zfsbootmenu: add and use recursive_umount function

zfsbootmenu/bin/zfs-chroot

@@ -2,28 +2,7 @@
 # vim: softtabstop=2 shiftwidth=2 expandtab
 
 cleanup() {
-  local mounts mp skip mp_re depth filesystem
-
-  if [ -n "${mountpoint}" ]; then
-    if ! umount -R "${mountpoint}" >/dev/null 2>&1 ; then
-      # thanks, busybox
-      mounts=()
-      mp_re="^${mountpoint}"
-
-      # shellcheck disable=SC2034
-      while read -r skip mp skip skip ; do
-        if [[ "${mp}" =~ ${mp_re} ]]; then
-          depth="${mp//[!\/]/}"
-          mounts+=( "${#depth},${mp}" )
-        fi
-      done < /proc/self/mounts
-
-      while IFS=$'\n' read -r filesystem; do
-        umount "${filesystem#*,}" || zerror "unable to unmount ${filesystem#*,}"
-      done <<<"$( printf '%s\n' "${mounts[@]}" | sort -n -k1 -r )"
-    fi
-  fi
-
+  [ -n "${mountpoint}" ] && recursive_umount "${mountpoint}"
   mount_efivarfs
 
   trap - HUP INT QUIT ABRT EXIT

zfsbootmenu/lib/zfsbootmenu-core.sh

@@ -427,7 +427,7 @@ kexec_kernel() {
   then
     zerror "unable to load ${mnt}${kernel} and ${mnt}${initramfs} into memory"
     zerror "${output}"
-    umount "${mnt}"
+    recursive_umount "${mnt}"
     timed_prompt -d 10 \
       -m "$( colorize red 'Unable to load kernel or initramfs into memory' )" \
       -m "$( colorize orange "${mnt}${kernel}" )" \
@@ -2272,3 +2272,40 @@ is_zfs_filesystem() {
 
   return 1
 }
+
+# arg1: mount point
+# returns: 0 if everything was unmounted, 1 if not
+
+recursive_umount() {
+  local mounts mountpoint mp skip mp_re depth filesystem ret
+
+  mountpoint="${1}"
+  if [ -z "${mountpoint}" ]; then
+    zerror "mountpoint undefined"
+    return 1
+  fi
+
+  ret=0
+  if ! umount -R "${mountpoint}" >/dev/null 2>&1 ; then
+    mounts=()
+    mp_re="^${mountpoint}"
+
+    # shellcheck disable=SC2034
+    while read -r skip mp skip skip ; do
+      if [[ "${mp}" =~ ${mp_re} ]]; then
+        depth="${mp//[!\/]/}"
+        mounts+=( "${#depth},${mp}" )
+      fi
+    done < /proc/self/mounts
+
+    while IFS=$'\n' read -r filesystem; do
+      if ! umount "${filesystem#*,}" >/dev/null 2>&1 ; then
+        zerror "unable to unmount ${filesystem#*,}"
+        ret=1
+      fi
+    done <<<"$( printf '%s\n' "${mounts[@]}" | sort -n -k1 -r )"
+  fi
+
+  return ${ret}
+}
+