Re: 5.4.20: cannot mount device that blipped off the bus: duplicate device fsid:devid for

[Nikolay Borisov <nborisov@suse.com>]

On 21.03.20 г. 22:23 ч., Marc MERLIN wrote:
> /dev/sde blipped off the bus (hardware issue?) and came
> back as /dev/sdq.
> Except btrfs won't let me scan or mount it.
> 
> I was able to btrfs check it though and that came back clean.
> 
> gargamel:~# ls -l /dev/sde
> ls: cannot access '/dev/sde': No such file or directory
> 
> 
> gargamel:~# mount /dev/sdq1 /mnt/mnt
> mount: /mnt/mnt: mount(2) system call failed: File exists.
> gargamel:~# dmesg |tail -1
> [2560371.195249] BTRFS warning (device sde1): duplicate device fsid:devid for 727c7ba3-f6f9-462a-8472-453dd7d46d8a:1 old:/dev/sde1 new:/dev/sdq1
> 
> gargamel:~# btrfs device scan
> Scanning for Btrfs filesystems
> ERROR: device scan failed on '/dev/sdq1': File exists
> ERROR: there are 1 errors while registering devices
> gargamel:~# dmesg |tail -1
> [2560416.434529] BTRFS warning (device sde1): duplicate device fsid:devid for 727c7ba3-f6f9-462a-8472-453dd7d46d8a:1 old:/dev/sde1 new:/dev/sdq1
> 
> gargamel:~# grep sde /proc/mounts 
> cgroup2 /sys/fs/cgroup/unified cgroup2 rw,nosuid,nodev,noexec,relatime,nsdelegate 0 0
> gargamel:~# 
> 
> gargamel:~# lsblk -f |grep 727c7ba3-f6f9-462a-8472-453dd7d46d8a
> └─sdq1                            btrfs             btrfs_space                 727c7ba3-f6f9-462a-8472-453dd7d46d8a   
> gargamel:~# 
> 
> So, that FS isn't a duplicate anymore and I see to have no way out except reboot
> which I'll do now.
> 
> Was there another way around it? Obviously this is not desirable
> behaviour, in the past, I was able to remount the device when it came
> back.
> 

Presumably you could have used the device forget functionality that got
introduced in 5.1, i.e the BTRFS_IOC_FORGET_DEV ioctl. For more info
check out: 228a73abde5c04428678e917b271f8526cfd90ed

> Thanks,
> Marc
>