linux-kernel - Re: [PATCH 5.10 01/25] md: revert io stats accounting

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Date:   Wed, 26 Jan 2022 16:19:04 +0100
From:   Guillaume Morin <guillaume@...infr.org>
To:     Jack Wang <jack.wang.usish@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org>,
        Guoqing Jiang <jiangguoqing@...inos.cn>,
        Song Liu <song@...nel.org>,
        Guillaume Morin <guillaume@...infr.org>
Subject: Re: [PATCH 5.10 01/25] md: revert io stats accounting

On 26 Jan 13:37, Jack Wang wrote:
> > > >
> > > > -       if (bio->bi_end_io != md_end_io) {
> > > > -               struct md_io *md_io;
> > > > -
> > > > -               md_io = mempool_alloc(&mddev->md_io_pool, GFP_NOIO);
> > > > -               md_io->mddev = mddev;
> > > > -               md_io->orig_bi_end_io = bio->bi_end_io;
> > > > -               md_io->orig_bi_private = bio->bi_private;
> > > > -
> > > > -               bio->bi_end_io = md_end_io;
> > > > -               bio->bi_private = md_io;
> > > > -
> > > > -               md_io->start_time = part_start_io_acct(mddev->gendisk,
> > > > -                                                      &md_io->part, bio);
> > > > -       }
> > > > -
> > > > +       /*
> > > > +        * save the sectors now since our bio can
> > > > +        * go away inside make_request
> > > > +        */
> > > > +       sectors = bio_sectors(bio);
> > > This code snip is not inside the original patch, and it's not in
> > > latest upstream too.
> > > >         /* bio could be mergeable after passing to underlayer */
> > > >         bio->bi_opf &= ~REQ_NOMERGE;
> > > >
> > > >         md_handle_request(mddev, bio);
> > > >
> > > > +       part_stat_lock();
> > > > +       part_stat_inc(&mddev->gendisk->part0, ios[sgrp]);
> > > > +       part_stat_add(&mddev->gendisk->part0, sectors[sgrp], sectors);
> > > > +       part_stat_unlock();
> > > > +
> > > same here, this code snip is not inside the original patch, and it's
> > > not in latest upstream too.
> >
> > Is it a problem?
> Not sure, might cause some confusion regarding io stats.

Have you observed anything weird? Because if you don't include this, I
don't see where these stats are updated at all. Could you explain
please?

-- 
Guillaume Morin <guillaume@...infr.org>