Enumerate block device slaves as UnderlyingDeviceInfo

Signed-off-by: W. Andrew Denton <git@flying-snail.net>

blockdevice/stats.go

@@ -21,9 +21,8 @@ import (
 	"os"
 	"strings"
 
-	"github.com/prometheus/procfs/internal/util"
-
 	"github.com/prometheus/procfs/internal/fs"
+	"github.com/prometheus/procfs/internal/util"
 )
 
 // Info contains identifying information for a block device such as a disk drive
@@ -196,13 +195,20 @@ type DeviceMapperInfo struct {
 	Uuid string
 }
 
+// UnderlyingDevices models the list of devices that this device is built from.
+type UnderlyingDeviceInfo struct {
+	// DeviceNames is the list of devices names
+	DeviceNames []string
+}
+
 const (
 	procDiskstatsPath   = "diskstats"
 	procDiskstatsFormat = "%d %d %s %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d"
 	sysBlockPath        = "block"
 	sysBlockStatFormat  = "%d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d"
 	sysBlockQueue       = "queue"
 	sysBlockDm          = "dm"
+	sysUnderlyingDev    = "slaves"
 )
 
 // FS represents the pseudo-filesystems proc and sys, which provides an
@@ -445,3 +451,16 @@ func (fs FS) SysBlockDeviceMapperInfo(device string) (DeviceMapperInfo, error) {
 	}
 	return info, nil
 }
+
+func (fs FS) SysBlockDeviceUnderlyingDevices(device string) (UnderlyingDeviceInfo, error) {
+	underlyingDir, err := os.Open(fs.sys.Path(sysBlockPath, device, sysUnderlyingDev))
+	if err != nil {
+		return UnderlyingDeviceInfo{}, err
+	}
+	underlying, err := underlyingDir.Readdirnames(0)
+	if err != nil {
+		return UnderlyingDeviceInfo{}, err
+	}
+	return UnderlyingDeviceInfo{DeviceNames: underlying}, nil
+
+}

blockdevice/stats_test.go

@@ -14,6 +14,7 @@
 package blockdevice
 
 import (
+	"os"
 	"reflect"
 	"testing"
 )
@@ -177,4 +178,44 @@ func TestBlockDmInfo(t *testing.T) {
 	if !reflect.DeepEqual(dm0Info, dm0InfoExpected) {
 		t.Errorf("Incorrect BlockQueueStat, expected: \n%+v, got: \n%+v", dm0InfoExpected, dm0Info)
 	}
+
+	dm1Info, err := blockdevice.SysBlockDeviceMapperInfo(devices[1])
+	if err != nil {
+		if _, ok := err.(*os.PathError); ok {
+			// Fail the test if there's an error other than PathError.
+			if !os.IsNotExist(err) {
+				t.Fatal(err)
+			}
+		} else {
+			t.Fatal(err)
+		}
+	} else {
+		t.Fatal("SysBlockDeviceMapperInfo on sda was supposed to fail.")
+	}
+	dm1InfoExpected := DeviceMapperInfo{}
+	if !reflect.DeepEqual(dm1Info, dm1InfoExpected) {
+		t.Errorf("Incorrect BlockQueueStat, expected: \n%+v, got: \n%+v", dm0InfoExpected, dm0Info)
+	}
+}
+
+func TestSysBlockDeviceUnderlyingDevices(t *testing.T) {
+	blockdevice, err := NewFS("../fixtures/proc", "../fixtures/sys")
+	if err != nil {
+		t.Fatalf("failed to access blockdevice fs: %v", err)
+	}
+	devices, err := blockdevice.SysBlockDevices()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	underlying0, err := blockdevice.SysBlockDeviceUnderlyingDevices(devices[0])
+	if err != nil {
+		t.Fatal(err)
+	}
+	underlying0Expected := UnderlyingDeviceInfo{
+		DeviceNames: []string{"sda"},
+	}
+	if !reflect.DeepEqual(underlying0, underlying0Expected) {
+		t.Errorf("Incorrect BlockQueueStat, expected: \n%+v, got: \n%+v", underlying0Expected, underlying0)
+	}
 }