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 310363 2016-12-21 11:32:08Z kib $"); 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 * 67 * This pager handles anonymous (no handle) swap-backed memory, just 68 * like the swap pager. It allows several optimizations based on the 69 * fact that no pages of a default object can be swapped out. The 70 * most important optimization is in vm_fault(), where the pager is 71 * never asked for a non-resident page. Instead, a freshly allocated 72 * zeroed page is used. 73 * 74 * On the first request to page out a page from a default object, the 75 * object is converted to swap pager type. 76 */ 77struct pagerops defaultpagerops = { 78 .pgo_alloc = default_pager_alloc, 79 .pgo_dealloc = default_pager_dealloc, 80 .pgo_getpages = default_pager_getpages, 81 .pgo_putpages = default_pager_putpages, 82 .pgo_haspage = default_pager_haspage, 83}; 84 85/* 86 * no_pager_alloc just returns an initialized object. 87 */ 88static vm_object_t 89default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot, 90 vm_ooffset_t offset, struct ucred *cred) 91{ 92 vm_object_t object; 93 94 if (handle != NULL) 95 panic("default_pager_alloc: handle specified"); 96 if (cred != NULL) { 97 if (!swap_reserve_by_cred(size, cred)) 98 return (NULL); 99 crhold(cred); 100 } 101 object = vm_object_allocate(OBJT_DEFAULT, 102 OFF_TO_IDX(round_page(offset + size))); 103 if (cred != NULL) { 104 VM_OBJECT_WLOCK(object); 105 object->cred = cred; 106 object->charge = size; 107 VM_OBJECT_WUNLOCK(object); 108 } 109 return (object); 110} 111 112/* 113 * deallocate resources associated with default objects. The default objects 114 * have no special resources allocated to them, but the vm_page's being used 115 * in this object might. Still, we do not have to do anything - we will free 116 * the swapblk in the underlying vm_page's when we free the vm_page or 117 * garbage collect the vm_page cache list. 118 */ 119static void 120default_pager_dealloc(object) 121 vm_object_t object; 122{ 123 /* 124 * OBJT_DEFAULT objects have no special resources allocated to them. 125 */ 126 object->type = OBJT_DEAD; 127} 128 129/* 130 * Load pages from backing store. Since OBJT_DEFAULT is converted to 131 * OBJT_SWAP at the time a swap-backed vm_page_t is freed, we will never 132 * see a vm_page with assigned swap here. 133 */ 134static int 135default_pager_getpages(object, m, count, reqpage) 136 vm_object_t object; 137 vm_page_t *m; 138 int count; 139 int reqpage; 140{ 141 return VM_PAGER_FAIL; 142} 143 144/* 145 * Store pages to backing store. We should assign swap and initiate 146 * I/O. We do not actually convert the object to OBJT_SWAP here. The 147 * object will be converted when the written-out vm_page_t is moved from the 148 * cache to the free list. 149 */ 150static void 151default_pager_putpages(vm_object_t object, vm_page_t *m, int count, 152 int flags, int *rtvals) 153{ 154 155 swappagerops.pgo_putpages(object, m, count, flags, rtvals); 156} 157 158/* 159 * Tell us whether the backing store for the requested (object,index) is 160 * synchronized. i.e. tell us whether we can throw the page away and 161 * reload it later. So, for example, if we are in the process of writing 162 * the page to its backing store, or if no backing store has been assigned, 163 * it is not yet synchronized. 164 * 165 * It is possible to have fully-synchronized swap assigned without the 166 * object having been converted. We just call swap_pager_haspage() to 167 * deal with it since it must already deal with it plus deal with swap 168 * meta-data structures. 169 */ 170static boolean_t 171default_pager_haspage(object, pindex, before, after) 172 vm_object_t object; 173 vm_pindex_t pindex; 174 int *before; 175 int *after; 176{ 177 return FALSE; 178} 179 180