Date:   Mon, 28 Mar 2022 14:18:41 +0300
From:   Kirill Tkhai <kirill.tkhai@...nvz.org>
To:     agk@...hat.com, snitzer@...hat.com, dm-devel@...hat.com,
        song@...nel.org, linux-kernel@...r.kernel.org,
        khorenko@...tuozzo.com, kirill.tkhai@...nvz.org
Subject: [PATCH 4/4] dm-qcow2: Add helper for working with dm-qcow2 devices

This scripts allows to create and remove dm-qcow2 device,
create internal snapshot, resize virtual device size,
or check image consistency on live device.

Signed-off-by: Kirill Tkhai <kirill.tkhai@...nvz.org>
---
 scripts/qcow2-dm.sh |  249 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 249 insertions(+)
 create mode 100755 scripts/qcow2-dm.sh

diff --git a/scripts/qcow2-dm.sh b/scripts/qcow2-dm.sh
new file mode 100755
index 000000000000..7d9bda44c1d6
--- /dev/null
+++ b/scripts/qcow2-dm.sh
@@ -0,0 +1,249 @@
+#!/bin/bash
+#
+# This requires parameter dm_qcow2.kernel_sets_dirty_bit=y
+
+usage () {
+    cat <<EOF
+Usage:
+	$prog_name create <file.qcow2> <dev_name>
+	$prog_name remove <file.qcow2>
+	$prog_name check [qemu-img check optional args] <file.qcow2>
+	$prog_name snapshot [qemu-img snapshot optional args] <file.qcow2>
+	$prog_name resize [qemu-img resize optional args] <file.qcow2> [+ | -]size
+EOF
+}
+
+get_img_size () {
+	sz=`qemu-img info -f qcow2 $1 | grep "virtual size" | sed 's/.*(\(.*\) bytes)/\1/'`
+	echo $sz
+}
+
+get_nr_imgs () {
+	nr=`echo $1 | sed "s/.*qcow2 \(\w\) .*$/\1/"`
+	echo $nr
+}
+
+get_dev_of_image () {
+	abs_path=$1
+
+	while read line; do
+		dev=`echo $line | sed "s/:.*//"`
+		nr_imgs=$(get_nr_imgs "$line")
+		top_img_id=$((nr_imgs - 1))
+
+		top_img_path=`dmsetup message $dev 0 get_img_name $top_img_id`
+		if [ -z "$top_img_path" ]; then
+			echo >&2 "Error during search of device"; exit 1;
+			return 1
+		fi
+
+		if [ "$abs_path" != "$top_img_path" ]; then
+			continue
+		fi
+
+		echo $dev
+		return 0
+
+	done < <(LANG=C dmsetup table --target=qcow2 | grep -v "No devices found")
+
+	return 0
+}
+
+create () {
+	if [ "$#" -ne 2 ]; then
+		echo >&2 "Wrong number of arguments."; usage; exit 1;
+	fi
+
+	file=$1
+	dev=$2
+	files=()
+	fds=""
+
+	qemu-img check $file || exit 1
+
+	disk_sz=$(get_img_size "$file")
+	echo disk_sz=$disk_sz
+	if [ -z "$disk_sz" ]; then
+		echo "Can't get disk size."; exit 1;
+	fi
+
+	while :; do
+		if [ ! -f "$file" ]; then
+			echo "$file does not exist."; exit 1;
+		fi
+
+		files+=("$file")
+
+		exec {fd}<>$file || exit 1
+		flock -x $fd || exit 1
+		fds="$fd $fds"
+
+		file=`qemu-img info $file | grep "backing file:" | sed "s/backing file: //"`
+		if [ -z "$file" ]; then
+			break
+		fi
+	done
+
+	echo "Create device [$dev] of size $disk_sz from [${files[*]}]."
+	dmsetup create $dev --table "0 $((disk_sz / 512)) qcow2 ${fds}"
+}
+
+reload_device () {
+	disk_sz=$(get_img_size "$abs_path")
+	if [ -z "$disk_sz" ]; then
+		echo "Can't get disk size."; return;
+	fi
+
+	line=`dmsetup table $dev`
+	nr_imgs=$(get_nr_imgs "$line")
+	top_img_id=$((nr_imgs - 1))
+	fds=""
+
+	for id in `seq 0 $top_img_id`;
+	do
+		file=`dmsetup message $dev 0 get_img_name $id`
+		if [ -z "$file" ]; then
+			echo "Can't get image file."; return;
+		fi
+		exec {fd}<>$file || exit 1
+
+		fds="$fds $fd"
+	done
+
+	echo "Reloading $dev."
+	dmsetup reload $dev --table "0 $((disk_sz / 512)) qcow2 ${fds}"
+}
+
+remove () {
+	if [ "$#" -ne 1 ]; then
+		echo >&2 "Wrong number of arguments."; usage; exit 1;
+	fi
+	user_path=$1
+	abs_path=`realpath $user_path`
+
+	dev=$(get_dev_of_image "$abs_path")
+	if [ -z "$dev" ]; then
+		echo >&2 "Can't find device with [$user_path] top image."; exit 1
+	fi
+
+	echo "Removing device [$dev]."
+	dmsetup remove $dev
+	ret=$?
+
+	if [ $ret -eq 0 ]; then
+		#Sanity check
+		echo "Checking [$abs_path]."
+		qemu-img check $abs_path
+	fi
+	exit $ret
+}
+
+qemu_img () {
+	wants_reload=0
+	if [ $1 == "--wants_reload" ]; then
+		wants_reload=1
+		shift
+	fi
+
+	if [ "$#" -lt 3 ]; then
+		echo >&2 "Wrong number of arguments."; usage; exit 1;
+	fi
+
+	user_path=$1
+	cmd=$2
+	abs_path=`realpath $user_path`
+	qemu_img_args=${@: 2}
+
+	dev=$(get_dev_of_image "$abs_path")
+	if [ -z "$dev" ]; then
+		echo >&2 "Can't find device by [$user_path]."; return 1
+	fi
+
+	echo "Suspending $dev."
+	dmsetup suspend $dev || exit 1
+
+	if [ "$cmd" != "check" ]; then
+		echo "Checking $abs_path"
+		qemu-img check $abs_path
+		ret=$?
+		if [ $ret -ne 0 ]; then
+			echo "Resuming $dev."
+			dmsetup resume $dev
+			exit 1
+		fi
+	fi
+
+	echo "===== Call:  qemu-img $qemu_img_args. ====="
+	qemu-img $qemu_img_args
+	ret=$?
+	if [ $ret -ne 0 ]; then
+		echo >&2 "Failed during qemu-img call."
+	fi
+	echo "===== End of qemu-img $qemu_img_args. ====="
+
+	if [ $wants_reload -ne 0 ]; then
+		reload_device $dev $abs_path
+	fi
+
+	echo "Resuming $dev."
+	dmsetup resume $dev || exit 1
+	if [ $? -ne 0 ]; then
+		ret=$?
+	fi
+
+	return $ret
+}
+
+check () {
+	user_path=${@: -1}
+	qemu_img_args=$@
+
+	qemu_img $user_path check $qemu_img_args
+	return $?
+}
+
+snapshot () {
+	user_path=${@: -1}
+	qemu_img_args=$@
+
+	qemu_img $user_path snapshot $qemu_img_args
+	return $?
+}
+
+resize () {
+	user_path=${@:(-2):1}
+	qemu_img_args=$@
+
+	qemu_img --wants_reload $user_path resize $qemu_img_args
+	return $?
+}
+
+prog_name=$(basename $0)
+
+case $1 in
+	"create")
+		shift
+		create "$@"
+		exit 0
+		;;
+	"remove")
+		shift
+		remove "$@"
+		;;
+	"check")
+		shift
+		check "$@"
+		;;
+	"snapshot")
+		shift
+		snapshot "$@"
+		;;
+	"resize")
+		shift
+		resize "$@"
+		;;
+	*)
+		usage
+		exit 1
+	        ;;
+esac

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