fix: reduce an extra readdir() attempted on non-legacy setups (#11301)

to verify moving content and preserving legacy content,
we have way to detect the objects through readdir()
this path is not necessary for most common cases on
newer setups, avoid readdir() to save multiple system
calls.

also fix the CheckFile behavior for most common
use case i.e without legacy format.

cmd/xl-storage.go

@@ -1808,7 +1808,10 @@ func (s *xlStorage) CheckFile(ctx context.Context, volume string, path string) e
 
 		st, _ := os.Lstat(filePath)
 		if st == nil {
-			if s.formatLegacy {
+			if !s.formatLegacy {
+				return errPathNotFound
+			}
+
 			filePathOld := pathJoin(volumeDir, p, xlStorageFormatFileV1)
 			if err := checkPathLength(filePathOld); err != nil {
 				return err
@@ -1819,7 +1822,6 @@ func (s *xlStorage) CheckFile(ctx context.Context, volume string, path string) e
 				return errPathNotFound
 			}
 		}
-		}
 
 		if st != nil {
 			if !st.Mode().IsRegular() {
@@ -2110,6 +2112,11 @@ func (s *xlStorage) RenameData(ctx context.Context, srcVolume, srcPath, dataDir,
 		// It is possible that some drives may not have `xl.meta` file
 		// in such scenarios verify if atleast `part.1` files exist
 		// to verify for legacy version.
+		if s.formatLegacy {
+			// We only need this code if we are moving
+			// from `xl.json` to `xl.meta`, we can avoid
+			// one extra readdir operation here for all
+			// new deployments.
 			currentDataPath := pathJoin(dstVolumeDir, dstPath)
 			entries, err := readDirN(currentDataPath, 1)
 			if err != nil && err != errFileNotFound {
@@ -2125,6 +2132,7 @@ func (s *xlStorage) RenameData(ctx context.Context, srcVolume, srcPath, dataDir,
 				}
 			}
 		}
+	}
 
 	if legacyPreserved {
 		// Preserve all the legacy data, could be slow, but at max there can be 10,000 parts.

cmd/xl-storage_test.go

@@ -1719,7 +1719,7 @@ func TestXLStorageCheckFile(t *testing.T) {
 
 	for i, testCase := range testCases {
 		if err := xlStorage.CheckFile(context.Background(), testCase.srcVol, testCase.srcPath); err != testCase.expectedErr {
-			t.Fatalf("TestXLStorage case %d: Expected: \"%s\", got: \"%s\"", i+1, testCase.expectedErr, err)
+			t.Errorf("TestXLStorage case %d: Expected: \"%s\", got: \"%s\"", i+1, testCase.expectedErr, err)
 		}
 	}
 }