On 8/9/18 11:15 AM, Giuseppe Della Bianca wrote:
> Hi.
> 
> My system: 
> - Fedora 28 x86_64
> - kernel-4.17.7-200
> - btrfs-progs-4.15.1-1
> 
> The command 'btrfs subvolume sync -s 2 xyz' hangs in this case:
> 
> - Run command 'btrfs subvolume sync -s 2 xyz' .
> - After some time the kernel reports an error on the filesystem.
>   (error that existed before the command was launched.)
> - The filesystem goes in read-only mode.
> - The command hangs.

Can you provide the output of 'dmesg' and the contents of
/proc/<pid>/stack where <pid> is the pid of the btrfs command process?

-Jeff
-- 
Jeff Mahoney
SUSE Labs