Re: [PATCH v2] fat: Provide option for setting timezone offset

[Jan Kara <jack@suse.cz>]

On Tue 13-11-12 11:23:29, OGAWA Hirofumi wrote:
> Jan Kara <jack@suse.cz> writes:
> 
> > So far FAT either offsets time stamps by sys_tz.minuteswest or leaves them
> > as they are (when tz=UTC mount option is used). However in some cases it
> > is useful if one can specify time stamp offset on his own (e.g. when time
> > zone of the camera connected is different from time zone of the computer,
> > or when HW clock is in UTC and thus sys_tz.minuteswest == 0).
> >
> > So provide a mount option time_offset= which allows user to specify offset in
> > minutes that should be applied to time stamps on the filesystem.
> 
> Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
  Thanks! Since you CCed Andrew, I presume you want him to pick up the
patch and push it to Linus?

								Honza

> > Signed-off-by: Jan Kara <jack@suse.cz>
> > ---
> >  Documentation/filesystems/vfat.txt |    9 +++++++++
> >  fs/fat/fat.h                       |    3 ++-
> >  fs/fat/inode.c                     |   25 ++++++++++++++++++++-----
> >  fs/fat/misc.c                      |    9 ++++++---
> >  4 files changed, 37 insertions(+), 9 deletions(-)
> >
> > diff --git a/Documentation/filesystems/vfat.txt b/Documentation/filesystems/vfat.txt
> > index de1e6c4..d230dd9 100644
> > --- a/Documentation/filesystems/vfat.txt
> > +++ b/Documentation/filesystems/vfat.txt
> > @@ -111,6 +111,15 @@ tz=UTC        -- Interpret timestamps as UTC rather than local time.
> >                   useful when mounting devices (like digital cameras)
> >                   that are set to UTC in order to avoid the pitfalls of
> >                   local time.
> > +time_offset=minutes
> > +	      -- Set offset for conversion of timestamps from local time
> > +		 used by FAT to UTC. I.e. <minutes> minutes will be subtracted
> > +		 from each timestamp to convert it to UTC used internally by
> > +		 Linux. This is useful when time zone set in sys_tz is
> > +		 not the time zone used by the filesystem. Note that this
> > +		 option still does not provide correct time stamps in all
> > +		 cases in presence of DST - time stamps in a different DST
> > +		 setting will be off by one hour.
> >  
> >  showexec      -- If set, the execute permission bits of the file will be
> >  		 allowed only if the extension part of the name is .EXE,
> > diff --git a/fs/fat/fat.h b/fs/fat/fat.h
> > index 623f36f..12701a5 100644
> > --- a/fs/fat/fat.h
> > +++ b/fs/fat/fat.h
> > @@ -29,6 +29,7 @@ struct fat_mount_options {
> >  	unsigned short fs_fmask;
> >  	unsigned short fs_dmask;
> >  	unsigned short codepage;   /* Codepage for shortname conversions */
> > +	int time_offset;	   /* Offset of timestamps from UTC (in minutes) */
> >  	char *iocharset;           /* Charset used for filename input/display */
> >  	unsigned short shortname;  /* flags for shortname display/create rule */
> >  	unsigned char name_check;  /* r = relaxed, n = normal, s = strict */
> > @@ -45,7 +46,7 @@ struct fat_mount_options {
> >  		 flush:1,	   /* write things quickly */
> >  		 nocase:1,	   /* Does this need case conversion? 0=need case conversion*/
> >  		 usefree:1,	   /* Use free_clusters for FAT32 */
> > -		 tz_utc:1,	   /* Filesystem timestamps are in UTC */
> > +		 tz_set:1,	   /* Filesystem timestamps' offset set */
> >  		 rodir:1,	   /* allow ATTR_RO for directory */
> >  		 discard:1,	   /* Issue discard requests on deletions */
> >  		 nfs:1;		   /* Do extra work needed for NFS export */
> > diff --git a/fs/fat/inode.c b/fs/fat/inode.c
> > index 5bafaad..e3ef664 100644
> > --- a/fs/fat/inode.c
> > +++ b/fs/fat/inode.c
> > @@ -777,8 +777,12 @@ static int fat_show_options(struct seq_file *m, struct dentry *root)
> >  	}
> >  	if (opts->flush)
> >  		seq_puts(m, ",flush");
> > -	if (opts->tz_utc)
> > -		seq_puts(m, ",tz=UTC");
> > +	if (opts->tz_set) {
> > +		if (opts->time_offset)
> > +			seq_printf(m, ",time_offset=%d", opts->time_offset);
> > +		else
> > +			seq_puts(m, ",tz=UTC");
> > +	}
> >  	if (opts->errors == FAT_ERRORS_CONT)
> >  		seq_puts(m, ",errors=continue");
> >  	else if (opts->errors == FAT_ERRORS_PANIC)
> > @@ -800,7 +804,8 @@ enum {
> >  	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_obsolete, Opt_flush, Opt_tz_utc, Opt_rodir, Opt_err_cont,
> > -	Opt_err_panic, Opt_err_ro, Opt_discard, Opt_nfs, Opt_err,
> > +	Opt_err_panic, Opt_err_ro, Opt_discard, Opt_nfs, Opt_time_offset,
> > +	Opt_err,
> >  };
> >  
> >  static const match_table_t fat_tokens = {
> > @@ -825,6 +830,7 @@ static const match_table_t fat_tokens = {
> >  	{Opt_immutable, "sys_immutable"},
> >  	{Opt_flush, "flush"},
> >  	{Opt_tz_utc, "tz=UTC"},
> > +	{Opt_time_offset, "time_offset=%d"},
> >  	{Opt_err_cont, "errors=continue"},
> >  	{Opt_err_panic, "errors=panic"},
> >  	{Opt_err_ro, "errors=remount-ro"},
> > @@ -909,7 +915,7 @@ static int parse_options(struct super_block *sb, char *options, int is_vfat,
> >  	opts->utf8 = opts->unicode_xlate = 0;
> >  	opts->numtail = 1;
> >  	opts->usefree = opts->nocase = 0;
> > -	opts->tz_utc = 0;
> > +	opts->tz_set = 0;
> >  	opts->nfs = 0;
> >  	opts->errors = FAT_ERRORS_RO;
> >  	*debug = 0;
> > @@ -1005,8 +1011,17 @@ static int parse_options(struct super_block *sb, char *options, int is_vfat,
> >  		case Opt_flush:
> >  			opts->flush = 1;
> >  			break;
> > +		case Opt_time_offset:
> > +			if (match_int(&args[0], &option))
> > +				return 0;
> > +			if (option < -12 * 60 || option > 12 * 60)
> > +				return 0;
> > +			opts->tz_set = 1;
> > +			opts->time_offset = option;
> > +			break;
> >  		case Opt_tz_utc:
> > -			opts->tz_utc = 1;
> > +			opts->tz_set = 1;
> > +			opts->time_offset = 0;
> >  			break;
> >  		case Opt_err_cont:
> >  			opts->errors = FAT_ERRORS_CONT;
> > diff --git a/fs/fat/misc.c b/fs/fat/misc.c
> > index 6d93360..5eb600d 100644
> > --- a/fs/fat/misc.c
> > +++ b/fs/fat/misc.c
> > @@ -212,8 +212,10 @@ void fat_time_fat2unix(struct msdos_sb_info *sbi, struct timespec *ts,
> >  		   + days_in_year[month] + day
> >  		   + DAYS_DELTA) * SECS_PER_DAY;
> >  
> > -	if (!sbi->options.tz_utc)
> > +	if (!sbi->options.tz_set)
> >  		second += sys_tz.tz_minuteswest * SECS_PER_MIN;
> > +	else
> > +		second -= sbi->options.time_offset * SECS_PER_MIN;
> >  
> >  	if (time_cs) {
> >  		ts->tv_sec = second + (time_cs / 100);
> > @@ -229,8 +231,9 @@ void fat_time_unix2fat(struct msdos_sb_info *sbi, struct timespec *ts,
> >  		       __le16 *time, __le16 *date, u8 *time_cs)
> >  {
> >  	struct tm tm;
> > -	time_to_tm(ts->tv_sec, sbi->options.tz_utc ? 0 :
> > -		   -sys_tz.tz_minuteswest * 60, &tm);
> > +	time_to_tm(ts->tv_sec,
> > +		   (sbi->options.tz_set ? sbi->options.time_offset :
> > +		   -sys_tz.tz_minuteswest) * SECS_PER_MIN, &tm);
> >  
> >  	/*  FAT can only support year between 1980 to 2107 */
> >  	if (tm.tm_year < 1980 - 1900) {
> 
> -- 
> OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR