From 581b097951991e58ee3219987646ffaeee78eec3 Mon Sep 17 00:00:00 2001
From: SeongJae Park <sj@kernel.org>
Date: Fri, 10 Dec 2021 14:46:55 -0800
Subject: [PATCH] selftests/damon: test debugfs file reads/writes with huge
 count

commit b4a002889d24979295ed3c2bf1d5fcfb3901026a upstream.

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.

Link: https://lkml.kernel.org/r/20211201150440.1088-11-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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

diff --git a/tools/testing/selftests/damon/.gitignore b/tools/testing/selftests/damon/.gitignore
new file mode 100644
index 0000000000000..c6c2965a66075
--- /dev/null
+++ b/tools/testing/selftests/damon/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+huge_count_read_write
diff --git a/tools/testing/selftests/damon/Makefile b/tools/testing/selftests/damon/Makefile
index 8a3f2cd9fec0c..f0aa954b5d135 100644
--- a/tools/testing/selftests/damon/Makefile
+++ b/tools/testing/selftests/damon/Makefile
@@ -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
 
diff --git a/tools/testing/selftests/damon/debugfs_attrs.sh b/tools/testing/selftests/damon/debugfs_attrs.sh
index bfabb19dc0d3d..ecda972e87775 100644
--- a/tools/testing/selftests/damon/debugfs_attrs.sh
+++ b/tools/testing/selftests/damon/debugfs_attrs.sh
@@ -72,4 +72,22 @@ test_write_succ "$file" "" "$orig_content" "empty input"
 test_content "$file" "$orig_content" "" "empty input written"
 echo "$orig_content" > "$file"
 
+# 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"
diff --git a/tools/testing/selftests/damon/huge_count_read_write.c b/tools/testing/selftests/damon/huge_count_read_write.c
new file mode 100644
index 0000000000000..ad7a6b4cf3387
--- /dev/null
+++ b/tools/testing/selftests/damon/huge_count_read_write.c
@@ -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;
+}
-- 
2.30.2