linux-kernel - Re: XFS memory allocation deadlock in 2.6.38

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Message-ID: <BANLkTikzpC9DdaoWaUTvO98jnjFdJOomwQ@mail.gmail.com>
Date:	Mon, 28 Mar 2011 17:25:24 -0700
From:	Michel Lespinasse <walken@...gle.com>
To:	Sean Noonan <Sean.Noonan@...sigma.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Martin Bligh <Martin.Bligh@...sigma.com>,
	Trammell Hudson <Trammell.Hudson@...sigma.com>,
	Christos Zoulas <Christos.Zoulas@...sigma.com>,
	"linux-xfs@....sgi.com" <linux-xfs@....sgi.com>,
	Stephen Degler <Stephen.Degler@...sigma.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Dave Chinner <david@...morbit.com>
Subject: Re: XFS memory allocation deadlock in 2.6.38

On Mon, Mar 28, 2011 at 2:34 PM, Sean Noonan <Sean.Noonan@...sigma.com> wrote:
>> Could you test if you see the deadlock before
>> 5ecfda041e4b4bd858d25bbf5a16c2a6c06d7272 without MAP_POPULATE ?
>
> Built and tested 72ddc8f72270758951ccefb7d190f364d20215ab.
> Confirmed that the original bug does not present in this version.
> Confirmed that removing MAP_POPULATE does cause the deadlock to occur.

It seems that the test (without MAP_POPULATE) reveals that the root
cause is an xfs bug, which had been hidden up to now by MAP_POPULATE
preallocating disk blocks (but could always be triggered by the same
test without the MAP_POPULATE flag). I'm not sure how to go about
debugging the xfs deadlock; it would probably be best if an xfs person
could have a look ?

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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