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 name of the device,
11 * owned by root and have a default mode of 0600. Subsystems can
12 * 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 umode_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, umode_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)
171 /* parent directories do not exist, create them */
172 path = kstrdup(nodepath, GFP_KERNEL);
182 err = dev_mkdir(path, 0755);
183 if (err && err != -EEXIST)
192 static int handle_create(const char *nodename, umode_t mode, struct device *dev)
194 struct dentry *dentry;
198 dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
199 if (dentry == ERR_PTR(-ENOENT)) {
200 create_path(nodename);
201 dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
204 return PTR_ERR(dentry);
206 err = vfs_mknod(path.dentry->d_inode,
207 dentry, mode, dev->devt);
209 struct iattr newattrs;
211 /* fixup possibly umasked mode */
212 newattrs.ia_mode = mode;
213 newattrs.ia_valid = ATTR_MODE;
214 mutex_lock(&dentry->d_inode->i_mutex);
215 notify_change(dentry, &newattrs);
216 mutex_unlock(&dentry->d_inode->i_mutex);
218 /* mark as kernel-created inode */
219 dentry->d_inode->i_private = &thread;
223 mutex_unlock(&path.dentry->d_inode->i_mutex);
228 static int dev_rmdir(const char *name)
231 struct dentry *dentry;
234 dentry = kern_path_locked(name, &parent);
236 return PTR_ERR(dentry);
237 if (dentry->d_inode) {
238 if (dentry->d_inode->i_private == &thread)
239 err = vfs_rmdir(parent.dentry->d_inode, dentry);
246 mutex_unlock(&parent.dentry->d_inode->i_mutex);
251 static int delete_path(const char *nodepath)
256 path = kstrdup(nodepath, GFP_KERNEL);
263 base = strrchr(path, '/');
267 err = dev_rmdir(path);
276 static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
278 /* did we create it */
279 if (inode->i_private != &thread)
282 /* does the dev_t match */
283 if (is_blockdev(dev)) {
284 if (!S_ISBLK(stat->mode))
287 if (!S_ISCHR(stat->mode))
290 if (stat->rdev != dev->devt)
297 static int handle_remove(const char *nodename, struct device *dev)
300 struct dentry *dentry;
304 dentry = kern_path_locked(nodename, &parent);
306 return PTR_ERR(dentry);
308 if (dentry->d_inode) {
310 err = vfs_getattr(parent.mnt, dentry, &stat);
311 if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
312 struct iattr newattrs;
314 * before unlinking this node, reset permissions
315 * of possible references like hardlinks
319 newattrs.ia_mode = stat.mode & ~0777;
321 ATTR_UID|ATTR_GID|ATTR_MODE;
322 mutex_lock(&dentry->d_inode->i_mutex);
323 notify_change(dentry, &newattrs);
324 mutex_unlock(&dentry->d_inode->i_mutex);
325 err = vfs_unlink(parent.dentry->d_inode, dentry);
326 if (!err || err == -ENOENT)
333 mutex_unlock(&parent.dentry->d_inode->i_mutex);
336 if (deleted && strchr(nodename, '/'))
337 delete_path(nodename);
342 * If configured, or requested by the commandline, devtmpfs will be
343 * auto-mounted after the kernel mounted the root filesystem.
345 int devtmpfs_mount(const char *mntdir)
355 err = sys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT, NULL);
357 printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
359 printk(KERN_INFO "devtmpfs: mounted\n");
363 static DECLARE_COMPLETION(setup_done);
365 static int handle(const char *name, umode_t mode, struct device *dev)
368 return handle_create(name, mode, dev);
370 return handle_remove(name, dev);
373 static int devtmpfsd(void *p)
375 char options[] = "mode=0755";
377 *err = sys_unshare(CLONE_NEWNS);
380 *err = sys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
383 sys_chdir("/.."); /* will traverse into overmounted root */
385 complete(&setup_done);
387 spin_lock(&req_lock);
389 struct req *req = requests;
391 spin_unlock(&req_lock);
393 struct req *next = req->next;
394 req->err = handle(req->name, req->mode, req->dev);
395 complete(&req->done);
398 spin_lock(&req_lock);
400 __set_current_state(TASK_INTERRUPTIBLE);
401 spin_unlock(&req_lock);
406 complete(&setup_done);
411 * Create devtmpfs instance, driver-core devices will add their device
414 int __init devtmpfs_init(void)
416 int err = register_filesystem(&dev_fs_type);
418 printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
423 thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
424 if (!IS_ERR(thread)) {
425 wait_for_completion(&setup_done);
427 err = PTR_ERR(thread);
432 printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
433 unregister_filesystem(&dev_fs_type);
437 printk(KERN_INFO "devtmpfs: initialized\n");