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
  8struct dentry;
  9struct iattr;
 10struct inode;
 11struct iomap;
 12struct super_block;
 13struct 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 */
 26enum 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
142struct 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
166enum handle_to_path_flags {
167	HANDLE_CHECK_PERMS   = (1 << 0),
168	HANDLE_CHECK_SUBTREE = (1 << 1),
169};
170
171struct 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 * See Documentation/filesystems/nfs/exporting.rst for details on how to use
204 * this interface correctly.
205 *
206 * encode_fh:
207 *    @encode_fh should store in the file handle fragment @fh (using at most
208 *    @max_len bytes) information that can be used by @decode_fh to recover the
209 *    file referred to by the &struct dentry @de.  If @flag has CONNECTABLE bit
210 *    set, the encode_fh() should store sufficient information so that a good
211 *    attempt can be made to find not only the file but also it's place in the
212 *    filesystem.   This typically means storing a reference to de->d_parent in
213 *    the filehandle fragment.  encode_fh() should return the fileid_type on
214 *    success and on error returns 255 (if the space needed to encode fh is
215 *    greater than @max_len*4 bytes). On error @max_len contains the minimum
216 *    size(in 4 byte unit) needed to encode the file handle.
217 *
218 * fh_to_dentry:
219 *    @fh_to_dentry is given a &struct super_block (@sb) and a file handle
220 *    fragment (@fh, @fh_len). It should return a &struct dentry which refers
221 *    to the same file that the file handle fragment refers to.  If it cannot,
222 *    it should return a %NULL pointer if the file cannot be found, or an
223 *    %ERR_PTR error code of %ENOMEM if a memory allocation failure occurred.
224 *    Any other error code is treated like %NULL, and will cause an %ESTALE error
225 *    for callers of exportfs_decode_fh().
226 *    Any suitable dentry can be returned including, if necessary, a new dentry
227 *    created with d_alloc_root.  The caller can then find any other extant
228 *    dentries by following the d_alias links.
229 *
230 * fh_to_parent:
231 *    Same as @fh_to_dentry, except that it returns a pointer to the parent
232 *    dentry if it was encoded into the filehandle fragment by @encode_fh.
233 *
234 * get_name:
235 *    @get_name should find a name for the given @child in the given @parent
236 *    directory.  The name should be stored in the @name (with the
237 *    understanding that it is already pointing to a %NAME_MAX+1 sized
238 *    buffer.   get_name() should return %0 on success, a negative error code
239 *    or error.  @get_name will be called without @parent->i_rwsem held.
240 *
241 * get_parent:
242 *    @get_parent should find the parent directory for the given @child which
243 *    is also a directory.  In the event that it cannot be found, or storage
244 *    space cannot be allocated, a %ERR_PTR should be returned.
245 *
246 * permission:
247 *    Allow filesystems to specify a custom permission function.
248 *
249 * open:
250 *    Allow filesystems to specify a custom open function.
251 *
252 * commit_metadata:
253 *    @commit_metadata should commit metadata changes to stable storage.
254 *
255 * Locking rules:
256 *    get_parent is called with child->d_inode->i_rwsem down
257 *    get_name is not (which is possibly inconsistent)
258 */
259
260struct export_operations {
261	int (*encode_fh)(struct inode *inode, __u32 *fh, int *max_len,
262			struct inode *parent);
263	struct dentry * (*fh_to_dentry)(struct super_block *sb, struct fid *fid,
264			int fh_len, int fh_type);
265	struct dentry * (*fh_to_parent)(struct super_block *sb, struct fid *fid,
266			int fh_len, int fh_type);
267	int (*get_name)(struct dentry *parent, char *name,
268			struct dentry *child);
269	struct dentry * (*get_parent)(struct dentry *child);
270	int (*commit_metadata)(struct inode *inode);
271
272	int (*get_uuid)(struct super_block *sb, u8 *buf, u32 *len, u64 *offset);
273	int (*map_blocks)(struct inode *inode, loff_t offset,
274			  u64 len, struct iomap *iomap,
275			  bool write, u32 *device_generation);
276	int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
277			     int nr_iomaps, struct iattr *iattr);
278	int (*permission)(struct handle_to_path_ctx *ctx, unsigned int oflags);
279	struct file * (*open)(const struct path *path, unsigned int oflags);
280#define	EXPORT_OP_NOWCC			(0x1) /* don't collect v3 wcc data */
281#define	EXPORT_OP_NOSUBTREECHK		(0x2) /* no subtree checking */
282#define	EXPORT_OP_CLOSE_BEFORE_UNLINK	(0x4) /* close files before unlink */
283#define EXPORT_OP_REMOTE_FS		(0x8) /* Filesystem is remote */
284#define EXPORT_OP_NOATOMIC_ATTR		(0x10) /* Filesystem cannot supply
285						  atomic attribute updates
286						*/
287#define EXPORT_OP_FLUSH_ON_CLOSE	(0x20) /* fs flushes file data on close */
288#define EXPORT_OP_NOLOCKS		(0x40) /* no file locking support */
289	unsigned long	flags;
290};
291
292/**
293 * exportfs_cannot_lock() - check if export implements file locking
294 * @export_ops:	the nfs export operations to check
295 *
296 * Returns true if the export does not support file locking.
297 */
298static inline bool
299exportfs_cannot_lock(const struct export_operations *export_ops)
300{
301	return export_ops->flags & EXPORT_OP_NOLOCKS;
302}
303
304extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
305				    int *max_len, struct inode *parent,
306				    int flags);
307extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
308			      int *max_len, int flags);
309
310static inline bool exportfs_can_encode_fid(const struct export_operations *nop)
311{
312	return !nop || nop->encode_fh;
313}
314
315static inline bool exportfs_can_decode_fh(const struct export_operations *nop)
316{
317	return nop && nop->fh_to_dentry;
318}
319
320static inline bool exportfs_may_export(const struct export_operations *nop)
321{
322	/*
323	 * Do not allow nfs export for filesystems with custom ->open() or
324	 * ->permission() ops, which nfsd does not respect (e.g. pidfs, nsfs).
325	 */
326	return exportfs_can_decode_fh(nop) && !nop->open && !nop->permission;
327}
328
329static inline bool exportfs_can_encode_fh(const struct export_operations *nop,
330					  int fh_flags)
331{
332	/*
333	 * If a non-decodeable file handle was requested, we only need to make
334	 * sure that filesystem did not opt-out of encoding fid.
335	 */
336	if (fh_flags & EXPORT_FH_FID)
337		return exportfs_can_encode_fid(nop);
338
339	/* Normal file handles cannot be created without export ops */
340	if (!nop)
341		return false;
342
343	/*
344	 * If a connectable file handle was requested, we need to make sure that
345	 * filesystem can also decode connected file handles.
346	 */
347	if ((fh_flags & EXPORT_FH_CONNECTABLE) && !nop->fh_to_parent)
348		return false;
349
350	/*
351	 * If a decodeable file handle was requested, we need to make sure that
352	 * filesystem can also decode file handles.
353	 */
354	return exportfs_can_decode_fh(nop);
355}
356
357static inline int exportfs_encode_fid(struct inode *inode, struct fid *fid,
358				      int *max_len)
359{
360	return exportfs_encode_inode_fh(inode, fid, max_len, NULL,
361					EXPORT_FH_FID);
362}
363
364extern struct dentry *exportfs_decode_fh_raw(struct vfsmount *mnt,
365					     struct fid *fid, int fh_len,
366					     int fileid_type,
367					     unsigned int flags,
368					     int (*acceptable)(void *, struct dentry *),
369					     void *context);
370extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
371	int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
372	void *context);
373
374/*
375 * Generic helpers for filesystems.
376 */
377int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
378			    struct inode *parent);
379struct dentry *generic_fh_to_dentry(struct super_block *sb,
380	struct fid *fid, int fh_len, int fh_type,
381	struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
382struct dentry *generic_fh_to_parent(struct super_block *sb,
383	struct fid *fid, int fh_len, int fh_type,
384	struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen));
385
386#endif /* LINUX_EXPORTFS_H */