From 811c814677b83874fb631f6c07576765303b615a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C4=90o=C3=A0n=20Tr=E1=BA=A7n=20C=C3=B4ng=20Danh?=
 <congdanhqx@gmail.com>
Date: Sat, 3 Oct 2020 14:23:26 +0700
Subject: [PATCH] rootfs-block: only write root argument for block device
MIME-Version: 1.0
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Content-Transfer-Encoding: 8bit

Some filesystem (e.g. ZFS, and btrfs subvolumes) don't use block
devices. Should they be mounted as `/`, `find_root_block_device`
yields nothing, hence dracut will append this problematic argument
to kernel cmdline:

	root=/dev/block

On a machine that employ root ZFS on LUKS, which was setup with
an OpenPGP-encrypted key file, this argument renders that machine
unbootable. Remove that `root=/dev/block` manually could boot the
machine.

Let check if that device is a block device before write down `root`
argument. This is consistent with the check for block device in
`find_block_device`.

Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
---
 modules.d/95rootfs-block/module-setup.sh | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/modules.d/95rootfs-block/module-setup.sh b/modules.d/95rootfs-block/module-setup.sh
index 987373b4..c3982207 100755
--- a/modules.d/95rootfs-block/module-setup.sh
+++ b/modules.d/95rootfs-block/module-setup.sh
@@ -30,7 +30,8 @@ cmdline_journal() {
 }
 
 cmdline_rootfs() {
-    local _dev=/dev/block/$(find_root_block_device)
+    local _block=$(find_root_block_device)
+    local _dev=/dev/block/$_block
     local _fstype _flags _subvol
 
     # "--no-hostonly-default-device" can result in empty root_devs
@@ -38,17 +39,21 @@ cmdline_rootfs() {
         return
     fi
 
-    if [ -e $_dev ]; then
+    if [ -n "$_block" -a -b $_dev ]; then
         printf " root=%s" "$(shorten_persistent_dev "$(get_persistent_dev "$_dev")")"
-        _fstype="$(find_mp_fstype /)"
-        _flags="$(find_mp_fsopts /)"
+    fi
+    _fstype="$(find_mp_fstype /)"
+    _flags="$(find_mp_fsopts /)"
+    if [ -n "$_fstype" ]; then
         printf " rootfstype=%s" "$_fstype"
-        if [[ $use_fstab != yes ]] && [[ $_fstype = btrfs ]]; then
-            _subvol=$(findmnt -e -v -n -o FSROOT --target /) \
-		&& _subvol=${_subvol#/}
-            _flags="$_flags,${_subvol:+subvol=$_subvol}"
-        fi
-        printf " rootflags=%s" "${_flags#,}"
+    fi
+    if [[ $use_fstab != yes ]] && [[ $_fstype = btrfs ]]; then
+        _subvol=$(findmnt -e -v -n -o FSROOT --target /) \
+            && _subvol=${_subvol#/}
+        _flags="$_flags${_subvol:+,subvol=$_subvol}"
+    fi
+    if [ -n "$_flags" ]; then
+        printf " rootflags=%s" "$_flags"
     fi
 }