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From: Anthony Liguori <anthony@codemonkey.ws>
To: Michael Tokarev <mjt@tls.msk.ru>
Cc: Christoph Hellwig <hch@infradead.org>,
	KVM list <kvm@vger.kernel.org>, Kevin Wolf <kwolf@redhat.com>
Subject: Re: JFYI: ext4 bug triggerable by kvm
Date: Tue, 17 Aug 2010 09:44:49 -0500	[thread overview]
Message-ID: <4C6AA061.80704@codemonkey.ws> (raw)
In-Reply-To: <4C6A9F4F.8040209@msgid.tls.msk.ru>

On 08/17/2010 09:40 AM, Michael Tokarev wrote:
>
>>> fsync() being slow is orthogonal to my point.  I don't see why we
>>> need to do an fsync() on *every* write.  It should only be necessary
>>> when a guest injects an actual barrier.
>>>        
> We don't do sync on every write, but O_SYNC implies that.
> And apparently it is what happening behind the scenes in
> ext4 O_SYNC case.
>    

I think the real issue is we're mixing host configuration with guest 
visible state.

With O_SYNC, we're causing cache=writethrough to do writethrough through 
two layers of the storage heirarchy.  I don't think that's necessary or 
desirable though.

Regards,

Anthony Liguori

> But ok....
>
> /mjt
>    


  reply	other threads:[~2010-08-17 14:44 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-08-16 14:00 JFYI: ext4 bug triggerable by kvm Michael Tokarev
2010-08-16 14:43 ` Anthony Liguori
2010-08-16 18:42   ` Christoph Hellwig
2010-08-16 20:34     ` Anthony Liguori
2010-08-17  9:07       ` Christoph Hellwig
2010-08-17  9:23         ` Avi Kivity
2010-08-17 11:17           ` Christoph Hellwig
2010-08-17 12:56         ` Anthony Liguori
2010-08-17 13:07           ` Christoph Hellwig
2010-08-17 14:20             ` Anthony Liguori
2010-08-17 14:28               ` Christoph Hellwig
2010-08-17 14:39                 ` Anthony Liguori
2010-08-17 14:45                   ` Christoph Hellwig
2010-08-17 14:53                     ` Avi Kivity
2010-08-17 14:54                     ` Anthony Liguori
2010-08-17 15:01                       ` Avi Kivity
2010-08-17 15:02                       ` Christoph Hellwig
2010-08-17 14:40                 ` Michael Tokarev
2010-08-17 14:44                   ` Anthony Liguori [this message]
2010-08-17 14:46                     ` Christoph Hellwig
2010-08-17 14:57                       ` Anthony Liguori
2010-08-17 14:59                       ` Avi Kivity
2010-08-17 15:04                         ` Christoph Hellwig

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