sma: add bdev QoS helper functions

These helper functions can be used by any device manager that wants to
provide volume-level QoS support using bdev-based QoS mechanism.  A
device manager is responsible for making sure that a volume exists and
is attached to a given device, but the validity of the QoS parameters is
checked within the helper functions.

Signed-off-by: Konrad Sztyber <konrad.sztyber@intel.com>
Change-Id: I4d0efcf190a64b289b4cfbdf872f77e40a013d1f
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/14268
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: Karol Latecki <karol.latecki@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

python/spdk/sma/qos.py

@@ -0,0 +1,59 @@
+import grpc
+
+from spdk.rpc.client import JSONRPCException
+from .common import format_volume_id
+from .proto import sma_pb2
+
+
+LIMIT_UNDEFINED = (1 << 64) - 1
+
+
+class QosException(Exception):
+    def __init__(self, code, message):
+        self.code = code
+        self.message = message
+
+
+def set_volume_bdev_qos(client, params):
+    class BdevLimit:
+        def __init__(self, name, transform=lambda v: v):
+            self.name = name
+            self._transform = transform
+
+        def get_value(self, value):
+            return self._transform(value)
+
+    supported_limits = {
+            'rw_iops': BdevLimit('rw_ios_per_sec', lambda v: v * 1000),
+            'rd_bandwidth': BdevLimit('r_mbytes_per_sec'),
+            'wr_bandwidth': BdevLimit('w_mbytes_per_sec'),
+            'rw_bandwidth': BdevLimit('rw_mbytes_per_sec')
+    }
+    # Check that none of the unsupported fields aren't set either
+    if params.HasField('maximum'):
+        for field, value in params.maximum.ListFields():
+            if field.name in supported_limits.keys():
+                continue
+            if value != 0 and value != LIMIT_UNDEFINED:
+                raise QosException(grpc.StatusCode.INVALID_ARGUMENT,
+                                   f'Unsupported QoS limit: maximum.{field.name}')
+    try:
+        rpc_params = {'name': format_volume_id(params.volume_id)}
+        for name, limit in supported_limits.items():
+            value = getattr(params.maximum, name)
+            if value != LIMIT_UNDEFINED:
+                rpc_params[limit.name] = limit.get_value(value)
+        client.call('bdev_set_qos_limit', rpc_params)
+    except JSONRPCException:
+        raise QosException(grpc.StatusCode.INTERNAL, 'Failed to set QoS')
+
+
+def get_bdev_qos_capabilities():
+    return sma_pb2.GetQosCapabilitiesResponse(
+            max_volume_caps=sma_pb2.GetQosCapabilitiesResponse.QosCapabilities(
+                rw_iops=True,
+                rw_bandwidth=True,
+                rd_bandwidth=True,
+                wr_bandwidth=True
+                ),
+            )