2 * devtmpfs - kernel-maintained tmpfs-based /dev
4 * Copyright (C) 2009, Kay Sievers <kay.sievers@vrfy.org>
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
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.
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>
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>
28 static struct task_struct *thread;
30 #if defined CONFIG_DEVTMPFS_MOUNT
31 static int mount_dev = 1;
36 static DEFINE_SPINLOCK(req_lock);
40 struct completion done;
43 mode_t mode; /* 0 => delete */
47 static int __init mount_param(char *str)
49 mount_dev = simple_strtoul(str, NULL, 0);
52 __setup("devtmpfs.mount=", mount_param);
54 static struct dentry *dev_mount(struct file_system_type *fs_type, int flags,
55 const char *dev_name, void *data)
58 return mount_single(fs_type, flags, data, shmem_fill_super);
60 return mount_single(fs_type, flags, data, ramfs_fill_super);
64 static struct file_system_type dev_fs_type = {
67 .kill_sb = kill_litter_super,
71 static inline int is_blockdev(struct device *dev)
73 return dev->class == &block_class;
76 static inline int is_blockdev(struct device *dev) { return 0; }
79 int devtmpfs_create_node(struct device *dev)
81 const char *tmp = NULL;
88 req.name = device_get_devnode(dev, &req.mode, &tmp);
101 init_completion(&req.done);
103 spin_lock(&req_lock);
106 spin_unlock(&req_lock);
108 wake_up_process(thread);
109 wait_for_completion(&req.done);
116 int devtmpfs_delete_node(struct device *dev)
118 const char *tmp = NULL;
124 req.name = device_get_devnode(dev, NULL, &tmp);
131 init_completion(&req.done);
133 spin_lock(&req_lock);
136 spin_unlock(&req_lock);
138 wake_up_process(thread);
139 wait_for_completion(&req.done);
145 static int dev_mkdir(const char *name, mode_t mode)
147 struct dentry *dentry;
151 dentry = kern_path_create(AT_FDCWD, name, &path, 1);
153 return PTR_ERR(dentry);
155 err = vfs_mkdir(path.dentry->d_inode, dentry, mode);
157 /* mark as kernel-created inode */
158 dentry->d_inode->i_private = &thread;
160 mutex_unlock(&path.dentry->d_inode->i_mutex);
165 static int create_path(const char *nodepath)
169 err = dev_mkdir(nodepath, 0755);
170 if (err == -ENOENT) {
174 /* parent directories do not exist, create them */
175 path = kstrdup(nodepath, GFP_KERNEL);
186 err = dev_mkdir(path, 0755);
187 if (err && err != -EEXIST)
198 static int handle_create(const char *nodename, mode_t mode, struct device *dev)
200 struct dentry *dentry;
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);
210 return PTR_ERR(dentry);
212 err = vfs_mknod(path.dentry->d_inode,
213 dentry, mode, dev->devt);
215 struct iattr newattrs;
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);
224 /* mark as kernel-created inode */
225 dentry->d_inode->i_private = &thread;
229 mutex_unlock(&path.dentry->d_inode->i_mutex);
234 static int dev_rmdir(const char *name)
237 struct dentry *dentry;
240 err = kern_path_parent(name, &nd);
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,
258 err = PTR_ERR(dentry);
261 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
266 static int delete_path(const char *nodepath)
271 path = kstrdup(nodepath, GFP_KERNEL);
278 base = strrchr(path, '/');
282 err = dev_rmdir(path);
291 static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
293 /* did we create it */
294 if (inode->i_private != &thread)
297 /* does the dev_t match */
298 if (is_blockdev(dev)) {
299 if (!S_ISBLK(stat->mode))
302 if (!S_ISCHR(stat->mode))
305 if (stat->rdev != dev->devt)
312 static int handle_remove(const char *nodename, struct device *dev)
315 struct dentry *dentry;
320 err = kern_path_parent(nodename, &nd);
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;
332 * before unlinking this node, reset permissions
333 * of possible references like hardlinks
337 newattrs.ia_mode = stat.mode & ~0777;
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,
345 if (!err || err == -ENOENT)
353 err = PTR_ERR(dentry);
355 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
358 if (deleted && strchr(nodename, '/'))
359 delete_path(nodename);
364 * If configured, or requested by the commandline, devtmpfs will be
365 * auto-mounted after the kernel mounted the root filesystem.
367 int devtmpfs_mount(const char *mntdir)
377 err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
379 printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
381 printk(KERN_INFO "devtmpfs: mounted\n");
385 static __initdata DECLARE_COMPLETION(setup_done);
387 static int handle(const char *name, mode_t mode, struct device *dev)
390 return handle_create(name, mode, dev);
392 return handle_remove(name, dev);
395 static int devtmpfsd(void *p)
397 char options[] = "mode=0755";
399 *err = sys_unshare(CLONE_NEWNS);
402 *err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
405 sys_chdir("/.."); /* will traverse into overmounted root */
407 complete(&setup_done);
409 spin_lock(&req_lock);
411 struct req *req = requests;
413 spin_unlock(&req_lock);
415 req->err = handle(req->name, req->mode, req->dev);
416 complete(&req->done);
419 spin_lock(&req_lock);
421 set_current_state(TASK_INTERRUPTIBLE);
422 spin_unlock(&req_lock);
424 __set_current_state(TASK_RUNNING);
428 complete(&setup_done);
433 * Create devtmpfs instance, driver-core devices will add their device
436 int __init devtmpfs_init(void)
438 int err = register_filesystem(&dev_fs_type);
440 printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
445 thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
446 if (!IS_ERR(thread)) {
447 wait_for_completion(&setup_done);
449 err = PTR_ERR(thread);
454 printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
455 unregister_filesystem(&dev_fs_type);
459 printk(KERN_INFO "devtmpfs: initialized\n");