SERVER-45760 Clarify the required lock modes for MultiIndexBlock::init() and MultiIndexBlock::commit()

2 files changed, 9 insertions, 2 deletions

diff --git a/src/mongo/db/catalog/multi_index_block.cpp b/src/mongo/db/catalog/multi_index_block.cpp
index 6ee21034efc..d1d9d146262 100644
--- a/src/mongo/db/catalog/multi_index_block.cpp
+++ b/src/mongo/db/catalog/multi_index_block.cpp
@@ -203,6 +203,9 @@ StatusWith<std::vector<BSONObj>> MultiIndexBlock::init(OperationContext* opCtx,
                                                        Collection* collection,
                                                        const std::vector<BSONObj>& indexSpecs,
                                                        OnInitFn onInit) {
+    invariant(opCtx->lockState()->isCollectionLockedForMode(collection->ns(), MODE_IX),
+              str::stream() << "Collection " << collection->ns() << " with UUID "
+                            << collection->uuid() << " is holding the incorrect lock");
     if (State::kAborted == _getState()) {
         return {ErrorCodes::IndexBuildAborted,
                 str::stream() << "Index build aborted: " << _abortReason
@@ -742,6 +745,10 @@ Status MultiIndexBlock::commit(OperationContext* opCtx,
                                Collection* collection,
                                OnCreateEachFn onCreateEach,
                                OnCommitFn onCommit) {
+    invariant(opCtx->lockState()->isCollectionLockedForMode(collection->ns(), MODE_X),
+              str::stream() << "Collection " << collection->ns() << " with UUID "
+                            << collection->uuid() << " is holding the incorrect lock");
+
     // UUIDs are not guaranteed during startup because the check happens after indexes are rebuilt.
     if (_collectionUUID) {
         invariant(_collectionUUID.get() == collection->uuid());
diff --git a/src/mongo/db/catalog/multi_index_block.h b/src/mongo/db/catalog/multi_index_block.h
index 7ffb1470d77..178b0a971c0 100644
--- a/src/mongo/db/catalog/multi_index_block.h
+++ b/src/mongo/db/catalog/multi_index_block.h
@@ -128,7 +128,7 @@ public:
      *
      * Does not need to be called inside of a WriteUnitOfWork (but can be due to nesting).
      *
-     * Requires holding an exclusive database lock.
+     * Requires holding an intent lock on the collection.
      */
     using OnInitFn = std::function<Status(std::vector<BSONObj>& specs)>;
     StatusWith<std::vector<BSONObj>> init(OperationContext* opCtx,
@@ -227,7 +227,7 @@ public:
      * `onCreateEach` will be called after each index has been marked as "ready".
      * `onCommit` will be called after all indexes have been marked "ready".
      *
-     * Requires holding an exclusive database lock.
+     * Requires holding an exclusive lock on the collection.
      */
     using OnCommitFn = std::function<void()>;
     using OnCreateEachFn = std::function<void(const BSONObj& spec)>;