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        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
  99static 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
 116static 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
 136static 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
 153static 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
 173static const struct file_operations fuse_ctl_abort_ops = {
 174        .open = nonseekable_open,
 175        .write = fuse_conn_abort_write,
 176        .llseek = no_llseek,
 177};
 178
 179static const struct file_operations fuse_ctl_waiting_ops = {
 180        .open = nonseekable_open,
 181        .read = fuse_conn_waiting_read,
 182        .llseek = no_llseek,
 183};
 184
 185static 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
 192static 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
 199static 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 */
 238int 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(parent->d_inode);
 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 */
 277void 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                dentry->d_inode->i_private = NULL;
 287                d_drop(dentry);
 288                dput(dentry);
 289        }
 290        drop_nlink(fuse_control_sb->s_root->d_inode);
 291}
 292
 293static 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
 319static 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
 325static 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
 338static 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
 345int __init fuse_ctl_init(void)
 346{
 347        return register_filesystem(&fuse_ctl_fs_type);
 348}
 349
 350void fuse_ctl_cleanup(void)
 351{
 352        unregister_filesystem(&fuse_ctl_fs_type);
 353}
 354
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