linux-kernel - Re: [ 36/71] ext4: lock i_mutex when truncating orphan inodes

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Message-ID: <20130118034747.GF2872@herton-Z68MA-D2H-B3>
Date:	Fri, 18 Jan 2013 01:47:48 -0200
From:	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	alan@...rguk.ukuu.org.uk,
	Alexander Beregalov <a.beregalov@...il.com>,
	Theodore Tso <tytso@....edu>, Zheng Liu <wenqing.lz@...bao.com>
Subject: Re: [ 36/71] ext4: lock i_mutex when truncating orphan inodes

On Thu, Jan 17, 2013 at 04:46:16PM -0800, Greg Kroah-Hartman wrote:
> On Thu, Jan 17, 2013 at 06:07:11PM -0200, Herton Ronaldo Krzesinski wrote:
> > On Tue, Jan 15, 2013 at 02:54:33PM -0800, Greg Kroah-Hartman wrote:
> > > 3.0-stable review patch.  If anyone has any objections, please let me know.
> > > 
> > > ------------------
> > > 
> > > From: Theodore Ts'o <tytso@....edu>
> > > 
> > > commit 721e3eba21e43532e438652dd8f1fcdfce3187e7 upstream.
> > > 
> > > Commit c278531d39 added a warning when ext4_flush_unwritten_io() is
> > > called without i_mutex being taken.  It had previously not been taken
> > > during orphan cleanup since races weren't possible at that point in
> > > the mount process, but as a result of this c278531d39, we will now see
> > > a kernel WARN_ON in this case.  Take the i_mutex in
> > > ext4_orphan_cleanup() to suppress this warning.
> > > 
> > > Reported-by: Alexander Beregalov <a.beregalov@...il.com>
> > > Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> > > Reviewed-by: Zheng Liu <wenqing.lz@...bao.com>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > 
> > 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

> 
> thanks,
> 
> greg k-h
> 

-- 
[]'s
Herton
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