From a11117c7b36d53cfd18c4d211ce30a4419ee477d Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@redhat.com>
Date: Wed, 12 Aug 2015 15:12:09 +0100
Subject: [PATCH] dm btree: add ref counting ops for the leaves of top level
 btrees

commit b0dc3c8bc157c60b1d470163882be8c13e1950af upstream.

When using nested btrees, the top leaves of the top levels contain
block addresses for the root of the next tree down.  If we shadow a
shared leaf node the leaf values (sub tree roots) should be incremented
accordingly.

This is only an issue if there is metadata sharing in the top levels.
Which only occurs if metadata snapshots are being used (as is possible
with dm-thinp).  And could result in a block from the thinp metadata
snap being reused early, thus corrupting the thinp metadata snap.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
[bwh: Backported to 3.2:
 - Drop change to remove_one()
 - Remove const pointer qualifications]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
Reading git-format-patch failed