NFS: Add FS-Cache option bit and debug bit

Add FS-Cache option bit to nfs_server struct.  This is set to indicate local
on-disk caching is enabled for a particular superblock.

Also add debug bit for local caching operations.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 29b1e40..a749f85 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -96,6 +96,8 @@
 	unsigned int		acdirmin;
 	unsigned int		acdirmax;
 	unsigned int		namelen;
+	unsigned int		options;	/* extra options enabled by mount */
+#define NFS_OPTION_FSCACHE	0x00000001	/* - local caching enabled */
 
 	struct nfs_fsid		fsid;
 	__u64			maxfilesize;	/* maximum file size */