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From: Andreas Dilger <adilger@dilger.ca>
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Subject: Re: stat Size and Blocks numbers don't decrease after deletion
Date: Mon, 10 Jun 2024 14:55:01 -0600
In-Reply-To: <CAPXz4EPz+JVCBJ8AF3u9JKzQZk1JWZvf4oW9VVJxVTry8rJz6A@mail.gmail.com>
Cc: Ext4 Developers List <linux-ext4@vger.kernel.org>,
 Harshad Shirwadkar <harshadshirwadkar@gmail.com>
To: Nic Bretz <bretznic@gmail.com>
References: <CAPXz4EPz+JVCBJ8AF3u9JKzQZk1JWZvf4oW9VVJxVTry8rJz6A@mail.gmail.com>


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On Jun 7, 2024, at 10:25 AM, Nic Bretz <bretznic@gmail.com> wrote:
>=20
> When I create a new directory and new files in it, I see its size and
> blocks increase when running stat. After deleting all files, the size
> and blocks of the directory don't decrease in stat.

Correct, ext4 does not shrink directories after they have been =
populated.
There was a patch series at =
https://patchwork.ozlabs.org/project/linux-ext4/patch/20190821182740.97127=
-1-harshadshirwadkar@gmail.com/ that fell
into a crack and was never landed.  However, I think that patch would
still be interesting to revive.

> I was thinking that ext4 runs defragmentation in the background and
> eventually those two numbers will decrease. It looks like they don't.

No, ext4 does not do any kind of automatic background scanning or
filesystem changes.  You can run (offline) "e2fsck -fD" if there is
a big problem with large empty directories.

Cheers, Andreas


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