Hi,
I'm investigating BTRFS using an external USB HDD on a Linux Debian
Stretch/Sid system.

The drive is not reliable. And I noticed when there is an error and the
USB device appears to be dead to the kernel, I am later unable to
remount rw the drive. I can mount it read only though.

This seems to be a systematic behavior. And it occasionally happens when
the computer wake up from sleep and the drive is still attached.

Power cycling the disk do not change anything, but restarting the
computer "solves" the issue.


I believe this may be caused by BTRFS having issues since the kernel
assign a different device name to the drive when it bring it back
inline? Or BTRFS didn't realize the "original" drive has gone away?


Attached are the dmesg output corresponding to my issue.
Initially, the drive was mounted rw and associated to the /dev/sdb
device, the btrfs partition being /dev/sdb1
After the failure, I power cycled the drive, and the kernel brought it
back as /dev/sdc

I can mount /dev/sdc1 read only.
But I'm unable to mount it read-write. Interestingly, the message in
dmesg still mention /dev/sdb1 as the device whereas it should be /dev/sdc1.



sylvain@bulbizarre:~$ uname -a
Linux bulbizarre 4.9.0-2-amd64 #1 SMP Debian 4.9.18-1 (2017-03-30)
x86_64 GNU/Linux
sylvain@bulbizarre:~$ btrfs --version
btrfs-progs v4.7.3
sylvain@bulbizarre:~$ sudo btrfs fi show
Label: 'G-Drive'  uuid: 9465dad3-6604-4437-883e-f66386d69ac8
    Total devices 1 FS bytes used 503.34GiB
    devid    1 size 931.51GiB used 507.02GiB path /dev/sdc1



Any clue to help me mounting back the disk without having to restart the
system would be greatly appreciated!
Regards,
- Sylvain.

-- 
-- Sylvain Leroux
-- sylvain@chicoree.fr
-- http://www.chicoree.fr