2 * Copyright (c) 2003-2022 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * Copyright (c) 1991, 1993
37 * The Regents of the University of California. All rights reserved.
38 * Copyright (c) 1994 John S. Dyson
39 * All rights reserved.
40 * Copyright (c) 1994 David Greenman
41 * All rights reserved.
44 * This code is derived from software contributed to Berkeley by
45 * The Mach Operating System project at Carnegie-Mellon University.
47 * Redistribution and use in source and binary forms, with or without
48 * modification, are permitted provided that the following conditions
50 * 1. Redistributions of source code must retain the above copyright
51 * notice, this list of conditions and the following disclaimer.
52 * 2. Redistributions in binary form must reproduce the above copyright
53 * notice, this list of conditions and the following disclaimer in the
54 * documentation and/or other materials provided with the distribution.
55 * 3. Neither the name of the University nor the names of its contributors
56 * may be used to endorse or promote products derived from this software
57 * without specific prior written permission.
59 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
60 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
61 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
62 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
63 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
64 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
65 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
66 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
67 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
68 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
73 * Copyright (c) 1987, 1990 Carnegie-Mellon University.
74 * All rights reserved.
76 * Authors: Avadis Tevanian, Jr., Michael Wayne Young
78 * Permission to use, copy, modify and distribute this software and
79 * its documentation is hereby granted, provided that both the copyright
80 * notice and this permission notice appear in all copies of the
81 * software, derivative works or modified versions, and any portions
82 * thereof, and that both notices appear in supporting documentation.
84 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
85 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
86 * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
88 * Carnegie Mellon requests users of this software to return to
90 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
91 * School of Computer Science
92 * Carnegie Mellon University
93 * Pittsburgh PA 15213-3890
95 * any improvements or extensions that they make and grant Carnegie the
96 * rights to redistribute these changes.
100 * Page fault handling module.
105 #include <sys/param.h>
106 #include <sys/systm.h>
107 #include <sys/kernel.h>
108 #include <sys/proc.h>
109 #include <sys/vnode.h>
110 #include <sys/resourcevar.h>
111 #include <sys/vmmeter.h>
112 #include <sys/vkernel.h>
113 #include <sys/lock.h>
114 #include <sys/sysctl.h>
116 #include <cpu/lwbuf.h>
119 #include <vm/vm_param.h>
121 #include <vm/vm_map.h>
122 #include <vm/vm_object.h>
123 #include <vm/vm_page.h>
124 #include <vm/vm_pageout.h>
125 #include <vm/vm_kern.h>
126 #include <vm/vm_pager.h>
127 #include <vm/vnode_pager.h>
128 #include <vm/swap_pager.h>
129 #include <vm/vm_extern.h>
131 #include <vm/vm_page2.h>
133 #define VM_FAULT_MAX_QUICK 16
136 vm_page_t mary
[VM_FAULT_MAX_QUICK
];
140 vm_map_backing_t first_ba
;
141 vm_prot_t first_prot
;
143 vm_map_entry_t entry
;
144 int lookup_still_valid
; /* 0=inv 1=valid/rel -1=valid/atomic */
151 int first_ba_held
; /* 0=unlocked 1=locked/rel -1=lock/atomic */
155 __read_mostly
static int debug_fault
= 0;
156 SYSCTL_INT(_vm
, OID_AUTO
, debug_fault
, CTLFLAG_RW
, &debug_fault
, 0, "");
157 __read_mostly
static int debug_cluster
= 0;
158 SYSCTL_INT(_vm
, OID_AUTO
, debug_cluster
, CTLFLAG_RW
, &debug_cluster
, 0, "");
160 static int virtual_copy_enable
= 1;
161 SYSCTL_INT(_vm
, OID_AUTO
, virtual_copy_enable
, CTLFLAG_RW
,
162 &virtual_copy_enable
, 0, "");
164 __read_mostly
int vm_shared_fault
= 1;
165 TUNABLE_INT("vm.shared_fault", &vm_shared_fault
);
166 SYSCTL_INT(_vm
, OID_AUTO
, shared_fault
, CTLFLAG_RW
,
167 &vm_shared_fault
, 0, "Allow shared token on vm_object");
168 __read_mostly
static int vm_fault_bypass_count
= 1;
169 TUNABLE_INT("vm.fault_bypass", &vm_fault_bypass_count
);
170 SYSCTL_INT(_vm
, OID_AUTO
, fault_bypass
, CTLFLAG_RW
,
171 &vm_fault_bypass_count
, 0, "Allow fast vm_fault shortcut");
174 * Define here for debugging ioctls. Note that these are globals, so
175 * they were cause a ton of cache line bouncing. Only use for debugging
178 /*#define VM_FAULT_QUICK_DEBUG */
179 #ifdef VM_FAULT_QUICK_DEBUG
180 static long vm_fault_bypass_success_count
= 0;
181 SYSCTL_LONG(_vm
, OID_AUTO
, fault_bypass_success_count
, CTLFLAG_RW
,
182 &vm_fault_bypass_success_count
, 0, "");
183 static long vm_fault_bypass_failure_count1
= 0;
184 SYSCTL_LONG(_vm
, OID_AUTO
, fault_bypass_failure_count1
, CTLFLAG_RW
,
185 &vm_fault_bypass_failure_count1
, 0, "");
186 static long vm_fault_bypass_failure_count2
= 0;
187 SYSCTL_LONG(_vm
, OID_AUTO
, fault_bypass_failure_count2
, CTLFLAG_RW
,
188 &vm_fault_bypass_failure_count2
, 0, "");
189 static long vm_fault_bypass_failure_count3
= 0;
190 SYSCTL_LONG(_vm
, OID_AUTO
, fault_bypass_failure_count3
, CTLFLAG_RW
,
191 &vm_fault_bypass_failure_count3
, 0, "");
192 static long vm_fault_bypass_failure_count4
= 0;
193 SYSCTL_LONG(_vm
, OID_AUTO
, fault_bypass_failure_count4
, CTLFLAG_RW
,
194 &vm_fault_bypass_failure_count4
, 0, "");
197 static int vm_fault_bypass(struct faultstate
*fs
, vm_pindex_t first_pindex
,
198 vm_pindex_t first_count
, int *mextcountp
,
199 vm_prot_t fault_type
);
200 static int vm_fault_object(struct faultstate
*, vm_pindex_t
, vm_prot_t
, int);
201 static void vm_set_nosync(vm_page_t m
, vm_map_entry_t entry
);
202 static void vm_prefault(pmap_t pmap
, vm_offset_t addra
,
203 vm_map_entry_t entry
, int prot
, int fault_flags
);
204 static void vm_prefault_quick(pmap_t pmap
, vm_offset_t addra
,
205 vm_map_entry_t entry
, int prot
, int fault_flags
);
208 release_page(struct faultstate
*fs
)
210 vm_page_deactivate(fs
->mary
[0]);
211 vm_page_wakeup(fs
->mary
[0]);
216 unlock_map(struct faultstate
*fs
)
218 if (fs
->ba
!= fs
->first_ba
)
219 vm_object_drop(fs
->ba
->object
);
220 if (fs
->first_ba
&& fs
->first_ba_held
== 1) {
221 vm_object_drop(fs
->first_ba
->object
);
222 fs
->first_ba_held
= 0;
228 * NOTE: If lookup_still_valid == -1 the map is assumed to be locked
229 * and caller expects it to remain locked atomically.
231 if (fs
->lookup_still_valid
== 1 && fs
->map
) {
232 vm_map_lookup_done(fs
->map
, fs
->entry
, 0);
233 fs
->lookup_still_valid
= 0;
239 * Clean up after a successful call to vm_fault_object() so another call
240 * to vm_fault_object() can be made.
243 cleanup_fault(struct faultstate
*fs
)
246 * We allocated a junk page for a COW operation that did
247 * not occur, the page must be freed.
249 if (fs
->ba
!= fs
->first_ba
) {
250 KKASSERT(fs
->first_shared
== 0);
253 * first_m could be completely valid and we got here
254 * because of a PG_RAM, don't mistakenly free it!
256 if ((fs
->first_m
->valid
& VM_PAGE_BITS_ALL
) ==
258 vm_page_wakeup(fs
->first_m
);
260 vm_page_free(fs
->first_m
);
262 vm_object_pip_wakeup(fs
->ba
->object
);
266 * Reset fs->ba without calling unlock_map(), so we need a
267 * little duplication.
269 vm_object_drop(fs
->ba
->object
);
270 fs
->ba
= fs
->first_ba
;
275 unlock_things(struct faultstate
*fs
)
279 if (fs
->vp
!= NULL
) {
287 * Virtual copy tests. Used by the fault code to determine if a
288 * page can be moved from an orphan vm_object into its shadow
289 * instead of copying its contents.
292 virtual_copy_test(struct faultstate
*fs
)
295 * Must be holding exclusive locks
297 if (fs
->first_shared
|| fs
->shared
|| virtual_copy_enable
== 0)
301 * Map, if present, has not changed
303 if (fs
->map
&& fs
->map_generation
!= fs
->map
->timestamp
)
309 if (fs
->ba
->object
->ref_count
!= 1)
313 * No one else can look this object up
315 if (fs
->ba
->object
->handle
!= NULL
)
319 * No other ways to look the object up
321 if (fs
->ba
->object
->type
!= OBJT_DEFAULT
&&
322 fs
->ba
->object
->type
!= OBJT_SWAP
)
326 * We don't chase down the shadow chain
328 if (fs
->ba
!= fs
->first_ba
->backing_ba
)
335 virtual_copy_ok(struct faultstate
*fs
)
337 if (virtual_copy_test(fs
)) {
339 * Grab the lock and re-test changeable items.
341 if (fs
->lookup_still_valid
== 0 && fs
->map
) {
342 if (lockmgr(&fs
->map
->lock
, LK_EXCLUSIVE
|LK_NOWAIT
))
344 fs
->lookup_still_valid
= 1;
345 if (virtual_copy_test(fs
)) {
346 fs
->map_generation
= ++fs
->map
->timestamp
;
349 fs
->lookup_still_valid
= 0;
350 lockmgr(&fs
->map
->lock
, LK_RELEASE
);
360 * Determine if the pager for the current object *might* contain the page.
362 * We only need to try the pager if this is not a default object (default
363 * objects are zero-fill and have no real pager), and if we are not taking
364 * a wiring fault or if the FS entry is wired.
366 #define TRYPAGER(fs) \
367 (fs->ba->object->type != OBJT_DEFAULT && \
368 (((fs->fault_flags & VM_FAULT_WIRE_MASK) == 0) || \
369 (fs->wflags & FW_WIRED)))
374 * Handle a page fault occuring at the given address, requiring the given
375 * permissions, in the map specified. If successful, the page is inserted
376 * into the associated physical map.
378 * NOTE: The given address should be truncated to the proper page address.
380 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
381 * a standard error specifying why the fault is fatal is returned.
383 * The map in question must be referenced, and remains so.
384 * The caller may hold no locks.
385 * No other requirements.
388 vm_fault(vm_map_t map
, vm_offset_t vaddr
, vm_prot_t fault_type
, int fault_flags
)
390 vm_pindex_t first_pindex
;
391 vm_pindex_t first_count
;
392 struct faultstate fs
;
394 #if !defined(NO_SWAPPING)
405 inherit_prot
= fault_type
& VM_PROT_NOSYNC
;
407 fs
.fault_flags
= fault_flags
;
409 fs
.shared
= vm_shared_fault
;
410 fs
.first_shared
= vm_shared_fault
;
414 * vm_map interactions
417 if ((lp
= td
->td_lwp
) != NULL
)
418 lp
->lwp_flags
|= LWP_PAGING
;
422 * vm_fault_bypass() can shortcut us.
425 fs
.first_ba_held
= 0;
429 * Find the vm_map_entry representing the backing store and resolve
430 * the top level object and page index. This may have the side
431 * effect of executing a copy-on-write on the map entry,
432 * creating a shadow object, or splitting an anonymous entry for
433 * performance, but will not COW any actual VM pages.
435 * On success fs.map is left read-locked and various other fields
436 * are initialized but not otherwise referenced or locked.
438 * NOTE! vm_map_lookup will try to upgrade the fault_type to
439 * VM_FAULT_WRITE if the map entry is a virtual page table
440 * and also writable, so we can set the 'A'accessed bit in
441 * the virtual page table entry.
444 result
= vm_map_lookup(&fs
.map
, vaddr
, fault_type
,
445 &fs
.entry
, &fs
.first_ba
,
446 &first_pindex
, &first_count
,
447 &fs
.first_prot
, &fs
.wflags
);
450 * If the lookup failed or the map protections are incompatible,
451 * the fault generally fails.
453 * The failure could be due to TDF_NOFAULT if vm_map_lookup()
454 * tried to do a COW fault.
456 * If the caller is trying to do a user wiring we have more work
459 if (result
!= KERN_SUCCESS
) {
460 if (result
== KERN_FAILURE_NOFAULT
) {
461 result
= KERN_FAILURE
;
464 if (result
!= KERN_PROTECTION_FAILURE
||
465 (fs
.fault_flags
& VM_FAULT_WIRE_MASK
) != VM_FAULT_USER_WIRE
)
467 if (result
== KERN_INVALID_ADDRESS
&& growstack
&&
468 map
!= kernel_map
&& curproc
!= NULL
) {
469 result
= vm_map_growstack(map
, vaddr
);
470 if (result
== KERN_SUCCESS
) {
475 result
= KERN_FAILURE
;
481 * If we are user-wiring a r/w segment, and it is COW, then
482 * we need to do the COW operation. Note that we don't
483 * currently COW RO sections now, because it is NOT desirable
484 * to COW .text. We simply keep .text from ever being COW'ed
485 * and take the heat that one cannot debug wired .text sections.
487 * XXX Try to allow the above by specifying OVERRIDE_WRITE.
489 result
= vm_map_lookup(&fs
.map
, vaddr
,
490 VM_PROT_READ
| VM_PROT_WRITE
|
491 VM_PROT_OVERRIDE_WRITE
,
492 &fs
.entry
, &fs
.first_ba
,
493 &first_pindex
, &first_count
,
494 &fs
.first_prot
, &fs
.wflags
);
495 if (result
!= KERN_SUCCESS
) {
496 /* could also be KERN_FAILURE_NOFAULT */
497 result
= KERN_FAILURE
;
502 * If we don't COW now, on a user wire, the user will never
503 * be able to write to the mapping. If we don't make this
504 * restriction, the bookkeeping would be nearly impossible.
506 * XXX We have a shared lock, this will have a MP race but
507 * I don't see how it can hurt anything.
509 if ((fs
.first_prot
& VM_PROT_WRITE
) == 0) {
510 atomic_clear_char(&fs
.entry
->max_protection
,
516 * fs.map is read-locked
518 * Misc checks. Save the map generation number to detect races.
520 fs
.lookup_still_valid
= 1;
522 fs
.ba
= fs
.first_ba
; /* so unlock_things() works */
523 fs
.prot
= fs
.first_prot
; /* default (used by uksmap) */
525 if (fs
.entry
->eflags
& (MAP_ENTRY_NOFAULT
| MAP_ENTRY_KSTACK
)) {
526 if (fs
.entry
->eflags
& MAP_ENTRY_NOFAULT
) {
527 panic("vm_fault: fault on nofault entry, addr: %p",
530 if ((fs
.entry
->eflags
& MAP_ENTRY_KSTACK
) &&
531 vaddr
>= fs
.entry
->ba
.start
&&
532 vaddr
< fs
.entry
->ba
.start
+ PAGE_SIZE
) {
533 panic("vm_fault: fault on stack guard, addr: %p",
539 * A user-kernel shared map has no VM object and bypasses
540 * everything. We execute the uksmap function with a temporary
541 * fictitious vm_page. The address is directly mapped with no
544 if (fs
.entry
->maptype
== VM_MAPTYPE_UKSMAP
) {
545 struct vm_page fakem
;
547 bzero(&fakem
, sizeof(fakem
));
548 fakem
.pindex
= first_pindex
;
549 fakem
.flags
= PG_FICTITIOUS
| PG_UNQUEUED
;
550 fakem
.busy_count
= PBUSY_LOCKED
;
551 fakem
.valid
= VM_PAGE_BITS_ALL
;
552 fakem
.pat_mode
= VM_MEMATTR_DEFAULT
;
553 if (fs
.entry
->ba
.uksmap(&fs
.entry
->ba
, UKSMAPOP_FAULT
,
554 fs
.entry
->aux
.dev
, &fakem
)) {
555 result
= KERN_FAILURE
;
559 pmap_enter(fs
.map
->pmap
, vaddr
, &fakem
, fs
.prot
| inherit_prot
,
560 (fs
.wflags
& FW_WIRED
), fs
.entry
);
565 * A system map entry may return a NULL object. No object means
566 * no pager means an unrecoverable kernel fault.
568 if (fs
.first_ba
== NULL
) {
569 panic("vm_fault: unrecoverable fault at %p in entry %p",
570 (void *)vaddr
, fs
.entry
);
574 * Fail here if not a trivial anonymous page fault and TDF_NOFAULT
577 * Unfortunately a deadlock can occur if we are forced to page-in
578 * from swap, but diving all the way into the vm_pager_get_page()
579 * function to find out is too much. Just check the object type.
581 * The deadlock is a CAM deadlock on a busy VM page when trying
582 * to finish an I/O if another process gets stuck in
583 * vop_helper_read_shortcut() due to a swap fault.
585 if ((td
->td_flags
& TDF_NOFAULT
) &&
587 fs
.first_ba
->object
->type
== OBJT_VNODE
||
588 fs
.first_ba
->object
->type
== OBJT_SWAP
||
589 fs
.first_ba
->backing_ba
)) {
590 result
= KERN_FAILURE
;
596 * If the entry is wired the page protection level is limited to
597 * what the vm_map_lookup() allowed us.
599 * XXX it is unclear if this code is still needed as vm_map_lookup()
600 * no longer prevents protection changes on locked memory. REMOVE
601 * IF WE DETERMINE THAT THIS CODE IS NO LONGER NEEDED.
603 if (fs
.wflags
& FW_WIRED
)
604 fault_type
= fs
.first_prot
;
607 * We generally want to avoid unnecessary exclusive modes on backing
608 * and terminal objects because this can seriously interfere with
609 * heavily fork()'d processes (particularly /bin/sh scripts).
611 * However, we also want to avoid unnecessary retries due to needed
612 * shared->exclusive promotion for common faults. Exclusive mode is
613 * always needed if any page insertion, rename, or free occurs in an
614 * object (and also indirectly if any I/O is done).
616 * The main issue here is going to be fs.first_shared. If the
617 * first_object has a backing object which isn't shadowed and the
618 * process is single-threaded we might as well use an exclusive
619 * lock/chain right off the bat.
622 /* WORK IN PROGRESS, CODE REMOVED */
623 if (fs
.first_shared
&& fs
.first_object
->backing_object
&&
624 LIST_EMPTY(&fs
.first_object
->shadow_head
) &&
625 td
->td_proc
&& td
->td_proc
->p_nthreads
== 1) {
631 * VM_FAULT_UNSWAP - swap_pager_unswapped() needs an exclusive object
632 * VM_FAULT_DIRTY - may require swap_pager_unswapped() later, but
633 * we can try shared first.
635 if (fault_flags
& VM_FAULT_UNSWAP
)
639 * Try to shortcut the entire mess and run the fault lockless.
640 * This will burst in multiple pages via fs->mary[].
642 if (vm_fault_bypass_count
&&
643 vm_fault_bypass(&fs
, first_pindex
, first_count
,
644 &mextcount
, fault_type
) == KERN_SUCCESS
) {
645 fault_flags
&= ~VM_FAULT_BURST
;
650 * Exclusive heuristic (alloc page vs page exists)
652 if (fs
.first_ba
->flags
& VM_MAP_BACK_EXCL_HEUR
)
656 * Obtain a top-level object lock, shared or exclusive depending
657 * on fs.first_shared. If a shared lock winds up being insufficient
658 * we will retry with an exclusive lock.
660 * The vnode pager lock is always shared.
663 vm_object_hold_shared(fs
.first_ba
->object
);
665 vm_object_hold(fs
.first_ba
->object
);
667 fs
.vp
= vnode_pager_lock(fs
.first_ba
);
668 fs
.first_ba_held
= 1;
671 * The page we want is at (first_object, first_pindex).
673 * Now we have the actual (object, pindex), fault in the page. If
674 * vm_fault_object() fails it will unlock and deallocate the FS
675 * data. If it succeeds everything remains locked and fs->ba->object
676 * will have an additional PIP count if fs->ba != fs->first_ba.
678 * vm_fault_object will set fs->prot for the pmap operation. It is
679 * allowed to set VM_PROT_WRITE if fault_type == VM_PROT_READ if the
680 * page can be safely written. However, it will force a read-only
681 * mapping for a read fault if the memory is managed by a virtual
684 * If the fault code uses the shared object lock shortcut
685 * we must not try to burst (we can't allocate VM pages).
687 result
= vm_fault_object(&fs
, first_pindex
, fault_type
, 1);
689 if (debug_fault
> 0) {
691 kprintf("VM_FAULT result %d addr=%jx type=%02x flags=%02x "
692 "fs.m=%p fs.prot=%02x fs.wflags=%02x fs.entry=%p\n",
693 result
, (intmax_t)vaddr
, fault_type
, fault_flags
,
694 fs
.mary
[0], fs
.prot
, fs
.wflags
, fs
.entry
);
697 if (result
== KERN_TRY_AGAIN
) {
701 if (result
!= KERN_SUCCESS
) {
707 * On success vm_fault_object() does not unlock or deallocate, and fs.m
708 * will contain a busied page. It does drop fs->ba if appropriate.
710 * Enter the page into the pmap and do pmap-related adjustments.
712 * WARNING! Soft-busied fs.m's can only be manipulated in limited
715 KKASSERT(fs
.lookup_still_valid
!= 0);
716 vm_page_flag_set(fs
.mary
[0], PG_REFERENCED
);
718 for (n
= 0; n
< mextcount
; ++n
) {
719 pmap_enter(fs
.map
->pmap
, vaddr
+ (n
<< PAGE_SHIFT
),
720 fs
.mary
[n
], fs
.prot
| inherit_prot
,
721 fs
.wflags
& FW_WIRED
, fs
.entry
);
725 * If the page is not wired down, then put it where the pageout daemon
728 * NOTE: We cannot safely wire, unwire, or adjust queues for a
731 for (n
= 0; n
< mextcount
; ++n
) {
733 KKASSERT(fs
.mary
[n
]->busy_count
& PBUSY_MASK
);
734 KKASSERT((fs
.fault_flags
& VM_FAULT_WIRE_MASK
) == 0);
735 vm_page_sbusy_drop(fs
.mary
[n
]);
737 if (fs
.fault_flags
& VM_FAULT_WIRE_MASK
) {
738 if (fs
.wflags
& FW_WIRED
)
739 vm_page_wire(fs
.mary
[n
]);
741 vm_page_unwire(fs
.mary
[n
], 1);
743 vm_page_activate(fs
.mary
[n
]);
745 KKASSERT(fs
.mary
[n
]->busy_count
& PBUSY_LOCKED
);
746 vm_page_wakeup(fs
.mary
[n
]);
751 * Burst in a few more pages if possible. The fs.map should still
752 * be locked. To avoid interlocking against a vnode->getblk
753 * operation we had to be sure to unbusy our primary vm_page above
756 * A normal burst can continue down backing store, only execute
757 * if we are holding an exclusive lock, otherwise the exclusive
758 * locks the burst code gets might cause excessive SMP collisions.
760 * A quick burst can be utilized when there is no backing object
761 * (i.e. a shared file mmap).
763 if ((fault_flags
& VM_FAULT_BURST
) &&
764 (fs
.fault_flags
& VM_FAULT_WIRE_MASK
) == 0 &&
765 (fs
.wflags
& FW_WIRED
) == 0) {
766 if (fs
.first_shared
== 0 && fs
.shared
== 0) {
767 vm_prefault(fs
.map
->pmap
, vaddr
,
768 fs
.entry
, fs
.prot
, fault_flags
);
770 vm_prefault_quick(fs
.map
->pmap
, vaddr
,
771 fs
.entry
, fs
.prot
, fault_flags
);
777 * Unlock everything, and return
781 mycpu
->gd_cnt
.v_vm_faults
++;
784 ++td
->td_lwp
->lwp_ru
.ru_majflt
;
786 ++td
->td_lwp
->lwp_ru
.ru_minflt
;
790 /*vm_object_deallocate(fs.first_ba->object);*/
793 result
= KERN_SUCCESS
;
795 if (fs
.first_ba
&& fs
.first_ba
->object
&& fs
.first_ba_held
== 1) {
796 vm_object_drop(fs
.first_ba
->object
);
797 fs
.first_ba_held
= 0;
801 lp
->lwp_flags
&= ~LWP_PAGING
;
803 #if !defined(NO_SWAPPING)
805 * Check the process RSS limit and force deactivation and
806 * (asynchronous) paging if necessary. This is a complex operation,
807 * only do it for direct user-mode faults, for now.
809 * To reduce overhead implement approximately a ~16MB hysteresis.
812 if ((fault_flags
& VM_FAULT_USERMODE
) && lp
&&
813 p
->p_limit
&& map
->pmap
&& vm_pageout_memuse_mode
>= 1 &&
818 limit
= OFF_TO_IDX(qmin(p
->p_rlimit
[RLIMIT_RSS
].rlim_cur
,
819 p
->p_rlimit
[RLIMIT_RSS
].rlim_max
));
820 size
= pmap_resident_tlnw_count(map
->pmap
);
821 if (limit
>= 0 && size
> 4096 && size
- 4096 >= limit
) {
822 vm_pageout_map_deactivate_pages(map
, limit
);
827 if (result
!= KERN_SUCCESS
&& debug_fault
< 0) {
828 kprintf("VM_FAULT %d:%d (%s) result %d "
829 "addr=%jx type=%02x flags=%02x "
830 "fs.m=%p fs.prot=%02x fs.wflags=%02x fs.entry=%p\n",
831 (curthread
->td_proc
? curthread
->td_proc
->p_pid
: -1),
832 (curthread
->td_lwp
? curthread
->td_lwp
->lwp_tid
: -1),
835 (intmax_t)vaddr
, fault_type
, fault_flags
,
836 fs
.mary
[0], fs
.prot
, fs
.wflags
, fs
.entry
);
837 while (debug_fault
< 0 && (debug_fault
& 1))
838 tsleep(&debug_fault
, 0, "DEBUG", hz
);
845 * Attempt a lockless vm_fault() shortcut. The stars have to align for this
846 * to work. But if it does we can get our page only soft-busied and not
847 * have to touch the vm_object or vnode locks at all.
851 vm_fault_bypass(struct faultstate
*fs
, vm_pindex_t first_pindex
,
852 vm_pindex_t first_count
, int *mextcountp
,
853 vm_prot_t fault_type
)
856 vm_object_t obj
; /* NOT LOCKED */
861 * Don't waste time if the object is only being used by one vm_map.
863 obj
= fs
->first_ba
->object
;
865 if (obj
->flags
& OBJ_ONEMAPPING
)
870 * This will try to wire/unwire a page, which can't be done with
871 * a soft-busied page.
873 if (fs
->fault_flags
& VM_FAULT_WIRE_MASK
)
877 * Ok, try to get the vm_page quickly via the hash table. The
878 * page will be soft-busied on success (NOT hard-busied).
880 m
= vm_page_hash_get(obj
, first_pindex
);
882 #ifdef VM_FAULT_QUICK_DEBUG
883 ++vm_fault_bypass_failure_count2
;
887 if ((obj
->flags
& OBJ_DEAD
) ||
888 m
->valid
!= VM_PAGE_BITS_ALL
||
889 m
->queue
- m
->pc
!= PQ_ACTIVE
||
890 (m
->flags
& PG_SWAPPED
)) {
891 vm_page_sbusy_drop(m
);
892 #ifdef VM_FAULT_QUICK_DEBUG
893 ++vm_fault_bypass_failure_count3
;
899 * The page is already fully valid, ACTIVE, and is not PG_SWAPPED.
901 * Don't map the page writable when emulating the dirty bit, a
902 * fault must be taken for proper emulation (vkernel).
904 if (curthread
->td_lwp
&& curthread
->td_lwp
->lwp_vmspace
&&
905 pmap_emulate_ad_bits(&curthread
->td_lwp
->lwp_vmspace
->vm_pmap
)) {
906 if ((fault_type
& VM_PROT_WRITE
) == 0)
907 fs
->prot
&= ~VM_PROT_WRITE
;
911 * If this is a write fault the object and the page must already
912 * be writable. Since we don't hold an object lock and only a
913 * soft-busy on the page, we cannot manipulate the object or
914 * the page state (other than the page queue).
916 if (fs
->prot
& VM_PROT_WRITE
) {
917 if ((obj
->flags
& (OBJ_WRITEABLE
| OBJ_MIGHTBEDIRTY
)) !=
918 (OBJ_WRITEABLE
| OBJ_MIGHTBEDIRTY
) ||
919 m
->dirty
!= VM_PAGE_BITS_ALL
) {
920 vm_page_sbusy_drop(m
);
921 #ifdef VM_FAULT_QUICK_DEBUG
922 ++vm_fault_bypass_failure_count4
;
926 vm_set_nosync(m
, fs
->entry
);
930 * Set page and potentially burst in more
932 * Even though we are only soft-busied we can still move pages
933 * around in the normal queue(s). The soft-busy prevents the
934 * page from being removed from the object, etc (normal operation).
936 * However, in this fast path it is excessively important to avoid
937 * any hard locks, so we use a special passive version of activate.
941 vm_page_soft_activate(m
);
943 if (vm_fault_bypass_count
> 1) {
944 nlim
= vm_fault_bypass_count
;
945 if (nlim
> VM_FAULT_MAX_QUICK
) /* array limit(+1) */
946 nlim
= VM_FAULT_MAX_QUICK
;
947 if (nlim
> first_count
) /* user limit */
950 for (n
= 1; n
< nlim
; ++n
) {
951 m
= vm_page_hash_get(obj
, first_pindex
+ n
);
954 if (m
->valid
!= VM_PAGE_BITS_ALL
||
955 m
->queue
- m
->pc
!= PQ_ACTIVE
||
956 (m
->flags
& PG_SWAPPED
)) {
957 vm_page_sbusy_drop(m
);
960 if (fs
->prot
& VM_PROT_WRITE
) {
961 if ((obj
->flags
& (OBJ_WRITEABLE
|
962 OBJ_MIGHTBEDIRTY
)) !=
963 (OBJ_WRITEABLE
| OBJ_MIGHTBEDIRTY
) ||
964 m
->dirty
!= VM_PAGE_BITS_ALL
) {
965 vm_page_sbusy_drop(m
);
969 vm_page_soft_activate(m
);
975 #ifdef VM_FAULT_QUICK_DEBUG
976 ++vm_fault_bypass_success_count
;
983 * Fault in the specified virtual address in the current process map,
984 * returning a held VM page or NULL. See vm_fault_page() for more
990 vm_fault_page_quick(vm_offset_t va
, vm_prot_t fault_type
,
991 int *errorp
, int *busyp
)
993 struct lwp
*lp
= curthread
->td_lwp
;
996 m
= vm_fault_page(&lp
->lwp_vmspace
->vm_map
, va
,
997 fault_type
, VM_FAULT_NORMAL
,
1003 * Fault in the specified virtual address in the specified map, doing all
1004 * necessary manipulation of the object store and all necessary I/O. Return
1005 * a held VM page or NULL, and set *errorp. The related pmap is not
1008 * If busyp is not NULL then *busyp will be set to TRUE if this routine
1009 * decides to return a busied page (aka VM_PROT_WRITE), or FALSE if it
1010 * does not (VM_PROT_WRITE not specified or busyp is NULL). If busyp is
1011 * NULL the returned page is only held.
1013 * If the caller has no intention of writing to the page's contents, busyp
1014 * can be passed as NULL along with VM_PROT_WRITE to force a COW operation
1015 * without busying the page.
1017 * The returned page will also be marked PG_REFERENCED.
1019 * If the page cannot be faulted writable and VM_PROT_WRITE was specified, an
1020 * error will be returned.
1025 vm_fault_page(vm_map_t map
, vm_offset_t vaddr
, vm_prot_t fault_type
,
1026 int fault_flags
, int *errorp
, int *busyp
)
1028 vm_pindex_t first_pindex
;
1029 vm_pindex_t first_count
;
1030 struct faultstate fs
;
1035 vm_prot_t orig_fault_type
= fault_type
;
1040 fs
.fault_flags
= fault_flags
;
1041 KKASSERT((fault_flags
& VM_FAULT_WIRE_MASK
) == 0);
1044 * Dive the pmap (concurrency possible). If we find the
1045 * appropriate page we can terminate early and quickly.
1047 * This works great for normal programs but will always return
1048 * NULL for host lookups of vkernel maps in VMM mode.
1050 * NOTE: pmap_fault_page_quick() might not busy the page. If
1051 * VM_PROT_WRITE is set in fault_type and pmap_fault_page_quick()
1052 * returns non-NULL, it will safely dirty the returned vm_page_t
1053 * for us. We cannot safely dirty it here (it might not be
1056 fs
.mary
[0] = pmap_fault_page_quick(map
->pmap
, vaddr
, fault_type
, busyp
);
1063 * Otherwise take a concurrency hit and do a formal page
1067 fs
.shared
= vm_shared_fault
;
1068 fs
.first_shared
= vm_shared_fault
;
1073 * VM_FAULT_UNSWAP - swap_pager_unswapped() needs an exclusive object
1074 * VM_FAULT_DIRTY - may require swap_pager_unswapped() later, but
1075 * we can try shared first.
1077 if (fault_flags
& VM_FAULT_UNSWAP
) {
1078 fs
.first_shared
= 0;
1083 * Find the vm_map_entry representing the backing store and resolve
1084 * the top level object and page index. This may have the side
1085 * effect of executing a copy-on-write on the map entry and/or
1086 * creating a shadow object, but will not COW any actual VM pages.
1088 * On success fs.map is left read-locked and various other fields
1089 * are initialized but not otherwise referenced or locked.
1091 * NOTE! vm_map_lookup will upgrade the fault_type to VM_FAULT_WRITE
1092 * if the map entry is a virtual page table and also writable,
1093 * so we can set the 'A'accessed bit in the virtual page table
1097 fs
.first_ba_held
= 0;
1098 result
= vm_map_lookup(&fs
.map
, vaddr
, fault_type
,
1099 &fs
.entry
, &fs
.first_ba
,
1100 &first_pindex
, &first_count
,
1101 &fs
.first_prot
, &fs
.wflags
);
1103 if (result
!= KERN_SUCCESS
) {
1104 if (result
== KERN_FAILURE_NOFAULT
) {
1105 *errorp
= KERN_FAILURE
;
1109 if (result
!= KERN_PROTECTION_FAILURE
||
1110 (fs
.fault_flags
& VM_FAULT_WIRE_MASK
) != VM_FAULT_USER_WIRE
)
1112 if (result
== KERN_INVALID_ADDRESS
&& growstack
&&
1113 map
!= kernel_map
&& curproc
!= NULL
) {
1114 result
= vm_map_growstack(map
, vaddr
);
1115 if (result
== KERN_SUCCESS
) {
1120 result
= KERN_FAILURE
;
1128 * If we are user-wiring a r/w segment, and it is COW, then
1129 * we need to do the COW operation. Note that we don't
1130 * currently COW RO sections now, because it is NOT desirable
1131 * to COW .text. We simply keep .text from ever being COW'ed
1132 * and take the heat that one cannot debug wired .text sections.
1134 result
= vm_map_lookup(&fs
.map
, vaddr
,
1135 VM_PROT_READ
| VM_PROT_WRITE
|
1136 VM_PROT_OVERRIDE_WRITE
,
1137 &fs
.entry
, &fs
.first_ba
,
1138 &first_pindex
, &first_count
,
1139 &fs
.first_prot
, &fs
.wflags
);
1140 if (result
!= KERN_SUCCESS
) {
1141 /* could also be KERN_FAILURE_NOFAULT */
1142 *errorp
= KERN_FAILURE
;
1148 * If we don't COW now, on a user wire, the user will never
1149 * be able to write to the mapping. If we don't make this
1150 * restriction, the bookkeeping would be nearly impossible.
1152 * XXX We have a shared lock, this will have a MP race but
1153 * I don't see how it can hurt anything.
1155 if ((fs
.first_prot
& VM_PROT_WRITE
) == 0) {
1156 atomic_clear_char(&fs
.entry
->max_protection
,
1162 * fs.map is read-locked
1164 * Misc checks. Save the map generation number to detect races.
1166 fs
.lookup_still_valid
= 1;
1168 fs
.ba
= fs
.first_ba
;
1170 if (fs
.entry
->eflags
& MAP_ENTRY_NOFAULT
) {
1171 panic("vm_fault: fault on nofault entry, addr: %lx",
1176 * A user-kernel shared map has no VM object and bypasses
1177 * everything. We execute the uksmap function with a temporary
1178 * fictitious vm_page. The address is directly mapped with no
1181 if (fs
.entry
->maptype
== VM_MAPTYPE_UKSMAP
) {
1182 struct vm_page fakem
;
1184 bzero(&fakem
, sizeof(fakem
));
1185 fakem
.pindex
= first_pindex
;
1186 fakem
.flags
= PG_FICTITIOUS
| PG_UNQUEUED
;
1187 fakem
.busy_count
= PBUSY_LOCKED
;
1188 fakem
.valid
= VM_PAGE_BITS_ALL
;
1189 fakem
.pat_mode
= VM_MEMATTR_DEFAULT
;
1190 if (fs
.entry
->ba
.uksmap(&fs
.entry
->ba
, UKSMAPOP_FAULT
,
1191 fs
.entry
->aux
.dev
, &fakem
)) {
1192 *errorp
= KERN_FAILURE
;
1197 fs
.mary
[0] = PHYS_TO_VM_PAGE(fakem
.phys_addr
);
1198 vm_page_hold(fs
.mary
[0]);
1200 *busyp
= 0; /* don't need to busy R or W */
1208 * A system map entry may return a NULL object. No object means
1209 * no pager means an unrecoverable kernel fault.
1211 if (fs
.first_ba
== NULL
) {
1212 panic("vm_fault: unrecoverable fault at %p in entry %p",
1213 (void *)vaddr
, fs
.entry
);
1217 * Fail here if not a trivial anonymous page fault and TDF_NOFAULT
1220 * Unfortunately a deadlock can occur if we are forced to page-in
1221 * from swap, but diving all the way into the vm_pager_get_page()
1222 * function to find out is too much. Just check the object type.
1224 if ((curthread
->td_flags
& TDF_NOFAULT
) &&
1226 fs
.first_ba
->object
->type
== OBJT_VNODE
||
1227 fs
.first_ba
->object
->type
== OBJT_SWAP
||
1228 fs
.first_ba
->backing_ba
)) {
1229 *errorp
= KERN_FAILURE
;
1236 * If the entry is wired the page protection level is limited to
1237 * what the vm_map_lookup() allowed us.
1239 * XXX it is unclear if this code is still needed as vm_map_lookup()
1240 * no longer prevents protection changes on locked memory. REMOVE
1241 * IF WE DETERMINE THAT THIS CODE IS NO LONGER NEEDED.
1243 if (fs
.wflags
& FW_WIRED
)
1244 fault_type
= fs
.first_prot
;
1247 * Make a reference to this object to prevent its disposal while we
1248 * are messing with it. Once we have the reference, the map is free
1249 * to be diddled. Since objects reference their shadows (and copies),
1250 * they will stay around as well.
1252 * The reference should also prevent an unexpected collapse of the
1253 * parent that might move pages from the current object into the
1254 * parent unexpectedly, resulting in corruption.
1256 * Bump the paging-in-progress count to prevent size changes (e.g.
1257 * truncation operations) during I/O. This must be done after
1258 * obtaining the vnode lock in order to avoid possible deadlocks.
1260 if (fs
.first_ba
->flags
& VM_MAP_BACK_EXCL_HEUR
)
1261 fs
.first_shared
= 0;
1263 if (fs
.first_shared
)
1264 vm_object_hold_shared(fs
.first_ba
->object
);
1266 vm_object_hold(fs
.first_ba
->object
);
1267 fs
.first_ba_held
= 1;
1269 fs
.vp
= vnode_pager_lock(fs
.first_ba
); /* shared */
1272 * The page we want is at (first_object, first_pindex).
1274 * Now we have the actual (object, pindex), fault in the page. If
1275 * vm_fault_object() fails it will unlock and deallocate the FS
1276 * data. If it succeeds everything remains locked and fs->ba->object
1277 * will have an additinal PIP count if fs->ba != fs->first_ba.
1280 result
= vm_fault_object(&fs
, first_pindex
, fault_type
, 1);
1282 if (result
== KERN_TRY_AGAIN
) {
1283 KKASSERT(fs
.first_ba_held
== 0);
1285 didcow
|= fs
.wflags
& FW_DIDCOW
;
1288 if (result
!= KERN_SUCCESS
) {
1294 if ((orig_fault_type
& VM_PROT_WRITE
) &&
1295 (fs
.prot
& VM_PROT_WRITE
) == 0) {
1296 *errorp
= KERN_PROTECTION_FAILURE
;
1303 * Generally speaking we don't want to update the pmap because
1304 * this routine can be called many times for situations that do
1305 * not require updating the pmap, not to mention the page might
1306 * already be in the pmap.
1308 * However, if our vm_map_lookup() results in a COW, we need to
1309 * at least remove the pte from the pmap to guarantee proper
1310 * visibility of modifications made to the process. For example,
1311 * modifications made by vkernel uiocopy/related routines and
1312 * modifications made by ptrace().
1314 vm_page_flag_set(fs
.mary
[0], PG_REFERENCED
);
1316 pmap_enter(fs
.map
->pmap
, vaddr
, fs
.mary
[0], fs
.prot
,
1317 fs
.wflags
& FW_WIRED
, NULL
);
1318 mycpu
->gd_cnt
.v_vm_faults
++;
1319 if (curthread
->td_lwp
)
1320 ++curthread
->td_lwp
->lwp_ru
.ru_minflt
;
1322 if ((fs
.wflags
| didcow
) & FW_DIDCOW
) {
1323 pmap_remove(fs
.map
->pmap
,
1325 (vaddr
& ~PAGE_MASK
) + PAGE_SIZE
);
1329 * On success vm_fault_object() does not unlock or deallocate, and
1330 * fs.mary[0] will contain a busied page. So we must unlock here
1331 * after having messed with the pmap.
1336 * Return a held page. We are not doing any pmap manipulation so do
1337 * not set PG_MAPPED. However, adjust the page flags according to
1338 * the fault type because the caller may not use a managed pmapping
1339 * (so we don't want to lose the fact that the page will be dirtied
1340 * if a write fault was specified).
1342 if (fault_type
& VM_PROT_WRITE
)
1343 vm_page_dirty(fs
.mary
[0]);
1344 vm_page_activate(fs
.mary
[0]);
1346 if (curthread
->td_lwp
) {
1348 curthread
->td_lwp
->lwp_ru
.ru_majflt
++;
1350 curthread
->td_lwp
->lwp_ru
.ru_minflt
++;
1355 * Unlock everything, and return the held or busied page.
1358 if (fault_type
& VM_PROT_WRITE
) {
1359 vm_page_dirty(fs
.mary
[0]);
1363 vm_page_hold(fs
.mary
[0]);
1364 vm_page_wakeup(fs
.mary
[0]);
1367 vm_page_hold(fs
.mary
[0]);
1368 vm_page_wakeup(fs
.mary
[0]);
1370 /*vm_object_deallocate(fs.first_ba->object);*/
1374 KKASSERT(fs
.first_ba_held
== 0);
1380 * Fault in the specified (object,offset), dirty the returned page as
1381 * needed. If the requested fault_type cannot be done NULL and an
1382 * error is returned.
1384 * A held (but not busied) page is returned.
1386 * The passed in object must be held as specified by the shared
1390 vm_fault_object_page(vm_object_t object
, vm_ooffset_t offset
,
1391 vm_prot_t fault_type
, int fault_flags
,
1392 int *sharedp
, int *errorp
)
1395 vm_pindex_t first_pindex
;
1396 vm_pindex_t first_count
;
1397 struct faultstate fs
;
1398 struct vm_map_entry entry
;
1401 * Since we aren't actually faulting the page into a
1402 * pmap we can just fake the entry.ba.
1404 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
1405 bzero(&entry
, sizeof(entry
));
1406 entry
.maptype
= VM_MAPTYPE_NORMAL
;
1407 entry
.protection
= entry
.max_protection
= fault_type
;
1408 entry
.ba
.backing_ba
= NULL
;
1409 entry
.ba
.object
= object
;
1410 entry
.ba
.offset
= 0;
1413 fs
.fault_flags
= fault_flags
;
1415 fs
.shared
= vm_shared_fault
;
1416 fs
.first_shared
= *sharedp
;
1419 fs
.first_ba_held
= -1; /* object held across call, prevent drop */
1420 KKASSERT((fault_flags
& VM_FAULT_WIRE_MASK
) == 0);
1423 * VM_FAULT_UNSWAP - swap_pager_unswapped() needs an exclusive object
1424 * VM_FAULT_DIRTY - may require swap_pager_unswapped() later, but
1425 * we can try shared first.
1427 if (fs
.first_shared
&& (fault_flags
& VM_FAULT_UNSWAP
)) {
1428 fs
.first_shared
= 0;
1429 vm_object_upgrade(object
);
1433 * Retry loop as needed (typically for shared->exclusive transitions)
1436 *sharedp
= fs
.first_shared
;
1437 first_pindex
= OFF_TO_IDX(offset
);
1439 fs
.first_ba
= &entry
.ba
;
1440 fs
.ba
= fs
.first_ba
;
1442 fs
.first_prot
= fault_type
;
1446 * Make a reference to this object to prevent its disposal while we
1447 * are messing with it. Once we have the reference, the map is free
1448 * to be diddled. Since objects reference their shadows (and copies),
1449 * they will stay around as well.
1451 * The reference should also prevent an unexpected collapse of the
1452 * parent that might move pages from the current object into the
1453 * parent unexpectedly, resulting in corruption.
1455 * Bump the paging-in-progress count to prevent size changes (e.g.
1456 * truncation operations) during I/O. This must be done after
1457 * obtaining the vnode lock in order to avoid possible deadlocks.
1460 fs
.vp
= vnode_pager_lock(fs
.first_ba
);
1462 fs
.lookup_still_valid
= 1;
1466 * Now we have the actual (object, pindex), fault in the page. If
1467 * vm_fault_object() fails it will unlock and deallocate the FS
1468 * data. If it succeeds everything remains locked and fs->ba->object
1469 * will have an additinal PIP count if fs->ba != fs->first_ba.
1471 * On KERN_TRY_AGAIN vm_fault_object() leaves fs.first_ba intact.
1472 * We may have to upgrade its lock to handle the requested fault.
1474 result
= vm_fault_object(&fs
, first_pindex
, fault_type
, 0);
1476 if (result
== KERN_TRY_AGAIN
) {
1477 if (fs
.first_shared
== 0 && *sharedp
)
1478 vm_object_upgrade(object
);
1481 if (result
!= KERN_SUCCESS
) {
1486 if ((fault_type
& VM_PROT_WRITE
) && (fs
.prot
& VM_PROT_WRITE
) == 0) {
1487 *errorp
= KERN_PROTECTION_FAILURE
;
1493 * On success vm_fault_object() does not unlock or deallocate, so we
1494 * do it here. Note that the returned fs.m will be busied.
1499 * Return a held page. We are not doing any pmap manipulation so do
1500 * not set PG_MAPPED. However, adjust the page flags according to
1501 * the fault type because the caller may not use a managed pmapping
1502 * (so we don't want to lose the fact that the page will be dirtied
1503 * if a write fault was specified).
1505 vm_page_hold(fs
.mary
[0]);
1506 vm_page_activate(fs
.mary
[0]);
1507 if ((fault_type
& VM_PROT_WRITE
) || (fault_flags
& VM_FAULT_DIRTY
))
1508 vm_page_dirty(fs
.mary
[0]);
1509 if (fault_flags
& VM_FAULT_UNSWAP
)
1510 swap_pager_unswapped(fs
.mary
[0]);
1513 * Indicate that the page was accessed.
1515 vm_page_flag_set(fs
.mary
[0], PG_REFERENCED
);
1517 if (curthread
->td_lwp
) {
1519 curthread
->td_lwp
->lwp_ru
.ru_majflt
++;
1521 curthread
->td_lwp
->lwp_ru
.ru_minflt
++;
1526 * Unlock everything, and return the held page.
1528 vm_page_wakeup(fs
.mary
[0]);
1529 /*vm_object_deallocate(fs.first_ba->object);*/
1536 * This is the core of the vm_fault code.
1538 * Do all operations required to fault-in (fs.first_ba->object, pindex).
1539 * Run through the backing store as necessary and do required COW or virtual
1540 * copy operations. The caller has already fully resolved the vm_map_entry
1541 * and, if appropriate, has created a copy-on-write layer. All we need to
1542 * do is iterate the object chain.
1544 * On failure (fs) is unlocked and deallocated and the caller may return or
1545 * retry depending on the failure code. On success (fs) is NOT unlocked or
1546 * deallocated, fs.mary[0] will contained a resolved, busied page, and fs.ba's
1547 * object will have an additional PIP count if it is not equal to
1550 * If locks based on fs->first_shared or fs->shared are insufficient,
1551 * clear the appropriate field(s) and return RETRY. COWs require that
1552 * first_shared be 0, while page allocations (or frees) require that
1553 * shared be 0. Renames require that both be 0.
1555 * NOTE! fs->[first_]shared might be set with VM_FAULT_DIRTY also set.
1556 * we will have to retry with it exclusive if the vm_page is
1559 * fs->first_ba->object must be held on call.
1563 vm_fault_object(struct faultstate
*fs
, vm_pindex_t first_pindex
,
1564 vm_prot_t fault_type
, int allow_nofault
)
1566 vm_map_backing_t next_ba
;
1570 ASSERT_LWKT_TOKEN_HELD(vm_object_token(fs
->first_ba
->object
));
1571 fs
->prot
= fs
->first_prot
;
1572 pindex
= first_pindex
;
1573 KKASSERT(fs
->ba
== fs
->first_ba
);
1575 vm_object_pip_add(fs
->first_ba
->object
, 1);
1578 * If a read fault occurs we try to upgrade the page protection
1579 * and make it also writable if possible. There are three cases
1580 * where we cannot make the page mapping writable:
1582 * (1) The mapping is read-only or the VM object is read-only,
1583 * fs->prot above will simply not have VM_PROT_WRITE set.
1585 * (2) If the VM page is read-only or copy-on-write, upgrading would
1586 * just result in an unnecessary COW fault.
1588 * (3) If the pmap specifically requests A/M bit emulation, downgrade
1591 if (curthread
->td_lwp
&& curthread
->td_lwp
->lwp_vmspace
&&
1592 pmap_emulate_ad_bits(&curthread
->td_lwp
->lwp_vmspace
->vm_pmap
)) {
1593 if ((fault_type
& VM_PROT_WRITE
) == 0)
1594 fs
->prot
&= ~VM_PROT_WRITE
;
1597 /* vm_object_hold(fs->ba->object); implied b/c ba == first_ba */
1601 * If the object is dead, we stop here
1603 if (fs
->ba
->object
->flags
& OBJ_DEAD
) {
1604 vm_object_pip_wakeup(fs
->first_ba
->object
);
1606 return (KERN_PROTECTION_FAILURE
);
1610 * See if the page is resident. Wait/Retry if the page is
1611 * busy (lots of stuff may have changed so we can't continue
1614 * We can theoretically allow the soft-busy case on a read
1615 * fault if the page is marked valid, but since such
1616 * pages are typically already pmap'd, putting that
1617 * special case in might be more effort then it is
1618 * worth. We cannot under any circumstances mess
1619 * around with a vm_page_t->busy page except, perhaps,
1622 fs
->mary
[0] = vm_page_lookup_busy_try(fs
->ba
->object
, pindex
,
1625 vm_object_pip_wakeup(fs
->first_ba
->object
);
1627 vm_page_sleep_busy(fs
->mary
[0], TRUE
, "vmpfw");
1628 mycpu
->gd_cnt
.v_intrans
++;
1630 return (KERN_TRY_AGAIN
);
1634 * The page is busied for us.
1636 * If reactivating a page from PQ_CACHE we may have
1639 int queue
= fs
->mary
[0]->queue
;
1640 vm_page_unqueue_nowakeup(fs
->mary
[0]);
1642 if ((queue
- fs
->mary
[0]->pc
) == PQ_CACHE
&&
1643 vm_paging_severe()) {
1644 vm_page_activate(fs
->mary
[0]);
1645 vm_page_wakeup(fs
->mary
[0]);
1647 vm_object_pip_wakeup(fs
->first_ba
->object
);
1649 if (allow_nofault
== 0 ||
1650 (curthread
->td_flags
& TDF_NOFAULT
) == 0) {
1655 if (td
->td_proc
&& (td
->td_proc
->p_flags
& P_LOWMEMKILL
))
1656 return (KERN_PROTECTION_FAILURE
);
1658 return (KERN_TRY_AGAIN
);
1662 * If it still isn't completely valid (readable),
1663 * or if a read-ahead-mark is set on the VM page,
1664 * jump to readrest, else we found the page and
1667 * We can release the spl once we have marked the
1670 if (fs
->mary
[0]->object
!= kernel_object
) {
1671 if ((fs
->mary
[0]->valid
& VM_PAGE_BITS_ALL
) !=
1675 if (fs
->mary
[0]->flags
& PG_RAM
) {
1678 vm_page_flag_clear(fs
->mary
[0], PG_RAM
);
1682 atomic_clear_int(&fs
->first_ba
->flags
,
1683 VM_MAP_BACK_EXCL_HEUR
);
1684 break; /* break to PAGE HAS BEEN FOUND */
1688 * Page is not resident, If this is the search termination
1689 * or the pager might contain the page, allocate a new page.
1691 if (TRYPAGER(fs
) || fs
->ba
== fs
->first_ba
) {
1693 * If this is a SWAP object we can use the shared
1694 * lock to check existence of a swap block. If
1695 * there isn't one we can skip to the next object.
1697 * However, if this is the first object we allocate
1698 * a page now just in case we need to copy to it
1701 if (fs
->ba
!= fs
->first_ba
&&
1702 fs
->ba
->object
->type
== OBJT_SWAP
) {
1703 if (swap_pager_haspage_locked(fs
->ba
->object
,
1710 * Allocating, must be exclusive.
1712 atomic_set_int(&fs
->first_ba
->flags
,
1713 VM_MAP_BACK_EXCL_HEUR
);
1714 if (fs
->ba
== fs
->first_ba
&& fs
->first_shared
) {
1715 fs
->first_shared
= 0;
1716 vm_object_pip_wakeup(fs
->first_ba
->object
);
1718 return (KERN_TRY_AGAIN
);
1720 if (fs
->ba
!= fs
->first_ba
&& fs
->shared
) {
1721 fs
->first_shared
= 0;
1723 vm_object_pip_wakeup(fs
->first_ba
->object
);
1725 return (KERN_TRY_AGAIN
);
1729 * If the page is beyond the object size we fail
1731 if (pindex
>= fs
->ba
->object
->size
) {
1732 vm_object_pip_wakeup(fs
->first_ba
->object
);
1734 return (KERN_PROTECTION_FAILURE
);
1738 * Allocate a new page for this object/offset pair.
1740 * It is possible for the allocation to race, so
1743 * Does not apply to OBJT_MGTDEVICE (e.g. gpu / drm
1744 * subsystem). For OBJT_MGTDEVICE the pages are not
1745 * indexed in the VM object at all but instead directly
1746 * entered into the pmap.
1749 if (fs
->ba
->object
->type
== OBJT_MGTDEVICE
)
1752 if (!vm_paging_severe()) {
1753 fs
->mary
[0] = vm_page_alloc(fs
->ba
->object
,
1755 ((fs
->vp
|| fs
->ba
->backing_ba
) ?
1756 VM_ALLOC_NULL_OK
| VM_ALLOC_NORMAL
:
1757 VM_ALLOC_NULL_OK
| VM_ALLOC_NORMAL
|
1758 VM_ALLOC_USE_GD
| VM_ALLOC_ZERO
));
1760 if (fs
->mary
[0] == NULL
) {
1761 vm_object_pip_wakeup(fs
->first_ba
->object
);
1763 if (allow_nofault
== 0 ||
1764 (curthread
->td_flags
& TDF_NOFAULT
) == 0) {
1769 if (td
->td_proc
&& (td
->td_proc
->p_flags
& P_LOWMEMKILL
))
1770 return (KERN_PROTECTION_FAILURE
);
1772 return (KERN_TRY_AGAIN
);
1776 * Fall through to readrest. We have a new page which
1777 * will have to be paged (since m->valid will be 0).
1783 * We have found an invalid or partially valid page, a
1784 * page with a read-ahead mark which might be partially or
1785 * fully valid (and maybe dirty too), or we have allocated
1788 * Attempt to fault-in the page if there is a chance that the
1789 * pager has it, and potentially fault in additional pages
1792 * If TRYPAGER is true then fs.mary[0] will be non-NULL and
1796 u_char behavior
= vm_map_entry_behavior(fs
->entry
);
1802 if (behavior
== MAP_ENTRY_BEHAV_RANDOM
)
1808 * Doing I/O may synchronously insert additional
1809 * pages so we can't be shared at this point either.
1811 * NOTE: We can't free fs->mary[0] here in the
1812 * allocated case (fs->ba != fs->first_ba) as
1813 * this would require an exclusively locked
1816 if (fs
->ba
== fs
->first_ba
&& fs
->first_shared
) {
1818 vm_page_deactivate(fs
->mary
[0]);
1819 vm_page_wakeup(fs
->mary
[0]);
1822 fs
->first_shared
= 0;
1823 vm_object_pip_wakeup(fs
->first_ba
->object
);
1825 return (KERN_TRY_AGAIN
);
1827 if (fs
->ba
!= fs
->first_ba
&& fs
->shared
) {
1829 vm_page_deactivate(fs
->mary
[0]);
1830 vm_page_wakeup(fs
->mary
[0]);
1833 fs
->first_shared
= 0;
1835 vm_object_pip_wakeup(fs
->first_ba
->object
);
1837 return (KERN_TRY_AGAIN
);
1840 object
= fs
->ba
->object
;
1843 /* object is held, no more access to entry or ba's */
1846 * Acquire the page data. We still hold object
1847 * and the page has been BUSY's.
1849 * We own the page, but we must re-issue the lookup
1850 * because the pager may have replaced it (for example,
1851 * in order to enter a fictitious page into the
1852 * object). In this situation the pager will have
1853 * cleaned up the old page and left the new one
1856 * If we got here through a PG_RAM read-ahead
1857 * mark the page may be partially dirty and thus
1858 * not freeable. Don't bother checking to see
1859 * if the pager has the page because we can't free
1860 * it anyway. We have to depend on the get_page
1861 * operation filling in any gaps whether there is
1862 * backing store or not.
1864 * We must dispose of the page (fs->mary[0]) and also
1865 * possibly first_m (the fronting layer). If
1866 * this is a write fault leave the page intact
1867 * because we will probably have to copy fs->mary[0]
1868 * to fs->first_m on the retry. If this is a
1869 * read fault we probably won't need the page.
1871 * For OBJT_MGTDEVICE (and eventually all types),
1872 * fs->mary[0] is not pre-allocated and may be set
1873 * to a vm_page (busied for us) without being inserted
1874 * into the object. In this case we want to return
1875 * the vm_page directly so the caller can issue the
1878 rv
= vm_pager_get_page(object
, pindex
,
1879 &fs
->mary
[0], seqaccess
);
1881 if (rv
== VM_PAGER_OK
) {
1883 if (object
->type
== OBJT_MGTDEVICE
) {
1887 fs
->mary
[0] = vm_page_lookup(object
, pindex
);
1889 vm_page_activate(fs
->mary
[0]);
1890 vm_page_wakeup(fs
->mary
[0]);
1899 vm_object_pip_wakeup(fs
->first_ba
->object
);
1901 return (KERN_TRY_AGAIN
);
1905 * If the pager doesn't have the page, continue on
1906 * to the next object. Retain the vm_page if this
1907 * is the first object, we may need to copy into
1910 if (rv
== VM_PAGER_FAIL
) {
1911 if (fs
->ba
!= fs
->first_ba
) {
1913 vm_page_free(fs
->mary
[0]);
1921 * Remove the bogus page (which does not exist at this
1924 * Also wake up any other process that may want to bring
1927 * If this is the top-level object, we must leave the
1928 * busy page to prevent another process from rushing
1929 * past us, and inserting the page in that object at
1930 * the same time that we are.
1932 if (rv
== VM_PAGER_ERROR
) {
1934 kprintf("vm_fault: pager read error, "
1939 kprintf("vm_fault: pager read error, "
1942 curthread
->td_comm
);
1947 * I/O error or data outside pager's range.
1950 vnode_pager_freepage(fs
->mary
[0]);
1954 vm_page_free(first_m
);
1955 first_m
= NULL
; /* safety */
1957 vm_object_pip_wakeup(object
);
1961 case VM_PAGER_ERROR
:
1962 return (KERN_FAILURE
);
1964 return (KERN_PROTECTION_FAILURE
);
1966 return (KERN_PROTECTION_FAILURE
);
1971 * Data outside the range of the pager or an I/O error
1973 * The page may have been wired during the pagein,
1974 * e.g. by the buffer cache, and cannot simply be
1975 * freed. Call vnode_pager_freepage() to deal with it.
1977 * The object is not held shared so we can safely
1980 if (fs
->ba
!= fs
->first_ba
) {
1983 * XXX - we cannot just fall out at this
1984 * point, m has been freed and is invalid!
1989 * XXX - the check for kernel_map is a kludge to work
1990 * around having the machine panic on a kernel space
1991 * fault w/ I/O error.
1993 if (((fs
->map
!= kernel_map
) &&
1994 (rv
== VM_PAGER_ERROR
)) || (rv
== VM_PAGER_BAD
)) {
1996 /* from just above */
1997 KKASSERT(fs
->first_shared
== 0);
1998 vnode_pager_freepage(fs
->m
);
2008 * We get here if the object has a default pager (or unwiring)
2009 * or the pager doesn't have the page.
2011 * fs->first_m will be used for the COW unless we find a
2012 * deeper page to be mapped read-only, in which case the
2013 * unlock*(fs) will free first_m.
2015 if (fs
->ba
== fs
->first_ba
)
2016 fs
->first_m
= fs
->mary
[0];
2019 * Move on to the next object. The chain lock should prevent
2020 * the backing_object from getting ripped out from under us.
2022 * The object lock for the next object is governed by
2025 next_ba
= fs
->ba
->backing_ba
;
2026 if (next_ba
== NULL
) {
2028 * If there's no object left, fill the page in the top
2029 * object with zeros.
2031 if (fs
->ba
!= fs
->first_ba
) {
2032 vm_object_pip_wakeup(fs
->ba
->object
);
2033 vm_object_drop(fs
->ba
->object
);
2034 fs
->ba
= fs
->first_ba
;
2035 pindex
= first_pindex
;
2036 fs
->mary
[0] = fs
->first_m
;
2041 * Zero the page and mark it valid.
2043 vm_page_zero_fill(fs
->mary
[0]);
2044 mycpu
->gd_cnt
.v_zfod
++;
2045 fs
->mary
[0]->valid
= VM_PAGE_BITS_ALL
;
2046 break; /* break to PAGE HAS BEEN FOUND */
2050 vm_object_hold_shared(next_ba
->object
);
2052 vm_object_hold(next_ba
->object
);
2053 KKASSERT(next_ba
== fs
->ba
->backing_ba
);
2054 pindex
-= OFF_TO_IDX(fs
->ba
->offset
);
2055 pindex
+= OFF_TO_IDX(next_ba
->offset
);
2057 if (fs
->ba
!= fs
->first_ba
) {
2058 vm_object_pip_wakeup(fs
->ba
->object
);
2059 vm_object_lock_swap(); /* flip ba/next_ba */
2060 vm_object_drop(fs
->ba
->object
);
2063 vm_object_pip_add(next_ba
->object
, 1);
2067 * PAGE HAS BEEN FOUND. [Loop invariant still holds -- the object lock
2070 * object still held.
2071 * vm_map may not be locked (determined by fs->lookup_still_valid)
2073 * local shared variable may be different from fs->shared.
2075 * If the page is being written, but isn't already owned by the
2076 * top-level object, we have to copy it into a new page owned by the
2079 KASSERT((fs
->mary
[0]->busy_count
& PBUSY_LOCKED
) != 0,
2080 ("vm_fault: not busy after main loop"));
2082 if (fs
->ba
!= fs
->first_ba
) {
2084 * We only really need to copy if we want to write it.
2086 if (fault_type
& VM_PROT_WRITE
) {
2088 /* CODE REFACTOR IN PROGRESS, REMOVE OPTIMIZATION */
2090 * This allows pages to be virtually copied from a
2091 * backing_object into the first_object, where the
2092 * backing object has no other refs to it, and cannot
2093 * gain any more refs. Instead of a bcopy, we just
2094 * move the page from the backing object to the
2095 * first object. Note that we must mark the page
2096 * dirty in the first object so that it will go out
2097 * to swap when needed.
2099 if (virtual_copy_ok(fs
)) {
2101 * (first_m) and (m) are both busied. We have
2102 * move (m) into (first_m)'s object/pindex
2103 * in an atomic fashion, then free (first_m).
2105 * first_object is held so second remove
2106 * followed by the rename should wind
2107 * up being atomic. vm_page_free() might
2108 * block so we don't do it until after the
2111 vm_page_protect(fs
->first_m
, VM_PROT_NONE
);
2112 vm_page_remove(fs
->first_m
);
2113 vm_page_rename(fs
->mary
[0],
2114 fs
->first_ba
->object
,
2116 vm_page_free(fs
->first_m
);
2117 fs
->first_m
= fs
->mary
[0];
2119 mycpu
->gd_cnt
.v_cow_optim
++;
2124 * Oh, well, lets copy it.
2126 * We used to unmap the original page here
2127 * because vm_fault_page() didn't and this
2128 * would cause havoc for the umtx*() code
2129 * and the procfs code.
2131 * This is no longer necessary. The
2132 * vm_fault_page() routine will now unmap the
2133 * page after a COW, and the umtx code will
2134 * recover on its own.
2137 * NOTE: Since fs->mary[0] is a backing page,
2138 * it is read-only, so there isn't any
2139 * copy race vs writers.
2141 KKASSERT(fs
->first_shared
== 0);
2142 vm_page_copy(fs
->mary
[0], fs
->first_m
);
2143 /* pmap_remove_specific(
2144 &curthread->td_lwp->lwp_vmspace->vm_pmap,
2149 * We no longer need the old page or object.
2155 * fs->ba != fs->first_ba due to above conditional
2157 vm_object_pip_wakeup(fs
->ba
->object
);
2158 vm_object_drop(fs
->ba
->object
);
2159 fs
->ba
= fs
->first_ba
;
2162 * Only use the new page below...
2164 mycpu
->gd_cnt
.v_cow_faults
++;
2165 fs
->mary
[0] = fs
->first_m
;
2166 pindex
= first_pindex
;
2169 * If it wasn't a write fault avoid having to copy
2170 * the page by mapping it read-only from backing
2171 * store. The process is not allowed to modify
2174 fs
->prot
&= ~VM_PROT_WRITE
;
2179 * Relock the map if necessary, then check the generation count.
2180 * relock_map() will update fs->timestamp to account for the
2181 * relocking if necessary.
2183 * If the count has changed after relocking then all sorts of
2184 * crap may have happened and we have to retry.
2186 * NOTE: The relock_map() can fail due to a deadlock against
2187 * the vm_page we are holding BUSY.
2189 KKASSERT(fs
->lookup_still_valid
!= 0);
2191 if (fs
->lookup_still_valid
== 0 && fs
->map
) {
2192 if (relock_map(fs
) ||
2193 fs
->map
->timestamp
!= fs
->map_generation
) {
2195 vm_object_pip_wakeup(fs
->first_ba
->object
);
2197 return (KERN_TRY_AGAIN
);
2203 * If the fault is a write, we know that this page is being
2204 * written NOW so dirty it explicitly to save on pmap_is_modified()
2207 * If this is a NOSYNC mmap we do not want to set PG_NOSYNC
2208 * if the page is already dirty to prevent data written with
2209 * the expectation of being synced from not being synced.
2210 * Likewise if this entry does not request NOSYNC then make
2211 * sure the page isn't marked NOSYNC. Applications sharing
2212 * data should use the same flags to avoid ping ponging.
2214 * Also tell the backing pager, if any, that it should remove
2215 * any swap backing since the page is now dirty.
2217 vm_page_activate(fs
->mary
[0]);
2218 if (fs
->prot
& VM_PROT_WRITE
) {
2219 vm_object_set_writeable_dirty(fs
->first_ba
->object
);
2220 vm_set_nosync(fs
->mary
[0], fs
->entry
);
2221 if (fs
->fault_flags
& VM_FAULT_DIRTY
) {
2222 vm_page_dirty(fs
->mary
[0]);
2223 if (fs
->mary
[0]->flags
& PG_SWAPPED
) {
2225 * If the page is swapped out we have to call
2226 * swap_pager_unswapped() which requires an
2227 * exclusive object lock. If we are shared,
2228 * we must clear the shared flag and retry.
2230 if ((fs
->ba
== fs
->first_ba
&&
2231 fs
->first_shared
) ||
2232 (fs
->ba
!= fs
->first_ba
&& fs
->shared
)) {
2233 vm_page_wakeup(fs
->mary
[0]);
2235 if (fs
->ba
== fs
->first_ba
)
2236 fs
->first_shared
= 0;
2239 vm_object_pip_wakeup(
2240 fs
->first_ba
->object
);
2242 return (KERN_TRY_AGAIN
);
2244 swap_pager_unswapped(fs
->mary
[0]);
2250 * We found our page at backing layer ba. Leave the layer state
2254 vm_object_pip_wakeup(fs
->first_ba
->object
);
2256 if (fs
->ba
!= fs
->first_ba
)
2257 vm_object_drop(fs
->ba
->object
);
2261 * Page had better still be busy. We are still locked up and
2262 * fs->ba->object will have another PIP reference for the case
2263 * where fs->ba != fs->first_ba.
2265 KASSERT(fs
->mary
[0]->busy_count
& PBUSY_LOCKED
,
2266 ("vm_fault: page %p not busy!", fs
->mary
[0]));
2269 * Sanity check: page must be completely valid or it is not fit to
2270 * map into user space. vm_pager_get_pages() ensures this.
2272 if (fs
->mary
[0]->valid
!= VM_PAGE_BITS_ALL
) {
2273 vm_page_zero_invalid(fs
->mary
[0], TRUE
);
2274 kprintf("Warning: page %p partially invalid on fault\n",
2278 return (KERN_SUCCESS
);
2282 * Wire down a range of virtual addresses in a map. The entry in question
2283 * should be marked in-transition and the map must be locked. We must
2284 * release the map temporarily while faulting-in the page to avoid a
2285 * deadlock. Note that the entry may be clipped while we are blocked but
2286 * will never be freed.
2288 * map must be locked on entry.
2291 vm_fault_wire(vm_map_t map
, vm_map_entry_t entry
,
2292 boolean_t user_wire
, int kmflags
)
2294 boolean_t fictitious
;
2305 wire_prot
= VM_PROT_READ
;
2306 fault_flags
= VM_FAULT_USER_WIRE
;
2308 wire_prot
= VM_PROT_READ
| VM_PROT_WRITE
;
2309 fault_flags
= VM_FAULT_CHANGE_WIRING
;
2311 if (kmflags
& KM_NOTLBSYNC
)
2312 wire_prot
|= VM_PROT_NOSYNC
;
2314 pmap
= vm_map_pmap(map
);
2315 start
= entry
->ba
.start
;
2316 end
= entry
->ba
.end
;
2318 switch(entry
->maptype
) {
2319 case VM_MAPTYPE_NORMAL
:
2320 fictitious
= entry
->ba
.object
&&
2321 ((entry
->ba
.object
->type
== OBJT_DEVICE
) ||
2322 (entry
->ba
.object
->type
== OBJT_MGTDEVICE
));
2324 case VM_MAPTYPE_UKSMAP
:
2332 if (entry
->eflags
& MAP_ENTRY_KSTACK
)
2338 * We simulate a fault to get the page and enter it in the physical
2341 for (va
= start
; va
< end
; va
+= PAGE_SIZE
) {
2342 rv
= vm_fault(map
, va
, wire_prot
, fault_flags
);
2344 while (va
> start
) {
2346 m
= pmap_unwire(pmap
, va
);
2347 if (m
&& !fictitious
) {
2348 vm_page_busy_wait(m
, FALSE
, "vmwrpg");
2349 vm_page_unwire(m
, 1);
2364 * Unwire a range of virtual addresses in a map. The map should be
2368 vm_fault_unwire(vm_map_t map
, vm_map_entry_t entry
)
2370 boolean_t fictitious
;
2377 pmap
= vm_map_pmap(map
);
2378 start
= entry
->ba
.start
;
2379 end
= entry
->ba
.end
;
2380 fictitious
= entry
->ba
.object
&&
2381 ((entry
->ba
.object
->type
== OBJT_DEVICE
) ||
2382 (entry
->ba
.object
->type
== OBJT_MGTDEVICE
));
2383 if (entry
->eflags
& MAP_ENTRY_KSTACK
)
2387 * Since the pages are wired down, we must be able to get their
2388 * mappings from the physical map system.
2390 for (va
= start
; va
< end
; va
+= PAGE_SIZE
) {
2391 m
= pmap_unwire(pmap
, va
);
2392 if (m
&& !fictitious
) {
2393 vm_page_busy_wait(m
, FALSE
, "vmwrpg");
2394 vm_page_unwire(m
, 1);
2401 * Simulate write faults to bring all data into the head object, return
2402 * KERN_SUCCESS on success (which should be always unless the system runs
2405 * The caller will handle destroying the backing_ba's.
2408 vm_fault_collapse(vm_map_t map
, vm_map_entry_t entry
)
2410 struct faultstate fs
;
2417 bzero(&fs
, sizeof(fs
));
2418 object
= entry
->ba
.object
;
2420 fs
.first_prot
= entry
->max_protection
| /* optional VM_PROT_EXECUTE */
2421 VM_PROT_READ
| VM_PROT_WRITE
| VM_PROT_OVERRIDE_WRITE
;
2422 fs
.fault_flags
= VM_FAULT_NORMAL
;
2425 fs
.lookup_still_valid
= -1; /* leave map atomically locked */
2426 fs
.first_ba
= &entry
->ba
;
2427 fs
.first_ba_held
= -1; /* leave object held */
2431 vm_object_hold(object
);
2434 scan
= entry
->ba
.start
;
2437 while (scan
< entry
->ba
.end
) {
2438 pindex
= OFF_TO_IDX(entry
->ba
.offset
+ (scan
- entry
->ba
.start
));
2440 if (vm_page_lookup(object
, pindex
)) {
2446 fs
.ba
= fs
.first_ba
;
2447 fs
.prot
= fs
.first_prot
;
2449 rv
= vm_fault_object(&fs
, pindex
, fs
.first_prot
, 1);
2450 if (rv
== KERN_TRY_AGAIN
)
2452 if (rv
!= KERN_SUCCESS
)
2454 vm_page_flag_set(fs
.mary
[0], PG_REFERENCED
);
2455 vm_page_activate(fs
.mary
[0]);
2456 vm_page_wakeup(fs
.mary
[0]);
2459 KKASSERT(entry
->ba
.object
== object
);
2460 vm_object_drop(object
);
2463 * If the fronting object did not have every page we have to clear
2464 * the pmap range due to the pages being changed so we can fault-in
2467 if (all_shadowed
== 0)
2468 pmap_remove(map
->pmap
, entry
->ba
.start
, entry
->ba
.end
);
2474 * Copy all of the pages from one map entry to another. If the source
2475 * is wired down we just use vm_page_lookup(). If not we use
2476 * vm_fault_object().
2478 * The source and destination maps must be locked for write.
2479 * The source and destination maps token must be held
2481 * No other requirements.
2483 * XXX do segment optimization
2486 vm_fault_copy_entry(vm_map_t dst_map
, vm_map_t src_map
,
2487 vm_map_entry_t dst_entry
, vm_map_entry_t src_entry
)
2489 vm_object_t dst_object
;
2490 vm_object_t src_object
;
2491 vm_ooffset_t dst_offset
;
2492 vm_ooffset_t src_offset
;
2498 src_object
= src_entry
->ba
.object
;
2499 src_offset
= src_entry
->ba
.offset
;
2502 * Create the top-level object for the destination entry. (Doesn't
2503 * actually shadow anything - we copy the pages directly.)
2505 vm_map_entry_allocate_object(dst_entry
);
2506 dst_object
= dst_entry
->ba
.object
;
2508 prot
= dst_entry
->max_protection
;
2511 * Loop through all of the pages in the entry's range, copying each
2512 * one from the source object (it should be there) to the destination
2515 vm_object_hold(src_object
);
2516 vm_object_hold(dst_object
);
2518 for (vaddr
= dst_entry
->ba
.start
, dst_offset
= 0;
2519 vaddr
< dst_entry
->ba
.end
;
2520 vaddr
+= PAGE_SIZE
, dst_offset
+= PAGE_SIZE
) {
2523 * Allocate a page in the destination object
2526 dst_m
= vm_page_alloc(dst_object
,
2527 OFF_TO_IDX(dst_offset
),
2529 if (dst_m
== NULL
) {
2532 } while (dst_m
== NULL
);
2535 * Find the page in the source object, and copy it in.
2536 * (Because the source is wired down, the page will be in
2539 src_m
= vm_page_lookup(src_object
,
2540 OFF_TO_IDX(dst_offset
+ src_offset
));
2542 panic("vm_fault_copy_wired: page missing");
2544 vm_page_copy(src_m
, dst_m
);
2547 * Enter it in the pmap...
2549 pmap_enter(dst_map
->pmap
, vaddr
, dst_m
, prot
, FALSE
, dst_entry
);
2552 * Mark it no longer busy, and put it on the active list.
2554 vm_page_activate(dst_m
);
2555 vm_page_wakeup(dst_m
);
2557 vm_object_drop(dst_object
);
2558 vm_object_drop(src_object
);
2564 * This routine checks around the requested page for other pages that
2565 * might be able to be faulted in. This routine brackets the viable
2566 * pages for the pages to be paged in.
2569 * m, rbehind, rahead
2572 * marray (array of vm_page_t), reqpage (index of requested page)
2575 * number of pages in marray
2578 vm_fault_additional_pages(vm_page_t m
, int rbehind
, int rahead
,
2579 vm_page_t
*marray
, int *reqpage
)
2583 vm_pindex_t pindex
, startpindex
, endpindex
, tpindex
;
2585 int cbehind
, cahead
;
2591 * we don't fault-ahead for device pager
2593 if ((object
->type
== OBJT_DEVICE
) ||
2594 (object
->type
== OBJT_MGTDEVICE
)) {
2601 * if the requested page is not available, then give up now
2603 if (!vm_pager_has_page(object
, pindex
, &cbehind
, &cahead
)) {
2604 *reqpage
= 0; /* not used by caller, fix compiler warn */
2608 if ((cbehind
== 0) && (cahead
== 0)) {
2614 if (rahead
> cahead
) {
2618 if (rbehind
> cbehind
) {
2623 * Do not do any readahead if we have insufficient free memory.
2625 * XXX code was broken disabled before and has instability
2626 * with this conditonal fixed, so shortcut for now.
2628 if (burst_fault
== 0 || vm_page_count_severe()) {
2635 * scan backward for the read behind pages -- in memory
2637 * Assume that if the page is not found an interrupt will not
2638 * create it. Theoretically interrupts can only remove (busy)
2639 * pages, not create new associations.
2642 if (rbehind
> pindex
) {
2646 startpindex
= pindex
- rbehind
;
2649 vm_object_hold(object
);
2650 for (tpindex
= pindex
; tpindex
> startpindex
; --tpindex
) {
2651 if (vm_page_lookup(object
, tpindex
- 1))
2656 while (tpindex
< pindex
) {
2657 rtm
= vm_page_alloc(object
, tpindex
, VM_ALLOC_SYSTEM
|
2660 for (j
= 0; j
< i
; j
++) {
2661 vm_page_free(marray
[j
]);
2663 vm_object_drop(object
);
2672 vm_object_drop(object
);
2678 * Assign requested page
2685 * Scan forwards for read-ahead pages
2687 tpindex
= pindex
+ 1;
2688 endpindex
= tpindex
+ rahead
;
2689 if (endpindex
> object
->size
)
2690 endpindex
= object
->size
;
2692 vm_object_hold(object
);
2693 while (tpindex
< endpindex
) {
2694 if (vm_page_lookup(object
, tpindex
))
2696 rtm
= vm_page_alloc(object
, tpindex
, VM_ALLOC_SYSTEM
|
2704 vm_object_drop(object
);
2712 * vm_prefault() provides a quick way of clustering pagefaults into a
2713 * processes address space. It is a "cousin" of pmap_object_init_pt,
2714 * except it runs at page fault time instead of mmap time.
2716 * vm.fast_fault Enables pre-faulting zero-fill pages
2718 * vm.prefault_pages Number of pages (1/2 negative, 1/2 positive) to
2719 * prefault. Scan stops in either direction when
2720 * a page is found to already exist.
2722 * This code used to be per-platform pmap_prefault(). It is now
2723 * machine-independent and enhanced to also pre-fault zero-fill pages
2724 * (see vm.fast_fault) as well as make them writable, which greatly
2725 * reduces the number of page faults programs incur.
2727 * Application performance when pre-faulting zero-fill pages is heavily
2728 * dependent on the application. Very tiny applications like /bin/echo
2729 * lose a little performance while applications of any appreciable size
2730 * gain performance. Prefaulting multiple pages also reduces SMP
2731 * congestion and can improve SMP performance significantly.
2733 * NOTE! prot may allow writing but this only applies to the top level
2734 * object. If we wind up mapping a page extracted from a backing
2735 * object we have to make sure it is read-only.
2737 * NOTE! The caller has already handled any COW operations on the
2738 * vm_map_entry via the normal fault code. Do NOT call this
2739 * shortcut unless the normal fault code has run on this entry.
2741 * The related map must be locked.
2742 * No other requirements.
2744 __read_mostly
static int vm_prefault_pages
= 8;
2745 SYSCTL_INT(_vm
, OID_AUTO
, prefault_pages
, CTLFLAG_RW
, &vm_prefault_pages
, 0,
2746 "Maximum number of pages to pre-fault");
2747 __read_mostly
static int vm_fast_fault
= 1;
2748 SYSCTL_INT(_vm
, OID_AUTO
, fast_fault
, CTLFLAG_RW
, &vm_fast_fault
, 0,
2749 "Burst fault zero-fill regions");
2752 * Set PG_NOSYNC if the map entry indicates so, but only if the page
2753 * is not already dirty by other means. This will prevent passive
2754 * filesystem syncing as well as 'sync' from writing out the page.
2757 vm_set_nosync(vm_page_t m
, vm_map_entry_t entry
)
2759 if (entry
->eflags
& MAP_ENTRY_NOSYNC
) {
2761 vm_page_flag_set(m
, PG_NOSYNC
);
2763 vm_page_flag_clear(m
, PG_NOSYNC
);
2768 vm_prefault(pmap_t pmap
, vm_offset_t addra
, vm_map_entry_t entry
, int prot
,
2771 vm_map_backing_t ba
; /* first ba */
2785 * Get stable max count value, disabled if set to 0
2787 maxpages
= vm_prefault_pages
;
2793 * We do not currently prefault mappings that use virtual page
2794 * tables. We do not prefault foreign pmaps.
2796 if (entry
->maptype
!= VM_MAPTYPE_NORMAL
)
2798 lp
= curthread
->td_lwp
;
2799 if (lp
== NULL
|| (pmap
!= vmspace_pmap(lp
->lwp_vmspace
)))
2803 * Limit pre-fault count to 1024 pages.
2805 if (maxpages
> 1024)
2809 object
= entry
->ba
.object
;
2810 KKASSERT(object
!= NULL
);
2813 * NOTE: VM_FAULT_DIRTY allowed later so must hold object exclusively
2814 * now (or do something more complex XXX).
2816 vm_object_hold(object
);
2820 for (i
= 0; i
< maxpages
; ++i
) {
2821 vm_object_t lobject
;
2822 vm_object_t nobject
;
2823 vm_map_backing_t last_ba
; /* last ba */
2824 vm_map_backing_t next_ba
; /* last ba */
2829 * This can eat a lot of time on a heavily contended
2830 * machine so yield on the tick if needed.
2836 * Calculate the page to pre-fault, stopping the scan in
2837 * each direction separately if the limit is reached.
2842 addr
= addra
- ((i
+ 1) >> 1) * PAGE_SIZE
;
2846 addr
= addra
+ ((i
+ 2) >> 1) * PAGE_SIZE
;
2848 if (addr
< entry
->ba
.start
) {
2854 if (addr
>= entry
->ba
.end
) {
2862 * Skip pages already mapped, and stop scanning in that
2863 * direction. When the scan terminates in both directions
2866 if (pmap_prefault_ok(pmap
, addr
) == 0) {
2877 * Follow the backing layers to obtain the page to be mapped
2880 * If we reach the terminal object without finding a page
2881 * and we determine it would be advantageous, then allocate
2882 * a zero-fill page for the base object. The base object
2883 * is guaranteed to be OBJT_DEFAULT for this case.
2885 * In order to not have to check the pager via *haspage*()
2886 * we stop if any non-default object is encountered. e.g.
2887 * a vnode or swap object would stop the loop.
2889 index
= ((addr
- entry
->ba
.start
) + entry
->ba
.offset
) >>
2896 /*vm_object_hold(lobject); implied */
2898 while ((m
= vm_page_lookup_busy_try(lobject
, pindex
,
2899 TRUE
, &error
)) == NULL
) {
2900 if (lobject
->type
!= OBJT_DEFAULT
)
2902 if ((next_ba
= last_ba
->backing_ba
) == NULL
) {
2903 if (vm_fast_fault
== 0)
2905 if ((prot
& VM_PROT_WRITE
) == 0 ||
2911 * NOTE: Allocated from base object
2913 m
= vm_page_alloc(object
, index
,
2922 /* lobject = object .. not needed */
2925 if (next_ba
->offset
& PAGE_MASK
)
2927 nobject
= next_ba
->object
;
2928 vm_object_hold(nobject
);
2929 pindex
-= last_ba
->offset
>> PAGE_SHIFT
;
2930 pindex
+= next_ba
->offset
>> PAGE_SHIFT
;
2931 if (last_ba
!= ba
) {
2932 vm_object_lock_swap();
2933 vm_object_drop(lobject
);
2937 pprot
&= ~VM_PROT_WRITE
;
2941 * NOTE: A non-NULL (m) will be associated with lobject if
2942 * it was found there, otherwise it is probably a
2943 * zero-fill page associated with the base object.
2945 * Give-up if no page is available.
2949 vm_object_drop(lobject
);
2954 * The object must be marked dirty if we are mapping a
2955 * writable page. Note that (m) does not have to be
2956 * entered into the object, so use lobject or object
2957 * as appropriate instead of m->object.
2959 * Do this before we potentially drop the object.
2961 if (pprot
& VM_PROT_WRITE
) {
2962 vm_object_set_writeable_dirty(
2963 (allocated
? object
: lobject
));
2967 * Do not conditionalize on PG_RAM. If pages are present in
2968 * the VM system we assume optimal caching. If caching is
2969 * not optimal the I/O gravy train will be restarted when we
2970 * hit an unavailable page. We do not want to try to restart
2971 * the gravy train now because we really don't know how much
2972 * of the object has been cached. The cost for restarting
2973 * the gravy train should be low (since accesses will likely
2974 * be I/O bound anyway).
2977 vm_object_drop(lobject
);
2980 * Enter the page into the pmap if appropriate. If we had
2981 * allocated the page we have to place it on a queue. If not
2982 * we just have to make sure it isn't on the cache queue
2983 * (pages on the cache queue are not allowed to be mapped).
2985 * When allocated is TRUE, m corresponds to object,
2990 * Page must be zerod.
2992 vm_page_zero_fill(m
);
2993 mycpu
->gd_cnt
.v_zfod
++;
2994 m
->valid
= VM_PAGE_BITS_ALL
;
2997 * Handle dirty page case
2999 if (pprot
& VM_PROT_WRITE
)
3000 vm_set_nosync(m
, entry
);
3001 pmap_enter(pmap
, addr
, m
, pprot
, 0, entry
);
3003 /* REMOVE ME, a burst counts as one fault */
3004 mycpu
->gd_cnt
.v_vm_faults
++;
3005 if (curthread
->td_lwp
)
3006 ++curthread
->td_lwp
->lwp_ru
.ru_minflt
;
3008 vm_page_deactivate(m
);
3009 if (pprot
& VM_PROT_WRITE
) {
3010 /*vm_object_set_writeable_dirty(object);*/
3011 vm_set_nosync(m
, entry
);
3012 if (fault_flags
& VM_FAULT_DIRTY
) {
3015 swap_pager_unswapped(m
);
3020 /* couldn't busy page, no wakeup */
3022 ((m
->valid
& VM_PAGE_BITS_ALL
) == VM_PAGE_BITS_ALL
) &&
3023 (m
->flags
& PG_FICTITIOUS
) == 0) {
3025 * A fully valid page not undergoing soft I/O can
3026 * be immediately entered into the pmap.
3028 * When allocated is false, m corresponds to lobject.
3030 if ((m
->queue
- m
->pc
) == PQ_CACHE
)
3031 vm_page_deactivate(m
);
3032 if (pprot
& VM_PROT_WRITE
) {
3033 /*vm_object_set_writeable_dirty(lobject);*/
3034 vm_set_nosync(m
, entry
);
3035 if (fault_flags
& VM_FAULT_DIRTY
) {
3038 swap_pager_unswapped(m
);
3041 if (pprot
& VM_PROT_WRITE
)
3042 vm_set_nosync(m
, entry
);
3043 pmap_enter(pmap
, addr
, m
, pprot
, 0, entry
);
3045 /* REMOVE ME, a burst counts as one fault */
3046 mycpu
->gd_cnt
.v_vm_faults
++;
3047 if (curthread
->td_lwp
)
3048 ++curthread
->td_lwp
->lwp_ru
.ru_minflt
;
3055 vm_object_drop(object
);
3059 * Object can be held shared
3062 vm_prefault_quick(pmap_t pmap
, vm_offset_t addra
,
3063 vm_map_entry_t entry
, int prot
, int fault_flags
)
3076 * Get stable max count value, disabled if set to 0
3078 maxpages
= vm_prefault_pages
;
3084 * We do not currently prefault mappings that use virtual page
3085 * tables. We do not prefault foreign pmaps.
3087 if (entry
->maptype
!= VM_MAPTYPE_NORMAL
)
3089 lp
= curthread
->td_lwp
;
3090 if (lp
== NULL
|| (pmap
!= vmspace_pmap(lp
->lwp_vmspace
)))
3092 object
= entry
->ba
.object
;
3093 if (entry
->ba
.backing_ba
!= NULL
)
3095 ASSERT_LWKT_TOKEN_HELD(vm_object_token(object
));
3098 * Limit pre-fault count to 1024 pages.
3100 if (maxpages
> 1024)
3105 for (i
= 0; i
< maxpages
; ++i
) {
3109 * Calculate the page to pre-fault, stopping the scan in
3110 * each direction separately if the limit is reached.
3115 addr
= addra
- ((i
+ 1) >> 1) * PAGE_SIZE
;
3119 addr
= addra
+ ((i
+ 2) >> 1) * PAGE_SIZE
;
3121 if (addr
< entry
->ba
.start
) {
3127 if (addr
>= entry
->ba
.end
) {
3135 * Follow the VM object chain to obtain the page to be mapped
3136 * into the pmap. This version of the prefault code only
3137 * works with terminal objects.
3139 * The page must already exist. If we encounter a problem
3142 * WARNING! We cannot call swap_pager_unswapped() or insert
3143 * a new vm_page with a shared token.
3145 pindex
= ((addr
- entry
->ba
.start
) + entry
->ba
.offset
) >>
3149 * Skip pages already mapped, and stop scanning in that
3150 * direction. When the scan terminates in both directions
3153 if (pmap_prefault_ok(pmap
, addr
) == 0) {
3164 * Shortcut the read-only mapping case using the far more
3165 * efficient vm_page_lookup_sbusy_try() function. This
3166 * allows us to acquire the page soft-busied only which
3167 * is especially nice for concurrent execs of the same
3170 * The lookup function also validates page suitability
3171 * (all valid bits set, and not fictitious).
3173 * If the page is in PQ_CACHE we have to fall-through
3174 * and hard-busy it so we can move it out of PQ_CACHE.
3176 if ((prot
& VM_PROT_WRITE
) == 0) {
3177 m
= vm_page_lookup_sbusy_try(object
, pindex
,
3181 if ((m
->queue
- m
->pc
) != PQ_CACHE
) {
3182 pmap_enter(pmap
, addr
, m
, prot
, 0, entry
);
3184 /* REMOVE ME, a burst counts as one fault */
3185 mycpu
->gd_cnt
.v_vm_faults
++;
3186 if (curthread
->td_lwp
)
3187 ++curthread
->td_lwp
->lwp_ru
.ru_minflt
;
3189 vm_page_sbusy_drop(m
);
3192 vm_page_sbusy_drop(m
);
3196 * Fallback to normal vm_page lookup code. This code
3197 * hard-busies the page. Not only that, but the page
3198 * can remain in that state for a significant period
3199 * time due to pmap_enter()'s overhead.
3201 m
= vm_page_lookup_busy_try(object
, pindex
, TRUE
, &error
);
3202 if (m
== NULL
|| error
)
3206 * Stop if the page cannot be trivially entered into the
3209 if (((m
->valid
& VM_PAGE_BITS_ALL
) != VM_PAGE_BITS_ALL
) ||
3210 (m
->flags
& PG_FICTITIOUS
) ||
3211 ((m
->flags
& PG_SWAPPED
) &&
3212 (prot
& VM_PROT_WRITE
) &&
3213 (fault_flags
& VM_FAULT_DIRTY
))) {
3219 * Enter the page into the pmap. The object might be held
3220 * shared so we can't do any (serious) modifying operation
3223 if ((m
->queue
- m
->pc
) == PQ_CACHE
)
3224 vm_page_deactivate(m
);
3225 if (prot
& VM_PROT_WRITE
) {
3226 vm_object_set_writeable_dirty(m
->object
);
3227 vm_set_nosync(m
, entry
);
3228 if (fault_flags
& VM_FAULT_DIRTY
) {
3230 /* can't happeen due to conditional above */
3231 /* swap_pager_unswapped(m); */
3234 pmap_enter(pmap
, addr
, m
, prot
, 0, entry
);
3236 /* REMOVE ME, a burst counts as one fault */
3237 mycpu
->gd_cnt
.v_vm_faults
++;
3238 if (curthread
->td_lwp
)
3239 ++curthread
->td_lwp
->lwp_ru
.ru_minflt
;