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
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9 * notice, this list of conditions and the following disclaimer.
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12 * documentation and/or other materials provided with the distribution.
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14 * must display the following acknowledgement:
15 * This product includes software developed by David Greenman.
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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.
39 * $FreeBSD: src/sys/vm/default_pager.c,v 1.23 1999/11/07 20:03:53 alc Exp $
40 * $DragonFly: src/sys/vm/default_pager.c,v 1.5 2006/03/27 01:54:18 dillon Exp $
43 #include <sys/param.h>
44 #include <sys/systm.h>
47 #include <vm/vm_object.h>
48 #include <vm/vm_page.h>
49 #include <vm/vm_pager.h>
50 #include <vm/swap_pager.h>
52 static vm_object_t default_pager_alloc (void *, off_t, vm_prot_t, off_t);
53 static void default_pager_dealloc (vm_object_t);
54 static int default_pager_getpages (vm_object_t, vm_page_t *, int, int);
55 static void default_pager_putpages (vm_object_t, vm_page_t *, int,
57 static boolean_t default_pager_haspage (vm_object_t, vm_pindex_t, int *,
60 * pagerops for OBJT_DEFAULT - "default pager".
62 struct pagerops defaultpagerops = {
65 default_pager_dealloc,
66 default_pager_getpages,
67 default_pager_putpages,
68 default_pager_haspage,
73 * no_pager_alloc just returns an initialized object.
76 default_pager_alloc(void *handle, off_t size, vm_prot_t prot, off_t offset)
79 panic("default_pager_alloc: handle specified");
81 return vm_object_allocate(OBJT_DEFAULT, OFF_TO_IDX(round_page(offset + size)));
85 * deallocate resources associated with default objects. The default objects
86 * have no special resources allocated to them, but the vm_page's being used
87 * in this object might. Still, we do not have to do anything - we will free
88 * the swapblk in the underlying vm_page's when we free the vm_page or
89 * garbage collect the vm_page cache list.
93 default_pager_dealloc(vm_object_t object)
96 * OBJT_DEFAULT objects have no special resources allocated to them.
101 * Load pages from backing store. Since OBJT_DEFAULT is converted to
102 * OBJT_SWAP at the time a swap-backed vm_page_t is freed, we will never
103 * see a vm_page with assigned swap here.
107 default_pager_getpages(vm_object_t object, vm_page_t *m, int count, int reqpage)
109 return VM_PAGER_FAIL;
113 * Store pages to backing store. We should assign swap and initiate
114 * I/O. We do not actually convert the object to OBJT_SWAP here. The
115 * object will be converted when the written-out vm_page_t is moved from the
116 * cache to the free list.
120 default_pager_putpages(vm_object_t object, vm_page_t *m, int c, boolean_t sync,
123 swap_pager_putpages(object, m, c, sync, rtvals);
127 * Tell us whether the backing store for the requested (object,index) is
128 * synchronized. i.e. tell us whether we can throw the page away and
129 * reload it later. So, for example, if we are in the process of writing
130 * the page to its backing store, or if no backing store has been assigned,
131 * it is not yet synchronized.
133 * It is possible to have fully-synchronized swap assigned without the
134 * object having been converted. We just call swap_pager_haspage() to
135 * deal with it since it must already deal with it plus deal with swap
136 * meta-data structures.
140 default_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,