switch devtmpfs to kern_path_create()
[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/sched.h>
25 #include <linux/slab.h>
26 #include <linux/kthread.h>
27
28 static struct task_struct *thread;
29
30 #if defined CONFIG_DEVTMPFS_MOUNT
31 static int mount_dev = 1;
32 #else
33 static int mount_dev;
34 #endif
35
36 static DEFINE_SPINLOCK(req_lock);
37
38 static struct req {
39         struct req *next;
40         struct completion done;
41         int err;
42         const char *name;
43         mode_t mode;    /* 0 => delete */
44         struct device *dev;
45 } *requests;
46
47 static int __init mount_param(char *str)
48 {
49         mount_dev = simple_strtoul(str, NULL, 0);
50         return 1;
51 }
52 __setup("devtmpfs.mount=", mount_param);
53
54 static struct dentry *dev_mount(struct file_system_type *fs_type, int flags,
55                       const char *dev_name, void *data)
56 {
57 #ifdef CONFIG_TMPFS
58         return mount_single(fs_type, flags, data, shmem_fill_super);
59 #else
60         return mount_single(fs_type, flags, data, ramfs_fill_super);
61 #endif
62 }
63
64 static struct file_system_type dev_fs_type = {
65         .name = "devtmpfs",
66         .mount = dev_mount,
67         .kill_sb = kill_litter_super,
68 };
69
70 #ifdef CONFIG_BLOCK
71 static inline int is_blockdev(struct device *dev)
72 {
73         return dev->class == &block_class;
74 }
75 #else
76 static inline int is_blockdev(struct device *dev) { return 0; }
77 #endif
78
79 int devtmpfs_create_node(struct device *dev)
80 {
81         const char *tmp = NULL;
82         struct req req;
83
84         if (!thread)
85                 return 0;
86
87         req.mode = 0;
88         req.name = device_get_devnode(dev, &req.mode, &tmp);
89         if (!req.name)
90                 return -ENOMEM;
91
92         if (req.mode == 0)
93                 req.mode = 0600;
94         if (is_blockdev(dev))
95                 req.mode |= S_IFBLK;
96         else
97                 req.mode |= S_IFCHR;
98
99         req.dev = dev;
100
101         init_completion(&req.done);
102
103         spin_lock(&req_lock);
104         req.next = requests;
105         requests = &req;
106         spin_unlock(&req_lock);
107
108         wake_up_process(thread);
109         wait_for_completion(&req.done);
110
111         kfree(tmp);
112
113         return req.err;
114 }
115
116 int devtmpfs_delete_node(struct device *dev)
117 {
118         const char *tmp = NULL;
119         struct req req;
120
121         if (!thread)
122                 return 0;
123
124         req.name = device_get_devnode(dev, NULL, &tmp);
125         if (!req.name)
126                 return -ENOMEM;
127
128         req.mode = 0;
129         req.dev = dev;
130
131         init_completion(&req.done);
132
133         spin_lock(&req_lock);
134         req.next = requests;
135         requests = &req;
136         spin_unlock(&req_lock);
137
138         wake_up_process(thread);
139         wait_for_completion(&req.done);
140
141         kfree(tmp);
142         return req.err;
143 }
144
145 static int dev_mkdir(const char *name, mode_t mode)
146 {
147         struct dentry *dentry;
148         struct path path;
149         int err;
150
151         dentry = kern_path_create(AT_FDCWD, name, &path, 1);
152         if (IS_ERR(dentry))
153                 return PTR_ERR(dentry);
154
155         err = vfs_mkdir(path.dentry->d_inode, dentry, mode);
156         if (!err)
157                 /* mark as kernel-created inode */
158                 dentry->d_inode->i_private = &thread;
159         dput(dentry);
160         mutex_unlock(&path.dentry->d_inode->i_mutex);
161         path_put(&path);
162         return err;
163 }
164
165 static int create_path(const char *nodepath)
166 {
167         int err;
168
169         err = dev_mkdir(nodepath, 0755);
170         if (err == -ENOENT) {
171                 char *path;
172                 char *s;
173
174                 /* parent directories do not exist, create them */
175                 path = kstrdup(nodepath, GFP_KERNEL);
176                 if (!path) {
177                         err = -ENOMEM;
178                         goto out;
179                 }
180                 s = path;
181                 for (;;) {
182                         s = strchr(s, '/');
183                         if (!s)
184                                 break;
185                         s[0] = '\0';
186                         err = dev_mkdir(path, 0755);
187                         if (err && err != -EEXIST)
188                                 break;
189                         s[0] = '/';
190                         s++;
191                 }
192                 kfree(path);
193         }
194 out:
195         return err;
196 }
197
198 static int handle_create(const char *nodename, mode_t mode, struct device *dev)
199 {
200         struct dentry *dentry;
201         struct path path;
202         int err;
203
204         dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
205         if (dentry == ERR_PTR(-ENOENT)) {
206                 create_path(nodename);
207                 dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
208         }
209         if (IS_ERR(dentry))
210                 return PTR_ERR(dentry);
211
212         err = vfs_mknod(path.dentry->d_inode,
213                         dentry, mode, dev->devt);
214         if (!err) {
215                 struct iattr newattrs;
216
217                 /* fixup possibly umasked mode */
218                 newattrs.ia_mode = mode;
219                 newattrs.ia_valid = ATTR_MODE;
220                 mutex_lock(&dentry->d_inode->i_mutex);
221                 notify_change(dentry, &newattrs);
222                 mutex_unlock(&dentry->d_inode->i_mutex);
223
224                 /* mark as kernel-created inode */
225                 dentry->d_inode->i_private = &thread;
226         }
227         dput(dentry);
228
229         mutex_unlock(&path.dentry->d_inode->i_mutex);
230         path_put(&path);
231         return err;
232 }
233
234 static int dev_rmdir(const char *name)
235 {
236         struct nameidata nd;
237         struct dentry *dentry;
238         int err;
239
240         err = kern_path_parent(name, &nd);
241         if (err)
242                 return err;
243
244         mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
245         dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
246         if (!IS_ERR(dentry)) {
247                 if (dentry->d_inode) {
248                         if (dentry->d_inode->i_private == &thread)
249                                 err = vfs_rmdir(nd.path.dentry->d_inode,
250                                                 dentry);
251                         else
252                                 err = -EPERM;
253                 } else {
254                         err = -ENOENT;
255                 }
256                 dput(dentry);
257         } else {
258                 err = PTR_ERR(dentry);
259         }
260
261         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
262         path_put(&nd.path);
263         return err;
264 }
265
266 static int delete_path(const char *nodepath)
267 {
268         const char *path;
269         int err = 0;
270
271         path = kstrdup(nodepath, GFP_KERNEL);
272         if (!path)
273                 return -ENOMEM;
274
275         for (;;) {
276                 char *base;
277
278                 base = strrchr(path, '/');
279                 if (!base)
280                         break;
281                 base[0] = '\0';
282                 err = dev_rmdir(path);
283                 if (err)
284                         break;
285         }
286
287         kfree(path);
288         return err;
289 }
290
291 static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
292 {
293         /* did we create it */
294         if (inode->i_private != &thread)
295                 return 0;
296
297         /* does the dev_t match */
298         if (is_blockdev(dev)) {
299                 if (!S_ISBLK(stat->mode))
300                         return 0;
301         } else {
302                 if (!S_ISCHR(stat->mode))
303                         return 0;
304         }
305         if (stat->rdev != dev->devt)
306                 return 0;
307
308         /* ours */
309         return 1;
310 }
311
312 static int handle_remove(const char *nodename, struct device *dev)
313 {
314         struct nameidata nd;
315         struct dentry *dentry;
316         struct kstat stat;
317         int deleted = 1;
318         int err;
319
320         err = kern_path_parent(nodename, &nd);
321         if (err)
322                 return err;
323
324         mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
325         dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
326         if (!IS_ERR(dentry)) {
327                 if (dentry->d_inode) {
328                         err = vfs_getattr(nd.path.mnt, dentry, &stat);
329                         if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
330                                 struct iattr newattrs;
331                                 /*
332                                  * before unlinking this node, reset permissions
333                                  * of possible references like hardlinks
334                                  */
335                                 newattrs.ia_uid = 0;
336                                 newattrs.ia_gid = 0;
337                                 newattrs.ia_mode = stat.mode & ~0777;
338                                 newattrs.ia_valid =
339                                         ATTR_UID|ATTR_GID|ATTR_MODE;
340                                 mutex_lock(&dentry->d_inode->i_mutex);
341                                 notify_change(dentry, &newattrs);
342                                 mutex_unlock(&dentry->d_inode->i_mutex);
343                                 err = vfs_unlink(nd.path.dentry->d_inode,
344                                                  dentry);
345                                 if (!err || err == -ENOENT)
346                                         deleted = 1;
347                         }
348                 } else {
349                         err = -ENOENT;
350                 }
351                 dput(dentry);
352         } else {
353                 err = PTR_ERR(dentry);
354         }
355         mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
356
357         path_put(&nd.path);
358         if (deleted && strchr(nodename, '/'))
359                 delete_path(nodename);
360         return err;
361 }
362
363 /*
364  * If configured, or requested by the commandline, devtmpfs will be
365  * auto-mounted after the kernel mounted the root filesystem.
366  */
367 int devtmpfs_mount(const char *mntdir)
368 {
369         int err;
370
371         if (!mount_dev)
372                 return 0;
373
374         if (!thread)
375                 return 0;
376
377         err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
378         if (err)
379                 printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
380         else
381                 printk(KERN_INFO "devtmpfs: mounted\n");
382         return err;
383 }
384
385 static __initdata DECLARE_COMPLETION(setup_done);
386
387 static int handle(const char *name, mode_t mode, struct device *dev)
388 {
389         if (mode)
390                 return handle_create(name, mode, dev);
391         else
392                 return handle_remove(name, dev);
393 }
394
395 static int devtmpfsd(void *p)
396 {
397         char options[] = "mode=0755";
398         int *err = p;
399         *err = sys_unshare(CLONE_NEWNS);
400         if (*err)
401                 goto out;
402         *err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
403         if (*err)
404                 goto out;
405         sys_chdir("/.."); /* will traverse into overmounted root */
406         sys_chroot(".");
407         complete(&setup_done);
408         while (1) {
409                 spin_lock(&req_lock);
410                 while (requests) {
411                         struct req *req = requests;
412                         requests = NULL;
413                         spin_unlock(&req_lock);
414                         while (req) {
415                                 req->err = handle(req->name, req->mode, req->dev);
416                                 complete(&req->done);
417                                 req = req->next;
418                         }
419                         spin_lock(&req_lock);
420                 }
421                 set_current_state(TASK_INTERRUPTIBLE);
422                 spin_unlock(&req_lock);
423                 schedule();
424                 __set_current_state(TASK_RUNNING);
425         }
426         return 0;
427 out:
428         complete(&setup_done);
429         return *err;
430 }
431
432 /*
433  * Create devtmpfs instance, driver-core devices will add their device
434  * nodes here.
435  */
436 int __init devtmpfs_init(void)
437 {
438         int err = register_filesystem(&dev_fs_type);
439         if (err) {
440                 printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
441                        "type %i\n", err);
442                 return err;
443         }
444
445         thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
446         if (!IS_ERR(thread)) {
447                 wait_for_completion(&setup_done);
448         } else {
449                 err = PTR_ERR(thread);
450                 thread = NULL;
451         }
452
453         if (err) {
454                 printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
455                 unregister_filesystem(&dev_fs_type);
456                 return err;
457         }
458
459         printk(KERN_INFO "devtmpfs: initialized\n");
460         return 0;
461 }