~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/fs/filesystems.c

Version: ~ [ linux-5.2 ] ~ [ linux-5.1.16 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.57 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.132 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.184 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.184 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.69 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  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>
 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>
 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 
 46 static struct file_system_type **find_filesystem(const char *name, unsigned len)
 47 {
 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;
 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 
 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;
 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);
113                         synchronize_rcu();
114                         return 0;
115                 }
116                 tmp = &(*tmp)->next;
117         }
118         write_unlock(&file_systems_lock);
119 
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  */
184 SYSCALL_DEFINE3(sysfs, int, option, unsigned long, arg1, unsigned long, arg2)
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 
204 int __init get_filesystem_list(char *buf)
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 
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 
258 static struct file_system_type *__get_fs_type(const char *name, int len)
259 {
260         struct file_system_type *fs;
261 
262         read_lock(&file_systems_lock);
263         fs = *(find_filesystem(name, len));
264         if (fs && !try_module_get(fs->owner))
265                 fs = NULL;
266         read_unlock(&file_systems_lock);
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);
279 
280         if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
281                 put_filesystem(fs);
282                 fs = NULL;
283         }
284         return fs;
285 }
286 
287 EXPORT_SYMBOL(get_fs_type);
288 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp