[lisa] Plumb lisafs through runsc.

lisafs is only supported in VFS2. Added a runsc flag which enables lisafs.
When the flag is enabled, the gofer process and the client communicate using
lisafs protocol instead of 9P.

Added a filesystem option in fsimpl/gofer which indicates if lisafs is being
used. That will be used to gate lisafs on the gofer client.

Note that this change does not make the gofer client use lisafs just yet.

Updates #5465

PiperOrigin-RevId: 397917844

1 files changed, 52 insertions, 0 deletions

diff --git a/runsc/fsgofer/lisafs.go b/runsc/fsgofer/lisafs.go
new file mode 100644
index 000000000..9d745f461
--- /dev/null
+++ b/runsc/fsgofer/lisafs.go
@@ -0,0 +1,52 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package fsgofer
+
+import (
+	"gvisor.dev/gvisor/pkg/lisafs"
+)
+
+// LisafsServer implements lisafs.ServerImpl for fsgofer.
+type LisafsServer struct {
+	lisafs.Server
+	config Config
+}
+
+var _ lisafs.ServerImpl = (*LisafsServer)(nil)
+
+// NewLisafsServer initializes a new lisafs server for fsgofer.
+func NewLisafsServer(config Config) *LisafsServer {
+	s := &LisafsServer{config: config}
+	s.Server.Init(s)
+	return s
+}
+
+// Mount implements lisafs.ServerImpl.Mount.
+func (s *LisafsServer) Mount(c *lisafs.Connection, mountPath string) (lisafs.ControlFDImpl, lisafs.Inode, error) {
+	panic("unimplemented")
+}
+
+// MaxMessageSize implements lisafs.ServerImpl.MaxMessageSize.
+func (s *LisafsServer) MaxMessageSize() uint32 {
+	return lisafs.MaxMessageSize()
+}
+
+// SupportedMessages implements lisafs.ServerImpl.SupportedMessages.
+func (s *LisafsServer) SupportedMessages() []lisafs.MID {
+	return []lisafs.MID{
+		lisafs.Mount,
+		lisafs.Channel,
+	}
+}