default_pager.c revision 12662 
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 *	$Id: default_pager.c,v 1.2 1995/07/13 10:29:34 davidg Exp $
32 */
33
34#include <sys/param.h>
35#include <sys/systm.h>
36#include <sys/kernel.h>
37#include <sys/malloc.h>
38#include <sys/queue.h>
39
40#include <vm/vm.h>
41#include <vm/vm_param.h>
42#include <vm/vm_prot.h>
43#include <vm/vm_object.h>
44#include <vm/vm_page.h>
45#include <vm/vm_pager.h>
46#include <vm/default_pager.h>
47#include <vm/swap_pager.h>
48
49/*
50 * pagerops for OBJT_DEFAULT - "default pager".
51 */
52struct pagerops defaultpagerops = {
53	NULL,
54	default_pager_alloc,
55	default_pager_dealloc,
56	default_pager_getpages,
57	default_pager_putpages,
58	default_pager_haspage,
59	NULL
60};
61
62/*
63 * no_pager_alloc just returns an initialized object.
64 */
65vm_object_t
66default_pager_alloc(handle, size, prot, offset)
67	void *handle;
68	register vm_size_t size;
69	vm_prot_t prot;
70	vm_offset_t offset;
71{
72	if (handle != NULL)
73		panic("default_pager_alloc: handle specified");
74
75	return vm_object_allocate(OBJT_DEFAULT, offset + size);
76}
77
78void
79default_pager_dealloc(object)
80	vm_object_t object;
81{
82	/*
83	 * OBJT_DEFAULT objects have no special resources allocated to them.
84	 */
85}
86
87/*
88 * The default pager has no backing store, so we always return
89 * failure.
90 */
91int
92default_pager_getpages(object, m, count, reqpage)
93	vm_object_t object;
94	vm_page_t *m;
95	int count;
96	int reqpage;
97{
98	return VM_PAGER_FAIL;
99}
100
101int
102default_pager_putpages(object, m, c, sync, rtvals)
103	vm_object_t object;
104	vm_page_t *m;
105	int c;
106	boolean_t sync;
107	int *rtvals;
108{
109	int i;
110
111	/*
112	 * Try to convert the object type into a OBJT_SWAP.
113	 * If the swp structure allocation fails, convert it
114	 * back to OBJT_DEFAULT and return failure. Otherwise
115	 * pass this putpages to the swap pager.
116	 */
117	object->type = OBJT_SWAP;
118
119	if (swap_pager_swp_alloc(object, M_KERNEL) != 0) {
120		object->type = OBJT_DEFAULT;
121		for (i = 0; i < c; i++)
122			rtvals[i] = VM_PAGER_FAIL;
123		return VM_PAGER_FAIL;
124	}
125
126	return swap_pager_putpages(object, m, c, sync, rtvals);
127}
128
129boolean_t
130default_pager_haspage(object, offset, before, after)
131	vm_object_t object;
132	vm_offset_t offset;
133	int *before;
134	int *after;
135{
136	return FALSE;
137}
138