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   * struct export_operations - for nfsd to communicate with file systems
165   * @encode_fh:      encode a file handle fragment from a dentry
166   * @fh_to_dentry:   find the implied object and get a dentry for it
167   * @fh_to_parent:   find the implied object's parent and get a dentry for it
168   * @get_name:       find the name for a given inode in a given directory
169   * @get_parent:     find the parent of a given directory
170   * @commit_metadata: commit metadata changes to stable storage
171   *
172   * See Documentation/filesystems/nfs/exporting.rst for details on how to use
173   * this interface correctly.
174   *
175   * encode_fh:
176   *    @encode_fh should store in the file handle fragment @fh (using at most
177   *    @max_len bytes) information that can be used by @decode_fh to recover the
178   *    file referred to by the &struct dentry @de.  If @flag has CONNECTABLE bit
179   *    set, the encode_fh() should store sufficient information so that a good
180   *    attempt can be made to find not only the file but also it's place in the
181   *    filesystem.   This typically means storing a reference to de->d_parent in
182   *    the filehandle fragment.  encode_fh() should return the fileid_type on
183   *    success and on error returns 255 (if the space needed to encode fh is
184   *    greater than @max_len*4 bytes). On error @max_len contains the minimum
185   *    size(in 4 byte unit) needed to encode the file handle.
186   *
187   * fh_to_dentry:
188   *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle
189   *    fragment (@fh, @fh_len). It should return a &struct dentry which refers
190   *    to the same file that the file handle fragment refers to.  If it cannot,
191   *    it should return a %NULL pointer if the file cannot be found, or an
192   *    %ERR_PTR error code of %ENOMEM if a memory allocation failure occurred.
193   *    Any other error code is treated like %NULL, and will cause an %ESTALE error
194   *    for callers of exportfs_decode_fh().
195   *    Any suitable dentry can be returned including, if necessary, a new dentry
196   *    created with d_alloc_root.  The caller can then find any other extant
197   *    dentries by following the d_alias links.
198   *
199   * fh_to_parent:
200   *    Same as @fh_to_dentry, except that it returns a pointer to the parent
201   *    dentry if it was encoded into the filehandle fragment by @encode_fh.
202   *
203   * get_name:
204   *    @get_name should find a name for the given @child in the given @parent
205   *    directory.  The name should be stored in the @name (with the
206   *    understanding that it is already pointing to a %NAME_MAX+1 sized
207   *    buffer.   get_name() should return %0 on success, a negative error code
208   *    or error.  @get_name will be called without @parent->i_mutex held.
209   *
210   * get_parent:
211   *    @get_parent should find the parent directory for the given @child which
212   *    is also a directory.  In the event that it cannot be found, or storage
213   *    space cannot be allocated, a %ERR_PTR should be returned.
214   *
215   * commit_metadata:
216   *    @commit_metadata should commit metadata changes to stable storage.
217   *
218   * Locking rules:
219   *    get_parent is called with child->d_inode->i_mutex down
220   *    get_name is not (which is possibly inconsistent)
221   */
222  
223  struct export_operations {
224  	int (*encode_fh)(struct inode *inode, __u32 *fh, int *max_len,
225  			struct inode *parent);
226  	struct dentry * (*fh_to_dentry)(struct super_block *sb, struct fid *fid,
227  			int fh_len, int fh_type);
228  	struct dentry * (*fh_to_parent)(struct super_block *sb, struct fid *fid,
229  			int fh_len, int fh_type);
230  	int (*get_name)(struct dentry *parent, char *name,
231  			struct dentry *child);
232  	struct dentry * (*get_parent)(struct dentry *child);
233  	int (*commit_metadata)(struct inode *inode);
234  
235  	int (*get_uuid)(struct super_block *sb, u8 *buf, u32 *len, u64 *offset);
236  	int (*map_blocks)(struct inode *inode, loff_t offset,
237  			  u64 len, struct iomap *iomap,
238  			  bool write, u32 *device_generation);
239  	int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
240  			     int nr_iomaps, struct iattr *iattr);
241  #define	EXPORT_OP_NOWCC			(0x1) /* don't collect v3 wcc data */
242  #define	EXPORT_OP_NOSUBTREECHK		(0x2) /* no subtree checking */
243  #define	EXPORT_OP_CLOSE_BEFORE_UNLINK	(0x4) /* close files before unlink */
244  #define EXPORT_OP_REMOTE_FS		(0x8) /* Filesystem is remote */
245  #define EXPORT_OP_NOATOMIC_ATTR		(0x10) /* Filesystem cannot supply
246  						  atomic attribute updates
247  						*/
248  #define EXPORT_OP_FLUSH_ON_CLOSE	(0x20) /* fs flushes file data on close */
249  #define EXPORT_OP_ASYNC_LOCK		(0x40) /* fs can do async lock request */
250  	unsigned long	flags;
251  };
252  
253  /**
254   * exportfs_lock_op_is_async() - export op supports async lock operation
255   * @export_ops:	the nfs export operations to check
256   *
257   * Returns true if the nfs export_operations structure has
258   * EXPORT_OP_ASYNC_LOCK in their flags set
259   */
260  static inline bool
exportfs_lock_op_is_async(const struct export_operations * export_ops)261  exportfs_lock_op_is_async(const struct export_operations *export_ops)
262  {
263  	return export_ops->flags & EXPORT_OP_ASYNC_LOCK;
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  
exportfs_can_encode_fid(const struct export_operations * nop)272  static inline bool exportfs_can_encode_fid(const struct export_operations *nop)
273  {
274  	return !nop || nop->encode_fh;
275  }
276  
exportfs_can_decode_fh(const struct export_operations * nop)277  static inline bool exportfs_can_decode_fh(const struct export_operations *nop)
278  {
279  	return nop && nop->fh_to_dentry;
280  }
281  
exportfs_can_encode_fh(const struct export_operations * nop,int fh_flags)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  
exportfs_encode_fid(struct inode * inode,struct fid * fid,int * max_len)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 */
329