Re: [PATCH 2/2] mkfs: Show progress during block discard

[Pavel Reichl <preichl@redhat.com>]

On Thu, Nov 21, 2019 at 10:59 PM Darrick J. Wong
<darrick.wong@oracle.com> wrote:
>
> On Thu, Nov 21, 2019 at 10:44:45PM +0100, Pavel Reichl wrote:
> > Signed-off-by: Pavel Reichl <preichl@redhat.com>
> > ---
> >  mkfs/xfs_mkfs.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
> > index a02d6f66..07b8bd78 100644
> > --- a/mkfs/xfs_mkfs.c
> > +++ b/mkfs/xfs_mkfs.c
> > @@ -1248,6 +1248,7 @@ discard_blocks(dev_t dev, uint64_t nsectors)
> >       const uint64_t  step            = (uint64_t)2<<30;
> >       /* Sector size is 512 bytes */
> >       const uint64_t  count           = nsectors << 9;
> > +     uint64_t        prev_done       = (uint64_t) ~0;
> >
> >       fd = libxfs_device_to_fd(dev);
> >       if (fd <= 0)
> > @@ -1255,6 +1256,7 @@ discard_blocks(dev_t dev, uint64_t nsectors)
> >
> >       while (offset < count) {
> >               uint64_t        tmp_step = step;
> > +             uint64_t        done = offset * 100 / count;
> >
> >               if ((offset + step) > count)
> >                       tmp_step = count - offset;
> > @@ -1268,7 +1270,13 @@ discard_blocks(dev_t dev, uint64_t nsectors)
> >                       return;
> >
> >               offset += tmp_step;
> > +
> > +             if (prev_done != done) {
>
> Hmm... so this prints the status message every increase percentage
> point, right?

Not at all, the 'least change' it prints is one percent but that's the
maximum granularity i.e. I tested with 10 GB file and the output was:

Discarding:  0% done
Discarding: 20% done
Discarding: 40% done
Discarding: 60% done
Discarding: 80% done
Discarding is done.

So ATM there could be up to 102 lines - please propose a different idea.


>
> > +                     prev_done = done;
> > +                     fprintf(stderr, _("Discarding: %2lu%% done\n"), done);
>
> This isn't an error, so why output to stderr?
My bad, sorry.

>
> FWIW if it's a tty you might consider ending that string with \r so the
> status messages don't scroll off the screen.  Or possibly only reporting
> status if stdout is a tty?

Do I get it right that you propose to not flow the terminal with
dozens of lines which just update the percentage but instead keep
updating the same line? If so, I do like that.

>
> --D
>
> > +             }
> >       }
> > +     fprintf(stderr, _("Discarding is done.\n"));
> >  }
> >
> >  static __attribute__((noreturn)) void
> > --
> > 2.23.0
> >
>