ARM: pm: convert sa11x0 to generic suspend/resume support
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / filesystems.c
blob751d6b255a12ab1abcf71e817f80f4ce11bbd647
1 /*
2 * linux/fs/filesystems.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * table of configured filesystems
7 */
9 #include <linux/syscalls.h>
10 #include <linux/fs.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 <asm/uaccess.h>
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.
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 void get_filesystem(struct file_system_type *fs)
38 __module_get(fs->owner);
41 void put_filesystem(struct file_system_type *fs)
43 module_put(fs->owner);
46 static struct file_system_type **find_filesystem(const char *name, unsigned len)
48 struct file_system_type **p;
49 for (p=&file_systems; *p; p=&(*p)->next)
50 if (strlen((*p)->name) == len &&
51 strncmp((*p)->name, name, len) == 0)
52 break;
53 return p;
56 /**
57 * register_filesystem - register a new filesystem
58 * @fs: the file system structure
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.
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.
69 int register_filesystem(struct file_system_type * fs)
71 int res = 0;
72 struct file_system_type ** p;
74 BUG_ON(strchr(fs->name, '.'));
75 if (fs->next)
76 return -EBUSY;
77 INIT_LIST_HEAD(&fs->fs_supers);
78 write_lock(&file_systems_lock);
79 p = find_filesystem(fs->name, strlen(fs->name));
80 if (*p)
81 res = -EBUSY;
82 else
83 *p = fs;
84 write_unlock(&file_systems_lock);
85 return res;
88 EXPORT_SYMBOL(register_filesystem);
90 /**
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);
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);
113 return 0;
115 tmp = &(*tmp)->next;
117 write_unlock(&file_systems_lock);
119 synchronize_rcu();
121 return -EINVAL;
124 EXPORT_SYMBOL(unregister_filesystem);
126 static int fs_index(const char __user * __name)
128 struct file_system_type * tmp;
129 char * name;
130 int err, index;
132 name = getname(__name);
133 err = PTR_ERR(name);
134 if (IS_ERR(name))
135 return err;
137 err = -EINVAL;
138 read_lock(&file_systems_lock);
139 for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
140 if (strcmp(tmp->name,name) == 0) {
141 err = index;
142 break;
145 read_unlock(&file_systems_lock);
146 putname(name);
147 return err;
150 static int fs_name(unsigned int index, char __user * buf)
152 struct file_system_type * tmp;
153 int len, res;
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))
158 break;
159 read_unlock(&file_systems_lock);
160 if (!tmp)
161 return -EINVAL;
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;
166 put_filesystem(tmp);
167 return res;
170 static int fs_maxindex(void)
172 struct file_system_type * tmp;
173 int index;
175 read_lock(&file_systems_lock);
176 for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
178 read_unlock(&file_systems_lock);
179 return index;
183 * Whee.. Weird sysv syscall.
185 SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
187 int retval = -EINVAL;
189 switch (option) {
190 case 1:
191 retval = fs_index((const char __user *) arg1);
192 break;
194 case 2:
195 retval = fs_name(arg1, (char __user *) arg2);
196 break;
198 case 3:
199 retval = fs_maxindex();
200 break;
202 return retval;
205 int __init get_filesystem_list(char *buf)
207 int len = 0;
208 struct file_system_type * tmp;
210 read_lock(&file_systems_lock);
211 tmp = file_systems;
212 while (tmp && len < PAGE_SIZE - 80) {
213 len += sprintf(buf+len, "%s\t%s\n",
214 (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
215 tmp->name);
216 tmp = tmp->next;
218 read_unlock(&file_systems_lock);
219 return len;
222 #ifdef CONFIG_PROC_FS
223 static int filesystems_proc_show(struct seq_file *m, void *v)
225 struct file_system_type * tmp;
227 read_lock(&file_systems_lock);
228 tmp = file_systems;
229 while (tmp) {
230 seq_printf(m, "%s\t%s\n",
231 (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
232 tmp->name);
233 tmp = tmp->next;
235 read_unlock(&file_systems_lock);
236 return 0;
239 static int filesystems_proc_open(struct inode *inode, struct file *file)
241 return single_open(file, filesystems_proc_show, NULL);
244 static const struct file_operations filesystems_proc_fops = {
245 .open = filesystems_proc_open,
246 .read = seq_read,
247 .llseek = seq_lseek,
248 .release = single_release,
251 static int __init proc_filesystems_init(void)
253 proc_create("filesystems", 0, NULL, &filesystems_proc_fops);
254 return 0;
256 module_init(proc_filesystems_init);
257 #endif
259 static struct file_system_type *__get_fs_type(const char *name, int len)
261 struct file_system_type *fs;
263 read_lock(&file_systems_lock);
264 fs = *(find_filesystem(name, len));
265 if (fs && !try_module_get(fs->owner))
266 fs = NULL;
267 read_unlock(&file_systems_lock);
268 return fs;
271 struct file_system_type *get_fs_type(const char *name)
273 struct file_system_type *fs;
274 const char *dot = strchr(name, '.');
275 int len = dot ? dot - name : strlen(name);
277 fs = __get_fs_type(name, len);
278 if (!fs && (request_module("%.*s", len, name) == 0))
279 fs = __get_fs_type(name, len);
281 if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
282 put_filesystem(fs);
283 fs = NULL;
285 return fs;
288 EXPORT_SYMBOL(get_fs_type);