Hi all, I run into a BUG_ON(!buffer_mapped(bh)) crash with below script. $ rbd-nbd map mypool/myimg $ mkfs.ext4 /dev/nbd0 $ mount /dev/nbd0 /mnt/ $ rbd-nbd unmap /dev/nbd0 $ umount /mnt [ 1248.870131] kernel BUG at /home/mlin/linux/fs/buffer.c:3103! [ 1248.871214] invalid opcode: 0000 [#1] SMP [ 1248.879468] CPU: 0 PID: 2450 Comm: umount Tainted: G E 4.11.0-rc2+ #2 [ 1248.896579] Call Trace: [ 1248.897056] __sync_dirty_buffer+0x6e/0xe0 [ 1248.897870] ext4_commit_super+0x1eb/0x290 [ext4] [ 1248.898795] ext4_put_super+0x2fa/0x3c0 [ext4] [ 1248.899662] generic_shutdown_super+0x6f/0x100 [ 1248.900525] kill_block_super+0x27/0x70 [ 1248.901257] deactivate_locked_super+0x43/0x70 [ 1248.902112] deactivate_super+0x46/0x60 [ 1248.902869] cleanup_mnt+0x3f/0x80 [ 1248.903526] __cleanup_mnt+0x12/0x20 [ 1248.904218] task_work_run+0x83/0xb0 [ 1248.904941] exit_to_usermode_loop+0x59/0x7b [ 1248.905769] do_syscall_64+0x165/0x180 [ 1248.907603] entry_SYSCALL64_slow_path+0x25/0x25 Last year, Ratna posted a patch to fix it. https://lkml.org/lkml/2016/4/20/257 Ratna's script to reproduce the bug. $ qemu-img create -f qcow2 f.img 1G $ mkfs.ext4 f.img $ qemu-nbd -c /dev/nbd0 f.img $ mount /dev/nbd0 dir $ killall -KILL qemu-nbd $ sleep 1 $ ls dir $ umount dir I ported Rantna's patch to 4.11-rc2 and confirmed that it fixes the crash. Jan Kara had some comments about this bug: http://www.kernelhub.org/?p=2&msg=361407 I hope to fix this bug in the upstream kernel first and then back port it to our production system. Please see "PATCH 1/1" for detail. Thanks, Ming
