + 1;
1895 endpindex = tpindex + rahead;
1896 if (endpindex > object->size)
1897 endpindex = object->size;
1899 lwkt_gettoken(&vm_token);
1900 while (tpindex < endpindex) {
1901 if (vm_page_lookup(object, tpindex))
1903 rtm = vm_page_alloc(object, tpindex, VM_ALLOC_SYSTEM);
1910 lwkt_reltoken(&vm_token);
1918 * vm_prefault() provides a quick way of clustering pagefaults into a
1919 * processes address space. It is a "cousin" of pmap_object_init_pt,
1920 * except it runs at page fault time instead of mmap time.
1922 * This code used to be per-platform pmap_prefault(). It is now
1923 * machine-independent and enhanced to also pre-fault zero-fill pages
1924 * (see vm.fast_fault) as well as make them writable, which greatly
1925 * reduces the number of page faults programs incur.
1927 * Application performance when pre-faulting zero-fill pages is heavily
1928 * dependent on the application. Very tiny applications like /bin/echo
1929 * lose a little performance while applications of any appreciable size
1930 * gain performance. Prefaulting multiple pages also reduces SMP
1931 * congestion and can improve SMP performance significantly.
1933 * NOTE! prot may allow writing but this only applies to the top level
1934 * object. If we wind up mapping a page extracted from a backing
1935 * object we have to make sure it is read-only.
1937 * NOTE! The caller has already handled any COW operations on the
1938 * vm_map_entry via the normal fault code. Do NOT call this
1939 * shortcut unless the normal fault code has run on this entry.
1941 * No other requirements.
1945 #define PAGEORDER_SIZE (PFBAK+PFFOR)
1947 static int vm_prefault_pageorder[] = {
1948 -PAGE_SIZE, PAGE_SIZE,
1949 -2 * PAGE_SIZE, 2 * PAGE_SIZE,
1950 -3 * PAGE_SIZE, 3 * PAGE_SIZE,
1951 -4 * PAGE_SIZE, 4 * PAGE_SIZE
1955 * Set PG_NOSYNC if the map entry indicates so, but only if the page
1956 * is not already dirty by other means. This will prevent passive
1957 * filesystem syncing as well as 'sync' from writing out the page.
1960 vm_set_nosync(vm_page_t m, vm_map_entry_t entry)
1962 if (entry->eflags & MAP_ENTRY_NOSYNC) {
1964 vm_page_flag_set(m, PG_NOSYNC);
1966 vm_page_flag_clear(m, PG_NOSYNC);
1971 vm_prefault(pmap_t pmap, vm_offset_t addra, vm_map_entry_t entry, int prot)
1984 * We do not currently prefault mappings that use virtual page
1985 * tables. We do not prefault foreign pmaps.
1987 if (entry->maptype == VM_MAPTYPE_VPAGETABLE)
1989 lp = curthread->td_lwp;
1990 if (lp == NULL || (pmap != vmspace_pmap(lp->lwp_vmspace)))
1993 object = entry->object.vm_object;
1995 starta = addra - PFBAK * PAGE_SIZE;
1996 if (starta < entry->start)
1997 starta = entry->start;
1998 else if (starta > addra)
2001 lwkt_gettoken(&vm_token);
2002 for (i = 0; i < PAGEORDER_SIZE; i++) {
2003 vm_object_t lobject;
2006 addr = addra + vm_prefault_pageorder[i];
2007 if (addr > addra + (PFFOR * PAGE_SIZE))
2010 if (addr < starta || addr >= entry->end)
2013 if (pmap_prefault_ok(pmap, addr) == 0)
2017 * Follow the VM object chain to obtain the page to be mapped
2020 * If we reach the terminal object without finding a page
2021 * and we determine it would be advantageous, then allocate
2022 * a zero-fill page for the base object. The base object
2023 * is guaranteed to be OBJT_DEFAULT for this case.
2025 * In order to not have to check the pager via *haspage*()
2026 * we stop if any non-default object is encountered. e.g.
2027 * a vnode or swap object would stop the loop.
2029 index = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
2034 while ((m = vm_page_lookup(lobject, pindex)) == NULL) {
2035 if (lobject->type != OBJT_DEFAULT)
2037 if (lobject->backing_object == NULL) {
2038 if (vm_fast_fault == 0)
2040 if (vm_prefault_pageorder[i] < 0 ||
2041 (prot & VM_PROT_WRITE) == 0 ||
2042 vm_page_count_min(0)) {
2045 /* note: allocate from base object */
2046 m = vm_page_alloc(object, index,
2047 VM_ALLOC_NORMAL | VM_ALLOC_ZERO);
2049 if ((m->flags & PG_ZERO) == 0) {
2050 vm_page_zero_fill(m);
2053 pmap_page_assertzero(VM_PAGE_TO_PHYS(m));
2055 vm_page_flag_clear(m, PG_ZERO);
2056 mycpu->gd_cnt.v_ozfod++;
2058 mycpu->gd_cnt.v_zfod++;
2059 m->valid = VM_PAGE_BITS_ALL;
2062 /* lobject = object .. not needed */
2065 if (lobject->backing_object_offset & PAGE_MASK)
2067 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
2068 lobject = lobject->backing_object;
2069 pprot &= ~VM_PROT_WRITE;
2072 * NOTE: lobject now invalid (if we did a zero-fill we didn't
2073 * bother assigning lobject = object).
2075 * Give-up if the page is not available.
2081 * Do not conditionalize on PG_RAM. If pages are present in
2082 * the VM system we assume optimal caching. If caching is
2083 * not optimal the I/O gravy train will be restarted when we
2084 * hit an unavailable page. We do not want to try to restart
2085 * the gravy train now because we really don't know how much
2086 * of the object has been cached. The cost for restarting
2087 * the gravy train should be low (since accesses will likely
2088 * be I/O bound anyway).
2090 * The object must be marked dirty if we are mapping a
2093 if (pprot & VM_PROT_WRITE)
2094 vm_object_set_writeable_dirty(m->object);
2097 * Enter the page into the pmap if appropriate. If we had
2098 * allocated the page we have to place it on a queue. If not
2099 * we just have to make sure it isn't on the cache queue
2100 * (pages on the cache queue are not allowed to be mapped).
2103 if (pprot & VM_PROT_WRITE)
2104 vm_set_nosync(m, entry);
2105 pmap_enter(pmap, addr, m, pprot, 0);
2106 vm_page_deactivate(m);
2108 } else if (((m->valid & VM_PAGE_BITS_ALL) == VM_PAGE_BITS_ALL) &&
2110 (m->flags & (PG_BUSY | PG_FICTITIOUS)) == 0) {
2112 if ((m->queue - m->pc) == PQ_CACHE) {
2113 vm_page_deactivate(m);
2116 if (pprot & VM_PROT_WRITE)
2117 vm_set_nosync(m, entry);
2118 pmap_enter(pmap, addr, m, pprot, 0);
2122 lwkt_reltoken(&vm_token);