main/postmarketos-initramfs: use mdev properly (MR 4204)

Drop in mdev.conf and the /lib/mdev/persistent-storage script, these
cause /dev/disk/by-* to be populated in the ramdisk, making it
possible to do look up partition by-label and by-partlabel for free,
compared to findfs which can take some time.

As a first optimisation based on this, check for some partitions using
these paths and prioritise them when looking for subpartitions. Drop the
first find_boot_partition call as it doesn't really save time over the
call in the while loop.

The mdev config also handles setting up /dev/null, /dev/random, etc, so
these don't have to be done manually.

main/postmarketos-initramfs/00-initramfs-base.files

@@ -3,8 +3,11 @@
 /bin/sh
 /etc/deviceinfo
 /etc/unudhcpd.conf
+/lib/mdev/persistent-storage
+/sbin/blkid
 /usr/share/misc/source_deviceinfo
 /usr/bin/unudhcpd
 /usr/sbin/kpartx
 /usr/share/initramfs/init.sh:/init
 /usr/share/initramfs/init_functions.sh:/init_functions.sh
+/usr/share/initramfs/mdev.conf:/etc/mdev.conf

main/postmarketos-initramfs/APKBUILD

@@ -33,6 +33,7 @@ source="
 	init.sh
 	init_functions.sh
 	unudhcpd.conf
+	mdev.conf
 	"
 arch="noarch"
 license="GPL-2.0-or-later"
@@ -63,6 +64,9 @@ package() {
 		-t "$pkgdir"/usr/share/mkinitfs/files-extra/
 	mkdir -p "$pkgdir"/etc/mkinitfs/files-extra
 
+	install -Dm644 "$srcdir"/mdev.conf \
+		-t "$pkgdir"/usr/share/initramfs/
+
 	mkdir -p "$pkgdir"/usr/share/mkinitfs/hooks
 	mkdir -p "$pkgdir"/usr/share/mkinitfs/hooks-extra
 	mkdir -p "$pkgdir"/etc/mkinitfs/hooks

main/postmarketos-initramfs/init.sh

@@ -13,7 +13,6 @@ export PATH=/usr/bin:/bin:/usr/sbin:/sbin
 
 # Mount everything, set up logging, modules, mdev
 mount_proc_sys_dev
-create_device_nodes
 setup_log
 setup_firmware_path
 # shellcheck disable=SC2154

main/postmarketos-initramfs/init_functions.sh

@@ -36,12 +36,6 @@ mount_proc_sys_dev() {
 	mount -t devpts devpts /dev/pts
 }
 
-create_device_nodes() {
-	mknod -m 666 /dev/null c 1 3
-	mknod -m 644 /dev/random c 1 8
-	mknod -m 644 /dev/urandom c 1 9
-}
-
 setup_firmware_path() {
 	# Add the postmarketOS-specific path to the firmware search paths.
 	# This should be sufficient on kernel 3.10+, before that we need
@@ -110,16 +104,19 @@ setup_dynamic_partitions() {
 }
 
 mount_subpartitions() {
-	# Do not create subpartition mappings if pmOS_boot
-	# already exists (e.g. installed on an sdcard)
-	[ -n "$(find_boot_partition)" ] && return
+	try_parts="/dev/disk/by-partlabel/userdata /dev/disk/by-partlabel/system* /dev/mapper/system*"
+	android_parts=""
+	for x in $try_parts; do
+		[ -e "$x" ] && android_parts="$android_parts $x"
+	done
+
 	attempt_start=$(get_uptime_seconds)
 	wait_seconds=10
 	echo "Trying to mount subpartitions for $wait_seconds seconds..."
 	while [ -z "$(find_boot_partition)" ]; do
-		partitions="$(grep -v "loop\|ram" < /proc/diskstats |\
+		partitions="$android_parts $(grep -v "loop\|ram" < /proc/diskstats |\
 			sed 's/\(\s\+[0-9]\+\)\+\s\+//;s/ .*//;s/^/\/dev\//')"
-		echo "$partitions" | while read -r partition; do
+		for partition in $partitions; do
 			case "$(kpartx -l "$partition" 2>/dev/null | wc -l)" in
 				2)
 					echo "Mount subpartitions of $partition"

main/postmarketos-initramfs/mdev.conf

@@ -0,0 +1,33 @@
+#
+# This is an mdev config for the postmarketOS initramfs
+#
+
+# Devices:
+# Syntax: %s %d:%d %s
+# devices user:group mode
+
+$MODALIAS=.*	0:0	0660	@modprobe -q -b "$MODALIAS"
+
+# null does already exist; therefore ownership has to be changed with command
+null	0:0 0666	@chmod 666 $MDEV
+zero	0:0 0666
+full	0:0 0666
+
+random	0:0 0666
+urandom	0:0 0444
+hwrandom 0:0 0660
+
+console 0:0 0600
+
+kmem	0:0 0640
+mem	0:0 0640
+
+# Set up /dev/disk/by-* symlinks
+dasd.*		0:0 0660 */lib/mdev/persistent-storage
+mmcblk.*	0:0 0660 */lib/mdev/persistent-storage
+nbd.*		0:0 0660 */lib/mdev/persistent-storage
+nvme.*		0:0 0660 */lib/mdev/persistent-storage
+sd[a-z].*	0:0 0660 */lib/mdev/persistent-storage
+sr[0-9]+	0:0 0660 */lib/mdev/persistent-storage
+vd[a-z].*	0:0 0660 */lib/mdev/persistent-storage
+xvd[a-z].*	0:0 0660 */lib/mdev/persistent-storage