Fix an endless recursion and double fault which could occur when accessing
[dragonfly.git] / sys / vfs / nullfs / null_vfsops.c
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1/*
2 * Copyright (c) 1992, 1993, 1995
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software donated to Berkeley by
6 * Jan-Simon Pendry.
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_vfsops.c 8.2 (Berkeley) 1/21/94
37 *
38 * @(#)lofs_vfsops.c 1.2 (Berkeley) 6/18/92
39 * $FreeBSD: src/sys/miscfs/nullfs/null_vfsops.c,v 1.35.2.3 2001/07/26 20:37:11 iedowse Exp $
3ea4f8fe 40 * $DragonFly: src/sys/vfs/nullfs/null_vfsops.c,v 1.30 2008/09/05 23:27:12 dillon Exp $
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41 */
42
43/*
44 * Null Layer
45 * (See null_vnops.c for a description of what this does.)
46 */
47
48#include <sys/param.h>
49#include <sys/systm.h>
50#include <sys/kernel.h>
51#include <sys/proc.h>
52#include <sys/malloc.h>
53#include <sys/vnode.h>
54#include <sys/mount.h>
fad57d0e 55#include <sys/nlookup.h>
1f2de5d4 56#include "null.h"
984263bc 57
66a1ddf5 58extern struct vop_ops null_vnode_vops;
0961aa92 59
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60static MALLOC_DEFINE(M_NULLFSMNT, "NULLFS mount", "NULLFS mount structure");
61
984263bc 62static int nullfs_root(struct mount *mp, struct vnode **vpp);
984263bc 63static int nullfs_statfs(struct mount *mp, struct statfs *sbp,
acde96db 64 struct ucred *cred);
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65
66/*
67 * Mount null layer
68 */
69static int
acde96db 70nullfs_mount(struct mount *mp, char *path, caddr_t data, struct ucred *cred)
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71{
72 int error = 0;
73 struct null_args args;
8cb8b61a 74 struct vnode *rootvp;
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75 struct null_mount *xmp;
76 u_int size;
fad57d0e 77 struct nlookupdata nd;
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78
79 NULLFSDEBUG("nullfs_mount(mp = %p)\n", (void *)mp);
80
81 /*
82 * Update is a no-op
83 */
84 if (mp->mnt_flag & MNT_UPDATE) {
85 return (EOPNOTSUPP);
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86 }
87
88 /*
89 * Get argument
90 */
91 error = copyin(data, (caddr_t)&args, sizeof(struct null_args));
92 if (error)
93 return (error);
94
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95 /*
96 * Find lower node
97 */
8cb8b61a 98 rootvp = NULL;
fad57d0e 99 error = nlookup_init(&nd, args.target, UIO_USERSPACE, NLC_FOLLOW);
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100 if (error)
101 goto fail1;
102 error = nlookup(&nd);
103 if (error)
104 goto fail2;
105 error = cache_vget(&nd.nl_nch, nd.nl_cred, LK_EXCLUSIVE, &rootvp);
106 if (error)
107 goto fail2;
984263bc 108
77652cad 109 xmp = (struct null_mount *) kmalloc(sizeof(struct null_mount),
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110 M_NULLFSMNT, M_WAITOK); /* XXX */
111
112 /*
113 * Save reference to underlying FS
28623bf9 114 *
8cb8b61a 115 * As lite stacking enters the scene, the old way of doing this
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116 * -- via the vnode -- is not good enough anymore. Use the
117 * underlying filesystem's namecache handle as our mount point
118 * root, adjusting the mount to point to us.
119 *
120 * NCF_ISMOUNTPT is normally set on the mount point, but we also
121 * want to set it on the base directory being mounted to prevent
122 * that directory from being destroyed out from under the nullfs
123 * mount.
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124 *
125 * The forwarding mount pointer (xmp->nullm_vfs) must be set to
126 * the actual target filesystem. If the target filesystem was
127 * resolved via a nullfs mount nd.nl_nch.mount will be pointing
128 * to the nullfs mount structure instead of the target filesystem,
129 * which would otherwise cause the mount VOPS and VFSOPS to recurse
130 * endlessly. If we are mounting via a nullfs mount we inherit
131 * its read-only state, if set.
8cb8b61a 132 */
28623bf9 133 xmp->nullm_vfs = nd.nl_nch.mount;
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134 if (xmp->nullm_vfs != rootvp->v_mount) {
135 if (xmp->nullm_vfs->mnt_flag & MNT_RDONLY)
136 mp->mnt_flag |= MNT_RDONLY;
137 xmp->nullm_vfs = rootvp->v_mount;
138 }
139
140 /*
141 * ncmountpt is the parent glue. When mounting a nullfs via a nullfs
142 * we retain the parent nullfs to create a unique chain tuple.
143 */
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144 mp->mnt_ncmountpt = nd.nl_nch;
145 cache_changemount(&mp->mnt_ncmountpt, mp);
146 mp->mnt_ncmountpt.ncp->nc_flag |= NCF_ISMOUNTPT;
147 cache_unlock(&mp->mnt_ncmountpt);
148 cache_zero(&nd.nl_nch);
8cb8b61a 149 nlookup_done(&nd);
984263bc 150
66a1ddf5 151 vfs_add_vnodeops(mp, &null_vnode_vops, &mp->mnt_vn_norm_ops);
0961aa92 152
28623bf9 153 vn_unlock(rootvp); /* leave reference intact */
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154
155 /*
156 * Keep a held reference to the root vnode.
157 * It is vrele'd in nullfs_unmount.
158 */
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159 xmp->nullm_rootvp = rootvp;
160 /*
161 * XXX What's the proper safety condition for querying
162 * the underlying mount? Is this flag tuning necessary
163 * at all?
164 */
165 if (xmp->nullm_vfs->mnt_flag & MNT_LOCAL)
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166 mp->mnt_flag |= MNT_LOCAL;
167 mp->mnt_data = (qaddr_t) xmp;
168 vfs_getnewfsid(mp);
169
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170 (void) copyinstr(args.target, mp->mnt_stat.f_mntfromname, MNAMELEN - 1,
171 &size);
172 bzero(mp->mnt_stat.f_mntfromname + size, MNAMELEN - size);
acde96db 173 (void)nullfs_statfs(mp, &mp->mnt_stat, cred);
984263bc 174 NULLFSDEBUG("nullfs_mount: lower %s, alias at %s\n",
75ffff0d 175 mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntfromname);
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176
177 /*
178 * So unmount won't complain about namecache refs still existing
179 */
180 mp->mnt_kern_flag |= MNTK_NCALIASED;
984263bc 181 return (0);
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182fail2:
183 nlookup_done(&nd);
184fail1:
185 return (error);
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186}
187
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188/*
189 * Free reference to null layer
190 */
191static int
acde96db 192nullfs_unmount(struct mount *mp, int mntflags)
984263bc 193{
b81dacf0 194 struct null_mount *xmp;
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195 int flags = 0;
196
197 NULLFSDEBUG("nullfs_unmount: mp = %p\n", (void *)mp);
198
199 if (mntflags & MNT_FORCE)
200 flags |= FORCECLOSE;
201
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202 /*
203 * Finally, throw away the null_mount structure
204 */
8e77d370 205 xmp = (void *)mp->mnt_data;
984263bc 206 mp->mnt_data = 0;
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207 if (xmp->nullm_rootvp) {
208 vrele(xmp->nullm_rootvp);
209 xmp->nullm_rootvp = NULL;
210 }
211 kfree(xmp, M_NULLFSMNT);
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212 return 0;
213}
214
215static int
dadab5e9 216nullfs_root(struct mount *mp, struct vnode **vpp)
984263bc 217{
984263bc 218 struct vnode *vp;
44b1cf3d 219 int error;
984263bc 220
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221 NULLFSDEBUG("nullfs_root(mp = %p, vp = %p)\n", (void *)mp,
222 (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp);
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223
224 /*
225 * Return locked reference to root.
226 */
227 vp = MOUNTTONULLMOUNT(mp)->nullm_rootvp;
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228 error = vget(vp, LK_EXCLUSIVE | LK_RETRY);
229 if (error == 0)
230 *vpp = vp;
231 return (error);
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232}
233
234static int
f4a3189a 235nullfs_quotactl(struct mount *mp, int cmd, uid_t uid, caddr_t arg,
acde96db 236 struct ucred *cred)
984263bc 237{
acde96db 238 return VFS_QUOTACTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, uid, arg, cred);
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239}
240
241static int
acde96db 242nullfs_statfs(struct mount *mp, struct statfs *sbp, struct ucred *cred)
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243{
244 int error;
245 struct statfs mstat;
246
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247 NULLFSDEBUG("nullfs_statfs(mp = %p, vp = %p)\n", (void *)mp,
248 (void *)MOUNTTONULLMOUNT(mp)->nullm_rootvp);
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249
250 bzero(&mstat, sizeof(mstat));
251
acde96db 252 error = VFS_STATFS(MOUNTTONULLMOUNT(mp)->nullm_vfs, &mstat, cred);
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253 if (error)
254 return (error);
255
256 /* now copy across the "interesting" information and fake the rest */
257 sbp->f_type = mstat.f_type;
258 sbp->f_flags = mstat.f_flags;
259 sbp->f_bsize = mstat.f_bsize;
260 sbp->f_iosize = mstat.f_iosize;
261 sbp->f_blocks = mstat.f_blocks;
262 sbp->f_bfree = mstat.f_bfree;
263 sbp->f_bavail = mstat.f_bavail;
264 sbp->f_files = mstat.f_files;
265 sbp->f_ffree = mstat.f_ffree;
266 if (sbp != &mp->mnt_stat) {
267 bcopy(&mp->mnt_stat.f_fsid, &sbp->f_fsid, sizeof(sbp->f_fsid));
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268 bcopy(mp->mnt_stat.f_mntfromname, sbp->f_mntfromname, MNAMELEN);
269 }
270 return (0);
271}
272
984263bc 273static int
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274nullfs_checkexp(struct mount *mp, struct sockaddr *nam, int *extflagsp,
275 struct ucred **credanonp)
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276{
277
278 return VFS_CHECKEXP(MOUNTTONULLMOUNT(mp)->nullm_vfs, nam,
279 extflagsp, credanonp);
280}
281
984263bc 282static int
f4a3189a 283nullfs_extattrctl(struct mount *mp, int cmd, const char *attrname, caddr_t arg,
acde96db 284 struct ucred *cred)
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285{
286 return VFS_EXTATTRCTL(MOUNTTONULLMOUNT(mp)->nullm_vfs, cmd, attrname,
acde96db 287 arg, cred);
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288}
289
290
291static struct vfsops null_vfsops = {
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292 .vfs_mount = nullfs_mount,
293 .vfs_unmount = nullfs_unmount,
294 .vfs_root = nullfs_root,
295 .vfs_quotactl = nullfs_quotactl,
296 .vfs_statfs = nullfs_statfs,
297 .vfs_sync = vfs_stdsync,
43c45e8f 298 .vfs_checkexp = nullfs_checkexp,
43c45e8f 299 .vfs_extattrctl = nullfs_extattrctl
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300};
301
302VFS_SET(null_vfsops, null, VFCF_LOOPBACK);