gfs2: Remove freeze_go_demote_ok

Before commit b77b4a48 ("gfs2: Rework freeze / thaw logic"), the
freeze glock was kept around in the glock cache in shared mode without
being actively held while a filesystem is in thawed state.  In that
state, memory pressure could have eventually evicted the freeze glock,
and the freeze_go_demote_ok callback was needed to prevent that from
happening.

With the freeze / thaw rework, the freeze glock is now always actively
held in shared mode while a filesystem is thawed, and the
freeze_go_demote_ok hack is no longer needed.
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/glops.c

@@ -613,18 +613,6 @@ static int freeze_go_xmote_bh(struct gfs2_glock *gl)
 	return 0;
 }
 
-/**
- * freeze_go_demote_ok
- * @gl: the glock
- *
- * Always returns 0
- */
-
-static int freeze_go_demote_ok(const struct gfs2_glock *gl)
-{
-	return 0;
-}
-
 /**
  * iopen_go_callback - schedule the dcache entry for the inode to be deleted
  * @gl: the glock
@@ -744,7 +732,6 @@ const struct gfs2_glock_operations gfs2_rgrp_glops = {
 
 const struct gfs2_glock_operations gfs2_freeze_glops = {
 	.go_xmote_bh = freeze_go_xmote_bh,
-	.go_demote_ok = freeze_go_demote_ok,
 	.go_callback = freeze_go_callback,
 	.go_type = LM_TYPE_NONDISK,
 	.go_flags = GLOF_NONDISK,