FYI, we noticed the following commit: https://git.kernel.org/pub/scm/linux/kernel/git/josef/btrfs-next.git kill-btree-inode commit ab7724daa909923e8dd5baca685ccc1dfa3fa413 ("writeback: introduce super_operations->write_metadata") in testcase: boot on test machine: qemu-system-x86_64 -enable-kvm -m 512M caused below changes: +---------------------------------------+------------+------------+ | | ac04c3c6a3 | ab7724daa9 | +---------------------------------------+------------+------------+ | boot_successes | 83 | 2 | | boot_failures | 0 | 31 | | BUG:spinlock_bad_magic_on_CPU | 0 | 31 | | message:BUG:spinlock_bad_magic_on_CPU | 0 | 0.0 | | pattern:BUG:spinlock_bad_magic_on_CPU | 0 | 0 | +---------------------------------------+------------+------------+ Unmounting remote filesystems... Deactivating swap... Unmounting local filesystems... [ 71.770706] BUG: spinlock bad magic on CPU#0, umount/538 [ 71.771434] lock: 0xffffffff81e57d28, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0 [ 71.772491] CPU: 0 PID: 538 Comm: umount Not tainted 4.7.0-11586-gab7724d #2 [ 71.773416] 0000000000000000 ffff88001c3cbcd8 ffffffff8134902b ffff88001c3cbcf8 [ 71.774459] ffffffff81108bd2 ffffffff81e57d28 ffffffff81cc22e0 ffff88001c3cbd18 [ 71.775488] ffffffff81108c4e ffffffff81e57d28 0000000000000001 ffff88001c3cbd48 [ 71.776520] Call Trace: [ 71.776861] [<ffffffff8134902b>] dump_stack+0x19/0x1b [ 71.777544] [<ffffffff81108bd2>] spin_dump+0x8e/0xcc [ 71.778214] [<ffffffff81108c4e>] spin_bug+0x3e/0x43 [ 71.778859] [<ffffffff81108fef>] do_raw_spin_lock+0x1cb/0x1ec [ 71.779617] [<ffffffff818654a4>] _raw_spin_lock+0x14/0x16 [ 71.780331] [<ffffffff8122b8a7>] deactivate_locked_super+0x93/0xd9 [ 71.781144] [<ffffffff8122c360>] deactivate_super+0xf0/0x100 [ 71.781887] [<ffffffff8125bfbd>] cleanup_mnt+0xad/0xe0 [ 71.782567] [<ffffffff8125d867>] __cleanup_mnt+0x12/0x14 [ 71.783274] [<ffffffff810e8fa6>] task_work_run+0xbf/0x115 [ 71.783982] [<ffffffff81002055>] exit_to_usermode_loop+0x1bc/0x1e3 [ 71.784804] [<ffffffff8125c20c>] ? mntput_no_expire+0x21c/0x2b5 [ 71.785585] [<ffffffff8100232e>] syscall_return_slowpath+0xb6/0xd6 [ 71.786394] [<ffffffff81865690>] entry_SYSCALL_64_fastpath+0xb6/0xb8 Elapsed time: 80 Thanks, Kernel Test Robot