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#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 */
  21static struct super_block *fuse_control_sb;
  22
  23static 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
  34static 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
  47static 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
  67static 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
  76static 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
 102static 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
 119static 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
 144static 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
 161static 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);
 200out:
 201        return ret;
 202}
 203
 204static const struct file_operations fuse_ctl_abort_ops = {
 205        .open = nonseekable_open,
 206        .write = fuse_conn_abort_write,
 207        .llseek = no_llseek,
 208};
 209
 210static const struct file_operations fuse_ctl_waiting_ops = {
 211        .open = nonseekable_open,
 212        .read = fuse_conn_waiting_read,
 213        .llseek = no_llseek,
 214};
 215
 216static 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
 223static 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
 230static 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 */
 273int 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 */
 312void 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
 331static int fuse_ctl_fill_super(struct super_block *sb, struct fs_context *fctx)
 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
 357static int fuse_ctl_get_tree(struct fs_context *fc)
 358{
 359        return get_tree_single(fc, fuse_ctl_fill_super);
 360}
 361
 362static const struct fs_context_operations fuse_ctl_context_ops = {
 363        .get_tree       = fuse_ctl_get_tree,
 364};
 365
 366static int fuse_ctl_init_fs_context(struct fs_context *fc)
 367{
 368        fc->ops = &fuse_ctl_context_ops;
 369        return 0;
 370}
 371
 372static 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
 385static 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};
 391MODULE_ALIAS_FS("fusectl");
 392
 393int __init fuse_ctl_init(void)
 394{
 395        return register_filesystem(&fuse_ctl_fs_type);
 396}
 397
 398void __exit fuse_ctl_cleanup(void)
 399{
 400        unregister_filesystem(&fuse_ctl_fs_type);
 401}
 402