From 1e7bac1ef754b3112eb78c64a7382d286e454424 Mon Sep 17 00:00:00 2001
From: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Date: Sat, 13 Jul 2013 21:02:54 +0800
Subject: [PATCH] Btrfs: set qgroup_ulist to be null after calling ulist_free()

We call ulist_free(qgroup_ulist) in btrfs_free_qgroup_config(),
and btrfs_free_qgroup_config() may be called in two cases:

(1)umount filesystem
(2)disabling quota

However, if we firstly disable quota and then umount filesystem,
a double free happens. Fix it.

Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
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Reading git-format-patch failed