Allow to use _max qos option together with per_gb

With this patch it'll become possible to limit max performance of volume
even when qos is set per_gb. As a result operator will be able to set
min and max options, with per gb increment, until the max value.

Change-Id: I3c6c9e1c50100cfa56dcadf6445729484cdd616d

cinder/tests/unit/volume/test_connection.py

@@ -259,6 +259,7 @@ class VolumeConnectionTestCase(base.BaseVolumeTestCase):
                           'read_iops_sec_per_gb': 7700,
                           'total_iops_sec_per_gb_min': 900000,
                           'total_iops_sec_per_gb': 300000,
+                          'total_iops_sec_max': 15000000,
                           'read_bytes_sec_per_gb_min': 30,
                           'read_bytes_sec_per_gb': 10,
                           'write_bytes_sec_per_gb_min': 120,
@@ -326,6 +327,7 @@ class VolumeConnectionTestCase(base.BaseVolumeTestCase):
                           'read_iops_sec_per_gb': 7700,
                           'total_iops_sec_per_gb_min': 900000,
                           'total_iops_sec_per_gb': 300000,
+                          'total_iops_sec_max': 15000000,
                           'read_bytes_sec_per_gb_min': 30,
                           'read_bytes_sec_per_gb': 10,
                           'write_bytes_sec_per_gb_min': 120,
@@ -343,7 +345,7 @@ class VolumeConnectionTestCase(base.BaseVolumeTestCase):
             mock_get_target.return_value = None
             qos_specs_expected = {'write_iops_sec': 3000,
                                   'read_iops_sec': 770000,
-                                  'total_iops_sec': 30000000,
+                                  'total_iops_sec': 15000000,
                                   'read_bytes_sec': 1000,
                                   'write_bytes_sec': 4000,
                                   'total_bytes_sec': 104857600}

cinder/volume/manager.py

@@ -1619,10 +1619,13 @@ class VolumeManager(manager.CleanableManager,
                 for option in tune_opts:
                     option_per_gb = '%s_per_gb' % option
                     option_per_gb_min = '%s_per_gb_min' % option
+                    option_max = '%s_max' % option
                     if option_per_gb in specs:
                         minimum_value = int(specs.pop(option_per_gb_min, 0))
                         value = int(specs[option_per_gb]) * volume_size
-                        specs[option] = max(minimum_value, value)
+                        per_gb_value = max(minimum_value, value)
+                        max_value = int(specs.pop(option_max, per_gb_value))
+                        specs[option] = min(per_gb_value, max_value)
                         specs.pop(option_per_gb)
 
         qos_spec = dict(qos_specs=specs)

doc/source/admin/blockstorage-capacity-based-qos.rst

@@ -42,6 +42,10 @@ is very small and ends up with an unusable volume because of performance.
 * `write_bytes_sec_per_gb_min`
 * `total_bytes_sec_per_gb_min`
 
+Capacity based options might be used in conjunction with basic options,
+like `*_sec_max`, in order to set upper limits for volumes. This may be useful
+for large volumes, which may consume all storage performance.
+
 For example, in order to create a QoS with 30 IOPs total writes per GB and
 a throughput of 1MB per GB, you might use the Cinder client in the following
 way: