vm_objec.c

open bsd vm device design

						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();
		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);

			/* 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.
		 */

		src_object->ref_count--;	/* remove ref. from old_copy */
		old_copy->shadow = new_copy;
		new_copy->ref_count++;		/* locking not needed - we
						   have the only pointer */
		vm_object_unlock(old_copy);	/* done with old_copy */
	}

	new_start = (vm_offset_t) 0;	/* always shadow original at 0 */
	new_end   = (vm_offset_t) new_copy->size; /* for the whole object */

	/*
	 *	Point the new copy at the existing object.
	 */

	new_copy->shadow = src_object;
	new_copy->shadow_offset = new_start;
	src_object->ref_count++;
	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.
 */

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;

	/*
	 *	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, adding
	 *	a reference to it.  Our caller changes his reference
	 *	to point to the new object, removing a reference to
	 *	the source object.  Net result: no change of reference
	 *	count.
	 */
	result->shadow = 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;