On 2019/2/6 上午6:18, Stephen R. van den Berg wrote:
> Are these Sysreq+w dumps not usable?
> 
Sorry for the late reply.

The hang looks pretty strange, and doesn't really look like previous
deadlock caused by tree block locking.
But some strange behavior about metadata dirty pages:

This looks like to be the cause of the problem.

kworker/u16:1   D    0 19178      2 0x80000000
Workqueue: btrfs-endio-write btrfs_endio_write_helper
Call Trace:
 ? __schedule+0x4db/0x524
 ? schedule+0x60/0x71
 ? schedule_timeout+0xb2/0xec
 ? __next_timer_interrupt+0xae/0xae
 ? io_schedule_timeout+0x1b/0x3d
 ? balance_dirty_pages+0x7a7/0x861
 ? usleep_range+0x7e/0x7e
 ? schedule+0x60/0x71
 ? schedule_timeout+0x32/0xec
 ? balance_dirty_pages_ratelimited+0x204/0x225
 ? btrfs_finish_ordered_io+0x584/0x5ac
 ? normal_work_helper+0xfe/0x243
 ? process_one_work+0x18d/0x271
 ? rescuer_thread+0x278/0x278
 ? worker_thread+0x194/0x23f
 ? kthread+0xeb/0xf0
 ? kthread_associate_blkcg+0x86/0x86
 ? ret_from_fork+0x35/0x40

But I'm not familiar with balance_dirty_pages part, thus can't provide
much details about this.

Thanks,
Qu