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 .llseek = no_llseek, 187 }; 188 189 static const struct file_operations fuse_ctl_waiting_ops = { 190 .open = nonseekable_open, 191 .read = fuse_conn_waiting_read, 192 .llseek = no_llseek, 193 }; 194 195 static const struct file_operations fuse_conn_max_background_ops = { 196 .open = nonseekable_open, 197 .read = fuse_conn_max_background_read, 198 .write = fuse_conn_max_background_write, 199 .llseek = no_llseek, 200 }; 201 202 static const struct file_operations fuse_conn_congestion_threshold_ops = { 203 .open = nonseekable_open, 204 .read = fuse_conn_congestion_threshold_read, 205 .write = fuse_conn_congestion_threshold_write, 206 .llseek = no_llseek, 207 }; 208 209 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent, 210 struct fuse_conn *fc, 211 const char *name, 212 int mode, int nlink, 213 const struct inode_operations *iop, 214 const struct file_operations *fop) 215 { 216 struct dentry *dentry; 217 struct inode *inode; 218 219 BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES); 220 dentry = d_alloc_name(parent, name); 221 if (!dentry) 222 return NULL; 223 224 inode = new_inode(fuse_control_sb); 225 if (!inode) { 226 dput(dentry); 227 return NULL; 228 } 229 230 inode->i_ino = get_next_ino(); 231 inode->i_mode = mode; 232 inode->i_uid = fc->user_id; 233 inode->i_gid = fc->group_id; 234 simple_inode_init_ts(inode); 235 /* setting ->i_op to NULL is not allowed */ 236 if (iop) 237 inode->i_op = iop; 238 inode->i_fop = fop; 239 set_nlink(inode, nlink); 240 inode->i_private = fc; 241 d_add(dentry, inode); 242 243 fc->ctl_dentry[fc->ctl_ndents++] = dentry; 244 245 return dentry; 246 } 247 248 /* 249 * Add a connection to the control filesystem (if it exists). Caller 250 * must hold fuse_mutex 251 */ 252 int fuse_ctl_add_conn(struct fuse_conn *fc) 253 { 254 struct dentry *parent; 255 char name[32]; 256 257 if (!fuse_control_sb || fc->no_control) 258 return 0; 259 260 parent = fuse_control_sb->s_root; 261 inc_nlink(d_inode(parent)); 262 sprintf(name, "%u", fc->dev); 263 parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2, 264 &simple_dir_inode_operations, 265 &simple_dir_operations); 266 if (!parent) 267 goto err; 268 269 if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1, 270 NULL, &fuse_ctl_waiting_ops) || 271 !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1, 272 NULL, &fuse_ctl_abort_ops) || 273 !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600, 274 1, NULL, &fuse_conn_max_background_ops) || 275 !fuse_ctl_add_dentry(parent, fc, "congestion_threshold", 276 S_IFREG | 0600, 1, NULL, 277 &fuse_conn_congestion_threshold_ops)) 278 goto err; 279 280 return 0; 281 282 err: 283 fuse_ctl_remove_conn(fc); 284 return -ENOMEM; 285 } 286 287 /* 288 * Remove a connection from the control filesystem (if it exists). 289 * Caller must hold fuse_mutex 290 */ 291 void fuse_ctl_remove_conn(struct fuse_conn *fc) 292 { 293 int i; 294 295 if (!fuse_control_sb || fc->no_control) 296 return; 297 298 for (i = fc->ctl_ndents - 1; i >= 0; i--) { 299 struct dentry *dentry = fc->ctl_dentry[i]; 300 d_inode(dentry)->i_private = NULL; 301 if (!i) { 302 /* Get rid of submounts: */ 303 d_invalidate(dentry); 304 } 305 dput(dentry); 306 } 307 drop_nlink(d_inode(fuse_control_sb->s_root)); 308 } 309 310 static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fsc) 311 { 312 static const struct tree_descr empty_descr = {""}; 313 struct fuse_conn *fc; 314 int err; 315 316 err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr); 317 if (err) 318 return err; 319 320 mutex_lock(&fuse_mutex); 321 BUG_ON(fuse_control_sb); 322 fuse_control_sb = sb; 323 list_for_each_entry(fc, &fuse_conn_list, entry) { 324 err = fuse_ctl_add_conn(fc); 325 if (err) { 326 fuse_control_sb = NULL; 327 mutex_unlock(&fuse_mutex); 328 return err; 329 } 330 } 331 mutex_unlock(&fuse_mutex); 332 333 return 0; 334 } 335 336 static int fuse_ctl_get_tree(struct fs_context *fsc) 337 { 338 return get_tree_single(fsc, fuse_ctl_fill_super); 339 } 340 341 static const struct fs_context_operations fuse_ctl_context_ops = { 342 .get_tree = fuse_ctl_get_tree, 343 }; 344 345 static int fuse_ctl_init_fs_context(struct fs_context *fsc) 346 { 347 fsc->ops = &fuse_ctl_context_ops; 348 return 0; 349 } 350 351 static void fuse_ctl_kill_sb(struct super_block *sb) 352 { 353 struct fuse_conn *fc; 354 355 mutex_lock(&fuse_mutex); 356 fuse_control_sb = NULL; 357 list_for_each_entry(fc, &fuse_conn_list, entry) 358 fc->ctl_ndents = 0; 359 mutex_unlock(&fuse_mutex); 360 361 kill_litter_super(sb); 362 } 363 364 static struct file_system_type fuse_ctl_fs_type = { 365 .owner = THIS_MODULE, 366 .name = "fusectl", 367 .init_fs_context = fuse_ctl_init_fs_context, 368 .kill_sb = fuse_ctl_kill_sb, 369 }; 370 MODULE_ALIAS_FS("fusectl"); 371 372 int __init fuse_ctl_init(void) 373 { 374 return register_filesystem(&fuse_ctl_fs_type); 375 } 376 377 void __exit fuse_ctl_cleanup(void) 378 { 379 unregister_filesystem(&fuse_ctl_fs_type); 380 } 381