virtiofsd: change cache mod to const

Change cache mod from literal to const and place them in one place.

Also set default cache mode from `none` to `never` in
`pkg/katautils/config-settings.go.in`.

Fixes: #6151

Signed-off-by: Bin Liu <bin@hyper.sh>

src/runtime/pkg/katautils/config-settings.go.in

@@ -80,7 +80,7 @@ const defaultHotplugVFIOOnRootBus bool = false
 const defaultPCIeRootPort = 0
 const defaultEntropySource = "/dev/urandom"
 const defaultGuestHookPath string = ""
-const defaultVirtioFSCacheMode = "none"
+const defaultVirtioFSCacheMode = "never"
 const defaultDisableImageNvdimm = false
 const defaultVhostUserStorePath string = "/var/run/kata-containers/vhost-user/"
 const defaultRxRateLimiterMaxRate = uint64(0)

src/runtime/virtcontainers/clh.go

@@ -80,7 +80,6 @@ const (
 	clhAPISocket                           = "clh-api.sock"
 	virtioFsSocket                         = "virtiofsd.sock"
 	defaultClhPath                         = "/usr/local/bin/cloud-hypervisor"
-	virtioFsCacheAlways                    = "always"
 )
 
 // Interface that hides the implementation of openAPI client

src/runtime/virtcontainers/clh_test.go

@@ -60,7 +60,7 @@ func newClhConfig() (HypervisorConfig, error) {
 		DefaultBridges:                defaultBridges,
 		DefaultMaxVCPUs:               uint32(64),
 		SharedFS:                      config.VirtioFS,
-		VirtioFSCache:                 virtioFsCacheAlways,
+		VirtioFSCache:                 typeVirtioFSCacheModeAlways,
 		VirtioFSDaemon:                testVirtiofsdPath,
 		NetRateLimiterBwMaxRate:       int64(0),
 		NetRateLimiterBwOneTimeBurst:  int64(0),

src/runtime/virtcontainers/kata_agent.go

@@ -88,7 +88,6 @@ var (
 	type9pFs                     = "9p"
 	typeVirtioFS                 = "virtiofs"
 	typeOverlayFS                = "overlay"
-	typeVirtioFSNoCache          = "never"
 	kata9pDevType                = "9p"
 	kataMmioBlkDevType           = "mmioblk"
 	kataBlkDevType               = "blk"
@@ -805,7 +804,7 @@ func setupStorages(ctx context.Context, sandbox *Sandbox) []*grpc.Storage {
 			// directly map contents from the host. When set to 'never', the mount
 			// options should not contain 'dax' lest the virtio-fs daemon crashing
 			// with an invalid address reference.
-			if sandbox.config.HypervisorConfig.VirtioFSCache != typeVirtioFSNoCache {
+			if sandbox.config.HypervisorConfig.VirtioFSCache != typeVirtioFSCacheModeNever {
 				// If virtio_fs_cache_size = 0, dax should not be used.
 				if sandbox.config.HypervisorConfig.VirtioFSCacheSize != 0 {
 					sharedDirVirtioFSOptions = append(sharedDirVirtioFSOptions, sharedDirVirtioFSDaxOptions)

src/runtime/virtcontainers/virtiofsd.go

@@ -37,6 +37,13 @@ var (
 	errUnimplemented                     = errors.New("unimplemented")
 )
 
+const (
+	typeVirtioFSCacheModeNever  = "never"
+	typeVirtioFSCacheModeNone   = "none"
+	typeVirtioFSCacheModeAlways = "always"
+	typeVirtioFSCacheModeAuto   = "auto"
+)
+
 type VirtiofsDaemon interface {
 	// Start virtiofs daemon, return pid of virtiofs daemon process
 	Start(context.Context, onQuitFunc) (pid int, err error)
@@ -216,11 +223,11 @@ func (v *virtiofsd) valid() error {
 	}
 
 	if v.cache == "" {
-		v.cache = "auto"
-	} else if v.cache == "none" {
+		v.cache = typeVirtioFSCacheModeAuto
+	} else if v.cache == typeVirtioFSCacheModeNone {
 		v.Logger().Warn("virtio-fs cache mode `none` is deprecated since Kata Containers 2.5.0 and will be removed in the future release, please use `never` instead. For more details please refer to https://github.com/kata-containers/kata-containers/issues/4234.")
-		v.cache = "never"
-	} else if v.cache != "auto" && v.cache != "always" && v.cache != "never" {
+		v.cache = typeVirtioFSCacheModeNever
+	} else if v.cache != typeVirtioFSCacheModeAuto && v.cache != typeVirtioFSCacheModeAlways && v.cache != typeVirtioFSCacheModeNever {
 		return errVirtiofsdInvalidVirtiofsCacheMode(v.cache)
 	}