From 37f2fe55d11156839b87d6cf74d686956d72dc06 Mon Sep 17 00:00:00 2001
From: Xunlei Pang <xlpang@redhat.com>
Date: Wed, 16 Aug 2017 13:55:17 +0800
Subject: [PATCH 1/2] dracut.sh: introduce "--no-hostonly-default-device"
 argument

Kdump doesn't need default host devices like root, swap, fstab, etc,
we only care about the dump target which can be added via "--mount"
or "--add-device". We met several issues that kdump kernel failed
due to one of those host devices added by dracut, additionally, the
needless devices(e.g. LVM) consume some appreciable amount of memory
which is more likely to cause OOM under memory-limited kdump.

So this patch introduced "--no-hostonly-default-device" to avoid
adding those default devices as host_devs.

Signed-off-by: Xunlei Pang <xlpang@redhat.com>
---
 dracut.8.asc | 4 ++++
 dracut.sh    | 9 ++++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/dracut.8.asc b/dracut.8.asc
index ca169189..23c53cc4 100644
--- a/dracut.8.asc
+++ b/dracut.8.asc
@@ -323,6 +323,10 @@ provide a valid _/etc/fstab_.
 **--no-hostonly-cmdline**:
     Do not store kernel command line arguments needed in the initramfs
 
+**--no-hostonly-default-device**:
+    Do not generate implicit host devices like root, swap, fstab, etc.
+    Use "--mount" or "--add-device" to explicitly add devices as needed.
+
 **--hostonly-i18n**:
     Install only needed keyboard and font files according to the host configuration (default).
 
diff --git a/dracut.sh b/dracut.sh
index 3a136d46..8d7ee70a 100755
--- a/dracut.sh
+++ b/dracut.sh
@@ -151,6 +151,10 @@ Creates initial ramdisk images for preloading modules
                         in the initramfs
   --no-hostonly-cmdline Do not store kernel command line arguments needed
                         in the initramfs
+  --no-hostonly-default-device
+                        Do not generate implicit host devices like root,
+                        swap, fstab, etc. Use "--mount" or "--add-device"
+                        to explicitly add devices as needed.
   --hostonly-i18n       Install only needed keyboard and font files according
                         to the host configuration (default).
   --no-hostonly-i18n    Install all keyboard and font files available.
@@ -345,6 +349,7 @@ rearrange_params()
         --long no-host-only \
         --long hostonly-cmdline \
         --long no-hostonly-cmdline \
+        --long no-hostonly-default-device \
         --long persistent-policy: \
         --long fstab \
         --long help \
@@ -539,6 +544,8 @@ while :; do
                        i18n_install_all_l="yes" ;;
         --no-hostonly-cmdline)
                        hostonly_cmdline_l="no" ;;
+        --no-hostonly-default-device)
+                       hostonly_default_device="no" ;;
         --persistent-policy)
                        persistent_policy_l="$2";       PARMS_TO_STORE+=" '$2'"; shift;;
         --fstab)       use_fstab_l="yes" ;;
@@ -1133,7 +1140,7 @@ if (( ${#add_device_l[@]} )); then
     push_host_devs "${add_device_l[@]}"
 fi
 
-if [[ $hostonly ]]; then
+if [[ $hostonly ]] && [[ "$hostonly_default_device" != "no" ]]; then
     # in hostonly mode, determine all devices, which have to be accessed
     # and examine them for filesystem types
 

From 5634a31156070487210a8e362e8f088c5c4dc615 Mon Sep 17 00:00:00 2001
From: Xunlei Pang <xlpang@redhat.com>
Date: Fri, 18 Aug 2017 10:40:27 +0800
Subject: [PATCH 2/2] rootfs-block/module-setup.sh: check root_devs in
 cmdline_rootfs()

In case of "--no-hostonly-default-device", we do not need
the root device, thus add this check.

Also fixed the stale "root_dev" export.

Signed-off-by: Xunlei Pang <xlpang@redhat.com>
---
 dracut.sh                                | 2 +-
 modules.d/95rootfs-block/module-setup.sh | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/dracut.sh b/dracut.sh
index 8d7ee70a..681a6b7a 100755
--- a/dracut.sh
+++ b/dracut.sh
@@ -1307,7 +1307,7 @@ export initdir dracutbasedir \
     dracutmodules force_add_dracutmodules add_dracutmodules omit_dracutmodules \
     mods_to_load \
     fw_dir drivers_dir debug no_kernel kernel_only \
-    omit_drivers mdadmconf lvmconf root_dev \
+    omit_drivers mdadmconf lvmconf root_devs \
     use_fstab fstab_lines libdirs fscks nofscks ro_mnt \
     stdloglvl sysloglvl fileloglvl kmsgloglvl logfile \
     debug host_fs_types host_devs swap_devs sshkey add_fstab \
diff --git a/modules.d/95rootfs-block/module-setup.sh b/modules.d/95rootfs-block/module-setup.sh
index 2b06bac2..987373b4 100755
--- a/modules.d/95rootfs-block/module-setup.sh
+++ b/modules.d/95rootfs-block/module-setup.sh
@@ -32,6 +32,12 @@ cmdline_journal() {
 cmdline_rootfs() {
     local _dev=/dev/block/$(find_root_block_device)
     local _fstype _flags _subvol
+
+    # "--no-hostonly-default-device" can result in empty root_devs
+    if [ "${#root_devs[@]}" -eq 0 ]; then
+        return
+    fi
+
     if [ -e $_dev ]; then
         printf " root=%s" "$(shorten_persistent_dev "$(get_persistent_dev "$_dev")")"
         _fstype="$(find_mp_fstype /)"