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)
118 #define VM_FAULT_READ_MAX (1 + VM_FAULT_READ_AHEAD_MAX)
120 #define VM_FAULT_DONTNEED_MIN 1048576
123 /* Fault parameters. */
126 vm_prot_t fault_type;
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 (defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \
303 __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv)) && \
311 MPASS(fs->vp == NULL);
313 vm_object_busy(fs->first_object);
314 m = vm_page_lookup(fs->first_object, fs->first_pindex);
315 /* A busy page can be mapped for read|execute access. */
316 if (m == NULL || ((fs->prot & VM_PROT_WRITE) != 0 &&
317 vm_page_busied(m)) || !vm_page_all_valid(m)) {
323 #if (defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \
324 __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv)) && \
326 if ((m->flags & PG_FICTITIOUS) == 0 &&
327 (m_super = vm_reserv_to_superpage(m)) != NULL &&
328 rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start &&
329 roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end &&
330 (vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) &
331 (pagesizes[m_super->psind] - 1)) && !fs->wired &&
332 pmap_ps_enabled(fs->map->pmap)) {
333 flags = PS_ALL_VALID;
334 if ((fs->prot & VM_PROT_WRITE) != 0) {
336 * Create a superpage mapping allowing write access
337 * only if none of the constituent pages are busy and
338 * all of them are already dirty (except possibly for
339 * the page that was faulted on).
341 flags |= PS_NONE_BUSY;
342 if ((fs->first_object->flags & OBJ_UNMANAGED) == 0)
343 flags |= PS_ALL_DIRTY;
345 if (vm_page_ps_test(m_super, flags, m)) {
347 psind = m_super->psind;
348 vaddr = rounddown2(vaddr, pagesizes[psind]);
349 /* Preset the modified bit for dirty superpages. */
350 if ((flags & PS_ALL_DIRTY) != 0)
351 fs->fault_type |= VM_PROT_WRITE;
355 rv = pmap_enter(fs->map->pmap, vaddr, m_map, fs->prot, fs->fault_type |
356 PMAP_ENTER_NOSLEEP | (fs->wired ? PMAP_ENTER_WIRED : 0), psind);
357 if (rv != KERN_SUCCESS)
359 if (fs->m_hold != NULL) {
363 if (psind == 0 && !fs->wired)
364 vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true);
365 VM_OBJECT_RUNLOCK(fs->first_object);
366 vm_fault_dirty(fs, m);
367 vm_map_lookup_done(fs->map, fs->entry);
368 curthread->td_ru.ru_minflt++;
371 vm_object_unbusy(fs->first_object);
376 vm_fault_restore_map_lock(struct faultstate *fs)
379 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
380 MPASS(REFCOUNT_COUNT(fs->first_object->paging_in_progress) > 0);
382 if (!vm_map_trylock_read(fs->map)) {
383 VM_OBJECT_WUNLOCK(fs->first_object);
384 vm_map_lock_read(fs->map);
385 VM_OBJECT_WLOCK(fs->first_object);
387 fs->lookup_still_valid = true;
391 vm_fault_populate_check_page(vm_page_t m)
395 * Check each page to ensure that the pager is obeying the
396 * interface: the page must be installed in the object, fully
397 * valid, and exclusively busied.
400 MPASS(vm_page_all_valid(m));
401 MPASS(vm_page_xbusied(m));
405 vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first,
411 VM_OBJECT_ASSERT_WLOCKED(object);
412 MPASS(first <= last);
413 for (pidx = first, m = vm_page_lookup(object, pidx);
414 pidx <= last; pidx++, m = vm_page_next(m)) {
415 vm_fault_populate_check_page(m);
416 vm_page_deactivate(m);
422 vm_fault_populate(struct faultstate *fs)
426 vm_pindex_t map_first, map_last, pager_first, pager_last, pidx;
427 int i, npages, psind, rv;
429 MPASS(fs->object == fs->first_object);
430 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
431 MPASS(REFCOUNT_COUNT(fs->first_object->paging_in_progress) > 0);
432 MPASS(fs->first_object->backing_object == NULL);
433 MPASS(fs->lookup_still_valid);
435 pager_first = OFF_TO_IDX(fs->entry->offset);
436 pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1;
441 * Call the pager (driver) populate() method.
443 * There is no guarantee that the method will be called again
444 * if the current fault is for read, and a future fault is
445 * for write. Report the entry's maximum allowed protection
448 rv = vm_pager_populate(fs->first_object, fs->first_pindex,
449 fs->fault_type, fs->entry->max_protection, &pager_first, &pager_last);
451 VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
452 if (rv == VM_PAGER_BAD) {
454 * VM_PAGER_BAD is the backdoor for a pager to request
455 * normal fault handling.
457 vm_fault_restore_map_lock(fs);
458 if (fs->map->timestamp != fs->map_generation)
459 return (KERN_RESTART);
460 return (KERN_NOT_RECEIVER);
462 if (rv != VM_PAGER_OK)
463 return (KERN_FAILURE); /* AKA SIGSEGV */
465 /* Ensure that the driver is obeying the interface. */
466 MPASS(pager_first <= pager_last);
467 MPASS(fs->first_pindex <= pager_last);
468 MPASS(fs->first_pindex >= pager_first);
469 MPASS(pager_last < fs->first_object->size);
471 vm_fault_restore_map_lock(fs);
472 if (fs->map->timestamp != fs->map_generation) {
473 vm_fault_populate_cleanup(fs->first_object, pager_first,
475 return (KERN_RESTART);
479 * The map is unchanged after our last unlock. Process the fault.
481 * The range [pager_first, pager_last] that is given to the
482 * pager is only a hint. The pager may populate any range
483 * within the object that includes the requested page index.
484 * In case the pager expanded the range, clip it to fit into
487 map_first = OFF_TO_IDX(fs->entry->offset);
488 if (map_first > pager_first) {
489 vm_fault_populate_cleanup(fs->first_object, pager_first,
491 pager_first = map_first;
493 map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1;
494 if (map_last < pager_last) {
495 vm_fault_populate_cleanup(fs->first_object, map_last + 1,
497 pager_last = map_last;
499 for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx);
501 pidx += npages, m = vm_page_next(&m[npages - 1])) {
502 vaddr = fs->entry->start + IDX_TO_OFF(pidx) - fs->entry->offset;
503 #if defined(__aarch64__) || defined(__amd64__) || (defined(__arm__) && \
504 __ARM_ARCH >= 6) || defined(__i386__) || defined(__riscv)
506 if (psind > 0 && ((vaddr & (pagesizes[psind] - 1)) != 0 ||
507 pidx + OFF_TO_IDX(pagesizes[psind]) - 1 > pager_last ||
508 !pmap_ps_enabled(fs->map->pmap) || fs->wired))
513 npages = atop(pagesizes[psind]);
514 for (i = 0; i < npages; i++) {
515 vm_fault_populate_check_page(&m[i]);
516 vm_fault_dirty(fs, &m[i]);
518 VM_OBJECT_WUNLOCK(fs->first_object);
519 rv = pmap_enter(fs->map->pmap, vaddr, m, fs->prot, fs->fault_type |
520 (fs->wired ? PMAP_ENTER_WIRED : 0), psind);
521 #if defined(__amd64__)
522 if (psind > 0 && rv == KERN_FAILURE) {
523 for (i = 0; i < npages; i++) {
524 rv = pmap_enter(fs->map->pmap, vaddr + ptoa(i),
525 &m[i], fs->prot, fs->fault_type |
526 (fs->wired ? PMAP_ENTER_WIRED : 0), 0);
527 MPASS(rv == KERN_SUCCESS);
531 MPASS(rv == KERN_SUCCESS);
533 VM_OBJECT_WLOCK(fs->first_object);
534 for (i = 0; i < npages; i++) {
535 if ((fs->fault_flags & VM_FAULT_WIRE) != 0)
538 vm_page_activate(&m[i]);
539 if (fs->m_hold != NULL && m[i].pindex == fs->first_pindex) {
540 (*fs->m_hold) = &m[i];
543 vm_page_xunbusy(&m[i]);
546 curthread->td_ru.ru_majflt++;
547 return (KERN_SUCCESS);
550 static int prot_fault_translation;
551 SYSCTL_INT(_machdep, OID_AUTO, prot_fault_translation, CTLFLAG_RWTUN,
552 &prot_fault_translation, 0,
553 "Control signal to deliver on protection fault");
555 /* compat definition to keep common code for signal translation */
556 #define UCODE_PAGEFLT 12
558 _Static_assert(UCODE_PAGEFLT == T_PAGEFLT, "T_PAGEFLT");
564 * Handle a page fault occurring at the given address,
565 * requiring the given permissions, in the map specified.
566 * If successful, the page is inserted into the
567 * associated physical map.
569 * NOTE: the given address should be truncated to the
570 * proper page address.
572 * KERN_SUCCESS is returned if the page fault is handled; otherwise,
573 * a standard error specifying why the fault is fatal is returned.
575 * The map in question must be referenced, and remains so.
576 * Caller may hold no locks.
579 vm_fault_trap(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
580 int fault_flags, int *signo, int *ucode)
584 MPASS(signo == NULL || ucode != NULL);
586 if (map != kernel_map && KTRPOINT(curthread, KTR_FAULT))
587 ktrfault(vaddr, fault_type);
589 result = vm_fault(map, trunc_page(vaddr), fault_type, fault_flags,
591 KASSERT(result == KERN_SUCCESS || result == KERN_FAILURE ||
592 result == KERN_INVALID_ADDRESS ||
593 result == KERN_RESOURCE_SHORTAGE ||
594 result == KERN_PROTECTION_FAILURE ||
595 result == KERN_OUT_OF_BOUNDS,
596 ("Unexpected Mach error %d from vm_fault()", result));
598 if (map != kernel_map && KTRPOINT(curthread, KTR_FAULTEND))
601 if (result != KERN_SUCCESS && signo != NULL) {
604 case KERN_INVALID_ADDRESS:
606 *ucode = SEGV_MAPERR;
608 case KERN_RESOURCE_SHORTAGE:
612 case KERN_OUT_OF_BOUNDS:
616 case KERN_PROTECTION_FAILURE:
617 if (prot_fault_translation == 0) {
619 * Autodetect. This check also covers
620 * the images without the ABI-tag ELF
623 if (SV_CURPROC_ABI() == SV_ABI_FREEBSD &&
624 curproc->p_osrel >= P_OSREL_SIGSEGV) {
626 *ucode = SEGV_ACCERR;
629 *ucode = UCODE_PAGEFLT;
631 } else if (prot_fault_translation == 1) {
632 /* Always compat mode. */
634 *ucode = UCODE_PAGEFLT;
636 /* Always SIGSEGV mode. */
638 *ucode = SEGV_ACCERR;
642 KASSERT(0, ("Unexpected Mach error %d from vm_fault()",
651 vm_fault_lock_vnode(struct faultstate *fs, bool objlocked)
656 if (fs->object->type != OBJT_VNODE)
657 return (KERN_SUCCESS);
658 vp = fs->object->handle;
660 ASSERT_VOP_LOCKED(vp, "saved vnode is not locked");
661 return (KERN_SUCCESS);
665 * Perform an unlock in case the desired vnode changed while
666 * the map was unlocked during a retry.
670 locked = VOP_ISLOCKED(vp);
671 if (locked != LK_EXCLUSIVE)
675 * We must not sleep acquiring the vnode lock while we have
676 * the page exclusive busied or the object's
677 * paging-in-progress count incremented. Otherwise, we could
680 error = vget(vp, locked | LK_CANRECURSE | LK_NOWAIT, curthread);
683 return (KERN_SUCCESS);
688 unlock_and_deallocate(fs);
690 fault_deallocate(fs);
691 error = vget(vp, locked | LK_RETRY | LK_CANRECURSE, curthread);
694 KASSERT(error == 0, ("vm_fault: vget failed %d", error));
695 return (KERN_RESOURCE_SHORTAGE);
699 * Calculate the desired readahead. Handle drop-behind.
701 * Returns the number of readahead blocks to pass to the pager.
704 vm_fault_readahead(struct faultstate *fs)
709 KASSERT(fs->lookup_still_valid, ("map unlocked"));
710 era = fs->entry->read_ahead;
711 behavior = vm_map_entry_behavior(fs->entry);
712 if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
714 } else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
715 nera = VM_FAULT_READ_AHEAD_MAX;
716 if (fs->vaddr == fs->entry->next_read)
717 vm_fault_dontneed(fs, fs->vaddr, nera);
718 } else if (fs->vaddr == fs->entry->next_read) {
720 * This is a sequential fault. Arithmetically
721 * increase the requested number of pages in
722 * the read-ahead window. The requested
723 * number of pages is "# of sequential faults
724 * x (read ahead min + 1) + read ahead min"
726 nera = VM_FAULT_READ_AHEAD_MIN;
729 if (nera > VM_FAULT_READ_AHEAD_MAX)
730 nera = VM_FAULT_READ_AHEAD_MAX;
732 if (era == VM_FAULT_READ_AHEAD_MAX)
733 vm_fault_dontneed(fs, fs->vaddr, nera);
736 * This is a non-sequential fault.
742 * A read lock on the map suffices to update
743 * the read ahead count safely.
745 fs->entry->read_ahead = nera;
752 vm_fault_lookup(struct faultstate *fs)
756 KASSERT(!fs->lookup_still_valid,
757 ("vm_fault_lookup: Map already locked."));
758 result = vm_map_lookup(&fs->map, fs->vaddr, fs->fault_type |
759 VM_PROT_FAULT_LOOKUP, &fs->entry, &fs->first_object,
760 &fs->first_pindex, &fs->prot, &fs->wired);
761 if (result != KERN_SUCCESS) {
766 fs->map_generation = fs->map->timestamp;
768 if (fs->entry->eflags & MAP_ENTRY_NOFAULT) {
769 panic("%s: fault on nofault entry, addr: %#lx",
770 __func__, (u_long)fs->vaddr);
773 if (fs->entry->eflags & MAP_ENTRY_IN_TRANSITION &&
774 fs->entry->wiring_thread != curthread) {
775 vm_map_unlock_read(fs->map);
776 vm_map_lock(fs->map);
777 if (vm_map_lookup_entry(fs->map, fs->vaddr, &fs->entry) &&
778 (fs->entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
780 fs->entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
781 vm_map_unlock_and_wait(fs->map, 0);
783 vm_map_unlock(fs->map);
784 return (KERN_RESOURCE_SHORTAGE);
787 MPASS((fs->entry->eflags & MAP_ENTRY_GUARD) == 0);
790 fs->fault_type = fs->prot | (fs->fault_type & VM_PROT_COPY);
792 KASSERT((fs->fault_flags & VM_FAULT_WIRE) == 0,
793 ("!fs->wired && VM_FAULT_WIRE"));
794 fs->lookup_still_valid = true;
796 return (KERN_SUCCESS);
800 vm_fault_relookup(struct faultstate *fs)
802 vm_object_t retry_object;
803 vm_pindex_t retry_pindex;
804 vm_prot_t retry_prot;
807 if (!vm_map_trylock_read(fs->map))
808 return (KERN_RESTART);
810 fs->lookup_still_valid = true;
811 if (fs->map->timestamp == fs->map_generation)
812 return (KERN_SUCCESS);
814 result = vm_map_lookup_locked(&fs->map, fs->vaddr, fs->fault_type,
815 &fs->entry, &retry_object, &retry_pindex, &retry_prot,
817 if (result != KERN_SUCCESS) {
819 * If retry of map lookup would have blocked then
820 * retry fault from start.
822 if (result == KERN_FAILURE)
823 return (KERN_RESTART);
826 if (retry_object != fs->first_object ||
827 retry_pindex != fs->first_pindex)
828 return (KERN_RESTART);
831 * Check whether the protection has changed or the object has
832 * been copied while we left the map unlocked. Changing from
833 * read to write permission is OK - we leave the page
834 * write-protected, and catch the write fault. Changing from
835 * write to read permission means that we can't mark the page
836 * write-enabled after all.
838 fs->prot &= retry_prot;
839 fs->fault_type &= retry_prot;
841 return (KERN_RESTART);
843 /* Reassert because wired may have changed. */
844 KASSERT(fs->wired || (fs->fault_flags & VM_FAULT_WIRE) == 0,
845 ("!wired && VM_FAULT_WIRE"));
847 return (KERN_SUCCESS);
851 vm_fault_cow(struct faultstate *fs)
853 bool is_first_object_locked;
856 * This allows pages to be virtually copied from a backing_object
857 * into the first_object, where the backing object has no other
858 * refs to it, and cannot gain any more refs. Instead of a bcopy,
859 * we just move the page from the backing object to the first
860 * object. Note that we must mark the page dirty in the first
861 * object so that it will go out to swap when needed.
863 is_first_object_locked = false;
866 * Only one shadow object and no other refs.
868 fs->object->shadow_count == 1 && fs->object->ref_count == 1 &&
870 * No other ways to look the object up
872 fs->object->handle == NULL && (fs->object->flags & OBJ_ANON) != 0 &&
874 * We don't chase down the shadow chain and we can acquire locks.
876 (is_first_object_locked = VM_OBJECT_TRYWLOCK(fs->first_object)) &&
877 fs->object == fs->first_object->backing_object &&
878 VM_OBJECT_TRYWLOCK(fs->object)) {
881 * Remove but keep xbusy for replace. fs->m is moved into
882 * fs->first_object and left busy while fs->first_m is
883 * conditionally freed.
885 vm_page_remove_xbusy(fs->m);
886 vm_page_replace(fs->m, fs->first_object, fs->first_pindex,
888 vm_page_dirty(fs->m);
889 #if VM_NRESERVLEVEL > 0
891 * Rename the reservation.
893 vm_reserv_rename(fs->m, fs->first_object, fs->object,
894 OFF_TO_IDX(fs->first_object->backing_object_offset));
896 VM_OBJECT_WUNLOCK(fs->object);
897 VM_OBJECT_WUNLOCK(fs->first_object);
900 VM_CNT_INC(v_cow_optim);
902 if (is_first_object_locked)
903 VM_OBJECT_WUNLOCK(fs->first_object);
905 * Oh, well, lets copy it.
907 pmap_copy_page(fs->m, fs->first_m);
908 vm_page_valid(fs->first_m);
909 if (fs->wired && (fs->fault_flags & VM_FAULT_WIRE) == 0) {
910 vm_page_wire(fs->first_m);
911 vm_page_unwire(fs->m, PQ_INACTIVE);
914 * Save the cow page to be released after
915 * pmap_enter is complete.
921 * fs->object != fs->first_object due to above
924 vm_object_pip_wakeup(fs->object);
927 * Only use the new page below...
929 fs->object = fs->first_object;
930 fs->pindex = fs->first_pindex;
932 VM_CNT_INC(v_cow_faults);
937 vm_fault_next(struct faultstate *fs)
939 vm_object_t next_object;
942 * The requested page does not exist at this object/
943 * offset. Remove the invalid page from the object,
944 * waking up anyone waiting for it, and continue on to
945 * the next object. However, if this is the top-level
946 * object, we must leave the busy page in place to
947 * prevent another process from rushing past us, and
948 * inserting the page in that object at the same time
951 if (fs->object == fs->first_object) {
955 fault_page_free(&fs->m);
958 * Move on to the next object. Lock the next object before
959 * unlocking the current one.
961 VM_OBJECT_ASSERT_WLOCKED(fs->object);
962 next_object = fs->object->backing_object;
963 if (next_object == NULL)
965 MPASS(fs->first_m != NULL);
966 KASSERT(fs->object != next_object, ("object loop %p", next_object));
967 VM_OBJECT_WLOCK(next_object);
968 vm_object_pip_add(next_object, 1);
969 if (fs->object != fs->first_object)
970 vm_object_pip_wakeup(fs->object);
971 fs->pindex += OFF_TO_IDX(fs->object->backing_object_offset);
972 VM_OBJECT_WUNLOCK(fs->object);
973 fs->object = next_object;
979 vm_fault_zerofill(struct faultstate *fs)
983 * If there's no object left, fill the page in the top
986 if (fs->object != fs->first_object) {
987 vm_object_pip_wakeup(fs->object);
988 fs->object = fs->first_object;
989 fs->pindex = fs->first_pindex;
991 MPASS(fs->first_m != NULL);
992 MPASS(fs->m == NULL);
997 * Zero the page if necessary and mark it valid.
999 if ((fs->m->flags & PG_ZERO) == 0) {
1000 pmap_zero_page(fs->m);
1002 VM_CNT_INC(v_ozfod);
1005 vm_page_valid(fs->m);
1009 * Allocate a page directly or via the object populate method.
1012 vm_fault_allocate(struct faultstate *fs)
1014 struct domainset *dset;
1019 if ((fs->object->flags & OBJ_SIZEVNLOCK) != 0) {
1020 rv = vm_fault_lock_vnode(fs, true);
1021 MPASS(rv == KERN_SUCCESS || rv == KERN_RESOURCE_SHORTAGE);
1022 if (rv == KERN_RESOURCE_SHORTAGE)
1026 if (fs->pindex >= fs->object->size)
1027 return (KERN_OUT_OF_BOUNDS);
1029 if (fs->object == fs->first_object &&
1030 (fs->first_object->flags & OBJ_POPULATE) != 0 &&
1031 fs->first_object->shadow_count == 0) {
1032 rv = vm_fault_populate(fs);
1038 case KERN_NOT_RECEIVER:
1040 * Pager's populate() method
1041 * returned VM_PAGER_BAD.
1045 panic("inconsistent return codes");
1050 * Allocate a new page for this object/offset pair.
1052 * Unlocked read of the p_flag is harmless. At worst, the P_KILLED
1053 * might be not observed there, and allocation can fail, causing
1054 * restart and new reading of the p_flag.
1056 dset = fs->object->domain.dr_policy;
1058 dset = curthread->td_domain.dr_policy;
1059 if (!vm_page_count_severe_set(&dset->ds_mask) || P_KILLED(curproc)) {
1060 #if VM_NRESERVLEVEL > 0
1061 vm_object_color(fs->object, atop(fs->vaddr) - fs->pindex);
1063 alloc_req = P_KILLED(curproc) ?
1064 VM_ALLOC_SYSTEM : VM_ALLOC_NORMAL;
1065 if (fs->object->type != OBJT_VNODE &&
1066 fs->object->backing_object == NULL)
1067 alloc_req |= VM_ALLOC_ZERO;
1068 fs->m = vm_page_alloc(fs->object, fs->pindex, alloc_req);
1070 if (fs->m == NULL) {
1071 unlock_and_deallocate(fs);
1072 if (vm_pfault_oom_attempts < 0 ||
1073 fs->oom < vm_pfault_oom_attempts) {
1075 vm_waitpfault(dset, vm_pfault_oom_wait * hz);
1079 "proc %d (%s) failed to alloc page on fault, starting OOM\n",
1080 curproc->p_pid, curproc->p_comm);
1081 vm_pageout_oom(VM_OOM_MEM_PF);
1084 return (KERN_RESOURCE_SHORTAGE);
1088 return (KERN_NOT_RECEIVER);
1092 * Call the pager to retrieve the page if there is a chance
1093 * that the pager has it, and potentially retrieve additional
1094 * pages at the same time.
1097 vm_fault_getpages(struct faultstate *fs, int nera, int *behindp, int *aheadp)
1099 vm_offset_t e_end, e_start;
1100 int ahead, behind, cluster_offset, rv;
1104 * Prepare for unlocking the map. Save the map
1105 * entry's start and end addresses, which are used to
1106 * optimize the size of the pager operation below.
1107 * Even if the map entry's addresses change after
1108 * unlocking the map, using the saved addresses is
1111 e_start = fs->entry->start;
1112 e_end = fs->entry->end;
1113 behavior = vm_map_entry_behavior(fs->entry);
1116 * Release the map lock before locking the vnode or
1117 * sleeping in the pager. (If the current object has
1118 * a shadow, then an earlier iteration of this loop
1119 * may have already unlocked the map.)
1123 rv = vm_fault_lock_vnode(fs, false);
1124 MPASS(rv == KERN_SUCCESS || rv == KERN_RESOURCE_SHORTAGE);
1125 if (rv == KERN_RESOURCE_SHORTAGE)
1127 KASSERT(fs->vp == NULL || !fs->map->system_map,
1128 ("vm_fault: vnode-backed object mapped by system map"));
1131 * Page in the requested page and hint the pager,
1132 * that it may bring up surrounding pages.
1134 if (nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM ||
1135 P_KILLED(curproc)) {
1139 /* Is this a sequential fault? */
1145 * Request a cluster of pages that is
1146 * aligned to a VM_FAULT_READ_DEFAULT
1147 * page offset boundary within the
1148 * object. Alignment to a page offset
1149 * boundary is more likely to coincide
1150 * with the underlying file system
1151 * block than alignment to a virtual
1154 cluster_offset = fs->pindex % VM_FAULT_READ_DEFAULT;
1155 behind = ulmin(cluster_offset,
1156 atop(fs->vaddr - e_start));
1157 ahead = VM_FAULT_READ_DEFAULT - 1 - cluster_offset;
1159 ahead = ulmin(ahead, atop(e_end - fs->vaddr) - 1);
1163 rv = vm_pager_get_pages(fs->object, &fs->m, 1, behindp, aheadp);
1164 if (rv == VM_PAGER_OK)
1165 return (KERN_SUCCESS);
1166 if (rv == VM_PAGER_ERROR)
1167 printf("vm_fault: pager read error, pid %d (%s)\n",
1168 curproc->p_pid, curproc->p_comm);
1170 * If an I/O error occurred or the requested page was
1171 * outside the range of the pager, clean up and return
1174 if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD)
1175 return (KERN_OUT_OF_BOUNDS);
1176 return (KERN_NOT_RECEIVER);
1180 * Wait/Retry if the page is busy. We have to do this if the page is
1181 * either exclusive or shared busy because the vm_pager may be using
1182 * read busy for pageouts (and even pageins if it is the vnode pager),
1183 * and we could end up trying to pagein and pageout the same page
1186 * We can theoretically allow the busy case on a read fault if the page
1187 * is marked valid, but since such pages are typically already pmap'd,
1188 * putting that special case in might be more effort then it is worth.
1189 * We cannot under any circumstances mess around with a shared busied
1190 * page except, perhaps, to pmap it.
1193 vm_fault_busy_sleep(struct faultstate *fs)
1196 * Reference the page before unlocking and
1197 * sleeping so that the page daemon is less
1198 * likely to reclaim it.
1200 vm_page_aflag_set(fs->m, PGA_REFERENCED);
1201 if (fs->object != fs->first_object) {
1202 fault_page_release(&fs->first_m);
1203 vm_object_pip_wakeup(fs->first_object);
1205 vm_object_pip_wakeup(fs->object);
1207 if (fs->m == vm_page_lookup(fs->object, fs->pindex))
1208 vm_page_busy_sleep(fs->m, "vmpfw", false);
1210 VM_OBJECT_WUNLOCK(fs->object);
1211 VM_CNT_INC(v_intrans);
1212 vm_object_deallocate(fs->first_object);
1216 vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
1217 int fault_flags, vm_page_t *m_hold)
1219 struct faultstate fs;
1220 int ahead, behind, faultcount;
1221 int nera, result, rv;
1222 bool dead, hardfault;
1224 VM_CNT_INC(v_vm_faults);
1226 if ((curthread->td_pflags & TDP_NOFAULTING) != 0)
1227 return (KERN_PROTECTION_FAILURE);
1232 fs.fault_flags = fault_flags;
1234 fs.lookup_still_valid = false;
1241 fs.fault_type = fault_type;
1244 * Find the backing store object and offset into it to begin the
1247 result = vm_fault_lookup(&fs);
1248 if (result != KERN_SUCCESS) {
1249 if (result == KERN_RESOURCE_SHORTAGE)
1255 * Try to avoid lock contention on the top-level object through
1256 * special-case handling of some types of page faults, specifically,
1257 * those that are mapping an existing page from the top-level object.
1258 * Under this condition, a read lock on the object suffices, allowing
1259 * multiple page faults of a similar type to run in parallel.
1261 if (fs.vp == NULL /* avoid locked vnode leak */ &&
1262 (fs.fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0) {
1263 VM_OBJECT_RLOCK(fs.first_object);
1264 rv = vm_fault_soft_fast(&fs);
1265 if (rv == KERN_SUCCESS)
1267 if (!VM_OBJECT_TRYUPGRADE(fs.first_object)) {
1268 VM_OBJECT_RUNLOCK(fs.first_object);
1269 VM_OBJECT_WLOCK(fs.first_object);
1272 VM_OBJECT_WLOCK(fs.first_object);
1276 * Make a reference to this object to prevent its disposal while we
1277 * are messing with it. Once we have the reference, the map is free
1278 * to be diddled. Since objects reference their shadows (and copies),
1279 * they will stay around as well.
1281 * Bump the paging-in-progress count to prevent size changes (e.g.
1282 * truncation operations) during I/O.
1284 vm_object_reference_locked(fs.first_object);
1285 vm_object_pip_add(fs.first_object, 1);
1287 fs.m_cow = fs.m = fs.first_m = NULL;
1290 * Search for the page at object/offset.
1292 fs.object = fs.first_object;
1293 fs.pindex = fs.first_pindex;
1295 KASSERT(fs.m == NULL,
1296 ("page still set %p at loop start", fs.m));
1298 * If the object is marked for imminent termination,
1299 * we retry here, since the collapse pass has raced
1300 * with us. Otherwise, if we see terminally dead
1301 * object, return fail.
1303 if ((fs.object->flags & OBJ_DEAD) != 0) {
1304 dead = fs.object->type == OBJT_DEAD;
1305 unlock_and_deallocate(&fs);
1307 return (KERN_PROTECTION_FAILURE);
1313 * See if page is resident
1315 fs.m = vm_page_lookup(fs.object, fs.pindex);
1317 if (vm_page_tryxbusy(fs.m) == 0) {
1318 vm_fault_busy_sleep(&fs);
1323 * The page is marked busy for other processes and the
1324 * pagedaemon. If it still is completely valid we
1327 if (vm_page_all_valid(fs.m)) {
1328 VM_OBJECT_WUNLOCK(fs.object);
1329 break; /* break to PAGE HAS BEEN FOUND. */
1332 VM_OBJECT_ASSERT_WLOCKED(fs.object);
1335 * Page is not resident. If the pager might contain the page
1336 * or this is the beginning of the search, allocate a new
1337 * page. (Default objects are zero-fill, so there is no real
1340 if (fs.m == NULL && (fs.object->type != OBJT_DEFAULT ||
1341 fs.object == fs.first_object)) {
1342 rv = vm_fault_allocate(&fs);
1345 unlock_and_deallocate(&fs);
1347 case KERN_RESOURCE_SHORTAGE:
1351 case KERN_OUT_OF_BOUNDS:
1352 unlock_and_deallocate(&fs);
1354 case KERN_NOT_RECEIVER:
1357 panic("vm_fault: Unhandled rv %d", rv);
1362 * Default objects have no pager so no exclusive busy exists
1363 * to protect this page in the chain. Skip to the next
1364 * object without dropping the lock to preserve atomicity of
1367 if (fs.object->type != OBJT_DEFAULT) {
1369 * At this point, we have either allocated a new page
1370 * or found an existing page that is only partially
1373 * We hold a reference on the current object and the
1374 * page is exclusive busied. The exclusive busy
1375 * prevents simultaneous faults and collapses while
1376 * the object lock is dropped.
1378 VM_OBJECT_WUNLOCK(fs.object);
1381 * If the pager for the current object might have
1382 * the page, then determine the number of additional
1383 * pages to read and potentially reprioritize
1384 * previously read pages for earlier reclamation.
1385 * These operations should only be performed once per
1386 * page fault. Even if the current pager doesn't
1387 * have the page, the number of additional pages to
1388 * read will apply to subsequent objects in the
1391 if (nera == -1 && !P_KILLED(curproc))
1392 nera = vm_fault_readahead(&fs);
1394 rv = vm_fault_getpages(&fs, nera, &behind, &ahead);
1395 if (rv == KERN_SUCCESS) {
1396 faultcount = behind + 1 + ahead;
1398 break; /* break to PAGE HAS BEEN FOUND. */
1400 if (rv == KERN_RESOURCE_SHORTAGE)
1402 VM_OBJECT_WLOCK(fs.object);
1403 if (rv == KERN_OUT_OF_BOUNDS) {
1404 fault_page_free(&fs.m);
1405 unlock_and_deallocate(&fs);
1411 * The page was not found in the current object. Try to
1412 * traverse into a backing object or zero fill if none is
1415 if (vm_fault_next(&fs))
1417 VM_OBJECT_WUNLOCK(fs.object);
1418 vm_fault_zerofill(&fs);
1419 /* Don't try to prefault neighboring pages. */
1421 break; /* break to PAGE HAS BEEN FOUND. */
1425 * PAGE HAS BEEN FOUND. A valid page has been found and exclusively
1426 * busied. The object lock must no longer be held.
1428 vm_page_assert_xbusied(fs.m);
1429 VM_OBJECT_ASSERT_UNLOCKED(fs.object);
1432 * If the page is being written, but isn't already owned by the
1433 * top-level object, we have to copy it into a new page owned by the
1436 if (fs.object != fs.first_object) {
1438 * We only really need to copy if we want to write it.
1440 if ((fs.fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1443 * We only try to prefault read-only mappings to the
1444 * neighboring pages when this copy-on-write fault is
1445 * a hard fault. In other cases, trying to prefault
1446 * is typically wasted effort.
1448 if (faultcount == 0)
1452 fs.prot &= ~VM_PROT_WRITE;
1457 * We must verify that the maps have not changed since our last
1460 if (!fs.lookup_still_valid) {
1461 result = vm_fault_relookup(&fs);
1462 if (result != KERN_SUCCESS) {
1463 fault_deallocate(&fs);
1464 if (result == KERN_RESTART)
1469 VM_OBJECT_ASSERT_UNLOCKED(fs.object);
1472 * If the page was filled by a pager, save the virtual address that
1473 * should be faulted on next under a sequential access pattern to the
1474 * map entry. A read lock on the map suffices to update this address
1478 fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE;
1481 * Page must be completely valid or it is not fit to
1482 * map into user space. vm_pager_get_pages() ensures this.
1484 vm_page_assert_xbusied(fs.m);
1485 KASSERT(vm_page_all_valid(fs.m),
1486 ("vm_fault: page %p partially invalid", fs.m));
1488 vm_fault_dirty(&fs, fs.m);
1491 * Put this page into the physical map. We had to do the unlock above
1492 * because pmap_enter() may sleep. We don't put the page
1493 * back on the active queue until later so that the pageout daemon
1494 * won't find it (yet).
1496 pmap_enter(fs.map->pmap, vaddr, fs.m, fs.prot,
1497 fs.fault_type | (fs.wired ? PMAP_ENTER_WIRED : 0), 0);
1498 if (faultcount != 1 && (fs.fault_flags & VM_FAULT_WIRE) == 0 &&
1500 vm_fault_prefault(&fs, vaddr,
1501 faultcount > 0 ? behind : PFBAK,
1502 faultcount > 0 ? ahead : PFFOR, false);
1505 * If the page is not wired down, then put it where the pageout daemon
1508 if ((fs.fault_flags & VM_FAULT_WIRE) != 0)
1511 vm_page_activate(fs.m);
1512 if (fs.m_hold != NULL) {
1513 (*fs.m_hold) = fs.m;
1516 vm_page_xunbusy(fs.m);
1520 * Unlock everything, and return
1522 fault_deallocate(&fs);
1524 VM_CNT_INC(v_io_faults);
1525 curthread->td_ru.ru_majflt++;
1527 if (racct_enable && fs.object->type == OBJT_VNODE) {
1529 if ((fs.fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
1530 racct_add_force(curproc, RACCT_WRITEBPS,
1531 PAGE_SIZE + behind * PAGE_SIZE);
1532 racct_add_force(curproc, RACCT_WRITEIOPS, 1);
1534 racct_add_force(curproc, RACCT_READBPS,
1535 PAGE_SIZE + ahead * PAGE_SIZE);
1536 racct_add_force(curproc, RACCT_READIOPS, 1);
1538 PROC_UNLOCK(curproc);
1542 curthread->td_ru.ru_minflt++;
1544 return (KERN_SUCCESS);
1548 * Speed up the reclamation of pages that precede the faulting pindex within
1549 * the first object of the shadow chain. Essentially, perform the equivalent
1550 * to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes
1551 * the faulting pindex by the cluster size when the pages read by vm_fault()
1552 * cross a cluster-size boundary. The cluster size is the greater of the
1553 * smallest superpage size and VM_FAULT_DONTNEED_MIN.
1555 * When "fs->first_object" is a shadow object, the pages in the backing object
1556 * that precede the faulting pindex are deactivated by vm_fault(). So, this
1557 * function must only be concerned with pages in the first object.
1560 vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
1562 vm_map_entry_t entry;
1563 vm_object_t first_object, object;
1564 vm_offset_t end, start;
1565 vm_page_t m, m_next;
1566 vm_pindex_t pend, pstart;
1569 object = fs->object;
1570 VM_OBJECT_ASSERT_UNLOCKED(object);
1571 first_object = fs->first_object;
1572 /* Neither fictitious nor unmanaged pages can be reclaimed. */
1573 if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
1574 VM_OBJECT_RLOCK(first_object);
1575 size = VM_FAULT_DONTNEED_MIN;
1576 if (MAXPAGESIZES > 1 && size < pagesizes[1])
1577 size = pagesizes[1];
1578 end = rounddown2(vaddr, size);
1579 if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) &&
1580 (entry = fs->entry)->start < end) {
1581 if (end - entry->start < size)
1582 start = entry->start;
1585 pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED);
1586 pstart = OFF_TO_IDX(entry->offset) + atop(start -
1588 m_next = vm_page_find_least(first_object, pstart);
1589 pend = OFF_TO_IDX(entry->offset) + atop(end -
1591 while ((m = m_next) != NULL && m->pindex < pend) {
1592 m_next = TAILQ_NEXT(m, listq);
1593 if (!vm_page_all_valid(m) ||
1598 * Don't clear PGA_REFERENCED, since it would
1599 * likely represent a reference by a different
1602 * Typically, at this point, prefetched pages
1603 * are still in the inactive queue. Only
1604 * pages that triggered page faults are in the
1605 * active queue. The test for whether the page
1606 * is in the inactive queue is racy; in the
1607 * worst case we will requeue the page
1610 if (!vm_page_inactive(m))
1611 vm_page_deactivate(m);
1614 VM_OBJECT_RUNLOCK(first_object);
1619 * vm_fault_prefault provides a quick way of clustering
1620 * pagefaults into a processes address space. It is a "cousin"
1621 * of vm_map_pmap_enter, except it runs at page fault time instead
1625 vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
1626 int backward, int forward, bool obj_locked)
1629 vm_map_entry_t entry;
1630 vm_object_t backing_object, lobject;
1631 vm_offset_t addr, starta;
1636 pmap = fs->map->pmap;
1637 if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
1642 if (addra < backward * PAGE_SIZE) {
1643 starta = entry->start;
1645 starta = addra - backward * PAGE_SIZE;
1646 if (starta < entry->start)
1647 starta = entry->start;
1651 * Generate the sequence of virtual addresses that are candidates for
1652 * prefaulting in an outward spiral from the faulting virtual address,
1653 * "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra
1654 * + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
1655 * If the candidate address doesn't have a backing physical page, then
1656 * the loop immediately terminates.
1658 for (i = 0; i < 2 * imax(backward, forward); i++) {
1659 addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
1661 if (addr > addra + forward * PAGE_SIZE)
1664 if (addr < starta || addr >= entry->end)
1667 if (!pmap_is_prefaultable(pmap, addr))
1670 pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
1671 lobject = entry->object.vm_object;
1673 VM_OBJECT_RLOCK(lobject);
1674 while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
1675 lobject->type == OBJT_DEFAULT &&
1676 (backing_object = lobject->backing_object) != NULL) {
1677 KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
1678 0, ("vm_fault_prefault: unaligned object offset"));
1679 pindex += lobject->backing_object_offset >> PAGE_SHIFT;
1680 VM_OBJECT_RLOCK(backing_object);
1681 if (!obj_locked || lobject != entry->object.vm_object)
1682 VM_OBJECT_RUNLOCK(lobject);
1683 lobject = backing_object;
1686 if (!obj_locked || lobject != entry->object.vm_object)
1687 VM_OBJECT_RUNLOCK(lobject);
1690 if (vm_page_all_valid(m) &&
1691 (m->flags & PG_FICTITIOUS) == 0)
1692 pmap_enter_quick(pmap, addr, m, entry->protection);
1693 if (!obj_locked || lobject != entry->object.vm_object)
1694 VM_OBJECT_RUNLOCK(lobject);
1699 * Hold each of the physical pages that are mapped by the specified range of
1700 * virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
1701 * and allow the specified types of access, "prot". If all of the implied
1702 * pages are successfully held, then the number of held pages is returned
1703 * together with pointers to those pages in the array "ma". However, if any
1704 * of the pages cannot be held, -1 is returned.
1707 vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
1708 vm_prot_t prot, vm_page_t *ma, int max_count)
1710 vm_offset_t end, va;
1713 boolean_t pmap_failed;
1717 end = round_page(addr + len);
1718 addr = trunc_page(addr);
1721 * Check for illegal addresses.
1723 if (addr < vm_map_min(map) || addr > end || end > vm_map_max(map))
1726 if (atop(end - addr) > max_count)
1727 panic("vm_fault_quick_hold_pages: count > max_count");
1728 count = atop(end - addr);
1731 * Most likely, the physical pages are resident in the pmap, so it is
1732 * faster to try pmap_extract_and_hold() first.
1734 pmap_failed = FALSE;
1735 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
1736 *mp = pmap_extract_and_hold(map->pmap, va, prot);
1739 else if ((prot & VM_PROT_WRITE) != 0 &&
1740 (*mp)->dirty != VM_PAGE_BITS_ALL) {
1742 * Explicitly dirty the physical page. Otherwise, the
1743 * caller's changes may go unnoticed because they are
1744 * performed through an unmanaged mapping or by a DMA
1747 * The object lock is not held here.
1748 * See vm_page_clear_dirty_mask().
1755 * One or more pages could not be held by the pmap. Either no
1756 * page was mapped at the specified virtual address or that
1757 * mapping had insufficient permissions. Attempt to fault in
1758 * and hold these pages.
1760 * If vm_fault_disable_pagefaults() was called,
1761 * i.e., TDP_NOFAULTING is set, we must not sleep nor
1762 * acquire MD VM locks, which means we must not call
1763 * vm_fault(). Some (out of tree) callers mark
1764 * too wide a code area with vm_fault_disable_pagefaults()
1765 * already, use the VM_PROT_QUICK_NOFAULT flag to request
1766 * the proper behaviour explicitly.
1768 if ((prot & VM_PROT_QUICK_NOFAULT) != 0 &&
1769 (curthread->td_pflags & TDP_NOFAULTING) != 0)
1771 for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
1772 if (*mp == NULL && vm_fault(map, va, prot,
1773 VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
1778 for (mp = ma; mp < ma + count; mp++)
1780 vm_page_unwire(*mp, PQ_INACTIVE);
1786 * vm_fault_copy_entry
1788 * Create new shadow object backing dst_entry with private copy of
1789 * all underlying pages. When src_entry is equal to dst_entry,
1790 * function implements COW for wired-down map entry. Otherwise,
1791 * it forks wired entry into dst_map.
1793 * In/out conditions:
1794 * The source and destination maps must be locked for write.
1795 * The source map entry must be wired down (or be a sharing map
1796 * entry corresponding to a main map entry that is wired down).
1799 vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map,
1800 vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
1801 vm_ooffset_t *fork_charge)
1803 vm_object_t backing_object, dst_object, object, src_object;
1804 vm_pindex_t dst_pindex, pindex, src_pindex;
1805 vm_prot_t access, prot;
1815 upgrade = src_entry == dst_entry;
1816 access = prot = dst_entry->protection;
1818 src_object = src_entry->object.vm_object;
1819 src_pindex = OFF_TO_IDX(src_entry->offset);
1821 if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
1822 dst_object = src_object;
1823 vm_object_reference(dst_object);
1826 * Create the top-level object for the destination entry.
1827 * Doesn't actually shadow anything - we copy the pages
1830 dst_object = vm_object_allocate_anon(atop(dst_entry->end -
1831 dst_entry->start), NULL, NULL, 0);
1832 #if VM_NRESERVLEVEL > 0
1833 dst_object->flags |= OBJ_COLORED;
1834 dst_object->pg_color = atop(dst_entry->start);
1836 dst_object->domain = src_object->domain;
1837 dst_object->charge = dst_entry->end - dst_entry->start;
1840 VM_OBJECT_WLOCK(dst_object);
1841 KASSERT(upgrade || dst_entry->object.vm_object == NULL,
1842 ("vm_fault_copy_entry: vm_object not NULL"));
1843 if (src_object != dst_object) {
1844 dst_entry->object.vm_object = dst_object;
1845 dst_entry->offset = 0;
1846 dst_entry->eflags &= ~MAP_ENTRY_VN_EXEC;
1848 if (fork_charge != NULL) {
1849 KASSERT(dst_entry->cred == NULL,
1850 ("vm_fault_copy_entry: leaked swp charge"));
1851 dst_object->cred = curthread->td_ucred;
1852 crhold(dst_object->cred);
1853 *fork_charge += dst_object->charge;
1854 } else if ((dst_object->type == OBJT_DEFAULT ||
1855 dst_object->type == OBJT_SWAP) &&
1856 dst_object->cred == NULL) {
1857 KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
1859 dst_object->cred = dst_entry->cred;
1860 dst_entry->cred = NULL;
1864 * If not an upgrade, then enter the mappings in the pmap as
1865 * read and/or execute accesses. Otherwise, enter them as
1868 * A writeable large page mapping is only created if all of
1869 * the constituent small page mappings are modified. Marking
1870 * PTEs as modified on inception allows promotion to happen
1871 * without taking potentially large number of soft faults.
1874 access &= ~VM_PROT_WRITE;
1877 * Loop through all of the virtual pages within the entry's
1878 * range, copying each page from the source object to the
1879 * destination object. Since the source is wired, those pages
1880 * must exist. In contrast, the destination is pageable.
1881 * Since the destination object doesn't share any backing storage
1882 * with the source object, all of its pages must be dirtied,
1883 * regardless of whether they can be written.
1885 for (vaddr = dst_entry->start, dst_pindex = 0;
1886 vaddr < dst_entry->end;
1887 vaddr += PAGE_SIZE, dst_pindex++) {
1890 * Find the page in the source object, and copy it in.
1891 * Because the source is wired down, the page will be
1894 if (src_object != dst_object)
1895 VM_OBJECT_RLOCK(src_object);
1896 object = src_object;
1897 pindex = src_pindex + dst_pindex;
1898 while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
1899 (backing_object = object->backing_object) != NULL) {
1901 * Unless the source mapping is read-only or
1902 * it is presently being upgraded from
1903 * read-only, the first object in the shadow
1904 * chain should provide all of the pages. In
1905 * other words, this loop body should never be
1906 * executed when the source mapping is already
1909 KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
1911 ("vm_fault_copy_entry: main object missing page"));
1913 VM_OBJECT_RLOCK(backing_object);
1914 pindex += OFF_TO_IDX(object->backing_object_offset);
1915 if (object != dst_object)
1916 VM_OBJECT_RUNLOCK(object);
1917 object = backing_object;
1919 KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
1921 if (object != dst_object) {
1923 * Allocate a page in the destination object.
1925 dst_m = vm_page_alloc(dst_object, (src_object ==
1926 dst_object ? src_pindex : 0) + dst_pindex,
1928 if (dst_m == NULL) {
1929 VM_OBJECT_WUNLOCK(dst_object);
1930 VM_OBJECT_RUNLOCK(object);
1931 vm_wait(dst_object);
1932 VM_OBJECT_WLOCK(dst_object);
1935 pmap_copy_page(src_m, dst_m);
1936 VM_OBJECT_RUNLOCK(object);
1937 dst_m->dirty = dst_m->valid = src_m->valid;
1940 if (vm_page_busy_acquire(dst_m, VM_ALLOC_WAITFAIL) == 0)
1942 if (dst_m->pindex >= dst_object->size) {
1944 * We are upgrading. Index can occur
1945 * out of bounds if the object type is
1946 * vnode and the file was truncated.
1948 vm_page_xunbusy(dst_m);
1952 VM_OBJECT_WUNLOCK(dst_object);
1955 * Enter it in the pmap. If a wired, copy-on-write
1956 * mapping is being replaced by a write-enabled
1957 * mapping, then wire that new mapping.
1959 * The page can be invalid if the user called
1960 * msync(MS_INVALIDATE) or truncated the backing vnode
1961 * or shared memory object. In this case, do not
1962 * insert it into pmap, but still do the copy so that
1963 * all copies of the wired map entry have similar
1966 if (vm_page_all_valid(dst_m)) {
1967 pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
1968 access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
1972 * Mark it no longer busy, and put it on the active list.
1974 VM_OBJECT_WLOCK(dst_object);
1977 if (src_m != dst_m) {
1978 vm_page_unwire(src_m, PQ_INACTIVE);
1979 vm_page_wire(dst_m);
1981 KASSERT(vm_page_wired(dst_m),
1982 ("dst_m %p is not wired", dst_m));
1985 vm_page_activate(dst_m);
1987 vm_page_xunbusy(dst_m);
1989 VM_OBJECT_WUNLOCK(dst_object);
1991 dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
1992 vm_object_deallocate(src_object);
1997 * Block entry into the machine-independent layer's page fault handler by
1998 * the calling thread. Subsequent calls to vm_fault() by that thread will
1999 * return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of
2000 * spurious page faults.
2003 vm_fault_disable_pagefaults(void)
2006 return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
2010 vm_fault_enable_pagefaults(int save)
2013 curthread_pflags_restore(save);