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: > > > > 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 <jack@xxxxxxxx> SUSE Labs, CR