From 49cf74f4f6caf8a570c60ca92c48548e525199b9 Mon Sep 17 00:00:00 2001
From: Justin Cormack <justin.cormack@docker.com>
Date: Tue, 22 Aug 2017 16:23:20 +0100
Subject: [PATCH] Switch to having the moby tool specify how to do mounts

This removes all the code that had knowledge of how to do read only
and read write container mounts, and just uses the runtime config.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>
---
 pkg/init/cmd/service/prepare.go | 60 ++++++++-------------------------
 1 file changed, 14 insertions(+), 46 deletions(-)

diff --git a/pkg/init/cmd/service/prepare.go b/pkg/init/cmd/service/prepare.go
index ce1ed6443..9c72857f4 100644
--- a/pkg/init/cmd/service/prepare.go
+++ b/pkg/init/cmd/service/prepare.go
@@ -66,7 +66,6 @@ func getRuntimeConfig(path string) Runtime {
 
 // parseMountOptions takes fstab style mount options and parses them for
 // use with a standard mount() syscall
-// taken from containerd, where it is not exported
 func parseMountOptions(options []string) (int, string) {
 	var (
 		flag int
@@ -93,14 +92,18 @@ func parseMountOptions(options []string) (int, string) {
 		"norelatime":    {true, unix.MS_RELATIME},
 		"nostrictatime": {true, unix.MS_STRICTATIME},
 		"nosuid":        {false, unix.MS_NOSUID},
+		"private":       {false, unix.MS_PRIVATE},
 		"rbind":         {false, unix.MS_BIND | unix.MS_REC},
 		"relatime":      {false, unix.MS_RELATIME},
 		"remount":       {false, unix.MS_REMOUNT},
 		"ro":            {false, unix.MS_RDONLY},
 		"rw":            {true, unix.MS_RDONLY},
+		"shared":        {false, unix.MS_SHARED},
+		"slave":         {false, unix.MS_SLAVE},
 		"strictatime":   {false, unix.MS_STRICTATIME},
 		"suid":          {true, unix.MS_NOSUID},
 		"sync":          {false, unix.MS_SYNCHRONOUS},
+		"unbindable":    {false, unix.MS_UNBINDABLE},
 	}
 	for _, o := range options {
 		// If the option does not exist in the flags table or the flag
@@ -130,6 +133,16 @@ func prepareFilesystem(path string, runtime Runtime) error {
 		if err != nil {
 			return fmt.Errorf("Cannot create directory for mount destination %s: %v", mount.Destination, err)
 		}
+		// also mkdir upper and work directories on overlay
+		for _, o := range mount.Options {
+			eq := strings.SplitN(o, "=", 2)
+			if len(eq) == 2 && (eq[0] == "upperdir" || eq[0] == "workdir") {
+				err := os.MkdirAll(eq[1], mode)
+				if err != nil {
+					return fmt.Errorf("Cannot create directory for overlay %s=%s: %v", eq[0], eq[1], err)
+				}
+			}
+		}
 		opts, data := parseMountOptions(mount.Options)
 		if err := unix.Mount(mount.Source, mount.Destination, mount.Type, uintptr(opts), data); err != nil {
 			return fmt.Errorf("Failed to mount %s: %v", mount.Source, err)
@@ -144,51 +157,6 @@ func prepareFilesystem(path string, runtime Runtime) error {
 		}
 	}
 
-	// see if we are dealing with a read only or read write container
-	if _, err := os.Stat(filepath.Join(path, "lower")); err != nil {
-		if os.IsNotExist(err) {
-			return prepareRO(path)
-		}
-		return err
-	}
-	return prepareRW(path)
-}
-
-func prepareRO(path string) error {
-	// make rootfs a mount point, as runc doesn't like it much otherwise
-	rootfs := filepath.Join(path, "rootfs")
-	if err := unix.Mount(rootfs, rootfs, "", unix.MS_BIND, ""); err != nil {
-		return err
-	}
-	return nil
-}
-
-func prepareRW(path string) error {
-	// mount a tmpfs on tmp for upper and workdirs
-	// make it private as nothing else should be using this
-	tmp := filepath.Join(path, "tmp")
-	if err := unix.Mount("tmpfs", tmp, "tmpfs", 0, "size=10%"); err != nil {
-		return err
-	}
-	// make it private as nothing else should be using this
-	if err := unix.Mount("", tmp, "", unix.MS_REMOUNT|unix.MS_PRIVATE, ""); err != nil {
-		return err
-	}
-	upper := filepath.Join(tmp, "upper")
-	// make the mount points
-	if err := os.Mkdir(upper, 0755); err != nil {
-		return err
-	}
-	work := filepath.Join(tmp, "work")
-	if err := os.Mkdir(work, 0755); err != nil {
-		return err
-	}
-	lower := filepath.Join(path, "lower")
-	rootfs := filepath.Join(path, "rootfs")
-	opt := fmt.Sprintf("lowerdir=%s,upperdir=%s,workdir=%s", lower, upper, work)
-	if err := unix.Mount("overlay", rootfs, "overlay", 0, opt); err != nil {
-		return err
-	}
 	return nil
 }