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 = READ_ONCE(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 spin_lock(&fc->lock); 129 fc->max_background = val; 130 fc->blocked = fc->num_background >= fc->max_background; 131 if (!fc->blocked) 132 wake_up(&fc->blocked_waitq); 133 spin_unlock(&fc->lock); 134 fuse_conn_put(fc); 135 } 136 } 137 138 return ret; 139 } 140 141 static ssize_t fuse_conn_congestion_threshold_read(struct file *file, 142 char __user *buf, size_t len, 143 loff_t *ppos) 144 { 145 struct fuse_conn *fc; 146 unsigned val; 147 148 fc = fuse_ctl_file_conn_get(file); 149 if (!fc) 150 return 0; 151 152 val = READ_ONCE(fc->congestion_threshold); 153 fuse_conn_put(fc); 154 155 return fuse_conn_limit_read(file, buf, len, ppos, val); 156 } 157 158 static ssize_t fuse_conn_congestion_threshold_write(struct file *file, 159 const char __user *buf, 160 size_t count, loff_t *ppos) 161 { 162 unsigned uninitialized_var(val); 163 struct fuse_conn *fc; 164 ssize_t ret; 165 166 ret = fuse_conn_limit_write(file, buf, count, ppos, &val, 167 max_user_congthresh); 168 if (ret <= 0) 169 goto out; 170 fc = fuse_ctl_file_conn_get(file); 171 if (!fc) 172 goto out; 173 174 spin_lock(&fc->lock); 175 fc->congestion_threshold = val; 176 if (fc->sb) { 177 if (fc->num_background < fc->congestion_threshold) { 178 clear_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC); 179 clear_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC); 180 } else { 181 set_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC); 182 set_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC); 183 } 184 } 185 spin_unlock(&fc->lock); 186 fuse_conn_put(fc); 187 out: 188 return ret; 189 } 190 191 static const struct file_operations fuse_ctl_abort_ops = { 192 .open = nonseekable_open, 193 .write = fuse_conn_abort_write, 194 .llseek = no_llseek, 195 }; 196 197 static const struct file_operations fuse_ctl_waiting_ops = { 198 .open = nonseekable_open, 199 .read = fuse_conn_waiting_read, 200 .llseek = no_llseek, 201 }; 202 203 static const struct file_operations fuse_conn_max_background_ops = { 204 .open = nonseekable_open, 205 .read = fuse_conn_max_background_read, 206 .write = fuse_conn_max_background_write, 207 .llseek = no_llseek, 208 }; 209 210 static const struct file_operations fuse_conn_congestion_threshold_ops = { 211 .open = nonseekable_open, 212 .read = fuse_conn_congestion_threshold_read, 213 .write = fuse_conn_congestion_threshold_write, 214 .llseek = no_llseek, 215 }; 216 217 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent, 218 struct fuse_conn *fc, 219 const char *name, 220 int mode, int nlink, 221 const struct inode_operations *iop, 222 const struct file_operations *fop) 223 { 224 struct dentry *dentry; 225 struct inode *inode; 226 227 BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES); 228 dentry = d_alloc_name(parent, name); 229 if (!dentry) 230 return NULL; 231 232 inode = new_inode(fuse_control_sb); 233 if (!inode) { 234 dput(dentry); 235 return NULL; 236 } 237 238 inode->i_ino = get_next_ino(); 239 inode->i_mode = mode; 240 inode->i_uid = fc->user_id; 241 inode->i_gid = fc->group_id; 242 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); 243 /* setting ->i_op to NULL is not allowed */ 244 if (iop) 245 inode->i_op = iop; 246 inode->i_fop = fop; 247 set_nlink(inode, nlink); 248 inode->i_private = fc; 249 d_add(dentry, inode); 250 251 fc->ctl_dentry[fc->ctl_ndents++] = dentry; 252 253 return dentry; 254 } 255 256 /* 257 * Add a connection to the control filesystem (if it exists). Caller 258 * must hold fuse_mutex 259 */ 260 int fuse_ctl_add_conn(struct fuse_conn *fc) 261 { 262 struct dentry *parent; 263 char name[32]; 264 265 if (!fuse_control_sb) 266 return 0; 267 268 parent = fuse_control_sb->s_root; 269 inc_nlink(d_inode(parent)); 270 sprintf(name, "%u", fc->dev); 271 parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2, 272 &simple_dir_inode_operations, 273 &simple_dir_operations); 274 if (!parent) 275 goto err; 276 277 if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1, 278 NULL, &fuse_ctl_waiting_ops) || 279 !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1, 280 NULL, &fuse_ctl_abort_ops) || 281 !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600, 282 1, NULL, &fuse_conn_max_background_ops) || 283 !fuse_ctl_add_dentry(parent, fc, "congestion_threshold", 284 S_IFREG | 0600, 1, NULL, 285 &fuse_conn_congestion_threshold_ops)) 286 goto err; 287 288 return 0; 289 290 err: 291 fuse_ctl_remove_conn(fc); 292 return -ENOMEM; 293 } 294 295 /* 296 * Remove a connection from the control filesystem (if it exists). 297 * Caller must hold fuse_mutex 298 */ 299 void fuse_ctl_remove_conn(struct fuse_conn *fc) 300 { 301 int i; 302 303 if (!fuse_control_sb) 304 return; 305 306 for (i = fc->ctl_ndents - 1; i >= 0; i--) { 307 struct dentry *dentry = fc->ctl_dentry[i]; 308 d_inode(dentry)->i_private = NULL; 309 if (!i) { 310 /* Get rid of submounts: */ 311 d_invalidate(dentry); 312 } 313 dput(dentry); 314 } 315 drop_nlink(d_inode(fuse_control_sb->s_root)); 316 } 317 318 static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent) 319 { 320 static const struct tree_descr empty_descr = {""}; 321 struct fuse_conn *fc; 322 int err; 323 324 err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr); 325 if (err) 326 return err; 327 328 mutex_lock(&fuse_mutex); 329 BUG_ON(fuse_control_sb); 330 fuse_control_sb = sb; 331 list_for_each_entry(fc, &fuse_conn_list, entry) { 332 err = fuse_ctl_add_conn(fc); 333 if (err) { 334 fuse_control_sb = NULL; 335 mutex_unlock(&fuse_mutex); 336 return err; 337 } 338 } 339 mutex_unlock(&fuse_mutex); 340 341 return 0; 342 } 343 344 static struct dentry *fuse_ctl_mount(struct file_system_type *fs_type, 345 int flags, const char *dev_name, void *raw_data) 346 { 347 return mount_single(fs_type, flags, raw_data, fuse_ctl_fill_super); 348 } 349 350 static void fuse_ctl_kill_sb(struct super_block *sb) 351 { 352 struct fuse_conn *fc; 353 354 mutex_lock(&fuse_mutex); 355 fuse_control_sb = NULL; 356 list_for_each_entry(fc, &fuse_conn_list, entry) 357 fc->ctl_ndents = 0; 358 mutex_unlock(&fuse_mutex); 359 360 kill_litter_super(sb); 361 } 362 363 static struct file_system_type fuse_ctl_fs_type = { 364 .owner = THIS_MODULE, 365 .name = "fusectl", 366 .mount = fuse_ctl_mount, 367 .kill_sb = fuse_ctl_kill_sb, 368 }; 369 MODULE_ALIAS_FS("fusectl"); 370 371 int __init fuse_ctl_init(void) 372 { 373 return register_filesystem(&fuse_ctl_fs_type); 374 } 375 376 void __exit fuse_ctl_cleanup(void) 377 { 378 unregister_filesystem(&fuse_ctl_fs_type); 379 } 380