linux-kernel - Re: JFFS2 deadlock

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Date:	Mon, 1 Feb 2016 19:54:29 +0100
From:	Thomas.Betker@...de-schwarz.com
To:	dwmw2@...radead.org
Cc:	computersforpeace@...il.com,
	Artem Bityutskiy <dedekind1@...il.com>,
	Deng Chao <deng.chao1@....com.cn>,
	Joakim Tjernlund <Joakim.Tjernlund@...inera.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	linux-mtd <linux-mtd-bounces@...ts.infradead.org>,
	Ming Liu <liu.ming50@...il.com>,
	"sztomi89@...il.com" <sztomi89@...il.com>,
	Thomas Betker <thomas.betker@...enet.de>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	wangzaiwei <wangzaiwei@...-vision.cn>
Subject: Re: JFFS2 deadlock

Hello David:

> > Subject: [PATCH] Revert "jffs2: Fix lock acquisition order bug in 
> > jffs2_write_begin"
> > http://article.gmane.org/gmane.linux.drivers.mtd/62951
> > 
> > This is a patch revising my original patch, which I sent to linux-mtd 
on 
> > 10-Nov-2015. I didn't see a response yet, but it's one of the 
outstanding 
> > patches above.
> 
> That looks necessary but not sufficient. I think we need this
> (untested) patch on top of it, to ensure that we *always* take the page
> lock before f->sem?
> 
> Please could you try what's in the tree at
> http://git.infradead.org/users/dwmw2/jffs2-fixes.git

I have been using a variant of Deng Chao's patch here for a long time, so 
that one has been tested quite a bit: 
http://lists.infradead.org/pipermail/linux-mtd/2013-August/048352.html. 
The problem with that patch was that it modified mm/filemap.c and 
include/linux/pagemap.h, which we were not too happy about.

Your patch looks much simpler, and I will definitely test it. It may take 
a few days, though, as I have to unearth the test scripts, and find a time 
slot for testing.

Best regards,
Thomas Betker