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