@@ -21,6 +21,7 @@ import (

 	"github.com/docker/docker/daemon/graphdriver"

 	"github.com/docker/docker/dockerversion"

 	"github.com/docker/docker/pkg/devicemapper"

+	"github.com/docker/docker/pkg/dmesg"

 	"github.com/docker/docker/pkg/idtools"

 	"github.com/docker/docker/pkg/loopback"

 	"github.com/docker/docker/pkg/mount"

@@ -1199,7 +1200,7 @@ func (devices *DeviceSet) growFS(info *devInfo) error {

 	options = joinMountOptions(options, devices.mountOptions)

 	if err := mount.Mount(info.DevName(), fsMountPoint, devices.BaseDeviceFilesystem, options); err != nil {

-		return fmt.Errorf("Error mounting '%s' on '%s': %s", info.DevName(), fsMountPoint, err)

+		return fmt.Errorf("Error mounting '%s' on '%s': %s\n%v", info.DevName(), fsMountPoint, err, string(dmesg.Dmesg(256)))

 	}

 	defer unix.Unmount(fsMountPoint, unix.MNT_DETACH)

@@ -2390,7 +2391,7 @@ func (devices *DeviceSet) MountDevice(hash, path, mountLabel string) error {

 	options = joinMountOptions(options, label.FormatMountLabel("", mountLabel))

 	if err := mount.Mount(info.DevName(), path, fstype, options); err != nil {

-		return fmt.Errorf("devmapper: Error mounting '%s' on '%s': %s", info.DevName(), path, err)

+		return fmt.Errorf("devmapper: Error mounting '%s' on '%s': %s\n%v", info.DevName(), path, err, string(dmesg.Dmesg(256)))

 	}

 	if fstype == "xfs" && devices.xfsNospaceRetries != "" {

new file mode 100644

@@ -0,0 +1,20 @@

+// +build linux

+

+package dmesg

+

+import (

+	"unsafe"

+

+	"golang.org/x/sys/unix"

+)

+

+// Dmesg returns last messages from the kernel log, up to size bytes

+func Dmesg(size int) []byte {

+	t := uintptr(3) // SYSLOG_ACTION_READ_ALL

+	b := make([]byte, size)

+	amt, _, err := unix.Syscall(unix.SYS_SYSLOG, t, uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)))

+	if err != 0 {

+		return []byte{}

+	}

+	return b[:amt]

+}

new file mode 100644

@@ -0,0 +1,9 @@

+package dmesg

+

+import (

+	"testing"

+)

+

+func TestDmesg(t *testing.T) {

+	t.Logf("dmesg output follows:\n%v", string(Dmesg(512)))

+}