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 struct fuse_mount *fm; 168 ssize_t ret; 169 170 ret = fuse_conn_limit_write(file, buf, count, ppos, &val, 171 max_user_congthresh); 172 if (ret <= 0) 173 goto out; 174 fc = fuse_ctl_file_conn_get(file); 175 if (!fc) 176 goto out; 177 178 down_read(&fc->killsb); 179 spin_lock(&fc->bg_lock); 180 fc->congestion_threshold = val; 181 182 /* 183 * Get any fuse_mount belonging to this fuse_conn; s_bdi is 184 * shared between all of them 185 */ 186 187 if (!list_empty(&fc->mounts)) { 188 fm = list_first_entry(&fc->mounts, struct fuse_mount, fc_entry); 189 if (fc->num_background < fc->congestion_threshold) { 190 clear_bdi_congested(fm->sb->s_bdi, BLK_RW_SYNC); 191 clear_bdi_congested(fm->sb->s_bdi, BLK_RW_ASYNC); 192 } else { 193 set_bdi_congested(fm->sb->s_bdi, BLK_RW_SYNC); 194 set_bdi_congested(fm->sb->s_bdi, BLK_RW_ASYNC); 195 } 196 } 197 spin_unlock(&fc->bg_lock); 198 up_read(&fc->killsb); 199 fuse_conn_put(fc); 200 out: 201 return ret; 202 } 203 204 static const struct file_operations fuse_ctl_abort_ops = { 205 .open = nonseekable_open, 206 .write = fuse_conn_abort_write, 207 .llseek = no_llseek, 208 }; 209 210 static const struct file_operations fuse_ctl_waiting_ops = { 211 .open = nonseekable_open, 212 .read = fuse_conn_waiting_read, 213 .llseek = no_llseek, 214 }; 215 216 static const struct file_operations fuse_conn_max_background_ops = { 217 .open = nonseekable_open, 218 .read = fuse_conn_max_background_read, 219 .write = fuse_conn_max_background_write, 220 .llseek = no_llseek, 221 }; 222 223 static const struct file_operations fuse_conn_congestion_threshold_ops = { 224 .open = nonseekable_open, 225 .read = fuse_conn_congestion_threshold_read, 226 .write = fuse_conn_congestion_threshold_write, 227 .llseek = no_llseek, 228 }; 229 230 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent, 231 struct fuse_conn *fc, 232 const char *name, 233 int mode, int nlink, 234 const struct inode_operations *iop, 235 const struct file_operations *fop) 236 { 237 struct dentry *dentry; 238 struct inode *inode; 239 240 BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES); 241 dentry = d_alloc_name(parent, name); 242 if (!dentry) 243 return NULL; 244 245 inode = new_inode(fuse_control_sb); 246 if (!inode) { 247 dput(dentry); 248 return NULL; 249 } 250 251 inode->i_ino = get_next_ino(); 252 inode->i_mode = mode; 253 inode->i_uid = fc->user_id; 254 inode->i_gid = fc->group_id; 255 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); 256 /* setting ->i_op to NULL is not allowed */ 257 if (iop) 258 inode->i_op = iop; 259 inode->i_fop = fop; 260 set_nlink(inode, nlink); 261 inode->i_private = fc; 262 d_add(dentry, inode); 263 264 fc->ctl_dentry[fc->ctl_ndents++] = dentry; 265 266 return dentry; 267 } 268 269 /* 270 * Add a connection to the control filesystem (if it exists). Caller 271 * must hold fuse_mutex 272 */ 273 int fuse_ctl_add_conn(struct fuse_conn *fc) 274 { 275 struct dentry *parent; 276 char name[32]; 277 278 if (!fuse_control_sb) 279 return 0; 280 281 parent = fuse_control_sb->s_root; 282 inc_nlink(d_inode(parent)); 283 sprintf(name, "%u", fc->dev); 284 parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2, 285 &simple_dir_inode_operations, 286 &simple_dir_operations); 287 if (!parent) 288 goto err; 289 290 if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1, 291 NULL, &fuse_ctl_waiting_ops) || 292 !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1, 293 NULL, &fuse_ctl_abort_ops) || 294 !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600, 295 1, NULL, &fuse_conn_max_background_ops) || 296 !fuse_ctl_add_dentry(parent, fc, "congestion_threshold", 297 S_IFREG | 0600, 1, NULL, 298 &fuse_conn_congestion_threshold_ops)) 299 goto err; 300 301 return 0; 302 303 err: 304 fuse_ctl_remove_conn(fc); 305 return -ENOMEM; 306 } 307 308 /* 309 * Remove a connection from the control filesystem (if it exists). 310 * Caller must hold fuse_mutex 311 */ 312 void fuse_ctl_remove_conn(struct fuse_conn *fc) 313 { 314 int i; 315 316 if (!fuse_control_sb) 317 return; 318 319 for (i = fc->ctl_ndents - 1; i >= 0; i--) { 320 struct dentry *dentry = fc->ctl_dentry[i]; 321 d_inode(dentry)->i_private = NULL; 322 if (!i) { 323 /* Get rid of submounts: */ 324 d_invalidate(dentry); 325 } 326 dput(dentry); 327 } 328 drop_nlink(d_inode(fuse_control_sb->s_root)); 329 } 330 331 static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fctx) 332 { 333 static const struct tree_descr empty_descr = {""}; 334 struct fuse_conn *fc; 335 int err; 336 337 err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr); 338 if (err) 339 return err; 340 341 mutex_lock(&fuse_mutex); 342 BUG_ON(fuse_control_sb); 343 fuse_control_sb = sb; 344 list_for_each_entry(fc, &fuse_conn_list, entry) { 345 err = fuse_ctl_add_conn(fc); 346 if (err) { 347 fuse_control_sb = NULL; 348 mutex_unlock(&fuse_mutex); 349 return err; 350 } 351 } 352 mutex_unlock(&fuse_mutex); 353 354 return 0; 355 } 356 357 static int fuse_ctl_get_tree(struct fs_context *fc) 358 { 359 return get_tree_single(fc, fuse_ctl_fill_super); 360 } 361 362 static const struct fs_context_operations fuse_ctl_context_ops = { 363 .get_tree = fuse_ctl_get_tree, 364 }; 365 366 static int fuse_ctl_init_fs_context(struct fs_context *fc) 367 { 368 fc->ops = &fuse_ctl_context_ops; 369 return 0; 370 } 371 372 static void fuse_ctl_kill_sb(struct super_block *sb) 373 { 374 struct fuse_conn *fc; 375 376 mutex_lock(&fuse_mutex); 377 fuse_control_sb = NULL; 378 list_for_each_entry(fc, &fuse_conn_list, entry) 379 fc->ctl_ndents = 0; 380 mutex_unlock(&fuse_mutex); 381 382 kill_litter_super(sb); 383 } 384 385 static struct file_system_type fuse_ctl_fs_type = { 386 .owner = THIS_MODULE, 387 .name = "fusectl", 388 .init_fs_context = fuse_ctl_init_fs_context, 389 .kill_sb = fuse_ctl_kill_sb, 390 }; 391 MODULE_ALIAS_FS("fusectl"); 392 393 int __init fuse_ctl_init(void) 394 { 395 return register_filesystem(&fuse_ctl_fs_type); 396 } 397 398 void __exit fuse_ctl_cleanup(void) 399 { 400 unregister_filesystem(&fuse_ctl_fs_type); 401 } 402