libct: simplify setIOPriority/setupScheduler calls

Move the nil check to inside those functions, simplifying the callers.

Signed-off-by: Kir Kolyshkin <[email protected]>

libcontainer/init_linux.go

@@ -676,6 +676,9 @@ func setupRlimits(limits []configs.Rlimit, pid int) error {
 }
 
 func setupScheduler(config *configs.Config) error {
+	if config.Scheduler == nil {
+		return nil
+	}
 	attr, err := configs.ToSchedAttr(config.Scheduler)
 	if err != nil {
 		return err

libcontainer/process_linux.go

@@ -125,10 +125,8 @@ func (p *setnsProcess) signal(sig os.Signal) error {
 func (p *setnsProcess) start() (retErr error) {
 	defer p.comm.closeParent()
 
-	if p.process.IOPriority != nil {
-		if err := setIOPriority(p.process.IOPriority); err != nil {
-			return err
-		}
+	if err := setIOPriority(p.process.IOPriority); err != nil {
+		return err
 	}
 
 	// get the "before" value of oom kill count
@@ -992,6 +990,9 @@ func initWaiter(r io.Reader) chan error {
 func setIOPriority(ioprio *configs.IOPriority) error {
 	const ioprioWhoPgrp = 1
 
+	if ioprio == nil {
+		return nil
+	}
 	class, ok := configs.IOPrioClassMapping[ioprio.Class]
 	if !ok {
 		return fmt.Errorf("invalid io priority class: %s", ioprio.Class)

libcontainer/setns_init_linux.go

@@ -72,10 +72,8 @@ func (l *linuxSetnsInit) Init() error {
 		unix.Umask(int(*l.config.Config.Umask))
 	}
 
-	if l.config.Config.Scheduler != nil {
-		if err := setupScheduler(l.config.Config); err != nil {
-			return err
-		}
+	if err := setupScheduler(l.config.Config); err != nil {
+		return err
 	}
 
 	// Tell our parent that we're ready to exec. This must be done before the

libcontainer/standard_init_linux.go

@@ -156,15 +156,12 @@ func (l *linuxStandardInit) Init() error {
 		}
 	}
 
-	if l.config.Config.Scheduler != nil {
-		if err := setupScheduler(l.config.Config); err != nil {
-			return err
-		}
+	if err := setupScheduler(l.config.Config); err != nil {
+		return err
 	}
-	if l.config.Config.IOPriority != nil {
-		if err := setIOPriority(l.config.Config.IOPriority); err != nil {
-			return err
-		}
+
+	if err := setIOPriority(l.config.Config.IOPriority); err != nil {
+		return err
 	}
 
 	// Tell our parent that we're ready to exec. This must be done before the