xl: Remove check-dir in ReadVersion (#11200)

The only purpose of check-dir flag in
ReadVersion is to return 404 when
an object has xl.meta but without data.

This is causing an extract call to the disk 
which can be penalizing in case of busy system
where disks receive many concurrent access.

cmd/erasure-object_test.go

@@ -288,16 +288,38 @@ func TestGetObjectNoQuorum(t *testing.T) {
 	bucket := "bucket"
 	object := "object"
 	opts := ObjectOptions{}
+
+	// Test use case 1: All disks are online, xl.meta are present, but data are missing
+	_, err = obj.PutObject(ctx, bucket, object, mustGetPutObjReader(t, bytes.NewReader([]byte("abcd")), int64(len("abcd")), "", ""), opts)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, disk := range xl.getDisks() {
+		files, _ := disk.ListDir(ctx, bucket, object, -1)
+		for _, file := range files {
+			if file != "xl.meta" {
+				disk.Delete(ctx, bucket, pathJoin(object, file), true)
+			}
+		}
+	}
+
+	err = xl.GetObject(ctx, bucket, object, 0, int64(len("abcd")), ioutil.Discard, "", opts)
+	if err != toObjectErr(errFileNotFound, bucket, object) {
+		t.Errorf("Expected GetObject to fail with %v, but failed with %v", toObjectErr(errErasureWriteQuorum, bucket, object), err)
+	}
+
+	// Test use case 2: Make 9 disks offline, which leaves less than quorum number of disks
+	// in a 16 disk Erasure setup. The original disks are 'replaced' with
+	// naughtyDisks that fail after 'f' successful StorageAPI method
+	// invocations, where f - [0,2)
+
 	// Create "object" under "bucket".
 	_, err = obj.PutObject(ctx, bucket, object, mustGetPutObjReader(t, bytes.NewReader([]byte("abcd")), int64(len("abcd")), "", ""), opts)
 	if err != nil {
 		t.Fatal(err)
 	}
 
-	// Make 9 disks offline, which leaves less than quorum number of disks
-	// in a 16 disk Erasure setup. The original disks are 'replaced' with
-	// naughtyDisks that fail after 'f' successful StorageAPI method
-	// invocations, where f - [0,2)
 	for f := 0; f < 2; f++ {
 		diskErrors := make(map[int]error)
 		for i := 0; i <= f; i++ {
@@ -320,9 +342,84 @@ func TestGetObjectNoQuorum(t *testing.T) {
 		// Fetch object from store.
 		err = xl.GetObject(ctx, bucket, object, 0, int64(len("abcd")), ioutil.Discard, "", opts)
 		if err != toObjectErr(errErasureReadQuorum, bucket, object) {
-			t.Errorf("Expected putObject to fail with %v, but failed with %v", toObjectErr(errErasureWriteQuorum, bucket, object), err)
+			t.Errorf("Expected GetObject to fail with %v, but failed with %v", toObjectErr(errErasureWriteQuorum, bucket, object), err)
 		}
 	}
+
+}
+
+func TestHeadObjectNoQuorum(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	// Create an instance of xl backend.
+	obj, fsDirs, err := prepareErasure16(ctx)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Cleanup backend directories.
+	defer obj.Shutdown(context.Background())
+	defer removeRoots(fsDirs)
+
+	z := obj.(*erasureServerPools)
+	xl := z.serverPools[0].sets[0]
+
+	// Create "bucket"
+	err = obj.MakeBucketWithLocation(ctx, "bucket", BucketOptions{})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	bucket := "bucket"
+	object := "object"
+	opts := ObjectOptions{}
+
+	// Test use case 1: All disks are online, xl.meta are present, but data are missing
+	_, err = obj.PutObject(ctx, bucket, object, mustGetPutObjReader(t, bytes.NewReader([]byte("abcd")), int64(len("abcd")), "", ""), opts)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, disk := range xl.getDisks() {
+		files, _ := disk.ListDir(ctx, bucket, object, -1)
+		for _, file := range files {
+			if file != "xl.meta" {
+				disk.Delete(ctx, bucket, pathJoin(object, file), true)
+			}
+		}
+	}
+
+	_, err = xl.GetObjectInfo(ctx, bucket, object, opts)
+	if err != nil {
+		t.Errorf("Expected StatObject to succeed if data dir are not found, but failed with %v", err)
+	}
+
+	// Test use case 2: Make 9 disks offline, which leaves less than quorum number of disks
+	// in a 16 disk Erasure setup. The original disks are 'replaced' with
+	// naughtyDisks that fail after 'f' successful StorageAPI method
+	// invocations, where f - [0,2)
+
+	// Create "object" under "bucket".
+	_, err = obj.PutObject(ctx, bucket, object, mustGetPutObjReader(t, bytes.NewReader([]byte("abcd")), int64(len("abcd")), "", ""), opts)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	erasureDisks := xl.getDisks()
+	for i := range erasureDisks[:10] {
+		erasureDisks[i] = nil
+	}
+
+	z.serverPools[0].erasureDisksMu.Lock()
+	xl.getDisks = func() []StorageAPI {
+		return erasureDisks
+	}
+	z.serverPools[0].erasureDisksMu.Unlock()
+
+	// Fetch object from store.
+	_, err = xl.GetObjectInfo(ctx, bucket, object, opts)
+	if err != toObjectErr(errErasureReadQuorum, bucket, object) {
+		t.Errorf("Expected getObjectInfo to fail with %v, but failed with %v", toObjectErr(errErasureWriteQuorum, bucket, object), err)
+	}
 }
 
 func TestPutObjectNoQuorum(t *testing.T) {