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1/* getroot.c: get the root dentry for an NFS mount
2 *
3 * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/module.h>
13#include <linux/init.h>
14
15#include <linux/time.h>
16#include <linux/kernel.h>
17#include <linux/mm.h>
18#include <linux/string.h>
19#include <linux/stat.h>
20#include <linux/errno.h>
21#include <linux/unistd.h>
22#include <linux/sunrpc/clnt.h>
23#include <linux/sunrpc/stats.h>
24#include <linux/nfs_fs.h>
25#include <linux/nfs_mount.h>
26#include <linux/nfs4_mount.h>
27#include <linux/lockd/bind.h>
28#include <linux/seq_file.h>
29#include <linux/mount.h>
30#include <linux/nfs_idmap.h>
31#include <linux/vfs.h>
32#include <linux/namei.h>
33#include <linux/security.h>
34
35#include <asm/system.h>
36#include <asm/uaccess.h>
37
38#include "nfs4_fs.h"
39#include "delegation.h"
40#include "internal.h"
41
42#define NFSDBG_FACILITY NFSDBG_CLIENT
43
44/*
45 * Set the superblock root dentry.
46 * Note that this function frees the inode in case of error.
47 */
48static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode)
49{
50 /* The mntroot acts as the dummy root dentry for this superblock */
51 if (sb->s_root == NULL) {
52 sb->s_root = d_alloc_root(inode);
53 if (sb->s_root == NULL) {
54 iput(inode);
55 return -ENOMEM;
56 }
57 ihold(inode);
58 /*
59 * Ensure that this dentry is invisible to d_find_alias().
60 * Otherwise, it may be spliced into the tree by
61 * d_materialise_unique if a parent directory from the same
62 * filesystem gets mounted at a later time.
63 * This again causes shrink_dcache_for_umount_subtree() to
64 * Oops, since the test for IS_ROOT() will fail.
65 */
66 spin_lock(&sb->s_root->d_inode->i_lock);
67 spin_lock(&sb->s_root->d_lock);
68 list_del_init(&sb->s_root->d_alias);
69 spin_unlock(&sb->s_root->d_lock);
70 spin_unlock(&sb->s_root->d_inode->i_lock);
71 }
72 return 0;
73}
74
75/*
76 * get an NFS2/NFS3 root dentry from the root filehandle
77 */
78struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh,
79 const char *devname)
80{
81 struct nfs_server *server = NFS_SB(sb);
82 struct nfs_fsinfo fsinfo;
83 struct dentry *ret;
84 struct inode *inode;
85 void *name = kstrdup(devname, GFP_KERNEL);
86 int error;
87
88 if (!name)
89 return ERR_PTR(-ENOMEM);
90
91 /* get the actual root for this mount */
92 fsinfo.fattr = nfs_alloc_fattr();
93 if (fsinfo.fattr == NULL) {
94 kfree(name);
95 return ERR_PTR(-ENOMEM);
96 }
97
98 error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
99 if (error < 0) {
100 dprintk("nfs_get_root: getattr error = %d\n", -error);
101 ret = ERR_PTR(error);
102 goto out;
103 }
104
105 inode = nfs_fhget(sb, mntfh, fsinfo.fattr);
106 if (IS_ERR(inode)) {
107 dprintk("nfs_get_root: get root inode failed\n");
108 ret = ERR_CAST(inode);
109 goto out;
110 }
111
112 error = nfs_superblock_set_dummy_root(sb, inode);
113 if (error != 0) {
114 ret = ERR_PTR(error);
115 goto out;
116 }
117
118 /* root dentries normally start off anonymous and get spliced in later
119 * if the dentry tree reaches them; however if the dentry already
120 * exists, we'll pick it up at this point and use it as the root
121 */
122 ret = d_obtain_alias(inode);
123 if (IS_ERR(ret)) {
124 dprintk("nfs_get_root: get root dentry failed\n");
125 goto out;
126 }
127
128 security_d_instantiate(ret, inode);
129 spin_lock(&ret->d_lock);
130 if (IS_ROOT(ret) && !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
131 ret->d_fsdata = name;
132 name = NULL;
133 }
134 spin_unlock(&ret->d_lock);
135out:
136 if (name)
137 kfree(name);
138 nfs_free_fattr(fsinfo.fattr);
139 return ret;
140}
141
142#ifdef CONFIG_NFS_V4
143
144int nfs4_get_rootfh(struct nfs_server *server, struct nfs_fh *mntfh)
145{
146 struct nfs_fsinfo fsinfo;
147 int ret = -ENOMEM;
148
149 dprintk("--> nfs4_get_rootfh()\n");
150
151 fsinfo.fattr = nfs_alloc_fattr();
152 if (fsinfo.fattr == NULL)
153 goto out;
154
155 /* Start by getting the root filehandle from the server */
156 ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
157 if (ret < 0) {
158 dprintk("nfs4_get_rootfh: getroot error = %d\n", -ret);
159 goto out;
160 }
161
162 if (!(fsinfo.fattr->valid & NFS_ATTR_FATTR_TYPE)
163 || !S_ISDIR(fsinfo.fattr->mode)) {
164 printk(KERN_ERR "nfs4_get_rootfh:"
165 " getroot encountered non-directory\n");
166 ret = -ENOTDIR;
167 goto out;
168 }
169
170 if (fsinfo.fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) {
171 printk(KERN_ERR "nfs4_get_rootfh:"
172 " getroot obtained referral\n");
173 ret = -EREMOTE;
174 goto out;
175 }
176
177 memcpy(&server->fsid, &fsinfo.fattr->fsid, sizeof(server->fsid));
178out:
179 nfs_free_fattr(fsinfo.fattr);
180 dprintk("<-- nfs4_get_rootfh() = %d\n", ret);
181 return ret;
182}
183
184/*
185 * get an NFS4 root dentry from the root filehandle
186 */
187struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh,
188 const char *devname)
189{
190 struct nfs_server *server = NFS_SB(sb);
191 struct nfs_fattr *fattr = NULL;
192 struct dentry *ret;
193 struct inode *inode;
194 void *name = kstrdup(devname, GFP_KERNEL);
195 int error;
196
197 dprintk("--> nfs4_get_root()\n");
198
199 if (!name)
200 return ERR_PTR(-ENOMEM);
201
202 /* get the info about the server and filesystem */
203 error = nfs4_server_capabilities(server, mntfh);
204 if (error < 0) {
205 dprintk("nfs_get_root: getcaps error = %d\n",
206 -error);
207 kfree(name);
208 return ERR_PTR(error);
209 }
210
211 fattr = nfs_alloc_fattr();
212 if (fattr == NULL) {
213 kfree(name);
214 return ERR_PTR(-ENOMEM);
215 }
216
217 /* get the actual root for this mount */
218 error = server->nfs_client->rpc_ops->getattr(server, mntfh, fattr);
219 if (error < 0) {
220 dprintk("nfs_get_root: getattr error = %d\n", -error);
221 ret = ERR_PTR(error);
222 goto out;
223 }
224
225 if (fattr->valid & NFS_ATTR_FATTR_FSID &&
226 !nfs_fsid_equal(&server->fsid, &fattr->fsid))
227 memcpy(&server->fsid, &fattr->fsid, sizeof(server->fsid));
228
229 inode = nfs_fhget(sb, mntfh, fattr);
230 if (IS_ERR(inode)) {
231 dprintk("nfs_get_root: get root inode failed\n");
232 ret = ERR_CAST(inode);
233 goto out;
234 }
235
236 error = nfs_superblock_set_dummy_root(sb, inode);
237 if (error != 0) {
238 ret = ERR_PTR(error);
239 goto out;
240 }
241
242 /* root dentries normally start off anonymous and get spliced in later
243 * if the dentry tree reaches them; however if the dentry already
244 * exists, we'll pick it up at this point and use it as the root
245 */
246 ret = d_obtain_alias(inode);
247 if (IS_ERR(ret)) {
248 dprintk("nfs_get_root: get root dentry failed\n");
249 goto out;
250 }
251
252 security_d_instantiate(ret, inode);
253 spin_lock(&ret->d_lock);
254 if (IS_ROOT(ret) && !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
255 ret->d_fsdata = name;
256 name = NULL;
257 }
258 spin_unlock(&ret->d_lock);
259out:
260 if (name)
261 kfree(name);
262 nfs_free_fattr(fattr);
263 dprintk("<-- nfs4_get_root()\n");
264 return ret;
265}
266
267#endif /* CONFIG_NFS_V4 */
1// SPDX-License-Identifier: GPL-2.0-or-later
2/* getroot.c: get the root dentry for an NFS mount
3 *
4 * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#include <linux/module.h>
9#include <linux/init.h>
10
11#include <linux/time.h>
12#include <linux/kernel.h>
13#include <linux/mm.h>
14#include <linux/string.h>
15#include <linux/stat.h>
16#include <linux/errno.h>
17#include <linux/unistd.h>
18#include <linux/sunrpc/clnt.h>
19#include <linux/sunrpc/stats.h>
20#include <linux/nfs_fs.h>
21#include <linux/nfs_mount.h>
22#include <linux/lockd/bind.h>
23#include <linux/seq_file.h>
24#include <linux/mount.h>
25#include <linux/vfs.h>
26#include <linux/namei.h>
27#include <linux/security.h>
28
29#include <linux/uaccess.h>
30
31#include "internal.h"
32
33#define NFSDBG_FACILITY NFSDBG_CLIENT
34
35/*
36 * Set the superblock root dentry.
37 * Note that this function frees the inode in case of error.
38 */
39static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode)
40{
41 /* The mntroot acts as the dummy root dentry for this superblock */
42 if (sb->s_root == NULL) {
43 sb->s_root = d_make_root(inode);
44 if (sb->s_root == NULL)
45 return -ENOMEM;
46 ihold(inode);
47 /*
48 * Ensure that this dentry is invisible to d_find_alias().
49 * Otherwise, it may be spliced into the tree by
50 * d_splice_alias if a parent directory from the same
51 * filesystem gets mounted at a later time.
52 * This again causes shrink_dcache_for_umount_subtree() to
53 * Oops, since the test for IS_ROOT() will fail.
54 */
55 spin_lock(&d_inode(sb->s_root)->i_lock);
56 spin_lock(&sb->s_root->d_lock);
57 hlist_del_init(&sb->s_root->d_u.d_alias);
58 spin_unlock(&sb->s_root->d_lock);
59 spin_unlock(&d_inode(sb->s_root)->i_lock);
60 }
61 return 0;
62}
63
64/*
65 * get an NFS2/NFS3 root dentry from the root filehandle
66 */
67struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh,
68 const char *devname)
69{
70 struct nfs_server *server = NFS_SB(sb);
71 struct nfs_fsinfo fsinfo;
72 struct dentry *ret;
73 struct inode *inode;
74 void *name = kstrdup(devname, GFP_KERNEL);
75 int error;
76
77 if (!name)
78 return ERR_PTR(-ENOMEM);
79
80 /* get the actual root for this mount */
81 fsinfo.fattr = nfs_alloc_fattr();
82 if (fsinfo.fattr == NULL) {
83 kfree(name);
84 return ERR_PTR(-ENOMEM);
85 }
86
87 error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
88 if (error < 0) {
89 dprintk("nfs_get_root: getattr error = %d\n", -error);
90 ret = ERR_PTR(error);
91 goto out;
92 }
93
94 inode = nfs_fhget(sb, mntfh, fsinfo.fattr, NULL);
95 if (IS_ERR(inode)) {
96 dprintk("nfs_get_root: get root inode failed\n");
97 ret = ERR_CAST(inode);
98 goto out;
99 }
100
101 error = nfs_superblock_set_dummy_root(sb, inode);
102 if (error != 0) {
103 ret = ERR_PTR(error);
104 goto out;
105 }
106
107 /* root dentries normally start off anonymous and get spliced in later
108 * if the dentry tree reaches them; however if the dentry already
109 * exists, we'll pick it up at this point and use it as the root
110 */
111 ret = d_obtain_root(inode);
112 if (IS_ERR(ret)) {
113 dprintk("nfs_get_root: get root dentry failed\n");
114 goto out;
115 }
116
117 security_d_instantiate(ret, inode);
118 spin_lock(&ret->d_lock);
119 if (IS_ROOT(ret) && !ret->d_fsdata &&
120 !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
121 ret->d_fsdata = name;
122 name = NULL;
123 }
124 spin_unlock(&ret->d_lock);
125out:
126 kfree(name);
127 nfs_free_fattr(fsinfo.fattr);
128 return ret;
129}