linux-kernel - Re: [LTP] [PATCH 1/1] zram01.sh: Workaround division by 0 on vfat on ppc64le

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Date:   Mon, 21 Nov 2022 09:59:55 +0100
From:   Petr Vorel <pvorel@...e.cz>
To:     Li Wang <liwang@...hat.com>
Cc:     ltp@...ts.linux.it, Jens Axboe <axboe@...nel.dk>,
        Minchan Kim <minchan@...nel.org>, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org,
        OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>,
        linux-kselftest@...r.kernel.org,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Nitin Gupta <ngupta@...are.org>
Subject: Re: [LTP] [PATCH 1/1] zram01.sh: Workaround division by 0 on vfat on
 ppc64le

Hi Li,

> Hi Petr,

> On Tue, Nov 8, 2022 at 3:12 AM Petr Vorel <pvorel@...e.cz> wrote:

> > Repeatedly read /sys/block/zram*/mm_stat for 1 sec. This should fix bug
> > on ppc64le on stable kernels, where mem_used_total is often 0.

> > Signed-off-by: Petr Vorel <pvorel@...e.cz>
> > ---
> >  .../kernel/device-drivers/zram/zram01.sh      | 27 +++++++++++++++++--
> >  1 file changed, 25 insertions(+), 2 deletions(-)

> > diff --git a/testcases/kernel/device-drivers/zram/zram01.sh
> > b/testcases/kernel/device-drivers/zram/zram01.sh
> > index 58d233f91..76a8ccab4 100755
> > --- a/testcases/kernel/device-drivers/zram/zram01.sh
> > +++ b/testcases/kernel/device-drivers/zram/zram01.sh
> > @@ -105,6 +105,26 @@ zram_mount()
> >         tst_res TPASS "mount of zram device(s) succeeded"
> >  }

> > +read_mem_used_total()
> > +{
> > +       echo $(awk '{print $3}' $1)
> > +}
> > +
> > +# Reads /sys/block/zram*/mm_stat until mem_used_total is not 0.
> > +loop_read_mem_used_total()


> This is not a looping function to check if mem_used_total is equal to zero,
> the loop part is by means of the TST_RETRY_FUNC macro.
Thanks for your review!

> So, I'd suggest renaming it to check_read_mem_used_total().
Agree. Unfortunately even this didn't help on ppc64le system where I was able to
reproduce it, thus probably not worth to merge.

Unfortunately later I was not able to reproduce the problem any more, I'll try
it more this week.

Kind regards,
Petr

> Reviewed-by: Li Wang <liwang@...hat.com>



> > +{
> > +       local file="$1"
> > +       local mem_used_total
> > +
> > +       tst_res TINFO "$file"
> > +       cat $file >&2
> > +
> > +       mem_used_total=$(read_mem_used_total $file)
> > +       [ "$mem_used_total" -eq 0 ] && return 1
> > +
> > +       return 0
> > +}
> > +
> >  zram_fill_fs()
> >  {
> >         local mem_used_total
> > @@ -133,9 +153,12 @@ zram_fill_fs()
> >                         continue
> >                 fi

> > -               mem_used_total=`awk '{print $3}'
> > "/sys/block/zram$i/mm_stat"`
> > +               TST_RETRY_FUNC "loop_read_mem_used_total
> > /sys/block/zram$i/mm_stat" 0
> > +               mem_used_total=$(read_mem_used_total
> > /sys/block/zram$i/mm_stat)
> > +               tst_res TINFO "mem_used_total: $mem_used_total"
> > +
> >                 v=$((100 * 1024 * $b / $mem_used_total))
> > -               r=`echo "scale=2; $v / 100 " | bc`
> > +               r=$(echo "scale=2; $v / 100 " | bc)

> >                 if [ "$v" -lt 100 ]; then
> >                         tst_res TFAIL "compression ratio: $r:1"
> > --
> > 2.38.0


> > --
> > Mailing list info: https://lists.linux.it/listinfo/ltp