fs/fuse/control.c

   1 /*
   2   FUSE: Filesystem in Userspace
   3   Copyright (C) 2001-2008  Miklos Szeredi <[email protected]>
   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->bg_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->bg_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->bg_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->bg_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 }