disk: replace the lvm name generation with genUniqueString()

Replace the heart of the lvm name generator with the new function.
Update the vg.CreateMountpoint() test, because the old implementation
was off by one and would fail when '99' was available.

pkg/disk/disk.go

@@ -259,6 +259,8 @@ func NewVolIDFromRand(r *rand.Rand) string {
 // the existing set. If the base itself does not exist, it is returned as is,
 // otherwise a two digit number is added and incremented until a unique string
 // is found.
+// This function is mimicking what blivet does for avoiding name collisions.
+// See blivet/blivet.py#L1060 commit 2eb4bd4
 func genUniqueString(base string, existing map[string]bool) (string, error) {
 	if !existing[base] {
 		return base, nil

pkg/disk/lvm.go

@@ -95,25 +95,9 @@ func (vg *LVMVolumeGroup) genLVName(base string) (string, error) {
 
 	base = lvname(base) // if the mountpoint is used (i.e. if the base contains /), sanitize it and append 'lv'
 
-	var exists bool
-	name := base
-
-	// Make sure that we don't collide with an existing volume, e.g. 'home/test'
-	// and /home/test_test would collide. We try 100 times and then give up. This
-	// is mimicking what blivet does. See blivet/blivet.py#L1060 commit 2eb4bd4
-	for i := 0; i < 100; i++ {
-		exists = names[name]
-		if !exists {
-			break
-		}
-
-		name = fmt.Sprintf("%s%02d", base, i)
-	}
-
-	if exists {
-		return "", fmt.Errorf("could not create logical volume: name collision")
-	}
-	return name, nil
+	// Make sure that we don't collide with an existing volume, e.g.
+	// 'home/test' and /home_test would collide.
+	return genUniqueString(base, names)
 }
 
 // CreateLogicalVolume creates a new logical volume on the volume group. If a

pkg/disk/lvm_test.go

@@ -30,7 +30,7 @@ func TestLVMVCreateMountpoint(t *testing.T) {
 	assert.Equal("home_testlv00", dedup.Name)
 
 	// Lets collide it
-	for i := 0; i < 98; i++ {
+	for i := 0; i < 99; i++ {
 		_, err = vg.CreateMountpoint("/home/test", 0)
 		assert.NoError(err)
 	}