--- a/make/test/JtregNativeHotspot.gmk	Tue Dec 12 14:14:06 2017 -0500
+++ b/make/test/JtregNativeHotspot.gmk	Tue Dec 12 19:06:19 2017 -0500
@@ -113,6 +113,7 @@
     BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libHandshakeTransitionTest := -lc
     BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libHasNoEntryPoint := -lc
     BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libReturnError := -lc
+    BUILD_HOTSPOT_JTREG_LIBRARIES_LDFLAGS_libTestCheckedEnsureLocalCapacity := -lc
 endif
 
 ifeq ($(OPENJDK_TARGET_OS), linux)

--- a/src/hotspot/share/prims/jniCheck.cpp	Tue Dec 12 14:14:06 2017 -0500
+++ b/src/hotspot/share/prims/jniCheck.cpp	Tue Dec 12 19:06:19 2017 -0500
@@ -826,7 +826,10 @@
     }
     jint result = UNCHECKED()->EnsureLocalCapacity(env, capacity);
     if (result == JNI_OK) {
-      add_planned_handle_capacity(thr->active_handles(), capacity);
+      // increase local ref capacity if needed
+      if ((size_t)capacity > thr->active_handles()->get_planned_capacity()) {
+        add_planned_handle_capacity(thr->active_handles(), capacity);
+      }
     }
     functionExit(thr);
     return result;

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/runtime/jni/checked/TestCheckedEnsureLocalCapacity.java	Tue Dec 12 19:06:19 2017 -0500
@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/* @test
+ * @bug 8193222
+ * @summary Check EnsureLocalCapacity doesn't shrink unexpectedly
+ * @library /test/lib
+ * @run main/othervm/native TestCheckedEnsureLocalCapacity launch
+ */
+import jdk.test.lib.process.ProcessTools;
+import jdk.test.lib.process.OutputAnalyzer;
+
+public class TestCheckedEnsureLocalCapacity {
+
+    static {
+        System.loadLibrary("TestCheckedEnsureLocalCapacity");
+    }
+
+    // Calls EnsureLocalCapacity(capacity) and then creates "copies" number
+    // of LocalRefs to "o".
+    // If capacity > copies no warning should ensue (with the bug fixed).
+    // If copies > capacity + warning-threshold then we still get a warning.
+    private static native void ensureCapacity(Object o, int capacity, int copies);
+
+    private static int[][] testArgs = {
+        { 60, 45 }, // good: capacity > copies
+        { 1, 45 }   // bad: copies >> capacity
+    };
+
+    private static final String EXCEED_WARNING =
+        "^WARNING: JNI local refs: \\d++, exceeds capacity:";
+
+    private static final String WARNING = "^WARNING: ";
+
+    public static void main(String[] args) throws Throwable {
+        if (args.length == 2) {
+            ensureCapacity(new Object(),
+                           Integer.parseInt(args[0]),
+                           Integer.parseInt(args[1]));
+            return;
+        }
+
+        // No warning
+        ProcessTools.executeTestJvm("-Xcheck:jni",
+                                    "TestCheckedEnsureLocalCapacity",
+                                    Integer.toString(testArgs[0][0]),
+                                    Integer.toString(testArgs[0][1])).
+            shouldHaveExitValue(0).
+            // check no capacity warning
+            stdoutShouldNotMatch(EXCEED_WARNING).
+            // check no other warning
+            stdoutShouldNotMatch(WARNING).
+            reportDiagnosticSummary();
+
+        // Warning
+        ProcessTools.executeTestJvm("-Xcheck:jni",
+                                    "TestCheckedEnsureLocalCapacity",
+                                    Integer.toString(testArgs[1][0]),
+                                    Integer.toString(testArgs[1][1])).
+            shouldHaveExitValue(0).
+            // check for capacity warning
+            stdoutShouldMatch(EXCEED_WARNING).
+            reportDiagnosticSummary();
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/runtime/jni/checked/libTestCheckedEnsureLocalCapacity.c	Tue Dec 12 19:06:19 2017 -0500
@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#include <jni.h>
+#include <stdio.h>
+
+void reduceLocalCapacity(JNIEnv* env) {
+    puts("reduceLocalCapacity: setting to 1");
+    (*env)->EnsureLocalCapacity(env,1);
+}
+
+JNIEXPORT void JNICALL
+Java_TestCheckedEnsureLocalCapacity_ensureCapacity(JNIEnv *env,
+                                                   jobject unused,
+                                                   jobject target,
+                                                   jint capacity,
+                                                   jint copies) {
+  int i;
+  printf("ensureCapacity: setting to %d\n", capacity);
+  (*env)->EnsureLocalCapacity(env, capacity); // set high
+  reduceLocalCapacity(env);     // sets low
+
+  printf("ensureCapacity: creating %d LocalRefs\n", copies);
+  for (i = 0; i < copies; i++) {
+    target = (*env)->NewLocalRef(env, target);
+  }
+
+  puts("ensureCapacity: done");
+}