default_pager.c revision 76827 
1/*
2 * Copyright (c) 1995, David Greenman
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. All advertising materials mentioning features or use of this software
14 *    must display the following acknowledgement:
15 *	This product includes software developed by David Greenman.
16 * 4. The name of the author may not be used to endorse or promote products
17 *    derived from this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 *
31 * The default pager is responsible for supplying backing store to unbacked
32 * storage.  The backing store is usually swap so we just fall through to
33 * the swap routines.  However, since swap metadata has not been assigned,
34 * the swap routines assign and manage the swap backing store through the
35 * vm_page->swapblk field.  The object is only converted when the page is
36 * physically freed after having been cleaned and even then vm_page->swapblk
37 * is maintained whenever a resident page also has swap backing store.
38 *
39 * $FreeBSD: head/sys/vm/default_pager.c 76827 2001-05-19 01:28:09Z alfred $
40 */
41
42#include <sys/param.h>
43#include <sys/systm.h>
44#include <sys/lock.h>
45#include <sys/mutex.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/vm_zone.h>
52#include <vm/swap_pager.h>
53
54static vm_object_t default_pager_alloc __P((void *, vm_ooffset_t, vm_prot_t,
55		vm_ooffset_t));
56static void default_pager_dealloc __P((vm_object_t));
57static int default_pager_getpages __P((vm_object_t, vm_page_t *, int, int));
58static void default_pager_putpages __P((vm_object_t, vm_page_t *, int,
59		boolean_t, int *));
60static boolean_t default_pager_haspage __P((vm_object_t, vm_pindex_t, int *,
61		int *));
62/*
63 * pagerops for OBJT_DEFAULT - "default pager".
64 */
65struct pagerops defaultpagerops = {
66	NULL,
67	default_pager_alloc,
68	default_pager_dealloc,
69	default_pager_getpages,
70	default_pager_putpages,
71	default_pager_haspage,
72	NULL
73};
74
75/*
76 * no_pager_alloc just returns an initialized object.
77 */
78static vm_object_t
79default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
80		    vm_ooffset_t offset)
81{
82	if (handle != NULL)
83		panic("default_pager_alloc: handle specified");
84
85	return vm_object_allocate(OBJT_DEFAULT, OFF_TO_IDX(round_page(offset + size)));
86}
87
88/*
89 * deallocate resources associated with default objects.   The default objects
90 * have no special resources allocated to them, but the vm_page's being used
91 * in this object might.  Still, we do not have to do anything - we will free
92 * the swapblk in the underlying vm_page's when we free the vm_page or
93 * garbage collect the vm_page cache list.
94 */
95
96static void
97default_pager_dealloc(object)
98	vm_object_t object;
99{
100	/*
101	 * OBJT_DEFAULT objects have no special resources allocated to them.
102	 */
103}
104
105/*
106 * Load pages from backing store.  Since OBJT_DEFAULT is converted to
107 * OBJT_SWAP at the time a swap-backed vm_page_t is freed, we will never
108 * see a vm_page with assigned swap here.
109 */
110
111static int
112default_pager_getpages(object, m, count, reqpage)
113	vm_object_t object;
114	vm_page_t *m;
115	int count;
116	int reqpage;
117{
118	return VM_PAGER_FAIL;
119}
120
121/*
122 * Store pages to backing store.  We should assign swap and initiate
123 * I/O.  We do not actually convert the object to OBJT_SWAP here.  The
124 * object will be converted when the written-out vm_page_t is moved from the
125 * cache to the free list.
126 */
127
128static void
129default_pager_putpages(object, m, c, sync, rtvals)
130	vm_object_t object;
131	vm_page_t *m;
132	int c;
133	boolean_t sync;
134	int *rtvals;
135{
136	swap_pager_putpages(object, m, c, sync, rtvals);
137}
138
139/*
140 * Tell us whether the backing store for the requested (object,index) is
141 * synchronized.  i.e. tell us whether we can throw the page away and
142 * reload it later.  So, for example, if we are in the process of writing
143 * the page to its backing store, or if no backing store has been assigned,
144 * it is not yet synchronized.
145 *
146 * It is possible to have fully-synchronized swap assigned without the
147 * object having been converted.  We just call swap_pager_haspage() to
148 * deal with it since it must already deal with it plus deal with swap
149 * meta-data structures.
150 */
151
152static boolean_t
153default_pager_haspage(object, pindex, before, after)
154	vm_object_t object;
155	vm_pindex_t pindex;
156	int *before;
157	int *after;
158{
159	return FALSE;
160}
161
162