default_pager.c revision 216128 
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
40#include <sys/cdefs.h>
41__FBSDID("$FreeBSD: head/sys/vm/default_pager.c 216128 2010-12-02 17:37:16Z trasz $");
42
43#include <sys/param.h>
44#include <sys/systm.h>
45#include <sys/lock.h>
46#include <sys/proc.h>
47#include <sys/resourcevar.h>
48#include <sys/mutex.h>
49
50#include <vm/vm.h>
51#include <vm/vm_object.h>
52#include <vm/vm_page.h>
53#include <vm/vm_pager.h>
54#include <vm/swap_pager.h>
55
56static vm_object_t default_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
57    vm_ooffset_t, struct ucred *);
58static void default_pager_dealloc(vm_object_t);
59static int default_pager_getpages(vm_object_t, vm_page_t *, int, int);
60static void default_pager_putpages(vm_object_t, vm_page_t *, int,
61		boolean_t, int *);
62static boolean_t default_pager_haspage(vm_object_t, vm_pindex_t, int *,
63		int *);
64/*
65 * pagerops for OBJT_DEFAULT - "default pager".
66 */
67struct pagerops defaultpagerops = {
68	.pgo_alloc =	default_pager_alloc,
69	.pgo_dealloc =	default_pager_dealloc,
70	.pgo_getpages =	default_pager_getpages,
71	.pgo_putpages =	default_pager_putpages,
72	.pgo_haspage =	default_pager_haspage,
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, struct ucred *cred)
81{
82	vm_object_t object;
83
84	if (handle != NULL)
85		panic("default_pager_alloc: handle specified");
86	if (cred != NULL) {
87		if (!swap_reserve_by_cred(size, cred))
88			return (NULL);
89		crhold(cred);
90	}
91	object = vm_object_allocate(OBJT_DEFAULT,
92	    OFF_TO_IDX(round_page(offset + size)));
93	if (cred != NULL) {
94		VM_OBJECT_LOCK(object);
95		object->cred = cred;
96		object->charge = size;
97		VM_OBJECT_UNLOCK(object);
98	}
99	return (object);
100}
101
102/*
103 * deallocate resources associated with default objects.   The default objects
104 * have no special resources allocated to them, but the vm_page's being used
105 * in this object might.  Still, we do not have to do anything - we will free
106 * the swapblk in the underlying vm_page's when we free the vm_page or
107 * garbage collect the vm_page cache list.
108 */
109static void
110default_pager_dealloc(object)
111	vm_object_t object;
112{
113	/*
114	 * OBJT_DEFAULT objects have no special resources allocated to them.
115	 */
116}
117
118/*
119 * Load pages from backing store.  Since OBJT_DEFAULT is converted to
120 * OBJT_SWAP at the time a swap-backed vm_page_t is freed, we will never
121 * see a vm_page with assigned swap here.
122 */
123static int
124default_pager_getpages(object, m, count, reqpage)
125	vm_object_t object;
126	vm_page_t *m;
127	int count;
128	int reqpage;
129{
130	return VM_PAGER_FAIL;
131}
132
133/*
134 * Store pages to backing store.  We should assign swap and initiate
135 * I/O.  We do not actually convert the object to OBJT_SWAP here.  The
136 * object will be converted when the written-out vm_page_t is moved from the
137 * cache to the free list.
138 */
139static void
140default_pager_putpages(object, m, c, sync, rtvals)
141	vm_object_t object;
142	vm_page_t *m;
143	int c;
144	boolean_t sync;
145	int *rtvals;
146{
147	swappagerops.pgo_putpages(object, m, c, sync, rtvals);
148}
149
150/*
151 * Tell us whether the backing store for the requested (object,index) is
152 * synchronized.  i.e. tell us whether we can throw the page away and
153 * reload it later.  So, for example, if we are in the process of writing
154 * the page to its backing store, or if no backing store has been assigned,
155 * it is not yet synchronized.
156 *
157 * It is possible to have fully-synchronized swap assigned without the
158 * object having been converted.  We just call swap_pager_haspage() to
159 * deal with it since it must already deal with it plus deal with swap
160 * meta-data structures.
161 */
162static boolean_t
163default_pager_haspage(object, pindex, before, after)
164	vm_object_t object;
165	vm_pindex_t pindex;
166	int *before;
167	int *after;
168{
169	return FALSE;
170}
171
172