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
9 * filesystem. The node is named after the the name of the device,
10 * or the susbsytem can provide a custom name. All devices are
11 * owned by root and have a mode of 0600.
14 #include <linux/kernel.h>
15 #include <linux/syscalls.h>
16 #include <linux/mount.h>
17 #include <linux/device.h>
18 #include <linux/genhd.h>
19 #include <linux/namei.h>
21 #include <linux/shmem_fs.h>
22 #include <linux/cred.h>
23 #include <linux/init_task.h>
25 static struct vfsmount *dev_mnt;
27 #if defined CONFIG_DEVTMPFS_MOUNT
28 static int dev_mount = 1;
33 static int __init mount_param(char *str)
35 dev_mount = simple_strtoul(str, NULL, 0);
38 __setup("devtmpfs.mount=", mount_param);
40 static int dev_get_sb(struct file_system_type *fs_type, int flags,
41 const char *dev_name, void *data, struct vfsmount *mnt)
43 return get_sb_single(fs_type, flags, data, shmem_fill_super, mnt);
46 static struct file_system_type dev_fs_type = {
49 .kill_sb = kill_litter_super,
53 static inline int is_blockdev(struct device *dev)
55 return dev->class == &block_class;
58 static inline int is_blockdev(struct device *dev) { return 0; }
61 static int dev_mkdir(const char *name, mode_t mode)
64 struct dentry *dentry;
67 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
68 name, LOOKUP_PARENT, &nd);
72 dentry = lookup_create(&nd, 1);
73 if (!IS_ERR(dentry)) {
74 err = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
77 err = PTR_ERR(dentry);
79 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
85 static int create_path(const char *nodepath)
91 path = kstrdup(nodepath, GFP_KERNEL);
95 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
96 path, LOOKUP_PARENT, &nd);
98 struct dentry *dentry;
100 /* create directory right away */
101 dentry = lookup_create(&nd, 1);
102 if (!IS_ERR(dentry)) {
103 err = vfs_mkdir(nd.path.dentry->d_inode,
107 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
110 } else if (err == -ENOENT) {
113 /* parent directories do not exist, create them */
120 err = dev_mkdir(path, 0755);
121 if (err && err != -EEXIST)
132 int devtmpfs_create_node(struct device *dev)
134 const char *tmp = NULL;
135 const char *nodename;
136 const struct cred *curr_cred;
139 struct dentry *dentry;
145 nodename = device_get_nodename(dev, &tmp);
149 if (is_blockdev(dev))
154 curr_cred = override_creds(&init_cred);
155 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
156 nodename, LOOKUP_PARENT, &nd);
157 if (err == -ENOENT) {
158 /* create missing parent directories */
159 create_path(nodename);
160 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
161 nodename, LOOKUP_PARENT, &nd);
166 dentry = lookup_create(&nd, 0);
167 if (!IS_ERR(dentry)) {
168 err = vfs_mknod(nd.path.dentry->d_inode,
169 dentry, mode, dev->devt);
170 /* mark as kernel created inode */
172 dentry->d_inode->i_private = &dev_mnt;
175 err = PTR_ERR(dentry);
177 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
182 revert_creds(curr_cred);
186 static int dev_rmdir(const char *name)
189 struct dentry *dentry;
192 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
193 name, LOOKUP_PARENT, &nd);
197 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
198 dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
199 if (!IS_ERR(dentry)) {
201 err = vfs_rmdir(nd.path.dentry->d_inode, dentry);
206 err = PTR_ERR(dentry);
208 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
214 static int delete_path(const char *nodepath)
219 path = kstrdup(nodepath, GFP_KERNEL);
226 base = strrchr(path, '/');
230 err = dev_rmdir(path);
239 static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
241 /* did we create it */
242 if (inode->i_private != &dev_mnt)
245 /* does the dev_t match */
246 if (is_blockdev(dev)) {
247 if (!S_ISBLK(stat->mode))
250 if (!S_ISCHR(stat->mode))
253 if (stat->rdev != dev->devt)
260 int devtmpfs_delete_node(struct device *dev)
262 const char *tmp = NULL;
263 const char *nodename;
264 const struct cred *curr_cred;
266 struct dentry *dentry;
274 nodename = device_get_nodename(dev, &tmp);
278 curr_cred = override_creds(&init_cred);
279 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
280 nodename, LOOKUP_PARENT, &nd);
284 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
285 dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
286 if (!IS_ERR(dentry)) {
287 if (dentry->d_inode) {
288 err = vfs_getattr(nd.path.mnt, dentry, &stat);
289 if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
290 err = vfs_unlink(nd.path.dentry->d_inode,
292 if (!err || err == -ENOENT)
300 err = PTR_ERR(dentry);
302 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
305 if (deleted && strchr(nodename, '/'))
306 delete_path(nodename);
309 revert_creds(curr_cred);
314 * If configured, or requested by the commandline, devtmpfs will be
315 * auto-mounted after the kernel mounted the root filesystem.
317 int devtmpfs_mount(const char *mountpoint)
328 err = kern_path(mountpoint, LOOKUP_FOLLOW, &path);
331 err = do_add_mount(dev_mnt, &path, 0, NULL);
333 printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
335 printk(KERN_INFO "devtmpfs: mounted\n");
341 * Create devtmpfs instance, driver-core devices will add their device
344 int __init devtmpfs_init(void)
347 struct vfsmount *mnt;
349 err = register_filesystem(&dev_fs_type);
351 printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
356 mnt = kern_mount(&dev_fs_type);
359 printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
360 unregister_filesystem(&dev_fs_type);
365 printk(KERN_INFO "devtmpfs: initialized\n");