linux-kernel - Re: [PATCH] exfat: use local UTC offset when EXFAT_TZ

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Message-ID: <CAKYAXd_vFjVcHJxn5xau5hFNHBXc2K7o1wFHbkhz9TcCteG2Rw@mail.gmail.com>
Date:   Tue, 5 Oct 2021 13:30:23 +0900
From:   Namjae Jeon <linkinjeon@...nel.org>
To:     Sungjong Seo <sj1557.seo@...sung.com>
Cc:     Chung-Chiang Cheng <cccheng@...ology.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        shepjeng@...il.com
Subject: Re: [PATCH] exfat: use local UTC offset when EXFAT_TZ_VALID isn't set

2021-10-05 13:05 GMT+09:00, Sungjong Seo <sj1557.seo@...sung.com>:
>> 2021-10-01 22:19 GMT+09:00, Sungjong Seo <sj1557.seo@...sung.com>:
>> > Hello, Namjae,
>> Hi Sungjong,
>> >
>> > I found an important difference between the code we first wrote and
>> > the code that has changed since our initial patch review. This
>> > difference seems to cause compatibility issues when reading saved
>> timestamps without timezone.
>> > (In our initial patch review, there were concerns about possible
>> > compatibility issues.) I think the code that reads timestamps without
>> > timezone should go back to the concept we wrote in the first place
>> > like reported patch.
>> Are you talking about using sys_tz?
> Yes, exactly, a part like below.
Have you read discussion about this before ?
Let me know what I am missing something.

>
> +static inline int exfat_tz_offset(struct exfat_sb_info *sbi) {
> +	return (sbi->options.tz_set ? -sbi->options.time_offset :
> +			sys_tz.tz_minuteswest) * SECS_PER_MIN; }
> +
>
>>
>> > It could be an answer of another timestamp issue.
>> What is another timestamp issue ?
>
> What I'm saying is "timestamp incompatibilities in exfat-fs" from Reiner
> <reinerstallknecht@...il.com>
> I think it might be the same issue with this.
Have you checked fuse-exfat patch he shared ? It was exfat timezone support.
I am not sure how it is related to sys_tz...

Thanks!
>
>>
>> >
>> > Could you please let me know what you think?
>> >
>> > Thanks.
>> >> -----Original Message-----
>> >> From: Namjae Jeon [mailto:linkinjeon@...nel.org]
>> >> Sent: Friday, September 10, 2021 10:01 AM
>> >> To: Chung-Chiang Cheng <cccheng@...ology.com>
>> >> Cc: sj1557.seo@...sung.com; linux-fsdevel@...r.kernel.org; linux-
>> >> kernel@...r.kernel.org; shepjeng@...il.com
>> >> Subject: Re: [PATCH] exfat: use local UTC offset when EXFAT_TZ_VALID
>> >> isn't set
>> >>
>> >> 2021-09-09 15:55 GMT+09:00, Chung-Chiang Cheng <cccheng@...ology.com>:
>> >> > EXFAT_TZ_VALID is corresponding to OffsetValid field in exfat
>> >> > specification [1]. If this bit isn't set, timestamps should be
>> >> > treated as having the same UTC offset as the current local time.
>> >> >
>> >> > This patch uses the existing mount option 'time_offset' as fat does.
>> >> > If time_offset isn't set, local UTC offset in sys_tz will be used
>> >> > as the default value.
>> >> >
>> >> > Link: [1]
>> >> > https://protect2.fireeye.com/v1/url?k=cba4edf5-943fd4c8-cba566ba-0c
>> >> > c47
>> >> > a31309a-e70aa065be678729&q=1&e=225feff2-841f-404c-9a2e-c12064b232d0
>> >> > &u=
>> >> > https%3A%2F%2Fdocs.microsoft.com%2Fen-us%2Fwindows%2Fwin32%2Ffileio
>> >> > %2F exfat-specification%2374102-offsetvalid-field
>> >> > Signed-off-by: Chung-Chiang Cheng <cccheng@...ology.com>
>> >> Please read this discussion:
>> >>  https://patchwork.kernel.org/project/linux-
>> >> fsdevel/patch/20200115082447.19520-10-namjae.jeon@...sung.com/
>> >>
>> >> Thanks!
>> >
>> >
>
>