HealObjects should remove objects without quorum (#7407)

This PR adds a way to list objects without quorum
such that they can purged by `mc admin heal --remove`

cmd/xl-v1-healing_test.go

@@ -58,6 +58,91 @@ func TestUndoMakeBucket(t *testing.T) {
 	}
 }
 
+func TestHealObjectCorrupted(t *testing.T) {
+	nDisks := 16
+	fsDirs, err := getRandomDisks(nDisks)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer removeRoots(fsDirs)
+
+	// Everything is fine, should return nil
+	obj, _, err := initObjectLayer(mustGetNewEndpointList(fsDirs...))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	bucket := "bucket"
+	object := "object"
+	data := bytes.Repeat([]byte("a"), 5*1024*1024)
+	var opts ObjectOptions
+
+	err = obj.MakeBucketWithLocation(context.Background(), bucket, "")
+	if err != nil {
+		t.Fatalf("Failed to make a bucket - %v", err)
+	}
+
+	// Create an object with multiple parts uploaded in decreasing
+	// part number.
+	uploadID, err := obj.NewMultipartUpload(context.Background(), bucket, object, opts)
+	if err != nil {
+		t.Fatalf("Failed to create a multipart upload - %v", err)
+	}
+
+	var uploadedParts []CompletePart
+	for _, partID := range []int{2, 1} {
+		pInfo, err1 := obj.PutObjectPart(context.Background(), bucket, object, uploadID, partID, mustGetPutObjReader(t, bytes.NewReader(data), int64(len(data)), "", ""), opts)
+		if err1 != nil {
+			t.Fatalf("Failed to upload a part - %v", err1)
+		}
+		uploadedParts = append(uploadedParts, CompletePart{
+			PartNumber: pInfo.PartNumber,
+			ETag:       pInfo.ETag,
+		})
+	}
+
+	_, err = obj.CompleteMultipartUpload(context.Background(), bucket, object, uploadID, uploadedParts, ObjectOptions{})
+	if err != nil {
+		t.Fatalf("Failed to complete multipart upload - %v", err)
+	}
+
+	// Remove the object backend files from the first disk.
+	xl := obj.(*xlObjects)
+	firstDisk := xl.storageDisks[0]
+	err = firstDisk.DeleteFile(bucket, filepath.Join(object, xlMetaJSONFile))
+	if err != nil {
+		t.Fatalf("Failed to delete a file - %v", err)
+	}
+
+	_, err = obj.HealObject(context.Background(), bucket, object, false, false, madmin.HealNormalScan)
+	if err != nil {
+		t.Fatalf("Failed to heal object - %v", err)
+	}
+
+	_, err = firstDisk.StatFile(bucket, filepath.Join(object, xlMetaJSONFile))
+	if err != nil {
+		t.Errorf("Expected xl.json file to be present but stat failed - %v", err)
+	}
+
+	// Delete xl.json from more than read quorum number of disks, to create a corrupted situation.
+	for i := 0; i <= len(xl.storageDisks)/2; i++ {
+		xl.storageDisks[i].DeleteFile(bucket, filepath.Join(object, xlMetaJSONFile))
+	}
+
+	// Try healing now, expect to receive errDiskNotFound.
+	_, err = obj.HealObject(context.Background(), bucket, object, false, true, madmin.HealDeepScan)
+	if err != nil {
+		t.Errorf("Expected nil but received %v", err)
+	}
+
+	// since majority of xl.jsons are not available, object should be successfully deleted.
+	_, err = obj.GetObjectInfo(context.Background(), bucket, object, ObjectOptions{})
+	if _, ok := err.(ObjectNotFound); !ok {
+		t.Errorf("Expect %v but received %v", ObjectNotFound{Bucket: bucket, Object: object}, err)
+	}
+}
+
 // Tests healing of object.
 func TestHealObjectXL(t *testing.T) {
 	nDisks := 16