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          * 64 bit inode number, 32 bit generation number.
 103          */
 104         FILEID_INO64_GEN = 0x81,
 105
 106         /*
 107          * 64 bit inode number, 32 bit generation number,
 108          * 64 bit parent inode number, 32 bit parent generation.
 109          */
 110         FILEID_INO64_GEN_PARENT = 0x82,
 111
 112         /*
 113          * 128 bit child FID (struct lu_fid)
 114          * 128 bit parent FID (struct lu_fid)
 115          */
 116         FILEID_LUSTRE = 0x97,
 117
 118         /*
 119          * 64 bit inode number, 32 bit subvolume, 32 bit generation number:
 120          */
 121         FILEID_BCACHEFS_WITHOUT_PARENT = 0xb1,
 122         FILEID_BCACHEFS_WITH_PARENT = 0xb2,
 123
 124         /*
 125          * 64 bit unique kernfs id
 126          */
 127         FILEID_KERNFS = 0xfe,
 128
 129         /*
 130          * Filesystems must not use 0xff file ID.
 131          */
 132         FILEID_INVALID = 0xff,
 133 };
 134
 135 struct fid {
 136         union {
 137                 struct {
 138                         u32 ino;
 139                         u32 gen;
 140                         u32 parent_ino;
 141                         u32 parent_gen;
 142                 } i32;
 143                 struct {
 144                         u64 ino;
 145                         u32 gen;
 146                 } __packed i64;
 147                 struct {
 148                         u32 block;
 149                         u16 partref;
 150                         u16 parent_partref;
 151                         u32 generation;
 152                         u32 parent_block;
 153                         u32 parent_generation;
 154                 } udf;
 155                 DECLARE_FLEX_ARRAY(__u32, raw);
 156         };
 157 };
 158
 159 #define EXPORT_FH_CONNECTABLE   0x1 /* Encode file handle with parent */
 160 #define EXPORT_FH_FID           0x2 /* File handle may be non-decodeable */
 161 #define EXPORT_FH_DIR_ONLY      0x4 /* Only decode file handle for a directory */
 162
 163 /*
 164  * Filesystems use only lower 8 bits of file_handle type for fid_type.
 165  * name_to_handle_at() uses upper 16 bits of type as user flags to be
 166  * interpreted by open_by_handle_at().
 167  */
 168 #define FILEID_USER_FLAGS_MASK  0xffff0000
 169 #define FILEID_USER_FLAGS(type) ((type) & FILEID_USER_FLAGS_MASK)
 170
 171 /* Flags supported in encoded handle_type that is exported to user */
 172 #define FILEID_IS_CONNECTABLE   0x10000
 173 #define FILEID_IS_DIR           0x20000
 174 #define FILEID_VALID_USER_FLAGS (FILEID_IS_CONNECTABLE | FILEID_IS_DIR)
 175
 176 /**
 177  * struct export_operations - for nfsd to communicate with file systems
 178  * @encode_fh:      encode a file handle fragment from a dentry
 179  * @fh_to_dentry:   find the implied object and get a dentry for it
 180  * @fh_to_parent:   find the implied object's parent and get a dentry for it
 181  * @get_name:       find the name for a given inode in a given directory
 182  * @get_parent:     find the parent of a given directory
 183  * @commit_metadata: commit metadata changes to stable storage
 184  *
 185  * See Documentation/filesystems/nfs/exporting.rst for details on how to use
 186  * this interface correctly.
 187  *
 188  * encode_fh:
 189  *    @encode_fh should store in the file handle fragment @fh (using at most
 190  *    @max_len bytes) information that can be used by @decode_fh to recover the
 191  *    file referred to by the &struct dentry @de.  If @flag has CONNECTABLE bit
 192  *    set, the encode_fh() should store sufficient information so that a good
 193  *    attempt can be made to find not only the file but also it's place in the
 194  *    filesystem.   This typically means storing a reference to de->d_parent in
 195  *    the filehandle fragment.  encode_fh() should return the fileid_type on
 196  *    success and on error returns 255 (if the space needed to encode fh is
 197  *    greater than @max_len*4 bytes). On error @max_len contains the minimum
 198  *    size(in 4 byte unit) needed to encode the file handle.
 199  *
 200  * fh_to_dentry:
 201  *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle
 202  *    fragment (@fh, @fh_len). It should return a &struct dentry which refers
 203  *    to the same file that the file handle fragment refers to.  If it cannot,
 204  *    it should return a %NULL pointer if the file cannot be found, or an
 205  *    %ERR_PTR error code of %ENOMEM if a memory allocation failure occurred.
 206  *    Any other error code is treated like %NULL, and will cause an %ESTALE error
 207  *    for callers of exportfs_decode_fh().
 208  *    Any suitable dentry can be returned including, if necessary, a new dentry
 209  *    created with d_alloc_root.  The caller can then find any other extant
 210  *    dentries by following the d_alias links.
 211  *
 212  * fh_to_parent:
 213  *    Same as @fh_to_dentry, except that it returns a pointer to the parent
 214  *    dentry if it was encoded into the filehandle fragment by @encode_fh.
 215  *
 216  * get_name:
 217  *    @get_name should find a name for the given @child in the given @parent
 218  *    directory.  The name should be stored in the @name (with the
 219  *    understanding that it is already pointing to a %NAME_MAX+1 sized
 220  *    buffer.   get_name() should return %0 on success, a negative error code
 221  *    or error.  @get_name will be called without @parent->i_mutex held.
 222  *
 223  * get_parent:
 224  *    @get_parent should find the parent directory for the given @child which
 225  *    is also a directory.  In the event that it cannot be found, or storage
 226  *    space cannot be allocated, a %ERR_PTR should be returned.
 227  *
 228  * commit_metadata:
 229  *    @commit_metadata should commit metadata changes to stable storage.
 230  *
 231  * Locking rules:
 232  *    get_parent is called with child->d_inode->i_mutex down
 233  *    get_name is not (which is possibly inconsistent)
 234  */
 235
 236 struct export_operations {
 237         int (*encode_fh)(struct inode *inode, __u32 *fh, int *max_len,
 238                         struct inode *parent);
 239         struct dentry * (*fh_to_dentry)(struct super_block *sb, struct fid *fid,
 240                         int fh_len, int fh_type);
 241         struct dentry * (*fh_to_parent)(struct super_block *sb, struct fid *fid,
 242                         int fh_len, int fh_type);
 243         int (*get_name)(struct dentry *parent, char *name,
 244                         struct dentry *child);
 245         struct dentry * (*get_parent)(struct dentry *child);
 246         int (*commit_metadata)(struct inode *inode);
 247
 248         int (*get_uuid)(struct super_block *sb, u8 *buf, u32 *len, u64 *offset);
 249         int (*map_blocks)(struct inode *inode, loff_t offset,
 250                           u64 len, struct iomap *iomap,
 251                           bool write, u32 *device_generation);
 252         int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
 253                              int nr_iomaps, struct iattr *iattr);
 254 #define EXPORT_OP_NOWCC                 (0x1) /* don't collect v3 wcc data */
 255 #define EXPORT_OP_NOSUBTREECHK          (0x2) /* no subtree checking */
 256 #define EXPORT_OP_CLOSE_BEFORE_UNLINK   (0x4) /* close files before unlink */
 257 #define EXPORT_OP_REMOTE_FS             (0x8) /* Filesystem is remote */
 258 #define EXPORT_OP_NOATOMIC_ATTR         (0x10) /* Filesystem cannot supply
 259                                                   atomic attribute updates
 260                                                 */
 261 #define EXPORT_OP_FLUSH_ON_CLOSE        (0x20) /* fs flushes file data on close */
 262 #define EXPORT_OP_ASYNC_LOCK            (0x40) /* fs can do async lock request */
 263         unsigned long   flags;
 264 };
 265
 266 extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
 267                                     int *max_len, struct inode *parent,
 268                                     int flags);
 269 extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
 270                               int *max_len, int flags);
 271
 272 static inline bool exportfs_can_encode_fid(const struct export_operations *nop)
 273 {
 274         return !nop || nop->encode_fh;
 275 }
 276
 277 static inline bool exportfs_can_decode_fh(const struct export_operations *nop)
 278 {
 279         return nop && nop->fh_to_dentry;
 280 }
 281
 282 static inline bool exportfs_can_encode_fh(const struct export_operations *nop,
 283                                           int fh_flags)
 284 {
 285         /*
 286          * If a non-decodeable file handle was requested, we only need to make
 287          * sure that filesystem did not opt-out of encoding fid.
 288          */
 289         if (fh_flags & EXPORT_FH_FID)
 290                 return exportfs_can_encode_fid(nop);
 291
 292         /*
 293          * If a decodeable file handle was requested, we need to make sure that
 294          * filesystem can also decode file handles.
 295          */
 296         return exportfs_can_decode_fh(nop);
 297 }
 298
 299 static inline int exportfs_encode_fid(struct inode *inode, struct fid *fid,
 300                                       int *max_len)
 301 {
 302         return exportfs_encode_inode_fh(inode, fid, max_len, NULL,
 303                                         EXPORT_FH_FID);
 304 }
 305
 306 extern struct dentry *exportfs_decode_fh_raw(struct vfsmount *mnt,
 307                                              struct fid *fid, int fh_len,
 308                                              int fileid_type,
 309                                              unsigned int flags,
 310                                              int (*acceptable)(void *, struct dentry *),
 311                                              void *context);
 312 extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
 313         int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
 314         void *context);
 315
 316 /*
 317  * Generic helpers for filesystems.
 318  */
 319 int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
 320                             struct inode *parent);
 321 struct dentry *generic_fh_to_dentry(struct super_block *sb,
 322         struct fid *fid, int fh_len, int fh_type,
 323         struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
 324 struct dentry *generic_fh_to_parent(struct super_block *sb,
 325         struct fid *fid, int fh_len, int fh_type,
 326         struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
 327
 328 #endif /* LINUX_EXPORTFS_H */