fix: quorum calculation mistake with reduced parity (#10186)

With reduced parity our write quorum should be same
as read quorum, but code was still assuming

```
readQuorum+1
```

In all situations which is not necessary.

cmd/erasure-metadata.go

@@ -88,9 +88,10 @@ func (fi FileInfo) IsValid() bool {
 		// for erasure coding information
 		return true
 	}
-	data := fi.Erasure.DataBlocks
+	dataBlocks := fi.Erasure.DataBlocks
-	parity := fi.Erasure.ParityBlocks
+	parityBlocks := fi.Erasure.ParityBlocks
-	return ((data >= parity) && (data != 0) && (parity != 0))
+	return ((dataBlocks >= parityBlocks) &&
+		(dataBlocks != 0) && (parityBlocks != 0))
 }
 
 // ToObjectInfo - Converts metadata to object info.
@@ -323,7 +324,18 @@ func objectQuorumFromMeta(ctx context.Context, er erasureObjects, partsMetaData
 		return 0, 0, err
 	}
 
+	dataBlocks := latestFileInfo.Erasure.DataBlocks
+	parityBlocks := globalStorageClass.GetParityForSC(latestFileInfo.Metadata[xhttp.AmzStorageClass])
+	if parityBlocks == 0 {
+		parityBlocks = dataBlocks
+	}
+
+	writeQuorum := dataBlocks
+	if dataBlocks == parityBlocks {
+		writeQuorum = dataBlocks + 1
+	}
+
 	// Since all the valid erasure code meta updated at the same time are equivalent, pass dataBlocks
 	// from latestFileInfo to get the quorum
-	return latestFileInfo.Erasure.DataBlocks, latestFileInfo.Erasure.DataBlocks + 1, nil
+	return dataBlocks, writeQuorum, nil
 }

cmd/erasure-multipart.go

@@ -367,7 +367,7 @@ func (er erasureObjects) PutObjectPart(ctx context.Context, bucket, object, uplo
 		writers[i] = newBitrotWriter(disk, minioMetaTmpBucket, tmpPartPath, erasure.ShardFileSize(data.Size()), DefaultBitrotAlgorithm, erasure.ShardSize())
 	}
 
-	n, err := erasure.Encode(ctx, data, writers, buffer, fi.Erasure.DataBlocks+1)
+	n, err := erasure.Encode(ctx, data, writers, buffer, writeQuorum)
 	closeBitrotWriters(writers)
 	if err != nil {
 		return pi, toObjectErr(err, bucket, object)

cmd/erasure-object.go

@@ -670,7 +670,7 @@ func (er erasureObjects) putObject(ctx context.Context, bucket string, object st
 		writers[i] = newBitrotWriter(disk, minioMetaTmpBucket, tempErasureObj, erasure.ShardFileSize(data.Size()), DefaultBitrotAlgorithm, erasure.ShardSize())
 	}
 
-	n, erasureErr := erasure.Encode(ctx, data, writers, buffer, fi.Erasure.DataBlocks+1)
+	n, erasureErr := erasure.Encode(ctx, data, writers, buffer, writeQuorum)
 	closeBitrotWriters(writers)
 	if erasureErr != nil {
 		return ObjectInfo{}, toObjectErr(erasureErr, minioMetaTmpBucket, tempErasureObj)

cmd/erasure-object_test.go

@@ -420,6 +420,8 @@ func testObjectQuorumFromMeta(obj ObjectLayer, instanceType string, dirs []strin
 
 	parts1, errs1 := readAllFileInfo(ctx, erasureDisks, bucket, object1, "")
 
+	parts1SC := globalStorageClass
+
 	// Object for test case 2 - No StorageClass defined, MetaData in PutObject requesting RRS Class
 	object2 := "object2"
 	metadata2 := make(map[string]string)
@@ -430,6 +432,7 @@ func testObjectQuorumFromMeta(obj ObjectLayer, instanceType string, dirs []strin
 	}
 
 	parts2, errs2 := readAllFileInfo(ctx, erasureDisks, bucket, object2, "")
+	parts2SC := globalStorageClass
 
 	// Object for test case 3 - No StorageClass defined, MetaData in PutObject requesting Standard Storage Class
 	object3 := "object3"
@@ -441,6 +444,7 @@ func testObjectQuorumFromMeta(obj ObjectLayer, instanceType string, dirs []strin
 	}
 
 	parts3, errs3 := readAllFileInfo(ctx, erasureDisks, bucket, object3, "")
+	parts3SC := globalStorageClass
 
 	// Object for test case 4 - Standard StorageClass defined as Parity 6, MetaData in PutObject requesting Standard Storage Class
 	object4 := "object4"
@@ -458,6 +462,11 @@ func testObjectQuorumFromMeta(obj ObjectLayer, instanceType string, dirs []strin
 	}
 
 	parts4, errs4 := readAllFileInfo(ctx, erasureDisks, bucket, object4, "")
+	parts4SC := storageclass.Config{
+		Standard: storageclass.StorageClass{
+			Parity: 6,
+		},
+	}
 
 	// Object for test case 5 - RRS StorageClass defined as Parity 2, MetaData in PutObject requesting RRS Class
 	// Reset global storage class flags
@@ -476,6 +485,11 @@ func testObjectQuorumFromMeta(obj ObjectLayer, instanceType string, dirs []strin
 	}
 
 	parts5, errs5 := readAllFileInfo(ctx, erasureDisks, bucket, object5, "")
+	parts5SC := storageclass.Config{
+		RRS: storageclass.StorageClass{
+			Parity: 2,
+		},
+	}
 
 	// Object for test case 6 - RRS StorageClass defined as Parity 2, MetaData in PutObject requesting Standard Storage Class
 	object6 := "object6"
@@ -493,6 +507,11 @@ func testObjectQuorumFromMeta(obj ObjectLayer, instanceType string, dirs []strin
 	}
 
 	parts6, errs6 := readAllFileInfo(ctx, erasureDisks, bucket, object6, "")
+	parts6SC := storageclass.Config{
+		RRS: storageclass.StorageClass{
+			Parity: 2,
+		},
+	}
 
 	// Object for test case 7 - Standard StorageClass defined as Parity 5, MetaData in PutObject requesting RRS Class
 	// Reset global storage class flags
@@ -511,25 +530,32 @@ func testObjectQuorumFromMeta(obj ObjectLayer, instanceType string, dirs []strin
 	}
 
 	parts7, errs7 := readAllFileInfo(ctx, erasureDisks, bucket, object7, "")
+	parts7SC := storageclass.Config{
+		Standard: storageclass.StorageClass{
+			Parity: 5,
+		},
+	}
 
 	tests := []struct {
 		parts               []FileInfo
 		errs                []error
 		expectedReadQuorum  int
 		expectedWriteQuorum int
+		storageClassCfg     storageclass.Config
 		expectedError       error
 	}{
-		{parts1, errs1, 8, 9, nil},
+		{parts1, errs1, 8, 9, parts1SC, nil},
-		{parts2, errs2, 14, 15, nil},
+		{parts2, errs2, 14, 14, parts2SC, nil},
-		{parts3, errs3, 8, 9, nil},
+		{parts3, errs3, 8, 9, parts3SC, nil},
-		{parts4, errs4, 10, 11, nil},
+		{parts4, errs4, 10, 10, parts4SC, nil},
-		{parts5, errs5, 14, 15, nil},
+		{parts5, errs5, 14, 14, parts5SC, nil},
-		{parts6, errs6, 8, 9, nil},
+		{parts6, errs6, 8, 9, parts6SC, nil},
-		{parts7, errs7, 14, 15, nil},
+		{parts7, errs7, 14, 14, parts7SC, nil},
 	}
 	for _, tt := range tests {
 		tt := tt
 		t.(*testing.T).Run("", func(t *testing.T) {
+			globalStorageClass = tt.storageClassCfg
 			actualReadQuorum, actualWriteQuorum, err := objectQuorumFromMeta(ctx, *xl, tt.parts, tt.errs)
 			if tt.expectedError != nil && err == nil {
 				t.Errorf("Expected %s, got %s", tt.expectedError, err)