jbd2: clear BH_Delay & BH_Unwritten in journal_unmap_buffer

journal_unmap_buffer()'s zap_buffer: code clears a lot of buffer head
state ala discard_buffer(), but does not touch _Delay or _Unwritten as
discard_buffer() does.

This can be problematic in some areas of the ext4 code which assume
that if they have found a buffer marked unwritten or delay, then it's
a live one.  Perhaps those spots should check whether it is mapped
as well, but if jbd2 is going to tear down a buffer, let's really
tear it down completely.

Without this I get some fsx failures on sub-page-block filesystems
up until v3.2, at which point 4e96b2dbbf1d7e81f22047a50f862555a6cb87cb
and 189e868fa8fdca702eb9db9d8afc46b5cb9144c9 make the failures go
away, because buried within that large change is some more flag
clearing.  I still think it's worth doing in jbd2, since
->invalidatepage leads here directly, and it's the right place
to clear away these flags.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
void jbd2_buffer_frozen_trigger(struct journal_head *jh, void *mapped_data,
				struct jbd2_buffer_trigger_type *triggers)
{
	struct buffer_head *bh = jh2bh(jh);

	if (!triggers || !triggers->t_frozen)
		return;

	triggers->t_frozen(triggers, bh, mapped_data, bh->b_size);
}

void jbd2_buffer_frozen_trigger(struct journal_head *jh, void *mapped_data,
				struct jbd2_buffer_trigger_type *triggers)
{
	struct buffer_head *bh = jh2bh(jh);

	if (!triggers || !triggers->t_frozen)
		return;

	triggers->t_frozen(triggers, bh, mapped_data, bh->b_size);
}
