/*
    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/init.h>
  #include <linux/module.h>
  
  #define FUSE_CTL_SUPER_MAGIC 0x65735543
  
  /*
   * This is non-NULL when the single instance of the control filesystem
   * exists.  Protected by fuse_mutex
   */
  static struct super_block *fuse_control_sb;
  
  static struct fuse_conn *fuse_ctl_file_conn_get(struct file *file)
  {
  	struct fuse_conn *fc;
  	mutex_lock(&fuse_mutex);

  	fc = file->f_path.dentry->d_inode->i_private;

  	if (fc)
  		fc = fuse_conn_get(fc);
  	mutex_unlock(&fuse_mutex);
  	return fc;
  }
  
  static ssize_t fuse_conn_abort_write(struct file *file, const char __user *buf,
  				     size_t count, loff_t *ppos)
  {
  	struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
  	if (fc) {
  		fuse_abort_conn(fc);
  		fuse_conn_put(fc);
  	}
  	return count;
  }
  
  static ssize_t fuse_conn_waiting_read(struct file *file, char __user *buf,
  				      size_t len, loff_t *ppos)
  {
  	char tmp[32];
  	size_t size;
  
  	if (!*ppos) {

  		long value;

  		struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
  		if (!fc)
  			return 0;

  		value = atomic_read(&fc->num_waiting);
  		file->private_data = (void *)value;

  		fuse_conn_put(fc);
  	}
  	size = sprintf(tmp, "%ld
  ", (long)file->private_data);
  	return simple_read_from_buffer(buf, len, ppos, tmp, size);
  }

  static ssize_t fuse_conn_limit_read(struct file *file, char __user *buf,
  				    size_t len, loff_t *ppos, unsigned val)
  {
  	char tmp[32];
  	size_t size = sprintf(tmp, "%u
  ", val);
  
  	return simple_read_from_buffer(buf, len, ppos, tmp, size);
  }
  
  static ssize_t fuse_conn_limit_write(struct file *file, const char __user *buf,
  				     size_t count, loff_t *ppos, unsigned *val,
  				     unsigned global_limit)
  {
  	unsigned long t;
  	char tmp[32];
  	unsigned limit = (1 << 16) - 1;
  	int err;
  
  	if (*ppos || count >= sizeof(tmp) - 1)
  		return -EINVAL;
  
  	if (copy_from_user(tmp, buf, count))
  		return -EINVAL;
  
  	tmp[count] = '\0';
  
  	err = strict_strtoul(tmp, 0, &t);
  	if (err)
  		return err;
  
  	if (!capable(CAP_SYS_ADMIN))
  		limit = min(limit, global_limit);
  
  	if (t > limit)
  		return -EINVAL;
  
  	*val = t;
  
  	return count;
  }
  
  static ssize_t fuse_conn_max_background_read(struct file *file,
  					     char __user *buf, size_t len,
  					     loff_t *ppos)
  {
  	struct fuse_conn *fc;
  	unsigned val;
  
  	fc = fuse_ctl_file_conn_get(file);
  	if (!fc)
  		return 0;
  
  	val = fc->max_background;
  	fuse_conn_put(fc);
  
  	return fuse_conn_limit_read(file, buf, len, ppos, val);
  }
  
  static ssize_t fuse_conn_max_background_write(struct file *file,
  					      const char __user *buf,
  					      size_t count, loff_t *ppos)
  {
  	unsigned val;
  	ssize_t ret;
  
  	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
  				    max_user_bgreq);
  	if (ret > 0) {
  		struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
  		if (fc) {
  			fc->max_background = val;
  			fuse_conn_put(fc);
  		}
  	}
  
  	return ret;
  }
  
  static ssize_t fuse_conn_congestion_threshold_read(struct file *file,
  						   char __user *buf, size_t len,
  						   loff_t *ppos)
  {
  	struct fuse_conn *fc;
  	unsigned val;
  
  	fc = fuse_ctl_file_conn_get(file);
  	if (!fc)
  		return 0;
  
  	val = fc->congestion_threshold;
  	fuse_conn_put(fc);
  
  	return fuse_conn_limit_read(file, buf, len, ppos, val);
  }
  
  static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
  						    const char __user *buf,
  						    size_t count, loff_t *ppos)
  {
  	unsigned val;
  	ssize_t ret;
  
  	ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
  				    max_user_congthresh);
  	if (ret > 0) {
  		struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
  		if (fc) {
  			fc->congestion_threshold = val;
  			fuse_conn_put(fc);
  		}
  	}
  
  	return ret;
  }

  static const struct file_operations fuse_ctl_abort_ops = {
  	.open = nonseekable_open,
  	.write = fuse_conn_abort_write,

  	.llseek = no_llseek,

  };
  
  static const struct file_operations fuse_ctl_waiting_ops = {
  	.open = nonseekable_open,
  	.read = fuse_conn_waiting_read,

  	.llseek = no_llseek,

  };

  static const struct file_operations fuse_conn_max_background_ops = {
  	.open = nonseekable_open,
  	.read = fuse_conn_max_background_read,
  	.write = fuse_conn_max_background_write,

  	.llseek = no_llseek,

  };
  
  static const struct file_operations fuse_conn_congestion_threshold_ops = {
  	.open = nonseekable_open,
  	.read = fuse_conn_congestion_threshold_read,
  	.write = fuse_conn_congestion_threshold_write,

  	.llseek = no_llseek,

  };

  static struct dentry *fuse_ctl_add_dentry(struct dentry *parent,
  					  struct fuse_conn *fc,
  					  const char *name,
  					  int mode, int nlink,

  					  const struct inode_operations *iop,

  					  const struct file_operations *fop)
  {
  	struct dentry *dentry;
  	struct inode *inode;
  
  	BUG_ON(fc->ctl_ndents >= FUSE_CTL_NUM_DENTRIES);
  	dentry = d_alloc_name(parent, name);
  	if (!dentry)
  		return NULL;
  
  	fc->ctl_dentry[fc->ctl_ndents++] = dentry;
  	inode = new_inode(fuse_control_sb);
  	if (!inode)
  		return NULL;

  	inode->i_ino = get_next_ino();

  	inode->i_mode = mode;
  	inode->i_uid = fc->user_id;
  	inode->i_gid = fc->group_id;
  	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  	/* setting ->i_op to NULL is not allowed */
  	if (iop)
  		inode->i_op = iop;
  	inode->i_fop = fop;
  	inode->i_nlink = nlink;

  	inode->i_private = fc;

  	d_add(dentry, inode);
  	return dentry;
  }
  
  /*
   * Add a connection to the control filesystem (if it exists).  Caller

   * must hold fuse_mutex

   */
  int fuse_ctl_add_conn(struct fuse_conn *fc)
  {
  	struct dentry *parent;
  	char name[32];
  
  	if (!fuse_control_sb)
  		return 0;
  
  	parent = fuse_control_sb->s_root;

  	inc_nlink(parent->d_inode);

  	sprintf(name, "%u", fc->dev);

  	parent = fuse_ctl_add_dentry(parent, fc, name, S_IFDIR | 0500, 2,
  				     &simple_dir_inode_operations,
  				     &simple_dir_operations);
  	if (!parent)
  		goto err;
  
  	if (!fuse_ctl_add_dentry(parent, fc, "waiting", S_IFREG | 0400, 1,

  				 NULL, &fuse_ctl_waiting_ops) ||

  	    !fuse_ctl_add_dentry(parent, fc, "abort", S_IFREG | 0200, 1,

  				 NULL, &fuse_ctl_abort_ops) ||
  	    !fuse_ctl_add_dentry(parent, fc, "max_background", S_IFREG | 0600,
  				 1, NULL, &fuse_conn_max_background_ops) ||
  	    !fuse_ctl_add_dentry(parent, fc, "congestion_threshold",
  				 S_IFREG | 0600, 1, NULL,
  				 &fuse_conn_congestion_threshold_ops))

  		goto err;
  
  	return 0;
  
   err:
  	fuse_ctl_remove_conn(fc);
  	return -ENOMEM;
  }
  
  /*
   * Remove a connection from the control filesystem (if it exists).

   * Caller must hold fuse_mutex

   */
  void fuse_ctl_remove_conn(struct fuse_conn *fc)
  {
  	int i;
  
  	if (!fuse_control_sb)
  		return;
  
  	for (i = fc->ctl_ndents - 1; i >= 0; i--) {
  		struct dentry *dentry = fc->ctl_dentry[i];

  		dentry->d_inode->i_private = NULL;

  		d_drop(dentry);
  		dput(dentry);
  	}

  	drop_nlink(fuse_control_sb->s_root->d_inode);

  }
  
  static int fuse_ctl_fill_super(struct super_block *sb, void *data, int silent)
  {
  	struct tree_descr empty_descr = {""};
  	struct fuse_conn *fc;
  	int err;
  
  	err = simple_fill_super(sb, FUSE_CTL_SUPER_MAGIC, &empty_descr);
  	if (err)
  		return err;
  
  	mutex_lock(&fuse_mutex);
  	BUG_ON(fuse_control_sb);
  	fuse_control_sb = sb;
  	list_for_each_entry(fc, &fuse_conn_list, entry) {
  		err = fuse_ctl_add_conn(fc);
  		if (err) {
  			fuse_control_sb = NULL;
  			mutex_unlock(&fuse_mutex);
  			return err;
  		}
  	}
  	mutex_unlock(&fuse_mutex);
  
  	return 0;
  }

  static struct dentry *fuse_ctl_mount(struct file_system_type *fs_type,
  			int flags, const char *dev_name, void *raw_data)

  {

  	return mount_single(fs_type, flags, raw_data, fuse_ctl_fill_super);

  }
  
  static void fuse_ctl_kill_sb(struct super_block *sb)
  {

  	struct fuse_conn *fc;

  	mutex_lock(&fuse_mutex);
  	fuse_control_sb = NULL;

  	list_for_each_entry(fc, &fuse_conn_list, entry)
  		fc->ctl_ndents = 0;

  	mutex_unlock(&fuse_mutex);
  
  	kill_litter_super(sb);
  }
  
  static struct file_system_type fuse_ctl_fs_type = {
  	.owner		= THIS_MODULE,
  	.name		= "fusectl",

  	.mount		= fuse_ctl_mount,

  	.kill_sb	= fuse_ctl_kill_sb,
  };
  
  int __init fuse_ctl_init(void)
  {
  	return register_filesystem(&fuse_ctl_fs_type);
  }
  
  void fuse_ctl_cleanup(void)
  {
  	unregister_filesystem(&fuse_ctl_fs_type);
  }