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Re: XFS memory allocation deadlock in 2.6.38

To: Sean Noonan <Sean.Noonan@xxxxxxxxxxxx>
Subject: Re: XFS memory allocation deadlock in 2.6.38
From: Michel Lespinasse <walken@xxxxxxxxxx>
Date: Mon, 28 Mar 2011 17:25:24 -0700
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Martin Bligh <Martin.Bligh@xxxxxxxxxxxx>, Trammell Hudson <Trammell.Hudson@xxxxxxxxxxxx>, Christos Zoulas <Christos.Zoulas@xxxxxxxxxxxx>, "linux-xfs@xxxxxxxxxxx" <linux-xfs@xxxxxxxxxxx>, Stephen Degler <Stephen.Degler@xxxxxxxxxxxx>, "linux-mm@xxxxxxxxx" <linux-mm@xxxxxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>
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On Mon, Mar 28, 2011 at 2:34 PM, Sean Noonan <Sean.Noonan@xxxxxxxxxxxx> 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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