[deliverable/linux.git] / fs / devpts / inode.c

/* -*- linux-c -*- --------------------------------------------------------- *
 *
 * linux/fs/devpts/inode.c
 *
 *  Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
 *
 * This file is part of the Linux kernel and is made available under
 * the terms of the GNU General Public License, version 2, or at your
 * option, any later version, incorporated herein by reference.
 *
 * ------------------------------------------------------------------------- */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/tty.h>
#include <linux/mutex.h>
#include <linux/idr.h>
#include <linux/devpts_fs.h>
#include <linux/parser.h>
#include <linux/fsnotify.h>
#include <linux/seq_file.h>

#define DEVPTS_SUPER_MAGIC 0x1cd1

#define DEVPTS_DEFAULT_MODE 0600
#define PTMX_MINOR	2

extern int pty_limit;			/* Config limit on Unix98 ptys */
static DEFINE_MUTEX(allocated_ptys_lock);

static struct vfsmount *devpts_mnt;

struct pts_mount_opts {
	int setuid;
	int setgid;
	uid_t   uid;
	gid_t   gid;
	umode_t mode;
};

enum {
	Opt_uid, Opt_gid, Opt_mode,
	Opt_err
};

static const match_table_t tokens = {
	{Opt_uid, "uid=%u"},
	{Opt_gid, "gid=%u"},
	{Opt_mode, "mode=%o"},
	{Opt_err, NULL}
};

struct pts_fs_info {
	struct ida allocated_ptys;
	struct pts_mount_opts mount_opts;
};

static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)
{
	return sb->s_fs_info;
}

static inline struct super_block *pts_sb_from_inode(struct inode *inode)
{
	if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
		return inode->i_sb;

	return devpts_mnt->mnt_sb;
}

static int devpts_remount(struct super_block *sb, int *flags, char *data)
{
	char *p;
	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	struct pts_mount_opts *opts = &fsi->mount_opts;

	opts->setuid  = 0;
	opts->setgid  = 0;
	opts->uid     = 0;
	opts->gid     = 0;
	opts->mode    = DEVPTS_DEFAULT_MODE;

	while ((p = strsep(&data, ",")) != NULL) {
		substring_t args[MAX_OPT_ARGS];
		int token;
		int option;

		if (!*p)
			continue;

		token = match_token(p, tokens, args);
		switch (token) {
		case Opt_uid:
			if (match_int(&args[0], &option))
				return -EINVAL;
			opts->uid = option;
			opts->setuid = 1;
			break;
		case Opt_gid:
			if (match_int(&args[0], &option))
				return -EINVAL;
			opts->gid = option;
			opts->setgid = 1;
			break;
		case Opt_mode:
			if (match_octal(&args[0], &option))
				return -EINVAL;
			opts->mode = option & S_IALLUGO;
			break;
		default:
			printk(KERN_ERR "devpts: called with bogus options\n");
			return -EINVAL;
		}
	}

	return 0;
}

static int devpts_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
	struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
	struct pts_mount_opts *opts = &fsi->mount_opts;

	if (opts->setuid)
		seq_printf(seq, ",uid=%u", opts->uid);
	if (opts->setgid)
		seq_printf(seq, ",gid=%u", opts->gid);
	seq_printf(seq, ",mode=%03o", opts->mode);

	return 0;
}

static const struct super_operations devpts_sops = {
	.statfs		= simple_statfs,
	.remount_fs	= devpts_remount,
	.show_options	= devpts_show_options,
};

static void *new_pts_fs_info(void)
{
	struct pts_fs_info *fsi;

	fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
	if (!fsi)
		return NULL;

	ida_init(&fsi->allocated_ptys);
	fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;

	return fsi;
}

static int
devpts_fill_super(struct super_block *s, void *data, int silent)
{
	struct inode * inode;

	s->s_blocksize = 1024;
	s->s_blocksize_bits = 10;
	s->s_magic = DEVPTS_SUPER_MAGIC;
	s->s_op = &devpts_sops;
	s->s_time_gran = 1;

	s->s_fs_info = new_pts_fs_info();
	if (!s->s_fs_info)
		goto fail;

	inode = new_inode(s);
	if (!inode)
		goto free_fsi;
	inode->i_ino = 1;
	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	inode->i_blocks = 0;
	inode->i_uid = inode->i_gid = 0;
	inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR;
	inode->i_op = &simple_dir_inode_operations;
	inode->i_fop = &simple_dir_operations;
	inode->i_nlink = 2;

	s->s_root = d_alloc_root(inode);
	if (s->s_root)
		return 0;
	
	printk("devpts: get root dentry failed\n");
	iput(inode);

free_fsi:
	kfree(s->s_fs_info);
fail:
	return -ENOMEM;
}

static int devpts_get_sb(struct file_system_type *fs_type,
	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
	return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
}

static void devpts_kill_sb(struct super_block *sb)
{
	struct pts_fs_info *fsi = DEVPTS_SB(sb);

	kfree(fsi);
	kill_anon_super(sb);
}

static struct file_system_type devpts_fs_type = {
	.owner		= THIS_MODULE,
	.name		= "devpts",
	.get_sb		= devpts_get_sb,
	.kill_sb	= devpts_kill_sb,
};

/*
 * The normal naming convention is simply /dev/pts/<number>; this conforms
 * to the System V naming convention
 */

int devpts_new_index(struct inode *ptmx_inode)
{
	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	int index;
	int ida_ret;

retry:
	if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) {
		return -ENOMEM;
	}

	mutex_lock(&allocated_ptys_lock);
	ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
	if (ida_ret < 0) {
		mutex_unlock(&allocated_ptys_lock);
		if (ida_ret == -EAGAIN)
			goto retry;
		return -EIO;
	}

	if (index >= pty_limit) {
		ida_remove(&fsi->allocated_ptys, index);
		mutex_unlock(&allocated_ptys_lock);
		return -EIO;
	}
	mutex_unlock(&allocated_ptys_lock);
	return index;
}

void devpts_kill_index(struct inode *ptmx_inode, int idx)
{
	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	struct pts_fs_info *fsi = DEVPTS_SB(sb);

	mutex_lock(&allocated_ptys_lock);
	ida_remove(&fsi->allocated_ptys, idx);
	mutex_unlock(&allocated_ptys_lock);
}

int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
{
	int number = tty->index; /* tty layer puts index from devpts_new_index() in here */
	struct tty_driver *driver = tty->driver;
	dev_t device = MKDEV(driver->major, driver->minor_start+number);
	struct dentry *dentry;
	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	struct inode *inode = new_inode(sb);
	struct dentry *root = sb->s_root;
	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	struct pts_mount_opts *opts = &fsi->mount_opts;
	char s[12];

	/* We're supposed to be given the slave end of a pty */
	BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
	BUG_ON(driver->subtype != PTY_TYPE_SLAVE);

	if (!inode)
		return -ENOMEM;

	inode->i_ino = number+2;
	inode->i_uid = config.setuid ? config.uid : current_fsuid();
	inode->i_gid = config.setgid ? config.gid : current_fsgid();
	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	init_special_inode(inode, S_IFCHR|opts->mode, device);
	inode->i_private = tty;
	tty->driver_data = inode;

	sprintf(s, "%d", number);

	mutex_lock(&root->d_inode->i_mutex);

	dentry = d_alloc_name(root, s);
	if (!IS_ERR(dentry)) {
		d_add(dentry, inode);
		fsnotify_create(root->d_inode, dentry);
	}

	mutex_unlock(&root->d_inode->i_mutex);

	return 0;
}

struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
{
	BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));

	if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
		return (struct tty_struct *)pts_inode->i_private;
	return NULL;
}

void devpts_pty_kill(struct tty_struct *tty)
{
	struct inode *inode = tty->driver_data;
	struct super_block *sb = pts_sb_from_inode(inode);
	struct dentry *root = sb->s_root;
	struct dentry *dentry;

	BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));

	mutex_lock(&root->d_inode->i_mutex);

	dentry = d_find_alias(inode);
	if (dentry && !IS_ERR(dentry)) {
		inode->i_nlink--;
		d_delete(dentry);
		dput(dentry);
	}

	mutex_unlock(&root->d_inode->i_mutex);
}

static int __init init_devpts_fs(void)
{
	int err = register_filesystem(&devpts_fs_type);
	if (!err) {
		devpts_mnt = kern_mount(&devpts_fs_type);
		if (IS_ERR(devpts_mnt))
			err = PTR_ERR(devpts_mnt);
	}
	return err;
}

static void __exit exit_devpts_fs(void)
{
	unregister_filesystem(&devpts_fs_type);
	mntput(devpts_mnt);
}

module_init(init_devpts_fs)
module_exit(exit_devpts_fs)
MODULE_LICENSE("GPL");
Commit	Line	Data
1da177e4 LT	1	/* -- linux-c -- --------------------------------------------------------- *
	2	*
	3	* linux/fs/devpts/inode.c
	4	*
	5	* Copyright 1998-2004 H. Peter Anvin -- All Rights Reserved
	6	*
	7	* This file is part of the Linux kernel and is made available under
	8	* the terms of the GNU General Public License, version 2, or at your
	9	* option, any later version, incorporated herein by reference.
	10	*
	11	* ------------------------------------------------------------------------- */
	12
	13	#include <linux/module.h>
	14	#include <linux/init.h>
	15	#include <linux/fs.h>
	16	#include <linux/sched.h>
	17	#include <linux/namei.h>
	18	#include <linux/mount.h>
	19	#include <linux/tty.h>
718a9163 SB	20	#include <linux/mutex.h>
718a9163 SB	21	#include <linux/idr.h>
1da177e4	22	#include <linux/devpts_fs.h>
7a673c6b	23	#include <linux/parser.h>
3972b7f6	24	#include <linux/fsnotify.h>
b87a267e	25	#include <linux/seq_file.h>
1da177e4 LT	26
	27	#define DEVPTS_SUPER_MAGIC 0x1cd1
	28
b87a267e	29	#define DEVPTS_DEFAULT_MODE 0600
527b3e47	30	#define PTMX_MINOR 2
b87a267e	31
718a9163	32	extern int pty_limit; /* Config limit on Unix98 ptys */
718a9163 SB	33	static DEFINE_MUTEX(allocated_ptys_lock);
718a9163 SB	34
1da177e4	35	static struct vfsmount *devpts_mnt;
1da177e4	36
31af0abb	37	struct pts_mount_opts {
1da177e4 LT	38	int setuid;
	39	int setgid;
	40	uid_t uid;
	41	gid_t gid;
	42	umode_t mode;
31af0abb	43	};
1da177e4	44
7a673c6b DP	45	enum {
	46	Opt_uid, Opt_gid, Opt_mode,
	47	Opt_err
	48	};
	49
a447c093	50	static const match_table_t tokens = {
7a673c6b DP	51	{Opt_uid, "uid=%u"},
	52	{Opt_gid, "gid=%u"},
	53	{Opt_mode, "mode=%o"},
	54	{Opt_err, NULL}
	55	};
	56
e76b7c01 SB	57	struct pts_fs_info {
e76b7c01 SB	58	struct ida allocated_ptys;
31af0abb	59	struct pts_mount_opts mount_opts;
e76b7c01 SB	60	};
	61
	62	static inline struct pts_fs_info DEVPTS_SB(struct super_block sb)
	63	{
	64	return sb->s_fs_info;
	65	}
	66
59e55e6c SB	67	static inline struct super_block pts_sb_from_inode(struct inode inode)
	68	{
	69	if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
	70	return inode->i_sb;
	71
	72	return devpts_mnt->mnt_sb;
	73	}
	74
1da177e4 LT	75	static int devpts_remount(struct super_block sb, int flags, char *data)
1da177e4 LT	76	{
7a673c6b	77	char *p;
31af0abb SB	78	struct pts_fs_info *fsi = DEVPTS_SB(sb);
31af0abb SB	79	struct pts_mount_opts *opts = &fsi->mount_opts;
7a673c6b	80
31af0abb SB	81	opts->setuid = 0;
	82	opts->setgid = 0;
	83	opts->uid = 0;
	84	opts->gid = 0;
	85	opts->mode = DEVPTS_DEFAULT_MODE;
7a673c6b DP	86
	87	while ((p = strsep(&data, ",")) != NULL) {
	88	substring_t args[MAX_OPT_ARGS];
	89	int token;
	90	int option;
	91
	92	if (!*p)
1da177e4	93	continue;
7a673c6b DP	94
	95	token = match_token(p, tokens, args);
	96	switch (token) {
	97	case Opt_uid:
	98	if (match_int(&args[0], &option))
	99	return -EINVAL;
31af0abb SB	100	opts->uid = option;
31af0abb SB	101	opts->setuid = 1;
7a673c6b DP	102	break;
	103	case Opt_gid:
	104	if (match_int(&args[0], &option))
	105	return -EINVAL;
31af0abb SB	106	opts->gid = option;
31af0abb SB	107	opts->setgid = 1;
7a673c6b DP	108	break;
	109	case Opt_mode:
	110	if (match_octal(&args[0], &option))
	111	return -EINVAL;
31af0abb	112	opts->mode = option & S_IALLUGO;
7a673c6b DP	113	break;
	114	default:
	115	printk(KERN_ERR "devpts: called with bogus options\n");
1da177e4 LT	116	return -EINVAL;
	117	}
	118	}
1da177e4 LT	119
	120	return 0;
	121	}
	122
b87a267e MS	123	static int devpts_show_options(struct seq_file seq, struct vfsmount vfs)
b87a267e MS	124	{
31af0abb SB	125	struct pts_fs_info *fsi = DEVPTS_SB(vfs->mnt_sb);
	126	struct pts_mount_opts *opts = &fsi->mount_opts;
	127
	128	if (opts->setuid)
	129	seq_printf(seq, ",uid=%u", opts->uid);
	130	if (opts->setgid)
	131	seq_printf(seq, ",gid=%u", opts->gid);
	132	seq_printf(seq, ",mode=%03o", opts->mode);
b87a267e MS	133
	134	return 0;
	135	}
	136
ee9b6d61	137	static const struct super_operations devpts_sops = {
1da177e4 LT	138	.statfs = simple_statfs,
1da177e4 LT	139	.remount_fs = devpts_remount,
b87a267e	140	.show_options = devpts_show_options,
1da177e4 LT	141	};
1da177e4 LT	142
e76b7c01 SB	143	static void *new_pts_fs_info(void)
	144	{
	145	struct pts_fs_info *fsi;
	146
	147	fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
	148	if (!fsi)
	149	return NULL;
	150
	151	ida_init(&fsi->allocated_ptys);
31af0abb	152	fsi->mount_opts.mode = DEVPTS_DEFAULT_MODE;
e76b7c01 SB	153
	154	return fsi;
	155	}
	156
1da177e4 LT	157	static int
	158	devpts_fill_super(struct super_block s, void data, int silent)
	159	{
	160	struct inode * inode;
	161
	162	s->s_blocksize = 1024;
	163	s->s_blocksize_bits = 10;
	164	s->s_magic = DEVPTS_SUPER_MAGIC;
	165	s->s_op = &devpts_sops;
1da177e4 LT	166	s->s_time_gran = 1;
1da177e4 LT	167
e76b7c01 SB	168	s->s_fs_info = new_pts_fs_info();
	169	if (!s->s_fs_info)
	170	goto fail;
	171
1da177e4 LT	172	inode = new_inode(s);
1da177e4 LT	173	if (!inode)
e76b7c01	174	goto free_fsi;
1da177e4 LT	175	inode->i_ino = 1;
	176	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
	177	inode->i_blocks = 0;
1da177e4 LT	178	inode->i_uid = inode->i_gid = 0;
	179	inode->i_mode = S_IFDIR \| S_IRUGO \| S_IXUGO \| S_IWUSR;
	180	inode->i_op = &simple_dir_inode_operations;
	181	inode->i_fop = &simple_dir_operations;
	182	inode->i_nlink = 2;
	183
59e55e6c	184	s->s_root = d_alloc_root(inode);
1da177e4 LT	185	if (s->s_root)
	186	return 0;
	187
	188	printk("devpts: get root dentry failed\n");
	189	iput(inode);
e76b7c01 SB	190
	191	free_fsi:
	192	kfree(s->s_fs_info);
1da177e4 LT	193	fail:
	194	return -ENOMEM;
	195	}
	196
454e2398 DH	197	static int devpts_get_sb(struct file_system_type *fs_type,
454e2398 DH	198	int flags, const char dev_name, void data, struct vfsmount *mnt)
1da177e4	199	{
454e2398	200	return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
1da177e4 LT	201	}
1da177e4 LT	202
e76b7c01 SB	203	static void devpts_kill_sb(struct super_block *sb)
	204	{
	205	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	206
	207	kfree(fsi);
	208	kill_anon_super(sb);
	209	}
	210
1da177e4 LT	211	static struct file_system_type devpts_fs_type = {
	212	.owner = THIS_MODULE,
	213	.name = "devpts",
	214	.get_sb = devpts_get_sb,
e76b7c01	215	.kill_sb = devpts_kill_sb,
1da177e4 LT	216	};
	217
	218	/*
	219	* The normal naming convention is simply /dev/pts/<number>; this conforms
	220	* to the System V naming convention
	221	*/
	222
15f1a633	223	int devpts_new_index(struct inode *ptmx_inode)
718a9163	224	{
e76b7c01 SB	225	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
e76b7c01 SB	226	struct pts_fs_info *fsi = DEVPTS_SB(sb);
718a9163	227	int index;
7ee7c12b	228	int ida_ret;
718a9163 SB	229
718a9163 SB	230	retry:
e76b7c01	231	if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) {
718a9163 SB	232	return -ENOMEM;
	233	}
	234
	235	mutex_lock(&allocated_ptys_lock);
e76b7c01	236	ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
7ee7c12b	237	if (ida_ret < 0) {
718a9163	238	mutex_unlock(&allocated_ptys_lock);
7ee7c12b	239	if (ida_ret == -EAGAIN)
718a9163 SB	240	goto retry;
	241	return -EIO;
	242	}
	243
	244	if (index >= pty_limit) {
e76b7c01	245	ida_remove(&fsi->allocated_ptys, index);
718a9163 SB	246	mutex_unlock(&allocated_ptys_lock);
	247	return -EIO;
	248	}
	249	mutex_unlock(&allocated_ptys_lock);
	250	return index;
	251	}
	252
15f1a633	253	void devpts_kill_index(struct inode *ptmx_inode, int idx)
718a9163	254	{
e76b7c01 SB	255	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	256	struct pts_fs_info *fsi = DEVPTS_SB(sb);
	257
718a9163	258	mutex_lock(&allocated_ptys_lock);
e76b7c01	259	ida_remove(&fsi->allocated_ptys, idx);
718a9163 SB	260	mutex_unlock(&allocated_ptys_lock);
	261	}
	262
15f1a633	263	int devpts_pty_new(struct inode ptmx_inode, struct tty_struct tty)
1da177e4	264	{
718a9163	265	int number = tty->index; /* tty layer puts index from devpts_new_index() in here */
1da177e4 LT	266	struct tty_driver *driver = tty->driver;
	267	dev_t device = MKDEV(driver->major, driver->minor_start+number);
	268	struct dentry *dentry;
59e55e6c SB	269	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
	270	struct inode *inode = new_inode(sb);
	271	struct dentry *root = sb->s_root;
31af0abb SB	272	struct pts_fs_info *fsi = DEVPTS_SB(sb);
31af0abb SB	273	struct pts_mount_opts *opts = &fsi->mount_opts;
89a52e10	274	char s[12];
1da177e4 LT	275
	276	/* We're supposed to be given the slave end of a pty */
	277	BUG_ON(driver->type != TTY_DRIVER_TYPE_PTY);
	278	BUG_ON(driver->subtype != PTY_TYPE_SLAVE);
	279
	280	if (!inode)
	281	return -ENOMEM;
	282
	283	inode->i_ino = number+2;
ec4c2aac DH	284	inode->i_uid = config.setuid ? config.uid : current_fsuid();
ec4c2aac DH	285	inode->i_gid = config.setgid ? config.gid : current_fsgid();
1da177e4	286	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
31af0abb	287	init_special_inode(inode, S_IFCHR\|opts->mode, device);
8e18e294	288	inode->i_private = tty;
a6f37daa	289	tty->driver_data = inode;
1da177e4	290
89a52e10 SB	291	sprintf(s, "%d", number);
89a52e10 SB	292
59e55e6c	293	mutex_lock(&root->d_inode->i_mutex);
89a52e10	294
59e55e6c	295	dentry = d_alloc_name(root, s);
89a52e10 SB	296	if (!IS_ERR(dentry)) {
89a52e10 SB	297	d_add(dentry, inode);
59e55e6c	298	fsnotify_create(root->d_inode, dentry);
3972b7f6	299	}
1da177e4	300
59e55e6c	301	mutex_unlock(&root->d_inode->i_mutex);
1da177e4 LT	302
	303	return 0;
	304	}
	305
15f1a633	306	struct tty_struct devpts_get_tty(struct inode pts_inode, int number)
1da177e4	307	{
527b3e47	308	BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
1da177e4	309
527b3e47 SB	310	if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
	311	return (struct tty_struct *)pts_inode->i_private;
	312	return NULL;
1da177e4 LT	313	}
1da177e4 LT	314
15f1a633	315	void devpts_pty_kill(struct tty_struct *tty)
1da177e4	316	{
a6f37daa	317	struct inode *inode = tty->driver_data;
59e55e6c SB	318	struct super_block *sb = pts_sb_from_inode(inode);
59e55e6c SB	319	struct dentry *root = sb->s_root;
a6f37daa	320	struct dentry *dentry;
1da177e4	321
a6f37daa SB	322	BUG_ON(inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
a6f37daa SB	323
59e55e6c	324	mutex_lock(&root->d_inode->i_mutex);
a6f37daa SB	325
	326	dentry = d_find_alias(inode);
	327	if (dentry && !IS_ERR(dentry)) {
	328	inode->i_nlink--;
	329	d_delete(dentry);
1da177e4 LT	330	dput(dentry);
1da177e4 LT	331	}
a6f37daa	332
59e55e6c	333	mutex_unlock(&root->d_inode->i_mutex);
1da177e4 LT	334	}
	335
	336	static int __init init_devpts_fs(void)
	337	{
	338	int err = register_filesystem(&devpts_fs_type);
	339	if (!err) {
	340	devpts_mnt = kern_mount(&devpts_fs_type);
	341	if (IS_ERR(devpts_mnt))
	342	err = PTR_ERR(devpts_mnt);
	343	}
	344	return err;
	345	}
	346
	347	static void __exit exit_devpts_fs(void)
	348	{
	349	unregister_filesystem(&devpts_fs_type);
	350	mntput(devpts_mnt);
	351	}
	352
	353	module_init(init_devpts_fs)
	354	module_exit(exit_devpts_fs)
	355	MODULE_LICENSE("GPL");