linux-kernel - Re: [PATCH v3 2/3] fat: make ctime and mtime identical explicitly

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Date:   Fri, 22 Apr 2022 16:24:10 +0800
From:   Chung-Chiang Cheng <shepjeng@...il.com>
To:     OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Cc:     Chung-Chiang Cheng <cccheng@...ology.com>,
        linux-kernel@...r.kernel.org, kernel@...heng.net
Subject: Re: [PATCH v3 2/3] fat: make ctime and mtime identical explicitly

On Fri, Apr 15, 2022 at 9:28 PM OGAWA Hirofumi
<hirofumi@...l.parknet.co.jp> wrote:
>
> Chung-Chiang Cheng <cccheng@...ology.com> writes:
>
> > -     fat_truncate_time(dir, NULL, S_ATIME|S_MTIME);
> > +     fat_truncate_time(dir, NULL, S_ATIME|S_CTIME|S_MTIME);
>
> fat_truncate_time() updates i_ctime too. So S_CTIME should not be
> necessary here. And I think this is better to use only S_MTIME to tell
> this is the point of mtime update.
>
> (And, in fat_truncate_time(), I think S_CTIME is not required, because
> we ignore ctime change, isn't it?)
>
> >       clear_nlink(inode);
> > -     fat_truncate_time(inode, NULL, S_CTIME);
> > +     fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
>
> This is the point to update ctime. You want to affect ctime change to
> mtime? As I said in previous post, I think we are better to ignore ctime
> change, because it may become yet another incompatible behavior.
>

Thanks for the feedback. I will change the behavior to ignore ctime
updates in the next version of the patch.