System I/O hang with 'seos' module loaded

Issue

• System I/O hang with seos module loaded

• I/O hung and processes blocked. Oldest 5 processes:

crash> ps -m | grep UN | tail -n5
[  0 02:21:00.721] [UN]  PID: 19181  TASK: ffff881539e76040  CPU: 9   COMMAND: "oracle"
[  0 02:21:00.765] [UN]  PID: 29194  TASK: ffff8805882bd540  CPU: 16  COMMAND: "ora_lgwr_sisid0"
[  0 02:21:00.764] [UN]  PID: 19175  TASK: ffff885010ea6ae0  CPU: 1   COMMAND: "oracle"
[  0 02:21:00.863] [UN]  PID: 12922  TASK: ffff881284ea8080  CPU: 5   COMMAND: "ora_j000_sisid0"
[  0 02:21:00.870] [UN]  PID: 28918  TASK: ffff8801c253aae0  CPU: 11  COMMAND: "ora_dbw2_sisid0"

• Processes hung trying to get I/O flushed to disk:

crash> bt ffff8801c253aae0
PID: 28918  TASK: ffff8801c253aae0  CPU: 11  COMMAND: "ora_dbw2_sisid0"
 #0 [ffff8802941bba18] schedule at ffffffff81529970
 #1 [ffff8802941bbaf0] schedule_timeout at ffffffff8152a8c5
 #2 [ffff8802941bbba0] wait_for_common at ffffffff8152a543
 #3 [ffff8802941bbc30] wait_for_completion at ffffffff8152a65d
 #4 [ffff8802941bbc40] __blkdev_issue_flush at ffffffff8127531d
 #5 [ffff8802941bbca0] blkdev_issue_flush at ffffffff81275366
 #6 [ffff8802941bbcb0] ext4_sync_file at ffffffffa02a70a5 [ext4]
 #7 [ffff8802941bbd00] vfs_fsync_range at ffffffff811c07f1
 #8 [ffff8802941bbd50] generic_write_sync at ffffffff811c089b
 #9 [ffff8802941bbd60] generic_file_aio_write at ffffffff811269e6
#10 [ffff8802941bbdb0] ext4_file_write at ffffffffa02a6e08 [ext4]
#11 [ffff8802941bbdf0] aio_rw_vect_retry at ffffffff811daf44
#12 [ffff8802941bbe20] aio_run_iocb at ffffffff811dc904
#13 [ffff8802941bbe50] do_io_submit at ffffffff811ddd31
#14 [ffff8802941bbf70] sys_io_submit at ffffffff811de3d0
#15 [ffff8802941bbf80] system_call_fastpath at ffffffff8100b072
    RIP: 0000003fc8200667  RSP: 00007ffffd8e2678  RFLAGS: 00000206
    RAX: 00000000000000d1  RBX: ffffffff8100b072  RCX: 0000800000010000
    RDX: 00007ffffd8db2e0  RSI: 0000000000000001  RDI: 00007f415a719000
    RBP: 00007ffffd8dd310   R8: 00007ffffd8ddbb8   R9: 00000002ca1b82d0
    R10: 0000000000000001  R11: 0000000000000246  R12: ffffffff811de3d0
    R13: ffff8802941bbf78  R14: 0000000000000001  R15: 00007ffffd8ddbb8
    ORIG_RAX: 00000000000000d1  CS: 0033  SS: 002b