#ifndef LINUX_EXPORTFS_H
#define LINUX_EXPORTFS_H 1
#include <linux/types.h>
struct dentry;
struct super_block;
/**
* struct export_operations - for nfsd to communicate with file systems
* @decode_fh: decode a file handle fragment and return a &struct dentry
* @encode_fh: encode a file handle fragment from a dentry
* @get_name: find the name for a given inode in a given directory
* @get_parent: find the parent of a given directory
* @get_dentry: find a dentry for the inode given a file handle sub-fragment
* @find_exported_dentry:
* set by the exporting module to a standard helper function.
*
* Description:
* The export_operations structure provides a means for nfsd to communicate
* with a particular exported file system - particularly enabling nfsd and
* the filesystem to co-operate when dealing with file handles.
*
* export_operations contains two basic operation for dealing with file
* handles, decode_fh() and encode_fh(), and allows for some other
* operations to be defined which standard helper routines use to get
* specific information from the filesystem.
*
* nfsd encodes information use to determine which filesystem a filehandle
* applies to in the initial part of the file handle. The remainder, termed
* a file handle fragment, is controlled completely by the filesystem. The
* standard helper routines assume that this fragment will contain one or
* two sub-fragments, one which identifies the file, and one which may be
* used to identify the (a) directory containing the file.
*
* In some situations, nfsd needs to get a dentry which is connected into a
* specific part of the file tree. To allow for this, it passes the
* function acceptable() together with a @context which can be used to see
* if the dentry is acceptable. As there can be multiple dentrys for a
* given file, the filesystem should check each one for acceptability before
* looking for the next. As soon as an acceptable one is found, it should
* be returned.
*
* decode_fh:
* @decode_fh is given a &struct super_block (@sb), a file handle fragment
* (@fh, @fh_len) and an acceptability testing function (@acceptable,
* @context). It should return a &struct dentry which refers to the same
* file that the file handle fragment refers to, and which passes the
* acceptability test. If it cannot, it should return a %NULL pointer if
* the file was found but no acceptable &dentries were available, or a
* %ERR_PTR error code indicating why it couldn't be found (e.g. %ENOENT or
* %ENOMEM).
*
* 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 refered 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 number of bytes
* stored or a negative error code such as %-ENOSPC
*
* 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.
*
* get_dentry:
* Given a &super_block (@sb) and a pointer to a file-system specific inode
* identifier, possibly an inode number, (@inump) get_dentry() should find
* the identified inode and return a dentry for that inode. 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 dentrys by
* following the d_alias links. If a new dentry was created using
* d_alloc_root, DCACHE_NFSD_DISCONNECTED should be set, and the dentry
* should be d_rehash()ed.
*
* If the inode cannot be found, either a %NULL pointer or an %ERR_PTR code
* can be returned. The @inump will be whatever was passed to
* nfsd_find_fh_dentry() in either the @obj or @parent parameters.
*
* Locking rules:
* get_parent is called with child->d_inode->i_mutex down
* get_name is not (which is possibly inconsistent)
*/
struct export_operations {
struct dentry *(*decode_fh)(struct super_block *sb, __u32 *fh,
int fh_len, int fh_type,
int (*acceptable)(void *context, struct dentry *de),
void *context);
int (*encode_fh)(struct dentry *de, __u32 *fh, int *max_len,
int connectable);
int (*get_name)(struct dentry *parent, char *name,
struct dentry *child);
struct dentry * (*get_parent)(struct dentry *child);
struct dentry * (*get_dentry)(struct super_block *sb, void *inump);
/* This is set by the exporting module to a standard helper */
struct dentry * (*find_exported_dentry)(
struct super_block *sb, void *obj, void *parent,
int (*acceptable)(void *context, struct dentry *de),
void *context);
};
extern struct dentry *find_exported_dentry(struct super_block *sb, void *obj,
void *parent, int (*acceptable)(void *context, struct dentry *de),
void *context);
#endif /* LINUX_EXPORTFS_H */
