[BUG] fs/dlm: A possible sleep-in-atomic bug in dlm_master_lookup

[Jia-Ju Bai]

According to fs/dlm/lock.c, the kernel may sleep under a spinlock,
and the function call path is:
dlm_master_lookup (acquire the spinlock)
  dlm_send_rcom_lookup_dump
    create_rcom
      dlm_lowcomms_get_buffer
        nodeid2con
          mutex_lock --> may sleep

This bug is found by my static analysis tool and my code review.

Thanks,
Jia-Ju Bai