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From: Olga Kornievskaia <aglo@umich.edu>
Date: Thu, 26 Jan 2017 15:01:54 -0500
Message-ID: <CAN-5tyEo-VS6y1-WVJMDXSzN2vxDtJOSckiYK=HmqLyPvBpWFQ@mail.gmail.com>
Subject: regression from commit 24408f5282
To: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: linux-nfs <linux-nfs@vger.kernel.org>
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Sender: linux-nfs-owner@vger.kernel.org
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Hi Trond,

There is regression in the upstream code, it leaves dangling DS
mounts. Problem didn't exist in 4.9 and appeared in 4.10.

Simple test is : mount, echo 1 > /mnt/foobar, unmount /mnt. Watch the
DS mount keep going.

The last commit at which the code works is: fe1cf9469d7 "pNFS: Clear
all layout segment state in pnfs_mark_layout_stateaid_invalid".

Applying commit 24408f5282 "pNFS: Fix bugs in _pnfs_return_layout"
introduces the problem.