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
32#include <sys/cdefs.h>
33__FBSDID("$FreeBSD: stable/11/sys/vm/default_pager.c 315473 2017-03-18 05:38:10Z alc $");
34
35#include <sys/param.h>
36#include <sys/systm.h>
37#include <sys/lock.h>
38#include <sys/proc.h>
39#include <sys/resourcevar.h>
40#include <sys/rwlock.h>
41
42#include <vm/vm.h>
43#include <vm/vm_object.h>
44#include <vm/vm_page.h>
45#include <vm/vm_pager.h>
46#include <vm/swap_pager.h>
47
48static vm_object_t	default_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
49			    vm_ooffset_t, struct ucred *);
50static void		default_pager_dealloc(vm_object_t);
51static int		default_pager_getpages(vm_object_t, vm_page_t *, int,
52			    int *, int *);
53static void		default_pager_putpages(vm_object_t, vm_page_t *, int,
54			    boolean_t, int *);
55static boolean_t	default_pager_haspage(vm_object_t, vm_pindex_t, int *,
56			    int *);
57
58/*
59 * pagerops for OBJT_DEFAULT - "default pager".
60 *
61 * This pager handles anonymous (no handle) swap-backed memory, just
62 * like the swap pager.  It allows several optimizations based on the
63 * fact that no pages of a default object can be swapped out.  The
64 * most important optimization is in vm_fault(), where the pager is
65 * never asked for a non-resident page.  Instead, a freshly allocated
66 * zeroed page is used.
67 *
68 * On the first request to page out a page from a default object, the
69 * object is converted to swap pager type.
70 */
71struct pagerops defaultpagerops = {
72	.pgo_alloc =	default_pager_alloc,
73	.pgo_dealloc =	default_pager_dealloc,
74	.pgo_getpages =	default_pager_getpages,
75	.pgo_putpages =	default_pager_putpages,
76	.pgo_haspage =	default_pager_haspage,
77};
78
79/*
80 * Return an initialized object.
81 */
82static vm_object_t
83default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
84    vm_ooffset_t offset, struct ucred *cred)
85{
86	vm_object_t object;
87
88	if (handle != NULL)
89		panic("default_pager_alloc: handle specified");
90	if (cred != NULL) {
91		if (!swap_reserve_by_cred(size, cred))
92			return (NULL);
93		crhold(cred);
94	}
95	object = vm_object_allocate(OBJT_DEFAULT,
96	    OFF_TO_IDX(round_page(offset + size)));
97	if (cred != NULL) {
98		object->cred = cred;
99		object->charge = size;
100	}
101	return (object);
102}
103
104/*
105 * Deallocate resources associated with the object.
106 */
107static void
108default_pager_dealloc(vm_object_t object)
109{
110
111	/* Reserved swap is released by vm_object_destroy(). */
112	object->type = OBJT_DEAD;
113}
114
115/*
116 * Load pages from backing store.
117 */
118static int
119default_pager_getpages(vm_object_t object, vm_page_t *m, int count,
120    int *rbehind, int *rahead)
121{
122
123	/*
124	 * Since an OBJT_DEFAULT object is converted to OBJT_SWAP by the first
125	 * call to the putpages method, this function will never be called on
126	 * a vm_page with assigned swap.
127	 */
128	return (VM_PAGER_FAIL);
129}
130
131/*
132 * Store pages to backing store.
133 */
134static void
135default_pager_putpages(vm_object_t object, vm_page_t *m, int count,
136    int flags, int *rtvals)
137{
138
139	/* The swap pager will convert the object to OBJT_SWAP. */
140	swappagerops.pgo_putpages(object, m, count, flags, rtvals);
141}
142
143/*
144 * Tell us whether the requested (object,index) is available from the object's
145 * backing store.
146 */
147static boolean_t
148default_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
149    int *after)
150{
151
152	/* An OBJT_DEFAULT object has no backing store. */
153	return (FALSE);
154}
155
156