[linux-2.6-block.git] / drivers / base / devtmpfs.c

// SPDX-License-Identifier: GPL-2.0
/*
 * devtmpfs - kernel-maintained tmpfs-based /dev
 *
 * Copyright (C) 2009, Kay Sievers <kay.sievers@vrfy.org>
 *
 * 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.
 */

#define pr_fmt(fmt) "devtmpfs: " fmt

#include <linux/kernel.h>
#include <linux/syscalls.h>
#include <linux/mount.h>
#include <linux/device.h>
#include <linux/blkdev.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 <linux/init_syscalls.h>
#include <uapi/linux/mount.h>
#include "base.h"

#ifdef CONFIG_DEVTMPFS_SAFE
#define DEVTMPFS_MFLAGS       (MS_SILENT | MS_NOEXEC | MS_NOSUID)
#else
#define DEVTMPFS_MFLAGS       (MS_SILENT)
#endif

static struct task_struct *thread;

static int __initdata mount_dev = IS_ENABLED(CONFIG_DEVTMPFS_MOUNT);

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 vfsmount *mnt;

static struct file_system_type internal_fs_type = {
	.name = "devtmpfs",
#ifdef CONFIG_TMPFS
	.init_fs_context = shmem_init_fs_context,
#else
	.init_fs_context = ramfs_init_fs_context,
#endif
	.kill_sb = kill_litter_super,
};

/* Simply take a ref on the existing mount */
static int devtmpfs_get_tree(struct fs_context *fc)
{
	struct super_block *sb = mnt->mnt_sb;

	atomic_inc(&sb->s_active);
	down_write(&sb->s_umount);
	fc->root = dget(sb->s_root);
	return 0;
}

/* Ops are filled in during init depending on underlying shmem or ramfs type */
struct fs_context_operations devtmpfs_context_ops = {};

/* Call the underlying initialization and set to our ops */
static int devtmpfs_init_fs_context(struct fs_context *fc)
{
	int ret;
#ifdef CONFIG_TMPFS
	ret = shmem_init_fs_context(fc);
#else
	ret = ramfs_init_fs_context(fc);
#endif
	if (ret < 0)
		return ret;

	fc->ops = &devtmpfs_context_ops;

	return 0;
}

static struct file_system_type dev_fs_type = {
	.name = "devtmpfs",
	.init_fs_context = devtmpfs_init_fs_context,
};

static int devtmpfs_submit_req(struct req *req, const char *tmp)
{
	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_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;

	return devtmpfs_submit_req(&req, tmp);
}

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;

	return devtmpfs_submit_req(&req, tmp);
}

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

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

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

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(&nop_mnt_idmap, 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(&nop_mnt_idmap, 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_inode(dentry)->i_private == &thread)
		err = vfs_rmdir(&nop_mnt_idmap, d_inode(parent.dentry),
				dentry);
	else
		err = -EPERM;

	dput(dentry);
	inode_unlock(d_inode(parent.dentry));
	path_put(&parent);
	return err;
}

static int delete_path(const char *nodepath)
{
	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)
{
	/* did we create it */
	if (inode->i_private != &thread)
		return 0;

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

	/* ours */
	return 1;
}

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

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

	inode = d_inode(dentry);
	if (dev_mynode(dev, inode)) {
		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 = inode->i_mode & ~0777;
		newattrs.ia_valid =
			ATTR_UID|ATTR_GID|ATTR_MODE;
		inode_lock(d_inode(dentry));
		notify_change(&nop_mnt_idmap, dentry, &newattrs, NULL);
		inode_unlock(d_inode(dentry));
		err = vfs_unlink(&nop_mnt_idmap, d_inode(parent.dentry),
				 dentry, NULL);
		if (!err || err == -ENOENT)
			deleted = 1;
	}
	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 __init devtmpfs_mount(void)
{
	int err;

	if (!mount_dev)
		return 0;

	if (!thread)
		return 0;

	err = init_mount("devtmpfs", "dev", "devtmpfs", DEVTMPFS_MFLAGS, NULL);
	if (err)
		pr_info("error mounting %d\n", err);
	else
		pr_info("mounted\n");
	return err;
}

static __initdata 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 void __noreturn devtmpfs_work_loop(void)
{
	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();
	}
}

static noinline int __init devtmpfs_setup(void *p)
{
	int err;

	err = ksys_unshare(CLONE_NEWNS);
	if (err)
		goto out;
	err = init_mount("devtmpfs", "/", "devtmpfs", DEVTMPFS_MFLAGS, NULL);
	if (err)
		goto out;
	init_chdir("/.."); /* will traverse into overmounted root */
	init_chroot(".");
out:
	*(int *)p = err;
	return err;
}

/*
 * The __ref is because devtmpfs_setup needs to be __init for the routines it
 * calls.  That call is done while devtmpfs_init, which is marked __init,
 * synchronously waits for it to complete.
 */
static int __ref devtmpfsd(void *p)
{
	int err = devtmpfs_setup(p);

	complete(&setup_done);
	if (err)
		return err;
	devtmpfs_work_loop();
	return 0;
}

/*
 * Get the underlying (shmem/ramfs) context ops to build ours
 */
static int devtmpfs_configure_context(void)
{
	struct fs_context *fc;

	fc = fs_context_for_reconfigure(mnt->mnt_root, mnt->mnt_sb->s_flags,
					MS_RMT_MASK);
	if (IS_ERR(fc))
		return PTR_ERR(fc);

	/* Set up devtmpfs_context_ops based on underlying type */
	devtmpfs_context_ops.free	      = fc->ops->free;
	devtmpfs_context_ops.dup	      = fc->ops->dup;
	devtmpfs_context_ops.parse_param      = fc->ops->parse_param;
	devtmpfs_context_ops.parse_monolithic = fc->ops->parse_monolithic;
	devtmpfs_context_ops.get_tree	      = &devtmpfs_get_tree;
	devtmpfs_context_ops.reconfigure      = fc->ops->reconfigure;

	put_fs_context(fc);

	return 0;
}

/*
 * Create devtmpfs instance, driver-core devices will add their device
 * nodes here.
 */
int __init devtmpfs_init(void)
{
	char opts[] = "mode=0755";
	int err;

	mnt = vfs_kern_mount(&internal_fs_type, 0, "devtmpfs", opts);
	if (IS_ERR(mnt)) {
		pr_err("unable to create devtmpfs %ld\n", PTR_ERR(mnt));
		return PTR_ERR(mnt);
	}

	err = devtmpfs_configure_context();
	if (err) {
		pr_err("unable to configure devtmpfs type %d\n", err);
		return err;
	}

	err = register_filesystem(&dev_fs_type);
	if (err) {
		pr_err("unable to register devtmpfs type %d\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) {
		pr_err("unable to create devtmpfs %d\n", err);
		unregister_filesystem(&dev_fs_type);
		thread = NULL;
		return err;
	}

	pr_info("initialized\n");
	return 0;
}
Commit	Line	Data
	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* devtmpfs - kernel-maintained tmpfs-based /dev
	4	*
	5	* Copyright (C) 2009, Kay Sievers <kay.sievers@vrfy.org>
	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
	10	* filesystem.
	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.
	14	*/
	15
	16	#define pr_fmt(fmt) "devtmpfs: " fmt
	17
	18	#include <linux/kernel.h>
	19	#include <linux/syscalls.h>
	20	#include <linux/mount.h>
	21	#include <linux/device.h>
	22	#include <linux/blkdev.h>
	23	#include <linux/namei.h>
	24	#include <linux/fs.h>
	25	#include <linux/shmem_fs.h>
	26	#include <linux/ramfs.h>
	27	#include <linux/sched.h>
	28	#include <linux/slab.h>
	29	#include <linux/kthread.h>
	30	#include <linux/init_syscalls.h>
	31	#include <uapi/linux/mount.h>
	32	#include "base.h"
	33
	34	#ifdef CONFIG_DEVTMPFS_SAFE
	35	#define DEVTMPFS_MFLAGS (MS_SILENT \| MS_NOEXEC \| MS_NOSUID)
	36	#else
	37	#define DEVTMPFS_MFLAGS (MS_SILENT)
	38	#endif
	39
	40	static struct task_struct *thread;
	41
	42	static int __initdata mount_dev = IS_ENABLED(CONFIG_DEVTMPFS_MOUNT);
	43
	44	static DEFINE_SPINLOCK(req_lock);
	45
	46	static struct req {
	47	struct req *next;
	48	struct completion done;
	49	int err;
	50	const char *name;
	51	umode_t mode; /* 0 => delete */
	52	kuid_t uid;
	53	kgid_t gid;
	54	struct device *dev;
	55	} *requests;
	56
	57	static int __init mount_param(char *str)
	58	{
	59	mount_dev = simple_strtoul(str, NULL, 0);
	60	return 1;
	61	}
	62	__setup("devtmpfs.mount=", mount_param);
	63
	64	static struct vfsmount *mnt;
	65
	66	static struct file_system_type internal_fs_type = {
	67	.name = "devtmpfs",
	68	#ifdef CONFIG_TMPFS
	69	.init_fs_context = shmem_init_fs_context,
	70	#else
	71	.init_fs_context = ramfs_init_fs_context,
	72	#endif
	73	.kill_sb = kill_litter_super,
	74	};
	75
	76	/* Simply take a ref on the existing mount */
	77	static int devtmpfs_get_tree(struct fs_context *fc)
	78	{
	79	struct super_block *sb = mnt->mnt_sb;
	80
	81	atomic_inc(&sb->s_active);
	82	down_write(&sb->s_umount);
	83	fc->root = dget(sb->s_root);
	84	return 0;
	85	}
	86
	87	/* Ops are filled in during init depending on underlying shmem or ramfs type */
	88	struct fs_context_operations devtmpfs_context_ops = {};
	89
	90	/* Call the underlying initialization and set to our ops */
	91	static int devtmpfs_init_fs_context(struct fs_context *fc)
	92	{
	93	int ret;
	94	#ifdef CONFIG_TMPFS
	95	ret = shmem_init_fs_context(fc);
	96	#else
	97	ret = ramfs_init_fs_context(fc);
	98	#endif
	99	if (ret < 0)
	100	return ret;
	101
	102	fc->ops = &devtmpfs_context_ops;
	103
	104	return 0;
	105	}
	106
	107	static struct file_system_type dev_fs_type = {
	108	.name = "devtmpfs",
	109	.init_fs_context = devtmpfs_init_fs_context,
	110	};
	111
	112	static int devtmpfs_submit_req(struct req req, const char tmp)
	113	{
	114	init_completion(&req->done);
	115
	116	spin_lock(&req_lock);
	117	req->next = requests;
	118	requests = req;
	119	spin_unlock(&req_lock);
	120
	121	wake_up_process(thread);
	122	wait_for_completion(&req->done);
	123
	124	kfree(tmp);
	125
	126	return req->err;
	127	}
	128
	129	int devtmpfs_create_node(struct device *dev)
	130	{
	131	const char *tmp = NULL;
	132	struct req req;
	133
	134	if (!thread)
	135	return 0;
	136
	137	req.mode = 0;
	138	req.uid = GLOBAL_ROOT_UID;
	139	req.gid = GLOBAL_ROOT_GID;
	140	req.name = device_get_devnode(dev, &req.mode, &req.uid, &req.gid, &tmp);
	141	if (!req.name)
	142	return -ENOMEM;
	143
	144	if (req.mode == 0)
	145	req.mode = 0600;
	146	if (is_blockdev(dev))
	147	req.mode \|= S_IFBLK;
	148	else
	149	req.mode \|= S_IFCHR;
	150
	151	req.dev = dev;
	152
	153	return devtmpfs_submit_req(&req, tmp);
	154	}
	155
	156	int devtmpfs_delete_node(struct device *dev)
	157	{
	158	const char *tmp = NULL;
	159	struct req req;
	160
	161	if (!thread)
	162	return 0;
	163
	164	req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp);
	165	if (!req.name)
	166	return -ENOMEM;
	167
	168	req.mode = 0;
	169	req.dev = dev;
	170
	171	return devtmpfs_submit_req(&req, tmp);
	172	}
	173
	174	static int dev_mkdir(const char *name, umode_t mode)
	175	{
	176	struct dentry *dentry;
	177	struct path path;
	178
	179	dentry = kern_path_create(AT_FDCWD, name, &path, LOOKUP_DIRECTORY);
	180	if (IS_ERR(dentry))
	181	return PTR_ERR(dentry);
	182
	183	dentry = vfs_mkdir(&nop_mnt_idmap, d_inode(path.dentry), dentry, mode);
	184	if (!IS_ERR(dentry))
	185	/* mark as kernel-created inode */
	186	d_inode(dentry)->i_private = &thread;
	187	done_path_create(&path, dentry);
	188	return PTR_ERR_OR_ZERO(dentry);
	189	}
	190
	191	static int create_path(const char *nodepath)
	192	{
	193	char *path;
	194	char *s;
	195	int err = 0;
	196
	197	/* parent directories do not exist, create them */
	198	path = kstrdup(nodepath, GFP_KERNEL);
	199	if (!path)
	200	return -ENOMEM;
	201
	202	s = path;
	203	for (;;) {
	204	s = strchr(s, '/');
	205	if (!s)
	206	break;
	207	s[0] = '\0';
	208	err = dev_mkdir(path, 0755);
	209	if (err && err != -EEXIST)
	210	break;
	211	s[0] = '/';
	212	s++;
	213	}
	214	kfree(path);
	215	return err;
	216	}
	217
	218	static int handle_create(const char *nodename, umode_t mode, kuid_t uid,
	219	kgid_t gid, struct device *dev)
	220	{
	221	struct dentry *dentry;
	222	struct path path;
	223	int err;
	224
	225	dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
	226	if (dentry == ERR_PTR(-ENOENT)) {
	227	create_path(nodename);
	228	dentry = kern_path_create(AT_FDCWD, nodename, &path, 0);
	229	}
	230	if (IS_ERR(dentry))
	231	return PTR_ERR(dentry);
	232
	233	err = vfs_mknod(&nop_mnt_idmap, d_inode(path.dentry), dentry, mode,
	234	dev->devt);
	235	if (!err) {
	236	struct iattr newattrs;
	237
	238	newattrs.ia_mode = mode;
	239	newattrs.ia_uid = uid;
	240	newattrs.ia_gid = gid;
	241	newattrs.ia_valid = ATTR_MODE\|ATTR_UID\|ATTR_GID;
	242	inode_lock(d_inode(dentry));
	243	notify_change(&nop_mnt_idmap, dentry, &newattrs, NULL);
	244	inode_unlock(d_inode(dentry));
	245
	246	/* mark as kernel-created inode */
	247	d_inode(dentry)->i_private = &thread;
	248	}
	249	done_path_create(&path, dentry);
	250	return err;
	251	}
	252
	253	static int dev_rmdir(const char *name)
	254	{
	255	struct path parent;
	256	struct dentry *dentry;
	257	int err;
	258
	259	dentry = kern_path_locked(name, &parent);
	260	if (IS_ERR(dentry))
	261	return PTR_ERR(dentry);
	262	if (d_inode(dentry)->i_private == &thread)
	263	err = vfs_rmdir(&nop_mnt_idmap, d_inode(parent.dentry),
	264	dentry);
	265	else
	266	err = -EPERM;
	267
	268	dput(dentry);
	269	inode_unlock(d_inode(parent.dentry));
	270	path_put(&parent);
	271	return err;
	272	}
	273
	274	static int delete_path(const char *nodepath)
	275	{
	276	char *path;
	277	int err = 0;
	278
	279	path = kstrdup(nodepath, GFP_KERNEL);
	280	if (!path)
	281	return -ENOMEM;
	282
	283	for (;;) {
	284	char *base;
	285
	286	base = strrchr(path, '/');
	287	if (!base)
	288	break;
	289	base[0] = '\0';
	290	err = dev_rmdir(path);
	291	if (err)
	292	break;
	293	}
	294
	295	kfree(path);
	296	return err;
	297	}
	298
	299	static int dev_mynode(struct device dev, struct inode inode)
	300	{
	301	/* did we create it */
	302	if (inode->i_private != &thread)
	303	return 0;
	304
	305	/* does the dev_t match */
	306	if (is_blockdev(dev)) {
	307	if (!S_ISBLK(inode->i_mode))
	308	return 0;
	309	} else {
	310	if (!S_ISCHR(inode->i_mode))
	311	return 0;
	312	}
	313	if (inode->i_rdev != dev->devt)
	314	return 0;
	315
	316	/* ours */
	317	return 1;
	318	}
	319
	320	static int handle_remove(const char nodename, struct device dev)
	321	{
	322	struct path parent;
	323	struct dentry *dentry;
	324	struct inode *inode;
	325	int deleted = 0;
	326	int err = 0;
	327
	328	dentry = kern_path_locked(nodename, &parent);
	329	if (IS_ERR(dentry))
	330	return PTR_ERR(dentry);
	331
	332	inode = d_inode(dentry);
	333	if (dev_mynode(dev, inode)) {
	334	struct iattr newattrs;
	335	/*
	336	* before unlinking this node, reset permissions
	337	* of possible references like hardlinks
	338	*/
	339	newattrs.ia_uid = GLOBAL_ROOT_UID;
	340	newattrs.ia_gid = GLOBAL_ROOT_GID;
	341	newattrs.ia_mode = inode->i_mode & ~0777;
	342	newattrs.ia_valid =
	343	ATTR_UID\|ATTR_GID\|ATTR_MODE;
	344	inode_lock(d_inode(dentry));
	345	notify_change(&nop_mnt_idmap, dentry, &newattrs, NULL);
	346	inode_unlock(d_inode(dentry));
	347	err = vfs_unlink(&nop_mnt_idmap, d_inode(parent.dentry),
	348	dentry, NULL);
	349	if (!err \|\| err == -ENOENT)
	350	deleted = 1;
	351	}
	352	dput(dentry);
	353	inode_unlock(d_inode(parent.dentry));
	354
	355	path_put(&parent);
	356	if (deleted && strchr(nodename, '/'))
	357	delete_path(nodename);
	358	return err;
	359	}
	360
	361	/*
	362	* If configured, or requested by the commandline, devtmpfs will be
	363	* auto-mounted after the kernel mounted the root filesystem.
	364	*/
	365	int __init devtmpfs_mount(void)
	366	{
	367	int err;
	368
	369	if (!mount_dev)
	370	return 0;
	371
	372	if (!thread)
	373	return 0;
	374
	375	err = init_mount("devtmpfs", "dev", "devtmpfs", DEVTMPFS_MFLAGS, NULL);
	376	if (err)
	377	pr_info("error mounting %d\n", err);
	378	else
	379	pr_info("mounted\n");
	380	return err;
	381	}
	382
	383	static __initdata DECLARE_COMPLETION(setup_done);
	384
	385	static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid,
	386	struct device *dev)
	387	{
	388	if (mode)
	389	return handle_create(name, mode, uid, gid, dev);
	390	else
	391	return handle_remove(name, dev);
	392	}
	393
	394	static void __noreturn devtmpfs_work_loop(void)
	395	{
	396	while (1) {
	397	spin_lock(&req_lock);
	398	while (requests) {
	399	struct req *req = requests;
	400	requests = NULL;
	401	spin_unlock(&req_lock);
	402	while (req) {
	403	struct req *next = req->next;
	404	req->err = handle(req->name, req->mode,
	405	req->uid, req->gid, req->dev);
	406	complete(&req->done);
	407	req = next;
	408	}
	409	spin_lock(&req_lock);
	410	}
	411	__set_current_state(TASK_INTERRUPTIBLE);
	412	spin_unlock(&req_lock);
	413	schedule();
	414	}
	415	}
	416
	417	static noinline int __init devtmpfs_setup(void *p)
	418	{
	419	int err;
	420
	421	err = ksys_unshare(CLONE_NEWNS);
	422	if (err)
	423	goto out;
	424	err = init_mount("devtmpfs", "/", "devtmpfs", DEVTMPFS_MFLAGS, NULL);
	425	if (err)
	426	goto out;
	427	init_chdir("/.."); /* will traverse into overmounted root */
	428	init_chroot(".");
	429	out:
	430	(int )p = err;
	431	return err;
	432	}
	433
	434	/*
	435	* The __ref is because devtmpfs_setup needs to be __init for the routines it
	436	* calls. That call is done while devtmpfs_init, which is marked __init,
	437	* synchronously waits for it to complete.
	438	*/
	439	static int __ref devtmpfsd(void *p)
	440	{
	441	int err = devtmpfs_setup(p);
	442
	443	complete(&setup_done);
	444	if (err)
	445	return err;
	446	devtmpfs_work_loop();
	447	return 0;
	448	}
	449
	450	/*
	451	* Get the underlying (shmem/ramfs) context ops to build ours
	452	*/
	453	static int devtmpfs_configure_context(void)
	454	{
	455	struct fs_context *fc;
	456
	457	fc = fs_context_for_reconfigure(mnt->mnt_root, mnt->mnt_sb->s_flags,
	458	MS_RMT_MASK);
	459	if (IS_ERR(fc))
	460	return PTR_ERR(fc);
	461
	462	/* Set up devtmpfs_context_ops based on underlying type */
	463	devtmpfs_context_ops.free = fc->ops->free;
	464	devtmpfs_context_ops.dup = fc->ops->dup;
	465	devtmpfs_context_ops.parse_param = fc->ops->parse_param;
	466	devtmpfs_context_ops.parse_monolithic = fc->ops->parse_monolithic;
	467	devtmpfs_context_ops.get_tree = &devtmpfs_get_tree;
	468	devtmpfs_context_ops.reconfigure = fc->ops->reconfigure;
	469
	470	put_fs_context(fc);
	471
	472	return 0;
	473	}
	474
	475	/*
	476	* Create devtmpfs instance, driver-core devices will add their device
	477	* nodes here.
	478	*/
	479	int __init devtmpfs_init(void)
	480	{
	481	char opts[] = "mode=0755";
	482	int err;
	483
	484	mnt = vfs_kern_mount(&internal_fs_type, 0, "devtmpfs", opts);
	485	if (IS_ERR(mnt)) {
	486	pr_err("unable to create devtmpfs %ld\n", PTR_ERR(mnt));
	487	return PTR_ERR(mnt);
	488	}
	489
	490	err = devtmpfs_configure_context();
	491	if (err) {
	492	pr_err("unable to configure devtmpfs type %d\n", err);
	493	return err;
	494	}
	495
	496	err = register_filesystem(&dev_fs_type);
	497	if (err) {
	498	pr_err("unable to register devtmpfs type %d\n", err);
	499	return err;
	500	}
	501
	502	thread = kthread_run(devtmpfsd, &err, "kdevtmpfs");
	503	if (!IS_ERR(thread)) {
	504	wait_for_completion(&setup_done);
	505	} else {
	506	err = PTR_ERR(thread);
	507	thread = NULL;
	508	}
	509
	510	if (err) {
	511	pr_err("unable to create devtmpfs %d\n", err);
	512	unregister_filesystem(&dev_fs_type);
	513	thread = NULL;
	514	return err;
	515	}
	516
	517	pr_info("initialized\n");
	518	return 0;
	519	}