[bug report] task hang while testing xfstests generic/323

[Jiufei Xue <jiufei.xue@linux.alibaba.com>]

Hi,

when I tested xfstests/generic/323 with NFSv4.1 and v4.2, the task
changed to zombie occasionally while a thread is hanging with the
following stack:

[<0>] rpc_wait_bit_killable+0x1e/0xa0 [sunrpc]
[<0>] nfs4_do_close+0x21b/0x2c0 [nfsv4]
[<0>] __put_nfs_open_context+0xa2/0x110 [nfs]
[<0>] nfs_file_release+0x35/0x50 [nfs]
[<0>] __fput+0xa2/0x1c0
[<0>] task_work_run+0x82/0xa0
[<0>] do_exit+0x2ac/0xc20
[<0>] do_group_exit+0x39/0xa0
[<0>] get_signal+0x1ce/0x5d0
[<0>] do_signal+0x36/0x620
[<0>] exit_to_usermode_loop+0x5e/0xc2
[<0>] do_syscall_64+0x16c/0x190
[<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[<0>] 0xffffffffffffffff

Since commit 12f275cdd163(NFSv4: Retry CLOSE and DELEGRETURN on
NFS4ERR_OLD_STATEID), the client will retry to close the file when
stateid generation number in client is lower than server. 

The original intention of this commit is retrying the operation while
racing with an OPEN. However, in this case the stateid generation remains
mismatch forever.

Any suggestions?

Thanks,
Jiufei