Merge tag 'fuse-update-4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/mszered...
[sfrench/cifs-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_inode(file)->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, true);
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         unsigned limit = (1 << 16) - 1;
79         int err;
80
81         if (*ppos)
82                 return -EINVAL;
83
84         err = kstrtoul_from_user(buf, count, 0, &t);
85         if (err)
86                 return err;
87
88         if (!capable(CAP_SYS_ADMIN))
89                 limit = min(limit, global_limit);
90
91         if (t > limit)
92                 return -EINVAL;
93
94         *val = t;
95
96         return count;
97 }
98
99 static ssize_t fuse_conn_max_background_read(struct file *file,
100                                              char __user *buf, size_t len,
101                                              loff_t *ppos)
102 {
103         struct fuse_conn *fc;
104         unsigned val;
105
106         fc = fuse_ctl_file_conn_get(file);
107         if (!fc)
108                 return 0;
109
110         val = fc->max_background;
111         fuse_conn_put(fc);
112
113         return fuse_conn_limit_read(file, buf, len, ppos, val);
114 }
115
116 static ssize_t fuse_conn_max_background_write(struct file *file,
117                                               const char __user *buf,
118                                               size_t count, loff_t *ppos)
119 {
120         unsigned uninitialized_var(val);
121         ssize_t ret;
122
123         ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
124                                     max_user_bgreq);
125         if (ret > 0) {
126                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
127                 if (fc) {
128                         fc->max_background = val;
129                         fuse_conn_put(fc);
130                 }
131         }
132
133         return ret;
134 }
135
136 static ssize_t fuse_conn_congestion_threshold_read(struct file *file,
137                                                    char __user *buf, size_t len,
138                                                    loff_t *ppos)
139 {
140         struct fuse_conn *fc;
141         unsigned val;
142
143         fc = fuse_ctl_file_conn_get(file);
144         if (!fc)
145                 return 0;
146
147         val = fc->congestion_threshold;
148         fuse_conn_put(fc);
149
150         return fuse_conn_limit_read(file, buf, len, ppos, val);
151 }
152
153 static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
154                                                     const char __user *buf,
155                                                     size_t count, loff_t *ppos)
156 {
157         unsigned uninitialized_var(val);
158         ssize_t ret;
159
160         ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
161                                     max_user_congthresh);
162         if (ret > 0) {
163                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
164                 if (fc) {
165                         fc->congestion_threshold = val;
166                         fuse_conn_put(fc);
167                 }
168         }
169
170         return ret;
171 }
172
173 static const struct file_operations fuse_ctl_abort_ops = {
174         .open = nonseekable_open,
175         .write = fuse_conn_abort_write,
176         .llseek = no_llseek,
177 };
178
179 static const struct file_operations fuse_ctl_waiting_ops = {
180         .open = nonseekable_open,
181         .read = fuse_conn_waiting_read,
182         .llseek = no_llseek,
183 };
184
185 static const struct file_operations fuse_conn_max_background_ops = {
186         .open = nonseekable_open,
187         .read = fuse_conn_max_background_read,
188         .write = fuse_conn_max_background_write,
189         .llseek = no_llseek,
190 };
191
192 static const struct file_operations fuse_conn_congestion_threshold_ops = {
193         .open = nonseekable_open,
194         .read = fuse_conn_congestion_threshold_read,
195         .write = fuse_conn_congestion_threshold_write,
196         .llseek = no_llseek,
197 };
198
199 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
200                                           struct fuse_conn *fc,
201                                           const char *name,
202                                           int mode, int nlink,
203                                           const struct inode_operations *iop,
204                                           const struct file_operations *fop)
205 {
206         struct dentry *dentry;
207         struct inode *inode;
208
209         BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
210         dentry = d_alloc_name(parent, name);
211         if (!dentry)
212                 return NULL;
213
214         inode = new_inode(fuse_control_sb);
215         if (!inode) {
216                 dput(dentry);
217                 return NULL;
218         }
219
220         inode->i_ino = get_next_ino();
221         inode->i_mode = mode;
222         inode->i_uid = fc->user_id;
223         inode->i_gid = fc->group_id;
224         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
225         /* setting ->i_op to NULL is not allowed */
226         if (iop)
227                 inode->i_op = iop;
228         inode->i_fop = fop;
229         set_nlink(inode, nlink);
230         inode->i_private = fc;
231         d_add(dentry, inode);
232
233         fc->ctl_dentry[fc->ctl_ndents++] = dentry;
234
235         return dentry;
236 }
237
238 /*
239  * Add a connection to the control filesystem (if it exists).  Caller
240  * must hold fuse_mutex
241  */
242 int fuse_ctl_add_conn(struct fuse_conn *fc)
243 {
244         struct dentry *parent;
245         char name[32];
246
247         if (!fuse_control_sb)
248                 return 0;
249
250         parent = fuse_control_sb->s_root;
251         inc_nlink(d_inode(parent));
252         sprintf(name, "%u", fc->dev);
253         parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
254                                      &simple_dir_inode_operations,
255                                      &simple_dir_operations);
256         if (!parent)
257                 goto err;
258
259         if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
260                                  NULL, &fuse_ctl_waiting_ops) ||
261             !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
262                                  NULL, &fuse_ctl_abort_ops) ||
263             !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
264                                  1, NULL, &fuse_conn_max_background_ops) ||
265             !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
266                                  S_IFREG | 0600, 1, NULL,
267                                  &fuse_conn_congestion_threshold_ops))
268                 goto err;
269
270         return 0;
271
272  err:
273         fuse_ctl_remove_conn(fc);
274         return -ENOMEM;
275 }
276
277 /*
278  * Remove a connection from the control filesystem (if it exists).
279  * Caller must hold fuse_mutex
280  */
281 void fuse_ctl_remove_conn(struct fuse_conn *fc)
282 {
283         int i;
284
285         if (!fuse_control_sb)
286                 return;
287
288         for (i = fc->ctl_ndents - 1; i >= 0; i--) {
289                 struct dentry *dentry = fc->ctl_dentry[i];
290                 d_inode(dentry)->i_private = NULL;
291                 if (!i) {
292                         /* Get rid of submounts: */
293                         d_invalidate(dentry);
294                 }
295                 dput(dentry);
296         }
297         drop_nlink(d_inode(fuse_control_sb->s_root));
298 }
299
300 static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent)
301 {
302         static const struct tree_descr empty_descr = {""};
303         struct fuse_conn *fc;
304         int err;
305
306         err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
307         if (err)
308                 return err;
309
310         mutex_lock(&fuse_mutex);
311         BUG_ON(fuse_control_sb);
312         fuse_control_sb = sb;
313         list_for_each_entry(fc, &fuse_conn_list, entry) {
314                 err = fuse_ctl_add_conn(fc);
315                 if (err) {
316                         fuse_control_sb = NULL;
317                         mutex_unlock(&fuse_mutex);
318                         return err;
319                 }
320         }
321         mutex_unlock(&fuse_mutex);
322
323         return 0;
324 }
325
326 static struct dentry *fuse_ctl_mount(struct file_system_type *fs_type,
327                         int flags, const char *dev_name, void *raw_data)
328 {
329         return mount_single(fs_type, flags, raw_data, fuse_ctl_fill_super);
330 }
331
332 static void fuse_ctl_kill_sb(struct super_block *sb)
333 {
334         struct fuse_conn *fc;
335
336         mutex_lock(&fuse_mutex);
337         fuse_control_sb = NULL;
338         list_for_each_entry(fc, &fuse_conn_list, entry)
339                 fc->ctl_ndents = 0;
340         mutex_unlock(&fuse_mutex);
341
342         kill_litter_super(sb);
343 }
344
345 static struct file_system_type fuse_ctl_fs_type = {
346         .owner          = THIS_MODULE,
347         .name           = "fusectl",
348         .mount          = fuse_ctl_mount,
349         .kill_sb        = fuse_ctl_kill_sb,
350 };
351 MODULE_ALIAS_FS("fusectl");
352
353 int __init fuse_ctl_init(void)
354 {
355         return register_filesystem(&fuse_ctl_fs_type);
356 }
357
358 void __exit fuse_ctl_cleanup(void)
359 {
360         unregister_filesystem(&fuse_ctl_fs_type);
361 }