From 00b0711188f34ef4ea5c31f39bc70cf1fafbd907 Mon Sep 17 00:00:00 2001
From: Zhansong Gao <zhsgao@hotmail.com>
Date: Mon, 3 Jul 2023 17:18:14 +0800
Subject: [PATCH] mds: client is evicted when an export subtree task is
 interrupted

The importer will force open some sessions provided by the exporter but the client does not know about
the new sessions until the exporter notifies it, and the notifications cannot be sent if the exporter
is interrupted. The client does not renew the sessions regularly that it does not know about, so the client
will be evicted by the importer after `session_autoclose` seconds (300 seconds by default).

The sessions that are forced opened in the importer need to be closed when the import process is reversed.

Signed-off-by: Zhansong Gao <zhsgao@hotmail.com>
---
 src/mds/Migrator.cc  |  9 ++++++---
 src/mds/Server.cc    | 30 ++++++++++++++++++++++++++++--
 src/mds/Server.h     |  3 ++-
 src/mds/SessionMap.h |  4 ++++
 4 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/src/mds/Migrator.cc b/src/mds/Migrator.cc
index d60f8e0b3b6..6b12f710db4 100644
--- a/src/mds/Migrator.cc
+++ b/src/mds/Migrator.cc
@@ -2949,10 +2949,14 @@ void Migrator::import_reverse(CDir *dir)
       }
       in->put(CInode::PIN_IMPORTINGCAPS);
     }
+  }
+
+  if (stat.state == IMPORT_LOGGINGSTART || stat.state == IMPORT_ACKING) {
     for (auto& p : stat.session_map) {
       Session *session = p.second.first;
       session->dec_importing();
     }
+    mds->server->close_forced_opened_sessions(stat.session_map);
   }
 	 
   // log our failure
@@ -3054,10 +3058,9 @@ void Migrator::import_logged_start(dirfrag_t df, CDir *dir, mds_rank_t from,
   dout(7) << *dir << dendl;
 
   map<dirfrag_t, import_state_t>::iterator it = import_state.find(dir->dirfrag());
-  if (it == import_state.end() ||
-      it->second.state != IMPORT_LOGGINGSTART) {
+  ceph_assert(it != import_state.end());
+  if (it->second.state != IMPORT_LOGGINGSTART) {
     dout(7) << "import " << df << " must have aborted" << dendl;
-    mds->server->finish_force_open_sessions(imported_session_map);
     return;
   }
 
diff --git a/src/mds/Server.cc b/src/mds/Server.cc
index cf286b46d46..5874a3dce56 100644
--- a/src/mds/Server.cc
+++ b/src/mds/Server.cc
@@ -615,6 +615,9 @@ void Server::handle_client_session(const cref_t<MClientSession> &m)
       mds->send_message(reply, m->get_connection());
       return;
     }
+    if (!session->client_opened) {
+      session->client_opened = true;
+    }
     if (session->is_opening() ||
 	session->is_open() ||
 	session->is_stale() ||
@@ -1054,7 +1057,7 @@ version_t Server::prepare_force_open_sessions(map<client_t,entity_inst_t>& cm,
   return pv;
 }
 
-void Server::finish_force_open_sessions(const map<client_t,pair<Session*,uint64_t> >& smap,
+void Server::finish_force_open_sessions(map<client_t,pair<Session*,uint64_t> >& smap,
 					bool dec_import)
 {
   /*
@@ -1073,7 +1076,7 @@ void Server::finish_force_open_sessions(const map<client_t,pair<Session*,uint64_
 	dout(10) << "force_open_sessions skipping changed " << session->info.inst << dendl;
       } else {
 	dout(10) << "force_open_sessions opened " << session->info.inst << dendl;
-	mds->sessionmap.set_state(session, Session::STATE_OPEN);
+	it.second.second = mds->sessionmap.set_state(session, Session::STATE_OPEN);
 	mds->sessionmap.touch_session(session);
         metrics_handler->add_session(session);
 
@@ -1103,6 +1106,29 @@ void Server::finish_force_open_sessions(const map<client_t,pair<Session*,uint64_
   dout(10) << __func__ << ": final v " << mds->sessionmap.get_version() << dendl;
 }
 
+void Server::close_forced_opened_sessions(const map<client_t,pair<Session*,uint64_t> >& smap)
+{
+  dout(10) << __func__ << " on " << smap.size() << " clients" << dendl;
+
+  for (auto &it : smap) {
+    Session *session = it.second.first;
+    uint64_t sseq = it.second.second;
+    if (sseq == 0)
+      continue;
+    if (session->get_state_seq() != sseq) {
+      dout(10) << "skipping changed session (" << session->get_state_name() << ") "
+	       << session->info.inst << dendl;
+      continue;
+    }
+    if (session->client_opened)
+      continue;
+    dout(10) << "closing forced opened session (" << session->get_state_name() << ") "
+	     << session->info.inst << dendl;
+    ceph_assert(!session->is_importing());
+    journal_close_session(session, Session::STATE_CLOSING, NULL);
+  }
+}
+
 class C_MDS_TerminatedSessions : public ServerContext {
   void finish(int r) override {
     server->terminating_sessions = false;
diff --git a/src/mds/Server.h b/src/mds/Server.h
index 68842ea01cb..5f9a763e550 100644
--- a/src/mds/Server.h
+++ b/src/mds/Server.h
@@ -129,8 +129,9 @@ public:
   version_t prepare_force_open_sessions(std::map<client_t,entity_inst_t> &cm,
 					std::map<client_t,client_metadata_t>& cmm,
 					std::map<client_t,std::pair<Session*,uint64_t> >& smap);
-  void finish_force_open_sessions(const std::map<client_t,std::pair<Session*,uint64_t> >& smap,
+  void finish_force_open_sessions(std::map<client_t,std::pair<Session*,uint64_t> >& smap,
 				  bool dec_import=true);
+  void close_forced_opened_sessions(const std::map<client_t,std::pair<Session*,uint64_t> >& smap);
   void flush_client_sessions(std::set<client_t>& client_set, MDSGatherBuilder& gather);
   void finish_flush_session(Session *session, version_t seq);
   void terminate_sessions();
diff --git a/src/mds/SessionMap.h b/src/mds/SessionMap.h
index 9e82f00a9bf..bfe7dcd4895 100644
--- a/src/mds/SessionMap.h
+++ b/src/mds/SessionMap.h
@@ -417,6 +417,10 @@ public:
   session_info_t info;                         ///< durable bits
   MDSAuthCaps auth_caps;
 
+  // True if the session is opened by the client.
+  // False if the session is forced to open, until it is opened again by the client.
+  bool client_opened = false;
+
   xlist<Session*>::item item_session_list;
 
   std::list<ceph::ref_t<Message>> preopen_out_queue;  ///< messages for client, queued before they connect