Move RemovePaths into cgroups pkg for reuse

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

cgroups/fs/apply_raw.go

@@ -64,21 +64,23 @@ func Apply(c *cgroups.Cgroup, pid int) (map[string]string, error) {
 	}
 
 	paths := make(map[string]string)
+	defer func() {
+		if err != nil {
+			cgroups.RemovePaths(paths)
+		}
+	}()
 	for name, sys := range subsystems {
 		if err := sys.Set(d); err != nil {
-			for _, p := range paths {
-				os.RemoveAll(p)
-			}
 			return nil, err
 		}
+		// FIXME: Apply should, ideally, be reentrant or be broken up into a separate
+		// create and join phase so that the cgroup hierarchy for a container can be
+		// created then join consists of writing the process pids to cgroup.procs
 		p, err := d.path(name)
 		if err != nil {
 			if cgroups.IsNotFound(err) {
 				continue
 			}
-			for _, p := range paths {
-				os.RemoveAll(p)
-			}
 			return nil, err
 		}
 		paths[name] = p

cgroups/utils.go

@@ -189,6 +189,17 @@ func EnterPid(cgroupPaths map[string]string, pid int) error {
 			}
 		}
 	}
-
 	return nil
 }
+
+// RemovePaths iterates over the provided paths removing them.
+// If an error is encountered the removal proceeds and the first error is
+// returned to ensure a partial removal is not possible.
+func RemovePaths(paths map[string]string) (err error) {
+	for _, path := range paths {
+		if rerr := os.RemoveAll(path); err == nil {
+			err = rerr
+		}
+	}
+	return err
+}

namespaces/exec.go

@@ -10,6 +10,7 @@ import (
 	"syscall"
 
 	"github.com/docker/libcontainer"
+	"github.com/docker/libcontainer/cgroups"
 	"github.com/docker/libcontainer/cgroups/fs"
 	"github.com/docker/libcontainer/cgroups/systemd"
 	"github.com/docker/libcontainer/network"
@@ -63,7 +64,7 @@ func Exec(container *libcontainer.Config, stdin io.Reader, stdout, stderr io.Wri
 	if err != nil {
 		return terminate(err)
 	}
-	defer removeCgroupPaths(cgroupPaths)
+	defer cgroups.RemovePaths(cgroupPaths)
 
 	var networkState network.NetworkState
 	if err := InitializeNetworking(container, command.Process.Pid, &networkState); err != nil {
@@ -172,13 +173,3 @@ func InitializeNetworking(container *libcontainer.Config, nspid int, networkStat
 	}
 	return nil
 }
-
-// removeCgroupPaths takes the subsystem paths for each cgroup that was
-// setup for the container and removes them from the cgroup filesystem.
-// Errors are ignored during the removal because we don't want to end up
-// with partially removed cgroups.
-func removeCgroupPaths(paths map[string]string) {
-	for _, path := range paths {
-		os.RemoveAll(path)
-	}
-}