1 #ifndef LINUX_EXPORTFS_H
2 #define LINUX_EXPORTFS_H 1
4 #include <linux/types.h>
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.
17 * The filesystem must not use the value '0' or '0xff'.
21 * The root, or export point, of the filesystem.
22 * (Never actually passed down to the filesystem.
27 * 32bit inode number, 32 bit generation number.
32 * 32bit inode number, 32 bit generation number,
33 * 32 bit parent directory inode number.
35 FILEID_INO32_GEN_PARENT = 2,
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
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.
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.
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.
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
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
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
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.
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.
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.
121 * get_parent is called with child->d_inode->i_mutex down
122 * get_name is not (which is possibly inconsistent)
125 struct export_operations {
126 int (*encode_fh)(struct dentry *de, __u32 *fh, int *max_len,
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);
132 int (*get_name)(struct dentry *parent, char *name,
133 struct dentry *child);
134 struct dentry * (*get_parent)(struct dentry *child);
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,
140 int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
144 * Generic helpers for filesystems.
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));
153 #endif /* LINUX_EXPORTFS_H */