From: Zhaolei <zhaolei@cn.fujitsu.com>
Date: Thu, 6 Aug 2015 14:39:36 +0000 (+0800)
Subject: btrfs: Add WARN_ON() for double lock in btrfs_tree_lock()
X-Git-Tag: omap-for-v4.3/fixes-rc1~86^2~18
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=166f66d0bc94a14ec4bc6ee6ab079532df4a8d9e;p=pandora-kernel.git

btrfs: Add WARN_ON() for double lock in btrfs_tree_lock()

When a task trying to double lock a extent buffer, there are no
lockdep warning about it because this lock may be in "blocking_lock"
state, and make us hard to debug.

This patch add a WARN_ON() for above condition, it can not report
all deadlock cases(as lock between tasks), but at least helps us
some.

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