sys/miscfs/overlay/overlay_vnops.c

   1 /*      $NetBSD: overlay_vnops.c,v 1.9.16.4 2005/11/10 14:10:32 skrll 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 1.16 2005/12/11 12:24:51 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 1.9.16.4 2005/11/10 14:10:32 skrll 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/malloc.h>
 139 #include <sys/buf.h>
 140 #include <miscfs/genfs/genfs.h>
 141 #include <miscfs/overlay/overlay.h>
 142 #include <miscfs/genfs/layer_extern.h>
 143
 144 /*
 145  * Global vfs data structures
 146  */
 147 int (**overlay_vnodeop_p)(void *);
 148 const struct vnodeopv_entry_desc overlay_vnodeop_entries[] = {
 149         { &vop_default_desc,  layer_bypass },
 150
 151         { &vop_lookup_desc,   layer_lookup },
 152         { &vop_setattr_desc,  layer_setattr },
 153         { &vop_getattr_desc,  layer_getattr },
 154         { &vop_access_desc,   layer_access },
 155         { &vop_lock_desc,     layer_lock },
 156         { &vop_unlock_desc,   layer_unlock },
 157         { &vop_islocked_desc, layer_islocked },
 158         { &vop_fsync_desc,    layer_fsync },
 159         { &vop_inactive_desc, layer_inactive },
 160         { &vop_reclaim_desc,  layer_reclaim },
 161         { &vop_print_desc,    layer_print },
 162         { &vop_remove_desc,   layer_remove },
 163         { &vop_rename_desc,   layer_rename },
 164         { &vop_rmdir_desc,    layer_rmdir },
 165
 166         { &vop_open_desc,     layer_open },     /* mount option handling */
 167
 168         { &vop_bwrite_desc,   layer_bwrite },
 169         { &vop_bmap_desc,     layer_bmap },
 170         { &vop_getpages_desc, layer_getpages },
 171         { &vop_putpages_desc, layer_putpages },
 172
 173         { NULL, NULL }
 174 };
 175 const struct vnodeopv_desc overlay_vnodeop_opv_desc =
 176         { &overlay_vnodeop_p, overlay_vnodeop_entries };