1 /* $NetBSD: overlay_vnops.c,v 1.9 2002/01/04 07:19:34 chs Exp $ */ 2 3 /* 4 * Copyright (c) 1999, 2000 National Aeronautics & Space Administration 5 * All rights reserved. 6 * 7 * This software was written by William Studenmund of the 8 * Numerical Aerospace Simulation Facility, NASA Ames Research Center. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the National Aeronautics & Space Administration 19 * nor the names of its contributors may be used to endorse or promote 20 * products derived from this software without specific prior written 21 * permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE NATIONAL AERONAUTICS & SPACE ADMINISTRATION 24 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 25 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 26 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE ADMINISTRATION OR CONTRIB- 27 * UTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, 28 * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 29 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 30 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 31 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 32 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 33 * POSSIBILITY OF SUCH DAMAGE. 34 */ 35 /* 36 * Copyright (c) 1992, 1993 37 * The Regents of the University of California. All rights reserved. 38 * 39 * This code is derived from software contributed to Berkeley by 40 * John Heidemann of the UCLA Ficus project. 41 * 42 * Redistribution and use in source and binary forms, with or without 43 * modification, are permitted provided that the following conditions 44 * are met: 45 * 1. Redistributions of source code must retain the above copyright 46 * notice, this list of conditions and the following disclaimer. 47 * 2. Redistributions in binary form must reproduce the above copyright 48 * notice, this list of conditions and the following disclaimer in the 49 * documentation and/or other materials provided with the distribution. 50 * 3. All advertising materials mentioning features or use of this software 51 * must display the following acknowledgement: 52 * This product includes software developed by the University of 53 * California, Berkeley and its contributors. 54 * 4. Neither the name of the University nor the names of its contributors 55 * may be used to endorse or promote products derived from this software 56 * without specific prior written permission. 57 * 58 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 59 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 60 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 61 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 62 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 63 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 64 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 65 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 66 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 67 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 68 * SUCH DAMAGE. 69 * 70 * @(#)null_vnops.c 8.6 (Berkeley) 5/27/95 71 * 72 * Ancestors: 73 * @(#)lofs_vnops.c 1.2 (Berkeley) 6/18/92 74 * $Id: overlay_vnops.c,v 1.9 2002/01/04 07:19:34 chs Exp $ 75 * ...and... 76 * @(#)null_vnodeops.c 1.20 92/07/07 UCLA Ficus project 77 */ 78 79 /* 80 * Overlay Layer 81 * 82 * (See mount_overlay(8) for more information.) 83 * 84 * The overlay layer has two purposes. First, it serves as a demonstration 85 * of layering by providing a layer which really does nothing (the null 86 * layer makes the underlying files appear elsewhere in the file hierarchy). 87 * Second, the overlay layer can serve as a prototype layer. Since it 88 * provides all necessary layer framework, new file system layers can be 89 * created very easily by starting with an overlay layer. 90 * 91 * The remainder of this comment examines the overlay layer as a basis 92 * for constructing new layers. 93 * 94 * 95 * INSTANTIATING NEW OVERLAY LAYERS 96 * 97 * New overlay layers are created with mount_overlay(8). 98 * mount_overlay(8) takes two arguments, an ignored string 99 * and the pathname which the overlay will mount over. After 100 * the overlay layer is put into place, all access to the mount 101 * point path will proceed through the overlay layer. 102 * 103 * 104 * OPERATION OF AN OVERLAY LAYER 105 * 106 * The operation of an overlay layer is identical to that of a null 107 * layer. See the null layer (and layerfs) documentation for more info. 108 * 109 * 110 * CREATING OTHER FILE SYSTEM LAYERS 111 * 112 * One of the easiest ways to construct new file system layers is to make 113 * a copy of either the null layer or the overlay layer, rename all files 114 * and variables, and then begin modifying the copy. sed(1) can be used to 115 * easily rename all variables. 116 * 117 * The choice between using a null and an overlay layer depends on 118 * the desirability of retaining access to the underlying filestore. 119 * For instance, the umap filesystem presents both a uid-translated and an 120 * untranslated view of the underlying files, and so it is based off of 121 * the null layer. However a layer implementing Access Control Lists 122 * might prefer to block access to the underlying filestore, for which 123 * the overlay layer is a better basis. 124 * 125 * 126 * INVOKING OPERATIONS ON LOWER LAYERS 127 * 128 * See the null layer documentation. 129 * 130 */ 131 132 #include <sys/cdefs.h> 133 __KERNEL_RCSID(0, "$NetBSD: overlay_vnops.c,v 1.9 2002/01/04 07:19:34 chs Exp $"); 134 135 #include <sys/param.h> 136 #include <sys/systm.h> 137 #include <sys/proc.h> 138 #include <sys/time.h> 139 #include <sys/vnode.h> 140 #include <sys/mount.h> 141 #include <sys/namei.h> 142 #include <sys/malloc.h> 143 #include <sys/buf.h> 144 #include <miscfs/genfs/genfs.h> 145 #include <miscfs/overlay/overlay.h> 146 #include <miscfs/genfs/layer_extern.h> 147 148 /* 149 * Global vfs data structures 150 */ 151 int (**overlay_vnodeop_p) __P((void *)); 152 const struct vnodeopv_entry_desc overlay_vnodeop_entries[] = { 153 { &vop_default_desc, layer_bypass }, 154 155 { &vop_lookup_desc, layer_lookup }, 156 { &vop_setattr_desc, layer_setattr }, 157 { &vop_getattr_desc, layer_getattr }, 158 { &vop_access_desc, layer_access }, 159 { &vop_lock_desc, layer_lock }, 160 { &vop_unlock_desc, layer_unlock }, 161 { &vop_islocked_desc, layer_islocked }, 162 { &vop_fsync_desc, layer_fsync }, 163 { &vop_inactive_desc, layer_inactive }, 164 { &vop_reclaim_desc, layer_reclaim }, 165 { &vop_print_desc, layer_print }, 166 167 { &vop_open_desc, layer_open }, /* mount option handling */ 168 169 { &vop_strategy_desc, layer_strategy }, 170 { &vop_bwrite_desc, layer_bwrite }, 171 { &vop_bmap_desc, layer_bmap }, 172 { &vop_getpages_desc, layer_getpages }, 173 { &vop_putpages_desc, layer_putpages }, 174 175 { NULL, NULL } 176 }; 177 const struct vnodeopv_desc overlay_vnodeop_opv_desc = 178 { &overlay_vnodeop_p, overlay_vnodeop_entries }; 179