From ee8a1a8b160a87dc3a9c81a86796aa4db85ea815 Mon Sep 17 00:00:00 2001
From: Peng Tao <tao.peng@primarydata.com>
Date: Tue, 20 Jan 2015 07:44:29 +0800
Subject: [PATCH] nfs: fix dio deadlock when O_DIRECT flag is flipped

We only support swap file calling nfs_direct_IO. However, application
might be able to get to nfs_direct_IO if it toggles O_DIRECT flag
during IO and it can deadlock because we grab inode->i_mutex in
nfs_file_direct_write(). So return 0 for such case. Then the generic
layer will fall back to buffer IO.

Signed-off-by: Peng Tao <tao.peng@primarydata.com>
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
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