2 * Copyright (c) 1995, David Greenman
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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17 * derived from this software without specific prior written permission.
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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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.
40 #include <sys/cdefs.h>
41 __FBSDID("$FreeBSD$");
43 #include <sys/param.h>
44 #include <sys/systm.h>
47 #include <sys/mutex.h>
50 #include <vm/vm_object.h>
51 #include <vm/vm_page.h>
52 #include <vm/vm_pager.h>
53 #include <vm/swap_pager.h>
55 static vm_object_t default_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
57 static void default_pager_dealloc(vm_object_t);
58 static int default_pager_getpages(vm_object_t, vm_page_t *, int, int);
59 static void default_pager_putpages(vm_object_t, vm_page_t *, int,
61 static boolean_t default_pager_haspage(vm_object_t, vm_pindex_t, int *,
64 * pagerops for OBJT_DEFAULT - "default pager".
66 struct pagerops defaultpagerops = {
67 .pgo_alloc = default_pager_alloc,
68 .pgo_dealloc = default_pager_dealloc,
69 .pgo_getpages = default_pager_getpages,
70 .pgo_putpages = default_pager_putpages,
71 .pgo_haspage = default_pager_haspage,
75 * no_pager_alloc just returns an initialized object.
78 default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
82 panic("default_pager_alloc: handle specified");
84 return vm_object_allocate(OBJT_DEFAULT, OFF_TO_IDX(round_page(offset + size)));
88 * deallocate resources associated with default objects. The default objects
89 * have no special resources allocated to them, but the vm_page's being used
90 * in this object might. Still, we do not have to do anything - we will free
91 * the swapblk in the underlying vm_page's when we free the vm_page or
92 * garbage collect the vm_page cache list.
95 default_pager_dealloc(object)
99 * OBJT_DEFAULT objects have no special resources allocated to them.
104 * Load pages from backing store. Since OBJT_DEFAULT is converted to
105 * OBJT_SWAP at the time a swap-backed vm_page_t is freed, we will never
106 * see a vm_page with assigned swap here.
109 default_pager_getpages(object, m, count, reqpage)
115 return VM_PAGER_FAIL;
119 * Store pages to backing store. We should assign swap and initiate
120 * I/O. We do not actually convert the object to OBJT_SWAP here. The
121 * object will be converted when the written-out vm_page_t is moved from the
122 * cache to the free list.
125 default_pager_putpages(object, m, c, sync, rtvals)
132 swappagerops.pgo_putpages(object, m, c, sync, rtvals);
136 * Tell us whether the backing store for the requested (object,index) is
137 * synchronized. i.e. tell us whether we can throw the page away and
138 * reload it later. So, for example, if we are in the process of writing
139 * the page to its backing store, or if no backing store has been assigned,
140 * it is not yet synchronized.
142 * It is possible to have fully-synchronized swap assigned without the
143 * object having been converted. We just call swap_pager_haspage() to
144 * deal with it since it must already deal with it plus deal with swap
145 * meta-data structures.
148 default_pager_haspage(object, pindex, before, after)