sys/vfs/nullfs/null_vnops.c

   1 /*
   2  * Copyright (c) 1992, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * John Heidemann of the UCLA Ficus project.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  *      @(#)null_vnops.c        8.6 (Berkeley) 5/27/95
  37  *
  38  * Ancestors:
  39  *      @(#)lofs_vnops.c        1.2 (Berkeley) 6/18/92
  40  * $FreeBSD: src/sys/miscfs/nullfs/null_vnops.c,v 1.38.2.6 2002/07/31 00:32:28 semenu Exp $
  41  * $DragonFly: src/sys/vfs/nullfs/null_vnops.c,v 1.30 2008/09/17 21:44:25 dillon Exp $
  42  *      ...and...
  43  *      @(#)null_vnodeops.c 1.20 92/07/07 UCLA Ficus project
  44  *
  45  * $FreeBSD: src/sys/miscfs/nullfs/null_vnops.c,v 1.38.2.6 2002/07/31 00:32:28 semenu Exp $
  46  */
  47
  48 /*
  49  * Null Layer
  50  *
  51  * (See mount_null(8) for more information.)
  52  *
  53  * The null layer duplicates a portion of the file system
  54  * name space under a new name.  In this respect, it is
  55  * similar to the loopback file system.  It differs from
  56  * the loopback fs in two respects:  it is implemented using
  57  * a stackable layers techniques, and its "null-node"s stack above
  58  * all lower-layer vnodes, not just over directory vnodes.
  59  *
  60  * The null layer has two purposes.  First, it serves as a demonstration
  61  * of layering by proving a layer which does nothing.  (It actually
  62  * does everything the loopback file system does, which is slightly
  63  * more than nothing.)  Second, the null layer can serve as a prototype
  64  * layer.  Since it provides all necessary layer framework,
  65  * new file system layers can be created very easily be starting
  66  * with a null layer.
  67  *
  68  * The remainder of this man page examines the null layer as a basis
  69  * for constructing new layers.
  70  *
  71  *
  72  * INSTANTIATING NEW NULL LAYERS
  73  *
  74  * New null layers are created with mount_null(8).
  75  * Mount_null(8) takes two arguments, the pathname
  76  * of the lower vfs (target-pn) and the pathname where the null
  77  * layer will appear in the namespace (alias-pn).  After
  78  * the null layer is put into place, the contents
  79  * of target-pn subtree will be aliased under alias-pn.
  80  *
  81  *
  82  * OPERATION OF A NULL LAYER
  83  *
  84  * The null layer is the minimum file system layer,
  85  * simply bypassing all possible operations to the lower layer
  86  * for processing there.  The majority of its activity used to center
  87  * on a so-called bypass routine, through which nullfs vnodes
  88  * passed on operation to their underlying peer.
  89  *
  90  * However, with the current implementation nullfs doesn't have any private
  91  * vnodes, rather it relies on DragonFly's namecache API. That gives a much
  92  * more lightweight null layer, as namecache structures are pure data, with
  93  * no private operations, so there is no need of subtle dispatching routines.
  94  *
  95  * Unlike the old code, this implementation is not a general skeleton overlay
  96  * filesystem: to get more comprehensive overlaying, we will need vnode
  97  * operation dispatch. Other overlay filesystems, like unionfs might be
  98  * able to get on with a hybrid solution: overlay some vnodes, and rely
  99  * on namecache API for the rest.
 100  */
 101
 102 #include <sys/param.h>
 103 #include <sys/systm.h>
 104 #include <sys/kernel.h>
 105 #include <sys/sysctl.h>
 106 #include <sys/vnode.h>
 107 #include <sys/mount.h>
 108 #include <sys/mountctl.h>
 109 #include <sys/proc.h>
 110 #include <sys/namei.h>
 111 #include <sys/malloc.h>
 112 #include <sys/buf.h>
 113 #include "null.h"
 114
 115 static int      null_nresolve(struct vop_nresolve_args *ap);
 116 static int      null_ncreate(struct vop_ncreate_args *ap);
 117 static int      null_nmkdir(struct vop_nmkdir_args *ap);
 118 static int      null_nmknod(struct vop_nmknod_args *ap);
 119 static int      null_nlink(struct vop_nlink_args *ap);
 120 static int      null_nsymlink(struct vop_nsymlink_args *ap);
 121 static int      null_nwhiteout(struct vop_nwhiteout_args *ap);
 122 static int      null_nremove(struct vop_nremove_args *ap);
 123 static int      null_nrmdir(struct vop_nrmdir_args *ap);
 124 static int      null_nrename(struct vop_nrename_args *ap);
 125 static int      null_mountctl(struct vop_mountctl_args *ap);
 126
 127 static int
 128 null_nresolve(struct vop_nresolve_args *ap)
 129 {
 130         ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops;
 131
 132         return vop_nresolve_ap(ap);
 133 }
 134
 135 static int
 136 null_ncreate(struct vop_ncreate_args *ap)
 137 {
 138         ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops;
 139
 140         return vop_ncreate_ap(ap);
 141 }
 142
 143 static int
 144 null_nmkdir(struct vop_nmkdir_args *ap)
 145 {
 146         ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops;
 147
 148         return vop_nmkdir_ap(ap);
 149 }
 150
 151 static int
 152 null_nmknod(struct vop_nmknod_args *ap)
 153 {
 154         ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops;
 155
 156         return vop_nmknod_ap(ap);
 157 }
 158
 159 static int
 160 null_nlink(struct vop_nlink_args *ap)
 161 {
 162         ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops;
 163
 164         return vop_nlink_ap(ap);
 165 }
 166
 167 static int
 168 null_nsymlink(struct vop_nsymlink_args *ap)
 169 {
 170         ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops;
 171
 172         return vop_nsymlink_ap(ap);
 173 }
 174
 175 static int
 176 null_nwhiteout(struct vop_nwhiteout_args *ap)
 177 {
 178         ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops;
 179
 180         return vop_nwhiteout_ap(ap);
 181 }
 182
 183 static int
 184 null_nremove(struct vop_nremove_args *ap)
 185 {
 186         ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops;
 187
 188         return vop_nremove_ap(ap);
 189 }
 190
 191 static int
 192 null_nrmdir(struct vop_nrmdir_args *ap)
 193 {
 194         ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops;
 195
 196         return vop_nrmdir_ap(ap);
 197 }
 198
 199 static int
 200 null_nrename(struct vop_nrename_args *ap)
 201 {
 202         struct mount *lmp;
 203
 204         lmp = MOUNTTONULLMOUNT(ap->a_fnch->mount)->nullm_vfs;
 205         if (lmp != MOUNTTONULLMOUNT(ap->a_tnch->mount)->nullm_vfs)
 206                 return (EINVAL);
 207
 208         ap->a_head.a_ops = lmp->mnt_vn_norm_ops;
 209
 210         return vop_nrename_ap(ap);
 211 }
 212
 213 static int
 214 null_mountctl(struct vop_mountctl_args *ap)
 215 {
 216         struct mount *mp;
 217         int error;
 218
 219         mp = ap->a_head.a_ops->head.vv_mount;
 220
 221         switch(ap->a_op) {
 222         case MOUNTCTL_SET_EXPORT:
 223                 if (ap->a_ctllen != sizeof(struct export_args))
 224                         error = EINVAL;
 225                 else
 226                         error = nullfs_export(mp, ap->a_op, (const void *)ap->a_ctl);
 227                 break;
 228         case MOUNTCTL_MOUNTFLAGS:
 229                 error = vop_stdmountctl(ap);
 230                 break;
 231         default:
 232                 error = EOPNOTSUPP;
 233                 break;
 234         }
 235         return (error);
 236 #if 0
 237         ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops;
 238
 239         return vop_mountctl_ap(ap);
 240 #endif
 241 }
 242
 243 /*
 244  * Global vfs data structures
 245  */
 246 struct vop_ops null_vnode_vops = {
 247         .vop_nresolve =         null_nresolve,
 248         .vop_ncreate =          null_ncreate,
 249         .vop_nmkdir =           null_nmkdir,
 250         .vop_nmknod =           null_nmknod,
 251         .vop_nlink =            null_nlink,
 252         .vop_nsymlink =         null_nsymlink,
 253         .vop_nwhiteout =        null_nwhiteout,
 254         .vop_nremove =          null_nremove,
 255         .vop_nrmdir =           null_nrmdir,
 256         .vop_nrename =          null_nrename,
 257         .vop_mountctl =         null_mountctl
 258 };
 259