btrfs on md RAID-5 /etc/fstab mounting: open_ctree failed

btrfs on md RAID-5 /etc/fstab mounting: open_ctree failed

[Tomasz Chmielewski]

My btrfs on md RAID-5 mounts in an odd way and fails to mount via 
/etc/fstab (kernel is 4.8-rc8).

This is /etc/fstab entry for btrfs:

/dev/md2 /data btrfs noatime,compress-force=zlib,device=/dev/md2 0 0


Following a system restart, it didn't mount with these in dmesg:

[   11.099524] Btrfs loaded, crc32c=crc32c-intel
[   11.100125] BTRFS: device label data devid 1 transid 118760 /dev/md2
[   11.187585] BTRFS info (device md2): force zlib compression
[   11.187587] BTRFS info (device md2): disk space caching is enabled
[   11.187588] BTRFS info (device md2): has skinny extents
[  106.215206] BTRFS: open_ctree failed



Then, it mounted fine after I did "mount -a":

[  243.131317] BTRFS info (device md2): force zlib compression
[  243.131320] BTRFS info (device md2): disk space caching is enabled
[  243.131322] BTRFS info (device md2): has skinny extents


It's the same after each reboot.

Is it expected? How do I make it "automount" via /etc/fstab?


# btrfs fi show /data
Label: 'data'  uuid: fddbd057-4fa6-4b2e-a9ca-993829bab4b9
         Total devices 1 FS bytes used 11.69TiB
         devid    1 size 16.30TiB used 11.88TiB path /dev/md2

# btrfs fi df /data
Data, single: total=11.79TiB, used=11.64TiB
System, DUP: total=8.00MiB, used=1.27MiB
Metadata, DUP: total=48.00GiB, used=45.88GiB
GlobalReserve, single: total=512.00MiB, used=0.00B


In /proc/mdstat:

md2 : active raid5 sdc3[2] sdd3[4] sda3[0] sdb3[1]
       17500952064 blocks super 1.2 level 5, 512k chunk, algorithm 2 
[4/4] [UUUU]


Tomasz Chmielewski
https://lxadm.com