linux-kernel - Re: [PATCH next/mmotm] ext4: fix cache_es after merge

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Message-ID: <20120927225357.GA19675@gmail.com>
Date:	Fri, 28 Sep 2012 06:53:57 +0800
From:	Zheng Liu <gnehzuil.liu@...il.com>
To:	Theodore Ts'o <tytso@....edu>, Hugh Dickins <hughd@...gle.com>,
	Zheng Liu <wenqing.lz@...bao.com>,
	Yongqiang Yang <xiaoqiangnk@...il.com>,
	Allison Henderson <achender@...ux.vnet.ibm.com>,
	Lukas Czerner <lczerner@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH next/mmotm] ext4: fix cache_es after merge_left

On Thu, Sep 27, 2012 at 04:39:20PM -0400, Theodore Ts'o wrote:
> On Thu, Sep 27, 2012 at 01:31:28PM -0700, Hugh Dickins wrote:
> > Kernel build with CONFIG_DEBUG_SLAB or CONFIG_SLUB_DEBUG slub_debug=FPZ
> > gives me kernel BUG at fs/ext4/extents_status.c:142!  That's the
> > BUG_ON(es->start + es->len < es->start) in extent_status_end() called
> > from ext4_es_insert_extent().  tree->cache_es has been freed and poisoned.
> > 
> > This comes from when ext4_es_try_to_merge_left() merges es into leftward
> > es1, but ext4_es_insert_extent()'s out then updates cache_es to the freed
> > extent_status.  ext4_es_try_to_merge_right() does not pose a problem.
> > 
> > Change ext4_es_try_to_merge_left() to return whichever extent_status
> > should be recorded in tree->cache_es.  Remove cache_es update from
> > both of them, leaving that to ext4_es_insert_extent()'s out label.
> > 
> > Signed-off-by: Hugh Dickins <hughd@...gle.com>
> 
> Hugh, thanks for finding this bug!
> 
> Zheng, you were going to send me an updated patch series; can you take
> care of merging this patch into your patch series (and crediting Hugh
> with a Signed-off-by as appropriate)?

Yeah, thanks for fixing it, although I have fixed this problem in my new
patch set.  I will add a Signed-off-by into the patch.

Regards,
Zheng
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