Fix a couple of bugs in db_stress fault injection (#6700)

Summary:
1. Fix a memory leak in FaultInjectionTestFS in the stack trace related
code
2. Check status of all MultiGet keys before deciding whether an error
was swallowed, instead of assuming an ok status for any key means an
undetected error
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6700

Test Plan: Run db_stress with asan and fault injection

Reviewed By: cheng-chang

Differential Revision: D21021498

Pulled By: anand1976

fbshipit-source-id: 489191efd1ab0fa834923a1e1d57253a7a315465

db_stress_tool/no_batched_ops_stress.cc

@@ -169,7 +169,7 @@ class NonBatchedOpsStressTest : public StressTest {
           // stack trace at the same time
           MutexLock l(thread->shared->GetMutex());
           fprintf(stderr, "Didn't get expected error from Get\n");
-          fprintf(stderr, "Callstack that injected the error\n");
+          fprintf(stderr, "Callstack that injected the fault\n");
           fault_fs_guard->PrintFaultBacktrace();
           std::terminate();
         }
@@ -290,24 +290,31 @@ class NonBatchedOpsStressTest : public StressTest {
 #endif
     }
 
-    for (const auto& s : statuses) {
-      if (s.ok()) {
 #ifndef NDEBUG
     if (fault_fs_guard && error_count && !SharedState::filter_read_error) {
+      int stat_nok = 0;
+      for (const auto& s : statuses) {
+        if (!s.ok() && !s.IsNotFound()) {
+          stat_nok++;
+        }
+      }
+
+      if (stat_nok < error_count) {
         // Grab mutex so multiple thread don't try to print the
         // stack trace at the same time
         MutexLock l(thread->shared->GetMutex());
         fprintf(stderr, "Didn't get expected error from MultiGet\n");
-          fprintf(stderr, "Callstack that injected the error\n");
+        fprintf(stderr, "Callstack that injected the fault\n");
         fault_fs_guard->PrintFaultBacktrace();
         std::terminate();
-        } else {
+      }
+    }
 #endif // NDEBUG
+
+    for (const auto& s : statuses) {
+      if (s.ok()) {
         // found case
         thread->stats.AddGets(1, 1);
-#ifndef NDEBUG
-        }
-#endif // NDEBUG
       } else if (s.IsNotFound()) {
         // not found case
         thread->stats.AddGets(1, 0);

test_util/fault_injection_test_fs.cc

@@ -473,6 +473,9 @@ IOStatus FaultInjectionTestFS::InjectError(ErrorOperation op,
 
   if (ctx->rand.OneIn(ctx->one_in)) {
     ctx->count++;
+    if (ctx->callstack) {
+      free(ctx->callstack);
+    }
     ctx->callstack = port::SaveStack(&ctx->frames);
     switch (op) {
       case kRead:
@@ -530,6 +533,7 @@ void FaultInjectionTestFS::PrintFaultBacktrace() {
     return;
   }
   port::PrintAndFreeStack(ctx->callstack, ctx->frames);
+  ctx->callstack = nullptr;
 #endif
 }
 

test_util/fault_injection_test_fs.h

@@ -366,7 +366,13 @@ class FaultInjectionTestFS : public FileSystemWrapper {
     explicit ErrorContext(uint32_t seed)
       : rand(seed),
         enable_error_injection(false),
+        callstack(nullptr),
     frames(0) {}
+    ~ErrorContext() {
+      if (callstack) {
+        free(callstack);
+      }
+    }
   };
 
   std::unique_ptr<ThreadLocalPtr> thread_local_error_;