new file mode 100644
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+huge_count_read_write
@@ -1,6 +1,8 @@
# SPDX-License-Identifier: GPL-2.0
# Makefile for damon selftests
+TEST_GEN_FILES += huge_count_read_write
+
TEST_FILES = _chk_dependency.sh
TEST_PROGS = debugfs_attrs.sh
@@ -105,4 +105,22 @@ orig_monitor_on=$(cat "$DBGFS/monitor_on")
test_write_fail "$DBGFS/monitor_on" "on" "orig_monitor_on" "empty target ids"
echo "$orig_target_ids" > "$DBGFS/target_ids"
+# Test huge count read write
+# ==========================
+
+dmesg -C
+
+for file in "$DBGFS/"*
+do
+ ./huge_count_read_write "$file"
+done
+
+if dmesg | grep -q WARNING
+then
+ dmesg
+ exit 1
+else
+ exit 0
+fi
+
echo "PASS"
new file mode 100644
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Author: SeongJae Park <sj@kernel.org>
+ */
+
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+
+void write_read_with_huge_count(char *file)
+{
+ int filedesc = open(file, O_RDWR);
+ char buf[25];
+ int ret;
+
+ printf("%s %s\n", __func__, file);
+ if (filedesc < 0) {
+ fprintf(stderr, "failed opening %s\n", file);
+ exit(1);
+ }
+
+ write(filedesc, "", 0xfffffffful);
+ perror("after write: ");
+ ret = read(filedesc, buf, 0xfffffffful);
+ perror("after read: ");
+ close(filedesc);
+}
+
+int main(int argc, char *argv[])
+{
+ if (argc != 2) {
+ fprintf(stderr, "Usage: %s <file>\n", argv[0]);
+ exit(1);
+ }
+ write_read_with_huge_count(argv[1]);
+
+ return 0;
+}
DAMON debugfs interface users were able to trigger warning by writing some files with arbitrarily large 'count' parameter. The issue is fixed with commit db7a347b26fe ("mm/damon/dbgfs: use '__GFP_NOWARN' for user-specified size buffer allocation"). This commit adds a test case for the issue in DAMON selftests to avoid future regressions. Signed-off-by: SeongJae Park <sj@kernel.org> --- tools/testing/selftests/damon/.gitignore | 2 + tools/testing/selftests/damon/Makefile | 2 + .../testing/selftests/damon/debugfs_attrs.sh | 18 +++++++++ .../selftests/damon/huge_count_read_write.c | 39 +++++++++++++++++++ 4 files changed, 61 insertions(+) create mode 100644 tools/testing/selftests/damon/.gitignore create mode 100644 tools/testing/selftests/damon/huge_count_read_write.c