GFS2: Don't try to deallocate unlinked inodes when mounted ro

This adds a couple of missing tests to avoid read-only nodes
from attempting to deallocate unlinked inodes.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Reported-by: Michel Andre de la Porte <madelaporte@ubi.com>

fs/gfs2/glops.c

@@ -385,6 +385,10 @@ static int trans_go_demote_ok(const struct gfs2_glock *gl)
 static void iopen_go_callback(struct gfs2_glock *gl)
 {
 	struct gfs2_inode *ip = (struct gfs2_inode *)gl->gl_object;
+	struct gfs2_sbd *sdp = gl->gl_sbd;
+
+	if (sdp->sd_vfs->s_flags & MS_RDONLY)
+		return;
 
 	if (gl->gl_demote_state == LM_ST_UNLOCKED &&
 	    gl->gl_state == LM_ST_SHARED && ip) {