Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/sameo/mfd-2.6
[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 const struct file_operations fuse_ctl_abort_ops = {
65         .open = nonseekable_open,
66         .write = fuse_conn_abort_write,
67 };
68
69 static const struct file_operations fuse_ctl_waiting_ops = {
70         .open = nonseekable_open,
71         .read = fuse_conn_waiting_read,
72 };
73
74 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
75                                           struct fuse_conn *fc,
76                                           const char *name,
77                                           int mode, int nlink,
78                                           const struct inode_operations *iop,
79                                           const struct file_operations *fop)
80 {
81         struct dentry *dentry;
82         struct inode *inode;
83
84         BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
85         dentry = d_alloc_name(parent, name);
86         if (!dentry)
87                 return NULL;
88
89         fc->ctl_dentry[fc->ctl_ndents++] = dentry;
90         inode = new_inode(fuse_control_sb);
91         if (!inode)
92                 return NULL;
93
94         inode->i_mode = mode;
95         inode->i_uid = fc->user_id;
96         inode->i_gid = fc->group_id;
97         inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
98         /* setting ->i_op to NULL is not allowed */
99         if (iop)
100                 inode->i_op = iop;
101         inode->i_fop = fop;
102         inode->i_nlink = nlink;
103         inode->i_private = fc;
104         d_add(dentry, inode);
105         return dentry;
106 }
107
108 /*
109  * Add a connection to the control filesystem (if it exists).  Caller
110  * must hold fuse_mutex
111  */
112 int fuse_ctl_add_conn(struct fuse_conn *fc)
113 {
114         struct dentry *parent;
115         char name[32];
116
117         if (!fuse_control_sb)
118                 return 0;
119
120         parent = fuse_control_sb->s_root;
121         inc_nlink(parent->d_inode);
122         sprintf(name, "%u", fc->dev);
123         parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
124                                      &simple_dir_inode_operations,
125                                      &simple_dir_operations);
126         if (!parent)
127                 goto err;
128
129         if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
130                                 NULL, &fuse_ctl_waiting_ops) ||
131             !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
132                                  NULL, &fuse_ctl_abort_ops))
133                 goto err;
134
135         return 0;
136
137  err:
138         fuse_ctl_remove_conn(fc);
139         return -ENOMEM;
140 }
141
142 /*
143  * Remove a connection from the control filesystem (if it exists).
144  * Caller must hold fuse_mutex
145  */
146 void fuse_ctl_remove_conn(struct fuse_conn *fc)
147 {
148         int i;
149
150         if (!fuse_control_sb)
151                 return;
152
153         for (i = fc->ctl_ndents - 1; i >= 0; i--) {
154                 struct dentry *dentry = fc->ctl_dentry[i];
155                 dentry->d_inode->i_private = NULL;
156                 d_drop(dentry);
157                 dput(dentry);
158         }
159         fuse_control_sb->s_root->d_inode->i_nlink--;
160 }
161
162 static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent)
163 {
164         struct tree_descr empty_descr = {""};
165         struct fuse_conn *fc;
166         int err;
167
168         err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
169         if (err)
170                 return err;
171
172         mutex_lock(&fuse_mutex);
173         BUG_ON(fuse_control_sb);
174         fuse_control_sb = sb;
175         list_for_each_entry(fc, &fuse_conn_list, entry) {
176                 err = fuse_ctl_add_conn(fc);
177                 if (err) {
178                         fuse_control_sb = NULL;
179                         mutex_unlock(&fuse_mutex);
180                         return err;
181                 }
182         }
183         mutex_unlock(&fuse_mutex);
184
185         return 0;
186 }
187
188 static int fuse_ctl_get_sb(struct file_system_type *fs_type, int flags,
189                         const char *dev_name, void *raw_data,
190                         struct vfsmount *mnt)
191 {
192         return get_sb_single(fs_type, flags, raw_data,
193                                 fuse_ctl_fill_super, mnt);
194 }
195
196 static void fuse_ctl_kill_sb(struct super_block *sb)
197 {
198         struct fuse_conn *fc;
199
200         mutex_lock(&fuse_mutex);
201         fuse_control_sb = NULL;
202         list_for_each_entry(fc, &fuse_conn_list, entry)
203                 fc->ctl_ndents = 0;
204         mutex_unlock(&fuse_mutex);
205
206         kill_litter_super(sb);
207 }
208
209 static struct file_system_type fuse_ctl_fs_type = {
210         .owner          = THIS_MODULE,
211         .name           = "fusectl",
212         .get_sb         = fuse_ctl_get_sb,
213         .kill_sb        = fuse_ctl_kill_sb,
214 };
215
216 int __init fuse_ctl_init(void)
217 {
218         return register_filesystem(&fuse_ctl_fs_type);
219 }
220
221 void fuse_ctl_cleanup(void)
222 {
223         unregister_filesystem(&fuse_ctl_fs_type);
224 }