include/linux/exportfs.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef LINUX_EXPORTFS_H
   3 #define LINUX_EXPORTFS_H 1
   4
   5 #include <linux/types.h>
   6
   7 struct dentry;
   8 struct iattr;
   9 struct inode;
  10 struct iomap;
  11 struct super_block;
  12 struct vfsmount;
  13
  14 /* limit the handle size to NFSv4 handle size now */
  15 #define MAX_HANDLE_SZ 128
  16
  17 /*
  18  * The fileid_type identifies how the file within the filesystem is encoded.
  19  * In theory this is freely set and parsed by the filesystem, but we try to
  20  * stick to conventions so we can share some generic code and don't confuse
  21  * sniffers like ethereal/wireshark.
  22  *
  23  * The filesystem must not use the value '0' or '0xff'.
  24  */
  25 enum fid_type {
  26         /*
  27          * The root, or export point, of the filesystem.
  28          * (Never actually passed down to the filesystem.
  29          */
  30         FILEID_ROOT = 0,
  31
  32         /*
  33          * 32bit inode number, 32 bit generation number.
  34          */
  35         FILEID_INO32_GEN = 1,
  36
  37         /*
  38          * 32bit inode number, 32 bit generation number,
  39          * 32 bit parent directory inode number.
  40          */
  41         FILEID_INO32_GEN_PARENT = 2,
  42
  43         /*
  44          * 64 bit object ID, 64 bit root object ID,
  45          * 32 bit generation number.
  46          */
  47         FILEID_BTRFS_WITHOUT_PARENT = 0x4d,
  48
  49         /*
  50          * 64 bit object ID, 64 bit root object ID,
  51          * 32 bit generation number,
  52          * 64 bit parent object ID, 32 bit parent generation.
  53          */
  54         FILEID_BTRFS_WITH_PARENT = 0x4e,
  55
  56         /*
  57          * 64 bit object ID, 64 bit root object ID,
  58          * 32 bit generation number,
  59          * 64 bit parent object ID, 32 bit parent generation,
  60          * 64 bit parent root object ID.
  61          */
  62         FILEID_BTRFS_WITH_PARENT_ROOT = 0x4f,
  63
  64         /*
  65          * 32 bit block number, 16 bit partition reference,
  66          * 16 bit unused, 32 bit generation number.
  67          */
  68         FILEID_UDF_WITHOUT_PARENT = 0x51,
  69
  70         /*
  71          * 32 bit block number, 16 bit partition reference,
  72          * 16 bit unused, 32 bit generation number,
  73          * 32 bit parent block number, 32 bit parent generation number
  74          */
  75         FILEID_UDF_WITH_PARENT = 0x52,
  76
  77         /*
  78          * 64 bit checkpoint number, 64 bit inode number,
  79          * 32 bit generation number.
  80          */
  81         FILEID_NILFS_WITHOUT_PARENT = 0x61,
  82
  83         /*
  84          * 64 bit checkpoint number, 64 bit inode number,
  85          * 32 bit generation number, 32 bit parent generation.
  86          * 64 bit parent inode number.
  87          */
  88         FILEID_NILFS_WITH_PARENT = 0x62,
  89
  90         /*
  91          * 32 bit generation number, 40 bit i_pos.
  92          */
  93         FILEID_FAT_WITHOUT_PARENT = 0x71,
  94
  95         /*
  96          * 32 bit generation number, 40 bit i_pos,
  97          * 32 bit parent generation number, 40 bit parent i_pos
  98          */
  99         FILEID_FAT_WITH_PARENT = 0x72,
 100
 101         /*
 102          * 128 bit child FID (struct lu_fid)
 103          * 128 bit parent FID (struct lu_fid)
 104          */
 105         FILEID_LUSTRE = 0x97,
 106
 107         /*
 108          * Filesystems must not use 0xff file ID.
 109          */
 110         FILEID_INVALID = 0xff,
 111 };
 112
 113 struct fid {
 114         union {
 115                 struct {
 116                         u32 ino;
 117                         u32 gen;
 118                         u32 parent_ino;
 119                         u32 parent_gen;
 120                 } i32;
 121                 struct {
 122                         u32 block;
 123                         u16 partref;
 124                         u16 parent_partref;
 125                         u32 generation;
 126                         u32 parent_block;
 127                         u32 parent_generation;
 128                 } udf;
 129                 __u32 raw[0];
 130         };
 131 };
 132
 133 /**
 134  * struct export_operations - for nfsd to communicate with file systems
 135  * @encode_fh:      encode a file handle fragment from a dentry
 136  * @fh_to_dentry:   find the implied object and get a dentry for it
 137  * @fh_to_parent:   find the implied object's parent and get a dentry for it
 138  * @get_name:       find the name for a given inode in a given directory
 139  * @get_parent:     find the parent of a given directory
 140  * @commit_metadata: commit metadata changes to stable storage
 141  *
 142  * See Documentation/filesystems/nfs/Exporting for details on how to use
 143  * this interface correctly.
 144  *
 145  * encode_fh:
 146  *    @encode_fh should store in the file handle fragment @fh (using at most
 147  *    @max_len bytes) information that can be used by @decode_fh to recover the
 148  *    file referred to by the &struct dentry @de.  If the @connectable flag is
 149  *    set, the encode_fh() should store sufficient information so that a good
 150  *    attempt can be made to find not only the file but also it's place in the
 151  *    filesystem.   This typically means storing a reference to de->d_parent in
 152  *    the filehandle fragment.  encode_fh() should return the fileid_type on
 153  *    success and on error returns 255 (if the space needed to encode fh is
 154  *    greater than @max_len*4 bytes). On error @max_len contains the minimum
 155  *    size(in 4 byte unit) needed to encode the file handle.
 156  *
 157  * fh_to_dentry:
 158  *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle
 159  *    fragment (@fh, @fh_len). It should return a &struct dentry which refers
 160  *    to the same file that the file handle fragment refers to.  If it cannot,
 161  *    it should return a %NULL pointer if the file cannot be found, or an
 162  *    %ERR_PTR error code of %ENOMEM if a memory allocation failure occurred.
 163  *    Any other error code is treated like %NULL, and will cause an %ESTALE error
 164  *    for callers of exportfs_decode_fh().
 165  *    Any suitable dentry can be returned including, if necessary, a new dentry
 166  *    created with d_alloc_root.  The caller can then find any other extant
 167  *    dentries by following the d_alias links.
 168  *
 169  * fh_to_parent:
 170  *    Same as @fh_to_dentry, except that it returns a pointer to the parent
 171  *    dentry if it was encoded into the filehandle fragment by @encode_fh.
 172  *
 173  * get_name:
 174  *    @get_name should find a name for the given @child in the given @parent
 175  *    directory.  The name should be stored in the @name (with the
 176  *    understanding that it is already pointing to a a %NAME_MAX+1 sized
 177  *    buffer.   get_name() should return %0 on success, a negative error code
 178  *    or error.  @get_name will be called without @parent->i_mutex held.
 179  *
 180  * get_parent:
 181  *    @get_parent should find the parent directory for the given @child which
 182  *    is also a directory.  In the event that it cannot be found, or storage
 183  *    space cannot be allocated, a %ERR_PTR should be returned.
 184  *
 185  * commit_metadata:
 186  *    @commit_metadata should commit metadata changes to stable storage.
 187  *
 188  * Locking rules:
 189  *    get_parent is called with child->d_inode->i_mutex down
 190  *    get_name is not (which is possibly inconsistent)
 191  */
 192
 193 struct export_operations {
 194         int (*encode_fh)(struct inode *inode, __u32 *fh, int *max_len,
 195                         struct inode *parent);
 196         struct dentry * (*fh_to_dentry)(struct super_block *sb, struct fid *fid,
 197                         int fh_len, int fh_type);
 198         struct dentry * (*fh_to_parent)(struct super_block *sb, struct fid *fid,
 199                         int fh_len, int fh_type);
 200         int (*get_name)(struct dentry *parent, char *name,
 201                         struct dentry *child);
 202         struct dentry * (*get_parent)(struct dentry *child);
 203         int (*commit_metadata)(struct inode *inode);
 204
 205         int (*get_uuid)(struct super_block *sb, u8 *buf, u32 *len, u64 *offset);
 206         int (*map_blocks)(struct inode *inode, loff_t offset,
 207                           u64 len, struct iomap *iomap,
 208                           bool write, u32 *device_generation);
 209         int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
 210                              int nr_iomaps, struct iattr *iattr);
 211 };
 212
 213 extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
 214                                     int *max_len, struct inode *parent);
 215 extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
 216         int *max_len, int connectable);
 217 extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
 218         int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
 219         void *context);
 220
 221 /*
 222  * Generic helpers for filesystems.
 223  */
 224 extern struct dentry *generic_fh_to_dentry(struct super_block *sb,
 225         struct fid *fid, int fh_len, int fh_type,
 226         struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
 227 extern struct dentry *generic_fh_to_parent(struct super_block *sb,
 228         struct fid *fid, int fh_len, int fh_type,
 229         struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
 230
 231 #endif /* LINUX_EXPORTFS_H */