commit 2f375ab9c55bf22bf77ed9e3082b93e77ea10f55
author Yan <yanzheng@21cn.com> Fri Feb 01 14:58:07 2008 -0500
committer Chris Mason <chris.mason@oracle.com> Thu Sep 25 11:04:00 2008 -0400
tree c51ceb5867351915e4466ecafbe88b8e8f575d89
parent 60cde612c8eb51ba79dabb4088f149c6a9802fdf

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>