linux-kernel - Re: [PATCH 03/20] timestamp_truncate: Replace users of timespec64

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Message-ID: <CABeXuvq_9YTTGZwmxO1WuEivuttDesNHKxeSQL5SsvkBSR884Q@mail.gmail.com>
Date:   Tue, 30 Jul 2019 17:08:30 -0700
From:   Deepa Dinamani <deepa.kernel@...il.com>
To:     Anton Altaparmakov <anton@...era.com>
Cc:     OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        y2038 Mailman List <y2038@...ts.linaro.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Artem Bityutskiy <dedekind1@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        stoph Hellwig <hch@....de>, Jaegeuk Kim <jaegeuk@...nel.org>,
        Joel Becker <jlbec@...lplan.org>,
        Richard Weinberger <richard@....at>, Tejun Heo <tj@...nel.org>,
        "yuchao0@...wei.com" <yuchao0@...wei.com>,
        "Linux F2FS DEV, Mailing List" 
        <linux-f2fs-devel@...ts.sourceforge.net>,
        "linux-ntfs-dev@...ts.sourceforge.net" 
        <linux-ntfs-dev@...ts.sourceforge.net>,
        linux-mtd <linux-mtd@...ts.infradead.org>
Subject: Re: [PATCH 03/20] timestamp_truncate: Replace users of timespec64_trunc

On Tue, Jul 30, 2019 at 3:28 PM Anton Altaparmakov <anton@...era.com> wrote:
>
> Hi Deepa,
>
> > On 30 Jul 2019, at 18:26, Deepa Dinamani <deepa.kernel@...il.com> wrote:
> >
> > On Tue, Jul 30, 2019 at 1:27 AM OGAWA Hirofumi
> > <hirofumi@...l.parknet.co.jp> wrote:
> >>
> >> Deepa Dinamani <deepa.kernel@...il.com> writes:
> >>
> >>> diff --git a/fs/fat/misc.c b/fs/fat/misc.c
> >>> index 1e08bd54c5fb..53bb7c6bf993 100644
> >>> --- a/fs/fat/misc.c
> >>> +++ b/fs/fat/misc.c
> >>> @@ -307,8 +307,9 @@ int fat_truncate_time(struct inode *inode, struct timespec64 *now, int flags)
> >>>              inode->i_atime = (struct timespec64){ seconds, 0 };
> >>>      }
> >>>      if (flags & S_CTIME) {
> >>> -             if (sbi->options.isvfat)
> >>> -                     inode->i_ctime = timespec64_trunc(*now, 10000000);
> >>> +             if (sbi->options.isvfat) {
> >>> +                     inode->i_ctime = timestamp_truncate(*now, inode);
> >>> +             }
> >>>              else
> >>>                      inode->i_ctime = fat_timespec64_trunc_2secs(*now);
> >>>      }
> >>
> >> Looks like broken. It changed to sb->s_time_gran from 10000000, and
> >> changed coding style.
> >
> > This is using a new api: timestamp_truncate(). granularity is gotten
> > by inode->sb->s_time_gran. See Patch [2/20]:
> > https://lkml.org/lkml/2019/7/29/1853
> >
> > So this is not broken if fat is filling in the right granularity in the sb.
>
> It is broken for FAT because FAT has different granularities for different timestamps so it cannot put the correct value in the sb as that only allows one granularity.  Your patch is totally broken for fat as it would be immediately obvious if you spent a few minutes looking at the code...

It seemed to me that FAT had already covered the special cases (2s and
1d) granularities by using internal functions. This one could also be
an inlined calculation, but I will just drop the FAT part from this
patch and leave it as is for now.

Thanks,
Deepa