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Date: Mon, 29 Dec 2014 10:50:36 +0800
From: Anand Jain <Anand.Jain@oracle.com>
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To: Ankur Tank <Ankur.Tank@LntTechservices.com>,
        "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: btrfs doesn't format eMMC if previous filesystem is ext4
References: <CFB3B8F56DDE9F45B45EBDEBED372A6644232D@POCITMSEXMB05.LntUniverse.com>
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On 12/26/2014 11:24 PM, Ankur Tank wrote:
> Hi,
>
> I wanted to test btrfs on the eMMC of beaglebone black based custom board.
> Precondition: eMMC is formatted with ext4 filesystem
> Use case:
>          Format eMMC with mkfs.btrfs  -L  <label>  <dev>
> Result:
>          Mkfs.btrfs denies formatting eMMC because its existing filesystem
>
> # mkfs.btrfs -L "1storage" /dev/mmcblk0p2
> /dev/mmcblk0p2 appears to contain an existing filesystem (ext4).
> Error: Use the -f option to force overwrite.
>
> If I add "-f" its possible to format the eMMC.
>
> # mkfs.btrfs -f -L "1storage" /dev/mmcblk0p2
> Detected a SSD, turning off metadata duplication.  Mkfs with -m dup if you want to force metadata duplication.
> Btrfs v3.17
> See http://btrfs.wiki.kernel.org for more information.
>
> Performing full device TRIM (1.72GiB) ...
> Turning ON incompat feature 'extref': increased hardlink limit per file to 65536
> [273917.692896] btrfs: device label 1storage devid 1 transid 3 /dev/mmcblk0p2
> fs created label 1storage on /dev/mmcblk0p2
>          nodesize 16384 leafsize 16384 sectorsize 4096 size 1.72GiB
>
> I had downloaded debian package from following link
> https://packages.debian.org/sid/armhf/btrfs-tools/download
>
> Is it a bug ? or I am missing something ?

  I don't see any bug. Can you be more specific ? Thanks.

> Thank you,
>
> Regards,
> Ankur
> L&T Technology Services Ltd
>
> www.LntTechservices.com<http://www.lnttechservices.com/>
>
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