dur thread sometimes falls back to a writelock, in that case don't tr…

…y to get writelock if fsync + locked

src/mongo/db/dur.cpp

@@ -72,6 +72,8 @@ using namespace mongoutils;
 
 namespace mongo {
 
+    extern bool lockedForWriting;
+
     namespace dur {
 
         void PREPLOGBUFFER(JSectHeader& outParm);
@@ -701,6 +703,11 @@ namespace mongo {
                 }
             }
 
+            if ( lockedForWriting ) {
+                warning() << "group commit delayed beacuse of fsync + lock" << endl;
+                return;
+            }
+
             // starvation on read locks could occur.  so if read lock acquisition is slow, try to get a
             // write lock instead.  otherwise journaling could be delayed too long (too much data will 
             // not accumulate though, as commitIfNeeded logic will have executed in the meantime if there