linux-kernel - Re: [PATCH 2.6.27.y 2/3] ext4: Fix file fragmentation during large file write.

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Message-ID: <20100529010657.GM26177@thunk.org>
Date:	Fri, 28 May 2010 21:06:57 -0400
From:	tytso@....edu
To:	"Jayson R. King" <dev@...sonking.com>
Cc:	Stable team <stable@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Dave Chinner <david@...morbit.com>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	Kay Diederichs <Kay.Diederichs@...-konstanz.de>
Subject: Re: [PATCH 2.6.27.y 2/3] ext4: Fix file fragmentation during large
 file write.

On Fri, May 28, 2010 at 02:26:57PM -0500, Jayson R. King wrote:
> From: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> Date: Thu Oct 16 10:10:36 2008 -0400
> Subject: ext4: Fix file fragmentation during large file write.
> 
> commit 22208dedbd7626e5fc4339c417f8d24cc21f79d7 upstream.
> 
> The range_cyclic writeback mode uses the address_space writeback_index
> as the start index for writeback.  With delayed allocation we were
> updating writeback_index wrongly resulting in highly fragmented file.
> This patch reduces the number of extents reduced from 4000 to 27 for a
> 3GB file.

This isn't a critical bug fix either.  I don't really care a whole
lot, since I don't plan to support ext4 with all of these patches but
if you haven't been doing a full set of testing with these patches,
I'd be very concerned about whether ext4 would be stable after
applying this patch series.

What sort of testing _have_ you done?

						- Ted

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