From 1708cc5723cb775703b42a0ce8e521019c42dd67 Mon Sep 17 00:00:00 2001
From: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Date: Sat, 28 Dec 2013 19:52:39 +0800
Subject: [PATCH] Btrfs: fix an oops when we fail to relocate tree blocks

During balance test, we hit an oops:
[ 2013.841551] kernel BUG at fs/btrfs/relocation.c:1174!

The problem is that if we fail to relocate tree blocks, we should
update backref cache, otherwise, some pending nodes are not updated
while snapshot check @cache->last_trans is within one transaction
and won't update it and then oops happen.

Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
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