Christoph Hellwig | a569425 | 2007-07-17 04:04:28 -0700 | [diff] [blame] | 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; |
Christoph Hellwig | d37065c | 2007-07-17 04:04:30 -0700 | [diff] [blame] | 8 | struct vfsmount; |
Christoph Hellwig | a569425 | 2007-07-17 04:04:28 -0700 | [diff] [blame] | 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 | |
Christoph Hellwig | d37065c | 2007-07-17 04:04:30 -0700 | [diff] [blame] | 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 | |
Christoph Hellwig | a569425 | 2007-07-17 04:04:28 -0700 | [diff] [blame] | 126 | #endif /* LINUX_EXPORTFS_H */ |