8257746: Regression introduced with JDK-8250984 - memory might be nul…

…l in some machines

Reviewed-by: sgehwolf
Backport-of: abc4300

src/java.base/linux/classes/jdk/internal/platform/cgroupv1/Metrics.java

@@ -474,14 +474,14 @@ public long getTcpMemoryUsage() {
     }
 
     public long getMemoryAndSwapFailCount() {
-        if (!memory.isSwapEnabled()) {
+        if (memory != null && !memory.isSwapEnabled()) {
             return getMemoryFailCount();
         }
         return SubSystem.getLongValue(memory, "memory.memsw.failcnt");
     }
 
     public long getMemoryAndSwapLimit() {
-        if (!memory.isSwapEnabled()) {
+        if (memory != null && !memory.isSwapEnabled()) {
             return getMemoryLimit();
         }
         long retval = SubSystem.getLongValue(memory, "memory.memsw.limit_in_bytes");
@@ -500,14 +500,14 @@ public long getMemoryAndSwapLimit() {
     }
 
     public long getMemoryAndSwapMaxUsage() {
-        if (!memory.isSwapEnabled()) {
+        if (memory != null && !memory.isSwapEnabled()) {
             return getMemoryMaxUsage();
         }
         return SubSystem.getLongValue(memory, "memory.memsw.max_usage_in_bytes");
     }
 
     public long getMemoryAndSwapUsage() {
-        if (!memory.isSwapEnabled()) {
+        if (memory != null && !memory.isSwapEnabled()) {
             return getMemoryUsage();
         }
         return SubSystem.getLongValue(memory, "memory.memsw.usage_in_bytes");