linux-kernel - Re: [rfc][patch 0/3] a faster buffered write deadlock fix?

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Message-ID: <20070209020402.GC17334@wotan.suse.de>
Date:	Fri, 9 Feb 2007 03:04:02 +0100
From:	Nick Piggin <npiggin@...e.de>
To:	Mark Fasheh <mark.fasheh@...cle.com>
Cc:	Linux Filesystems <linux-fsdevel@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [rfc][patch 0/3] a faster buffered write deadlock fix?

On Thu, Feb 08, 2007 at 04:38:01PM -0800, Mark Fasheh wrote:
> On Thu, Feb 08, 2007 at 02:07:15PM +0100, Nick Piggin wrote:
> > The problem is that the existing aops interface is crap. "correct, fast,
> > compatible -- choose any 2"
> 
> Agreed. There's lots of problems with the interface (imho), but my biggest
> two issues are the page lock being held on ->prepare_write() /
> ->commit_write() and the fact that the file system only sees the write one
> page at a time
> 
> 
> > So I have finally finished a first slightly-working draft of my new aops
> > op (perform_write) proposal. I would be interested to hear comments about
> > it.  Most of my issues and concerns are in the patch headers themselves,
> > so reply to them.
> 
> I like ->perform_write(). It allows the file system to make re-use of the
> checks in the generic write path, but gives a maximum amount of information
> about the overall operation to be done. There's an added advantage in that
> some file systems (ocfs2 is one of these) want to be more careful about
> ordering page locks, which should be much easier with it.

Yeah, if possible I like a range based interface rather than page
based. As you say it gives the most information with the least constraints.

> If this goes in, it could probably be helpful to me in some of the code I'm
> currently writing which needs to be better about page lock / cluster lock
> ordering and wants to see as much of the (allocating) writes as possible.

I think it would be important to have a non trivial user of this new API
before it goes into mainline. It would be great if you could look at
using it, after it passes some review.

Thanks,
Nick
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