From 93314e3b64fd2e77237fdba7cfcc0d38dcd05579 Mon Sep 17 00:00:00 2001
From: Zhaolei <zhaolei@cn.fujitsu.com>
Date: Thu, 6 Aug 2015 21:56:58 +0800
Subject: [PATCH] btrfs: abort transaction on btrfs_reloc_cow_block()

When btrfs_reloc_cow_block() failed in __btrfs_cow_block(), current
code just return a err-value to caller, but leave new_created extent
buffer exist and locked.

Then subsequent code (in relocate) try to lock above eb again,
and caused deadlock without any dmesg.
(eb lock use wait_event(), so no lockdep message)

It is hard to do recover work in __btrfs_cow_block() at this error
point, but we can abort transaction to avoid deadlock and operate on
unstable state.a

It also helps developer to find wrong place quickly.
(better than a frozen fs without any dmesg before patch)

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
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