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[linux-2.6.git] / drivers / base / devtmpfs.c
1 /*
2  * devtmpfs - kernel-maintained tmpfs-based /dev
3  *
4  * Copyright (C) 2009, Kay Sievers <kay.sievers@vrfy.org>
5  *
6  * During bootup, before any driver core device is registered,
7  * devtmpfs, a tmpfs-based filesystem is created. Every driver-core
8  * device which requests a device node, will add a node in this
9  * filesystem.
10  * By default, all devices are named after the the name of the
11  * device, owned by root and have a default mode of 0600. Subsystems
12  * can overwrite the default setting if needed.
13  */
14
15 #include <linux/kernel.h>
16 #include <linux/syscalls.h>
17 #include <linux/mount.h>
18 #include <linux/device.h>
19 #include <linux/genhd.h>
20 #include <linux/namei.h>
21 #include <linux/fs.h>
22 #include <linux/shmem_fs.h>
23 #include <linux/ramfs.h>
24 #include <linux/cred.h>
25 #include <linux/sched.h>
26 #include <linux/init_task.h>
27 #include <linux/slab.h>
28
29 static struct vfsmount *dev_mnt;
30
31 #if defined CONFIG_DEVTMPFS_MOUNT
32 static int mount_dev = 1;
33 #else
34 static int mount_dev;
35 #endif
36
37 static DEFINE_MUTEX(dirlock);
38
39 static int __init mount_param(char *str)
40 {
41         mount_dev = simple_strtoul(str, NULL, 0);
42         return 1;
43 }
44 __setup("devtmpfs.mount=", mount_param);
45
46 static struct dentry *dev_mount(struct file_system_type *fs_type, int flags,
47                       const char *dev_name, void *data)
48 {
49 #ifdef CONFIG_TMPFS
50         return mount_single(fs_type, flags, data, shmem_fill_super);
51 #else
52         return mount_single(fs_type, flags, data, ramfs_fill_super);
53 #endif
54 }
55
56 static struct file_system_type dev_fs_type = {
57         .name = "devtmpfs",
58         .mount = dev_mount,
59         .kill_sb = kill_litter_super,
60 };
61
62 #ifdef CONFIG_BLOCK
63 static inline int is_blockdev(struct device *dev)
64 {
65         return dev->class == &block_class;
66 }
67 #else
68 static inline int is_blockdev(struct device *dev) { return 0; }
69 #endif
70
71 static int dev_mkdir(const char *name, mode_t mode)
72 {
73         struct nameidata nd;
74         struct dentry *dentry;
75         int err;
76
77         err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
78                               name, LOOKUP_PARENT, &nd);
79         if (err)
80                 return err;
81
82         dentry = lookup_create(&nd, 1);
83         if (!IS_ERR(dentry)) {
84                 err = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
85                 if (!err)
86                         /* mark as kernel-created inode */
87                         dentry->d_inode->i_private = &dev_mnt;
88                 dput(dentry);
89         } else {
90                 err = PTR_ERR(dentry);
91         }
92
93         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
94         path_put(&nd.path);
95         return err;
96 }
97
98 static int create_path(const char *nodepath)
99 {
100         int err;
101
102         mutex_lock(&dirlock);
103         err = dev_mkdir(nodepath, 0755);
104         if (err == -ENOENT) {
105                 char *path;
106                 char *s;
107
108                 /* parent directories do not exist, create them */
109                 path = kstrdup(nodepath, GFP_KERNEL);
110                 if (!path) {
111                         err = -ENOMEM;
112                         goto out;
113                 }
114                 s = path;
115                 for (;;) {
116                         s = strchr(s, '/');
117                         if (!s)
118                                 break;
119                         s[0] = '\0';
120                         err = dev_mkdir(path, 0755);
121                         if (err && err != -EEXIST)
122                                 break;
123                         s[0] = '/';
124                         s++;
125                 }
126                 kfree(path);
127         }
128 out:
129         mutex_unlock(&dirlock);
130         return err;
131 }
132
133 int devtmpfs_create_node(struct device *dev)
134 {
135         const char *tmp = NULL;
136         const char *nodename;
137         const struct cred *curr_cred;
138         mode_t mode = 0;
139         struct nameidata nd;
140         struct dentry *dentry;
141         int err;
142
143         if (!dev_mnt)
144                 return 0;
145
146         nodename = device_get_devnode(dev, &mode, &tmp);
147         if (!nodename)
148                 return -ENOMEM;
149
150         if (mode == 0)
151                 mode = 0600;
152         if (is_blockdev(dev))
153                 mode |= S_IFBLK;
154         else
155                 mode |= S_IFCHR;
156
157         curr_cred = override_creds(&init_cred);
158
159         err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
160                               nodename, LOOKUP_PARENT, &nd);
161         if (err == -ENOENT) {
162                 create_path(nodename);
163                 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
164                                       nodename, LOOKUP_PARENT, &nd);
165         }
166         if (err)
167                 goto out;
168
169         dentry = lookup_create(&nd, 0);
170         if (!IS_ERR(dentry)) {
171                 err = vfs_mknod(nd.path.dentry->d_inode,
172                                 dentry, mode, dev->devt);
173                 if (!err) {
174                         struct iattr newattrs;
175
176                         /* fixup possibly umasked mode */
177                         newattrs.ia_mode = mode;
178                         newattrs.ia_valid = ATTR_MODE;
179                         mutex_lock(&dentry->d_inode->i_mutex);
180                         notify_change(dentry, &newattrs);
181                         mutex_unlock(&dentry->d_inode->i_mutex);
182
183                         /* mark as kernel-created inode */
184                         dentry->d_inode->i_private = &dev_mnt;
185                 }
186                 dput(dentry);
187         } else {
188                 err = PTR_ERR(dentry);
189         }
190
191         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
192         path_put(&nd.path);
193 out:
194         kfree(tmp);
195         revert_creds(curr_cred);
196         return err;
197 }
198
199 static int dev_rmdir(const char *name)
200 {
201         struct nameidata nd;
202         struct dentry *dentry;
203         int err;
204
205         err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
206                               name, LOOKUP_PARENT, &nd);
207         if (err)
208                 return err;
209
210         mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
211         dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
212         if (!IS_ERR(dentry)) {
213                 if (dentry->d_inode) {
214                         if (dentry->d_inode->i_private == &dev_mnt)
215                                 err = vfs_rmdir(nd.path.dentry->d_inode,
216                                                 dentry);
217                         else
218                                 err = -EPERM;
219                 } else {
220                         err = -ENOENT;
221                 }
222                 dput(dentry);
223         } else {
224                 err = PTR_ERR(dentry);
225         }
226
227         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
228         path_put(&nd.path);
229         return err;
230 }
231
232 static int delete_path(const char *nodepath)
233 {
234         const char *path;
235         int err = 0;
236
237         path = kstrdup(nodepath, GFP_KERNEL);
238         if (!path)
239                 return -ENOMEM;
240
241         mutex_lock(&dirlock);
242         for (;;) {
243                 char *base;
244
245                 base = strrchr(path, '/');
246                 if (!base)
247                         break;
248                 base[0] = '\0';
249                 err = dev_rmdir(path);
250                 if (err)
251                         break;
252         }
253         mutex_unlock(&dirlock);
254
255         kfree(path);
256         return err;
257 }
258
259 static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
260 {
261         /* did we create it */
262         if (inode->i_private != &dev_mnt)
263                 return 0;
264
265         /* does the dev_t match */
266         if (is_blockdev(dev)) {
267                 if (!S_ISBLK(stat->mode))
268                         return 0;
269         } else {
270                 if (!S_ISCHR(stat->mode))
271                         return 0;
272         }
273         if (stat->rdev != dev->devt)
274                 return 0;
275
276         /* ours */
277         return 1;
278 }
279
280 int devtmpfs_delete_node(struct device *dev)
281 {
282         const char *tmp = NULL;
283         const char *nodename;
284         const struct cred *curr_cred;
285         struct nameidata nd;
286         struct dentry *dentry;
287         struct kstat stat;
288         int deleted = 1;
289         int err;
290
291         if (!dev_mnt)
292                 return 0;
293
294         nodename = device_get_devnode(dev, NULL, &tmp);
295         if (!nodename)
296                 return -ENOMEM;
297
298         curr_cred = override_creds(&init_cred);
299         err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
300                               nodename, LOOKUP_PARENT, &nd);
301         if (err)
302                 goto out;
303
304         mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
305         dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
306         if (!IS_ERR(dentry)) {
307                 if (dentry->d_inode) {
308                         err = vfs_getattr(nd.path.mnt, dentry, &stat);
309                         if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
310                                 struct iattr newattrs;
311                                 /*
312                                  * before unlinking this node, reset permissions
313                                  * of possible references like hardlinks
314                                  */
315                                 newattrs.ia_uid = 0;
316                                 newattrs.ia_gid = 0;
317                                 newattrs.ia_mode = stat.mode & ~0777;
318                                 newattrs.ia_valid =
319                                         ATTR_UID|ATTR_GID|ATTR_MODE;
320                                 mutex_lock(&dentry->d_inode->i_mutex);
321                                 notify_change(dentry, &newattrs);
322                                 mutex_unlock(&dentry->d_inode->i_mutex);
323                                 err = vfs_unlink(nd.path.dentry->d_inode,
324                                                  dentry);
325                                 if (!err || err == -ENOENT)
326                                         deleted = 1;
327                         }
328                 } else {
329                         err = -ENOENT;
330                 }
331                 dput(dentry);
332         } else {
333                 err = PTR_ERR(dentry);
334         }
335         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
336
337         path_put(&nd.path);
338         if (deleted && strchr(nodename, '/'))
339                 delete_path(nodename);
340 out:
341         kfree(tmp);
342         revert_creds(curr_cred);
343         return err;
344 }
345
346 /*
347  * If configured, or requested by the commandline, devtmpfs will be
348  * auto-mounted after the kernel mounted the root filesystem.
349  */
350 int devtmpfs_mount(const char *mntdir)
351 {
352         int err;
353
354         if (!mount_dev)
355                 return 0;
356
357         if (!dev_mnt)
358                 return 0;
359
360         err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
361         if (err)
362                 printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
363         else
364                 printk(KERN_INFO "devtmpfs: mounted\n");
365         return err;
366 }
367
368 /*
369  * Create devtmpfs instance, driver-core devices will add their device
370  * nodes here.
371  */
372 int __init devtmpfs_init(void)
373 {
374         int err;
375         struct vfsmount *mnt;
376         char options[] = "mode=0755";
377
378         err = register_filesystem(&dev_fs_type);
379         if (err) {
380                 printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
381                        "type %i\n", err);
382                 return err;
383         }
384
385         mnt = kern_mount_data(&dev_fs_type, options);
386         if (IS_ERR(mnt)) {
387                 err = PTR_ERR(mnt);
388                 printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
389                 unregister_filesystem(&dev_fs_type);
390                 return err;
391         }
392         dev_mnt = mnt;
393
394         printk(KERN_INFO "devtmpfs: initialized\n");
395         return 0;
396 }