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a5694255 CH |
1 | #ifndef LINUX_EXPORTFS_H |
2 | #define LINUX_EXPORTFS_H 1 | |
3 | ||
4 | #include <linux/types.h> | |
5 | ||
6 | struct dentry; | |
7 | struct super_block; | |
d37065cd | 8 | struct vfsmount; |
a5694255 CH |
9 | |
10 | ||
11 | /** | |
12 | * struct export_operations - for nfsd to communicate with file systems | |
13 | * @decode_fh: decode a file handle fragment and return a &struct dentry | |
14 | * @encode_fh: encode a file handle fragment from a dentry | |
15 | * @get_name: find the name for a given inode in a given directory | |
16 | * @get_parent: find the parent of a given directory | |
17 | * @get_dentry: find a dentry for the inode given a file handle sub-fragment | |
18 | * @find_exported_dentry: | |
19 | * set by the exporting module to a standard helper function. | |
20 | * | |
21 | * Description: | |
22 | * The export_operations structure provides a means for nfsd to communicate | |
23 | * with a particular exported file system - particularly enabling nfsd and | |
24 | * the filesystem to co-operate when dealing with file handles. | |
25 | * | |
26 | * export_operations contains two basic operation for dealing with file | |
27 | * handles, decode_fh() and encode_fh(), and allows for some other | |
28 | * operations to be defined which standard helper routines use to get | |
29 | * specific information from the filesystem. | |
30 | * | |
31 | * nfsd encodes information use to determine which filesystem a filehandle | |
32 | * applies to in the initial part of the file handle. The remainder, termed | |
33 | * a file handle fragment, is controlled completely by the filesystem. The | |
34 | * standard helper routines assume that this fragment will contain one or | |
35 | * two sub-fragments, one which identifies the file, and one which may be | |
36 | * used to identify the (a) directory containing the file. | |
37 | * | |
38 | * In some situations, nfsd needs to get a dentry which is connected into a | |
39 | * specific part of the file tree. To allow for this, it passes the | |
40 | * function acceptable() together with a @context which can be used to see | |
41 | * if the dentry is acceptable. As there can be multiple dentrys for a | |
42 | * given file, the filesystem should check each one for acceptability before | |
43 | * looking for the next. As soon as an acceptable one is found, it should | |
44 | * be returned. | |
45 | * | |
46 | * decode_fh: | |
47 | * @decode_fh is given a &struct super_block (@sb), a file handle fragment | |
48 | * (@fh, @fh_len) and an acceptability testing function (@acceptable, | |
49 | * @context). It should return a &struct dentry which refers to the same | |
50 | * file that the file handle fragment refers to, and which passes the | |
51 | * acceptability test. If it cannot, it should return a %NULL pointer if | |
52 | * the file was found but no acceptable &dentries were available, or a | |
53 | * %ERR_PTR error code indicating why it couldn't be found (e.g. %ENOENT or | |
54 | * %ENOMEM). | |
55 | * | |
56 | * encode_fh: | |
57 | * @encode_fh should store in the file handle fragment @fh (using at most | |
58 | * @max_len bytes) information that can be used by @decode_fh to recover the | |
59 | * file refered to by the &struct dentry @de. If the @connectable flag is | |
60 | * set, the encode_fh() should store sufficient information so that a good | |
61 | * attempt can be made to find not only the file but also it's place in the | |
62 | * filesystem. This typically means storing a reference to de->d_parent in | |
63 | * the filehandle fragment. encode_fh() should return the number of bytes | |
64 | * stored or a negative error code such as %-ENOSPC | |
65 | * | |
66 | * get_name: | |
67 | * @get_name should find a name for the given @child in the given @parent | |
68 | * directory. The name should be stored in the @name (with the | |
69 | * understanding that it is already pointing to a a %NAME_MAX+1 sized | |
70 | * buffer. get_name() should return %0 on success, a negative error code | |
71 | * or error. @get_name will be called without @parent->i_mutex held. | |
72 | * | |
73 | * get_parent: | |
74 | * @get_parent should find the parent directory for the given @child which | |
75 | * is also a directory. In the event that it cannot be found, or storage | |
76 | * space cannot be allocated, a %ERR_PTR should be returned. | |
77 | * | |
78 | * get_dentry: | |
79 | * Given a &super_block (@sb) and a pointer to a file-system specific inode | |
80 | * identifier, possibly an inode number, (@inump) get_dentry() should find | |
81 | * the identified inode and return a dentry for that inode. Any suitable | |
82 | * dentry can be returned including, if necessary, a new dentry created with | |
83 | * d_alloc_root. The caller can then find any other extant dentrys by | |
84 | * following the d_alias links. If a new dentry was created using | |
85 | * d_alloc_root, DCACHE_NFSD_DISCONNECTED should be set, and the dentry | |
86 | * should be d_rehash()ed. | |
87 | * | |
88 | * If the inode cannot be found, either a %NULL pointer or an %ERR_PTR code | |
89 | * can be returned. The @inump will be whatever was passed to | |
90 | * nfsd_find_fh_dentry() in either the @obj or @parent parameters. | |
91 | * | |
92 | * Locking rules: | |
93 | * get_parent is called with child->d_inode->i_mutex down | |
94 | * get_name is not (which is possibly inconsistent) | |
95 | */ | |
96 | ||
97 | struct export_operations { | |
98 | struct dentry *(*decode_fh)(struct super_block *sb, __u32 *fh, | |
99 | int fh_len, int fh_type, | |
100 | int (*acceptable)(void *context, struct dentry *de), | |
101 | void *context); | |
102 | int (*encode_fh)(struct dentry *de, __u32 *fh, int *max_len, | |
103 | int connectable); | |
104 | int (*get_name)(struct dentry *parent, char *name, | |
105 | struct dentry *child); | |
106 | struct dentry * (*get_parent)(struct dentry *child); | |
107 | struct dentry * (*get_dentry)(struct super_block *sb, void *inump); | |
108 | ||
109 | /* This is set by the exporting module to a standard helper */ | |
110 | struct dentry * (*find_exported_dentry)( | |
111 | struct super_block *sb, void *obj, void *parent, | |
112 | int (*acceptable)(void *context, struct dentry *de), | |
113 | void *context); | |
114 | }; | |
115 | ||
116 | extern struct dentry *find_exported_dentry(struct super_block *sb, void *obj, | |
117 | void *parent, int (*acceptable)(void *context, struct dentry *de), | |
118 | void *context); | |
119 | ||
d37065cd CH |
120 | extern int exportfs_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len, |
121 | int connectable); | |
122 | extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, __u32 *fh, | |
123 | int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *), | |
124 | void *context); | |
125 | ||
a5694255 | 126 | #endif /* LINUX_EXPORTFS_H */ |