On Thu, Mar 28, 2019 at 06:07:50PM +0800, Jiufei Xue wrote: > We hit a BUG at fs/buffer.c:3057 if we detached the nbd device > before unmounting ext4 filesystem. > > The typical chain of events leading to the BUG: > jbd2_write_superblock > submit_bh > submit_bh_wbc > BUG_ON(!buffer_mapped(bh)); > > The block device is removed and all the pages are invalidated. JBD2 > was trying to write journal superblock to the block device which is > no longer present. > > Fix this by checking the journal superblock's buffer head prior to > submitting. Thanks, applied. - Ted
