linux-ext4 - Re: [PATCH] e4defrag: fallocate donor file only once

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Message-ID: <6149e97b0909030100p1930c0fra28663724e51114@mail.gmail.com>
Date:	Thu, 3 Sep 2009 16:00:49 +0800
From:	Peng Tao <bergwolf@...il.com>
To:	Greg Freemyer <greg.freemyer@...il.com>
Cc:	linux-ext4@...r.kernel.org, Theodore Tso <tytso@....edu>,
	Akira Fujita <a-fujita@...jp.nec.com>
Subject: Re: [PATCH] e4defrag: fallocate donor file only once

On Thu, Sep 3, 2009 at 6:09 AM, Greg Freemyer<greg.freemyer@...il.com> wrote:
> On Wed, Sep 2, 2009 at 11:35 AM, Peng Tao<bergwolf@...il.com> wrote:
>> If we allocate the donor file once for all, it will have a better chance
>> to be continuous.
>>
>> Signed-off-by: "Peng Tao" <bergwolf@...il.com>
>
> Seems like an improvement, but I'm not seeing any special handling for
> sparse files.  (Not before or after this patch.)
>
> Seems like there should be an outer loop that identifies contiguous
> data block sets in a sparse file and defrags them individually as
> opposed to trying to defrag the entire file at once.
>
> My impression is that with a large sparse file, e4defrag currently
> (with or without this patch) would fallocate a full non-sparse donor
> set of blocks the full size of the original file, then swap in just
> the truly allocated blocks?
Thanks for the reminder. The original code takes good care of sparse
files in join_extents(). Please ignore my patch.

Sorry for the noise.

>
> If so, that is not very optimum.
>
> Greg
>



-- 
Cheers,
Peng Tao
State Key Laboratory of Networking and Switching Technology
Beijing Univ. of Posts and Telecoms.
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