mds: add the event when creating the batch head

This could help us the debug the slow request or deadlock bugs and
we could know which stage the request has been in.

Fixes: https://tracker.ceph.com/issues/67280
Signed-off-by: Xiubo Li <[email protected]>

Author: lxbsz

src/mds/Server.cc

@@ -4135,6 +4135,7 @@ void Server::handle_client_getattr(const MDRequestRef& mdr, bool is_lookup)
       auto em = dn->batch_ops.emplace(std::piecewise_construct, std::forward_as_tuple(mask), std::forward_as_tuple());
       if (em.second) {
 	em.first->second = std::make_unique<Batch_Getattr_Lookup>(this, mdr);
+        mdr->mark_event("creating lookup batch head");
       } else {
 	dout(20) << __func__ << ": LOOKUP op, wait for previous same getattr ops to respond. " << *mdr << dendl;
 	em.first->second->add_request(mdr);
@@ -4147,6 +4148,7 @@ void Server::handle_client_getattr(const MDRequestRef& mdr, bool is_lookup)
       auto em = in->batch_ops.emplace(std::piecewise_construct, std::forward_as_tuple(mask), std::forward_as_tuple());
       if (em.second) {
 	em.first->second = std::make_unique<Batch_Getattr_Lookup>(this, mdr);
+        mdr->mark_event("creating getattr batch head");
       } else {
 	dout(20) << __func__ << ": GETATTR op, wait for previous same getattr ops to respond. " << *mdr << dendl;
 	em.first->second->add_request(mdr);