1 files changed, 126 insertions, 0 deletions

diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
new file mode 100644
index 000000000000..8872fe8392d6
--- /dev/null
+++ b/include/linux/exportfs.h
@@ -0,0 +1,126 @@
+#ifndef LINUX_EXPORTFS_H
+#define LINUX_EXPORTFS_H 1
+
+#include <linux/types.h>
+
+struct dentry;
+struct super_block;
+struct vfsmount;
+
+
+/**
+ * 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);
+
+extern int exportfs_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
+        int connectable);
+extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, __u32 *fh,
+        int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
+        void *context);
+
+#endif /* LINUX_EXPORTFS_H */