include/linux/exportfs.h

   1 #ifndef LINUX_EXPORTFS_H
   2 #define LINUX_EXPORTFS_H 1
   3
   4 #include <linux/types.h>
   5
   6 struct dentry;
   7 struct inode;
   8 struct super_block;
   9 struct 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  */
  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 };
  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
  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
 103 struct 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
 115 extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
 116         int *max_len, int connectable);
 117 extern 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  */
 124 extern 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));
 127 extern 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 */