linux-kernel - Re: Device loses barrier support (was: Fixed patch for simple barriers.)

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Message-ID: <20081204142015.GQ6703@one.firstfloor.org>
Date:	Thu, 4 Dec 2008 15:20:15 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Mikulas Patocka <mpatocka@...hat.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	xfs@....sgi.com, Alasdair G Kergon <agk@...hat.com>,
	Andi Kleen <andi-suse@...stfloor.org>,
	Milan Broz <mbroz@...hat.com>
Subject: Re: Device loses barrier support (was: Fixed patch for simple barriers.)

> the 1st write request ends with success
> the 2nd write request ends with -EOPNOTSUPP
> the 3rd write request ends with success
> 
> --- when you first see -EOPNOTSUPP, you have already corrupted filesystem 
> (the 3rd write passed while the filesystem expected that it would be 

There's no passing of requests during pvmove. It's a really strong
barrier.

> finished after the 2nd write) and you are in an interrupt context, where 
> you can't reissue -EOPNOTSUPP request. So what do you want to do?

The barrier aware file systems I know of just resubmit synchronously when 
a barrier fails.

-Andi
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