default_pager.c revision 79224
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 * $FreeBSD: head/sys/vm/default_pager.c 79224 2001-07-04 16:20:28Z dillon $ 40 */ 41 42#include <sys/param.h> 43#include <sys/systm.h> 44#include <sys/lock.h> 45#include <sys/proc.h> 46#include <sys/mutex.h> 47 48#include <vm/vm.h> 49#include <vm/vm_object.h> 50#include <vm/vm_page.h> 51#include <vm/vm_pager.h> 52#include <vm/vm_zone.h> 53#include <vm/swap_pager.h> 54 55static vm_object_t default_pager_alloc __P((void *, vm_ooffset_t, vm_prot_t, 56 vm_ooffset_t)); 57static void default_pager_dealloc __P((vm_object_t)); 58static int default_pager_getpages __P((vm_object_t, vm_page_t *, int, int)); 59static void default_pager_putpages __P((vm_object_t, vm_page_t *, int, 60 boolean_t, int *)); 61static boolean_t default_pager_haspage __P((vm_object_t, vm_pindex_t, int *, 62 int *)); 63/* 64 * pagerops for OBJT_DEFAULT - "default pager". 65 */ 66struct pagerops defaultpagerops = { 67 NULL, 68 default_pager_alloc, 69 default_pager_dealloc, 70 default_pager_getpages, 71 default_pager_putpages, 72 default_pager_haspage, 73 NULL 74}; 75 76/* 77 * no_pager_alloc just returns an initialized object. 78 */ 79static vm_object_t 80default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot, 81 vm_ooffset_t offset) 82{ 83 if (handle != NULL) 84 panic("default_pager_alloc: handle specified"); 85 86 return vm_object_allocate(OBJT_DEFAULT, OFF_TO_IDX(round_page(offset + size))); 87} 88 89/* 90 * deallocate resources associated with default objects. The default objects 91 * have no special resources allocated to them, but the vm_page's being used 92 * in this object might. Still, we do not have to do anything - we will free 93 * the swapblk in the underlying vm_page's when we free the vm_page or 94 * garbage collect the vm_page cache list. 95 */ 96 97static void 98default_pager_dealloc(object) 99 vm_object_t object; 100{ 101 /* 102 * OBJT_DEFAULT objects have no special resources allocated to them. 103 */ 104} 105 106/* 107 * Load pages from backing store. Since OBJT_DEFAULT is converted to 108 * OBJT_SWAP at the time a swap-backed vm_page_t is freed, we will never 109 * see a vm_page with assigned swap here. 110 */ 111 112static int 113default_pager_getpages(object, m, count, reqpage) 114 vm_object_t object; 115 vm_page_t *m; 116 int count; 117 int reqpage; 118{ 119 return VM_PAGER_FAIL; 120} 121 122/* 123 * Store pages to backing store. We should assign swap and initiate 124 * I/O. We do not actually convert the object to OBJT_SWAP here. The 125 * object will be converted when the written-out vm_page_t is moved from the 126 * cache to the free list. 127 */ 128 129static void 130default_pager_putpages(object, m, c, sync, rtvals) 131 vm_object_t object; 132 vm_page_t *m; 133 int c; 134 boolean_t sync; 135 int *rtvals; 136{ 137 swap_pager_putpages(object, m, c, sync, rtvals); 138} 139 140/* 141 * Tell us whether the backing store for the requested (object,index) is 142 * synchronized. i.e. tell us whether we can throw the page away and 143 * reload it later. So, for example, if we are in the process of writing 144 * the page to its backing store, or if no backing store has been assigned, 145 * it is not yet synchronized. 146 * 147 * It is possible to have fully-synchronized swap assigned without the 148 * object having been converted. We just call swap_pager_haspage() to 149 * deal with it since it must already deal with it plus deal with swap 150 * meta-data structures. 151 */ 152 153static boolean_t 154default_pager_haspage(object, pindex, before, after) 155 vm_object_t object; 156 vm_pindex_t pindex; 157 int *before; 158 int *after; 159{ 160 return FALSE; 161} 162 163