linux/fs/fuse/control.c
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   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 */
  20static struct super_block *fuse_control_sb;
  21
  22static 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
  33static 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
  44static 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
  64static 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
  73static 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
 105static 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
 122static 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
 142static 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
 159static 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
 179static const struct file_operations fuse_ctl_abort_ops = {
 180        .open = nonseekable_open,
 181        .write = fuse_conn_abort_write,
 182        .llseek = no_llseek,
 183};
 184
 185static const struct file_operations fuse_ctl_waiting_ops = {
 186        .open = nonseekable_open,
 187        .read = fuse_conn_waiting_read,
 188        .llseek = no_llseek,
 189};
 190
 191static 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
 198static 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
 205static 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        inode->i_nlink = 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 */
 244int 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 */
 283void 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
 299static 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
 325static 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
 331static 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
 344static 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
 351int __init fuse_ctl_init(void)
 352{
 353        return register_filesystem(&fuse_ctl_fs_type);
 354}
 355
 356void fuse_ctl_cleanup(void)
 357{
 358        unregister_filesystem(&fuse_ctl_fs_type);
 359}
 360