Issue

Multiple nodes in a cluster are panicking with this message:

<1>BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
<1>IP: [<ffffffff814fed21>] mutex_lock+0x21/0x50
<4>PGD 0 
<4>Oops: 0002 [#1] SMP 
<4>last sysfs file: /sys/devices/pci0000:7f/0000:7f:13.6/irq
<4>CPU 3 
<4>Modules linked in: xfs fuse ipmi_si mptctl mptbase dell_rbu nfsd nfs_acl auth_rpcgss exportfs lockd sunrpc dlm configfs ipmi_devintf ipmi_msghandler rdma_ucm(U) ib_ucm(U) rdma_cm(U) iw_cm(U) ib_addr(U) ib_ipoib(U) ib_cm(U) ib_sa(U) ipv6 ib_uverbs(U) ib_umad(U) iw_nes(U) libcrc32c iw_cxgb3(U) cxgb3(U) ib_qib(U) dca mlx4_ib(U) ib_mthca(U) ib_mad(U) ib_core(U) power_meter sg mlx4_en(U) mlx4_core(U) shpchp tg3 dcdbas microcode sb_edac edac_core iTCO_wdt iTCO_vendor_support ext4 mbcache jbd2 dm_round_robin sr_mod cdrom sd_mod crc_t10dif mpt2sas scsi_transport_sas raid_class ahci wmi megaraid_sas dm_multipath dm_mirror dm_region_hash dm_log dm_mod scsi_dh_rdac [last unloaded: ipmi_si]
<4>
<4>Pid: 7216, comm: xfssyncd/dm-8 Not tainted 2.6.32-279.el6.x86_64 #1 Dell Inc. PowerEdge R620/0PXXHP
<4>RIP: 0010:[<ffffffff814fed21>]  [<ffffffff814fed21>] mutex_lock+0x21/0x50
<4>RSP: 0018:ffff880fe38ebdd0  EFLAGS: 00010246
<4>RAX: 0000000000000000 RBX: 0000000000000020 RCX: 0000000000000017
<4>RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000020
<4>RBP: ffff880fe38ebde0 R08: 0000000000000000 R09: ffff881fc15818c8
<4>R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002
<4>R13: 0000000000000010 R14: 0000000000000000 R15: 0000000000000020
<4>FS:  0000000000000000(0000) GS:ffff881078820000(0000) knlGS:0000000000000000
<4>CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
<4>CR2: 0000000000000020 CR3: 0000000001a85000 CR4: 00000000000406e0
<4>DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
<4>DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
<4>Process xfssyncd/dm-8 (pid: 7216, threadinfo ffff880fe38ea000, task ffff880fbaafcae0)
<4>Stack:
<4> ffff882019570800 0000000000000002 ffff880fe38ebe40 ffffffffa05c7c09
<4><d> ffffffffffffff10 0000000019570800 ffff882000000002 ffff882019570800
<4><d> ffff882019570bb0 ffff882019570800 ffff882019570ba0 ffff880fe38ebea0
<4>Call Trace:
<4> [<ffffffffa05c7c09>] xfs_qm_sync+0x59/0x1a0 [xfs]
<4> [<ffffffffa062a7f8>] xfs_sync_worker+0x48/0x90 [xfs]
<4> [<ffffffffa062a71e>] xfssyncd+0x17e/0x210 [xfs]
<4> [<ffffffffa062a5a0>] ? xfssyncd+0x0/0x210 [xfs]
<4> [<ffffffff81091d66>] kthread+0x96/0xa0
<4> [<ffffffff8100c14a>] child_rip+0xa/0x20
<4> [<ffffffff81091cd0>] ? kthread+0x0/0xa0
<4> [<ffffffff8100c140>] ? child_rip+0x0/0x20
<4>Code: ff ff 85 c0 75 ed eb d6 66 90 55 48 89 e5 48 83 ec 10 48 89 1c 24 4c 89 64 24 08 0f 1f 44 00 00 48 89 fb e8 a2 f4 ff ff 48 89 df <f0> ff 0f 79 05 e8 25 00 00 00 65 48 8b 04 25 c8 cb 00 00 48 2d 
<1>RIP  [<ffffffff814fed21>] mutex_lock+0x21/0x50
<4> RSP <ffff880fe38ebdd0>
<4>CR2: 0000000000000020