linux-kernel - Re: [PATCH] ext4: fix a big-endian bug when an extent is zeroed out

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Message-ID: <87bo9vre4f.fsf@openvz.org>
Date:	Wed, 03 Apr 2013 16:29:52 +0400
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	Theodore Ts'o <tytso@....edu>,
	Christian Kujau <lists@...dbynature.de>,
	CAI Qian <caiqian@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-s390 <linux-s390@...r.kernel.org>,
	Steve Best <sbest@...hat.com>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4: fix a big-endian bug when an extent is zeroed out

On Wed, 3 Apr 2013 08:20:58 -0400, Theodore Ts'o <tytso@....edu> wrote:
> On Wed, Apr 03, 2013 at 06:22:04PM +0800, Zheng Liu wrote:
> > Subject: [PATCH] ext4: fix a big-endian bug when an extent is zeroed out
> > 
> > From: Zheng Liu <wenqing.lz@...bao.com>
> > 
> > When an extent was zeroed out, we forgot to do convert from cpu to le16.
> > It could make us hit a BUG_ON when we try to write dirty pages out.  So
> > fix it.
> > 
> > Signed-off-by: Zheng Liu <wenqing.lz@...bao.com>
> 
> Thanks for finding this!  I think we should push this to Linus right
> away, and not wait for the next merge window.  The bug has been here
> for a long time, but it was unmasked by the fact that we unbroke
> extent zeroing in 3.9-rcX.
IMHO you have to pick this one http://patchwork.ozlabs.org/patch/233397
because it also fix  ext_to_indirect_migration and inode's csum
> 
> I have two big questions.  (1) Shouldn't Eric Whitney have picked this
> up with his ARM pandaboard testing, since IIRC it's big-endian as
> well?  If not, is there something we can do to improve our testing wrt
> to big-endian systems?
> 
> And (2) does it make sense to have an inline function
> ext4_ext_set_len(len)?  It might save some lines of code, but more
> importantly, it might make it less likely that we will overlook this
> sort of bug in the future.
Let's live it for now, later I'll cleanup/optimize this 'zero_ex'
at least from from ext4_split_extent_at because at the end we are shure
that 'ex' is fully mapped and initialized
> 
> 					- Ted
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