From a67c2f9768e43f2b166fec74f1249c47564d79f1 Mon Sep 17 00:00:00 2001
From: "Yan, Zheng" <zyan@redhat.com>
Date: Tue, 30 Sep 2014 12:31:30 +0800
Subject: [PATCH] mds: Add session to sessionmap when its state becomes opening

following sequence events may happen.
- client sends reconnect message to a recovering MDS.
- MDS::ms_verify_authorizer() create a session for the client, the
  session is in closed state.
- MDS::handle_client_reconnect() sends session close message to
  the client.
- client closes the old connection and opens a new connection
- MDS::ms_verify_authorizer() is called for a new connection
- MDS::ms_handle_reset() is called for the old connection
- MDS::ms_handle_accept() is called for the new connection

MDS::ms_handle_reset() removes client's session from the session map, this
can cause null pointer dereference when handling client request. The fix
is add session to sessionmap when its state becomes 'opening' and remove
session from sessionmap when its state becomes 'closed'

Signed-off-by: Yan, Zheng <zyan@redhat.com>
---
 src/mds/MDS.cc    | 3 ---
 src/mds/Server.cc | 4 ++++
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/mds/MDS.cc b/src/mds/MDS.cc
index 5661fb51dc043..74719cdd97e15 100644
--- a/src/mds/MDS.cc
+++ b/src/mds/MDS.cc
@@ -2240,7 +2240,6 @@ bool MDS::ms_handle_reset(Connection *con)
       dout(3) << "ms_handle_reset closing connection for session " << session->info.inst << dendl;
       con->mark_down();
       con->set_priv(NULL);
-      sessionmap.remove_session(session);
     }
     session->put();
   } else {
@@ -2266,7 +2265,6 @@ void MDS::ms_handle_remote_reset(Connection *con)
       dout(3) << "ms_handle_remote_reset closing connection for session " << session->info.inst << dendl;
       con->mark_down();
       con->set_priv(NULL);
-      sessionmap.remove_session(session);
     }
     session->put();
   }
@@ -2312,7 +2310,6 @@ bool MDS::ms_verify_authorizer(Connection *con, int peer_type,
       dout(10) << " new session " << s << " for " << s->info.inst << " con " << con << dendl;
       con->set_priv(s);
       s->connection = con;
-      sessionmap.add_session(s);
     } else {
       dout(10) << " existing session " << s << " for " << s->info.inst << " existing con " << s->connection
 	       << ", new/authorizing con " << con << dendl;
diff --git a/src/mds/Server.cc b/src/mds/Server.cc
index 90eca043e4b0d..a8c14b1b6a284 100644
--- a/src/mds/Server.cc
+++ b/src/mds/Server.cc
@@ -233,6 +233,9 @@ void Server::handle_client_session(MClientSession *m)
       dout(20) << "  " << i->first << ": " << i->second << dendl;
     }
 
+    if (session->is_closed())
+      mds->sessionmap.add_session(session);
+
     sseq = mds->sessionmap.set_state(session, Session::STATE_OPENING);
     mds->sessionmap.touch_session(session);
     pv = ++mds->sessionmap.projected;
@@ -383,6 +386,7 @@ void Server::_session_logged(Session *session, uint64_t state_seq, bool open, ve
       mds->send_message_client(new MClientSession(CEPH_SESSION_CLOSE), session);
       mds->sessionmap.set_state(session, Session::STATE_CLOSED);
       session->clear();
+      mds->sessionmap.remove_session(session);
     } else if (session->is_killing()) {
       // destroy session, close connection
       if (session->connection != NULL) {
-- 
2.47.3