From: Jan Kara <jack@suse.cz>
Subject: Re: [RFC] Ext3 online defrag
Date: Wed, 25 Oct 2006 20:36:56 +0200
Message-ID: <20061025183656.GD9940@atrey.karlin.mff.cuni.cz>
References: <20061023122710.GA12034@atrey.karlin.mff.cuni.cz> <20061023141641.GA29649@thunk.org> <20061023151447.GL3509@schatzie.adilger.int> <20061023160310.GB11353@atrey.karlin.mff.cuni.cz> <20061023172906.GO3509@schatzie.adilger.int>
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To: adilger@clusterfs.com, Theodore Tso <tytso@mit.edu>,
	linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org
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Sender: linux-ext4-owner@vger.kernel.org

> On Oct 23, 2006  18:03 +0200, Jan Kara wrote:
> > Andreas Dilger wrote:
> > > I would in fact go so far as to allow only a single extent to be specified
> > > per call.  This is to avoid the passing of any pointers as part of the
> > > interface (hello ioctl police :-), and also makes the kernel code simpler.
> > > I don't think the syscall/ioctl overhead is significant compared to the
> > > journal and IO overhead.
> >
> > ...it makes it kind of
> > harder to tell where indirect blocks would go - and it would be
> > impossible for the defragmenter to force some unusual placement of
> > indirect blocks...
> 
> It would be possible to specify indirect block relocation in same manner
> as regular block relocation I think.  Allocate a new block, copy contents,
> flush block from cache, fix up reference (inode, dindirect), commit.
  Yes, but there's a question of the interface to this operation. How to
specify which indirect block I mean? Obviously we could introduce
separate call for remapping indirect blocks but I find this solution
kind of clumsy...

							Bye
								Honza
-- 
Jan Kara <jack@suse.cz>
SuSE CR Labs