Create directory for disk backing file, if needed

- This allows mounting a backing disk file from within the container
  filesystem or image, e.g.

  --env=RUNCVM_DISKS=/disks/docker,/var/lib/docker,ext4,1G

Author: struanb

runcvm-scripts/runcvm-ctr-qemu

@@ -52,6 +52,12 @@ do_disk() {
       error "Error: disk spec '$spec' invalid: size must be specified if src '$src' does not exist"
     fi
 
+    # Create directory for disk backing file, if needed.
+    local dir="$(busybox dirname "$src")"
+    if ! [ -d "$dir" ]; then
+      mkdir -p $(busybox dirname "$src")
+    fi
+
     busybox truncate -s "$size" "$src" >&2 || error "Error: disk spec '$spec' invalid: truncate on '$src' with size '$size' failed"
     mke2fs -F -t "$fs" "$src" >&2 || error "Error: disk spec '$spec' invalid: mke2fs on '$src' with fs '$fs' failed"
   fi