default_pager.c revision 284100
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 284100 2015-06-06 20:37:40Z jhb $"); 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 */ 67struct pagerops defaultpagerops = { 68 .pgo_alloc = default_pager_alloc, 69 .pgo_dealloc = default_pager_dealloc, 70 .pgo_getpages = default_pager_getpages, 71 .pgo_putpages = default_pager_putpages, 72 .pgo_haspage = default_pager_haspage, 73}; 74 75/* 76 * no_pager_alloc just returns an initialized object. 77 */ 78static vm_object_t 79default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot, 80 vm_ooffset_t offset, struct ucred *cred) 81{ 82 vm_object_t object; 83 84 if (handle != NULL) 85 panic("default_pager_alloc: handle specified"); 86 if (cred != NULL) { 87 if (!swap_reserve_by_cred(size, cred)) 88 return (NULL); 89 crhold(cred); 90 } 91 object = vm_object_allocate(OBJT_DEFAULT, 92 OFF_TO_IDX(round_page(offset + size))); 93 if (cred != NULL) { 94 VM_OBJECT_WLOCK(object); 95 object->cred = cred; 96 object->charge = size; 97 VM_OBJECT_WUNLOCK(object); 98 } 99 return (object); 100} 101 102/* 103 * deallocate resources associated with default objects. The default objects 104 * have no special resources allocated to them, but the vm_page's being used 105 * in this object might. Still, we do not have to do anything - we will free 106 * the swapblk in the underlying vm_page's when we free the vm_page or 107 * garbage collect the vm_page cache list. 108 */ 109static void 110default_pager_dealloc(object) 111 vm_object_t object; 112{ 113 /* 114 * OBJT_DEFAULT objects have no special resources allocated to them. 115 */ 116 object->type = OBJT_DEAD; 117} 118 119/* 120 * Load pages from backing store. Since OBJT_DEFAULT is converted to 121 * OBJT_SWAP at the time a swap-backed vm_page_t is freed, we will never 122 * see a vm_page with assigned swap here. 123 */ 124static int 125default_pager_getpages(object, m, count, reqpage) 126 vm_object_t object; 127 vm_page_t *m; 128 int count; 129 int reqpage; 130{ 131 return VM_PAGER_FAIL; 132} 133 134/* 135 * Store pages to backing store. We should assign swap and initiate 136 * I/O. We do not actually convert the object to OBJT_SWAP here. The 137 * object will be converted when the written-out vm_page_t is moved from the 138 * cache to the free list. 139 */ 140static void 141default_pager_putpages(vm_object_t object, vm_page_t *m, int count, 142 int flags, int *rtvals) 143{ 144 145 swappagerops.pgo_putpages(object, m, count, flags, rtvals); 146} 147 148/* 149 * Tell us whether the backing store for the requested (object,index) is 150 * synchronized. i.e. tell us whether we can throw the page away and 151 * reload it later. So, for example, if we are in the process of writing 152 * the page to its backing store, or if no backing store has been assigned, 153 * it is not yet synchronized. 154 * 155 * It is possible to have fully-synchronized swap assigned without the 156 * object having been converted. We just call swap_pager_haspage() to 157 * deal with it since it must already deal with it plus deal with swap 158 * meta-data structures. 159 */ 160static boolean_t 161default_pager_haspage(object, pindex, before, after) 162 vm_object_t object; 163 vm_pindex_t pindex; 164 int *before; 165 int *after; 166{ 167 return FALSE; 168} 169 170