diff --git a/doc/source/cli/nova-status.rst b/doc/source/cli/nova-status.rst
index f958c24663b7..54c14ef701ba 100644
--- a/doc/source/cli/nova-status.rst
+++ b/doc/source/cli/nova-status.rst
@@ -130,6 +130,10 @@ Upgrade
   * The "API Service Version" upgrade check was removed since the corresponding
     code for that check was removed in Stein.
 
+  **20.0.0 (Train)**
+
+  * Checks for the Placement API are modified to require version 1.31.
+
 See Also
 ========
 
diff --git a/nova/cmd/status.py b/nova/cmd/status.py
index b2a06a9bdb7d..4d93a650937a 100644
--- a/nova/cmd/status.py
+++ b/nova/cmd/status.py
@@ -44,11 +44,11 @@ from nova import version
 
 CONF = nova.conf.CONF
 
-# NOTE(efried): 1.30 is required by nova-compute to support resource provider
-# reshaping (inventory and allocation data migration).
+# NOTE(tetsuro): 1.31 is required by nova-scheduler to use in_tree
+# queryparam to get allocation candidates.
 # NOTE: If you bump this version, remember to update the history
 # section in the nova-status man page (doc/source/cli/nova-status).
-MIN_PLACEMENT_MICROVERSION = "1.30"
+MIN_PLACEMENT_MICROVERSION = "1.31"
 
 
 class UpgradeCommands(upgradecheck.UpgradeCommands):
diff --git a/nova/scheduler/client/report.py b/nova/scheduler/client/report.py
index e636caef61a0..bcd01caace5b 100644
--- a/nova/scheduler/client/report.py
+++ b/nova/scheduler/client/report.py
@@ -43,7 +43,7 @@ LOG = logging.getLogger(__name__)
 WARN_EVERY = 10
 RESHAPER_VERSION = '1.30'
 CONSUMER_GENERATION_VERSION = '1.28'
-NESTED_AC_VERSION = '1.29'
+INTREE_AC_VERSION = '1.31'
 ALLOW_RESERVED_EQUAL_TOTAL_INVENTORY_VERSION = '1.26'
 POST_RPS_RETURNS_PAYLOAD_API_VERSION = '1.20'
 AGGREGATE_GENERATION_VERSION = '1.19'
@@ -311,7 +311,7 @@ class SchedulerReportClient(object):
         """
         # Note that claim_resources() will use this version as well to
         # make allocations by `PUT /allocations/{consumer_uuid}`
-        version = NESTED_AC_VERSION
+        version = INTREE_AC_VERSION
         qparams = resources.to_querystring()
         url = "/allocation_candidates?%s" % qparams
         resp = self.get(url, version=version,
diff --git a/nova/scheduler/utils.py b/nova/scheduler/utils.py
index ae49f92351bf..caa14b51f4f2 100644
--- a/nova/scheduler/utils.py
+++ b/nova/scheduler/utils.py
@@ -268,6 +268,7 @@ class ResourceRequest(object):
             required_traits = request_group.required_traits
             forbidden_traits = request_group.forbidden_traits
             aggregates = request_group.aggregates
+            in_tree = request_group.in_tree
 
             resource_query = ",".join(
                 sorted("%s:%s" % (rc, amount)
@@ -289,6 +290,8 @@ class ResourceRequest(object):
                     aggs.append(('member_of%s' % suffix,
                                  'in:' + ','.join(sorted(agglist))))
                 qs_params.extend(sorted(aggs))
+            if in_tree:
+                qs_params.append(('in_tree%s' % suffix, in_tree))
             return qs_params
 
         if self._limit is not None:
diff --git a/nova/tests/unit/scheduler/client/test_report.py b/nova/tests/unit/scheduler/client/test_report.py
index 7d6f677f6abb..4a9dcd4869f6 100644
--- a/nova/tests/unit/scheduler/client/test_report.py
+++ b/nova/tests/unit/scheduler/client/test_report.py
@@ -2088,7 +2088,7 @@ class TestProviderOperations(SchedulerReportClientTestCase):
         expected_url = '/allocation_candidates?%s' % parse.urlencode(
             expected_query)
         self.ks_adap_mock.get.assert_called_once_with(
-            expected_url, microversion='1.29',
+            expected_url, microversion='1.31',
             headers={'X-Openstack-Request-Id': self.context.global_id})
         self.assertEqual(mock.sentinel.alloc_reqs, alloc_reqs)
         self.assertEqual(mock.sentinel.p_sums, p_sums)
@@ -2128,7 +2128,7 @@ class TestProviderOperations(SchedulerReportClientTestCase):
             expected_query)
         self.assertEqual(mock.sentinel.alloc_reqs, alloc_reqs)
         self.ks_adap_mock.get.assert_called_once_with(
-            expected_url, microversion='1.29',
+            expected_url, microversion='1.31',
             headers={'X-Openstack-Request-Id': self.context.global_id})
         self.assertEqual(mock.sentinel.p_sums, p_sums)
 
@@ -2150,7 +2150,7 @@ class TestProviderOperations(SchedulerReportClientTestCase):
         res = self.client.get_allocation_candidates(self.context, resources)
 
         self.ks_adap_mock.get.assert_called_once_with(
-            mock.ANY, microversion='1.29',
+            mock.ANY, microversion='1.31',
             headers={'X-Openstack-Request-Id': self.context.global_id})
         url = self.ks_adap_mock.get.call_args[0][0]
         split_url = parse.urlsplit(url)
diff --git a/nova/tests/unit/scheduler/test_utils.py b/nova/tests/unit/scheduler/test_utils.py
index 5bc3238ea191..3b22602d9e35 100644
--- a/nova/tests/unit/scheduler/test_utils.py
+++ b/nova/tests/unit/scheduler/test_utils.py
@@ -445,6 +445,7 @@ class TestUtils(test.NoDBTestCase):
                 self.context, fake_spec, self.mock_host_manager)
         self.assertResourceRequestsEqual(expected, resources)
         expected_querystring = (
+            'in_tree=12345678-1234-1234-1234-123456789012&'
             'limit=1000&resources=DISK_GB%3A15%2CMEMORY_MB%3A1024%2CVCPU%3A1')
         self.assertEqual(expected_querystring, resources.to_querystring())
         self.mock_host_manager.get_compute_nodes_by_host_or_node.\
@@ -477,6 +478,7 @@ class TestUtils(test.NoDBTestCase):
                 self.context, fake_spec, self.mock_host_manager)
         self.assertResourceRequestsEqual(expected, resources)
         expected_querystring = (
+            'in_tree=12345678-1234-1234-1234-123456789012&'
             'limit=1000&resources=DISK_GB%3A15%2CMEMORY_MB%3A1024%2CVCPU%3A1')
         self.assertEqual(expected_querystring, resources.to_querystring())
         self.mock_host_manager.get_compute_nodes_by_host_or_node.\
@@ -550,6 +552,7 @@ class TestUtils(test.NoDBTestCase):
                 self.context, fake_spec, self.mock_host_manager)
         self.assertResourceRequestsEqual(expected, resources)
         expected_querystring = (
+            'in_tree=12345678-1234-1234-1234-123456789012&'
             'limit=1000&resources=DISK_GB%3A15%2CMEMORY_MB%3A1024%2CVCPU%3A1')
         self.assertEqual(expected_querystring, resources.to_querystring())
         self.mock_host_manager.get_compute_nodes_by_host_or_node.\
diff --git a/releasenotes/notes/use-placement-in-tree-756cb20af66b08bd.yaml b/releasenotes/notes/use-placement-in-tree-756cb20af66b08bd.yaml
new file mode 100644
index 000000000000..c610a35a4454
--- /dev/null
+++ b/releasenotes/notes/use-placement-in-tree-756cb20af66b08bd.yaml
@@ -0,0 +1,14 @@
+---
+fixes:
+  - |
+    There had been `bug 1777591`_ that placement filters out the specified
+    target host when deploying an instance by the random limitation. In
+    previous releases the bug has been worked around by unlimiting the results
+    from the Placement service if the target host is specified. From this
+    release, the Nova scheduler uses more optimized path retrieving only the
+    target host information from placement. Note that it still uses the unlimit
+    workaround if a target host is specified without a specific node and
+    multiple nodes are found for the target host. This can happen in some of
+    the virt drivers such as the Ironic driver.
+
+    .. _bug 1777591: https://bugs.launchpad.net/nova/+bug/1777591