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freebsd-dev/sys/vm/vm_fault.c
Mateusz Guzik 0e71f4f77c vm: add unlocked page lookup before trying vm_fault_soft_fast 
Shaves a read lock + tryupgrade trip most of the time.

Stats from doing a kernel build (counters not present in the tree):
vm.fault_soft_fast_ok: 262653
vm.fault_soft_fast_failed_other: 41
vm.fault_soft_fast_failed_no_page: 39595772
vm.fault_soft_fast_failed_page_busy: 1929
vm.fault_soft_fast_failed_page_invalid: 22183

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D39268
2023-03-25 22:14:59 +00:00

2284 lines
64 KiB
C
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/*-
* SPDX-License-Identifier: (BSD-4-Clause AND MIT-CMU)
*
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
* Copyright (c) 1994 John S. Dyson
* All rights reserved.
* Copyright (c) 1994 David Greenman
* All rights reserved.
*
*
* This code is derived from software contributed to Berkeley by
* The Mach Operating System project at Carnegie-Mellon University.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* from: @(#)vm_fault.c 8.4 (Berkeley) 1/12/94
*
*
* Copyright (c) 1987, 1990 Carnegie-Mellon University.
* All rights reserved.
*
* Authors: Avadis Tevanian, Jr., Michael Wayne Young
*
* Permission to use, copy, modify and distribute this software and
* its documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
/*
* Page fault handling module.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ktrace.h"
#include "opt_vm.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/mman.h>
#include <sys/mutex.h>
#include <sys/pctrie.h>
#include <sys/proc.h>
#include <sys/racct.h>
#include <sys/refcount.h>
#include <sys/resourcevar.h>
#include <sys/rwlock.h>
#include <sys/signalvar.h>
#include <sys/sysctl.h>
#include <sys/sysent.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>
#ifdef KTRACE
#include <sys/ktrace.h>
#endif
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/vm_kern.h>
#include <vm/vm_pager.h>
#include <vm/vm_extern.h>
#include <vm/vm_reserv.h>
#define PFBAK 4
#define PFFOR 4
#define VM_FAULT_READ_DEFAULT (1 + VM_FAULT_READ_AHEAD_INIT)
#define VM_FAULT_DONTNEED_MIN 1048576
struct faultstate {
/* Fault parameters. */
vm_offset_t vaddr;
vm_page_t *m_hold;
vm_prot_t fault_type;
vm_prot_t prot;
int fault_flags;
boolean_t wired;
/* Control state. */
struct timeval oom_start_time;
bool oom_started;
int nera;
bool can_read_lock;
/* Page reference for cow. */
vm_page_t m_cow;
/* Current object. */
vm_object_t object;
vm_pindex_t pindex;
vm_page_t m;
/* Top-level map object. */
vm_object_t first_object;
vm_pindex_t first_pindex;
vm_page_t first_m;
/* Map state. */
vm_map_t map;
vm_map_entry_t entry;
int map_generation;
bool lookup_still_valid;
/* Vnode if locked. */
struct vnode *vp;
};
/*
* Return codes for internal fault routines.
*/
enum fault_status {
FAULT_SUCCESS = 1, /* Return success to user. */
FAULT_FAILURE, /* Return failure to user. */
FAULT_CONTINUE, /* Continue faulting. */
FAULT_RESTART, /* Restart fault. */
FAULT_OUT_OF_BOUNDS, /* Invalid address for pager. */
FAULT_HARD, /* Performed I/O. */
FAULT_SOFT, /* Found valid page. */
FAULT_PROTECTION_FAILURE, /* Invalid access. */
};
enum fault_next_status {
FAULT_NEXT_GOTOBJ = 1,
FAULT_NEXT_NOOBJ,
FAULT_NEXT_RESTART,
};
static void vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr,
int ahead);
static void vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
int backward, int forward, bool obj_locked);
static int vm_pfault_oom_attempts = 3;
SYSCTL_INT(_vm, OID_AUTO, pfault_oom_attempts, CTLFLAG_RWTUN,
&vm_pfault_oom_attempts, 0,
"Number of page allocation attempts in page fault handler before it "
"triggers OOM handling");
static int vm_pfault_oom_wait = 10;
SYSCTL_INT(_vm, OID_AUTO, pfault_oom_wait, CTLFLAG_RWTUN,
&vm_pfault_oom_wait, 0,
"Number of seconds to wait for free pages before retrying "
"the page fault handler");
static inline void
vm_fault_page_release(vm_page_t *mp)
{
vm_page_t m;
m = *mp;
if (m != NULL) {
/*
* We are likely to loop around again and attempt to busy
* this page. Deactivating it leaves it available for
* pageout while optimizing fault restarts.
*/
vm_page_deactivate(m);
vm_page_xunbusy(m);
*mp = NULL;
}
}
static inline void
vm_fault_page_free(vm_page_t *mp)
{
vm_page_t m;
m = *mp;
if (m != NULL) {
VM_OBJECT_ASSERT_WLOCKED(m->object);
if (!vm_page_wired(m))
vm_page_free(m);
else
vm_page_xunbusy(m);
*mp = NULL;
}
}
/*
* Return true if a vm_pager_get_pages() call is needed in order to check
* whether the pager might have a particular page, false if it can be determined
* immediately that the pager can not have a copy. For swap objects, this can
* be checked quickly.
*/
static inline bool
vm_fault_object_needs_getpages(vm_object_t object)
{
VM_OBJECT_ASSERT_LOCKED(object);
return ((object->flags & OBJ_SWAP) == 0 ||
!pctrie_is_empty(&object->un_pager.swp.swp_blks));
}
static inline void
vm_fault_unlock_map(struct faultstate *fs)
{
if (fs->lookup_still_valid) {
vm_map_lookup_done(fs->map, fs->entry);
fs->lookup_still_valid = false;
}
}
static void
vm_fault_unlock_vp(struct faultstate *fs)
{
if (fs->vp != NULL) {
vput(fs->vp);
fs->vp = NULL;
}
}
static void
vm_fault_deallocate(struct faultstate *fs)
{
vm_fault_page_release(&fs->m_cow);
vm_fault_page_release(&fs->m);
vm_object_pip_wakeup(fs->object);
if (fs->object != fs->first_object) {
VM_OBJECT_WLOCK(fs->first_object);
vm_fault_page_free(&fs->first_m);
VM_OBJECT_WUNLOCK(fs->first_object);
vm_object_pip_wakeup(fs->first_object);
}
vm_object_deallocate(fs->first_object);
vm_fault_unlock_map(fs);
vm_fault_unlock_vp(fs);
}
static void
vm_fault_unlock_and_deallocate(struct faultstate *fs)
{
VM_OBJECT_UNLOCK(fs->object);
vm_fault_deallocate(fs);
}
static void
vm_fault_dirty(struct faultstate *fs, vm_page_t m)
{
bool need_dirty;
if (((fs->prot & VM_PROT_WRITE) == 0 &&
(fs->fault_flags & VM_FAULT_DIRTY) == 0) ||
(m->oflags & VPO_UNMANAGED) != 0)
return;
VM_PAGE_OBJECT_BUSY_ASSERT(m);
need_dirty = ((fs->fault_type & VM_PROT_WRITE) != 0 &&
(fs->fault_flags & VM_FAULT_WIRE) == 0) ||
(fs->fault_flags & VM_FAULT_DIRTY) != 0;
vm_object_set_writeable_dirty(m->object);
/*
* If the fault is a write, we know that this page is being
* written NOW so dirty it explicitly to save on
* pmap_is_modified() calls later.
*
* Also, since the page is now dirty, we can possibly tell
* the pager to release any swap backing the page.
*/
if (need_dirty && vm_page_set_dirty(m) == 0) {
/*
* If this is a NOSYNC mmap we do not want to set PGA_NOSYNC
* if the page is already dirty to prevent data written with
* the expectation of being synced from not being synced.
* Likewise if this entry does not request NOSYNC then make
* sure the page isn't marked NOSYNC. Applications sharing
* data should use the same flags to avoid ping ponging.
*/
if ((fs->entry->eflags & MAP_ENTRY_NOSYNC) != 0)
vm_page_aflag_set(m, PGA_NOSYNC);
else
vm_page_aflag_clear(m, PGA_NOSYNC);
}
}
/*
* Unlocks fs.first_object and fs.map on success.
*/
static enum fault_status
vm_fault_soft_fast(struct faultstate *fs)
{
vm_page_t m, m_map;
#if VM_NRESERVLEVEL > 0
vm_page_t m_super;
int flags;
#endif
int psind;
vm_offset_t vaddr;
MPASS(fs->vp == NULL);
/*
* If we fail, vast majority of the time it is because the page is not
* there to begin with. Opportunistically perform the lookup and
* subsequent checks without the object lock, revalidate later.
*
* Note: a busy page can be mapped for read|execute access.
*/
m = vm_page_lookup_unlocked(fs->first_object, fs->first_pindex);
if (m == NULL || !vm_page_all_valid(m) ||
((fs->prot & VM_PROT_WRITE) != 0 && vm_page_busied(m))) {
VM_OBJECT_WLOCK(fs->first_object);
return (FAULT_FAILURE);
}
vaddr = fs->vaddr;
VM_OBJECT_RLOCK(fs->first_object);
/*
* Now that we stabilized the state, revalidate the page is in the shape
* we encountered above.
*/
if (m->object != fs->first_object || m->pindex != fs->first_pindex)
goto fail;
vm_object_busy(fs->first_object);
if (!vm_page_all_valid(m) ||
((fs->prot & VM_PROT_WRITE) != 0 && vm_page_busied(m)))
goto fail_busy;
m_map = m;
psind = 0;
#if VM_NRESERVLEVEL > 0
if ((m->flags & PG_FICTITIOUS) == 0 &&
(m_super = vm_reserv_to_superpage(m)) != NULL &&
rounddown2(vaddr, pagesizes[m_super->psind]) >= fs->entry->start &&
roundup2(vaddr + 1, pagesizes[m_super->psind]) <= fs->entry->end &&
(vaddr & (pagesizes[m_super->psind] - 1)) == (VM_PAGE_TO_PHYS(m) &
(pagesizes[m_super->psind] - 1)) && !fs->wired &&
pmap_ps_enabled(fs->map->pmap)) {
flags = PS_ALL_VALID;
if ((fs->prot & VM_PROT_WRITE) != 0) {
/*
* Create a superpage mapping allowing write access
* only if none of the constituent pages are busy and
* all of them are already dirty (except possibly for
* the page that was faulted on).
*/
flags |= PS_NONE_BUSY;
if ((fs->first_object->flags & OBJ_UNMANAGED) == 0)
flags |= PS_ALL_DIRTY;
}
if (vm_page_ps_test(m_super, flags, m)) {
m_map = m_super;
psind = m_super->psind;
vaddr = rounddown2(vaddr, pagesizes[psind]);
/* Preset the modified bit for dirty superpages. */
if ((flags & PS_ALL_DIRTY) != 0)
fs->fault_type |= VM_PROT_WRITE;
}
}
#endif
if (pmap_enter(fs->map->pmap, vaddr, m_map, fs->prot, fs->fault_type |
PMAP_ENTER_NOSLEEP | (fs->wired ? PMAP_ENTER_WIRED : 0), psind) !=
KERN_SUCCESS)
goto fail_busy;
if (fs->m_hold != NULL) {
(*fs->m_hold) = m;
vm_page_wire(m);
}
if (psind == 0 && !fs->wired)
vm_fault_prefault(fs, vaddr, PFBAK, PFFOR, true);
VM_OBJECT_RUNLOCK(fs->first_object);
vm_fault_dirty(fs, m);
vm_object_unbusy(fs->first_object);
vm_map_lookup_done(fs->map, fs->entry);
curthread->td_ru.ru_minflt++;
return (FAULT_SUCCESS);
fail_busy:
vm_object_unbusy(fs->first_object);
fail:
if (!VM_OBJECT_TRYUPGRADE(fs->first_object)) {
VM_OBJECT_RUNLOCK(fs->first_object);
VM_OBJECT_WLOCK(fs->first_object);
}
return (FAULT_FAILURE);
}
static void
vm_fault_restore_map_lock(struct faultstate *fs)
{
VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
MPASS(blockcount_read(&fs->first_object->paging_in_progress) > 0);
if (!vm_map_trylock_read(fs->map)) {
VM_OBJECT_WUNLOCK(fs->first_object);
vm_map_lock_read(fs->map);
VM_OBJECT_WLOCK(fs->first_object);
}
fs->lookup_still_valid = true;
}
static void
vm_fault_populate_check_page(vm_page_t m)
{
/*
* Check each page to ensure that the pager is obeying the
* interface: the page must be installed in the object, fully
* valid, and exclusively busied.
*/
MPASS(m != NULL);
MPASS(vm_page_all_valid(m));
MPASS(vm_page_xbusied(m));
}
static void
vm_fault_populate_cleanup(vm_object_t object, vm_pindex_t first,
vm_pindex_t last)
{
vm_page_t m;
vm_pindex_t pidx;
VM_OBJECT_ASSERT_WLOCKED(object);
MPASS(first <= last);
for (pidx = first, m = vm_page_lookup(object, pidx);
pidx <= last; pidx++, m = vm_page_next(m)) {
vm_fault_populate_check_page(m);
vm_page_deactivate(m);
vm_page_xunbusy(m);
}
}
static enum fault_status
vm_fault_populate(struct faultstate *fs)
{
vm_offset_t vaddr;
vm_page_t m;
vm_pindex_t map_first, map_last, pager_first, pager_last, pidx;
int bdry_idx, i, npages, psind, rv;
enum fault_status res;
MPASS(fs->object == fs->first_object);
VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
MPASS(blockcount_read(&fs->first_object->paging_in_progress) > 0);
MPASS(fs->first_object->backing_object == NULL);
MPASS(fs->lookup_still_valid);
pager_first = OFF_TO_IDX(fs->entry->offset);
pager_last = pager_first + atop(fs->entry->end - fs->entry->start) - 1;
vm_fault_unlock_map(fs);
vm_fault_unlock_vp(fs);
res = FAULT_SUCCESS;
/*
* Call the pager (driver) populate() method.
*
* There is no guarantee that the method will be called again
* if the current fault is for read, and a future fault is
* for write. Report the entry's maximum allowed protection
* to the driver.
*/
rv = vm_pager_populate(fs->first_object, fs->first_pindex,
fs->fault_type, fs->entry->max_protection, &pager_first,
&pager_last);
VM_OBJECT_ASSERT_WLOCKED(fs->first_object);
if (rv == VM_PAGER_BAD) {
/*
* VM_PAGER_BAD is the backdoor for a pager to request
* normal fault handling.
*/
vm_fault_restore_map_lock(fs);
if (fs->map->timestamp != fs->map_generation)
return (FAULT_RESTART);
return (FAULT_CONTINUE);
}
if (rv != VM_PAGER_OK)
return (FAULT_FAILURE); /* AKA SIGSEGV */
/* Ensure that the driver is obeying the interface. */
MPASS(pager_first <= pager_last);
MPASS(fs->first_pindex <= pager_last);
MPASS(fs->first_pindex >= pager_first);
MPASS(pager_last < fs->first_object->size);
vm_fault_restore_map_lock(fs);
bdry_idx = (fs->entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) >>
MAP_ENTRY_SPLIT_BOUNDARY_SHIFT;
if (fs->map->timestamp != fs->map_generation) {
if (bdry_idx == 0) {
vm_fault_populate_cleanup(fs->first_object, pager_first,
pager_last);
} else {
m = vm_page_lookup(fs->first_object, pager_first);
if (m != fs->m)
vm_page_xunbusy(m);
}
return (FAULT_RESTART);
}
/*
* The map is unchanged after our last unlock. Process the fault.
*
* First, the special case of largepage mappings, where
* populate only busies the first page in superpage run.
*/
if (bdry_idx != 0) {
KASSERT(PMAP_HAS_LARGEPAGES,
("missing pmap support for large pages"));
m = vm_page_lookup(fs->first_object, pager_first);
vm_fault_populate_check_page(m);
VM_OBJECT_WUNLOCK(fs->first_object);
vaddr = fs->entry->start + IDX_TO_OFF(pager_first) -
fs->entry->offset;
/* assert alignment for entry */
KASSERT((vaddr & (pagesizes[bdry_idx] - 1)) == 0,
("unaligned superpage start %#jx pager_first %#jx offset %#jx vaddr %#jx",
(uintmax_t)fs->entry->start, (uintmax_t)pager_first,
(uintmax_t)fs->entry->offset, (uintmax_t)vaddr));
KASSERT((VM_PAGE_TO_PHYS(m) & (pagesizes[bdry_idx] - 1)) == 0,
("unaligned superpage m %p %#jx", m,
(uintmax_t)VM_PAGE_TO_PHYS(m)));
rv = pmap_enter(fs->map->pmap, vaddr, m, fs->prot,
fs->fault_type | (fs->wired ? PMAP_ENTER_WIRED : 0) |
PMAP_ENTER_LARGEPAGE, bdry_idx);
VM_OBJECT_WLOCK(fs->first_object);
vm_page_xunbusy(m);
if (rv != KERN_SUCCESS) {
res = FAULT_FAILURE;
goto out;
}
if ((fs->fault_flags & VM_FAULT_WIRE) != 0) {
for (i = 0; i < atop(pagesizes[bdry_idx]); i++)
vm_page_wire(m + i);
}
if (fs->m_hold != NULL) {
*fs->m_hold = m + (fs->first_pindex - pager_first);
vm_page_wire(*fs->m_hold);
}
goto out;
}
/*
* The range [pager_first, pager_last] that is given to the
* pager is only a hint. The pager may populate any range
* within the object that includes the requested page index.
* In case the pager expanded the range, clip it to fit into
* the map entry.
*/
map_first = OFF_TO_IDX(fs->entry->offset);
if (map_first > pager_first) {
vm_fault_populate_cleanup(fs->first_object, pager_first,
map_first - 1);
pager_first = map_first;
}
map_last = map_first + atop(fs->entry->end - fs->entry->start) - 1;
if (map_last < pager_last) {
vm_fault_populate_cleanup(fs->first_object, map_last + 1,
pager_last);
pager_last = map_last;
}
for (pidx = pager_first, m = vm_page_lookup(fs->first_object, pidx);
pidx <= pager_last;
pidx += npages, m = vm_page_next(&m[npages - 1])) {
vaddr = fs->entry->start + IDX_TO_OFF(pidx) - fs->entry->offset;
psind = m->psind;
if (psind > 0 && ((vaddr & (pagesizes[psind] - 1)) != 0 ||
pidx + OFF_TO_IDX(pagesizes[psind]) - 1 > pager_last ||
!pmap_ps_enabled(fs->map->pmap) || fs->wired))
psind = 0;
npages = atop(pagesizes[psind]);
for (i = 0; i < npages; i++) {
vm_fault_populate_check_page(&m[i]);
vm_fault_dirty(fs, &m[i]);
}
VM_OBJECT_WUNLOCK(fs->first_object);
rv = pmap_enter(fs->map->pmap, vaddr, m, fs->prot, fs->fault_type |
(fs->wired ? PMAP_ENTER_WIRED : 0), psind);
/*
* pmap_enter() may fail for a superpage mapping if additional
* protection policies prevent the full mapping.
* For example, this will happen on amd64 if the entire
* address range does not share the same userspace protection
* key. Revert to single-page mappings if this happens.
*/
MPASS(rv == KERN_SUCCESS ||
(psind > 0 && rv == KERN_PROTECTION_FAILURE));
if (__predict_false(psind > 0 &&
rv == KERN_PROTECTION_FAILURE)) {
MPASS(!fs->wired);
for (i = 0; i < npages; i++) {
rv = pmap_enter(fs->map->pmap, vaddr + ptoa(i),
&m[i], fs->prot, fs->fault_type, 0);
MPASS(rv == KERN_SUCCESS);
}
}
VM_OBJECT_WLOCK(fs->first_object);
for (i = 0; i < npages; i++) {
if ((fs->fault_flags & VM_FAULT_WIRE) != 0 &&
m[i].pindex == fs->first_pindex)
vm_page_wire(&m[i]);
else
vm_page_activate(&m[i]);
if (fs->m_hold != NULL &&
m[i].pindex == fs->first_pindex) {
(*fs->m_hold) = &m[i];
vm_page_wire(&m[i]);
}
vm_page_xunbusy(&m[i]);
}
}
out:
curthread->td_ru.ru_majflt++;
return (res);
}
static int prot_fault_translation;
SYSCTL_INT(_machdep, OID_AUTO, prot_fault_translation, CTLFLAG_RWTUN,
&prot_fault_translation, 0,
"Control signal to deliver on protection fault");
/* compat definition to keep common code for signal translation */
#define UCODE_PAGEFLT 12
#ifdef T_PAGEFLT
_Static_assert(UCODE_PAGEFLT == T_PAGEFLT, "T_PAGEFLT");
#endif
/*
* vm_fault_trap:
*
* Handle a page fault occurring at the given address,
* requiring the given permissions, in the map specified.
* If successful, the page is inserted into the
* associated physical map.
*
* NOTE: the given address should be truncated to the
* proper page address.
*
* KERN_SUCCESS is returned if the page fault is handled; otherwise,
* a standard error specifying why the fault is fatal is returned.
*
* The map in question must be referenced, and remains so.
* Caller may hold no locks.
*/
int
vm_fault_trap(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
int fault_flags, int *signo, int *ucode)
{
int result;
MPASS(signo == NULL || ucode != NULL);
#ifdef KTRACE
if (map != kernel_map && KTRPOINT(curthread, KTR_FAULT))
ktrfault(vaddr, fault_type);
#endif
result = vm_fault(map, trunc_page(vaddr), fault_type, fault_flags,
NULL);
KASSERT(result == KERN_SUCCESS || result == KERN_FAILURE ||
result == KERN_INVALID_ADDRESS ||
result == KERN_RESOURCE_SHORTAGE ||
result == KERN_PROTECTION_FAILURE ||
result == KERN_OUT_OF_BOUNDS,
("Unexpected Mach error %d from vm_fault()", result));
#ifdef KTRACE
if (map != kernel_map && KTRPOINT(curthread, KTR_FAULTEND))
ktrfaultend(result);
#endif
if (result != KERN_SUCCESS && signo != NULL) {
switch (result) {
case KERN_FAILURE:
case KERN_INVALID_ADDRESS:
*signo = SIGSEGV;
*ucode = SEGV_MAPERR;
break;
case KERN_RESOURCE_SHORTAGE:
*signo = SIGBUS;
*ucode = BUS_OOMERR;
break;
case KERN_OUT_OF_BOUNDS:
*signo = SIGBUS;
*ucode = BUS_OBJERR;
break;
case KERN_PROTECTION_FAILURE:
if (prot_fault_translation == 0) {
/*
* Autodetect. This check also covers
* the images without the ABI-tag ELF
* note.
*/
if (SV_CURPROC_ABI() == SV_ABI_FREEBSD &&
curproc->p_osrel >= P_OSREL_SIGSEGV) {
*signo = SIGSEGV;
*ucode = SEGV_ACCERR;
} else {
*signo = SIGBUS;
*ucode = UCODE_PAGEFLT;
}
} else if (prot_fault_translation == 1) {
/* Always compat mode. */
*signo = SIGBUS;
*ucode = UCODE_PAGEFLT;
} else {
/* Always SIGSEGV mode. */
*signo = SIGSEGV;
*ucode = SEGV_ACCERR;
}
break;
default:
KASSERT(0, ("Unexpected Mach error %d from vm_fault()",
result));
break;
}
}
return (result);
}
static bool
vm_fault_object_ensure_wlocked(struct faultstate *fs)
{
if (fs->object == fs->first_object)
VM_OBJECT_ASSERT_WLOCKED(fs->object);
if (!fs->can_read_lock) {
VM_OBJECT_ASSERT_WLOCKED(fs->object);
return (true);
}
if (VM_OBJECT_WOWNED(fs->object))
return (true);
if (VM_OBJECT_TRYUPGRADE(fs->object))
return (true);
return (false);
}
static enum fault_status
vm_fault_lock_vnode(struct faultstate *fs, bool objlocked)
{
struct vnode *vp;
int error, locked;
if (fs->object->type != OBJT_VNODE)
return (FAULT_CONTINUE);
vp = fs->object->handle;
if (vp == fs->vp) {
ASSERT_VOP_LOCKED(vp, "saved vnode is not locked");
return (FAULT_CONTINUE);
}
/*
* Perform an unlock in case the desired vnode changed while
* the map was unlocked during a retry.
*/
vm_fault_unlock_vp(fs);
locked = VOP_ISLOCKED(vp);
if (locked != LK_EXCLUSIVE)
locked = LK_SHARED;
/*
* We must not sleep acquiring the vnode lock while we have
* the page exclusive busied or the object's
* paging-in-progress count incremented. Otherwise, we could
* deadlock.
*/
error = vget(vp, locked | LK_CANRECURSE | LK_NOWAIT);
if (error == 0) {
fs->vp = vp;
return (FAULT_CONTINUE);
}
vhold(vp);
if (objlocked)
vm_fault_unlock_and_deallocate(fs);
else
vm_fault_deallocate(fs);
error = vget(vp, locked | LK_RETRY | LK_CANRECURSE);
vdrop(vp);
fs->vp = vp;
KASSERT(error == 0, ("vm_fault: vget failed %d", error));
return (FAULT_RESTART);
}
/*
* Calculate the desired readahead. Handle drop-behind.
*
* Returns the number of readahead blocks to pass to the pager.
*/
static int
vm_fault_readahead(struct faultstate *fs)
{
int era, nera;
u_char behavior;
KASSERT(fs->lookup_still_valid, ("map unlocked"));
era = fs->entry->read_ahead;
behavior = vm_map_entry_behavior(fs->entry);
if (behavior == MAP_ENTRY_BEHAV_RANDOM) {
nera = 0;
} else if (behavior == MAP_ENTRY_BEHAV_SEQUENTIAL) {
nera = VM_FAULT_READ_AHEAD_MAX;
if (fs->vaddr == fs->entry->next_read)
vm_fault_dontneed(fs, fs->vaddr, nera);
} else if (fs->vaddr == fs->entry->next_read) {
/*
* This is a sequential fault. Arithmetically
* increase the requested number of pages in
* the read-ahead window. The requested
* number of pages is "# of sequential faults
* x (read ahead min + 1) + read ahead min"
*/
nera = VM_FAULT_READ_AHEAD_MIN;
if (era > 0) {
nera += era + 1;
if (nera > VM_FAULT_READ_AHEAD_MAX)
nera = VM_FAULT_READ_AHEAD_MAX;
}
if (era == VM_FAULT_READ_AHEAD_MAX)
vm_fault_dontneed(fs, fs->vaddr, nera);
} else {
/*
* This is a non-sequential fault.
*/
nera = 0;
}
if (era != nera) {
/*
* A read lock on the map suffices to update
* the read ahead count safely.
*/
fs->entry->read_ahead = nera;
}
return (nera);
}
static int
vm_fault_lookup(struct faultstate *fs)
{
int result;
KASSERT(!fs->lookup_still_valid,
("vm_fault_lookup: Map already locked."));
result = vm_map_lookup(&fs->map, fs->vaddr, fs->fault_type |
VM_PROT_FAULT_LOOKUP, &fs->entry, &fs->first_object,
&fs->first_pindex, &fs->prot, &fs->wired);
if (result != KERN_SUCCESS) {
vm_fault_unlock_vp(fs);
return (result);
}
fs->map_generation = fs->map->timestamp;
if (fs->entry->eflags & MAP_ENTRY_NOFAULT) {
panic("%s: fault on nofault entry, addr: %#lx",
__func__, (u_long)fs->vaddr);
}
if (fs->entry->eflags & MAP_ENTRY_IN_TRANSITION &&
fs->entry->wiring_thread != curthread) {
vm_map_unlock_read(fs->map);
vm_map_lock(fs->map);
if (vm_map_lookup_entry(fs->map, fs->vaddr, &fs->entry) &&
(fs->entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
vm_fault_unlock_vp(fs);
fs->entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
vm_map_unlock_and_wait(fs->map, 0);
} else
vm_map_unlock(fs->map);
return (KERN_RESOURCE_SHORTAGE);
}
MPASS((fs->entry->eflags & MAP_ENTRY_GUARD) == 0);
if (fs->wired)
fs->fault_type = fs->prot | (fs->fault_type & VM_PROT_COPY);
else
KASSERT((fs->fault_flags & VM_FAULT_WIRE) == 0,
("!fs->wired && VM_FAULT_WIRE"));
fs->lookup_still_valid = true;
return (KERN_SUCCESS);
}
static int
vm_fault_relookup(struct faultstate *fs)
{
vm_object_t retry_object;
vm_pindex_t retry_pindex;
vm_prot_t retry_prot;
int result;
if (!vm_map_trylock_read(fs->map))
return (KERN_RESTART);
fs->lookup_still_valid = true;
if (fs->map->timestamp == fs->map_generation)
return (KERN_SUCCESS);
result = vm_map_lookup_locked(&fs->map, fs->vaddr, fs->fault_type,
&fs->entry, &retry_object, &retry_pindex, &retry_prot,
&fs->wired);
if (result != KERN_SUCCESS) {
/*
* If retry of map lookup would have blocked then
* retry fault from start.
*/
if (result == KERN_FAILURE)
return (KERN_RESTART);
return (result);
}
if (retry_object != fs->first_object ||
retry_pindex != fs->first_pindex)
return (KERN_RESTART);
/*
* Check whether the protection has changed or the object has
* been copied while we left the map unlocked. Changing from
* read to write permission is OK - we leave the page
* write-protected, and catch the write fault. Changing from
* write to read permission means that we can't mark the page
* write-enabled after all.
*/
fs->prot &= retry_prot;
fs->fault_type &= retry_prot;
if (fs->prot == 0)
return (KERN_RESTART);
/* Reassert because wired may have changed. */
KASSERT(fs->wired || (fs->fault_flags & VM_FAULT_WIRE) == 0,
("!wired && VM_FAULT_WIRE"));
return (KERN_SUCCESS);
}
static void
vm_fault_cow(struct faultstate *fs)
{
bool is_first_object_locked;
KASSERT(fs->object != fs->first_object,
("source and target COW objects are identical"));
/*
* This allows pages to be virtually copied from a backing_object
* into the first_object, where the backing object has no other
* refs to it, and cannot gain any more refs. Instead of a bcopy,
* we just move the page from the backing object to the first
* object. Note that we must mark the page dirty in the first
* object so that it will go out to swap when needed.
*/
is_first_object_locked = false;
if (
/*
* Only one shadow object and no other refs.
*/
fs->object->shadow_count == 1 && fs->object->ref_count == 1 &&
/*
* No other ways to look the object up
*/
fs->object->handle == NULL && (fs->object->flags & OBJ_ANON) != 0 &&
/*
* We don't chase down the shadow chain and we can acquire locks.
*/
(is_first_object_locked = VM_OBJECT_TRYWLOCK(fs->first_object)) &&
fs->object == fs->first_object->backing_object &&
VM_OBJECT_TRYWLOCK(fs->object)) {
/*
* Remove but keep xbusy for replace. fs->m is moved into
* fs->first_object and left busy while fs->first_m is
* conditionally freed.
*/
vm_page_remove_xbusy(fs->m);
vm_page_replace(fs->m, fs->first_object, fs->first_pindex,
fs->first_m);
vm_page_dirty(fs->m);
#if VM_NRESERVLEVEL > 0
/*
* Rename the reservation.
*/
vm_reserv_rename(fs->m, fs->first_object, fs->object,
OFF_TO_IDX(fs->first_object->backing_object_offset));
#endif
VM_OBJECT_WUNLOCK(fs->object);
VM_OBJECT_WUNLOCK(fs->first_object);
fs->first_m = fs->m;
fs->m = NULL;
VM_CNT_INC(v_cow_optim);
} else {
if (is_first_object_locked)
VM_OBJECT_WUNLOCK(fs->first_object);
/*
* Oh, well, lets copy it.
*/
pmap_copy_page(fs->m, fs->first_m);
vm_page_valid(fs->first_m);
if (fs->wired && (fs->fault_flags & VM_FAULT_WIRE) == 0) {
vm_page_wire(fs->first_m);
vm_page_unwire(fs->m, PQ_INACTIVE);
}
/*
* Save the cow page to be released after
* pmap_enter is complete.
*/
fs->m_cow = fs->m;
fs->m = NULL;
/*
* Typically, the shadow object is either private to this
* address space (OBJ_ONEMAPPING) or its pages are read only.
* In the highly unusual case where the pages of a shadow object
* are read/write shared between this and other address spaces,
* we need to ensure that any pmap-level mappings to the
* original, copy-on-write page from the backing object are
* removed from those other address spaces.
*
* The flag check is racy, but this is tolerable: if
* OBJ_ONEMAPPING is cleared after the check, the busy state
* ensures that new mappings of m_cow can't be created.
* pmap_enter() will replace an existing mapping in the current
* address space. If OBJ_ONEMAPPING is set after the check,
* removing mappings will at worse trigger some unnecessary page
* faults.
*/
vm_page_assert_xbusied(fs->m_cow);
if ((fs->first_object->flags & OBJ_ONEMAPPING) == 0)
pmap_remove_all(fs->m_cow);
}
vm_object_pip_wakeup(fs->object);
/*
* Only use the new page below...
*/
fs->object = fs->first_object;
fs->pindex = fs->first_pindex;
fs->m = fs->first_m;
VM_CNT_INC(v_cow_faults);
curthread->td_cow++;
}
static enum fault_next_status
vm_fault_next(struct faultstate *fs)
{
vm_object_t next_object;
if (fs->object == fs->first_object || !fs->can_read_lock)
VM_OBJECT_ASSERT_WLOCKED(fs->object);
else
VM_OBJECT_ASSERT_LOCKED(fs->object);
/*
* The requested page does not exist at this object/
* offset. Remove the invalid page from the object,
* waking up anyone waiting for it, and continue on to
* the next object. However, if this is the top-level
* object, we must leave the busy page in place to
* prevent another process from rushing past us, and
* inserting the page in that object at the same time
* that we are.
*/
if (fs->object == fs->first_object) {
fs->first_m = fs->m;
fs->m = NULL;
} else if (fs->m != NULL) {
if (!vm_fault_object_ensure_wlocked(fs)) {
fs->can_read_lock = false;
vm_fault_unlock_and_deallocate(fs);
return (FAULT_NEXT_RESTART);
}
vm_fault_page_free(&fs->m);
}
/*
* Move on to the next object. Lock the next object before
* unlocking the current one.
*/
next_object = fs->object->backing_object;
if (next_object == NULL)
return (FAULT_NEXT_NOOBJ);
MPASS(fs->first_m != NULL);
KASSERT(fs->object != next_object, ("object loop %p", next_object));
if (fs->can_read_lock)
VM_OBJECT_RLOCK(next_object);
else
VM_OBJECT_WLOCK(next_object);
vm_object_pip_add(next_object, 1);
if (fs->object != fs->first_object)
vm_object_pip_wakeup(fs->object);
fs->pindex += OFF_TO_IDX(fs->object->backing_object_offset);
VM_OBJECT_UNLOCK(fs->object);
fs->object = next_object;
return (FAULT_NEXT_GOTOBJ);
}
static void
vm_fault_zerofill(struct faultstate *fs)
{
/*
* If there's no object left, fill the page in the top
* object with zeros.
*/
if (fs->object != fs->first_object) {
vm_object_pip_wakeup(fs->object);
fs->object = fs->first_object;
fs->pindex = fs->first_pindex;
}
MPASS(fs->first_m != NULL);
MPASS(fs->m == NULL);
fs->m = fs->first_m;
fs->first_m = NULL;
/*
* Zero the page if necessary and mark it valid.
*/
if ((fs->m->flags & PG_ZERO) == 0) {
pmap_zero_page(fs->m);
} else {
VM_CNT_INC(v_ozfod);
}
VM_CNT_INC(v_zfod);
vm_page_valid(fs->m);
}
/*
* Initiate page fault after timeout. Returns true if caller should
* do vm_waitpfault() after the call.
*/
static bool
vm_fault_allocate_oom(struct faultstate *fs)
{
struct timeval now;
vm_fault_unlock_and_deallocate(fs);
if (vm_pfault_oom_attempts < 0)
return (true);
if (!fs->oom_started) {
fs->oom_started = true;
getmicrotime(&fs->oom_start_time);
return (true);
}
getmicrotime(&now);
timevalsub(&now, &fs->oom_start_time);
if (now.tv_sec < vm_pfault_oom_attempts * vm_pfault_oom_wait)
return (true);
if (bootverbose)
printf(
"proc %d (%s) failed to alloc page on fault, starting OOM\n",
curproc->p_pid, curproc->p_comm);
vm_pageout_oom(VM_OOM_MEM_PF);
fs->oom_started = false;
return (false);
}
/*
* Allocate a page directly or via the object populate method.
*/
static enum fault_status
vm_fault_allocate(struct faultstate *fs)
{
struct domainset *dset;
enum fault_status res;
if ((fs->object->flags & OBJ_SIZEVNLOCK) != 0) {
res = vm_fault_lock_vnode(fs, true);
MPASS(res == FAULT_CONTINUE || res == FAULT_RESTART);
if (res == FAULT_RESTART)
return (res);
}
if (fs->pindex >= fs->object->size) {
vm_fault_unlock_and_deallocate(fs);
return (FAULT_OUT_OF_BOUNDS);
}
if (fs->object == fs->first_object &&
(fs->first_object->flags & OBJ_POPULATE) != 0 &&
fs->first_object->shadow_count == 0) {
res = vm_fault_populate(fs);
switch (res) {
case FAULT_SUCCESS:
case FAULT_FAILURE:
case FAULT_RESTART:
vm_fault_unlock_and_deallocate(fs);
return (res);
case FAULT_CONTINUE:
/*
* Pager's populate() method
* returned VM_PAGER_BAD.
*/
break;
default:
panic("inconsistent return codes");
}
}
/*
* Allocate a new page for this object/offset pair.
*
* If the process has a fatal signal pending, prioritize the allocation
* with the expectation that the process will exit shortly and free some
* pages. In particular, the signal may have been posted by the page
* daemon in an attempt to resolve an out-of-memory condition.
*
* The unlocked read of the p_flag is harmless. At worst, the P_KILLED
* might be not observed here, and allocation fails, causing a restart
* and new reading of the p_flag.
*/
dset = fs->object->domain.dr_policy;
if (dset == NULL)
dset = curthread->td_domain.dr_policy;
if (!vm_page_count_severe_set(&dset->ds_mask) || P_KILLED(curproc)) {
#if VM_NRESERVLEVEL > 0
vm_object_color(fs->object, atop(fs->vaddr) - fs->pindex);
#endif
if (!vm_pager_can_alloc_page(fs->object, fs->pindex)) {
vm_fault_unlock_and_deallocate(fs);
return (FAULT_FAILURE);
}
fs->m = vm_page_alloc(fs->object, fs->pindex,
P_KILLED(curproc) ? VM_ALLOC_SYSTEM : 0);
}
if (fs->m == NULL) {
if (vm_fault_allocate_oom(fs))
vm_waitpfault(dset, vm_pfault_oom_wait * hz);
return (FAULT_RESTART);
}
fs->oom_started = false;
return (FAULT_CONTINUE);
}
/*
* Call the pager to retrieve the page if there is a chance
* that the pager has it, and potentially retrieve additional
* pages at the same time.
*/
static enum fault_status
vm_fault_getpages(struct faultstate *fs, int *behindp, int *aheadp)
{
vm_offset_t e_end, e_start;
int ahead, behind, cluster_offset, rv;
enum fault_status status;
u_char behavior;
/*
* Prepare for unlocking the map. Save the map
* entry's start and end addresses, which are used to
* optimize the size of the pager operation below.
* Even if the map entry's addresses change after
* unlocking the map, using the saved addresses is
* safe.
*/
e_start = fs->entry->start;
e_end = fs->entry->end;
behavior = vm_map_entry_behavior(fs->entry);
/*
* If the pager for the current object might have
* the page, then determine the number of additional
* pages to read and potentially reprioritize
* previously read pages for earlier reclamation.
* These operations should only be performed once per
* page fault. Even if the current pager doesn't
* have the page, the number of additional pages to
* read will apply to subsequent objects in the
* shadow chain.
*/
if (fs->nera == -1 && !P_KILLED(curproc))
fs->nera = vm_fault_readahead(fs);
/*
* Release the map lock before locking the vnode or
* sleeping in the pager. (If the current object has
* a shadow, then an earlier iteration of this loop
* may have already unlocked the map.)
*/
vm_fault_unlock_map(fs);
status = vm_fault_lock_vnode(fs, false);
MPASS(status == FAULT_CONTINUE || status == FAULT_RESTART);
if (status == FAULT_RESTART)
return (status);
KASSERT(fs->vp == NULL || !fs->map->system_map,
("vm_fault: vnode-backed object mapped by system map"));
/*
* Page in the requested page and hint the pager,
* that it may bring up surrounding pages.
*/
if (fs->nera == -1 || behavior == MAP_ENTRY_BEHAV_RANDOM ||
P_KILLED(curproc)) {
behind = 0;
ahead = 0;
} else {
/* Is this a sequential fault? */
if (fs->nera > 0) {
behind = 0;
ahead = fs->nera;
} else {
/*
* Request a cluster of pages that is
* aligned to a VM_FAULT_READ_DEFAULT
* page offset boundary within the
* object. Alignment to a page offset
* boundary is more likely to coincide
* with the underlying file system
* block than alignment to a virtual
* address boundary.
*/
cluster_offset = fs->pindex % VM_FAULT_READ_DEFAULT;
behind = ulmin(cluster_offset,
atop(fs->vaddr - e_start));
ahead = VM_FAULT_READ_DEFAULT - 1 - cluster_offset;
}
ahead = ulmin(ahead, atop(e_end - fs->vaddr) - 1);
}
*behindp = behind;
*aheadp = ahead;
rv = vm_pager_get_pages(fs->object, &fs->m, 1, behindp, aheadp);
if (rv == VM_PAGER_OK)
return (FAULT_HARD);
if (rv == VM_PAGER_ERROR)
printf("vm_fault: pager read error, pid %d (%s)\n",
curproc->p_pid, curproc->p_comm);
/*
* If an I/O error occurred or the requested page was
* outside the range of the pager, clean up and return
* an error.
*/
if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) {
VM_OBJECT_WLOCK(fs->object);
vm_fault_page_free(&fs->m);
vm_fault_unlock_and_deallocate(fs);
return (FAULT_OUT_OF_BOUNDS);
}
KASSERT(rv == VM_PAGER_FAIL,
("%s: unexpected pager error %d", __func__, rv));
return (FAULT_CONTINUE);
}
/*
* Wait/Retry if the page is busy. We have to do this if the page is
* either exclusive or shared busy because the vm_pager may be using
* read busy for pageouts (and even pageins if it is the vnode pager),
* and we could end up trying to pagein and pageout the same page
* simultaneously.
*
* We can theoretically allow the busy case on a read fault if the page
* is marked valid, but since such pages are typically already pmap'd,
* putting that special case in might be more effort then it is worth.
* We cannot under any circumstances mess around with a shared busied
* page except, perhaps, to pmap it.
*/
static void
vm_fault_busy_sleep(struct faultstate *fs)
{
/*
* Reference the page before unlocking and
* sleeping so that the page daemon is less
* likely to reclaim it.
*/
vm_page_aflag_set(fs->m, PGA_REFERENCED);
if (fs->object != fs->first_object) {
vm_fault_page_release(&fs->first_m);
vm_object_pip_wakeup(fs->first_object);
}
vm_object_pip_wakeup(fs->object);
vm_fault_unlock_map(fs);
if (fs->m != vm_page_lookup(fs->object, fs->pindex) ||
!vm_page_busy_sleep(fs->m, "vmpfw", 0))
VM_OBJECT_UNLOCK(fs->object);
VM_CNT_INC(v_intrans);
vm_object_deallocate(fs->first_object);
}
/*
* Handle page lookup, populate, allocate, page-in for the current
* object.
*
* The object is locked on entry and will remain locked with a return
* code of FAULT_CONTINUE so that fault may follow the shadow chain.
* Otherwise, the object will be unlocked upon return.
*/
static enum fault_status
vm_fault_object(struct faultstate *fs, int *behindp, int *aheadp)
{
enum fault_status res;
bool dead;
if (fs->object == fs->first_object || !fs->can_read_lock)
VM_OBJECT_ASSERT_WLOCKED(fs->object);
else
VM_OBJECT_ASSERT_LOCKED(fs->object);
/*
* If the object is marked for imminent termination, we retry
* here, since the collapse pass has raced with us. Otherwise,
* if we see terminally dead object, return fail.
*/
if ((fs->object->flags & OBJ_DEAD) != 0) {
dead = fs->object->type == OBJT_DEAD;
vm_fault_unlock_and_deallocate(fs);
if (dead)
return (FAULT_PROTECTION_FAILURE);
pause("vmf_de", 1);
return (FAULT_RESTART);
}
/*
* See if the page is resident.
*/
fs->m = vm_page_lookup(fs->object, fs->pindex);
if (fs->m != NULL) {
if (!vm_page_tryxbusy(fs->m)) {
vm_fault_busy_sleep(fs);
return (FAULT_RESTART);
}
/*
* The page is marked busy for other processes and the
* pagedaemon. If it is still completely valid we are
* done.
*/
if (vm_page_all_valid(fs->m)) {
VM_OBJECT_UNLOCK(fs->object);
return (FAULT_SOFT);
}
}
/*
* Page is not resident. If the pager might contain the page
* or this is the beginning of the search, allocate a new
* page.
*/
if (fs->m == NULL && (vm_fault_object_needs_getpages(fs->object) ||
fs->object == fs->first_object)) {
if (!vm_fault_object_ensure_wlocked(fs)) {
fs->can_read_lock = false;
vm_fault_unlock_and_deallocate(fs);
return (FAULT_RESTART);
}
res = vm_fault_allocate(fs);
if (res != FAULT_CONTINUE)
return (res);
}
/*
* Check to see if the pager can possibly satisfy this fault.
* If not, skip to the next object without dropping the lock to
* preserve atomicity of shadow faults.
*/
if (vm_fault_object_needs_getpages(fs->object)) {
/*
* At this point, we have either allocated a new page
* or found an existing page that is only partially
* valid.
*
* We hold a reference on the current object and the
* page is exclusive busied. The exclusive busy
* prevents simultaneous faults and collapses while
* the object lock is dropped.
*/
VM_OBJECT_UNLOCK(fs->object);
res = vm_fault_getpages(fs, behindp, aheadp);
if (res == FAULT_CONTINUE)
VM_OBJECT_WLOCK(fs->object);
} else {
res = FAULT_CONTINUE;
}
return (res);
}
int
vm_fault(vm_map_t map, vm_offset_t vaddr, vm_prot_t fault_type,
int fault_flags, vm_page_t *m_hold)
{
struct faultstate fs;
int ahead, behind, faultcount, rv;
enum fault_status res;
enum fault_next_status res_next;
bool hardfault;
VM_CNT_INC(v_vm_faults);
if ((curthread->td_pflags & TDP_NOFAULTING) != 0)
return (KERN_PROTECTION_FAILURE);
fs.vp = NULL;
fs.vaddr = vaddr;
fs.m_hold = m_hold;
fs.fault_flags = fault_flags;
fs.map = map;
fs.lookup_still_valid = false;
fs.oom_started = false;
fs.nera = -1;
fs.can_read_lock = true;
faultcount = 0;
hardfault = false;
RetryFault:
fs.fault_type = fault_type;
/*
* Find the backing store object and offset into it to begin the
* search.
*/
rv = vm_fault_lookup(&fs);
if (rv != KERN_SUCCESS) {
if (rv == KERN_RESOURCE_SHORTAGE)
goto RetryFault;
return (rv);
}
/*
* Try to avoid lock contention on the top-level object through
* special-case handling of some types of page faults, specifically,
* those that are mapping an existing page from the top-level object.
* Under this condition, a read lock on the object suffices, allowing
* multiple page faults of a similar type to run in parallel.
*/
if (fs.vp == NULL /* avoid locked vnode leak */ &&
(fs.entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) == 0 &&
(fs.fault_flags & (VM_FAULT_WIRE | VM_FAULT_DIRTY)) == 0) {
res = vm_fault_soft_fast(&fs);
if (res == FAULT_SUCCESS) {
VM_OBJECT_ASSERT_UNLOCKED(fs.first_object);
return (KERN_SUCCESS);
}
VM_OBJECT_ASSERT_WLOCKED(fs.first_object);
} else {
VM_OBJECT_WLOCK(fs.first_object);
}
/*
* Make a reference to this object to prevent its disposal while we
* are messing with it. Once we have the reference, the map is free
* to be diddled. Since objects reference their shadows (and copies),
* they will stay around as well.
*
* Bump the paging-in-progress count to prevent size changes (e.g.
* truncation operations) during I/O.
*/
vm_object_reference_locked(fs.first_object);
vm_object_pip_add(fs.first_object, 1);
fs.m_cow = fs.m = fs.first_m = NULL;
/*
* Search for the page at object/offset.
*/
fs.object = fs.first_object;
fs.pindex = fs.first_pindex;
if ((fs.entry->eflags & MAP_ENTRY_SPLIT_BOUNDARY_MASK) != 0) {
res = vm_fault_allocate(&fs);
switch (res) {
case FAULT_RESTART:
goto RetryFault;
case FAULT_SUCCESS:
return (KERN_SUCCESS);
case FAULT_FAILURE:
return (KERN_FAILURE);
case FAULT_OUT_OF_BOUNDS:
return (KERN_OUT_OF_BOUNDS);
case FAULT_CONTINUE:
break;
default:
panic("vm_fault: Unhandled status %d", res);
}
}
while (TRUE) {
KASSERT(fs.m == NULL,
("page still set %p at loop start", fs.m));
res = vm_fault_object(&fs, &behind, &ahead);
switch (res) {
case FAULT_SOFT:
goto found;
case FAULT_HARD:
faultcount = behind + 1 + ahead;
hardfault = true;
goto found;
case FAULT_RESTART:
goto RetryFault;
case FAULT_SUCCESS:
return (KERN_SUCCESS);
case FAULT_FAILURE:
return (KERN_FAILURE);
case FAULT_OUT_OF_BOUNDS:
return (KERN_OUT_OF_BOUNDS);
case FAULT_PROTECTION_FAILURE:
return (KERN_PROTECTION_FAILURE);
case FAULT_CONTINUE:
break;
default:
panic("vm_fault: Unhandled status %d", res);
}
/*
* The page was not found in the current object. Try to
* traverse into a backing object or zero fill if none is
* found.
*/
res_next = vm_fault_next(&fs);
if (res_next == FAULT_NEXT_RESTART)
goto RetryFault;
else if (res_next == FAULT_NEXT_GOTOBJ)
continue;
MPASS(res_next == FAULT_NEXT_NOOBJ);
if ((fs.fault_flags & VM_FAULT_NOFILL) != 0) {
if (fs.first_object == fs.object)
vm_fault_page_free(&fs.first_m);
vm_fault_unlock_and_deallocate(&fs);
return (KERN_OUT_OF_BOUNDS);
}
VM_OBJECT_UNLOCK(fs.object);
vm_fault_zerofill(&fs);
/* Don't try to prefault neighboring pages. */
faultcount = 1;
break;
}
found:
/*
* A valid page has been found and exclusively busied. The
* object lock must no longer be held.
*/
vm_page_assert_xbusied(fs.m);
VM_OBJECT_ASSERT_UNLOCKED(fs.object);
/*
* If the page is being written, but isn't already owned by the
* top-level object, we have to copy it into a new page owned by the
* top-level object.
*/
if (fs.object != fs.first_object) {
/*
* We only really need to copy if we want to write it.
*/
if ((fs.fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
vm_fault_cow(&fs);
/*
* We only try to prefault read-only mappings to the
* neighboring pages when this copy-on-write fault is
* a hard fault. In other cases, trying to prefault
* is typically wasted effort.
*/
if (faultcount == 0)
faultcount = 1;
} else {
fs.prot &= ~VM_PROT_WRITE;
}
}
/*
* We must verify that the maps have not changed since our last
* lookup.
*/
if (!fs.lookup_still_valid) {
rv = vm_fault_relookup(&fs);
if (rv != KERN_SUCCESS) {
vm_fault_deallocate(&fs);
if (rv == KERN_RESTART)
goto RetryFault;
return (rv);
}
}
VM_OBJECT_ASSERT_UNLOCKED(fs.object);
/*
* If the page was filled by a pager, save the virtual address that
* should be faulted on next under a sequential access pattern to the
* map entry. A read lock on the map suffices to update this address
* safely.
*/
if (hardfault)
fs.entry->next_read = vaddr + ptoa(ahead) + PAGE_SIZE;
/*
* Page must be completely valid or it is not fit to
* map into user space. vm_pager_get_pages() ensures this.
*/
vm_page_assert_xbusied(fs.m);
KASSERT(vm_page_all_valid(fs.m),
("vm_fault: page %p partially invalid", fs.m));
vm_fault_dirty(&fs, fs.m);
/*
* Put this page into the physical map. We had to do the unlock above
* because pmap_enter() may sleep. We don't put the page
* back on the active queue until later so that the pageout daemon
* won't find it (yet).
*/
pmap_enter(fs.map->pmap, vaddr, fs.m, fs.prot,
fs.fault_type | (fs.wired ? PMAP_ENTER_WIRED : 0), 0);
if (faultcount != 1 && (fs.fault_flags & VM_FAULT_WIRE) == 0 &&
fs.wired == 0)
vm_fault_prefault(&fs, vaddr,
faultcount > 0 ? behind : PFBAK,
faultcount > 0 ? ahead : PFFOR, false);
/*
* If the page is not wired down, then put it where the pageout daemon
* can find it.
*/
if ((fs.fault_flags & VM_FAULT_WIRE) != 0)
vm_page_wire(fs.m);
else
vm_page_activate(fs.m);
if (fs.m_hold != NULL) {
(*fs.m_hold) = fs.m;
vm_page_wire(fs.m);
}
vm_page_xunbusy(fs.m);
fs.m = NULL;
/*
* Unlock everything, and return
*/
vm_fault_deallocate(&fs);
if (hardfault) {
VM_CNT_INC(v_io_faults);
curthread->td_ru.ru_majflt++;
#ifdef RACCT
if (racct_enable && fs.object->type == OBJT_VNODE) {
PROC_LOCK(curproc);
if ((fs.fault_type & (VM_PROT_COPY | VM_PROT_WRITE)) != 0) {
racct_add_force(curproc, RACCT_WRITEBPS,
PAGE_SIZE + behind * PAGE_SIZE);
racct_add_force(curproc, RACCT_WRITEIOPS, 1);
} else {
racct_add_force(curproc, RACCT_READBPS,
PAGE_SIZE + ahead * PAGE_SIZE);
racct_add_force(curproc, RACCT_READIOPS, 1);
}
PROC_UNLOCK(curproc);
}
#endif
} else
curthread->td_ru.ru_minflt++;
return (KERN_SUCCESS);
}
/*
* Speed up the reclamation of pages that precede the faulting pindex within
* the first object of the shadow chain. Essentially, perform the equivalent
* to madvise(..., MADV_DONTNEED) on a large cluster of pages that precedes
* the faulting pindex by the cluster size when the pages read by vm_fault()
* cross a cluster-size boundary. The cluster size is the greater of the
* smallest superpage size and VM_FAULT_DONTNEED_MIN.
*
* When "fs->first_object" is a shadow object, the pages in the backing object
* that precede the faulting pindex are deactivated by vm_fault(). So, this
* function must only be concerned with pages in the first object.
*/
static void
vm_fault_dontneed(const struct faultstate *fs, vm_offset_t vaddr, int ahead)
{
vm_map_entry_t entry;
vm_object_t first_object;
vm_offset_t end, start;
vm_page_t m, m_next;
vm_pindex_t pend, pstart;
vm_size_t size;
VM_OBJECT_ASSERT_UNLOCKED(fs->object);
first_object = fs->first_object;
/* Neither fictitious nor unmanaged pages can be reclaimed. */
if ((first_object->flags & (OBJ_FICTITIOUS | OBJ_UNMANAGED)) == 0) {
VM_OBJECT_RLOCK(first_object);
size = VM_FAULT_DONTNEED_MIN;
if (MAXPAGESIZES > 1 && size < pagesizes[1])
size = pagesizes[1];
end = rounddown2(vaddr, size);
if (vaddr - end >= size - PAGE_SIZE - ptoa(ahead) &&
(entry = fs->entry)->start < end) {
if (end - entry->start < size)
start = entry->start;
else
start = end - size;
pmap_advise(fs->map->pmap, start, end, MADV_DONTNEED);
pstart = OFF_TO_IDX(entry->offset) + atop(start -
entry->start);
m_next = vm_page_find_least(first_object, pstart);
pend = OFF_TO_IDX(entry->offset) + atop(end -
entry->start);
while ((m = m_next) != NULL && m->pindex < pend) {
m_next = TAILQ_NEXT(m, listq);
if (!vm_page_all_valid(m) ||
vm_page_busied(m))
continue;
/*
* Don't clear PGA_REFERENCED, since it would
* likely represent a reference by a different
* process.
*
* Typically, at this point, prefetched pages
* are still in the inactive queue. Only
* pages that triggered page faults are in the
* active queue. The test for whether the page
* is in the inactive queue is racy; in the
* worst case we will requeue the page
* unnecessarily.
*/
if (!vm_page_inactive(m))
vm_page_deactivate(m);
}
}
VM_OBJECT_RUNLOCK(first_object);
}
}
/*
* vm_fault_prefault provides a quick way of clustering
* pagefaults into a processes address space. It is a "cousin"
* of vm_map_pmap_enter, except it runs at page fault time instead
* of mmap time.
*/
static void
vm_fault_prefault(const struct faultstate *fs, vm_offset_t addra,
int backward, int forward, bool obj_locked)
{
pmap_t pmap;
vm_map_entry_t entry;
vm_object_t backing_object, lobject;
vm_offset_t addr, starta;
vm_pindex_t pindex;
vm_page_t m;
int i;
pmap = fs->map->pmap;
if (pmap != vmspace_pmap(curthread->td_proc->p_vmspace))
return;
entry = fs->entry;
if (addra < backward * PAGE_SIZE) {
starta = entry->start;
} else {
starta = addra - backward * PAGE_SIZE;
if (starta < entry->start)
starta = entry->start;
}
/*
* Generate the sequence of virtual addresses that are candidates for
* prefaulting in an outward spiral from the faulting virtual address,
* "addra". Specifically, the sequence is "addra - PAGE_SIZE", "addra
* + PAGE_SIZE", "addra - 2 * PAGE_SIZE", "addra + 2 * PAGE_SIZE", ...
* If the candidate address doesn't have a backing physical page, then
* the loop immediately terminates.
*/
for (i = 0; i < 2 * imax(backward, forward); i++) {
addr = addra + ((i >> 1) + 1) * ((i & 1) == 0 ? -PAGE_SIZE :
PAGE_SIZE);
if (addr > addra + forward * PAGE_SIZE)
addr = 0;
if (addr < starta || addr >= entry->end)
continue;
if (!pmap_is_prefaultable(pmap, addr))
continue;
pindex = ((addr - entry->start) + entry->offset) >> PAGE_SHIFT;
lobject = entry->object.vm_object;
if (!obj_locked)
VM_OBJECT_RLOCK(lobject);
while ((m = vm_page_lookup(lobject, pindex)) == NULL &&
!vm_fault_object_needs_getpages(lobject) &&
(backing_object = lobject->backing_object) != NULL) {
KASSERT((lobject->backing_object_offset & PAGE_MASK) ==
0, ("vm_fault_prefault: unaligned object offset"));
pindex += lobject->backing_object_offset >> PAGE_SHIFT;
VM_OBJECT_RLOCK(backing_object);
if (!obj_locked || lobject != entry->object.vm_object)
VM_OBJECT_RUNLOCK(lobject);
lobject = backing_object;
}
if (m == NULL) {
if (!obj_locked || lobject != entry->object.vm_object)
VM_OBJECT_RUNLOCK(lobject);
break;
}
if (vm_page_all_valid(m) &&
(m->flags & PG_FICTITIOUS) == 0)
pmap_enter_quick(pmap, addr, m, entry->protection);
if (!obj_locked || lobject != entry->object.vm_object)
VM_OBJECT_RUNLOCK(lobject);
}
}
/*
* Hold each of the physical pages that are mapped by the specified range of
* virtual addresses, ["addr", "addr" + "len"), if those mappings are valid
* and allow the specified types of access, "prot". If all of the implied
* pages are successfully held, then the number of held pages is returned
* together with pointers to those pages in the array "ma". However, if any
* of the pages cannot be held, -1 is returned.
*/
int
vm_fault_quick_hold_pages(vm_map_t map, vm_offset_t addr, vm_size_t len,
vm_prot_t prot, vm_page_t *ma, int max_count)
{
vm_offset_t end, va;
vm_page_t *mp;
int count;
boolean_t pmap_failed;
if (len == 0)
return (0);
end = round_page(addr + len);
addr = trunc_page(addr);
if (!vm_map_range_valid(map, addr, end))
return (-1);
if (atop(end - addr) > max_count)
panic("vm_fault_quick_hold_pages: count > max_count");
count = atop(end - addr);
/*
* Most likely, the physical pages are resident in the pmap, so it is
* faster to try pmap_extract_and_hold() first.
*/
pmap_failed = FALSE;
for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE) {
*mp = pmap_extract_and_hold(map->pmap, va, prot);
if (*mp == NULL)
pmap_failed = TRUE;
else if ((prot & VM_PROT_WRITE) != 0 &&
(*mp)->dirty != VM_PAGE_BITS_ALL) {
/*
* Explicitly dirty the physical page. Otherwise, the
* caller's changes may go unnoticed because they are
* performed through an unmanaged mapping or by a DMA
* operation.
*
* The object lock is not held here.
* See vm_page_clear_dirty_mask().
*/
vm_page_dirty(*mp);
}
}
if (pmap_failed) {
/*
* One or more pages could not be held by the pmap. Either no
* page was mapped at the specified virtual address or that
* mapping had insufficient permissions. Attempt to fault in
* and hold these pages.
*
* If vm_fault_disable_pagefaults() was called,
* i.e., TDP_NOFAULTING is set, we must not sleep nor
* acquire MD VM locks, which means we must not call
* vm_fault(). Some (out of tree) callers mark
* too wide a code area with vm_fault_disable_pagefaults()
* already, use the VM_PROT_QUICK_NOFAULT flag to request
* the proper behaviour explicitly.
*/
if ((prot & VM_PROT_QUICK_NOFAULT) != 0 &&
(curthread->td_pflags & TDP_NOFAULTING) != 0)
goto error;
for (mp = ma, va = addr; va < end; mp++, va += PAGE_SIZE)
if (*mp == NULL && vm_fault(map, va, prot,
VM_FAULT_NORMAL, mp) != KERN_SUCCESS)
goto error;
}
return (count);
error:
for (mp = ma; mp < ma + count; mp++)
if (*mp != NULL)
vm_page_unwire(*mp, PQ_INACTIVE);
return (-1);
}
/*
* Routine:
* vm_fault_copy_entry
* Function:
* Create new object backing dst_entry with private copy of all
* underlying pages. When src_entry is equal to dst_entry, function
* implements COW for wired-down map entry. Otherwise, it forks
* wired entry into dst_map.
*
* In/out conditions:
* The source and destination maps must be locked for write.
* The source map entry must be wired down (or be a sharing map
* entry corresponding to a main map entry that is wired down).
*/
void
vm_fault_copy_entry(vm_map_t dst_map, vm_map_t src_map __unused,
vm_map_entry_t dst_entry, vm_map_entry_t src_entry,
vm_ooffset_t *fork_charge)
{
vm_object_t backing_object, dst_object, object, src_object;
vm_pindex_t dst_pindex, pindex, src_pindex;
vm_prot_t access, prot;
vm_offset_t vaddr;
vm_page_t dst_m;
vm_page_t src_m;
bool upgrade;
upgrade = src_entry == dst_entry;
KASSERT(upgrade || dst_entry->object.vm_object == NULL,
("vm_fault_copy_entry: vm_object not NULL"));
/*
* If not an upgrade, then enter the mappings in the pmap as
* read and/or execute accesses. Otherwise, enter them as
* write accesses.
*
* A writeable large page mapping is only created if all of
* the constituent small page mappings are modified. Marking
* PTEs as modified on inception allows promotion to happen
* without taking potentially large number of soft faults.
*/
access = prot = dst_entry->protection;
if (!upgrade)
access &= ~VM_PROT_WRITE;
src_object = src_entry->object.vm_object;
src_pindex = OFF_TO_IDX(src_entry->offset);
if (upgrade && (dst_entry->eflags & MAP_ENTRY_NEEDS_COPY) == 0) {
dst_object = src_object;
vm_object_reference(dst_object);
} else {
/*
* Create the top-level object for the destination entry.
* Doesn't actually shadow anything - we copy the pages
* directly.
*/
dst_object = vm_object_allocate_anon(atop(dst_entry->end -
dst_entry->start), NULL, NULL, 0);
#if VM_NRESERVLEVEL > 0
dst_object->flags |= OBJ_COLORED;
dst_object->pg_color = atop(dst_entry->start);
#endif
dst_object->domain = src_object->domain;
dst_object->charge = dst_entry->end - dst_entry->start;
dst_entry->object.vm_object = dst_object;
dst_entry->offset = 0;
dst_entry->eflags &= ~MAP_ENTRY_VN_EXEC;
}
VM_OBJECT_WLOCK(dst_object);
if (fork_charge != NULL) {
KASSERT(dst_entry->cred == NULL,
("vm_fault_copy_entry: leaked swp charge"));
dst_object->cred = curthread->td_ucred;
crhold(dst_object->cred);
*fork_charge += dst_object->charge;
} else if ((dst_object->flags & OBJ_SWAP) != 0 &&
dst_object->cred == NULL) {
KASSERT(dst_entry->cred != NULL, ("no cred for entry %p",
dst_entry));
dst_object->cred = dst_entry->cred;
dst_entry->cred = NULL;
}
/*
* Loop through all of the virtual pages within the entry's
* range, copying each page from the source object to the
* destination object. Since the source is wired, those pages
* must exist. In contrast, the destination is pageable.
* Since the destination object doesn't share any backing storage
* with the source object, all of its pages must be dirtied,
* regardless of whether they can be written.
*/
for (vaddr = dst_entry->start, dst_pindex = 0;
vaddr < dst_entry->end;
vaddr += PAGE_SIZE, dst_pindex++) {
again:
/*
* Find the page in the source object, and copy it in.
* Because the source is wired down, the page will be
* in memory.
*/
if (src_object != dst_object)
VM_OBJECT_RLOCK(src_object);
object = src_object;
pindex = src_pindex + dst_pindex;
while ((src_m = vm_page_lookup(object, pindex)) == NULL &&
(backing_object = object->backing_object) != NULL) {
/*
* Unless the source mapping is read-only or
* it is presently being upgraded from
* read-only, the first object in the shadow
* chain should provide all of the pages. In
* other words, this loop body should never be
* executed when the source mapping is already
* read/write.
*/
KASSERT((src_entry->protection & VM_PROT_WRITE) == 0 ||
upgrade,
("vm_fault_copy_entry: main object missing page"));
VM_OBJECT_RLOCK(backing_object);
pindex += OFF_TO_IDX(object->backing_object_offset);
if (object != dst_object)
VM_OBJECT_RUNLOCK(object);
object = backing_object;
}
KASSERT(src_m != NULL, ("vm_fault_copy_entry: page missing"));
if (object != dst_object) {
/*
* Allocate a page in the destination object.
*/
dst_m = vm_page_alloc(dst_object, (src_object ==
dst_object ? src_pindex : 0) + dst_pindex,
VM_ALLOC_NORMAL);
if (dst_m == NULL) {
VM_OBJECT_WUNLOCK(dst_object);
VM_OBJECT_RUNLOCK(object);
vm_wait(dst_object);
VM_OBJECT_WLOCK(dst_object);
goto again;
}
/*
* See the comment in vm_fault_cow().
*/
if (src_object == dst_object &&
(object->flags & OBJ_ONEMAPPING) == 0)
pmap_remove_all(src_m);
pmap_copy_page(src_m, dst_m);
/*
* The object lock does not guarantee that "src_m" will
* transition from invalid to valid, but it does ensure
* that "src_m" will not transition from valid to
* invalid.
*/
dst_m->dirty = dst_m->valid = src_m->valid;
VM_OBJECT_RUNLOCK(object);
} else {
dst_m = src_m;
if (vm_page_busy_acquire(dst_m, VM_ALLOC_WAITFAIL) == 0)
goto again;
if (dst_m->pindex >= dst_object->size) {
/*
* We are upgrading. Index can occur
* out of bounds if the object type is
* vnode and the file was truncated.
*/
vm_page_xunbusy(dst_m);
break;
}
}
/*
* Enter it in the pmap. If a wired, copy-on-write
* mapping is being replaced by a write-enabled
* mapping, then wire that new mapping.
*
* The page can be invalid if the user called
* msync(MS_INVALIDATE) or truncated the backing vnode
* or shared memory object. In this case, do not
* insert it into pmap, but still do the copy so that
* all copies of the wired map entry have similar
* backing pages.
*/
if (vm_page_all_valid(dst_m)) {
VM_OBJECT_WUNLOCK(dst_object);
pmap_enter(dst_map->pmap, vaddr, dst_m, prot,
access | (upgrade ? PMAP_ENTER_WIRED : 0), 0);
VM_OBJECT_WLOCK(dst_object);
}
/*
* Mark it no longer busy, and put it on the active list.
*/
if (upgrade) {
if (src_m != dst_m) {
vm_page_unwire(src_m, PQ_INACTIVE);
vm_page_wire(dst_m);
} else {
KASSERT(vm_page_wired(dst_m),
("dst_m %p is not wired", dst_m));
}
} else {
vm_page_activate(dst_m);
}
vm_page_xunbusy(dst_m);
}
VM_OBJECT_WUNLOCK(dst_object);
if (upgrade) {
dst_entry->eflags &= ~(MAP_ENTRY_COW | MAP_ENTRY_NEEDS_COPY);
vm_object_deallocate(src_object);
}
}
/*
* Block entry into the machine-independent layer's page fault handler by
* the calling thread. Subsequent calls to vm_fault() by that thread will
* return KERN_PROTECTION_FAILURE. Enable machine-dependent handling of
* spurious page faults.
*/
int
vm_fault_disable_pagefaults(void)
{
return (curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR));
}
void
vm_fault_enable_pagefaults(int save)
{
curthread_pflags_restore(save);
}
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