From c15e8ae74071482d69179c7e5e5e6bdc882d2beb Mon Sep 17 00:00:00 2001
From: Lingzhi Deng <lingzhi.deng@mongodb.com>
Date: Tue, 3 Mar 2020 10:46:39 -0500
Subject: SERVER-45626: Introduce AutoGetOplog for consistent oplog locking
 rules

---
 src/mongo/db/catalog_raii.cpp | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

(limited to 'src/mongo/db/catalog_raii.cpp')

diff --git a/src/mongo/db/catalog_raii.cpp b/src/mongo/db/catalog_raii.cpp
index 156727191dd..aacce83a287 100644
--- a/src/mongo/db/catalog_raii.cpp
+++ b/src/mongo/db/catalog_raii.cpp
@@ -182,4 +182,37 @@ ReadSourceScope::~ReadSourceScope() {
     }
 }
 
+AutoGetOplog::AutoGetOplog(OperationContext* opCtx, OplogAccessMode mode, Date_t deadline)
+    : _shouldNotConflictWithSecondaryBatchApplicationBlock(opCtx->lockState()) {
+    if (mode == OplogAccessMode::kLogOp) {
+        // Invariant that global lock is already held for kLogOp mode.
+        invariant(opCtx->lockState()->isWriteLocked());
+    } else {
+        _globalLock.emplace(opCtx,
+                            mode == OplogAccessMode::kRead ? MODE_IS : MODE_IX,
+                            deadline,
+                            Lock::InterruptBehavior::kThrow);
+    }
+
+    // Obtain database and collection intent locks for non-document-locking storage engines.
+    if (!opCtx->getServiceContext()->getStorageEngine()->supportsDocLocking()) {
+        auto lockMode = (mode == OplogAccessMode::kRead) ? MODE_IS : MODE_IX;
+
+        // If mode is kLogOp, only acquire the database lock if it is not already held.
+        if (mode != OplogAccessMode::kLogOp ||
+            !opCtx->lockState()->isDbLockedForMode(NamespaceString::kLocalDb, lockMode)) {
+            _dbWriteLock.emplace(opCtx, NamespaceString::kLocalDb, lockMode, deadline);
+        }
+
+        // If mode is kLogOp, only acquire the collection lock if it is not already held.
+        if (mode != OplogAccessMode::kLogOp ||
+            !opCtx->lockState()->isCollectionLockedForMode(NamespaceString::kRsOplogNamespace,
+                                                           lockMode)) {
+            _collWriteLock.emplace(opCtx, NamespaceString::kRsOplogNamespace, lockMode, deadline);
+        }
+    }
+    _oplogInfo = repl::LocalOplogInfo::get(opCtx);
+    _oplog = _oplogInfo->getCollection();
+}
+
 }  // namespace mongo
-- 
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