Move filesystem creation from GetFilesystem to RegistryImpl.

Move root dentry and filesystem creation from GetFilesystem to
NewRegistryImpl, create IPCNamespace.InitPosixQueues to create a new
mqueue filesystem for each ipc namespace, and update GetFilesystem to
retreive fs and root dentry from IPCNamespace and return them.

Updates #136

3 files changed, 22 insertions, 5 deletions

diff --git a/pkg/sentry/kernel/BUILD b/pkg/sentry/kernel/BUILD
index 6ff3deb97..9f30a7706 100644
--- a/pkg/sentry/kernel/BUILD
+++ b/pkg/sentry/kernel/BUILD
@@ -249,6 +249,7 @@ go_library(
         "//pkg/sentry/fs/timerfd",
         "//pkg/sentry/fsbridge",
         "//pkg/sentry/fsimpl/kernfs",
+        "//pkg/sentry/fsimpl/mqfs",
         "//pkg/sentry/fsimpl/pipefs",
         "//pkg/sentry/fsimpl/sockfs",
         "//pkg/sentry/fsimpl/timerfd",
diff --git a/pkg/sentry/kernel/ipc_namespace.go b/pkg/sentry/kernel/ipc_namespace.go
index aa9c3fb31..11b4545c6 100644
--- a/pkg/sentry/kernel/ipc_namespace.go
+++ b/pkg/sentry/kernel/ipc_namespace.go
@@ -15,12 +15,16 @@
 package kernel
 
 import (
+	"fmt"
+
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/mqfs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/mq"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/msgqueue"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/semaphore"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/shm"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
 )
 
 // IPCNamespace represents an IPC namespace.
@@ -72,12 +76,19 @@ func (i *IPCNamespace) ShmRegistry() *shm.Registry {
 	return i.shms
 }
 
-// SetPosixQueues sets value of posixQueues if the value is currently nil,
-// otherwise returns without doing anything.
-func (i *IPCNamespace) SetPosixQueues(r *mq.Registry) {
-	if i.posixQueues == nil {
-		i.posixQueues = r
+// InitPosixQueues creates a new POSIX queue registry, and returns an error if
+// the registry was previously initialized.
+func (i *IPCNamespace) InitPosixQueues(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials) error {
+	if i.posixQueues != nil {
+		return fmt.Errorf("IPCNamespace.InitPosixQueues: already initialized")
+	}
+
+	impl, err := mqfs.NewRegistryImpl(ctx, vfsObj, creds)
+	if err != nil {
+		return err
 	}
+	i.posixQueues = mq.NewRegistry(impl)
+	return nil
 }
 
 // PosixQueues returns the posix message queue registry for this namespace.
diff --git a/pkg/sentry/kernel/mq/mq.go b/pkg/sentry/kernel/mq/mq.go
index be46f78c8..739ea2f1c 100644
--- a/pkg/sentry/kernel/mq/mq.go
+++ b/pkg/sentry/kernel/mq/mq.go
@@ -79,6 +79,11 @@ func (r *Registry) Destroy(ctx context.Context) {
 	r.impl.Destroy(ctx)
 }
 
+// Impl returns RegistryImpl inside r.
+func (r *Registry) Impl() RegistryImpl {
+	return r.impl
+}
+
 // Queue represents a POSIX message queue.
 //
 // +stateify savable