Issue

• Crash in dm-thin due to general protection fault from null pointer access

• Backtrace of crash:

PID: 37793  TASK: ffff880db793dc00  CPU: 45  COMMAND: "kworker/u288:1"
 #0 [ffff8832650c3a18] machine_kexec at ffffffff81051beb
 #1 [ffff8832650c3a78] crash_kexec at ffffffff810f2742
 #2 [ffff8832650c3b48] oops_end at ffffffff8163ea08
 #3 [ffff8832650c3b70] die at ffffffff8101859b
 #4 [ffff8832650c3ba0] do_general_protection at ffffffff8163e2fe
 #5 [ffff8832650c3bd0] general_protection at ffffffff8163dba8
    [exception RIP: mutex_lock+0x15]
    RIP: ffffffff81639355  RSP: ffff8832650c3c88  RFLAGS: 00010246
    RAX: 0000000000000000  RBX: 7261765f61766f6e  RCX: ffff8832650c3fd8
    RDX: 0000000000000000  RSI: ffff883fcb82dcc0  RDI: 7261765f61766f6e
    RBP: ffff8832650c3c90   R8: ffff881fa164dca0   R9: df81028c2f04dc98
    R10: df81028c2f04dc98  R11: 0000000000000001  R12: ffff883fcb82dcc0
    R13: ffff8832650c3cb0  R14: 7261765f61766f6e  R15: 0000000000000001
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
 #6 [ffff8832650c3c98] dm_bufio_prefetch at ffffffffa081f7c6 [dm_bufio]
 #7 [ffff8832650c3d30] dm_bm_prefetch at ffffffffa0827d66 [dm_persistent_data]
 #8 [ffff8832650c3d40] dm_tm_issue_prefetches at ffffffffa082abcb [dm_persistent_data]
 #9 [ffff8832650c3d68] dm_pool_issue_prefetches at ffffffffa086a4d2 [dm_thin_pool]
#10 [ffff8832650c3d78] do_worker at ffffffffa0866e50 [dm_thin_pool]
#11 [ffff8832650c3e20] process_one_work at ffffffff8109d5db
#12 [ffff8832650c3e68] worker_thread at ffffffff8109e3ab
#13 [ffff8832650c3ec8] kthread at ffffffff810a5acf
#14 [ffff8832650c3f50] ret_from_fork at ffffffff816460d8

• Exception:

[4168075.566163] general protection fault: 0000 [#1] SMP 
[4168075.629325] Modules linked in: dell_rbu vhost_net vhost macvtap macvlan tun vfat fat usb_storage xt_set ip_set_hash_net ip_set nfnetlink mpt3sas mptctl mptbase ip6table_raw nf_conntrack_ipv6 nf_defrag_ipv6 xt_CT iptable_nat nf_nat_ipv4 nf_nat iptable_mangle xt_mac nf_conntrack_ipv4 nf_defrag_ipv4 xt_comment xt_physdev xt_multiport xt_conntrack veth bridge iptable_raw ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter dm_thin_pool dm_persistent_data dm_bio_prison dm_bufio dm_mod binfmt_misc iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi 8021q garp stp mrp llc rdma_ucm(OE) ib_ucm(OE) rdma_cm(OE) iw_cm(OE) ib_ipoib(OE) ib_cm(OE) ib_uverbs(OE) ib_umad(OE) mlx5_ib(OE) mlx5_core(OE) mlx4_en(OE) mlx4_ib(OE) ib_sa(OE) ib_mad(OE) ib_core(OE) ib_addr(OE) ib_netlink(OE) mlx4_core(OE) mlx_compat(OE)
[4168076.531768]  vport_vxlan vxlan ip6_udp_tunnel udp_tunnel openvswitch nls_utf8 isofs iTCO_wdt iTCO_vendor_support dcdbas intel_powerclamp coretemp intel_rapl kvm_intel kvm crc32_pclmul ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd pcspkr ipmi_devintf sg sb_edac edac_core mei_me mei lpc_ich mfd_core shpchp ipmi_si ipmi_msghandler acpi_power_meter nf_conntrack nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables xfs libcrc32c sd_mod crc_t10dif crct10dif_generic mgag200 syscopyarea sysfillrect sysimgblt i2c_algo_bit drm_kms_helper ixgbe ttm crct10dif_pclmul crct10dif_common crc32c_intel dca ahci mdio drm libahci ptp pps_core mpt2sas libata i2c_core raid_class scsi_transport_sas wmi [last unloaded: dell_rbu]
[4168077.346374] CPU: 45 PID: 37793 Comm: kworker/u288:1 Tainted: G           OE  ------------   3.10.0-327.18.2.el7.x86_64 #1
[4168077.487131] Hardware name: Dell Inc. PowerEdge C6320/04FNTC, BIOS 1.1.3 09/18/2015
[4168077.584127] Workqueue: dm-thin do_worker [dm_thin_pool]
[4168077.659325] task: ffff880db793dc00 ti: ffff8832650c0000 task.ti: ffff8832650c0000

• Superblock read error prior to crash:

[4167972.247891] device-mapper: thin: 253:5: metadata operation 'dm_pool_commit_metadata' failed: error = -5
[4167972.247893] device-mapper: thin: 253:5: aborting current metadata transaction
...
[4167972.248404] device-mapper: thin: 253:5: failed to abort metadata transaction
[4167972.248407] device-mapper: thin: 253:5: switching pool to failure mode
[4167972.248410] device-mapper: thin metadata: couldn't read superblock
[4167972.248410] device-mapper: thin: 253:5: failed to set 'needs_check' flag in metadata
[4167972.248414] device-mapper: thin: 253:5: dm_pool_get_metadata_transaction_id returned -22