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#include <sys/user.h>
44
45#include <vm/vm.h>
46#include <vm/vm_object.h>
47#include <vm/vm_page.h>
48#include <vm/vm_pager.h>
49#include <vm/swap_pager.h>
50
51static vm_object_t	default_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
52			    vm_ooffset_t, struct ucred *);
53static void		default_pager_dealloc(vm_object_t);
54static int		default_pager_getpages(vm_object_t, vm_page_t *, int,
55			    int *, int *);
56static void		default_pager_putpages(vm_object_t, vm_page_t *, int,
57			    boolean_t, int *);
58static boolean_t	default_pager_haspage(vm_object_t, vm_pindex_t, int *,
59			    int *);
60
61/*
62 * pagerops for OBJT_DEFAULT - "default pager".
63 *
64 * This pager handles anonymous (no handle) swap-backed memory, just
65 * like the swap pager.  It allows several optimizations based on the
66 * fact that no pages of a default object can be swapped out.  The
67 * most important optimization is in vm_fault(), where the pager is
68 * never asked for a non-resident page.  Instead, a freshly allocated
69 * zeroed page is used.
70 *
71 * On the first request to page out a page from a default object, the
72 * object is converted to swap pager type.
73 */
74const struct pagerops defaultpagerops = {
75	.pgo_kvme_type = KVME_TYPE_DEFAULT,
76	.pgo_alloc =	default_pager_alloc,
77	.pgo_dealloc =	default_pager_dealloc,
78	.pgo_getpages =	default_pager_getpages,
79	.pgo_putpages =	default_pager_putpages,
80	.pgo_haspage =	default_pager_haspage,
81};
82
83/*
84 * Return an initialized object.
85 */
86static vm_object_t
87default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
88    vm_ooffset_t offset, struct ucred *cred)
89{
90	vm_object_t object;
91
92	if (handle != NULL)
93		panic("default_pager_alloc: handle specified");
94	if (cred != NULL) {
95		if (!swap_reserve_by_cred(size, cred))
96			return (NULL);
97		crhold(cred);
98	}
99	object = vm_object_allocate(OBJT_DEFAULT,
100	    OFF_TO_IDX(round_page(offset + size)));
101	if (cred != NULL) {
102		object->cred = cred;
103		object->charge = size;
104	}
105	return (object);
106}
107
108/*
109 * Deallocate resources associated with the object.
110 */
111static void
112default_pager_dealloc(vm_object_t object)
113{
114
115	/* Reserved swap is released by vm_object_destroy(). */
116	object->type = OBJT_DEAD;
117}
118
119/*
120 * Load pages from backing store.
121 */
122static int
123default_pager_getpages(vm_object_t object, vm_page_t *m, int count,
124    int *rbehind, int *rahead)
125{
126
127	/*
128	 * Since an OBJT_DEFAULT object is converted to OBJT_SWAP by the first
129	 * call to the putpages method, this function will never be called on
130	 * a vm_page with assigned swap.
131	 */
132	return (VM_PAGER_FAIL);
133}
134
135/*
136 * Store pages to backing store.
137 */
138static void
139default_pager_putpages(vm_object_t object, vm_page_t *m, int count,
140    int flags, int *rtvals)
141{
142
143	/* The swap pager will convert the object to OBJT_SWAP. */
144	swappagerops.pgo_putpages(object, m, count, flags, rtvals);
145}
146
147/*
148 * Tell us whether the requested (object,index) is available from the object's
149 * backing store.
150 */
151static boolean_t
152default_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
153    int *after)
154{
155
156	/* An OBJT_DEFAULT object has no backing store. */
157	return (FALSE);
158}
159