all: Add Prometheus-style metrics to expose some internal performance counters (fixes #5175) (#9003)

lib/fs/filesystem_copy_range_test.go

@@ -320,7 +320,15 @@ func TestCopyRange(tttt *testing.T) {
 								t.Fatal(err)
 							}
 
-							if err := impl(src.(basicFile), dst.(basicFile), testCase.srcOffset, testCase.dstOffset, testCase.copySize); err != nil {
+							srcBasic, ok := unwrap(src).(basicFile)
+							if !ok {
+								t.Fatal("src file is not a basic file")
+							}
+							dstBasic, ok := unwrap(dst).(basicFile)
+							if !ok {
+								t.Fatal("dst file is not a basic file")
+							}
+							if err := impl(srcBasic, dstBasic, testCase.srcOffset, testCase.dstOffset, testCase.copySize); err != nil {
 								if err == syscall.ENOTSUP {
 									// Test runner can adjust directory in which to run the tests, that allow broader tests.
 									t.Skip("Not supported on the current filesystem, set STFSTESTPATH env var.")