ipq40xx: Linksys: sysupgrade: Ensure OEM volumes are removed

When OEM volumes are present in the [alt_]firmware partition,
sysupgrade will write a new kernel, but will fail to write
the root file system. The next boot will hang indefinitely

    Waiting for root device /dev/ubiblock0_0...

Modified ipq40xx/base-files/lib/upgrade/linksys.sh
to remove both `squashfs` and `ubifs` if found
on the target firmware partition's UBI device.

Run-tested-on: Linksys EA8300

Signed-off-by: Jeff Kletsky <git-commits@allycomm.com>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
[applied some shellcheck suggestions as well]

target/linux/ipq40xx/base-files/lib/upgrade/linksys.sh

@@ -1,11 +1,10 @@
 linksys_get_target_firmware() {
-
 	local cur_boot_part mtd_ubi0
 
-	cur_boot_part=$(/usr/sbin/fw_printenv -n boot_part)
+	cur_boot_part="$(/usr/sbin/fw_printenv -n boot_part)"
-	if [ -z "${cur_boot_part}" ] ; then
+	if [ -z "${cur_boot_part}" ]; then
 		mtd_ubi0=$(cat /sys/devices/virtual/ubi/ubi0/mtd_num)
-		case $(egrep "^mtd${mtd_ubi0}:" /proc/mtd | cut -d '"' -f 2) in
+		case "$(grep -E "^mtd${mtd_ubi0}:" /proc/mtd | cut -d '"' -f 2)" in
 		kernel|rootfs)
 			cur_boot_part=1
 			;;
@@ -25,7 +24,7 @@ linksys_get_target_firmware() {
 	#      else run bootpart2;
 	#  fi
 
-	case $cur_boot_part in
+	case "$cur_boot_part" in
 	1)
 		fw_setenv -s - <<-EOF
 			boot_part 2
@@ -55,16 +54,19 @@ linksys_get_root_magic() {
 platform_do_upgrade_linksys() {
 	local magic_long="$(get_magic_long "$1")"
 
+	local rm_oem_fw_vols="squashfs ubifs"	# from OEM [alt_]rootfs UBI
+	local vol
+
 	mkdir -p /var/lock
 	local part_label="$(linksys_get_target_firmware)"
 	touch /var/lock/fw_printenv.lock
 
-	if [ ! -n "$part_label" ]; then
+	if [ -z "$part_label" ]; then
 		echo "cannot find target partition"
 		exit 1
 	fi
 
-	local target_mtd=$(find_mtd_part $part_label)
+	local target_mtd=$(find_mtd_part "$part_label")
 
 	[ "$magic_long" = "73797375" ] && {
 		CI_KERNPART="$part_label"
@@ -74,47 +76,47 @@ platform_do_upgrade_linksys() {
 			CI_UBIPART="alt_rootfs"
 		fi
 
-		# remove "squashfs" vol (in case we are flashing over a stock image, which is also UBI)
+		local mtdnum="$(find_mtd_index "$CI_UBIPART")"
-
-		local mtdnum="$( find_mtd_index "$CI_UBIPART" )"
 		if [ ! "$mtdnum" ]; then
 			echo "cannot find ubi mtd partition $CI_UBIPART"
 			return 1
 		fi
 
-		local ubidev="$( nand_find_ubi "$CI_UBIPART" )"
+		local ubidev="$(nand_find_ubi "$CI_UBIPART")"
 		if [ ! "$ubidev" ]; then
 			ubiattach -m "$mtdnum"
 			sync
-			ubidev="$( nand_find_ubi "$CI_UBIPART" )"
+			ubidev="$(nand_find_ubi "$CI_UBIPART")"
 		fi
 
 		if [ "$ubidev" ]; then
-			local squash_ubivol="$( nand_find_volume $ubidev squashfs )"
+			for vol in $rm_oem_fw_vols; do
-			# kill volume
+				ubirmvol "/dev/$ubidev" -N "$vol" 2>/dev/null
-			[ "$squash_ubivol" ] && ubirmvol /dev/$ubidev -N squashfs || true
+			done
 		fi
 
 		# complete std upgrade
 		nand_upgrade_tar "$1"
 	}
+
 	[ "$magic_long" = "27051956" ] && {
 		# This magic is for a uImage (which is a sysupgrade image)
 		# check firmwares' rootfs types
-		local oldroot="$(linksys_get_root_magic $target_mtd)"
+		local oldroot="$(linksys_get_root_magic "$target_mtd")"
 		local newroot="$(linksys_get_root_magic "$1")"
 
-		if [ "$newroot" = "55424923" -a "$oldroot" = "55424923" ]; then
+		if [ "$newroot" = "55424923" ] && [ "$oldroot" = "55424923" ]; then
 			# we're upgrading from a firmware with UBI to one with UBI
 			# erase everything to be safe
-			# - Is that really needed? Won't remove (or comment) the if, because it may be needed in a future device.
+			# - Is that really needed? Won't remove (or comment) the if,
+			#   because it may be needed in a future device.
 			#mtd erase $part_label
 			#get_image "$1" | mtd -n write - $part_label
 			echo "writing \"$1\" UBI image to \"$part_label\" (UBI)..."
-			get_image "$1" | mtd write - $part_label
+			get_image "$1" | mtd write - "$part_label"
 		else
 			echo "writing \"$1\" image to \"$part_label\""
-			get_image "$1" | mtd write - $part_label
+			get_image "$1" | mtd write - "$part_label"
 		fi
 	}
 }