fatfs: add UTC timestamp option

Provide a new mount option ("tz=UTC") for DOS (vfat/msdos) filesystems,
allowing timestamps to be in coordinated universal time (UTC) rather than
local time in applications where doing this is advantageous.

In particular, portable devices that use fat/vfat (such as digital
cameras) can benefit from using UTC in their internal clocks, thus
avoiding daylight saving time errors and general time ambiguity issues.
The user of the device does not have to worry about changing the time when
moving from place or when daylight saving changes.

The new mount option, when set, disables the counter-adjustment that Linux
currently makes to FAT timestamp info in anticipation of the normal
userspace time zone correction.  When used in this new mode, all daylight
saving time and time zone handling is done in userspace as is normal for
many other filesystems (like ext3).  The default mode, which remains
unchanged, is still appropriate when mounting volumes written in Windows
(because of its use of local time).

I originally based this patch on one submitted last year by Paul Collins,
but I updated it to work with current source and changed variable/option
naming.  Ogawa Hirofumi (who maintains these filesystems) and I discussed
this patch at length on lkml, and he suggested using the option name in
the attached version of the patch.  Barry Bouwsma pointed out a good
addition to the patch as well.

Signed-off-by: Joe Peterson <joe@skyrush.com>
Signed-off-by: Paul Collins <paul@ondioline.org>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Barry Bouwsma <free_beer_for_all@yahoo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 4c35477bc94cba7528a0da6d85972fd876961301..cd4a0162e10d6dea7507507cf25a13fd93d93f04 100644 (file)
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -1101,7 +1101,7 @@ int fat_alloc_new_dir(struct inode *dir, struct timespec *ts)
                goto error_free;
        }
 
-       fat_date_unix2dos(ts->tv_sec, &time, &date);
+       fat_date_unix2dos(ts->tv_sec, &time, &date, sbi->options.tz_utc);
 
        de = (struct msdos_dir_entry *)bhs[0]->b_data;
        /* filling the new directory slots ("." and ".." entries) */

diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 60deb5fd11885f54931295e3bd22b25cfa6f9b7c..23676f9d79ce294d4bbe35931f44044fce709606 100644 (file)
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -382,17 +382,20 @@ static int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
        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));
+               date_dos2unix(le16_to_cpu(de->time), le16_to_cpu(de->date),
+                             sbi->options.tz_utc);
        inode->i_mtime.tv_nsec = 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)) + secs;
+                                     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));
+                       date_dos2unix(0, le16_to_cpu(de->adate),
+                                     sbi->options.tz_utc);
                inode->i_atime.tv_nsec = 0;
        } else
                inode->i_ctime = inode->i_atime = inode->i_mtime;
@@ -591,11 +594,14 @@ 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);
+       fat_date_unix2dos(inode->i_mtime.tv_sec, &raw_entry->time,
+                         &raw_entry->date, sbi->options.tz_utc);
        if (sbi->options.isvfat) {
                __le16 atime;
-               fat_date_unix2dos(inode->i_ctime.tv_sec,&raw_entry->ctime,&raw_entry->cdate);
-               fat_date_unix2dos(inode->i_atime.tv_sec,&atime,&raw_entry->adate);
+               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;
        }
@@ -836,6 +842,8 @@ static int fat_show_options(struct seq_file *m, struct vfsmount *mnt)
        }
        if (sbi->options.flush)
                seq_puts(m, ",flush");
+       if (opts->tz_utc)
+               seq_puts(m, ",tz=UTC");
 
        return 0;
 }
@@ -848,7 +856,7 @@ enum {
        Opt_charset, Opt_shortname_lower, Opt_shortname_win95,
        Opt_shortname_winnt, Opt_shortname_mixed, Opt_utf8_no, Opt_utf8_yes,
        Opt_uni_xl_no, Opt_uni_xl_yes, Opt_nonumtail_no, Opt_nonumtail_yes,
-       Opt_obsolate, Opt_flush, Opt_err,
+       Opt_obsolate, Opt_flush, Opt_tz_utc, Opt_err,
 };
 
 static match_table_t fat_tokens = {
@@ -883,6 +891,7 @@ static match_table_t fat_tokens = {
        {Opt_obsolate, "cvf_options=%100s"},
        {Opt_obsolate, "posix"},
        {Opt_flush, "flush"},
+       {Opt_tz_utc, "tz=UTC"},
        {Opt_err, NULL},
 };
 static match_table_t msdos_tokens = {
@@ -947,6 +956,7 @@ static int parse_options(char *options, int is_vfat, int silent, int *debug,
        opts->utf8 = opts->unicode_xlate = 0;
        opts->numtail = 1;
        opts->usefree = opts->nocase = 0;
+       opts->tz_utc = 0;
        *debug = 0;
 
        if (!options)
@@ -1036,6 +1046,9 @@ static int parse_options(char *options, int is_vfat, int silent, int *debug,
                case Opt_flush:
                        opts->flush = 1;
                        break;
+               case Opt_tz_utc:
+                       opts->tz_utc = 1;
+                       break;
 
                /* msdos specific */
                case Opt_dots:

diff --git a/fs/fat/misc.c b/fs/fat/misc.c
index 61f23511eacf41ec34649a84f1cc7e601ff61a68..79fb98ad36d4d2e2913c26bb5ab5b56358594eea 100644 (file)
--- a/fs/fat/misc.c
+++ b/fs/fat/misc.c
@@ -142,7 +142,7 @@ static int day_n[] = {
 };
 
 /* 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 date_dos2unix(unsigned short time, unsigned short date, int tz_utc)
 {
        int month, year, secs;
 
@@ -156,16 +156,18 @@ int date_dos2unix(unsigned short time, unsigned short date)
            ((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 */
-       secs += sys_tz.tz_minuteswest*60;
+       if (!tz_utc)
+               secs += sys_tz.tz_minuteswest*60;
        return secs;
 }
 
 /* Convert linear UNIX date to a MS-DOS time/date pair. */
-void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date)
+void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date, int tz_utc)
 {
        int day, year, nl_day, month;
 
-       unix_date -= sys_tz.tz_minuteswest*60;
+       if (!tz_utc)
+               unix_date -= sys_tz.tz_minuteswest*60;
 
        /* Jan 1 GMT 00:00:00 1980. But what about another time zone? */
        if (unix_date < 315532800)

diff --git a/fs/msdos/namei.c b/fs/msdos/namei.c
index e4ad6c6b753e976f0d6ecce98603d629f410b825..e844b9809d27de0aa1447dec920087b6978b8c7c 100644 (file)
--- a/fs/msdos/namei.c
+++ b/fs/msdos/namei.c
@@ -237,6 +237,7 @@ static int msdos_add_entry(struct inode *dir, const unsigned char *name,
                           int is_dir, int is_hid, int cluster,
                           struct timespec *ts, struct fat_slot_info *sinfo)
 {
+       struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
        struct msdos_dir_entry de;
        __le16 time, date;
        int err;
@@ -246,7 +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);
+       fat_date_unix2dos(ts->tv_sec, &time, &date, sbi->options.tz_utc);
        de.cdate = de.adate = 0;
        de.ctime = 0;
        de.ctime_cs = 0;

diff --git a/fs/vfat/namei.c b/fs/vfat/namei.c
index b546ba69be8224f79253e75770a93ff2fdb8a621..155c10b4adbd4a0d3e518b7558d07e4501bee11b 100644 (file)
--- a/fs/vfat/namei.c
+++ b/fs/vfat/namei.c
@@ -621,7 +621,7 @@ 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);
+       fat_date_unix2dos(ts->tv_sec, &time, &date, sbi->options.tz_utc);
        de->time = de->ctime = time;
        de->date = de->cdate = de->adate = date;
        de->ctime_cs = 0;

diff --git a/include/linux/msdos_fs.h b/include/linux/msdos_fs.h
index 3346c9c8f17ad7db4f72b896c074e33950604f25..ba63858056c7a5f0d3e7017fb19808e6e9dae5b1 100644 (file)
--- a/include/linux/msdos_fs.h
+++ b/include/linux/msdos_fs.h
@@ -203,7 +203,8 @@ struct fat_mount_options {
                 numtail:1,       /* Does first alias have a numeric '~1' type tail? */
                 flush:1,         /* write things quickly */
                 nocase:1,        /* Does this need case conversion? 0=need case conversion*/
-                usefree:1;       /* Use free_clusters for FAT32 */
+                usefree:1,       /* Use free_clusters for FAT32 */
+                tz_utc:1;        /* Filesystem timestamps are in UTC */
 };
 
 #define FAT_HASH_BITS  8
@@ -434,8 +435,9 @@ 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);
-extern void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date);
+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 int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs);
 
 int fat_cache_init(void);