selftests: ublk: add group-based test targets

Add convenient Makefile targets for running specific test groups:
- run_generic, run_batch, run_null, run_loop, run_stripe, run_stress, etc.
- run_all for running all tests

Test groups are auto-detected from TEST_PROGS using pattern matching
(test_<group>_<num>.sh -> group), and targets are generated dynamically
using define/eval templates.

Supports parallel execution via JOBS variable:
- JOBS=1 (default): sequential with kselftest TAP output
- JOBS>1: parallel execution with xargs -P

Usage examples:
  make run_null           # Sequential execution
  make run_stress JOBS=4  # Parallel with 4 jobs
  make run_all JOBS=8     # Run all tests with 8 parallel jobs

With JOBS=8, running time of `make run_all` is reduced to 2m2s from 6m5s
in my test VM.

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

Author: Ming Lei

tools/testing/selftests/ublk/Makefile

@@ -72,3 +72,39 @@ $(OUTPUT)/kublk: $(filter-out $(STANDALONE_UTILS),$(wildcard *.c))
 
 check:
 	shellcheck -x -f gcc *.sh
+
+# Test groups for running subsets of tests
+# JOBS=1 (default): sequential with kselftest TAP output
+# JOBS>1: parallel execution with xargs -P
+# Usage: make run_null JOBS=4
+JOBS ?= 1
+
+# Auto-detect test groups from TEST_PROGS (test_<group>_<num>.sh -> group)
+TEST_GROUPS := $(shell echo "$(TEST_PROGS)" | tr ' ' '\n' | \
+	sed 's/test_\([^_]*\)_.*/\1/' | sort -u)
+
+# Template for group test targets
+# $(1) = group name (e.g., null, generic, stress)
+define RUN_GROUP
+run_$(1): all
+	@if [ $$(JOBS) -gt 1 ]; then \
+		echo $$(filter test_$(1)_%.sh,$$(TEST_PROGS)) | tr ' ' '\n' | \
+			xargs -P $$(JOBS) -n1 sh -c './"$$$$0"' || true; \
+	else \
+		$$(call RUN_TESTS, $$(filter test_$(1)_%.sh,$$(TEST_PROGS))); \
+	fi
+.PHONY: run_$(1)
+endef
+
+# Generate targets for each discovered test group
+$(foreach group,$(TEST_GROUPS),$(eval $(call RUN_GROUP,$(group))))
+
+# Run all tests (parallel when JOBS>1)
+run_all: all
+	@if [ $(JOBS) -gt 1 ]; then \
+		echo $(TEST_PROGS) | tr ' ' '\n' | \
+			xargs -P $(JOBS) -n1 sh -c './"$$0"' || true; \
+	else \
+		$(call RUN_TESTS, $(TEST_PROGS)); \
+	fi
+.PHONY: run_all