ramcloud-build-scripts/increment_fix.patch

diff --git a/src/MasterService.cc b/src/MasterService.cc
index 93cfb5d..38d250f 100644
--- a/src/MasterService.cc
+++ b/src/MasterService.cc
@@ -1750,25 +1750,38 @@ MasterService::increment(const WireFormat::Increment::Request* reqHdr,
     Status *status = &respHdr->common.status;
 
     Buffer value;
+    uint64_t version;
+    int64_t newValue;
     RejectRules rejectRules = reqHdr->rejectRules;
-    *status = objectManager.readObject(key, &value, &rejectRules, NULL);
-    if (*status != STATUS_OK)
-        return;
+    RejectRules updateRejectRules;
+    memset(&updateRejectRules, 0, sizeof(updateRejectRules));
 
-    if (value.getTotalLength() != sizeof(int64_t)) {
-        *status = STATUS_INVALID_OBJECT;
-        return;
-    }
+    do {
+        value.reset();
+        *status = objectManager.readObject(key, &value, &rejectRules, &version);
+        if (*status != STATUS_OK)
+            return;
+
+        if (value.getTotalLength() != sizeof(int64_t)) {
+            *status = STATUS_INVALID_OBJECT;
+            return;
+        }
+
+        const int64_t oldValue = *value.getOffset<int64_t>(0);
+        newValue = oldValue + reqHdr->incrementValue;
+
+        // Write the new value back
+        Buffer newValueBuffer;
+        newValueBuffer.append(&newValue, sizeof(int64_t));
 
-    const int64_t oldValue = *value.getOffset<int64_t>(0);
-    int64_t newValue = oldValue + reqHdr->incrementValue;
+        // reject rule to check atomic update
+        updateRejectRules.givenVersion = version;
+        updateRejectRules.versionNeGiven = true;
 
-    // Write the new value back
-    Buffer newValueBuffer;
-    newValueBuffer.append(&newValue, sizeof(int64_t));
+        *status = objectManager.writeObject(key, newValueBuffer,
+            &updateRejectRules, &respHdr->version);
+    } while (*status == STATUS_WRONG_VERSION);
 
-    *status = objectManager.writeObject(key, newValueBuffer,
-        &rejectRules, &respHdr->version);
     if (*status != STATUS_OK)
         return;
     objectManager.syncChanges();