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	1	/*
	2	* (MPSAFE)
	3	*
	4	* Copyright (c) 1995, David Greenman
	5	* All rights reserved.
	6	*
	7	* Redistribution and use in source and binary forms, with or without
	8	* modification, are permitted provided that the following conditions
	9	* are met:
	10	* 1. Redistributions of source code must retain the above copyright
	11	* notice, this list of conditions and the following disclaimer.
	12	* 2. Redistributions in binary form must reproduce the above copyright
	13	* notice, this list of conditions and the following disclaimer in the
	14	* documentation and/or other materials provided with the distribution.
	15	* 3. All advertising materials mentioning features or use of this software
	16	* must display the following acknowledgement:
	17	* This product includes software developed by David Greenman.
	18	* 4. The name of the author may not be used to endorse or promote products
	19	* derived from this software without specific prior written permission.
	20	*
	21	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
	22	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	23	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	24	* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
	25	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	26	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	27	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	28	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	29	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	30	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	31	* SUCH DAMAGE.
	32	*
	33	* The default pager is responsible for supplying backing store to unbacked
	34	* storage. The backing store is usually swap so we just fall through to
	35	* the swap routines. However, since swap metadata has not been assigned,
	36	* the swap routines assign and manage the swap backing store through the
	37	* vm_page->swapblk field. The object is only converted when the page is
	38	* physically freed after having been cleaned and even then vm_page->swapblk
	39	* is maintained whenever a resident page also has swap backing store.
	40	*
	41	* $FreeBSD: src/sys/vm/default_pager.c,v 1.23 1999/11/07 20:03:53 alc Exp $
	42	*/
	43
	44	#include <sys/param.h>
	45	#include <sys/systm.h>
	46
	47	#include <vm/vm.h>
	48	#include <vm/vm_object.h>
	49	#include <vm/vm_page.h>
	50	#include <vm/vm_pager.h>
	51	#include <vm/swap_pager.h>
	52
	53	static void default_pager_dealloc (vm_object_t);
	54	static int default_pager_getpage (vm_object_t, vm_page_t *, int);
	55	static void default_pager_putpages (vm_object_t, vm_page_t *, int,
	56	boolean_t, int *);
	57	static boolean_t default_pager_haspage (vm_object_t, vm_pindex_t);
	58	/*
	59	* pagerops for OBJT_DEFAULT - "default pager".
	60	*/
	61	struct pagerops defaultpagerops = {
	62	default_pager_dealloc,
	63	default_pager_getpage,
	64	default_pager_putpages,
	65	default_pager_haspage
	66	};
	67
	68	/*
	69	* no_pager_alloc just returns an initialized object.
	70	*/
	71	vm_object_t
	72	default_pager_alloc(void *handle, off_t size, vm_prot_t prot, off_t offset)
	73	{
	74	vm_object_t object;
	75
	76	if (handle != NULL)
	77	panic("default_pager_alloc: handle specified");
	78
	79	object = vm_object_allocate(OBJT_DEFAULT,
	80	OFF_TO_IDX(round_page64(offset + size)));
	81	return (object);
	82	}
	83
	84	/*
	85	* deallocate resources associated with default objects. The default objects
	86	* have no special resources allocated to them, but the vm_page's being used
	87	* in this object might. Still, we do not have to do anything - we will free
	88	* the swapblk in the underlying vm_page's when we free the vm_page or
	89	* garbage collect the vm_page cache list.
	90	*/
	91	static void
	92	default_pager_dealloc(vm_object_t object)
	93	{
	94	/*
	95	* OBJT_DEFAULT objects have no special resources allocated to them.
	96	*/
	97	KKASSERT(object->swblock_count == 0);
	98	}
	99
	100	/*
	101	* Load pages from backing store. Since OBJT_DEFAULT is converted to
	102	* OBJT_SWAP at the time a swap-backed vm_page_t is freed, we will never
	103	* see a vm_page with assigned swap here.
	104	*/
	105	static int
	106	default_pager_getpage(vm_object_t object, vm_page_t *mpp, int seqaccess)
	107	{
	108	return VM_PAGER_FAIL;
	109	}
	110
	111	/*
	112	* Store pages to backing store. We should assign swap and initiate
	113	* I/O. We do not actually convert the object to OBJT_SWAP here. The
	114	* object will be converted when the written-out vm_page_t is moved from the
	115	* cache to the free list.
	116	*/
	117	static void
	118	default_pager_putpages(vm_object_t object, vm_page_t *mpp, int count,
	119	boolean_t sync, int *rtvals)
	120	{
	121	swap_pager_putpages(object, mpp, count, sync, rtvals);
	122	}
	123
	124	/*
	125	* Tell us whether the backing store for the requested (object,index) is
	126	* synchronized. i.e. tell us whether we can throw the page away and
	127	* reload it later. So, for example, if we are in the process of writing
	128	* the page to its backing store, or if no backing store has been assigned,
	129	* it is not yet synchronized.
	130	*
	131	* It is possible to have fully-synchronized swap assigned without the
	132	* object having been converted. We just call swap_pager_haspage() to
	133	* deal with it since it must already deal with it plus deal with swap
	134	* meta-data structures.
	135	*/
	136	static boolean_t
	137	default_pager_haspage(vm_object_t object, vm_pindex_t pindex)
	138	{
	139	return FALSE;
	140	}