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
null_nresolve(struct vop_nresolve_args * ap)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
null_ncreate(struct vop_ncreate_args * ap)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
null_nmkdir(struct vop_nmkdir_args * ap)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
null_nmknod(struct vop_nmknod_args * ap)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
null_nlink(struct vop_nlink_args * ap)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
null_nsymlink(struct vop_nsymlink_args * ap)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
null_nwhiteout(struct vop_nwhiteout_args * ap)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
null_nremove(struct vop_nremove_args * ap)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
null_nrmdir(struct vop_nrmdir_args * ap)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
null_nrename(struct vop_nrename_args * ap)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
null_mountctl(struct vop_mountctl_args * ap)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
252