1 /*-
2 * SPDX-License-Identifier: BSD-4-Clause
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
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
36
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/lock.h>
40 #include <sys/proc.h>
41 #include <sys/resourcevar.h>
42 #include <sys/rwlock.h>
43
44 #include <vm/vm.h>
45 #include <vm/vm_object.h>
46 #include <vm/vm_page.h>
47 #include <vm/vm_pager.h>
48 #include <vm/swap_pager.h>
49
50 static vm_object_t default_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
51 vm_ooffset_t, struct ucred *);
52 static void default_pager_dealloc(vm_object_t);
53 static int default_pager_getpages(vm_object_t, vm_page_t *, int,
54 int *, 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, int *,
58 int *);
59
60 /*
61 * pagerops for OBJT_DEFAULT - "default pager".
62 *
63 * This pager handles anonymous (no handle) swap-backed memory, just
64 * like the swap pager. It allows several optimizations based on the
65 * fact that no pages of a default object can be swapped out. The
66 * most important optimization is in vm_fault(), where the pager is
67 * never asked for a non-resident page. Instead, a freshly allocated
68 * zeroed page is used.
69 *
70 * On the first request to page out a page from a default object, the
71 * object is converted to swap pager type.
72 */
73 struct pagerops defaultpagerops = {
74 .pgo_alloc = default_pager_alloc,
75 .pgo_dealloc = default_pager_dealloc,
76 .pgo_getpages = default_pager_getpages,
77 .pgo_putpages = default_pager_putpages,
78 .pgo_haspage = default_pager_haspage,
79 };
80
81 /*
82 * Return an initialized object.
83 */
84 static vm_object_t
default_pager_alloc(void * handle,vm_ooffset_t size,vm_prot_t prot,vm_ooffset_t offset,struct ucred * cred)85 default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
86 vm_ooffset_t offset, struct ucred *cred)
87 {
88 vm_object_t object;
89
90 if (handle != NULL)
91 panic("default_pager_alloc: handle specified");
92 if (cred != NULL) {
93 if (!swap_reserve_by_cred(size, cred))
94 return (NULL);
95 crhold(cred);
96 }
97 object = vm_object_allocate(OBJT_DEFAULT,
98 OFF_TO_IDX(round_page(offset + size)));
99 if (cred != NULL) {
100 object->cred = cred;
101 object->charge = size;
102 }
103 return (object);
104 }
105
106 /*
107 * Deallocate resources associated with the object.
108 */
109 static void
default_pager_dealloc(vm_object_t object)110 default_pager_dealloc(vm_object_t object)
111 {
112
113 /* Reserved swap is released by vm_object_destroy(). */
114 object->type = OBJT_DEAD;
115 }
116
117 /*
118 * Load pages from backing store.
119 */
120 static int
default_pager_getpages(vm_object_t object,vm_page_t * m,int count,int * rbehind,int * rahead)121 default_pager_getpages(vm_object_t object, vm_page_t *m, int count,
122 int *rbehind, int *rahead)
123 {
124
125 /*
126 * Since an OBJT_DEFAULT object is converted to OBJT_SWAP by the first
127 * call to the putpages method, this function will never be called on
128 * a vm_page with assigned swap.
129 */
130 return (VM_PAGER_FAIL);
131 }
132
133 /*
134 * Store pages to backing store.
135 */
136 static void
default_pager_putpages(vm_object_t object,vm_page_t * m,int count,int flags,int * rtvals)137 default_pager_putpages(vm_object_t object, vm_page_t *m, int count,
138 int flags, int *rtvals)
139 {
140
141 /* The swap pager will convert the object to OBJT_SWAP. */
142 swappagerops.pgo_putpages(object, m, count, flags, rtvals);
143 }
144
145 /*
146 * Tell us whether the requested (object,index) is available from the object's
147 * backing store.
148 */
149 static boolean_t
default_pager_haspage(vm_object_t object,vm_pindex_t pindex,int * before,int * after)150 default_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
151 int *after)
152 {
153
154 /* An OBJT_DEFAULT object has no backing store. */
155 return (FALSE);
156 }
157