1 /* mntpt.c: mountpoint management
2 *
3 * Copyright (C) 2002 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/kernel.h>
13 #include <linux/module.h>
14 #include <linux/init.h>
15 #include <linux/sched.h>
16 #include <linux/slab.h>
17 #include <linux/fs.h>
18 #include <linux/pagemap.h>
19 #include <linux/mount.h>
20 #include <linux/namei.h>
21 #include <linux/namespace.h>
22 #include "super.h"
23 #include "cell.h"
24 #include "volume.h"
25 #include "vnode.h"
26 #include "internal.h"
27
28
29 static struct dentry *afs_mntpt_lookup(struct inode *dir,
30 struct dentry *dentry,
31 struct nameidata *nd);
32 static int afs_mntpt_open(struct inode *inode, struct file *file);
33 static int afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd);
34
35 struct file_operations afs_mntpt_file_operations = {
36 .open = afs_mntpt_open,
37 };
38
39 struct inode_operations afs_mntpt_inode_operations = {
40 .lookup = afs_mntpt_lookup,
41 .follow_link = afs_mntpt_follow_link,
42 .readlink = page_readlink,
43 .getattr = afs_inode_getattr,
44 };
45
46 static LIST_HEAD(afs_vfsmounts);
47
48 static void afs_mntpt_expiry_timed_out(struct afs_timer *timer);
49
50 struct afs_timer_ops afs_mntpt_expiry_timer_ops = {
51 .timed_out = afs_mntpt_expiry_timed_out,
52 };
53
54 struct afs_timer afs_mntpt_expiry_timer;
55
56 unsigned long afs_mntpt_expiry_timeout = 20;
57
58 /*****************************************************************************/
59 /*
60 * check a symbolic link to see whether it actually encodes a mountpoint
61 * - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
62 */
63 int afs_mntpt_check_symlink(struct afs_vnode *vnode)
64 {
65 struct page *page;
66 filler_t *filler;
67 size_t size;
68 char *buf;
69 int ret;
70
71 _enter("{%u,%u}", vnode->fid.vnode, vnode->fid.unique);
72
73 /* read the contents of the symlink into the pagecache */
74 filler = (filler_t *) AFS_VNODE_TO_I(vnode)->i_mapping->a_ops->readpage;
75
76 page = read_cache_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0,
77 filler, NULL);
78 if (IS_ERR(page)) {
79 ret = PTR_ERR(page);
80 goto out;
81 }
82
83 ret = -EIO;
84 wait_on_page_locked(page);
85 buf = kmap(page);
86 if (!PageUptodate(page))
87 goto out_free;
88 if (PageError(page))
89 goto out_free;
90
91 /* examine the symlink's contents */
92 size = vnode->status.size;
93 _debug("symlink to %*.*s", size, (int) size, buf);
94
95 if (size > 2 &&
96 (buf[0] == '%' || buf[0] == '#') &&
97 buf[size - 1] == '.'
98 ) {
99 _debug("symlink is a mountpoint");
100 spin_lock(&vnode->lock);
101 vnode->flags |= AFS_VNODE_MOUNTPOINT;
102 spin_unlock(&vnode->lock);
103 }
104
105 ret = 0;
106
107 out_free:
108 kunmap(page);
109 page_cache_release(page);
110 out:
111 _leave(" = %d", ret);
112 return ret;
113
114 } /* end afs_mntpt_check_symlink() */
115
116 /*****************************************************************************/
117 /*
118 * no valid lookup procedure on this sort of dir
119 */
120 static struct dentry *afs_mntpt_lookup(struct inode *dir,
121 struct dentry *dentry,
122 struct nameidata *nd)
123 {
124 kenter("%p,%p{%p{%s},%s}",
125 dir,
126 dentry,
127 dentry->d_parent,
128 dentry->d_parent ?
129 dentry->d_parent->d_name.name : (const unsigned char *) "",
130 dentry->d_name.name);
131
132 return ERR_PTR(-EREMOTE);
133 } /* end afs_mntpt_lookup() */
134
135 /*****************************************************************************/
136 /*
137 * no valid open procedure on this sort of dir
138 */
139 static int afs_mntpt_open(struct inode *inode, struct file *file)
140 {
141 kenter("%p,%p{%p{%s},%s}",
142 inode, file,
143 file->f_dentry->d_parent,
144 file->f_dentry->d_parent ?
145 file->f_dentry->d_parent->d_name.name :
146 (const unsigned char *) "",
147 file->f_dentry->d_name.name);
148
149 return -EREMOTE;
150 } /* end afs_mntpt_open() */
151
152 /*****************************************************************************/
153 /*
154 * create a vfsmount to be automounted
155 */
156 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
157 {
158 struct afs_super_info *super;
159 struct vfsmount *mnt;
160 struct page *page = NULL;
161 size_t size;
162 char *buf, *devname = NULL, *options = NULL;
163 filler_t *filler;
164 int ret;
165
166 kenter("{%s}", mntpt->d_name.name);
167
168 BUG_ON(!mntpt->d_inode);
169
170 ret = -EINVAL;
171 size = mntpt->d_inode->i_size;
172 if (size > PAGE_SIZE - 1)
173 goto error;
174
175 ret = -ENOMEM;
176 devname = (char *) get_zeroed_page(GFP_KERNEL);
177 if (!devname)
178 goto error;
179
180 options = (char *) get_zeroed_page(GFP_KERNEL);
181 if (!options)
182 goto error;
183
184 /* read the contents of the AFS special symlink */
185 filler = (filler_t *)mntpt->d_inode->i_mapping->a_ops->readpage;
186
187 page = read_cache_page(mntpt->d_inode->i_mapping, 0, filler, NULL);
188 if (IS_ERR(page)) {
189 ret = PTR_ERR(page);
190 goto error;
191 }
192
193 ret = -EIO;
194 wait_on_page_locked(page);
195 if (!PageUptodate(page) || PageError(page))
196 goto error;
197
198 buf = kmap(page);
199 memcpy(devname, buf, size);
200 kunmap(page);
201 page_cache_release(page);
202 page = NULL;
203
204 /* work out what options we want */
205 super = AFS_FS_S(mntpt->d_sb);
206 memcpy(options, "cell=", 5);
207 strcpy(options + 5, super->volume->cell->name);
208 if (super->volume->type == AFSVL_RWVOL)
209 strcat(options, ",rwpath");
210
211 /* try and do the mount */
212 kdebug("--- attempting mount %s -o %s ---", devname, options);
213 mnt = do_kern_mount("afs", 0, devname, options);
214 kdebug("--- mount result %p ---", mnt);
215
216 free_page((unsigned long) devname);
217 free_page((unsigned long) options);
218 kleave(" = %p", mnt);
219 return mnt;
220
221 error:
222 if (page)
223 page_cache_release(page);
224 if (devname)
225 free_page((unsigned long) devname);
226 if (options)
227 free_page((unsigned long) options);
228 kleave(" = %d", ret);
229 return ERR_PTR(ret);
230 } /* end afs_mntpt_do_automount() */
231
232 /*****************************************************************************/
233 /*
234 * follow a link from a mountpoint directory, thus causing it to be mounted
235 */
236 static int afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd)
237 {
238 struct vfsmount *newmnt;
239 struct dentry *old_dentry;
240 int err;
241
242 kenter("%p{%s},{%s:%p{%s}}",
243 dentry,
244 dentry->d_name.name,
245 nd->mnt->mnt_devname,
246 dentry,
247 nd->dentry->d_name.name);
248
249 newmnt = afs_mntpt_do_automount(dentry);
250 if (IS_ERR(newmnt)) {
251 path_release(nd);
252 return PTR_ERR(newmnt);
253 }
254
255 old_dentry = nd->dentry;
256 nd->dentry = dentry;
257 err = do_add_mount(newmnt, nd, 0, &afs_vfsmounts);
258 nd->dentry = old_dentry;
259
260 path_release(nd);
261
262 if (!err) {
263 mntget(newmnt);
264 nd->mnt = newmnt;
265 dget(newmnt->mnt_root);
266 nd->dentry = newmnt->mnt_root;
267 }
268
269 kleave(" = %d", err);
270 return err;
271 } /* end afs_mntpt_follow_link() */
272
273 /*****************************************************************************/
274 /*
275 * handle mountpoint expiry timer going off
276 */
277 static void afs_mntpt_expiry_timed_out(struct afs_timer *timer)
278 {
279 kenter("");
280
281 mark_mounts_for_expiry(&afs_vfsmounts);
282
283 afs_kafstimod_add_timer(&afs_mntpt_expiry_timer,
284 afs_mntpt_expiry_timeout * HZ);
285
286 kleave("");
287 } /* end afs_mntpt_expiry_timed_out() */
288
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