mm: bdi: expose the BDI object in sysfs for FUSE
[linux-2.6.git] / fs / fuse / control.c
1 /*
2   FUSE: Filesystem in Userspace
3   Copyright (C) 2001-2006  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                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
52                 if (!fc)
53                         return 0;
54
55                 file->private_data=(void *)(long)atomic_read(&fc->num_waiting);
56                 fuse_conn_put(fc);
57         }
58         size = sprintf(tmp, "%ld\n", (long)file->private_data);
59         return simple_read_from_buffer(buf, len, ppos, tmp, size);
60 }
61
62 static const struct file_operations fuse_ctl_abort_ops = {
63         .open = nonseekable_open,
64         .write = fuse_conn_abort_write,
65 };
66
67 static const struct file_operations fuse_ctl_waiting_ops = {
68         .open = nonseekable_open,
69         .read = fuse_conn_waiting_read,
70 };
71
72 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
73                                           struct fuse_conn *fc,
74                                           const char *name,
75                                           int mode, int nlink,
76                                           const struct inode_operations *iop,
77                                           const struct file_operations *fop)
78 {
79         struct dentry *dentry;
80         struct inode *inode;
81
82         BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
83         dentry = d_alloc_name(parent, name);
84         if (!dentry)
85                 return NULL;
86
87         fc->ctl_dentry[fc->ctl_ndents++] = dentry;
88         inode = new_inode(fuse_control_sb);
89         if (!inode)
90                 return NULL;
91
92         inode->i_mode = mode;
93         inode->i_uid = fc->user_id;
94         inode->i_gid = fc->group_id;
95         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
96         /* setting ->i_op to NULL is not allowed */
97         if (iop)
98                 inode->i_op = iop;
99         inode->i_fop = fop;
100         inode->i_nlink = nlink;
101         inode->i_private = fc;
102         d_add(dentry, inode);
103         return dentry;
104 }
105
106 /*
107  * Add a connection to the control filesystem (if it exists).  Caller
108  * must hold fuse_mutex
109  */
110 int fuse_ctl_add_conn(struct fuse_conn *fc)
111 {
112         struct dentry *parent;
113         char name[32];
114
115         if (!fuse_control_sb)
116                 return 0;
117
118         parent = fuse_control_sb->s_root;
119         inc_nlink(parent->d_inode);
120         sprintf(name, "%u", fc->dev);
121         parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
122                                      &simple_dir_inode_operations,
123                                      &simple_dir_operations);
124         if (!parent)
125                 goto err;
126
127         if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
128                                 NULL, &fuse_ctl_waiting_ops) ||
129             !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
130                                  NULL, &fuse_ctl_abort_ops))
131                 goto err;
132
133         return 0;
134
135  err:
136         fuse_ctl_remove_conn(fc);
137         return -ENOMEM;
138 }
139
140 /*
141  * Remove a connection from the control filesystem (if it exists).
142  * Caller must hold fuse_mutex
143  */
144 void fuse_ctl_remove_conn(struct fuse_conn *fc)
145 {
146         int i;
147
148         if (!fuse_control_sb)
149                 return;
150
151         for (i = fc->ctl_ndents - 1; i >= 0; i--) {
152                 struct dentry *dentry = fc->ctl_dentry[i];
153                 dentry->d_inode->i_private = NULL;
154                 d_drop(dentry);
155                 dput(dentry);
156         }
157         fuse_control_sb->s_root->d_inode->i_nlink--;
158 }
159
160 static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent)
161 {
162         struct tree_descr empty_descr = {""};
163         struct fuse_conn *fc;
164         int err;
165
166         err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
167         if (err)
168                 return err;
169
170         mutex_lock(&fuse_mutex);
171         BUG_ON(fuse_control_sb);
172         fuse_control_sb = sb;
173         list_for_each_entry(fc, &fuse_conn_list, entry) {
174                 err = fuse_ctl_add_conn(fc);
175                 if (err) {
176                         fuse_control_sb = NULL;
177                         mutex_unlock(&fuse_mutex);
178                         return err;
179                 }
180         }
181         mutex_unlock(&fuse_mutex);
182
183         return 0;
184 }
185
186 static int fuse_ctl_get_sb(struct file_system_type *fs_type, int flags,
187                         const char *dev_name, void *raw_data,
188                         struct vfsmount *mnt)
189 {
190         return get_sb_single(fs_type, flags, raw_data,
191                                 fuse_ctl_fill_super, mnt);
192 }
193
194 static void fuse_ctl_kill_sb(struct super_block *sb)
195 {
196         struct fuse_conn *fc;
197
198         mutex_lock(&fuse_mutex);
199         fuse_control_sb = NULL;
200         list_for_each_entry(fc, &fuse_conn_list, entry)
201                 fc->ctl_ndents = 0;
202         mutex_unlock(&fuse_mutex);
203
204         kill_litter_super(sb);
205 }
206
207 static struct file_system_type fuse_ctl_fs_type = {
208         .owner          = THIS_MODULE,
209         .name           = "fusectl",
210         .get_sb         = fuse_ctl_get_sb,
211         .kill_sb        = fuse_ctl_kill_sb,
212 };
213
214 int __init fuse_ctl_init(void)
215 {
216         return register_filesystem(&fuse_ctl_fs_type);
217 }
218
219 void fuse_ctl_cleanup(void)
220 {
221         unregister_filesystem(&fuse_ctl_fs_type);
222 }