RE: [PATCH] exfat: introduce mount option 'sys_tz'

["Sungjong Seo" <sj1557.seo@samsung.com>]

> EXFAT_TZ_VALID bit in {create,modify,access}_tz is corresponding to
> OffsetValid field in exfat specification [1]. When this bit isn't set,
> timestamps should be treated as having the same UTC offset as the current
> local time.
> 
> Currently, there is an option 'time_offset' for users to specify the UTC
> offset for this issue. This patch introduces a new mount option 'sys_tz'
> to use system timezone as time offset.
> 
> Link: [1] https://protect2.fireeye.com/v1/url?k=6c606ee0-0d1d8463-
> 6c61e5af-74fe48600158-7870d6304b957d98&q=1&e=3704e121-39fa-4c75-a3c8-
> a4e968c00dbf&u=https%3A%2F%2Fdocs.microsoft.com%2Fen-
> us%2Fwindows%2Fwin32%2Ffileio%2Fexfat-specification%2374102-offsetvalid-
> field
> 
> Signed-off-by: Chung-Chiang Cheng <cccheng@synology.com>

Looks good!
Acked-by: Sungjong Seo <sj1557.seo@samsung.com>

> ---
>  fs/exfat/exfat_fs.h |  1 +
>  fs/exfat/misc.c     | 10 ++++++++--
>  fs/exfat/super.c    |  9 ++++++++-
>  3 files changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h index
> c6800b880920..82e507413291 100644
> --- a/fs/exfat/exfat_fs.h
> +++ b/fs/exfat/exfat_fs.h
> @@ -203,6 +203,7 @@ struct exfat_mount_options {
>  	/* on error: continue, panic, remount-ro */
>  	enum exfat_error_mode errors;
>  	unsigned utf8:1, /* Use of UTF-8 character set */
> +		 sys_tz:1, /* Use local timezone */
>  		 discard:1, /* Issue discard requests on deletions */
>  		 keep_last_dots:1; /* Keep trailing periods in paths */
>  	int time_offset; /* Offset of timestamps from UTC (in minutes) */
> diff --git a/fs/exfat/misc.c b/fs/exfat/misc.c index
> d5bd8e6d9741..9380e0188b55 100644
> --- a/fs/exfat/misc.c
> +++ b/fs/exfat/misc.c
> @@ -74,6 +74,13 @@ static void exfat_adjust_tz(struct timespec64 *ts, u8
> tz_off)
>  		ts->tv_sec += TIMEZONE_SEC(0x80 - tz_off);  }
> 
> +static inline int exfat_tz_offset(struct exfat_sb_info *sbi) {
> +	if (sbi->options.sys_tz)
> +		return -sys_tz.tz_minuteswest;
> +	return sbi->options.time_offset;
> +}
> +
>  /* Convert a EXFAT time/date pair to a UNIX date (seconds since 1 1 70).
> */  void exfat_get_entry_time(struct exfat_sb_info *sbi, struct timespec64
> *ts,
>  		u8 tz, __le16 time, __le16 date, u8 time_cs) @@ -96,8 +103,7
> @@ void exfat_get_entry_time(struct exfat_sb_info *sbi, struct timespec64
> *ts,
>  		/* Adjust timezone to UTC0. */
>  		exfat_adjust_tz(ts, tz & ~EXFAT_TZ_VALID);
>  	else
> -		/* Convert from local time to UTC using time_offset. */
> -		ts->tv_sec -= sbi->options.time_offset * SECS_PER_MIN;
> +		ts->tv_sec -= exfat_tz_offset(sbi) * SECS_PER_MIN;
>  }
> 
>  /* Convert linear UNIX date to a EXFAT time/date pair. */ diff --git
> a/fs/exfat/super.c b/fs/exfat/super.c index 8ca21e7917d1..3e0f67b2103e
> 100644
> --- a/fs/exfat/super.c
> +++ b/fs/exfat/super.c
> @@ -170,7 +170,9 @@ static int exfat_show_options(struct seq_file *m,
> struct dentry *root)
>  		seq_puts(m, ",discard");
>  	if (opts->keep_last_dots)
>  		seq_puts(m, ",keep_last_dots");
> -	if (opts->time_offset)
> +	if (opts->sys_tz)
> +		seq_puts(m, ",sys_tz");
> +	else if (opts->time_offset)
>  		seq_printf(m, ",time_offset=%d", opts->time_offset);
>  	return 0;
>  }
> @@ -214,6 +216,7 @@ enum {
>  	Opt_errors,
>  	Opt_discard,
>  	Opt_keep_last_dots,
> +	Opt_sys_tz,
>  	Opt_time_offset,
> 
>  	/* Deprecated options */
> @@ -241,6 +244,7 @@ static const struct fs_parameter_spec
> exfat_parameters[] = {
>  	fsparam_enum("errors",			Opt_errors,
> exfat_param_enums),
>  	fsparam_flag("discard",			Opt_discard),
>  	fsparam_flag("keep_last_dots",		Opt_keep_last_dots),
> +	fsparam_flag("sys_tz",			Opt_sys_tz),
>  	fsparam_s32("time_offset",		Opt_time_offset),
>  	__fsparam(NULL, "utf8",			Opt_utf8,
> fs_param_deprecated,
>  		  NULL),
> @@ -298,6 +302,9 @@ static int exfat_parse_param(struct fs_context *fc,
> struct fs_parameter *param)
>  	case Opt_keep_last_dots:
>  		opts->keep_last_dots = 1;
>  		break;
> +	case Opt_sys_tz:
> +		opts->sys_tz = 1;
> +		break;
>  	case Opt_time_offset:
>  		/*
>  		 * Make the limit 24 just in case someone invents something
> --
> 2.34.1