linux/include/linux/exportfs.h
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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/* limit the handle size to NFSv4 handle size now */
  12#define MAX_HANDLE_SZ 128
  13
  14/*
  15 * The fileid_type identifies how the file within the filesystem is encoded.
  16 * In theory this is freely set and parsed by the filesystem, but we try to
  17 * stick to conventions so we can share some generic code and don't confuse
  18 * sniffers like ethereal/wireshark.
  19 *
  20 * The filesystem must not use the value '0' or '0xff'.
  21 */
  22enum fid_type {
  23        /*
  24         * The root, or export point, of the filesystem.
  25         * (Never actually passed down to the filesystem.
  26         */
  27        FILEID_ROOT = 0,
  28
  29        /*
  30         * 32bit inode number, 32 bit generation number.
  31         */
  32        FILEID_INO32_GEN = 1,
  33
  34        /*
  35         * 32bit inode number, 32 bit generation number,
  36         * 32 bit parent directory inode number.
  37         */
  38        FILEID_INO32_GEN_PARENT = 2,
  39
  40        /*
  41         * 64 bit object ID, 64 bit root object ID,
  42         * 32 bit generation number.
  43         */
  44        FILEID_BTRFS_WITHOUT_PARENT = 0x4d,
  45
  46        /*
  47         * 64 bit object ID, 64 bit root object ID,
  48         * 32 bit generation number,
  49         * 64 bit parent object ID, 32 bit parent generation.
  50         */
  51        FILEID_BTRFS_WITH_PARENT = 0x4e,
  52
  53        /*
  54         * 64 bit object ID, 64 bit root object ID,
  55         * 32 bit generation number,
  56         * 64 bit parent object ID, 32 bit parent generation,
  57         * 64 bit parent root object ID.
  58         */
  59        FILEID_BTRFS_WITH_PARENT_ROOT = 0x4f,
  60
  61        /*
  62         * 32 bit block number, 16 bit partition reference,
  63         * 16 bit unused, 32 bit generation number.
  64         */
  65        FILEID_UDF_WITHOUT_PARENT = 0x51,
  66
  67        /*
  68         * 32 bit block number, 16 bit partition reference,
  69         * 16 bit unused, 32 bit generation number,
  70         * 32 bit parent block number, 32 bit parent generation number
  71         */
  72        FILEID_UDF_WITH_PARENT = 0x52,
  73
  74        /*
  75         * 64 bit checkpoint number, 64 bit inode number,
  76         * 32 bit generation number.
  77         */
  78        FILEID_NILFS_WITHOUT_PARENT = 0x61,
  79
  80        /*
  81         * 64 bit checkpoint number, 64 bit inode number,
  82         * 32 bit generation number, 32 bit parent generation.
  83         * 64 bit parent inode number.
  84         */
  85        FILEID_NILFS_WITH_PARENT = 0x62,
  86};
  87
  88struct fid {
  89        union {
  90                struct {
  91                        u32 ino;
  92                        u32 gen;
  93                        u32 parent_ino;
  94                        u32 parent_gen;
  95                } i32;
  96                struct {
  97                        u32 block;
  98                        u16 partref;
  99                        u16 parent_partref;
 100                        u32 generation;
 101                        u32 parent_block;
 102                        u32 parent_generation;
 103                } udf;
 104                __u32 raw[0];
 105        };
 106};
 107
 108/**
 109 * struct export_operations - for nfsd to communicate with file systems
 110 * @encode_fh:      encode a file handle fragment from a dentry
 111 * @fh_to_dentry:   find the implied object and get a dentry for it
 112 * @fh_to_parent:   find the implied object's parent and get a dentry for it
 113 * @get_name:       find the name for a given inode in a given directory
 114 * @get_parent:     find the parent of a given directory
 115 * @commit_metadata: commit metadata changes to stable storage
 116 *
 117 * See Documentation/filesystems/nfs/Exporting for details on how to use
 118 * this interface correctly.
 119 *
 120 * encode_fh:
 121 *    @encode_fh should store in the file handle fragment @fh (using at most
 122 *    @max_len bytes) information that can be used by @decode_fh to recover the
 123 *    file referred to by the &struct dentry @de.  If the @connectable flag is
 124 *    set, the encode_fh() should store sufficient information so that a good
 125 *    attempt can be made to find not only the file but also it's place in the
 126 *    filesystem.   This typically means storing a reference to de->d_parent in
 127 *    the filehandle fragment.  encode_fh() should return the fileid_type on
 128 *    success and on error returns 255 (if the space needed to encode fh is
 129 *    greater than @max_len*4 bytes). On error @max_len contains the minimum
 130 *    size(in 4 byte unit) needed to encode the file handle.
 131 *
 132 * fh_to_dentry:
 133 *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle
 134 *    fragment (@fh, @fh_len). It should return a &struct dentry which refers
 135 *    to the same file that the file handle fragment refers to.  If it cannot,
 136 *    it should return a %NULL pointer if the file was found but no acceptable
 137 *    &dentries were available, or an %ERR_PTR error code indicating why it
 138 *    couldn't be found (e.g. %ENOENT or %ENOMEM).  Any suitable dentry can be
 139 *    returned including, if necessary, a new dentry created with d_alloc_root.
 140 *    The caller can then find any other extant dentries by following the
 141 *    d_alias links.
 142 *
 143 * fh_to_parent:
 144 *    Same as @fh_to_dentry, except that it returns a pointer to the parent
 145 *    dentry if it was encoded into the filehandle fragment by @encode_fh.
 146 *
 147 * get_name:
 148 *    @get_name should find a name for the given @child in the given @parent
 149 *    directory.  The name should be stored in the @name (with the
 150 *    understanding that it is already pointing to a a %NAME_MAX+1 sized
 151 *    buffer.   get_name() should return %0 on success, a negative error code
 152 *    or error.  @get_name will be called without @parent->i_mutex held.
 153 *
 154 * get_parent:
 155 *    @get_parent should find the parent directory for the given @child which
 156 *    is also a directory.  In the event that it cannot be found, or storage
 157 *    space cannot be allocated, a %ERR_PTR should be returned.
 158 *
 159 * commit_metadata:
 160 *    @commit_metadata should commit metadata changes to stable storage.
 161 *
 162 * Locking rules:
 163 *    get_parent is called with child->d_inode->i_mutex down
 164 *    get_name is not (which is possibly inconsistent)
 165 */
 166
 167struct export_operations {
 168        int (*encode_fh)(struct inode *inode, __u32 *fh, int *max_len,
 169                        struct inode *parent);
 170        struct dentry * (*fh_to_dentry)(struct super_block *sb, struct fid *fid,
 171                        int fh_len, int fh_type);
 172        struct dentry * (*fh_to_parent)(struct super_block *sb, struct fid *fid,
 173                        int fh_len, int fh_type);
 174        int (*get_name)(struct dentry *parent, char *name,
 175                        struct dentry *child);
 176        struct dentry * (*get_parent)(struct dentry *child);
 177        int (*commit_metadata)(struct inode *inode);
 178};
 179
 180extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
 181        int *max_len, int connectable);
 182extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
 183        int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
 184        void *context);
 185
 186/*
 187 * Generic helpers for filesystems.
 188 */
 189extern struct dentry *generic_fh_to_dentry(struct super_block *sb,
 190        struct fid *fid, int fh_len, int fh_type,
 191        struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
 192extern struct dentry *generic_fh_to_parent(struct super_block *sb,
 193        struct fid *fid, int fh_len, int fh_type,
 194        struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
 195
 196#endif /* LINUX_EXPORTFS_H */
 197
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