VMAX driver - Incorrect stats reporting

There is an issue in the way free_capacity_gb is being calculated for
the VMAX driver - it is using 'total_allocated_capacity' instead of
calculating using 'total_used_cap', or taking 'fba_free_capacity'. There
is also excess queries being made (and logs being produced), as the
capacities are being requested for each pool. This is unnecessary since
WLP support was removed - the capacities are reported at an SRP level
and so will be the same for each service level/ workload combination.
This patch rectifies these issues.

Change-Id: Icdafd47865e3cf1e5b687f39f15b8ebfccbf67a3
Closes-Bug: 1731930

cinder/tests/unit/volume/drivers/dell_emc/vmax/test_vmax.py

@@ -507,9 +507,10 @@ class VMAXCommonData(object):
     srp_details = {"srpSloDemandId": ["Bronze", "Diamond", "Gold",
                                       "None", "Optimized", "Silver"],
                    "srpId": srp,
-                   "total_allocated_cap_gb": 5244.7,
+                   "total_used_cap_gb": 5244.7,
                    "total_usable_cap_gb": 20514.4,
                    "total_subscribed_cap_gb": 84970.1,
+                   "fba_used_capacity": 5244.7,
                    "reserved_cap_percent": 10}
 
     volume_details = [{"cap_gb": 2,
@@ -2994,7 +2995,7 @@ class VMAXProvisionTest(test.TestCase):
         array_info = self.common.pool_info['arrays_info'][0]
         ref_stats = (self.data.srp_details['total_usable_cap_gb'],
                      float(self.data.srp_details['total_usable_cap_gb']
-                           - self.data.srp_details['total_allocated_cap_gb']),
+                           - self.data.srp_details['total_used_cap_gb']),
                      self.data.srp_details['total_subscribed_cap_gb'],
                      self.data.srp_details['reserved_cap_percent'])
         stats = self.provision.get_srp_pool_stats(array, array_info)

cinder/volume/drivers/dell_emc/vmax/common.py

@@ -817,6 +817,9 @@ class VMAXCommon(object):
                 (location_info, total_capacity_gb, free_capacity_gb,
                  provisioned_capacity_gb,
                  array_reserve_percent) = self._update_srp_stats(array_info)
+                arrays[array_info['SerialNumber']] = (
+                    [total_capacity_gb, free_capacity_gb,
+                     provisioned_capacity_gb, array_reserve_percent])
             else:
                 already_queried = True
             pool_name = ("%(slo)s+%(workload)s+%(srpName)s+%(array)s"

cinder/volume/drivers/dell_emc/vmax/provision.py

@@ -294,7 +294,6 @@ class VMAXProvision(object):
         """
         total_capacity_gb = 0
         remaining_capacity_gb = 0
-        allocated_capacity_gb = None
         subscribed_capacity_gb = 0
         array_reserve_percent = 0
         srp = array_info['srpName']
@@ -310,19 +309,17 @@ class VMAXProvision(object):
             return 0, 0, 0, 0, False
         try:
             total_capacity_gb = srp_details['total_usable_cap_gb']
-            allocated_capacity_gb = srp_details['total_allocated_cap_gb']
+            try:
+                used_capacity_gb = srp_details['total_used_cap_gb']
+                remaining_capacity_gb = float(
+                    total_capacity_gb - used_capacity_gb)
+            except KeyError:
+                remaining_capacity_gb = srp_details['fba_free_capacity']
             subscribed_capacity_gb = srp_details['total_subscribed_cap_gb']
-            remaining_capacity_gb = float(
-                total_capacity_gb - allocated_capacity_gb)
             array_reserve_percent = srp_details['reserved_cap_percent']
         except KeyError:
             pass
 
-        LOG.debug(
-            "Remaining capacity %(remaining_capacity_gb)s "
-            "GBs is determined from SRP capacity ",
-            {'remaining_capacity_gb': remaining_capacity_gb})
-
         return (total_capacity_gb, remaining_capacity_gb,
                 subscribed_capacity_gb, array_reserve_percent)