linux-kernel - Re: [PATCH] md/raid1: only update stack limits with the device in use

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Message-ID: <CAPhsuW5+Qxa4SKoaFrqZWKDmLaR0arXV7vqDX-Hy_OCEjmtA1w@mail.gmail.com>
Date:   Fri, 8 Sep 2023 13:42:11 -0700
From:   Song Liu <song@...nel.org>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     Li Nan <linan122@...wei.com>, linux-raid@...r.kernel.org,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com,
        houtao1@...wei.com, yangerkun@...wei.com,
        "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH] md/raid1: only update stack limits with the device in use

On Wed, Sep 6, 2023 at 11:30 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> Hi,
>
> 在 2023/09/06 17:37, Li Nan 写道:
> > Spare device affects array stack limits is unreasonable. For example,
> > create a raid1 with two 512 byte devices, the logical_block_size of array
> > will be 512. But after add a 4k devcie as spare, logical_block_size of
> > array will change as follows.
> >
> >    mdadm -C /dev/md0 -n 2 -l 10 /dev/sd[ab]   //sd[ab] is 512
> >    //logical_block_size of md0: 512
> >
> >    mdadm --add /dev/md0 /dev/sdc                      //sdc is 4k
> >    //logical_block_size of md0: 512
> >
> >    mdadm -S /dev/md0
> >    mdadm -A /dev/md0 /dev/sd[ab]
> >    //logical_block_size of md0: 4k
> >
> > This will confuse users, as nothing has been changed, why did the
> > logical_block_size of array change?
> >
> > Now, only update logical_block_size of array with the device in use.
> >
> > Signed-off-by: Li Nan <linan122@...wei.com>
> > ---
> >   drivers/md/raid1.c | 19 ++++++++-----------
> >   1 file changed, 8 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
> > index 95504612b7e2..d75c5dd89e86 100644
> > --- a/drivers/md/raid1.c
> > +++ b/drivers/md/raid1.c
> > @@ -3140,19 +3140,16 @@ static int raid1_run(struct mddev *mddev)
>
> I'm not sure about this behaviour, 'logical_block_size' can be
> increased while adding new underlying disk, the key point is not when
> to increase 'logical_block_size'. If there is a mounted fs, or
> partition in the array, I think the array will be corrupted.

How common is such fs/partition corruption? I think some fs and partition
table can work properly with 512=>4096 change?

Thanks,
Song

>
> Perhaps once that array is started, logical_block_size should not be
> changed anymore, this will require 'logical_block_size' to be metadate
> inside raid superblock. And the array should deny any new disk with
> bigger logical_block_size.
>
> Thanks,
> Kuai
>
>
> >       if (mddev->queue)
> >               blk_queue_max_write_zeroes_sectors(mddev->queue, 0);
> >
> > -     rdev_for_each(rdev, mddev) {
> > -             if (!mddev->gendisk)
> > -                     continue;
> > -             disk_stack_limits(mddev->gendisk, rdev->bdev,
> > -                               rdev->data_offset << 9);
> > -     }
> > -
> >       mddev->degraded = 0;
> > -     for (i = 0; i < conf->raid_disks; i++)
> > -             if (conf->mirrors[i].rdev == NULL ||
> > -                 !test_bit(In_sync, &conf->mirrors[i].rdev->flags) ||
> > -                 test_bit(Faulty, &conf->mirrors[i].rdev->flags))
> > +     for (i = 0; i < conf->raid_disks; i++) {
> > +             rdev = conf->mirrors[i].rdev;
> > +             if (rdev && mddev->gendisk)
> > +                     disk_stack_limits(mddev->gendisk, rdev->bdev,
> > +                                       rdev->data_offset << 9);
> > +             if (!rdev || !test_bit(In_sync, &rdev->flags) ||
> > +                 test_bit(Faulty, &rdev->flags))
> >                       mddev->degraded++;
> > +     }
> >       /*
> >        * RAID1 needs at least one disk in active
> >        */
> >
>