osdc: After write try merge bh.

Fixes:http://tracker.ceph.com/issues/17270

Signed-off-by: Jianpeng Ma <jianpeng.ma@intel.com>

src/osdc/ObjectCacher.cc

@@ -182,6 +182,7 @@ void ObjectCacher::Object::merge_left(BufferHead *left, BufferHead *right)
 
   // hose right
   delete right;
+  right = nullptr; //see bh_write_commit
 
   ldout(oc->cct, 10) << "merge_left result " << *left << dendl;
 }
@@ -1114,6 +1115,7 @@ void ObjectCacher::bh_write_commit(int64_t poolid, sobject_t oid,
       }
     }
 
+    list <BufferHead*> hit;
     // apply to bh's!
     for (map<loff_t, BufferHead*>::const_iterator p = ob->data_lower_bound(start);
 	 p != ob->data.end();
@@ -1148,6 +1150,7 @@ void ObjectCacher::bh_write_commit(int64_t poolid, sobject_t oid,
 	bh->set_journal_tid(0);
 	if (bh->get_nocache())
 	  bh_lru_rest.lru_bottouch(bh);
+	hit.push_back(bh);
 	ldout(cct, 10) << "bh_write_commit clean " << *bh << dendl;
       } else {
 	mark_dirty(bh);
@@ -1156,6 +1159,13 @@ void ObjectCacher::bh_write_commit(int64_t poolid, sobject_t oid,
 		       << dendl;
       }
     }
+
+    while (!hit.empty()) {
+      BufferHead *bh = hit.front();
+      hit.pop_front();
+      if (bh)
+	ob->try_merge_bh(bh);
+    }
   }
 
   // update last_commit.