linux-ext4 - Re: [PATCH] ext4: let ext4_ext_convet_to_initialized initialize var(eh) before using it

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Date:	Wed, 2 Nov 2011 01:22:59 -0700
From:	Eric Gouriou <egouriou@...gle.com>
To:	"Ted Ts'o" <tytso@....edu>
Cc:	Yongqiang Yang <xiaoqiangnk@...il.com>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: let ext4_ext_convet_to_initialized initialize
 var(eh) before using it

[Resend of my earlier message with HTML gunk removed and one edit. ]

On Tue, Nov 1, 2011 at 15:52, Ted Ts'o <tytso@....edu> wrote:
>
> On Tue, Nov 01, 2011 at 09:21:21AM +0800, Yongqiang Yang wrote:
> > ext4_ext_convert_to_initialized() does not initialize eh before using it
> > and this is introduced in commit 864d21652.
> >
> > Cc:Eric Gouriou <egouriou@...gle.com>
> > Cc:"Theodore Ts'o" <tytso@....edu>
> > Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
>
> >               eof_block = map->m_lblk + map->m_len;
> >
> >       depth = ext_depth(inode);
> > +     eh = path[depth].p_hdr;
> >       ex = path[depth].p_ext;
> >       ee_block = le32_to_cpu(ex->ee_block);
> >       ee_len = ext4_ext_get_actual_len(ex);
>
> Hmmm, nice catch.
>
> Looks like Eric dropped this line when he forward ported this patch to
> v3.1.

Indeed I screwed up. Apologies for the trouble. I tested the patch thoroughly
on our kernel version, ported it to ~ 2.6.39 and tested. This was a few months
ago and could not find the time to complete the work then. When I got a chance
to resume the effort, the upstream kernel had changed but I was not supposed
to even build it due to security concerns with the kernel.org sources.
So I redid
the port blind, verified [the file] built but did not test.

>  Interestingly, I did test this using xfstests, and it didn't
> complain.  Which probably means we don't have a good test coverage
> that triggers the specific preconditions of this optimization.  Oops.
> I'll fix this up now.
>
> Eric, when you have a chance, could you work up an xfstests test that
> automates the various tests that you ran manually when you developed
> this patch?  Thanks!!

Sure, but the "chance" may not manifest itself soon.

 Eric

>
>                                                - Ted
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