1 /*
2 * linux/fs/nfs/namespace.c
3 *
4 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
5 * - Modified by David Howells <dhowells@redhat.com>
6 *
7 * NFS namespace
8 */
9
10 #include <linux/dcache.h>
11 #include <linux/mount.h>
12 #include <linux/namei.h>
13 #include <linux/nfs_fs.h>
14 #include <linux/string.h>
15 #include <linux/sunrpc/clnt.h>
16 #include <linux/vfs.h>
17 #include "internal.h"
18
19 #define NFSDBG_FACILITY NFSDBG_VFS
20
21 static void nfs_expire_automounts(struct work_struct *work);
22
23 static LIST_HEAD(nfs_automount_list);
24 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
25 int nfs_mountpoint_expiry_timeout = 500 * HZ;
26
27 static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
28 const struct dentry *dentry,
29 struct nfs_fh *fh,
30 struct nfs_fattr *fattr);
31
32 /*
33 * nfs_path - reconstruct the path given an arbitrary dentry
34 * @base - arbitrary string to prepend to the path
35 * @droot - pointer to root dentry for mountpoint
36 * @dentry - pointer to dentry
37 * @buffer - result buffer
38 * @buflen - length of buffer
39 *
40 * Helper function for constructing the path from the
41 * root dentry to an arbitrary hashed dentry.
42 *
43 * This is mainly for use in figuring out the path on the
44 * server side when automounting on top of an existing partition.
45 */
46 char *nfs_path(const char *base,
47 const struct dentry *droot,
48 const struct dentry *dentry,
49 char *buffer, ssize_t buflen)
50 {
51 char *end = buffer+buflen;
52 int namelen;
53
54 *--end = '\0';
55 buflen--;
56 spin_lock(&dcache_lock);
57 while (!IS_ROOT(dentry) && dentry != droot) {
58 namelen = dentry->d_name.len;
59 buflen -= namelen + 1;
60 if (buflen < 0)
61 goto Elong_unlock;
62 end -= namelen;
63 memcpy(end, dentry->d_name.name, namelen);
64 *--end = '/';
65 dentry = dentry->d_parent;
66 }
67 spin_unlock(&dcache_lock);
68 if (*end != '/') {
69 if (--buflen < 0)
70 goto Elong;
71 *--end = '/';
72 }
73 namelen = strlen(base);
74 /* Strip off excess slashes in base string */
75 while (namelen > 0 && base[namelen - 1] == '/')
76 namelen--;
77 buflen -= namelen;
78 if (buflen < 0)
79 goto Elong;
80 end -= namelen;
81 memcpy(end, base, namelen);
82 return end;
83 Elong_unlock:
84 spin_unlock(&dcache_lock);
85 Elong:
86 return ERR_PTR(-ENAMETOOLONG);
87 }
88
89 /*
90 * nfs_follow_mountpoint - handle crossing a mountpoint on the server
91 * @dentry - dentry of mountpoint
92 * @nd - nameidata info
93 *
94 * When we encounter a mountpoint on the server, we want to set up
95 * a mountpoint on the client too, to prevent inode numbers from
96 * colliding, and to allow "df" to work properly.
97 * On NFSv4, we also want to allow for the fact that different
98 * filesystems may be migrated to different servers in a failover
99 * situation, and that different filesystems may want to use
100 * different security flavours.
101 */
102 static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
103 {
104 struct vfsmount *mnt;
105 struct nfs_server *server = NFS_SERVER(dentry->d_inode);
106 struct dentry *parent;
107 struct nfs_fh fh;
108 struct nfs_fattr fattr;
109 int err;
110
111 dprintk("--> nfs_follow_mountpoint()\n");
112
113 err = -ESTALE;
114 if (IS_ROOT(dentry))
115 goto out_err;
116
117 dprintk("%s: enter\n", __func__);
118 dput(nd->path.dentry);
119 nd->path.dentry = dget(dentry);
120
121 /* Look it up again */
122 parent = dget_parent(nd->path.dentry);
123 err = server->nfs_client->rpc_ops->lookup(parent->d_inode,
124 &nd->path.dentry->d_name,
125 &fh, &fattr);
126 dput(parent);
127 if (err != 0)
128 goto out_err;
129
130 if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL)
131 mnt = nfs_do_refmount(nd->path.mnt, nd->path.dentry);
132 else
133 mnt = nfs_do_submount(nd->path.mnt, nd->path.dentry, &fh,
134 &fattr);
135 err = PTR_ERR(mnt);
136 if (IS_ERR(mnt))
137 goto out_err;
138
139 mntget(mnt);
140 err = do_add_mount(mnt, &nd->path, nd->path.mnt->mnt_flags|MNT_SHRINKABLE,
141 &nfs_automount_list);
142 if (err < 0) {
143 mntput(mnt);
144 if (err == -EBUSY)
145 goto out_follow;
146 goto out_err;
147 }
148 path_put(&nd->path);
149 nd->path.mnt = mnt;
150 nd->path.dentry = dget(mnt->mnt_root);
151 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
152 out:
153 dprintk("%s: done, returned %d\n", __func__, err);
154
155 dprintk("<-- nfs_follow_mountpoint() = %d\n", err);
156 return ERR_PTR(err);
157 out_err:
158 path_put(&nd->path);
159 goto out;
160 out_follow:
161 while (d_mountpoint(nd->path.dentry) &&
162 follow_down(&nd->path))
163 ;
164 err = 0;
165 goto out;
166 }
167
168 const struct inode_operations nfs_mountpoint_inode_operations = {
169 .follow_link = nfs_follow_mountpoint,
170 .getattr = nfs_getattr,
171 };
172
173 const struct inode_operations nfs_referral_inode_operations = {
174 .follow_link = nfs_follow_mountpoint,
175 };
176
177 static void nfs_expire_automounts(struct work_struct *work)
178 {
179 struct list_head *list = &nfs_automount_list;
180
181 mark_mounts_for_expiry(list);
182 if (!list_empty(list))
183 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
184 }
185
186 void nfs_release_automount_timer(void)
187 {
188 if (list_empty(&nfs_automount_list))
189 cancel_delayed_work(&nfs_automount_task);
190 }
191
192 /*
193 * Clone a mountpoint of the appropriate type
194 */
195 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
196 const char *devname,
197 struct nfs_clone_mount *mountdata)
198 {
199 #ifdef CONFIG_NFS_V4
200 struct vfsmount *mnt = ERR_PTR(-EINVAL);
201 switch (server->nfs_client->rpc_ops->version) {
202 case 2:
203 case 3:
204 mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
205 break;
206 case 4:
207 mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
208 }
209 return mnt;
210 #else
211 return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
212 #endif
213 }
214
215 /**
216 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
217 * @mnt_parent - mountpoint of parent directory
218 * @dentry - parent directory
219 * @fh - filehandle for new root dentry
220 * @fattr - attributes for new root inode
221 *
222 */
223 static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
224 const struct dentry *dentry,
225 struct nfs_fh *fh,
226 struct nfs_fattr *fattr)
227 {
228 struct nfs_clone_mount mountdata = {
229 .sb = mnt_parent->mnt_sb,
230 .dentry = dentry,
231 .fh = fh,
232 .fattr = fattr,
233 };
234 struct vfsmount *mnt = ERR_PTR(-ENOMEM);
235 char *page = (char *) __get_free_page(GFP_USER);
236 char *devname;
237
238 dprintk("--> nfs_do_submount()\n");
239
240 dprintk("%s: submounting on %s/%s\n", __func__,
241 dentry->d_parent->d_name.name,
242 dentry->d_name.name);
243 if (page == NULL)
244 goto out;
245 devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE);
246 mnt = (struct vfsmount *)devname;
247 if (IS_ERR(devname))
248 goto free_page;
249 mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata);
250 free_page:
251 free_page((unsigned long)page);
252 out:
253 dprintk("%s: done\n", __func__);
254
255 dprintk("<-- nfs_do_submount() = %p\n", mnt);
256 return mnt;
257 }
258
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