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/cred.h>
24 #include <linux/sched.h>
25 #include <linux/init_task.h>
26 #include <linux/slab.h>
28 static struct vfsmount *dev_mnt;
30 #if defined CONFIG_DEVTMPFS_MOUNT
31 static int dev_mount = 1;
36 static DEFINE_MUTEX(dirlock);
38 static int __init mount_param(char *str)
40 dev_mount = simple_strtoul(str, NULL, 0);
43 __setup("devtmpfs.mount=", mount_param);
45 static int dev_get_sb(struct file_system_type *fs_type, int flags,
46 const char *dev_name, void *data, struct vfsmount *mnt)
48 return get_sb_single(fs_type, flags, data, shmem_fill_super, mnt);
51 static struct file_system_type dev_fs_type = {
54 .kill_sb = kill_litter_super,
58 static inline int is_blockdev(struct device *dev)
60 return dev->class == &block_class;
63 static inline int is_blockdev(struct device *dev) { return 0; }
66 static int dev_mkdir(const char *name, mode_t mode)
69 struct dentry *dentry;
72 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
73 name, LOOKUP_PARENT, &nd);
77 dentry = lookup_create(&nd, 1);
78 if (!IS_ERR(dentry)) {
79 err = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
81 /* mark as kernel-created inode */
82 dentry->d_inode->i_private = &dev_mnt;
85 err = PTR_ERR(dentry);
88 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
93 static int create_path(const char *nodepath)
98 err = dev_mkdir(nodepath, 0755);
103 /* parent directories do not exist, create them */
104 path = kstrdup(nodepath, GFP_KERNEL);
115 err = dev_mkdir(path, 0755);
116 if (err && err != -EEXIST)
124 mutex_unlock(&dirlock);
128 int devtmpfs_create_node(struct device *dev)
130 const char *tmp = NULL;
131 const char *nodename;
132 const struct cred *curr_cred;
135 struct dentry *dentry;
141 nodename = device_get_devnode(dev, &mode, &tmp);
147 if (is_blockdev(dev))
152 curr_cred = override_creds(&init_cred);
154 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
155 nodename, LOOKUP_PARENT, &nd);
156 if (err == -ENOENT) {
157 create_path(nodename);
158 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
159 nodename, LOOKUP_PARENT, &nd);
164 dentry = lookup_create(&nd, 0);
165 if (!IS_ERR(dentry)) {
166 err = vfs_mknod(nd.path.dentry->d_inode,
167 dentry, mode, dev->devt);
169 struct iattr newattrs;
171 /* fixup possibly umasked mode */
172 newattrs.ia_mode = mode;
173 newattrs.ia_valid = ATTR_MODE;
174 mutex_lock(&dentry->d_inode->i_mutex);
175 notify_change(dentry, &newattrs);
176 mutex_unlock(&dentry->d_inode->i_mutex);
178 /* mark as kernel-created inode */
179 dentry->d_inode->i_private = &dev_mnt;
183 err = PTR_ERR(dentry);
186 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
190 revert_creds(curr_cred);
194 static int dev_rmdir(const char *name)
197 struct dentry *dentry;
200 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
201 name, LOOKUP_PARENT, &nd);
205 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
206 dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
207 if (!IS_ERR(dentry)) {
208 if (dentry->d_inode) {
209 if (dentry->d_inode->i_private == &dev_mnt)
210 err = vfs_rmdir(nd.path.dentry->d_inode,
219 err = PTR_ERR(dentry);
222 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
227 static int delete_path(const char *nodepath)
232 path = kstrdup(nodepath, GFP_KERNEL);
236 mutex_lock(&dirlock);
240 base = strrchr(path, '/');
244 err = dev_rmdir(path);
248 mutex_unlock(&dirlock);
254 static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
256 /* did we create it */
257 if (inode->i_private != &dev_mnt)
260 /* does the dev_t match */
261 if (is_blockdev(dev)) {
262 if (!S_ISBLK(stat->mode))
265 if (!S_ISCHR(stat->mode))
268 if (stat->rdev != dev->devt)
275 int devtmpfs_delete_node(struct device *dev)
277 const char *tmp = NULL;
278 const char *nodename;
279 const struct cred *curr_cred;
281 struct dentry *dentry;
289 nodename = device_get_devnode(dev, NULL, &tmp);
293 curr_cred = override_creds(&init_cred);
294 err = vfs_path_lookup(dev_mnt->mnt_root, dev_mnt,
295 nodename, LOOKUP_PARENT, &nd);
299 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
300 dentry = lookup_one_len(nd.last.name, nd.path.dentry, nd.last.len);
301 if (!IS_ERR(dentry)) {
302 if (dentry->d_inode) {
303 err = vfs_getattr(nd.path.mnt, dentry, &stat);
304 if (!err && dev_mynode(dev, dentry->d_inode, &stat)) {
305 struct iattr newattrs;
307 * before unlinking this node, reset permissions
308 * of possible references like hardlinks
312 newattrs.ia_mode = stat.mode & ~0777;
314 ATTR_UID|ATTR_GID|ATTR_MODE;
315 mutex_lock(&dentry->d_inode->i_mutex);
316 notify_change(dentry, &newattrs);
317 mutex_unlock(&dentry->d_inode->i_mutex);
318 err = vfs_unlink(nd.path.dentry->d_inode,
320 if (!err || err == -ENOENT)
328 err = PTR_ERR(dentry);
330 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
333 if (deleted && strchr(nodename, '/'))
334 delete_path(nodename);
337 revert_creds(curr_cred);
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");
364 * Create devtmpfs instance, driver-core devices will add their device
367 int __init devtmpfs_init(void)
370 struct vfsmount *mnt;
371 char options[] = "mode=0755";
373 err = register_filesystem(&dev_fs_type);
375 printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
380 mnt = kern_mount_data(&dev_fs_type, options);
383 printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
384 unregister_filesystem(&dev_fs_type);
389 printk(KERN_INFO "devtmpfs: initialized\n");