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 */
20static struct super_block *fuse_control_sb;
21
22static 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
33static 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
44static 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
64static 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
73static 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
99static 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
116static 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
136static 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
153static 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
173static const struct file_operations fuse_ctl_abort_ops = {
174	.open = nonseekable_open,
175	.write = fuse_conn_abort_write,
176	.llseek = no_llseek,
177};
178
179static const struct file_operations fuse_ctl_waiting_ops = {
180	.open = nonseekable_open,
181	.read = fuse_conn_waiting_read,
182	.llseek = no_llseek,
183};
184
185static 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
192static 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
199static 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	fc->ctl_dentry[fc->ctl_ndents++] = dentry;
215	inode = new_inode(fuse_control_sb);
216	if (!inode)
217		return NULL;
218
219	inode->i_ino = get_next_ino();
220	inode->i_mode = mode;
221	inode->i_uid = fc->user_id;
222	inode->i_gid = fc->group_id;
223	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
224	/* setting ->i_op to NULL is not allowed */
225	if (iop)
226		inode->i_op = iop;
227	inode->i_fop = fop;
228	set_nlink(inode, nlink);
229	inode->i_private = fc;
230	d_add(dentry, inode);
231	return dentry;
232}
233
234/*
235 * Add a connection to the control filesystem (if it exists).  Caller
236 * must hold fuse_mutex
237 */
238int fuse_ctl_add_conn(struct fuse_conn *fc)
239{
240	struct dentry *parent;
241	char name[32];
242
243	if (!fuse_control_sb)
244		return 0;
245
246	parent = fuse_control_sb->s_root;
247	inc_nlink(parent->d_inode);
248	sprintf(name, "%u", fc->dev);
249	parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
250				     &simple_dir_inode_operations,
251				     &simple_dir_operations);
252	if (!parent)
253		goto err;
254
255	if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
256				 NULL, &fuse_ctl_waiting_ops) ||
257	    !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
258				 NULL, &fuse_ctl_abort_ops) ||
259	    !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
260				 1, NULL, &fuse_conn_max_background_ops) ||
261	    !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
262				 S_IFREG | 0600, 1, NULL,
263				 &fuse_conn_congestion_threshold_ops))
264		goto err;
265
266	return 0;
267
268 err:
269	fuse_ctl_remove_conn(fc);
270	return -ENOMEM;
271}
272
273/*
274 * Remove a connection from the control filesystem (if it exists).
275 * Caller must hold fuse_mutex
276 */
277void fuse_ctl_remove_conn(struct fuse_conn *fc)
278{
279	int i;
280
281	if (!fuse_control_sb)
282		return;
283
284	for (i = fc->ctl_ndents - 1; i >= 0; i--) {
285		struct dentry *dentry = fc->ctl_dentry[i];
286		dentry->d_inode->i_private = NULL;
287		d_drop(dentry);
288		dput(dentry);
289	}
290	drop_nlink(fuse_control_sb->s_root->d_inode);
291}
292
293static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent)
294{
295	struct tree_descr empty_descr = {""};
296	struct fuse_conn *fc;
297	int err;
298
299	err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
300	if (err)
301		return err;
302
303	mutex_lock(&fuse_mutex);
304	BUG_ON(fuse_control_sb);
305	fuse_control_sb = sb;
306	list_for_each_entry(fc, &fuse_conn_list, entry) {
307		err = fuse_ctl_add_conn(fc);
308		if (err) {
309			fuse_control_sb = NULL;
310			mutex_unlock(&fuse_mutex);
311			return err;
312		}
313	}
314	mutex_unlock(&fuse_mutex);
315
316	return 0;
317}
318
319static struct dentry *fuse_ctl_mount(struct file_system_type *fs_type,
320			int flags, const char *dev_name, void *raw_data)
321{
322	return mount_single(fs_type, flags, raw_data, fuse_ctl_fill_super);
323}
324
325static void fuse_ctl_kill_sb(struct super_block *sb)
326{
327	struct fuse_conn *fc;
328
329	mutex_lock(&fuse_mutex);
330	fuse_control_sb = NULL;
331	list_for_each_entry(fc, &fuse_conn_list, entry)
332		fc->ctl_ndents = 0;
333	mutex_unlock(&fuse_mutex);
334
335	kill_litter_super(sb);
336}
337
338static struct file_system_type fuse_ctl_fs_type = {
339	.owner		= THIS_MODULE,
340	.name		= "fusectl",
341	.mount		= fuse_ctl_mount,
342	.kill_sb	= fuse_ctl_kill_sb,
343};
344MODULE_ALIAS_FS("fusectl");
345
346int __init fuse_ctl_init(void)
347{
348	return register_filesystem(&fuse_ctl_fs_type);
349}
350
351void __exit fuse_ctl_cleanup(void)
352{
353	unregister_filesystem(&fuse_ctl_fs_type);
354}
355