[openwrt/openwrt] base-files: upgrade: take down loop and LVM before upgrade

[LEDE Commits]

dangole pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/a2b9ec0231707378e7e9ccaa140c5ebe664abd70

commit a2b9ec0231707378e7e9ccaa140c5ebe664abd70
Author: Daniel Golle <daniel at makrotopia.org>
AuthorDate: Sat May 1 20:21:54 2021 +0100

    base-files: upgrade: take down loop and LVM before upgrade
    
    Users of devices with large block storage may choose to have an LVM
    partition on the same device which is used for booting OpenWrt.
    The presents a problem during sysupgrade as the root device is then
    still busy and changing partitions will not work as desired,
    leading to data corruption in case the newly flashed image is larger
    than the currently installed one.
    Having loop devices setup causes similar havoc.
    Make sure all volume groups are offline and all loop devices have been
    released before sysupgrade.
    
    Signed-off-by: Daniel Golle <daniel at makrotopia.org>
---
 package/base-files/files/lib/upgrade/stage2 | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/package/base-files/files/lib/upgrade/stage2 b/package/base-files/files/lib/upgrade/stage2
index 23d356a447..e2259e3472 100755
--- a/package/base-files/files/lib/upgrade/stage2
+++ b/package/base-files/files/lib/upgrade/stage2
@@ -33,6 +33,9 @@ supivot() { # <new_root> <old_root>
 }
 
 switch_to_ramfs() {
+	RAMFS_COPY_LOSETUP="$(command -v losetup)"
+	RAMFS_COPY_LVM="$(command -v lvm)"
+
 	for binary in \
 		/bin/busybox /bin/ash /bin/sh /bin/mount /bin/umount	\
 		pivot_root mount_root reboot sync kill sleep		\
@@ -43,6 +46,7 @@ switch_to_ramfs() {
 		ubiupdatevol ubiattach ubiblock ubiformat		\
 		ubidetach ubirsvol ubirmvol ubimkvol			\
 		snapshot snapshot_tool date				\
+		$RAMFS_COPY_LOSETUP $RAMFS_COPY_LVM			\
 		$RAMFS_COPY_BIN
 	do
 		local file="$(command -v "$binary" 2>/dev/null)"
@@ -60,6 +64,12 @@ switch_to_ramfs() {
 	/bin/mount -o remount,ro /mnt
 	/bin/umount -l /mnt
 
+	[ "$RAMFS_COPY_LOSETUP" ] && losetup -D
+	[ "$RAMFS_COPY_LVM" ] && {
+		mkdir -p /tmp/lvm/cache
+		$RAMFS_COPY_LVM vgchange -aln --ignorelockingfailure
+	}
+
 	grep /overlay /proc/mounts > /dev/null && {
 		/bin/mount -o noatime,remount,ro /overlay
 		/bin/umount -l /overlay