features/quota: Make dht_statfs_cbk more fool proof from quota_deem_statfs

Problem:
The function depends on the fact that if quota-deem-statfs option is enabled,
all of the subvolumes send their xdata with quota-deem-statfs flag ON. But,
this may not be true in case of errors in some of the subvolumes.

There is a decision/policy made which assumes quota-deem-statfs to be ON if at
least ONE of the subvolumes sends the flag ON. By this, df reports quota
modified statfs values if *at least ONE* of the bricks sends the
quota-deem-statfs flag ON. This can be visualized with the below "Transition
Diagram/State Machine".

        Event: Each Quota deem statfs status from the individual bricks
        Action: Decision taken on the calculation of the statvfs received
        State: Whether quota deem statfs is ON or OFF (0: OFF, 1: ON)
        Input: Event from individual bricks

              ___                  ___
             /   \   OFF*         /   \  (OFF|ON)*
            |     |              |     |
             \   /        ON      \   /
        -----> 0  ----------------> 1

The below Transition Function depicts the relation between the statfs
calculation based on the events received.

         State          Event          action
        -------------------------------------
          OFF            OFF            OFF
          OFF            ON            REPLACE
          ON             OFF           NEGLECT
          ON             ON            COMPARE

Change-Id: I0e8fb7d3945a3ca3dde0bb99de6cd397e27a3162
BUG: 1048786
Signed-off-by: Varun Shastry <vshastry@redhat.com>
Reviewed-on: http://review.gluster.org/6652
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
Tested-by: Raghavendra G <rgowdapp@redhat.com>

0 files changed, 0 insertions, 0 deletions