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                 if (fc->abort_err)
  39                         fc->aborted = true;
  40                 fuse_abort_conn(fc);
  41                 fuse_conn_put(fc);
  42         }
  43         return count;
  44 }
  45
  46 static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
  47                                       size_t len, loff_t *ppos)
  48 {
  49         char tmp[32];
  50         size_t size;
  51
  52         if (!*ppos) {
  53                 long value;
  54                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
  55                 if (!fc)
  56                         return 0;
  57
  58                 value = atomic_read(&fc->num_waiting);
  59                 file->private_data = (void *)value;
  60                 fuse_conn_put(fc);
  61         }
  62         size = sprintf(tmp, "%ld\n", (long)file->private_data);
  63         return simple_read_from_buffer(buf, len, ppos, tmp, size);
  64 }
  65
  66 static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf,
  67                                     size_t len, loff_t *ppos, unsigned val)
  68 {
  69         char tmp[32];
  70         size_t size = sprintf(tmp, "%u\n", val);
  71
  72         return simple_read_from_buffer(buf, len, ppos, tmp, size);
  73 }
  74
  75 static ssize_t fuse_conn_limit_write(struct file *file, const char __user *buf,
  76                                      size_t count, loff_t *ppos, unsigned *val,
  77                                      unsigned global_limit)
  78 {
  79         unsigned long t;
  80         unsigned limit = (1 << 16) - 1;
  81         int err;
  82
  83         if (*ppos)
  84                 return -EINVAL;
  85
  86         err = kstrtoul_from_user(buf, count, 0, &t);
  87         if (err)
  88                 return err;
  89
  90         if (!capable(CAP_SYS_ADMIN))
  91                 limit = min(limit, global_limit);
  92
  93         if (t > limit)
  94                 return -EINVAL;
  95
  96         *val = t;
  97
  98         return count;
  99 }
 100
 101 static ssize_t fuse_conn_max_background_read(struct file *file,
 102                                              char __user *buf, size_t len,
 103                                              loff_t *ppos)
 104 {
 105         struct fuse_conn *fc;
 106         unsigned val;
 107
 108         fc = fuse_ctl_file_conn_get(file);
 109         if (!fc)
 110                 return 0;
 111
 112         val = READ_ONCE(fc->max_background);
 113         fuse_conn_put(fc);
 114
 115         return fuse_conn_limit_read(file, buf, len, ppos, val);
 116 }
 117
 118 static ssize_t fuse_conn_max_background_write(struct file *file,
 119                                               const char __user *buf,
 120                                               size_t count, loff_t *ppos)
 121 {
 122         unsigned uninitialized_var(val);
 123         ssize_t ret;
 124
 125         ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
 126                                     max_user_bgreq);
 127         if (ret > 0) {
 128                 struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
 129                 if (fc) {
 130                         spin_lock(&fc->bg_lock);
 131                         fc->max_background = val;
 132                         fc->blocked = fc->num_background >= fc->max_background;
 133                         if (!fc->blocked)
 134                                 wake_up(&fc->blocked_waitq);
 135                         spin_unlock(&fc->bg_lock);
 136                         fuse_conn_put(fc);
 137                 }
 138         }
 139
 140         return ret;
 141 }
 142
 143 static ssize_t fuse_conn_congestion_threshold_read(struct file *file,
 144                                                    char __user *buf, size_t len,
 145                                                    loff_t *ppos)
 146 {
 147         struct fuse_conn *fc;
 148         unsigned val;
 149
 150         fc = fuse_ctl_file_conn_get(file);
 151         if (!fc)
 152                 return 0;
 153
 154         val = READ_ONCE(fc->congestion_threshold);
 155         fuse_conn_put(fc);
 156
 157         return fuse_conn_limit_read(file, buf, len, ppos, val);
 158 }
 159
 160 static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
 161                                                     const char __user *buf,
 162                                                     size_t count, loff_t *ppos)
 163 {
 164         unsigned uninitialized_var(val);
 165         struct fuse_conn *fc;
 166         ssize_t ret;
 167
 168         ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
 169                                     max_user_congthresh);
 170         if (ret <= 0)
 171                 goto out;
 172         fc = fuse_ctl_file_conn_get(file);
 173         if (!fc)
 174                 goto out;
 175
 176         spin_lock(&fc->bg_lock);
 177         fc->congestion_threshold = val;
 178         if (fc->sb) {
 179                 if (fc->num_background < fc->congestion_threshold) {
 180                         clear_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC);
 181                         clear_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC);
 182                 } else {
 183                         set_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC);
 184                         set_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC);
 185                 }
 186         }
 187         spin_unlock(&fc->bg_lock);
 188         fuse_conn_put(fc);
 189 out:
 190         return ret;
 191 }
 192
 193 static const struct file_operations fuse_ctl_abort_ops = {
 194         .open = nonseekable_open,
 195         .write = fuse_conn_abort_write,
 196         .llseek = no_llseek,
 197 };
 198
 199 static const struct file_operations fuse_ctl_waiting_ops = {
 200         .open = nonseekable_open,
 201         .read = fuse_conn_waiting_read,
 202         .llseek = no_llseek,
 203 };
 204
 205 static const struct file_operations fuse_conn_max_background_ops = {
 206         .open = nonseekable_open,
 207         .read = fuse_conn_max_background_read,
 208         .write = fuse_conn_max_background_write,
 209         .llseek = no_llseek,
 210 };
 211
 212 static const struct file_operations fuse_conn_congestion_threshold_ops = {
 213         .open = nonseekable_open,
 214         .read = fuse_conn_congestion_threshold_read,
 215         .write = fuse_conn_congestion_threshold_write,
 216         .llseek = no_llseek,
 217 };
 218
 219 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
 220                                           struct fuse_conn *fc,
 221                                           const char *name,
 222                                           int mode, int nlink,
 223                                           const struct inode_operations *iop,
 224                                           const struct file_operations *fop)
 225 {
 226         struct dentry *dentry;
 227         struct inode *inode;
 228
 229         BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
 230         dentry = d_alloc_name(parent, name);
 231         if (!dentry)
 232                 return NULL;
 233
 234         inode = new_inode(fuse_control_sb);
 235         if (!inode) {
 236                 dput(dentry);
 237                 return NULL;
 238         }
 239
 240         inode->i_ino = get_next_ino();
 241         inode->i_mode = mode;
 242         inode->i_uid = fc->user_id;
 243         inode->i_gid = fc->group_id;
 244         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 245         /* setting ->i_op to NULL is not allowed */
 246         if (iop)
 247                 inode->i_op = iop;
 248         inode->i_fop = fop;
 249         set_nlink(inode, nlink);
 250         inode->i_private = fc;
 251         d_add(dentry, inode);
 252
 253         fc->ctl_dentry[fc->ctl_ndents++] = dentry;
 254
 255         return dentry;
 256 }
 257
 258 /*
 259  * Add a connection to the control filesystem (if it exists).  Caller
 260  * must hold fuse_mutex
 261  */
 262 int fuse_ctl_add_conn(struct fuse_conn *fc)
 263 {
 264         struct dentry *parent;
 265         char name[32];
 266
 267         if (!fuse_control_sb)
 268                 return 0;
 269
 270         parent = fuse_control_sb->s_root;
 271         inc_nlink(d_inode(parent));
 272         sprintf(name, "%u", fc->dev);
 273         parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
 274                                      &simple_dir_inode_operations,
 275                                      &simple_dir_operations);
 276         if (!parent)
 277                 goto err;
 278
 279         if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
 280                                  NULL, &fuse_ctl_waiting_ops) ||
 281             !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
 282                                  NULL, &fuse_ctl_abort_ops) ||
 283             !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
 284                                  1, NULL, &fuse_conn_max_background_ops) ||
 285             !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
 286                                  S_IFREG | 0600, 1, NULL,
 287                                  &fuse_conn_congestion_threshold_ops))
 288                 goto err;
 289
 290         return 0;
 291
 292  err:
 293         fuse_ctl_remove_conn(fc);
 294         return -ENOMEM;
 295 }
 296
 297 /*
 298  * Remove a connection from the control filesystem (if it exists).
 299  * Caller must hold fuse_mutex
 300  */
 301 void fuse_ctl_remove_conn(struct fuse_conn *fc)
 302 {
 303         int i;
 304
 305         if (!fuse_control_sb)
 306                 return;
 307
 308         for (i = fc->ctl_ndents - 1; i >= 0; i--) {
 309                 struct dentry *dentry = fc->ctl_dentry[i];
 310                 d_inode(dentry)->i_private = NULL;
 311                 if (!i) {
 312                         /* Get rid of submounts: */
 313                         d_invalidate(dentry);
 314                 }
 315                 dput(dentry);
 316         }
 317         drop_nlink(d_inode(fuse_control_sb->s_root));
 318 }
 319
 320 static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent)
 321 {
 322         static const struct tree_descr empty_descr = {""};
 323         struct fuse_conn *fc;
 324         int err;
 325
 326         err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
 327         if (err)
 328                 return err;
 329
 330         mutex_lock(&fuse_mutex);
 331         BUG_ON(fuse_control_sb);
 332         fuse_control_sb = sb;
 333         list_for_each_entry(fc, &fuse_conn_list, entry) {
 334                 err = fuse_ctl_add_conn(fc);
 335                 if (err) {
 336                         fuse_control_sb = NULL;
 337                         mutex_unlock(&fuse_mutex);
 338                         return err;
 339                 }
 340         }
 341         mutex_unlock(&fuse_mutex);
 342
 343         return 0;
 344 }
 345
 346 static struct dentry *fuse_ctl_mount(struct file_system_type *fs_type,
 347                         int flags, const char *dev_name, void *raw_data)
 348 {
 349         return mount_single(fs_type, flags, raw_data, fuse_ctl_fill_super);
 350 }
 351
 352 static void fuse_ctl_kill_sb(struct super_block *sb)
 353 {
 354         struct fuse_conn *fc;
 355
 356         mutex_lock(&fuse_mutex);
 357         fuse_control_sb = NULL;
 358         list_for_each_entry(fc, &fuse_conn_list, entry)
 359                 fc->ctl_ndents = 0;
 360         mutex_unlock(&fuse_mutex);
 361
 362         kill_litter_super(sb);
 363 }
 364
 365 static struct file_system_type fuse_ctl_fs_type = {
 366         .owner          = THIS_MODULE,
 367         .name           = "fusectl",
 368         .mount          = fuse_ctl_mount,
 369         .kill_sb        = fuse_ctl_kill_sb,
 370 };
 371 MODULE_ALIAS_FS("fusectl");
 372
 373 int __init fuse_ctl_init(void)
 374 {
 375         return register_filesystem(&fuse_ctl_fs_type);
 376 }
 377
 378 void __exit fuse_ctl_cleanup(void)
 379 {
 380         unregister_filesystem(&fuse_ctl_fs_type);
 381 }