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