feat(dracut): add zfs detection

zfs detection is currently done by the zfs dracut module installed by
downstream, resulting in a lot of duplicated code. This commit puts zfs
detection into the core dracut logic, allowing for detection of zfs
partitions to be done at the same time as all others. It also allows for
dracut to correctly create a `root=` cmdline parameter for zfs.

Signed-off-by: Savyasachee Jha <hi@savyasacheejha.com>

dracut-functions.sh

@@ -780,6 +780,14 @@ btrfs_devs() {
         done
 }
 
+zfs_devs() {
+    local _mp="$1"
+    zpool list -H -v -P "${_mp%%/*}" | awk -F$'\t' '$2 ~ /^\// {print $2}' \
+        | while read -r _dev; do
+            realpath "${_dev}"
+        done
+}
+
 iface_for_remote_addr() {
     # shellcheck disable=SC2046
     set -- $(ip -o route get to "$1")

dracut.sh

@@ -1456,6 +1456,10 @@ for line in "${fstab_lines[@]}"; do
                 push_host_devs "$i"
             done
         done
+    elif [[ $3 == zfs ]]; then
+        for mp in $(zfs_devs "$1"); do
+            push_host_devs "$mp"
+        done
     fi
     push_host_devs "$dev"
     host_fs_types["$dev"]="$3"
@@ -1508,7 +1512,13 @@ if [[ $hostonly ]] && [[ $hostonly_default_device != "no" ]]; then
                 [[ $mp == "/" ]] && root_devs+=("$i")
                 push_host_devs "$i"
             done
+        elif [[ $(find_mp_fstype "$mp") == zfs ]]; then
+            for i in $(zfs_devs "$(findmnt -n -o SOURCE "$mp")"); do
+                [[ $mp == "/" ]] && root_devs+=("$i")
+                push_host_devs "$i"
+            done
         fi
+
     done
 
     # TODO - with sysroot, /proc/swaps is not relevant
@@ -1561,6 +1571,10 @@ if [[ $hostonly ]] && [[ $hostonly_default_device != "no" ]]; then
                 for i in $(btrfs_devs "$_m"); do
                     push_host_devs "$i"
                 done
+            elif [[ $_t == zfs ]]; then
+                for i in $(zfs_devs "$_d"); do
+                    push_host_devs "$i"
+                done
             fi
         done < "$dracutsysrootdir"/etc/fstab
     fi
@@ -2588,6 +2602,9 @@ freeze_ok_for_fstype() {
         msdos)
             return 1
             ;;
+        zfs)
+            return 1
+            ;;
         btrfs)
             freeze_ok_for_btrfs "$outfile"
             ;;

modules.d/95rootfs-block/module-setup.sh

@@ -44,6 +44,11 @@ cmdline_rootfs() {
         printf " root=%s" "$(shorten_persistent_dev "$(get_persistent_dev "$_dev")")"
     fi
     _fstype="$(find_mp_fstype /)"
+    if [[ ${_fstype} == "zfs" ]]; then
+        local _root_ds
+        _root_ds="$(findmnt -n -o SOURCE /)"
+        printf " root=zfs:%s" "${_root_ds// /+}"
+    fi
     _flags="$(find_mp_fsopts /)"
     if [ -n "$_fstype" ]; then
         printf " rootfstype=%s" "$_fstype"