From: Hugo Mills <hugo@carfax.org.uk>
To: "Holger Hoffstätte" <holger.hoffstaette@googlemail.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: Btrfs-progs-3.16: fs metadata is both single and dup?
Date: Tue, 2 Sep 2014 13:13:49 +0100 [thread overview]
Message-ID: <20140902121349.GF18897@carfax.org.uk> (raw)
In-Reply-To: <pan.2014.09.02.12.05.33@googlemail.com>
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On Tue, Sep 02, 2014 at 12:05:33PM +0000, Holger Hoffstätte wrote:
>
> I updated to progs-3.16 and noticed during testing:
>
> root>losetup
> NAME SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE
> /dev/loop0 0 0 0 0 /tmp/img
>
> root>mkfs.btrfs -f /dev/loop0
> Btrfs v3.16
> See http://btrfs.wiki.kernel.org for more information.
>
> Performing full device TRIM (8.00GiB) ...
> Turning ON incompat feature 'extref': increased hardlink limit per file
> to 65536
> fs created label (null) on /dev/loop0
> nodesize 16384 leafsize 16384 sectorsize 4096 size 8.00GiB
> root>mkdir /tmp/btrfs
> root>mount /dev/loop0 /tmp/btrfs
>
> All fine until here..
>
> root>btrfs filesystem df /tmp/btrfs
> Data, single: total=8.00MiB, used=64.00KiB
> System, DUP: total=8.00MiB, used=16.00KiB
> System, single: total=4.00MiB, used=0.00
> Metadata, DUP: total=409.56MiB, used=112.00KiB
> Metadata, single: total=8.00MiB, used=0.00
Note that the "single" chunks are empty, and will remain so.
[snip]
> So where does the confusing initial display come from? I'm running this
> against a (very patched) 3.14.17, but don't remember ever seeing this
> with btrfs-progs-3.14.2.
Your memory is faulty, I'm afraid. It's always done that -- at
least since I started using btrfs, several years ago.
I believe it comes from mkfs creating a trivial basic filesystem
(with the single profiles), and then setting enough flags on it that
the kernel can bootstrap it with the desired chunks in it -- but I may
be wrong about that.
Hugo.
--
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
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next prev parent reply other threads:[~2014-09-02 12:13 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-02 12:05 Btrfs-progs-3.16: fs metadata is both single and dup? Holger Hoffstätte
2014-09-02 12:13 ` Hugo Mills [this message]
2014-09-02 12:34 ` Holger Hoffstätte
2014-09-03 4:53 ` Duncan
2014-09-03 7:33 ` Hugo Mills
2014-09-03 8:41 ` Duncan
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