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