Fix init script cgroup mounting workarounds to be more similar to cgroupfs-mount and thus work properly

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)

contrib/init/sysvinit-debian/docker

@@ -50,20 +50,34 @@ fail_unless_root() {
 	fi
 }
 
+cgroupfs_mount() {
+	# see also https://github.com/tianon/cgroupfs-mount/blob/master/cgroupfs-mount
+	if grep -v '^#' /etc/fstab | grep -q cgroup \
+		|| [ ! -e /proc/cgroups ] \
+		|| [ ! -d /sys/fs/cgroup ]; then
+		return
+	fi
+	if ! mountpoint -q /sys/fs/cgroup; then
+		mount -t tmpfs -o uid=0,gid=0,mode=0755 cgroup /sys/fs/cgroup
+	fi
+	(
+		cd /sys/fs/cgroup
+		for sys in $(awk '!/^#/ { if ($4 == 1) print $1 }' /proc/cgroups); do
+			mkdir -p $sys
+			if ! mountpoint -q $sys; then
+				if ! mount -n -t cgroup -o $sys cgroup $sys; then
+					rmdir $sys || true
+				fi
+			fi
+		done
+	)
+}
+
 case "$1" in
 	start)
 		fail_unless_root
 
-		if ! grep -q cgroup /proc/mounts; then
-			# rough approximation of cgroupfs-mount
-			mount -t tmpfs -o uid=0,gid=0,mode=0755 cgroup /sys/fs/cgroup
-			for sys in $(cut -d'	' -f1 /proc/cgroups); do
-				mkdir -p /sys/fs/cgroup/$sys
-				if ! mount -n -t cgroup -o $sys cgroup /sys/fs/cgroup/$sys 2>/dev/null; then
-					rmdir /sys/fs/cgroup/$sys 2>/dev/null || true
-				fi
-			done
-		fi
+		cgroupfs_mount
 
 		touch /var/log/docker.log
 		chgrp docker /var/log/docker.log

contrib/init/upstart/docker.conf

@@ -5,6 +5,29 @@ stop on runlevel [!2345]
 
 respawn
 
+pre-start script
+	# see also https://github.com/tianon/cgroupfs-mount/blob/master/cgroupfs-mount
+	if grep -v '^#' /etc/fstab | grep -q cgroup \
+		|| [ ! -e /proc/cgroups ] \
+		|| [ ! -d /sys/fs/cgroup ]; then
+		exit 0
+	fi
+	if ! mountpoint -q /sys/fs/cgroup; then
+		mount -t tmpfs -o uid=0,gid=0,mode=0755 cgroup /sys/fs/cgroup
+	fi
+	(
+		cd /sys/fs/cgroup
+		for sys in $(awk '!/^#/ { if ($4 == 1) print $1 }' /proc/cgroups); do
+			mkdir -p $sys
+			if ! mountpoint -q $sys; then
+				if ! mount -n -t cgroup -o $sys cgroup $sys; then
+					rmdir $sys || true
+				fi
+			fi
+		done
+	)
+end script
+
 script
 	# modify these in /etc/default/$UPSTART_JOB (/etc/default/docker)
 	DOCKER=/usr/bin/$UPSTART_JOB
@@ -12,15 +35,5 @@ script
 	if [ -f /etc/default/$UPSTART_JOB ]; then
 		. /etc/default/$UPSTART_JOB
 	fi
-	if ! grep -q cgroup /proc/mounts; then
-		# rough approximation of cgroupfs-mount
-		mount -t tmpfs -o uid=0,gid=0,mode=0755 cgroup /sys/fs/cgroup
-		for sys in $(cut -d'	' -f1 /proc/cgroups); do
-			mkdir -p /sys/fs/cgroup/$sys
-			if ! mount -n -t cgroup -o $sys cgroup /sys/fs/cgroup/$sys 2>/dev/null; then
-				rmdir /sys/fs/cgroup/$sys 2>/dev/null || true
-			fi
-		done
-	fi
 	"$DOCKER" -d $DOCKER_OPTS
 end script