RHEL5: panic in diskstats_show due to block device delete

Issue

• Crash in diskstats_show

Unable to handle kernel NULL pointer dereference at 0000000000000030 RIP: 
 [<ffffffff8014f56f>] diskstats_show+0x20e/0x723
PGD 11ea8fd067 PUD 11e303c067 PMD 0 
Oops: 0000 [1] SMP 
last sysfs file: /devices/pci0000:00/0000:00:1c.2/0000:04:00.1/irq
CPU 22 
Modules linked in: nfs nfs_acl tcp_diag inet_diag mptctl mptbase vxodm(PFU) vxgms(PU) vxglm(PU) vxfen(PU) gab(PU) llt(PU) autofs4 dmpaa(PU) vxspec(PFU) vxio(PFU) vxdmp(PU) lockd sunrpc bonding be2iscsi ib_iser rdma_cm ib_cm iw_cm ib_sa ib_mad ib_core ib_addr iscsi_tcp bnx2i cnic ipv6 xfrm_nalgo crypto_api uio cxgb3i libcxgbi cxgb3 8021q libiscsi_tcp libiscsi2 scsi_transport_iscsi2 scsi_transport_iscsi vxportal(PFU) fdd(PFU) vxfs(PU) exportfs emcpvlumd(PU) emcpxcrypt(PU) emcpdm(PU) emcpmpx(PU) emcpgpx(PU) emcp(PU) dm_multipath scsi_dh video backlight sbs power_meter hwmon i2c_ec i2c_core dell_wmi wmi button battery asus_acpi acpi_memhotplug ac parport_pc lp parport joydev sr_mod cdrom tpm_tis i7core_edac tpm shpchp hpilo serio_raw tpm_bios edac_mc sg bnx2 pcspkr dm_raid45 dm_message dm_region_hash dm_mem_cache dm_snapshot dm_zero dm_mirror dm_log dm_mod lpfc scsi_transport_fc usb_storage ata_piix libata cciss sd_mod scsi_mod ext3 jbd uhci_hcd ohci_hcd ehci_hcd
Pid: 15993, comm: cmaperfd Tainted: PF    --------------------    2.6.18-348.4.1.el5 #1
RIP: 0010:[<ffffffff8014f56f>]  [<ffffffff8014f56f>] diskstats_show+0x20e/0x723
RSP: 0018:ffff8111e326bda8  EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff8110808badc0 RCX: 0000000000000013
RDX: 0000000000000013 RSI: ffffffff804c1ae0 RDI: 0000000000000013
RBP: ffff811029b6ea00 R08: 0000000000000013 R09: 000000000000002d
R10: ffffffff804c1ae0 R11: 000000000000000a R12: 0000000000000190
R13: 00000000000003a4 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff81121fc566c0(0063) knlGS:00000000f7dcc6c0
CS:  0010 DS: 002b ES: 002b CR0: 000000008005003b
CR2: 0000000000000030 CR3: 00000011ec728000 CR4: 00000000000006a0
Process cmaperfd (pid: 15993, threadinfo ffff8111e326a000, task ffff8111f7da9080)
Stack:  ffff8110808badc0 00000000b63bbcf8 0000000ff2da96e0 0000000000000000
 0000000000000000 0000000000000000 0000000000000000 0000000000000000
 0000000000000000 0000000000000000 0000000000000000 0000000000000000
Call Trace:
 [<ffffffff8003fa49>] seq_read+0x1b8/0x28c
 [<ffffffff8010c264>] proc_reg_read+0x7e/0x99
 [<ffffffff8000b735>] vfs_read+0xcb/0x171
 [<ffffffff80011da7>] sys_read+0x45/0x6e
 [<ffffffff800614b5>] sysenter_do_call+0x1e/0x76

Code: 4c 03 70 30 e8 c1 88 00 00 89 c1 81 f9 fe 00 00 00 7e d3 48 
RIP  [<ffffffff8014f56f>] diskstats_show+0x20e/0x723
 RSP <ffff8111e326bda8>