1 /* $NetBSD: overlay_vnops.c,v 1.25 2020/05/16 18:31:51 christos 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. Neither the name of the University nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 64 * SUCH DAMAGE. 65 * 66 * @(#)null_vnops.c 8.6 (Berkeley) 5/27/95 67 * 68 * Ancestors: 69 * @(#)lofs_vnops.c 1.2 (Berkeley) 6/18/92 70 * $Id: overlay_vnops.c,v 1.25 2020/05/16 18:31:51 christos Exp $ 71 * ...and... 72 * @(#)null_vnodeops.c 1.20 92/07/07 UCLA Ficus project 73 */ 74 75 /* 76 * Overlay Layer 77 * 78 * (See mount_overlay(8) for more information.) 79 * 80 * The overlay layer has two purposes. First, it serves as a demonstration 81 * of layering by providing a layer which really does nothing (the null 82 * layer makes the underlying files appear elsewhere in the file hierarchy). 83 * Second, the overlay layer can serve as a prototype layer. Since it 84 * provides all necessary layer framework, new file system layers can be 85 * created very easily by starting with an overlay layer. 86 * 87 * The remainder of this comment examines the overlay layer as a basis 88 * for constructing new layers. 89 * 90 * 91 * INSTANTIATING NEW OVERLAY LAYERS 92 * 93 * New overlay layers are created with mount_overlay(8). 94 * mount_overlay(8) takes two arguments, an ignored string 95 * and the pathname which the overlay will mount over. After 96 * the overlay layer is put into place, all access to the mount 97 * point path will proceed through the overlay layer. 98 * 99 * 100 * OPERATION OF AN OVERLAY LAYER 101 * 102 * The operation of an overlay layer is identical to that of a null 103 * layer. See the null layer (and layerfs) documentation for more info. 104 * 105 * 106 * CREATING OTHER FILE SYSTEM LAYERS 107 * 108 * One of the easiest ways to construct new file system layers is to make 109 * a copy of either the null layer or the overlay layer, rename all files 110 * and variables, and then begin modifying the copy. sed(1) can be used to 111 * easily rename all variables. 112 * 113 * The choice between using a null and an overlay layer depends on 114 * the desirability of retaining access to the underlying filestore. 115 * For instance, the umap filesystem presents both a uid-translated and an 116 * untranslated view of the underlying files, and so it is based off of 117 * the null layer. However a layer implementing Access Control Lists 118 * might prefer to block access to the underlying filestore, for which 119 * the overlay layer is a better basis. 120 * 121 * 122 * INVOKING OPERATIONS ON LOWER LAYERS 123 * 124 * See the null layer documentation. 125 * 126 */ 127 128 #include <sys/cdefs.h> 129 __KERNEL_RCSID(0, "$NetBSD: overlay_vnops.c,v 1.25 2020/05/16 18:31:51 christos Exp $"); 130 131 #include <sys/param.h> 132 #include <sys/systm.h> 133 #include <sys/proc.h> 134 #include <sys/time.h> 135 #include <sys/vnode.h> 136 #include <sys/mount.h> 137 #include <sys/namei.h> 138 #include <sys/buf.h> 139 #include <miscfs/genfs/genfs.h> 140 #include <miscfs/overlay/overlay.h> 141 #include <miscfs/genfs/layer_extern.h> 142 143 /* 144 * Global vfs data structures 145 */ 146 int (**overlay_vnodeop_p)(void *); 147 const struct vnodeopv_entry_desc overlay_vnodeop_entries[] = { 148 { &vop_default_desc, layer_bypass }, 149 150 { &vop_lookup_desc, layer_lookup }, 151 { &vop_setattr_desc, layer_setattr }, 152 { &vop_getattr_desc, layer_getattr }, 153 { &vop_access_desc, layer_access }, 154 { &vop_accessx_desc, genfs_accessx }, 155 { &vop_fsync_desc, layer_fsync }, 156 { &vop_inactive_desc, layer_inactive }, 157 { &vop_reclaim_desc, layer_reclaim }, 158 { &vop_print_desc, layer_print }, 159 { &vop_remove_desc, layer_remove }, 160 { &vop_rename_desc, layer_rename }, 161 { &vop_revoke_desc, layer_revoke }, 162 { &vop_rmdir_desc, layer_rmdir }, 163 164 { &vop_open_desc, layer_open }, /* mount option handling */ 165 { &vop_close_desc, layer_close }, 166 167 { &vop_bmap_desc, layer_bmap }, 168 { &vop_getpages_desc, layer_getpages }, 169 { &vop_putpages_desc, layer_putpages }, 170 171 { NULL, NULL } 172 }; 173 const struct vnodeopv_desc overlay_vnodeop_opv_desc = 174 { &overlay_vnodeop_p, overlay_vnodeop_entries }; 175