2 * linux/fs/filesystems.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * table of configured filesystems
9 #include <linux/syscalls.h>
11 #include <linux/proc_fs.h>
12 #include <linux/seq_file.h>
13 #include <linux/kmod.h>
14 #include <linux/init.h>
15 #include <linux/module.h>
16 #include <linux/slab.h>
17 #include <linux/uaccess.h>
20 * Handling of filesystem drivers list.
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.
32 static struct file_system_type *file_systems;
33 static DEFINE_RWLOCK(file_systems_lock);
35 /* WARNING: This can be used only if we _already_ own a reference */
36 struct file_system_type *get_filesystem(struct file_system_type *fs)
38 __module_get(fs->owner);
42 void put_filesystem(struct file_system_type *fs)
44 module_put(fs->owner);
47 static struct file_system_type **find_filesystem(const char *name, unsigned len)
49 struct file_system_type **p;
50 for (p = &file_systems; *p; p = &(*p)->next)
51 if (strncmp((*p)->name, name, len) == 0 &&
58 * register_filesystem - register a new filesystem
59 * @fs: the file system structure
61 * Adds the file system passed to the list of file systems the kernel
62 * is aware of for mount and other syscalls. Returns 0 on success,
63 * or a negative errno code on an error.
65 * The &struct file_system_type that is passed is linked into the kernel
66 * structures and must not be freed until the file system has been
70 int register_filesystem(struct file_system_type * fs)
73 struct file_system_type ** p;
75 BUG_ON(strchr(fs->name, '.'));
78 write_lock(&file_systems_lock);
79 p = find_filesystem(fs->name, strlen(fs->name));
84 write_unlock(&file_systems_lock);
88 EXPORT_SYMBOL(register_filesystem);
91 * unregister_filesystem - unregister a file system
92 * @fs: filesystem to unregister
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.
98 * Once this function has returned the &struct file_system_type structure
99 * may be freed or reused.
102 int unregister_filesystem(struct file_system_type * fs)
104 struct file_system_type ** tmp;
106 write_lock(&file_systems_lock);
112 write_unlock(&file_systems_lock);
118 write_unlock(&file_systems_lock);
123 EXPORT_SYMBOL(unregister_filesystem);
125 #ifdef CONFIG_SYSFS_SYSCALL
126 static int fs_index(const char __user * __name)
128 struct file_system_type * tmp;
129 struct filename *name;
132 name = getname(__name);
138 read_lock(&file_systems_lock);
139 for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
140 if (strcmp(tmp->name, name->name) == 0) {
145 read_unlock(&file_systems_lock);
150 static int fs_name(unsigned int index, char __user * buf)
152 struct file_system_type * tmp;
155 read_lock(&file_systems_lock);
156 for (tmp = file_systems; tmp; tmp = tmp->next, index--)
157 if (index <= 0 && try_module_get(tmp->owner))
159 read_unlock(&file_systems_lock);
163 /* OK, we got the reference, so we can safely block */
164 len = strlen(tmp->name) + 1;
165 res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
170 static int fs_maxindex(void)
172 struct file_system_type * tmp;
175 read_lock(&file_systems_lock);
176 for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
178 read_unlock(&file_systems_lock);
183 * Whee.. Weird sysv syscall.
185 SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
187 int retval = -EINVAL;
191 retval = fs_index((const char __user *) arg1);
195 retval = fs_name(arg1, (char __user *) arg2);
199 retval = fs_maxindex();
206 int __init get_filesystem_list(char *buf)
209 struct file_system_type * tmp;
211 read_lock(&file_systems_lock);
213 while (tmp && len < PAGE_SIZE - 80) {
214 len += sprintf(buf+len, "%s\t%s\n",
215 (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
219 read_unlock(&file_systems_lock);
223 #ifdef CONFIG_PROC_FS
224 static int filesystems_proc_show(struct seq_file *m, void *v)
226 struct file_system_type * tmp;
228 read_lock(&file_systems_lock);
231 seq_printf(m, "%s\t%s\n",
232 (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
236 read_unlock(&file_systems_lock);
240 static int filesystems_proc_open(struct inode *inode, struct file *file)
242 return single_open(file, filesystems_proc_show, NULL);
245 static const struct file_operations filesystems_proc_fops = {
246 .open = filesystems_proc_open,
249 .release = single_release,
252 static int __init proc_filesystems_init(void)
254 proc_create("filesystems", 0, NULL, &filesystems_proc_fops);
257 module_init(proc_filesystems_init);
260 static struct file_system_type *__get_fs_type(const char *name, int len)
262 struct file_system_type *fs;
264 read_lock(&file_systems_lock);
265 fs = *(find_filesystem(name, len));
266 if (fs && !try_module_get(fs->owner))
268 read_unlock(&file_systems_lock);
272 struct file_system_type *get_fs_type(const char *name)
274 struct file_system_type *fs;
275 const char *dot = strchr(name, '.');
276 int len = dot ? dot - name : strlen(name);
278 fs = __get_fs_type(name, len);
279 if (!fs && (request_module("fs-%.*s", len, name) == 0)) {
280 fs = __get_fs_type(name, len);
281 WARN_ONCE(!fs, "request_module fs-%.*s succeeded, but still no fs?\n", len, name);
284 if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
291 EXPORT_SYMBOL(get_fs_type);