From b0feb9d96e71a88d7eec56f41b8f23e92af889b0 Mon Sep 17 00:00:00 2001
From: Miao Xie <miaox@cn.fujitsu.com>
Date: Wed, 15 May 2013 07:48:20 +0000
Subject: [PATCH] Btrfs: introduce grab/put functions for the root of the
 fs/file tree

The grab/put funtions will be used in the next patch, which need grab
the root object and ensure it is not freed. We use reference counter
instead of the srcu lock is to aovid blocking the memory reclaim task,
which invokes synchronize_srcu().

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
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