[PATCH 04/21] fat: Fix and cleanup timestamp conversion

From: OGAWA Hirofumi
Date: Wed Oct 15 2008 - 10:11:57 EST

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This cleans date_dos2unix()/fat_date_unix2dos() up. New code should be
much more readable.

And this fixes those old functions. Those doesn't handle 2100
correctly. 2100 isn't leap year, but old one handles it as leap year.
Also, with this, centi sec is handled and is fixed.

Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
---

fs/fat/dir.c | 6 +-
fs/fat/fat.h | 7 +-
fs/fat/inode.c | 34 +++--------
fs/fat/misc.c | 146 ++++++++++++++++++++++++++++++++++++--------------
fs/fat/namei_msdos.c | 2
fs/fat/namei_vfat.c | 5 +
6 files changed, 129 insertions(+), 71 deletions(-)

diff -puN fs/fat/misc.c~fat_timestamp-fix fs/fat/misc.c
--- linux-2.6/fs/fat/misc.c~fat_timestamp-fix 2008-08-24 22:57:36.000000000 +0900
+++ linux-2.6-hirofumi/fs/fat/misc.c 2008-08-24 22:57:36.000000000 +0900
@@ -135,65 +135,131 @@ int fat_chain_add(struct inode *inode, i

extern struct timezone sys_tz;

+/*
+ * The epoch of FAT timestamp is 1980.
+ * : bits : value
+ * date: 0 - 4: day (1 - 31)
+ * date: 5 - 8: month (1 - 12)
+ * date: 9 - 15: year (0 - 127) from 1980
+ * time: 0 - 4: sec (0 - 29) 2sec counts
+ * time: 5 - 10: min (0 - 59)
+ * time: 11 - 15: hour (0 - 23)
+ */
+#define SECS_PER_MIN 60
+#define SECS_PER_HOUR (60 * 60)
+#define SECS_PER_DAY (SECS_PER_HOUR * 24)
+#define UNIX_SECS_1980 315532800L
+#if BITS_PER_LONG == 64
+#define UNIX_SECS_2108 4354819200L
+#endif
+/* days between 1.1.70 and 1.1.80 (2 leap days) */
+#define DAYS_DELTA (365 * 10 + 2)
+/* 120 (2100 - 1980) isn't leap year */
+#define YEAR_2100 120
+#define IS_LEAP_YEAR(y) (!((y) & 3) && (y) != YEAR_2100)
+
/* Linear day numbers of the respective 1sts in non-leap years. */
-static int day_n[] = {
- /* Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec */
- 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 0, 0, 0, 0
+static time_t days_in_year[] = {
+ /* Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec */
+ 0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 0, 0, 0,
};

-/* Convert a MS-DOS time/date pair to a UNIX date (seconds since 1 1 70). */
-int date_dos2unix(unsigned short time, unsigned short date, int tz_utc)
+/* Convert a FAT time/date pair to a UNIX date (seconds since 1 1 70). */
+void fat_time_fat2unix(struct msdos_sb_info *sbi, struct timespec *ts,
+ __le16 __time, __le16 __date, u8 time_cs)
{
- int month, year, secs;
+ u16 time = le16_to_cpu(__time), date = le16_to_cpu(__date);
+ time_t second, day, leap_day, month, year;

- /*
- * first subtract and mask after that... Otherwise, if
- * date == 0, bad things happen
- */
- month = ((date >> 5) - 1) & 15;
- year = date >> 9;
- secs = (time & 31)*2+60*((time >> 5) & 63)+(time >> 11)*3600+86400*
- ((date & 31)-1+day_n[month]+(year/4)+year*365-((year & 3) == 0 &&
- month < 2 ? 1 : 0)+3653);
- /* days since 1.1.70 plus 80's leap day */
- if (!tz_utc)
- secs += sys_tz.tz_minuteswest*60;
- return secs;
+ year = date >> 9;
+ month = max(1, (date >> 5) & 0xf);
+ day = max(1, date & 0x1f) - 1;
+
+ leap_day = (year + 3) / 4;
+ if (year > YEAR_2100) /* 2100 isn't leap year */
+ leap_day--;
+ if (IS_LEAP_YEAR(year) && month > 2)
+ leap_day++;
+
+ second = (time & 0x1f) << 1;
+ second += ((time >> 5) & 0x3f) * SECS_PER_MIN;
+ second += (time >> 11) * SECS_PER_HOUR;
+ second += (year * 365 + leap_day
+ + days_in_year[month] + day
+ + DAYS_DELTA) * SECS_PER_DAY;
+
+ if (!sbi->options.tz_utc)
+ second += sys_tz.tz_minuteswest * SECS_PER_MIN;
+
+ if (time_cs) {
+ ts->tv_sec = second + (time_cs / 100);
+ ts->tv_nsec = (time_cs % 100) * 10000000;
+ } else {
+ ts->tv_sec = second;
+ ts->tv_nsec = 0;
+ }
}

-/* Convert linear UNIX date to a MS-DOS time/date pair. */
-void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date, int tz_utc)
+/* Convert linear UNIX date to a FAT time/date pair. */
+void fat_time_unix2fat(struct msdos_sb_info *sbi, struct timespec *ts,
+ __le16 *time, __le16 *date, u8 *time_cs)
{
- int day, year, nl_day, month;
+ time_t second = ts->tv_sec;
+ time_t day, leap_day, month, year;

- if (!tz_utc)
- unix_date -= sys_tz.tz_minuteswest*60;
+ if (!sbi->options.tz_utc)
+ second -= sys_tz.tz_minuteswest * SECS_PER_MIN;

/* Jan 1 GMT 00:00:00 1980. But what about another time zone? */
- if (unix_date < 315532800)
- unix_date = 315532800;
+ if (second < UNIX_SECS_1980) {
+ *time = 0;
+ *date = cpu_to_le16((0 << 9) | (1 << 5) | 1);
+ if (time_cs)
+ *time_cs = 0;
+ return;
+ }
+#if BITS_PER_LONG == 64
+ if (second >= UNIX_SECS_2108) {
+ *time = cpu_to_le16((23 << 11) | (59 << 5) | 29);
+ *date = cpu_to_le16((127 << 9) | (12 << 5) | 31);
+ if (time_cs)
+ *time_cs = 199;
+ return;
+ }
+#endif

- *time = cpu_to_le16((unix_date % 60)/2+(((unix_date/60) % 60) << 5)+
- (((unix_date/3600) % 24) << 11));
- day = unix_date/86400-3652;
- year = day/365;
- if ((year+3)/4+365*year > day)
+ day = second / SECS_PER_DAY - DAYS_DELTA;
+ year = day / 365;
+ leap_day = (year + 3) / 4;
+ if (year > YEAR_2100) /* 2100 isn't leap year */
+ leap_day--;
+ if (year * 365 + leap_day > day)
year--;
- day -= (year+3)/4+365*year;
- if (day == 59 && !(year & 3)) {
- nl_day = day;
+ leap_day = (year + 3) / 4;
+ if (year > YEAR_2100) /* 2100 isn't leap year */
+ leap_day--;
+ day -= year * 365 + leap_day;
+
+ if (IS_LEAP_YEAR(year) && day == days_in_year[3]) {
month = 2;
} else {
- nl_day = (year & 3) || day <= 59 ? day : day-1;
- for (month = 0; month < 12; month++) {
- if (day_n[month] > nl_day)
+ if (IS_LEAP_YEAR(year) && day > days_in_year[3])
+ day--;
+ for (month = 1; month < 12; month++) {
+ if (days_in_year[month + 1] > day)
break;
}
}
- *date = cpu_to_le16(nl_day-day_n[month-1]+1+(month << 5)+(year << 9));
-}
+ day -= days_in_year[month];

-EXPORT_SYMBOL_GPL(fat_date_unix2dos);
+ *time = cpu_to_le16(((second / SECS_PER_HOUR) % 24) << 11
+ | ((second / SECS_PER_MIN) % 60) << 5
+ | (second % SECS_PER_MIN) >> 1);
+ *date = cpu_to_le16((year << 9) | (month << 5) | (day + 1));
+ if (time_cs)
+ *time_cs = (ts->tv_sec & 1) * 100 + ts->tv_nsec / 10000000;
+}
+EXPORT_SYMBOL_GPL(fat_time_unix2fat);

int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs)
{
diff -puN fs/fat/fat.h~fat_timestamp-fix fs/fat/fat.h
--- linux-2.6/fs/fat/fat.h~fat_timestamp-fix 2008-08-24 22:57:36.000000000 +0900
+++ linux-2.6-hirofumi/fs/fat/fat.h 2008-08-24 22:57:36.000000000 +0900
@@ -263,9 +263,10 @@ extern int fat_flush_inodes(struct super
extern void fat_fs_panic(struct super_block *s, const char *fmt, ...);
extern void fat_clusters_flush(struct super_block *sb);
extern int fat_chain_add(struct inode *inode, int new_dclus, int nr_cluster);
-extern int date_dos2unix(unsigned short time, unsigned short date, int tz_utc);
-extern void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date,
- int tz_utc);
+extern void fat_time_fat2unix(struct msdos_sb_info *sbi, struct timespec *ts,
+ __le16 __time, __le16 __date, u8 time_cs);
+extern void fat_time_unix2fat(struct msdos_sb_info *sbi, struct timespec *ts,
+ __le16 *time, __le16 *date, u8 *time_cs);
extern int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs);

int fat_cache_init(void);
diff -puN fs/fat/inode.c~fat_timestamp-fix fs/fat/inode.c
--- linux-2.6/fs/fat/inode.c~fat_timestamp-fix 2008-08-24 22:57:36.000000000 +0900
+++ linux-2.6-hirofumi/fs/fat/inode.c 2008-08-24 22:57:36.000000000 +0900
@@ -381,22 +381,12 @@ static int fat_fill_inode(struct inode *
MSDOS_I(inode)->i_attrs = de->attr & ATTR_UNUSED;
inode->i_blocks = ((inode->i_size + (sbi->cluster_size - 1))
& ~((loff_t)sbi->cluster_size - 1)) >> 9;
- inode->i_mtime.tv_sec =
- date_dos2unix(le16_to_cpu(de->time), le16_to_cpu(de->date),
- sbi->options.tz_utc);
- inode->i_mtime.tv_nsec = 0;
+
+ fat_time_fat2unix(sbi, &inode->i_mtime, de->time, de->date, 0);
if (sbi->options.isvfat) {
- int secs = de->ctime_cs / 100;
- int csecs = de->ctime_cs % 100;
- inode->i_ctime.tv_sec =
- date_dos2unix(le16_to_cpu(de->ctime),
- le16_to_cpu(de->cdate),
- sbi->options.tz_utc) + secs;
- inode->i_ctime.tv_nsec = csecs * 10000000;
- inode->i_atime.tv_sec =
- date_dos2unix(0, le16_to_cpu(de->adate),
- sbi->options.tz_utc);
- inode->i_atime.tv_nsec = 0;
+ fat_time_fat2unix(sbi, &inode->i_ctime, de->ctime,
+ de->cdate, de->ctime_cs);
+ fat_time_fat2unix(sbi, &inode->i_atime, 0, de->adate, 0);
} else
inode->i_ctime = inode->i_atime = inode->i_mtime;

@@ -591,16 +581,14 @@ retry:
raw_entry->attr = fat_attr(inode);
raw_entry->start = cpu_to_le16(MSDOS_I(inode)->i_logstart);
raw_entry->starthi = cpu_to_le16(MSDOS_I(inode)->i_logstart >> 16);
- fat_date_unix2dos(inode->i_mtime.tv_sec, &raw_entry->time,
- &raw_entry->date, sbi->options.tz_utc);
+ fat_time_unix2fat(sbi, &inode->i_mtime, &raw_entry->time,
+ &raw_entry->date, NULL);
if (sbi->options.isvfat) {
__le16 atime;
- fat_date_unix2dos(inode->i_ctime.tv_sec, &raw_entry->ctime,
- &raw_entry->cdate, sbi->options.tz_utc);
- fat_date_unix2dos(inode->i_atime.tv_sec, &atime,
- &raw_entry->adate, sbi->options.tz_utc);
- raw_entry->ctime_cs = (inode->i_ctime.tv_sec & 1) * 100 +
- inode->i_ctime.tv_nsec / 10000000;
+ fat_time_unix2fat(sbi, &inode->i_ctime, &raw_entry->ctime,
+ &raw_entry->cdate, &raw_entry->ctime_cs);
+ fat_time_unix2fat(sbi, &inode->i_atime, &atime,
+ &raw_entry->adate, NULL);
}
spin_unlock(&sbi->inode_hash_lock);
mark_buffer_dirty(bh);
diff -puN fs/fat/dir.c~fat_timestamp-fix fs/fat/dir.c
--- linux-2.6/fs/fat/dir.c~fat_timestamp-fix 2008-08-24 22:57:36.000000000 +0900
+++ linux-2.6-hirofumi/fs/fat/dir.c 2008-08-24 22:57:36.000000000 +0900
@@ -1088,6 +1088,7 @@ int fat_alloc_new_dir(struct inode *dir,
struct msdos_dir_entry *de;
sector_t blknr;
__le16 date, time;
+ u8 time_cs;
int err, cluster;

err = fat_alloc_clusters(dir, &cluster, 1);
@@ -1101,7 +1102,7 @@ int fat_alloc_new_dir(struct inode *dir,
goto error_free;
}

- fat_date_unix2dos(ts->tv_sec, &time, &date, sbi->options.tz_utc);
+ fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);

de = (struct msdos_dir_entry *)bhs[0]->b_data;
/* filling the new directory slots ("." and ".." entries) */
@@ -1111,13 +1112,14 @@ int fat_alloc_new_dir(struct inode *dir,
de[0].lcase = de[1].lcase = 0;
de[0].time = de[1].time = time;
de[0].date = de[1].date = date;
- de[0].ctime_cs = de[1].ctime_cs = 0;
if (sbi->options.isvfat) {
/* extra timestamps */
de[0].ctime = de[1].ctime = time;
+ de[0].ctime_cs = de[1].ctime_cs = time_cs;
de[0].adate = de[0].cdate = de[1].adate = de[1].cdate = date;
} else {
de[0].ctime = de[1].ctime = 0;
+ de[0].ctime_cs = de[1].ctime_cs = 0;
de[0].adate = de[0].cdate = de[1].adate = de[1].cdate = 0;
}
de[0].start = cpu_to_le16(cluster);
diff -puN fs/fat/namei_msdos.c~fat_timestamp-fix fs/fat/namei_msdos.c
--- linux-2.6/fs/fat/namei_msdos.c~fat_timestamp-fix 2008-08-24 22:57:36.000000000 +0900
+++ linux-2.6-hirofumi/fs/fat/namei_msdos.c 2008-08-24 22:57:36.000000000 +0900
@@ -247,7 +247,7 @@ static int msdos_add_entry(struct inode
if (is_hid)
de.attr |= ATTR_HIDDEN;
de.lcase = 0;
- fat_date_unix2dos(ts->tv_sec, &time, &date, sbi->options.tz_utc);
+ fat_time_unix2fat(sbi, ts, &time, &date, NULL);
de.cdate = de.adate = 0;
de.ctime = 0;
de.ctime_cs = 0;
diff -puN fs/fat/namei_vfat.c~fat_timestamp-fix fs/fat/namei_vfat.c
--- linux-2.6/fs/fat/namei_vfat.c~fat_timestamp-fix 2008-08-24 22:57:36.000000000 +0900
+++ linux-2.6-hirofumi/fs/fat/namei_vfat.c 2008-08-24 22:57:36.000000000 +0900
@@ -568,6 +568,7 @@ static int vfat_build_slots(struct inode
unsigned char msdos_name[MSDOS_NAME];
wchar_t *uname;
__le16 time, date;
+ u8 time_cs;
int err, ulen, usize, i;
loff_t offset;

@@ -620,10 +621,10 @@ shortname:
memcpy(de->name, msdos_name, MSDOS_NAME);
de->attr = is_dir ? ATTR_DIR : ATTR_ARCH;
de->lcase = lcase;
- fat_date_unix2dos(ts->tv_sec, &time, &date, sbi->options.tz_utc);
+ fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);
de->time = de->ctime = time;
de->date = de->cdate = de->adate = date;
- de->ctime_cs = 0;
+ de->ctime_cs = time_cs;
de->start = cpu_to_le16(cluster);
de->starthi = cpu_to_le16(cluster >> 16);
de->size = 0;
_
--
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