fix: improve NewObjectReader implementation for careful cleanup usage (#12199)

cleanup functions should never be cleaned before the reader is
instantiated, this type of design leads to situations where order
of lockers and places for them to use becomes confusing.

Allow WithCleanupFuncs() if the caller wishes to add cleanupFns
to be run upon close() or an error during initialization of the
reader.

Also make sure streams are closed before we unlock the resources,
this allows for ordered cleanup of resources.

cmd/erasure-object.go

@@ -186,25 +186,30 @@ func (er erasureObjects) GetObjectNInfo(ctx context.Context, bucket, object stri
 	if objInfo.TransitionStatus == lifecycle.TransitionComplete {
 		// If transitioned, stream from transition tier unless object is restored locally or restore date is past.
 		if onDisk := isRestoredObjectOnDisk(objInfo.UserDefined); !onDisk {
-			return getTransitionedObjectReader(ctx, bucket, object, rs, h, objInfo, opts)
+			gr, err := getTransitionedObjectReader(ctx, bucket, object, rs, h, objInfo, opts)
+			if err != nil {
+				return nil, err
+			}
+			unlockOnDefer = false
+			return gr.WithCleanupFuncs(nsUnlocker), nil
 		}
 	}
-	unlockOnDefer = false
-	fn, off, length, nErr := NewGetObjectReader(rs, objInfo, opts, nsUnlocker)
-	if nErr != nil {
-		return nil, nErr
+
+	fn, off, length, err := NewGetObjectReader(rs, objInfo, opts)
+	if err != nil {
+		return nil, err
 	}
+	unlockOnDefer = false
 	pr, pw := io.Pipe()
 	go func() {
-		err := er.getObjectWithFileInfo(ctx, bucket, object, off, length, pw, fi, metaArr, onlineDisks)
-		pw.CloseWithError(err)
+		pw.CloseWithError(er.getObjectWithFileInfo(ctx, bucket, object, off, length, pw, fi, metaArr, onlineDisks))
 	}()
 
 	// Cleanup function to cause the go routine above to exit, in
 	// case of incomplete read.
 	pipeCloser := func() { pr.Close() }
 
-	return fn(pr, h, opts.CheckPrecondFn, pipeCloser)
+	return fn(pr, h, opts.CheckPrecondFn, pipeCloser, nsUnlocker)
 }
 
 // GetObject - reads an object erasured coded across multiple