b=16774

b=16774

cache the extent lock gotten before doing I/O in "ll_file_aio_read"
and "ll_file_aio_write", then "ll_read_page", "ll_read_ahead_page"
and "ll_writepage" will save much time spent on "ldlm_lock_match"
(in cache_add_extent) to find the appropriate extent lock

1, using current->journal_info to store the locks(struct ll_thread_data)
2, replace o_reget_short_lock, o_release_short_lock with o_get_lock in obd_ops

i=johann@sun.com
i=oleg.drokin@sun.com