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NetBSD/sys/vm/vm_object.c

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/* $NetBSD: vm_object.c,v 1.53 1998/03/01 02:24:01 fvdl Exp $ */
/*-
* Copyright (c) 1997 Charles M. Hannum. All rights reserved.
*
* 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 Charles M. Hannum.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
*/
/*
* Copyright (c) 1991, 1993
* The Regents of the University of California. 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.
*
* @(#)vm_object.c 8.7 (Berkeley) 5/11/95
*
*
* 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.
*/
/*
* Virtual memory object module.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <vm/vm.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
/*
* Virtual memory objects maintain the actual data
* associated with allocated virtual memory. A given
* page of memory exists within exactly one object.
*
* An object is only deallocated when all "references"
* are given up. Only one "reference" to a given
* region of an object should be writeable.
*
* Associated with each object is a list of all resident
* memory pages belonging to that object; this list is
* maintained by the "vm_page" module, and locked by the object's
* lock.
*
* Each object also records a "pager" routine which is
* used to retrieve (and store) pages to the proper backing
* storage. In addition, objects may be backed by other
* objects from which they were virtual-copied.
*
* The only items within the object structure which are
* modified after time of creation are:
* reference count locked by object's lock
* pager routine locked by object's lock
*
*/
struct vm_object kernel_object_store;
struct vm_object kmem_object_store;
#define VM_OBJECT_HASH_COUNT 157
int vm_cache_max = 100; /* can patch if necessary */
struct vm_object_hash_head vm_object_hashtable[VM_OBJECT_HASH_COUNT];
long object_collapses = 0;
long object_bypasses = 0;
boolean_t vm_object_collapse_allowed = TRUE;
#ifndef VMDEBUG
#define VMDEBUG 0
#endif
#ifdef DEBUG
#define VMDEBUG_SHADOW 0x1
#define VMDEBUG_SHADOW_VERBOSE 0x2
#define VMDEBUG_COLLAPSE 0x4
#define VMDEBUG_COLLAPSE_PAGEIN 0x8
int vmdebug = VMDEBUG;
#endif
static void _vm_object_allocate __P((vm_size_t, vm_object_t));
int vm_object_bypass __P((vm_object_t));
int vm_object_overlay __P((vm_object_t));
int vm_object_remove_from_pager
__P((vm_object_t, vm_offset_t, vm_offset_t));
void vm_object_set_shadow __P((vm_object_t, vm_object_t));
void vm_object_terminate __P((vm_object_t));
/*
* vm_object_init:
*
* Initialize the VM objects module.
*/
void
vm_object_init(size)
vm_size_t size;
{
register int i;
TAILQ_INIT(&vm_object_cached_list);
TAILQ_INIT(&vm_object_list);
vm_object_count = 0;
simple_lock_init(&vm_cache_lock);
simple_lock_init(&vm_object_list_lock);
for (i = 0; i < VM_OBJECT_HASH_COUNT; i++)
TAILQ_INIT(&vm_object_hashtable[i]);
kernel_object = &kernel_object_store;
_vm_object_allocate(size, kernel_object);
kmem_object = &kmem_object_store;
_vm_object_allocate(VM_KMEM_SIZE + VM_MBUF_SIZE, kmem_object);
}
/*
* vm_object_allocate:
*
* Returns a new object with the given size.
*/
vm_object_t
vm_object_allocate(size)
vm_size_t size;
{
register vm_object_t result;
result = (vm_object_t)
malloc((u_long)sizeof *result, M_VMOBJ, M_WAITOK);
_vm_object_allocate(size, result);
return(result);
}
static void
_vm_object_allocate(size, object)
vm_size_t size;
register vm_object_t object;
{
TAILQ_INIT(&object->memq);
vm_object_lock_init(object);
object->ref_count = 1;
object->resident_page_count = 0;
object->size = size;
object->flags = OBJ_INTERNAL; /* vm_allocate_with_pager will reset */
object->paging_in_progress = 0;
object->copy = NULL;
/*
* Object starts out read-write, with no pager.
*/
object->pager = NULL;
object->paging_offset = 0;
object->shadow = NULL;
object->shadow_offset = (vm_offset_t) 0;
LIST_INIT(&object->shadowers);
simple_lock(&vm_object_list_lock);
TAILQ_INSERT_TAIL(&vm_object_list, object, object_list);
vm_object_count++;
cnt.v_nzfod += atop(size);
simple_unlock(&vm_object_list_lock);
}
/*
* vm_object_reference:
*
* Gets another reference to the given object.
*/
void
vm_object_reference(object)
register vm_object_t object;
{
if (object == NULL)
return;
vm_object_lock(object);
object->ref_count++;
vm_object_unlock(object);
}
/*
* vm_object_deallocate:
*
* Release a reference to the specified object,
* gained either through a vm_object_allocate
* or a vm_object_reference call. When all references
* are gone, storage associated with this object
* may be relinquished.
*
* No object may be locked.
*/
void
vm_object_deallocate(object)
register vm_object_t object;
{
/*
* While "temp" is used for other things as well, we
* initialize it to NULL here for being able to check
* if we are in the first revolution of the loop.
*/
vm_object_t temp = NULL;
while (object != NULL) {
/*
* The cache holds a reference (uncounted) to
* the object; we must lock it before removing
* the object.
*/
vm_object_cache_lock();
/*
* Lose the reference
*/
vm_object_lock(object);
if (--(object->ref_count) != 0) {
/*
* If there are still references, then
* we are done.
*/
vm_object_cache_unlock();
/*
* If this is a deallocation of a shadow
* reference (which it is unless it's the
* first time round) and this operation made
* us singly-shadowed, try to collapse us
* with our shadower.
*/
vm_object_unlock(object);
if (temp != NULL &&
(temp = object->shadowers.lh_first) != NULL &&
temp->shadowers_list.le_next == NULL) {
if (!vm_object_lock_try(temp))
return;
temp->ref_count++;
vm_object_collapse(temp);
vm_object_unlock(temp);
vm_object_deallocate(temp);
}
return;
}
/*
* See if this object can persist. If so, enter
* it in the cache, then deactivate all of its
* pages.
*/
if (object->flags & OBJ_CANPERSIST) {
TAILQ_INSERT_TAIL(&vm_object_cached_list, object,
cached_list);
vm_object_cached++;
vm_object_cache_unlock();
vm_object_deactivate_pages(object);
vm_object_unlock(object);
vm_object_cache_trim();
return;
}
/*
* Make sure no one can look us up now.
*/
vm_object_remove(object->pager);
vm_object_cache_unlock();
/*
* Deallocate the object, and move on to the backing object.
*/
temp = object->shadow;
vm_object_reference(temp);
vm_object_terminate(object);
object = temp;
}
}
/*
* vm_object_terminate actually destroys the specified object, freeing
* up all previously used resources.
*
* The object must be locked.
*/
void
vm_object_terminate(object)
register vm_object_t object;
{
register vm_page_t p;
vm_object_t shadow_object;
/*
* Protect against simultaneous collapses.
*/
object->flags |= OBJ_FADING;
/*
* Wait until the pageout daemon is through with the object or a
* potential collapse operation is finished.
*/
vm_object_paging_wait(object,"vmterm");
/*
* Detach the object from its shadow if we are the shadow's
* copy.
*/
if ((shadow_object = object->shadow) != NULL) {
vm_object_lock(shadow_object);
vm_object_set_shadow(object, NULL);
if (shadow_object->copy == object)
shadow_object->copy = NULL;
#if 0
else if (shadow_object->copy != NULL)
panic("vm_object_terminate: copy/shadow inconsistency");
#endif
vm_object_unlock(shadow_object);
}
/*
* If not an internal object clean all the pages, removing them
* from paging queues as we go.
*
* XXX need to do something in the event of a cleaning error.
*/
if ((object->flags & OBJ_INTERNAL) == 0) {
(void) vm_object_page_clean(object, 0, 0, TRUE, TRUE);
vm_object_unlock(object);
}
/*
* Now free the pages.
* For internal objects, this also removes them from paging queues.
*/
while ((p = object->memq.tqh_first) != NULL) {
VM_PAGE_CHECK(p);
vm_page_lock_queues();
vm_page_free(p);
cnt.v_pfree++;
vm_page_unlock_queues();
}
if ((object->flags & OBJ_INTERNAL) != 0)
vm_object_unlock(object);
/*
* Let the pager know object is dead.
*/
if (object->pager != NULL)
vm_pager_deallocate(object->pager);
simple_lock(&vm_object_list_lock);
TAILQ_REMOVE(&vm_object_list, object, object_list);
vm_object_count--;
simple_unlock(&vm_object_list_lock);
/*
* Free the space for the object.
*/
free((caddr_t)object, M_VMOBJ);
}
/*
* vm_object_page_clean
*
* Clean all dirty pages in the specified range of object.
* If syncio is TRUE, page cleaning is done synchronously.
* If de_queue is TRUE, pages are removed from any paging queue
* they were on, otherwise they are left on whatever queue they
* were on before the cleaning operation began.
*
* Odd semantics: if start == end, we clean everything.
*
* The object must be locked.
*
* Returns TRUE if all was well, FALSE if there was a pager error
* somewhere. We attempt to clean (and dequeue) all pages regardless
* of where an error occurs.
*/
boolean_t
vm_object_page_clean(object, start, end, syncio, de_queue)
register vm_object_t object;
register vm_offset_t start;
register vm_offset_t end;
boolean_t syncio;
boolean_t de_queue;
{
register vm_page_t p;
int onqueue = 0;
boolean_t noerror = TRUE;
if (object == NULL)
return (TRUE);
/*
* If it is an internal object and there is no pager, attempt to
* allocate one. Note that vm_object_collapse may relocate one
* from a collapsed object so we must recheck afterward.
*/
if ((object->flags & OBJ_INTERNAL) && object->pager == NULL) {
vm_object_collapse(object);
if (object->pager == NULL) {
vm_pager_t pager;
vm_object_unlock(object);
pager = vm_pager_allocate(PG_DFLT, (caddr_t)0,
object->size, VM_PROT_ALL,
(vm_offset_t)0);
if (pager)
vm_object_setpager(object, pager, 0, FALSE);
vm_object_lock(object);
}
}
if (object->pager == NULL)
return (FALSE);
again:
/*
* Wait until the pageout daemon is through with the object.
*/
vm_object_paging_wait(object,"vclean");
/*
* Loop through the object page list cleaning as necessary.
*/
for (p = object->memq.tqh_first; p != NULL; p = p->listq.tqe_next) {
if ((start == end || (p->offset >= start && p->offset < end)) &&
!(p->flags & PG_FICTITIOUS)) {
if ((p->flags & PG_CLEAN) &&
pmap_is_modified(VM_PAGE_TO_PHYS(p)))
p->flags &= ~PG_CLEAN;
/*
* Remove the page from any paging queue.
* This needs to be done if either we have been
* explicitly asked to do so or it is about to
* be cleaned (see comment below).
*/
if (de_queue || !(p->flags & PG_CLEAN)) {
vm_page_lock_queues();
if (p->flags & PG_ACTIVE) {
TAILQ_REMOVE(&vm_page_queue_active,
p, pageq);
p->flags &= ~PG_ACTIVE;
cnt.v_active_count--;
onqueue = 1;
} else if (p->flags & PG_INACTIVE) {
TAILQ_REMOVE(&vm_page_queue_inactive,
p, pageq);
p->flags &= ~PG_INACTIVE;
cnt.v_inactive_count--;
onqueue = -1;
} else
onqueue = 0;
vm_page_unlock_queues();
}
/*
* To ensure the state of the page doesn't change
* during the clean operation we do two things.
* First we set the busy bit and write-protect all
* mappings to ensure that write accesses to the
* page block (in vm_fault). Second, we remove
* the page from any paging queue to foil the
* pageout daemon (vm_pageout_scan).
*/
pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_READ);
if (!(p->flags & PG_CLEAN)) {
p->flags |= PG_BUSY;
vm_object_paging_begin(object);
vm_object_unlock(object);
/*
* XXX if put fails we mark the page as
* clean to avoid an infinite loop.
* Will loose changes to the page.
*/
if (vm_pager_put(object->pager, p, syncio)) {
printf("%s: pager_put error\n",
"vm_object_page_clean");
p->flags |= PG_CLEAN;
noerror = FALSE;
}
vm_object_lock(object);
vm_object_paging_end(object);
if (!de_queue && onqueue) {
vm_page_lock_queues();
if (onqueue > 0)
vm_page_activate(p);
else
vm_page_deactivate(p);
vm_page_unlock_queues();
}
p->flags &= ~PG_BUSY;
PAGE_WAKEUP(p);
goto again;
}
}
}
return (noerror);
}
/*
* vm_object_deactivate_pages
*
* Deactivate all pages in the specified object. (Keep its pages
* in memory even though it is no longer referenced.)
*
* The object must be locked.
*/
void
vm_object_deactivate_pages(object)
register vm_object_t object;
{
register vm_page_t p, next;
for (p = object->memq.tqh_first; p != NULL; p = next) {
next = p->listq.tqe_next;
vm_page_lock_queues();
if (p->flags & PG_ACTIVE)
vm_page_deactivate(p);
vm_page_unlock_queues();
}
}
/*
* Trim the object cache to size.
*/
void
vm_object_cache_trim()
{
register vm_object_t object;
vm_object_cache_lock();
while (vm_object_cached > vm_cache_max) {
object = vm_object_cached_list.tqh_first;
vm_object_cache_unlock();
if (object != vm_object_lookup(object->pager))
panic("vm_object_deactivate: I'm sooo confused.");
pager_cache(object, FALSE);
vm_object_cache_lock();
}
vm_object_cache_unlock();
}
/*
* vm_object_pmap_copy:
*
* Makes all physical pages in the specified
* object range copy-on-write. No writeable
* references to these pages should remain.
*
* The object must *not* be locked.
*/
void
vm_object_pmap_copy(object, start, end)
register vm_object_t object;
register vm_offset_t start;
register vm_offset_t end;
{
register vm_page_t p;
if (object == NULL)
return;
vm_object_lock(object);
for (p = object->memq.tqh_first; p != NULL; p = p->listq.tqe_next) {
if ((start <= p->offset) && (p->offset < end)) {
pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_READ);
p->flags |= PG_COPYONWRITE;
}
}
vm_object_unlock(object);
}
/*
* vm_object_pmap_remove:
*
* Removes all physical pages in the specified
* object range from all physical maps.
*
* The object must *not* be locked.
*/
void
vm_object_pmap_remove(object, start, end)
register vm_object_t object;
register vm_offset_t start;
register vm_offset_t end;
{
register vm_page_t p;
if (object == NULL)
return;
vm_object_lock(object);
for (p = object->memq.tqh_first; p != NULL; p = p->listq.tqe_next)
if ((start <= p->offset) && (p->offset < end))
pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_NONE);
vm_object_unlock(object);
}
/*
* vm_object_copy:
*
* Create a new object which is a copy of an existing
* object, and mark all of the pages in the existing
* object 'copy-on-write'. The new object has one reference.
* Returns the new object.
*
* May defer the copy until later if the object is not backed
* up by a non-default pager.
*/
void
vm_object_copy(src_object, src_offset, size,
dst_object, dst_offset, src_needs_copy)
register vm_object_t src_object;
vm_offset_t src_offset;
vm_size_t size;
vm_object_t *dst_object; /* OUT */
vm_offset_t *dst_offset; /* OUT */
boolean_t *src_needs_copy; /* OUT */
{
register vm_object_t new_copy;
register vm_object_t old_copy;
vm_offset_t new_start, new_end;
register vm_page_t p;
if (src_object == NULL) {
/*
* Nothing to copy
*/
*dst_object = NULL;
*dst_offset = 0;
*src_needs_copy = FALSE;
return;
}
/*
* If the object's pager is null_pager or the
* default pager, we don't have to make a copy
* of it. Instead, we set the needs copy flag and
* make a shadow later.
*/
vm_object_lock(src_object);
if (src_object->pager == NULL ||
(src_object->flags & OBJ_INTERNAL)) {
/*
* Make another reference to the object.
*/
src_object->ref_count++;
/*
* Mark all of the pages copy-on-write.
*/
for (p = src_object->memq.tqh_first; p; p = p->listq.tqe_next)
if (src_offset <= p->offset &&
p->offset < src_offset + size)
p->flags |= PG_COPYONWRITE;
vm_object_unlock(src_object);
*dst_object = src_object;
*dst_offset = src_offset;
/*
* Must make a shadow when write is desired
*/
*src_needs_copy = TRUE;
return;
}
/*
* Try to collapse the object before copying it.
*/
vm_object_collapse(src_object);
/*
* If the object has a pager, the pager wants to
* see all of the changes. We need a copy-object
* for the changed pages.
*
* If there is a copy-object, and it is empty,
* no changes have been made to the object since the
* copy-object was made. We can use the same copy-
* object.
*/
Retry1:
old_copy = src_object->copy;
if (old_copy != NULL) {
/*
* Try to get the locks (out of order)
*/
if (!vm_object_lock_try(old_copy)) {
vm_object_unlock(src_object);
/* XXX should spin a bit here... */
vm_object_lock(src_object);
goto Retry1;
}
if (old_copy->resident_page_count == 0 &&
old_copy->pager == NULL) {
/*
* Return another reference to
* the existing copy-object.
*/
old_copy->ref_count++;
vm_object_unlock(old_copy);
vm_object_unlock(src_object);
*dst_object = old_copy;
*dst_offset = src_offset;
*src_needs_copy = FALSE;
return;
}
vm_object_unlock(old_copy);
}
vm_object_unlock(src_object);
/*
* If the object has a pager, the pager wants
* to see all of the changes. We must make
* a copy-object and put the changed pages there.
*
* The copy-object is always made large enough to
* completely shadow the original object, since
* it may have several users who want to shadow
* the original object at different points.
*/
new_copy = vm_object_allocate(src_object->size);
Retry2:
vm_object_lock(src_object);
/*
* Copy object may have changed while we were unlocked
*/
old_copy = src_object->copy;
if (old_copy != NULL) {
/*
* Try to get the locks (out of order)
*/
if (!vm_object_lock_try(old_copy)) {
vm_object_unlock(src_object);
goto Retry2;
}
/*
* Consistency check
*/
if (old_copy->shadow != src_object ||
old_copy->shadow_offset != (vm_offset_t) 0)
panic("vm_object_copy: copy/shadow inconsistency");
/*
* Make the old copy-object shadow the new one.
* It will receive no more pages from the original
* object. Locking of new_copy not needed. We
* have the only pointer.
*/
vm_object_set_shadow(old_copy, new_copy);
vm_object_unlock(old_copy);
}
new_start = (vm_offset_t)0;
new_end = (vm_offset_t)new_copy->size;
/*
* Point the new copy at the existing object.
*/
vm_object_set_shadow(new_copy, src_object);
new_copy->shadow_offset = new_start;
src_object->copy = new_copy;
/*
* Mark all the affected pages of the existing object
* copy-on-write.
*/
for (p = src_object->memq.tqh_first; p != NULL; p = p->listq.tqe_next)
if ((new_start <= p->offset) && (p->offset < new_end))
p->flags |= PG_COPYONWRITE;
vm_object_unlock(src_object);
*dst_object = new_copy;
*dst_offset = src_offset - new_start;
*src_needs_copy = FALSE;
}
/*
* vm_object_shadow:
*
* Create a new object which is backed by the
* specified existing object range. The source
* object reference is deallocated.
*
* The new object and offset into that object
* are returned in the source parameters.
*
* The old object should not be locked.
*/
void
vm_object_shadow(object, offset, length)
vm_object_t *object; /* IN/OUT */
vm_offset_t *offset; /* IN/OUT */
vm_size_t length;
{
register vm_object_t source;
register vm_object_t result;
source = *object;
#ifdef DIAGNOSTIC
if (source == NULL)
panic("vm_object_shadow: attempt to shadow null object");
#endif
/*
* Allocate a new object with the given length
*/
if ((result = vm_object_allocate(length)) == NULL)
panic("vm_object_shadow: no object for shadowing");
/*
* The new object shadows the source object. Our caller changes his
* reference to point to the new object, removing a reference to the
* source object.
*/
vm_object_lock(source);
vm_object_set_shadow(result, source);
source->ref_count--;
vm_object_unlock(source);
/*
* Store the offset into the source object,
* and fix up the offset into the new object.
*/
result->shadow_offset = *offset;
/*
* Return the new things
*/
*offset = 0;
*object = result;
}
/*
* Set the specified object's pager to the specified pager.
*/
void
vm_object_setpager(object, pager, paging_offset, read_only)
vm_object_t object;
vm_pager_t pager;
vm_offset_t paging_offset;
boolean_t read_only;
{
#ifdef lint
read_only++; /* No longer used */
#endif
vm_object_lock(object); /* XXX ? */
object->pager = pager;
object->paging_offset = paging_offset;
vm_object_unlock(object); /* XXX ? */
}
/*
* vm_object_hash hashes the pager/id pair.
*/
#define vm_object_hash(pager) \
(((unsigned long)pager)%VM_OBJECT_HASH_COUNT)
/*
* vm_object_lookup looks in the object cache for an object with the
* specified pager and paging id.
*/
vm_object_t
vm_object_lookup(pager)
vm_pager_t pager;
{
register vm_object_hash_entry_t entry;
vm_object_t object;
vm_object_cache_lock();
for (entry = vm_object_hashtable[vm_object_hash(pager)].tqh_first;
entry != NULL;
entry = entry->hash_links.tqe_next) {
object = entry->object;
if (object->pager == pager) {
vm_object_lock(object);
if (object->ref_count == 0) {
TAILQ_REMOVE(&vm_object_cached_list, object,
cached_list);
vm_object_cached--;
}
object->ref_count++;
vm_object_unlock(object);
vm_object_cache_unlock();
return(object);
}
}
vm_object_cache_unlock();
return(NULL);
}
/*
* vm_object_enter enters the specified object/pager/id into
* the hash table.
*/
void
vm_object_enter(object, pager)
vm_object_t object;
vm_pager_t pager;
{
struct vm_object_hash_head *bucket;
register vm_object_hash_entry_t entry;
/*
* We don't cache null objects, and we can't cache
* objects with the null pager.
*/
if (object == NULL)
return;
if (pager == NULL)
return;
bucket = &vm_object_hashtable[vm_object_hash(pager)];
entry = (vm_object_hash_entry_t)
malloc((u_long)sizeof *entry, M_VMOBJHASH, M_WAITOK);
entry->object = object;
object->flags |= OBJ_CANPERSIST;
vm_object_cache_lock();
TAILQ_INSERT_TAIL(bucket, entry, hash_links);
vm_object_cache_unlock();
}
/*
* vm_object_remove:
*
* Remove the pager from the hash table.
* Note: This assumes that the object cache
* is locked. XXX this should be fixed
* by reorganizing vm_object_deallocate.
*/
void
vm_object_remove(pager)
register vm_pager_t pager;
{
struct vm_object_hash_head *bucket;
register vm_object_hash_entry_t entry;
register vm_object_t object;
bucket = &vm_object_hashtable[vm_object_hash(pager)];
for (entry = bucket->tqh_first;
entry != NULL;
entry = entry->hash_links.tqe_next) {
object = entry->object;
if (object->pager == pager) {
TAILQ_REMOVE(bucket, entry, hash_links);
free((caddr_t)entry, M_VMOBJHASH);
break;
}
}
}
/*
* vm_object_cache_clear removes all objects from the cache.
*/
void
vm_object_cache_clear()
{
register vm_object_t object;
/*
* Remove each object in the cache by scanning down the
* list of cached objects.
*/
vm_object_cache_lock();
while ((object = vm_object_cached_list.tqh_first) != NULL) {
vm_object_cache_unlock();
/*
* Note: it is important that we use vm_object_lookup
* to gain a reference, and not vm_object_reference, because
* the logic for removing an object from the cache lies in
* lookup.
*/
if (object != vm_object_lookup(object->pager))
panic("vm_object_cache_clear: I'm sooo confused.");
pager_cache(object, FALSE);
vm_object_cache_lock();
}
vm_object_cache_unlock();
}
/*
* vm_object_remove_from_pager:
*
* Tell object's pager that it needn't back the page
* anymore. If the pager ends up empty, deallocate it.
*/
int
vm_object_remove_from_pager(object, from, to)
vm_object_t object;
vm_offset_t from, to;
{
vm_pager_t pager = object->pager;
int cnt = 0;
if (pager == NULL)
return 0;
cnt = vm_pager_remove(pager, from, to);
/* If pager became empty, remove it. */
if (cnt > 0 && vm_pager_count(pager) == 0) {
vm_pager_deallocate(pager);
object->pager = NULL;
}
return(cnt);
}
#define FREE_PAGE(m) { \
PAGE_WAKEUP(m); \
vm_page_lock_queues(); \
vm_page_free(m); \
vm_page_unlock_queues(); \
}
/*
* vm_object_overlay:
*
* Internal function to vm_object_collapse called when
* it has been shown that a collapse operation is likely
* to succeed. We know that the backing object is only
* referenced by me and that paging is not in progress.
*/
int
vm_object_overlay(object)
vm_object_t object;
{
vm_object_t backing_object = object->shadow;
vm_offset_t backing_offset = object->shadow_offset;
vm_offset_t new_offset, paged_offset;
vm_page_t backing_page, next_page, page;
int rv;
#ifdef DEBUG
if (vmdebug & VMDEBUG_COLLAPSE)
printf("vm_object_overlay(0x%p)\n", object);
#endif
/*
* Protect against multiple collapses.
*/
backing_object->flags |= OBJ_FADING;
/*
* The algorithm used is roughly like this:
* (1) Trim a potential pager in the backing
* object so it'll only hold pages in reach.
* (2) Loop over all the resident pages in the
* shadow object and either remove them if
* they are shadowed or move them into the
* shadowing object.
* (3) Loop over the paged out pages in the
* shadow object. Start pageins on those
* that aren't shadowed, and just deallocate
* the others. In each iteration check if
* other users of these objects have caused
* pageins resulting in new resident pages.
* This can happen while we are waiting for
* a pagein of ours. If such resident pages
* turn up, restart from (2).
*/
/*
* First, trim the backing object to the size of the parent object.
*/
if (backing_object->pager != NULL) {
if (backing_offset > 0)
vm_object_remove_from_pager(backing_object, 0,
backing_offset);
if (backing_offset + object->size < backing_object->size)
vm_object_remove_from_pager(backing_object,
backing_offset + object->size,
backing_object->size);
}
/*
* At this point, there may still be asynchronous paging in the parent
* object. Any pages being paged in will be represented by fake pages.
* There are three cases:
* 1) The page is being paged in from the parent object's own pager.
* In this case, we just delete our copy, since it's not needed.
* 2) The page is being paged in from the backing object. We prevent
* this case by waiting for paging to complete on the backing object
* before continuing.
* 3) The page is being paged in from a backing object behind the one
* we're deleting. We'll never notice this case, because the
* backing object we're deleting won't have the page.
*
* XXXXX FIXME
* Because pagedaemon can call vm_object_collapse(), we must *not*
* sleep waiting for pages.
*/
RetryRename:
#if 0 /* XXXXX FIXME */
vm_object_unlock(object);
vm_object_paging_wait(backing_object,"vpagew");
vm_object_lock(object);
/*
* While we were asleep, the parent object might have been deleted. If
* so, the backing object will now have only one reference (the one we
* hold). If this happened, just deallocate the backing object and
* return failure status so vm_object_collapse() will stop. This will
* continue vm_object_deallocate() where it stopped due to our
* reference.
*/
if (backing_object->ref_count == 1)
goto fail;
#else
if (vm_object_paging(backing_object))
goto fail;
#endif
/*
* Next, move any pages in core from the backing object to the
* parent.
*/
for (backing_page = backing_object->memq.tqh_first;
backing_page != NULL;
backing_page = next_page) {
next_page = backing_page->listq.tqe_next;
new_offset = backing_page->offset - backing_offset;
#ifdef DIAGNOSTIC
if (backing_page->flags & (PG_BUSY | PG_FAKE))
panic("vm_object_overlay: busy or fake page in backing_object");
#endif
/*
* If the parent has a page here, or if this page falls
* outside the parent, delete it.
*
* Otherwise, move the page into the parent object.
*/
if (backing_page->offset >= backing_offset &&
new_offset < object->size &&
((page = vm_page_lookup(object, new_offset)) == NULL) &&
(object->pager == NULL ||
!vm_pager_has_page(object->pager, new_offset))) {
/*
* If the backing page was ever paged out, it was due
* to it being dirty at one point. Unless we have no
* pager allocated to the front object (thus will move
* forward the shadow's one), mark it dirty again so
* it won't be thrown away without being paged out to
* the front pager.
*
* XXX
* Should be able to move a page from one pager to
* another.
*/
if (object->pager != NULL &&
vm_object_remove_from_pager(backing_object,
backing_page->offset,
backing_page->offset + PAGE_SIZE))
backing_page->flags &= ~PG_CLEAN;
/*
* Finally, actually move the page into the parent
* object.
*/
vm_page_rename(backing_page, object, new_offset);
} else {
/*
* Just discard the backing page, and any backing
* store it might have had.
*/
if (backing_object->pager != NULL)
vm_object_remove_from_pager(backing_object,
backing_page->offset,
backing_page->offset + PAGE_SIZE);
vm_page_lock_queues();
vm_page_free(backing_page);
vm_page_unlock_queues();
}
}
/*
* If the backing object has no pager, then we're done.
*/
if (backing_object->pager == NULL)
goto done;
/*
* If the parent object has no pager, then simply move the pager
* from the backing object.
*/
if (object->pager == NULL) {
object->pager = backing_object->pager;
object->paging_offset = backing_object->paging_offset +
backing_offset;
backing_object->pager = NULL;
goto done;
}
/*
* Now, find all paged out pages in the backing object, and page
* them in.
*/
paged_offset = 0;
while ((paged_offset = vm_pager_next(backing_object->pager,
paged_offset)) < backing_object->size) {
new_offset = paged_offset - backing_offset;
/*
* If the parent object already has this page, delete it.
* Otherwise, start a pagein.
*/
if (((page = vm_page_lookup(object, new_offset)) == NULL) &&
(object->pager == NULL ||
!vm_pager_has_page(object->pager, new_offset))) {
/*
* First, allocate a page and mark it busy so another
* thread won't try to page it in simultaneously.
*/
backing_page = vm_page_alloc(backing_object,
paged_offset);
if (backing_page == NULL) {
#if 0 /* XXXXX FIXME */
vm_object_unlock(backing_object);
vm_object_unlock(object);
vm_wait("fVmcollapse");
vm_object_lock(object);
vm_object_lock(backing_object);
goto RetryRename;
#else
goto fail;
#endif
}
vm_object_paging_begin(backing_object);
vm_object_unlock(backing_object);
vm_object_unlock(object);
/*
* Call the pager to retrieve the data, if any.
*/
cnt.v_pageins++;
rv = vm_pager_get(backing_object->pager, backing_page,
TRUE);
vm_object_lock(object);
vm_object_lock(backing_object);
vm_object_paging_end(backing_object);
/*
* IO error or page outside the range of the pager:
* cleanup and return an error.
*/
if (rv == VM_PAGER_ERROR || rv == VM_PAGER_BAD) {
FREE_PAGE(backing_page);
goto fail;
}
#ifdef DIAGNOSTIC
if (rv != VM_PAGER_OK)
panic("vm_object_overlay: pager returned %d",
rv);
#endif
/*
* The pager might have moved the page while we
* were asleep, so look it up again.
*/
backing_page = vm_page_lookup(backing_object,
paged_offset);
/*
* Force the parent object's pager to eventually
* page out the page again.
*/
cnt.v_pgpgin++;
backing_page->flags &= ~(PG_FAKE | PG_CLEAN);
PAGE_WAKEUP(backing_page);
goto RetryRename;
} else {
/*
* Just discard the backing page.
*/
vm_object_remove_from_pager(backing_object,
paged_offset, paged_offset + PAGE_SIZE);
paged_offset += PAGE_SIZE;
/*
* If the backing object no longer has a pager, then
* we're done.
*/
if (backing_object->pager == NULL)
goto done;
}
}
done:
/*
* Object now shadows whatever backing_object did.
*/
if (backing_object->shadow)
vm_object_lock(backing_object->shadow);
vm_object_set_shadow(object, backing_object->shadow);
if (backing_object->shadow)
vm_object_unlock(backing_object->shadow);
object->shadow_offset += backing_object->shadow_offset;
/*
* Since backing_object is no longer used, this will delete it.
*/
#ifdef notdef
if (backing_object->ref_count != 1)
panic("vm_object_overlay: backing_object still referenced");
#endif
object_collapses++;
vm_object_unlock(backing_object);
vm_object_deallocate(backing_object);
return KERN_SUCCESS;
fail:
backing_object->flags &= ~OBJ_FADING;
vm_object_unlock(backing_object);
vm_object_deallocate(backing_object);
return KERN_FAILURE;
}
/*
* vm_object_bypass:
*
* Internal function to vm_object_collapse called when collapsing
* the object with its backing one is not allowed but there may
* be an opportunity to bypass the backing object and shadow the
* next object in the chain instead.
*/
int
vm_object_bypass(object)
vm_object_t object;
{
vm_object_t backing_object = object->shadow;
vm_offset_t backing_offset = object->shadow_offset;
vm_offset_t new_offset;
vm_page_t backing_page, page;
/*
* If all of the pages in the backing object are shadowed by the parent
* object, the parent object no longer has to shadow the backing
* object; it can shadow the next one in the chain.
*
* Since we're not actually saving any space here, it's not worth
* bothering to slog through the backing object's pager looking for
* pages, or waiting for paging to complete. Also, we must not bypass
* an object that's currently being collapsed into.
*
* See comments in vm_object_overlay() regarding simultaneous paging in
* the parent object.
*/
if (vm_object_paging(backing_object) ||
backing_object->pager != NULL) {
goto fail;
}
/*
* Should have a check for a 'small' number
* of pages here.
*/
for (backing_page = backing_object->memq.tqh_first;
backing_page != NULL;
backing_page = backing_page->listq.tqe_next) {
new_offset = backing_page->offset - backing_offset;
#ifdef DIAGNOSTIC
if (backing_page->flags & (PG_BUSY | PG_FAKE))
panic("vm_object_bypass: busy or fake page in backing_object");
#endif
/*
* If the parent has a page here, or if this page falls
* outside the parent, keep going.
*
* Otherwise, the backing_object must be left in the chain.
*/
if (backing_page->offset >= backing_offset &&
new_offset < object->size &&
((page = vm_page_lookup(object, new_offset)) == NULL) &&
(object->pager == NULL ||
!vm_pager_has_page(object->pager, new_offset))) {
/*
* Page still needed. Can't go any further.
*/
goto fail;
}
}
/*
* Object now shadows whatever backing_object did.
*/
if (backing_object->shadow)
vm_object_lock(backing_object->shadow);
vm_object_set_shadow(object, backing_object->shadow);
if (backing_object->shadow)
vm_object_unlock(backing_object->shadow);
object->shadow_offset += backing_object->shadow_offset;
/*
* Backing object might have had a copy pointer
* to us. If it did, clear it.
*/
if (backing_object->copy == object)
backing_object->copy = NULL;
/*
* Since backing_object's ref_count was at least 2, it will not
* vanish, but we need to decrease its reference count anyway.
*/
object_bypasses++;
vm_object_unlock(backing_object);
vm_object_deallocate(backing_object);
return KERN_SUCCESS;
fail:
vm_object_unlock(backing_object);
vm_object_deallocate(backing_object);
return KERN_FAILURE;
}
/*
* vm_object_collapse:
*
* Collapse an object with the object backing it.
* Pages in the backing object are moved into the
* parent, and the backing object is deallocated.
*
* Requires that the object be locked and the page
* queues be unlocked.
*
*/
void
vm_object_collapse(object)
register vm_object_t object;
{
register vm_object_t backing_object;
int rv;
if (!vm_object_collapse_allowed)
return;
if (object == NULL)
return;
do {
/*
* Verify that the conditions are right for collapse:
*
* There is a backing object, ...
*/
if ((backing_object = object->shadow) == NULL)
return;
vm_object_lock(backing_object);
/*
* ... the backing object is not read_only, is internal,
* and is not already being collapsed, ...
*/
if ((backing_object->flags & (OBJ_INTERNAL | OBJ_FADING))
!= OBJ_INTERNAL) {
vm_object_unlock(backing_object);
return;
}
/*
* the backing object isn't be a copy-object.
* The shadow_offset for the copy-object must stay
* as 0. Furthermore (for the 'we have all the
* pages' case), if we bypass backing_object and
* just shadow the next object in the chain, old
* pages from that object would then have to be copied
* BOTH into the (former) backing_object and into the
* parent object.
*/
if (backing_object->shadow != NULL &&
backing_object->shadow->copy != NULL) {
vm_object_unlock(backing_object);
return;
}
/*
* Grab a reference to the backing object so that it
* can't be deallocated behind our back.
*/
backing_object->ref_count++;
#ifdef DIAGNOSTIC
if (backing_object->ref_count == 1)
panic("vm_object_collapse: collapsing unreferenced object");
#endif
/*
* If there is exactly one reference to the backing
* object, we can collapse it into the parent,
* otherwise we might be able to bypass it completely.
*/
if (backing_object->ref_count == 2)
rv = vm_object_overlay(object);
else
rv = vm_object_bypass(object);
/*
* Try again with this object's new backing object.
*/
} while (rv == KERN_SUCCESS);
}
/*
* vm_object_page_remove: [internal]
*
* Removes all physical pages in the specified
* object range from the object's list of pages.
*
* The object must be locked.
*/
void
vm_object_page_remove(object, start, end)
register vm_object_t object;
register vm_offset_t start;
register vm_offset_t end;
{
register vm_page_t p, next;
if (object == NULL)
return;
for (p = object->memq.tqh_first; p != NULL; p = next) {
next = p->listq.tqe_next;
if ((start <= p->offset) && (p->offset < end)) {
pmap_page_protect(VM_PAGE_TO_PHYS(p), VM_PROT_NONE);
vm_page_lock_queues();
vm_page_free(p);
vm_page_unlock_queues();
}
}
}
/*
* Routine: vm_object_coalesce
* Function: Coalesces two objects backing up adjoining
* regions of memory into a single object.
*
* returns TRUE if objects were combined.
*
* NOTE: Only works at the moment if the second object is NULL -
* if it's not, which object do we lock first?
*
* Parameters:
* prev_object First object to coalesce
* prev_offset Offset into prev_object
* next_object Second object into coalesce
* next_offset Offset into next_object
*
* prev_size Size of reference to prev_object
* next_size Size of reference to next_object
*
* Conditions:
* The object must *not* be locked.
*/
boolean_t
vm_object_coalesce(prev_object, next_object, prev_offset, next_offset,
prev_size, next_size)
register vm_object_t prev_object;
vm_object_t next_object;
vm_offset_t prev_offset, next_offset;
vm_size_t prev_size, next_size;
{
vm_size_t newsize;
#ifdef lint
next_offset++;
#endif
if (next_object != NULL) {
return(FALSE);
}
if (prev_object == NULL) {
return(TRUE);
}
vm_object_lock(prev_object);
/*
* Try to collapse the object first
*/
vm_object_collapse(prev_object);
/*
* Can't coalesce if:
* . more than one reference
* . paged out
* . shadows another object
* . has a copy elsewhere
* (any of which mean that the pages not mapped to
* prev_entry may be in use anyway)
*/
if (prev_object->ref_count > 1 ||
prev_object->pager != NULL ||
prev_object->shadow != NULL ||
prev_object->copy != NULL) {
vm_object_unlock(prev_object);
return(FALSE);
}
/*
* Remove any pages that may still be in the object from
* a previous deallocation.
*/
vm_object_page_remove(prev_object, prev_offset + prev_size,
prev_offset + prev_size + next_size);
/*
* Extend the object if necessary.
*/
newsize = prev_offset + prev_size + next_size;
if (newsize > prev_object->size)
prev_object->size = newsize;
vm_object_unlock(prev_object);
return(TRUE);
}
/*
* vm_object_print: [ debug ]
*/
void
vm_object_print(object, full)
vm_object_t object;
boolean_t full;
{
_vm_object_print(object, full, printf);
}
void
_vm_object_print(object, full, pr)
vm_object_t object;
boolean_t full;
void (*pr) __P((const char *, ...));
{
register vm_page_t p;
char *delim;
vm_object_t o;
register int count;
extern int indent;
if (object == NULL)
return;
iprintf(pr, "Object 0x%lx: size=0x%lx, res=%d, ref=%d, flags=0x%x, ",
(long) object, (long) object->size,
object->resident_page_count, object->ref_count,
object->flags);
(*pr)("pip=%d, pager=0x%lx+0x%lx, shadow=(0x%lx)+0x%lx\n",
object->paging_in_progress,
(long) object->pager, (long) object->paging_offset,
(long) object->shadow, (long) object->shadow_offset);
(*pr)("shadowers=(");
delim = "";
for (o = object->shadowers.lh_first; o; o = o->shadowers_list.le_next) {
(*pr)("%s0x%x", delim, o);
delim = ", ";
};
(*pr)(")\n");
(*pr)("cache: next=0x%lx, prev=0x%lx\n",
(long)object->cached_list.tqe_next,
(long)object->cached_list.tqe_prev);
if (!full)
return;
indent += 2;
count = 0;
for (p = object->memq.tqh_first; p != NULL; p = p->listq.tqe_next) {
if (count == 0)
iprintf(pr, "memory:=");
else if (count == 6) {
(*pr)("\n");
iprintf(pr, " ...");
count = 0;
} else
(*pr)(",");
count++;
(*pr)("(off=0x%x,page=0x%x)", p->offset, VM_PAGE_TO_PHYS(p));
}
if (count != 0)
(*pr)("\n");
indent -= 2;
}
/*
* vm_object_set_shadow:
*
* Maintain the shadow graph so that back-link consistency is
* always kept.
*
* Assumes both objects as well as the old shadow to be locked
* (unless NULL of course).
*/
void
vm_object_set_shadow(object, shadow)
vm_object_t object, shadow;
{
vm_object_t old_shadow = object->shadow;
#ifdef DEBUG
if (vmdebug & VMDEBUG_SHADOW)
printf("vm_object_set_shadow(object=0x%p, shadow=0x%p) "
"old_shadow=0x%p\n", object, shadow, old_shadow);
if (vmdebug & VMDEBUG_SHADOW_VERBOSE) {
vm_object_print(object, 0);
vm_object_print(old_shadow, 0);
vm_object_print(shadow, 0);
}
#endif
if (old_shadow == shadow)
return;
if (old_shadow) {
old_shadow->ref_count--;
LIST_REMOVE(object, shadowers_list);
}
if (shadow) {
shadow->ref_count++;
LIST_INSERT_HEAD(&shadow->shadowers, object, shadowers_list);
}
object->shadow = shadow;
#ifdef DEBUG
if (vmdebug & VMDEBUG_SHADOW_VERBOSE) {
vm_object_print(object, 0);
vm_object_print(old_shadow, 0);
vm_object_print(shadow, 0);
}
#endif
}
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