[<0>] wb_wait_for_completion+0x56/0x80
[<0>] __writeback_inodes_sb_nr+0xa2/0xd0
[<0>] sync_filesystem+0x2d/0x90
[<0>] ovl_sync_fs+0x59/0x90 [overlay]
[<0>] sync_filesystem+0x7a/0x90
[<0>] generic_shutdown_super+0x22/0x120
[<0>] kill_anon_super+0x14/0x30
[<0>] deactivate_locked_super+0x31/0xa0
[<0>] cleanup_mnt+0x131/0x190
[<0>] task_work_run+0x5c/0x90
[<0>] exit_to_user_mode_loop+0x122/0x130
[<0>] exit_to_user_mode_prepare+0xb6/0x100
[<0>] syscall_exit_to_user_mode+0x12/0x30
[<0>] do_syscall_64+0x69/0x90
[<0>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
