SERVER-44311 Change renameBetweenDBs to lock the source DB using MODE_IX

1 files changed, 4 insertions, 1 deletions

diff --git a/src/mongo/db/catalog/rename_collection.cpp b/src/mongo/db/catalog/rename_collection.cpp
index a4aef447476..0731fa184e4 100644
--- a/src/mongo/db/catalog/rename_collection.cpp
+++ b/src/mongo/db/catalog/rename_collection.cpp
@@ -449,7 +449,10 @@ Status renameBetweenDBs(OperationContext* opCtx,
     boost::optional<Lock::DBLock> sourceDbLock;
     boost::optional<Lock::CollectionLock> sourceCollLock;
     if (!opCtx->lockState()->isCollectionLockedForMode(source, MODE_S)) {
-        sourceDbLock.emplace(opCtx, source.db(), MODE_IS);
+        // Lock the DB using MODE_IX to ensure we have the global lock in that mode, as to prevent
+        // upgrade from MODE_IS to MODE_IX, which caused deadlock on systems not supporting Database
+        // locking and should be avoided in general.
+        sourceDbLock.emplace(opCtx, source.db(), MODE_IX);
         sourceCollLock.emplace(opCtx, source, MODE_S);
     }