Unsupported btrfs option

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Unsupported btrfs option

Postby slick666 » Mon Dec 23, 2013 5:44 am

Dear Forum,

I've been trying to create a btrfs file system on my pgpgoplugv4 and running into this frustrating condition where the file system it creates doesn't seem to be supported by the Kernel. On top of that there doesn't seem to be a way to turn this feature off.

Here are the steps
Code: Select all
sudo mkfs.btrfs -f -L Backup /dev/sdc1
[sudo] password for landon:

WARNING! - Btrfs v3.12 IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using

Turning ON incompat feature 'extref': increased hardlink limit per file to 65536
fs created label Backup on /dev/sdc1
        nodesize 16384 leafsize 16384 sectorsize 4096 size 2.73TiB
Btrfs v3.12


The Turning ON incompat feature 'extref': is what I think is the problem but as you can see from the command I didn't actually enable that. Here is the Error.

Code: Select all
sudo mount /dev/sdc1 /Backup/
mount: wrong fs type, bad option, bad superblock on /dev/sdc1,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try
       dmesg | tail or so.


Looking in DMESG we can see the issue.

Code: Select all
dmesg | tail
[24422.008968] xhci_hcd 0000:00:01.0: WARN: Stalled endpoint
[24461.664344] device label Backup devid 1 transid 4 /dev/sdc1
[24461.666902] BTRFS: couldn't mount because of unsupported optional features (40).
[24461.679808] btrfs: open_ctree failed
[25239.661958] device label Backup devid 1 transid 4 /dev/sdc1
[25239.664567] BTRFS: couldn't mount because of unsupported optional features (40).
[25239.677093] btrfs: open_ctree failed
[25791.608302] device label Backup devid 1 transid 4 /dev/sdc1
[25791.610852] BTRFS: couldn't mount because of unsupported optional features (40).
[25791.622765] btrfs: open_ctree failed


The important line looks like [25791.610852] BTRFS: couldn't mount because of unsupported optional features (40).. Looking at the features we can see this more clearly.

Code: Select all
mkfs.btrfs -O list-all
Filesystem features available at mkfs time:
mixed-bg            - mixed data and metadata block groups (0x4)
extref              - increased hardlink limit per file to 65536 (0x40, default)
raid56              - raid56 extended format (0x80)
skinny-metadata     - reduced-size metadata extent refs (0x100)


We can see here that the feature "40" is the extref, the same warning we saw earlier. We can also see that is has a "default" notation as well so the warning we saw earlier would make sense. The problem I'm running into is that I can't seem to find ANY way to tall mkfs.btrfs to NOT enable this feature. Also looking at btrfstune there seems to be a way to turn this on byt not off. (Perhaps it's not possible to go back after it's been turned on in the file system.) If anyone has run into this and found a work around please let me know.

Thanks
slick666
 
Posts: 6
Joined: Mon Dec 23, 2013 5:30 am

Re: Unsupported btrfs option

Postby moonman » Mon Dec 23, 2013 6:10 am

What kernel? "uname -a" if 3.1.10 then that's why

Also -O ^extref will disable the feature. (Notice the ^)
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Re: Unsupported btrfs option

Postby slick666 » Tue Dec 24, 2013 10:30 am

turns out that was the issue.

Code: Select all
uname -a
Linux alarm 3.1.10-29-ARCH #1 PREEMPT Mon Dec 16 16:08:40 MST 2013 armv5tel GNU/Linux


using the -O ^extref option got it working for me. Although I guess I would prefer to have the updated Kernel I can't think of a reason I would need the extended ref option.
slick666
 
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Re: Unsupported btrfs option

Postby WarheadsSE » Tue Dec 24, 2013 1:22 pm

Switching to linux-kirkwood && linux-kirkwood-headers would be a good start.
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Re: Unsupported btrfs option

Postby cls42 » Sat Jan 04, 2014 8:52 pm

mkfs.btrfs -O ^extref
solved my problem, thanks!
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