add 'Destroy' test

Checks the correct operation of the blksnap when deleting a snapshot
during I/O operations to the snapshot image and to the device under
tracking.
See: https://lore.kernel.org/all/86068780-bab3-2fc2-3f6f-1868be119b38@veeam.com/

tests/7000-destroy.sh

@@ -0,0 +1,91 @@
+#!/bin/bash -e
+#
+# SPDX-License-Identifier: GPL-2.0+
+
+
+if [ -z $1 ]
+then
+	DIFF_STORAGE_DIR=${HOME}
+else
+	DIFF_STORAGE_DIR=$1
+fi
+echo "Diff storage directory ${DIFF_STORAGE_DIR}"
+
+. ./functions.sh
+. ./blksnap.sh
+
+echo "---"
+echo "Destroy test start"
+
+blksnap_load
+
+# check module is ready
+blksnap_version
+
+TESTDIR=/tmp/blksnap-test
+rm -rf ${TESTDIR}
+mkdir -p ${TESTDIR}
+
+MPDIR=/mnt/blksnap-test
+rm -rf ${MPDIR}
+mkdir -p ${MPDIR}
+
+
+# create first device
+IMAGEFILE_1=${TESTDIR}/simple_1.img
+imagefile_make ${IMAGEFILE_1} 128
+echo "new image file ${IMAGEFILE_1}"
+
+DEVICE_1=$(loop_device_attach ${IMAGEFILE_1})
+echo "new device ${DEVICE_1}"
+
+MOUNTPOINT_1=${MPDIR}/simple_1
+mkdir -p ${MOUNTPOINT_1}
+mount ${DEVICE_1} ${MOUNTPOINT_1}
+
+echo "Write to original before taking snapshot"
+generate_files ${MOUNTPOINT_1} "before" 9
+drop_cache
+
+blksnap_snapshot_create "${DEVICE_1}"
+
+DIFF_STORAGE=${DIFF_STORAGE_DIR}/diff_storage0
+rm -f ${DIFF_STORAGE}
+fallocate --length 128MiB ${DIFF_STORAGE}
+blksnap_snapshot_appendstorage ${DIFF_STORAGE}
+
+blksnap_snapshot_take
+
+echo "mount snapshot"
+DEVICE_IMAGE_1=$(blksnap_get_image ${DEVICE_1})
+IMAGE_1=${TESTDIR}/image0
+mkdir -p ${IMAGE_1}
+mount ${DEVICE_IMAGE_1} ${IMAGE_1}
+
+echo "Write to original after taking snapshot"
+generate_files ${MOUNTPOINT_1} "after" 4 &
+
+dd if=${DEVICE_IMAGE_1} of=/dev/zero &
+
+echo "Write to snapshot"
+generate_files ${IMAGE_1} "snapshot" 4 &
+
+dd if=${DEVICE_IMAGE_1} of=/dev/zero &
+
+echo "Destroy snapshot ..."
+blksnap_snapshot_destroy
+
+umount --lazy --force ${IMAGE_1}
+
+rm ${DIFF_STORAGE}
+
+echo "Destroy device"
+blksnap_detach ${DEVICE_1}
+umount ${MOUNTPOINT_1}
+loop_device_detach ${DEVICE_1}
+imagefile_cleanup ${IMAGEFILE_1}
+
+blksnap_unload
+
+echo "Destroy test finish"
+echo "---"