linux-kernel - Re: Btrfs for mainline

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Message-Id: <200901052132.22620.nickpiggin@yahoo.com.au>
Date:	Mon, 5 Jan 2009 21:32:22 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Chris Mason <chris.mason@...cle.com>
Cc:	Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-btrfs@...r.kernel.org
Subject: Re: Btrfs for mainline

On Saturday 03 January 2009 06:38:07 Chris Mason wrote:
> On Sat, 2009-01-03 at 01:37 +0900, Ryusuke Konishi wrote:
> > Hi,
> >
> > On Wed, 31 Dec 2008 18:19:09 -0500, Chris Mason <chris.mason@...cle.com> 
wrote:
> > > This has only btrfs as a module and would be the fastest way to see
> > > the .c files.  btrfs doesn't have any changes outside of fs/Makefile
> > > and fs/Kconfig
>
> [ ... ]
>
> > In addition, there seem to be well-separated reusable routines such as
> > async-thread (enhanced workqueue) and extent_map.  Do you intend to
> > move these into lib/ or so?
>
> Sorry, looks like I hit send too soon that time.  The async-thread code
> is very self contained, and was intended for generic use.  Pushing that
> into lib is probably a good idea.
>
> The extent_map and extent_buffer code was also intended for generic use.
> It needs some love and care (making it work for blocksize != pagesize)
> before I'd suggest moving it out of fs/btrfs.

I'm yet to be convinced it is a good idea to use extents for this. Been a
long time since we visited the issue, but when you converted ext2 to use
the extent mapping stuff, it actually went slower, and complexity went up
a lot (IIRC possibly required allocations in the writeback path).

So I think it is a fine idea to live in btrfs until it is more proven and
found useful elsewhere.

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