[PATCH] kunit: fat: test cluster and directory i_pos layout helpers

Adi Nata
2026-04-05T01:19:34Z

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.

Signed-off-by: Adi Nata <adinata.softwareengineer@gmail.com>
---
fs/fat/fat_test.c | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)

diff --git a/fs/fat/fat_test.c b/fs/fat/fat_test.c
index 1f0062659067..add44178f28e 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;
@@ -181,6 +212,8 @@ static void fat_time_unix2fat_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),
{},
--
2.47.3