Re: [gentoo-user] Can't create valid btrfs on NVMe

[Rich Freeman <rich0@gentoo.org>]

On Thu, Aug 18, 2016 at 8:57 AM, J. Roeleveld <joost@antarean.org> wrote:
> On Wednesday, August 17, 2016 11:26:13 PM Neil Bothwick wrote:
>> I'm putting together a new desktop using a Samsung SM951 NVMe drive. I
>> booted sysrescd, partitioned the drive and ran
>>
>> mkfs.btrfs /dev/nvme0n1p3
>> mount /dev/nvme0n1p3 /mnt/custom
>>
>> df -T, mount and findmnt all show this is mounted as a btrfs filesystem,
>> e.g.
>>
>> /dev/nvme0n1p3 on /mnt/custom type btrfs (rw,relatime,ssd,space_cache)
>>
>> I can create files in here but cannot do anything btrfs-y
>>
>> % btrfs filesystem show /mnt/custom
>> ERROR: not a valid btrfs filesystem: /mnt/custom
>>
>> % btrfs subvolume create /mnt/custom/test
>> Create subvolume '/mnt/custom/test'
>> ERROR: cannot create subvolume: Inappropriate ioctl for device
>>
>> Google has been no help at all.
>
> I've got a similar drive in my desktop and it actually works.
> Difference: I am using Ext4.
>
> Can you try Ext4 and see if it works?
> Next test: Does it work with a non-NVMe drive?
>
> Also, which kernel version?

I think you guys are going down the wrong road.  The kernel drivers
are almost certainly working for the drive, otherwise the filesystem
wouldn't work at all, and I'm sure a million ext4 users would have
noticed a problem by now.

This is almost certainly a bug in btrfs-progs, or maybe the btrfs
filesystem driver in the kernel.

I'd suggest raising this on the btrfs mailing list, where it is going
to get a lot more attention from the people who develop btrfs.  There
are a few of us who use it around here, but I'd have to spend a day
tweaking the btrfs-progs source to have a guess at where this is
bailing out.  I suspect somebody over there would have an answer
almost immediately.

-- 
Rich