correctly calculate read quorum based on the available fileInfo (#14000)

The current usage of assuming `default` parity of `4` is not correct
for all objects stored on MinIO, objects in .minio.sys have maximum
parity, healing won't trigger on these objects due to incorrect
verification of quorum.

cmd/erasure-healing_test.go

@@ -329,6 +329,131 @@ func TestHealingDanglingObject(t *testing.T) {
 	}
 }
 
+func TestHealCorrectQuorum(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	resetGlobalHealState()
+	defer resetGlobalHealState()
+
+	nDisks := 32
+	fsDirs, err := getRandomDisks(nDisks)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer removeRoots(fsDirs)
+
+	pools := mustGetPoolEndpoints(fsDirs[:16]...)
+	pools = append(pools, mustGetPoolEndpoints(fsDirs[16:]...)...)
+
+	// Everything is fine, should return nil
+	objLayer, _, err := initObjectLayer(ctx, pools)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	bucket := getRandomBucketName()
+	object := getRandomObjectName()
+	data := bytes.Repeat([]byte("a"), 5*1024*1024)
+	var opts ObjectOptions
+
+	err = objLayer.MakeBucketWithLocation(ctx, bucket, BucketOptions{})
+	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 := objLayer.NewMultipartUpload(ctx, 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 := objLayer.PutObjectPart(ctx, 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 = objLayer.CompleteMultipartUpload(ctx, bucket, object, uploadID, uploadedParts, ObjectOptions{})
+	if err != nil {
+		t.Fatalf("Failed to complete multipart upload - %v", err)
+	}
+
+	cfgFile := pathJoin(bucketConfigPrefix, bucket, ".test.bin")
+	if err = saveConfig(ctx, objLayer, cfgFile, data); err != nil {
+		t.Fatal(err)
+	}
+
+	hopts := madmin.HealOpts{
+		DryRun:   false,
+		Remove:   true,
+		ScanMode: madmin.HealNormalScan,
+	}
+
+	// Test 1: Remove the object backend files from the first disk.
+	z := objLayer.(*erasureServerPools)
+	for _, set := range z.serverPools {
+		er := set.sets[0]
+		erasureDisks := er.getDisks()
+
+		fileInfos, errs := readAllFileInfo(ctx, erasureDisks, bucket, object, "", false)
+		nfi, err := getLatestFileInfo(ctx, fileInfos, errs)
+		if errors.Is(err, errFileNotFound) {
+			continue
+		}
+		if err != nil {
+			t.Fatalf("Failed to getLatestFileInfo - %v", err)
+		}
+
+		for i := 0; i < nfi.Erasure.ParityBlocks; i++ {
+			erasureDisks[i].Delete(context.Background(), bucket, pathJoin(object, xlStorageFormatFile), false)
+		}
+
+		// Try healing now, it should heal the content properly.
+		_, err = objLayer.HealObject(ctx, bucket, object, "", hopts)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		fileInfos, errs = readAllFileInfo(ctx, erasureDisks, bucket, object, "", false)
+		if countErrs(errs, nil) != len(fileInfos) {
+			t.Fatal("Expected all xl.meta healed, but partial heal detected")
+		}
+
+		fileInfos, errs = readAllFileInfo(ctx, erasureDisks, minioMetaBucket, cfgFile, "", false)
+		nfi, err = getLatestFileInfo(ctx, fileInfos, errs)
+		if errors.Is(err, errFileNotFound) {
+			continue
+		}
+		if err != nil {
+			t.Fatalf("Failed to getLatestFileInfo - %v", err)
+		}
+
+		for i := 0; i < nfi.Erasure.ParityBlocks; i++ {
+			erasureDisks[i].Delete(context.Background(), minioMetaBucket, pathJoin(cfgFile, xlStorageFormatFile), false)
+		}
+
+		// Try healing now, it should heal the content properly.
+		_, err = objLayer.HealObject(ctx, minioMetaBucket, cfgFile, "", hopts)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		fileInfos, errs = readAllFileInfo(ctx, erasureDisks, minioMetaBucket, cfgFile, "", false)
+		if countErrs(errs, nil) != len(fileInfos) {
+			t.Fatal("Expected all xl.meta healed, but partial heal detected")
+		}
+	}
+}
+
 func TestHealObjectCorruptedPools(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()