From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH] virtio-blk: fallback to draining the queue if barrier
 ops 	are not supported
Date: Thu, 15 Oct 2009 01:53:22 +0900
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Cc: Christoph Hellwig <hch@lst.de>,
	Matthew Tippett <tippettm@gmail.com>,
	Dustin Kirkland <dustin.kirkland@gmail.com>,
	Anthony Liguori <anthony@codemonkey.ws>, RW <kvm@tauceti.net>,
	kvm@vger.kernel.org
To: Javier Guerra <javier@guerrag.com>
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On 10/14/2009 11:46 PM, Javier Guerra wrote:
> On Wed, Oct 14, 2009 at 7:03 AM, Avi Kivity<avi@redhat.com>  wrote:
>    
>> Early implementations of virtio devices did not support barrier operations,
>> but did commit the data to disk.  In such cases, drain the queue to emulate
>> barrier operations.
>>      
> would this help on the (i think common) situation with XFS on a
> virtio-enabled VM, using LVM-backed storage; where LVM just loses
> barriers.
>    

No, it's a guest only patch.  If LVM loses barriers, I don't think 
anything can restore them.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.