Do not mount unassembled dmraid arrays

Some of the dmraid device configurations might exist in non-safe
(non-working) mode. An example is an array is constructed incrementally from
multiple devices. The first device creates an array that is reported via
udev, but this array is not usable, it needs more block devices added to
start serving I/O.

Instead of starting to use an mdarray at "add" udev device we have to
check whether 'mdadm --incremental' actually starts the array. Use 'mdadm
--export' to get status of the array and mount it only when MD_STARTED
property is set (i.e. array is live).

Fixes #97

init/main.go

@@ -101,7 +101,7 @@ var (
 // from subsystem “block”.
 func addBlockDevice(devname string) error {
 	// Some devices might receive multiple udev add events
-	// Avoid processing these node twice by tracking what has been added already
+	// Avoid processing these nodes twice by tracking what has been added already
 	addedDevicesMutex.Lock()
 	if _, ok := addedDevices[devname]; ok {
 		addedDevicesMutex.Unlock()
@@ -190,12 +190,23 @@ func handleMdraidBlockDevice(info *blkInfo, devpath string) error {
 			return fmt.Errorf("unknown raid level for device %s", devpath)
 		}
 
-		cmd := exec.Command("mdadm", "--incremental", devpath)
-		if verbosityLevel >= levelDebug {
-			cmd.Stderr = os.Stderr
-			cmd.Stdout = os.Stdout
+		out, err := exec.Command("mdadm", "--export", "--incremental", devpath).CombinedOutput()
+		if err != nil {
+			return err
 		}
-		return cmd.Run()
+
+		props := parseProperties(string(out))
+		arrayName, hasArrayName := props["MD_DEVNAME"]
+		if !hasArrayName {
+			return fmt.Errorf("mdraid array at %s does not have a MD_DEVNAME property", info.uuid.toString())
+		}
+
+		if started, ok := props["MD_STARTED"]; !ok || started != "yes" {
+			debug("mdraid array %s is not complete, ignore it", arrayName)
+			return nil
+		}
+
+		return addBlockDevice("md/" + arrayName)
 	} else {
 		debug("MdRaid support is disabled, ignoring mdraid device %s", devpath)
 		return nil

init/udev.go

@@ -6,7 +6,6 @@ import (
 	"log"
 	"net"
 	"os"
-	"os/exec"
 	"path"
 	"regexp"
 	"strconv"
@@ -142,7 +141,6 @@ func handleNetworkUevent(ev *uevent.Uevent) error {
 
 var (
 	dmNameRe = regexp.MustCompile(`dm-\d+`)
-	mdNameRe = regexp.MustCompile(`md\d+`)
 )
 
 func handleBlockDeviceUevent(ev *uevent.Uevent) error {
@@ -157,42 +155,13 @@ func handleBlockDeviceUevent(ev *uevent.Uevent) error {
 		return err
 	}
 
-	if mdNameRe.MatchString(devName) {
-		return handleMdRaidUevent(ev)
-	}
-
 	if ev.Action == "add" {
 		return addBlockDevice(devName)
 	}
 
 	return nil
 }
 
-func handleMdRaidUevent(ev *uevent.Uevent) error {
-	devName := ev.Vars["DEVNAME"]
-
-	if err := addBlockDevice(devName); err != nil {
-		return err
-	}
-
-	// for mdraid there is a special case - add /dev/md/ArrayName symlink
-	out, err := exec.Command("mdadm", "--export", "--detail", "/dev/"+devName).CombinedOutput()
-	if err != nil {
-		return err
-	}
-
-	props := parseProperties(string(out))
-	if n, ok := props["MD_DEVNAME"]; ok {
-		if err := addBlockDevice("md/" + n); err != nil {
-			return err
-		}
-	} else {
-		return fmt.Errorf("mdraid array %s does not have a MD_DEVNAME property", devName)
-	}
-
-	return nil
-}
-
 var errIgnoredMapperEvent = fmt.Errorf("ignored device mapper event")
 
 // handleMapperDeviceUevent handles device mapper related uevent