[mirror_ubuntu-jammy-kernel.git] / include / linux / exportfs.h

#ifndef LINUX_EXPORTFS_H
#define LINUX_EXPORTFS_H 1

#include <linux/types.h>

struct dentry;
struct inode;
struct super_block;
struct vfsmount;

/*
 * 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,
};

struct fid {
	union {
		struct {
			u32 ino;
			u32 gen;
			u32 parent_ino;
			u32 parent_gen;
		} i32;
		__u32 raw[6];
	};
};

/**
 * 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
 *
 * 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.
 *
 * 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
 *
 * 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.
 *
 * 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 dentry *de, __u32 *fh, int *max_len,
			int connectable);
	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);
};

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 */
Commit	Line	Data
a5694255 CH	1	#ifndef LINUX_EXPORTFS_H
	2	#define LINUX_EXPORTFS_H 1
	3
	4	#include <linux/types.h>
	5
	6	struct dentry;
2596110a	7	struct inode;
a5694255	8	struct super_block;
d37065cd	9	struct vfsmount;
a5694255	10
6e91ea2b CH	11	/*
	12	* The fileid_type identifies how the file within the filesystem is encoded.
	13	* In theory this is freely set and parsed by the filesystem, but we try to
	14	* stick to conventions so we can share some generic code and don't confuse
	15	* sniffers like ethereal/wireshark.
	16	*
	17	* The filesystem must not use the value '0' or '0xff'.
	18	*/
	19	enum fid_type {
	20	/*
	21	* The root, or export point, of the filesystem.
	22	* (Never actually passed down to the filesystem.
	23	*/
	24	FILEID_ROOT = 0,
	25
	26	/*
	27	* 32bit inode number, 32 bit generation number.
	28	*/
	29	FILEID_INO32_GEN = 1,
	30
	31	/*
	32	* 32bit inode number, 32 bit generation number,
	33	* 32 bit parent directory inode number.
	34	*/
	35	FILEID_INO32_GEN_PARENT = 2,
	36	};
	37
	38	struct fid {
	39	union {
	40	struct {
	41	u32 ino;
	42	u32 gen;
	43	u32 parent_ino;
	44	u32 parent_gen;
	45	} i32;
	46	__u32 raw[6];
	47	};
	48	};
a5694255 CH	49
	50	/**
	51	* struct export_operations - for nfsd to communicate with file systems
	52	* @decode_fh: decode a file handle fragment and return a &struct dentry
	53	* @encode_fh: encode a file handle fragment from a dentry
	54	* @get_name: find the name for a given inode in a given directory
	55	* @get_parent: find the parent of a given directory
	56	* @get_dentry: find a dentry for the inode given a file handle sub-fragment
a5694255 CH	57	*
	58	* Description:
	59	* The export_operations structure provides a means for nfsd to communicate
	60	* with a particular exported file system - particularly enabling nfsd and
	61	* the filesystem to co-operate when dealing with file handles.
	62	*
	63	* export_operations contains two basic operation for dealing with file
	64	* handles, decode_fh() and encode_fh(), and allows for some other
	65	* operations to be defined which standard helper routines use to get
	66	* specific information from the filesystem.
	67	*
	68	* nfsd encodes information use to determine which filesystem a filehandle
	69	* applies to in the initial part of the file handle. The remainder, termed
	70	* a file handle fragment, is controlled completely by the filesystem. The
	71	* standard helper routines assume that this fragment will contain one or
	72	* two sub-fragments, one which identifies the file, and one which may be
	73	* used to identify the (a) directory containing the file.
	74	*
	75	* In some situations, nfsd needs to get a dentry which is connected into a
	76	* specific part of the file tree. To allow for this, it passes the
	77	* function acceptable() together with a @context which can be used to see
	78	* if the dentry is acceptable. As there can be multiple dentrys for a
	79	* given file, the filesystem should check each one for acceptability before
	80	* looking for the next. As soon as an acceptable one is found, it should
	81	* be returned.
	82	*
a5694255 CH	83	* encode_fh:
	84	* @encode_fh should store in the file handle fragment @fh (using at most
	85	* @max_len bytes) information that can be used by @decode_fh to recover the
	86	* file refered to by the &struct dentry @de. If the @connectable flag is
	87	* set, the encode_fh() should store sufficient information so that a good
	88	* attempt can be made to find not only the file but also it's place in the
	89	* filesystem. This typically means storing a reference to de->d_parent in
	90	* the filehandle fragment. encode_fh() should return the number of bytes
	91	* stored or a negative error code such as %-ENOSPC
	92	*
2596110a CH	93	* fh_to_dentry:
	94	* @fh_to_dentry is given a &struct super_block (@sb) and a file handle
	95	* fragment (@fh, @fh_len). It should return a &struct dentry which refers
	96	* to the same file that the file handle fragment refers to. If it cannot,
	97	* it should return a %NULL pointer if the file was found but no acceptable
	98	* &dentries were available, or an %ERR_PTR error code indicating why it
	99	* couldn't be found (e.g. %ENOENT or %ENOMEM). Any suitable dentry can be
	100	* returned including, if necessary, a new dentry created with d_alloc_root.
	101	* The caller can then find any other extant dentries by following the
	102	* d_alias links.
	103	*
	104	* fh_to_parent:
	105	* Same as @fh_to_dentry, except that it returns a pointer to the parent
	106	* dentry if it was encoded into the filehandle fragment by @encode_fh.
	107	*
a5694255 CH	108	* get_name:
	109	* @get_name should find a name for the given @child in the given @parent
	110	* directory. The name should be stored in the @name (with the
	111	* understanding that it is already pointing to a a %NAME_MAX+1 sized
	112	* buffer. get_name() should return %0 on success, a negative error code
	113	* or error. @get_name will be called without @parent->i_mutex held.
	114	*
	115	* get_parent:
	116	* @get_parent should find the parent directory for the given @child which
	117	* is also a directory. In the event that it cannot be found, or storage
	118	* space cannot be allocated, a %ERR_PTR should be returned.
	119	*
a5694255 CH	120	* Locking rules:
	121	* get_parent is called with child->d_inode->i_mutex down
	122	* get_name is not (which is possibly inconsistent)
	123	*/
	124
	125	struct export_operations {
a5694255 CH	126	int (encode_fh)(struct dentry de, __u32 fh, int max_len,
a5694255 CH	127	int connectable);
2596110a CH	128	struct dentry * (fh_to_dentry)(struct super_block sb, struct fid *fid,
	129	int fh_len, int fh_type);
	130	struct dentry * (fh_to_parent)(struct super_block sb, struct fid *fid,
	131	int fh_len, int fh_type);
a5694255 CH	132	int (get_name)(struct dentry parent, char *name,
	133	struct dentry *child);
	134	struct dentry * (get_parent)(struct dentry child);
a5694255 CH	135	};
a5694255 CH	136
6e91ea2b CH	137	extern int exportfs_encode_fh(struct dentry dentry, struct fid fid,
	138	int *max_len, int connectable);
	139	extern struct dentry exportfs_decode_fh(struct vfsmount mnt, struct fid *fid,
d37065cd CH	140	int fh_len, int fileid_type, int (acceptable)(void , struct dentry *),
	141	void *context);
	142
2596110a CH	143	/*
	144	* Generic helpers for filesystems.
	145	*/
	146	extern struct dentry generic_fh_to_dentry(struct super_block sb,
	147	struct fid *fid, int fh_len, int fh_type,
	148	struct inode (get_inode) (struct super_block *sb, u64 ino, u32 gen));
	149	extern struct dentry generic_fh_to_parent(struct super_block sb,
	150	struct fid *fid, int fh_len, int fh_type,
	151	struct inode (get_inode) (struct super_block *sb, u64 ino, u32 gen));
	152
a5694255	153	#endif /* LINUX_EXPORTFS_H */