RHEL6: NFS4 WRITE continuously sent and completing with NFS4ERR_BAD_STATEID (10025) with NetApp due to multiple filehandles for same file

Issue

• hung task timeout and/or panic, with the process triggering the panic doing a close on an NFS file, flushing pages, and waiting on page writeback to complete
• hung task backtrace similar to the following

INFO: task foo:4347 blocked for more than 720 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
foo         D 0000000000000012     0  4347    798 0x00000080
 ffff88101240fc78 0000000000000082 0000000000000000 ffff88020acfd840
 ffff88101240fd08 ffffffff8112dd37 ffff88101240fc58 0000000000000282
 ffff881012791098 ffff88101240ffd8 000000000000fb88 ffff881012791098
Call Trace:
 [<ffffffff8150e3e3>] io_schedule+0x73/0xc0
 [<ffffffff81119d3d>] sync_page+0x3d/0x50
 [<ffffffff8150ed9f>] __wait_on_bit+0x5f/0x90
 [<ffffffff81119f73>] wait_on_page_bit+0x73/0x80
 [<ffffffff8111a39b>] wait_on_page_writeback_range+0xfb/0x190
 [<ffffffff8111a568>] filemap_write_and_wait_range+0x78/0x90
 [<ffffffff811b1ace>] vfs_fsync_range+0x7e/0xe0
 [<ffffffff811b1b9d>] vfs_fsync+0x1d/0x20
 [<ffffffffa03a6670>] nfs_file_flush+0x70/0xa0 [nfs]
...

• just prior to the process going blocked, we sometimes see the following message:

nfs4_reclaim_open_state: unhandled error -10026. Zeroing state

• In addition, sometime prior to the problem, one or more bad sequence-id messages may be seen.

NFS: v4 server nfs-server  returned a bad sequence-id error!