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: 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 $ 41 */ 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 46 #include <vm/vm.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> 51 52 static void default_pager_dealloc (vm_object_t); 53 static int default_pager_getpage (vm_object_t, vm_page_t *, int); 54 static void default_pager_putpages (vm_object_t, vm_page_t *, int, 55 boolean_t, int *); 56 static boolean_t default_pager_haspage (vm_object_t, vm_pindex_t); 57 /* 58 * pagerops for OBJT_DEFAULT - "default pager". 59 */ 60 struct pagerops defaultpagerops = { 61 default_pager_dealloc, 62 default_pager_getpage, 63 default_pager_putpages, 64 default_pager_haspage 65 }; 66 67 /* 68 * no_pager_alloc just returns an initialized object. 69 */ 70 vm_object_t 71 default_pager_alloc(void *handle, off_t size, vm_prot_t prot, off_t offset) 72 { 73 vm_object_t object; 74 75 if (handle != NULL) 76 panic("default_pager_alloc: handle specified"); 77 78 object = vm_object_allocate(OBJT_DEFAULT, 79 OFF_TO_IDX(round_page64(offset + size))); 80 return (object); 81 } 82 83 /* 84 * deallocate resources associated with default objects. The default objects 85 * have no special resources allocated to them, but the vm_page's being used 86 * in this object might. Still, we do not have to do anything - we will free 87 * the swapblk in the underlying vm_page's when we free the vm_page or 88 * garbage collect the vm_page cache list. 89 */ 90 91 static void 92 default_pager_dealloc(vm_object_t object) 93 { 94 /* 95 * OBJT_DEFAULT objects have no special resources allocated to them. 96 */ 97 KKASSERT(object->swblock_count == 0); 98 } 99 100 /* 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. 104 */ 105 106 static int 107 default_pager_getpage(vm_object_t object, vm_page_t *mpp, int seqaccess) 108 { 109 return VM_PAGER_FAIL; 110 } 111 112 /* 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. 117 */ 118 119 static void 120 default_pager_putpages(vm_object_t object, vm_page_t *m, int c, boolean_t sync, 121 int *rtvals) 122 { 123 swap_pager_putpages(object, m, c, sync, rtvals); 124 } 125 126 /* 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. 132 * 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. 137 */ 138 139 static boolean_t 140 default_pager_haspage(vm_object_t object, vm_pindex_t pindex) 141 { 142 return FALSE; 143 } 144