1 /* 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/slab.h>
16 #include <linux/fs.h>
17 #include <linux/pagemap.h>
18 #include <linux/mount.h>
19 #include <linux/namei.h>
20 #include <linux/mnt_namespace.h>
21 #include "internal.h"
22
23
24 static struct dentry *afs_mntpt_lookup(struct inode *dir,
25 struct dentry *dentry,
26 struct nameidata *nd);
27 static int afs_mntpt_open(struct inode *inode, struct file *file);
28 static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd);
29 static void afs_mntpt_expiry_timed_out(struct work_struct *work);
30
31 const struct file_operations afs_mntpt_file_operations = {
32 .open = afs_mntpt_open,
33 };
34
35 const struct inode_operations afs_mntpt_inode_operations = {
36 .lookup = afs_mntpt_lookup,
37 .follow_link = afs_mntpt_follow_link,
38 .readlink = page_readlink,
39 .getattr = afs_getattr,
40 };
41
42 static LIST_HEAD(afs_vfsmounts);
43 static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
44
45 static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
46
47 /*
48 * check a symbolic link to see whether it actually encodes a mountpoint
49 * - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
50 */
51 int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)
52 {
53 struct file file = {
54 .private_data = key,
55 };
56 struct page *page;
57 size_t size;
58 char *buf;
59 int ret;
60
61 _enter("{%x:%u,%u}",
62 vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
63
64 /* read the contents of the symlink into the pagecache */
65 page = read_mapping_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0, &file);
66 if (IS_ERR(page)) {
67 ret = PTR_ERR(page);
68 goto out;
69 }
70
71 ret = -EIO;
72 if (PageError(page))
73 goto out_free;
74
75 buf = kmap(page);
76
77 /* examine the symlink's contents */
78 size = vnode->status.size;
79 _debug("symlink to %*.*s", (int) size, (int) size, buf);
80
81 if (size > 2 &&
82 (buf[0] == '%' || buf[0] == '#') &&
83 buf[size - 1] == '.'
84 ) {
85 _debug("symlink is a mountpoint");
86 spin_lock(&vnode->lock);
87 set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
88 spin_unlock(&vnode->lock);
89 }
90
91 ret = 0;
92
93 kunmap(page);
94 out_free:
95 page_cache_release(page);
96 out:
97 _leave(" = %d", ret);
98 return ret;
99 }
100
101 /*
102 * no valid lookup procedure on this sort of dir
103 */
104 static struct dentry *afs_mntpt_lookup(struct inode *dir,
105 struct dentry *dentry,
106 struct nameidata *nd)
107 {
108 _enter("%p,%p{%p{%s},%s}",
109 dir,
110 dentry,
111 dentry->d_parent,
112 dentry->d_parent ?
113 dentry->d_parent->d_name.name : (const unsigned char *) "",
114 dentry->d_name.name);
115
116 return ERR_PTR(-EREMOTE);
117 }
118
119 /*
120 * no valid open procedure on this sort of dir
121 */
122 static int afs_mntpt_open(struct inode *inode, struct file *file)
123 {
124 _enter("%p,%p{%p{%s},%s}",
125 inode, file,
126 file->f_path.dentry->d_parent,
127 file->f_path.dentry->d_parent ?
128 file->f_path.dentry->d_parent->d_name.name :
129 (const unsigned char *) "",
130 file->f_path.dentry->d_name.name);
131
132 return -EREMOTE;
133 }
134
135 /*
136 * create a vfsmount to be automounted
137 */
138 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
139 {
140 struct afs_super_info *super;
141 struct vfsmount *mnt;
142 struct page *page = NULL;
143 size_t size;
144 char *buf, *devname = NULL, *options = NULL;
145 int ret;
146
147 _enter("{%s}", mntpt->d_name.name);
148
149 BUG_ON(!mntpt->d_inode);
150
151 ret = -EINVAL;
152 size = mntpt->d_inode->i_size;
153 if (size > PAGE_SIZE - 1)
154 goto error;
155
156 ret = -ENOMEM;
157 devname = (char *) get_zeroed_page(GFP_KERNEL);
158 if (!devname)
159 goto error;
160
161 options = (char *) get_zeroed_page(GFP_KERNEL);
162 if (!options)
163 goto error;
164
165 /* read the contents of the AFS special symlink */
166 page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
167 if (IS_ERR(page)) {
168 ret = PTR_ERR(page);
169 goto error;
170 }
171
172 ret = -EIO;
173 if (PageError(page))
174 goto error;
175
176 buf = kmap(page);
177 memcpy(devname, buf, size);
178 kunmap(page);
179 page_cache_release(page);
180 page = NULL;
181
182 /* work out what options we want */
183 super = AFS_FS_S(mntpt->d_sb);
184 memcpy(options, "cell=", 5);
185 strcpy(options + 5, super->volume->cell->name);
186 if (super->volume->type == AFSVL_RWVOL)
187 strcat(options, ",rwpath");
188
189 /* try and do the mount */
190 _debug("--- attempting mount %s -o %s ---", devname, options);
191 mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);
192 _debug("--- mount result %p ---", mnt);
193
194 free_page((unsigned long) devname);
195 free_page((unsigned long) options);
196 _leave(" = %p", mnt);
197 return mnt;
198
199 error:
200 if (page)
201 page_cache_release(page);
202 if (devname)
203 free_page((unsigned long) devname);
204 if (options)
205 free_page((unsigned long) options);
206 _leave(" = %d", ret);
207 return ERR_PTR(ret);
208 }
209
210 /*
211 * follow a link from a mountpoint directory, thus causing it to be mounted
212 */
213 static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd)
214 {
215 struct vfsmount *newmnt;
216 int err;
217
218 _enter("%p{%s},{%s:%p{%s},}",
219 dentry,
220 dentry->d_name.name,
221 nd->path.mnt->mnt_devname,
222 dentry,
223 nd->path.dentry->d_name.name);
224
225 dput(nd->path.dentry);
226 nd->path.dentry = dget(dentry);
227
228 newmnt = afs_mntpt_do_automount(nd->path.dentry);
229 if (IS_ERR(newmnt)) {
230 path_put(&nd->path);
231 return (void *)newmnt;
232 }
233
234 mntget(newmnt);
235 err = do_add_mount(newmnt, nd, MNT_SHRINKABLE, &afs_vfsmounts);
236 switch (err) {
237 case 0:
238 path_put(&nd->path);
239 nd->path.mnt = newmnt;
240 nd->path.dentry = dget(newmnt->mnt_root);
241 schedule_delayed_work(&afs_mntpt_expiry_timer,
242 afs_mntpt_expiry_timeout * HZ);
243 break;
244 case -EBUSY:
245 /* someone else made a mount here whilst we were busy */
246 while (d_mountpoint(nd->path.dentry) &&
247 follow_down(&nd->path.mnt, &nd->path.dentry))
248 ;
249 err = 0;
250 default:
251 mntput(newmnt);
252 break;
253 }
254
255 _leave(" = %d", err);
256 return ERR_PTR(err);
257 }
258
259 /*
260 * handle mountpoint expiry timer going off
261 */
262 static void afs_mntpt_expiry_timed_out(struct work_struct *work)
263 {
264 _enter("");
265
266 if (!list_empty(&afs_vfsmounts)) {
267 mark_mounts_for_expiry(&afs_vfsmounts);
268 schedule_delayed_work(&afs_mntpt_expiry_timer,
269 afs_mntpt_expiry_timeout * HZ);
270 }
271
272 _leave("");
273 }
274
275 /*
276 * kill the AFS mountpoint timer if it's still running
277 */
278 void afs_mntpt_kill_timer(void)
279 {
280 _enter("");
281
282 ASSERT(list_empty(&afs_vfsmounts));
283 cancel_delayed_work(&afs_mntpt_expiry_timer);
284 flush_scheduled_work();
285 }
286
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