mds: add comment explaining unusual locking for MDSIOContextBase

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>

diff --git a/src/mds/MDSContext.cc b/src/mds/MDSContext.cc
index bec31daad6a43c03134cad7b33c7e0f75947b193..34b15a4f08bf96ccdc38318d783c688a6f15dee1 100644 (file)
--- a/src/mds/MDSContext.cc
+++ b/src/mds/MDSContext.cc
@@ -90,6 +90,9 @@ void MDSIOContextBase::complete(int r) {
 
   dout(10) << "MDSIOContextBase::complete: " << typeid(*this).name() << dendl;
   ceph_assert(mds != NULL);
+  // Note, MDSIOContext is passed outside the MDS and, strangely, we grab the
+  // lock here when MDSContext::complete would otherwise assume the lock is
+  // already acquired.
   std::lock_guard l(mds->mds_lock);
 
   if (mds->is_daemon_stopping()) {