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         struct fuse_mount *fm;
 168         ssize_t ret;
 169
 170         ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
 171                                     max_user_congthresh);
 172         if (ret <= 0)
 173                 goto out;
 174         fc = fuse_ctl_file_conn_get(file);
 175         if (!fc)
 176                 goto out;
 177
 178         down_read(&fc->killsb);
 179         spin_lock(&fc->bg_lock);
 180         fc->congestion_threshold = val;
 181
 182         /*
 183          * Get any fuse_mount belonging to this fuse_conn; s_bdi is
 184          * shared between all of them
 185          */
 186
 187         if (!list_empty(&fc->mounts)) {
 188                 fm = list_first_entry(&fc->mounts, struct fuse_mount, fc_entry);
 189                 if (fc->num_background < fc->congestion_threshold) {
 190                         clear_bdi_congested(fm->sb->s_bdi, BLK_RW_SYNC);
 191                         clear_bdi_congested(fm->sb->s_bdi, BLK_RW_ASYNC);
 192                 } else {
 193                         set_bdi_congested(fm->sb->s_bdi, BLK_RW_SYNC);
 194                         set_bdi_congested(fm->sb->s_bdi, BLK_RW_ASYNC);
 195                 }
 196         }
 197         spin_unlock(&fc->bg_lock);
 198         up_read(&fc->killsb);
 199         fuse_conn_put(fc);
 200 out:
 201         return ret;
 202 }
 203
 204 static const struct file_operations fuse_ctl_abort_ops = {
 205         .open = nonseekable_open,
 206         .write = fuse_conn_abort_write,
 207         .llseek = no_llseek,
 208 };
 209
 210 static const struct file_operations fuse_ctl_waiting_ops = {
 211         .open = nonseekable_open,
 212         .read = fuse_conn_waiting_read,
 213         .llseek = no_llseek,
 214 };
 215
 216 static const struct file_operations fuse_conn_max_background_ops = {
 217         .open = nonseekable_open,
 218         .read = fuse_conn_max_background_read,
 219         .write = fuse_conn_max_background_write,
 220         .llseek = no_llseek,
 221 };
 222
 223 static const struct file_operations fuse_conn_congestion_threshold_ops = {
 224         .open = nonseekable_open,
 225         .read = fuse_conn_congestion_threshold_read,
 226         .write = fuse_conn_congestion_threshold_write,
 227         .llseek = no_llseek,
 228 };
 229
 230 static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
 231                                           struct fuse_conn *fc,
 232                                           const char *name,
 233                                           int mode, int nlink,
 234                                           const struct inode_operations *iop,
 235                                           const struct file_operations *fop)
 236 {
 237         struct dentry *dentry;
 238         struct inode *inode;
 239
 240         BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
 241         dentry = d_alloc_name(parent, name);
 242         if (!dentry)
 243                 return NULL;
 244
 245         inode = new_inode(fuse_control_sb);
 246         if (!inode) {
 247                 dput(dentry);
 248                 return NULL;
 249         }
 250
 251         inode->i_ino = get_next_ino();
 252         inode->i_mode = mode;
 253         inode->i_uid = fc->user_id;
 254         inode->i_gid = fc->group_id;
 255         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 256         /* setting ->i_op to NULL is not allowed */
 257         if (iop)
 258                 inode->i_op = iop;
 259         inode->i_fop = fop;
 260         set_nlink(inode, nlink);
 261         inode->i_private = fc;
 262         d_add(dentry, inode);
 263
 264         fc->ctl_dentry[fc->ctl_ndents++] = dentry;
 265
 266         return dentry;
 267 }
 268
 269 /*
 270  * Add a connection to the control filesystem (if it exists).  Caller
 271  * must hold fuse_mutex
 272  */
 273 int fuse_ctl_add_conn(struct fuse_conn *fc)
 274 {
 275         struct dentry *parent;
 276         char name[32];
 277
 278         if (!fuse_control_sb)
 279                 return 0;
 280
 281         parent = fuse_control_sb->s_root;
 282         inc_nlink(d_inode(parent));
 283         sprintf(name, "%u", fc->dev);
 284         parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
 285                                      &simple_dir_inode_operations,
 286                                      &simple_dir_operations);
 287         if (!parent)
 288                 goto err;
 289
 290         if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,
 291                                  NULL, &fuse_ctl_waiting_ops) ||
 292             !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,
 293                                  NULL, &fuse_ctl_abort_ops) ||
 294             !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
 295                                  1, NULL, &fuse_conn_max_background_ops) ||
 296             !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
 297                                  S_IFREG | 0600, 1, NULL,
 298                                  &fuse_conn_congestion_threshold_ops))
 299                 goto err;
 300
 301         return 0;
 302
 303  err:
 304         fuse_ctl_remove_conn(fc);
 305         return -ENOMEM;
 306 }
 307
 308 /*
 309  * Remove a connection from the control filesystem (if it exists).
 310  * Caller must hold fuse_mutex
 311  */
 312 void fuse_ctl_remove_conn(struct fuse_conn *fc)
 313 {
 314         int i;
 315
 316         if (!fuse_control_sb)
 317                 return;
 318
 319         for (i = fc->ctl_ndents - 1; i >= 0; i--) {
 320                 struct dentry *dentry = fc->ctl_dentry[i];
 321                 d_inode(dentry)->i_private = NULL;
 322                 if (!i) {
 323                         /* Get rid of submounts: */
 324                         d_invalidate(dentry);
 325                 }
 326                 dput(dentry);
 327         }
 328         drop_nlink(d_inode(fuse_control_sb->s_root));
 329 }
 330
 331 static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fsc)
 332 {
 333         static const struct tree_descr empty_descr = {""};
 334         struct fuse_conn *fc;
 335         int err;
 336
 337         err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
 338         if (err)
 339                 return err;
 340
 341         mutex_lock(&fuse_mutex);
 342         BUG_ON(fuse_control_sb);
 343         fuse_control_sb = sb;
 344         list_for_each_entry(fc, &fuse_conn_list, entry) {
 345                 err = fuse_ctl_add_conn(fc);
 346                 if (err) {
 347                         fuse_control_sb = NULL;
 348                         mutex_unlock(&fuse_mutex);
 349                         return err;
 350                 }
 351         }
 352         mutex_unlock(&fuse_mutex);
 353
 354         return 0;
 355 }
 356
 357 static int fuse_ctl_get_tree(struct fs_context *fsc)
 358 {
 359         return get_tree_single(fsc, fuse_ctl_fill_super);
 360 }
 361
 362 static const struct fs_context_operations fuse_ctl_context_ops = {
 363         .get_tree       = fuse_ctl_get_tree,
 364 };
 365
 366 static int fuse_ctl_init_fs_context(struct fs_context *fsc)
 367 {
 368         fsc->ops = &fuse_ctl_context_ops;
 369         return 0;
 370 }
 371
 372 static void fuse_ctl_kill_sb(struct super_block *sb)
 373 {
 374         struct fuse_conn *fc;
 375
 376         mutex_lock(&fuse_mutex);
 377         fuse_control_sb = NULL;
 378         list_for_each_entry(fc, &fuse_conn_list, entry)
 379                 fc->ctl_ndents = 0;
 380         mutex_unlock(&fuse_mutex);
 381
 382         kill_litter_super(sb);
 383 }
 384
 385 static struct file_system_type fuse_ctl_fs_type = {
 386         .owner          = THIS_MODULE,
 387         .name           = "fusectl",
 388         .init_fs_context = fuse_ctl_init_fs_context,
 389         .kill_sb        = fuse_ctl_kill_sb,
 390 };
 391 MODULE_ALIAS_FS("fusectl");
 392
 393 int __init fuse_ctl_init(void)
 394 {
 395         return register_filesystem(&fuse_ctl_fs_type);
 396 }
 397
 398 void __exit fuse_ctl_cleanup(void)
 399 {
 400         unregister_filesystem(&fuse_ctl_fs_type);
 401 }