/include/linux/exportfs.h

  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	/*
 38	 * 64 bit object ID, 64 bit root object ID,
 39	 * 32 bit generation number.
 40	 */
 41	FILEID_BTRFS_WITHOUT_PARENT = 0x4d,
 42
 43	/*
 44	 * 64 bit object ID, 64 bit root object ID,
 45	 * 32 bit generation number,
 46	 * 64 bit parent object ID, 32 bit parent generation.
 47	 */
 48	FILEID_BTRFS_WITH_PARENT = 0x4e,
 49
 50	/*
 51	 * 64 bit object ID, 64 bit root object ID,
 52	 * 32 bit generation number,
 53	 * 64 bit parent object ID, 32 bit parent generation,
 54	 * 64 bit parent root object ID.
 55	 */
 56	FILEID_BTRFS_WITH_PARENT_ROOT = 0x4f,
 57
 58	/*
 59	 * 32 bit block number, 16 bit partition reference,
 60	 * 16 bit unused, 32 bit generation number.
 61	 */
 62	FILEID_UDF_WITHOUT_PARENT = 0x51,
 63
 64	/*
 65	 * 32 bit block number, 16 bit partition reference,
 66	 * 16 bit unused, 32 bit generation number,
 67	 * 32 bit parent block number, 32 bit parent generation number
 68	 */
 69	FILEID_UDF_WITH_PARENT = 0x52,
 70};
 71
 72struct fid {
 73	union {
 74		struct {
 75			u32 ino;
 76			u32 gen;
 77			u32 parent_ino;
 78			u32 parent_gen;
 79		} i32;
 80 		struct {
 81 			u32 block;
 82 			u16 partref;
 83 			u16 parent_partref;
 84 			u32 generation;
 85 			u32 parent_block;
 86 			u32 parent_generation;
 87 		} udf;
 88		__u32 raw[0];
 89	};
 90};
 91
 92/**
 93 * struct export_operations - for nfsd to communicate with file systems
 94 * @encode_fh:      encode a file handle fragment from a dentry
 95 * @fh_to_dentry:   find the implied object and get a dentry for it
 96 * @fh_to_parent:   find the implied object's parent and get a dentry for it
 97 * @get_name:       find the name for a given inode in a given directory
 98 * @get_parent:     find the parent of a given directory
 99 * @commit_metadata: commit metadata changes to stable storage
100 *
101 * See Documentation/filesystems/nfs/Exporting for details on how to use
102 * this interface correctly.
103 *
104 * encode_fh:
105 *    @encode_fh should store in the file handle fragment @fh (using at most
106 *    @max_len bytes) information that can be used by @decode_fh to recover the
107 *    file refered to by the &struct dentry @de.  If the @connectable flag is
108 *    set, the encode_fh() should store sufficient information so that a good
109 *    attempt can be made to find not only the file but also it's place in the
110 *    filesystem.   This typically means storing a reference to de->d_parent in
111 *    the filehandle fragment.  encode_fh() should return the number of bytes
112 *    stored or a negative error code such as %-ENOSPC
113 *
114 * fh_to_dentry:
115 *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle
116 *    fragment (@fh, @fh_len). It should return a &struct dentry which refers
117 *    to the same file that the file handle fragment refers to.  If it cannot,
118 *    it should return a %NULL pointer if the file was found but no acceptable
119 *    &dentries were available, or an %ERR_PTR error code indicating why it
120 *    couldn't be found (e.g. %ENOENT or %ENOMEM).  Any suitable dentry can be
121 *    returned including, if necessary, a new dentry created with d_alloc_root.
122 *    The caller can then find any other extant dentries by following the
123 *    d_alias links.
124 *
125 * fh_to_parent:
126 *    Same as @fh_to_dentry, except that it returns a pointer to the parent
127 *    dentry if it was encoded into the filehandle fragment by @encode_fh.
128 *
129 * get_name:
130 *    @get_name should find a name for the given @child in the given @parent
131 *    directory.  The name should be stored in the @name (with the
132 *    understanding that it is already pointing to a a %NAME_MAX+1 sized
133 *    buffer.   get_name() should return %0 on success, a negative error code
134 *    or error.  @get_name will be called without @parent->i_mutex held.
135 *
136 * get_parent:
137 *    @get_parent should find the parent directory for the given @child which
138 *    is also a directory.  In the event that it cannot be found, or storage
139 *    space cannot be allocated, a %ERR_PTR should be returned.
140 *
141 * commit_metadata:
142 *    @commit_metadata should commit metadata changes to stable storage.
143 *
144 * Locking rules:
145 *    get_parent is called with child->d_inode->i_mutex down
146 *    get_name is not (which is possibly inconsistent)
147 */
148
149struct export_operations {
150	int (*encode_fh)(struct dentry *de, __u32 *fh, int *max_len,
151			int connectable);
152	struct dentry * (*fh_to_dentry)(struct super_block *sb, struct fid *fid,
153			int fh_len, int fh_type);
154	struct dentry * (*fh_to_parent)(struct super_block *sb, struct fid *fid,
155			int fh_len, int fh_type);
156	int (*get_name)(struct dentry *parent, char *name,
157			struct dentry *child);
158	struct dentry * (*get_parent)(struct dentry *child);
159	int (*commit_metadata)(struct inode *inode);
160};
161
162extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
163	int *max_len, int connectable);
164extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
165	int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
166	void *context);
167
168/*
169 * Generic helpers for filesystems.
170 */
171extern struct dentry *generic_fh_to_dentry(struct super_block *sb,
172	struct fid *fid, int fh_len, int fh_type,
173	struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
174extern struct dentry *generic_fh_to_parent(struct super_block *sb,
175	struct fid *fid, int fh_len, int fh_type,
176	struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
177
178#endif /* LINUX_EXPORTFS_H */