MRP-999: a tiny optimization and code cleanup

1) remove unnecessary multiplication in filter_do_bio
2) implement log2 with bitops in lprocfs_oh_tally_log2
3) convert devlock into rwlock for *rdonly*
4) clean up f_e_m_ext_inode_pages
5) optimize lprocfs counters in filter_preprw_read
6) cleanup oa checks in filter_preprw_read
7) remove meaningless assert for dr_pages filter_do_bio
8) scratchpad checks fixes
9) move oa updates from under spinlock in f_preprw_read

Change-Id: I91ed4a971c87f6849b82cc6e3baba5415a984e01
Reviewed-on: http://morpheus.xyus.xyratex.com:8443/gerrit/393
Tested-by: Jenkins
Reviewed-by: Alexander Boyko <Alexander_Boyko@xyratex.com>
Reviewed-by: Alexander Zarochentsev <alexander_zarochentsev@xyratex.com>
Tested-by: Alexander Lezhoev <Alexander_Lezhoev@xyratex.com>
Reviewed-by: Vitaly Fertman <Vitaly_Fertman@xyratex.com>
MRP-1027 llite: speedup in unlink/rmdir

Assume dchild argument is fully initialized in ->unlink and
->rmdir callbacks, so additional lookup for ELC is not needed.

Change-Id: Id6b1abac21d9b3538ab8e01dd49031e79fe8e8bb
Reviewed-on: http://morpheus.xyus.xyratex.com:8443/gerrit/426
Tested-by: Jenkins
Reviewed-by: Alexander Boyko <Alexander_Boyko@xyratex.com>
Tested-by: Alexander Lezhoev <Alexander_Lezhoev@xyratex.com>
Reviewed-by: Vitaly Fertman <Vitaly_Fertman@xyratex.com>
MRP-1040 quota: a fix for a lost qonoff sem release

Release mds_qonoff_sem on error in dqacq_adjust_qunit_sz().

Change-Id: I996a5f540597aa27eea03848e641757881772221
Reviewed-on: http://morpheus.xyus.xyratex.com:8443/gerrit/436
Reviewed-by: Alexander Boyko <Alexander_Boyko@xyratex.com>
Reviewed-by: Artem Blagodarenko <Artem_Blagodarenko@xyratex.com>
Tested-by: Jenkins
Tested-by: Alexander Lezhoev <Alexander_Lezhoev@xyratex.com>
Reviewed-by: Vitaly Fertman <Vitaly_Fertman@xyratex.com>