Fix encryption logic in systemd mount generator

Previously the generator would skip a dataset if it wasn't mountable by
'zfs mount -a' (legacy/none mountpoint, canmount off/noauto). This also
skipped the generation of key-load units for such datasets, breaking
the dependency handling for mountable child datasets.

Reviewed-by: Antonio Russo <antonio.e.russo@gmail.com>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: InsanePrawn <insane.prawny@gmail.com>
Closes #9611

etc/systemd/system-generators/zfs-mount-generator.in

@@ -74,6 +74,62 @@ process_line() {
   p_encroot="${11}"
   p_keyloc="${12}"
 
+  # Minimal pre-requisites to mount a ZFS dataset
+  wants="zfs-import.target"
+
+  # Handle encryption
+  if [ -n "${p_encroot}" ] &&
+      [ "${p_encroot}" != "-" ] ; then
+    keyloadunit="zfs-load-key-$(systemd-escape "${p_encroot}").service"
+    if [ "${p_encroot}" = "${dataset}" ] ; then
+        pathdep=""
+      if [ "${p_keyloc%%://*}" = "file" ] ; then
+        pathdep="RequiresMountsFor='${p_keyloc#file://}'"
+        keyloadcmd="@sbindir@/zfs load-key '${dataset}'"
+      elif [ "${p_keyloc}" = "prompt" ] ; then
+        keyloadcmd="/bin/sh -c 'set -eu;"\
+"keystatus=\"\$\$(@sbindir@/zfs get -H -o value keystatus \"${dataset}\")\";"\
+"[ \"\$\$keystatus\" = \"unavailable\" ] || exit 0;"\
+"count=0;"\
+"while [ \$\$count -lt 3 ];do"\
+"  systemd-ask-password --id=\"zfs:${dataset}\""\
+"    \"Enter passphrase for ${dataset}:\"|"\
+"    @sbindir@/zfs load-key \"${dataset}\" && exit 0;"\
+"  count=\$\$((count + 1));"\
+"done;"\
+"exit 1'"
+      else
+        printf 'zfs-mount-generator: (%s) invalid keylocation\n' \
+          "${dataset}" >/dev/kmsg
+      fi
+
+      # Generate the key-load .service unit
+      cat > "${dest_norm}/${keyloadunit}" << EOF
+# Automatically generated by zfs-mount-generator
+
+[Unit]
+Description=Load ZFS key for ${dataset}
+SourcePath=${cachefile}
+Documentation=man:zfs-mount-generator(8)
+DefaultDependencies=no
+Wants=${wants}
+After=${wants}
+${pathdep}
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=${keyloadcmd}
+ExecStop=@sbindir@/zfs unload-key '${dataset}'
+EOF
+    fi
+    # Update the dependencies for the mount file to require the
+    # key-loading unit.
+    wants="${wants} ${keyloadunit}"
+  fi
+
+  # Prepare the .mount unit
+
   # Check for canmount=off .
   if [ "${p_canmount}" = "off" ] ; then
     return
@@ -170,63 +226,14 @@ process_line() {
       "${dataset}" >/dev/kmsg
   fi
 
-  # Minimal pre-requisites to mount a ZFS dataset
-  wants="zfs-import.target"
-  if [ -n "${p_encroot}" ] &&
-      [ "${p_encroot}" != "-" ] ; then
-    keyloadunit="zfs-load-key-$(systemd-escape "${p_encroot}").service"
-    if [ "${p_encroot}" = "${dataset}" ] ; then
-        pathdep=""
-      if [ "${p_keyloc%%://*}" = "file" ] ; then
-        pathdep="RequiresMountsFor='${p_keyloc#file://}'"
-        keyloadcmd="@sbindir@/zfs load-key '${dataset}'"
-      elif [ "${p_keyloc}" = "prompt" ] ; then
-        keyloadcmd="/bin/sh -c 'set -eu;"\
-"keystatus=\"\$\$(@sbindir@/zfs get -H -o value keystatus \"${dataset}\")\";"\
-"[ \"\$\$keystatus\" = \"unavailable\" ] || exit 0;"\
-"count=0;"\
-"while [ \$\$count -lt 3 ];do"\
-"  systemd-ask-password --id=\"zfs:${dataset}\""\
-"    \"Enter passphrase for ${dataset}:\"|"\
-"    @sbindir@/zfs load-key \"${dataset}\" && exit 0;"\
-"  count=\$\$((count + 1));"\
-"done;"\
-"exit 1'"
-      else
-        printf 'zfs-mount-generator: (%s) invalid keylocation\n' \
-          "${dataset}" >/dev/kmsg
-      fi
-      cat > "${dest_norm}/${keyloadunit}" << EOF
-# Automatically generated by zfs-mount-generator
-
-[Unit]
-Description=Load ZFS key for ${dataset}
-SourcePath=${cachefile}
-Documentation=man:zfs-mount-generator(8)
-DefaultDependencies=no
-Wants=${wants}
-After=${wants}
-${pathdep}
-
-[Service]
-Type=oneshot
-RemainAfterExit=yes
-ExecStart=${keyloadcmd}
-ExecStop=@sbindir@/zfs unload-key '${dataset}'
-EOF
-    fi
-    # Update the dependencies for the mount file to require the
-    # key-loading unit.
-    wants="${wants} ${keyloadunit}"
-  fi
-
   # If the mountpoint has already been created, give it precedence.
   if [ -e "${dest_norm}/${mountfile}" ] ; then
     printf 'zfs-mount-generator: %s already exists\n' "${mountfile}" \
       >/dev/kmsg
     return
   fi
 
+  # Create the .mount unit file.
   # By ordering before zfs-mount.service, we avoid race conditions.
   cat > "${dest_norm}/${mountfile}" << EOF
 # Automatically generated by zfs-mount-generator