From 2f375ab9c55bf22bf77ed9e3082b93e77ea10f55 Mon Sep 17 00:00:00 2001
From: Yan <yanzheng@21cn.com>
Date: Fri, 1 Feb 2008 14:58:07 -0500
Subject: [PATCH] Call btrfs_cow_block while lowering tree level.

When freeing root block of a tree,  btrfs_free_extent' parameter
'ref_generation' is from root block itseft.  When freeing non-root
block,  'ref_generation' is from its parent. so when converting a
non-root block to root block, we must guarantee its generation is
equal to its parent's generation.

Signed-off-by: Chris Mason <chris.mason@oracle.com>
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