XFS memory allocation deadlock in 2.6.38

[Michel Lespinasse]

On Mon, Mar 28, 2011 at 2:34 PM, Sean Noonan <Sean.Noonan at twosigma.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.