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 } 362