1 files changed, 107 insertions, 41 deletions

diff --git a/fs/fat/misc.c b/fs/fat/misc.c
index 91ad9be18ff9..a191e79e66a9 100644
--- a/fs/fat/misc.c
+++ b/fs/fat/misc.c
@@ -135,65 +135,131 @@ int fat_chain_add(struct inode *inode, int new_dclus, int nr_cluster)
 
 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;
-
-        *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)
+        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
+
+        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)
 {