FYI, we noticed the below changes on https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git wb-buf-throttle commit 1131f64d74958d495d8a6d5f9b981e86ed3beb7a ("blk-mq: don't throttle for virtual devices") +------------------------------------------+------------+------------+ | | f21fb0e42c | 1131f64d74 | +------------------------------------------+------------+------------+ | boot_successes | 6 | 0 | | boot_failures | 0 | 6 | | BUG:unable_to_handle_kernel | 0 | 6 | | Oops | 0 | 6 | | RIP:blk_wb_wait | 0 | 6 | | Kernel_panic-not_syncing:Fatal_exception | 0 | 6 | | backtrace:init | 0 | 6 | | backtrace:kernel_init_freeable | 0 | 6 | +------------------------------------------+------------+------------+ [ 8.897469] FDC 0 is a S82078B [ 8.984074] brd: module loaded [ 9.030737] loop: module loaded [ 9.045718] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 [ 9.048069] IP: [] blk_wb_wait+0x5/0x174 [ 9.049489] PGD 0 [ 9.050433] Oops: 0000 [#1] SMP [ 9.051614] Modules linked in: [ 9.052686] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.6.0-rc1-00028-g1131f64 #1 [ 9.054734] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014 [ 9.056997] task: ffff880012028040 ti: ffff880012024000 task.ti: ffff880012024000 [ 9.059068] RIP: 0010:[] [] blk_wb_wait+0x5/0x174 [ 9.061281] RSP: 0018:ffff8800120277b8 EFLAGS: 00010246 [ 9.062563] RAX: 0000000000000000 RBX: ffff88000cb7ca40 RCX: 0000000000000000 [ 9.064103] RDX: 0000000000000000 RSI: ffff88000cb7ca40 RDI: 0000000000000000 [ 9.065585] RBP: ffff880012027820 R08: 0000000000000000 R09: 0000000000000004 [ 9.067127] R10: ffffea0000313940 R11: 0000000000000000 R12: ffff88000c418008 [ 9.068670] R13: ffff880012028040 R14: 00000000ffffffff R15: ffff880012028040 [ 9.070208] FS: 0000000000000000(0000) GS:ffff880013400000(0000) knlGS:0000000000000000 [ 9.072425] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 9.074277] CR2: 0000000000000008 CR3: 0000000002418000 CR4: 00000000000406f0 [ 9.076404] Stack: [ 9.077575] ffffffff81531a08 ffff880012028040 0000000000000000 0000000081525471 [ 9.080881] ffff88000cb7ca40 0000000012028040 ffff8800120277f8 ffffffff81191334 [ 9.084175] ffff88000cb7ca40 ffff88000c418008 ffff880012028040 00000000ffffffff [ 9.087492] Call Trace: [ 9.088746] [] ? blk_sq_make_request+0x96/0x543 [ 9.090753] [] ? mempool_alloc_slab+0x1f/0x21 [ 9.092681] [] generic_make_request+0xbd/0x15b [ 9.094606] [] submit_bio+0x109/0x114 [ 9.096410] [] submit_bh_wbc+0xfe/0x109 [ 9.098358] [] submit_bh+0x10/0x12 [ 9.100083] [] block_read_full_page+0x28f/0x2ab [ 9.102017] [] ? I_BDEV+0x12/0x12 [ 9.103727] [] ? __add_to_page_cache_locked+0x2b6/0x394 [ 9.105794] [] ? blkdev_writepages+0x10/0x10 [ 9.107697] [] blkdev_readpage+0x18/0x1a [ 9.109535] [] do_read_cache_page+0xb7/0x2ef [ 9.111435] [] read_cache_page+0x1c/0x1e [ 9.113264] [] read_dev_sector+0x30/0xb5 [ 9.115090] [] read_lba+0xa2/0x121 [ 9.116830] [] ? efi_partition+0xd0/0x517 [ 9.118674] [] efi_partition+0xf1/0x517 [ 9.120490] [] ? vsnprintf+0x85/0x3b1 [ 9.122267] [] ? snprintf+0x36/0x3e [ 9.124013] [] check_partition+0x11c/0x1b2 [ 9.125899] [] ? check_partition+0x11c/0x1b2 [ 9.127800] [] rescan_partitions+0x7c/0x252 [ 9.129682] [] ? mutex_unlock+0xe/0x10 [ 9.131485] [] __blkdev_get+0x1c4/0x3dc [ 9.133290] [] blkdev_get+0x1c6/0x2fd [ 9.135066] [] add_disk+0x42d/0x456 [ 9.136826] [] ? revalidate_disk+0x78/0x84 [ 9.138697] [] ? vp_get+0x57/0x67 [ 9.140417] [] virtblk_probe+0x560/0x641 [ 9.142255] [] virtio_dev_probe+0x111/0x187 [ 9.144127] [] driver_probe_device+0x118/0x261 [ 9.146062] [] __driver_attach+0x73/0x95 [ 9.147914] [] ? driver_probe_device+0x261/0x261 [ 9.149856] [] bus_for_each_dev+0x6f/0x87 [ 9.151712] [] driver_attach+0x1e/0x20 [ 9.153512] [] bus_add_driver+0xf2/0x1e4 [ 9.155339] [] ? init_cryptoloop+0x28/0x28 [ 9.157196] [] driver_register+0x8a/0xc6 [ 9.159003] [] ? init_cryptoloop+0x28/0x28 [ 9.160858] [] register_virtio_driver+0x2b/0x2d [ 9.162793] [] init+0x5a/0x87 [ 9.164440] [] do_one_initcall+0xe7/0x177 [ 9.166298] [] kernel_init_freeable+0x1ca/0x252 [ 9.168240] [] kernel_init+0xe/0xf5 [ 9.169982] [] ret_from_fork+0x22/0x50 [ 9.171754] [] ? rest_init+0x13b/0x13b [ 9.173542] Code: 04 75 18 83 7f 08 00 74 1c 48 8b 05 6b 19 ed 00 48 3b 47 18 74 0f 48 89 47 18 c3 55 48 89 e5 e8 2b ff ff ff 5d c3 66 66 66 66 90 <44> 8b 47 08 31 c0 45 85 c0 0f 84 5f 01 00 00 48 8b 76 18 48 89 [ 9.186592] RIP [] blk_wb_wait+0x5/0x174 [ 9.188533] RSP [ 9.189968] CR2: 0000000000000008 [ 9.191392] ---[ end trace 75dbd78af8037ee6 ]--- [ 9.193041] Kernel panic - not syncing: Fatal exception FYI, raw QEMU command line is: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -kernel /pkg/linux/x86_64-nfsroot/gcc-5/1131f64d74958d495d8a6d5f9b981e86ed3beb7a/vmlinuz-4.6.0-rc1-00028-g1131f64 -append 'root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-kbuild-yocto-x86_64-43/bisect_boot-1-yocto-minimal-x86_64.cgz-x86_64-nfsroot-1131f64d74958d495d8a6d5f9b981e86ed3beb7a-20160401-52945-110sl1r-0.yaml ARCH=x86_64 kconfig=x86_64-nfsroot branch=linux-devel/devel-catchup-201604011147 commit=1131f64d74958d495d8a6d5f9b981e86ed3beb7a BOOT_IMAGE=/pkg/linux/x86_64-nfsroot/gcc-5/1131f64d74958d495d8a6d5f9b981e86ed3beb7a/vmlinuz-4.6.0-rc1-00028-g1131f64 max_uptime=600 RESULT_ROOT=/result/boot/1/vm-kbuild-yocto-x86_64/yocto-minimal-x86_64.cgz/x86_64-nfsroot/gcc-5/1131f64d74958d495d8a6d5f9b981e86ed3beb7a/0 LKP_SERVER=inn earlyprintk=ttyS0,115200 systemd.log_level=err debug apic=debug sysrq_always_enabled rcupdate.rcu_cpu_stall_timeout=100 panic=-1 softlockup_panic=1 nmi_watchdog=panic oops=panic load_ramdisk=2 prompt_ramdisk=0 console=ttyS0,115200 console=tty0 vga=normal rw ip=::::vm-kbuild-yocto-x86_64-43::dhcp drbd.minor_count=8' -initrd /fs/sdd1/initrd-vm-kbuild-yocto-x86_64-43 -m 320 -smp 1 -device e1000,netdev=net0 -netdev user,id=net0 -boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -drive file=/fs/sdd1/disk0-vm-kbuild-yocto-x86_64-43,media=disk,if=virtio -pidfile /dev/shm/kboot/pid-vm-kbuild-yocto-x86_64-43 -serial file:/dev/shm/kboot/serial-vm-kbuild-yocto-x86_64-43 -daemonize -display none -monitor null Thanks, Kernel Test Robot