staging/lustre/llite: deadlock taking lli_trunc_sem during file write

File write before io loop will take lli_trun_sem read semaphore to
protect osc_extent, while after generic_file_aio_write() done, it
could possible need to kill suid or sgid, which will call
ll_setattr_raw() to change the inode's attribute, and it does not
involve size.

So the ll_truc_sem write semaphore should be constrained
around ll_setattr_ost() to not come across the lli_trunc_sem read
semaphore get from the normal file write path.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Reviewed-on: http://review.whamcloud.com/9267
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4627


Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>