exportfs: make ->encode_fh() a mandatory method for NFS export

Rename the default helper for encoding FILEID_INO32_GEN* file handles to
generic_encode_ino32_fh() and convert the filesystems that used the
default implementation to use the generic helper explicitly.

After this change, exportfs_encode_inode_fh() no longer has a default
implementation to encode FILEID_INO32_GEN* file handles.

This is a step towards allowing filesystems to encode non-decodeable
file handles for fanotify without having to implement any
export_operations.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231023180801.2953446-3-amir73il@gmail.com
Acked-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 9 insertions, 7 deletions

diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 9ee205df8fa7..8f883c4758f5 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -343,20 +343,21 @@ out:
 }
 
 /**
- * export_encode_fh - default export_operations->encode_fh function
+ * generic_encode_ino32_fh - generic export_operations->encode_fh function
  * @inode:   the object to encode
- * @fid:     where to store the file handle fragment
- * @max_len: maximum length to store there
+ * @fh:      where to store the file handle fragment
+ * @max_len: maximum length to store there (in 4 byte units)
  * @parent:  parent directory inode, if wanted
  *
- * This default encode_fh function assumes that the 32 inode number
+ * This generic encode_fh function assumes that the 32 inode number
  * is suitable for locating an inode, and that the generation number
  * can be used to check that it is still valid.  It places them in the
  * filehandle fragment where export_decode_fh expects to find them.
  */
-static int export_encode_fh(struct inode *inode, struct fid *fid,
-		int *max_len, struct inode *parent)
+int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
+			    struct inode *parent)
 {
+	struct fid *fid = (void *)fh;
 	int len = *max_len;
 	int type = FILEID_INO32_GEN;
 
@@ -380,6 +381,7 @@ static int export_encode_fh(struct inode *inode, struct fid *fid,
 	*max_len = len;
 	return type;
 }
+EXPORT_SYMBOL_GPL(generic_encode_ino32_fh);
 
 /**
  * exportfs_encode_inode_fh - encode a file handle from inode
@@ -402,7 +404,7 @@ int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
 	if (nop && nop->encode_fh)
 		return nop->encode_fh(inode, fid->raw, max_len, parent);
 
-	return export_encode_fh(inode, fid, max_len, parent);
+	return -EOPNOTSUPP;
 }
 EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh);