0001-btrfs-qgroup-Add-extra-check-for-quota_root.patch

From 4ad22f2cc2a45b877e5d4e8381ac83be8d4fc147 Mon Sep 17 00:00:00 2001
From: quwenruo <quwenruo@cn.fujitsu.com>
Date: Sun, 20 Sep 2015 09:16:52 +0800
Subject: [PATCH] btrfs: qgroup: Add extra check for quota_root

Some strange bug implies even for qgroup rescan, it's still possible
quota_root is not initialized.

Root reason is still not sure, so this is just a temporary hotfix.

Signed-off-by: quwenruo <quwenruo@cn.fujitsu.com>
---
 fs/btrfs/qgroup.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 8a82029..a12ed9b 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -2312,6 +2312,13 @@ out:
    mutex_unlock(&fs_info->qgroup_rescan_lock);

    /*
+    * XXX: Unknown bug which may race with quota_root init, avoid to
+    * start transaction for NULL quota_root.
+    */
+   if (!fs_info->quota_root)
+       goto done;
+
+   /*
     * only update status, since the previous part has alreay updated the
     * qgroup info.
     */
--
2.5.1