osd: fix bench typo

gistfile1.diff

diff --git a/src/osd/OSD.cc b/src/osd/OSD.cc
index b67e406..c714cc7 100644
--- a/src/osd/OSD.cc
+++ b/src/osd/OSD.cc
@@ -4015,7 +4015,7 @@ void OSD::do_command(Connection *con, tid_t tid, vector<string>& cmd, bufferlist
     int64_t bsize;
     // default count 1G, size 4MB
     cmd_getval(g_ceph_context, cmdmap, "count", count, (int64_t)1 << 30);
-    cmd_getval(g_ceph_context, cmdmap, "bsize", bsize, (int64_t)4 << 20);
+    cmd_getval(g_ceph_context, cmdmap, "size", bsize, (int64_t)4 << 20);

     bufferlist bl;
     bufferptr bp(bsize);