linux-kernel - Re: [PATCH v9 09/13] exfat: add misc operations

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Date:   Thu, 2 Jan 2020 12:40:34 +0100
From:   Pali Rohár <pali.rohar@...il.com>
To:     Namjae Jeon <linkinjeon@...il.com>
Cc:     Namjae Jeon <namjae.jeon@...sung.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        gregkh@...uxfoundation.org, valdis.kletnieks@...edu, hch@....de,
        sj1557.seo@...sung.com
Subject: Re: [PATCH v9 09/13] exfat: add misc operations

On Thursday 02 January 2020 20:30:03 Namjae Jeon wrote:
> 2020-01-02 18:19 GMT+09:00, Pali Rohár <pali.rohar@...il.com>:
> > On Thursday 02 January 2020 16:20:32 Namjae Jeon wrote:
> >> This adds the implementation of misc operations for exfat.
> >>
> >> Signed-off-by: Namjae Jeon <namjae.jeon@...sung.com>
> >> Signed-off-by: Sungjong Seo <sj1557.seo@...sung.com>
> >> ---
> >>  fs/exfat/misc.c | 253 ++++++++++++++++++++++++++++++++++++++++++++++++
> >>  1 file changed, 253 insertions(+)
> >>  create mode 100644 fs/exfat/misc.c
> >>
> >> diff --git a/fs/exfat/misc.c b/fs/exfat/misc.c
> >> new file mode 100644
> >> index 000000000000..7f533bcb3b3f
> >> --- /dev/null
> >> +++ b/fs/exfat/misc.c
> >
> > ...
> >
> >> +/* <linux/time.h> externs sys_tz
> >> + * extern struct timezone sys_tz;
> >> + */
> >> +#define UNIX_SECS_1980    315532800L
> >> +
> >> +#if BITS_PER_LONG == 64
> >> +#define UNIX_SECS_2108    4354819200L
> >> +#endif
> >
> > ...
> >
> >> +#define TIMEZONE_CUR_OFFSET()	((sys_tz.tz_minuteswest / (-15)) & 0x7F)
> >> +/* Convert linear UNIX date to a FAT time/date pair. */
> >> +void exfat_time_unix2fat(struct exfat_sb_info *sbi, struct timespec64
> >> *ts,
> >> +		struct exfat_date_time *tp)
> >> +{
> >> +	time_t second = ts->tv_sec;
> >> +	time_t day, month, year;
> >> +	time_t ld; /* leap day */
> >
> > Question for other maintainers: Has kernel code already time_t defined
> > as 64bit? Or it is still just 32bit and 32bit systems and some time64_t
> > needs to be used? I remember that there was discussion about these
> > problems, but do not know if it was changed/fixed or not... Just a
> > pointer for possible Y2038 problem. As "ts" is of type timespec64, but
> > "second" of type time_t.
> My bad, I will change it with time64_t.

Now I have looked into sources and time_t is just typedef from
__kernel_old_time_t type. So it looks like that time64_t is the type
which should be used in new code.

But somebody else should confirm this information.

> >
> >> +
> >> +	/* Treats as local time with proper time */
> >> +	second -= sys_tz.tz_minuteswest * SECS_PER_MIN;
> >> +	tp->timezone.valid = 1;
> >> +	tp->timezone.off = TIMEZONE_CUR_OFFSET();
> >> +
> >> +	/* Jan 1 GMT 00:00:00 1980. But what about another time zone? */
> >> +	if (second < UNIX_SECS_1980) {
> >> +		tp->second  = 0;
> >> +		tp->minute  = 0;
> >> +		tp->hour = 0;
> >> +		tp->day  = 1;
> >> +		tp->month  = 1;
> >> +		tp->year = 0;
> >> +		return;
> >> +	}
> >> +
> >> +	if (second >= UNIX_SECS_2108) {
> >
> > Hello, this code cause compile errors on 32bit systems as UNIX_SECS_2108
> > macro is not defined when BITS_PER_LONG == 32.
> >
> > Value 4354819200 really cannot fit into 32bit signed integer, so you
> > should use 64bit signed integer. I would suggest to define this macro
> > value via LL not just L suffix (and it would work on both 32 and 64bit)
> Okay.
> >
> >   #define UNIX_SECS_2108    4354819200LL
> >
> >> +		tp->second  = 59;
> >> +		tp->minute  = 59;
> >> +		tp->hour = 23;
> >> +		tp->day  = 31;
> >> +		tp->month  = 12;
> >> +		tp->year = 127;
> >> +		return;
> >> +	}
> Okay, I will check it.
> Thanks for your review!
> >
> > --
> > Pali Rohár
> > pali.rohar@...il.com
> >

-- 
Pali Rohár
pali.rohar@...il.com