Introduce tri-state hostonly mode

Add a new option --hostonly-mode which accept an <mode> parameter, so we have a tri-state hostonly mode:

    * generic: by passing "--no-hostonly" or not passing anything.
               "--hostonly-mode" has no effect in such case.
    * sloppy: by passing "--hostonly --hostonly-mode sloppy". This
              is also the default mode when only "--hostonly" is given.
    * strict: by passing "--hostonly --hostonly-mode strict".

Sloppy mode is the original hostonly mode, the new introduced strict
mode will allow modules to ignore more drivers or do some extra job to
save memory and disk space, while making the image less portable.

Also introduced a helper function "optional_hostonly" to make it
easier for modules to leverage new hostonly mode.

To force install modules only in sloppy hostonly mode, use the form:

hostonly="$(optional_hostonly)" instmods <modules>

Signed-off-by: Kairui Song <kasong@redhat.com>

dracut-init.sh

@@ -267,6 +267,18 @@ inst_fsck_help() {
     (($? != 0)) && derror $DRACUT_INSTALL ${initdir:+-D "$initdir"} ${loginstall:+-L "$loginstall"} ${DRACUT_RESOLVE_DEPS:+-l}  ${DRACUT_FIPS_MODE:+-f} "$2" $_helper || :
 }
 
+# Use with form hostonly="$(optional_hostonly)" inst_xxxx <args>
+# If hosotnly mode is set to "strict", hostonly restrictions will still
+# be applied, else will ignore hostonly mode and try to install all
+# given modules.
+optional_hostonly() {
+    if [[ $hostonly_mode = "strict" ]]; then
+        printf -- "$hostonly"
+    else
+        printf ""
+    fi
+}
+
 mark_hostonly() {
     for i in "$@"; do
         echo "$i" >> "$initdir/lib/dracut/hostonly-files"

dracut.sh

@@ -147,6 +147,21 @@ Creates initial ramdisk images for preloading modules
   -H, --hostonly        Host-Only mode: Install only what is needed for
                         booting the local host instead of a generic host.
   -N, --no-hostonly     Disables Host-Only mode
+  --hostonly-mode <mode>
+                        Specify the hostonly mode to use. <mode> could be
+                        one of "sloppy" or "strict". "sloppy" mode is used
+                        by default.
+                        In "sloppy" hostonly mode, extra drivers and modules
+                        will be installed, so minor hardware change won't make
+                        the image unbootable (eg. changed keyboard), and the
+                        image is still portable among similar hosts.
+                        With "strict" mode enabled, anything not necessary
+                        for booting the local host in its current state will
+                        not be included, and modules may do some extra job
+                        to save more space. Minor change of hardware or
+                        environment could make the image unbootable.
+                        DO NOT use "strict" mode unless you know what you
+                        are doing.
   --hostonly-cmdline    Store kernel command line arguments needed
                         in the initramfs
   --no-hostonly-cmdline Do not store kernel command line arguments needed
@@ -352,6 +367,7 @@ rearrange_params()
         --long host-only \
         --long no-hostonly \
         --long no-host-only \
+        --long hostonly-mode: \
         --long hostonly-cmdline \
         --long no-hostonly-cmdline \
         --long no-hostonly-default-device \
@@ -540,6 +556,8 @@ while :; do
                        hostonly_l="yes" ;;
         -N|--no-hostonly|--no-host-only)
                        hostonly_l="no" ;;
+        --hostonly-mode)
+                       hostonly_mode_l="$2";           PARMS_TO_STORE+=" '$2'"; shift;;
         --hostonly-cmdline)
                        hostonly_cmdline_l="yes" ;;
         --hostonly-i18n)
@@ -726,6 +744,7 @@ stdloglvl=$((stdloglvl + verbosity_mod_l))
 [[ $prefix = "/" ]] && unset prefix
 [[ $hostonly_l ]] && hostonly=$hostonly_l
 [[ $hostonly_cmdline_l ]] && hostonly_cmdline=$hostonly_cmdline_l
+[[ $hostonly_mode_l ]] && hostonly_mode=$hostonly_mode_l
 [[ "$hostonly" == "yes" ]] && ! [[ $hostonly_cmdline ]] && hostonly_cmdline="yes"
 [[ $i18n_install_all_l ]] && i18n_install_all=$i18n_install_all_l
 [[ $persistent_policy_l ]] && persistent_policy=$persistent_policy_l
@@ -850,6 +869,19 @@ esac
 [[ $hostonly = yes ]] && hostonly="-h"
 [[ $hostonly != "-h" ]] && unset hostonly
 
+case $hostonly_mode in
+    '')
+        [[ $hostonly ]] && hostonly_mode="sloppy" ;;
+    sloppy|strict)
+        if [[ ! $hostonly ]]; then
+            unset hostonly_mode
+        fi
+        ;;
+    *)
+        printf "%s\n" "dracut: Invalid hostonly mode '$hostonly_mode'." >&2
+        exit 1
+esac
+
 [[ $reproducible == yes ]] && DRACUT_REPRODUCIBLE=1
 
 readonly TMPDIR="$(realpath -e "$tmpdir")"