/*

   *  inode.c - part of debugfs, a tiny little debug file system

   *
   *  Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
   *  Copyright (C) 2004 IBM Inc.
   *
   *	This program is free software; you can redistribute it and/or
   *	modify it under the terms of the GNU General Public License version
   *	2 as published by the Free Software Foundation.
   *
   *  debugfs is for people to use instead of /proc or /sys.
   *  See Documentation/DocBook/kernel-api for more details.
   *
   */

  #include <linux/module.h>
  #include <linux/fs.h>
  #include <linux/mount.h>
  #include <linux/pagemap.h>
  #include <linux/init.h>

  #include <linux/kobject.h>

  #include <linux/namei.h>
  #include <linux/debugfs.h>

  #include <linux/fsnotify.h>

  #include <linux/string.h>

  #include <linux/magic.h>

  #include <linux/slab.h>

  static struct vfsmount *debugfs_mount;
  static int debugfs_mount_count;

  static bool debugfs_registered;

  static struct inode *debugfs_get_inode(struct super_block *sb, int mode, dev_t dev,
  				       void *data, const struct file_operations *fops)

  {
  	struct inode *inode = new_inode(sb);
  
  	if (inode) {

  		inode->i_ino = get_next_ino();

  		inode->i_mode = mode;

  		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  		switch (mode & S_IFMT) {
  		default:
  			init_special_inode(inode, mode, dev);
  			break;
  		case S_IFREG:

  			inode->i_fop = fops ? fops : &debugfs_file_operations;
  			inode->i_private = data;

  			break;

  		case S_IFLNK:
  			inode->i_op = &debugfs_link_operations;

  			inode->i_fop = fops;
  			inode->i_private = data;

  			break;

  		case S_IFDIR:
  			inode->i_op = &simple_dir_inode_operations;

  			inode->i_fop = fops ? fops : &simple_dir_operations;
  			inode->i_private = data;

  			/* directory inodes start off with i_nlink == 2
  			 * (for "." entry) */

  			inc_nlink(inode);

  			break;
  		}
  	}
  	return inode; 
  }
  
  /* SMP-safe */
  static int debugfs_mknod(struct inode *dir, struct dentry *dentry,

  			 int mode, dev_t dev, void *data,
  			 const struct file_operations *fops)

  {

  	struct inode *inode;

  	int error = -EPERM;
  
  	if (dentry->d_inode)
  		return -EEXIST;

  	inode = debugfs_get_inode(dir->i_sb, mode, dev, data, fops);

  	if (inode) {
  		d_instantiate(dentry, inode);
  		dget(dentry);
  		error = 0;
  	}
  	return error;
  }

  static int debugfs_mkdir(struct inode *dir, struct dentry *dentry, int mode,
  			 void *data, const struct file_operations *fops)

  {
  	int res;
  
  	mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;

  	res = debugfs_mknod(dir, dentry, mode, 0, data, fops);

  	if (!res) {

  		inc_nlink(dir);

  		fsnotify_mkdir(dir, dentry);
  	}

  	return res;
  }

  static int debugfs_link(struct inode *dir, struct dentry *dentry, int mode,
  			void *data, const struct file_operations *fops)

  {
  	mode = (mode & S_IALLUGO) | S_IFLNK;

  	return debugfs_mknod(dir, dentry, mode, 0, data, fops);

  }

  static int debugfs_create(struct inode *dir, struct dentry *dentry, int mode,
  			  void *data, const struct file_operations *fops)

  {

  	int res;

  	mode = (mode & S_IALLUGO) | S_IFREG;

  	res = debugfs_mknod(dir, dentry, mode, 0, data, fops);

  	if (!res)
  		fsnotify_create(dir, dentry);
  	return res;

  }
  
  static inline int debugfs_positive(struct dentry *dentry)
  {
  	return dentry->d_inode && !d_unhashed(dentry);
  }
  
  static int debug_fill_super(struct super_block *sb, void *data, int silent)
  {
  	static struct tree_descr debug_files[] = {{""}};
  
  	return simple_fill_super(sb, DEBUGFS_MAGIC, debug_files);
  }

  static struct dentry *debug_mount(struct file_system_type *fs_type,

  			int flags, const char *dev_name,

  			void *data)

  {

  	return mount_single(fs_type, flags, data, debug_fill_super);

  }
  
  static struct file_system_type debug_fs_type = {
  	.owner =	THIS_MODULE,
  	.name =		"debugfs",

  	.mount =	debug_mount,

  	.kill_sb =	kill_litter_super,
  };
  
  static int debugfs_create_by_name(const char *name, mode_t mode,
  				  struct dentry *parent,

  				  struct dentry **dentry,
  				  void *data,
  				  const struct file_operations *fops)

  {
  	int error = 0;
  
  	/* If the parent is not specified, we create it in the root.
  	 * We need the root dentry to do this, which is in the super 
  	 * block. A pointer to that is in the struct vfsmount that we
  	 * have around.
  	 */

  	if (!parent)
  		parent = debugfs_mount->mnt_sb->s_root;

  
  	*dentry = NULL;

  	mutex_lock(&parent->d_inode->i_mutex);

  	*dentry = lookup_one_len(name, parent, strlen(name));

  	if (!IS_ERR(*dentry)) {

  		switch (mode & S_IFMT) {
  		case S_IFDIR:

  			error = debugfs_mkdir(parent->d_inode, *dentry, mode,
  					      data, fops);

  			break;
  		case S_IFLNK:

  			error = debugfs_link(parent->d_inode, *dentry, mode,
  					     data, fops);

  			break;
  		default:

  			error = debugfs_create(parent->d_inode, *dentry, mode,
  					       data, fops);

  			break;
  		}

  		dput(*dentry);

  	} else

  		error = PTR_ERR(*dentry);

  	mutex_unlock(&parent->d_inode->i_mutex);

  
  	return error;
  }
  
  /**
   * debugfs_create_file - create a file in the debugfs filesystem

   * @name: a pointer to a string containing the name of the file to create.

   * @mode: the permission that the file should have.

   * @parent: a pointer to the parent dentry for this file.  This should be a
   *          directory dentry if set.  If this paramater is NULL, then the
   *          file will be created in the root of the debugfs filesystem.
   * @data: a pointer to something that the caller will want to get to later

   *        on.  The inode.i_private pointer will point to this value on

   *        the open() call.
   * @fops: a pointer to a struct file_operations that should be used for
   *        this file.
   *
   * This is the basic "create a file" function for debugfs.  It allows for a

   * wide range of flexibility in creating a file, or a directory (if you want
   * to create a directory, the debugfs_create_dir() function is

   * recommended to be used instead.)
   *
   * This function will return a pointer to a dentry if it succeeds.  This
   * pointer must be passed to the debugfs_remove() function when the file is
   * to be removed (no automatic cleanup happens if your module is unloaded,

   * you are responsible here.)  If an error occurs, %NULL will be returned.

   *

   * If debugfs is not enabled in the kernel, the value -%ENODEV will be

   * returned.

   */
  struct dentry *debugfs_create_file(const char *name, mode_t mode,
  				   struct dentry *parent, void *data,

  				   const struct file_operations *fops)

  {
  	struct dentry *dentry = NULL;
  	int error;
  
  	pr_debug("debugfs: creating file '%s'
  ",name);

  	error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
  			      &debugfs_mount_count);

  	if (error)
  		goto exit;

  	error = debugfs_create_by_name(name, mode, parent, &dentry,
  				       data, fops);

  	if (error) {
  		dentry = NULL;

  		simple_release_fs(&debugfs_mount, &debugfs_mount_count);

  		goto exit;
  	}

  exit:
  	return dentry;
  }
  EXPORT_SYMBOL_GPL(debugfs_create_file);
  
  /**
   * debugfs_create_dir - create a directory in the debugfs filesystem

   * @name: a pointer to a string containing the name of the directory to
   *        create.
   * @parent: a pointer to the parent dentry for this file.  This should be a
   *          directory dentry if set.  If this paramater is NULL, then the
   *          directory will be created in the root of the debugfs filesystem.
   *
   * This function creates a directory in debugfs with the given name.
   *
   * This function will return a pointer to a dentry if it succeeds.  This
   * pointer must be passed to the debugfs_remove() function when the file is
   * to be removed (no automatic cleanup happens if your module is unloaded,

   * you are responsible here.)  If an error occurs, %NULL will be returned.

   *

   * If debugfs is not enabled in the kernel, the value -%ENODEV will be

   * returned.

   */
  struct dentry *debugfs_create_dir(const char *name, struct dentry *parent)
  {
  	return debugfs_create_file(name, 
  				   S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
  				   parent, NULL, NULL);
  }
  EXPORT_SYMBOL_GPL(debugfs_create_dir);
  
  /**

   * debugfs_create_symlink- create a symbolic link in the debugfs filesystem
   * @name: a pointer to a string containing the name of the symbolic link to
   *        create.
   * @parent: a pointer to the parent dentry for this symbolic link.  This
   *          should be a directory dentry if set.  If this paramater is NULL,
   *          then the symbolic link will be created in the root of the debugfs
   *          filesystem.
   * @target: a pointer to a string containing the path to the target of the
   *          symbolic link.
   *
   * This function creates a symbolic link with the given name in debugfs that
   * links to the given target path.
   *
   * This function will return a pointer to a dentry if it succeeds.  This
   * pointer must be passed to the debugfs_remove() function when the symbolic
   * link is to be removed (no automatic cleanup happens if your module is
   * unloaded, you are responsible here.)  If an error occurs, %NULL will be
   * returned.
   *
   * If debugfs is not enabled in the kernel, the value -%ENODEV will be

   * returned.

   */
  struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
  				      const char *target)
  {
  	struct dentry *result;
  	char *link;
  
  	link = kstrdup(target, GFP_KERNEL);
  	if (!link)
  		return NULL;
  
  	result = debugfs_create_file(name, S_IFLNK | S_IRWXUGO, parent, link,
  				     NULL);
  	if (!result)
  		kfree(link);
  	return result;
  }
  EXPORT_SYMBOL_GPL(debugfs_create_symlink);

  static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)

  {
  	int ret = 0;
  
  	if (debugfs_positive(dentry)) {
  		if (dentry->d_inode) {
  			dget(dentry);
  			switch (dentry->d_inode->i_mode & S_IFMT) {
  			case S_IFDIR:
  				ret = simple_rmdir(parent->d_inode, dentry);
  				break;
  			case S_IFLNK:
  				kfree(dentry->d_inode->i_private);
  				/* fall through */
  			default:
  				simple_unlink(parent->d_inode, dentry);
  				break;
  			}
  			if (!ret)
  				d_delete(dentry);
  			dput(dentry);
  		}
  	}

  	return ret;

  }

  /**

   * debugfs_remove - removes a file or directory from the debugfs filesystem

   * @dentry: a pointer to a the dentry of the file or directory to be
   *          removed.
   *
   * This function removes a file or directory in debugfs that was previously
   * created with a call to another debugfs function (like

   * debugfs_create_file() or variants thereof.)

   *
   * This function is required to be called in order for the file to be
   * removed, no automatic cleanup of files will happen when a module is
   * removed, you are responsible here.
   */
  void debugfs_remove(struct dentry *dentry)
  {
  	struct dentry *parent;

  	int ret;

  	if (!dentry)
  		return;
  
  	parent = dentry->d_parent;
  	if (!parent || !parent->d_inode)
  		return;

  	mutex_lock(&parent->d_inode->i_mutex);

  	ret = __debugfs_remove(dentry, parent);

  	mutex_unlock(&parent->d_inode->i_mutex);

  	if (!ret)
  		simple_release_fs(&debugfs_mount, &debugfs_mount_count);

  }
  EXPORT_SYMBOL_GPL(debugfs_remove);
  
  /**
   * debugfs_remove_recursive - recursively removes a directory
   * @dentry: a pointer to a the dentry of the directory to be removed.
   *
   * This function recursively removes a directory tree in debugfs that
   * was previously created with a call to another debugfs function
   * (like debugfs_create_file() or variants thereof.)
   *
   * This function is required to be called in order for the file to be
   * removed, no automatic cleanup of files will happen when a module is
   * removed, you are responsible here.
   */
  void debugfs_remove_recursive(struct dentry *dentry)
  {
  	struct dentry *child;
  	struct dentry *parent;
  
  	if (!dentry)
  		return;
  
  	parent = dentry->d_parent;
  	if (!parent || !parent->d_inode)
  		return;
  
  	parent = dentry;
  	mutex_lock(&parent->d_inode->i_mutex);
  
  	while (1) {
  		/*
  		 * When all dentries under "parent" has been removed,
  		 * walk up the tree until we reach our starting point.
  		 */
  		if (list_empty(&parent->d_subdirs)) {
  			mutex_unlock(&parent->d_inode->i_mutex);
  			if (parent == dentry)

  				break;

  			parent = parent->d_parent;
  			mutex_lock(&parent->d_inode->i_mutex);
  		}
  		child = list_entry(parent->d_subdirs.next, struct dentry,
  				d_u.d_child);

   next_sibling:

  
  		/*
  		 * If "child" isn't empty, walk down the tree and
  		 * remove all its descendants first.
  		 */
  		if (!list_empty(&child->d_subdirs)) {
  			mutex_unlock(&parent->d_inode->i_mutex);
  			parent = child;
  			mutex_lock(&parent->d_inode->i_mutex);
  			continue;

  		}

  		__debugfs_remove(child, parent);
  		if (parent->d_subdirs.next == &child->d_u.d_child) {
  			/*

  			 * Try the next sibling.
  			 */
  			if (child->d_u.d_child.next != &parent->d_subdirs) {
  				child = list_entry(child->d_u.d_child.next,
  						   struct dentry,
  						   d_u.d_child);
  				goto next_sibling;
  			}
  
  			/*

  			 * Avoid infinite loop if we fail to remove
  			 * one dentry.
  			 */
  			mutex_unlock(&parent->d_inode->i_mutex);
  			break;
  		}
  		simple_release_fs(&debugfs_mount, &debugfs_mount_count);

  	}

  
  	parent = dentry->d_parent;
  	mutex_lock(&parent->d_inode->i_mutex);
  	__debugfs_remove(dentry, parent);

  	mutex_unlock(&parent->d_inode->i_mutex);

  	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
  }

  EXPORT_SYMBOL_GPL(debugfs_remove_recursive);

  /**
   * debugfs_rename - rename a file/directory in the debugfs filesystem
   * @old_dir: a pointer to the parent dentry for the renamed object. This
   *          should be a directory dentry.
   * @old_dentry: dentry of an object to be renamed.
   * @new_dir: a pointer to the parent dentry where the object should be
   *          moved. This should be a directory dentry.
   * @new_name: a pointer to a string containing the target name.
   *
   * This function renames a file/directory in debugfs.  The target must not
   * exist for rename to succeed.
   *
   * This function will return a pointer to old_dentry (which is updated to
   * reflect renaming) if it succeeds. If an error occurs, %NULL will be
   * returned.
   *
   * If debugfs is not enabled in the kernel, the value -%ENODEV will be
   * returned.
   */
  struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
  		struct dentry *new_dir, const char *new_name)
  {
  	int error;
  	struct dentry *dentry = NULL, *trap;
  	const char *old_name;
  
  	trap = lock_rename(new_dir, old_dir);
  	/* Source or destination directories don't exist? */
  	if (!old_dir->d_inode || !new_dir->d_inode)
  		goto exit;
  	/* Source does not exist, cyclic rename, or mountpoint? */
  	if (!old_dentry->d_inode || old_dentry == trap ||
  	    d_mountpoint(old_dentry))
  		goto exit;
  	dentry = lookup_one_len(new_name, new_dir, strlen(new_name));
  	/* Lookup failed, cyclic rename or target exists? */
  	if (IS_ERR(dentry) || dentry == trap || dentry->d_inode)
  		goto exit;
  
  	old_name = fsnotify_oldname_init(old_dentry->d_name.name);
  
  	error = simple_rename(old_dir->d_inode, old_dentry, new_dir->d_inode,
  		dentry);
  	if (error) {
  		fsnotify_oldname_free(old_name);
  		goto exit;
  	}
  	d_move(old_dentry, dentry);
  	fsnotify_move(old_dir->d_inode, new_dir->d_inode, old_name,

  		S_ISDIR(old_dentry->d_inode->i_mode),

  		NULL, old_dentry);

  	fsnotify_oldname_free(old_name);
  	unlock_rename(new_dir, old_dir);
  	dput(dentry);
  	return old_dentry;
  exit:
  	if (dentry && !IS_ERR(dentry))
  		dput(dentry);
  	unlock_rename(new_dir, old_dir);
  	return NULL;
  }
  EXPORT_SYMBOL_GPL(debugfs_rename);

  /**
   * debugfs_initialized - Tells whether debugfs has been registered
   */
  bool debugfs_initialized(void)
  {
  	return debugfs_registered;
  }
  EXPORT_SYMBOL_GPL(debugfs_initialized);

  static struct kobject *debug_kobj;

  
  static int __init debugfs_init(void)
  {
  	int retval;

  	debug_kobj = kobject_create_and_add("debug", kernel_kobj);

  	if (!debug_kobj)
  		return -EINVAL;

  
  	retval = register_filesystem(&debug_fs_type);
  	if (retval)

  		kobject_put(debug_kobj);

  	else
  		debugfs_registered = true;

  	return retval;
  }

  core_initcall(debugfs_init);