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
;
125 static int debug_cluster
= 0;
126 SYSCTL_INT(_vm
, OID_AUTO
, debug_cluster
, CTLFLAG_RW
, &debug_cluster
, 0, "");
127 static int vm_shared_fault
= 1;
128 SYSCTL_INT(_vm
, OID_AUTO
, shared_fault
, CTLFLAG_RW
, &vm_shared_fault
, 0,
129 "Allow shared token on vm_object");
130 static long vm_shared_hit
= 0;
131 SYSCTL_LONG(_vm
, OID_AUTO
, shared_hit
, CTLFLAG_RW
, &vm_shared_hit
, 0,
132 "Successful shared faults");
133 static long vm_shared_miss
= 0;
134 SYSCTL_LONG(_vm
, OID_AUTO
, shared_miss
, CTLFLAG_RW
, &vm_shared_miss
, 0,
135 "Successful shared faults");
137 static int vm_fault_object(struct faultstate
*, vm_pindex_t
, vm_prot_t
);
138 static int vm_fault_vpagetable(struct faultstate
*, vm_pindex_t
*, vpte_t
, int);
140 static int vm_fault_additional_pages (vm_page_t
, int, int, vm_page_t
*, int *);
142 static void vm_set_nosync(vm_page_t m
, vm_map_entry_t entry
);
143 static void vm_prefault(pmap_t pmap
, vm_offset_t addra
,
144 vm_map_entry_t entry
, int prot
, int fault_flags
);
145 static void vm_prefault_quick(pmap_t pmap
, vm_offset_t addra
,
146 vm_map_entry_t entry
, int prot
, int fault_flags
);
149 release_page(struct faultstate
*fs
)
151 vm_page_deactivate(fs
->m
);
152 vm_page_wakeup(fs
->m
);
157 * NOTE: Once unlocked any cached fs->entry becomes invalid, any reuse
158 * requires relocking and then checking the timestamp.
160 * NOTE: vm_map_lock_read() does not bump fs->map->timestamp so we do
161 * not have to update fs->map_generation here.
163 * NOTE: This function can fail due to a deadlock against the caller's
164 * holding of a vm_page BUSY.
167 relock_map(struct faultstate
*fs
)
171 if (fs
->lookup_still_valid
== FALSE
&& fs
->map
) {
172 error
= vm_map_lock_read_to(fs
->map
);
174 fs
->lookup_still_valid
= TRUE
;
182 unlock_map(struct faultstate
*fs
)
184 if (fs
->lookup_still_valid
&& fs
->map
) {
185 vm_map_lookup_done(fs
->map
, fs
->entry
, 0);
186 fs
->lookup_still_valid
= FALSE
;
191 * Clean up after a successful call to vm_fault_object() so another call
192 * to vm_fault_object() can be made.
195 _cleanup_successful_fault(struct faultstate
*fs
, int relock
)
197 if (fs
->object
!= fs
->first_object
) {
198 vm_page_free(fs
->first_m
);
199 vm_object_pip_wakeup(fs
->object
);
202 fs
->object
= fs
->first_object
;
203 if (relock
&& fs
->lookup_still_valid
== FALSE
) {
205 vm_map_lock_read(fs
->map
);
206 fs
->lookup_still_valid
= TRUE
;
211 _unlock_things(struct faultstate
*fs
, int dealloc
)
213 _cleanup_successful_fault(fs
, 0);
215 /*vm_object_deallocate(fs->first_object);*/
216 /*fs->first_object = NULL; drop used later on */
219 if (fs
->vp
!= NULL
) {
225 #define unlock_things(fs) _unlock_things(fs, 0)
226 #define unlock_and_deallocate(fs) _unlock_things(fs, 1)
227 #define cleanup_successful_fault(fs) _cleanup_successful_fault(fs, 1)
232 * Determine if the pager for the current object *might* contain the page.
234 * We only need to try the pager if this is not a default object (default
235 * objects are zero-fill and have no real pager), and if we are not taking
236 * a wiring fault or if the FS entry is wired.
238 #define TRYPAGER(fs) \
239 (fs->object->type != OBJT_DEFAULT && \
240 (((fs->fault_flags & VM_FAULT_WIRE_MASK) == 0) || fs->wired))
245 * Handle a page fault occuring at the given address, requiring the given
246 * permissions, in the map specified. If successful, the page is inserted
247 * into the associated physical map.
249 * NOTE: The given address should be truncated to the proper page address.
251 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
252 * a standard error specifying why the fault is fatal is returned.
254 * The map in question must be referenced, and remains so.
255 * The caller may hold no locks.
256 * No other requirements.
259 vm_fault(vm_map_t map
, vm_offset_t vaddr
, vm_prot_t fault_type
, int fault_flags
)
262 vm_pindex_t first_pindex
;
263 struct faultstate fs
;
267 vm_page_pcpu_cache();
269 fs
.fault_flags
= fault_flags
;
273 if ((lp
= curthread
->td_lwp
) != NULL
)
274 lp
->lwp_flags
|= LWP_PAGING
;
276 lwkt_gettoken(&map
->token
);
280 * Find the vm_map_entry representing the backing store and resolve
281 * the top level object and page index. This may have the side
282 * effect of executing a copy-on-write on the map entry and/or
283 * creating a shadow object, but will not COW any actual VM pages.
285 * On success fs.map is left read-locked and various other fields
286 * are initialized but not otherwise referenced or locked.
288 * NOTE! vm_map_lookup will try to upgrade the fault_type to
289 * VM_FAULT_WRITE if the map entry is a virtual page table and also
290 * writable, so we can set the 'A'accessed bit in the virtual page
294 result
= vm_map_lookup(&fs
.map
, vaddr
, fault_type
,
295 &fs
.entry
, &fs
.first_object
,
296 &first_pindex
, &fs
.first_prot
, &fs
.wired
);
299 * If the lookup failed or the map protections are incompatible,
300 * the fault generally fails. However, if the caller is trying
301 * to do a user wiring we have more work to do.
303 if (result
!= KERN_SUCCESS
) {
304 if (result
!= KERN_PROTECTION_FAILURE
||
305 (fs
.fault_flags
& VM_FAULT_WIRE_MASK
) != VM_FAULT_USER_WIRE
)
307 if (result
== KERN_INVALID_ADDRESS
&& growstack
&&
308 map
!= &kernel_map
&& curproc
!= NULL
) {
309 result
= vm_map_growstack(curproc
, vaddr
);
310 if (result
== KERN_SUCCESS
) {
314 result
= KERN_FAILURE
;
320 * If we are user-wiring a r/w segment, and it is COW, then
321 * we need to do the COW operation. Note that we don't
322 * currently COW RO sections now, because it is NOT desirable
323 * to COW .text. We simply keep .text from ever being COW'ed
324 * and take the heat that one cannot debug wired .text sections.
326 result
= vm_map_lookup(&fs
.map
, vaddr
,
327 VM_PROT_READ
|VM_PROT_WRITE
|
328 VM_PROT_OVERRIDE_WRITE
,
329 &fs
.entry
, &fs
.first_object
,
330 &first_pindex
, &fs
.first_prot
,
332 if (result
!= KERN_SUCCESS
) {
333 result
= KERN_FAILURE
;
338 * If we don't COW now, on a user wire, the user will never
339 * be able to write to the mapping. If we don't make this
340 * restriction, the bookkeeping would be nearly impossible.
342 * XXX We have a shared lock, this will have a MP race but
343 * I don't see how it can hurt anything.
345 if ((fs
.entry
->protection
& VM_PROT_WRITE
) == 0)
346 fs
.entry
->max_protection
&= ~VM_PROT_WRITE
;
350 * fs.map is read-locked
352 * Misc checks. Save the map generation number to detect races.
354 fs
.map_generation
= fs
.map
->timestamp
;
356 if (fs
.entry
->eflags
& (MAP_ENTRY_NOFAULT
| MAP_ENTRY_KSTACK
)) {
357 if (fs
.entry
->eflags
& MAP_ENTRY_NOFAULT
) {
358 panic("vm_fault: fault on nofault entry, addr: %p",
361 if ((fs
.entry
->eflags
& MAP_ENTRY_KSTACK
) &&
362 vaddr
>= fs
.entry
->start
&&
363 vaddr
< fs
.entry
->start
+ PAGE_SIZE
) {
364 panic("vm_fault: fault on stack guard, addr: %p",
370 * A system map entry may return a NULL object. No object means
371 * no pager means an unrecoverable kernel fault.
373 if (fs
.first_object
== NULL
) {
374 panic("vm_fault: unrecoverable fault at %p in entry %p",
375 (void *)vaddr
, fs
.entry
);
379 * Attempt to shortcut the fault if the lookup returns a
380 * terminal object and the page is present. This allows us
381 * to obtain a shared token on the object instead of an exclusive
382 * token, which theoretically should allow concurrent faults.
384 * We cannot acquire a shared token on kernel_map, at least not
385 * on i386, because the i386 pmap code uses the kernel_object for
386 * its page table page management, resulting in a shared->exclusive
387 * sequence which will deadlock. This will not happen normally
388 * anyway, except on well cached pageable kmem (like pipe buffers),
389 * so it should not impact performance.
391 if (vm_shared_fault
&&
392 fs
.first_object
->backing_object
== NULL
&&
393 fs
.entry
->maptype
== VM_MAPTYPE_NORMAL
&&
394 fs
.map
!= &kernel_map
) {
396 vm_object_hold_shared(fs
.first_object
);
397 /*fs.vp = vnode_pager_lock(fs.first_object);*/
398 fs
.m
= vm_page_lookup_busy_try(fs
.first_object
,
401 if (error
== 0 && fs
.m
) {
403 * Activate the page and figure out if we can
404 * short-cut a quick mapping.
406 * WARNING! We cannot call swap_pager_unswapped()
407 * with a shared token! Note that we
408 * have to test fs.first_prot here.
410 vm_page_activate(fs
.m
);
411 if (fs
.m
->valid
== VM_PAGE_BITS_ALL
&&
412 ((fs
.m
->flags
& PG_SWAPPED
) == 0 ||
413 (fs
.first_prot
& VM_PROT_WRITE
) == 0 ||
414 (fs
.fault_flags
& VM_FAULT_DIRTY
) == 0)) {
415 fs
.lookup_still_valid
= TRUE
;
417 fs
.object
= fs
.first_object
;
418 fs
.prot
= fs
.first_prot
;
420 fault_type
= fs
.first_prot
;
421 if (fs
.prot
& VM_PROT_WRITE
) {
422 vm_object_set_writeable_dirty(
424 vm_set_nosync(fs
.m
, fs
.entry
);
425 if (fs
.fault_flags
& VM_FAULT_DIRTY
) {
428 swap_pager_unswapped(fs
.m
);
431 result
= KERN_SUCCESS
;
432 fault_flags
|= VM_FAULT_BURST_QUICK
;
433 fault_flags
&= ~VM_FAULT_BURST
;
437 vm_page_wakeup(fs
.m
);
440 vm_object_drop(fs
.first_object
); /* XXX drop on shared tok?*/
445 * Bump the paging-in-progress count to prevent size changes (e.g.
446 * truncation operations) during I/O. This must be done after
447 * obtaining the vnode lock in order to avoid possible deadlocks.
449 vm_object_hold(fs
.first_object
);
451 fs
.vp
= vnode_pager_lock(fs
.first_object
);
453 fs
.lookup_still_valid
= TRUE
;
455 fs
.object
= fs
.first_object
; /* so unlock_and_deallocate works */
458 * If the entry is wired we cannot change the page protection.
461 fault_type
= fs
.first_prot
;
464 * The page we want is at (first_object, first_pindex), but if the
465 * vm_map_entry is VM_MAPTYPE_VPAGETABLE we have to traverse the
466 * page table to figure out the actual pindex.
468 * NOTE! DEVELOPMENT IN PROGRESS, THIS IS AN INITIAL IMPLEMENTATION
471 if (fs
.entry
->maptype
== VM_MAPTYPE_VPAGETABLE
) {
472 result
= vm_fault_vpagetable(&fs
, &first_pindex
,
473 fs
.entry
->aux
.master_pde
,
475 if (result
== KERN_TRY_AGAIN
) {
476 vm_object_drop(fs
.first_object
);
479 if (result
!= KERN_SUCCESS
)
484 * Now we have the actual (object, pindex), fault in the page. If
485 * vm_fault_object() fails it will unlock and deallocate the FS
486 * data. If it succeeds everything remains locked and fs->object
487 * will have an additional PIP count if it is not equal to
490 * vm_fault_object will set fs->prot for the pmap operation. It is
491 * allowed to set VM_PROT_WRITE if fault_type == VM_PROT_READ if the
492 * page can be safely written. However, it will force a read-only
493 * mapping for a read fault if the memory is managed by a virtual
497 result
= vm_fault_object(&fs
, first_pindex
, fault_type
);
499 if (result
== KERN_TRY_AGAIN
) {
500 vm_object_drop(fs
.first_object
);
503 if (result
!= KERN_SUCCESS
)
508 * On success vm_fault_object() does not unlock or deallocate, and fs.m
509 * will contain a busied page.
511 * Enter the page into the pmap and do pmap-related adjustments.
513 vm_page_flag_set(fs
.m
, PG_REFERENCED
);
514 pmap_enter(fs
.map
->pmap
, vaddr
, fs
.m
, fs
.prot
, fs
.wired
, fs
.entry
);
515 mycpu
->gd_cnt
.v_vm_faults
++;
516 if (curthread
->td_lwp
)
517 ++curthread
->td_lwp
->lwp_ru
.ru_minflt
;
519 /*KKASSERT(fs.m->queue == PQ_NONE); page-in op may deactivate page */
520 KKASSERT(fs
.m
->flags
& PG_BUSY
);
523 * If the page is not wired down, then put it where the pageout daemon
526 if (fs
.fault_flags
& VM_FAULT_WIRE_MASK
) {
530 vm_page_unwire(fs
.m
, 1);
532 vm_page_activate(fs
.m
);
534 vm_page_wakeup(fs
.m
);
537 * Burst in a few more pages if possible. The fs.map should still
538 * be locked. To avoid interlocking against a vnode->getblk
539 * operation we had to be sure to unbusy our primary vm_page above
542 if (fault_flags
& VM_FAULT_BURST
) {
543 if ((fs
.fault_flags
& VM_FAULT_WIRE_MASK
) == 0
545 vm_prefault(fs
.map
->pmap
, vaddr
,
546 fs
.entry
, fs
.prot
, fault_flags
);
549 if (fault_flags
& VM_FAULT_BURST_QUICK
) {
550 if ((fs
.fault_flags
& VM_FAULT_WIRE_MASK
) == 0
552 vm_prefault_quick(fs
.map
->pmap
, vaddr
,
553 fs
.entry
, fs
.prot
, fault_flags
);
558 * Unlock everything, and return
562 if (curthread
->td_lwp
) {
564 curthread
->td_lwp
->lwp_ru
.ru_majflt
++;
566 curthread
->td_lwp
->lwp_ru
.ru_minflt
++;
570 /*vm_object_deallocate(fs.first_object);*/
572 /*fs.first_object = NULL; must still drop later */
574 result
= KERN_SUCCESS
;
577 vm_object_drop(fs
.first_object
);
578 lwkt_reltoken(&map
->token
);
580 lp
->lwp_flags
&= ~LWP_PAGING
;
585 * Fault in the specified virtual address in the current process map,
586 * returning a held VM page or NULL. See vm_fault_page() for more
592 vm_fault_page_quick(vm_offset_t va
, vm_prot_t fault_type
, int *errorp
)
594 struct lwp
*lp
= curthread
->td_lwp
;
597 m
= vm_fault_page(&lp
->lwp_vmspace
->vm_map
, va
,
598 fault_type
, VM_FAULT_NORMAL
, errorp
);
603 * Fault in the specified virtual address in the specified map, doing all
604 * necessary manipulation of the object store and all necessary I/O. Return
605 * a held VM page or NULL, and set *errorp. The related pmap is not
608 * The returned page will be properly dirtied if VM_PROT_WRITE was specified,
609 * and marked PG_REFERENCED as well.
611 * If the page cannot be faulted writable and VM_PROT_WRITE was specified, an
612 * error will be returned.
617 vm_fault_page(vm_map_t map
, vm_offset_t vaddr
, vm_prot_t fault_type
,
618 int fault_flags
, int *errorp
)
620 vm_pindex_t first_pindex
;
621 struct faultstate fs
;
623 vm_prot_t orig_fault_type
= fault_type
;
626 fs
.fault_flags
= fault_flags
;
627 KKASSERT((fault_flags
& VM_FAULT_WIRE_MASK
) == 0);
629 lwkt_gettoken(&map
->token
);
633 * Find the vm_map_entry representing the backing store and resolve
634 * the top level object and page index. This may have the side
635 * effect of executing a copy-on-write on the map entry and/or
636 * creating a shadow object, but will not COW any actual VM pages.
638 * On success fs.map is left read-locked and various other fields
639 * are initialized but not otherwise referenced or locked.
641 * NOTE! vm_map_lookup will upgrade the fault_type to VM_FAULT_WRITE
642 * if the map entry is a virtual page table and also writable,
643 * so we can set the 'A'accessed bit in the virtual page table entry.
646 result
= vm_map_lookup(&fs
.map
, vaddr
, fault_type
,
647 &fs
.entry
, &fs
.first_object
,
648 &first_pindex
, &fs
.first_prot
, &fs
.wired
);
650 if (result
!= KERN_SUCCESS
) {
657 * fs.map is read-locked
659 * Misc checks. Save the map generation number to detect races.
661 fs
.map_generation
= fs
.map
->timestamp
;
663 if (fs
.entry
->eflags
& MAP_ENTRY_NOFAULT
) {
664 panic("vm_fault: fault on nofault entry, addr: %lx",
669 * A system map entry may return a NULL object. No object means
670 * no pager means an unrecoverable kernel fault.
672 if (fs
.first_object
== NULL
) {
673 panic("vm_fault: unrecoverable fault at %p in entry %p",
674 (void *)vaddr
, fs
.entry
);
678 * Make a reference to this object to prevent its disposal while we
679 * are messing with it. Once we have the reference, the map is free
680 * to be diddled. Since objects reference their shadows (and copies),
681 * they will stay around as well.
683 * The reference should also prevent an unexpected collapse of the
684 * parent that might move pages from the current object into the
685 * parent unexpectedly, resulting in corruption.
687 * Bump the paging-in-progress count to prevent size changes (e.g.
688 * truncation operations) during I/O. This must be done after
689 * obtaining the vnode lock in order to avoid possible deadlocks.
691 vm_object_hold(fs
.first_object
);
692 fs
.vp
= vnode_pager_lock(fs
.first_object
);
694 fs
.lookup_still_valid
= TRUE
;
696 fs
.object
= fs
.first_object
; /* so unlock_and_deallocate works */
699 * If the entry is wired we cannot change the page protection.
702 fault_type
= fs
.first_prot
;
705 * The page we want is at (first_object, first_pindex), but if the
706 * vm_map_entry is VM_MAPTYPE_VPAGETABLE we have to traverse the
707 * page table to figure out the actual pindex.
709 * NOTE! DEVELOPMENT IN PROGRESS, THIS IS AN INITIAL IMPLEMENTATION
712 if (fs
.entry
->maptype
== VM_MAPTYPE_VPAGETABLE
) {
713 result
= vm_fault_vpagetable(&fs
, &first_pindex
,
714 fs
.entry
->aux
.master_pde
,
716 if (result
== KERN_TRY_AGAIN
) {
717 vm_object_drop(fs
.first_object
);
720 if (result
!= KERN_SUCCESS
) {
728 * Now we have the actual (object, pindex), fault in the page. If
729 * vm_fault_object() fails it will unlock and deallocate the FS
730 * data. If it succeeds everything remains locked and fs->object
731 * will have an additinal PIP count if it is not equal to
735 result
= vm_fault_object(&fs
, first_pindex
, fault_type
);
737 if (result
== KERN_TRY_AGAIN
) {
738 vm_object_drop(fs
.first_object
);
741 if (result
!= KERN_SUCCESS
) {
747 if ((orig_fault_type
& VM_PROT_WRITE
) &&
748 (fs
.prot
& VM_PROT_WRITE
) == 0) {
749 *errorp
= KERN_PROTECTION_FAILURE
;
750 unlock_and_deallocate(&fs
);
756 * DO NOT UPDATE THE PMAP!!! This function may be called for
757 * a pmap unrelated to the current process pmap, in which case
758 * the current cpu core will not be listed in the pmap's pm_active
759 * mask. Thus invalidation interlocks will fail to work properly.
761 * (for example, 'ps' uses procfs to read program arguments from
762 * each process's stack).
764 * In addition to the above this function will be called to acquire
765 * a page that might already be faulted in, re-faulting it
766 * continuously is a waste of time.
768 * XXX could this have been the cause of our random seg-fault
769 * issues? procfs accesses user stacks.
771 vm_page_flag_set(fs
.m
, PG_REFERENCED
);
773 pmap_enter(fs
.map
->pmap
, vaddr
, fs
.m
, fs
.prot
, fs
.wired
, NULL
);
774 mycpu
->gd_cnt
.v_vm_faults
++;
775 if (curthread
->td_lwp
)
776 ++curthread
->td_lwp
->lwp_ru
.ru_minflt
;
780 * On success vm_fault_object() does not unlock or deallocate, and fs.m
781 * will contain a busied page. So we must unlock here after having
782 * messed with the pmap.
787 * Return a held page. We are not doing any pmap manipulation so do
788 * not set PG_MAPPED. However, adjust the page flags according to
789 * the fault type because the caller may not use a managed pmapping
790 * (so we don't want to lose the fact that the page will be dirtied
791 * if a write fault was specified).
794 vm_page_activate(fs
.m
);
795 if (fault_type
& VM_PROT_WRITE
)
798 if (curthread
->td_lwp
) {
800 curthread
->td_lwp
->lwp_ru
.ru_majflt
++;
802 curthread
->td_lwp
->lwp_ru
.ru_minflt
++;
807 * Unlock everything, and return the held page.
809 vm_page_wakeup(fs
.m
);
810 /*vm_object_deallocate(fs.first_object);*/
811 /*fs.first_object = NULL; */
816 vm_object_drop(fs
.first_object
);
817 lwkt_reltoken(&map
->token
);
822 * Fault in the specified (object,offset), dirty the returned page as
823 * needed. If the requested fault_type cannot be done NULL and an
826 * A held (but not busied) page is returned.
831 vm_fault_object_page(vm_object_t object
, vm_ooffset_t offset
,
832 vm_prot_t fault_type
, int fault_flags
, int *errorp
)
835 vm_pindex_t first_pindex
;
836 struct faultstate fs
;
837 struct vm_map_entry entry
;
839 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
840 bzero(&entry
, sizeof(entry
));
841 entry
.object
.vm_object
= object
;
842 entry
.maptype
= VM_MAPTYPE_NORMAL
;
843 entry
.protection
= entry
.max_protection
= fault_type
;
846 fs
.fault_flags
= fault_flags
;
848 KKASSERT((fault_flags
& VM_FAULT_WIRE_MASK
) == 0);
852 fs
.first_object
= object
;
853 first_pindex
= OFF_TO_IDX(offset
);
855 fs
.first_prot
= fault_type
;
857 /*fs.map_generation = 0; unused */
860 * Make a reference to this object to prevent its disposal while we
861 * are messing with it. Once we have the reference, the map is free
862 * to be diddled. Since objects reference their shadows (and copies),
863 * they will stay around as well.
865 * The reference should also prevent an unexpected collapse of the
866 * parent that might move pages from the current object into the
867 * parent unexpectedly, resulting in corruption.
869 * Bump the paging-in-progress count to prevent size changes (e.g.
870 * truncation operations) during I/O. This must be done after
871 * obtaining the vnode lock in order to avoid possible deadlocks.
873 fs
.vp
= vnode_pager_lock(fs
.first_object
);
875 fs
.lookup_still_valid
= TRUE
;
877 fs
.object
= fs
.first_object
; /* so unlock_and_deallocate works */
880 /* XXX future - ability to operate on VM object using vpagetable */
881 if (fs
.entry
->maptype
== VM_MAPTYPE_VPAGETABLE
) {
882 result
= vm_fault_vpagetable(&fs
, &first_pindex
,
883 fs
.entry
->aux
.master_pde
,
885 if (result
== KERN_TRY_AGAIN
)
887 if (result
!= KERN_SUCCESS
) {
895 * Now we have the actual (object, pindex), fault in the page. If
896 * vm_fault_object() fails it will unlock and deallocate the FS
897 * data. If it succeeds everything remains locked and fs->object
898 * will have an additinal PIP count if it is not equal to
901 result
= vm_fault_object(&fs
, first_pindex
, fault_type
);
903 if (result
== KERN_TRY_AGAIN
)
905 if (result
!= KERN_SUCCESS
) {
910 if ((fault_type
& VM_PROT_WRITE
) && (fs
.prot
& VM_PROT_WRITE
) == 0) {
911 *errorp
= KERN_PROTECTION_FAILURE
;
912 unlock_and_deallocate(&fs
);
917 * On success vm_fault_object() does not unlock or deallocate, so we
918 * do it here. Note that the returned fs.m will be busied.
923 * Return a held page. We are not doing any pmap manipulation so do
924 * not set PG_MAPPED. However, adjust the page flags according to
925 * the fault type because the caller may not use a managed pmapping
926 * (so we don't want to lose the fact that the page will be dirtied
927 * if a write fault was specified).
930 vm_page_activate(fs
.m
);
931 if ((fault_type
& VM_PROT_WRITE
) || (fault_flags
& VM_FAULT_DIRTY
))
933 if (fault_flags
& VM_FAULT_UNSWAP
)
934 swap_pager_unswapped(fs
.m
);
937 * Indicate that the page was accessed.
939 vm_page_flag_set(fs
.m
, PG_REFERENCED
);
941 if (curthread
->td_lwp
) {
943 curthread
->td_lwp
->lwp_ru
.ru_majflt
++;
945 curthread
->td_lwp
->lwp_ru
.ru_minflt
++;
950 * Unlock everything, and return the held page.
952 vm_page_wakeup(fs
.m
);
953 /*vm_object_deallocate(fs.first_object);*/
954 /*fs.first_object = NULL; */
961 * Translate the virtual page number (first_pindex) that is relative
962 * to the address space into a logical page number that is relative to the
963 * backing object. Use the virtual page table pointed to by (vpte).
965 * This implements an N-level page table. Any level can terminate the
966 * scan by setting VPTE_PS. A linear mapping is accomplished by setting
967 * VPTE_PS in the master page directory entry set via mcontrol(MADV_SETMAP).
971 vm_fault_vpagetable(struct faultstate
*fs
, vm_pindex_t
*pindex
,
972 vpte_t vpte
, int fault_type
)
975 struct lwbuf lwb_cache
;
976 int vshift
= VPTE_FRAME_END
- PAGE_SHIFT
; /* index bits remaining */
977 int result
= KERN_SUCCESS
;
980 ASSERT_LWKT_TOKEN_HELD(vm_object_token(fs
->first_object
));
983 * We cannot proceed if the vpte is not valid, not readable
984 * for a read fault, or not writable for a write fault.
986 if ((vpte
& VPTE_V
) == 0) {
987 unlock_and_deallocate(fs
);
988 return (KERN_FAILURE
);
990 if ((fault_type
& VM_PROT_READ
) && (vpte
& VPTE_R
) == 0) {
991 unlock_and_deallocate(fs
);
992 return (KERN_FAILURE
);
994 if ((fault_type
& VM_PROT_WRITE
) && (vpte
& VPTE_W
) == 0) {
995 unlock_and_deallocate(fs
);
996 return (KERN_FAILURE
);
998 if ((vpte
& VPTE_PS
) || vshift
== 0)
1000 KKASSERT(vshift
>= VPTE_PAGE_BITS
);
1003 * Get the page table page. Nominally we only read the page
1004 * table, but since we are actively setting VPTE_M and VPTE_A,
1005 * tell vm_fault_object() that we are writing it.
1007 * There is currently no real need to optimize this.
1009 result
= vm_fault_object(fs
, (vpte
& VPTE_FRAME
) >> PAGE_SHIFT
,
1010 VM_PROT_READ
|VM_PROT_WRITE
);
1011 if (result
!= KERN_SUCCESS
)
1015 * Process the returned fs.m and look up the page table
1016 * entry in the page table page.
1018 vshift
-= VPTE_PAGE_BITS
;
1019 lwb
= lwbuf_alloc(fs
->m
, &lwb_cache
);
1020 ptep
= ((vpte_t
*)lwbuf_kva(lwb
) +
1021 ((*pindex
>> vshift
) & VPTE_PAGE_MASK
));
1025 * Page table write-back. If the vpte is valid for the
1026 * requested operation, do a write-back to the page table.
1028 * XXX VPTE_M is not set properly for page directory pages.
1029 * It doesn't get set in the page directory if the page table
1030 * is modified during a read access.
1032 vm_page_activate(fs
->m
);
1033 if ((fault_type
& VM_PROT_WRITE
) && (vpte
& VPTE_V
) &&
1035 if ((vpte
& (VPTE_M
|VPTE_A
)) != (VPTE_M
|VPTE_A
)) {
1036 atomic_set_long(ptep
, VPTE_M
| VPTE_A
);
1037 vm_page_dirty(fs
->m
);
1040 if ((fault_type
& VM_PROT_READ
) && (vpte
& VPTE_V
) &&
1042 if ((vpte
& VPTE_A
) == 0) {
1043 atomic_set_long(ptep
, VPTE_A
);
1044 vm_page_dirty(fs
->m
);
1048 vm_page_flag_set(fs
->m
, PG_REFERENCED
);
1049 vm_page_wakeup(fs
->m
);
1051 cleanup_successful_fault(fs
);
1054 * Combine remaining address bits with the vpte.
1056 /* JG how many bits from each? */
1057 *pindex
= ((vpte
& VPTE_FRAME
) >> PAGE_SHIFT
) +
1058 (*pindex
& ((1L << vshift
) - 1));
1059 return (KERN_SUCCESS
);
1064 * This is the core of the vm_fault code.
1066 * Do all operations required to fault-in (fs.first_object, pindex). Run
1067 * through the shadow chain as necessary and do required COW or virtual
1068 * copy operations. The caller has already fully resolved the vm_map_entry
1069 * and, if appropriate, has created a copy-on-write layer. All we need to
1070 * do is iterate the object chain.
1072 * On failure (fs) is unlocked and deallocated and the caller may return or
1073 * retry depending on the failure code. On success (fs) is NOT unlocked or
1074 * deallocated, fs.m will contained a resolved, busied page, and fs.object
1075 * will have an additional PIP count if it is not equal to fs.first_object.
1077 * fs->first_object must be held on call.
1081 vm_fault_object(struct faultstate
*fs
,
1082 vm_pindex_t first_pindex
, vm_prot_t fault_type
)
1084 vm_object_t next_object
;
1088 ASSERT_LWKT_TOKEN_HELD(vm_object_token(fs
->first_object
));
1089 fs
->prot
= fs
->first_prot
;
1090 fs
->object
= fs
->first_object
;
1091 pindex
= first_pindex
;
1093 vm_object_chain_acquire(fs
->first_object
);
1094 vm_object_pip_add(fs
->first_object
, 1);
1097 * If a read fault occurs we try to make the page writable if
1098 * possible. There are three cases where we cannot make the
1099 * page mapping writable:
1101 * (1) The mapping is read-only or the VM object is read-only,
1102 * fs->prot above will simply not have VM_PROT_WRITE set.
1104 * (2) If the mapping is a virtual page table we need to be able
1105 * to detect writes so we can set VPTE_M in the virtual page
1108 * (3) If the VM page is read-only or copy-on-write, upgrading would
1109 * just result in an unnecessary COW fault.
1111 * VM_PROT_VPAGED is set if faulting via a virtual page table and
1112 * causes adjustments to the 'M'odify bit to also turn off write
1113 * access to force a re-fault.
1115 if (fs
->entry
->maptype
== VM_MAPTYPE_VPAGETABLE
) {
1116 if ((fault_type
& VM_PROT_WRITE
) == 0)
1117 fs
->prot
&= ~VM_PROT_WRITE
;
1120 /* vm_object_hold(fs->object); implied b/c object == first_object */
1124 * The entire backing chain from first_object to object
1125 * inclusive is chainlocked.
1127 * If the object is dead, we stop here
1129 if (fs
->object
->flags
& OBJ_DEAD
) {
1130 vm_object_pip_wakeup(fs
->first_object
);
1131 vm_object_chain_release_all(fs
->first_object
,
1133 if (fs
->object
!= fs
->first_object
)
1134 vm_object_drop(fs
->object
);
1135 unlock_and_deallocate(fs
);
1136 return (KERN_PROTECTION_FAILURE
);
1140 * See if the page is resident. Wait/Retry if the page is
1141 * busy (lots of stuff may have changed so we can't continue
1144 * We can theoretically allow the soft-busy case on a read
1145 * fault if the page is marked valid, but since such
1146 * pages are typically already pmap'd, putting that
1147 * special case in might be more effort then it is
1148 * worth. We cannot under any circumstances mess
1149 * around with a vm_page_t->busy page except, perhaps,
1152 fs
->m
= vm_page_lookup_busy_try(fs
->object
, pindex
,
1155 vm_object_pip_wakeup(fs
->first_object
);
1156 vm_object_chain_release_all(fs
->first_object
,
1158 if (fs
->object
!= fs
->first_object
)
1159 vm_object_drop(fs
->object
);
1161 vm_page_sleep_busy(fs
->m
, TRUE
, "vmpfw");
1162 mycpu
->gd_cnt
.v_intrans
++;
1163 /*vm_object_deallocate(fs->first_object);*/
1164 /*fs->first_object = NULL;*/
1166 return (KERN_TRY_AGAIN
);
1170 * The page is busied for us.
1172 * If reactivating a page from PQ_CACHE we may have
1175 int queue
= fs
->m
->queue
;
1176 vm_page_unqueue_nowakeup(fs
->m
);
1178 if ((queue
- fs
->m
->pc
) == PQ_CACHE
&&
1179 vm_page_count_severe()) {
1180 vm_page_activate(fs
->m
);
1181 vm_page_wakeup(fs
->m
);
1183 vm_object_pip_wakeup(fs
->first_object
);
1184 vm_object_chain_release_all(fs
->first_object
,
1186 if (fs
->object
!= fs
->first_object
)
1187 vm_object_drop(fs
->object
);
1188 unlock_and_deallocate(fs
);
1190 return (KERN_TRY_AGAIN
);
1194 * If it still isn't completely valid (readable),
1195 * or if a read-ahead-mark is set on the VM page,
1196 * jump to readrest, else we found the page and
1199 * We can release the spl once we have marked the
1202 if (fs
->m
->object
!= &kernel_object
) {
1203 if ((fs
->m
->valid
& VM_PAGE_BITS_ALL
) !=
1207 if (fs
->m
->flags
& PG_RAM
) {
1210 vm_page_flag_clear(fs
->m
, PG_RAM
);
1214 break; /* break to PAGE HAS BEEN FOUND */
1218 * Page is not resident, If this is the search termination
1219 * or the pager might contain the page, allocate a new page.
1221 if (TRYPAGER(fs
) || fs
->object
== fs
->first_object
) {
1223 * If the page is beyond the object size we fail
1225 if (pindex
>= fs
->object
->size
) {
1226 vm_object_pip_wakeup(fs
->first_object
);
1227 vm_object_chain_release_all(fs
->first_object
,
1229 if (fs
->object
!= fs
->first_object
)
1230 vm_object_drop(fs
->object
);
1231 unlock_and_deallocate(fs
);
1232 return (KERN_PROTECTION_FAILURE
);
1236 * Allocate a new page for this object/offset pair.
1238 * It is possible for the allocation to race, so
1242 if (!vm_page_count_severe()) {
1243 fs
->m
= vm_page_alloc(fs
->object
, pindex
,
1244 ((fs
->vp
|| fs
->object
->backing_object
) ?
1245 VM_ALLOC_NULL_OK
| VM_ALLOC_NORMAL
:
1246 VM_ALLOC_NULL_OK
| VM_ALLOC_NORMAL
|
1247 VM_ALLOC_USE_GD
| VM_ALLOC_ZERO
));
1249 if (fs
->m
== NULL
) {
1250 vm_object_pip_wakeup(fs
->first_object
);
1251 vm_object_chain_release_all(fs
->first_object
,
1253 if (fs
->object
!= fs
->first_object
)
1254 vm_object_drop(fs
->object
);
1255 unlock_and_deallocate(fs
);
1257 return (KERN_TRY_AGAIN
);
1261 * Fall through to readrest. We have a new page which
1262 * will have to be paged (since m->valid will be 0).
1268 * We have found an invalid or partially valid page, a
1269 * page with a read-ahead mark which might be partially or
1270 * fully valid (and maybe dirty too), or we have allocated
1273 * Attempt to fault-in the page if there is a chance that the
1274 * pager has it, and potentially fault in additional pages
1277 * If TRYPAGER is true then fs.m will be non-NULL and busied
1283 u_char behavior
= vm_map_entry_behavior(fs
->entry
);
1285 if (behavior
== MAP_ENTRY_BEHAV_RANDOM
)
1292 * If sequential access is detected then attempt
1293 * to deactivate/cache pages behind the scan to
1294 * prevent resource hogging.
1296 * Use of PG_RAM to detect sequential access
1297 * also simulates multi-zone sequential access
1298 * detection for free.
1300 * NOTE: Partially valid dirty pages cannot be
1301 * deactivated without causing NFS picemeal
1304 if ((fs
->first_object
->type
!= OBJT_DEVICE
) &&
1305 (behavior
== MAP_ENTRY_BEHAV_SEQUENTIAL
||
1306 (behavior
!= MAP_ENTRY_BEHAV_RANDOM
&&
1307 (fs
->m
->flags
& PG_RAM
)))
1309 vm_pindex_t scan_pindex
;
1310 int scan_count
= 16;
1312 if (first_pindex
< 16) {
1316 scan_pindex
= first_pindex
- 16;
1317 if (scan_pindex
< 16)
1318 scan_count
= scan_pindex
;
1323 while (scan_count
) {
1326 mt
= vm_page_lookup(fs
->first_object
,
1330 if (vm_page_busy_try(mt
, TRUE
))
1333 if (mt
->valid
!= VM_PAGE_BITS_ALL
) {
1338 (PG_FICTITIOUS
| PG_UNMANAGED
|
1346 vm_page_test_dirty(mt
);
1350 vm_page_deactivate(mt
);
1365 * Avoid deadlocking against the map when doing I/O.
1366 * fs.object and the page is PG_BUSY'd.
1368 * NOTE: Once unlocked, fs->entry can become stale
1369 * so this will NULL it out.
1371 * NOTE: fs->entry is invalid until we relock the
1372 * map and verify that the timestamp has not
1378 * Acquire the page data. We still hold a ref on
1379 * fs.object and the page has been PG_BUSY's.
1381 * The pager may replace the page (for example, in
1382 * order to enter a fictitious page into the
1383 * object). If it does so it is responsible for
1384 * cleaning up the passed page and properly setting
1385 * the new page PG_BUSY.
1387 * If we got here through a PG_RAM read-ahead
1388 * mark the page may be partially dirty and thus
1389 * not freeable. Don't bother checking to see
1390 * if the pager has the page because we can't free
1391 * it anyway. We have to depend on the get_page
1392 * operation filling in any gaps whether there is
1393 * backing store or not.
1395 rv
= vm_pager_get_page(fs
->object
, &fs
->m
, seqaccess
);
1397 if (rv
== VM_PAGER_OK
) {
1399 * Relookup in case pager changed page. Pager
1400 * is responsible for disposition of old page
1403 * XXX other code segments do relookups too.
1404 * It's a bad abstraction that needs to be
1407 fs
->m
= vm_page_lookup(fs
->object
, pindex
);
1408 if (fs
->m
== NULL
) {
1409 vm_object_pip_wakeup(fs
->first_object
);
1410 vm_object_chain_release_all(
1411 fs
->first_object
, fs
->object
);
1412 if (fs
->object
!= fs
->first_object
)
1413 vm_object_drop(fs
->object
);
1414 unlock_and_deallocate(fs
);
1415 return (KERN_TRY_AGAIN
);
1419 break; /* break to PAGE HAS BEEN FOUND */
1423 * Remove the bogus page (which does not exist at this
1424 * object/offset); before doing so, we must get back
1425 * our object lock to preserve our invariant.
1427 * Also wake up any other process that may want to bring
1430 * If this is the top-level object, we must leave the
1431 * busy page to prevent another process from rushing
1432 * past us, and inserting the page in that object at
1433 * the same time that we are.
1435 if (rv
== VM_PAGER_ERROR
) {
1437 kprintf("vm_fault: pager read error, "
1442 kprintf("vm_fault: pager read error, "
1450 * Data outside the range of the pager or an I/O error
1452 * The page may have been wired during the pagein,
1453 * e.g. by the buffer cache, and cannot simply be
1454 * freed. Call vnode_pager_freepage() to deal with it.
1457 * XXX - the check for kernel_map is a kludge to work
1458 * around having the machine panic on a kernel space
1459 * fault w/ I/O error.
1461 if (((fs
->map
!= &kernel_map
) &&
1462 (rv
== VM_PAGER_ERROR
)) || (rv
== VM_PAGER_BAD
)) {
1463 vnode_pager_freepage(fs
->m
);
1465 vm_object_pip_wakeup(fs
->first_object
);
1466 vm_object_chain_release_all(fs
->first_object
,
1468 if (fs
->object
!= fs
->first_object
)
1469 vm_object_drop(fs
->object
);
1470 unlock_and_deallocate(fs
);
1471 if (rv
== VM_PAGER_ERROR
)
1472 return (KERN_FAILURE
);
1474 return (KERN_PROTECTION_FAILURE
);
1477 if (fs
->object
!= fs
->first_object
) {
1478 vnode_pager_freepage(fs
->m
);
1481 * XXX - we cannot just fall out at this
1482 * point, m has been freed and is invalid!
1488 * We get here if the object has a default pager (or unwiring)
1489 * or the pager doesn't have the page.
1491 if (fs
->object
== fs
->first_object
)
1492 fs
->first_m
= fs
->m
;
1495 * Move on to the next object. The chain lock should prevent
1496 * the backing_object from getting ripped out from under us.
1498 if ((next_object
= fs
->object
->backing_object
) != NULL
) {
1499 vm_object_hold(next_object
);
1500 vm_object_chain_acquire(next_object
);
1501 KKASSERT(next_object
== fs
->object
->backing_object
);
1502 pindex
+= OFF_TO_IDX(fs
->object
->backing_object_offset
);
1505 if (next_object
== NULL
) {
1507 * If there's no object left, fill the page in the top
1508 * object with zeros.
1510 if (fs
->object
!= fs
->first_object
) {
1511 if (fs
->first_object
->backing_object
!=
1513 vm_object_hold(fs
->first_object
->backing_object
);
1515 vm_object_chain_release_all(
1516 fs
->first_object
->backing_object
,
1518 if (fs
->first_object
->backing_object
!=
1520 vm_object_drop(fs
->first_object
->backing_object
);
1522 vm_object_pip_wakeup(fs
->object
);
1523 vm_object_drop(fs
->object
);
1524 fs
->object
= fs
->first_object
;
1525 pindex
= first_pindex
;
1526 fs
->m
= fs
->first_m
;
1531 * Zero the page if necessary and mark it valid.
1533 if ((fs
->m
->flags
& PG_ZERO
) == 0) {
1534 vm_page_zero_fill(fs
->m
);
1537 pmap_page_assertzero(VM_PAGE_TO_PHYS(fs
->m
));
1539 vm_page_flag_clear(fs
->m
, PG_ZERO
);
1540 mycpu
->gd_cnt
.v_ozfod
++;
1542 mycpu
->gd_cnt
.v_zfod
++;
1543 fs
->m
->valid
= VM_PAGE_BITS_ALL
;
1544 break; /* break to PAGE HAS BEEN FOUND */
1546 if (fs
->object
!= fs
->first_object
) {
1547 vm_object_pip_wakeup(fs
->object
);
1548 vm_object_lock_swap();
1549 vm_object_drop(fs
->object
);
1551 KASSERT(fs
->object
!= next_object
,
1552 ("object loop %p", next_object
));
1553 fs
->object
= next_object
;
1554 vm_object_pip_add(fs
->object
, 1);
1558 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
1561 * object still held.
1563 * If the page is being written, but isn't already owned by the
1564 * top-level object, we have to copy it into a new page owned by the
1567 KASSERT((fs
->m
->flags
& PG_BUSY
) != 0,
1568 ("vm_fault: not busy after main loop"));
1570 if (fs
->object
!= fs
->first_object
) {
1572 * We only really need to copy if we want to write it.
1574 if (fault_type
& VM_PROT_WRITE
) {
1576 * This allows pages to be virtually copied from a
1577 * backing_object into the first_object, where the
1578 * backing object has no other refs to it, and cannot
1579 * gain any more refs. Instead of a bcopy, we just
1580 * move the page from the backing object to the
1581 * first object. Note that we must mark the page
1582 * dirty in the first object so that it will go out
1583 * to swap when needed.
1587 * Map, if present, has not changed
1590 fs
->map_generation
== fs
->map
->timestamp
) &&
1592 * Only one shadow object
1594 (fs
->object
->shadow_count
== 1) &&
1596 * No COW refs, except us
1598 (fs
->object
->ref_count
== 1) &&
1600 * No one else can look this object up
1602 (fs
->object
->handle
== NULL
) &&
1604 * No other ways to look the object up
1606 ((fs
->object
->type
== OBJT_DEFAULT
) ||
1607 (fs
->object
->type
== OBJT_SWAP
)) &&
1609 * We don't chase down the shadow chain
1611 (fs
->object
== fs
->first_object
->backing_object
) &&
1614 * grab the lock if we need to
1616 (fs
->lookup_still_valid
||
1618 lockmgr(&fs
->map
->lock
, LK_EXCLUSIVE
|LK_NOWAIT
) == 0)
1621 * (first_m) and (m) are both busied. We have
1622 * move (m) into (first_m)'s object/pindex
1623 * in an atomic fashion, then free (first_m).
1625 * first_object is held so second remove
1626 * followed by the rename should wind
1627 * up being atomic. vm_page_free() might
1628 * block so we don't do it until after the
1631 fs
->lookup_still_valid
= 1;
1632 vm_page_protect(fs
->first_m
, VM_PROT_NONE
);
1633 vm_page_remove(fs
->first_m
);
1634 vm_page_rename(fs
->m
, fs
->first_object
,
1636 vm_page_free(fs
->first_m
);
1637 fs
->first_m
= fs
->m
;
1639 mycpu
->gd_cnt
.v_cow_optim
++;
1642 * Oh, well, lets copy it.
1644 * Why are we unmapping the original page
1645 * here? Well, in short, not all accessors
1646 * of user memory go through the pmap. The
1647 * procfs code doesn't have access user memory
1648 * via a local pmap, so vm_fault_page*()
1649 * can't call pmap_enter(). And the umtx*()
1650 * code may modify the COW'd page via a DMAP
1651 * or kernel mapping and not via the pmap,
1652 * leaving the original page still mapped
1653 * read-only into the pmap.
1655 * So we have to remove the page from at
1656 * least the current pmap if it is in it.
1657 * Just remove it from all pmaps.
1659 vm_page_copy(fs
->m
, fs
->first_m
);
1660 vm_page_protect(fs
->m
, VM_PROT_NONE
);
1661 vm_page_event(fs
->m
, VMEVENT_COW
);
1666 * We no longer need the old page or object.
1672 * We intend to revert to first_object, undo the
1673 * chain lock through to that.
1675 if (fs
->first_object
->backing_object
!= fs
->object
)
1676 vm_object_hold(fs
->first_object
->backing_object
);
1677 vm_object_chain_release_all(
1678 fs
->first_object
->backing_object
,
1680 if (fs
->first_object
->backing_object
!= fs
->object
)
1681 vm_object_drop(fs
->first_object
->backing_object
);
1684 * fs->object != fs->first_object due to above
1687 vm_object_pip_wakeup(fs
->object
);
1688 vm_object_drop(fs
->object
);
1691 * Only use the new page below...
1694 mycpu
->gd_cnt
.v_cow_faults
++;
1695 fs
->m
= fs
->first_m
;
1696 fs
->object
= fs
->first_object
;
1697 pindex
= first_pindex
;
1700 * If it wasn't a write fault avoid having to copy
1701 * the page by mapping it read-only.
1703 fs
->prot
&= ~VM_PROT_WRITE
;
1708 * Relock the map if necessary, then check the generation count.
1709 * relock_map() will update fs->timestamp to account for the
1710 * relocking if necessary.
1712 * If the count has changed after relocking then all sorts of
1713 * crap may have happened and we have to retry.
1715 * NOTE: The relock_map() can fail due to a deadlock against
1716 * the vm_page we are holding BUSY.
1718 if (fs
->lookup_still_valid
== FALSE
&& fs
->map
) {
1719 if (relock_map(fs
) ||
1720 fs
->map
->timestamp
!= fs
->map_generation
) {
1722 vm_object_pip_wakeup(fs
->first_object
);
1723 vm_object_chain_release_all(fs
->first_object
,
1725 if (fs
->object
!= fs
->first_object
)
1726 vm_object_drop(fs
->object
);
1727 unlock_and_deallocate(fs
);
1728 return (KERN_TRY_AGAIN
);
1733 * If the fault is a write, we know that this page is being
1734 * written NOW so dirty it explicitly to save on pmap_is_modified()
1737 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC
1738 * if the page is already dirty to prevent data written with
1739 * the expectation of being synced from not being synced.
1740 * Likewise if this entry does not request NOSYNC then make
1741 * sure the page isn't marked NOSYNC. Applications sharing
1742 * data should use the same flags to avoid ping ponging.
1744 * Also tell the backing pager, if any, that it should remove
1745 * any swap backing since the page is now dirty.
1747 vm_page_activate(fs
->m
);
1748 if (fs
->prot
& VM_PROT_WRITE
) {
1749 vm_object_set_writeable_dirty(fs
->m
->object
);
1750 vm_set_nosync(fs
->m
, fs
->entry
);
1751 if (fs
->fault_flags
& VM_FAULT_DIRTY
) {
1752 vm_page_dirty(fs
->m
);
1753 swap_pager_unswapped(fs
->m
);
1757 vm_object_pip_wakeup(fs
->first_object
);
1758 vm_object_chain_release_all(fs
->first_object
, fs
->object
);
1759 if (fs
->object
!= fs
->first_object
)
1760 vm_object_drop(fs
->object
);
1763 * Page had better still be busy. We are still locked up and
1764 * fs->object will have another PIP reference if it is not equal
1765 * to fs->first_object.
1767 KASSERT(fs
->m
->flags
& PG_BUSY
,
1768 ("vm_fault: page %p not busy!", fs
->m
));
1771 * Sanity check: page must be completely valid or it is not fit to
1772 * map into user space. vm_pager_get_pages() ensures this.
1774 if (fs
->m
->valid
!= VM_PAGE_BITS_ALL
) {
1775 vm_page_zero_invalid(fs
->m
, TRUE
);
1776 kprintf("Warning: page %p partially invalid on fault\n", fs
->m
);
1778 vm_page_flag_clear(fs
->m
, PG_ZERO
);
1780 return (KERN_SUCCESS
);
1784 * Wire down a range of virtual addresses in a map. The entry in question
1785 * should be marked in-transition and the map must be locked. We must
1786 * release the map temporarily while faulting-in the page to avoid a
1787 * deadlock. Note that the entry may be clipped while we are blocked but
1788 * will never be freed.
1793 vm_fault_wire(vm_map_t map
, vm_map_entry_t entry
, boolean_t user_wire
)
1795 boolean_t fictitious
;
1804 lwkt_gettoken(&map
->token
);
1806 pmap
= vm_map_pmap(map
);
1807 start
= entry
->start
;
1809 fictitious
= entry
->object
.vm_object
&&
1810 (entry
->object
.vm_object
->type
== OBJT_DEVICE
);
1811 if (entry
->eflags
& MAP_ENTRY_KSTACK
)
1817 * We simulate a fault to get the page and enter it in the physical
1820 for (va
= start
; va
< end
; va
+= PAGE_SIZE
) {
1822 rv
= vm_fault(map
, va
, VM_PROT_READ
,
1823 VM_FAULT_USER_WIRE
);
1825 rv
= vm_fault(map
, va
, VM_PROT_READ
|VM_PROT_WRITE
,
1826 VM_FAULT_CHANGE_WIRING
);
1829 while (va
> start
) {
1831 if ((pa
= pmap_extract(pmap
, va
)) == 0)
1833 pmap_change_wiring(pmap
, va
, FALSE
, entry
);
1835 m
= PHYS_TO_VM_PAGE(pa
);
1836 vm_page_busy_wait(m
, FALSE
, "vmwrpg");
1837 vm_page_unwire(m
, 1);
1847 lwkt_reltoken(&map
->token
);
1852 * Unwire a range of virtual addresses in a map. The map should be
1856 vm_fault_unwire(vm_map_t map
, vm_map_entry_t entry
)
1858 boolean_t fictitious
;
1866 lwkt_gettoken(&map
->token
);
1868 pmap
= vm_map_pmap(map
);
1869 start
= entry
->start
;
1871 fictitious
= entry
->object
.vm_object
&&
1872 (entry
->object
.vm_object
->type
== OBJT_DEVICE
);
1873 if (entry
->eflags
& MAP_ENTRY_KSTACK
)
1877 * Since the pages are wired down, we must be able to get their
1878 * mappings from the physical map system.
1880 for (va
= start
; va
< end
; va
+= PAGE_SIZE
) {
1881 pa
= pmap_extract(pmap
, va
);
1883 pmap_change_wiring(pmap
, va
, FALSE
, entry
);
1885 m
= PHYS_TO_VM_PAGE(pa
);
1886 vm_page_busy_wait(m
, FALSE
, "vmwupg");
1887 vm_page_unwire(m
, 1);
1892 lwkt_reltoken(&map
->token
);
1896 * Copy all of the pages from a wired-down map entry to another.
1898 * The source and destination maps must be locked for write.
1899 * The source and destination maps token must be held
1900 * The source map entry must be wired down (or be a sharing map
1901 * entry corresponding to a main map entry that is wired down).
1903 * No other requirements.
1905 * XXX do segment optimization
1908 vm_fault_copy_entry(vm_map_t dst_map
, vm_map_t src_map
,
1909 vm_map_entry_t dst_entry
, vm_map_entry_t src_entry
)
1911 vm_object_t dst_object
;
1912 vm_object_t src_object
;
1913 vm_ooffset_t dst_offset
;
1914 vm_ooffset_t src_offset
;
1920 src_object
= src_entry
->object
.vm_object
;
1921 src_offset
= src_entry
->offset
;
1924 * Create the top-level object for the destination entry. (Doesn't
1925 * actually shadow anything - we copy the pages directly.)
1927 vm_map_entry_allocate_object(dst_entry
);
1928 dst_object
= dst_entry
->object
.vm_object
;
1930 prot
= dst_entry
->max_protection
;
1933 * Loop through all of the pages in the entry's range, copying each
1934 * one from the source object (it should be there) to the destination
1937 vm_object_hold(src_object
);
1938 vm_object_hold(dst_object
);
1939 for (vaddr
= dst_entry
->start
, dst_offset
= 0;
1940 vaddr
< dst_entry
->end
;
1941 vaddr
+= PAGE_SIZE
, dst_offset
+= PAGE_SIZE
) {
1944 * Allocate a page in the destination object
1947 dst_m
= vm_page_alloc(dst_object
,
1948 OFF_TO_IDX(dst_offset
),
1950 if (dst_m
== NULL
) {
1953 } while (dst_m
== NULL
);
1956 * Find the page in the source object, and copy it in.
1957 * (Because the source is wired down, the page will be in
1960 src_m
= vm_page_lookup(src_object
,
1961 OFF_TO_IDX(dst_offset
+ src_offset
));
1963 panic("vm_fault_copy_wired: page missing");
1965 vm_page_copy(src_m
, dst_m
);
1966 vm_page_event(src_m
, VMEVENT_COW
);
1969 * Enter it in the pmap...
1972 vm_page_flag_clear(dst_m
, PG_ZERO
);
1973 pmap_enter(dst_map
->pmap
, vaddr
, dst_m
, prot
, FALSE
, dst_entry
);
1976 * Mark it no longer busy, and put it on the active list.
1978 vm_page_activate(dst_m
);
1979 vm_page_wakeup(dst_m
);
1981 vm_object_drop(dst_object
);
1982 vm_object_drop(src_object
);
1988 * This routine checks around the requested page for other pages that
1989 * might be able to be faulted in. This routine brackets the viable
1990 * pages for the pages to be paged in.
1993 * m, rbehind, rahead
1996 * marray (array of vm_page_t), reqpage (index of requested page)
1999 * number of pages in marray
2002 vm_fault_additional_pages(vm_page_t m
, int rbehind
, int rahead
,
2003 vm_page_t
*marray
, int *reqpage
)
2007 vm_pindex_t pindex
, startpindex
, endpindex
, tpindex
;
2009 int cbehind
, cahead
;
2015 * we don't fault-ahead for device pager
2017 if (object
->type
== OBJT_DEVICE
) {
2024 * if the requested page is not available, then give up now
2026 if (!vm_pager_has_page(object
, pindex
, &cbehind
, &cahead
)) {
2027 *reqpage
= 0; /* not used by caller, fix compiler warn */
2031 if ((cbehind
== 0) && (cahead
== 0)) {
2037 if (rahead
> cahead
) {
2041 if (rbehind
> cbehind
) {
2046 * Do not do any readahead if we have insufficient free memory.
2048 * XXX code was broken disabled before and has instability
2049 * with this conditonal fixed, so shortcut for now.
2051 if (burst_fault
== 0 || vm_page_count_severe()) {
2058 * scan backward for the read behind pages -- in memory
2060 * Assume that if the page is not found an interrupt will not
2061 * create it. Theoretically interrupts can only remove (busy)
2062 * pages, not create new associations.
2065 if (rbehind
> pindex
) {
2069 startpindex
= pindex
- rbehind
;
2072 vm_object_hold(object
);
2073 for (tpindex
= pindex
; tpindex
> startpindex
; --tpindex
) {
2074 if (vm_page_lookup(object
, tpindex
- 1))
2079 while (tpindex
< pindex
) {
2080 rtm
= vm_page_alloc(object
, tpindex
, VM_ALLOC_SYSTEM
|
2083 for (j
= 0; j
< i
; j
++) {
2084 vm_page_free(marray
[j
]);
2086 vm_object_drop(object
);
2095 vm_object_drop(object
);
2101 * Assign requested page
2108 * Scan forwards for read-ahead pages
2110 tpindex
= pindex
+ 1;
2111 endpindex
= tpindex
+ rahead
;
2112 if (endpindex
> object
->size
)
2113 endpindex
= object
->size
;
2115 vm_object_hold(object
);
2116 while (tpindex
< endpindex
) {
2117 if (vm_page_lookup(object
, tpindex
))
2119 rtm
= vm_page_alloc(object
, tpindex
, VM_ALLOC_SYSTEM
|
2127 vm_object_drop(object
);
2135 * vm_prefault() provides a quick way of clustering pagefaults into a
2136 * processes address space. It is a "cousin" of pmap_object_init_pt,
2137 * except it runs at page fault time instead of mmap time.
2139 * vm.fast_fault Enables pre-faulting zero-fill pages
2141 * vm.prefault_pages Number of pages (1/2 negative, 1/2 positive) to
2142 * prefault. Scan stops in either direction when
2143 * a page is found to already exist.
2145 * This code used to be per-platform pmap_prefault(). It is now
2146 * machine-independent and enhanced to also pre-fault zero-fill pages
2147 * (see vm.fast_fault) as well as make them writable, which greatly
2148 * reduces the number of page faults programs incur.
2150 * Application performance when pre-faulting zero-fill pages is heavily
2151 * dependent on the application. Very tiny applications like /bin/echo
2152 * lose a little performance while applications of any appreciable size
2153 * gain performance. Prefaulting multiple pages also reduces SMP
2154 * congestion and can improve SMP performance significantly.
2156 * NOTE! prot may allow writing but this only applies to the top level
2157 * object. If we wind up mapping a page extracted from a backing
2158 * object we have to make sure it is read-only.
2160 * NOTE! The caller has already handled any COW operations on the
2161 * vm_map_entry via the normal fault code. Do NOT call this
2162 * shortcut unless the normal fault code has run on this entry.
2164 * The related map must be locked.
2165 * No other requirements.
2167 static int vm_prefault_pages
= 8;
2168 SYSCTL_INT(_vm
, OID_AUTO
, prefault_pages
, CTLFLAG_RW
, &vm_prefault_pages
, 0,
2169 "Maximum number of pages to pre-fault");
2170 static int vm_fast_fault
= 1;
2171 SYSCTL_INT(_vm
, OID_AUTO
, fast_fault
, CTLFLAG_RW
, &vm_fast_fault
, 0,
2172 "Burst fault zero-fill regions");
2175 * Set PG_NOSYNC if the map entry indicates so, but only if the page
2176 * is not already dirty by other means. This will prevent passive
2177 * filesystem syncing as well as 'sync' from writing out the page.
2180 vm_set_nosync(vm_page_t m
, vm_map_entry_t entry
)
2182 if (entry
->eflags
& MAP_ENTRY_NOSYNC
) {
2184 vm_page_flag_set(m
, PG_NOSYNC
);
2186 vm_page_flag_clear(m
, PG_NOSYNC
);
2191 vm_prefault(pmap_t pmap
, vm_offset_t addra
, vm_map_entry_t entry
, int prot
,
2207 * Get stable max count value, disabled if set to 0
2209 maxpages
= vm_prefault_pages
;
2215 * We do not currently prefault mappings that use virtual page
2216 * tables. We do not prefault foreign pmaps.
2218 if (entry
->maptype
== VM_MAPTYPE_VPAGETABLE
)
2220 lp
= curthread
->td_lwp
;
2221 if (lp
== NULL
|| (pmap
!= vmspace_pmap(lp
->lwp_vmspace
)))
2225 * Limit pre-fault count to 1024 pages.
2227 if (maxpages
> 1024)
2230 object
= entry
->object
.vm_object
;
2231 KKASSERT(object
!= NULL
);
2232 KKASSERT(object
== entry
->object
.vm_object
);
2233 vm_object_hold(object
);
2234 vm_object_chain_acquire(object
);
2238 for (i
= 0; i
< maxpages
; ++i
) {
2239 vm_object_t lobject
;
2240 vm_object_t nobject
;
2245 * This can eat a lot of time on a heavily contended
2246 * machine so yield on the tick if needed.
2252 * Calculate the page to pre-fault, stopping the scan in
2253 * each direction separately if the limit is reached.
2258 addr
= addra
- ((i
+ 1) >> 1) * PAGE_SIZE
;
2262 addr
= addra
+ ((i
+ 2) >> 1) * PAGE_SIZE
;
2264 if (addr
< entry
->start
) {
2270 if (addr
>= entry
->end
) {
2278 * Skip pages already mapped, and stop scanning in that
2279 * direction. When the scan terminates in both directions
2282 if (pmap_prefault_ok(pmap
, addr
) == 0) {
2293 * Follow the VM object chain to obtain the page to be mapped
2296 * If we reach the terminal object without finding a page
2297 * and we determine it would be advantageous, then allocate
2298 * a zero-fill page for the base object. The base object
2299 * is guaranteed to be OBJT_DEFAULT for this case.
2301 * In order to not have to check the pager via *haspage*()
2302 * we stop if any non-default object is encountered. e.g.
2303 * a vnode or swap object would stop the loop.
2305 index
= ((addr
- entry
->start
) + entry
->offset
) >> PAGE_SHIFT
;
2310 KKASSERT(lobject
== entry
->object
.vm_object
);
2311 /*vm_object_hold(lobject); implied */
2313 while ((m
= vm_page_lookup_busy_try(lobject
, pindex
,
2314 TRUE
, &error
)) == NULL
) {
2315 if (lobject
->type
!= OBJT_DEFAULT
)
2317 if (lobject
->backing_object
== NULL
) {
2318 if (vm_fast_fault
== 0)
2320 if ((prot
& VM_PROT_WRITE
) == 0 ||
2321 vm_page_count_min(0)) {
2326 * NOTE: Allocated from base object
2328 m
= vm_page_alloc(object
, index
,
2337 /* lobject = object .. not needed */
2340 if (lobject
->backing_object_offset
& PAGE_MASK
)
2342 nobject
= lobject
->backing_object
;
2343 vm_object_hold(nobject
);
2344 KKASSERT(nobject
== lobject
->backing_object
);
2345 pindex
+= lobject
->backing_object_offset
>> PAGE_SHIFT
;
2346 if (lobject
!= object
) {
2347 vm_object_lock_swap();
2348 vm_object_drop(lobject
);
2351 pprot
&= ~VM_PROT_WRITE
;
2352 vm_object_chain_acquire(lobject
);
2356 * NOTE: A non-NULL (m) will be associated with lobject if
2357 * it was found there, otherwise it is probably a
2358 * zero-fill page associated with the base object.
2360 * Give-up if no page is available.
2363 if (lobject
!= object
) {
2364 if (object
->backing_object
!= lobject
)
2365 vm_object_hold(object
->backing_object
);
2366 vm_object_chain_release_all(
2367 object
->backing_object
, lobject
);
2368 if (object
->backing_object
!= lobject
)
2369 vm_object_drop(object
->backing_object
);
2370 vm_object_drop(lobject
);
2376 * The object must be marked dirty if we are mapping a
2377 * writable page. m->object is either lobject or object,
2378 * both of which are still held. Do this before we
2379 * potentially drop the object.
2381 if (pprot
& VM_PROT_WRITE
)
2382 vm_object_set_writeable_dirty(m
->object
);
2385 * Do not conditionalize on PG_RAM. If pages are present in
2386 * the VM system we assume optimal caching. If caching is
2387 * not optimal the I/O gravy train will be restarted when we
2388 * hit an unavailable page. We do not want to try to restart
2389 * the gravy train now because we really don't know how much
2390 * of the object has been cached. The cost for restarting
2391 * the gravy train should be low (since accesses will likely
2392 * be I/O bound anyway).
2394 if (lobject
!= object
) {
2395 if (object
->backing_object
!= lobject
)
2396 vm_object_hold(object
->backing_object
);
2397 vm_object_chain_release_all(object
->backing_object
,
2399 if (object
->backing_object
!= lobject
)
2400 vm_object_drop(object
->backing_object
);
2401 vm_object_drop(lobject
);
2405 * Enter the page into the pmap if appropriate. If we had
2406 * allocated the page we have to place it on a queue. If not
2407 * we just have to make sure it isn't on the cache queue
2408 * (pages on the cache queue are not allowed to be mapped).
2412 * Page must be zerod.
2414 if ((m
->flags
& PG_ZERO
) == 0) {
2415 vm_page_zero_fill(m
);
2418 pmap_page_assertzero(
2419 VM_PAGE_TO_PHYS(m
));
2421 vm_page_flag_clear(m
, PG_ZERO
);
2422 mycpu
->gd_cnt
.v_ozfod
++;
2424 mycpu
->gd_cnt
.v_zfod
++;
2425 m
->valid
= VM_PAGE_BITS_ALL
;
2428 * Handle dirty page case
2430 if (pprot
& VM_PROT_WRITE
)
2431 vm_set_nosync(m
, entry
);
2432 pmap_enter(pmap
, addr
, m
, pprot
, 0, entry
);
2433 mycpu
->gd_cnt
.v_vm_faults
++;
2434 if (curthread
->td_lwp
)
2435 ++curthread
->td_lwp
->lwp_ru
.ru_minflt
;
2436 vm_page_deactivate(m
);
2437 if (pprot
& VM_PROT_WRITE
) {
2438 /*vm_object_set_writeable_dirty(m->object);*/
2439 vm_set_nosync(m
, entry
);
2440 if (fault_flags
& VM_FAULT_DIRTY
) {
2443 swap_pager_unswapped(m
);
2448 /* couldn't busy page, no wakeup */
2450 ((m
->valid
& VM_PAGE_BITS_ALL
) == VM_PAGE_BITS_ALL
) &&
2451 (m
->flags
& PG_FICTITIOUS
) == 0) {
2453 * A fully valid page not undergoing soft I/O can
2454 * be immediately entered into the pmap.
2456 if ((m
->queue
- m
->pc
) == PQ_CACHE
)
2457 vm_page_deactivate(m
);
2458 if (pprot
& VM_PROT_WRITE
) {
2459 /*vm_object_set_writeable_dirty(m->object);*/
2460 vm_set_nosync(m
, entry
);
2461 if (fault_flags
& VM_FAULT_DIRTY
) {
2464 swap_pager_unswapped(m
);
2467 if (pprot
& VM_PROT_WRITE
)
2468 vm_set_nosync(m
, entry
);
2469 pmap_enter(pmap
, addr
, m
, pprot
, 0, entry
);
2470 mycpu
->gd_cnt
.v_vm_faults
++;
2471 if (curthread
->td_lwp
)
2472 ++curthread
->td_lwp
->lwp_ru
.ru_minflt
;
2478 vm_object_chain_release(object
);
2479 vm_object_drop(object
);
2483 vm_prefault_quick(pmap_t pmap
, vm_offset_t addra
,
2484 vm_map_entry_t entry
, int prot
, int fault_flags
)
2497 * Get stable max count value, disabled if set to 0
2499 maxpages
= vm_prefault_pages
;
2505 * We do not currently prefault mappings that use virtual page
2506 * tables. We do not prefault foreign pmaps.
2508 if (entry
->maptype
== VM_MAPTYPE_VPAGETABLE
)
2510 lp
= curthread
->td_lwp
;
2511 if (lp
== NULL
|| (pmap
!= vmspace_pmap(lp
->lwp_vmspace
)))
2515 * Limit pre-fault count to 1024 pages.
2517 if (maxpages
> 1024)
2520 object
= entry
->object
.vm_object
;
2521 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
2522 KKASSERT(object
->backing_object
== NULL
);
2526 for (i
= 0; i
< maxpages
; ++i
) {
2530 * Calculate the page to pre-fault, stopping the scan in
2531 * each direction separately if the limit is reached.
2536 addr
= addra
- ((i
+ 1) >> 1) * PAGE_SIZE
;
2540 addr
= addra
+ ((i
+ 2) >> 1) * PAGE_SIZE
;
2542 if (addr
< entry
->start
) {
2548 if (addr
>= entry
->end
) {
2556 * Skip pages already mapped, and stop scanning in that
2557 * direction. When the scan terminates in both directions
2560 if (pmap_prefault_ok(pmap
, addr
) == 0) {
2571 * Follow the VM object chain to obtain the page to be mapped
2572 * into the pmap. This version of the prefault code only
2573 * works with terminal objects.
2575 * WARNING! We cannot call swap_pager_unswapped() with a
2578 pindex
= ((addr
- entry
->start
) + entry
->offset
) >> PAGE_SHIFT
;
2580 m
= vm_page_lookup_busy_try(object
, pindex
, TRUE
, &error
);
2581 if (m
== NULL
|| error
)
2584 if (((m
->valid
& VM_PAGE_BITS_ALL
) == VM_PAGE_BITS_ALL
) &&
2585 (m
->flags
& PG_FICTITIOUS
) == 0 &&
2586 ((m
->flags
& PG_SWAPPED
) == 0 ||
2587 (prot
& VM_PROT_WRITE
) == 0 ||
2588 (fault_flags
& VM_FAULT_DIRTY
) == 0)) {
2590 * A fully valid page not undergoing soft I/O can
2591 * be immediately entered into the pmap.
2593 if ((m
->queue
- m
->pc
) == PQ_CACHE
)
2594 vm_page_deactivate(m
);
2595 if (prot
& VM_PROT_WRITE
) {
2596 vm_object_set_writeable_dirty(m
->object
);
2597 vm_set_nosync(m
, entry
);
2598 if (fault_flags
& VM_FAULT_DIRTY
) {
2601 swap_pager_unswapped(m
);
2604 pmap_enter(pmap
, addr
, m
, prot
, 0, entry
);
2605 mycpu
->gd_cnt
.v_vm_faults
++;
2606 if (curthread
->td_lwp
)
2607 ++curthread
->td_lwp
->lwp_ru
.ru_minflt
;