Prefer root mountpoint for ZFS summaries

internal/hostmetrics/zfs.go

@@ -328,14 +328,17 @@ func bestZFSMountpoints(datasets []zfsDatasetUsage) map[string]string {
 }
 
 func zfsMountpointScore(ds zfsDatasetUsage) int {
-	if ds.Dataset != "" && !strings.Contains(ds.Dataset, "/") {
+	if strings.TrimSpace(ds.Mountpoint) == "/" {
 		return 0
 	}
+	if ds.Dataset != "" && !strings.Contains(ds.Dataset, "/") {
+		return 1
+	}
 	path := strings.Trim(ds.Mountpoint, "/")
 	if path == "" {
-		return 1
+		return 0
 	}
-	return 1 + strings.Count(path, "/")
+	return 2 + strings.Count(path, "/")
 }
 
 func zfsPoolFromDevice(device string) string {

internal/hostmetrics/zfs_test.go

@@ -593,6 +593,14 @@ func TestBestZFSMountpoints(t *testing.T) {
 			},
 			want: map[string]string{"rpool": "/"},
 		},
+		{
+			name: "root mountpoint beats pool root mounted elsewhere",
+			datasets: []zfsDatasetUsage{
+				{Pool: "rpool", Dataset: "rpool", Mountpoint: "/mnt/storage"},
+				{Pool: "rpool", Dataset: "rpool/ROOT/pve-1", Mountpoint: "/"},
+			},
+			want: map[string]string{"rpool": "/"},
+		},
 		{
 			name: "skip empty pool",
 			datasets: []zfsDatasetUsage{
@@ -651,39 +659,44 @@ func TestZfsMountpointScore(t *testing.T) {
 		want int
 	}{
 		{
-			name: "root dataset gets score 0",
+			name: "root mountpoint gets score 0",
-			ds:   zfsDatasetUsage{Dataset: "tank", Mountpoint: "/tank"},
+			ds:   zfsDatasetUsage{Dataset: "rpool/ROOT/ubuntu", Mountpoint: "/"},
 			want: 0,
 		},
+		{
+			name: "root dataset mounted elsewhere gets score 1",
+			ds:   zfsDatasetUsage{Dataset: "tank", Mountpoint: "/tank"},
+			want: 1,
+		},
 		{
 			name: "child dataset at root mountpoint",
 			ds:   zfsDatasetUsage{Dataset: "rpool/ROOT/ubuntu", Mountpoint: "/"},
-			want: 1, // path empty after trim("/"), returns 1
+			want: 0,
 		},
 		{
 			name: "child dataset shallow path",
 			ds:   zfsDatasetUsage{Dataset: "tank/data", Mountpoint: "/data"},
-			want: 1, // path="data" has 0 slashes, 1+0=1
+			want: 2, // non-root mountpoints rank after / and pool root datasets
 		},
 		{
 			name: "child dataset deep path",
 			ds:   zfsDatasetUsage{Dataset: "tank/a/b/c", Mountpoint: "/a/b/c"},
-			want: 3, // path="a/b/c" has 2 slashes, 1+2=3
+			want: 4, // path="a/b/c" has 2 slashes, 2+2=4
 		},
 		{
 			name: "empty dataset falls through to path scoring",
 			ds:   zfsDatasetUsage{Dataset: "", Mountpoint: "/tank"},
-			want: 1, // empty dataset passes first check, path="tank" has 0 slashes, 1+0=1
+			want: 2, // empty dataset passes first check, path="tank" has 0 slashes, 2+0=2
 		},
 		{
 			name: "trailing slash stripped from mountpoint",
 			ds:   zfsDatasetUsage{Dataset: "tank/data", Mountpoint: "/data/"},
-			want: 1, // path="data" has 0 slashes, 1+0=1
+			want: 2, // path="data" has 0 slashes, 2+0=2
 		},
 		{
 			name: "very deep mountpoint",
 			ds:   zfsDatasetUsage{Dataset: "tank/deep", Mountpoint: "/a/b/c/d/e"},
-			want: 5, // path="a/b/c/d/e" has 4 slashes, 1+4=5
+			want: 6, // path="a/b/c/d/e" has 4 slashes, 2+4=6
 		},
 	}