2 * SPDX-License-Identifier: (BSD-4-Clause AND MIT-CMU)
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.
73 * Page fault handling module.
76 #include <sys/cdefs.h>
77 __FBSDID("$FreeBSD$");
79 #include "opt_ktrace.h"
82 #include <sys/param.h>
83 #include <sys/systm.h>
84 #include <sys/kernel.h>
87 #include <sys/mutex.h>
89 #include <sys/racct.h>
90 #include <sys/refcount.h>
91 #include <sys/resourcevar.h>
92 #include <sys/rwlock.h>
93 #include <sys/signalvar.h>
94 #include <sys/sysctl.h>
95 #include <sys/sysent.h>
96 #include <sys/vmmeter.h>
97 #include <sys/vnode.h>
99 #include <sys/ktrace.h>
103 #include <vm/vm_param.h>
105 #include <vm/vm_map.h>
106 #include <vm/vm_object.h>
107 #include <vm/vm_page.h>
108 #include <vm/vm_pageout.h>
109 #include <vm/vm_kern.h>
110 #include <vm/vm_pager.h>
111 #include <vm/vm_extern.h>
112 #include <vm/vm_reserv.h>
117 #define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT)
119 #define VM_FAULT_DONTNEED_MIN 1048576
122 /* Fault parameters. */
125 vm_prot_t fault_type;
128 struct timeval oom_start_time;
132 /* Page reference for cow. */
135 /* Current object. */
140 /* Top-level map object. */
141 vm_object_t first_object;
142 vm_pindex_t first_pindex;
147 vm_map_entry_t entry;
149 bool lookup_still_valid;
151 /* Vnode if locked. */
155 static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr,
157 static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
158 int backward, int forward, bool obj_locked);
160 static int vm_pfault_oom_attempts = 3;
161 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_attempts, CTLFLAG_RWTUN,
162 &vm_pfault_oom_attempts, 0,
163 "Number of page allocation attempts in page fault handler before it "
164 "triggers OOM handling");
166 static int vm_pfault_oom_wait = 10;
167 SYSCTL_INT(_vm, OID_AUTO, pfault_oom_wait, CTLFLAG_RWTUN,
168 &vm_pfault_oom_wait, 0,
169 "Number of seconds to wait for free pages before retrying "
170 "the page fault handler");
173 fault_page_release(vm_page_t *mp)
180 * We are likely to loop around again and attempt to busy
181 * this page. Deactivating it leaves it available for
182 * pageout while optimizing fault restarts.
184 vm_page_deactivate(m);
191 fault_page_free(vm_page_t *mp)
197 VM_OBJECT_ASSERT_WLOCKED(m->object);
198 if (!vm_page_wired(m))
207 unlock_map(struct faultstate *fs)
210 if (fs->lookup_still_valid) {
211 vm_map_lookup_done(fs->map, fs->entry);
212 fs->lookup_still_valid = false;
217 unlock_vp(struct faultstate *fs)
220 if (fs->vp != NULL) {
227 fault_deallocate(struct faultstate *fs)
230 fault_page_release(&fs->m_cow);
231 fault_page_release(&fs->m);
232 vm_object_pip_wakeup(fs->object);
233 if (fs->object != fs->first_object) {
234 VM_OBJECT_WLOCK(fs->first_object);
235 fault_page_free(&fs->first_m);
236 VM_OBJECT_WUNLOCK(fs->first_object);
237 vm_object_pip_wakeup(fs->first_object);
239 vm_object_deallocate(fs->first_object);
245 unlock_and_deallocate(struct faultstate *fs)
248 VM_OBJECT_WUNLOCK(fs->object);
249 fault_deallocate(fs);
253 vm_fault_dirty(struct faultstate *fs, vm_page_t m)
257 if (((fs->prot & VM_PROT_WRITE) == 0 &&
258 (fs->fault_flags & VM_FAULT_DIRTY) == 0) ||
259 (m->oflags & VPO_UNMANAGED) != 0)
262 VM_PAGE_OBJECT_BUSY_ASSERT(m);
264 need_dirty = ((fs->fault_type & VM_PROT_WRITE) != 0 &&
265 (fs->fault_flags & VM_FAULT_WIRE) == 0) ||
266 (fs->fault_flags & VM_FAULT_DIRTY) != 0;
268 vm_object_set_writeable_dirty(m->object);
271 * If the fault is a write, we know that this page is being
272 * written NOW so dirty it explicitly to save on
273 * pmap_is_modified() calls later.
275 * Also, since the page is now dirty, we can possibly tell
276 * the pager to release any swap backing the page.
278 if (need_dirty && vm_page_set_dirty(m) == 0) {
280 * If this is a NOSYNC mmap we do not want to set PGA_NOSYNC
281 * if the page is already dirty to prevent data written with
282 * the expectation of being synced from not being synced.
283 * Likewise if this entry does not request NOSYNC then make
284 * sure the page isn't marked NOSYNC. Applications sharing
285 * data should use the same flags to avoid ping ponging.
287 if ((fs->entry->eflags & MAP_ENTRY_NOSYNC) != 0)
288 vm_page_aflag_set(m, PGA_NOSYNC);
290 vm_page_aflag_clear(m, PGA_NOSYNC);
296 * Unlocks fs.first_object and fs.map on success.
299 vm_fault_soft_fast(struct faultstate *fs)
302 #if VM_NRESERVLEVEL > 0
309 MPASS(fs->vp == NULL);
311 vm_object_busy(fs->first_object);
312 m = vm_page_lookup(fs->first_object, fs->first_pindex);
313 /* A busy page can be mapped for read|execute access. */
314 if (m == NULL || ((fs->prot & VM_PROT_WRITE) != 0 &&
315 vm_page_busied(m)) || !vm_page_all_valid(m)) {
321 #if VM_NRESERVLEVEL > 0
322 if ((m->flags & PG_FICTITIOUS) == 0 &&
323 (m_super = vm_reserv_to_superpage(m)) != NULL &&
324 rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start &&
325 roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end &&
326 (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) &
327 (pagesizes[m_super->psind] - 1)) && !fs->wired &&
328 pmap_ps_enabled(fs->map->pmap)) {
329 flags = PS_ALL_VALID;
330 if ((fs->prot & VM_PROT_WRITE) != 0) {
332 * Create a superpage mapping allowing write access
333 * only if none of the constituent pages are busy and
334 * all of them are already dirty (except possibly for
335 * the page that was faulted on).
337 flags |= PS_NONE_BUSY;
338 if ((fs->first_object->flags & OBJ_UNMANAGED) == 0)
339 flags |= PS_ALL_DIRTY;
341 if (vm_page_ps_test(m_super, flags, m)) {
343 psind = m_super->psind;
344 vaddr = rounddown2(vaddr, pagesizes[psind]);
345 /* Preset the modified bit for dirty superpages. */
346 if ((flags & PS_ALL_DIRTY) != 0)
347 fs->fault_type |= VM_PROT_WRITE;
351 rv = pmap_enter(fs->map->pmap, vaddr, m_map, fs->prot, fs->fault_type |
352 PMAP_ENTER_NOSLEEP | (fs->wired ? PMAP_ENTER_WIRED : 0), psind);
353 if (rv != KERN_SUCCESS)
355 if (fs->m_hold != NULL) {
359 if (psind == 0 && !fs->wired)
360 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true);
361 VM_OBJECT_RUNLOCK(fs->first_object);
362 vm_fault_dirty(fs, m);
363 vm_map_lookup_done(fs->map, fs->entry);
364 curthread->td_ru.ru_minflt++;
367 vm_object_unbusy(fs->first_object);
372 vm_fault_restore_map_lock(struct faultstate *fs)
375 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
376 MPASS(blockcount_read(&fs->first_object->paging_in_progress) > 0);
378 if (!vm_map_trylock_read(fs->map)) {
379 VM_OBJECT_WUNLOCK(fs->first_object);
380 vm_map_lock_read(fs->map);
381 VM_OBJECT_WLOCK(fs->first_object);
383 fs->lookup_still_valid = true;
387 vm_fault_populate_check_page(vm_page_t m)
391 * Check each page to ensure that the pager is obeying the
392 * interface: the page must be installed in the object, fully
393 * valid, and exclusively busied.
396 MPASS(vm_page_all_valid(m));
397 MPASS(vm_page_xbusied(m));
401 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first,
407 VM_OBJECT_ASSERT_WLOCKED(object);
408 MPASS(first <= last);
409 for (pidx = first, m = vm_page_lookup(object, pidx);
410 pidx <= last; pidx++, m = vm_page_next(m)) {
411 vm_fault_populate_check_page(m);
412 vm_page_deactivate(m);
418 vm_fault_populate(struct faultstate *fs)
422 vm_pindex_t map_first, map_last, pager_first, pager_last, pidx;
423 int bdry_idx, i, npages, psind, rv;
425 MPASS(fs->object == fs->first_object);
426 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
427 MPASS(blockcount_read(&fs->first_object->paging_in_progress) > 0);
428 MPASS(fs->first_object->backing_object == NULL);
429 MPASS(fs->lookup_still_valid);
431 pager_first = OFF_TO_IDX(fs->entry->offset);
432 pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1;
437 * Call the pager (driver) populate() method.
439 * There is no guarantee that the method will be called again
440 * if the current fault is for read, and a future fault is
441 * for write. Report the entry's maximum allowed protection
444 rv = vm_pager_populate(fs->first_object, fs->first_pindex,
445 fs->fault_type, fs->entry->max_protection, &pager_first,
448 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
449 if (rv == VM_PAGER_BAD) {
451 * VM_PAGER_BAD is the backdoor for a pager to request
452 * normal fault handling.
454 vm_fault_restore_map_lock(fs);
455 if (fs->map->timestamp != fs->map_generation)
456 return (KERN_RESTART);
457 return (KERN_NOT_RECEIVER);
459 if (rv != VM_PAGER_OK)
460 return (KERN_FAILURE); /* AKA SIGSEGV */
462 /* Ensure that the driver is obeying the interface. */
463 MPASS(pager_first <= pager_last);
464 MPASS(fs->first_pindex <= pager_last);
465 MPASS(fs->first_pindex >= pager_first);
466 MPASS(pager_last < fs->first_object->size);
468 vm_fault_restore_map_lock(fs);
469 bdry_idx = (fs->entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) >>
470 MAP_ENTRY_SPLIT_BOUNDARY_SHIFT;
471 if (fs->map->timestamp != fs->map_generation) {
473 vm_fault_populate_cleanup(fs->first_object, pager_first,
476 m = vm_page_lookup(fs->first_object, pager_first);
480 return (KERN_RESTART);
484 * The map is unchanged after our last unlock. Process the fault.
486 * First, the special case of largepage mappings, where
487 * populate only busies the first page in superpage run.
490 KASSERT(PMAP_HAS_LARGEPAGES,
491 ("missing pmap support for large pages"));
492 m = vm_page_lookup(fs->first_object, pager_first);
493 vm_fault_populate_check_page(m);
494 VM_OBJECT_WUNLOCK(fs->first_object);
495 vaddr = fs->entry->start + IDX_TO_OFF(pager_first) -
497 /* assert alignment for entry */
498 KASSERT((vaddr & (pagesizes[bdry_idx] - 1)) == 0,
499 ("unaligned superpage start %#jx pager_first %#jx offset %#jx vaddr %#jx",
500 (uintmax_t)fs->entry->start, (uintmax_t)pager_first,
501 (uintmax_t)fs->entry->offset, (uintmax_t)vaddr));
502 KASSERT((VM_PAGE_TO_PHYS(m) & (pagesizes[bdry_idx] - 1)) == 0,
503 ("unaligned superpage m %p %#jx", m,
504 (uintmax_t)VM_PAGE_TO_PHYS(m)));
505 rv = pmap_enter(fs->map->pmap, vaddr, m, fs->prot,
506 fs->fault_type | (fs->wired ? PMAP_ENTER_WIRED : 0) |
507 PMAP_ENTER_LARGEPAGE, bdry_idx);
508 VM_OBJECT_WLOCK(fs->first_object);
510 if (rv != KERN_SUCCESS)
512 if ((fs->fault_flags & VM_FAULT_WIRE) != 0) {
513 for (i = 0; i < atop(pagesizes[bdry_idx]); i++)
516 if (fs->m_hold != NULL) {
517 *fs->m_hold = m + (fs->first_pindex - pager_first);
518 vm_page_wire(*fs->m_hold);
524 * The range [pager_first, pager_last] that is given to the
525 * pager is only a hint. The pager may populate any range
526 * within the object that includes the requested page index.
527 * In case the pager expanded the range, clip it to fit into
530 map_first = OFF_TO_IDX(fs->entry->offset);
531 if (map_first > pager_first) {
532 vm_fault_populate_cleanup(fs->first_object, pager_first,
534 pager_first = map_first;
536 map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1;
537 if (map_last < pager_last) {
538 vm_fault_populate_cleanup(fs->first_object, map_last + 1,
540 pager_last = map_last;
542 for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx);
544 pidx += npages, m = vm_page_next(&m[npages - 1])) {
545 vaddr = fs->entry->start + IDX_TO_OFF(pidx) - fs->entry->offset;
548 if (psind > 0 && ((vaddr & (pagesizes[psind] - 1)) != 0 ||
549 pidx + OFF_TO_IDX(pagesizes[psind]) - 1 > pager_last ||
550 !pmap_ps_enabled(fs->map->pmap) || fs->wired))
553 npages = atop(pagesizes[psind]);
554 for (i = 0; i < npages; i++) {
555 vm_fault_populate_check_page(&m[i]);
556 vm_fault_dirty(fs, &m[i]);
558 VM_OBJECT_WUNLOCK(fs->first_object);
559 rv = pmap_enter(fs->map->pmap, vaddr, m, fs->prot, fs->fault_type |
560 (fs->wired ? PMAP_ENTER_WIRED : 0), psind);
563 * pmap_enter() may fail for a superpage mapping if additional
564 * protection policies prevent the full mapping.
565 * For example, this will happen on amd64 if the entire
566 * address range does not share the same userspace protection
567 * key. Revert to single-page mappings if this happens.
569 MPASS(rv == KERN_SUCCESS ||
570 (psind > 0 && rv == KERN_PROTECTION_FAILURE));
571 if (__predict_false(psind > 0 &&
572 rv == KERN_PROTECTION_FAILURE)) {
573 for (i = 0; i < npages; i++) {
574 rv = pmap_enter(fs->map->pmap, vaddr + ptoa(i),
575 &m[i], fs->prot, fs->fault_type |
576 (fs->wired ? PMAP_ENTER_WIRED : 0), 0);
577 MPASS(rv == KERN_SUCCESS);
581 VM_OBJECT_WLOCK(fs->first_object);
582 for (i = 0; i < npages; i++) {
583 if ((fs->fault_flags & VM_FAULT_WIRE) != 0)
586 vm_page_activate(&m[i]);
587 if (fs->m_hold != NULL && m[i].pindex == fs->first_pindex) {
588 (*fs->m_hold) = &m[i];
591 vm_page_xunbusy(&m[i]);
595 curthread->td_ru.ru_majflt++;
599 static int prot_fault_translation;
600 SYSCTL_INT(_machdep, OID_AUTO, prot_fault_translation, CTLFLAG_RWTUN,
601 &prot_fault_translation, 0,
602 "Control signal to deliver on protection fault");
604 /* compat definition to keep common code for signal translation */
605 #define UCODE_PAGEFLT 12
607 _Static_assert(UCODE_PAGEFLT == T_PAGEFLT, "T_PAGEFLT");
613 * Handle a page fault occurring at the given address,
614 * requiring the given permissions, in the map specified.
615 * If successful, the page is inserted into the
616 * associated physical map.
618 * NOTE: the given address should be truncated to the
619 * proper page address.
621 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
622 * a standard error specifying why the fault is fatal is returned.
624 * The map in question must be referenced, and remains so.
625 * Caller may hold no locks.
628 vm_fault_trap(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
629 int fault_flags, int *signo, int *ucode)
633 MPASS(signo == NULL || ucode != NULL);
635 if (map != kernel_map && KTRPOINT(curthread, KTR_FAULT))
636 ktrfault(vaddr, fault_type);
638 result = vm_fault(map, trunc_page(vaddr), fault_type, fault_flags,
640 KASSERT(result == KERN_SUCCESS || result == KERN_FAILURE ||
641 result == KERN_INVALID_ADDRESS ||
642 result == KERN_RESOURCE_SHORTAGE ||
643 result == KERN_PROTECTION_FAILURE ||
644 result == KERN_OUT_OF_BOUNDS,
645 ("Unexpected Mach error %d from vm_fault()", result));
647 if (map != kernel_map && KTRPOINT(curthread, KTR_FAULTEND))
650 if (result != KERN_SUCCESS && signo != NULL) {
653 case KERN_INVALID_ADDRESS:
655 *ucode = SEGV_MAPERR;
657 case KERN_RESOURCE_SHORTAGE:
661 case KERN_OUT_OF_BOUNDS:
665 case KERN_PROTECTION_FAILURE:
666 if (prot_fault_translation == 0) {
668 * Autodetect. This check also covers
669 * the images without the ABI-tag ELF
672 if (SV_CURPROC_ABI() == SV_ABI_FREEBSD &&
673 curproc->p_osrel >= P_OSREL_SIGSEGV) {
675 *ucode = SEGV_ACCERR;
678 *ucode = UCODE_PAGEFLT;
680 } else if (prot_fault_translation == 1) {
681 /* Always compat mode. */
683 *ucode = UCODE_PAGEFLT;
685 /* Always SIGSEGV mode. */
687 *ucode = SEGV_ACCERR;
691 KASSERT(0, ("Unexpected Mach error %d from vm_fault()",
700 vm_fault_lock_vnode(struct faultstate *fs, bool objlocked)
705 if (fs->object->type != OBJT_VNODE)
706 return (KERN_SUCCESS);
707 vp = fs->object->handle;
709 ASSERT_VOP_LOCKED(vp, "saved vnode is not locked");
710 return (KERN_SUCCESS);
714 * Perform an unlock in case the desired vnode changed while
715 * the map was unlocked during a retry.
719 locked = VOP_ISLOCKED(vp);
720 if (locked != LK_EXCLUSIVE)
724 * We must not sleep acquiring the vnode lock while we have
725 * the page exclusive busied or the object's
726 * paging-in-progress count incremented. Otherwise, we could
729 error = vget(vp, locked | LK_CANRECURSE | LK_NOWAIT);
732 return (KERN_SUCCESS);
737 unlock_and_deallocate(fs);
739 fault_deallocate(fs);
740 error = vget(vp, locked | LK_RETRY | LK_CANRECURSE);
743 KASSERT(error == 0, ("vm_fault: vget failed %d", error));
744 return (KERN_RESOURCE_SHORTAGE);
748 * Calculate the desired readahead. Handle drop-behind.
750 * Returns the number of readahead blocks to pass to the pager.
753 vm_fault_readahead(struct faultstate *fs)
758 KASSERT(fs->lookup_still_valid, ("map unlocked"));
759 era = fs->entry->read_ahead;
760 behavior = vm_map_entry_behavior(fs->entry);
761 if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
763 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
764 nera = VM_FAULT_READ_AHEAD_MAX;
765 if (fs->vaddr == fs->entry->next_read)
766 vm_fault_dontneed(fs, fs->vaddr, nera);
767 } else if (fs->vaddr == fs->entry->next_read) {
769 * This is a sequential fault. Arithmetically
770 * increase the requested number of pages in
771 * the read-ahead window. The requested
772 * number of pages is "# of sequential faults
773 * x (read ahead min + 1) + read ahead min"
775 nera = VM_FAULT_READ_AHEAD_MIN;
778 if (nera > VM_FAULT_READ_AHEAD_MAX)
779 nera = VM_FAULT_READ_AHEAD_MAX;
781 if (era == VM_FAULT_READ_AHEAD_MAX)
782 vm_fault_dontneed(fs, fs->vaddr, nera);
785 * This is a non-sequential fault.
791 * A read lock on the map suffices to update
792 * the read ahead count safely.
794 fs->entry->read_ahead = nera;
801 vm_fault_lookup(struct faultstate *fs)
805 KASSERT(!fs->lookup_still_valid,
806 ("vm_fault_lookup: Map already locked."));
807 result = vm_map_lookup(&fs->map, fs->vaddr, fs->fault_type |
808 VM_PROT_FAULT_LOOKUP, &fs->entry, &fs->first_object,
809 &fs->first_pindex, &fs->prot, &fs->wired);
810 if (result != KERN_SUCCESS) {
815 fs->map_generation = fs->map->timestamp;
817 if (fs->entry->eflags & MAP_ENTRY_NOFAULT) {
818 panic("%s: fault on nofault entry, addr: %#lx",
819 __func__, (u_long)fs->vaddr);
822 if (fs->entry->eflags & MAP_ENTRY_IN_TRANSITION &&
823 fs->entry->wiring_thread != curthread) {
824 vm_map_unlock_read(fs->map);
825 vm_map_lock(fs->map);
826 if (vm_map_lookup_entry(fs->map, fs->vaddr, &fs->entry) &&
827 (fs->entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
829 fs->entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
830 vm_map_unlock_and_wait(fs->map, 0);
832 vm_map_unlock(fs->map);
833 return (KERN_RESOURCE_SHORTAGE);
836 MPASS((fs->entry->eflags & MAP_ENTRY_GUARD) == 0);
839 fs->fault_type = fs->prot | (fs->fault_type & VM_PROT_COPY);
841 KASSERT((fs->fault_flags & VM_FAULT_WIRE) == 0,
842 ("!fs->wired && VM_FAULT_WIRE"));
843 fs->lookup_still_valid = true;
845 return (KERN_SUCCESS);
849 vm_fault_relookup(struct faultstate *fs)
851 vm_object_t retry_object;
852 vm_pindex_t retry_pindex;
853 vm_prot_t retry_prot;
856 if (!vm_map_trylock_read(fs->map))
857 return (KERN_RESTART);
859 fs->lookup_still_valid = true;
860 if (fs->map->timestamp == fs->map_generation)
861 return (KERN_SUCCESS);
863 result = vm_map_lookup_locked(&fs->map, fs->vaddr, fs->fault_type,
864 &fs->entry, &retry_object, &retry_pindex, &retry_prot,
866 if (result != KERN_SUCCESS) {
868 * If retry of map lookup would have blocked then
869 * retry fault from start.
871 if (result == KERN_FAILURE)
872 return (KERN_RESTART);
875 if (retry_object != fs->first_object ||
876 retry_pindex != fs->first_pindex)
877 return (KERN_RESTART);
880 * Check whether the protection has changed or the object has
881 * been copied while we left the map unlocked. Changing from
882 * read to write permission is OK - we leave the page
883 * write-protected, and catch the write fault. Changing from
884 * write to read permission means that we can't mark the page
885 * write-enabled after all.
887 fs->prot &= retry_prot;
888 fs->fault_type &= retry_prot;
890 return (KERN_RESTART);
892 /* Reassert because wired may have changed. */
893 KASSERT(fs->wired || (fs->fault_flags & VM_FAULT_WIRE) == 0,
894 ("!wired && VM_FAULT_WIRE"));
896 return (KERN_SUCCESS);
900 vm_fault_cow(struct faultstate *fs)
902 bool is_first_object_locked;
904 KASSERT(fs->object != fs->first_object,
905 ("source and target COW objects are identical"));
908 * This allows pages to be virtually copied from a backing_object
909 * into the first_object, where the backing object has no other
910 * refs to it, and cannot gain any more refs. Instead of a bcopy,
911 * we just move the page from the backing object to the first
912 * object. Note that we must mark the page dirty in the first
913 * object so that it will go out to swap when needed.
915 is_first_object_locked = false;
918 * Only one shadow object and no other refs.
920 fs->object->shadow_count == 1 && fs->object->ref_count == 1 &&
922 * No other ways to look the object up
924 fs->object->handle == NULL && (fs->object->flags & OBJ_ANON) != 0 &&
926 * We don't chase down the shadow chain and we can acquire locks.
928 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs->first_object)) &&
929 fs->object == fs->first_object->backing_object &&
930 VM_OBJECT_TRYWLOCK(fs->object)) {
932 * Remove but keep xbusy for replace. fs->m is moved into
933 * fs->first_object and left busy while fs->first_m is
934 * conditionally freed.
936 vm_page_remove_xbusy(fs->m);
937 vm_page_replace(fs->m, fs->first_object, fs->first_pindex,
939 vm_page_dirty(fs->m);
940 #if VM_NRESERVLEVEL > 0
942 * Rename the reservation.
944 vm_reserv_rename(fs->m, fs->first_object, fs->object,
945 OFF_TO_IDX(fs->first_object->backing_object_offset));
947 VM_OBJECT_WUNLOCK(fs->object);
948 VM_OBJECT_WUNLOCK(fs->first_object);
951 VM_CNT_INC(v_cow_optim);
953 if (is_first_object_locked)
954 VM_OBJECT_WUNLOCK(fs->first_object);
956 * Oh, well, lets copy it.
958 pmap_copy_page(fs->m, fs->first_m);
959 vm_page_valid(fs->first_m);
960 if (fs->wired && (fs->fault_flags & VM_FAULT_WIRE) == 0) {
961 vm_page_wire(fs->first_m);
962 vm_page_unwire(fs->m, PQ_INACTIVE);
965 * Save the cow page to be released after
966 * pmap_enter is complete.
972 * Typically, the shadow object is either private to this
973 * address space (OBJ_ONEMAPPING) or its pages are read only.
974 * In the highly unusual case where the pages of a shadow object
975 * are read/write shared between this and other address spaces,
976 * we need to ensure that any pmap-level mappings to the
977 * original, copy-on-write page from the backing object are
978 * removed from those other address spaces.
980 * The flag check is racy, but this is tolerable: if
981 * OBJ_ONEMAPPING is cleared after the check, the busy state
982 * ensures that new mappings of m_cow can't be created.
983 * pmap_enter() will replace an existing mapping in the current
984 * address space. If OBJ_ONEMAPPING is set after the check,
985 * removing mappings will at worse trigger some unnecessary page
988 vm_page_assert_xbusied(fs->m_cow);
989 if ((fs->first_object->flags & OBJ_ONEMAPPING) == 0)
990 pmap_remove_all(fs->m_cow);
993 vm_object_pip_wakeup(fs->object);
996 * Only use the new page below...
998 fs->object = fs->first_object;
999 fs->pindex = fs->first_pindex;
1000 fs->m = fs->first_m;
1001 VM_CNT_INC(v_cow_faults);
1002 curthread->td_cow++;
1006 vm_fault_next(struct faultstate *fs)
1008 vm_object_t next_object;
1011 * The requested page does not exist at this object/
1012 * offset. Remove the invalid page from the object,
1013 * waking up anyone waiting for it, and continue on to
1014 * the next object. However, if this is the top-level
1015 * object, we must leave the busy page in place to
1016 * prevent another process from rushing past us, and
1017 * inserting the page in that object at the same time
1020 if (fs->object == fs->first_object) {
1021 fs->first_m = fs->m;
1024 fault_page_free(&fs->m);
1027 * Move on to the next object. Lock the next object before
1028 * unlocking the current one.
1030 VM_OBJECT_ASSERT_WLOCKED(fs->object);
1031 next_object = fs->object->backing_object;
1032 if (next_object == NULL)
1034 MPASS(fs->first_m != NULL);
1035 KASSERT(fs->object != next_object, ("object loop %p", next_object));
1036 VM_OBJECT_WLOCK(next_object);
1037 vm_object_pip_add(next_object, 1);
1038 if (fs->object != fs->first_object)
1039 vm_object_pip_wakeup(fs->object);
1040 fs->pindex += OFF_TO_IDX(fs->object->backing_object_offset);
1041 VM_OBJECT_WUNLOCK(fs->object);
1042 fs->object = next_object;
1048 vm_fault_zerofill(struct faultstate *fs)
1052 * If there's no object left, fill the page in the top
1053 * object with zeros.
1055 if (fs->object != fs->first_object) {
1056 vm_object_pip_wakeup(fs->object);
1057 fs->object = fs->first_object;
1058 fs->pindex = fs->first_pindex;
1060 MPASS(fs->first_m != NULL);
1061 MPASS(fs->m == NULL);
1062 fs->m = fs->first_m;
1066 * Zero the page if necessary and mark it valid.
1068 if ((fs->m->flags & PG_ZERO) == 0) {
1069 pmap_zero_page(fs->m);
1071 VM_CNT_INC(v_ozfod);
1074 vm_page_valid(fs->m);
1078 * Initiate page fault after timeout. Returns true if caller should
1079 * do vm_waitpfault() after the call.
1082 vm_fault_allocate_oom(struct faultstate *fs)
1086 unlock_and_deallocate(fs);
1087 if (vm_pfault_oom_attempts < 0)
1089 if (!fs->oom_started) {
1090 fs->oom_started = true;
1091 getmicrotime(&fs->oom_start_time);
1096 timevalsub(&now, &fs->oom_start_time);
1097 if (now.tv_sec < vm_pfault_oom_attempts * vm_pfault_oom_wait)
1102 "proc %d (%s) failed to alloc page on fault, starting OOM\n",
1103 curproc->p_pid, curproc->p_comm);
1104 vm_pageout_oom(VM_OOM_MEM_PF);
1105 fs->oom_started = false;
1110 * Allocate a page directly or via the object populate method.
1113 vm_fault_allocate(struct faultstate *fs)
1115 struct domainset *dset;
1119 if ((fs->object->flags & OBJ_SIZEVNLOCK) != 0) {
1120 rv = vm_fault_lock_vnode(fs, true);
1121 MPASS(rv == KERN_SUCCESS || rv == KERN_RESOURCE_SHORTAGE);
1122 if (rv == KERN_RESOURCE_SHORTAGE)
1126 if (fs->pindex >= fs->object->size)
1127 return (KERN_OUT_OF_BOUNDS);
1129 if (fs->object == fs->first_object &&
1130 (fs->first_object->flags & OBJ_POPULATE) != 0 &&
1131 fs->first_object->shadow_count == 0) {
1132 rv = vm_fault_populate(fs);
1136 case KERN_PROTECTION_FAILURE:
1139 case KERN_NOT_RECEIVER:
1141 * Pager's populate() method
1142 * returned VM_PAGER_BAD.
1146 panic("inconsistent return codes");
1151 * Allocate a new page for this object/offset pair.
1153 * Unlocked read of the p_flag is harmless. At worst, the P_KILLED
1154 * might be not observed there, and allocation can fail, causing
1155 * restart and new reading of the p_flag.
1157 dset = fs->object->domain.dr_policy;
1159 dset = curthread->td_domain.dr_policy;
1160 if (!vm_page_count_severe_set(&dset->ds_mask) || P_KILLED(curproc)) {
1161 #if VM_NRESERVLEVEL > 0
1162 vm_object_color(fs->object, atop(fs->vaddr) - fs->pindex);
1164 alloc_req = P_KILLED(curproc) ?
1165 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
1166 if (fs->object->type != OBJT_VNODE &&
1167 fs->object->backing_object == NULL)
1168 alloc_req |= VM_ALLOC_ZERO;
1169 fs->m = vm_page_alloc(fs->object, fs->pindex, alloc_req);
1171 if (fs->m == NULL) {
1172 if (vm_fault_allocate_oom(fs))
1173 vm_waitpfault(dset, vm_pfault_oom_wait * hz);
1174 return (KERN_RESOURCE_SHORTAGE);
1176 fs->oom_started = false;
1178 return (KERN_NOT_RECEIVER);
1182 * Call the pager to retrieve the page if there is a chance
1183 * that the pager has it, and potentially retrieve additional
1184 * pages at the same time.
1187 vm_fault_getpages(struct faultstate *fs, int nera, int *behindp, int *aheadp)
1189 vm_offset_t e_end, e_start;
1190 int ahead, behind, cluster_offset, rv;
1194 * Prepare for unlocking the map. Save the map
1195 * entry's start and end addresses, which are used to
1196 * optimize the size of the pager operation below.
1197 * Even if the map entry's addresses change after
1198 * unlocking the map, using the saved addresses is
1201 e_start = fs->entry->start;
1202 e_end = fs->entry->end;
1203 behavior = vm_map_entry_behavior(fs->entry);
1206 * Release the map lock before locking the vnode or
1207 * sleeping in the pager. (If the current object has
1208 * a shadow, then an earlier iteration of this loop
1209 * may have already unlocked the map.)
1213 rv = vm_fault_lock_vnode(fs, false);
1214 MPASS(rv == KERN_SUCCESS || rv == KERN_RESOURCE_SHORTAGE);
1215 if (rv == KERN_RESOURCE_SHORTAGE)
1217 KASSERT(fs->vp == NULL || !fs->map->system_map,
1218 ("vm_fault: vnode-backed object mapped by system map"));
1221 * Page in the requested page and hint the pager,
1222 * that it may bring up surrounding pages.
1224 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM ||
1225 P_KILLED(curproc)) {
1229 /* Is this a sequential fault? */
1235 * Request a cluster of pages that is
1236 * aligned to a VM_FAULT_READ_DEFAULT
1237 * page offset boundary within the
1238 * object. Alignment to a page offset
1239 * boundary is more likely to coincide
1240 * with the underlying file system
1241 * block than alignment to a virtual
1244 cluster_offset = fs->pindex % VM_FAULT_READ_DEFAULT;
1245 behind = ulmin(cluster_offset,
1246 atop(fs->vaddr - e_start));
1247 ahead = VM_FAULT_READ_DEFAULT - 1 - cluster_offset;
1249 ahead = ulmin(ahead, atop(e_end - fs->vaddr) - 1);
1253 rv = vm_pager_get_pages(fs->object, &fs->m, 1, behindp, aheadp);
1254 if (rv == VM_PAGER_OK)
1255 return (KERN_SUCCESS);
1256 if (rv == VM_PAGER_ERROR)
1257 printf("vm_fault: pager read error, pid %d (%s)\n",
1258 curproc->p_pid, curproc->p_comm);
1260 * If an I/O error occurred or the requested page was
1261 * outside the range of the pager, clean up and return
1264 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD)
1265 return (KERN_OUT_OF_BOUNDS);
1266 return (KERN_NOT_RECEIVER);
1270 * Wait/Retry if the page is busy. We have to do this if the page is
1271 * either exclusive or shared busy because the vm_pager may be using
1272 * read busy for pageouts (and even pageins if it is the vnode pager),
1273 * and we could end up trying to pagein and pageout the same page
1276 * We can theoretically allow the busy case on a read fault if the page
1277 * is marked valid, but since such pages are typically already pmap'd,
1278 * putting that special case in might be more effort then it is worth.
1279 * We cannot under any circumstances mess around with a shared busied
1280 * page except, perhaps, to pmap it.
1283 vm_fault_busy_sleep(struct faultstate *fs)
1286 * Reference the page before unlocking and
1287 * sleeping so that the page daemon is less
1288 * likely to reclaim it.
1290 vm_page_aflag_set(fs->m, PGA_REFERENCED);
1291 if (fs->object != fs->first_object) {
1292 fault_page_release(&fs->first_m);
1293 vm_object_pip_wakeup(fs->first_object);
1295 vm_object_pip_wakeup(fs->object);
1297 if (fs->m == vm_page_lookup(fs->object, fs->pindex))
1298 vm_page_busy_sleep(fs->m, "vmpfw", false);
1300 VM_OBJECT_WUNLOCK(fs->object);
1301 VM_CNT_INC(v_intrans);
1302 vm_object_deallocate(fs->first_object);
1306 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
1307 int fault_flags, vm_page_t *m_hold)
1309 struct faultstate fs;
1310 int ahead, behind, faultcount;
1311 int nera, result, rv;
1312 bool dead, hardfault;
1314 VM_CNT_INC(v_vm_faults);
1316 if ((curthread->td_pflags & TDP_NOFAULTING) != 0)
1317 return (KERN_PROTECTION_FAILURE);
1322 fs.fault_flags = fault_flags;
1324 fs.lookup_still_valid = false;
1325 fs.oom_started = false;
1331 fs.fault_type = fault_type;
1334 * Find the backing store object and offset into it to begin the
1337 result = vm_fault_lookup(&fs);
1338 if (result != KERN_SUCCESS) {
1339 if (result == KERN_RESOURCE_SHORTAGE)
1345 * Try to avoid lock contention on the top-level object through
1346 * special-case handling of some types of page faults, specifically,
1347 * those that are mapping an existing page from the top-level object.
1348 * Under this condition, a read lock on the object suffices, allowing
1349 * multiple page faults of a similar type to run in parallel.
1351 if (fs.vp == NULL /* avoid locked vnode leak */ &&
1352 (fs.entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) == 0 &&
1353 (fs.fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0) {
1354 VM_OBJECT_RLOCK(fs.first_object);
1355 rv = vm_fault_soft_fast(&fs);
1356 if (rv == KERN_SUCCESS)
1358 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
1359 VM_OBJECT_RUNLOCK(fs.first_object);
1360 VM_OBJECT_WLOCK(fs.first_object);
1363 VM_OBJECT_WLOCK(fs.first_object);
1367 * Make a reference to this object to prevent its disposal while we
1368 * are messing with it. Once we have the reference, the map is free
1369 * to be diddled. Since objects reference their shadows (and copies),
1370 * they will stay around as well.
1372 * Bump the paging-in-progress count to prevent size changes (e.g.
1373 * truncation operations) during I/O.
1375 vm_object_reference_locked(fs.first_object);
1376 vm_object_pip_add(fs.first_object, 1);
1378 fs.m_cow = fs.m = fs.first_m = NULL;
1381 * Search for the page at object/offset.
1383 fs.object = fs.first_object;
1384 fs.pindex = fs.first_pindex;
1386 if ((fs.entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) != 0) {
1387 rv = vm_fault_allocate(&fs);
1390 unlock_and_deallocate(&fs);
1392 case KERN_RESOURCE_SHORTAGE:
1396 case KERN_PROTECTION_FAILURE:
1397 case KERN_OUT_OF_BOUNDS:
1398 unlock_and_deallocate(&fs);
1400 case KERN_NOT_RECEIVER:
1403 panic("vm_fault: Unhandled rv %d", rv);
1408 KASSERT(fs.m == NULL,
1409 ("page still set %p at loop start", fs.m));
1411 * If the object is marked for imminent termination,
1412 * we retry here, since the collapse pass has raced
1413 * with us. Otherwise, if we see terminally dead
1414 * object, return fail.
1416 if ((fs.object->flags & OBJ_DEAD) != 0) {
1417 dead = fs.object->type == OBJT_DEAD;
1418 unlock_and_deallocate(&fs);
1420 return (KERN_PROTECTION_FAILURE);
1426 * See if page is resident
1428 fs.m = vm_page_lookup(fs.object, fs.pindex);
1430 if (vm_page_tryxbusy(fs.m) == 0) {
1431 vm_fault_busy_sleep(&fs);
1436 * The page is marked busy for other processes and the
1437 * pagedaemon. If it still is completely valid we
1440 if (vm_page_all_valid(fs.m)) {
1441 VM_OBJECT_WUNLOCK(fs.object);
1442 break; /* break to PAGE HAS BEEN FOUND. */
1445 VM_OBJECT_ASSERT_WLOCKED(fs.object);
1448 * Page is not resident. If the pager might contain the page
1449 * or this is the beginning of the search, allocate a new
1450 * page. (Default objects are zero-fill, so there is no real
1453 if (fs.m == NULL && (fs.object->type != OBJT_DEFAULT ||
1454 fs.object == fs.first_object)) {
1455 rv = vm_fault_allocate(&fs);
1458 unlock_and_deallocate(&fs);
1460 case KERN_RESOURCE_SHORTAGE:
1464 case KERN_PROTECTION_FAILURE:
1465 case KERN_OUT_OF_BOUNDS:
1466 unlock_and_deallocate(&fs);
1468 case KERN_NOT_RECEIVER:
1471 panic("vm_fault: Unhandled rv %d", rv);
1476 * Default objects have no pager so no exclusive busy exists
1477 * to protect this page in the chain. Skip to the next
1478 * object without dropping the lock to preserve atomicity of
1481 if (fs.object->type != OBJT_DEFAULT) {
1483 * At this point, we have either allocated a new page
1484 * or found an existing page that is only partially
1487 * We hold a reference on the current object and the
1488 * page is exclusive busied. The exclusive busy
1489 * prevents simultaneous faults and collapses while
1490 * the object lock is dropped.
1492 VM_OBJECT_WUNLOCK(fs.object);
1495 * If the pager for the current object might have
1496 * the page, then determine the number of additional
1497 * pages to read and potentially reprioritize
1498 * previously read pages for earlier reclamation.
1499 * These operations should only be performed once per
1500 * page fault. Even if the current pager doesn't
1501 * have the page, the number of additional pages to
1502 * read will apply to subsequent objects in the
1505 if (nera == -1 && !P_KILLED(curproc))
1506 nera = vm_fault_readahead(&fs);
1508 rv = vm_fault_getpages(&fs, nera, &behind, &ahead);
1509 if (rv == KERN_SUCCESS) {
1510 faultcount = behind + 1 + ahead;
1512 break; /* break to PAGE HAS BEEN FOUND. */
1514 if (rv == KERN_RESOURCE_SHORTAGE)
1516 VM_OBJECT_WLOCK(fs.object);
1517 if (rv == KERN_OUT_OF_BOUNDS) {
1518 fault_page_free(&fs.m);
1519 unlock_and_deallocate(&fs);
1525 * The page was not found in the current object. Try to
1526 * traverse into a backing object or zero fill if none is
1529 if (vm_fault_next(&fs))
1531 if ((fs.fault_flags & VM_FAULT_NOFILL) != 0) {
1532 if (fs.first_object == fs.object)
1533 fault_page_free(&fs.first_m);
1534 unlock_and_deallocate(&fs);
1535 return (KERN_OUT_OF_BOUNDS);
1537 VM_OBJECT_WUNLOCK(fs.object);
1538 vm_fault_zerofill(&fs);
1539 /* Don't try to prefault neighboring pages. */
1541 break; /* break to PAGE HAS BEEN FOUND. */
1545 * PAGE HAS BEEN FOUND. A valid page has been found and exclusively
1546 * busied. The object lock must no longer be held.
1548 vm_page_assert_xbusied(fs.m);
1549 VM_OBJECT_ASSERT_UNLOCKED(fs.object);
1552 * If the page is being written, but isn't already owned by the
1553 * top-level object, we have to copy it into a new page owned by the
1556 if (fs.object != fs.first_object) {
1558 * We only really need to copy if we want to write it.
1560 if ((fs.fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1563 * We only try to prefault read-only mappings to the
1564 * neighboring pages when this copy-on-write fault is
1565 * a hard fault. In other cases, trying to prefault
1566 * is typically wasted effort.
1568 if (faultcount == 0)
1572 fs.prot &= ~VM_PROT_WRITE;
1577 * We must verify that the maps have not changed since our last
1580 if (!fs.lookup_still_valid) {
1581 result = vm_fault_relookup(&fs);
1582 if (result != KERN_SUCCESS) {
1583 fault_deallocate(&fs);
1584 if (result == KERN_RESTART)
1589 VM_OBJECT_ASSERT_UNLOCKED(fs.object);
1592 * If the page was filled by a pager, save the virtual address that
1593 * should be faulted on next under a sequential access pattern to the
1594 * map entry. A read lock on the map suffices to update this address
1598 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE;
1601 * Page must be completely valid or it is not fit to
1602 * map into user space. vm_pager_get_pages() ensures this.
1604 vm_page_assert_xbusied(fs.m);
1605 KASSERT(vm_page_all_valid(fs.m),
1606 ("vm_fault: page %p partially invalid", fs.m));
1608 vm_fault_dirty(&fs, fs.m);
1611 * Put this page into the physical map. We had to do the unlock above
1612 * because pmap_enter() may sleep. We don't put the page
1613 * back on the active queue until later so that the pageout daemon
1614 * won't find it (yet).
1616 pmap_enter(fs.map->pmap, vaddr, fs.m, fs.prot,
1617 fs.fault_type | (fs.wired ? PMAP_ENTER_WIRED : 0), 0);
1618 if (faultcount != 1 && (fs.fault_flags & VM_FAULT_WIRE) == 0 &&
1620 vm_fault_prefault(&fs, vaddr,
1621 faultcount > 0 ? behind : PFBAK,
1622 faultcount > 0 ? ahead : PFFOR, false);
1625 * If the page is not wired down, then put it where the pageout daemon
1628 if ((fs.fault_flags & VM_FAULT_WIRE) != 0)
1631 vm_page_activate(fs.m);
1632 if (fs.m_hold != NULL) {
1633 (*fs.m_hold) = fs.m;
1636 vm_page_xunbusy(fs.m);
1640 * Unlock everything, and return
1642 fault_deallocate(&fs);
1644 VM_CNT_INC(v_io_faults);
1645 curthread->td_ru.ru_majflt++;
1647 if (racct_enable && fs.object->type == OBJT_VNODE) {
1649 if ((fs.fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1650 racct_add_force(curproc, RACCT_WRITEBPS,
1651 PAGE_SIZE + behind * PAGE_SIZE);
1652 racct_add_force(curproc, RACCT_WRITEIOPS, 1);
1654 racct_add_force(curproc, RACCT_READBPS,
1655 PAGE_SIZE + ahead * PAGE_SIZE);
1656 racct_add_force(curproc, RACCT_READIOPS, 1);
1658 PROC_UNLOCK(curproc);
1662 curthread->td_ru.ru_minflt++;
1664 return (KERN_SUCCESS);
1668 * Speed up the reclamation of pages that precede the faulting pindex within
1669 * the first object of the shadow chain. Essentially, perform the equivalent
1670 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes
1671 * the faulting pindex by the cluster size when the pages read by vm_fault()
1672 * cross a cluster-size boundary. The cluster size is the greater of the
1673 * smallest superpage size and VM_FAULT_DONTNEED_MIN.
1675 * When "fs->first_object" is a shadow object, the pages in the backing object
1676 * that precede the faulting pindex are deactivated by vm_fault(). So, this
1677 * function must only be concerned with pages in the first object.
1680 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
1682 vm_map_entry_t entry;
1683 vm_object_t first_object, object;
1684 vm_offset_t end, start;
1685 vm_page_t m, m_next;
1686 vm_pindex_t pend, pstart;
1689 object = fs->object;
1690 VM_OBJECT_ASSERT_UNLOCKED(object);
1691 first_object = fs->first_object;
1692 /* Neither fictitious nor unmanaged pages can be reclaimed. */
1693 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1694 VM_OBJECT_RLOCK(first_object);
1695 size = VM_FAULT_DONTNEED_MIN;
1696 if (MAXPAGESIZES > 1 && size < pagesizes[1])
1697 size = pagesizes[1];
1698 end = rounddown2(vaddr, size);
1699 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) &&
1700 (entry = fs->entry)->start < end) {
1701 if (end - entry->start < size)
1702 start = entry->start;
1705 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED);
1706 pstart = OFF_TO_IDX(entry->offset) + atop(start -
1708 m_next = vm_page_find_least(first_object, pstart);
1709 pend = OFF_TO_IDX(entry->offset) + atop(end -
1711 while ((m = m_next) != NULL && m->pindex < pend) {
1712 m_next = TAILQ_NEXT(m, listq);
1713 if (!vm_page_all_valid(m) ||
1718 * Don't clear PGA_REFERENCED, since it would
1719 * likely represent a reference by a different
1722 * Typically, at this point, prefetched pages
1723 * are still in the inactive queue. Only
1724 * pages that triggered page faults are in the
1725 * active queue. The test for whether the page
1726 * is in the inactive queue is racy; in the
1727 * worst case we will requeue the page
1730 if (!vm_page_inactive(m))
1731 vm_page_deactivate(m);
1734 VM_OBJECT_RUNLOCK(first_object);
1739 * vm_fault_prefault provides a quick way of clustering
1740 * pagefaults into a processes address space. It is a "cousin"
1741 * of vm_map_pmap_enter, except it runs at page fault time instead
1745 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1746 int backward, int forward, bool obj_locked)
1749 vm_map_entry_t entry;
1750 vm_object_t backing_object, lobject;
1751 vm_offset_t addr, starta;
1756 pmap = fs->map->pmap;
1757 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1762 if (addra < backward * PAGE_SIZE) {
1763 starta = entry->start;
1765 starta = addra - backward * PAGE_SIZE;
1766 if (starta < entry->start)
1767 starta = entry->start;
1771 * Generate the sequence of virtual addresses that are candidates for
1772 * prefaulting in an outward spiral from the faulting virtual address,
1773 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra
1774 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1775 * If the candidate address doesn't have a backing physical page, then
1776 * the loop immediately terminates.
1778 for (i = 0; i < 2 * imax(backward, forward); i++) {
1779 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1781 if (addr > addra + forward * PAGE_SIZE)
1784 if (addr < starta || addr >= entry->end)
1787 if (!pmap_is_prefaultable(pmap, addr))
1790 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1791 lobject = entry->object.vm_object;
1793 VM_OBJECT_RLOCK(lobject);
1794 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1795 lobject->type == OBJT_DEFAULT &&
1796 (backing_object = lobject->backing_object) != NULL) {
1797 KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1798 0, ("vm_fault_prefault: unaligned object offset"));
1799 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1800 VM_OBJECT_RLOCK(backing_object);
1801 if (!obj_locked || lobject != entry->object.vm_object)
1802 VM_OBJECT_RUNLOCK(lobject);
1803 lobject = backing_object;
1806 if (!obj_locked || lobject != entry->object.vm_object)
1807 VM_OBJECT_RUNLOCK(lobject);
1810 if (vm_page_all_valid(m) &&
1811 (m->flags & PG_FICTITIOUS) == 0)
1812 pmap_enter_quick(pmap, addr, m, entry->protection);
1813 if (!obj_locked || lobject != entry->object.vm_object)
1814 VM_OBJECT_RUNLOCK(lobject);
1819 * Hold each of the physical pages that are mapped by the specified range of
1820 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1821 * and allow the specified types of access, "prot". If all of the implied
1822 * pages are successfully held, then the number of held pages is returned
1823 * together with pointers to those pages in the array "ma". However, if any
1824 * of the pages cannot be held, -1 is returned.
1827 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1828 vm_prot_t prot, vm_page_t *ma, int max_count)
1830 vm_offset_t end, va;
1833 boolean_t pmap_failed;
1837 end = round_page(addr + len);
1838 addr = trunc_page(addr);
1840 if (!vm_map_range_valid(map, addr, end))
1843 if (atop(end - addr) > max_count)
1844 panic("vm_fault_quick_hold_pages: count > max_count");
1845 count = atop(end - addr);
1848 * Most likely, the physical pages are resident in the pmap, so it is
1849 * faster to try pmap_extract_and_hold() first.
1851 pmap_failed = FALSE;
1852 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1853 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1856 else if ((prot & VM_PROT_WRITE) != 0 &&
1857 (*mp)->dirty != VM_PAGE_BITS_ALL) {
1859 * Explicitly dirty the physical page. Otherwise, the
1860 * caller's changes may go unnoticed because they are
1861 * performed through an unmanaged mapping or by a DMA
1864 * The object lock is not held here.
1865 * See vm_page_clear_dirty_mask().
1872 * One or more pages could not be held by the pmap. Either no
1873 * page was mapped at the specified virtual address or that
1874 * mapping had insufficient permissions. Attempt to fault in
1875 * and hold these pages.
1877 * If vm_fault_disable_pagefaults() was called,
1878 * i.e., TDP_NOFAULTING is set, we must not sleep nor
1879 * acquire MD VM locks, which means we must not call
1880 * vm_fault(). Some (out of tree) callers mark
1881 * too wide a code area with vm_fault_disable_pagefaults()
1882 * already, use the VM_PROT_QUICK_NOFAULT flag to request
1883 * the proper behaviour explicitly.
1885 if ((prot & VM_PROT_QUICK_NOFAULT) != 0 &&
1886 (curthread->td_pflags & TDP_NOFAULTING) != 0)
1888 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1889 if (*mp == NULL && vm_fault(map, va, prot,
1890 VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1895 for (mp = ma; mp < ma + count; mp++)
1897 vm_page_unwire(*mp, PQ_INACTIVE);
1903 * vm_fault_copy_entry
1905 * Create new shadow object backing dst_entry with private copy of
1906 * all underlying pages. When src_entry is equal to dst_entry,
1907 * function implements COW for wired-down map entry. Otherwise,
1908 * it forks wired entry into dst_map.
1910 * In/out conditions:
1911 * The source and destination maps must be locked for write.
1912 * The source map entry must be wired down (or be a sharing map
1913 * entry corresponding to a main map entry that is wired down).
1916 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1917 vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1918 vm_ooffset_t *fork_charge)
1920 vm_object_t backing_object, dst_object, object, src_object;
1921 vm_pindex_t dst_pindex, pindex, src_pindex;
1922 vm_prot_t access, prot;
1932 upgrade = src_entry == dst_entry;
1933 access = prot = dst_entry->protection;
1935 src_object = src_entry->object.vm_object;
1936 src_pindex = OFF_TO_IDX(src_entry->offset);
1938 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1939 dst_object = src_object;
1940 vm_object_reference(dst_object);
1943 * Create the top-level object for the destination entry.
1944 * Doesn't actually shadow anything - we copy the pages
1947 dst_object = vm_object_allocate_anon(atop(dst_entry->end -
1948 dst_entry->start), NULL, NULL, 0);
1949 #if VM_NRESERVLEVEL > 0
1950 dst_object->flags |= OBJ_COLORED;
1951 dst_object->pg_color = atop(dst_entry->start);
1953 dst_object->domain = src_object->domain;
1954 dst_object->charge = dst_entry->end - dst_entry->start;
1957 VM_OBJECT_WLOCK(dst_object);
1958 KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1959 ("vm_fault_copy_entry: vm_object not NULL"));
1960 if (src_object != dst_object) {
1961 dst_entry->object.vm_object = dst_object;
1962 dst_entry->offset = 0;
1963 dst_entry->eflags &= ~MAP_ENTRY_VN_EXEC;
1965 if (fork_charge != NULL) {
1966 KASSERT(dst_entry->cred == NULL,
1967 ("vm_fault_copy_entry: leaked swp charge"));
1968 dst_object->cred = curthread->td_ucred;
1969 crhold(dst_object->cred);
1970 *fork_charge += dst_object->charge;
1971 } else if ((dst_object->type == OBJT_DEFAULT ||
1972 (dst_object->flags & OBJ_SWAP) != 0) &&
1973 dst_object->cred == NULL) {
1974 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1976 dst_object->cred = dst_entry->cred;
1977 dst_entry->cred = NULL;
1981 * If not an upgrade, then enter the mappings in the pmap as
1982 * read and/or execute accesses. Otherwise, enter them as
1985 * A writeable large page mapping is only created if all of
1986 * the constituent small page mappings are modified. Marking
1987 * PTEs as modified on inception allows promotion to happen
1988 * without taking potentially large number of soft faults.
1991 access &= ~VM_PROT_WRITE;
1994 * Loop through all of the virtual pages within the entry's
1995 * range, copying each page from the source object to the
1996 * destination object. Since the source is wired, those pages
1997 * must exist. In contrast, the destination is pageable.
1998 * Since the destination object doesn't share any backing storage
1999 * with the source object, all of its pages must be dirtied,
2000 * regardless of whether they can be written.
2002 for (vaddr = dst_entry->start, dst_pindex = 0;
2003 vaddr < dst_entry->end;
2004 vaddr += PAGE_SIZE, dst_pindex++) {
2007 * Find the page in the source object, and copy it in.
2008 * Because the source is wired down, the page will be
2011 if (src_object != dst_object)
2012 VM_OBJECT_RLOCK(src_object);
2013 object = src_object;
2014 pindex = src_pindex + dst_pindex;
2015 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
2016 (backing_object = object->backing_object) != NULL) {
2018 * Unless the source mapping is read-only or
2019 * it is presently being upgraded from
2020 * read-only, the first object in the shadow
2021 * chain should provide all of the pages. In
2022 * other words, this loop body should never be
2023 * executed when the source mapping is already
2026 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
2028 ("vm_fault_copy_entry: main object missing page"));
2030 VM_OBJECT_RLOCK(backing_object);
2031 pindex += OFF_TO_IDX(object->backing_object_offset);
2032 if (object != dst_object)
2033 VM_OBJECT_RUNLOCK(object);
2034 object = backing_object;
2036 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
2038 if (object != dst_object) {
2040 * Allocate a page in the destination object.
2042 dst_m = vm_page_alloc(dst_object, (src_object ==
2043 dst_object ? src_pindex : 0) + dst_pindex,
2045 if (dst_m == NULL) {
2046 VM_OBJECT_WUNLOCK(dst_object);
2047 VM_OBJECT_RUNLOCK(object);
2048 vm_wait(dst_object);
2049 VM_OBJECT_WLOCK(dst_object);
2052 pmap_copy_page(src_m, dst_m);
2053 VM_OBJECT_RUNLOCK(object);
2054 dst_m->dirty = dst_m->valid = src_m->valid;
2057 if (vm_page_busy_acquire(dst_m, VM_ALLOC_WAITFAIL) == 0)
2059 if (dst_m->pindex >= dst_object->size) {
2061 * We are upgrading. Index can occur
2062 * out of bounds if the object type is
2063 * vnode and the file was truncated.
2065 vm_page_xunbusy(dst_m);
2069 VM_OBJECT_WUNLOCK(dst_object);
2072 * Enter it in the pmap. If a wired, copy-on-write
2073 * mapping is being replaced by a write-enabled
2074 * mapping, then wire that new mapping.
2076 * The page can be invalid if the user called
2077 * msync(MS_INVALIDATE) or truncated the backing vnode
2078 * or shared memory object. In this case, do not
2079 * insert it into pmap, but still do the copy so that
2080 * all copies of the wired map entry have similar
2083 if (vm_page_all_valid(dst_m)) {
2084 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
2085 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
2089 * Mark it no longer busy, and put it on the active list.
2091 VM_OBJECT_WLOCK(dst_object);
2094 if (src_m != dst_m) {
2095 vm_page_unwire(src_m, PQ_INACTIVE);
2096 vm_page_wire(dst_m);
2098 KASSERT(vm_page_wired(dst_m),
2099 ("dst_m %p is not wired", dst_m));
2102 vm_page_activate(dst_m);
2104 vm_page_xunbusy(dst_m);
2106 VM_OBJECT_WUNLOCK(dst_object);
2108 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
2109 vm_object_deallocate(src_object);
2114 * Block entry into the machine-independent layer's page fault handler by
2115 * the calling thread. Subsequent calls to vm_fault() by that thread will
2116 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of
2117 * spurious page faults.
2120 vm_fault_disable_pagefaults(void)
2123 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
2127 vm_fault_enable_pagefaults(int save)
2130 curthread_pflags_restore(save);