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

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Message-ID: <YfFk7guenfgvrDlD@bender.morinfr.org>
Date:   Wed, 26 Jan 2022 16:12:46 +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 11:09, 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.

Both snippets came from the code before 41d2d848e5c0 that the patch is
being reverted here.  As I explained in my original message, upstream is
different because of 99dfc43ecbf6 which is not in 5.10.

> I think would be good keep it as the upstream version.

If you don't include these lines, isn't this worse as it's not calling
either part_start_io_acct or bio_start_io_acct (in 99dfc43ecbf6)?

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