[linux.git] / drivers / base / devtmpfs.c

// SPDX-License-Identifier: GPL-2.0
/*
 * devtmpfs - kernel-maintained tmpfs-based /dev
 *
 * Copyright (C) 2009, Kay Sievers <[email protected]>
 *
 * During bootup, before any driver core device is registered,
 * devtmpfs, a tmpfs-based filesystem is created. Every driver-core
 * device which requests a device node, will add a node in this
 * filesystem.
 * By default, all devices are named after the name of the device,
 * owned by root and have a default mode of 0600. Subsystems can
 * overwrite the default setting if needed.
 */

#include <linux/kernel.h>
#include <linux/syscalls.h>
#include <linux/mount.h>
#include <linux/device.h>
#include <linux/genhd.h>
#include <linux/namei.h>
#include <linux/fs.h>
#include <linux/shmem_fs.h>
#include <linux/ramfs.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/kthread.h>
#include "base.h"

static struct task_struct *thread;

#if defined CONFIG_DEVTMPFS_MOUNT
static int mount_dev = 1;
#else
static int mount_dev;
#endif

static DEFINE_SPINLOCK(req_lock);

static struct req {
	struct req *next;
	struct completion done;
	int err;
	const char *name;
	umode_t mode;	/* 0 => delete */
	kuid_t uid;
	kgid_t gid;
	struct device *dev;
} *requests;

static int __init mount_param(char *str)
{
	mount_dev = simple_strtoul(str, NULL, 0);
	return 1;
}
__setup("devtmpfs.mount=", mount_param);

static struct dentry *dev_mount(struct file_system_type *fs_type, int flags,
		      const char *dev_name, void *data)
{
#ifdef CONFIG_TMPFS
	return mount_single(fs_type, flags, data, shmem_fill_super);
#else
	return mount_single(fs_type, flags, data, ramfs_fill_super);
#endif
}

static struct file_system_type dev_fs_type = {
	.name = "devtmpfs",
	.mount = dev_mount,
	.kill_sb = kill_litter_super,
};

#ifdef CONFIG_BLOCK
static inline int is_blockdev(struct device *dev)
{
	return dev->class == &block_class;
}
#else
static inline int is_blockdev(struct device *dev) { return 0; }
#endif

int devtmpfs_create_node(struct device *dev)
{
	const char *tmp = NULL;
	struct req req;

	if (!thread)
		return 0;

	req.mode = 0;
	req.uid = GLOBAL_ROOT_UID;
	req.gid = GLOBAL_ROOT_GID;
	req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp);
	if (!req.name)
		return -ENOMEM;

	if (req.mode == 0)
		req.mode = 0600;
	if (is_blockdev(dev))
		req.mode |= S_IFBLK;
	else
		req.mode |= S_IFCHR;

	req.dev = dev;

	init_completion(&req.done);

	spin_lock(&req_lock);
	req.next = requests;
	requests = &req;
	spin_unlock(&req_lock);

	wake_up_process(thread);
	wait_for_completion(&req.done);

	kfree(tmp);

	return req.err;
}

int devtmpfs_delete_node(struct device *dev)
{
	const char *tmp = NULL;
	struct req req;

	if (!thread)
		return 0;

	req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp);
	if (!req.name)
		return -ENOMEM;

	req.mode = 0;
	req.dev = dev;

	init_completion(&req.done);

	spin_lock(&req_lock);
	req.next = requests;
	requests = &req;
	spin_unlock(&req_lock);

	wake_up_process(thread);
	wait_for_completion(&req.done);

	kfree(tmp);
	return req.err;
}

static int dev_mkdir(const char *name, umode_t mode)
{
	struct dentry *dentry;
	struct path path;
	int err;

	dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);

	err = vfs_mkdir(d_inode(path.dentry), dentry, mode);
	if (!err)
		/* mark as kernel-created inode */
		d_inode(dentry)->i_private = &thread;
	done_path_create(&path, dentry);
	return err;
}

static int create_path(const char *nodepath)
{
	char *path;
	char *s;
	int err = 0;

	/* parent directories do not exist, create them */
	path = kstrdup(nodepath, GFP_KERNEL);
	if (!path)
		return -ENOMEM;

	s = path;
	for (;;) {
		s = strchr(s, '/');
		if (!s)
			break;
		s[0] = '\0';
		err = dev_mkdir(path, 0755);
		if (err && err != -EEXIST)
			break;
		s[0] = '/';
		s++;
	}
	kfree(path);
	return err;
}

static int handle_create(const char *nodename, umode_t mode, kuid_t uid,
			 kgid_t gid, struct device *dev)
{
	struct dentry *dentry;
	struct path path;
	int err;

	dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
	if (dentry == ERR_PTR(-ENOENT)) {
		create_path(nodename);
		dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
	}
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);

	err = vfs_mknod(d_inode(path.dentry), dentry, mode, dev->devt);
	if (!err) {
		struct iattr newattrs;

		newattrs.ia_mode = mode;
		newattrs.ia_uid = uid;
		newattrs.ia_gid = gid;
		newattrs.ia_valid = ATTR_MODE|ATTR_UID|ATTR_GID;
		inode_lock(d_inode(dentry));
		notify_change(dentry, &newattrs, NULL);
		inode_unlock(d_inode(dentry));

		/* mark as kernel-created inode */
		d_inode(dentry)->i_private = &thread;
	}
	done_path_create(&path, dentry);
	return err;
}

static int dev_rmdir(const char *name)
{
	struct path parent;
	struct dentry *dentry;
	int err;

	dentry = kern_path_locked(name, &parent);
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);
	if (d_really_is_positive(dentry)) {
		if (d_inode(dentry)->i_private == &thread)
			err = vfs_rmdir(d_inode(parent.dentry), dentry);
		else
			err = -EPERM;
	} else {
		err = -ENOENT;
	}
	dput(dentry);
	inode_unlock(d_inode(parent.dentry));
	path_put(&parent);
	return err;
}

static int delete_path(const char *nodepath)
{
	const char *path;
	int err = 0;

	path = kstrdup(nodepath, GFP_KERNEL);
	if (!path)
		return -ENOMEM;

	for (;;) {
		char *base;

		base = strrchr(path, '/');
		if (!base)
			break;
		base[0] = '\0';
		err = dev_rmdir(path);
		if (err)
			break;
	}

	kfree(path);
	return err;
}

static int dev_mynode(struct device *dev, struct inode *inode, struct kstat *stat)
{
	/* did we create it */
	if (inode->i_private != &thread)
		return 0;

	/* does the dev_t match */
	if (is_blockdev(dev)) {
		if (!S_ISBLK(stat->mode))
			return 0;
	} else {
		if (!S_ISCHR(stat->mode))
			return 0;
	}
	if (stat->rdev != dev->devt)
		return 0;

	/* ours */
	return 1;
}

static int handle_remove(const char *nodename, struct device *dev)
{
	struct path parent;
	struct dentry *dentry;
	int deleted = 0;
	int err;

	dentry = kern_path_locked(nodename, &parent);
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);

	if (d_really_is_positive(dentry)) {
		struct kstat stat;
		struct path p = {.mnt = parent.mnt, .dentry = dentry};
		err = vfs_getattr(&p, &stat, STATX_TYPE | STATX_MODE,
				  AT_STATX_SYNC_AS_STAT);
		if (!err && dev_mynode(dev, d_inode(dentry), &stat)) {
			struct iattr newattrs;
			/*
			 * before unlinking this node, reset permissions
			 * of possible references like hardlinks
			 */
			newattrs.ia_uid = GLOBAL_ROOT_UID;
			newattrs.ia_gid = GLOBAL_ROOT_GID;
			newattrs.ia_mode = stat.mode & ~0777;
			newattrs.ia_valid =
				ATTR_UID|ATTR_GID|ATTR_MODE;
			inode_lock(d_inode(dentry));
			notify_change(dentry, &newattrs, NULL);
			inode_unlock(d_inode(dentry));
			err = vfs_unlink(d_inode(parent.dentry), dentry, NULL);
			if (!err || err == -ENOENT)
				deleted = 1;
		}
	} else {
		err = -ENOENT;
	}
	dput(dentry);
	inode_unlock(d_inode(parent.dentry));

	path_put(&parent);
	if (deleted && strchr(nodename, '/'))
		delete_path(nodename);
	return err;
}

/*
 * If configured, or requested by the commandline, devtmpfs will be
 * auto-mounted after the kernel mounted the root filesystem.
 */
int devtmpfs_mount(const char *mntdir)
{
	int err;

	if (!mount_dev)
		return 0;

	if (!thread)
		return 0;

	err = ksys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT,
			 NULL);
	if (err)
		printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
	else
		printk(KERN_INFO "devtmpfs: mounted\n");
	return err;
}

static DECLARE_COMPLETION(setup_done);

static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid,
		  struct device *dev)
{
	if (mode)
		return handle_create(name, mode, uid, gid, dev);
	else
		return handle_remove(name, dev);
}

static int devtmpfsd(void *p)
{
	char options[] = "mode=0755";
	int *err = p;
	*err = ksys_unshare(CLONE_NEWNS);
	if (*err)
		goto out;
	*err = ksys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
	if (*err)
		goto out;
	ksys_chdir("/.."); /* will traverse into overmounted root */
	ksys_chroot(".");
	complete(&setup_done);
	while (1) {
		spin_lock(&req_lock);
		while (requests) {
			struct req *req = requests;
			requests = NULL;
			spin_unlock(&req_lock);
			while (req) {
				struct req *next = req->next;
				req->err = handle(req->name, req->mode,
						  req->uid, req->gid, req->dev);
				complete(&req->done);
				req = next;
			}
			spin_lock(&req_lock);
		}
		__set_current_state(TASK_INTERRUPTIBLE);
		spin_unlock(&req_lock);
		schedule();
	}
	return 0;
out:
	complete(&setup_done);
	return *err;
}

/*
 * Create devtmpfs instance, driver-core devices will add their device
 * nodes here.
 */
int __init devtmpfs_init(void)
{
	int err = register_filesystem(&dev_fs_type);
	if (err) {
		printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
		       "type %i\n", err);
		return err;
	}

	thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
	if (!IS_ERR(thread)) {
		wait_for_completion(&setup_done);
	} else {
		err = PTR_ERR(thread);
		thread = NULL;
	}

	if (err) {
		printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
		unregister_filesystem(&dev_fs_type);
		return err;
	}

	printk(KERN_INFO "devtmpfs: initialized\n");
	return 0;
}
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
2b2af54a KS	2	/*
	3	* devtmpfs - kernel-maintained tmpfs-based /dev
	4	*
	5	* Copyright (C) 2009, Kay Sievers <[email protected]>
	6	*
	7	* During bootup, before any driver core device is registered,
	8	* devtmpfs, a tmpfs-based filesystem is created. Every driver-core
	9	* device which requests a device node, will add a node in this
e454cea2	10	* filesystem.
02fbe5e6 PK	11	* By default, all devices are named after the name of the device,
	12	* owned by root and have a default mode of 0600. Subsystems can
	13	* overwrite the default setting if needed.
2b2af54a KS	14	*/
	15
	16	#include <linux/kernel.h>
	17	#include <linux/syscalls.h>
	18	#include <linux/mount.h>
	19	#include <linux/device.h>
	20	#include <linux/genhd.h>
	21	#include <linux/namei.h>
	22	#include <linux/fs.h>
	23	#include <linux/shmem_fs.h>
da5e4ef7	24	#include <linux/ramfs.h>
e454cea2	25	#include <linux/sched.h>
5a0e3ad6	26	#include <linux/slab.h>
2780f1ff	27	#include <linux/kthread.h>
c3a30420	28	#include "base.h"
2b2af54a	29
2780f1ff	30	static struct task_struct *thread;
2b2af54a KS	31
2b2af54a KS	32	#if defined CONFIG_DEVTMPFS_MOUNT
fc14f2fe	33	static int mount_dev = 1;
2b2af54a	34	#else
fc14f2fe	35	static int mount_dev;
2b2af54a KS	36	#endif
2b2af54a KS	37
2780f1ff AV	38	static DEFINE_SPINLOCK(req_lock);
	39
	40	static struct req {
	41	struct req *next;
	42	struct completion done;
	43	int err;
	44	const char *name;
2c9ede55	45	umode_t mode; /* 0 => delete */
4e4098a3 GKH	46	kuid_t uid;
4e4098a3 GKH	47	kgid_t gid;
2780f1ff AV	48	struct device *dev;
2780f1ff AV	49	} *requests;
ed413ae6	50
2b2af54a KS	51	static int __init mount_param(char *str)
2b2af54a KS	52	{
fc14f2fe	53	mount_dev = simple_strtoul(str, NULL, 0);
2b2af54a KS	54	return 1;
	55	}
	56	__setup("devtmpfs.mount=", mount_param);
	57
fc14f2fe AV	58	static struct dentry dev_mount(struct file_system_type fs_type, int flags,
fc14f2fe AV	59	const char dev_name, void data)
2b2af54a	60	{
da5e4ef7	61	#ifdef CONFIG_TMPFS
fc14f2fe	62	return mount_single(fs_type, flags, data, shmem_fill_super);
da5e4ef7	63	#else
fc14f2fe	64	return mount_single(fs_type, flags, data, ramfs_fill_super);
da5e4ef7	65	#endif
2b2af54a KS	66	}
	67
	68	static struct file_system_type dev_fs_type = {
	69	.name = "devtmpfs",
fc14f2fe	70	.mount = dev_mount,
2b2af54a KS	71	.kill_sb = kill_litter_super,
	72	};
	73
	74	#ifdef CONFIG_BLOCK
	75	static inline int is_blockdev(struct device *dev)
	76	{
	77	return dev->class == &block_class;
	78	}
	79	#else
	80	static inline int is_blockdev(struct device *dev) { return 0; }
	81	#endif
	82
2780f1ff AV	83	int devtmpfs_create_node(struct device *dev)
	84	{
	85	const char *tmp = NULL;
	86	struct req req;
	87
	88	if (!thread)
	89	return 0;
	90
	91	req.mode = 0;
4e4098a3 GKH	92	req.uid = GLOBAL_ROOT_UID;
4e4098a3 GKH	93	req.gid = GLOBAL_ROOT_GID;
3c2670e6	94	req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp);
2780f1ff AV	95	if (!req.name)
	96	return -ENOMEM;
	97
	98	if (req.mode == 0)
	99	req.mode = 0600;
	100	if (is_blockdev(dev))
	101	req.mode \|= S_IFBLK;
	102	else
	103	req.mode \|= S_IFCHR;
	104
	105	req.dev = dev;
	106
	107	init_completion(&req.done);
	108
	109	spin_lock(&req_lock);
	110	req.next = requests;
	111	requests = &req;
	112	spin_unlock(&req_lock);
	113
	114	wake_up_process(thread);
	115	wait_for_completion(&req.done);
	116
	117	kfree(tmp);
	118
	119	return req.err;
	120	}
	121
	122	int devtmpfs_delete_node(struct device *dev)
	123	{
	124	const char *tmp = NULL;
	125	struct req req;
	126
	127	if (!thread)
	128	return 0;
	129
3c2670e6	130	req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp);
2780f1ff AV	131	if (!req.name)
	132	return -ENOMEM;
	133
	134	req.mode = 0;
	135	req.dev = dev;
	136
	137	init_completion(&req.done);
	138
	139	spin_lock(&req_lock);
	140	req.next = requests;
	141	requests = &req;
	142	spin_unlock(&req_lock);
	143
	144	wake_up_process(thread);
	145	wait_for_completion(&req.done);
	146
	147	kfree(tmp);
	148	return req.err;
	149	}
	150
fbd48a69	151	static int dev_mkdir(const char *name, umode_t mode)
2b2af54a	152	{
2b2af54a	153	struct dentry *dentry;
69753a0f	154	struct path path;
2b2af54a KS	155	int err;
2b2af54a KS	156
1ac12b4b	157	dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
69753a0f AV	158	if (IS_ERR(dentry))
	159	return PTR_ERR(dentry);
	160
75c3cfa8	161	err = vfs_mkdir(d_inode(path.dentry), dentry, mode);
69753a0f AV	162	if (!err)
69753a0f AV	163	/* mark as kernel-created inode */
75c3cfa8	164	d_inode(dentry)->i_private = &thread;
921a1650	165	done_path_create(&path, dentry);
2b2af54a KS	166	return err;
	167	}
	168
	169	static int create_path(const char *nodepath)
	170	{
5da4e689 AV	171	char *path;
5da4e689 AV	172	char *s;
9d108d25	173	int err = 0;
2b2af54a	174
5da4e689 AV	175	/* parent directories do not exist, create them */
	176	path = kstrdup(nodepath, GFP_KERNEL);
	177	if (!path)
	178	return -ENOMEM;
	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++;
2b2af54a	191	}
5da4e689	192	kfree(path);
2b2af54a KS	193	return err;
	194	}
	195
4e4098a3 GKH	196	static int handle_create(const char *nodename, umode_t mode, kuid_t uid,
4e4098a3 GKH	197	kgid_t gid, struct device *dev)
2b2af54a	198	{
2b2af54a	199	struct dentry *dentry;
69753a0f	200	struct path path;
2b2af54a KS	201	int err;
2b2af54a KS	202
69753a0f AV	203	dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
69753a0f AV	204	if (dentry == ERR_PTR(-ENOENT)) {
2b2af54a	205	create_path(nodename);
69753a0f	206	dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
2b2af54a	207	}
69753a0f AV	208	if (IS_ERR(dentry))
	209	return PTR_ERR(dentry);
	210
75c3cfa8	211	err = vfs_mknod(d_inode(path.dentry), dentry, mode, dev->devt);
69753a0f AV	212	if (!err) {
	213	struct iattr newattrs;
	214
69753a0f	215	newattrs.ia_mode = mode;
4e4098a3 GKH	216	newattrs.ia_uid = uid;
4e4098a3 GKH	217	newattrs.ia_gid = gid;
3c2670e6	218	newattrs.ia_valid = ATTR_MODE\|ATTR_UID\|ATTR_GID;
5955102c	219	inode_lock(d_inode(dentry));
27ac0ffe	220	notify_change(dentry, &newattrs, NULL);
5955102c	221	inode_unlock(d_inode(dentry));
69753a0f AV	222
69753a0f AV	223	/* mark as kernel-created inode */
75c3cfa8	224	d_inode(dentry)->i_private = &thread;
2b2af54a	225	}
921a1650	226	done_path_create(&path, dentry);
2b2af54a KS	227	return err;
	228	}
	229
	230	static int dev_rmdir(const char *name)
	231	{
79714f72	232	struct path parent;
2b2af54a KS	233	struct dentry *dentry;
	234	int err;
	235
79714f72 AV	236	dentry = kern_path_locked(name, &parent);
	237	if (IS_ERR(dentry))
	238	return PTR_ERR(dentry);
75c3cfa8 DH	239	if (d_really_is_positive(dentry)) {
	240	if (d_inode(dentry)->i_private == &thread)
	241	err = vfs_rmdir(d_inode(parent.dentry), dentry);
79714f72 AV	242	else
79714f72 AV	243	err = -EPERM;
2b2af54a	244	} else {
79714f72	245	err = -ENOENT;
2b2af54a	246	}
79714f72	247	dput(dentry);
5955102c	248	inode_unlock(d_inode(parent.dentry));
79714f72	249	path_put(&parent);
2b2af54a KS	250	return err;
	251	}
	252
	253	static int delete_path(const char *nodepath)
	254	{
	255	const char *path;
	256	int err = 0;
	257
	258	path = kstrdup(nodepath, GFP_KERNEL);
	259	if (!path)
	260	return -ENOMEM;
	261
ed413ae6	262	for (;;) {
2b2af54a KS	263	char *base;
	264
	265	base = strrchr(path, '/');
	266	if (!base)
	267	break;
	268	base[0] = '\0';
	269	err = dev_rmdir(path);
	270	if (err)
	271	break;
	272	}
	273
	274	kfree(path);
	275	return err;
	276	}
	277
	278	static int dev_mynode(struct device dev, struct inode inode, struct kstat *stat)
	279	{
	280	/* did we create it */
2780f1ff	281	if (inode->i_private != &thread)
2b2af54a KS	282	return 0;
	283
	284	/* does the dev_t match */
	285	if (is_blockdev(dev)) {
	286	if (!S_ISBLK(stat->mode))
	287	return 0;
	288	} else {
	289	if (!S_ISCHR(stat->mode))
	290	return 0;
	291	}
	292	if (stat->rdev != dev->devt)
	293	return 0;
	294
	295	/* ours */
	296	return 1;
	297	}
	298
2780f1ff	299	static int handle_remove(const char nodename, struct device dev)
2b2af54a	300	{
79714f72	301	struct path parent;
2b2af54a	302	struct dentry *dentry;
fbde7c61	303	int deleted = 0;
2b2af54a KS	304	int err;
2b2af54a KS	305
79714f72 AV	306	dentry = kern_path_locked(nodename, &parent);
	307	if (IS_ERR(dentry))
	308	return PTR_ERR(dentry);
	309
75c3cfa8	310	if (d_really_is_positive(dentry)) {
79714f72	311	struct kstat stat;
3dadecce	312	struct path p = {.mnt = parent.mnt, .dentry = dentry};
a528d35e DH	313	err = vfs_getattr(&p, &stat, STATX_TYPE \| STATX_MODE,
a528d35e DH	314	AT_STATX_SYNC_AS_STAT);
75c3cfa8	315	if (!err && dev_mynode(dev, d_inode(dentry), &stat)) {
79714f72 AV	316	struct iattr newattrs;
	317	/*
	318	* before unlinking this node, reset permissions
	319	* of possible references like hardlinks
	320	*/
91fa2cca EB	321	newattrs.ia_uid = GLOBAL_ROOT_UID;
91fa2cca EB	322	newattrs.ia_gid = GLOBAL_ROOT_GID;
79714f72 AV	323	newattrs.ia_mode = stat.mode & ~0777;
	324	newattrs.ia_valid =
	325	ATTR_UID\|ATTR_GID\|ATTR_MODE;
5955102c	326	inode_lock(d_inode(dentry));
27ac0ffe	327	notify_change(dentry, &newattrs, NULL);
5955102c	328	inode_unlock(d_inode(dentry));
75c3cfa8	329	err = vfs_unlink(d_inode(parent.dentry), dentry, NULL);
79714f72 AV	330	if (!err \|\| err == -ENOENT)
79714f72 AV	331	deleted = 1;
2b2af54a	332	}
2b2af54a	333	} else {
79714f72	334	err = -ENOENT;
2b2af54a	335	}
79714f72	336	dput(dentry);
5955102c	337	inode_unlock(d_inode(parent.dentry));
2b2af54a	338
79714f72	339	path_put(&parent);
2b2af54a KS	340	if (deleted && strchr(nodename, '/'))
2b2af54a KS	341	delete_path(nodename);
2b2af54a KS	342	return err;
	343	}
	344
	345	/*
	346	* If configured, or requested by the commandline, devtmpfs will be
	347	* auto-mounted after the kernel mounted the root filesystem.
	348	*/
073120cc	349	int devtmpfs_mount(const char *mntdir)
2b2af54a	350	{
2b2af54a KS	351	int err;
2b2af54a KS	352
fc14f2fe	353	if (!mount_dev)
2b2af54a KS	354	return 0;
2b2af54a KS	355
2780f1ff	356	if (!thread)
2b2af54a KS	357	return 0;
2b2af54a KS	358
312db1aa DB	359	err = ksys_mount("devtmpfs", (char *)mntdir, "devtmpfs", MS_SILENT,
312db1aa DB	360	NULL);
2b2af54a KS	361	if (err)
	362	printk(KERN_INFO "devtmpfs: error mounting %i\n", err);
	363	else
	364	printk(KERN_INFO "devtmpfs: mounted\n");
2b2af54a KS	365	return err;
	366	}
	367
f9e0b159	368	static DECLARE_COMPLETION(setup_done);
2780f1ff	369
4e4098a3	370	static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid,
3c2670e6	371	struct device *dev)
2780f1ff AV	372	{
2780f1ff AV	373	if (mode)
3c2670e6	374	return handle_create(name, mode, uid, gid, dev);
2780f1ff AV	375	else
	376	return handle_remove(name, dev);
	377	}
	378
	379	static int devtmpfsd(void *p)
	380	{
	381	char options[] = "mode=0755";
	382	int *err = p;
9b32105e	383	*err = ksys_unshare(CLONE_NEWNS);
2780f1ff AV	384	if (*err)
2780f1ff AV	385	goto out;
312db1aa	386	*err = ksys_mount("devtmpfs", "/", "devtmpfs", MS_SILENT, options);
2780f1ff AV	387	if (*err)
2780f1ff AV	388	goto out;
447016e9	389	ksys_chdir("/.."); /* will traverse into overmounted root */
a16fe33a	390	ksys_chroot(".");
2780f1ff AV	391	complete(&setup_done);
	392	while (1) {
	393	spin_lock(&req_lock);
	394	while (requests) {
	395	struct req *req = requests;
	396	requests = NULL;
	397	spin_unlock(&req_lock);
	398	while (req) {
e13889ba	399	struct req *next = req->next;
3c2670e6 KS	400	req->err = handle(req->name, req->mode,
3c2670e6 KS	401	req->uid, req->gid, req->dev);
2780f1ff	402	complete(&req->done);
e13889ba	403	req = next;
2780f1ff AV	404	}
	405	spin_lock(&req_lock);
	406	}
65e6757b	407	__set_current_state(TASK_INTERRUPTIBLE);
2780f1ff AV	408	spin_unlock(&req_lock);
2780f1ff AV	409	schedule();
2780f1ff AV	410	}
	411	return 0;
	412	out:
	413	complete(&setup_done);
	414	return *err;
	415	}
	416
2b2af54a KS	417	/*
	418	* Create devtmpfs instance, driver-core devices will add their device
	419	* nodes here.
	420	*/
	421	int __init devtmpfs_init(void)
	422	{
2780f1ff	423	int err = register_filesystem(&dev_fs_type);
2b2af54a KS	424	if (err) {
	425	printk(KERN_ERR "devtmpfs: unable to register devtmpfs "
	426	"type %i\n", err);
	427	return err;
	428	}
	429
2780f1ff AV	430	thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
	431	if (!IS_ERR(thread)) {
	432	wait_for_completion(&setup_done);
	433	} else {
	434	err = PTR_ERR(thread);
	435	thread = NULL;
	436	}
	437
	438	if (err) {
2b2af54a KS	439	printk(KERN_ERR "devtmpfs: unable to create devtmpfs %i\n", err);
	440	unregister_filesystem(&dev_fs_type);
	441	return err;
	442	}
2b2af54a KS	443
	444	printk(KERN_INFO "devtmpfs: initialized\n");
	445	return 0;
	446	}