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Date: Thu, 17 Jan 2013 22:56:50 -0500
From: Theodore Ts'o <tytso@mit.edu>
To: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-kernel@vger.kernel.org, stable@vger.kernel.org,
	alan@lxorguk.ukuu.org.uk,
	Alexander Beregalov <a.beregalov@gmail.com>,
	Zheng Liu <wenqing.lz@taobao.com>
Subject: Re: [ 36/71] ext4: lock i_mutex when truncating orphan inodes
Message-ID: <20130118035650.GA13785@thunk.org>
References: <20130115225340.367496998@linuxfoundation.org>
 <20130115225343.033036403@linuxfoundation.org>
 <20130117200710.GD2872@herton-Z68MA-D2H-B3>
 <20130118004616.GA5730@kroah.com>
 <20130118034747.GF2872@herton-Z68MA-D2H-B3>
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On Fri, Jan 18, 2013 at 01:47:48AM -0200, Herton Ronaldo Krzesinski wrote:
> > > By the description and looking at commit c278531d39, this change isn't
> > > needed for 3.0 or 3.4 kernels (anything <= 3.6), they don't contain
> > > commit c278531d39.
> > 
> > Ah, good catch.  Should this be reverted from 3.0 and 3.4?
> 
> I judge it as unecessary from what I saw so far, can ext4 developers
> and/or people in Cc confirm? It should be harmless, only consequence is
> an uneeded lock being taken now in 3.0/3.4

It's not worth it to revert it.  The lock is being taken in a
completely non-fastpath, as well as guaranteed-to-be non-contended
code path.

We're not requiring that the lock be taken in 3.0 and 3.4, but
arguably it's still a good idea to take it from a consistency point of
view.

						- Ted