6 files changed, 130 insertions, 72 deletions

diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 08b23ad25f1c..a601c6d45bc0 100644
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -1089,6 +1089,7 @@ int fat_alloc_new_dir(struct inode *dir, struct timespec *ts)
         struct msdos_dir_entry *de;
         sector_t blknr;
         __le16 date, time;
+        u8 time_cs;
         int err, cluster;
 
         err = fat_alloc_clusters(dir, &cluster, 1);
@@ -1102,7 +1103,7 @@ int fat_alloc_new_dir(struct inode *dir, struct timespec *ts)
                 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) */
@@ -1112,13 +1113,14 @@ int fat_alloc_new_dir(struct inode *dir, struct timespec *ts)
         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 --git a/fs/fat/fat.h b/fs/fat/fat.h
index 51f1c42ca5e3..a2a570f81719 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -263,9 +263,10 @@ extern int fat_flush_inodes(struct super_block *sb, struct inode *i1,
 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 --git a/fs/fat/inode.c b/fs/fat/inode.c
index 3921de2013a4..079d9d5e0d36 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -381,22 +381,12 @@ static int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
         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 --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)
 {
diff --git a/fs/fat/namei_msdos.c b/fs/fat/namei_msdos.c
index c0a4d5cd99b2..e92e8158ebaf 100644
--- a/fs/fat/namei_msdos.c
+++ b/fs/fat/namei_msdos.c
@@ -247,7 +247,7 @@ static int msdos_add_entry(struct inode *dir, const unsigned char *name,
         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 --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index facf3bf0211a..1536bc3ca0f0 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -568,6 +568,7 @@ static int vfat_build_slots(struct inode *dir, const unsigned char *name,
         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;