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 #include <linux/path.h>
   7
   8 struct dentry;
   9 struct iattr;
  10 struct inode;
  11 struct iomap;
  12 struct super_block;
  13 struct vfsmount;
  14
  15 /* limit the handle size to NFSv4 handle size now */
  16 #define MAX_HANDLE_SZ 128
  17
  18 /*
  19  * The fileid_type identifies how the file within the filesystem is encoded.
  20  * In theory this is freely set and parsed by the filesystem, but we try to
  21  * stick to conventions so we can share some generic code and don't confuse
  22  * sniffers like ethereal/wireshark.
  23  *
  24  * The filesystem must not use the value '0' or '0xff'.
  25  */
  26 enum fid_type {
  27         /*
  28          * The root, or export point, of the filesystem.
  29          * (Never actually passed down to the filesystem.
  30          */
  31         FILEID_ROOT = 0,
  32
  33         /*
  34          * 32bit inode number, 32 bit generation number.
  35          */
  36         FILEID_INO32_GEN = 1,
  37
  38         /*
  39          * 32bit inode number, 32 bit generation number,
  40          * 32 bit parent directory inode number.
  41          */
  42         FILEID_INO32_GEN_PARENT = 2,
  43
  44         /*
  45          * 64 bit object ID, 64 bit root object ID,
  46          * 32 bit generation number.
  47          */
  48         FILEID_BTRFS_WITHOUT_PARENT = 0x4d,
  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          */
  55         FILEID_BTRFS_WITH_PARENT = 0x4e,
  56
  57         /*
  58          * 64 bit object ID, 64 bit root object ID,
  59          * 32 bit generation number,
  60          * 64 bit parent object ID, 32 bit parent generation,
  61          * 64 bit parent root object ID.
  62          */
  63         FILEID_BTRFS_WITH_PARENT_ROOT = 0x4f,
  64
  65         /*
  66          * 32 bit block number, 16 bit partition reference,
  67          * 16 bit unused, 32 bit generation number.
  68          */
  69         FILEID_UDF_WITHOUT_PARENT = 0x51,
  70
  71         /*
  72          * 32 bit block number, 16 bit partition reference,
  73          * 16 bit unused, 32 bit generation number,
  74          * 32 bit parent block number, 32 bit parent generation number
  75          */
  76         FILEID_UDF_WITH_PARENT = 0x52,
  77
  78         /*
  79          * 64 bit checkpoint number, 64 bit inode number,
  80          * 32 bit generation number.
  81          */
  82         FILEID_NILFS_WITHOUT_PARENT = 0x61,
  83
  84         /*
  85          * 64 bit checkpoint number, 64 bit inode number,
  86          * 32 bit generation number, 32 bit parent generation.
  87          * 64 bit parent inode number.
  88          */
  89         FILEID_NILFS_WITH_PARENT = 0x62,
  90
  91         /*
  92          * 32 bit generation number, 40 bit i_pos.
  93          */
  94         FILEID_FAT_WITHOUT_PARENT = 0x71,
  95
  96         /*
  97          * 32 bit generation number, 40 bit i_pos,
  98          * 32 bit parent generation number, 40 bit parent i_pos
  99          */
 100         FILEID_FAT_WITH_PARENT = 0x72,
 101
 102         /*
 103          * 64 bit inode number, 32 bit generation number.
 104          */
 105         FILEID_INO64_GEN = 0x81,
 106
 107         /*
 108          * 64 bit inode number, 32 bit generation number,
 109          * 64 bit parent inode number, 32 bit parent generation.
 110          */
 111         FILEID_INO64_GEN_PARENT = 0x82,
 112
 113         /*
 114          * 128 bit child FID (struct lu_fid)
 115          * 128 bit parent FID (struct lu_fid)
 116          */
 117         FILEID_LUSTRE = 0x97,
 118
 119         /*
 120          * 64 bit inode number, 32 bit subvolume, 32 bit generation number:
 121          */
 122         FILEID_BCACHEFS_WITHOUT_PARENT = 0xb1,
 123         FILEID_BCACHEFS_WITH_PARENT = 0xb2,
 124
 125         /*
 126          * 64 bit unique kernfs id
 127          */
 128         FILEID_KERNFS = 0xfe,
 129
 130         /*
 131          * Filesystems must not use 0xff file ID.
 132          */
 133         FILEID_INVALID = 0xff,
 134 };
 135
 136 struct fid {
 137         union {
 138                 struct {
 139                         u32 ino;
 140                         u32 gen;
 141                         u32 parent_ino;
 142                         u32 parent_gen;
 143                 } i32;
 144                 struct {
 145                         u64 ino;
 146                         u32 gen;
 147                 } __packed i64;
 148                 struct {
 149                         u32 block;
 150                         u16 partref;
 151                         u16 parent_partref;
 152                         u32 generation;
 153                         u32 parent_block;
 154                         u32 parent_generation;
 155                 } udf;
 156                 DECLARE_FLEX_ARRAY(__u32, raw);
 157         };
 158 };
 159
 160 enum handle_to_path_flags {
 161         HANDLE_CHECK_PERMS   = (1 << 0),
 162         HANDLE_CHECK_SUBTREE = (1 << 1),
 163 };
 164
 165 struct handle_to_path_ctx {
 166         struct path root;
 167         enum handle_to_path_flags flags;
 168         unsigned int fh_flags;
 169 };
 170
 171 #define EXPORT_FH_CONNECTABLE   0x1 /* Encode file handle with parent */
 172 #define EXPORT_FH_FID           0x2 /* File handle may be non-decodeable */
 173 #define EXPORT_FH_DIR_ONLY      0x4 /* Only decode file handle for a directory */
 174
 175 /*
 176  * Filesystems use only lower 8 bits of file_handle type for fid_type.
 177  * name_to_handle_at() uses upper 16 bits of type as user flags to be
 178  * interpreted by open_by_handle_at().
 179  */
 180 #define FILEID_USER_FLAGS_MASK  0xffff0000
 181 #define FILEID_USER_FLAGS(type) ((type) & FILEID_USER_FLAGS_MASK)
 182
 183 /* Flags supported in encoded handle_type that is exported to user */
 184 #define FILEID_IS_CONNECTABLE   0x10000
 185 #define FILEID_IS_DIR           0x20000
 186 #define FILEID_VALID_USER_FLAGS (FILEID_IS_CONNECTABLE | FILEID_IS_DIR)
 187
 188 /**
 189  * struct export_operations - for nfsd to communicate with file systems
 190  * @encode_fh:      encode a file handle fragment from a dentry
 191  * @fh_to_dentry:   find the implied object and get a dentry for it
 192  * @fh_to_parent:   find the implied object's parent and get a dentry for it
 193  * @get_name:       find the name for a given inode in a given directory
 194  * @get_parent:     find the parent of a given directory
 195  * @commit_metadata: commit metadata changes to stable storage
 196  *
 197  * See Documentation/filesystems/nfs/exporting.rst for details on how to use
 198  * this interface correctly.
 199  *
 200  * encode_fh:
 201  *    @encode_fh should store in the file handle fragment @fh (using at most
 202  *    @max_len bytes) information that can be used by @decode_fh to recover the
 203  *    file referred to by the &struct dentry @de.  If @flag has CONNECTABLE bit
 204  *    set, the encode_fh() should store sufficient information so that a good
 205  *    attempt can be made to find not only the file but also it's place in the
 206  *    filesystem.   This typically means storing a reference to de->d_parent in
 207  *    the filehandle fragment.  encode_fh() should return the fileid_type on
 208  *    success and on error returns 255 (if the space needed to encode fh is
 209  *    greater than @max_len*4 bytes). On error @max_len contains the minimum
 210  *    size(in 4 byte unit) needed to encode the file handle.
 211  *
 212  * fh_to_dentry:
 213  *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle
 214  *    fragment (@fh, @fh_len). It should return a &struct dentry which refers
 215  *    to the same file that the file handle fragment refers to.  If it cannot,
 216  *    it should return a %NULL pointer if the file cannot be found, or an
 217  *    %ERR_PTR error code of %ENOMEM if a memory allocation failure occurred.
 218  *    Any other error code is treated like %NULL, and will cause an %ESTALE error
 219  *    for callers of exportfs_decode_fh().
 220  *    Any suitable dentry can be returned including, if necessary, a new dentry
 221  *    created with d_alloc_root.  The caller can then find any other extant
 222  *    dentries by following the d_alias links.
 223  *
 224  * fh_to_parent:
 225  *    Same as @fh_to_dentry, except that it returns a pointer to the parent
 226  *    dentry if it was encoded into the filehandle fragment by @encode_fh.
 227  *
 228  * get_name:
 229  *    @get_name should find a name for the given @child in the given @parent
 230  *    directory.  The name should be stored in the @name (with the
 231  *    understanding that it is already pointing to a %NAME_MAX+1 sized
 232  *    buffer.   get_name() should return %0 on success, a negative error code
 233  *    or error.  @get_name will be called without @parent->i_mutex held.
 234  *
 235  * get_parent:
 236  *    @get_parent should find the parent directory for the given @child which
 237  *    is also a directory.  In the event that it cannot be found, or storage
 238  *    space cannot be allocated, a %ERR_PTR should be returned.
 239  *
 240  * permission:
 241  *    Allow filesystems to specify a custom permission function.
 242  *
 243  * open:
 244  *    Allow filesystems to specify a custom open function.
 245  *
 246  * commit_metadata:
 247  *    @commit_metadata should commit metadata changes to stable storage.
 248  *
 249  * Locking rules:
 250  *    get_parent is called with child->d_inode->i_mutex down
 251  *    get_name is not (which is possibly inconsistent)
 252  */
 253
 254 struct export_operations {
 255         int (*encode_fh)(struct inode *inode, __u32 *fh, int *max_len,
 256                         struct inode *parent);
 257         struct dentry * (*fh_to_dentry)(struct super_block *sb, struct fid *fid,
 258                         int fh_len, int fh_type);
 259         struct dentry * (*fh_to_parent)(struct super_block *sb, struct fid *fid,
 260                         int fh_len, int fh_type);
 261         int (*get_name)(struct dentry *parent, char *name,
 262                         struct dentry *child);
 263         struct dentry * (*get_parent)(struct dentry *child);
 264         int (*commit_metadata)(struct inode *inode);
 265
 266         int (*get_uuid)(struct super_block *sb, u8 *buf, u32 *len, u64 *offset);
 267         int (*map_blocks)(struct inode *inode, loff_t offset,
 268                           u64 len, struct iomap *iomap,
 269                           bool write, u32 *device_generation);
 270         int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
 271                              int nr_iomaps, struct iattr *iattr);
 272         int (*permission)(struct handle_to_path_ctx *ctx, unsigned int oflags);
 273         struct file * (*open)(struct path *path, unsigned int oflags);
 274 #define EXPORT_OP_NOWCC                 (0x1) /* don't collect v3 wcc data */
 275 #define EXPORT_OP_NOSUBTREECHK          (0x2) /* no subtree checking */
 276 #define EXPORT_OP_CLOSE_BEFORE_UNLINK   (0x4) /* close files before unlink */
 277 #define EXPORT_OP_REMOTE_FS             (0x8) /* Filesystem is remote */
 278 #define EXPORT_OP_NOATOMIC_ATTR         (0x10) /* Filesystem cannot supply
 279                                                   atomic attribute updates
 280                                                 */
 281 #define EXPORT_OP_FLUSH_ON_CLOSE        (0x20) /* fs flushes file data on close */
 282 #define EXPORT_OP_ASYNC_LOCK            (0x40) /* fs can do async lock request */
 283         unsigned long   flags;
 284 };
 285
 286 extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
 287                                     int *max_len, struct inode *parent,
 288                                     int flags);
 289 extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
 290                               int *max_len, int flags);
 291
 292 static inline bool exportfs_can_encode_fid(const struct export_operations *nop)
 293 {
 294         return !nop || nop->encode_fh;
 295 }
 296
 297 static inline bool exportfs_can_decode_fh(const struct export_operations *nop)
 298 {
 299         return nop && nop->fh_to_dentry;
 300 }
 301
 302 static inline bool exportfs_can_encode_fh(const struct export_operations *nop,
 303                                           int fh_flags)
 304 {
 305         /*
 306          * If a non-decodeable file handle was requested, we only need to make
 307          * sure that filesystem did not opt-out of encoding fid.
 308          */
 309         if (fh_flags & EXPORT_FH_FID)
 310                 return exportfs_can_encode_fid(nop);
 311
 312         /*
 313          * If a decodeable file handle was requested, we need to make sure that
 314          * filesystem can also decode file handles.
 315          */
 316         return exportfs_can_decode_fh(nop);
 317 }
 318
 319 static inline int exportfs_encode_fid(struct inode *inode, struct fid *fid,
 320                                       int *max_len)
 321 {
 322         return exportfs_encode_inode_fh(inode, fid, max_len, NULL,
 323                                         EXPORT_FH_FID);
 324 }
 325
 326 extern struct dentry *exportfs_decode_fh_raw(struct vfsmount *mnt,
 327                                              struct fid *fid, int fh_len,
 328                                              int fileid_type,
 329                                              unsigned int flags,
 330                                              int (*acceptable)(void *, struct dentry *),
 331                                              void *context);
 332 extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
 333         int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
 334         void *context);
 335
 336 /*
 337  * Generic helpers for filesystems.
 338  */
 339 int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
 340                             struct inode *parent);
 341 struct dentry *generic_fh_to_dentry(struct super_block *sb,
 342         struct fid *fid, int fh_len, int fh_type,
 343         struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
 344 struct dentry *generic_fh_to_parent(struct super_block *sb,
 345         struct fid *fid, int fh_len, int fh_type,
 346         struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
 347
 348 #endif /* LINUX_EXPORTFS_H */