linux-kernel - Re: [patch v3 1/3] block: add a non-queueable flush flag

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Date:	Wed, 04 May 2011 22:17:39 -0400
From:	Jeff Garzik <jgarzik@...ox.com>
To:	shaohua.li@...el.com
CC:	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	jaxboe@...ionio.com, htejun@...il.com, hch@...radead.org,
	djwong@...ibm.com, sshtylyov@...sta.com
Subject: Re: [patch v3 1/3] block: add a non-queueable flush flag

On 05/04/2011 09:59 PM, shaohua.li@...el.com wrote:
> flush request isn't queueable in some drives. Add a flag to let driver
> notify block layer about this. We can optimize flush performance with the
> knowledge.
>
> Signed-off-by: Shaohua Li<shaohua.li@...el.com>
> ---
>   block/blk-settings.c   |    6 ++++++
>   include/linux/blkdev.h |    7 +++++++
>   2 files changed, 13 insertions(+)

hmmm.

This assumes that flush on new hardware, by default, is queueable.

I think the sense should be reversed:  don't enable the optimization, 
unless we know the optimization works.

That seems safer than always enabling the optimization, unless we know 
it does not work.  That is not a fail-safe mode of operation.

	Jeff




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