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: stable/9/sys/vm/default_pager.c 284100 2015-06-06 20:37:40Z jhb $");
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
56 static vm_object_t default_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
57 vm_ooffset_t, struct ucred *);
58 static void default_pager_dealloc(vm_object_t);
59 static int default_pager_getpages(vm_object_t, vm_page_t *, int, int);
60 static void default_pager_putpages(vm_object_t, vm_page_t *, int,
61 boolean_t, int *);
62 static boolean_t default_pager_haspage(vm_object_t, vm_pindex_t, int *,
63 int *);
64 /*
65 * pagerops for OBJT_DEFAULT - "default pager".
66 */
67 struct 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 */
78 static vm_object_t
default_pager_alloc(void * handle,vm_ooffset_t size,vm_prot_t prot,vm_ooffset_t offset,struct ucred * cred)79 default_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 */
109 static void
default_pager_dealloc(object)110 default_pager_dealloc(object)
111 vm_object_t object;
112 {
113 /*
114 * OBJT_DEFAULT objects have no special resources allocated to them.
115 */
116 object->type = OBJT_DEAD;
117 }
118
119 /*
120 * Load pages from backing store. Since OBJT_DEFAULT is converted to
121 * OBJT_SWAP at the time a swap-backed vm_page_t is freed, we will never
122 * see a vm_page with assigned swap here.
123 */
124 static int
default_pager_getpages(object,m,count,reqpage)125 default_pager_getpages(object, m, count, reqpage)
126 vm_object_t object;
127 vm_page_t *m;
128 int count;
129 int reqpage;
130 {
131 return VM_PAGER_FAIL;
132 }
133
134 /*
135 * Store pages to backing store. We should assign swap and initiate
136 * I/O. We do not actually convert the object to OBJT_SWAP here. The
137 * object will be converted when the written-out vm_page_t is moved from the
138 * cache to the free list.
139 */
140 static void
default_pager_putpages(object,m,c,sync,rtvals)141 default_pager_putpages(object, m, c, sync, rtvals)
142 vm_object_t object;
143 vm_page_t *m;
144 int c;
145 boolean_t sync;
146 int *rtvals;
147 {
148 swappagerops.pgo_putpages(object, m, c, sync, rtvals);
149 }
150
151 /*
152 * Tell us whether the backing store for the requested (object,index) is
153 * synchronized. i.e. tell us whether we can throw the page away and
154 * reload it later. So, for example, if we are in the process of writing
155 * the page to its backing store, or if no backing store has been assigned,
156 * it is not yet synchronized.
157 *
158 * It is possible to have fully-synchronized swap assigned without the
159 * object having been converted. We just call swap_pager_haspage() to
160 * deal with it since it must already deal with it plus deal with swap
161 * meta-data structures.
162 */
163 static boolean_t
default_pager_haspage(object,pindex,before,after)164 default_pager_haspage(object, pindex, before, after)
165 vm_object_t object;
166 vm_pindex_t pindex;
167 int *before;
168 int *after;
169 {
170 return FALSE;
171 }
172
173