From: Adi Nata <adinata.softwareengineer@gmail.com>
Date: Sun, 5 Apr 2026 01:19:20 +0000 (+0800)
Subject: kunit: fat: test cluster and directory i_pos layout helpers
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=410002f8139cbf902f1567f0a8cbf0c5b6f43da2;p=thirdparty%2Flinux.git

kunit: fat: test cluster and directory i_pos layout helpers

Add KUnit coverage for fat_clus_to_blknr() and fat_get_blknr_offset()
using stub msdos_sb_info values so cluster-to-sector and i_pos split math
stays correct.

Link: https://lore.kernel.org/20260405011920.28622-1-adinata.softwareengineer@gmail.com
Signed-off-by: Adi Nata <adinata.softwareengineer@gmail.com>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/fs/fat/fat_test.c b/fs/fat/fat_test.c
index 886bf044a9f1d..4eeed9dca5494 100644
--- a/fs/fat/fat_test.c
+++ b/fs/fat/fat_test.c
@@ -20,6 +20,37 @@ static void fat_checksum_test(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, fat_checksum("ABCDEFGHA  "), (u8)98);
 }
 
+static void fat_clus_to_blknr_test(struct kunit *test)
+{
+	struct msdos_sb_info sbi = {
+		.sec_per_clus = 4,
+		.data_start = 100,
+	};
+
+	KUNIT_EXPECT_EQ(test, (sector_t)100,
+			fat_clus_to_blknr(&sbi, FAT_START_ENT));
+	KUNIT_EXPECT_EQ(test, (sector_t)112, fat_clus_to_blknr(&sbi, 5));
+}
+
+static void fat_get_blknr_offset_test(struct kunit *test)
+{
+	struct msdos_sb_info sbi = {
+		.dir_per_block = 16,
+		.dir_per_block_bits = 4,
+	};
+
+	sector_t blknr;
+	int offset;
+
+	fat_get_blknr_offset(&sbi, 0, &blknr, &offset);
+	KUNIT_EXPECT_EQ(test, (sector_t)0, blknr);
+	KUNIT_EXPECT_EQ(test, 0, offset);
+
+	fat_get_blknr_offset(&sbi, (10 << 4) | 7, &blknr, &offset);
+	KUNIT_EXPECT_EQ(test, (sector_t)10, blknr);
+	KUNIT_EXPECT_EQ(test, 7, offset);
+}
+
 struct fat_timestamp_testcase {
 	const char *name;
 	struct timespec64 ts;
@@ -341,6 +372,8 @@ static void fat_truncate_atime_test(struct kunit *test)
 
 static struct kunit_case fat_test_cases[] = {
 	KUNIT_CASE(fat_checksum_test),
+	KUNIT_CASE(fat_clus_to_blknr_test),
+	KUNIT_CASE(fat_get_blknr_offset_test),
 	KUNIT_CASE_PARAM(fat_time_fat2unix_test, fat_time_gen_params),
 	KUNIT_CASE_PARAM(fat_time_unix2fat_test, fat_time_gen_params),
 	KUNIT_CASE_PARAM(fat_time_unix2fat_clamp_test,