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