SERVER-43859: Take MODE_IX locks for collection creation.

Two concurrent storage transactions can now create collections with the same
collection name. These transactions will conflict at commit time; the first
committer will win and register their collection into the global catalog. The
losing transactions will bubble a WriteConflictException.

Top-level callers that should fail if the collection already existed must now
check and fail with a NamespaceExists error code. Previously, those callers
could rely on lower level code returning the NamespaceExists error.

Callers that were implicitly creating a collection may retry the operation,
using the now-registered collection.

These transaction-local collections (UncommittedCollections) are returned when
doing any CollectionCatalog::lookup* call.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/mongo/db/repair_database.cpp b/src/mongo/db/repair_database.cpp
index ced21031a10..533e0df0c6d 100644
--- a/src/mongo/db/repair_database.cpp
+++ b/src/mongo/db/repair_database.cpp
@@ -147,7 +147,7 @@ Status repairCollections(OperationContext* opCtx,
 
         log() << "Repairing collection " << nss;
 
-        auto collection = CollectionCatalog::get(opCtx).lookupCollectionByNamespace(nss);
+        auto collection = CollectionCatalog::get(opCtx).lookupCollectionByNamespace(opCtx, nss);
         Status status = engine->repairRecordStore(opCtx, collection->getCatalogId(), nss);
         if (!status.isOK())
             return status;
@@ -155,7 +155,7 @@ Status repairCollections(OperationContext* opCtx,
 
     for (const auto& nss : colls) {
         opCtx->checkForInterrupt();
-        auto collection = CollectionCatalog::get(opCtx).lookupCollectionByNamespace(nss);
+        auto collection = CollectionCatalog::get(opCtx).lookupCollectionByNamespace(opCtx, nss);
         auto swIndexNameObjs = getIndexNameObjs(opCtx, collection->getCatalogId());
         if (!swIndexNameObjs.isOK())
             return swIndexNameObjs.getStatus();