base-files: improve lib/upgrade/common.sh

Recently, upgrade device autodetection has been added to the mvebu target.
This exposes some shortcomings of the generic export_bootdevice function,
e.g. on the Turris Omnia: export_bootdevice silently reports the root
partition to be the boot device. This makes the sysupgrade process fail at
several places.

Fix this by clearly distinguishing between /proc/cmdline arguments which
specify the boot disk, and those which specify the root partition. Only in
the latter case, strip off the partition, and do it consistently.
root=PARTUUID=<pseudo PARTUUID for MBR> (any partition) and root=/dev/*
(any partition) are accepted.

The root of the problem is that the *existing* export_bootdevice in
/lib/upgrade/common.sh behaves differently, if the kernel is booted with
root=/dev/..., or if it is booted with root=PARTUUID=...

In the former case, it reports back major/minor of the root partition,
in the latter case it reports back major/minor of the complete boot disk.

Targets, which boot with root=/dev/... *and* use export_bootdevice /
export_partdevice, have added workarounds to this behaviour, by specifying
*negative* increments to the export_partdevice function.

Consequently, those targets have to be adapted to use positive increments,
otherwise they are broken by the change to export_bootdevice.

Fixes: 4e8345ff68 ("mvebu: base-files: autodetect upgrade device")
Signed-off-by: Klaus Kudielka <klaus.kudielka@gmail.com>
Tested-by: Tomasz Maciej Nowak <tomek_n@o2.pl>

1 files changed, 3 insertions, 8 deletions

diff --git a/target/linux/apm821xx/base-files/lib/upgrade/wdbook.sh b/target/linux/apm821xx/base-files/lib/upgrade/wdbook.sh
index 2287e0619d..c191271149 100644
--- a/target/linux/apm821xx/base-files/lib/upgrade/wdbook.sh
+++ b/target/linux/apm821xx/base-files/lib/upgrade/wdbook.sh
@@ -7,7 +7,7 @@ mbl_do_platform_check() {
 
 	[ "$#" -gt 1 ] && return 1
 
-	export_bootdevice && export_partdevice diskdev -2 || {
+	export_bootdevice && export_partdevice diskdev 0 || {
 		echo "Unable to determine upgrade device"
 		return 1
 	}
@@ -36,7 +36,7 @@ mbl_do_platform_check() {
 mbl_do_upgrade() {
 	local diskdev partdev diff
 
-	export_bootdevice && export_partdevice diskdev -2 || {
+	export_bootdevice && export_partdevice diskdev 0 || {
 		echo "Unable to determine upgrade device"
 		return 1
 	}
@@ -70,10 +70,6 @@ mbl_do_upgrade() {
 
 	#iterate over each partition from the image and write it to the boot disk
 	while read part start size; do
-		# root is /dev/sd[a|b]2 and not /dev/sd[a|b] this causes some problem
-		# one of which is this offset, I'm not sure what's the best fix, so
-		# here's a WA.
-		let part=$((part - 2))
 		if export_partdevice partdev $part; then
 			echo "Writing image to /dev/$partdev..."
 			get_image "$@" | dd of="/dev/$partdev" ibs="512" obs=1M skip="$start" count="$size" conv=fsync
@@ -90,8 +86,7 @@ mbl_do_upgrade() {
 mbl_copy_config() {
 	local partdev
 
-	# Same as above /dev/sd[a|b]2 is root, so /boot is -1
-	if export_partdevice partdev -1; then
+	if export_partdevice partdev 1; then
 		mount -t ext4 -o rw,noatime "/dev/$partdev" /mnt
 		cp -af "$CONF_TAR" /mnt/
 		umount /mnt