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Diffstat (limited to 'include/linux/exportfs.h')
| -rw-r--r-- | include/linux/exportfs.h | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h new file mode 100644 index 000000000000..fdc306fbba50 --- /dev/null +++ b/include/linux/exportfs.h @@ -0,0 +1,119 @@ +#ifndef LINUX_EXPORTFS_H +#define LINUX_EXPORTFS_H 1 + +#include <linux/types.h> + +struct dentry; +struct super_block; + + +/** + * struct export_operations - for nfsd to communicate with file systems + * @decode_fh: decode a file handle fragment and return a &struct dentry + * @encode_fh: encode a file handle fragment from a dentry + * @get_name: find the name for a given inode in a given directory + * @get_parent: find the parent of a given directory + * @get_dentry: find a dentry for the inode given a file handle sub-fragment + * @find_exported_dentry: + * set by the exporting module to a standard helper function. + * + * Description: + * The export_operations structure provides a means for nfsd to communicate + * with a particular exported file system - particularly enabling nfsd and + * the filesystem to co-operate when dealing with file handles. + * + * export_operations contains two basic operation for dealing with file + * handles, decode_fh() and encode_fh(), and allows for some other + * operations to be defined which standard helper routines use to get + * specific information from the filesystem. + * + * nfsd encodes information use to determine which filesystem a filehandle + * applies to in the initial part of the file handle. The remainder, termed + * a file handle fragment, is controlled completely by the filesystem. The + * standard helper routines assume that this fragment will contain one or + * two sub-fragments, one which identifies the file, and one which may be + * used to identify the (a) directory containing the file. + * + * In some situations, nfsd needs to get a dentry which is connected into a + * specific part of the file tree. To allow for this, it passes the + * function acceptable() together with a @context which can be used to see + * if the dentry is acceptable. As there can be multiple dentrys for a + * given file, the filesystem should check each one for acceptability before + * looking for the next. As soon as an acceptable one is found, it should + * be returned. + * + * decode_fh: + * @decode_fh is given a &struct super_block (@sb), a file handle fragment + * (@fh, @fh_len) and an acceptability testing function (@acceptable, + * @context). It should return a &struct dentry which refers to the same + * file that the file handle fragment refers to, and which passes the + * acceptability test. If it cannot, it should return a %NULL pointer if + * the file was found but no acceptable &dentries were available, or a + * %ERR_PTR error code indicating why it couldn't be found (e.g. %ENOENT or + * %ENOMEM). + * + * encode_fh: + * @encode_fh should store in the file handle fragment @fh (using at most + * @max_len bytes) information that can be used by @decode_fh to recover the + * file refered to by the &struct dentry @de. If the @connectable flag is + * set, the encode_fh() should store sufficient information so that a good + * attempt can be made to find not only the file but also it's place in the + * filesystem. This typically means storing a reference to de->d_parent in + * the filehandle fragment. encode_fh() should return the number of bytes + * stored or a negative error code such as %-ENOSPC + * + * get_name: + * @get_name should find a name for the given @child in the given @parent + * directory. The name should be stored in the @name (with the + * understanding that it is already pointing to a a %NAME_MAX+1 sized + * buffer. get_name() should return %0 on success, a negative error code + * or error. @get_name will be called without @parent->i_mutex held. + * + * get_parent: + * @get_parent should find the parent directory for the given @child which + * is also a directory. In the event that it cannot be found, or storage + * space cannot be allocated, a %ERR_PTR should be returned. + * + * get_dentry: + * Given a &super_block (@sb) and a pointer to a file-system specific inode + * identifier, possibly an inode number, (@inump) get_dentry() should find + * the identified inode and return a dentry for that inode. Any suitable + * dentry can be returned including, if necessary, a new dentry created with + * d_alloc_root. The caller can then find any other extant dentrys by + * following the d_alias links. If a new dentry was created using + * d_alloc_root, DCACHE_NFSD_DISCONNECTED should be set, and the dentry + * should be d_rehash()ed. + * + * If the inode cannot be found, either a %NULL pointer or an %ERR_PTR code + * can be returned. The @inump will be whatever was passed to + * nfsd_find_fh_dentry() in either the @obj or @parent parameters. + * + * Locking rules: + * get_parent is called with child->d_inode->i_mutex down + * get_name is not (which is possibly inconsistent) + */ + +struct export_operations { + struct dentry *(*decode_fh)(struct super_block *sb, __u32 *fh, + int fh_len, int fh_type, + int (*acceptable)(void *context, struct dentry *de), + void *context); + int (*encode_fh)(struct dentry *de, __u32 *fh, int *max_len, + int connectable); + int (*get_name)(struct dentry *parent, char *name, + struct dentry *child); + struct dentry * (*get_parent)(struct dentry *child); + struct dentry * (*get_dentry)(struct super_block *sb, void *inump); + + /* This is set by the exporting module to a standard helper */ + struct dentry * (*find_exported_dentry)( + struct super_block *sb, void *obj, void *parent, + int (*acceptable)(void *context, struct dentry *de), + void *context); +}; + +extern struct dentry *find_exported_dentry(struct super_block *sb, void *obj, + void *parent, int (*acceptable)(void *context, struct dentry *de), + void *context); + +#endif /* LINUX_EXPORTFS_H */ |