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/10/sys/vm/default_pager.c 310363 2016-12-21 11:32:08Z kib $");
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/rwlock.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 *
67 * This pager handles anonymous (no handle) swap-backed memory, just
68 * like the swap pager.  It allows several optimizations based on the
69 * fact that no pages of a default object can be swapped out.  The
70 * most important optimization is in vm_fault(), where the pager is
71 * never asked for a non-resident page.  Instead, a freshly allocated
72 * zeroed page is used.
73 *
74 * On the first request to page out a page from a default object, the
75 * object is converted to swap pager type.
76 */
77struct pagerops defaultpagerops = {
78	.pgo_alloc =	default_pager_alloc,
79	.pgo_dealloc =	default_pager_dealloc,
80	.pgo_getpages =	default_pager_getpages,
81	.pgo_putpages =	default_pager_putpages,
82	.pgo_haspage =	default_pager_haspage,
83};
84
85/*
86 * no_pager_alloc just returns an initialized object.
87 */
88static vm_object_t
89default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
90    vm_ooffset_t offset, struct ucred *cred)
91{
92	vm_object_t object;
93
94	if (handle != NULL)
95		panic("default_pager_alloc: handle specified");
96	if (cred != NULL) {
97		if (!swap_reserve_by_cred(size, cred))
98			return (NULL);
99		crhold(cred);
100	}
101	object = vm_object_allocate(OBJT_DEFAULT,
102	    OFF_TO_IDX(round_page(offset + size)));
103	if (cred != NULL) {
104		VM_OBJECT_WLOCK(object);
105		object->cred = cred;
106		object->charge = size;
107		VM_OBJECT_WUNLOCK(object);
108	}
109	return (object);
110}
111
112/*
113 * deallocate resources associated with default objects.   The default objects
114 * have no special resources allocated to them, but the vm_page's being used
115 * in this object might.  Still, we do not have to do anything - we will free
116 * the swapblk in the underlying vm_page's when we free the vm_page or
117 * garbage collect the vm_page cache list.
118 */
119static void
120default_pager_dealloc(object)
121	vm_object_t object;
122{
123	/*
124	 * OBJT_DEFAULT objects have no special resources allocated to them.
125	 */
126	object->type = OBJT_DEAD;
127}
128
129/*
130 * Load pages from backing store.  Since OBJT_DEFAULT is converted to
131 * OBJT_SWAP at the time a swap-backed vm_page_t is freed, we will never
132 * see a vm_page with assigned swap here.
133 */
134static int
135default_pager_getpages(object, m, count, reqpage)
136	vm_object_t object;
137	vm_page_t *m;
138	int count;
139	int reqpage;
140{
141	return VM_PAGER_FAIL;
142}
143
144/*
145 * Store pages to backing store.  We should assign swap and initiate
146 * I/O.  We do not actually convert the object to OBJT_SWAP here.  The
147 * object will be converted when the written-out vm_page_t is moved from the
148 * cache to the free list.
149 */
150static void
151default_pager_putpages(vm_object_t object, vm_page_t *m, int count,
152    int flags, int *rtvals)
153{
154
155	swappagerops.pgo_putpages(object, m, count, flags, rtvals);
156}
157
158/*
159 * Tell us whether the backing store for the requested (object,index) is
160 * synchronized.  i.e. tell us whether we can throw the page away and
161 * reload it later.  So, for example, if we are in the process of writing
162 * the page to its backing store, or if no backing store has been assigned,
163 * it is not yet synchronized.
164 *
165 * It is possible to have fully-synchronized swap assigned without the
166 * object having been converted.  We just call swap_pager_haspage() to
167 * deal with it since it must already deal with it plus deal with swap
168 * meta-data structures.
169 */
170static boolean_t
171default_pager_haspage(object, pindex, before, after)
172	vm_object_t object;
173	vm_pindex_t pindex;
174	int *before;
175	int *after;
176{
177	return FALSE;
178}
179
180