GNU Linux-libre 6.1.86-gnu
[releases.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 #include <linux/fs_context.h>
14
15 #define FUSE_CTL_SUPER_MAGIC 0x65735543
16
17 /*
18  * This is non-NULL when the single instance of the control filesystem
19  * exists.  Protected by fuse_mutex
20  */
21 static struct super_block *fuse_control_sb;
22
23 static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file)
24 {
25         struct fuse_conn *fc;
26         mutex_lock(&fuse_mutex);
27         fc = file_inode(file)->i_private;
28         if (fc)
29                 fc = fuse_conn_get(fc);
30         mutex_unlock(&fuse_mutex);
31         return fc;
32 }
33
34 static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf,
35                                      size_t count, loff_t *ppos)
36 {
37         struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
38         if (fc) {
39                 if (fc->abort_err)
40                         fc->aborted = true;
41                 fuse_abort_conn(fc);
42                 fuse_conn_put(fc);
43         }
44         return count;
45 }
46
47 static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
48                                       size_t len, loff_t *ppos)
49 {
50         char tmp[32];
51         size_t size;
52
53         if (!*ppos) {
54                 long value;
55                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
56                 if (!fc)
57                         return 0;
58
59                 value = atomic_read(&fc->num_waiting);
60                 file->private_data = (void *)value;
61                 fuse_conn_put(fc);
62         }
63         size = sprintf(tmp, "%ld\n", (long)file->private_data);
64         return simple_read_from_buffer(buf, len, ppos, tmp, size);
65 }
66
67 static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf,
68                                     size_t len, loff_t *ppos, unsigned val)
69 {
70         char tmp[32];
71         size_t size = sprintf(tmp, "%u\n", val);
72
73         return simple_read_from_buffer(buf, len, ppos, tmp, size);
74 }
75
76 static ssize_t fuse_conn_limit_write(struct file *file, const char __user *buf,
77                                      size_t count, loff_t *ppos, unsigned *val,
78                                      unsigned global_limit)
79 {
80         unsigned long t;
81         unsigned limit = (1 << 16) - 1;
82         int err;
83
84         if (*ppos)
85                 return -EINVAL;
86
87         err = kstrtoul_from_user(buf, count, 0, &t);
88         if (err)
89                 return err;
90
91         if (!capable(CAP_SYS_ADMIN))
92                 limit = min(limit, global_limit);
93
94         if (t > limit)
95                 return -EINVAL;
96
97         *val = t;
98
99         return count;
100 }
101
102 static ssize_t fuse_conn_max_background_read(struct file *file,
103                                              char __user *buf, size_t len,
104                                              loff_t *ppos)
105 {
106         struct fuse_conn *fc;
107         unsigned val;
108
109         fc = fuse_ctl_file_conn_get(file);
110         if (!fc)
111                 return 0;
112
113         val = READ_ONCE(fc->max_background);
114         fuse_conn_put(fc);
115
116         return fuse_conn_limit_read(file, buf, len, ppos, val);
117 }
118
119 static ssize_t fuse_conn_max_background_write(struct file *file,
120                                               const char __user *buf,
121                                               size_t count, loff_t *ppos)
122 {
123         unsigned val;
124         ssize_t ret;
125
126         ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
127                                     max_user_bgreq);
128         if (ret > 0) {
129                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
130                 if (fc) {
131                         spin_lock(&fc->bg_lock);
132                         fc->max_background = val;
133                         fc->blocked = fc->num_background >= fc->max_background;
134                         if (!fc->blocked)
135                                 wake_up(&fc->blocked_waitq);
136                         spin_unlock(&fc->bg_lock);
137                         fuse_conn_put(fc);
138                 }
139         }
140
141         return ret;
142 }
143
144 static ssize_t fuse_conn_congestion_threshold_read(struct file *file,
145                                                    char __user *buf, size_t len,
146                                                    loff_t *ppos)
147 {
148         struct fuse_conn *fc;
149         unsigned val;
150
151         fc = fuse_ctl_file_conn_get(file);
152         if (!fc)
153                 return 0;
154
155         val = READ_ONCE(fc->congestion_threshold);
156         fuse_conn_put(fc);
157
158         return fuse_conn_limit_read(file, buf, len, ppos, val);
159 }
160
161 static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
162                                                     const char __user *buf,
163                                                     size_t count, loff_t *ppos)
164 {
165         unsigned val;
166         struct fuse_conn *fc;
167         ssize_t ret;
168
169         ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
170                                     max_user_congthresh);
171         if (ret <= 0)
172                 goto out;
173         fc = fuse_ctl_file_conn_get(file);
174         if (!fc)
175                 goto out;
176
177         down_read(&fc->killsb);
178         spin_lock(&fc->bg_lock);
179         fc->congestion_threshold = val;
180         spin_unlock(&fc->bg_lock);
181         up_read(&fc->killsb);
182         fuse_conn_put(fc);
183 out:
184         return ret;
185 }
186
187 static const struct file_operations fuse_ctl_abort_ops = {
188         .open = nonseekable_open,
189         .write = fuse_conn_abort_write,
190         .llseek = no_llseek,
191 };
192
193 static const struct file_operations fuse_ctl_waiting_ops = {
194         .open = nonseekable_open,
195         .read = fuse_conn_waiting_read,
196         .llseek = no_llseek,
197 };
198
199 static const struct file_operations fuse_conn_max_background_ops = {
200         .open = nonseekable_open,
201         .read = fuse_conn_max_background_read,
202         .write = fuse_conn_max_background_write,
203         .llseek = no_llseek,
204 };
205
206 static const struct file_operations fuse_conn_congestion_threshold_ops = {
207         .open = nonseekable_open,
208         .read = fuse_conn_congestion_threshold_read,
209         .write = fuse_conn_congestion_threshold_write,
210         .llseek = no_llseek,
211 };
212
213 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
214                                           struct fuse_conn *fc,
215                                           const char *name,
216                                           int mode, int nlink,
217                                           const struct inode_operations *iop,
218                                           const struct file_operations *fop)
219 {
220         struct dentry *dentry;
221         struct inode *inode;
222
223         BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
224         dentry = d_alloc_name(parent, name);
225         if (!dentry)
226                 return NULL;
227
228         inode = new_inode(fuse_control_sb);
229         if (!inode) {
230                 dput(dentry);
231                 return NULL;
232         }
233
234         inode->i_ino = get_next_ino();
235         inode->i_mode = mode;
236         inode->i_uid = fc->user_id;
237         inode->i_gid = fc->group_id;
238         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
239         /* setting ->i_op to NULL is not allowed */
240         if (iop)
241                 inode->i_op = iop;
242         inode->i_fop = fop;
243         set_nlink(inode, nlink);
244         inode->i_private = fc;
245         d_add(dentry, inode);
246
247         fc->ctl_dentry[fc->ctl_ndents++] = dentry;
248
249         return dentry;
250 }
251
252 /*
253  * Add a connection to the control filesystem (if it exists).  Caller
254  * must hold fuse_mutex
255  */
256 int fuse_ctl_add_conn(struct fuse_conn *fc)
257 {
258         struct dentry *parent;
259         char name[32];
260
261         if (!fuse_control_sb || fc->no_control)
262                 return 0;
263
264         parent = fuse_control_sb->s_root;
265         inc_nlink(d_inode(parent));
266         sprintf(name, "%u", fc->dev);
267         parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
268                                      &simple_dir_inode_operations,
269                                      &simple_dir_operations);
270         if (!parent)
271                 goto err;
272
273         if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
274                                  NULL, &fuse_ctl_waiting_ops) ||
275             !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
276                                  NULL, &fuse_ctl_abort_ops) ||
277             !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
278                                  1, NULL, &fuse_conn_max_background_ops) ||
279             !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
280                                  S_IFREG | 0600, 1, NULL,
281                                  &fuse_conn_congestion_threshold_ops))
282                 goto err;
283
284         return 0;
285
286  err:
287         fuse_ctl_remove_conn(fc);
288         return -ENOMEM;
289 }
290
291 /*
292  * Remove a connection from the control filesystem (if it exists).
293  * Caller must hold fuse_mutex
294  */
295 void fuse_ctl_remove_conn(struct fuse_conn *fc)
296 {
297         int i;
298
299         if (!fuse_control_sb || fc->no_control)
300                 return;
301
302         for (i = fc->ctl_ndents - 1; i >= 0; i--) {
303                 struct dentry *dentry = fc->ctl_dentry[i];
304                 d_inode(dentry)->i_private = NULL;
305                 if (!i) {
306                         /* Get rid of submounts: */
307                         d_invalidate(dentry);
308                 }
309                 dput(dentry);
310         }
311         drop_nlink(d_inode(fuse_control_sb->s_root));
312 }
313
314 static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fsc)
315 {
316         static const struct tree_descr empty_descr = {""};
317         struct fuse_conn *fc;
318         int err;
319
320         err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
321         if (err)
322                 return err;
323
324         mutex_lock(&fuse_mutex);
325         BUG_ON(fuse_control_sb);
326         fuse_control_sb = sb;
327         list_for_each_entry(fc, &fuse_conn_list, entry) {
328                 err = fuse_ctl_add_conn(fc);
329                 if (err) {
330                         fuse_control_sb = NULL;
331                         mutex_unlock(&fuse_mutex);
332                         return err;
333                 }
334         }
335         mutex_unlock(&fuse_mutex);
336
337         return 0;
338 }
339
340 static int fuse_ctl_get_tree(struct fs_context *fsc)
341 {
342         return get_tree_single(fsc, fuse_ctl_fill_super);
343 }
344
345 static const struct fs_context_operations fuse_ctl_context_ops = {
346         .get_tree       = fuse_ctl_get_tree,
347 };
348
349 static int fuse_ctl_init_fs_context(struct fs_context *fsc)
350 {
351         fsc->ops = &fuse_ctl_context_ops;
352         return 0;
353 }
354
355 static void fuse_ctl_kill_sb(struct super_block *sb)
356 {
357         struct fuse_conn *fc;
358
359         mutex_lock(&fuse_mutex);
360         fuse_control_sb = NULL;
361         list_for_each_entry(fc, &fuse_conn_list, entry)
362                 fc->ctl_ndents = 0;
363         mutex_unlock(&fuse_mutex);
364
365         kill_litter_super(sb);
366 }
367
368 static struct file_system_type fuse_ctl_fs_type = {
369         .owner          = THIS_MODULE,
370         .name           = "fusectl",
371         .init_fs_context = fuse_ctl_init_fs_context,
372         .kill_sb        = fuse_ctl_kill_sb,
373 };
374 MODULE_ALIAS_FS("fusectl");
375
376 int __init fuse_ctl_init(void)
377 {
378         return register_filesystem(&fuse_ctl_fs_type);
379 }
380
381 void __exit fuse_ctl_cleanup(void)
382 {
383         unregister_filesystem(&fuse_ctl_fs_type);
384 }