Fix partitioner not identifying mmc/nvme partitions

We were expecting them to follow us the device name + numer at the end
but mmc and nvme partitions follow a different schema.

In order to make this work for anything and even new schemas that we may
not expect, we just get the actual device directly from udev by
resolving the /dev/disk/by-partlabel which links to the actual named
device.

Signed-off-by: Itxaka <itxaka@kairos.io>

pkg/elemental/elemental.go

@@ -103,7 +103,7 @@ func (e *Elemental) PartitionAndFormatDevice(i v1.SharedInstallSpec) error {
 		e.config.Logger.Errorf("Udevadm settle failed: %s", err)
 	}
 	// Partitions are in order so we can format them via that
-	for index, p := range table.GetPartitions() {
+	for _, p := range table.GetPartitions() {
 		for _, configPart := range i.GetPartitions().PartitionsByInstallOrder(i.GetExtraPartitions()) {
 			if configPart.Name == cnst.BiosPartName {
 				// Grub partition on non-EFI is not formatted. Grub is directly installed on it
@@ -112,7 +112,16 @@ func (e *Elemental) PartitionAndFormatDevice(i v1.SharedInstallSpec) error {
 			// we have to match the Fs it was asked with the partition in the system
 			if p.(*gpt.Partition).Name == configPart.Name {
 				e.config.Logger.Debugf("Formatting partition: %s", configPart.FilesystemLabel)
-				err = partitioner.FormatDevice(e.config.Runner, fmt.Sprintf("%s%d", i.GetTarget(), index+1), configPart.FS, configPart.FilesystemLabel)
+				// Get full partition path by the /dev/disk/by-partlabel/ facility
+				// So we don't need to infer the actual device under it but get udev to tell us
+				// So this works for "normal" devices that have the "expected" partitions (i.e. /dev/sda has /dev/sda1, /dev/sda2)
+				// And "weird" devices that have special subdevices like mmc or nvme
+				// i.e. /dev/mmcblk0 has /dev/mmcblk0p1, /dev/mmcblk0p2
+				device, err := filepath.EvalSymlinks(fmt.Sprintf("/dev/disk/by-partlabel/%s", configPart.Name))
+				if err != nil {
+					e.config.Logger.Errorf("Failed finding partition %s by partition label: %s", configPart.FilesystemLabel, err)
+				}
+				err = partitioner.FormatDevice(e.config.Runner, device, configPart.FS, configPart.FilesystemLabel)
 				if err != nil {
 					e.config.Logger.Errorf("Failed formatting partition: %s", err)
 					return err