Panic due to race condition between iput() and invalidate_inodes(), kernel BUG at fs/inode.c:1254

Issue

• A system panic occurred on the customer's system. This panic was related to EMC PowerPath driver because it was related to the gendisk structure for the EMCPowerPath device /dev/emcpowerb.
• The panic log was as follows.

 kernel BUG at fs/inode.c:1254!
 invalid opcode: 0000 [#1] SMP 
 last sysfs file: /sys/devices/virtual/block/emcpowerh/queue/rotational
 CPU 1 
 Modules linked in: fuse mptctl mptbase nfsd lockd nfs_acl auth_rpcgss sunrpc exportfs autofs4 smbus(U) ipmi_devintf cpufreq_ondemand acpi_cpufreq freq_table mperf bonding 8021q garp stp llc ipv6 emcpvlumd(P)(U) emcpxcrypt(P)(U) emcpdm(P)(U) emcpgpx(P)(U) emcpmpx(P)(U) emcp(P)(U) uinput iTCO_wdt iTCO_vendor_support microcode i2c_i801 lpc_ich mfd_core acpi_pad power_meter sg igb dca i2c_algo_bit i2c_core ptp pps_core ext4 jbd2 mbcache sr_mod cdrom sd_mod crc_t10dif ahci wmi qla2xxx scsi_transport_fc scsi_tgt megaraid_sas dm_mirror dm_region_hash dm_log dm_mod [last unloaded: emcpioc]

 Pid: 29320, comm: XXXXXXXX Tainted: P           ---------------    2.6.32-431.el6.x86_64 #1
 RIP: 0010:[<ffffffff811a63bf>]  [<ffffffff811a63bf>] generic_delete_inode+0x1bf/0x1d0
 RSP: 0018:ffff880429d9be08  EFLAGS: 00010287
 RAX: ffff8800280459b8 RBX: ffff880245d8eca8 RCX: 0000000000000034
 RDX: 0000000000000007 RSI: ffff880245d8eec0 RDI: ffff8800280459b0
 RBP: ffff880429d9be28 R08: 8038000000000000 R09: fd9c27a2b61fb007
 R10: 0000000000000001 R11: ffff8800262af498 R12: ffffffff81fcf800
 R13: ffffffffa013cef0 R14: 00000000ffffff9c R15: 0000000000000000
 FS:  0000000000000000(0000) GS:ffff880028280000(0063) knlGS:00000000560d0e00
 CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
 CR2: 00000000017ff1a8 CR3: 0000000322b60000 CR4: 00000000001407e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
 Process XXXXXXXX (pid: 29320, threadinfo ffff880429d9a000, task ffff88045500b500)
 Stack:
  ffff880429d9be38 ffff880245d8eca8 0000000000000000 00000000fffe2658
 <d> ffff880429d9be48 ffffffff811a6435 ffff8803a7b01088 ffff880245d8eca8
 <d> ffff880429d9be68 ffffffff811a5282 ffff880429d9be98 ffff880429d9be98
 Call Trace:
  [<ffffffff811a6435>] generic_drop_inode+0x65/0x80
  [<ffffffff811a5282>] iput+0x62/0x70
  [<ffffffff8119a769>] do_unlinkat+0x1a9/0x260
  [<ffffffff810e2067>] ? audit_syscall_entry+0x1d7/0x200
  [<ffffffff8119a836>] sys_unlink+0x16/0x20
  [<ffffffff81050c20>] sysenter_dispatch+0x7/0x2e
 Code: ff ff e9 43 ff ff ff 0f 0b 0f 1f 00 eb fb be ce 04 00 00 48 c7 c7 89 65 7c 81 e8 ad ba ec ff 48 8b 83 18 02 00 00 e9 a6 fe ff ff <0f> 0b eb fe 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 55 48 89 e5 
 RIP  [<ffffffff811a63bf>]
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• A file data loss occurred when user wrote the file on the PowerPath device