osd: fix the mem leak of RepGather

ReplicatedPG::new_repop() returns a pointer to RepGather with two refcounts,
one is held by ReplicatedPG::repop_queue, the other is supposed to be
held by the caller of this function. but it's caller
ReplicatedPG::submit_log_entries() assigns it to a
boost::intrusive_ptr<RepGather>() directly, why by default add_ref() in
its constructor. this makes the refcount 3. that's why we have a leak of
RepGather in `ReplicatedPG::new_repop(ObcLockManager&&,
boost::optional<std::function<void ()>>&&)`.

Fixes: http://tracker.ceph.com/issues/16801
Signed-off-by: Kefu Chai <kchai@redhat.com>

src/osd/ReplicatedPG.cc

@@ -8619,7 +8619,7 @@ ReplicatedPG::RepGather *ReplicatedPG::new_repop(
   return repop;
 }
 
-ReplicatedPG::RepGather *ReplicatedPG::new_repop(
+boost::intrusive_ptr<ReplicatedPG::RepGather> ReplicatedPG::new_repop(
   ObcLockManager &&manager,
   boost::optional<std::function<void(void)> > &&on_complete)
 {
@@ -8632,11 +8632,10 @@ ReplicatedPG::RepGather *ReplicatedPG::new_repop(
   repop->start = ceph_clock_now(cct);
 
   repop_queue.push_back(&repop->queue_item);
-  repop->get();
 
   osd->logger->inc(l_osd_op_wip);
 
-  return repop;
+  return boost::intrusive_ptr<RepGather>(repop);
 }
 
 void ReplicatedPG::remove_repop(RepGather *repop)

src/osd/ReplicatedPG.h

@@ -893,7 +893,7 @@ class ReplicatedPG : public PG, public PGBackend::Listener {
     OpContext *ctx,
     ObjectContextRef obc,
     ceph_tid_t rep_tid);
-  RepGather *new_repop(
+  boost::intrusive_ptr<RepGather> new_repop(
     ObcLockManager &&manager,
     boost::optional<std::function<void(void)> > &&on_complete);
   void remove_repop(RepGather *repop);