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