RHEL 6 Resilient Storage cluster node panics in unlock_buffer

Issue

• Cluster nodes are repeatedly panicking with the following log:

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff811a96e9>] unlock_buffer+0x9/0x20
PGD 0 
Oops: 0002 [#1] SMP 
last sysfs file: /sys/devices/pci0000:00/0000:00:17.0/0000:13:00.0/irq
CPU 0 
Modules linked in: gfs2 dlm configfs sunrpc vsock(U) be2iscsi iscsi_boot_sysfs bnx2i cnic uio cxgb4i cxgb4 cxgb3i libcxgbi cxgb3 mdio ib_iser rdma_cm ib_cm iw_cm ib_sa ib_mad ib_core ib_addr ipv6 iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ppdev parport_pc parport vmware_balloon vmxnet3 vmci(U) i2c_piix4 i2c_core sg shpchp ext4 mbcache jbd2 sd_mod crc_t10dif sr_mod cdrom vmw_pvscsi pata_acpi ata_generic ata_piix dm_mirror dm_region_hash dm_log dm_mod [last unloaded: scsi_wait_scan]

Pid: 27358, comm: qmgr Not tainted 2.6.32-220.13.1.el6.x86_64 #1 VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform
RIP: 0010:[<ffffffff811a96e9>]  [<ffffffff811a96e9>] unlock_buffer+0x9/0x20
RSP: 0018:ffff880109d2ba78  EFLAGS: 00010296
RAX: ffff88010c36c668 RBX: ffff88010a1a37b0 RCX: ffff8800b9b12c48
RDX: 0000000000000000 RSI: ffff88010a1a37b0 RDI: 0000000000000000
RBP: ffff880109d2ba78 R08: 5010000000000000 R09: ff3837be4a130a02
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88010c36c668
R13: ffff88010c36c000 R14: ffff88010a1a3790 R15: ffff88003740a870
FS:  00007fb9cff477c0(0000) GS:ffff880028200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000000000000 CR3: 000000010a6fc000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process qmgr (pid: 27358, threadinfo ffff880109d2a000, task ffff88010a061580)
Stack:
 ffff880109d2baa8 ffffffffa04035bf ffff8800a9c86c28 ffff88010c36c000
<0> ffff880109d2bb28 0000000000000000 ffff880109d2bac8 ffffffffa04192da
<0> 0000000000000003 ffff880134985418 ffff880109d2bd38 ffffffffa040dc7e
Call Trace:
 [<ffffffffa04035bf>] buf_lo_add+0x6f/0x170 [gfs2]
 [<ffffffffa04192da>] gfs2_trans_add_bh+0x3a/0x60 [gfs2]
 [<ffffffffa040dc7e>] gfs2_rename+0x8ee/0x940 [gfs2]
 [<ffffffffa040d4ca>] ? gfs2_rename+0x13a/0x940 [gfs2]
 [<ffffffffa040d4e8>] ? gfs2_rename+0x158/0x940 [gfs2]
 [<ffffffffa040d50c>] ? gfs2_rename+0x17c/0x940 [gfs2]
 [<ffffffffa03fa51f>] ? gfs2_glock_add_to_lru+0x5f/0x90 [gfs2]
 [<ffffffffa03fc043>] ? gfs2_holder_uninit+0x23/0x40 [gfs2]
 [<ffffffffa0414ac0>] ? gfs2_rindex_hold+0x40/0xe0 [gfs2]
 [<ffffffffa040d46a>] ? gfs2_rename+0xda/0x940 [gfs2]
 [<ffffffff8118475b>] vfs_rename+0x3ab/0x440
 [<ffffffff81186630>] sys_renameat+0x230/0x260
 [<ffffffff8117b8f4>] ? cp_new_stat+0xe4/0x100
 [<ffffffff8117bc06>] ? sys_newlstat+0x36/0x50
 [<ffffffff8118667b>] sys_rename+0x1b/0x20
 [<ffffffff8100b0f2>] system_call_fastpath+0x16/0x1b
Code: 48 8b 47 48 48 85 c0 74 04 31 f6 ff d0 e8 a0 3f 34 00 31 c0 c9 c3 66 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 0f 1f 44 00 00 <f0> 80 27 fb be 02 00 00 00 e8 f9 74 ee ff c9 c3 0f 1f 80 00 00 
RIP  [<ffffffff811a96e9>] unlock_buffer+0x9/0x20
 RSP <ffff880109d2ba78>
CR2: 0000000000000000