path: root/vm/memory_object.c

/*
 * Mach Operating System
 * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University.
 * Copyright (c) 1993,1994 The University of Utah and
 * the Computer Systems Laboratory (CSL).
 * All rights reserved.
 *
 * 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, THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF
 * THIS SOFTWARE IN ITS "AS IS" CONDITION, AND DISCLAIM 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 Mellon
 * the rights to redistribute these changes.
 */
/*
 *	File:	vm/memory_object.c
 *	Author:	Michael Wayne Young
 *
 *	External memory management interface control functions.
 */

/*
 *	Interface dependencies:
 */

#include <mach/std_types.h>	/* For pointer_t */
#include <mach/mach_types.h>

#include <mach/kern_return.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>
#include <mach/memory_object.h>
#include <mach/boolean.h>
#include <mach/vm_prot.h>
#include <mach/message.h>

#include <vm/memory_object_user.user.h>
#include <vm/memory_object_default.user.h>

/*
 *	Implementation dependencies:
 */
#include <vm/memory_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pageout.h>
#include <vm/pmap.h>		/* For copy_to_phys, pmap_clear_modify */
#include <kern/debug.h>		/* For panic() */
#include <kern/thread.h>		/* For current_thread() */
#include <kern/host.h>
#include <vm/vm_kern.h>		/* For kernel_map, vm_move */
#include <vm/vm_map.h>		/* For vm_map_pageable */
#include <ipc/ipc_port.h>

#if	MACH_PAGEMAP
#include <vm/vm_external.h>
#endif	/* MACH_PAGEMAP */

typedef	int		memory_object_lock_result_t; /* moved from below */


ipc_port_t	memory_manager_default = IP_NULL;

struct lock default_memory_manager_lock_data;

#define default_memory_manager_lock_init()			\
	lock_init(&default_memory_manager_lock_data, FALSE)
#define default_memory_manager_lock()				\
	lock_write(&default_memory_manager_lock_data)
#define default_memory_manager_unlock()				\
	lock_write_done(&default_memory_manager_lock_data)
/*
 *	Important note:
 *		All of these routines gain a reference to the
 *		object (first argument) as part of the automatic
 *		argument conversion. Explicit deallocation is necessary.
 */

kern_return_t memory_object_data_supply(
       vm_object_t		object,
	vm_offset_t		offset,
	vm_map_copy_t		data_copy,
	unsigned int		data_cnt,
	vm_prot_t		lock_value,
	boolean_t		precious,
	ipc_port_t		reply_to,
	mach_msg_type_name_t	reply_to_type)
{
	kern_return_t	result = KERN_SUCCESS;
	vm_offset_t	error_offset = 0;
	vm_page_t	m;
	vm_page_t	data_m;
	vm_size_t	original_length;
	vm_offset_t	original_offset;
	vm_page_t	*page_list;
	boolean_t	was_absent;
	vm_map_copy_t	orig_copy = data_copy;

	/*
	 *	Look for bogus arguments
	 */

	if (object == VM_OBJECT_NULL) {
		return(KERN_INVALID_ARGUMENT);
	}

	if (lock_value & ~VM_PROT_ALL) {
		vm_object_deallocate(object);
		return(KERN_INVALID_ARGUMENT);
	}

	if ((data_cnt % PAGE_SIZE) != 0) {
	    vm_object_deallocate(object);
	    return(KERN_INVALID_ARGUMENT);
	}

	/*
	 *	Adjust the offset from the memory object to the offset
	 *	within the vm_object.
	 */

	original_length = data_cnt;
	original_offset = offset;

	assert(data_copy->type == VM_MAP_COPY_PAGE_LIST);
	page_list = &data_copy->cpy_page_list[0];

	vm_object_lock(object);
	vm_object_paging_begin(object);
	offset -= object->paging_offset;

	/*
	 *	Loop over copy stealing pages for pagein.
	 */

	for (; data_cnt > 0 ; data_cnt -= PAGE_SIZE, offset += PAGE_SIZE) {

		assert(data_copy->cpy_npages > 0);
		data_m = *page_list;

		if (data_m == VM_PAGE_NULL || data_m->tabled ||
		    data_m->error || data_m->absent || data_m->fictitious) {

			panic("Data_supply: bad page");
		      }

		/*
		 *	Look up target page and check its state.
		 */

retry_lookup:
		m = vm_page_lookup(object,offset);
		if (m == VM_PAGE_NULL) {
		    was_absent = FALSE;
		}
		else {
		    if (m->absent && m->busy) {

			/*
			 *	Page was requested.  Free the busy
			 *	page waiting for it.  Insertion
			 *	of new page happens below.
			 */

			VM_PAGE_FREE(m);
			was_absent = TRUE;
		    }
		    else {

			/*
			 *	Have to wait for page that is busy and
			 *	not absent.  This is probably going to
			 *	be an error, but go back and check.
			 */
			if (m->busy) {
				PAGE_ASSERT_WAIT(m, FALSE);
				vm_object_unlock(object);
				thread_block((void (*)()) 0);
				vm_object_lock(object);
				goto retry_lookup;
			}

			/*
			 *	Page already present; error.
			 *	This is an error if data is precious.
			 */
			result = KERN_MEMORY_PRESENT;
			error_offset = offset + object->paging_offset;

			break;
		    }
		}

		/*
		 *	Ok to pagein page.  Target object now has no page
		 *	at offset.  Set the page parameters, then drop
		 *	in new page and set up pageout state.  Object is
		 *	still locked here.
		 *
		 *	Must clear busy bit in page before inserting it.
		 *	Ok to skip wakeup logic because nobody else
		 *	can possibly know about this page.
		 */

		data_m->busy = FALSE;
		data_m->dirty = FALSE;
		pmap_clear_modify(data_m->phys_addr);

		data_m->page_lock = lock_value;
		data_m->unlock_request = VM_PROT_NONE;
		data_m->precious = precious;

		vm_page_lock_queues();
		vm_page_insert(data_m, object, offset);

		if (was_absent)
			vm_page_activate(data_m);
		else
			vm_page_deactivate(data_m);

		vm_page_unlock_queues();

		/*
		 *	Null out this page list entry, and advance to next
		 *	page.
		 */

		*page_list++ = VM_PAGE_NULL;

		if (--(data_copy->cpy_npages) == 0 &&
		    vm_map_copy_has_cont(data_copy)) {
			vm_map_copy_t	new_copy;

			vm_object_unlock(object);

			vm_map_copy_invoke_cont(data_copy, &new_copy, &result);

			if (result == KERN_SUCCESS) {

			    /*
			     *	Consume on success requires that
			     *	we keep the original vm_map_copy
			     *	around in case something fails.
			     *	Free the old copy if it's not the original
			     */
			    if (data_copy != orig_copy) {
				vm_map_copy_discard(data_copy);
			    }

			    if ((data_copy = new_copy) != VM_MAP_COPY_NULL)
				page_list = &data_copy->cpy_page_list[0];

			    vm_object_lock(object);
			}
			else {
			    vm_object_lock(object);
			    error_offset = offset + object->paging_offset +
						PAGE_SIZE;
			    break;
			}
		}
	}

	/*
	 *	Send reply if one was requested.
	 */
	vm_object_paging_end(object);
	vm_object_unlock(object);

	if (vm_map_copy_has_cont(data_copy))
		vm_map_copy_abort_cont(data_copy);

	if (IP_VALID(reply_to)) {
		memory_object_supply_completed(
				reply_to, reply_to_type,
				object->pager_request,
				original_offset,
				original_length,
				result,
				error_offset);
	}

	vm_object_deallocate(object);

	/*
	 *	Consume on success:  The final data copy must be
	 *	be discarded if it is not the original.  The original
	 *	gets discarded only if this routine succeeds.
	 */
	if (data_copy != orig_copy)
		vm_map_copy_discard(data_copy);
	if (result == KERN_SUCCESS)
		vm_map_copy_discard(orig_copy);


	return(result);
}

/*
 *	If successful, destroys the map copy object.
 */
kern_return_t memory_object_data_provided(
	vm_object_t	object,
	vm_offset_t	offset,
	pointer_t	data,
	unsigned int	data_cnt,
	vm_prot_t	lock_value)
{
        return memory_object_data_supply(object, offset, (vm_map_copy_t) data,
					 data_cnt, lock_value, FALSE, IP_NULL,
					 0);
}

kern_return_t memory_object_data_error(
	vm_object_t	object,
	vm_offset_t	offset,
	vm_size_t	size,
	kern_return_t	error_value)
{
	if (object == VM_OBJECT_NULL)
		return(KERN_INVALID_ARGUMENT);

	if (size != round_page(size))
		return(KERN_INVALID_ARGUMENT);

	vm_object_lock(object);
	offset -= object->paging_offset;

	while (size != 0) {
		vm_page_t m;

		m = vm_page_lookup(object, offset);
		if ((m != VM_PAGE_NULL) && m->busy && m->absent) {
			m->error = TRUE;
			m->absent = FALSE;
			vm_object_absent_release(object);

			PAGE_WAKEUP_DONE(m);

			vm_page_lock_queues();
			vm_page_activate(m);
			vm_page_unlock_queues();
		}

		size -= PAGE_SIZE;
		offset += PAGE_SIZE;
	 }
	vm_object_unlock(object);

	vm_object_deallocate(object);
	return(KERN_SUCCESS);
}

kern_return_t memory_object_data_unavailable(
	vm_object_t	object,
	vm_offset_t	offset,
	vm_size_t	size)
{
#if	MACH_PAGEMAP
	vm_external_t	existence_info = VM_EXTERNAL_NULL;
#endif	/* MACH_PAGEMAP */

	if (object == VM_OBJECT_NULL)
		return(KERN_INVALID_ARGUMENT);

	if (size != round_page(size))
		return(KERN_INVALID_ARGUMENT);

#if	MACH_PAGEMAP
	if ((offset == 0) && (size > VM_EXTERNAL_LARGE_SIZE) &&
	    (object->existence_info == VM_EXTERNAL_NULL)) {
		existence_info = vm_external_create(VM_EXTERNAL_SMALL_SIZE);
	}
#endif	/* MACH_PAGEMAP */

	vm_object_lock(object);
#if	MACH_PAGEMAP
 	if (existence_info != VM_EXTERNAL_NULL) {
		object->existence_info = existence_info;
	}
	if ((offset == 0) && (size > VM_EXTERNAL_LARGE_SIZE)) {
		vm_object_unlock(object);
		vm_object_deallocate(object);
		return(KERN_SUCCESS);
	}
#endif	/* MACH_PAGEMAP */
	offset -= object->paging_offset;

	while (size != 0) {
		vm_page_t m;

		/*
		 *	We're looking for pages that are both busy and
		 *	absent (waiting to be filled), converting them
		 *	to just absent.
		 *
		 *	Pages that are just busy can be ignored entirely.
		 */

		m = vm_page_lookup(object, offset);
		if ((m != VM_PAGE_NULL) && m->busy && m->absent) {
			PAGE_WAKEUP_DONE(m);

			vm_page_lock_queues();
			vm_page_activate(m);
			vm_page_unlock_queues();
		}
		size -= PAGE_SIZE;
		offset += PAGE_SIZE;
	}

	vm_object_unlock(object);

	vm_object_deallocate(object);
	return(KERN_SUCCESS);
}

/*
 *	Routine:	memory_object_lock_page
 *
 *	Description:
 *		Perform the appropriate lock operations on the
 *		given page.  See the description of
 *		"memory_object_lock_request" for the meanings
 *		of the arguments.
 *
 *		Returns an indication that the operation
 *		completed, blocked, or that the page must
 *		be cleaned.
 */

#define	MEMORY_OBJECT_LOCK_RESULT_DONE		0
#define	MEMORY_OBJECT_LOCK_RESULT_MUST_BLOCK	1
#define	MEMORY_OBJECT_LOCK_RESULT_MUST_CLEAN	2
#define	MEMORY_OBJECT_LOCK_RESULT_MUST_RETURN	3

memory_object_lock_result_t memory_object_lock_page(
	vm_page_t		m,
	memory_object_return_t	should_return,
	boolean_t		should_flush,
	vm_prot_t		prot)
{
	/*
	 *	Don't worry about pages for which the kernel
	 *	does not have any data.
	 */

	if (m->absent)
		return(MEMORY_OBJECT_LOCK_RESULT_DONE);

	/*
	 *	If we cannot change access to the page,
	 *	either because a mapping is in progress
	 *	(busy page) or because a mapping has been
	 *	wired, then give up.
	 */

	if (m->busy)
		return(MEMORY_OBJECT_LOCK_RESULT_MUST_BLOCK);

	assert(!m->fictitious);

	if (m->wire_count != 0) {
		/*
		 *	If no change would take place
		 *	anyway, return successfully.
		 *
		 *	No change means:
		 *		Not flushing AND
		 *		No change to page lock [2 checks]  AND
		 *		Don't need to send page to manager
		 *
		 *	Don't need to send page to manager means:
		 *		No clean or return request OR (
		 *		    Page is not dirty [2 checks] AND (
		 *		        Page is not precious OR
		 *			No request to return precious pages ))
		 *
		 *	Now isn't that straightforward and obvious ?? ;-)
		 *
		 * XXX	This doesn't handle sending a copy of a wired
		 * XXX	page to the pager, but that will require some
		 * XXX	significant surgery.
		 */

		if (!should_flush &&
		    ((m->page_lock == prot) || (prot == VM_PROT_NO_CHANGE)) &&
		    ((should_return == MEMORY_OBJECT_RETURN_NONE) ||
		     (!m->dirty && !pmap_is_modified(m->phys_addr) &&
		      (!m->precious ||
		       should_return != MEMORY_OBJECT_RETURN_ALL)))) {
			/*
			 *	Restart page unlock requests,
			 *	even though no change took place.
			 *	[Memory managers may be expecting
			 *	to see new requests.]
			 */
			m->unlock_request = VM_PROT_NONE;
			PAGE_WAKEUP(m);

			return(MEMORY_OBJECT_LOCK_RESULT_DONE);
		}

		return(MEMORY_OBJECT_LOCK_RESULT_MUST_BLOCK);
	}

	/*
	 *	If the page is to be flushed, allow
	 *	that to be done as part of the protection.
	 */

	if (should_flush)
		prot = VM_PROT_ALL;

	/*
	 *	Set the page lock.
	 *
	 *	If we are decreasing permission, do it now;
	 *	let the fault handler take care of increases
	 *	(pmap_page_protect may not increase protection).
	 */

	if (prot != VM_PROT_NO_CHANGE) {
		if ((m->page_lock ^ prot) & prot) {
			pmap_page_protect(m->phys_addr, VM_PROT_ALL & ~prot);
		}
		m->page_lock = prot;

		/*
		 *	Restart any past unlock requests, even if no
		 *	change resulted.  If the manager explicitly
		 *	requested no protection change, then it is assumed
		 *	to be remembering past requests.
		 */

		m->unlock_request = VM_PROT_NONE;
		PAGE_WAKEUP(m);
	}

	/*
	 *	Handle cleaning.
	 */

	if (should_return != MEMORY_OBJECT_RETURN_NONE) {
		/*
		 *	Check whether the page is dirty.  If
		 *	write permission has not been removed,
		 *	this may have unpredictable results.
		 */

		if (!m->dirty)
			m->dirty = pmap_is_modified(m->phys_addr);

		if (m->dirty || (m->precious &&
				 should_return == MEMORY_OBJECT_RETURN_ALL)) {
			/*
			 *	If we weren't planning
			 *	to flush the page anyway,
			 *	we may need to remove the
			 *	page from the pageout
			 *	system and from physical
			 *	maps now.
			 */

			vm_page_lock_queues();
			VM_PAGE_QUEUES_REMOVE(m);
			vm_page_unlock_queues();

			if (!should_flush)
				pmap_page_protect(m->phys_addr,
						VM_PROT_NONE);

			/*
			 *	Cleaning a page will cause
			 *	it to be flushed.
			 */

			if (m->dirty)
				return(MEMORY_OBJECT_LOCK_RESULT_MUST_CLEAN);
			else
				return(MEMORY_OBJECT_LOCK_RESULT_MUST_RETURN);
		}
	}

	/*
	 *	Handle flushing
	 */

	if (should_flush) {
		VM_PAGE_FREE(m);
	} else {
		extern boolean_t vm_page_deactivate_hint;

		/*
		 *	XXX Make clean but not flush a paging hint,
		 *	and deactivate the pages.  This is a hack
		 *	because it overloads flush/clean with
		 *	implementation-dependent meaning.  This only
		 *	happens to pages that are already clean.
		 */

		if (vm_page_deactivate_hint &&
		    (should_return != MEMORY_OBJECT_RETURN_NONE)) {
			vm_page_lock_queues();
			vm_page_deactivate(m);
			vm_page_unlock_queues();
		}
	}

	return(MEMORY_OBJECT_LOCK_RESULT_DONE);
}

/*
 *	Routine:	memory_object_lock_request [user interface]
 *
 *	Description:
 *		Control use of the data associated with the given
 *		memory object.  For each page in the given range,
 *		perform the following operations, in order:
 *			1)  restrict access to the page (disallow
 *			    forms specified by "prot");
 *			2)  return data to the manager (if "should_return"
 *			    is RETURN_DIRTY and the page is dirty, or
 * 			    "should_return" is RETURN_ALL and the page
 *			    is either dirty or precious); and,
 *			3)  flush the cached copy (if "should_flush"
 *			    is asserted).
 *		The set of pages is defined by a starting offset
 *		("offset") and size ("size").  Only pages with the
 *		same page alignment as the starting offset are
 *		considered.
 *
 *		A single acknowledgement is sent (to the "reply_to"
 *		port) when these actions are complete.  If successful,
 *		the naked send right for reply_to is consumed.
 */

kern_return_t
memory_object_lock_request(
	vm_object_t		object,
	vm_offset_t		offset,
	vm_size_t		size,
	memory_object_return_t	should_return,
	boolean_t		should_flush,
	vm_prot_t		prot,
	ipc_port_t		reply_to,
	mach_msg_type_name_t	reply_to_type)
{
	vm_page_t		m;
	vm_offset_t		original_offset = offset;
	vm_size_t		original_size = size;
	vm_offset_t		paging_offset = 0;
	vm_object_t		new_object = VM_OBJECT_NULL;
	vm_offset_t		new_offset = 0;
	vm_offset_t		last_offset = offset;
	int			page_lock_result;
	int			pageout_action = 0; /* '=0' to quiet lint */

#define	DATA_WRITE_MAX	32
	vm_page_t		holding_pages[DATA_WRITE_MAX];

	/*
	 *	Check for bogus arguments.
	 */
	if (object == VM_OBJECT_NULL ||
		((prot & ~VM_PROT_ALL) != 0 && prot != VM_PROT_NO_CHANGE))
	    return (KERN_INVALID_ARGUMENT);

	size = round_page(size);

	/*
	 *	Lock the object, and acquire a paging reference to
	 *	prevent the memory_object and control ports from
	 *	being destroyed.
	 */

	vm_object_lock(object);
	vm_object_paging_begin(object);
	offset -= object->paging_offset;

	/*
	 *	To avoid blocking while scanning for pages, save
	 *	dirty pages to be cleaned all at once.
	 *
	 *	XXXO A similar strategy could be used to limit the
	 *	number of times that a scan must be restarted for
	 *	other reasons.  Those pages that would require blocking
	 *	could be temporarily collected in another list, or
	 *	their offsets could be recorded in a small array.
	 */

	/*
	 * XXX	NOTE: May want to consider converting this to a page list
	 * XXX	vm_map_copy interface.  Need to understand object
	 * XXX	coalescing implications before doing so.
	 */

#define	PAGEOUT_PAGES							\
MACRO_BEGIN								\
	vm_map_copy_t		copy;					\
	int			i;					\
	vm_page_t		hp;					\
									\
	vm_object_unlock(object);					\
									\
	(void) vm_map_copyin_object(new_object, 0, new_offset, &copy);	\
									\
	if (object->use_old_pageout) {					\
	    assert(pageout_action == MEMORY_OBJECT_LOCK_RESULT_MUST_CLEAN);  \
		(void) memory_object_data_write(			\
			object->pager,					\
			object->pager_request,				\
			paging_offset,					\
			(pointer_t) copy,				\
			new_offset);					\
	}								\
	else {								\
		(void) memory_object_data_return(			\
			object->pager,					\
			object->pager_request,				\
			paging_offset,					\
			(pointer_t) copy,				\
			new_offset,					\
	     (pageout_action == MEMORY_OBJECT_LOCK_RESULT_MUST_CLEAN),	\
			!should_flush);					\
	}								\
									\
	vm_object_lock(object);						\
									\
	for (i = 0; i < atop(new_offset); i++) {			\
	    hp = holding_pages[i];					\
	    if (hp != VM_PAGE_NULL)					\
		VM_PAGE_FREE(hp);					\
	}								\
									\
	new_object = VM_OBJECT_NULL;					\
MACRO_END

	for (;
	     size != 0;
	     size -= PAGE_SIZE, offset += PAGE_SIZE)
	{
	    /*
	     *	Limit the number of pages to be cleaned at once.
	     */
	    if (new_object != VM_OBJECT_NULL &&
		    new_offset >= PAGE_SIZE * DATA_WRITE_MAX)
	    {
		PAGEOUT_PAGES;
	    }

	    while ((m = vm_page_lookup(object, offset)) != VM_PAGE_NULL) {
		switch ((page_lock_result = memory_object_lock_page(m,
					should_return,
					should_flush,
					prot)))
		{
		    case MEMORY_OBJECT_LOCK_RESULT_DONE:
			/*
			 *	End of a cluster of dirty pages.
			 */
			if (new_object != VM_OBJECT_NULL) {
			    PAGEOUT_PAGES;
			    continue;
			}
			break;

		    case MEMORY_OBJECT_LOCK_RESULT_MUST_BLOCK:
			/*
			 *	Since it is necessary to block,
			 *	clean any dirty pages now.
			 */
			if (new_object != VM_OBJECT_NULL) {
			    PAGEOUT_PAGES;
			    continue;
			}

			PAGE_ASSERT_WAIT(m, FALSE);
			vm_object_unlock(object);
			thread_block((void (*)()) 0);
			vm_object_lock(object);
			continue;

		    case MEMORY_OBJECT_LOCK_RESULT_MUST_CLEAN:
		    case MEMORY_OBJECT_LOCK_RESULT_MUST_RETURN:
			/*
			 * The clean and return cases are similar.
			 *
			 * Mark the page busy since we unlock the
			 * object below.
			 */
			m->busy = TRUE;

			/*
			 * if this would form a discontiguous block,
			 * clean the old pages and start anew.
			 *
			 * NOTE: The first time through here, new_object
			 * is null, hiding the fact that pageout_action
			 * is not initialized.
			 */
			if (new_object != VM_OBJECT_NULL &&
			    (last_offset != offset ||
			     pageout_action != page_lock_result)) {
			        PAGEOUT_PAGES;
			}

			vm_object_unlock(object);

			/*
			 *	If we have not already allocated an object
			 *	for a range of pages to be written, do so
			 *	now.
			 */
			if (new_object == VM_OBJECT_NULL) {
			    new_object = vm_object_allocate(original_size);
			    new_offset = 0;
			    paging_offset = m->offset +
					object->paging_offset;
			    pageout_action = page_lock_result;
			}

			/*
			 *	Move or copy the dirty page into the
			 *	new object.
			 */
			m = vm_pageout_setup(m,
					m->offset + object->paging_offset,
					new_object,
					new_offset,
					should_flush);

			/*
			 *	Save the holding page if there is one.
			 */
			holding_pages[atop(new_offset)] = m;
			new_offset += PAGE_SIZE;
			last_offset = offset + PAGE_SIZE;

			vm_object_lock(object);
			break;
		}
		break;
	    }
	}

	/*
	 *	We have completed the scan for applicable pages.
	 *	Clean any pages that have been saved.
	 */
	if (new_object != VM_OBJECT_NULL) {
	    PAGEOUT_PAGES;
	}

	if (IP_VALID(reply_to)) {
		vm_object_unlock(object);

		/* consumes our naked send-once/send right for reply_to */
		(void) memory_object_lock_completed(reply_to, reply_to_type,
			object->pager_request, original_offset, original_size);

		vm_object_lock(object);
	}

	vm_object_paging_end(object);
	vm_object_unlock(object);
	vm_object_deallocate(object);

	return (KERN_SUCCESS);
}

kern_return_t
memory_object_set_attributes_common(
	vm_object_t	object,
	boolean_t	object_ready,
	boolean_t	may_cache,
	memory_object_copy_strategy_t copy_strategy,
	boolean_t use_old_pageout)
{
	if (object == VM_OBJECT_NULL)
		return(KERN_INVALID_ARGUMENT);

	/*
	 *	Verify the attributes of importance
	 */

	switch(copy_strategy) {
		case MEMORY_OBJECT_COPY_NONE:
		case MEMORY_OBJECT_COPY_CALL:
		case MEMORY_OBJECT_COPY_DELAY:
		case MEMORY_OBJECT_COPY_TEMPORARY:
			break;
		default:
			vm_object_deallocate(object);
			return(KERN_INVALID_ARGUMENT);
	}

	if (object_ready)
		object_ready = TRUE;
	if (may_cache)
		may_cache = TRUE;

	vm_object_lock(object);

	/*
	 *	Wake up anyone waiting for the ready attribute
	 *	to become asserted.
	 */

	if (object_ready && !object->pager_ready) {
		object->use_old_pageout = use_old_pageout;
		vm_object_wakeup(object, VM_OBJECT_EVENT_PAGER_READY);
	}

	/*
	 *	Copy the attributes
	 */

	object->can_persist = may_cache;
	object->pager_ready = object_ready;
	if (copy_strategy == MEMORY_OBJECT_COPY_TEMPORARY) {
		object->temporary = TRUE;
	} else {
		object->copy_strategy = copy_strategy;
	}

	vm_object_unlock(object);

	vm_object_deallocate(object);

	return(KERN_SUCCESS);
}

/*
 * XXX	rpd claims that reply_to could be obviated in favor of a client
 * XXX	stub that made change_attributes an RPC.  Need investigation.
 */

kern_return_t	memory_object_change_attributes(
	vm_object_t		object,
	boolean_t		may_cache,
	memory_object_copy_strategy_t copy_strategy,
	ipc_port_t		reply_to,
	mach_msg_type_name_t	reply_to_type)
{
	kern_return_t	result;

	/*
	 *	Do the work and throw away our object reference.  It
	 *	is important that the object reference be deallocated
	 *	BEFORE sending the reply.  The whole point of the reply
	 *	is that it shows up after the terminate message that
	 *	may be generated by setting the object uncacheable.
	 *
	 * XXX	may_cache may become a tri-valued variable to handle
	 * XXX	uncache if not in use.
	 */
	result = memory_object_set_attributes_common(object, TRUE,
						     may_cache, copy_strategy,
						     FALSE);

	if (IP_VALID(reply_to)) {

		/* consumes our naked send-once/send right for reply_to */
		(void) memory_object_change_completed(reply_to, reply_to_type,
			may_cache, copy_strategy);

	}

	return(result);
}

kern_return_t
memory_object_set_attributes(
	vm_object_t	object,
	boolean_t	object_ready,
	boolean_t	may_cache,
	memory_object_copy_strategy_t copy_strategy)
{
	return memory_object_set_attributes_common(object, object_ready,
						   may_cache, copy_strategy,
						   TRUE);
}

kern_return_t	memory_object_ready(
	vm_object_t	object,
	boolean_t	may_cache,
	memory_object_copy_strategy_t copy_strategy)
{
	return memory_object_set_attributes_common(object, TRUE,
						   may_cache, copy_strategy,
						   FALSE);
}

kern_return_t	memory_object_get_attributes(
	vm_object_t	object,
	boolean_t	*object_ready,
	boolean_t	*may_cache,
	memory_object_copy_strategy_t *copy_strategy)
{
	if (object == VM_OBJECT_NULL)
		return(KERN_INVALID_ARGUMENT);

	vm_object_lock(object);
	*may_cache = object->can_persist;
	*object_ready = object->pager_ready;
	*copy_strategy = object->copy_strategy;
	vm_object_unlock(object);

	vm_object_deallocate(object);

	return(KERN_SUCCESS);
}

/*
 *	If successful, consumes the supplied naked send right.
 */
kern_return_t	vm_set_default_memory_manager(host, default_manager)
	const host_t	host;
	ipc_port_t	*default_manager;
{
	ipc_port_t current_manager;
	ipc_port_t new_manager;
	ipc_port_t returned_manager;

	if (host == HOST_NULL)
		return(KERN_INVALID_HOST);

	new_manager = *default_manager;
	default_memory_manager_lock();
	current_manager = memory_manager_default;

	if (new_manager == IP_NULL) {
		/*
		 *	Retrieve the current value.
		 */

		returned_manager = ipc_port_copy_send(current_manager);
	} else {
		/*
		 *	Retrieve the current value,
		 *	and replace it with the supplied value.
		 *	We consume the supplied naked send right.
		 */

		returned_manager = current_manager;
		memory_manager_default = new_manager;

		/*
		 *	In case anyone's been waiting for a memory
		 *	manager to be established, wake them up.
		 */

		thread_wakeup((event_t) &memory_manager_default);
	}

	default_memory_manager_unlock();

	*default_manager = returned_manager;
	return(KERN_SUCCESS);
}

/*
 *	Routine:	memory_manager_default_reference
 *	Purpose:
 *		Returns a naked send right for the default
 *		memory manager.  The returned right is always
 *		valid (not IP_NULL or IP_DEAD).
 */

ipc_port_t	memory_manager_default_reference(void)
{
	ipc_port_t current_manager;

	default_memory_manager_lock();

	while (current_manager = ipc_port_copy_send(memory_manager_default),
	       !IP_VALID(current_manager)) {
		thread_sleep_lock((event_t) &memory_manager_default,
			     &default_memory_manager_lock_data,
			     FALSE);
		default_memory_manager_lock();
	}

	default_memory_manager_unlock();

	return current_manager;
}

/*
 *	Routine:	memory_manager_default_port
 *	Purpose:
 *		Returns true if the receiver for the port
 *		is the default memory manager.
 *
 *		This is a hack to let ds_read_done
 *		know when it should keep memory wired.
 */

boolean_t	memory_manager_default_port(port)
	const ipc_port_t port;
{
	ipc_port_t current;
	boolean_t result;

	default_memory_manager_lock();
	current = memory_manager_default;
	if (IP_VALID(current)) {
		/*
		 *	There is no point in bothering to lock
		 *	both ports, which would be painful to do.
		 *	If the receive rights are moving around,
		 *	we might be inaccurate.
		 */

		result = port->ip_receiver == current->ip_receiver;
	} else
		result = FALSE;
	default_memory_manager_unlock();

	return result;
}

void		memory_manager_default_init(void)
{
	memory_manager_default = IP_NULL;
	default_memory_manager_lock_init();
}