[PATCH v3 xfstests 2/2] generic: new test to check nlink returned by fstat()

[ChenXiaoSong <chenxiaosong@chenxiaosong.com>]

From: ChenXiaoSong <chenxiaosong@kylinos.cn>

Add a test to verify that fstat(2) returns the expected
st_nlink value as hardlinks are created and removed.

Regression test for kernel commit:
9dd1964ac59d ("smb/client: fix incorrect nlink returned by fstat()")

Suggested-by: Zorro Lang <zlang@kernel.org>
Signed-off-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
---
 tests/generic/798     | 60 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/798.out |  2 ++
 2 files changed, 62 insertions(+)
 create mode 100755 tests/generic/798
 create mode 100644 tests/generic/798.out

diff --git a/tests/generic/798 b/tests/generic/798
new file mode 100755
index 00000000..e44bb10a
--- /dev/null
+++ b/tests/generic/798
@@ -0,0 +1,60 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2026 KylinSoft Co., Ltd. All rights reserved.
+# Author(s): ChenXiaoSong <chenxiaosong@kylinos.cn>
+#
+# FS QA Test 798
+#
+# Check that fstat(2) returns the correct hard link count for a regular file.
+#
+#  from
+#  tests/generic/002
+#  Copyright (c) 2000-2001 Silicon Graphics, Inc.  All Rights Reserved.
+#
+. ./common/preamble
+_begin_fstest metadata auto quick hardlink
+
+_cleanup()
+{
+	cd /
+	rm -rf "$tmp".* "$testdir"
+}
+
+_require_test
+_require_hardlinks
+
+_fixed_by_fs_commit cifs 9dd1964ac59d \
+	"smb/client: fix incorrect nlink returned by fstat()"
+
+_get_nlink()
+{
+	$XFS_IO_PROG -c 'stat -r' "$1" |
+		sed -n 's/^stat\.nlink = //p'
+}
+
+status=0
+testdir=$TEST_DIR/$seq
+rm -rf "$testdir"
+mkdir "$testdir"
+
+touch "$testdir/tmp.1"
+for ((l = 2; l <= 20; l++)); do
+	ln "$testdir/tmp.1" "$testdir/tmp.$l"
+	nlink=$(_get_nlink "$testdir/tmp.1")
+	if [ "$nlink" != "$l" ]; then
+		echo "Expected nlink $l after creating link $l, got ${nlink:-nothing}"
+		status=1
+	fi
+done
+
+for ((l = 20; l >= 1; l--)); do
+	nlink=$(_get_nlink "$testdir/tmp.1")
+	if [ "$nlink" != "$l" ]; then
+		echo "Expected nlink $l before removing link $l, got ${nlink:-nothing}"
+		status=1
+	fi
+	rm -f "$testdir/tmp.$l"
+done
+
+echo "Silence is golden"
+exit $status
diff --git a/tests/generic/798.out b/tests/generic/798.out
new file mode 100644
index 00000000..216d6e93
--- /dev/null
+++ b/tests/generic/798.out
@@ -0,0 +1,2 @@
+QA output created by 798
+Silence is golden
-- 
2.43.0