roachtestutil: dynamically determine block device to stall

Previously, we hardcoded the block device on which to run
the disk-stalled* roachtests and the disk-stall operation.
This was a flaky approach as sometimes we'd use a local
ssd as a block device which had very different numbers
than a Google persistent disk.

This change updates the cgroup disk staller to programmatically
determine the major/minor device numbers for the block device
to stall (the one mounted at /mnt/data1). It also updates the
dmsetup disk staller to dynamically determine the block device
name mounted at /mnt/data1.

Fixes cockroachdb#123080, cockroachdb#123054.

Epic: none

Release note: None

pkg/cmd/roachtest/tests/disk_stall.go

@@ -456,10 +456,12 @@ type dmsetupDiskStaller struct {
 
 var _ diskStaller = (*dmsetupDiskStaller)(nil)
 
-func (s *dmsetupDiskStaller) device() string { return getDevice(s.t, s.c) }
+func (s *dmsetupDiskStaller) device(nodes option.NodeListOption) string {
+	return getDevice(s.t, s.c, nodes)
+}
 
 func (s *dmsetupDiskStaller) Setup(ctx context.Context) {
-	dev := s.device()
+	dev := s.device(s.c.All())
 	// snapd will run "snapd auto-import /dev/dm-0" via udev triggers when
 	// /dev/dm-0 is created. This possibly interferes with the dmsetup create
 	// reload, so uninstall snapd.
@@ -547,20 +549,28 @@ func (s *cgroupDiskStaller) Unstall(ctx context.Context, nodes option.NodeListOp
 	}
 }
 
-func (s *cgroupDiskStaller) device() (major, minor int) {
-	// TODO(jackson): Programmatically determine the device major,minor numbers.
-	// eg,:
-	//    deviceName := getDevice(s.t, s.c)
-	//    `cat /proc/partitions` and find `deviceName`
-	switch s.c.Cloud() {
-	case spec.GCE:
-		// ls -l /dev/sdb
-		// brw-rw---- 1 root disk 8, 16 Mar 27 22:08 /dev/sdb
-		return 8, 16
-	default:
-		s.t.Fatalf("unsupported cloud %q", s.c.Cloud())
+func (s *cgroupDiskStaller) device(nodes option.NodeListOption) (major, minor int) {
+	res, err := s.c.RunWithDetailsSingleNode(context.TODO(), s.t.L(), option.WithNodes(nodes[:1]), "lsblk | grep /mnt/data1 | awk '{print $2}'")
+	if err != nil {
+		s.t.Fatalf("error when determining block device: %s", err)
+		return 0, 0
+	}
+	parts := strings.Split(strings.TrimSpace(res.Stdout), ":")
+	if len(parts) != 2 {
+		s.t.Fatalf("unexpected output from lsblk: %s", res.Stdout)
+		return 0, 0
+	}
+	major, err = strconv.Atoi(parts[0])
+	if err != nil {
+		s.t.Fatalf("error when determining block device: %s", err)
+		return 0, 0
+	}
+	minor, err = strconv.Atoi(parts[1])
+	if err != nil {
+		s.t.Fatalf("error when determining block device: %s", err)
 		return 0, 0
 	}
+	return major, minor
 }
 
 type throughput struct {
@@ -589,7 +599,7 @@ func (rw bandwidthReadWrite) cgroupV2BandwidthProp() string {
 func (s *cgroupDiskStaller) setThroughput(
 	ctx context.Context, nodes option.NodeListOption, rw bandwidthReadWrite, bw throughput,
 ) error {
-	maj, min := s.device()
+	maj, min := s.device(nodes)
 	cockroachIOController := filepath.Join("/sys/fs/cgroup/system.slice", roachtestutil.SystemInterfaceSystemdUnitName()+".service", "io.max")
 
 	bytesPerSecondStr := "max"
@@ -606,25 +616,11 @@ func (s *cgroupDiskStaller) setThroughput(
 	))
 }
 
-func getDevice(t test.Test, c cluster.Cluster) string {
-	s := c.Spec()
-	switch c.Cloud() {
-	case spec.GCE:
-		switch s.LocalSSD {
-		case spec.LocalSSDDisable:
-			return "/dev/sdb"
-		case spec.LocalSSDPreferOn, spec.LocalSSDDefault:
-			// TODO(jackson): These spec values don't guarantee that we are actually
-			// using local SSDs, just that we might've.
-			return "/dev/nvme0n1"
-		default:
-			t.Fatalf("unsupported LocalSSD enum %v", s.LocalSSD)
-			return ""
-		}
-	case spec.AWS:
-		return "/dev/nvme1n1"
-	default:
-		t.Fatalf("unsupported cloud %q", c.Cloud())
+func getDevice(t test.Test, c cluster.Cluster, nodes option.NodeListOption) string {
+	res, err := c.RunWithDetailsSingleNode(context.TODO(), t.L(), option.WithNodes(nodes[:1]), "lsblk | grep /mnt/data1 | awk '{print $1}'")
+	if err != nil {
+		t.Fatalf("error when determining block device: %s", err)
 		return ""
 	}
+	return "/dev/" + strings.TrimSpace(res.Stdout)
 }