selftests: ublk: organize test directories by test ID

Set UBLK_TEST_DIR to ${TMPDIR:-./ublktest-dir}/${TID}.XXXXXX to create
per-test subdirectories organized by test ID. This makes it easier to
identify and debug specific test runs.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Ming Lei

tools/testing/selftests/ublk/test_common.sh

@@ -129,7 +129,9 @@ _prep_test() {
 	local type=$1
 	shift 1
 	modprobe ublk_drv > /dev/null 2>&1
-	UBLK_TEST_DIR=$(mktemp -d ${TMPDIR:-.}/ublktest-dir.XXXXXX)
+	local base_dir=${TMPDIR:-./ublktest-dir}
+	mkdir -p "$base_dir"
+	UBLK_TEST_DIR=$(mktemp -d ${base_dir}/${TID}.XXXXXX)
 	UBLK_TMP=$(mktemp ${UBLK_TEST_DIR}/ublk_test_XXXXX)
 	[ "$UBLK_TEST_QUIET" -eq 0 ] && echo "ublk $type: $*"
 	echo "ublk selftest: $TID starting at $(date '+%F %T')" | tee /dev/kmsg