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 #include <linux/fs_context.h> 14 15 #define FUSE_CTL_SUPER_MAGIC 0x65735543 16 17 /* 18 * This is non-NULL when the single instance of the control filesystem 19 * exists. Protected by fuse_mutex 20 */ 21 static struct super_block *fuse_control_sb; 22 23 static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file) 24 { 25 struct fuse_conn *fc; 26 mutex_lock(&fuse_mutex); 27 fc = file_inode(file)->i_private; 28 if (fc) 29 fc = fuse_conn_get(fc); 30 mutex_unlock(&fuse_mutex); 31 return fc; 32 } 33 34 static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf, 35 size_t count, loff_t *ppos) 36 { 37 struct fuse_conn *fc = fuse_ctl_file_conn_get(file); 38 if (fc) { 39 if (fc->abort_err) 40 fc->aborted = true; 41 fuse_abort_conn(fc); 42 fuse_conn_put(fc); 43 } 44 return count; 45 } 46 47 static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf, 48 size_t len, loff_t *ppos) 49 { 50 char tmp[32]; 51 size_t size; 52 53 if (!*ppos) { 54 long value; 55 struct fuse_conn *fc = fuse_ctl_file_conn_get(file); 56 if (!fc) 57 return 0; 58 59 value = atomic_read(&fc->num_waiting); 60 file->private_data = (void *)value; 61 fuse_conn_put(fc); 62 } 63 size = sprintf(tmp, "%ld\n", (long)file->private_data); 64 return simple_read_from_buffer(buf, len, ppos, tmp, size); 65 } 66 67 static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf, 68 size_t len, loff_t *ppos, unsigned val) 69 { 70 char tmp[32]; 71 size_t size = sprintf(tmp, "%u\n", val); 72 73 return simple_read_from_buffer(buf, len, ppos, tmp, size); 74 } 75 76 static ssize_t fuse_conn_limit_write(struct file *file, const char __user *buf, 77 size_t count, loff_t *ppos, unsigned *val, 78 unsigned global_limit) 79 { 80 unsigned long t; 81 unsigned limit = (1 << 16) - 1; 82 int err; 83 84 if (*ppos) 85 return -EINVAL; 86 87 err = kstrtoul_from_user(buf, count, 0, &t); 88 if (err) 89 return err; 90 91 if (!capable(CAP_SYS_ADMIN)) 92 limit = min(limit, global_limit); 93 94 if (t > limit) 95 return -EINVAL; 96 97 *val = t; 98 99 return count; 100 } 101 102 static ssize_t fuse_conn_max_background_read(struct file *file, 103 char __user *buf, size_t len, 104 loff_t *ppos) 105 { 106 struct fuse_conn *fc; 107 unsigned val; 108 109 fc = fuse_ctl_file_conn_get(file); 110 if (!fc) 111 return 0; 112 113 val = READ_ONCE(fc->max_background); 114 fuse_conn_put(fc); 115 116 return fuse_conn_limit_read(file, buf, len, ppos, val); 117 } 118 119 static ssize_t fuse_conn_max_background_write(struct file *file, 120 const char __user *buf, 121 size_t count, loff_t *ppos) 122 { 123 unsigned val; 124 ssize_t ret; 125 126 ret = fuse_conn_limit_write(file, buf, count, ppos, &val, 127 max_user_bgreq); 128 if (ret > 0) { 129 struct fuse_conn *fc = fuse_ctl_file_conn_get(file); 130 if (fc) { 131 spin_lock(&fc->bg_lock); 132 fc->max_background = val; 133 fc->blocked = fc->num_background >= fc->max_background; 134 if (!fc->blocked) 135 wake_up(&fc->blocked_waitq); 136 spin_unlock(&fc->bg_lock); 137 fuse_conn_put(fc); 138 } 139 } 140 141 return ret; 142 } 143 144 static ssize_t fuse_conn_congestion_threshold_read(struct file *file, 145 char __user *buf, size_t len, 146 loff_t *ppos) 147 { 148 struct fuse_conn *fc; 149 unsigned val; 150 151 fc = fuse_ctl_file_conn_get(file); 152 if (!fc) 153 return 0; 154 155 val = READ_ONCE(fc->congestion_threshold); 156 fuse_conn_put(fc); 157 158 return fuse_conn_limit_read(file, buf, len, ppos, val); 159 } 160 161 static ssize_t fuse_conn_congestion_threshold_write(struct file *file, 162 const char __user *buf, 163 size_t count, loff_t *ppos) 164 { 165 unsigned val; 166 struct fuse_conn *fc; 167 ssize_t ret; 168 169 ret = fuse_conn_limit_write(file, buf, count, ppos, &val, 170 max_user_congthresh); 171 if (ret <= 0) 172 goto out; 173 fc = fuse_ctl_file_conn_get(file); 174 if (!fc) 175 goto out; 176 177 WRITE_ONCE(fc->congestion_threshold, val); 178 fuse_conn_put(fc); 179 out: 180 return ret; 181 } 182 183 static const struct file_operations fuse_ctl_abort_ops = { 184 .open = nonseekable_open, 185 .write = fuse_conn_abort_write, 186 }; 187 188 static const struct file_operations fuse_ctl_waiting_ops = { 189 .open = nonseekable_open, 190 .read = fuse_conn_waiting_read, 191 }; 192 193 static const struct file_operations fuse_conn_max_background_ops = { 194 .open = nonseekable_open, 195 .read = fuse_conn_max_background_read, 196 .write = fuse_conn_max_background_write, 197 }; 198 199 static const struct file_operations fuse_conn_congestion_threshold_ops = { 200 .open = nonseekable_open, 201 .read = fuse_conn_congestion_threshold_read, 202 .write = fuse_conn_congestion_threshold_write, 203 }; 204 205 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent, 206 struct fuse_conn *fc, 207 const char *name, 208 int mode, int nlink, 209 const struct inode_operations *iop, 210 const struct file_operations *fop) 211 { 212 struct dentry *dentry; 213 struct inode *inode; 214 215 BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES); 216 dentry = d_alloc_name(parent, name); 217 if (!dentry) 218 return NULL; 219 220 inode = new_inode(fuse_control_sb); 221 if (!inode) { 222 dput(dentry); 223 return NULL; 224 } 225 226 inode->i_ino = get_next_ino(); 227 inode->i_mode = mode; 228 inode->i_uid = fc->user_id; 229 inode->i_gid = fc->group_id; 230 simple_inode_init_ts(inode); 231 /* setting ->i_op to NULL is not allowed */ 232 if (iop) 233 inode->i_op = iop; 234 inode->i_fop = fop; 235 set_nlink(inode, nlink); 236 inode->i_private = fc; 237 d_add(dentry, inode); 238 239 fc->ctl_dentry[fc->ctl_ndents++] = dentry; 240 241 return dentry; 242 } 243 244 /* 245 * Add a connection to the control filesystem (if it exists). Caller 246 * must hold fuse_mutex 247 */ 248 int fuse_ctl_add_conn(struct fuse_conn *fc) 249 { 250 struct dentry *parent; 251 char name[32]; 252 253 if (!fuse_control_sb || fc->no_control) 254 return 0; 255 256 parent = fuse_control_sb->s_root; 257 inc_nlink(d_inode(parent)); 258 sprintf(name, "%u", fc->dev); 259 parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2, 260 &simple_dir_inode_operations, 261 &simple_dir_operations); 262 if (!parent) 263 goto err; 264 265 if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1, 266 NULL, &fuse_ctl_waiting_ops) || 267 !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1, 268 NULL, &fuse_ctl_abort_ops) || 269 !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600, 270 1, NULL, &fuse_conn_max_background_ops) || 271 !fuse_ctl_add_dentry(parent, fc, "congestion_threshold", 272 S_IFREG | 0600, 1, NULL, 273 &fuse_conn_congestion_threshold_ops)) 274 goto err; 275 276 return 0; 277 278 err: 279 fuse_ctl_remove_conn(fc); 280 return -ENOMEM; 281 } 282 283 /* 284 * Remove a connection from the control filesystem (if it exists). 285 * Caller must hold fuse_mutex 286 */ 287 void fuse_ctl_remove_conn(struct fuse_conn *fc) 288 { 289 int i; 290 291 if (!fuse_control_sb || fc->no_control) 292 return; 293 294 for (i = fc->ctl_ndents - 1; i >= 0; i--) { 295 struct dentry *dentry = fc->ctl_dentry[i]; 296 d_inode(dentry)->i_private = NULL; 297 if (!i) { 298 /* Get rid of submounts: */ 299 d_invalidate(dentry); 300 } 301 dput(dentry); 302 } 303 drop_nlink(d_inode(fuse_control_sb->s_root)); 304 } 305 306 static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fsc) 307 { 308 static const struct tree_descr empty_descr = {""}; 309 struct fuse_conn *fc; 310 int err; 311 312 err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr); 313 if (err) 314 return err; 315 316 mutex_lock(&fuse_mutex); 317 BUG_ON(fuse_control_sb); 318 fuse_control_sb = sb; 319 list_for_each_entry(fc, &fuse_conn_list, entry) { 320 err = fuse_ctl_add_conn(fc); 321 if (err) { 322 fuse_control_sb = NULL; 323 mutex_unlock(&fuse_mutex); 324 return err; 325 } 326 } 327 mutex_unlock(&fuse_mutex); 328 329 return 0; 330 } 331 332 static int fuse_ctl_get_tree(struct fs_context *fsc) 333 { 334 return get_tree_single(fsc, fuse_ctl_fill_super); 335 } 336 337 static const struct fs_context_operations fuse_ctl_context_ops = { 338 .get_tree = fuse_ctl_get_tree, 339 }; 340 341 static int fuse_ctl_init_fs_context(struct fs_context *fsc) 342 { 343 fsc->ops = &fuse_ctl_context_ops; 344 return 0; 345 } 346 347 static void fuse_ctl_kill_sb(struct super_block *sb) 348 { 349 struct fuse_conn *fc; 350 351 mutex_lock(&fuse_mutex); 352 fuse_control_sb = NULL; 353 list_for_each_entry(fc, &fuse_conn_list, entry) 354 fc->ctl_ndents = 0; 355 mutex_unlock(&fuse_mutex); 356 357 kill_litter_super(sb); 358 } 359 360 static struct file_system_type fuse_ctl_fs_type = { 361 .owner = THIS_MODULE, 362 .name = "fusectl", 363 .init_fs_context = fuse_ctl_init_fs_context, 364 .kill_sb = fuse_ctl_kill_sb, 365 }; 366 MODULE_ALIAS_FS("fusectl"); 367 368 int __init fuse_ctl_init(void) 369 { 370 return register_filesystem(&fuse_ctl_fs_type); 371 } 372 373 void __exit fuse_ctl_cleanup(void) 374 { 375 unregister_filesystem(&fuse_ctl_fs_type); 376 } 377