selftests/damon: test non-context inputs to rm_contexts file

There was a bug[1] that triggered by writing non-context DAMON debugfs
file names to the 'rm_contexts' DAMON debugfs file.  Add a selftest for
the bug to avoid it happen again.

[1] https://lore.kernel.org/damon/000000000000ede3ac05ec4abf8e@google.com/

Link: https://lkml.kernel.org/r/20221107165001.5717-3-sj@kernel.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/damon/Makefile

@@ -7,6 +7,7 @@ TEST_FILES = _chk_dependency.sh _debugfs_common.sh
 TEST_PROGS = debugfs_attrs.sh debugfs_schemes.sh debugfs_target_ids.sh
 TEST_PROGS += debugfs_empty_targets.sh debugfs_huge_count_read_write.sh
 TEST_PROGS += debugfs_duplicate_context_creation.sh
+TEST_PROGS += debugfs_rm_non_contexts.sh
 TEST_PROGS += sysfs.sh
 TEST_PROGS += reclaim.sh lru_sort.sh
 

tools/testing/selftests/damon/debugfs_rm_non_contexts.sh

+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+source _debugfs_common.sh
+
+# Test putting non-ctx files/dirs to rm_contexts file
+# ===================================================
+
+dmesg -C
+
+for file in "$DBGFS/"*
+do
+	echo "$(basename "$f")" > "$DBGFS/rm_contexts"
+	if dmesg | grep -q BUG
+	then
+		dmesg
+		exit 1
+	fi
+done