[PATCH] 10_linux: avoid multi-device root= kernel argument

[Andrei Borzenkov <arvidjaar@gmail.com>]

If root filesystem is multidev btrfs, do not attempt to pass all devices as
kernel root= argument. This results in splitting command line in GRUB due to
embedded newline and even if we managed to quote it, kernel does not know how
to interpret it anyway. Multidev btrfs requires user space device scanning,
so passing single device would not work too.

This still respects user settings GRUB_DISABLE_LINUX_UUID. Not sure what we
should do in this case.

Closes: 45709

---
 util/grub.d/10_linux.in     | 4 +++-
 util/grub.d/20_linux_xen.in | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/util/grub.d/10_linux.in b/util/grub.d/10_linux.in
index 859b608..5a78513 100644
--- a/util/grub.d/10_linux.in
+++ b/util/grub.d/10_linux.in
@@ -43,9 +43,11 @@ case ${GRUB_DEVICE} in
   ;;
 esac
 
+# btrfs may reside on multiple devices. We cannot pass them as value of root= parameter
+# and mounting btrfs requires user space scanning, so force UUID in this case.
 if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
     || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
-    || uses_abstraction "${GRUB_DEVICE}" lvm; then
+    || test -e "${GRUB_DEVICE}" && uses_abstraction "${GRUB_DEVICE}" lvm; then
   LINUX_ROOT_DEVICE=${GRUB_DEVICE}
 else
   LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
diff --git a/util/grub.d/20_linux_xen.in b/util/grub.d/20_linux_xen.in
index f532fb9..46045db 100644
--- a/util/grub.d/20_linux_xen.in
+++ b/util/grub.d/20_linux_xen.in
@@ -43,9 +43,11 @@ case ${GRUB_DEVICE} in
   ;;
 esac
 
+# btrfs may reside on multiple devices. We cannot pass them as value of root= parameter
+# and mounting btrfs requires user space scanning, so force UUID in this case.
 if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
     || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
-    || uses_abstraction "${GRUB_DEVICE}" lvm; then
+    || test -e "${GRUB_DEVICE}" && uses_abstraction "${GRUB_DEVICE}" lvm; then
   LINUX_ROOT_DEVICE=${GRUB_DEVICE}
 else
   LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
-- 
tg: (ff84a9b..) u/btrfs-multidev (depends on: master)