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Subject: Re: [PATCH 2/2] ubifs: Allow O_DIRECT
From: Artem Bityutskiy <dedekind1@gmail.com>
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To: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>, Richard Weinberger
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Date: Thu, 20 Aug 2015 14:31:40 +0300
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On Thu, 2015-08-20 at 11:00 +0800, Dongsheng Yang wrote:
> On 08/20/2015 04:35 AM, Richard Weinberger wrote:
> > Currently UBIFS does not support direct IO, but some applications
> > blindly use the O_DIRECT flag.
> > Instead of failing upon open() we can do better and fall back
> > to buffered IO.
> 
> Hmmmm, to be honest, I am not sure we have to do it as Dave
> suggested. I think that's just a work-around for current fstests.
> 
> IMHO, perform a buffered IO when user request direct IO without
> any warning sounds not a good idea. Maybe adding a warning would
> make it better.
> 
> I think we need more discussion about AIO&DIO in ubifs, and actually
> I have a plan for it. But I have not listed the all cons and pros of
> it so far.
> 
> Artem, what's your opinion?

Yes, this is my worry too.

Basically, we need to see what is the "common practice" here, and
follow it. This requires a small research. What would be the most
popular Linux FS which does not support direct I/O? Can we check what
it does?

Artem.