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1da177e Linux-2.6.12-rc2
Linus Torvalds authored
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>
6827400 proc: move /proc/filesystems to fs/filesystems.c
Alexey Dobriyan authored
11 #include <linux/proc_fs.h>
12 #include <linux/seq_file.h>
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
13 #include <linux/kmod.h>
14 #include <linux/init.h>
15 #include <linux/module.h>
5a0e3ad include cleanup: Update gfp.h and slab.h includes to prepare for brea…
Tejun Heo authored
16 #include <linux/slab.h>
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
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
79c0b2d add filesystem subtype support
Miklos Szeredi authored
46 static struct file_system_type **find_filesystem(const char *name, unsigned len)
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
47 {
48 struct file_system_type **p;
49 for (p=&file_systems; *p; p=&(*p)->next)
79c0b2d add filesystem subtype support
Miklos Szeredi authored
50 if (strlen((*p)->name) == len &&
51 strncmp((*p)->name, name, len) == 0)
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
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
79c0b2d add filesystem subtype support
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74 BUG_ON(strchr(fs->name, '.'));
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
75 if (fs->next)
76 return -EBUSY;
77 write_lock(&file_systems_lock);
79c0b2d add filesystem subtype support
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78 p = find_filesystem(fs->name, strlen(fs->name));
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
79 if (*p)
80 res = -EBUSY;
81 else
82 *p = fs;
83 write_unlock(&file_systems_lock);
84 return res;
85 }
86
87 EXPORT_SYMBOL(register_filesystem);
88
89 /**
90 * unregister_filesystem - unregister a file system
91 * @fs: filesystem to unregister
92 *
93 * Remove a file system that was previously successfully registered
94 * with the kernel. An error is returned if the file system is not found.
95 * Zero is returned on a success.
96 *
97 * Once this function has returned the &struct file_system_type structure
98 * may be freed or reused.
99 */
100
101 int unregister_filesystem(struct file_system_type * fs)
102 {
103 struct file_system_type ** tmp;
104
105 write_lock(&file_systems_lock);
106 tmp = &file_systems;
107 while (*tmp) {
108 if (fs == *tmp) {
109 *tmp = fs->next;
110 fs->next = NULL;
111 write_unlock(&file_systems_lock);
fff3e5a fs: synchronize_rcu when unregister_filesystem success not failure
Milton Miller authored
112 synchronize_rcu();
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
113 return 0;
114 }
115 tmp = &(*tmp)->next;
116 }
117 write_unlock(&file_systems_lock);
31e6b01 fs: rcu-walk for path lookup
Nick Piggin authored
118
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
119 return -EINVAL;
120 }
121
122 EXPORT_SYMBOL(unregister_filesystem);
123
124 static int fs_index(const char __user * __name)
125 {
126 struct file_system_type * tmp;
127 char * name;
128 int err, index;
129
130 name = getname(__name);
131 err = PTR_ERR(name);
132 if (IS_ERR(name))
133 return err;
134
135 err = -EINVAL;
136 read_lock(&file_systems_lock);
137 for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
138 if (strcmp(tmp->name,name) == 0) {
139 err = index;
140 break;
141 }
142 }
143 read_unlock(&file_systems_lock);
144 putname(name);
145 return err;
146 }
147
148 static int fs_name(unsigned int index, char __user * buf)
149 {
150 struct file_system_type * tmp;
151 int len, res;
152
153 read_lock(&file_systems_lock);
154 for (tmp = file_systems; tmp; tmp = tmp->next, index--)
155 if (index <= 0 && try_module_get(tmp->owner))
156 break;
157 read_unlock(&file_systems_lock);
158 if (!tmp)
159 return -EINVAL;
160
161 /* OK, we got the reference, so we can safely block */
162 len = strlen(tmp->name) + 1;
163 res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
164 put_filesystem(tmp);
165 return res;
166 }
167
168 static int fs_maxindex(void)
169 {
170 struct file_system_type * tmp;
171 int index;
172
173 read_lock(&file_systems_lock);
174 for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
175 ;
176 read_unlock(&file_systems_lock);
177 return index;
178 }
179
180 /*
181 * Whee.. Weird sysv syscall.
182 */
1e7bfb2 [CVE-2009-0029] System call wrappers part 27
Heiko Carstens authored
183 SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
184 {
185 int retval = -EINVAL;
186
187 switch (option) {
188 case 1:
189 retval = fs_index((const char __user *) arg1);
190 break;
191
192 case 2:
193 retval = fs_name(arg1, (char __user *) arg2);
194 break;
195
196 case 3:
197 retval = fs_maxindex();
198 break;
199 }
200 return retval;
201 }
202
38e23c9 fs: Mark get_filesystem_list() as __init function.
Tetsuo Handa authored
203 int __init get_filesystem_list(char *buf)
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
204 {
205 int len = 0;
206 struct file_system_type * tmp;
207
208 read_lock(&file_systems_lock);
209 tmp = file_systems;
210 while (tmp && len < PAGE_SIZE - 80) {
211 len += sprintf(buf+len, "%s\t%s\n",
212 (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
213 tmp->name);
214 tmp = tmp->next;
215 }
216 read_unlock(&file_systems_lock);
217 return len;
218 }
219
6827400 proc: move /proc/filesystems to fs/filesystems.c
Alexey Dobriyan authored
220 #ifdef CONFIG_PROC_FS
221 static int filesystems_proc_show(struct seq_file *m, void *v)
222 {
223 struct file_system_type * tmp;
224
225 read_lock(&file_systems_lock);
226 tmp = file_systems;
227 while (tmp) {
228 seq_printf(m, "%s\t%s\n",
229 (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
230 tmp->name);
231 tmp = tmp->next;
232 }
233 read_unlock(&file_systems_lock);
234 return 0;
235 }
236
237 static int filesystems_proc_open(struct inode *inode, struct file *file)
238 {
239 return single_open(file, filesystems_proc_show, NULL);
240 }
241
242 static const struct file_operations filesystems_proc_fops = {
243 .open = filesystems_proc_open,
244 .read = seq_read,
245 .llseek = seq_lseek,
246 .release = single_release,
247 };
248
249 static int __init proc_filesystems_init(void)
250 {
251 proc_create("filesystems", 0, NULL, &filesystems_proc_fops);
252 return 0;
253 }
254 module_init(proc_filesystems_init);
255 #endif
256
d8e9650 vfs: remove duplicate code in get_fs_type()
Li Zefan authored
257 static struct file_system_type *__get_fs_type(const char *name, int len)
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
258 {
259 struct file_system_type *fs;
260
261 read_lock(&file_systems_lock);
79c0b2d add filesystem subtype support
Miklos Szeredi authored
262 fs = *(find_filesystem(name, len));
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
263 if (fs && !try_module_get(fs->owner))
264 fs = NULL;
265 read_unlock(&file_systems_lock);
d8e9650 vfs: remove duplicate code in get_fs_type()
Li Zefan authored
266 return fs;
267 }
268
269 struct file_system_type *get_fs_type(const char *name)
270 {
271 struct file_system_type *fs;
272 const char *dot = strchr(name, '.');
273 int len = dot ? dot - name : strlen(name);
274
275 fs = __get_fs_type(name, len);
276 if (!fs && (request_module("%.*s", len, name) == 0))
277 fs = __get_fs_type(name, len);
79c0b2d add filesystem subtype support
Miklos Szeredi authored
278
279 if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
280 put_filesystem(fs);
281 fs = NULL;
282 }
1da177e Linux-2.6.12-rc2
Linus Torvalds authored
283 return fs;
284 }
285
286 EXPORT_SYMBOL(get_fs_type);
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