linux-kernel - Re: [PATCH v7 05/13] fat: make fat_update

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Message-ID: <87h6p86p9z.fsf@mail.parknet.co.jp>
Date:   Thu, 10 Aug 2023 03:31:36 +0900
From:   OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:     Jeff Layton <jlayton@...nel.org>
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Subject: Re: [PATCH v7 05/13] fat: make fat_update_time get its own timestamp

Jeff Layton <jlayton@...nel.org> writes:

> On Thu, 2023-08-10 at 02:44 +0900, OGAWA Hirofumi wrote:
>> Jeff Layton <jlayton@...nel.org> writes:
>> 
> That would be wrong. The problem is that we're changing how update_time
> works:
>
> Previously, update_time was given a timestamp and a set of S_* flags to
> indicate which fields should be updated. Now, update_time is not given a
> timestamp. It needs to fetch it itself, but that subtly changes the
> meaning of the flags field.
>
> It now means "these fields needed to be updated when I last checked".
> The timestamp and i_version may now be different from when the flags
> field was set. This means that if any of S_CTIME/S_MTIME/S_VERSION were
> set that we need to attempt to update all 3 of them. They may now be
> different from the timestamp or version that we ultimately end up with.
>
> The above may look to you like it would always cause I_DIRTY_SYNC to be
> set on any ctime or mtime update, but inode_maybe_inc_iversion only
> returns true if it actually updated i_version, and it only does that if
> someone issued a ->getattr against the file since the last time it was
> updated.
>
> So, this shouldn't generate any more DIRTY_SYNC updates than it did
> before.

Again, if you claim so, why generic_update_time() doesn't work same? Why
only FAT does?

Or I'm misreading generic_update_time() patch?

Thanks.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>