rbd: move the detection of destination image ealier in rename op

Return earlier to avoid extra work of reading image data and omap if the
detection fails or the destination image already exists.

Signed-off-by: Zhiqiang Wang <zhiqiang.wang@intel.com>

diff --git a/src/librbd/internal.cc b/src/librbd/internal.cc
index 714c3b3ef381095147171d098c77c16e8ec4979b..2f1d8ca80943b3e7993a6fa5dd669535f86974d6 100644 (file)
--- a/src/librbd/internal.cc
+++ b/src/librbd/internal.cc
@@ -1212,6 +1212,17 @@ reprotect_and_return_err:
       return r;
     }
 
+    r = detect_format(io_ctx, dstname, NULL, NULL);
+    if (r < 0 && r != -ENOENT) {
+      lderr(cct) << "error checking for existing image called "
+                << dstname << ":" << cpp_strerror(r) << dendl;
+      return r;
+    }
+    if (r == 0) {
+      lderr(cct) << "rbd image " << dstname << " already exists" << dendl;
+      return -EEXIST;
+    }
+
     string src_oid =
       old_format ? old_header_name(srcname) : id_obj_name(srcname);
     string dst_oid =
@@ -1250,17 +1261,6 @@ reprotect_and_return_err:
        last_read = outbl.rbegin()->first;
     } while (r == MAX_READ);
 
-    r = detect_format(io_ctx, dstname, NULL, NULL);
-    if (r < 0 && r != -ENOENT) {
-      lderr(cct) << "error checking for existing image called "
-                << dstname << ":" << cpp_strerror(r) << dendl;
-      return r;
-    }
-    if (r == 0) {
-      lderr(cct) << "rbd image " << dstname << " already exists" << dendl;
-      return -EEXIST;
-    }
-
     librados::ObjectWriteOperation op;
     op.create(true);
     op.write_full(databl);