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From:   OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
To:     Jeff Layton <jlayton@kernel.org>
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Subject: Re: [PATCH v7 05/13] fat: make fat_update_time get its own timestamp
In-Reply-To: <874jl88ed1.fsf@mail.parknet.co.jp> (OGAWA Hirofumi's message of
        "Wed, 09 Aug 2023 23:44:26 +0900")
References: <20230807-mgctime-v7-0-d1dec143a704@kernel.org>
        <20230807-mgctime-v7-5-d1dec143a704@kernel.org>
        <87msz08vc7.fsf@mail.parknet.co.jp>
        <52bead1d6a33fec89944b96e2ec20d1ea8747a9a.camel@kernel.org>
        <878rak8hia.fsf@mail.parknet.co.jp>
        <7edc9239f73022b9c2a1d3f4f946153f85f94739.camel@kernel.org>
        <874jl88ed1.fsf@mail.parknet.co.jp>
Date:   Wed, 09 Aug 2023 23:52:10 +0900
Message-ID: <87zg306zfp.fsf@mail.parknet.co.jp>
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OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> writes:

> Jeff Layton <jlayton@kernel.org> writes:
>
>> I'm a little confused too. Why do you believe this will break
>> -o relatime handling? This patch changes two things:
>>
>> 1/ it has fat_update_time fetch its own timestamp (and ignore the "now"
>> parameter). This is in line with the changes in patch #3 of this series,
>> which explains the rationale for this in more detail.
>>
>> 2/ it changes fat_update_time to also update the i_version if any of
>> S_CTIME|S_MTIME|S_VERSION are set. relatime is all about the S_ATIME,
>> and it is specifically excluded from that set.
>>
>> The rationale for the second change is is also in patch #3, but
>> basically, we can't guarantee that current_time hasn't changed since we
>> last checked for inode_needs_update_time, so if any of
>> S_CTIME/S_MTIME/S_VERSION have changed, then we need to assume that any
>> of them may need to be changed and attempt to update all 3.
>>
>> That said, I think the logic in fat_update_time isn't quite right. I
>> think want something like this on top of this patch to ensure that the
>> S_CTIME and S_MTIME get updated, even if the flags only have S_VERSION
>> set.
>>
>> Thoughts?
>
> I'm not talking about "relatime" at all, I'm always talking about
> "lazytime".
>
> I_DIRTY_TIME delays to update on disk inode only if changed
> timestamp. But you changed it to I_DIRTY_SYNC, i.e. always update on
> disk inode by timestamp.

And if change like it, why doesn't same change goes to generic_update_time()?
It looks like generic_update_time() in this series doesn't work like you said.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>