gfs2: Protect gl->gl_object by spin lock

Put all remaining accesses to gl->gl_object under the
gl->gl_lockref.lock spinlock to prevent races.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 3814a60..56e2943 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -970,7 +970,7 @@
 			continue;
 		bn = be64_to_cpu(*p);
 		if (gfs2_holder_initialized(rd_gh)) {
-			rgd = (struct gfs2_rgrpd *)rd_gh->gh_gl->gl_object;
+			rgd = gfs2_glock2rgrp(rd_gh->gh_gl);
 			gfs2_assert_withdraw(sdp,
 				     gfs2_glock_is_locked_by_me(rd_gh->gh_gl));
 		} else {