xref: /linux/include/linux/exportfs.h (revision a1ff5a7d78a036d6c2178ee5acd6ba4946243800)
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