agent: judge whether /sys/devices/system/memory/block_size_bytes exist.

/sys/devices/system/memory/block_size_bytes will not exist when guestos
doesn't support memory hotplug. Add judgement when file
/sys/devices/system/memory/block_size_bytes doesn't exist.

Fixes kata-containers#394

Signed-off-by: Clare Chen <clare.chenhui@huawei.com>

grpc.go

@@ -47,9 +47,10 @@ const (
 )
 
 var (
-	sysfsCPUOnlinePath     = "/sys/devices/system/cpu"
-	sysfsMemOnlinePath     = "/sys/devices/system/memory"
-	sysfsConnectedCPUsPath = filepath.Join(sysfsCPUOnlinePath, "online")
+	sysfsCPUOnlinePath       = "/sys/devices/system/cpu"
+	sysfsMemOnlinePath       = "/sys/devices/system/memory"
+	sysfsMemoryBlockSizePath = "/sys/devices/system/memory/block_size_bytes"
+	sysfsConnectedCPUsPath   = filepath.Join(sysfsCPUOnlinePath, "online")
 )
 
 type onlineResource struct {
@@ -1320,13 +1321,21 @@ func (a *agentGRPC) ReseedRandomDev(ctx context.Context, req *pb.ReseedRandomDev
 func (a *agentGRPC) GetGuestDetails(ctx context.Context, req *pb.GuestDetailsRequest) (*pb.GuestDetailsResponse, error) {
 	var details pb.GuestDetailsResponse
 	if req.MemBlockSize {
-		data, err := ioutil.ReadFile("/sys/devices/system/memory/block_size_bytes")
+		data, err := ioutil.ReadFile(sysfsMemoryBlockSizePath)
 		if err != nil {
-			return nil, err
-		}
-		details.MemBlockSizeBytes, err = strconv.ParseUint(string(data[:len(data)-1]), 16, 64)
-		if err != nil {
-			return nil, err
+			if os.IsNotExist(err) {
+				agentLog.WithField("sysfsMemoryBlockSizePath", sysfsMemoryBlockSizePath).Info("Guest kernel config doesn't support memory hotplug")
+			} else {
+				return nil, err
+			}
+		} else {
+			if len(data) == 0 {
+				return nil, fmt.Errorf("%v is empty", sysfsMemoryBlockSizePath)
+			}
+			details.MemBlockSizeBytes, err = strconv.ParseUint(string(data[:len(data)-1]), 16, 64)
+			if err != nil {
+				return nil, err
+			}
 		}
 	}
 

grpc_test.go

@@ -14,10 +14,10 @@ import (
 	"path/filepath"
 	"reflect"
 	"sort"
+	"strconv"
 	"testing"
 	"time"
 
-	"strconv"
 	"sync"
 
 	pb "github.com/kata-containers/agent/protocols/grpc"
@@ -666,19 +666,38 @@ func TestGetGuestDetails(t *testing.T) {
 		MemBlockSize: true,
 	}
 
-	resp, err := a.GetGuestDetails(context.TODO(), req)
+	// sysfsMemoryBlockSizePath exist with error format
+	file, err := ioutil.TempFile("", "test")
 	assert.NoError(err)
-
-	data, err := ioutil.ReadFile("/sys/devices/system/memory/block_size_bytes")
+	sysfsMemoryBlockSizePath = file.Name()
+	// empty
+	_, err = a.GetGuestDetails(context.TODO(), req)
+	assert.Error(err)
+	// random string
+	err = ioutil.WriteFile(sysfsMemoryBlockSizePath, []byte(sysfsMemoryBlockSizePath), 0666)
 	assert.NoError(err)
+	_, err = a.GetGuestDetails(context.TODO(), req)
+	assert.Error(err)
 
+	// sysfsMemoryBlockSizePath exist with correct format
+	err = ioutil.WriteFile(sysfsMemoryBlockSizePath, []byte("123"), 0666)
+	assert.NoError(err)
+	resp, err := a.GetGuestDetails(context.TODO(), req)
+	assert.NoError(err)
+	data, err := ioutil.ReadFile(sysfsMemoryBlockSizePath)
+	assert.NoError(err)
 	size, err := strconv.ParseUint(string(data[:len(data)-1]), 16, 64)
 	assert.NoError(err)
-
 	assert.Equal(resp.MemBlockSizeBytes, size)
 
 	seccompSupport := a.haveSeccomp()
 	testAgentDetails(assert, resp.AgentDetails, seccompSupport)
+
+	// sysfsMemoryBlockSizePath not exist
+	os.Remove(sysfsMemoryBlockSizePath)
+	resp, err = a.GetGuestDetails(context.TODO(), req)
+	assert.NoError(err)
+	assert.Equal(resp.MemBlockSizeBytes, uint64(0))
 }
 
 func TestGetAgentDetails(t *testing.T) {