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

To: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Subject: Re: Device loses barrier support (was: Fixed patch for simple barriers.)
From: Andi Kleen <andi@xxxxxxxxxxxxxx>
Date: Thu, 4 Dec 2008 15:20:15 +0100
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, Alasdair G Kergon <agk@xxxxxxxxxx>, Andi Kleen <andi-suse@xxxxxxxxxxxxxx>, Milan Broz <mbroz@xxxxxxxxxx>
In-reply-to: <Pine.LNX.4.64.0812040836480.6118@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
References: <Pine.LNX.4.64.0812040009340.15169@xxxxxxxxxxxxxxxxxxxxxxxxxxx> <20081204100050.GN6703@xxxxxxxxxxxxxxxxxx> <Pine.LNX.4.64.0812040836480.6118@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.4.2.1i
> 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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