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