kickstart: Rewrite block devices detection

Instead of having a whitelist of block device types you can try to guess
if it is possible to scan partitions. The same code is used in systemd.

Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>

Author: legionus

features/kickstart/data/bin/kickstart

@@ -9,6 +9,9 @@
 . shell-error
 . shell-quote
 . shell-args
+. shell-var
+
+. initrd-sh-functions
 
 . "$0-sh-storage"
 . "$0-sh-installation"
@@ -145,62 +148,113 @@ KS_ORDERS=(
 	9200000000:shutdown
 )
 
-get_device_type()
+# Based on systemd code.
+# https://github.com/systemd/systemd/blob/main/src/shared/blockdev-util.c#L359
+ks_valid_block_device()
 {
-	local id="$1"; shift
-	local block=
-	local maj type
-
-	while read -r maj type; do
-		if [ -n "$block" ] && [ "$id" = "$maj" ]; then
-			echo "$type"
-			return 0
-		fi
+	local syspath="$1"
+	local attr
 
-		[ "$maj $type" != 'Block devices:' ] ||
-			block=1
-	done </proc/devices
-	return 1
+	[ -e "$syspath" ] ||
+		return 1
+
+	# With https://github.com/torvalds/linux/commit/a4217c6740dc64a3eb6815868a9260825e8c68c6 (v6.10,
+	# backported to v6.6+), the partscan status is directly exposed as
+	# 'partscan' sysattr.
+	if [ -r "$syspath/partscan" ]; then
+		readline attr "$syspath/partscan"
+
+		shell_var_is_yes "$attr" ||
+			return 1
+		return 0
+	fi
+
+	# For loopback block device, especially for v5.19 or newer. Even if this
+	# is enabled, we also need to check GENHD_FL_NO_PART flag through
+	# 'ext_range' and 'capability' sysfs attributes below.
+	if [ -r "$syspath/loop/partscan" ]; then
+		readline attr "$syspath/loop/partscan"
+
+		shell_var_is_yes "$attr" ||
+			return 1
+	fi
+
+	# With https://github.com/torvalds/linux/commit/1ebe2e5f9d68e94c524aba876f27b945669a7879 (v5.17),
+	# we can check the flag from 'ext_range' sysfs attribute directly.
+	#
+	# If the ext_range file doesn't exist then we are most likely looking at
+	# a partition block device, not the whole block device. And that means
+	# we have no partition scanning on for it (we do for its parent, but not
+	# for the partition itself).
+	[ -r "$syspath/ext_range" ] ||
+		return 1
+
+	readline attr "$syspath/ext_range"
+
+	# The value should be always positive, but the kernel uses '%d'
+	# for the attribute.
+	shell_var_is_number "$attr" ||
+		return 1
+
+	# With https://github.com/torvalds/linux/commit/e81cd5a983bb35dabd38ee472cf3fea1c63e0f23 (v6.3),
+	# the 'capability' sysfs attribute is deprecated, hence we cannot check
+	# flags from it.
+	if [ -r "$syspath/capability" ]; then
+		# With https://github.com/torvalds/linux/commit/430cc5d3ab4d0ba0bd011cfbb0035e46ba92920c (v5.17),
+		# the value of GENHD_FL_NO_PART is changed from 0x0200 to 0x0004
+		local GENHD_FL_NO_PART_v5_17=$(( 0x0200 ))
+		local GENHD_FL_NO_PART_v6_3=$((  0x0004 ))
+
+		readline attr "$f/capability"
+
+		# If one of the NO_PART flags is set, part scanning is
+		# definitely off.
+		shell_var_is_number "$attr" &&
+			[ "$(( $attr & ( $GENHD_FL_NO_PART_v5_17 | $GENHD_FL_NO_PART_v6_3 ) ))" -eq 0 ] ||
+			return 1
+	fi
+
+	# Otherwise, assume part scanning is on.
+	return 0
 }
 
 ks_block_devices()
 {
-	local retval="$1"; shift
-	local f dev
-	local maj min
-	local blocktype
+	local retval="$1"
+	local majmin dev
 	local exclude=','
 
-	for f in $(findmnt -lno SOURCE | sed -n -e 's,^/dev/,,p'); do
-		dev="$(readlink -f "/sys/class/block/$f")"
-		dev="${dev%/$f}"
-		dev="${dev##*/}"
-		exclude="$exclude$dev,"
+	for majmin in $(findmnt -lno MAJ:MIN |sed -e '/^ *0:.*/d' |sort -u); do
+		dev="$(readlink -f "/sys/dev/block/$majmin")" ||
+			continue
+		[ -z "${dev##*/virtual/block/*}" ] ||
+			dev="${dev%/*}"
+		exclude="${exclude}${majmin},"
 	done
 
 	set --
 
-	for f in $(set +f; printf '%s\n' /sys/block/*); do
-		[ -e "$f" ] ||
+	for majmin in $(set +f && cd /sys/dev/block && printf '%s\n' * |sort -nt:); do
+		[ -n "${exclude##*,$majmin,*}" ] ||
 			continue
 
-		maj=
-		min=
-		IFS=: read -r maj min < "$f/dev"
-		blocktype="$(get_device_type "$maj")"
-
-		case "$blocktype" in
-			sd|virtblk|mmc|blkext)
-				;;
-			*)
+		case "$majmin" in
+			# 0       - Unnamed devices (e.g. non-device mounts)
+			# 1 block - RAM disk
+			# 4 block - Aliases for dynamically allocated major
+			#           devices to be used when its not possible to
+			#           create the real device nodes because the
+			#           root filesystem is mounted read-only.
+			0:*|1:*|4:*)
 				continue
 				;;
 		esac
 
-		[ -n "${exclude##*,${f##*/},*}" ] ||
+		ks_valid_block_device "/sys/dev/block/$majmin" ||
 			continue
 
-		set -- "$@" "${f##*/}"
+		dev="$(readlink -f "/sys/dev/block/$majmin")"
+		set -- "$@" "${dev##*/}"
 	done
 
 	eval "$retval=\"\$*\""