4eba07661e5c562b50462d8feee6982e39fe2c4b
[linux-2.6.git] / fs / fuse / control.c
1 /*
2   FUSE: Filesystem in Userspace
3   Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>
4
5   This program can be distributed under the terms of the GNU GPL.
6   See the file COPYING.
7 */
8
9 #include "fuse_i.h"
10
11 #include <linux/init.h>
12 #include <linux/module.h>
13
14 #define FUSE_CTL_SUPER_MAGIC 0x65735543
15
16 /*
17  * This is non-NULL when the single instance of the control filesystem
18  * exists.  Protected by fuse_mutex
19  */
20 static struct super_block *fuse_control_sb;
21
22 static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file)
23 {
24         struct fuse_conn *fc;
25         mutex_lock(&fuse_mutex);
26         fc = file->f_path.dentry->d_inode->i_private;
27         if (fc)
28                 fc = fuse_conn_get(fc);
29         mutex_unlock(&fuse_mutex);
30         return fc;
31 }
32
33 static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf,
34                                      size_t count, loff_t *ppos)
35 {
36         struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
37         if (fc) {
38                 fuse_abort_conn(fc);
39                 fuse_conn_put(fc);
40         }
41         return count;
42 }
43
44 static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
45                                       size_t len, loff_t *ppos)
46 {
47         char tmp[32];
48         size_t size;
49
50         if (!*ppos) {
51                 long value;
52                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
53                 if (!fc)
54                         return 0;
55
56                 value = atomic_read(&fc->num_waiting);
57                 file->private_data = (void *)value;
58                 fuse_conn_put(fc);
59         }
60         size = sprintf(tmp, "%ld\n", (long)file->private_data);
61         return simple_read_from_buffer(buf, len, ppos, tmp, size);
62 }
63
64 static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf,
65                                     size_t len, loff_t *ppos, unsigned val)
66 {
67         char tmp[32];
68         size_t size = sprintf(tmp, "%u\n", val);
69
70         return simple_read_from_buffer(buf, len, ppos, tmp, size);
71 }
72
73 static ssize_t fuse_conn_limit_write(struct file *file, const char __user *buf,
74                                      size_t count, loff_t *ppos, unsigned *val,
75                                      unsigned global_limit)
76 {
77         unsigned long t;
78         char tmp[32];
79         unsigned limit = (1 << 16) - 1;
80         int err;
81
82         if (*ppos || count >= sizeof(tmp) - 1)
83                 return -EINVAL;
84
85         if (copy_from_user(tmp, buf, count))
86                 return -EINVAL;
87
88         tmp[count] = '\0';
89
90         err = strict_strtoul(tmp, 0, &t);
91         if (err)
92                 return err;
93
94         if (!capable(CAP_SYS_ADMIN))
95                 limit = min(limit, global_limit);
96
97         if (t > limit)
98                 return -EINVAL;
99
100         *val = t;
101
102         return count;
103 }
104
105 static ssize_t fuse_conn_max_background_read(struct file *file,
106                                              char __user *buf, size_t len,
107                                              loff_t *ppos)
108 {
109         struct fuse_conn *fc;
110         unsigned val;
111
112         fc = fuse_ctl_file_conn_get(file);
113         if (!fc)
114                 return 0;
115
116         val = fc->max_background;
117         fuse_conn_put(fc);
118
119         return fuse_conn_limit_read(file, buf, len, ppos, val);
120 }
121
122 static ssize_t fuse_conn_max_background_write(struct file *file,
123                                               const char __user *buf,
124                                               size_t count, loff_t *ppos)
125 {
126         unsigned val;
127         ssize_t ret;
128
129         ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
130                                     max_user_bgreq);
131         if (ret > 0) {
132                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
133                 if (fc) {
134                         fc->max_background = val;
135                         fuse_conn_put(fc);
136                 }
137         }
138
139         return ret;
140 }
141
142 static ssize_t fuse_conn_congestion_threshold_read(struct file *file,
143                                                    char __user *buf, size_t len,
144                                                    loff_t *ppos)
145 {
146         struct fuse_conn *fc;
147         unsigned val;
148
149         fc = fuse_ctl_file_conn_get(file);
150         if (!fc)
151                 return 0;
152
153         val = fc->congestion_threshold;
154         fuse_conn_put(fc);
155
156         return fuse_conn_limit_read(file, buf, len, ppos, val);
157 }
158
159 static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
160                                                     const char __user *buf,
161                                                     size_t count, loff_t *ppos)
162 {
163         unsigned val;
164         ssize_t ret;
165
166         ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
167                                     max_user_congthresh);
168         if (ret > 0) {
169                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
170                 if (fc) {
171                         fc->congestion_threshold = val;
172                         fuse_conn_put(fc);
173                 }
174         }
175
176         return ret;
177 }
178
179 static const struct file_operations fuse_ctl_abort_ops = {
180         .open = nonseekable_open,
181         .write = fuse_conn_abort_write,
182         .llseek = no_llseek,
183 };
184
185 static const struct file_operations fuse_ctl_waiting_ops = {
186         .open = nonseekable_open,
187         .read = fuse_conn_waiting_read,
188         .llseek = no_llseek,
189 };
190
191 static const struct file_operations fuse_conn_max_background_ops = {
192         .open = nonseekable_open,
193         .read = fuse_conn_max_background_read,
194         .write = fuse_conn_max_background_write,
195         .llseek = no_llseek,
196 };
197
198 static const struct file_operations fuse_conn_congestion_threshold_ops = {
199         .open = nonseekable_open,
200         .read = fuse_conn_congestion_threshold_read,
201         .write = fuse_conn_congestion_threshold_write,
202         .llseek = no_llseek,
203 };
204
205 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
206                                           struct fuse_conn *fc,
207                                           const char *name,
208                                           int mode, int nlink,
209                                           const struct inode_operations *iop,
210                                           const struct file_operations *fop)
211 {
212         struct dentry *dentry;
213         struct inode *inode;
214
215         BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
216         dentry = d_alloc_name(parent, name);
217         if (!dentry)
218                 return NULL;
219
220         fc->ctl_dentry[fc->ctl_ndents++] = dentry;
221         inode = new_inode(fuse_control_sb);
222         if (!inode)
223                 return NULL;
224
225         inode->i_ino = get_next_ino();
226         inode->i_mode = mode;
227         inode->i_uid = fc->user_id;
228         inode->i_gid = fc->group_id;
229         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
230         /* setting ->i_op to NULL is not allowed */
231         if (iop)
232                 inode->i_op = iop;
233         inode->i_fop = fop;
234         inode->i_nlink = nlink;
235         inode->i_private = fc;
236         d_add(dentry, inode);
237         return dentry;
238 }
239
240 /*
241  * Add a connection to the control filesystem (if it exists).  Caller
242  * must hold fuse_mutex
243  */
244 int fuse_ctl_add_conn(struct fuse_conn *fc)
245 {
246         struct dentry *parent;
247         char name[32];
248
249         if (!fuse_control_sb)
250                 return 0;
251
252         parent = fuse_control_sb->s_root;
253         inc_nlink(parent->d_inode);
254         sprintf(name, "%u", fc->dev);
255         parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
256                                      &simple_dir_inode_operations,
257                                      &simple_dir_operations);
258         if (!parent)
259                 goto err;
260
261         if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
262                                  NULL, &fuse_ctl_waiting_ops) ||
263             !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
264                                  NULL, &fuse_ctl_abort_ops) ||
265             !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
266                                  1, NULL, &fuse_conn_max_background_ops) ||
267             !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
268                                  S_IFREG | 0600, 1, NULL,
269                                  &fuse_conn_congestion_threshold_ops))
270                 goto err;
271
272         return 0;
273
274  err:
275         fuse_ctl_remove_conn(fc);
276         return -ENOMEM;
277 }
278
279 /*
280  * Remove a connection from the control filesystem (if it exists).
281  * Caller must hold fuse_mutex
282  */
283 void fuse_ctl_remove_conn(struct fuse_conn *fc)
284 {
285         int i;
286
287         if (!fuse_control_sb)
288                 return;
289
290         for (i = fc->ctl_ndents - 1; i >= 0; i--) {
291                 struct dentry *dentry = fc->ctl_dentry[i];
292                 dentry->d_inode->i_private = NULL;
293                 d_drop(dentry);
294                 dput(dentry);
295         }
296         drop_nlink(fuse_control_sb->s_root->d_inode);
297 }
298
299 static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent)
300 {
301         struct tree_descr empty_descr = {""};
302         struct fuse_conn *fc;
303         int err;
304
305         err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
306         if (err)
307                 return err;
308
309         mutex_lock(&fuse_mutex);
310         BUG_ON(fuse_control_sb);
311         fuse_control_sb = sb;
312         list_for_each_entry(fc, &fuse_conn_list, entry) {
313                 err = fuse_ctl_add_conn(fc);
314                 if (err) {
315                         fuse_control_sb = NULL;
316                         mutex_unlock(&fuse_mutex);
317                         return err;
318                 }
319         }
320         mutex_unlock(&fuse_mutex);
321
322         return 0;
323 }
324
325 static int fuse_ctl_get_sb(struct file_system_type *fs_type, int flags,
326                         const char *dev_name, void *raw_data,
327                         struct vfsmount *mnt)
328 {
329         return get_sb_single(fs_type, flags, raw_data,
330                                 fuse_ctl_fill_super, mnt);
331 }
332
333 static void fuse_ctl_kill_sb(struct super_block *sb)
334 {
335         struct fuse_conn *fc;
336
337         mutex_lock(&fuse_mutex);
338         fuse_control_sb = NULL;
339         list_for_each_entry(fc, &fuse_conn_list, entry)
340                 fc->ctl_ndents = 0;
341         mutex_unlock(&fuse_mutex);
342
343         kill_litter_super(sb);
344 }
345
346 static struct file_system_type fuse_ctl_fs_type = {
347         .owner          = THIS_MODULE,
348         .name           = "fusectl",
349         .get_sb         = fuse_ctl_get_sb,
350         .kill_sb        = fuse_ctl_kill_sb,
351 };
352
353 int __init fuse_ctl_init(void)
354 {
355         return register_filesystem(&fuse_ctl_fs_type);
356 }
357
358 void fuse_ctl_cleanup(void)
359 {
360         unregister_filesystem(&fuse_ctl_fs_type);
361 }