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