Hi Neil and all, I saw below NULL Pointer dereference in rdev_set_badblocks once: when this happened, both devices in raid1 almost failed at same time, a lot of io errors, after several minutes, super_written error and disable on device and then run into NULL pointer dereference. Could you comment on this? cat badblock_null.log Sep 3 14:31:19 pserver102 kernel: [534312.102156] Modules linked in: bridge stp llc nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_t ables raid1 md_mod dm_round_robin sd_mod crc_t10dif ib_srp scsi_transport_srp scsi_tgt xt_ETHOIP6(O) x_tables vhost_net(O) macvtap macvlan tun(O) nf_conntrack_ipv4 nf_conntrack nf_defrag_ipv4 rdma_ucm rdma_cm iw_cm ib_addr ib_ipoib ib_cm ib_sa ib_uverbs ib_umad ib_qib mlx4_ib i b_mthca ib_mad ib_core dm_multipath scsi_dh kvm_amd kvm sg powernow_k8 mperf crc32c_intel microcode tpm_tis tpm tpm_bios psmouse serio_raw evdev usb_storage scsi_mod amd64_edac_mod edac_core edac_mce_amd i2c_piix4 button processor thermal_sys mlx4_core Sep 3 14:31:19 pserver102 kernel: [534312.103339] Sep 3 14:31:19 pserver102 kernel: [534312.103432] Pid: 46599, comm: md2_raid1 Tainted: G O 3.4.51-4-pserver #1 Supermicro H8QG6/ H8QG6 Sep 3 14:31:19 pserver102 kernel: [534312.103658] RIP: 0010:[] [] rdev_set_badblocks+0x8/0x70 [md_mod ] Sep 3 14:31:19 pserver102 kernel: [534312.103870] RSP: 0018:ffff881fbc197c10 EFLAGS: 00010282 Sep 3 14:31:19 pserver102 kernel: [534312.103976] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 Sep 3 14:31:19 pserver102 kernel: [534312.104171] RDX: 0000000000000008 RSI: 00000000001ad300 RDI: 0000000000000000 Sep 3 14:31:19 pserver102 kernel: [534312.104358] RBP: ffff881803fa55c0 R08: ffffea0100092418 R09: 0000000000000001 Sep 3 14:31:19 pserver102 kernel: [534312.104550] R10: 0000000000000000 R11: dead000000100100 R12: 0000000000000000 Sep 3 14:31:19 pserver102 kernel: [534312.104762] R13: 00000000001ad300 R14: 0000000000000010 R15: 0000000000000008 Sep 3 14:31:19 pserver102 kernel: [534312.104960] FS: 00007f3722277700(0000) GS:ffff880807d00000(0000) knlGS:0000000000000000 Sep 3 14:31:19 pserver102 kernel: [534312.105158] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b Sep 3 14:31:19 pserver102 kernel: [534312.105263] CR2: 0000000000000058 CR3: 0000002003c15000 CR4: 00000000000407e0 Sep 3 14:31:19 pserver102 kernel: [534312.105456] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 Sep 3 14:31:19 pserver102 kernel: [534312.105654] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Sep 3 14:31:19 pserver102 kernel: [534312.105854] Process md2_raid1 (pid: 46599, threadinfo ffff881fbc196000, task ffff881fc44ccaf0) Sep 3 14:31:19 pserver102 kernel: [534312.106050] Stack: Sep 3 14:31:19 pserver102 kernel: [534312.106148] 00000000001ad300 0000000000000001 ffff880800f11800 ffffffffa02c8df3 Sep 3 14:31:19 pserver102 kernel: [534312.106351] ffff881fe461ef90 ffff881f00000020 0000100000000009 ffff880800f11800 Sep 3 14:31:19 pserver102 kernel: [534312.106558] ffff88180324e000 ffff88180324e000 ffff8818ffffffff ffff883ffa7c5b50 Sep 3 14:31:19 pserver102 kernel: [534312.106774] Call Trace: Sep 3 14:31:19 pserver102 kernel: [534312.106876] [] ? md_raid1_congested+0x1ab3/0x5560 [raid1] Sep 3 14:31:19 pserver102 kernel: [534312.106989] [] ? generic_make_request+0xaf/0xe0 Sep 3 14:31:19 pserver102 kernel: [534312.107101] [] ? md_raid1_congested+0x20fc/0x5560 [raid1] Sep 3 14:31:19 pserver102 kernel: [534312.107213] [] ? __schedule+0x2eb/0x750 Sep 3 14:31:19 pserver102 kernel: [534312.107320] [] ? lock_timer_base+0x33/0x70 Sep 3 14:31:19 pserver102 kernel: [534312.107429] [] ? try_to_del_timer_sync+0x7c/0xd0 Sep 3 14:31:19 pserver102 kernel: [534312.107538] [] ? lock_timer_base+0x70/0x70 Sep 3 14:31:19 pserver102 kernel: [534312.107652] [] ? md_rdev_init+0x23f/0x290 [md_mod] Sep 3 14:31:19 pserver102 kernel: [534312.107765] [] ? wake_up_bit+0x40/0x40 Sep 3 14:31:19 pserver102 kernel: [534312.107876] [] ? md_rdev_init+0x120/0x290 [md_mod] Sep 3 14:31:19 pserver102 kernel: [534312.107986] [] ? md_rdev_init+0x120/0x290 [md_mod] Sep 3 14:31:19 pserver102 kernel: [534312.108096] [] ? kthread+0x9e/0xb0 Sep 3 14:31:19 pserver102 kernel: [534312.108203] [] ? kernel_thread_helper+0x4/0x10 Sep 3 14:31:19 pserver102 kernel: [534312.108310] [] ? kthread_freezable_should_stop+0x60/0x60 Sep 3 14:31:19 pserver102 kernel: [534312.108424] [] ? gs_change+0x13/0x13 Sep 3 14:31:19 pserver102 kernel: [534312.108530] Code: 01 00 00 e8 5b 95 ff ff 48 8b 7b 18 48 89 de e8 bf 97 ff ff e9 88 fe ff ff 66 2e 0 f 1f 84 00 00 00 00 00 53 48 89 fb 48 83 ec 10 <48> 03 77 58 48 8d bf 30 01 00 00 e8 28 9d ff ff 85 c0 75 0c 48