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 *
127 * 64 bit namespace identifier, 32 bit namespace type, 32 bit inode number.
128 */
129 FILEID_NSFS = 0xf1,
130
131 /*
132 * 64 bit unique kernfs id
133 */
134 FILEID_KERNFS = 0xfe,
135
136 /*
137 * Filesystems must not use 0xff file ID.
138 */
139 FILEID_INVALID = 0xff,
140 };
141
142 struct fid {
143 union {
144 struct {
145 u32 ino;
146 u32 gen;
147 u32 parent_ino;
148 u32 parent_gen;
149 } i32;
150 struct {
151 u64 ino;
152 u32 gen;
153 } __packed i64;
154 struct {
155 u32 block;
156 u16 partref;
157 u16 parent_partref;
158 u32 generation;
159 u32 parent_block;
160 u32 parent_generation;
161 } udf;
162 DECLARE_FLEX_ARRAY(__u32, raw);
163 };
164 };
165
166 enum handle_to_path_flags {
167 HANDLE_CHECK_PERMS = (1 << 0),
168 HANDLE_CHECK_SUBTREE = (1 << 1),
169 };
170
171 struct handle_to_path_ctx {
172 struct path root;
173 enum handle_to_path_flags flags;
174 unsigned int fh_flags;
175 };
176
177 #define EXPORT_FH_CONNECTABLE 0x1 /* Encode file handle with parent */
178 #define EXPORT_FH_FID 0x2 /* File handle may be non-decodeable */
179 #define EXPORT_FH_DIR_ONLY 0x4 /* Only decode file handle for a directory */
180
181 /*
182 * Filesystems use only lower 8 bits of file_handle type for fid_type.
183 * name_to_handle_at() uses upper 16 bits of type as user flags to be
184 * interpreted by open_by_handle_at().
185 */
186 #define FILEID_USER_FLAGS_MASK 0xffff0000
187 #define FILEID_USER_FLAGS(type) ((type) & FILEID_USER_FLAGS_MASK)
188
189 /* Flags supported in encoded handle_type that is exported to user */
190 #define FILEID_IS_CONNECTABLE 0x10000
191 #define FILEID_IS_DIR 0x20000
192 #define FILEID_VALID_USER_FLAGS (FILEID_IS_CONNECTABLE | FILEID_IS_DIR)
193
194 /**
195 * struct export_operations - for nfsd to communicate with file systems
196 * @encode_fh: encode a file handle fragment from a dentry
197 * @fh_to_dentry: find the implied object and get a dentry for it
198 * @fh_to_parent: find the implied object's parent and get a dentry for it
199 * @get_name: find the name for a given inode in a given directory
200 * @get_parent: find the parent of a given directory
201 * @commit_metadata: commit metadata changes to stable storage
202 *
203 * Methods for open_by_handle(2) syscall with special kernel file systems:
204 * @permission: custom permission for opening a file by handle
205 * @open: custom open routine for opening file by handle
206 *
207 * See Documentation/filesystems/nfs/exporting.rst for details on how to use
208 * this interface correctly and the definition of the flags.
209 *
210 * @encode_fh:
211 * @encode_fh should store in the file handle fragment @fh (using at most
212 * @max_len bytes) information that can be used by @decode_fh to recover the
213 * file referred to by the &struct dentry @de. If @flag has CONNECTABLE bit
214 * set, the encode_fh() should store sufficient information so that a good
215 * attempt can be made to find not only the file but also it's place in the
216 * filesystem. This typically means storing a reference to de->d_parent in
217 * the filehandle fragment. encode_fh() should return the fileid_type on
218 * success and on error returns 255 (if the space needed to encode fh is
219 * greater than @max_len*4 bytes). On error @max_len contains the minimum
220 * size(in 4 byte unit) needed to encode the file handle.
221 *
222 * @fh_to_dentry:
223 * @fh_to_dentry is given a &struct super_block (@sb) and a file handle
224 * fragment (@fh, @fh_len). It should return a &struct dentry which refers
225 * to the same file that the file handle fragment refers to. If it cannot,
226 * it should return a %NULL pointer if the file cannot be found, or an
227 * %ERR_PTR error code of %ENOMEM if a memory allocation failure occurred.
228 * Any other error code is treated like %NULL, and will cause an %ESTALE error
229 * for callers of exportfs_decode_fh().
230 * Any suitable dentry can be returned including, if necessary, a new dentry
231 * created with d_alloc_root. The caller can then find any other extant
232 * dentries by following the d_alias links.
233 *
234 * @fh_to_parent:
235 * Same as @fh_to_dentry, except that it returns a pointer to the parent
236 * dentry if it was encoded into the filehandle fragment by @encode_fh.
237 *
238 * @get_name:
239 * @get_name should find a name for the given @child in the given @parent
240 * directory. The name should be stored in the @name (with the
241 * understanding that it is already pointing to a %NAME_MAX + 1 sized
242 * buffer. get_name() should return %0 on success, a negative error code
243 * or error. @get_name will be called without @parent->i_rwsem held.
244 *
245 * @get_parent:
246 * @get_parent should find the parent directory for the given @child which
247 * is also a directory. In the event that it cannot be found, or storage
248 * space cannot be allocated, a %ERR_PTR should be returned.
249 *
250 * @permission:
251 * Allow filesystems to specify a custom permission function for the
252 * open_by_handle_at(2) syscall instead of the default permission check.
253 * This custom permission function is not respected by nfsd.
254 *
255 * @open:
256 * Allow filesystems to specify a custom open function for the
257 * open_by_handle_at(2) syscall instead of the default file_open_root().
258 * This custom open function is not respected by nfsd.
259 *
260 * @commit_metadata:
261 * @commit_metadata should commit metadata changes to stable storage.
262 *
263 * @get_uuid:
264 * Get a filesystem unique signature exposed to clients.
265 *
266 * @map_blocks:
267 * Map and, if necessary, allocate blocks for a layout.
268 *
269 * @commit_blocks:
270 * Commit blocks in a layout once the client is done with them.
271 *
272 * @flags:
273 * Allows the filesystem to communicate to nfsd that it may want to do things
274 * differently when dealing with it.
275 *
276 * Locking rules:
277 * get_parent is called with child->d_inode->i_rwsem down
278 * get_name is not (which is possibly inconsistent)
279 */
280
281 struct export_operations {
282 int (*encode_fh)(struct inode *inode, __u32 *fh, int *max_len,
283 struct inode *parent);
284 struct dentry * (*fh_to_dentry)(struct super_block *sb, struct fid *fid,
285 int fh_len, int fh_type);
286 struct dentry * (*fh_to_parent)(struct super_block *sb, struct fid *fid,
287 int fh_len, int fh_type);
288 int (*get_name)(struct dentry *parent, char *name,
289 struct dentry *child);
290 struct dentry * (*get_parent)(struct dentry *child);
291 int (*commit_metadata)(struct inode *inode);
292
293 int (*get_uuid)(struct super_block *sb, u8 *buf, u32 *len, u64 *offset);
294 int (*map_blocks)(struct inode *inode, loff_t offset,
295 u64 len, struct iomap *iomap,
296 bool write, u32 *device_generation);
297 int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
298 int nr_iomaps, struct iattr *iattr);
299 int (*permission)(struct handle_to_path_ctx *ctx, unsigned int oflags);
300 struct file * (*open)(const struct path *path, unsigned int oflags);
301 #define EXPORT_OP_NOWCC (0x1) /* don't collect v3 wcc data */
302 #define EXPORT_OP_NOSUBTREECHK (0x2) /* no subtree checking */
303 #define EXPORT_OP_CLOSE_BEFORE_UNLINK (0x4) /* close files before unlink */
304 #define EXPORT_OP_REMOTE_FS (0x8) /* Filesystem is remote */
305 #define EXPORT_OP_NOATOMIC_ATTR (0x10) /* Filesystem cannot supply
306 atomic attribute updates
307 */
308 #define EXPORT_OP_FLUSH_ON_CLOSE (0x20) /* fs flushes file data on close */
309 #define EXPORT_OP_NOLOCKS (0x40) /* no file locking support */
310 unsigned long flags;
311 };
312
313 /**
314 * exportfs_cannot_lock() - check if export implements file locking
315 * @export_ops: the nfs export operations to check
316 *
317 * Returns true if the export does not support file locking.
318 */
319 static inline bool
exportfs_cannot_lock(const struct export_operations * export_ops)320 exportfs_cannot_lock(const struct export_operations *export_ops)
321 {
322 return export_ops->flags & EXPORT_OP_NOLOCKS;
323 }
324
325 extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
326 int *max_len, struct inode *parent,
327 int flags);
328 extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
329 int *max_len, int flags);
330
exportfs_can_encode_fid(const struct export_operations * nop)331 static inline bool exportfs_can_encode_fid(const struct export_operations *nop)
332 {
333 return !nop || nop->encode_fh;
334 }
335
exportfs_can_decode_fh(const struct export_operations * nop)336 static inline bool exportfs_can_decode_fh(const struct export_operations *nop)
337 {
338 return nop && nop->fh_to_dentry;
339 }
340
exportfs_may_export(const struct export_operations * nop)341 static inline bool exportfs_may_export(const struct export_operations *nop)
342 {
343 /*
344 * Do not allow nfs export for filesystems with custom ->open() or
345 * ->permission() ops, which nfsd does not respect (e.g. pidfs, nsfs).
346 */
347 return exportfs_can_decode_fh(nop) && !nop->open && !nop->permission;
348 }
349
exportfs_can_encode_fh(const struct export_operations * nop,int fh_flags)350 static inline bool exportfs_can_encode_fh(const struct export_operations *nop,
351 int fh_flags)
352 {
353 /*
354 * If a non-decodeable file handle was requested, we only need to make
355 * sure that filesystem did not opt-out of encoding fid.
356 */
357 if (fh_flags & EXPORT_FH_FID)
358 return exportfs_can_encode_fid(nop);
359
360 /* Normal file handles cannot be created without export ops */
361 if (!nop)
362 return false;
363
364 /*
365 * If a connectable file handle was requested, we need to make sure that
366 * filesystem can also decode connected file handles.
367 */
368 if ((fh_flags & EXPORT_FH_CONNECTABLE) && !nop->fh_to_parent)
369 return false;
370
371 /*
372 * If a decodeable file handle was requested, we need to make sure that
373 * filesystem can also decode file handles.
374 */
375 return exportfs_can_decode_fh(nop);
376 }
377
exportfs_encode_fid(struct inode * inode,struct fid * fid,int * max_len)378 static inline int exportfs_encode_fid(struct inode *inode, struct fid *fid,
379 int *max_len)
380 {
381 return exportfs_encode_inode_fh(inode, fid, max_len, NULL,
382 EXPORT_FH_FID);
383 }
384
385 extern struct dentry *exportfs_decode_fh_raw(struct vfsmount *mnt,
386 struct fid *fid, int fh_len,
387 int fileid_type,
388 unsigned int flags,
389 int (*acceptable)(void *, struct dentry *),
390 void *context);
391 extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
392 int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
393 void *context);
394
395 /*
396 * Generic helpers for filesystems.
397 */
398 int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
399 struct inode *parent);
400 struct dentry *generic_fh_to_dentry(struct super_block *sb,
401 struct fid *fid, int fh_len, int fh_type,
402 struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
403 struct dentry *generic_fh_to_parent(struct super_block *sb,
404 struct fid *fid, int fh_len, int fh_type,
405 struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
406
407 #endif /* LINUX_EXPORTFS_H */
408