[GFS2] Use a bio to read the superblock

This means that we don't need to create a special inode just to contain
a struct address_space in order to read a single disk block. Instead
we read the disk block directly. Its slightly faster, and uses slightly
less memory, but the real reason for doing this is that it removes a
special case from the glock code.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 0381d4c..91ac9c9 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -311,8 +311,7 @@
 	/* If this glock protects actual on-disk data or metadata blocks,
 	   create a VFS inode to manage the pages/buffers holding them. */
 	if (glops == &gfs2_inode_glops ||
-	    glops == &gfs2_rgrp_glops ||
-	    glops == &gfs2_meta_glops) {
+	    glops == &gfs2_rgrp_glops) {
 		gl->gl_aspace = gfs2_aspace_get(sdp);
 		if (!gl->gl_aspace) {
 			error = -ENOMEM;