fs/fuse/control.c

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