#ifndef LINUX_EXPORTFS_H
  #define LINUX_EXPORTFS_H 1
  
  #include <linux/types.h>
  
  struct dentry;
  struct inode;
  struct super_block;
  struct vfsmount;
  
  /* limit the handle size to NFSv4 handle size now */
  #define MAX_HANDLE_SZ 128
  
  /*
   * The fileid_type identifies how the file within the filesystem is encoded.
   * In theory this is freely set and parsed by the filesystem, but we try to
   * stick to conventions so we can share some generic code and don't confuse
   * sniffers like ethereal/wireshark.
   *
   * The filesystem must not use the value '0' or '0xff'.
   */
  enum fid_type {
  	/*
  	 * The root, or export point, of the filesystem.
  	 * (Never actually passed down to the filesystem.
  	 */
  	FILEID_ROOT = 0,
  
  	/*
  	 * 32bit inode number, 32 bit generation number.
  	 */
  	FILEID_INO32_GEN = 1,
  
  	/*
  	 * 32bit inode number, 32 bit generation number,
  	 * 32 bit parent directory inode number.
  	 */
  	FILEID_INO32_GEN_PARENT = 2,
  
  	/*
  	 * 64 bit object ID, 64 bit root object ID,
  	 * 32 bit generation number.
  	 */
  	FILEID_BTRFS_WITHOUT_PARENT = 0x4d,
  
  	/*
  	 * 64 bit object ID, 64 bit root object ID,
  	 * 32 bit generation number,
  	 * 64 bit parent object ID, 32 bit parent generation.
  	 */
  	FILEID_BTRFS_WITH_PARENT = 0x4e,
  
  	/*
  	 * 64 bit object ID, 64 bit root object ID,
  	 * 32 bit generation number,
  	 * 64 bit parent object ID, 32 bit parent generation,
  	 * 64 bit parent root object ID.
  	 */
  	FILEID_BTRFS_WITH_PARENT_ROOT = 0x4f,
  
  	/*
  	 * 32 bit block number, 16 bit partition reference,
  	 * 16 bit unused, 32 bit generation number.
  	 */
  	FILEID_UDF_WITHOUT_PARENT = 0x51,
  
  	/*
  	 * 32 bit block number, 16 bit partition reference,
  	 * 16 bit unused, 32 bit generation number,
  	 * 32 bit parent block number, 32 bit parent generation number
  	 */
  	FILEID_UDF_WITH_PARENT = 0x52,
  
  	/*
  	 * 64 bit checkpoint number, 64 bit inode number,
  	 * 32 bit generation number.
  	 */
  	FILEID_NILFS_WITHOUT_PARENT = 0x61,
  
  	/*
  	 * 64 bit checkpoint number, 64 bit inode number,
  	 * 32 bit generation number, 32 bit parent generation.
  	 * 64 bit parent inode number.
  	 */
  	FILEID_NILFS_WITH_PARENT = 0x62,
  
  	/*
  	 * 32 bit generation number, 40 bit i_pos.
  	 */
  	FILEID_FAT_WITHOUT_PARENT = 0x71,
  
  	/*
  	 * 32 bit generation number, 40 bit i_pos,
  	 * 32 bit parent generation number, 40 bit parent i_pos
  	 */
  	FILEID_FAT_WITH_PARENT = 0x72,
  
  	/*
  	 * Filesystems must not use 0xff file ID.
  	 */
  	FILEID_INVALID = 0xff,
  };
  
  struct fid {
  	union {
  		struct {
  			u32 ino;
  			u32 gen;
  			u32 parent_ino;
  			u32 parent_gen;
  		} i32;
   		struct {
   			u32 block;
   			u16 partref;
   			u16 parent_partref;
   			u32 generation;
   			u32 parent_block;
   			u32 parent_generation;
   		} udf;
  		__u32 raw[0];
  	};
  };
  
  /**
   * struct export_operations - for nfsd to communicate with file systems
   * @encode_fh:      encode a file handle fragment from a dentry
   * @fh_to_dentry:   find the implied object and get a dentry for it
   * @fh_to_parent:   find the implied object's parent and get a dentry for it
   * @get_name:       find the name for a given inode in a given directory
   * @get_parent:     find the parent of a given directory
   * @commit_metadata: commit metadata changes to stable storage
   *
   * See Documentation/filesystems/nfs/Exporting for details on how to use
   * this interface correctly.
   *
   * encode_fh:
   *    @encode_fh should store in the file handle fragment @fh (using at most
   *    @max_len bytes) information that can be used by @decode_fh to recover the
   *    file referred to by the &struct dentry @de.  If the @connectable flag is
   *    set, the encode_fh() should store sufficient information so that a good
   *    attempt can be made to find not only the file but also it's place in the
   *    filesystem.   This typically means storing a reference to de->d_parent in
   *    the filehandle fragment.  encode_fh() should return the fileid_type on
   *    success and on error returns 255 (if the space needed to encode fh is
   *    greater than @max_len*4 bytes). On error @max_len contains the minimum
   *    size(in 4 byte unit) needed to encode the file handle.
   *
   * fh_to_dentry:
   *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle
   *    fragment (@fh, @fh_len). It should return a &struct dentry which refers
   *    to the same file that the file handle fragment refers to.  If it cannot,
   *    it should return a %NULL pointer if the file was found but no acceptable
   *    &dentries were available, or an %ERR_PTR error code indicating why it
   *    couldn't be found (e.g. %ENOENT or %ENOMEM).  Any suitable dentry can be
   *    returned including, if necessary, a new dentry created with d_alloc_root.
   *    The caller can then find any other extant dentries by following the
   *    d_alias links.
   *
   * fh_to_parent:
   *    Same as @fh_to_dentry, except that it returns a pointer to the parent
   *    dentry if it was encoded into the filehandle fragment by @encode_fh.
   *
   * get_name:
   *    @get_name should find a name for the given @child in the given @parent
   *    directory.  The name should be stored in the @name (with the
   *    understanding that it is already pointing to a a %NAME_MAX+1 sized
   *    buffer.   get_name() should return %0 on success, a negative error code
   *    or error.  @get_name will be called without @parent->i_mutex held.
   *
   * get_parent:
   *    @get_parent should find the parent directory for the given @child which
   *    is also a directory.  In the event that it cannot be found, or storage
   *    space cannot be allocated, a %ERR_PTR should be returned.
   *
   * commit_metadata:
   *    @commit_metadata should commit metadata changes to stable storage.
   *
   * Locking rules:
   *    get_parent is called with child->d_inode->i_mutex down
   *    get_name is not (which is possibly inconsistent)
   */
  
  struct export_operations {
  	int (*encode_fh)(struct inode *inode, __u32 *fh, int *max_len,
  			struct inode *parent);
  	struct dentry * (*fh_to_dentry)(struct super_block *sb, struct fid *fid,
  			int fh_len, int fh_type);
  	struct dentry * (*fh_to_parent)(struct super_block *sb, struct fid *fid,
  			int fh_len, int fh_type);
  	int (*get_name)(struct dentry *parent, char *name,
  			struct dentry *child);
  	struct dentry * (*get_parent)(struct dentry *child);
  	int (*commit_metadata)(struct inode *inode);
  };
  
  extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
  				    int *max_len, struct inode *parent);
  extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
  	int *max_len, int connectable);
  extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
  	int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
  	void *context);
  
  /*
   * Generic helpers for filesystems.
   */
  extern struct dentry *generic_fh_to_dentry(struct super_block *sb,
  	struct fid *fid, int fh_len, int fh_type,
  	struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
  extern struct dentry *generic_fh_to_parent(struct super_block *sb,
  	struct fid *fid, int fh_len, int fh_type,
  	struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
  
  #endif /* LINUX_EXPORTFS_H */