[PATCH v2] fat: add KUnit tests for timestamp conversion helpers
From: aviv . daum
Date: Sun Mar 15 2026 - 18:24:44 EST
From: avivdaum <aviv.daum@xxxxxxxxx>
Extend fat_test with coverage for FAT timestamp edge cases that are not
currently exercised.
Add tests for fat_time_unix2fat() clamping at the UTC boundaries and
when time_offset pushes an otherwise valid timestamp outside the FAT
date range. Also cover the NULL time_cs path used by existing callers,
and verify fat_truncate_atime() truncation across timezone offsets.
Signed-off-by: avivdaum <aviv.daum@xxxxxxxxx>
v2:
- Compare __le16 values directly in unix2fat tests
---
fs/fat/fat_test.c | 181 ++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 173 insertions(+), 8 deletions(-)
diff --git a/fs/fat/fat_test.c b/fs/fat/fat_test.c
index 1f0062659..5c97a7fcc 100644
--- a/fs/fat/fat_test.c
+++ b/fs/fat/fat_test.c
@@ -29,6 +29,22 @@ struct fat_timestamp_testcase {
int time_offset;
};
+struct fat_unix2fat_clamp_testcase {
+ const char *name;
+ struct timespec64 ts;
+ __le16 time;
+ __le16 date;
+ u8 cs;
+ int time_offset;
+};
+
+struct fat_truncate_atime_testcase {
+ const char *name;
+ struct timespec64 ts;
+ struct timespec64 expected;
+ int time_offset;
+};
+
static struct fat_timestamp_testcase time_test_cases[] = {
{
.name = "Earliest possible UTC (1980-01-01 00:00:00)",
@@ -120,13 +136,92 @@ static struct fat_timestamp_testcase time_test_cases[] = {
},
};
+static struct fat_unix2fat_clamp_testcase unix2fat_clamp_test_cases[] = {
+ {
+ .name = "Clamp to earliest FAT date for 1979-12-31 23:59:59 UTC",
+ .ts = {.tv_sec = 315532799LL, .tv_nsec = 0L},
+ .time = cpu_to_le16(0),
+ .date = cpu_to_le16(33),
+ .cs = 0,
+ .time_offset = 0,
+ },
+ {
+ .name = "Clamp after time_offset=-60 pushes 1980-01-01 00:30 UTC below 1980",
+ .ts = {.tv_sec = 315534600LL, .tv_nsec = 0L},
+ .time = cpu_to_le16(0),
+ .date = cpu_to_le16(33),
+ .cs = 0,
+ .time_offset = -60,
+ },
+ {
+ .name = "Clamp to latest FAT date for 2108-01-01 00:00:00 UTC",
+ .ts = {.tv_sec = 4354819200LL, .tv_nsec = 0L},
+ .time = cpu_to_le16(49021),
+ .date = cpu_to_le16(65439),
+ .cs = 199,
+ .time_offset = 0,
+ },
+ {
+ .name = "Clamp after time_offset=60 pushes 2107-12-31 23:30 UTC beyond 2107",
+ .ts = {.tv_sec = 4354817400LL, .tv_nsec = 0L},
+ .time = cpu_to_le16(49021),
+ .date = cpu_to_le16(65439),
+ .cs = 199,
+ .time_offset = 60,
+ },
+};
+
+static struct fat_truncate_atime_testcase truncate_atime_test_cases[] = {
+ {
+ .name = "UTC atime truncates to 2004-02-29 00:00:00",
+ .ts = {.tv_sec = 1078058096LL, .tv_nsec = 789000000L},
+ .expected = {.tv_sec = 1078012800LL, .tv_nsec = 0L},
+ .time_offset = 0,
+ },
+ {
+ .name = "time_offset=-60 truncates 2004-02-29 00:30 UTC to previous local midnight",
+ .ts = {.tv_sec = 1078014645LL, .tv_nsec = 123000000L},
+ .expected = {.tv_sec = 1077930000LL, .tv_nsec = 0L},
+ .time_offset = -60,
+ },
+ {
+ .name = "time_offset=60 truncates 2004-02-29 23:30 UTC to next local midnight",
+ .ts = {.tv_sec = 1078097445LL, .tv_nsec = 123000000L},
+ .expected = {.tv_sec = 1078095600LL, .tv_nsec = 0L},
+ .time_offset = 60,
+ },
+};
+
static void time_testcase_desc(struct fat_timestamp_testcase *t,
char *desc)
{
strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
}
+static void unix2fat_clamp_testcase_desc(struct fat_unix2fat_clamp_testcase *t,
+ char *desc)
+{
+ strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
+}
+
+static void truncate_atime_testcase_desc(struct fat_truncate_atime_testcase *t,
+ char *desc)
+{
+ strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
+}
+
KUNIT_ARRAY_PARAM(fat_time, time_test_cases, time_testcase_desc);
+KUNIT_ARRAY_PARAM(fat_unix2fat_clamp, unix2fat_clamp_test_cases,
+ unix2fat_clamp_testcase_desc);
+KUNIT_ARRAY_PARAM(fat_truncate_atime, truncate_atime_test_cases,
+ truncate_atime_testcase_desc);
+
+static void fat_test_set_time_offset(struct msdos_sb_info *sbi, int time_offset)
+{
+ *sbi = (struct msdos_sb_info){};
+ sbi->options.tz_set = 1;
+ sbi->options.time_offset = time_offset;
+}
static void fat_time_fat2unix_test(struct kunit *test)
{
@@ -135,8 +230,7 @@ static void fat_time_fat2unix_test(struct kunit *test)
struct fat_timestamp_testcase *testcase =
(struct fat_timestamp_testcase *)test->param_value;
- fake_sb.options.tz_set = 1;
- fake_sb.options.time_offset = testcase->time_offset;
+ fat_test_set_time_offset(&fake_sb, testcase->time_offset);
fat_time_fat2unix(&fake_sb, &ts,
testcase->time,
@@ -160,18 +254,17 @@ static void fat_time_unix2fat_test(struct kunit *test)
struct fat_timestamp_testcase *testcase =
(struct fat_timestamp_testcase *)test->param_value;
- fake_sb.options.tz_set = 1;
- fake_sb.options.time_offset = testcase->time_offset;
+ fat_test_set_time_offset(&fake_sb, testcase->time_offset);
fat_time_unix2fat(&fake_sb, &testcase->ts,
&time, &date, &cs);
KUNIT_EXPECT_EQ_MSG(test,
- le16_to_cpu(testcase->time),
- le16_to_cpu(time),
+ testcase->time,
+ time,
"Time mismatch\n");
KUNIT_EXPECT_EQ_MSG(test,
- le16_to_cpu(testcase->date),
- le16_to_cpu(date),
+ testcase->date,
+ date,
"Date mismatch\n");
KUNIT_EXPECT_EQ_MSG(test,
testcase->cs,
@@ -179,10 +272,82 @@ static void fat_time_unix2fat_test(struct kunit *test)
"Centisecond mismatch\n");
}
+static void fat_time_unix2fat_clamp_test(struct kunit *test)
+{
+ static struct msdos_sb_info fake_sb;
+ __le16 date, time;
+ u8 cs;
+ struct fat_unix2fat_clamp_testcase *testcase =
+ (struct fat_unix2fat_clamp_testcase *)test->param_value;
+
+ fat_test_set_time_offset(&fake_sb, testcase->time_offset);
+
+ fat_time_unix2fat(&fake_sb, &testcase->ts, &time, &date, &cs);
+ KUNIT_EXPECT_EQ_MSG(test,
+ testcase->time,
+ time,
+ "Clamped time mismatch\n");
+ KUNIT_EXPECT_EQ_MSG(test,
+ testcase->date,
+ date,
+ "Clamped date mismatch\n");
+ KUNIT_EXPECT_EQ_MSG(test,
+ testcase->cs,
+ cs,
+ "Clamped centisecond mismatch\n");
+}
+
+static void fat_time_unix2fat_no_csec_test(struct kunit *test)
+{
+ static struct msdos_sb_info fake_sb;
+ struct timespec64 ts = {
+ .tv_sec = 946684799LL,
+ .tv_nsec = 0L,
+ };
+ __le16 date, time;
+
+ fat_test_set_time_offset(&fake_sb, 0);
+
+ fat_time_unix2fat(&fake_sb, &ts, &time, &date, NULL);
+ KUNIT_EXPECT_EQ_MSG(test,
+ 49021,
+ le16_to_cpu(time),
+ "Time mismatch without centiseconds\n");
+ KUNIT_EXPECT_EQ_MSG(test,
+ 10143,
+ le16_to_cpu(date),
+ "Date mismatch without centiseconds\n");
+}
+
+static void fat_truncate_atime_test(struct kunit *test)
+{
+ static struct msdos_sb_info fake_sb;
+ struct timespec64 actual;
+ struct fat_truncate_atime_testcase *testcase =
+ (struct fat_truncate_atime_testcase *)test->param_value;
+
+ fat_test_set_time_offset(&fake_sb, testcase->time_offset);
+
+ actual = fat_truncate_atime(&fake_sb, &testcase->ts);
+ KUNIT_EXPECT_EQ_MSG(test,
+ testcase->expected.tv_sec,
+ actual.tv_sec,
+ "Atime truncation seconds mismatch\n");
+ KUNIT_EXPECT_EQ_MSG(test,
+ testcase->expected.tv_nsec,
+ actual.tv_nsec,
+ "Atime truncation nanoseconds mismatch\n");
+}
+
static struct kunit_case fat_test_cases[] = {
KUNIT_CASE(fat_checksum_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,
+ fat_unix2fat_clamp_gen_params),
+ KUNIT_CASE(fat_time_unix2fat_no_csec_test),
+ KUNIT_CASE_PARAM(fat_truncate_atime_test,
+ fat_truncate_atime_gen_params),
{},
};
--
2.34.1