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 886bf044a9f1d4d3e5204c91d97797c7dd6fc976..4eeed9dca5494033b154d7b29f16f3197535bcf1 100644 (file)
--- 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,