On Sat 20-01-18 18:40:28, Theodore Ts'o wrote:

On Sat, Jan 20, 2018 at 04:41:00PM +0800, Hongzhi, Song wrote:

quoted

329.11 EXT4-fs (nbd0): mounted filesystem with ordered data mode. Opts:
(null)
329.12 block nbd0: Connection timed out
329.13 block nbd0: shutting down sockets

That's your problem.  I'm guessing qemu-nbd is dying for some reason,
which is causing the nbd device to fail (hence the "connection timed
out").

All those filesystem errors are obviously his problem but:

329.45 ------------[ cut here ]------------
329.46 kernel BUG at /kernel-source//fs/buffer.c:3091!
329.47 invalid opcode: 0000 [#1] PREEMPT SMP
...

is a kernel problem. Hongzhi, can you please track down which line in
submit_bh_wbc() is line 3091 in your sources? I'd be interested in which
assertion actually failed. My best bets would be on
	BUG_ON(!buffer_mapped(bh));
but I'm not sure...

								Honza

-- 
Jan Kara [off-list ref]
SUSE Labs, CR