linux-kernel - Re: [rfc] Ignore Fsync Calls in Laptop

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Message-Id: <201105250850.12179.oneukum@suse.de>
Date:	Wed, 25 May 2011 08:50:11 +0200
From:	Oliver Neukum <oneukum@...e.de>
To:	Dave Chinner <david@...morbit.com>
Cc:	"D. Jansen" <d.g.jansen@...glemail.com>,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	tytso@....edu
Subject: Re: [rfc] Ignore Fsync Calls in Laptop_Mode

Am Mittwoch, 25. Mai 2011, 02:00:03 schrieb Dave Chinner:
> Oh, you're talking about application level write ordering. IO
> "ordering" in filesystem speak is about guaranteeing the order of
> data vs metadata writes for ensuring consistency after a crash
> (e.g. ext3/4 default "data=ordered" mode). that's what I was
> refering to, not anythign to do with applications.
> 
> Besides, having to work out how to handle subtle application write
> ordering bugs because you changed fsync semantics is simply another
> reason for not changing behaviour in the first place.

Sure. I'd say changing the behavior is right out. The question is whether
we want an additional "superlaptop"-mode.
And even in this case it seems to me that fsync() cannot be reduced to
a nop because of ordering constraints. But perhaps we should then consider
exporting an ordering primitive to user space.

	Regards
		Oliver
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