[linux.git] / fs / filesystems.c

/*
 *  linux/fs/filesystems.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  table of configured filesystems
 */

#include <linux/syscalls.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/kmod.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <asm/uaccess.h>

/*
 * Handling of filesystem drivers list.
 * Rules:
 *	Inclusion to/removals from/scanning of list are protected by spinlock.
 *	During the unload module must call unregister_filesystem().
 *	We can access the fields of list element if:
 *		1) spinlock is held or
 *		2) we hold the reference to the module.
 *	The latter can be guaranteed by call of try_module_get(); if it
 *	returned 0 we must skip the element, otherwise we got the reference.
 *	Once the reference is obtained we can drop the spinlock.
 */

static struct file_system_type *file_systems;
static DEFINE_RWLOCK(file_systems_lock);

/* WARNING: This can be used only if we _already_ own a reference */
void get_filesystem(struct file_system_type *fs)
{
	__module_get(fs->owner);
}

void put_filesystem(struct file_system_type *fs)
{
	module_put(fs->owner);
}

static struct file_system_type **find_filesystem(const char *name, unsigned len)
{
	struct file_system_type **p;
	for (p=&file_systems; *p; p=&(*p)->next)
		if (strlen((*p)->name) == len &&
		    strncmp((*p)->name, name, len) == 0)
			break;
	return p;
}

/**
 *	register_filesystem - register a new filesystem
 *	@fs: the file system structure
 *
 *	Adds the file system passed to the list of file systems the kernel
 *	is aware of for mount and other syscalls. Returns 0 on success,
 *	or a negative errno code on an error.
 *
 *	The &struct file_system_type that is passed is linked into the kernel 
 *	structures and must not be freed until the file system has been
 *	unregistered.
 */
 
int register_filesystem(struct file_system_type * fs)
{
	int res = 0;
	struct file_system_type ** p;

	BUG_ON(strchr(fs->name, '.'));
	if (fs->next)
		return -EBUSY;
	INIT_LIST_HEAD(&fs->fs_supers);
	write_lock(&file_systems_lock);
	p = find_filesystem(fs->name, strlen(fs->name));
	if (*p)
		res = -EBUSY;
	else
		*p = fs;
	write_unlock(&file_systems_lock);
	return res;
}

EXPORT_SYMBOL(register_filesystem);

/**
 *	unregister_filesystem - unregister a file system
 *	@fs: filesystem to unregister
 *
 *	Remove a file system that was previously successfully registered
 *	with the kernel. An error is returned if the file system is not found.
 *	Zero is returned on a success.
 *	
 *	Once this function has returned the &struct file_system_type structure
 *	may be freed or reused.
 */
 
int unregister_filesystem(struct file_system_type * fs)
{
	struct file_system_type ** tmp;

	write_lock(&file_systems_lock);
	tmp = &file_systems;
	while (*tmp) {
		if (fs == *tmp) {
			*tmp = fs->next;
			fs->next = NULL;
			write_unlock(&file_systems_lock);
			synchronize_rcu();
			return 0;
		}
		tmp = &(*tmp)->next;
	}
	write_unlock(&file_systems_lock);

	return -EINVAL;
}

EXPORT_SYMBOL(unregister_filesystem);

static int fs_index(const char __user * __name)
{
	struct file_system_type * tmp;
	char * name;
	int err, index;

	name = getname(__name);
	err = PTR_ERR(name);
	if (IS_ERR(name))
		return err;

	err = -EINVAL;
	read_lock(&file_systems_lock);
	for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
		if (strcmp(tmp->name,name) == 0) {
			err = index;
			break;
		}
	}
	read_unlock(&file_systems_lock);
	putname(name);
	return err;
}

static int fs_name(unsigned int index, char __user * buf)
{
	struct file_system_type * tmp;
	int len, res;

	read_lock(&file_systems_lock);
	for (tmp = file_systems; tmp; tmp = tmp->next, index--)
		if (index <= 0 && try_module_get(tmp->owner))
			break;
	read_unlock(&file_systems_lock);
	if (!tmp)
		return -EINVAL;

	/* OK, we got the reference, so we can safely block */
	len = strlen(tmp->name) + 1;
	res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
	put_filesystem(tmp);
	return res;
}

static int fs_maxindex(void)
{
	struct file_system_type * tmp;
	int index;

	read_lock(&file_systems_lock);
	for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
		;
	read_unlock(&file_systems_lock);
	return index;
}

/*
 * Whee.. Weird sysv syscall. 
 */
SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
{
	int retval = -EINVAL;

	switch (option) {
		case 1:
			retval = fs_index((const char __user *) arg1);
			break;

		case 2:
			retval = fs_name(arg1, (char __user *) arg2);
			break;

		case 3:
			retval = fs_maxindex();
			break;
	}
	return retval;
}

int __init get_filesystem_list(char *buf)
{
	int len = 0;
	struct file_system_type * tmp;

	read_lock(&file_systems_lock);
	tmp = file_systems;
	while (tmp && len < PAGE_SIZE - 80) {
		len += sprintf(buf+len, "%s\t%s\n",
			(tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
			tmp->name);
		tmp = tmp->next;
	}
	read_unlock(&file_systems_lock);
	return len;
}

#ifdef CONFIG_PROC_FS
static int filesystems_proc_show(struct seq_file *m, void *v)
{
	struct file_system_type * tmp;

	read_lock(&file_systems_lock);
	tmp = file_systems;
	while (tmp) {
		seq_printf(m, "%s\t%s\n",
			(tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
			tmp->name);
		tmp = tmp->next;
	}
	read_unlock(&file_systems_lock);
	return 0;
}

static int filesystems_proc_open(struct inode *inode, struct file *file)
{
	return single_open(file, filesystems_proc_show, NULL);
}

static const struct file_operations filesystems_proc_fops = {
	.open		= filesystems_proc_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static int __init proc_filesystems_init(void)
{
	proc_create("filesystems", 0, NULL, &filesystems_proc_fops);
	return 0;
}
module_init(proc_filesystems_init);
#endif

static struct file_system_type *__get_fs_type(const char *name, int len)
{
	struct file_system_type *fs;

	read_lock(&file_systems_lock);
	fs = *(find_filesystem(name, len));
	if (fs && !try_module_get(fs->owner))
		fs = NULL;
	read_unlock(&file_systems_lock);
	return fs;
}

struct file_system_type *get_fs_type(const char *name)
{
	struct file_system_type *fs;
	const char *dot = strchr(name, '.');
	int len = dot ? dot - name : strlen(name);

	fs = __get_fs_type(name, len);
	if (!fs && (request_module("%.*s", len, name) == 0))
		fs = __get_fs_type(name, len);

	if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
		put_filesystem(fs);
		fs = NULL;
	}
	return fs;
}

EXPORT_SYMBOL(get_fs_type);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/fs/filesystems.c
	3	*
	4	* Copyright (C) 1991, 1992 Linus Torvalds
	5	*
	6	* table of configured filesystems
	7	*/
	8
	9	#include <linux/syscalls.h>
	10	#include <linux/fs.h>
68274007 AD	11	#include <linux/proc_fs.h>
68274007 AD	12	#include <linux/seq_file.h>
1da177e4 LT	13	#include <linux/kmod.h>
	14	#include <linux/init.h>
	15	#include <linux/module.h>
5a0e3ad6	16	#include <linux/slab.h>
1da177e4 LT	17	#include <asm/uaccess.h>
	18
	19	/*
	20	* Handling of filesystem drivers list.
	21	* Rules:
	22	* Inclusion to/removals from/scanning of list are protected by spinlock.
	23	* During the unload module must call unregister_filesystem().
	24	* We can access the fields of list element if:
	25	* 1) spinlock is held or
	26	* 2) we hold the reference to the module.
	27	* The latter can be guaranteed by call of try_module_get(); if it
	28	* returned 0 we must skip the element, otherwise we got the reference.
	29	* Once the reference is obtained we can drop the spinlock.
	30	*/
	31
	32	static struct file_system_type *file_systems;
	33	static DEFINE_RWLOCK(file_systems_lock);
	34
	35	/* WARNING: This can be used only if we _already_ own a reference */
	36	void get_filesystem(struct file_system_type *fs)
	37	{
	38	__module_get(fs->owner);
	39	}
	40
	41	void put_filesystem(struct file_system_type *fs)
	42	{
	43	module_put(fs->owner);
	44	}
	45
79c0b2df	46	static struct file_system_type *find_filesystem(const char name, unsigned len)
1da177e4 LT	47	{
	48	struct file_system_type **p;
	49	for (p=&file_systems; p; p=&(p)->next)
79c0b2df MS	50	if (strlen((*p)->name) == len &&
79c0b2df MS	51	strncmp((*p)->name, name, len) == 0)
1da177e4 LT	52	break;
	53	return p;
	54	}
	55
	56	/**
	57	* register_filesystem - register a new filesystem
	58	* @fs: the file system structure
	59	*
	60	* Adds the file system passed to the list of file systems the kernel
	61	* is aware of for mount and other syscalls. Returns 0 on success,
	62	* or a negative errno code on an error.
	63	*
	64	* The &struct file_system_type that is passed is linked into the kernel
	65	* structures and must not be freed until the file system has been
	66	* unregistered.
	67	*/
	68
	69	int register_filesystem(struct file_system_type * fs)
	70	{
	71	int res = 0;
	72	struct file_system_type ** p;
	73
79c0b2df	74	BUG_ON(strchr(fs->name, '.'));
1da177e4 LT	75	if (fs->next)
	76	return -EBUSY;
	77	INIT_LIST_HEAD(&fs->fs_supers);
	78	write_lock(&file_systems_lock);
79c0b2df	79	p = find_filesystem(fs->name, strlen(fs->name));
1da177e4 LT	80	if (*p)
	81	res = -EBUSY;
	82	else
	83	*p = fs;
	84	write_unlock(&file_systems_lock);
	85	return res;
	86	}
	87
	88	EXPORT_SYMBOL(register_filesystem);
	89
	90	/**
	91	* unregister_filesystem - unregister a file system
	92	* @fs: filesystem to unregister
	93	*
	94	* Remove a file system that was previously successfully registered
	95	* with the kernel. An error is returned if the file system is not found.
	96	* Zero is returned on a success.
	97	*
	98	* Once this function has returned the &struct file_system_type structure
	99	* may be freed or reused.
	100	*/
	101
	102	int unregister_filesystem(struct file_system_type * fs)
	103	{
	104	struct file_system_type ** tmp;
	105
	106	write_lock(&file_systems_lock);
	107	tmp = &file_systems;
	108	while (*tmp) {
	109	if (fs == *tmp) {
	110	*tmp = fs->next;
	111	fs->next = NULL;
	112	write_unlock(&file_systems_lock);
fff3e5ad	113	synchronize_rcu();
1da177e4 LT	114	return 0;
	115	}
	116	tmp = &(*tmp)->next;
	117	}
	118	write_unlock(&file_systems_lock);
31e6b01f	119
1da177e4 LT	120	return -EINVAL;
	121	}
	122
	123	EXPORT_SYMBOL(unregister_filesystem);
	124
	125	static int fs_index(const char __user * __name)
	126	{
	127	struct file_system_type * tmp;
	128	char * name;
	129	int err, index;
	130
	131	name = getname(__name);
	132	err = PTR_ERR(name);
	133	if (IS_ERR(name))
	134	return err;
	135
	136	err = -EINVAL;
	137	read_lock(&file_systems_lock);
	138	for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
	139	if (strcmp(tmp->name,name) == 0) {
	140	err = index;
	141	break;
	142	}
	143	}
	144	read_unlock(&file_systems_lock);
	145	putname(name);
	146	return err;
	147	}
	148
	149	static int fs_name(unsigned int index, char __user * buf)
	150	{
	151	struct file_system_type * tmp;
	152	int len, res;
	153
	154	read_lock(&file_systems_lock);
	155	for (tmp = file_systems; tmp; tmp = tmp->next, index--)
	156	if (index <= 0 && try_module_get(tmp->owner))
	157	break;
	158	read_unlock(&file_systems_lock);
	159	if (!tmp)
	160	return -EINVAL;
	161
	162	/* OK, we got the reference, so we can safely block */
	163	len = strlen(tmp->name) + 1;
	164	res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
	165	put_filesystem(tmp);
	166	return res;
	167	}
	168
	169	static int fs_maxindex(void)
	170	{
	171	struct file_system_type * tmp;
	172	int index;
	173
	174	read_lock(&file_systems_lock);
	175	for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
	176	;
	177	read_unlock(&file_systems_lock);
	178	return index;
	179	}
	180
	181	/*
	182	* Whee.. Weird sysv syscall.
	183	*/
1e7bfb21	184	SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
1da177e4 LT	185	{
	186	int retval = -EINVAL;
	187
	188	switch (option) {
	189	case 1:
	190	retval = fs_index((const char __user *) arg1);
	191	break;
	192
	193	case 2:
	194	retval = fs_name(arg1, (char __user *) arg2);
	195	break;
	196
	197	case 3:
	198	retval = fs_maxindex();
	199	break;
	200	}
	201	return retval;
	202	}
	203
38e23c95	204	int __init get_filesystem_list(char *buf)
1da177e4 LT	205	{
	206	int len = 0;
	207	struct file_system_type * tmp;
	208
	209	read_lock(&file_systems_lock);
	210	tmp = file_systems;
	211	while (tmp && len < PAGE_SIZE - 80) {
	212	len += sprintf(buf+len, "%s\t%s\n",
	213	(tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
	214	tmp->name);
	215	tmp = tmp->next;
	216	}
	217	read_unlock(&file_systems_lock);
	218	return len;
	219	}
	220
68274007 AD	221	#ifdef CONFIG_PROC_FS
	222	static int filesystems_proc_show(struct seq_file m, void v)
	223	{
	224	struct file_system_type * tmp;
	225
	226	read_lock(&file_systems_lock);
	227	tmp = file_systems;
	228	while (tmp) {
	229	seq_printf(m, "%s\t%s\n",
	230	(tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
	231	tmp->name);
	232	tmp = tmp->next;
	233	}
	234	read_unlock(&file_systems_lock);
	235	return 0;
	236	}
	237
	238	static int filesystems_proc_open(struct inode inode, struct file file)
	239	{
	240	return single_open(file, filesystems_proc_show, NULL);
	241	}
	242
	243	static const struct file_operations filesystems_proc_fops = {
	244	.open = filesystems_proc_open,
	245	.read = seq_read,
	246	.llseek = seq_lseek,
	247	.release = single_release,
	248	};
	249
	250	static int __init proc_filesystems_init(void)
	251	{
	252	proc_create("filesystems", 0, NULL, &filesystems_proc_fops);
	253	return 0;
	254	}
	255	module_init(proc_filesystems_init);
	256	#endif
	257
d8e9650d	258	static struct file_system_type __get_fs_type(const char name, int len)
1da177e4 LT	259	{
	260	struct file_system_type *fs;
	261
	262	read_lock(&file_systems_lock);
79c0b2df	263	fs = *(find_filesystem(name, len));
1da177e4 LT	264	if (fs && !try_module_get(fs->owner))
	265	fs = NULL;
	266	read_unlock(&file_systems_lock);
d8e9650d LZ	267	return fs;
	268	}
	269
	270	struct file_system_type get_fs_type(const char name)
	271	{
	272	struct file_system_type *fs;
	273	const char *dot = strchr(name, '.');
	274	int len = dot ? dot - name : strlen(name);
	275
	276	fs = __get_fs_type(name, len);
	277	if (!fs && (request_module("%.*s", len, name) == 0))
	278	fs = __get_fs_type(name, len);
79c0b2df MS	279
	280	if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
	281	put_filesystem(fs);
	282	fs = NULL;
	283	}
1da177e4 LT	284	return fs;
	285	}
	286
	287	EXPORT_SYMBOL(get_fs_type);