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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/gfp.h> |
12 | #include <linux/mount.h> |
13 | #include <linux/namei.h> |
14 | #include <linux/nfs_fs.h> |
15 | #include <linux/string.h> |
16 | #include <linux/sunrpc/clnt.h> |
17 | #include <linux/vfs.h> |
18 | #include "internal.h" |
19 | |
20 | #define NFSDBG_FACILITY NFSDBG_VFS |
21 | |
22 | static void nfs_expire_automounts(struct work_struct *work); |
23 | |
24 | static LIST_HEAD(nfs_automount_list); |
25 | static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts); |
26 | int nfs_mountpoint_expiry_timeout = 500 * HZ; |
27 | |
28 | static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent, |
29 | const struct dentry *dentry, |
30 | struct nfs_fh *fh, |
31 | struct nfs_fattr *fattr); |
32 | |
33 | /* |
34 | * nfs_path - reconstruct the path given an arbitrary dentry |
35 | * @base - arbitrary string to prepend to the path |
36 | * @droot - pointer to root dentry for mountpoint |
37 | * @dentry - pointer to dentry |
38 | * @buffer - result buffer |
39 | * @buflen - length of buffer |
40 | * |
41 | * Helper function for constructing the path from the |
42 | * root dentry to an arbitrary hashed dentry. |
43 | * |
44 | * This is mainly for use in figuring out the path on the |
45 | * server side when automounting on top of an existing partition. |
46 | */ |
47 | char *nfs_path(const char *base, |
48 | const struct dentry *droot, |
49 | const struct dentry *dentry, |
50 | char *buffer, ssize_t buflen) |
51 | { |
52 | char *end = buffer+buflen; |
53 | int namelen; |
54 | |
55 | *--end = '\0'; |
56 | buflen--; |
57 | spin_lock(&dcache_lock); |
58 | while (!IS_ROOT(dentry) && dentry != droot) { |
59 | namelen = dentry->d_name.len; |
60 | buflen -= namelen + 1; |
61 | if (buflen < 0) |
62 | goto Elong_unlock; |
63 | end -= namelen; |
64 | memcpy(end, dentry->d_name.name, namelen); |
65 | *--end = '/'; |
66 | dentry = dentry->d_parent; |
67 | } |
68 | spin_unlock(&dcache_lock); |
69 | if (*end != '/') { |
70 | if (--buflen < 0) |
71 | goto Elong; |
72 | *--end = '/'; |
73 | } |
74 | namelen = strlen(base); |
75 | /* Strip off excess slashes in base string */ |
76 | while (namelen > 0 && base[namelen - 1] == '/') |
77 | namelen--; |
78 | buflen -= namelen; |
79 | if (buflen < 0) |
80 | goto Elong; |
81 | end -= namelen; |
82 | memcpy(end, base, namelen); |
83 | return end; |
84 | Elong_unlock: |
85 | spin_unlock(&dcache_lock); |
86 | Elong: |
87 | return ERR_PTR(-ENAMETOOLONG); |
88 | } |
89 | |
90 | /* |
91 | * nfs_follow_mountpoint - handle crossing a mountpoint on the server |
92 | * @dentry - dentry of mountpoint |
93 | * @nd - nameidata info |
94 | * |
95 | * When we encounter a mountpoint on the server, we want to set up |
96 | * a mountpoint on the client too, to prevent inode numbers from |
97 | * colliding, and to allow "df" to work properly. |
98 | * On NFSv4, we also want to allow for the fact that different |
99 | * filesystems may be migrated to different servers in a failover |
100 | * situation, and that different filesystems may want to use |
101 | * different security flavours. |
102 | */ |
103 | static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd) |
104 | { |
105 | struct vfsmount *mnt; |
106 | struct nfs_server *server = NFS_SERVER(dentry->d_inode); |
107 | struct dentry *parent; |
108 | struct nfs_fh fh; |
109 | struct nfs_fattr fattr; |
110 | int err; |
111 | |
112 | dprintk("--> nfs_follow_mountpoint()\n"); |
113 | |
114 | err = -ESTALE; |
115 | if (IS_ROOT(dentry)) |
116 | goto out_err; |
117 | |
118 | dprintk("%s: enter\n", __func__); |
119 | dput(nd->path.dentry); |
120 | nd->path.dentry = dget(dentry); |
121 | |
122 | /* Look it up again */ |
123 | parent = dget_parent(nd->path.dentry); |
124 | err = server->nfs_client->rpc_ops->lookup(parent->d_inode, |
125 | &nd->path.dentry->d_name, |
126 | &fh, &fattr); |
127 | dput(parent); |
128 | if (err != 0) |
129 | goto out_err; |
130 | |
131 | if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) |
132 | mnt = nfs_do_refmount(nd->path.mnt, nd->path.dentry); |
133 | else |
134 | mnt = nfs_do_submount(nd->path.mnt, nd->path.dentry, &fh, |
135 | &fattr); |
136 | err = PTR_ERR(mnt); |
137 | if (IS_ERR(mnt)) |
138 | goto out_err; |
139 | |
140 | mntget(mnt); |
141 | err = do_add_mount(mnt, &nd->path, nd->path.mnt->mnt_flags|MNT_SHRINKABLE, |
142 | &nfs_automount_list); |
143 | if (err < 0) { |
144 | mntput(mnt); |
145 | if (err == -EBUSY) |
146 | goto out_follow; |
147 | goto out_err; |
148 | } |
149 | path_put(&nd->path); |
150 | nd->path.mnt = mnt; |
151 | nd->path.dentry = dget(mnt->mnt_root); |
152 | schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); |
153 | out: |
154 | dprintk("%s: done, returned %d\n", __func__, err); |
155 | |
156 | dprintk("<-- nfs_follow_mountpoint() = %d\n", err); |
157 | return ERR_PTR(err); |
158 | out_err: |
159 | path_put(&nd->path); |
160 | goto out; |
161 | out_follow: |
162 | while (d_mountpoint(nd->path.dentry) && |
163 | follow_down(&nd->path)) |
164 | ; |
165 | err = 0; |
166 | goto out; |
167 | } |
168 | |
169 | const struct inode_operations nfs_mountpoint_inode_operations = { |
170 | .follow_link = nfs_follow_mountpoint, |
171 | .getattr = nfs_getattr, |
172 | }; |
173 | |
174 | const struct inode_operations nfs_referral_inode_operations = { |
175 | .follow_link = nfs_follow_mountpoint, |
176 | }; |
177 | |
178 | static void nfs_expire_automounts(struct work_struct *work) |
179 | { |
180 | struct list_head *list = &nfs_automount_list; |
181 | |
182 | mark_mounts_for_expiry(list); |
183 | if (!list_empty(list)) |
184 | schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); |
185 | } |
186 | |
187 | void nfs_release_automount_timer(void) |
188 | { |
189 | if (list_empty(&nfs_automount_list)) |
190 | cancel_delayed_work(&nfs_automount_task); |
191 | } |
192 | |
193 | /* |
194 | * Clone a mountpoint of the appropriate type |
195 | */ |
196 | static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server, |
197 | const char *devname, |
198 | struct nfs_clone_mount *mountdata) |
199 | { |
200 | #ifdef CONFIG_NFS_V4 |
201 | struct vfsmount *mnt = ERR_PTR(-EINVAL); |
202 | switch (server->nfs_client->rpc_ops->version) { |
203 | case 2: |
204 | case 3: |
205 | mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); |
206 | break; |
207 | case 4: |
208 | mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata); |
209 | } |
210 | return mnt; |
211 | #else |
212 | return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); |
213 | #endif |
214 | } |
215 | |
216 | /** |
217 | * nfs_do_submount - set up mountpoint when crossing a filesystem boundary |
218 | * @mnt_parent - mountpoint of parent directory |
219 | * @dentry - parent directory |
220 | * @fh - filehandle for new root dentry |
221 | * @fattr - attributes for new root inode |
222 | * |
223 | */ |
224 | static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent, |
225 | const struct dentry *dentry, |
226 | struct nfs_fh *fh, |
227 | struct nfs_fattr *fattr) |
228 | { |
229 | struct nfs_clone_mount mountdata = { |
230 | .sb = mnt_parent->mnt_sb, |
231 | .dentry = dentry, |
232 | .fh = fh, |
233 | .fattr = fattr, |
234 | }; |
235 | struct vfsmount *mnt = ERR_PTR(-ENOMEM); |
236 | char *page = (char *) __get_free_page(GFP_USER); |
237 | char *devname; |
238 | |
239 | dprintk("--> nfs_do_submount()\n"); |
240 | |
241 | dprintk("%s: submounting on %s/%s\n", __func__, |
242 | dentry->d_parent->d_name.name, |
243 | dentry->d_name.name); |
244 | if (page == NULL) |
245 | goto out; |
246 | devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE); |
247 | mnt = (struct vfsmount *)devname; |
248 | if (IS_ERR(devname)) |
249 | goto free_page; |
250 | mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata); |
251 | free_page: |
252 | free_page((unsigned long)page); |
253 | out: |
254 | dprintk("%s: done\n", __func__); |
255 | |
256 | dprintk("<-- nfs_do_submount() = %p\n", mnt); |
257 | return mnt; |
258 | } |
259 |
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