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1#ifndef LINUX_EXPORTFS_H
2#define LINUX_EXPORTFS_H 1
3
4#include <linux/types.h>
5
6struct dentry;
7struct inode;
8struct super_block;
9struct vfsmount;
10
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 */
19enum 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
38struct 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};
49
50/**
51 * struct export_operations - for nfsd to communicate with file systems
52 * @encode_fh: encode a file handle fragment from a dentry
53 * @fh_to_dentry: find the implied object and get a dentry for it
54 * @fh_to_parent: find the implied object's parent and get a dentry for it
55 * @get_name: find the name for a given inode in a given directory
56 * @get_parent: find the parent of a given directory
57 *
58 * See Documentation/filesystems/Exporting for details on how to use
59 * this interface correctly.
60 *
61 * encode_fh:
62 * @encode_fh should store in the file handle fragment @fh (using at most
63 * @max_len bytes) information that can be used by @decode_fh to recover the
64 * file refered to by the &struct dentry @de. If the @connectable flag is
65 * set, the encode_fh() should store sufficient information so that a good
66 * attempt can be made to find not only the file but also it's place in the
67 * filesystem. This typically means storing a reference to de->d_parent in
68 * the filehandle fragment. encode_fh() should return the number of bytes
69 * stored or a negative error code such as %-ENOSPC
70 *
71 * fh_to_dentry:
72 * @fh_to_dentry is given a &struct super_block (@sb) and a file handle
73 * fragment (@fh, @fh_len). It should return a &struct dentry which refers
74 * to the same file that the file handle fragment refers to. If it cannot,
75 * it should return a %NULL pointer if the file was found but no acceptable
76 * &dentries were available, or an %ERR_PTR error code indicating why it
77 * couldn't be found (e.g. %ENOENT or %ENOMEM). Any suitable dentry can be
78 * returned including, if necessary, a new dentry created with d_alloc_root.
79 * The caller can then find any other extant dentries by following the
80 * d_alias links.
81 *
82 * fh_to_parent:
83 * Same as @fh_to_dentry, except that it returns a pointer to the parent
84 * dentry if it was encoded into the filehandle fragment by @encode_fh.
85 *
86 * get_name:
87 * @get_name should find a name for the given @child in the given @parent
88 * directory. The name should be stored in the @name (with the
89 * understanding that it is already pointing to a a %NAME_MAX+1 sized
90 * buffer. get_name() should return %0 on success, a negative error code
91 * or error. @get_name will be called without @parent->i_mutex held.
92 *
93 * get_parent:
94 * @get_parent should find the parent directory for the given @child which
95 * is also a directory. In the event that it cannot be found, or storage
96 * space cannot be allocated, a %ERR_PTR should be returned.
97 *
98 * Locking rules:
99 * get_parent is called with child->d_inode->i_mutex down
100 * get_name is not (which is possibly inconsistent)
101 */
102
103struct export_operations {
104 int (*encode_fh)(struct dentry *de, __u32 *fh, int *max_len,
105 int connectable);
106 struct dentry * (*fh_to_dentry)(struct super_block *sb, struct fid *fid,
107 int fh_len, int fh_type);
108 struct dentry * (*fh_to_parent)(struct super_block *sb, struct fid *fid,
109 int fh_len, int fh_type);
110 int (*get_name)(struct dentry *parent, char *name,
111 struct dentry *child);
112 struct dentry * (*get_parent)(struct dentry *child);
113};
114
115extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
116 int *max_len, int connectable);
117extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
118 int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
119 void *context);
120
121/*
122 * Generic helpers for filesystems.
123 */
124extern struct dentry *generic_fh_to_dentry(struct super_block *sb,
125 struct fid *fid, int fh_len, int fh_type,
126 struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
127extern struct dentry *generic_fh_to_parent(struct super_block *sb,
128 struct fid *fid, int fh_len, int fh_type,
129 struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
130
131#endif /* LINUX_EXPORTFS_H */