SERVER-30554 relax locking mode in applyOps when applying CRUD-only ops non-atomically

This allows concurrent applyOps commands to update the same collection on storage
engines that support document level concurrency.

(cherry picked from commit bca3f70566991afa2dfb38dc06494b0f6f04fffa)

3 files changed, 25 insertions, 2 deletions

diff --git a/jstests/replsets/apply_ops_concurrent_non_atomic_same_collection.js b/jstests/replsets/apply_ops_concurrent_non_atomic_same_collection.js
new file mode 100644
index 00000000000..004eeaaa52f
--- /dev/null
+++ b/jstests/replsets/apply_ops_concurrent_non_atomic_same_collection.js
@@ -0,0 +1,11 @@
+(function() {
+    'use strict';
+
+    load('jstests/replsets/libs/apply_ops_concurrent_non_atomic.js');
+
+    new ApplyOpsConcurrentNonAtomicTest({
+        ns1: 'test.coll',
+        ns2: 'test.coll',
+        requiresDocumentLevelConcurrency: true,
+    }).run();
+}());
diff --git a/jstests/replsets/apply_ops_concurrent_non_atomic_same_db.js b/jstests/replsets/apply_ops_concurrent_non_atomic_same_db.js
new file mode 100644
index 00000000000..10f874382a5
--- /dev/null
+++ b/jstests/replsets/apply_ops_concurrent_non_atomic_same_db.js
@@ -0,0 +1,11 @@
+(function() {
+    'use strict';
+
+    load('jstests/replsets/libs/apply_ops_concurrent_non_atomic.js');
+
+    new ApplyOpsConcurrentNonAtomicTest({
+        ns1: 'test.coll1',
+        ns2: 'test.coll2',
+        requiresDocumentLevelConcurrency: false,
+    }).run();
+}());
diff --git a/src/mongo/db/catalog/apply_ops.cpp b/src/mongo/db/catalog/apply_ops.cpp
index 5756a068917..28ca548c18f 100644
--- a/src/mongo/db/catalog/apply_ops.cpp
+++ b/src/mongo/db/catalog/apply_ops.cpp
@@ -158,7 +158,8 @@ Status _applyOps(OperationContext* opCtx,
                             invariant(opCtx->lockState()->isW());
                             status = repl::applyCommand_inlock(opCtx, opObj, true);
                         } else {
-                            Lock::DBLock dbWriteLock(opCtx->lockState(), nss.db(), MODE_X);
+                            Lock::DBLock dbWriteLock(opCtx->lockState(), nss.db(), MODE_IX);
+                            Lock::CollectionLock lock(opCtx->lockState(), nss.ns(), MODE_IX);
                             OldClientContext ctx(opCtx, ns);
 
                             status =
@@ -329,7 +330,7 @@ Status applyOps(OperationContext* opCtx,
     // There's only one case where we are allowed to take the database lock instead of the global
     // lock - no preconditions; only CRUD ops; and non-atomic mode.
     if (!hasPrecondition && areOpsCrudOnly && !allowAtomic) {
-        dbWriteLock.emplace(opCtx->lockState(), dbName, MODE_X);
+        dbWriteLock.emplace(opCtx->lockState(), dbName, MODE_IX);
     } else {
         globalWriteLock.emplace(opCtx->lockState());
     }