/*
    FUSE: Filesystem in Userspace

    Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>

  
    This program can be distributed under the terms of the GNU GPL.
    See the file COPYING.
  */
  
  #include "fuse_i.h"
  
  #include <linux/pagemap.h>
  #include <linux/slab.h>
  #include <linux/file.h>

  #include <linux/seq_file.h>
  #include <linux/init.h>
  #include <linux/module.h>

  #include <linux/moduleparam.h>

  #include <linux/fs_context.h>
  #include <linux/fs_parser.h>

  #include <linux/statfs.h>

  #include <linux/random.h>

  #include <linux/sched.h>

  #include <linux/exportfs.h>

  #include <linux/posix_acl.h>

  #include <linux/pid_namespace.h>

  
  MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
  MODULE_DESCRIPTION("Filesystem in Userspace");
  MODULE_LICENSE("GPL");

  static struct kmem_cache *fuse_inode_cachep;

  struct list_head fuse_conn_list;
  DEFINE_MUTEX(fuse_mutex);

  static int set_global_limit(const char *val, const struct kernel_param *kp);

  unsigned max_user_bgreq;

  module_param_call(max_user_bgreq, set_global_limit, param_get_uint,
  		  &max_user_bgreq, 0644);
  __MODULE_PARM_TYPE(max_user_bgreq, "uint");
  MODULE_PARM_DESC(max_user_bgreq,
   "Global limit for the maximum number of backgrounded requests an "
   "unprivileged user can set");

  unsigned max_user_congthresh;

  module_param_call(max_user_congthresh, set_global_limit, param_get_uint,
  		  &max_user_congthresh, 0644);
  __MODULE_PARM_TYPE(max_user_congthresh, "uint");
  MODULE_PARM_DESC(max_user_congthresh,
   "Global limit for the maximum congestion threshold an "
   "unprivileged user can set");

  #define FUSE_SUPER_MAGIC 0x65735546

  #define FUSE_DEFAULT_BLKSIZE 512

  /** Maximum number of outstanding background requests */
  #define FUSE_DEFAULT_MAX_BACKGROUND 12
  
  /** Congestion starts at 75% of maximum */
  #define FUSE_DEFAULT_CONGESTION_THRESHOLD (FUSE_DEFAULT_MAX_BACKGROUND * 3 / 4)

  #ifdef CONFIG_BLOCK
  static struct file_system_type fuseblk_fs_type;
  #endif

  struct fuse_forget_link *fuse_alloc_forget(void)

  {

  	return kzalloc(sizeof(struct fuse_forget_link), GFP_KERNEL_ACCOUNT);

  }

  static struct inode *fuse_alloc_inode(struct super_block *sb)
  {

  	struct fuse_inode *fi;

  	fi = kmem_cache_alloc(fuse_inode_cachep, GFP_KERNEL);
  	if (!fi)

  		return NULL;

  	fi->i_time = 0;

  	fi->inval_mask = 0;

  	fi->nodeid = 0;

  	fi->nlookup = 0;

  	fi->attr_version = 0;

  	fi->orig_ino = 0;

  	fi->state = 0;

  	mutex_init(&fi->mutex);

  	spin_lock_init(&fi->lock);

  	fi->forget = fuse_alloc_forget();
  	if (!fi->forget) {

  		kmem_cache_free(fuse_inode_cachep, fi);

  		return NULL;
  	}

  	return &fi->inode;

  }

  static void fuse_free_inode(struct inode *inode)

  {

  	struct fuse_inode *fi = get_fuse_inode(inode);

  	mutex_destroy(&fi->mutex);

  	kfree(fi->forget);

  	kmem_cache_free(fuse_inode_cachep, fi);

  }

  static void fuse_evict_inode(struct inode *inode)

  {

  	struct fuse_inode *fi = get_fuse_inode(inode);

  	truncate_inode_pages_final(&inode->i_data);

  	clear_inode(inode);

  	if (inode->i_sb->s_flags & SB_ACTIVE) {

  		struct fuse_conn *fc = get_fuse_conn(inode);

  		fuse_queue_forget(fc, fi->forget, fi->nodeid, fi->nlookup);
  		fi->forget = NULL;

  	}

  	if (S_ISREG(inode->i_mode) && !is_bad_inode(inode)) {
  		WARN_ON(!list_empty(&fi->write_files));
  		WARN_ON(!list_empty(&fi->queued_writes));
  	}

  }

  static int fuse_reconfigure(struct fs_context *fc)

  {

  	struct super_block *sb = fc->root->d_sb;

  	sync_filesystem(sb);

  	if (fc->sb_flags & SB_MANDLOCK)

  		return -EINVAL;
  
  	return 0;
  }

  /*
   * ino_t is 32-bits on 32-bit arch. We have to squash the 64-bit value down
   * so that it will fit.
   */
  static ino_t fuse_squash_ino(u64 ino64)
  {
  	ino_t ino = (ino_t) ino64;
  	if (sizeof(ino_t) < sizeof(u64))
  		ino ^= ino64 >> (sizeof(u64) - sizeof(ino_t)) * 8;
  	return ino;
  }

  void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
  				   u64 attr_valid)

  {

  	struct fuse_conn *fc = get_fuse_conn(inode);

  	struct fuse_inode *fi = get_fuse_inode(inode);

  	lockdep_assert_held(&fi->lock);

  	fi->attr_version = atomic64_inc_return(&fc->attr_version);

  	fi->i_time = attr_valid;

  	WRITE_ONCE(fi->inval_mask, 0);

  	inode->i_ino     = fuse_squash_ino(attr->ino);

  	inode->i_mode    = (inode->i_mode & S_IFMT) | (attr->mode & 07777);

  	set_nlink(inode, attr->nlink);

  	inode->i_uid     = make_kuid(fc->user_ns, attr->uid);
  	inode->i_gid     = make_kgid(fc->user_ns, attr->gid);

  	inode->i_blocks  = attr->blocks;
  	inode->i_atime.tv_sec   = attr->atime;
  	inode->i_atime.tv_nsec  = attr->atimensec;

  	/* mtime from server may be stale due to local buffered write */
  	if (!fc->writeback_cache || !S_ISREG(inode->i_mode)) {
  		inode->i_mtime.tv_sec   = attr->mtime;
  		inode->i_mtime.tv_nsec  = attr->mtimensec;

  		inode->i_ctime.tv_sec   = attr->ctime;
  		inode->i_ctime.tv_nsec  = attr->ctimensec;

  	}

  	if (attr->blksize != 0)
  		inode->i_blkbits = ilog2(attr->blksize);
  	else
  		inode->i_blkbits = inode->i_sb->s_blocksize_bits;

  	/*
  	 * Don't set the sticky bit in i_mode, unless we want the VFS
  	 * to check permissions.  This prevents failures due to the
  	 * check in may_delete().
  	 */
  	fi->orig_i_mode = inode->i_mode;

  	if (!fc->default_permissions)

  		inode->i_mode &= ~S_ISVTX;

  
  	fi->orig_ino = attr->ino;

  }
  
  void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
  			    u64 attr_valid, u64 attr_version)
  {
  	struct fuse_conn *fc = get_fuse_conn(inode);
  	struct fuse_inode *fi = get_fuse_inode(inode);

  	bool is_wb = fc->writeback_cache;

  	loff_t oldsize;

  	struct timespec64 old_mtime;

  	spin_lock(&fi->lock);

  	if ((attr_version != 0 && fi->attr_version > attr_version) ||
  	    test_bit(FUSE_I_SIZE_UNSTABLE, &fi->state)) {

  		spin_unlock(&fi->lock);

  		return;
  	}

  	old_mtime = inode->i_mtime;

  	fuse_change_attributes_common(inode, attr, attr_valid);

  	oldsize = inode->i_size;

  	/*
  	 * In case of writeback_cache enabled, the cached writes beyond EOF
  	 * extend local i_size without keeping userspace server in sync. So,
  	 * attr->size coming from server can be stale. We cannot trust it.
  	 */
  	if (!is_wb || !S_ISREG(inode->i_mode))
  		i_size_write(inode, attr->size);

  	spin_unlock(&fi->lock);

  	if (!is_wb && S_ISREG(inode->i_mode)) {

  		bool inval = false;
  
  		if (oldsize != attr->size) {

  			truncate_pagecache(inode, attr->size);

  			if (!fc->explicit_inval_data)
  				inval = true;

  		} else if (fc->auto_inval_data) {

  			struct timespec64 new_mtime = {

  				.tv_sec = attr->mtime,
  				.tv_nsec = attr->mtimensec,
  			};
  
  			/*
  			 * Auto inval mode also checks and invalidates if mtime
  			 * has changed.
  			 */

  			if (!timespec64_equal(&old_mtime, &new_mtime))

  				inval = true;
  		}
  
  		if (inval)
  			invalidate_inode_pages2(inode->i_mapping);

  	}

  }
  
  static void fuse_init_inode(struct inode *inode, struct fuse_attr *attr)
  {
  	inode->i_mode = attr->mode & S_IFMT;

  	inode->i_size = attr->size;

  	inode->i_mtime.tv_sec  = attr->mtime;
  	inode->i_mtime.tv_nsec = attr->mtimensec;

  	inode->i_ctime.tv_sec  = attr->ctime;
  	inode->i_ctime.tv_nsec = attr->ctimensec;

  	if (S_ISREG(inode->i_mode)) {
  		fuse_init_common(inode);

  		fuse_init_file_inode(inode);

  	} else if (S_ISDIR(inode->i_mode))
  		fuse_init_dir(inode);
  	else if (S_ISLNK(inode->i_mode))
  		fuse_init_symlink(inode);
  	else if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode) ||
  		 S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
  		fuse_init_common(inode);
  		init_special_inode(inode, inode->i_mode,
  				   new_decode_dev(attr->rdev));

  	} else
  		BUG();

  }

  int fuse_inode_eq(struct inode *inode, void *_nodeidp)

  {

  	u64 nodeid = *(u64 *) _nodeidp;

  	if (get_node_id(inode) == nodeid)
  		return 1;
  	else
  		return 0;
  }
  
  static int fuse_inode_set(struct inode *inode, void *_nodeidp)
  {

  	u64 nodeid = *(u64 *) _nodeidp;

  	get_fuse_inode(inode)->nodeid = nodeid;
  	return 0;
  }

  struct inode *fuse_iget(struct super_block *sb, u64 nodeid,

  			int generation, struct fuse_attr *attr,
  			u64 attr_valid, u64 attr_version)

  {
  	struct inode *inode;

  	struct fuse_inode *fi;

  	struct fuse_conn *fc = get_fuse_conn_super(sb);

  
   retry:
  	inode = iget5_locked(sb, nodeid, fuse_inode_eq, fuse_inode_set, &nodeid);
  	if (!inode)
  		return NULL;
  
  	if ((inode->i_state & I_NEW)) {

  		inode->i_flags |= S_NOATIME;

  		if (!fc->writeback_cache || !S_ISREG(attr->mode))

  			inode->i_flags |= S_NOCMTIME;

  		inode->i_generation = generation;

  		fuse_init_inode(inode, attr);
  		unlock_new_inode(inode);
  	} else if ((inode->i_mode ^ attr->mode) & S_IFMT) {

  		/* Inode has changed type, any I/O on the old should fail */
  		make_bad_inode(inode);
  		iput(inode);

  		goto retry;
  	}

  	fi = get_fuse_inode(inode);

  	spin_lock(&fi->lock);

  	fi->nlookup++;

  	spin_unlock(&fi->lock);

  	fuse_change_attributes(inode, attr, attr_valid, attr_version);

  	return inode;
  }

  int fuse_reverse_inval_inode(struct super_block *sb, u64 nodeid,
  			     loff_t offset, loff_t len)
  {

  	struct fuse_conn *fc = get_fuse_conn_super(sb);
  	struct fuse_inode *fi;

  	struct inode *inode;
  	pgoff_t pg_start;
  	pgoff_t pg_end;
  
  	inode = ilookup5(sb, nodeid, fuse_inode_eq, &nodeid);
  	if (!inode)
  		return -ENOENT;

  	fi = get_fuse_inode(inode);
  	spin_lock(&fi->lock);
  	fi->attr_version = atomic64_inc_return(&fc->attr_version);
  	spin_unlock(&fi->lock);

  	fuse_invalidate_attr(inode);

  	forget_all_cached_acls(inode);

  	if (offset >= 0) {

  		pg_start = offset >> PAGE_SHIFT;

  		if (len <= 0)
  			pg_end = -1;
  		else

  			pg_end = (offset + len - 1) >> PAGE_SHIFT;

  		invalidate_inode_pages2_range(inode->i_mapping,
  					      pg_start, pg_end);
  	}
  	iput(inode);
  	return 0;
  }

  bool fuse_lock_inode(struct inode *inode)

  {

  	bool locked = false;
  
  	if (!get_fuse_conn(inode)->parallel_dirops) {

  		mutex_lock(&get_fuse_inode(inode)->mutex);

  		locked = true;
  	}
  
  	return locked;

  }

  void fuse_unlock_inode(struct inode *inode, bool locked)

  {

  	if (locked)

  		mutex_unlock(&get_fuse_inode(inode)->mutex);
  }

  static void fuse_umount_begin(struct super_block *sb)

  {

  	struct fuse_conn *fc = get_fuse_conn_super(sb);
  
  	if (!fc->no_force_umount)
  		fuse_abort_conn(fc);

  }

  static void fuse_send_destroy(struct fuse_conn *fc)
  {

  	if (fc->conn_init) {
  		FUSE_ARGS(args);
  
  		args.opcode = FUSE_DESTROY;
  		args.force = true;
  		args.nocreds = true;
  		fuse_simple_request(fc, &args);

  	}
  }

  static void fuse_put_super(struct super_block *sb)
  {
  	struct fuse_conn *fc = get_fuse_conn_super(sb);

  	mutex_lock(&fuse_mutex);
  	list_del(&fc->entry);
  	fuse_ctl_remove_conn(fc);
  	mutex_unlock(&fuse_mutex);

  	fuse_conn_put(fc);

  }

  static void convert_fuse_statfs(struct kstatfs *stbuf, struct fuse_kstatfs *attr)
  {
  	stbuf->f_type    = FUSE_SUPER_MAGIC;
  	stbuf->f_bsize   = attr->bsize;

  	stbuf->f_frsize  = attr->frsize;

  	stbuf->f_blocks  = attr->blocks;
  	stbuf->f_bfree   = attr->bfree;
  	stbuf->f_bavail  = attr->bavail;
  	stbuf->f_files   = attr->files;
  	stbuf->f_ffree   = attr->ffree;
  	stbuf->f_namelen = attr->namelen;
  	/* fsid is left zero */
  }

  static int fuse_statfs(struct dentry *dentry, struct kstatfs *buf)

  {

  	struct super_block *sb = dentry->d_sb;

  	struct fuse_conn *fc = get_fuse_conn_super(sb);

  	FUSE_ARGS(args);

  	struct fuse_statfs_out outarg;
  	int err;

  	if (!fuse_allow_current_process(fc)) {

  		buf->f_type = FUSE_SUPER_MAGIC;
  		return 0;
  	}

  	memset(&outarg, 0, sizeof(outarg));

  	args.in_numargs = 0;
  	args.opcode = FUSE_STATFS;
  	args.nodeid = get_node_id(d_inode(dentry));
  	args.out_numargs = 1;
  	args.out_args[0].size = sizeof(outarg);
  	args.out_args[0].value = &outarg;

  	err = fuse_simple_request(fc, &args);

  	if (!err)
  		convert_fuse_statfs(buf, &outarg.st);

  	return err;
  }

  enum {

  	OPT_SOURCE,
  	OPT_SUBTYPE,

  	OPT_FD,
  	OPT_ROOTMODE,
  	OPT_USER_ID,

  	OPT_GROUP_ID,

  	OPT_DEFAULT_PERMISSIONS,
  	OPT_ALLOW_OTHER,

  	OPT_MAX_READ,

  	OPT_BLKSIZE,

  	OPT_ERR
  };

  static const struct fs_parameter_spec fuse_fs_parameters[] = {

  	fsparam_string	("source",		OPT_SOURCE),
  	fsparam_u32	("fd",			OPT_FD),
  	fsparam_u32oct	("rootmode",		OPT_ROOTMODE),
  	fsparam_u32	("user_id",		OPT_USER_ID),
  	fsparam_u32	("group_id",		OPT_GROUP_ID),
  	fsparam_flag	("default_permissions",	OPT_DEFAULT_PERMISSIONS),
  	fsparam_flag	("allow_other",		OPT_ALLOW_OTHER),
  	fsparam_u32	("max_read",		OPT_MAX_READ),
  	fsparam_u32	("blksize",		OPT_BLKSIZE),

  	fsparam_string	("subtype",		OPT_SUBTYPE),

  	{}
  };

  static int fuse_parse_param(struct fs_context *fc, struct fs_parameter *param)

  {

  	struct fs_parse_result result;
  	struct fuse_fs_context *ctx = fc->fs_private;
  	int opt;

  	if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
  		/*
  		 * Ignore options coming from mount(MS_REMOUNT) for backward
  		 * compatibility.
  		 */
  		if (fc->oldapi)
  			return 0;
  
  		return invalfc(fc, "No changes allowed in reconfigure");
  	}

  	opt = fs_parse(fc, fuse_fs_parameters, param, &result);

  	if (opt < 0)
  		return opt;
  
  	switch (opt) {
  	case OPT_SOURCE:
  		if (fc->source)

  			return invalfc(fc, "Multiple sources specified");

  		fc->source = param->string;
  		param->string = NULL;
  		break;
  
  	case OPT_SUBTYPE:
  		if (ctx->subtype)

  			return invalfc(fc, "Multiple subtypes specified");

  		ctx->subtype = param->string;
  		param->string = NULL;
  		return 0;
  
  	case OPT_FD:
  		ctx->fd = result.uint_32;

  		ctx->fd_present = true;

  		break;
  
  	case OPT_ROOTMODE:
  		if (!fuse_valid_type(result.uint_32))

  			return invalfc(fc, "Invalid rootmode");

  		ctx->rootmode = result.uint_32;

  		ctx->rootmode_present = true;

  		break;
  
  	case OPT_USER_ID:
  		ctx->user_id = make_kuid(fc->user_ns, result.uint_32);
  		if (!uid_valid(ctx->user_id))

  			return invalfc(fc, "Invalid user_id");

  		ctx->user_id_present = true;

  		break;
  
  	case OPT_GROUP_ID:
  		ctx->group_id = make_kgid(fc->user_ns, result.uint_32);
  		if (!gid_valid(ctx->group_id))

  			return invalfc(fc, "Invalid group_id");

  		ctx->group_id_present = true;

  		break;
  
  	case OPT_DEFAULT_PERMISSIONS:

  		ctx->default_permissions = true;

  		break;
  
  	case OPT_ALLOW_OTHER:

  		ctx->allow_other = true;

  		break;
  
  	case OPT_MAX_READ:
  		ctx->max_read = result.uint_32;
  		break;
  
  	case OPT_BLKSIZE:
  		if (!ctx->is_bdev)

  			return invalfc(fc, "blksize only supported for fuseblk");

  		ctx->blksize = result.uint_32;
  		break;
  
  	default:
  		return -EINVAL;

  	}

  
  	return 0;

  }

  static void fuse_free_fc(struct fs_context *fc)

  {

  	struct fuse_fs_context *ctx = fc->fs_private;

  	if (ctx) {
  		kfree(ctx->subtype);
  		kfree(ctx);
  	}

  }

  static int fuse_show_options(struct seq_file *m, struct dentry *root)

  {

  	struct super_block *sb = root->d_sb;
  	struct fuse_conn *fc = get_fuse_conn_super(sb);

  	if (fc->no_mount_options)
  		return 0;

  	seq_printf(m, ",user_id=%u", from_kuid_munged(fc->user_ns, fc->user_id));
  	seq_printf(m, ",group_id=%u", from_kgid_munged(fc->user_ns, fc->group_id));

  	if (fc->default_permissions)

  		seq_puts(m, ",default_permissions");

  	if (fc->allow_other)

  		seq_puts(m, ",allow_other");

  	if (fc->max_read != ~0)
  		seq_printf(m, ",max_read=%u", fc->max_read);

  	if (sb->s_bdev && sb->s_blocksize != FUSE_DEFAULT_BLKSIZE)
  		seq_printf(m, ",blksize=%lu", sb->s_blocksize);

  	return 0;
  }

  static void fuse_iqueue_init(struct fuse_iqueue *fiq,
  			     const struct fuse_iqueue_ops *ops,
  			     void *priv)

  {
  	memset(fiq, 0, sizeof(struct fuse_iqueue));

  	spin_lock_init(&fiq->lock);

  	init_waitqueue_head(&fiq->waitq);
  	INIT_LIST_HEAD(&fiq->pending);
  	INIT_LIST_HEAD(&fiq->interrupts);
  	fiq->forget_list_tail = &fiq->forget_list_head;

  	fiq->connected = 1;

  	fiq->ops = ops;
  	fiq->priv = priv;

  }

  static void fuse_pqueue_init(struct fuse_pqueue *fpq)
  {

  	unsigned int i;

  	spin_lock_init(&fpq->lock);

  	for (i = 0; i < FUSE_PQ_HASH_SIZE; i++)
  		INIT_LIST_HEAD(&fpq->processing[i]);

  	INIT_LIST_HEAD(&fpq->io);

  	fpq->connected = 1;

  }

  void fuse_conn_init(struct fuse_conn *fc, struct user_namespace *user_ns,
  		    const struct fuse_iqueue_ops *fiq_ops, void *fiq_priv)

  {

  	memset(fc, 0, sizeof(*fc));
  	spin_lock_init(&fc->lock);

  	spin_lock_init(&fc->bg_lock);

  	init_rwsem(&fc->killsb);

  	refcount_set(&fc->count, 1);

  	atomic_set(&fc->dev_count, 1);

  	init_waitqueue_head(&fc->blocked_waitq);

  	fuse_iqueue_init(&fc->iq, fiq_ops, fiq_priv);

  	INIT_LIST_HEAD(&fc->bg_queue);
  	INIT_LIST_HEAD(&fc->entry);

  	INIT_LIST_HEAD(&fc->devices);

  	atomic_set(&fc->num_waiting, 0);

  	fc->max_background = FUSE_DEFAULT_MAX_BACKGROUND;
  	fc->congestion_threshold = FUSE_DEFAULT_CONGESTION_THRESHOLD;

  	atomic64_set(&fc->khctr, 0);

  	fc->polled_files = RB_ROOT;

  	fc->blocked = 0;

  	fc->initialized = 0;

  	fc->connected = 1;

  	atomic64_set(&fc->attr_version, 1);

  	get_random_bytes(&fc->scramble_key, sizeof(fc->scramble_key));

  	fc->pid_ns = get_pid_ns(task_active_pid_ns(current));

  	fc->user_ns = get_user_ns(user_ns);

  	fc->max_pages = FUSE_DEFAULT_MAX_PAGES_PER_REQ;

  }

  EXPORT_SYMBOL_GPL(fuse_conn_init);

  void fuse_conn_put(struct fuse_conn *fc)
  {

  	if (refcount_dec_and_test(&fc->count)) {

  		struct fuse_iqueue *fiq = &fc->iq;
  
  		if (fiq->ops->release)
  			fiq->ops->release(fiq);

  		put_pid_ns(fc->pid_ns);

  		put_user_ns(fc->user_ns);

  		fc->release(fc);

  	}

  }

  EXPORT_SYMBOL_GPL(fuse_conn_put);

  
  struct fuse_conn *fuse_conn_get(struct fuse_conn *fc)
  {

  	refcount_inc(&fc->count);

  	return fc;
  }

  EXPORT_SYMBOL_GPL(fuse_conn_get);

  static struct inode *fuse_get_root_inode(struct super_block *sb, unsigned mode)

  {
  	struct fuse_attr attr;
  	memset(&attr, 0, sizeof(attr));
  
  	attr.mode = mode;
  	attr.ino = FUSE_ROOT_ID;

  	attr.nlink = 1;

  	return fuse_iget(sb, 1, 0, &attr, 0, 0);

  }

  struct fuse_inode_handle {

  	u64 nodeid;
  	u32 generation;
  };
  
  static struct dentry *fuse_get_dentry(struct super_block *sb,
  				      struct fuse_inode_handle *handle)
  {

  	struct fuse_conn *fc = get_fuse_conn_super(sb);

  	struct inode *inode;
  	struct dentry *entry;
  	int err = -ESTALE;
  
  	if (handle->nodeid == 0)
  		goto out_err;
  
  	inode = ilookup5(sb, handle->nodeid, fuse_inode_eq, &handle->nodeid);

  	if (!inode) {
  		struct fuse_entry_out outarg;

  		const struct qstr name = QSTR_INIT(".", 1);

  
  		if (!fc->export_support)
  			goto out_err;

  		err = fuse_lookup_name(sb, handle->nodeid, &name, &outarg,
  				       &inode);
  		if (err && err != -ENOENT)
  			goto out_err;
  		if (err || !inode) {
  			err = -ESTALE;
  			goto out_err;
  		}
  		err = -EIO;
  		if (get_node_id(inode) != handle->nodeid)
  			goto out_iput;
  	}

  	err = -ESTALE;
  	if (inode->i_generation != handle->generation)
  		goto out_iput;

  	entry = d_obtain_alias(inode);

  	if (!IS_ERR(entry) && get_node_id(inode) != FUSE_ROOT_ID)

  		fuse_invalidate_entry_cache(entry);

  
  	return entry;
  
   out_iput:
  	iput(inode);
   out_err:
  	return ERR_PTR(err);
  }

  static int fuse_encode_fh(struct inode *inode, u32 *fh, int *max_len,
  			   struct inode *parent)

  {

  	int len = parent ? 6 : 3;

  	u64 nodeid;
  	u32 generation;

  	if (*max_len < len) {
  		*max_len = len;

  		return  FILEID_INVALID;

  	}

  
  	nodeid = get_fuse_inode(inode)->nodeid;
  	generation = inode->i_generation;
  
  	fh[0] = (u32)(nodeid >> 32);
  	fh[1] = (u32)(nodeid & 0xffffffff);
  	fh[2] = generation;

  	if (parent) {

  		nodeid = get_fuse_inode(parent)->nodeid;
  		generation = parent->i_generation;

  
  		fh[3] = (u32)(nodeid >> 32);
  		fh[4] = (u32)(nodeid & 0xffffffff);
  		fh[5] = generation;
  	}
  
  	*max_len = len;

  	return parent ? 0x82 : 0x81;

  }
  
  static struct dentry *fuse_fh_to_dentry(struct super_block *sb,
  		struct fid *fid, int fh_len, int fh_type)
  {
  	struct fuse_inode_handle handle;
  
  	if ((fh_type != 0x81 && fh_type != 0x82) || fh_len < 3)
  		return NULL;
  
  	handle.nodeid = (u64) fid->raw[0] << 32;
  	handle.nodeid |= (u64) fid->raw[1];
  	handle.generation = fid->raw[2];
  	return fuse_get_dentry(sb, &handle);
  }
  
  static struct dentry *fuse_fh_to_parent(struct super_block *sb,
  		struct fid *fid, int fh_len, int fh_type)
  {
  	struct fuse_inode_handle parent;
  
  	if (fh_type != 0x82 || fh_len < 6)
  		return NULL;
  
  	parent.nodeid = (u64) fid->raw[3] << 32;
  	parent.nodeid |= (u64) fid->raw[4];
  	parent.generation = fid->raw[5];
  	return fuse_get_dentry(sb, &parent);
  }

  static struct dentry *fuse_get_parent(struct dentry *child)
  {

  	struct inode *child_inode = d_inode(child);

  	struct fuse_conn *fc = get_fuse_conn(child_inode);
  	struct inode *inode;
  	struct dentry *parent;
  	struct fuse_entry_out outarg;

  	const struct qstr name = QSTR_INIT("..", 2);

  	int err;
  
  	if (!fc->export_support)
  		return ERR_PTR(-ESTALE);

  	err = fuse_lookup_name(child_inode->i_sb, get_node_id(child_inode),
  			       &name, &outarg, &inode);

  	if (err) {
  		if (err == -ENOENT)
  			return ERR_PTR(-ESTALE);

  		return ERR_PTR(err);

  	}

  
  	parent = d_obtain_alias(inode);

  	if (!IS_ERR(parent) && get_node_id(inode) != FUSE_ROOT_ID)

  		fuse_invalidate_entry_cache(parent);

  
  	return parent;
  }

  
  static const struct export_operations fuse_export_operations = {
  	.fh_to_dentry	= fuse_fh_to_dentry,
  	.fh_to_parent	= fuse_fh_to_parent,
  	.encode_fh	= fuse_encode_fh,

  	.get_parent	= fuse_get_parent,

  };

  static const struct super_operations fuse_super_operations = {

  	.alloc_inode    = fuse_alloc_inode,

  	.free_inode     = fuse_free_inode,

  	.evict_inode	= fuse_evict_inode,

  	.write_inode	= fuse_write_inode,

  	.drop_inode	= generic_delete_inode,

  	.put_super	= fuse_put_super,

  	.umount_begin	= fuse_umount_begin,

  	.statfs		= fuse_statfs,

  	.show_options	= fuse_show_options,
  };

  static void sanitize_global_limit(unsigned *limit)
  {

  	/*
  	 * The default maximum number of async requests is calculated to consume
  	 * 1/2^13 of the total memory, assuming 392 bytes per request.
  	 */

  	if (*limit == 0)

  		*limit = ((totalram_pages() << PAGE_SHIFT) >> 13) / 392;

  
  	if (*limit >= 1 << 16)
  		*limit = (1 << 16) - 1;
  }

  static int set_global_limit(const char *val, const struct kernel_param *kp)

  {
  	int rv;
  
  	rv = param_set_uint(val, kp);
  	if (rv)
  		return rv;
  
  	sanitize_global_limit((unsigned *)kp->arg);
  
  	return 0;
  }
  
  static void process_init_limits(struct fuse_conn *fc, struct fuse_init_out *arg)
  {
  	int cap_sys_admin = capable(CAP_SYS_ADMIN);
  
  	if (arg->minor < 13)
  		return;
  
  	sanitize_global_limit(&max_user_bgreq);
  	sanitize_global_limit(&max_user_congthresh);

  	spin_lock(&fc->bg_lock);

  	if (arg->max_background) {
  		fc->max_background = arg->max_background;
  
  		if (!cap_sys_admin && fc->max_background > max_user_bgreq)
  			fc->max_background = max_user_bgreq;
  	}
  	if (arg->congestion_threshold) {
  		fc->congestion_threshold = arg->congestion_threshold;
  
  		if (!cap_sys_admin &&
  		    fc->congestion_threshold > max_user_congthresh)
  			fc->congestion_threshold = max_user_congthresh;
  	}

  	spin_unlock(&fc->bg_lock);

  }

  struct fuse_init_args {
  	struct fuse_args args;
  	struct fuse_init_in in;
  	struct fuse_init_out out;
  };
  
  static void process_init_reply(struct fuse_conn *fc, struct fuse_args *args,
  			       int error)

  {

  	struct fuse_init_args *ia = container_of(args, typeof(*ia), args);
  	struct fuse_init_out *arg = &ia->out;

  	if (error || arg->major != FUSE_KERNEL_VERSION)

  		fc->conn_error = 1;
  	else {

  		unsigned long ra_pages;

  		process_init_limits(fc, arg);

  		if (arg->minor >= 6) {

  			ra_pages = arg->max_readahead / PAGE_SIZE;

  			if (arg->flags & FUSE_ASYNC_READ)
  				fc->async_read = 1;

  			if (!(arg->flags & FUSE_POSIX_LOCKS))
  				fc->no_lock = 1;

  			if (arg->minor >= 17) {
  				if (!(arg->flags & FUSE_FLOCK_LOCKS))
  					fc->no_flock = 1;

  			} else {
  				if (!(arg->flags & FUSE_POSIX_LOCKS))
  					fc->no_flock = 1;

  			}

  			if (arg->flags & FUSE_ATOMIC_O_TRUNC)
  				fc->atomic_o_trunc = 1;

  			if (arg->minor >= 9) {
  				/* LOOKUP has dependency on proto version */
  				if (arg->flags & FUSE_EXPORT_SUPPORT)
  					fc->export_support = 1;
  			}

  			if (arg->flags & FUSE_BIG_WRITES)
  				fc->big_writes = 1;

  			if (arg->flags & FUSE_DONT_MASK)
  				fc->dont_mask = 1;

  			if (arg->flags & FUSE_AUTO_INVAL_DATA)
  				fc->auto_inval_data = 1;

  			else if (arg->flags & FUSE_EXPLICIT_INVAL_DATA)
  				fc->explicit_inval_data = 1;

  			if (arg->flags & FUSE_DO_READDIRPLUS) {

  				fc->do_readdirplus = 1;

  				if (arg->flags & FUSE_READDIRPLUS_AUTO)
  					fc->readdirplus_auto = 1;
  			}

  			if (arg->flags & FUSE_ASYNC_DIO)
  				fc->async_dio = 1;

  			if (arg->flags & FUSE_WRITEBACK_CACHE)
  				fc->writeback_cache = 1;

  			if (arg->flags & FUSE_PARALLEL_DIROPS)
  				fc->parallel_dirops = 1;

  			if (arg->flags & FUSE_HANDLE_KILLPRIV)
  				fc->handle_killpriv = 1;

  			if (arg->time_gran && arg->time_gran <= 1000000000)
  				fc->sb->s_time_gran = arg->time_gran;

  			if ((arg->flags & FUSE_POSIX_ACL)) {

  				fc->default_permissions = 1;

  				fc->posix_acl = 1;
  				fc->sb->s_xattr = fuse_acl_xattr_handlers;
  			}

  			if (arg->flags & FUSE_CACHE_SYMLINKS)
  				fc->cache_symlinks = 1;

  			if (arg->flags & FUSE_ABORT_ERROR)
  				fc->abort_err = 1;

  			if (arg->flags & FUSE_MAX_PAGES) {
  				fc->max_pages =
  					min_t(unsigned int, FUSE_MAX_MAX_PAGES,
  					max_t(unsigned int, arg->max_pages, 1));
  			}

  		} else {

  			ra_pages = fc->max_read / PAGE_SIZE;

  			fc->no_lock = 1;

  			fc->no_flock = 1;

  		}

  		fc->sb->s_bdi->ra_pages =
  				min(fc->sb->s_bdi->ra_pages, ra_pages);

  		fc->minor = arg->minor;
  		fc->max_write = arg->minor < 5 ? 4096 : arg->max_write;

  		fc->max_write = max_t(unsigned, 4096, fc->max_write);

  		fc->conn_init = 1;

  	}

  	kfree(ia);

  	fuse_set_initialized(fc);

  	wake_up_all(&fc->blocked_waitq);

  }

  void fuse_send_init(struct fuse_conn *fc)

  {

  	struct fuse_init_args *ia;

  	ia = kzalloc(sizeof(*ia), GFP_KERNEL | __GFP_NOFAIL);
  
  	ia->in.major = FUSE_KERNEL_VERSION;
  	ia->in.minor = FUSE_KERNEL_MINOR_VERSION;
  	ia->in.max_readahead = fc->sb->s_bdi->ra_pages * PAGE_SIZE;
  	ia->in.flags |=
  		FUSE_ASYNC_READ | FUSE_POSIX_LOCKS | FUSE_ATOMIC_O_TRUNC |

  		FUSE_EXPORT_SUPPORT | FUSE_BIG_WRITES | FUSE_DONT_MASK |

  		FUSE_SPLICE_WRITE | FUSE_SPLICE_MOVE | FUSE_SPLICE_READ |

  		FUSE_FLOCK_LOCKS | FUSE_HAS_IOCTL_DIR | FUSE_AUTO_INVAL_DATA |

  		FUSE_DO_READDIRPLUS | FUSE_READDIRPLUS_AUTO | FUSE_ASYNC_DIO |

  		FUSE_WRITEBACK_CACHE | FUSE_NO_OPEN_SUPPORT |

  		FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |

  		FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |

  		FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA;

  	ia->args.opcode = FUSE_INIT;
  	ia->args.in_numargs = 1;
  	ia->args.in_args[0].size = sizeof(ia->in);
  	ia->args.in_args[0].value = &ia->in;
  	ia->args.out_numargs = 1;

  	/* Variable length argument used for backward compatibility

  	   with interface version < 7.5.  Rest of init_out is zeroed
  	   by do_get_request(), so a short reply is not a problem */

  	ia->args.out_argvar = true;

  	ia->args.out_args[0].size = sizeof(ia->out);
  	ia->args.out_args[0].value = &ia->out;
  	ia->args.force = true;
  	ia->args.nocreds = true;
  	ia->args.end = process_init_reply;
  
  	if (fuse_simple_background(fc, &ia->args, GFP_KERNEL) != 0)
  		process_init_reply(fc, &ia->args, -ENOTCONN);

  }

  EXPORT_SYMBOL_GPL(fuse_send_init);

  void fuse_free_conn(struct fuse_conn *fc)

  {

  	WARN_ON(!list_empty(&fc->devices));

  	kfree_rcu(fc, rcu);

  }

  EXPORT_SYMBOL_GPL(fuse_free_conn);

  static int fuse_bdi_init(struct fuse_conn *fc, struct super_block *sb)
  {
  	int err;

  	char *suffix = "";

  	if (sb->s_bdev) {

  		suffix = "-fuseblk";

  		/*
  		 * sb->s_bdi points to blkdev's bdi however we want to redirect
  		 * it to our private bdi...
  		 */
  		bdi_put(sb->s_bdi);
  		sb->s_bdi = &noop_backing_dev_info;
  	}

  	err = super_setup_bdi_name(sb, "%u:%u%s", MAJOR(fc->dev),
  				   MINOR(fc->dev), suffix);

  	if (err)
  		return err;

  	sb->s_bdi->ra_pages = VM_READAHEAD_PAGES;

  	/* fuse does it's own writeback accounting */
  	sb->s_bdi->capabilities = BDI_CAP_NO_ACCT_WB | BDI_CAP_STRICTLIMIT;

  	/*
  	 * For a single fuse filesystem use max 1% of dirty +
  	 * writeback threshold.
  	 *
  	 * This gives about 1M of write buffer for memory maps on a
  	 * machine with 1G and 10% dirty_ratio, which should be more
  	 * than enough.
  	 *
  	 * Privileged users can raise it by writing to
  	 *
  	 *    /sys/class/bdi/<bdi>/max_ratio
  	 */

  	bdi_set_max_ratio(sb->s_bdi, 1);

  
  	return 0;
  }

  struct fuse_dev *fuse_dev_alloc(void)

  {
  	struct fuse_dev *fud;

  	struct list_head *pq;

  
  	fud = kzalloc(sizeof(struct fuse_dev), GFP_KERNEL);

  	if (!fud)
  		return NULL;

  	pq = kcalloc(FUSE_PQ_HASH_SIZE, sizeof(struct list_head), GFP_KERNEL);
  	if (!pq) {
  		kfree(fud);
  		return NULL;

  	}

  	fud->pq.processing = pq;

  	fuse_pqueue_init(&fud->pq);

  	return fud;
  }
  EXPORT_SYMBOL_GPL(fuse_dev_alloc);
  
  void fuse_dev_install(struct fuse_dev *fud, struct fuse_conn *fc)
  {
  	fud->fc = fuse_conn_get(fc);

  	spin_lock(&fc->lock);
  	list_add_tail(&fud->entry, &fc->devices);
  	spin_unlock(&fc->lock);

  }
  EXPORT_SYMBOL_GPL(fuse_dev_install);

  struct fuse_dev *fuse_dev_alloc_install(struct fuse_conn *fc)
  {
  	struct fuse_dev *fud;
  
  	fud = fuse_dev_alloc();
  	if (!fud)
  		return NULL;
  
  	fuse_dev_install(fud, fc);

  	return fud;
  }

  EXPORT_SYMBOL_GPL(fuse_dev_alloc_install);

  
  void fuse_dev_free(struct fuse_dev *fud)
  {
  	struct fuse_conn *fc = fud->fc;
  
  	if (fc) {
  		spin_lock(&fc->lock);
  		list_del(&fud->entry);
  		spin_unlock(&fc->lock);
  
  		fuse_conn_put(fc);
  	}

  	kfree(fud->pq.processing);

  	kfree(fud);
  }
  EXPORT_SYMBOL_GPL(fuse_dev_free);

  int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)

  {

  	struct fuse_dev *fud = NULL;

  	struct fuse_conn *fc = get_fuse_conn_super(sb);

  	struct inode *root;

  	struct dentry *root_dentry;

  	int err;

  	err = -EINVAL;

  	if (sb->s_flags & SB_MANDLOCK)

  		goto err;

  	sb->s_flags &= ~(SB_NOSEC | SB_I_VERSION);

  	if (ctx->is_bdev) {

  #ifdef CONFIG_BLOCK

  		err = -EINVAL;

  		if (!sb_set_blocksize(sb, ctx->blksize))

  			goto err;

  #endif

  	} else {

  		sb->s_blocksize = PAGE_SIZE;
  		sb->s_blocksize_bits = PAGE_SHIFT;

  	}

  
  	sb->s_subtype = ctx->subtype;
  	ctx->subtype = NULL;

  	sb->s_magic = FUSE_SUPER_MAGIC;
  	sb->s_op = &fuse_super_operations;

  	sb->s_xattr = fuse_xattr_handlers;

  	sb->s_maxbytes = MAX_LFS_FILESIZE;

  	sb->s_time_gran = 1;

  	sb->s_export_op = &fuse_export_operations;

  	sb->s_iflags |= SB_I_IMA_UNVERIFIABLE_SIGNATURE;
  	if (sb->s_user_ns != &init_user_ns)
  		sb->s_iflags |= SB_I_UNTRUSTED_MOUNTER;

  	/*
  	 * If we are not in the initial user namespace posix
  	 * acls must be translated.
  	 */
  	if (sb->s_user_ns != &init_user_ns)
  		sb->s_xattr = fuse_no_acl_xattr_handlers;

  	if (ctx->fudptr) {
  		err = -ENOMEM;
  		fud = fuse_dev_alloc_install(fc);
  		if (!fud)
  			goto err;
  	}

  	fc->dev = sb->s_dev;

  	fc->sb = sb;

  	err = fuse_bdi_init(fc, sb);
  	if (err)

  		goto err_dev_free;

  	/* Handle umasking inside the fuse code */

  	if (sb->s_flags & SB_POSIXACL)

  		fc->dont_mask = 1;

  	sb->s_flags |= SB_POSIXACL;

  	fc->default_permissions = ctx->default_permissions;
  	fc->allow_other = ctx->allow_other;
  	fc->user_id = ctx->user_id;
  	fc->group_id = ctx->group_id;
  	fc->max_read = max_t(unsigned, 4096, ctx->max_read);

  	fc->destroy = ctx->destroy;

  	fc->no_control = ctx->no_control;
  	fc->no_force_umount = ctx->no_force_umount;

  	fc->no_mount_options = ctx->no_mount_options;

  	err = -ENOMEM;

  	root = fuse_get_root_inode(sb, ctx->rootmode);

  	sb->s_d_op = &fuse_root_dentry_operations;

  	root_dentry = d_make_root(root);
  	if (!root_dentry)

  		goto err_dev_free;

  	/* Root dentry doesn't have .d_revalidate */

  	sb->s_d_op = &fuse_dentry_operations;

  	mutex_lock(&fuse_mutex);

  	err = -EINVAL;

  	if (ctx->fudptr && *ctx->fudptr)

  		goto err_unlock;

  	err = fuse_ctl_add_conn(fc);
  	if (err)
  		goto err_unlock;
  
  	list_add_tail(&fc->entry, &fuse_conn_list);

  	sb->s_root = root_dentry;

  	if (ctx->fudptr)
  		*ctx->fudptr = fud;

  	mutex_unlock(&fuse_mutex);

  	return 0;
  
   err_unlock:
  	mutex_unlock(&fuse_mutex);
  	dput(root_dentry);
   err_dev_free:

  	if (fud)
  		fuse_dev_free(fud);

   err:
  	return err;
  }
  EXPORT_SYMBOL_GPL(fuse_fill_super_common);
  
  static int fuse_fill_super(struct super_block *sb, struct fs_context *fsc)
  {
  	struct fuse_fs_context *ctx = fsc->fs_private;
  	struct file *file;
  	int err;
  	struct fuse_conn *fc;
  
  	err = -EINVAL;
  	file = fget(ctx->fd);
  	if (!file)
  		goto err;
  
  	/*
  	 * Require mount to happen from the same user namespace which
  	 * opened /dev/fuse to prevent potential attacks.
  	 */
  	if ((file->f_op != &fuse_dev_operations) ||
  	    (file->f_cred->user_ns != sb->s_user_ns))
  		goto err_fput;
  	ctx->fudptr = &file->private_data;
  
  	fc = kmalloc(sizeof(*fc), GFP_KERNEL);
  	err = -ENOMEM;
  	if (!fc)
  		goto err_fput;

  	fuse_conn_init(fc, sb->s_user_ns, &fuse_dev_fiq_ops, NULL);

  	fc->release = fuse_free_conn;
  	sb->s_fs_info = fc;
  
  	err = fuse_fill_super_common(sb, ctx);
  	if (err)
  		goto err_put_conn;

  	/*
  	 * atomic_dec_and_test() in fput() provides the necessary
  	 * memory barrier for file->private_data to be visible on all
  	 * CPUs after this
  	 */
  	fput(file);

  	fuse_send_init(get_fuse_conn_super(sb));

  	return 0;

   err_put_conn:

  	fuse_conn_put(fc);

  	sb->s_fs_info = NULL;

   err_fput:
  	fput(file);
   err:

  	return err;
  }

  static int fuse_get_tree(struct fs_context *fc)

  {

  	struct fuse_fs_context *ctx = fc->fs_private;
  
  	if (!ctx->fd_present || !ctx->rootmode_present ||
  	    !ctx->user_id_present || !ctx->group_id_present)
  		return -EINVAL;
  
  #ifdef CONFIG_BLOCK
  	if (ctx->is_bdev)
  		return get_tree_bdev(fc, fuse_fill_super);
  #endif
  
  	return get_tree_nodev(fc, fuse_fill_super);
  }
  
  static const struct fs_context_operations fuse_context_ops = {
  	.free		= fuse_free_fc,
  	.parse_param	= fuse_parse_param,

  	.reconfigure	= fuse_reconfigure,

  	.get_tree	= fuse_get_tree,
  };
  
  /*
   * Set up the filesystem mount context.
   */
  static int fuse_init_fs_context(struct fs_context *fc)
  {
  	struct fuse_fs_context *ctx;
  
  	ctx = kzalloc(sizeof(struct fuse_fs_context), GFP_KERNEL);
  	if (!ctx)
  		return -ENOMEM;
  
  	ctx->max_read = ~0;
  	ctx->blksize = FUSE_DEFAULT_BLKSIZE;
  
  #ifdef CONFIG_BLOCK

  	if (fc->fs_type == &fuseblk_fs_type) {

  		ctx->is_bdev = true;

  		ctx->destroy = true;
  	}

  #endif
  
  	fc->fs_private = ctx;
  	fc->ops = &fuse_context_ops;
  	return 0;

  }

  static void fuse_sb_destroy(struct super_block *sb)

  {
  	struct fuse_conn *fc = get_fuse_conn_super(sb);
  
  	if (fc) {

  		if (fc->destroy)
  			fuse_send_destroy(fc);

  		fuse_abort_conn(fc);

  		fuse_wait_aborted(fc);

  		down_write(&fc->killsb);
  		fc->sb = NULL;
  		up_write(&fc->killsb);
  	}

  }

  void fuse_kill_sb_anon(struct super_block *sb)

  {
  	fuse_sb_destroy(sb);

  	kill_anon_super(sb);
  }

  EXPORT_SYMBOL_GPL(fuse_kill_sb_anon);

  static struct file_system_type fuse_fs_type = {
  	.owner		= THIS_MODULE,
  	.name		= "fuse",

  	.fs_flags	= FS_HAS_SUBTYPE | FS_USERNS_MOUNT,

  	.init_fs_context = fuse_init_fs_context,

  	.parameters	= fuse_fs_parameters,

  	.kill_sb	= fuse_kill_sb_anon,

  };

  MODULE_ALIAS_FS("fuse");

  
  #ifdef CONFIG_BLOCK

  static void fuse_kill_sb_blk(struct super_block *sb)
  {

  	fuse_sb_destroy(sb);

  	kill_block_super(sb);
  }

  static struct file_system_type fuseblk_fs_type = {
  	.owner		= THIS_MODULE,
  	.name		= "fuseblk",

  	.init_fs_context = fuse_init_fs_context,

  	.parameters	= fuse_fs_parameters,

  	.kill_sb	= fuse_kill_sb_blk,

  	.fs_flags	= FS_REQUIRES_DEV | FS_HAS_SUBTYPE,

  };

  MODULE_ALIAS_FS("fuseblk");

  static inline int register_fuseblk(void)
  {
  	return register_filesystem(&fuseblk_fs_type);
  }
  
  static inline void unregister_fuseblk(void)
  {
  	unregister_filesystem(&fuseblk_fs_type);
  }
  #else
  static inline int register_fuseblk(void)
  {
  	return 0;
  }
  
  static inline void unregister_fuseblk(void)
  {
  }
  #endif

  static void fuse_inode_init_once(void *foo)

  {

  	struct inode *inode = foo;

  	inode_init_once(inode);

  }
  
  static int __init fuse_fs_init(void)
  {
  	int err;

  	fuse_inode_cachep = kmem_cache_create("fuse_inode",

  			sizeof(struct fuse_inode), 0,
  			SLAB_HWCACHE_ALIGN|SLAB_ACCOUNT|SLAB_RECLAIM_ACCOUNT,
  			fuse_inode_init_once);

  	err = -ENOMEM;
  	if (!fuse_inode_cachep)

  		goto out;
  
  	err = register_fuseblk();
  	if (err)
  		goto out2;
  
  	err = register_filesystem(&fuse_fs_type);
  	if (err)
  		goto out3;

  
  	return 0;

   out3:

  	unregister_fuseblk();

   out2:
  	kmem_cache_destroy(fuse_inode_cachep);

   out:

  	return err;
  }
  
  static void fuse_fs_cleanup(void)
  {
  	unregister_filesystem(&fuse_fs_type);

  	unregister_fuseblk();

  
  	/*
  	 * Make sure all delayed rcu free inodes are flushed before we
  	 * destroy cache.
  	 */
  	rcu_barrier();

  	kmem_cache_destroy(fuse_inode_cachep);
  }

  static struct kobject *fuse_kobj;

  static int fuse_sysfs_init(void)
  {
  	int err;

  	fuse_kobj = kobject_create_and_add("fuse", fs_kobj);

  	if (!fuse_kobj) {
  		err = -ENOMEM;

  		goto out_err;

  	}

  	err = sysfs_create_mount_point(fuse_kobj, "connections");
  	if (err)

  		goto out_fuse_unregister;
  
  	return 0;
  
   out_fuse_unregister:

  	kobject_put(fuse_kobj);

   out_err:
  	return err;
  }
  
  static void fuse_sysfs_cleanup(void)
  {

  	sysfs_remove_mount_point(fuse_kobj, "connections");

  	kobject_put(fuse_kobj);

  }

  static int __init fuse_init(void)
  {
  	int res;