diff --git a/src/osd/OSD.cc b/src/osd/OSD.cc
index f40a233257d12..6bd83c725a528 100644
--- a/src/osd/OSD.cc
+++ b/src/osd/OSD.cc
@@ -1570,7 +1570,7 @@ void OSDService::send_map(MOSDMap *m, Connection *con)
 }
 
 void OSDService::send_incremental_map(epoch_t since, Connection *con,
-                                      OSDMapRef& osdmap)
+                                      const OSDMapRef& osdmap)
 {
   epoch_t to = osdmap->get_epoch();
   dout(10) << "send_incremental_map " << since << " -> " << to
@@ -2007,7 +2007,7 @@ void OSDService::clear_sent_ready_to_merge()
   sent_ready_to_merge_source.clear();
 }
 
-void OSDService::prune_sent_ready_to_merge(OSDMapRef& osdmap)
+void OSDService::prune_sent_ready_to_merge(const OSDMapRef& osdmap)
 {
   std::lock_guard l(merge_lock);
   auto i = sent_ready_to_merge_source.begin();
@@ -3029,6 +3029,7 @@ float OSD::get_osd_snap_trim_sleep()
 
 int OSD::init()
 {
+  OSDMapRef osdmap;
   CompatSet initial, diff;
   std::lock_guard lock(osd_lock);
   if (is_stopping())
@@ -3145,13 +3146,14 @@ int OSD::init()
   }
 
   // load up "current" osdmap
-  assert_warn(!osdmap);
-  if (osdmap) {
+  assert_warn(!get_osdmap());
+  if (get_osdmap()) {
     derr << "OSD::init: unable to read current osdmap" << dendl;
     r = -EINVAL;
     goto out;
   }
   osdmap = get_map(superblock.current_epoch);
+  set_osdmap(osdmap);
 
   // make sure we don't have legacy pgs deleting
   {
@@ -4090,9 +4092,9 @@ int OSD::shutdown()
   }
 
   // note unmount epoch
-  dout(10) << "noting clean unmount in epoch " << osdmap->get_epoch() << dendl;
+  dout(10) << "noting clean unmount in epoch " << get_osdmap_epoch() << dendl;
   superblock.mounted = service.get_boot_epoch();
-  superblock.clean_thru = osdmap->get_epoch();
+  superblock.clean_thru = get_osdmap_epoch();
   ObjectStore::Transaction t;
   write_superblock(t);
   int r = store->queue_transaction(service.meta_ch, std::move(t));
@@ -4156,7 +4158,7 @@ int OSD::shutdown()
   osd_lock.Unlock();
 
   map_lock.get_write();
-  osdmap = OSDMapRef();
+  set_osdmap(OSDMapRef());
   map_lock.put_write();
 
   for (auto s : shards) {
@@ -4641,7 +4643,7 @@ void OSD::load_pgs()
     if (map_epoch > 0) {
       OSDMapRef pgosdmap = service.try_get_map(map_epoch);
       if (!pgosdmap) {
-	if (!osdmap->have_pg_pool(pgid.pool())) {
+	if (!get_osdmap()->have_pg_pool(pgid.pool())) {
 	  derr << __func__ << ": could not find map for epoch " << map_epoch
 	       << " on pg " << pgid << ", but the pool is not present in the "
 	       << "current map, so this is probably a result of bug 10617.  "
@@ -4657,7 +4659,7 @@ void OSD::load_pgs()
       }
       pg = _make_pg(pgosdmap, pgid);
     } else {
-      pg = _make_pg(osdmap, pgid);
+      pg = _make_pg(get_osdmap(), pgid);
     }
     if (!pg) {
       recursive_remove_collection(cct, store, pgid, *it);
@@ -4857,7 +4859,7 @@ void OSD::resume_creating_pg()
     while (spare_pgs > 0 && pg != pending_creates_from_osd.cend()) {
       dout(20) << __func__ << " pg " << pg->first << dendl;
       vector<int> acting;
-      osdmap->pg_to_up_acting_osds(pg->first, nullptr, nullptr, &acting, nullptr);
+      get_osdmap()->pg_to_up_acting_osds(pg->first, nullptr, nullptr, &acting, nullptr);
       service.queue_want_pg_temp(pg->first, twiddle(acting), true);
       pg = pending_creates_from_osd.erase(pg);
       do_sub_pg_creates = true;
@@ -4875,7 +4877,7 @@ void OSD::resume_creating_pg()
       do_renew_subs = true;
     }
   }
-  version_t start = osdmap->get_epoch() + 1;
+  version_t start = get_osdmap_epoch() + 1;
   if (have_pending_creates) {
     // don't miss any new osdmap deleting PGs
     if (monc->sub_want("osdmap", start, 0)) {
@@ -4924,7 +4926,7 @@ void OSD::build_initial_pg_history(
     pgid.pgid, &up, &up_primary, &acting, &acting_primary);
 
   ostringstream debug;
-  for (epoch_t e = created + 1; e <= osdmap->get_epoch(); ++e) {
+  for (epoch_t e = created + 1; e <= get_osdmap_epoch(); ++e) {
     OSDMapRef osdmap = service.get_map(e);
     int new_up_primary, new_acting_primary;
     vector<int> new_up, new_acting;
@@ -4990,7 +4992,7 @@ void OSD::_add_heartbeat_peer(int p)
 
   map<int,HeartbeatInfo>::iterator i = heartbeat_peers.find(p);
   if (i == heartbeat_peers.end()) {
-    pair<ConnectionRef,ConnectionRef> cons = service.get_con_osd_hb(p, osdmap->get_epoch());
+    pair<ConnectionRef,ConnectionRef> cons = service.get_con_osd_hb(p, get_osdmap_epoch());
     if (!cons.first)
       return;
     hi = &heartbeat_peers[p];
@@ -5015,7 +5017,7 @@ void OSD::_add_heartbeat_peer(int p)
   } else {
     hi = &i->second;
   }
-  hi->epoch = osdmap->get_epoch();
+  hi->epoch = get_osdmap_epoch();
 }
 
 void OSD::_remove_heartbeat_peer(int n)
@@ -5078,7 +5080,7 @@ void OSD::maybe_update_heartbeat_peers()
     _get_pgs(&pgs);
     for (auto& pg : pgs) {
       pg->with_heartbeat_peers([&](int peer) {
-	  if (osdmap->is_up(peer)) {
+	  if (get_osdmap()->is_up(peer)) {
 	    _add_heartbeat_peer(peer);
 	  }
 	});
@@ -5087,10 +5089,10 @@ void OSD::maybe_update_heartbeat_peers()
 
   // include next and previous up osds to ensure we have a fully-connected set
   set<int> want, extras;
-  const int next = osdmap->get_next_up_osd_after(whoami);
+  const int next = get_osdmap()->get_next_up_osd_after(whoami);
   if (next >= 0)
     want.insert(next);
-  int prev = osdmap->get_previous_up_osd_before(whoami);
+  int prev = get_osdmap()->get_previous_up_osd_before(whoami);
   if (prev >= 0 && prev != next)
     want.insert(prev);
 
@@ -5098,7 +5100,7 @@ void OSD::maybe_update_heartbeat_peers()
   // subtree level (e.g., hosts) for fast failure detection.
   auto min_down = cct->_conf.get_val<uint64_t>("mon_osd_min_down_reporters");
   auto subtree = cct->_conf.get_val<string>("mon_osd_reporter_subtree_level");
-  osdmap->get_random_up_osds_by_subtree(
+  get_osdmap()->get_random_up_osds_by_subtree(
     whoami, subtree, min_down, want, &want);
 
   for (set<int>::iterator p = want.begin(); p != want.end(); ++p) {
@@ -5110,13 +5112,13 @@ void OSD::maybe_update_heartbeat_peers()
   // remove down peers; enumerate extras
   map<int,HeartbeatInfo>::iterator p = heartbeat_peers.begin();
   while (p != heartbeat_peers.end()) {
-    if (!osdmap->is_up(p->first)) {
+    if (!get_osdmap()->is_up(p->first)) {
       int o = p->first;
       ++p;
       _remove_heartbeat_peer(o);
       continue;
     }
-    if (p->second.epoch < osdmap->get_epoch()) {
+    if (p->second.epoch < get_osdmap_epoch()) {
       extras.insert(p->first);
     }
     ++p;
@@ -5131,7 +5133,7 @@ void OSD::maybe_update_heartbeat_peers()
       extras.insert(n);
       _add_heartbeat_peer(n);
     }
-    n = osdmap->get_next_up_osd_after(n);
+    n = get_osdmap()->get_next_up_osd_after(n);
     if (n == next)
       break;  // came full circle; stop
   }
@@ -5627,7 +5629,7 @@ void OSD::heartbeat()
     if (now - last_mon_heartbeat > cct->_conf->osd_mon_heartbeat_interval && is_active()) {
       last_mon_heartbeat = now;
       dout(10) << "i have no heartbeat peers; checking mon for new map" << dendl;
-      osdmap_subscribe(osdmap->get_epoch() + 1, false);
+      osdmap_subscribe(get_osdmap_epoch() + 1, false);
     }
   }
 
@@ -5702,7 +5704,7 @@ void OSD::tick()
     if (now - last_mon_heartbeat > cct->_conf->osd_mon_heartbeat_interval) {
       last_mon_heartbeat = now;
       dout(1) << __func__ << " checking mon for new map" << dendl;
-      osdmap_subscribe(osdmap->get_epoch() + 1, false);
+      osdmap_subscribe(get_osdmap_epoch() + 1, false);
     }
   }
 
@@ -6210,6 +6212,7 @@ void OSD::_preboot(epoch_t oldest, epoch_t newest)
     heartbeat();
   }
 
+  const auto osdmap = get_osdmap();
   // if our map within recent history, try to add ourselves to the osdmap.
   if (osdmap->get_epoch() == 0) {
     derr << "waiting for initial osdmap" << dendl;
@@ -6246,7 +6249,7 @@ void OSD::_preboot(epoch_t oldest, epoch_t newest)
 		     << dendl;
 	    osd_lock.Unlock();
 	    for (auto shard : shards) {
-	      shard->wait_min_pg_epoch(osdmap->get_epoch());
+	      shard->wait_min_pg_epoch(get_osdmap_epoch());
 	    }
 	    osd_lock.Lock();
 	  }
@@ -6279,7 +6282,7 @@ void OSD::send_full_update()
   set<string> s;
   OSDMap::calc_state_set(state, s);
   dout(10) << __func__ << " want state " << s << dendl;
-  monc->send_mon_message(new MOSDFull(osdmap->get_epoch(), state));
+  monc->send_mon_message(new MOSDFull(get_osdmap_epoch(), state));
 }
 
 void OSD::start_waiting_for_healthy()
@@ -6289,7 +6292,7 @@ void OSD::start_waiting_for_healthy()
   last_heartbeat_resample = utime_t();
 
   // subscribe to osdmap updates, in case our peers really are known to be dead
-  osdmap_subscribe(osdmap->get_epoch() + 1, false);
+  osdmap_subscribe(get_osdmap_epoch() + 1, false);
 }
 
 bool OSD::_is_healthy()
@@ -6484,7 +6487,7 @@ void OSD::_collect_metadata(map<string,string> *pm)
 void OSD::queue_want_up_thru(epoch_t want)
 {
   map_lock.get_read();
-  epoch_t cur = osdmap->get_up_thru(whoami);
+  epoch_t cur = get_osdmap()->get_up_thru(whoami);
   std::lock_guard l(mon_report_lock);
   if (want > up_thru_wanted) {
     dout(10) << "queue_want_up_thru now " << want << " (was " << up_thru_wanted << ")"
@@ -6503,6 +6506,7 @@ void OSD::queue_want_up_thru(epoch_t want)
 void OSD::send_alive()
 {
   ceph_assert(mon_report_lock.is_locked());
+  const auto osdmap = get_osdmap();
   if (!osdmap->exists(whoami))
     return;
   epoch_t up_thru = osdmap->get_up_thru(whoami);
@@ -6586,6 +6590,7 @@ void OSD::send_failures()
   ceph_assert(mon_report_lock.is_locked());
   std::lock_guard l(heartbeat_lock);
   utime_t now = ceph_clock_now();
+  const auto osdmap = get_osdmap();
   while (!failure_queue.empty()) {
     int osd = failure_queue.begin()->first;
     if (!failure_pending.count(osd)) {
@@ -6618,7 +6623,7 @@ void OSD::cancel_pending_failures()
   while (it != failure_pending.end()) {
     dout(10) << __func__ << " canceling in-flight failure report for osd."
              << it->first << dendl;
-    send_still_alive(osdmap->get_epoch(), it->first, it->second.second);
+    send_still_alive(get_osdmap_epoch(), it->first, it->second.second);
     failure_pending.erase(it++);
   }
 }
@@ -6635,7 +6640,7 @@ void OSD::send_beacon(const ceph::coarse_mono_clock::time_point& now)
     MOSDBeacon* beacon = nullptr;
     {
       std::lock_guard l{min_last_epoch_clean_lock};
-      beacon = new MOSDBeacon(osdmap->get_epoch(), min_last_epoch_clean);
+      beacon = new MOSDBeacon(get_osdmap_epoch(), min_last_epoch_clean);
       beacon->pgs = min_last_epoch_clean_pgs;
       last_sent_beacon = now;
     }
@@ -6995,7 +7000,7 @@ int OSD::_do_command(
     } else {
       spg_t pcand;
       PGRef pg;
-      if (osdmap->get_primary_shard(pgid, &pcand) &&
+      if (get_osdmap()->get_primary_shard(pgid, &pcand) &&
 	  (pg = _lookup_lock_pg(pcand))) {
 	if (pg->is_primary()) {
 	  // simulate pg <pgid> cmd= for pg->do-command
@@ -7018,7 +7023,7 @@ int OSD::_do_command(
 
 	  // send them the latest diff to ensure they realize the mapping
 	  // has changed.
-	  service.send_incremental_map(osdmap->get_epoch() - 1, con, osdmap);
+	  service.send_incremental_map(get_osdmap_epoch() - 1, con, get_osdmap());
 
 	  // do not reply; they will get newer maps and realize they
 	  // need to resend.
@@ -7715,7 +7720,7 @@ void OSD::_dispatch(Message *m)
       if (m->trace)
         op->osd_trace.init("osd op", &trace_endpoint, &m->trace);
       // no map?  starting up?
-      if (!osdmap) {
+      if (!get_osdmap()) {
         dout(7) << "no OSDMap, not booted" << dendl;
 	logger->inc(l_osd_waiting_for_map);
         waiting_for_osdmap.push_back(op);
@@ -7751,7 +7756,7 @@ void OSD::handle_scrub(MOSDScrub *m)
     vector<spg_t> v;
     for (auto pgid : m->scrub_pgs) {
       spg_t pcand;
-      if (osdmap->get_primary_shard(pgid, &pcand) &&
+      if (get_osdmap()->get_primary_shard(pgid, &pcand) &&
 	  std::find(spgs.begin(), spgs.end(), pcand) != spgs.end()) {
 	v.push_back(pcand);
       }
@@ -8038,11 +8043,11 @@ MPGStats* OSD::collect_pg_stats()
   osd_stat_t cur_stat = service.get_osd_stat();
   cur_stat.os_perf_stat = store->get_cur_stats();
 
-  auto m = new MPGStats(monc->get_fsid(), osdmap->get_epoch(), had_for);
+  auto m = new MPGStats(monc->get_fsid(), get_osdmap_epoch(), had_for);
   m->osd_stat = cur_stat;
 
   std::lock_guard lec{min_last_epoch_clean_lock};
-  min_last_epoch_clean = osdmap->get_epoch();
+  min_last_epoch_clean = get_osdmap_epoch();
   min_last_epoch_clean_pgs.clear();
 
   std::set<int64_t> pool_set;
@@ -8135,7 +8140,7 @@ void OSD::wait_for_new_map(OpRequestRef op)
 {
   // ask?
   if (waiting_for_osdmap.empty()) {
-    osdmap_subscribe(osdmap->get_epoch() + 1, false);
+    osdmap_subscribe(get_osdmap_epoch() + 1, false);
   }
 
   logger->inc(l_osd_waiting_for_map);
@@ -8151,7 +8156,7 @@ void OSD::wait_for_new_map(OpRequestRef op)
 void OSD::note_down_osd(int peer)
 {
   ceph_assert(osd_lock.is_locked());
-  cluster_messenger->mark_down_addrs(osdmap->get_cluster_addrs(peer));
+  cluster_messenger->mark_down_addrs(get_osdmap()->get_cluster_addrs(peer));
 
   heartbeat_lock.Lock();
   failure_queue.erase(peer);
@@ -8169,7 +8174,7 @@ void OSD::note_down_osd(int peer)
 
 void OSD::note_up_osd(int peer)
 {
-  service.forget_peer_epoch(peer, osdmap->get_epoch() - 1);
+  service.forget_peer_epoch(peer, get_osdmap_epoch() - 1);
   heartbeat_set_peers_need_update();
 }
 
@@ -8257,10 +8262,11 @@ void OSD::handle_osd_map(MOSDMap *m)
 	osd_min = min;
       }
     }
+    epoch_t osdmap_epoch = get_osdmap_epoch();
     if (osd_min > 0 &&
-	osdmap->get_epoch() > max_lag &&
-	osdmap->get_epoch() - max_lag > osd_min) {
-      epoch_t need = osdmap->get_epoch() - max_lag;
+	osdmap_epoch > max_lag &&
+	osdmap_epoch - max_lag > osd_min) {
+      epoch_t need = osdmap_epoch - max_lag;
       dout(10) << __func__ << " waiting for pgs to catch up (need " << need
 	       << " max_lag " << max_lag << ")" << dendl;
       for (auto shard : shards) {
@@ -8406,7 +8412,7 @@ void OSD::handle_osd_map(MOSDMap *m)
       inc.decode(p);
 
       if (o->apply_incremental(inc) < 0) {
-	derr << "ERROR: bad fsid?  i have " << osdmap->get_fsid() << " and inc has " << inc.fsid << dendl;
+	derr << "ERROR: bad fsid?  i have " << get_osdmap()->get_fsid() << " and inc has " << inc.fsid << dendl;
 	ceph_abort_msg("bad fsid");
       }
 
@@ -8554,6 +8560,7 @@ void OSD::_committed_osd_maps(epoch_t first, epoch_t last, MOSDMap *m)
   bool do_shutdown = false;
   bool do_restart = false;
   bool network_error = false;
+  OSDMapRef osdmap;
 
   // advance through the new maps
   for (epoch_t cur = first; cur <= last; cur++) {
@@ -8571,6 +8578,7 @@ void OSD::_committed_osd_maps(epoch_t first, epoch_t last, MOSDMap *m)
     // kill connections to newly down osds
     bool waited_for_reservations = false;
     set<int> old;
+    osdmap = get_osdmap();
     osdmap->get_all_osds(old);
     for (set<int>::iterator p = old.begin(); p != old.end(); ++p) {
       if (*p != whoami &&
@@ -8602,7 +8610,8 @@ void OSD::_committed_osd_maps(epoch_t first, epoch_t last, MOSDMap *m)
       }
     }
 
-    osdmap = newmap;
+    osdmap = std::move(newmap);
+    set_osdmap(osdmap);
     epoch_t up_epoch;
     epoch_t boot_epoch;
     service.retrieve_epochs(&boot_epoch, &up_epoch, NULL);
@@ -8810,6 +8819,7 @@ void OSD::check_osdmap_features()
   // current memory location, and setting or clearing bits in integer
   // fields, and we are the only writer, this is not a problem.
 
+  const auto osdmap = get_osdmap();
   {
     Messenger::Policy p = client_messenger->get_default_policy();
     uint64_t mask;
@@ -9115,6 +9125,7 @@ bool OSD::advance_pg(
 void OSD::consume_map()
 {
   ceph_assert(osd_lock.is_locked());
+  auto osdmap = get_osdmap();
   dout(7) << "consume_map version " << osdmap->get_epoch() << dendl;
 
   /** make sure the cluster is speaking in SORTBITWISE, because we don't
@@ -9232,6 +9243,7 @@ void OSD::consume_map()
 void OSD::activate_map()
 {
   ceph_assert(osd_lock.is_locked());
+  auto osdmap = get_osdmap();
 
   dout(7) << "activate_map version " << osdmap->get_epoch() << dendl;
 
@@ -9309,7 +9321,7 @@ bool OSD::require_self_aliveness(const Message *m, epoch_t epoch)
   return true;
 }
 
-bool OSD::require_same_peer_instance(const Message *m, OSDMapRef& map,
+bool OSD::require_same_peer_instance(const Message *m, const OSDMapRef& map,
 				     bool is_fast_dispatch)
 {
   int from = m->get_source().num();
@@ -9348,6 +9360,7 @@ bool OSD::require_same_or_newer_map(OpRequestRef& op, epoch_t epoch,
 				    bool is_fast_dispatch)
 {
   const Message *m = op->get_req();
+  const auto osdmap = get_osdmap();
   dout(15) << "require_same_or_newer_map " << epoch
 	   << " (i am " << osdmap->get_epoch() << ") " << m << dendl;
 
@@ -9454,6 +9467,7 @@ void OSD::handle_pg_create(OpRequestRef op)
 
   op->mark_started();
 
+  const auto osdmap = get_osdmap();
   map<pg_t,utime_t>::const_iterator ci = m->ctimes.begin();
   for (map<pg_t,pg_create_t>::const_iterator p = m->mkpg.begin();
        p != m->mkpg.end();
@@ -10485,9 +10499,9 @@ int OSD::init_op_flags(OpRequestRef& op)
 
     // check for ec base pool
     int64_t poolid = m->get_pg().pool();
-    const pg_pool_t *pool = osdmap->get_pg_pool(poolid);
+    const pg_pool_t *pool = get_osdmap()->get_pg_pool(poolid);
     if (pool && pool->is_tier()) {
-      const pg_pool_t *base_pool = osdmap->get_pg_pool(pool->tier_of);
+      const pg_pool_t *base_pool = get_osdmap()->get_pg_pool(pool->tier_of);
       if (base_pool && base_pool->require_rollback()) {
         if ((iter->op.op != CEPH_OSD_OP_READ) &&
             (iter->op.op != CEPH_OSD_OP_CHECKSUM) &&
@@ -10769,7 +10783,7 @@ epoch_t OSDShard::get_max_waiting_epoch()
 }
 
 void OSDShard::consume_map(
-  OSDMapRef& new_osdmap,
+  const OSDMapRef& new_osdmap,
   unsigned *pushes_to_free)
 {
   std::lock_guard l(shard_lock);
diff --git a/src/osd/OSD.h b/src/osd/OSD.h
index c87deeb0eecb0..80ca9af538cd0 100644
--- a/src/osd/OSD.h
+++ b/src/osd/OSD.h
@@ -403,7 +403,7 @@ class OSDService {
   void forget_peer_epoch(int p, epoch_t e);
 
   void send_map(class MOSDMap *m, Connection *con);
-  void send_incremental_map(epoch_t since, Connection *con, OSDMapRef& osdmap);
+  void send_incremental_map(epoch_t since, Connection *con, const OSDMapRef& osdmap);
   MOSDMap *build_incremental_map_msg(epoch_t from, epoch_t to,
                                        OSDSuperblock& superblock);
   bool should_share_map(entity_name_t name, Connection *con, epoch_t epoch,
@@ -730,7 +730,7 @@ class OSDService {
   void send_ready_to_merge();
   void _send_ready_to_merge();
   void clear_sent_ready_to_merge();
-  void prune_sent_ready_to_merge(OSDMapRef& osdmap);
+  void prune_sent_ready_to_merge(const OSDMapRef& osdmap);
 
   // -- pg_temp --
 private:
@@ -1214,7 +1214,7 @@ struct OSDShard {
 
   /// push osdmap into shard
   void consume_map(
-    OSDMapRef& osdmap,
+    const OSDMapRef& osdmap,
     unsigned *pushes_to_free);
 
   void _wake_pg_slot(spg_t pgid, OSDShardPGSlot *slot);
@@ -1514,8 +1514,7 @@ class OSD : public Dispatcher,
 	 i != sessions_to_check.end();
 	 sessions_to_check.erase(i++)) {
       std::lock_guard l{(*i)->session_dispatch_lock};
-      SessionRef session = *i;
-      dispatch_session_waiting(session, osdmap);
+      dispatch_session_waiting(*i, get_osdmap());
     }
   }
   void session_handle_reset(SessionRef session) {
@@ -1883,11 +1882,17 @@ class OSD : public Dispatcher,
  protected:
 
   // -- osd map --
-  OSDMapRef       osdmap;
-  OSDMapRef get_osdmap() {
-    return osdmap;
+  // TODO: switch to std::atomic<OSDMapRef> when C++20 will be available.
+  OSDMapRef       _osdmap;
+  void set_osdmap(OSDMapRef osdmap) {
+    std::atomic_store(&_osdmap, osdmap);
+  }
+  OSDMapRef get_osdmap() const {
+    return std::atomic_load(&_osdmap);
   }
   epoch_t get_osdmap_epoch() const {
+    // XXX: performance?
+    auto osdmap = get_osdmap();
     return osdmap ? osdmap->get_epoch() : 0;
   }
 
@@ -2096,7 +2101,7 @@ class OSD : public Dispatcher,
    * address as in the given map.
    * @pre op was sent by an OSD using the cluster messenger
    */
-  bool require_same_peer_instance(const Message *m, OSDMapRef& map,
+  bool require_same_peer_instance(const Message *m, const OSDMapRef& map,
 				  bool is_fast_dispatch);
 
   bool require_same_or_newer_map(OpRequestRef& op, epoch_t e,